PRODUCTION OF ENANTIOPURE ALCOHOLS, AMINES AND ACIDS FROM RACEMIC EPOXIDES BY CASCADE BIOTRANSFORMATION INVOLVING EPOXIDE ISOMERIZATION AND DYNAMIC KINETIC RESOLUTION Field of Invention This invention relates to the production of enantiopure acids, amines and alcohols from racemic epoxides by cascade biotransformation involving enzymatic epoxide isomerization and dynamic kinetic resolution. Background The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge. Biocatalytic cascade reactions are a powerful tool for the green and sustainable synthesis of high-value chemicals from easily available starting materials in a one-pot system without isolation of intermediates. An interesting class of cascade reactions involves the conversion of racemic substrates to produce enantioenriched products via enzymatic dynamic kinetic resolution (DKR), which has been achieved by simple systems consisting of only racemization and enantioselective transformation. 2-Arylpropionic acids and 2-arylpropyl amines are two classes of chiral compounds which are bioactive and pharmaceutically relevant, making them attractive targets for cascade production. (S)-2-arylpropionic acids constitute the pharmacologically active form of profen drugs, which is the most widely used type of non-steroidal anti-inflammatory drugs (NSAIDs). Both (R)- and (S)-2-arylpropyl amines are precursors to several pharmaceuticals such as angiotensin receptor blockers, anti-cancer drug candidate OTS514 and AMPA receptor modulators (FIG.1). These compounds can be synthesized by asymmetric transformations from non-chiral substrates. (S)-2-arylpropionic acids, (R)- and (S)-2-arylpropyl amines can be prepared using metal-catalyzed asymmetric syntheses from terminal alkenes, but these methods require harsh conditions, toxic reagents and solvents, and specialized catalysts. The enzyme-catalyzed decarboxylation of prochiral arylmalonates to produce (S)-2-arylpropionic acids is known, but suffers from unwanted spontaneous non-stereoselective decarboxylation.   While enantioenriched 2-arylpropionic acids and 2-arylpropyl amines have been accessed through the cascade biotransformation of methyl-substituted styrenes, this approach is limited by the enantioselectivity, activity and substrate scope of styrene monooxygenase that catalyzes the stereoselective alkene epoxidation step. The enantioselective synthesis of 2-arylpropionic acids and 2-arylpropyl amines can also be achieved from racemic starting materials. While kinetic resolution of racemic substrates is limited by a 50% maximum theoretical yield, enzymatic DKR starting from 2-arylpropanals is an appealing approach to achieve high yield and enantioselectivity, in which 2-arylpropanals racemize spontaneously and undergo enantioselective oxidation catalyzed by alcohol dehydrogenase (ADH), or enantioselective amination catalyzed by transaminase (TA), respectively. Unfortunately, aldehydes such as 2-arylpropanals are unstable due to their tendency to undergo side reactions such as aerobic oxidation and aldol reactions. Furthermore, aldehydes are known to inhibit enzyme activity at elevated concentrations. There therefore is a need for an improved process for conducting reactions of this type, and which overcomes the drawbacks associated with existing methods. Summary of Invention It has been surprisingly found that it is possible to convert racemic epoxide materials into enantiopure acids, amines and alcohols via a cascade biotransformation that involves dynamic kinetic resolution. Aspects and embodiments of the current invention will now be described by reference to the following numbered clauses. 1. A method of producing an enantiomerically pure or enantiomerically enriched alcohol, acid or amine from a racemic 2-alkyl-3-phenyl oxirane or derivative thereof and/or a racemic 2-alkyl-2-phenyl oxirane or derivative thereof using at least two enzymes, which method comprises subjecting the 2-alkyl-3-phenyl oxirane or derivative thereof and/or the 2-alkyl-2- phenyl oxirane or derivative thereof to at least two enzyme-catalyzed chemical transformations in a one-pot reaction system. 2. The method according to Clause 1, wherein the method produces enantiomerically pure or enantiomerically enriched acids comprising the steps of: (a) generating a phenylalkanal or derivative thereof by reacting the 2-alkyl-3- phenyl oxirane or derivative thereof and/or the 2-alkyl-2-phenyl oxirane or derivative thereof   with a styrene oxide isomerase to form a phenylalkanal or derivative thereof that undergoes racemisation in situ; and (b) generating an enantiomerically pure or enantiomerically enriched phenylalkanacid or derivative thereof from a phenylalkanal or derivative thereof by conducting an oxidation reaction catalysed by an oxygenase, an oxidase or an alcohol dehydrogenase to form the enantiomerically enriched phenylalkanacid or derivative thereof using a dynamic kinetic resolution reaction. 3. The method according to Clause 1, wherein the method produces enantiomerically pure or enantiomerically enriched amines comprising the steps of: (a) generating a phenylalkanal or derivative thereof by reacting the 2-alkyl-3- phenyl oxirane or derivative thereof and/or the 2-alkyl-2-phenyl oxirane or derivative thereof with a styrene oxide isomerase to form a phenylalkanal or derivative thereof that undergoes racemisation in situ; and (b) generating an enantiomerically pure or enantiomerically enriched phenylalkanamine or derivative thereof from a phenylalkanal or derivative thereof by conducting a transamination reaction catalysed by a transaminase, an amine dehydrogenase, an imine reductase or a reductive aminase to form the enantiomerically enriched phenylalkanamine or derivative thereof using a dynamic kinetic resolution reaction. 4. The method according to Clause 1, wherein the method produces enantiomerically pure or enantiomerically enriched alcohols comprising the steps of: (a) generating a phenylalkanal or derivative thereof by reacting the 2-alkyl-3- phenyl oxirane or derivative thereof and/or the 2-alkyl-2-phenyl oxirane or derivative thereof with a styrene oxide isomerase to form a phenylalkanal or derivative thereof that undergoes racemisation in situ; and (b) generating an enantiomerically pure or enantiomerically enriched phenylalkanol or derivative thereof from a phenylalkanal or derivative thereof by conducting a reduction reaction catalysed by a reductase or an alcohol dehydrogenase to form the enantiomerically enriched phenylalkanol or derivative thereof using a dynamic kinetic resolution reaction. 5. The method according to any one of the preceding clauses, wherein the at least two enzymes used in the method are provided: (a) in whole cells genetically engineered to overexpress the at least two enzymes, optionally wherein the at least two overexpressed enzymes are located on one or more   plasmids or integrated in the chromosome of each of the one or more recombinant microbial cells; (b) in a cell-free extract; (c) as purified enzymes; or (d) as immobilized enzymes. 6. The method according to any one of Clauses 2 to 4, wherein the enzyme catalyzing the isomerization of the 2-alkyl-2-phenyl oxirane or derivative thereof into a phenylalkanal or derivative thereof is styrene oxide isomerase (SOI), or another isomerase, optionally wherein the enzyme is SOI. 7. The method according to Clause 2, wherein the enzyme catalyzing the oxidation of the phenylalkanal or derivative thereof to an enantiomerically enriched (S)-phenylalkanacid or derivative thereof is ADH9v1 or its mutants or similar enzymes with more than 50% identity. 8. The method according to Clause 2 or Clause 7, wherein the method further comprises a redox co-factor. 9. The method according to Clause 8, wherein the redox co-factor is NAD ⁺ or NADP ⁺ . 10. The method according to Clause 9, wherein the method also uses a NAD ⁺ cofactor regenerating enzyme, optionally wherein the NAD ⁺ cofactor regenerating enzyme is NADH oxidase (NOX). 11. The method according to Clause 3, wherein the enzyme catalyzing the oxidation of the phenylalkanal or derivative thereof to an enantiomerically enriched: (a) (S)-phenylalkanamine or derivative thereof is HnTA or its mutants or similar enzymes with more than 50% identity; or (b) (R)-phenylalkanamine or derivative thereof is MmTA or its mutants or similar enzymes with more than 50% identity. 12. The method according to Clause 3 or Clause 11, wherein the method further comprises pyridoxal phosphate. 13. The method according to any one of Clauses 3, 11 and 12, wherein when the reaction is conducted in the absence of a cell, it further comprises L-alanine, optionally   wherein, when L-alanine is present, the method further comprises alanine dehydrogenase to regenerate L-alanine. 14. The method according to Clause 4, wherein the method further comprises a redox co-factor. 15. The method according to Clause 14, wherein the redox co-factor is NADH or NADPH 16. The method according to Clause 15, wherein the method also uses a NADH or NADPH cofactor regenerating enzyme, optionally wherein the NADH or NADPH cofactor regenerating enzyme is a glucose dehydrogenase, optionally wherein a reaction medium of the reaction further comprises one or more of glucose and a sacrificial alcohol (e.g. isopropyl alcohol and/or ethanol). 17. The method according to any one of the preceding clauses, wherein the one-pot reaction system comprises use of an aqueous medium (e.g. an aqueous buffer medium). 18. The method according to Clause 17, further comprising an organic co-solvent, optionally wherein the organic co-solvent is selected from one or more of the group consisting of dimethyl sulfoxide, dimethylformamide, acetone or acetonitrile. 19. The method according to any one of Clauses 1 to 16, wherein the one-pot reaction system comprises use of a bi-phasic medium, optionally wherein the bi-phasic medium consists of an aqueous (e.g. aqueous buffer) and solid resin medium, or an aqueous (e.g. aqueous buffer) and organic solvent medium or an alcohol and organic solvent medium. 20. The method according to Clause 19, wherein the organic solvent medium is selected from one or more alkanes solvents and/or one or more ester solvents, optionally wherein the organic solvent medium is selected from one or both of hexane and hexadecane. Drawings FIG.1 depicts the concept of one-pot enzymatic cascade reactions to convert racemic trans- β-methyl epoxide 1 or α-methyl epoxide 2 to (S)-2-arylpropionic acids 4, (R)- or (S)-2- arylpropylamines 5. a) Conversion of 1 or 2 to (S)-4 via SOI-catalyzed isomerization, spontaneous racemization, and ADH-catalyzed (S)-enantioselective oxidation. b) Conversion of 1 or 2 to (R)-5 via SOI-catalyzed isomerization, spontaneous racemization, and TA-   catalyzed (R)-enantioselective amination. c) Conversion of 1 or 2 to (S)-5 via SOI-catalyzed isomerization, spontaneous racemization, and TA-catalyzed (S)-enantioselective amination. FIG. 2 depicts the biocatalytic cascade conversion of racemic trans-β-methyl epoxide 1a or α-methyl epoxide 2a to (S)-2-phenylpropionic acid 4a. a) Time-course of one-pot cascade conversion of racemic 1a or 2a into (S)-4a via SOI-catalyzed isomerization, spontaneous racemization, and ADH9v1-catalyzed enantioselective oxidation. b) Reduced formation of side product 6a and enhanced ee of product (S)-4a for the cascade conversion of 1a or 2a involving SOI-catalyzed in situ generation of 3a, compared to directly using 3a to produce (S)-4a. Average values from triplicate experiments are shown. Other reaction conditions: 10 mM substrate, 0.2 mM NAD ⁺ , 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. FIG. 3 depicts the biocatalytic cascade conversion of racemic trans-β-methyl epoxide 1a or α-methyl epoxide 2a to (R)-2-phenylpropyl amine 5a. a) Time-course of one-pot cascade conversion of racemic 1a or 2a into (R)-5a via SOI-catalyzed isomerization, spontaneous racemization, and MmTA-catalyzed (R)-enantioselective amination. b) Reduced formation of side product 6a for the cascade conversion of 1a or 2a involving SOI-catalyzed in situ generation of 3a, compared to directly using 3a to produce (R)-5a. Average values from triplicate experiments are shown. Other reaction conditions: 2.5 mM substrate, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. FIG. 4 depicts the results of the screening of transaminases for the conversion of rac-3a to 5a, and ee of 5a obtained. WC = whole cells, CFE = cell-free extract, L-ala = L-alanine, D- ala = D-alanine, IPAm = isopropylamine. Conditions for whole-cell reaction: 10 mM rac-3a, 10 g cdw/L E. coli (transaminase), 250 mM amine donor, 1 mM PLP, 100 mM KP buffer pH 8.0, 2%v/v DMSO co-solvent. Conditions for cell-free extract reaction: 10 mM rac-3a, 4–6 g _protein /L CFE containing transaminase, 250 mM amine donor, 1 mM PLP, 100 mM KP buffer pH 8.0, 2%v/v DMSO co-solvent. Conversions and ee determined by HPLC. Note: After screening using WC and CFE, and testing different amine donors, the results for the conditions giving the highest conversion to amine are shown here. The following enzymes were screened: transaminase from Hyphomonas neptunium (HnTA), Bacillus megaterium (BmTA), Vibrio fluvialis (VfTA), mutant VfTA (mVfTA), Chromobacterum violaceum (CvTA), Aspergillus terreus (AtTA), Ancylobacter sp. (AsTA), Arthrobacter sp. (ArRTA), Martelella mediterranea (MmTA), Rugeria pomeroyi (RpTA) and Neosartoria fischeri (NfTA). Either resting whole cells or cell-free extract were used, and different amine donors were tested.   FIG. 5 depicts the SDS-PAGE of SOI cell-free extract (19.7 kDa), purified ADH9v1 (26.9 kDa), NOX (49.7 kDa), MmTA (49.6 kDa) and HnTA (35.8 kDa). FIG. 6 depicts the SDS-PAGE of E. coli (ADH9v1-NOX) (Lane 1: total cell protein and 2: soluble protein) and E. coli (SOI-MmTA-AlaDH) (Lane 3: soluble protein and 4: total cell protein). FIG. 7 depicts the results of the screening of co-solvent and amount (%v/v). Conditions: 5 mM 3a, 0.1 g/L ADH9v1, 0.1 g/L NOX, 0.1 mM NAD ⁺ , 100 mM potassium phosphate buffer, pH 8, 20 h, 30°C, 250 rpm. FIG. 8 depicts the results of the screening of buffer system and pH. Conditions: 5 mM 3a, 0.1 g/L ADH9v1, 0.1 g/L NOX, 0.1 mM NAD ⁺ , 100 mM buffer, 2%v/v DMSO, 20 h, 30°C, 250 rpm. KP = potassium phosphate, Tris = Tris-HCl buffer. FIG. 9 depicts the results of the screening of buffer system and pH for conversion of rac-2- phenylpropanal 3a to 2-phenylpropylamine 5a. Conditions: 5 mM rac-3a, 2 g _protein /L MmTA or 1 g _protein /L HnTA, 250 mM L-alanine or isopropylamine respectively, 1 mM PLP, 100 mM KP or Tris buffer, 2% DMSO co-solvent. KP = potassium phosphate buffer, Tris = Tris-HCl buffer. FIG. 10 depicts the HPLC chromatograms of (a) standard of 4a, (b) standard of 6a, (c) standard of 3a (purified by distillation prior to use), (d) sample of biotransformation of 10 mM 1a to 4a and 6a catalyzed by 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1 and 0.2 g/L NOX taken at 16 h, (e) sample of biotransformation of 10 mM 3a into 4a and 6a catalyzed by 0.2 g/L ADH9v1 and 0.2 g/L NOX taken at 16 h. Other reaction conditions: 0.2 mM NAD ⁺ , 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C. HPLC conditions: SB-C18 column, 50% acetonitrile, 50% H ₂ O+TFA, 0.5 mL/min. FIG.11 depicts the HPLC chromatograms of (a) standard 5a, (b) standard 6a, (c) sample of biotransformation of 2.5 mM 1a to 5a catalyzed by 3 g _protein /L SOI CFE and 3 g/L MmTA taken at 16 h, (d) sample of biotransformation of 2.5 mM 3a into 5a and 6a catalyzed by 3 g/L MmTA taken at 16 h. Other reaction conditions: 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C. HPLC conditions: SB-C18 column, 30% acetonitrile, 70% H ₂ O+TFA, 0.5 mL/min.   FIG. 12 depicts the HPLC chromatograms of (a) standard 4a and (b) sample of biotransformation of 1a to 4a. Conditions: 10 mM 1a, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 13 depicts the HPLC chromatograms of (a) standard 4a and (b) sample of biotransformation of 2a to 4a. Conditions: 10 mM 2a, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 14 depicts the HPLC chromatograms of (a) standard 4b and (b) sample of biotransformation of 1b to 4b. Conditions: 5 mM 1b, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 15 depicts the HPLC chromatograms of (a) standard 4b and (b) sample of biotransformation of 2b to 4b. Conditions: 2.5 mM 2b, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 16 depicts the HPLC chromatograms of (a) standard 4c and (b) sample of biotransformation of 1c to 4c. Conditions: 5 mM 1c, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 17 depicts the HPLC chromatograms of (a) standard 4c and (b) sample of biotransformation of 2c to 4c. Conditions: 5 mM 2c, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 18 depicts the HPLC chromatograms of (a) standard 4d and (b) sample of biotransformation of 1d to 4d. Conditions: 5 mM 1d, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 19 depicts the HPLC chromatograms of (a) standard 4d and (b) sample of biotransformation of 2d to 4d. Conditions: 2.5 mM 2d, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 20 depicts the HPLC chromatograms of (a) standard 4e and (b) sample of biotransformation of 1e to 4e. Conditions: 2.5 mM 1e, 0.3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h.   FIG. 21 depicts the HPLC chromatograms of (a) standard 4e and (b) sample of biotransformation of 2e to 4e. Conditions: 5 mM 2e, 0.3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 22 depicts the HPLC chromatograms of (a) standard 4f and (b) sample of biotransformation of 1f to 4f. Conditions: 1 mM 1f, 8 g _protein /L SOI CFE, 0.4 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 23 depicts the HPLC chromatograms of (a) standard 4f and (b) sample of biotransformation of 2f to 4f. Conditions: 0.5 mM 2f, 8 g _protein /L SOI CFE, 0.4 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 24 depicts the HPLC chromatograms of (a) standard 4g and (b) sample of biotransformation of 1g to 4g. Conditions: 1 mM 1g, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 25 depicts the HPLC chromatograms of (a) standard 4g and (b) sample of biotransformation of 2g to 4g. Conditions: 1 mM 2g, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 26 depicts the HPLC chromatograms of (a) standard 4h and (b) sample of biotransformation of 1h to 4h. Conditions: 0.5 mM 1h, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.1 g/L NOX, 0.1 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 27 depicts the HPLC chromatograms of (a) standard 4h and (b) sample of biotransformation of 2h to 4h. Conditions: 2.5 mM 2h, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 28 depicts the HPLC chromatograms of (a) standard 5a, (b) sample of biotransformation of 2.5 mM 1a to (R)-5a using SOI + MmTA, (c) sample of biotransformation of 2.5 mM 1a to (S)-5a using SOI + HnTA, (d) sample of biotransformation of 2.5 mM 2a to (R)-5a using SOI + MmTA, (e) sample of biotransformation of 2.5 mM 2a to (S)-5a using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h.   Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG. 29 depicts the HPLC chromatograms of (a) standard 5b, (b) sample of biotransformation of 1.25 mM 1b to (R)-5b using SOI + MmTA, (c) sample of biotransformation of 2.5 mM 1b to (S)-5b using SOI + HnTA, (d) sample of biotransformation of 2.5 mM 2b to (R)-5b using SOI + MmTA, (e) sample of biotransformation of 2.5 mM 2b to (S)-5b using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG. 30 depicts the HPLC chromatograms of (a) standard 5c, (b) sample of biotransformation of 2.5 mM 1c to (R)-5c using SOI + MmTA, (c) sample of biotransformation of 2.5 mM 1c to (S)-5c using SOI + HnTA, (d) sample of biotransformation of 2.5 mM 2c to (R)-5c using SOI + MmTA, (e) sample of biotransformation of 2.5 mM 2c to (S)-5c using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG. 31 depicts the HPLC chromatograms of (a) standard 5d, (b) sample of biotransformation of 1.25 mM 1d to (R)-5d using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 1d to (S)-5d using SOI + HnTA, (d) sample of biotransformation of 1.25 mM 2d to (R)-5d using SOI + MmTA, (e) sample of biotransformation of 1.25 mM 2d to (S)-5d using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h.   FIG. 32 depicts the HPLC chromatograms of (a) standard 5e, (b) sample of biotransformation of 1.25 mM 1e to (R)-5e using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 1e to (S)-5e using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG. 33 depicts the HPLC chromatograms of (a) standard 5g, (b) sample of biotransformation of 1.25 mM 2g to (R)-5g using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 2g to (S)-5g using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG. 34 depicts the HPLC chromatograms of (a) standard 5h, (b) sample of biotransformation of 1.25 mM 2h to (R)-5h using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 2h to (S)-5h using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG. 35 depicts the chiral HPLC chromatograms of (a) racemic 4a standard, (b) (S)-4a standard, (c) sample of biotransformation of 1a to 4a. Conditions: 10 mM 1a, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (d) sample of biotransformation of 2a to 4a. Conditions: 10 mM 2a, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG.36 depicts the chiral HPLC chromatograms of (a) synthesized 4b standard, (b) sample of biotransformation of 1b to 4b. Conditions: 5 mM 1b, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (c)   sample of biotransformation of 2b to 4b. Conditions: 2.5 mM 2b, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 37 depicts the chiral HPLC chromatograms of (a) synthesized 4c standard, (b) sample of biotransformation of 1c to 4c. Conditions: 5 mM 1c, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (c) sample of biotransformation of 2c to 4c. Conditions: 5 mM 2c, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG.38 depicts the chiral HPLC chromatograms of (a) synthesized 4d standard, (b) sample of biotransformation of 1d to 4d. Conditions: 5 mM 1d, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (c) sample of biotransformation of 2d to 4d. Conditions: 2.5 mM 2d, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 39 depicts the chiral HPLC chromatograms of (a) synthesized 4e standard, (b) sample of biotransformation of 1e to 4e. Conditions: 2.5 mM 1e, 0.3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (c) sample of biotransformation of 2e to 4e. Conditions: 5 mM 2e, 0.3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 40 depicts the chiral HPLC chromatograms of (a) synthesized 4f standard, (b) synthesized (R)-4f standard, (c) sample of biotransformation of 1f to 4f. Conditions: 1 mM 1f, 8 g _protein /L SOI CFE, 0.4 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (d) sample of biotransformation of 2f to 4f. Conditions: 0.5 mM 2f, 8 g _protein /L SOI CFE, 0.4 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG.41 depicts the chiral HPLC chromatograms of (a) synthesized 4g standard, (b) sample of biotransformation of 1g to 4g. Conditions: 1 mM 1g, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (c) sample of biotransformation of 2g to 4g. Conditions: 1 mM 2g, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG.42 depicts the chiral HPLC chromatograms of (a) synthesized 4h standard, (b) sample of biotransformation of 1h to 4h. Conditions: 0.5 mM 1h, 3 g _protein /L SOI CFE, 0.2 g/L   ADH9v1, 0.1 g/L NOX, 0.1 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h, and (c) sample of biotransformation of 2h to 4h. Conditions: 2.5 mM 2h, 3 g _protein /L SOI CFE, 0.2 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 2%v/v DMSO, 100 mM KP buffer (pH 8), 30°C, 16 h. FIG. 43 depicts the chiral HPLC chromatograms of (a) racemic 5a standard, (b) (S)-5a standard, (c) sample of biotransformation of 2.5 mM 1a to (R)-5a using SOI + MmTA, (d) sample of biotransformation of 2.5 mM 2a to (R)-5a using SOI + MmTA, (e) sample of biotransformation of 2.5 mM 1a to (S)-5a using SOI + HnTA, (f) sample of biotransformation of 2.5 mM 2a to (S)-5a using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG.44 depicts the chiral HPLC chromatograms of (a) synthesized 5b standard, (b) sample of biotransformation of 1.25 mM 1b to (R)-5b using SOI + MmTA, (c) sample of biotransformation of 2.5 mM 2b to (R)-5b using SOI + MmTA, (d) sample of biotransformation of 2.5 mM 1b to (S)-5b using SOI + HnTA, (e) sample of biotransformation of 2.5 mM 2b to (S)-5b using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. All samples were derivatized to the benzamide using benzoyl chloride. FIG. 45 depicts the chiral HPLC chromatograms of (a) synthesized 5c standard, (b) sample of biotransformation of 2.5 mM 1c to (R)-5c using SOI + MmTA, (c) sample of biotransformation of 2.5 mM 2c to (R)-5c using SOI + MmTA, (d) sample of biotransformation of 2.5 mM 1c to (S)-5c using SOI + HnTA, (e) sample of biotransformation of 2.5 mM 2c to (S)-5c using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. All samples were derivatized to the benzamide using benzoyl chloride.   FIG.46 depicts the chiral HPLC chromatograms of (a) synthesized 5d standard, (b) sample of biotransformation of 1.25 mM 1d to (R)-5d using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 2d to (R)-5d using SOI + MmTA, (d) sample of biotransformation of 1.25 mM 1d to (S)-5d using SOI + HnTA, (e) sample of biotransformation of 1.25 mM 2d to (S)-5d using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. All samples were derivatized to the benzamide using benzoyl chloride. FIG. 47 depicts the chiral HPLC chromatograms of (a) synthesized 5e standard, (b) sample of biotransformation of 1.25 mM 1e to (R)-5e using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 1e to (S)-5e using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. FIG.48 depicts the chiral HPLC chromatograms of (a) synthesized 5g standard, (b) sample of biotransformation of 1.25 mM 2g to (R)-5g using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 2g to (S)-5g using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. All samples were derivatized to the benzamide using benzoyl chloride. FIG.49 depicts the chiral HPLC chromatograms of (a) synthesized 5h standard, (b) sample of biotransformation of 1.25 mM 2h to (R)-5h using SOI + MmTA, (c) sample of biotransformation of 1.25 mM 2h to (S)-5h using SOI + HnTA. Conditions when using SOI + MmTA: 3 g _protein /L SOI CFE, 3 g/L MmTA, 1 mM PLP, 250 mM L-alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Conditions when using SOI + HnTA: 3 g _protein /L SOI CFE, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. All samples were derivatized to the benzamide using benzoyl chloride.   Description In this invention, enantiopure 2-arylpropionic acids, 2-arylpropyl amines and 2-arylpropyl alcohols are produced from racemic epoxides by cascade biotransformation involving enzymatic epoxide isomerization and dynamic kinetic resolution. Conventionally, the enantioselective chemical synthesis of these valuable molecules containing a methyl group on the chiral center of the β-carbon is challenging. These enantiopure acids, amines and alcohol, are valuable molecules.2-arylpropionic acids are an important class of nonsteroidal anti-inflammatory drugs (NSAIDs). 2-arylpropyl amines are known to constitute the core structure of many biologically active compounds, such as Fendiline, an anti-anginal agent for treatment of coronary disease. 2-arylpropyl alcohols are used in the manufacture of fragrances, and are also common precursors to 2- arylpropionic acid via oxidation. Commercial syntheses of enantiopure 2-arylpropanols and 2-arylpropionic acids involve the multistep chemical synthesis of the racemic product, followed by diastereomeric salt crystallization or enzymatic resolution. However, these classical resolution methods have a maximum theoretical yield of 50%. Otherwise, more sophisticated methods tested on the laboratory scale include asymmetric hydrogenation and hydroformylation, which require expensive precious metal catalysts like ruthenium or rhodium. For the commercial synthesis of chiral free amines, a common procedure is the asymmetric hydrogenation enamines or imines under harsh conditions of high pressure and in the presence of synthetically challenging chiral ligands. Overall, these traditional chemical methods utilize toxic chemicals and organic solvents. A notable feature that differentiates existing technologies from this invention is the incorporation of the unique 1,2-methyl shift and 1,2-hydride shift isomerization of racemic epoxide catalyzed by SOI. This allows the in situ generation of the relatively unstable 2- arylpropanal intermediate, which can then subsequently undergo oxidation, transamination or reduction in the same pot without isolation, to produce the enantiopure acid, amine or alcohol product respectively. Since the 2-arylpropanal intermediate is quickly reacted after being formed, there are no side reactions occurring, making the cascade biotransformation clean and efficient.   Thus, in a first aspect of the invention, there is provided a method of producing an enantiomerically pure or enantiomerically enriched alcohol, acid or amine from a racemic 2- alkyl-3-phenyl oxirane or derivative thereof and/or a racemic 2-alkyl-2-phenyl oxirane or derivative thereof using at least two enzymes, which method comprises subjecting the 2- alkyl-3-phenyl oxirane or derivative thereof and/or the 2-alkyl-2-phenyl oxirane or derivative thereof to at least two enzyme-catalyzed chemical transformations in a one-pot reaction system. As will be appreciated, the enzymes selected in the method above will generally be selective to produce an alcohol, an acid or an amine from any given starting material(s). Said starting materials being a racemic 2-alkyl-3-phenyl oxirane or derivative thereof and/or a racemic 2- alkyl-2-phenyl oxirane or derivative thereof. In embodiments herein, the word “comprising” may be interpreted as requiring the features mentioned, but not limiting the presence of other features. Alternatively, the word “comprising” may also relate to the situation where only the components/features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of” or “consists essentially of”). It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention. In other words, the word “comprising” and synonyms thereof may be replaced by the phrase “consisting of” or the phrase “consists essentially of” or synonyms thereof and vice versa. The phrase, “consists essentially of” and its pseudonyms may be interpreted herein to refer to a material where minor impurities may be present. For example, the material may be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greater than 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure. As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a composition” includes mixtures of two or more such compositions, and the like. It will be understood that the terms “enantiomerically pure” and “enantiomerically enriched” refer to enantiomers of a compound. “Enantiomers” refer to two stereoisomers of a compound which are non-superimposable mirror images of one another. Stereochemical definitions and conventions used herein generally follow S. P. Parker, Ed.,   McGraw-Hill Dictionary of Chemical Terms (1984) McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S., “Stereochemistry of Organic Compounds”, John Wiley & Sons, Inc., New York, 1994. The compounds of the invention may contain asymmetric or chiral centers, and therefore exist in different stereoisomeric forms. It is intended that all stereoisomeric forms of the compounds of the invention, including but not limited to, diastereomers, enantiomers and atropisomers, as well as mixtures thereof such as racemic mixtures, form part of the present invention. Many organic compounds exist in optically active forms, i.e., they have the ability to rotate the plane of plane-polarized light. In describing an optically active compound, the prefixes D and L, or R and S, are used to denote the absolute configuration of the molecule about its chiral center(s). The prefixes D and L or (+) and (−) are employed to designate the sign of rotation of plane-polarized light by the compound, with (−) or l (L) meaning that the compound is levorotatory. A compound prefixed with (+) or d (D) is dextrorotatory. For a given chemical structure, these stereoisomers are identical except that they are mirror images of one another. A specific stereoisomer may also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture. A 50:50 mixture of enantiomers is referred to as a racemic mixture or a racemate, which may occur where there has been no stereoselection or stereospecificity in a chemical reaction or process. The terms “racemic mixture” and “racemate” refer to an equimolar mixture of two enantiomeric species, devoid of optical activity. When referred to herein, the term “enantiomerically enriched” may refer to an enantiomeric excess of 50% or more. For example, the methods disclosed herein may provide a final product having an enantiomeric excess of 60%, 70%, 80%, 90%, 95%, 98%, or 99% or more. In embodiments of the invention, only one enantiomer or diastereomer of a chiral compound is provided by the process described herein (i.e. the compound is “enantiomerically pure”). When used herein, the term “derivative thereof” as applied to the substrate compounds used herein, it relates to a compound where the benzene ring contains one or more substituents (e.g. 1, 2, 3, 4 or 5, such as 1 to 3, such as 1 or 2 substituents) that are not H. Said substituents may be halo, alkyl, cycloalkyl, aryl, heterocyclic, OH, NH ₂ , SH and combinations thereof (e.g. alkyl aryl, Oalkyl, N(alkyl)H, N(alkyl) ₂ , N(alkyl)(aryl) etc). Unless otherwise stated, the term "alkyl" refers to an unbranched or branched, saturated or unsaturated hydrocarbyl radical (so forming, for example, an alkenyl or alkynyl), which may be substituted or unsubstituted (with, for example, one or more halogen atoms). The alkyl group may be C _1-10 alkyl and, more preferably, C _1-6 alkyl (such as ethyl, propyl, (e.g. n-propyl   or isopropyl), butyl (e.g. branched or unbranched butyl), pentyl or, more preferably, methyl). The terms “alkenyl” and “alkynyl” are to be interpreted accordingly. Unless otherwise stated, the term "cycloalkyl" refers to an unbranched or branched, saturated or unsaturated hydrocarbyl radical (so forming, for example, a cycloalkenyl group) that may be substituted or unsubstituted. The cycloalkyl group may be C _3-12 cycloalkyl and, more preferably, C _5-10 (e.g. C _5-7 ) cycloalkyl. The term “cycloalkenyl” is to be interpreted accordingly. The term "halogen", when used herein, includes fluorine, chlorine, bromine and iodine. The term "aryl" when used herein includes C _6-14 (such as C _6-13 (e.g. C _6-10 )) aryl groups that may be substituted or unsubstituted. Such groups may be monocyclic, bicyclic or tricyclic and have between 6 and 14 ring carbon atoms, in which at least one ring is aromatic. The point of attachment of aryl groups may be via any atom of the ring system. However, when aryl groups are bicyclic or tricyclic, they are linked to the rest of the molecule via an aromatic ring. C _6-14 aryl groups include phenyl, naphthyl and the like, such as 1,2,3,4- tetrahydronaphthyl, indanyl, indenyl and fluorenyl. Most preferred aryl groups include phenyl. When used herein, the term “aryl alkyl” is to be interpreted in line with the definitions provided hereinbefore for “alkyl” and “aryl”, where the point of attachment of the group to the rest of the compound of formula (I) or (II) is through the alkyl portion of the aryl alkyl group. When used herein, the term “heterocyclic” refers to a fully saturated, partly unsaturated, wholly aromatic or partly aromatic ring system in which one or more (e.g. one to four) of the atoms in the ring system is other than carbon (i.e. a heteroatom, which heteroatom is preferably selected from N, O and S), and in which the total number of atoms in the ring system is between three and twelve (e.g. between five and ten). The heterocyclic groups may be substituted or unsubstituted. Heterocyclic groups that may be mentioned include 7- azabicyclo[2.2.1]heptanyl, 6-azabicyclo[3.1.1]heptanyl, 6-azabicyclo[3.2.1]octanyl, 8- azabicyclo[3.2.1]octanyl, aziridinyl, azetidinyl, dihydropyranyl, dihydropyridyl, dihydropyrrolyl (including 2,5-dihydropyrrolyl), dioxolanyl (including 1,3-dioxolanyl), dioxanyl (including 1,3- dioxanyl and 1,4-dioxanyl), dithianyl (including 1,4-dithianyl), dithiolanyl (including 1,3- dithiolanyl), imidazolidinyl, imidazolinyl, morpholinyl, 7-oxabicyclo[2.2.1]heptanyl, 6- oxabicyclo[3.2.1]octanyl, oxetanyl, oxiranyl, piperazinyl, piperidinyl, pyranyl, pyrazolidinyl, pyrrolidinonyl, pyrrolidinyl, pyrrolinyl, quinuclidinyl, sulfolanyl, 3-sulfolenyl, tetrahydropyranyl, tetrahydrofuranyl, tetrahydropyridyl (such as 1,2,3,4-tetrahydropyridyl and 1,2,3,6-   tetrahydropyridyl), thietanyl, thirranyl, thiolanyl, thiomorpholinyl, trithianyl (including 1,3,5- trithianyi), tropanyl, benzothiadiazolyl (including 2,1,3-benzothiadiazolyl), isothiochromanyl and, more preferably, acridinyl, benzimidazolyl, benzodioxanyl, benzodioxepinyl, benzodioxolyl (including 1,3-benzodioxolyl), benzofuranyl, benzofurazanyl, benzothiazolyl, benzoxadiazolyl (including 2,1,3-benzoxadiazolyl), benzoxazinyl (including 3,4-dihydro- 2H- 1 ,4-benzoxazinyl), benzoxazolyl, benzomorpholinyl, benzoselenadiazolyl (including 2,1,3- benzoselenadiazolyl), benzothienyl, carbazolyl, chromanyl, cinnolinyl, furanyl, imidazolyl, imidazo[1,2-a]pyridyl, indazolyl, indolinyl, indolyl, isobenzofuranyl, isochromanyl, isoindolinyl, isoindolyl, isoquinolinyl, isothiaziolyl, isoxazolyl, naphthyridinyl (including 1,6-naphthyridinyl or, preferably, 1,5-naphthyridinyl and 1,8-naphthyridinyl), oxadiazolyl (including 1,2,3- oxadiazolyl, 1,2,4-oxadiazolyl and 1 ,3,4-oxadiazolyl), oxazolyl, phenazinyl, phenothiazinyl, phthalazinyl, pteridinyl, purinyl, pyranyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridyl, pyrimidinyl, pyrrolyl, quinazolinyl, quinolinyl, quinolizinyl, quinoxalinyl, tetrahydroisoquinolinyl (including 1,2,3,4-tetrahydroisoquinolinyl and 5,6,7,8-tetrahydroisoquinolinyl), tetrahydroquinolinyl (including 1,2,3,4-tetrahydroquinolinyl and 5,6,7,8-tetrahydroquinolinyl), tetrazolyl, thiadiazolyl (including 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl and 1,3,4-thiadiazolyl), thiazolyl, thiochromanyl, thiophenetyl, thienyl, triazolyl (including 1,2,3-triazolyl, 1,2,4-triazolyl and 1,3,4-triazolyl) and the like. Substituents on heterocyclic groups may, where appropriate, be located on any atom in the ring system including a heteroatom. The point of attachment of heterocyclic groups may be via any atom in the ring system including (where appropriate) a heteroatom (such as a nitrogen atom), or an atom on any fused carbocyclic ring that may be present as part of the ring system. Heterocyclic groups may also be in the N- or S- oxidised form. Heterocyclic groups that may be mentioned herein include cyclic amino groups such as pyrrolidinyl, piperidyl, piperazinyl, morpholinyl or a cyclic ether such as tetrahydrofuranyl. When used herein, the term “heterocyclic alkyl” is to be interpreted in line with the definitions provided hereinbefore for “alkyl” and “heterocyclic”, where the point of attachment of the group to the rest of the compound of formula (I) or (II) is through the alkyl portion of the heterocyclic alkyl group. The substituents mentioned herein may be substituted or unsubstituted. When the substituents are substituted, they may be substituted with one or more of the groups selected from the group of halogen (e.g., a single halogen atom or multiple halogen atoms forming, in the latter case, groups such as CF ₃ or an alkyl group bearing Cl ₃ ), cyano, nitro, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, heterocycle, aryl, OR _a , SR _a , S(═O)R _e , S(═O) ₂ R _e , P(═O) ₂ R _e , S(═O) ₂ OR _e , P(═O) ₂ OR _e , NR _b R _c , NR _b S(═O) ₂ R _e , NR _b P(═O) ₂ R _e , S(═O) ₂ NR _b R _c , P(═O) ₂ NR _b R _c , C(═O)OR _e , C(═O)R _a , C(═O)NR _b R _c , OC(═O)R _a , OC(═O)NR _b R _c ,   NR _b C(═O)OR _e , NR _d C(═O)NR _b R _c , NR _d S(═O) ₂ NR _b R _c , NR _d P(═O) ₂ NR _b R _c , NR _b C(═O)R _a , or NR _b P(═O) ₂ R _e , wherein R _a is hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, heterocycle, or aryl; R _b , R _c and R _d are independently hydrogen, alkyl, cycloalkyl, heterocycle, aryl, or said R _b and R _c together with the N to which they are bonded optionally form a heterocycle; and R _e is alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, heterocycle, or aryl. It will be appreciated that these substituted groups may be unsubstituted or are themselves substituted with one or more halogen atoms. For the avoidance of doubt, in cases in which the identity of two or more may be the same, the actual identities of the respective substituents are not in any way interdependent unless otherwise specified. Specific substrate derivatives that may be mentioned herein include those in which the phenyl ring of the substrate is mono- or disubstituted by (a) substituent(s) selected from F, Cl, Br, CH ₃ or OCH ₃ . For example, the phenyl ring of styrene and/or phenylalanine may be monosubstituted by o-F, m-F, p-F, m-Cl, p-Cl, m-Br, p-Br, m-CH ₃ , p-CH ₃ , or p-OCH ₃ . In certain embodiments of the invention, the method may be directed towards the production of enantiomerically pure or enantiomerically enriched acids. This may be achieved by a method that comprises the steps of: (a) generating a phenylalkanal or derivative thereof by reacting the 2-alkyl-3- phenyl oxirane or derivative thereof and/or the 2-alkyl-2-phenyl oxirane or derivative thereof with a styrene oxide isomerase to form a phenylalkanal or derivative thereof that undergoes racemisation in situ; and (b) generating an enantiomerically pure or enantiomerically enriched phenylalkanacid or derivative thereof from a phenylalkanal or derivative thereof by conducting an oxidation reaction catalysed by an oxygenase, an oxidase or an alcohol dehydrogenase to form the enantiomerically enriched phenylalkanacid or derivative thereof using a dynamic kinetic resolution reaction. In other embodiments of the invention, the method may be directed towards the production of enantiomerically pure or enantiomerically enriched amines. This may be achieved by a method that comprises the steps of: (a) generating a phenylalkanal or derivative thereof by reacting the 2-alkyl-3- phenyl oxirane or derivative thereof and/or the 2-alkyl-2-phenyl oxirane or derivative thereof with a styrene oxide isomerase to form a phenylalkanal or derivative thereof that undergoes racemisation in situ; and   (b) generating an enantiomerically pure or enantiomerically enriched phenylalkanamine or derivative thereof from a phenylalkanal or derivative thereof by conducting a transamination reaction catalysed by a transaminase, an amine dehydrogenase, an imine reductase or a reductive aminase to form the enantiomerically enriched phenylalkanamine or derivative thereof using a dynamic kinetic resolution reaction. In the transamination reaction disclosed herein, a stoichiometric amino group donor such as L-alanine, D-alanine or isopropylamine may be used. In certain embodiments, the amino group donor may be added in excess to the reaction mixture (e.g. 250 mM of alanine to 5 mM of substrate) to push the equilibrium in favour of the desired product. Alternatively, the constructs and cell extracts etc. used herein may instead include expression vehicles for glucose dehydrogenase and one of an amine dehydrogenase (e.g. alanine dehydrogenase) or amine reductase, which in combination with glucose and one of NADH or NADPH, allows one to regenerate L-alanine for use in the transamination step. Any suitable enzyme may be used to perform the oxidation of the phenylalkanal or derivative thereof to an enantiomerically enriched amine. In particular embodiments that may be mentioned herein, the enzyme catalyzing the oxidation of the phenylalkanal or derivative thereof to an enantiomerically enriched: (a) (S)-phenylalkanamine or derivative thereof may be HnTA or its mutants or similar enzymes with more than 50% identity; or (b) (R)-phenylalkanamine or derivative thereof may be MmTA or its mutants or similar enzymes with more than 50% identity. In embodiments of the invention directed towards the production of enantiomerically pure or enantiomerically enriched amines, the methods may further comprise pyridoxal phosphate. In embodiments of the invention directed towards the production of enantiomerically pure or enantiomerically enriched amines that are conducted in the absence of a cell, then the method will further comprise L-alanine. In such embodiments, the amount of L-alanine may be stoichiometric or it may be used in a more catalytic manner through the inclusion of a suitable enzyme to regenerate the L-alanine (e.g. alanine dehydrogenase). In other embodiments of the invention, the method may be directed towards the production of enantiomerically pure or enantiomerically enriched alcohols. This may be achieved by a method that comprises the steps of:   (a) generating a phenylalkanal or derivative thereof by reacting the 2-alkyl-3- phenyl oxirane or derivative thereof and/or the 2-alkyl-2-phenyl oxirane or derivative thereof with a styrene oxide isomerase to form a phenylalkanal or derivative thereof that undergoes racemisation in situ; and (b) generating an enantiomerically pure or enantiomerically enriched phenylalkanol or derivative thereof from a phenylalkanal or derivative thereof by conducting a reduction reaction catalysed by a reductase or an alcohol dehydrogenase to form the enantiomerically enriched phenylalkanol or derivative thereof using a dynamic kinetic resolution reaction. In embodiments of the invention directed to the production of enantiomerically pure or enantiomerically enriched alcohols, then a redox co-factor may be included. Any suitable redox co-factor may be used herein. For example, the redox co-factor may be NADH or NADPH. In embodiments where the method includes NADH or NADPH, the method may further use a NADH or NADPH cofactor regenerating enzyme. Any suitable a NADH or NADPH cofactor regenerating enzyme may be used in said methods. For example, the NADH or NADPH cofactor regenerating enzyme may be a glucose dehydrogenase. In such embodiments, the reaction medium may further comprise one or more of glucose and a sacrificial alcohol (e.g. isopropyl alcohol and/or ethanol). The methods described herein make use of enzymes to catalyse a sequence of reactions. While these reactions may be performed individually or, more particularly, two or more of them in combination, all of the reactions may be combined into a cascade reaction sequence that provides the product from the initial starting material in one pot, thereby eliminating the need for isolation of the intermediates and, potentially, increasing the overall yield of the reaction sequence. These cascade reactions may involve the use of one or more reactive components selected from the group consisting of cells, immobilized cells, cell extracts, isolated enzymes and immobilized enzymes in said reaction vessel. Thus, the at least two enzymes used in the methods disclosed herein may be provided: (a) in whole cells genetically engineered to overexpress the at least two enzymes (e.g. the at least two overexpressed enzymes are located on one or more plasmids or integrated in the chromosome of each of the one or more recombinant microbial cells); (b) in a cell-free extract; (c) as purified enzymes; or (d) as immobilized enzymes. In embodiments of the above methods, the the enzyme catalyzing the isomerization of the 2- alkyl-2-phenyl oxirane or derivative thereof into a phenylalkanal or derivative thereof may be   styrene oxide isomerase (SOI), or another isomerase, optionally wherein the enzyme is SOI. The another isomerase may be any suitable isomerase that can effect the same transformation. In embodiments relating to the production of enantiomerically pure or enriched (S)- phenylalkanacid or derivatives thereof, the enzyme catalyzing the oxidation of the phenylalkanal or derivative thereof to said enantiomerically enriched (S)-phenylalkanacid or derivative thereof may be ADH9v1 or its mutants or similar enzymes with more than 50% identity. In methods of producing enantiomerically pure or enantiomerically enriched acids, the method may further comprise a redox co-factor. While any suitable redox co-factore may be used, the redox co-factor may be NAD ⁺ or NADP ⁺ in certain embodiments of the invention. In embodiments where the method uses NAD ⁺ , it may also use a NAD ⁺ cofactor regenerating enzyme (e.g. the NAD ⁺ cofactor regenerating enzyme may be NADH oxidase (NOX)). In embodiments of the above methods, the one-pot reaction system may comprise use of an aqueous medium (e.g. an aqueous buffer medium). In certain embodiments, the aqueous medium may further comprise an organic co-solvent. Any suitable organic co-solvent may be used in the methods disclosed herein. For example, the organic co-solvent may be selected from one or more of the group consisting of dimethyl sulfoxide, dimethylformamide, acetone or acetonitrile. In alternative embodiments, the one-pot reaction system may make use of a bi-phasic medium. Any suitable bi-phasic medium may be used in the methods herein. For example, the bi-phasic medium may consists of an aqueous (e.g. aqueous buffer) and solid resin medium, or an aqueous (e.g. aqueous buffer) and organic solvent medium or an alcohol and organic solvent medium. Any suitable organic solvent may be used in the bi-phasic medium. Examples of suitable organic solvents for this purpose include, but are not limited to, one or more alkane solvents and/or one or more ester solvents. In particular embodiments that may be mentioned herein, the organic solvent medium may selected from one or both of hexane and hexadecane. The terms "amino acid" or "amino acid sequence," as used herein, refer to an oligopeptide, peptide, polypeptide, or protein sequence, or a fragment of any of these, and to naturally occurring or synthetic molecules. Where "amino acid sequence" is recited herein to refer to   an amino acid sequence of a naturally occurring protein molecule, "amino acid sequence" and like terms are not meant to limit the amino acid sequence to the complete native amino acid sequence associated with the recited protein molecule. The term "isolated" or “purified” is herein defined as a biological component (such as a nucleic acid, peptide or protein) that has been substantially separated, produced apart from, or purified away from other biological components in the cell of the organism in which the component naturally occurs, i.e., other chromosomal and extra-chromosomal DNA and RNA, and proteins. Nucleic acids, peptides and proteins which have been isolated thus include nucleic acids and proteins purified by standard purification methods. The term also embraces nucleic acids, peptides and proteins prepared by recombinant expression in a host cell as well as chemically synthesized nucleic acids. The phrases "nucleic acid" or "nucleic acid sequence," as used herein, refer to an oligonucleotide, nucleotide, polynucleotide, or any fragment thereof, to DNA or RNA of genomic or synthetic origin which may be single-stranded or double-stranded and may represent the sense or the antisense strand, to peptide nucleic acid (PNA), or to any DNA- like or RNA-like material. In the context of the invention, "fragments" refers to those nucleic acid sequences which are greater than about 60 nucleotides in length, and most preferably are at least about 100 nucleotides, at least about 1000 nucleotides, or at least about 10,000 nucleotides in length which are not full-length native sequence but retain catalytic enzyme activity. The term "oligonucleotide," as used herein, refers to a nucleic acid sequence of at least about 6 nucleotides to 60 nucleotides, preferably about 15 to 30 nucleotides, and most preferably about 20 to 25 nucleotides, which can be used in PCR amplification or in a hybridization assay or microarray. As used herein, the term "oligonucleotide" is substantially equivalent to the terms "amplimers," "primers," "oligomers," and "probes," as these terms are commonly defined in the art. The terms ‘variant’ and ‘mutant’ are used interchangeably herein. The at least one nucleic acids encoding at least one catalytic enzyme may encode a variant or mutant of the exemplified catalytic enzyme which retains activity. A "variant" of a catalytic enzyme, as used herein, refers to an amino acid sequence that is altered by one or more amino acids. The variant may have "conservative" changes, wherein a substituted amino acid has similar structural or chemical properties (e.g., replacement of leucine with isoleucine). More rarely, a variant may have "nonconservative" changes (e.g., replacement of glycine with tryptophan).   Analogous minor variations may also include amino acid deletions or insertions, or both. Guidance in determining which amino acid residues may be substituted, inserted, or deleted without abolishing catalytic activity may be found using computer programs well known in the art, for example, DNASTAR software. In some embodiments, variant enzymes are at least 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or more, homologous or identical at the amino acid level to an exemplary amino acid sequence described herein (e.g., catalase, alcohol dehydrogenase, α-transaminase) or a functional fragment thereof— e.g., over a length of about: 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% of the length of the mature reference sequence. A vector can include one or more catalytic enzyme nucleic acid(s) in a form suitable for expression of the nucleic acid(s) in a host cell. Preferably the recombinant expression vector includes one or more regulatory sequences operatively linked to the nucleic acid sequence(s) to be expressed. The term "regulatory sequence" includes promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Regulatory sequences include those which direct constitutive expression of a nucleotide sequence, as well as tissue-specific regulatory and/or inducible sequences such as the T7 IPTG-inducible promoters disclosed in the Examples herein. The design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, and the like. The expression vectors of the invention can be introduced into host cells to thereby produce proteins or polypeptides, including fusion proteins or polypeptides, encoded by nucleic acids as described herein (e.g., catalytic enzyme proteins, fusion proteins, and the like). The recombinant expression vectors of the invention can be designed for expression of catalytic enzyme proteins in prokaryotic or eukaryotic cells. For example, polypeptides of the invention can be expressed in bacteria (e.g., E. coli), insect cells (e.g., using baculovirus expression vectors), yeast cells or mammalian cells. Suitable host cells are discussed further in Goeddel, (1990) Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, Calif. Alternatively, the recombinant expression vector(s) can be transcribed and translated in vitro, for example using T7 promoter regulatory sequences and T7 polymerase. Expression of proteins in prokaryotes is most often carried out in E. coli with vectors containing constitutive or inducible promoters directing the expression of either fusion or non-fusion proteins. Fusion vectors add a number of amino acids to a protein encoded therein, usually to the amino terminus of the recombinant protein. Such fusion vectors   typically serve three purposes: 1) to increase expression of recombinant protein; 2) to increase the solubility of the recombinant protein; and 3) to aid in the purification of the recombinant protein by acting as a ligand in affinity purification. Often, a proteolytic cleavage site is introduced at the junction of the fusion moiety and the recombinant protein to enable separation of the recombinant protein from the fusion moiety subsequent to purification of the fusion protein. Such enzymes, and their cognate recognition sequences, include Factor Xa, thrombin and enterokinase. Typical fusion expression vectors include pGEX (Pharmacia Biotech Inc; Smith, D. B. and Johnson, K. S. Gene 1988, 67: 31-40), pMAL (New England Biolabs, Beverly, Mass.) and pRIT5 (Pharmacia, Piscataway, N.J.) which fuse glutathione S- transferase (GST), maltose E binding protein, or protein A, respectively, to the target recombinant protein. To maximize recombinant protein expression in E. coli is to express the protein in a host bacterium with an impaired capacity to proteolytically cleave the recombinant protein (Gottesman, S. Gene Expression Technology: Methods in Enzymology 1990185, Academic Press, San Diego, Calif. 119-128). Another strategy is to alter the nucleic acid sequence of the nucleic acid to be inserted into an expression vector so that the individual codons for each amino acid are those preferentially utilized in E. coli (Wada et al., Nucleic Acids Res. 1992 20: 2111-2118). Such alteration of nucleic acid sequences of the invention can be carried out by standard DNA synthesis techniques and is described in the Examples. The catalytic enzyme expression vector can be a yeast expression vector, a vector for expression in insect cells, e.g., a baculovirus expression vector, a vector for expression in bacterial cells, e.g. a plasmid vector, or a vector suitable for expression in mammalian cells. When used in mammalian cells, the expression vector's control functions can be provided by viral regulatory elements. For example, commonly used promoters are derived from polyoma, Adenovirus 2, cytomegalovirus and Simian Virus 40. In a preferred embodiment, the promoter is an inducible promoter, e.g., a promoter regulated by a steroid hormone, by a polypeptide hormone (e.g., by means of a signal transduction pathway), by a chemical (e.g., Isopropyl β-D-1-thiogalactopyranoside (IPTG)) or by a heterologous polypeptide. Another aspect the invention provides at least one expression construct comprising at least one nucleic acid sequence that is heterologous according to any aspect of the invention.   Preferably the at least one construct comprises a plasmid suitable for expression of at least one catalytic enzyme in a bacterium. Another aspect the invention provides a host cell which includes at least one nucleic acid molecule described herein, e.g., at least one catalytic enzyme nucleic acid molecule within a recombinant expression vector or a catalytic enzyme nucleic acid molecule containing sequences which allow homologous recombination into a specific site of the host cell's genome. The terms "host cell" and "recombinant host cell" are used interchangeably herein. Such terms refer not only to the particular subject cell but to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein. A host cell can be any prokaryotic or eukaryotic cell. For example, at least one catalytic enzyme protein can be expressed in bacterial cells (such as E. coli), insect cells (such as Spodoptera frugiperda Sf9 cells), yeast or mammalian cells (such as Chinese hamster ovary cells (CHO) or COS cells (African green monkey kidney cells CV-1 origin SV40 cells; Gluzman Cell 1981, I23: 175-182)). Other suitable host cells are known to those skilled in the art. One or more vector DNAs can be introduced into host cells via conventional transformation or transfection techniques. As used herein, the terms "transformation" and "transfection" are intended to refer to a variety of art-recognized techniques for introducing foreign nucleic acid (e.g., DNA) into a host cell, including calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, lipofection, or electroporation. For example, according to the invention a host cell may comprise one, two, three, four or more plasmids, each of which may express at least one catalytic enzyme directed to a chemical transformation in the pathway from an alkene starting material to the desired final product. The host cell may also include a vector to express catalytic enzymes for providing the alkene by, for example, generating a vinyl carboxylic acid from an α-amino acid by a deamination reaction catalyzed by an ammonia lyase and generating the alkene from the vinyl carboxylic acid in a decarboxylation reaction catalyzed by a decarboxylase. In one aspect of the invention there is provided one or more recombinant prokaryotic or eukaryotic cells selected from the group comprising bacterial cells, yeast cells, mammalian cells and insect cells, wherein said cells comprise at least one expression construct and/or   heterologous nucleic acid molecule that encodes at least one catalytic enzyme required in the pathway from alkene to enantiomerically pure or enantiomerically enriched final product. The cells may contain a single expression vector or construct, such as a plasmid, which expresses a single catalytic enzyme or co-expresses a plurality of catalytic enzymes as described herein under the control of at least one regulatory element. The catalytic enzymes may be arranged in the plasmid as an individual artificial operon under the control of a promoter with one ribosome-binding site before every gene, or arranged with individual promoters. Accordingly, a one-pot synthesis cascade may be achieved with cells expressing all required catalytic enzymes on one or several plasmids, or with different recombinant cells which each express a specific repertoire of catalytic enzymes, providing the necessary cells are included for a particular chemical transformation. In another preferred embodiment, said catalytic enzymes for use in the invention have at least 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or more, homology or amino acid identity with at least one enzyme mentioned herein. A host cell of the invention can be used to produce (i.e., express) one or more catalytic enzyme proteins. Accordingly, the invention further provides methods for producing one or more catalytic enzyme proteins, e.g., one or more catalytic enzyme proteins described herein, using the host cells of the invention. In one embodiment, the method includes culturing the host cell of the invention (into which one or more recombinant expression vector(s) encoding one or more catalytic enzyme proteins has/have been introduced) in a suitable medium such that one or more catalytic enzyme proteins is/are produced. In another embodiment, the method further includes isolating one or more catalytic enzyme proteins from the medium or the host cell. According to another aspect of the invention there is provided a kit comprising at least one recombinant cell, expression construct or isolated nucleic acid according to any aspect of the invention. Preferably, the kit can be used to provide one or more components for a one-pot system to enzyme-catalyze the production of an enantiomerically pure or enantiomerically enriched final product from a suitable starting material. The current invention overcomes issues with the current synthetic methods used to make the target molecules, which often start using expensive or unstable substrates. The racemic epoxide starting materials used herein are cheap and stable, whereas the products are enantiopure and of high value.   Some current synthetic methods used to make the target molecules utilise classical chiral resolution of the final product, which has a maximum theoretical yield of 50%. Using enzymatic dynamic kinetic resolution, this invention allows for a theoretical maximum of 100% yield. Current synthesis of the target molecules are multi-step and generate waste with low overall yields. The development of a one-pot cascade biotransformation reduces waste generation by removing the need for intermediate isolation and side-product generation. Current synthesis of target molecules mainly utilise toxic chemicals and solvents. The use of biocatalysts with high activity replaces the need for toxic chemicals typically used for synthesis of said molecules. The current invention allows for the one-pot conversion of racemic trans-methyl epoxide and α-methyl epoxide into enantiopure 2-arylpropionic acids via cascade biotransformation. This allows for the use of cheap racemic epoxide substrates to provide enantiopure 2- arylpropionic acids (NSAIDs molecules). This method relies upon the highly enantioselective enzymatic dynamic kinetic resolution using ADH9v1 (and other such enzymes) to produce enantiopure 2-arylpropionic acids in high e.e. and a theoretical maxium yield of 100%. The current invention allows for the one-pot conversion of racemic trans-methyl epoxide and α-methyl epoxide into enantiopure 2-arylpropyl amines via cascade biotransformation. This allows for the use of cheap racemic epoxide substrates to provide enantiopure 2-arylpropyl amines. This method relies upon the highly enantioselective enzymatic dynamic kinetic resolution using MmTA and HnTA (and other such enzymes) to produce enantiopure 2- arylpropyl amines in high e.e. and a theoretical maxium yield of 100%. The current invention allows for the one-pot conversion of racemic trans-methyl epoxide and α-methyl epoxide into enantiopure 2-arylpropyl alcohols via cascade biotransformation. This allows for the use of cheap racemic epoxide substrates to enantiopure 2-arylpropyl alcohols. This method relies upon the highly enantioselective enzymatic dynamic kinetic resolution using ADH (and other such enzymes) to produce enantiopure 2-arylpropyl alcohols in high e.e. and a theoretical maxium yield of 100%. The cascade biotransformations disclosed herein involve a SOI-catalyzed highly regioselective 1,2-methyl shift isomerization of trans-methyl epoxides or 1,2-hydride shift of   α-methyl epoxides. The high activity of this SOI-catalyzed isomerization reaction has potential for industrial application. In particular embodiments, this allows for a one-pot process using cell-free extract containing SOI, purified ADH9v1 and purified NOX to produce enantiopure 2-arylpropionic acids. In particular embodiments, this allows for a one-pot process using cell-free extract containing SOI and purified MmTA or HnTA to produce enantiopure 2-arylpropyl amines. The above transformations are simple and efficient one-pot cascade reaction sequences with no side reactions, minimal waste generation and no need for isolation of intermediates. Aspects and embodiments of the invention are discussed in the following numbered statements. 1. A process to produce enantiopure acids, amines and alcohols from racemic epoxides by cascade biotransformation involving enzymatic epoxide isomerization and dynamic kinetic resolution. 2. In Statement 1, the cascade to produce produce enantiopure 2-arylpropionic acids from racemic trans-methyl or α-methyl epoxides consists of an enzyme catalyzing the isomerization of the epoxide into 2-arylpropanal, and an enzyme for the oxidation of 2-arylpropanal. 3. In Statement 1, the cascade to produce produce enantiopure 2-arylpropyl amines from racemic trans-methyl or α-methyl epoxides consists of an enzyme catalyzing the isomerization of the epoxide into 2-arylpropanal, and an enzyme for the transamination of 2-arylpropanal. 4. In Statement 1, the cascade to produce produce enantiopure 2-arylpropyl alcohols from racemic trans-methyl or α-methyl epoxides consists of an enzyme catalyzing the isomerization of the epoxide into 2-arylpropanal, and an enzyme for the reduction of 2-arylpropanal. 5. In Statement 1, the biotransformations can use whole cells harbouring the relevant enzymes, cell-free extract containing the relevant enzymes, purified enzymes or immobilized enzymes. 6. In Statement 1, the products can be isolated from the one-pot reaction by crystallization or extraction by organic solvents such as (but not limited to) ethyl acetate, dichloromethane, diethyl ether, hexanes.   7. In Statement 1, the biotransformations can be performed in aqueous buffer, aqueous buffer mixed with organic co-solvent, or medium made up of two immiscible liquid phases. 8. In Statement 7, the organic co-solvent can be dimethyl sulfoxide, dimethylformamide, acetone or acetonitrile. 9. In Statement 7, the two immiscible liquid phases can be made up of aqueous buffer and hexane, aqueous buffer and hexadecane, or hexane and isopropyl alcohol. 10. In Statements 2-4, the 2-arylpropanal intermediate produced undergoes spontaneous racemization. 11. In Statements 2-4, the enzyme catalyzing the isomerization of the epoxide into 2- arylpropanal can be styrene oxide isomerase (SOI), or other isomerases. 12. In Statement 2, the enzyme catalyzing the oxidation of aldehyde can be ADH9v1, other oxygenases, oxidases or alcohol dehydrogenases. 13. In Statement 2, if NAD(P)+ is a redox co-factor, it can be regenerated using NAD(P)H oxidase or a sacrificial ketone such as acetone. 14. In Statement 3, the enzyme catalyzing the transamination of aldehyde can be transminases like MmTA and HnTA, other transaminases, amine dehydrogenases, imine reductases or reductive aminases. 15. In Statement 3, additional enzymes such as alanine dehydrogenase can be used to regenerate the L-alanine amine donor molecule in the reaction. 16. In Statement 4, the enzyme catalyzing the reduction of aldehyde can be reductases or alcohol dehydrogenases. 17. In Statement 4, if NAD(P)H is a redox co-factor, it can be regenerated using glucose dehydrogenase supplemented with glucose in the reaction medium, or a sacrificial alcohol such as isopropyl alcohol or ethanol. The one-pot cascade transformations disclosed herein, which use multiple enzymatic reactions involving DKR to convert racemic substrates to produce high-value chiral chemicals in high ee and high yield is demonstrated in extensive detail in the examples below. Unique cascade reactions of racemic epoxides to produce (S)-2-arylpropionic acids, (R)- and (S)-2-arylpropyl amines were demonstrated, consisting of SOI-catalyzed Meinwald rearrangement of racemic epoxides for in situ generation of 2-arylpropanal, spontaneous racemization of 2-arylpropanal, and ADH-catalyzed (S)-enantioselective oxidation or TA- catalyzed (R)- or (S)-enantioselective amination, respectively. High-yielding synthesis with the cascades was achieved by using isolated enzymes as well as whole-cell biocatalysts expressing the required enzymes (see the examples section   below). The cascade reactions can accept two classes of racemic methyl-substituted epoxides – trans-β-methyl epoxide or α-methyl epoxide – which are stable and easily accessible. Both racemic trans-β-methyl epoxides and racemic α-methyl epoxides can be accessed via well-established chemical methods. The cascade biotransformations of the racemic epoxides successfully produced (S)-arylpropionic acids, (R)-arylpropyl amines and (S)-arylpropyl amines in generally high ee and yield. These products possess various aryl group substitutions and include drug molecules and their precursors. The substrate scope of the cascade reactions involving DKR starting from racemic epoxides disclosed herein in the examples is wider than previously reported cascade biotransformations from methyl styrenes in which the enantioselectivity is determined by the styrene monooxygenase-catalyzed epoxidation step. The cascade reactions involve SOI- catalyzed redox-neutral isomerization of epoxides for the in situ generation of 2-arylpropanal intermediates, which was shown to reduce side reaction associated with aldehyde instability, when compared with DKR reactions involving direct enzymatic oxidation or amination of unstable 2-arylpropanals. The disclosed invention allows for the engineering of new multi-enzymatic cascade reactions involving DKR for green and sustainable synthesis of valuable chiral chemicals in high ee and yield from easily available racemic starting materials. The developed cascade reactions using cell-free or whole-cell systems are potentially useful for the practical synthesis of pharmaceutically useful (S)-2-arylpropionic acids, (R)- and (S)-2-arylpropyl amines. Further aspects and embodiments of the invention will now be discussed by reference to the following non-limiting examples. Examples Materials and Methods 1. Chemicals The following chemicals were purchased from commercial suppliers and used without further purification. Sigma-Aldrich: 2-phenylpropanal 3a (98%), (±)-2-phenylpropionic acid 4a (97%), (S)-2- phenylpropionic acid (S)-4a (97%), 2-phenyl-1-propylamine 5a (99%), (S)-2-phenyl-1-   propylamine (S)-5a (99%), acetophenone 6a (99%), trans-β-methylstyrene (99%), tritylium tetrafluoroborate (>99.9%), 2-methyl-2-butene (≥95.0%), Oxone® (>99.9%), o-tolualdehyde (97%), m-tolualdehyde (97%), p-tolualdehyde (97%), 2-naphthaldehyde (98%), trans- anethole (99%), 4-chlorobenzaldehyde (97%), 4-bromobenzaldehyde (99%), 4- isobutylbenzaldehyde (AldrichCPR), trimethylsulfoxonium iodide (98%), potassium tert- butoxide (≥98%), 2’-methylacetophenone (98%), 3’-methylacetophenone (98%), 4’- methylacetophenone (95%), 2-acetonaphthone (99%), 4’-methoxyacetophenone (99%), 4’- chloroacetophenone (97%), 4’-bromoacetophenone (98%), triethylamine (≥99.5%), dichloromethane (≥99.8%, anhydrous), benzyl alcohol (≥99.0%), trifluoroacetic acid TFA (99%), sodium sulfate (ACS, anhydrous), sodium bicarbonate (≥99.7%), sodium chloride (>99%), imidazole (>99%), Bradford reagent, β-nicotinamide adenine dinucleotide hydrate (98%, Grade II, free acid), L-alanine (98%), pyridoxal 5′-phosphate hydrate (≥98%). Tokyo Chemical Industry Co., Ltd. (TCI): 2-phenylpropylene oxide 2a (>95%), dimethylsulfoxide (≥99.0 %). Merck: silica gel 60 (0.040–0.063 mm). Apollo Scientific: kanamycin sulfate salt (95%). Gold Biotechnology: Isopropyl β-D-1-thiogalactopyranoside (IPTG, >99%). Fisher Scientific: dichloromethane (HPLC), acetone (HPLC), isopropanol (HPLC), acetonitrile (HPLC), ethyl acetate (analytical), diethyl ether (analytical), hexanes (HPLC), methanol (HPLC). Biomed Diagnostics, Singapore: LB Broth, Bacto Tryptone and Bacto Yeast Extract. 1st Base, Singapore: 1.0 M Tris buffer, 1.0 M potassium phosphate buffer (ultrapure grade, various pH). 2. Strains used E. coli (pRSF-SOI) ^[1] , E. coli (pRSF-HLADH) ^[1] and E. coli (pRSF-EcALDH) ^[2] were used in our previous work. ^[1] S. Wu, J. Liu, Z. Li, ACS Catal.2017, 7, 5225–5233.   ^[2] R. Xin, W. W. L. See, H. Yun, X. Li, Z. Li, Angew. Chem. Int. Ed.2022, 61, e202204889. E. coli (pRSF-HnTA), E. coli (pRSF-BmTA), E. coli (pRSF-VfTA), E. coli (pRSF-mVfTA), E. coli (pRSF-CvTA), E. coli (pRSF-AtTA), E. coli (pRSF-ArRTA), E. coli (pRSF-MmTA), E. coli (pRSF-NfTA) were used in our previous work. ^{[3] [3]} B. S. Sekar, J. Mao, B. R. Lukito, Z. Wang, Z. Li, Adv. Synth. Catal.2021, 363, 1892–1903. E. coli (pRSF-ADH9v1) was engineered by cloning the ADH9v1 gene from our previous work ^[4] and inserting it into BamHI/XhoI site of pRSFDuet-1 plasmid. The resulting plasmid was transformed into E. coli T7 Expression competent strain to give E. coli (ADH9v1). ^[4] S. Wu, Y. Zhou, D. Seet, Z. Li, Adv. Synth. Catal.2017, 359, 2132–2141. E. coli (pRSF-NOX) was engineered by cloning the NOX gene from our previous work ^[5] and inserting it into BamHI/NotI site of pRSFDuet-1 plasmid. The resulting plasmid was transformed into E. coli T7 Expression competent strain to give E. coli (NOX). ^[5] J. Zhang, S. Wu, J. Wu, Z. Li, ACS Catal.2015, 5, 51–58. E. coli (ADH9v1-NOX) was engineered by cloning the ADH9v1 gene and NOX gene, and inserting them into NcoI(BspHI)/NotI and NotI/KpnI sites of pRSFDuet-1 plasmid, respectively. The resulting plasmid was transformed into E. coli T7 Expression competent strain to give E. coli (ADH9v1-NOX). E. coli (SOI-MmTA-AlaDH) was engineered by cloning the SOI gene, MmTA gene and AlaDH gene ^[1] from our previous work, and inserting them into SacI/NotI, NdeI/XhoI and BamHI/SacI sites of pRSFDuet-1 plasmid, respectively. The resulting plasmid was transformed into E. coli T7 Expression competent strain to give E. coli (SOI-MmTA-AlaDH). E. coli (pRSF-SyADH), E. coli (pRSF-AsTA) and E. coli (pRSF-RpTA) were obtained by transforming pRSFDuet-1 plasmid containing their respective reported gene sequences (synthesized commercially, optimized for expression in E. coli) into E. coli T7 Expression competent strain. Their DNA or protein sequences are shown below. SyADH ^[6] (SEQ ID: 1):   3. Analytical Methods 3.1 HPLC / HPLC-MS/ GC-MS analysis HPLC analysis of the concentrations of acid products 4a-h: samples were analysed using an Agilent 1260 Infinity II HPLC system with a photodiode array detector (210 nm) under reversed phase condition, at 25 °C. Column: Poroshell 120 SB-C18 column (2.7 μm, 4.6 × 150 mm). Flow rate: 0.5 mL/min. Mobile phase for 4a, 4b, 4c, 4d, 4e, 4g, 4h: 50% water with 0.1% TFA, 50% acetonitrile. Retention times: 4a – 4.1 min, 4b – 4.5 min, 4c – 4.6 min, 4d – 4.6 min, 4e – 5.8 min, 4g – 5.2 min, 4h – 5.0 min. Mobile phase for 4f: 65% water with 0.1% TFA, 35% acetonitrile. Retention time: 4f – 7.3 min. HPLC analysis of the concentrations of amine products 5a-e and 5g-h: samples were analyzed using a Shimadzu LCMS-2020 HPLC system with a photodiode array detector (210 nm) under reversed phase condition, at 25 °C. Column: Poroshell 120 SB-C18 column (2.7 μm, 4.6 × 150 mm). Flow rate: 0.5 mL/min. Mobile phase for 5a, 5c, 5g, 5h: 60% water with 0.1% TFA, 40% acetonitrile. Retention times: 5a – 3.6 min, 5c – 4.0 min, 5g – 4.3 min, 5h – 4.5 min. Mobile phase for 5b, 5d, 5e: 70% water with 0.1% TFA, 30% acetonitrile. Retention times: 5b – 5.4 min, 5d – 5.7 min, 5e – 9.3 min. UPLC-QTOF-MS analysis of acids: samples were analyzed using a Waters Acquity™ Ultra Performance LC connected to a Bruker compact™ QTOF mass spectrometer (-ve ESI) or Agilent 6546 LC-QTOF (-ve ESI). Poroshell 120 SB-C18 column (2.7 μm, 4.6 × 150 mm) at 25 °C was used with a photodiode array detector (210 nm). Mobile phase: gradient elution, A = water with 0.1% formic acid, B = acetonitrile, flow rate: 0.2 mL/min. A/B ratio 50:50 at 0 min increase to 20:80 at 14 min, decrease to 50:50 at 15 min. GC-QTOF-MS analysis of amines: samples were analyzed using an Agilent 7200 GC- QTOF (+ve EI) or Agilent 6546 LC-QTOF (+ve ESI). 3.2 Chiral HPLC analysis Chiral HPLC analysis of the ee of acid products 4a-h:   For 4a, 4b, 4d, 4e, 4f, 4g, 4h, samples were analysed using an Agilent 1260 Infinity II HPLC system under reversed-phase conditions. Daicel Chiralpak AD-3R column (150×4.6 mm, 3 μm) at 25 °C was used with a photodiode array detector (210 nm). Mobile phase for 4a: 80% water with 0.1% TFA, 20% acetonitrile, flow rate: 1.0 mL/min. Retention time: 4a – t _R1 = 10.7 min and t _R2 = 11.2 min. Mobile phase for 4b, 4d, 4h, 4e: 70% water with 0.1% TFA, 30% acetonitrile, flow rate: 0.5 mL/min. Retention times: 4b – t _R1 = 12.1 min and t _R2 = 12.7 min, 4d – t _R1 = 15.9 min and t _R2 = 16.4 min, 4h – t _R1 = 27.5 min and t _R2 = 28.9 min, 4e – t _R1 = 33.9 min and t _R2 = 35.1 min. Mobile phase for 4g: 60% water with 0.1% TFA, 40% acetonitrile, flow rate: 0.5 mL/min.4g – Retention times: t _R1 = 9.7 min and t _R2 = 10.2 min. Mobile phase for 4f: A = water with 0.1% TFA, B = acetonitrile, flow rate: 0.5 mL/min. A/B ratio 90:10 from 0 to 5 min; increase to 80:20 at 10 min; increase to 70:30 at 30 min; increase to 60:40 at 40 min. Retention time: 4f – t _R1 = 28.5 min and t _R2 = 29.0 min. For 4c, samples were analysed using a Shimadzu Prominence LC-20 HPLC system equipped with a SPD-M20A photodiode array detector under normal phase condition. Daicel Chiralpak AD-H column (250×4.6 mm, 5 μm) at 25 °C with a photodiode array detector (210 nm). Mobile phase for 4c: 10% isopropanol, 90% n-hexane, flow rate: 1.0 mL/min. Retention time: 4c – t _R1 = 4.8 min and t _R2 = 5.2 min. Chiral HPLC analysis of the ee of amine products 5a-e and 5g-h: For 5a and 5e, samples were analyzed using a Shimadzu LCMS-2020 HPLC system with a photodiode array detector (210 nm) under reversed phase condition, at 25 °C. Conditions for 5a: Column: Daicel Crownpak CR(+) column (5 μm, 4.0 × 150 mm). 90% water with 0.1% TFA, 10% methanol. Flow rate: 1.0 mL/min. Retention time: 5a – t _R1 = 8.6 min and t _R2 = 10.5 min. Conditions for 5e: Column: Daicel Crownpak CR-I(+) column (5 μm, 3.0 × 150 mm). 90% water with 0.1% TFA, 10% acetonitrile. Flow rate: 0.5 mL/min. Retention time: 5e – t _R1 = 11.4 min and t _R2 = 15.4 min. For 5b, 5c, 5d, 5g and 5h, samples were first derivatized to the benzoyl amide before chiral HPLC analysis (Z. Liu, Z.-Y. Qin, L. Zhu, S. V. Athavale, A. Sengupta, Z.-J. Jia, M. Garcia- Borràs, K. N. Houk, F. H. Arnold, J. Am. Chem. Soc. 2022, 144, 80–85.). To 500 μL of reaction sample containing the corresponding amine 5, 5 μL benzoyl chloride and 500 μL saturated sodium bicarbonate were added. The tube was shaken at room temperature for 16 hours, and the mixture was extracted with 2×500 μL ethyl acetate. The combined organic phases were dried over anhydrous sodium sulfate and concentrated in vacuo. The derivatized product was then redissolved in the appropriate mobile phase for chiral HPLC   analysis. Samples were analysed using a Shimadzu Prominence LC-20 HPLC system equipped with a SPD-M20A photodiode array detector under normal phase condition. Daicel Chiralpak OD-H column (5 μm, 4.6 × 250 mm) at 25 °C with a photodiode array detector (210 nm). Mobile phase for 5b, 5c: 10% isopropanol, 90% hexanes. Flow rate: 1.0 mL/min. Retention time: 5b – t _R1 = 10.5 min and t _R2 = 19.5 min, 5c – t _R1 = 9.7 min and t _R2 = 12.5 min. Mobile phase for 5d, 5g, 5h: 5% isopropanol, 95% hexanes. Flow rate: 0.75 mL/min. Retention time: 5d – t _R1 = 21.3 min and t _R2 = 24.6 min, 5g – t _R1 = 30.4 min and t _R2 = 32.9 min, 5h – t _R1 = 32.3 min and t _R2 = 34.9 min. 3.3 Summary of assignment of absolute configuration for acid 4 and amine 5 products Table 1. Summary of methods of assignment of absolute configurations. 3.4 NMR measurements ¹ H and ¹³ C NMR spectra were recorded on a Bruker Avance III HD (400 MHz) spectrometer. Chemical shifts are reported in parts per million (ppm), and the residual solvent peak was used as an internal reference: 1H (chloroform δ 7.26(1)), 13C (chloroform δ 77.16 (3)), 1H (methanol δ 4.87 (1), 3.31 (5)), 13C (methanol δ 49.1 (7)). Data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, br = broad), coupling constants (Hz) and integration. 4. Synthesis of substrates and product standards 4.1 Synthesis of epoxide substrates 1a – 1h   The following synthesis was carried out with modifications from reported procedures (Veluru Ramesh Naidu, J. Bah, J. Franzén, Eur. J. Org. Chem. 2015, 2015, 1834–1839.; P. E. Daniel, A. E. Weber, S. J. Malcolmson, Org. Lett.2017, 19, 3490–3493.). The corresponding aldehyde (3 equiv.) and 2-methyl-2-butene (1 equiv.) were added to a solution of tritylium tetrafluoroborate (20 mol%) dissolved in dichloromethane (0.3 M) and stirred at room temperature for 16 h. The reaction mixture was then quenched with saturated sodium bicarbonate solution and extracted with dichloromethane (×2). The combined organic layers were dried over anhydrous sodium sulfate and concentrated. Purification by silica gel column chromatography (100% hexanes) gave the trans-alkene as a colourless to yellow liquid. The trans-alkene was dissolved in a mixture of acetone/acetonitrile/sat. sodium bicarbonate solution (2:1:1, 0.05 M). Oxone (2.2 equiv.) dissolved in minimal deionized water was added at room temperature and the reaction was stirred for 16 h. Majority of the acetone in the reaction mixture was removed under reduced pressure, followed by extraction with diethyl ether (×2). The combined organic layers were dried over anhydrous sodium sulfate and concentrated to give the pure epoxide without further purification. trans-1-phenylpropylene oxide 1a: Synthesized according to the epoxidation procedure starting from trans-β-methylstyrene. Obtained as a colourless oil (70% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.38 – 7.24 (m, 5H), 3.58 (d, J = 2.1 Hz, 1H), 3.04 (qd, J = 5.1, 2.0 Hz, 1H), 1.46 (d, J = 5.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 137.87, 128.57, 128.17, 125.68, 59.67, 59.20, 18.06. trans-1-(2-methylphenyl)propylene oxide 1b: Obtained as a colourless oil (26% yield over 2 steps). ¹ H NMR (400 MHz, Chloroformd) δ 7.24 – 7.09 (m, 4H), 3.71 (d, J = 2.2 Hz, 1H), 2.93 (qd, J = 5.1, 2.2 Hz, 1H), 2.40 (s, 3H), 1.49 (d, J = 5.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 136.16, 135.89, 129.84, 127.62, 126.23, 124.29, 58.17, 57.76, 18.97, 18.13.   trans-1-(3-methylphenyl)propylene oxide 1c: Obtained as a colourless oil (41% yield over 2 steps). ¹ H NMR (400 MHz, Chloroformd) δ 7.22 – 7.10 (m, 4H), 3.71 (d, J = 2.2 Hz, 1H), 2.93 (qd, J = 5.1, 2.2 Hz, 1H), 2.40 (s, 3H), 1.49 (d, J = 5.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 136.16, 135.89, 129.84, 127.62, 126.23, 124.29, 58.17, 57.76, 18.97, 18.13. trans-1-(4-methylphenyl)propylene oxide 1d: Obtained as a colourless oil (23% yield over 2 steps). ¹ H NMR (400 MHz, Chloroformd) δ 7.15 (s, 4H), 3.54 (d, J = 2.1 Hz, 1H), 3.03 (qd, J = 5.1, 2.1 Hz, 1H), 2.34 (s, 3H), 1.44 (d, J = 5.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform- d) δ 137.96, 134.84, 129.27, 125.67, 59.69, 59.01, 21.32, 18.05. trans-1-(2-naphthyl)propylene oxide 1e: Obtained as an off-white solid (27% yield over 2 steps). ¹ H NMR (400 MHz, Chloroform-d) δ 7.87 – 7.75 (m, 4H), 7.52 – 7.43 (m, 2H), 7.35 – 7.30 (m, 1H), 3.75 (d, J = 2.0 Hz, 1H), 3.15 (qd, J = 5.1, 2.1 Hz, 1H), 1.51 (d, J = 5.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 135.38, 133.38, 133.32, 128.42, 127.89, 127.89, 126.44, 126.11, 125.14, 123.11, 59.91, 59.27, 18.12. trans-1-(4-methoxyphenyl)propylene oxide 1f: Synthesized according to the epoxidation procedure starting from trans-anethole. Obtained as a colourless oil (90% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.10 (d, J = 8.7 Hz, 2H), 6.79 (d, J = 8.8 Hz, 2H), 3.71 (s, 3H), 3.44 (d, J = 2.1 Hz, 1H), 2.95 (qd, J = 5.1, 2.1 Hz, 1H), 1.35 (d, J = 5.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 159.67, 129.79, 126.97, 114.02, 59.52, 58.83, 55.40, 17.98. trans-1-(4-chlorophenyl)propylene oxide 1g: Obtained as a colourless oil (37% yield over 2 steps). ¹ H NMR (400 MHz, Chloroformd) δ 7.35 – 7.28 (m, 2H), 7.23 – 7.15 (m, 2H), 3.55 (d, J = 2.0 Hz, 1H), 2.99 (qd, J = 5.1, 2.1 Hz, 1H), 1.45 (d, J = 5.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 136.48, 133.89, 128.76, 127.03, 59.28, 59.00, 17.98. trans-1-(4-bromophenyl)propylene oxide 1h: Obtained as a colourless oil (45% yield over 2 steps). ¹ H NMR (400 MHz, Chloroformd) δ 7.46 (d, J = 8.4 Hz, 2H), 7.13 (d, J = 8.5 Hz, 2H), 3.53 (d, J = 2.0 Hz, 1H), 2.98 (qd, J = 5.1, 2.0 Hz, 1H), 1.45 (d, J = 5.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 137.02, 131.70, 127.35, 121.97, 59.27, 59.04, 17.98. 4.2 Synthesis of epoxide substrates 2b – 2h   The following synthesis was carried out following reported procedures (A. Cabré, J. Cabezas-Giménez, G. Sciortino, G. Ujaque, X. Verdaguer, A. Lledós, A. Riera, Adv. Synth. Catal. 2019, 361, 3624–3631.; C. Molinaro, A.-A. Guilbault, B. Kosjek, Org. Lett. 2010, 12, 3772–3775.). Trimethylsulfoxonium iodide (1.5 equiv.) was first dissolved in DMSO (1.6 mL/mmol), and potassium tert-butoxide (1.2 equiv.) was then added with vigorous stirring. After 10 minutes, a solution of the corresponding ketone dissolved in DMSO (0.7 mL/mmol) was added dropwise to the suspension. The resulting reaction mixture was stirred at rt for 16 h. The reaction was quenched with saturated sodium bicarbonate solution and extracted with hexanes (×2). The combined organic layers were dried over anhydrous sodium sulfate and concentrated. In most cases, the reaction proceeded to completion and the pure epoxide was obtained after work up without further purification. 2-(2-methylphenyl)propylene oxide 2b: For this epoxide, the reaction could not go to completion even with addition of more reactants. Purification using a short column of neutralized silica gel (equilibrated with 1% triethylamine in hexanes) using an eluent of 1:5:94 triethylamine/ethyl acetate/hexanes gave the epoxide product as a colourless oil (55% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.41 – 7.33 (m, 1H), 7.23 – 7.11 (m, 3H), 2.97 (d, J = 5.4 Hz, 1H), 2.83 (dd, J = 5.3, 0.8 Hz, 1H), 2.42 (s, 3H), 1.60 (s, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 139.95, 135.22, 130.21, 127.68, 127.00, 125.95, 58.42, 54.85, 23.64, 19.22. 2-(3-methylphenyl)propylene oxide 2c: Obtained as a colourless liquid (93% yield). Obtained as a colourless oil. ¹ H NMR (400 MHz, Chloroform-d) δ 7.26 – 7.14 (m, 3H), 7.09 (d, 1H), 2.96 (d, J = 5.4 Hz, 1H), 2.80 (d, J = 5.4 Hz, 1H), 2.36 (s, 3H), 1.71 (s, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 141.27, 138.16, 128.39, 128.35, 126.06, 122.60, 57.11, 56.94, 22.06, 21.60. 2-(4-methylphenyl)propylene oxide 2d: Obtained as a colourless liquid (95% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.18 – 7.16 (m, 2H), 7.07 – 7.05 (m, 2H), 2.87 (d, J = 3.78   Hz, 1H), 2.71 (d, J = 3.78 Hz, 1H), 2.25 (s, 3H), 1.62 (s, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 138.40, 137.35, 129.22, 125.45, 57.24, 56.89, 22.09, 21.26. 2-(2-naphthyl)propylene oxide 2e: Obtained as a white solid (95% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.73 – 7.66 (m, 4H), 7.35 –7.30 (m, 3H), 2.90 (d, J = 3.78 Hz, 1H), 2.75 (d, J = 3.78 Hz, 1H), 1.68 (s, 3H). ¹³ C NMR (101 MHz, Chloroform-d): δ 138.71, 133.20, 132.78, 128.18, 127.99, 127.67, 126.30, 126.04, 124.51, 123.23, 57.11, 56.99, 21.91. 2-(4-methoxyphenyl)propylene oxide 2f: This epoxide product was rather unstable to the aqueous workup conditions and prolonged storage. The obtained substrate was used immediately for reaction. Obtained as a colourless liquid (84% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.32 – 7.24 (m, 2H), 6.90 – 6.81 (m, 2H), 3.80 (s, 3H), 2.95 (d, J = 5.3 Hz, 1H), 2.80 (d, J = 5.3 Hz, 1H), 1.70 (s, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 159.14, 133.38, 126.71, 113.85, 57.18, 56.68, 55.43, 22.12. 2-(4-chlorophenyl)propylene oxide 2g: Obtained as a colourless liquid (96% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.31 (s, 4H), 2.99 (d, J = 2.98 Hz, 1H), 2.77 (d, J = 2.97 Hz, 1H), 1.71 (s, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 139.88, 133.38, 128.57, 126.86, 57.11, 56.39, 21.72. 2-(4-bromophenyl)propylene oxide 2h: Obtained as a colourless liquid (89% yield). ¹ H NMR (400 MHz, Chloroform-d) δ 7.49-7.46 (m, 2H), 7.26-7.24 (m, 2H), 2.99 (d, J = 7.66 Hz, 1H), 2.77 (d, J = 7.66 Hz, 1H), 1.71 (s, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 140.34, 131.46, 127.14, 121.45, 57.02, 56.38, 21.61. 4.3 Synthesis of acid standards 4b-h using SOI, EcALDH and NOX 25 mL potassium phosphate buffer (100 mM, pH 8.0, 1 mM NAD ⁺ ) containing 5 g _protein /L SOI CFE, 5 g/L EcALDH CFE and 0.5 g/L NOX CFE was prepared. The corresponding epoxide (1b-h) dissolved in DMSO was added (final concentrations: 25 mM 1, 2%v/v DMSO), and   the reaction was shaken at 250 rpm at 30 °C for 16 h. The reaction was quenched with 15 mL 1 M HCl and the product was extracted using 2×30 mL of ethyl acetate. The organic layers were combined, dried over anhydrous sodium sulfate and concentrated. Purification by silica gel column chromatography (9:1 hexanes/ethyl acetate) gave the acid product 4b-h. 2-(2-methylphenyl)propionic acid 4b: ¹ H NMR (400 MHz, Chloroform-d) δ 7.32 – 7.16 (m, 4H), 3.99 (q, J = 7.1 Hz, 1H), 2.38 (s, 3H), 1.50 (d, J = 7.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.76, 138.47, 136.06, 130.70, 127.36, 126.70, 126.61, 41.21, 19.78, 17.68. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759, found 163.0802. 2-(3-methylphenyl)propionic acid 4c: ¹ H NMR (400 MHz, Chloroform-d) δ 7.25 – 7.05 (m, 4H), 3.70 (q, J = 7.2 Hz, 1H), 2.35 (s, 3H), 1.50 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.28, 139.85, 138.51, 128.73, 128.45, 128.31, 124.75, 45.35, 21.56, 18.25. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759, found 163.0808. 2-(4-methylphenyl)propionic acid 4d: ¹ H NMR (400 MHz, Chloroform-d) δ 7.21 (d, J = 8.1 Hz, 2H), 7.14 (d, J = 8.1 Hz, 2H), 3.70 (q, J = 7.2 Hz, 1H), 2.33 (s, 3H), 1.50 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.49, 137.23, 136.95, 129.52, 127.59, 45.00, 21.19, 18.26. HRMS-ESI: m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0765, found 163.0768. 2-(2-naphthyl)propionic acid 4e: ¹ H NMR (400 MHz, Chloroform-d) δ 7.90 – 7.74 (m, 4H), 7.52 – 7.41 (m, 3H), 3.92 (q, J = 7.2 Hz, 1H), 1.61 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.60, 137.29, 133.55, 132.82, 128.55, 127.96, 127.76, 126.49, 126.36, 126.07, 125.83, 45.58, 18.26. HRMS-ESI: m/z of [M–H] ^– calcd for [C ₁₃ H ₁₁ O ₂ ] required 199.0765, found 199.0766. 2-(4-methoxyphenyl)propionic acid 4f: ¹ H NMR (400 MHz, Chloroform-d) δ 7.27 (d, J = 9.0 Hz, 2H), 6.89 (d, J = 9.0 Hz, 2H), 3.82 (s, 3H), 3.72 (q, J = 7.2 Hz, 1H), 1.52 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 181.07, 159.00, 132.00, 128.76, 114.20, 55.40, 44.62, 18.28. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₃ ] required 179.0714, found 179.0768. 2-(4-chlorophenyl)propionic acid 4g: ¹ H NMR (400 MHz, Chloroform-d) δ 7.32 – 7.07 (m, 4H), 3.64 (q, J = 7.2 Hz, 1H), 1.42 (d, 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.47, 138.25, 133.46, 129.14, 128.97, 44.88, 18.19. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₉ H ₈ ClO ₂ ] required 183.0218, found 183.0247.   2-(4-bromophenyl)propionic acid 4h: ¹ H NMR (400 MHz, Chloroform-d) δ 7.45 (d, J = 8.4 Hz, 2H), 7.19 (d, J = 8.4 Hz, 2H), 3.70 (q, J = 7.2 Hz, 1H), 1.50 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 179.86, 138.81, 131.94, 129.51, 121.55, 44.89, 18.16. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₉ H ₈ BrO ₂ ] required 226.9708, found 226.9733. 4.4 Synthesis of amine standards 5b-e and 5g-h using SOI and BmTA 40 mL potassium phosphate buffer (100 mM, pH 8.0, 100 mM L-alanine, 1 mM pyridoxal phosphate) containing 5 g cdw/L E. coli (SOI) and 15 g cdw/L E. coli (BmTA) was prepared. The corresponding epoxide (1b-e or 2g-h) dissolved in DMSO was added (final concentrations: 5 mM 1 or 2, 2%v/v DMSO), and the reaction was shaken at 250 rpm at 30 °C for 16 h. To isolate the amine compound, the reaction mixture was basified by adding KOH pellets until pH≥12. The product was then extracted with 3×30 mL ethyl acetate, and the combined ethyl acetate layers were dried over anhydrous sodium sulfate and concentrated. Purification by silica gel column chromatography (2:1:97 MeOH/triethylamine/ dichloromethane) gave 5b-e or 5g-h. 2-(2-methylphenyl)propyl amine 5b: ¹ H NMR (400 MHz, Methanol-d4) δ 7.25 – 6.98 (m, 5H), 3.31 (h, J = 7.1 Hz, 1H), 3.17 – 2.95 (m, 2H), 2.28 (s, 3H), 1.21 (d, J = 6.9 Hz, 3H). ¹³ C NMR (101 MHz, Methanol-d4) δ 141.55, 137.22, 132.08, 128.28, 128.08, 126.31, 46.23, 34.52, 19.72, 19.67. HRMS (EI): m/z of [M] ⁺ calcd for [C ₁₀ H ₁₅ N] required 149.1199, found 149.1199. 2-(3-methylphenyl)propyl amine 5c: ¹ H NMR (400 MHz, Chloroform-d) δ 7.24 – 7.16 (m, 1H), 7.07 – 6.95 (m, 3H), 2.92 – 2.81 (m, 2H), 2.75 (h, J = 6.9 Hz, 1H), 2.34 (s, 3H), 2.07 (br, NH ₂ ), 1.25 (d, J = 6.9 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 144.89, 138.21, 128.56, 128.26, 127.29, 124.44, 49.37, 43.32, 21.59, 19.46. HRMS (EI): m/z of [M] ⁺ calcd for [C ₁₀ H ₁₅ N] required 149.1199, found 149.1194. 2-(4-methylphenyl)propyl amine 5d: ¹ H NMR (400 MHz, Chloroform-d) δ 7.11 (q, J = 8.1 Hz, 4H), 2.92 – 2.67 (m, 3H), 2.32 (s, 3H), 2.48 (br, NH ₂ ), 1.24 (d, J = 6.7 Hz, 3H). ¹³ C NMR   (101 MHz, Chloroform-d) δ 141.70, 136.12, 129.41, 127.33, 49.16, 21.12, 19.53. HRMS (EI): m/z of [M] ⁺ calcd for [C ₁₀ H ₁₅ N] required 149.1199, found 149.1193. 2-(2-naphthyl)propyl amine 5e: ¹ H NMR (400 MHz, Methanol-d4) δ 7.76 – 7.68 (m, 3H), 7.61 – 7.56 (m, 1H), 7.39 – 7.25 (m, 3H), 2.91 – 2.70 (m, 3H), 1.25 (d, J = 6.7 Hz, 3H). ¹³ C NMR (101 MHz, Methanol-d4) δ 143.65, 135.28, 134.10, 129.48, 128.76, 128.73, 127.17, 127.02, 126.72, 126.57, 49.71, 44.15, 19.89. HRMS (EI): m/z of [M] ⁺ calcd for [C ₁₃ H ₁₅ N] required 185.1199, found 185.1198. 2-(4-chlorophenyl)propyl amine 5g: ¹ H NMR (400 MHz, Chloroform-d) δ 7.27 (d, J = 8.0 Hz, 2H), 7.13 (d, J = 8.0 Hz, 2H), 2.90 – 2.66 (m, 3H), 1.42 (br, NH ₂ ), 1.22 (d, J = 6.6 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 143.53, 132.12, 128.80, 128.75, 49.37, 42.90, 19.32. HRMS (ESI): m/z of [M+H] ⁺ calcd for [C ₉ H ₁₃ ClN] required 170.0731, found 170.0736. 2-(4-bromophenyl)propyl amine 5h: 1H NMR (400 MHz, Chloroform-d) δ 7.43 (d, J = 7.4 Hz, 2H), 7.09 (d, J = 7.9 Hz, 2H), 2.92 – 2.70 (m, 3H), 2.13 (br, NH ₂ ), 1.24 (d, J = 6.6 Hz, 3H). 13C NMR (101 MHz, Chloroform-d) δ 144.19, 131.73, 129.25, 120.18, 49.46, 43.15, 19.30. HRMS (ESI): m/z of [M+H] ⁺ calcd for [C ₉ H ₁₃ BrN] required 214.0226, found 214.0227. 5. Supplementary Experimental Methods 5.1 Growth of E. coli expressing enzymes and enzyme purification Procedure for culturing of E. coli strains: E. coli strain expressing the required enzyme(s) was initially inoculated in LB medium (1 mL) with kanamycin (50 mg/L). The cells grew for 8−10 h at 37 °C at 250 rpm and were then inoculated into a 500 mL tri-baffled flask containing TB medium (100 mL) and kanamycin (50 mg/L). The cells continued to grow at 37 °C and 250 rpm for about 2 h to reach an OD ₆₀₀ of about 0.6, and then isopropyl β-D-1- thiogalactopyranoside (IPTG, 0.5 mM final concentration) was added to induce the enzyme expression. The cells further grew at 22 °C overnight (12 h), and were harvested by centrifugation (5000 g, 8 min). The cell pellet was resuspended in the required buffer and in some experiments used directly as resting whole cell catalysts. Procedure for making cell-free extract (CFE): The cells were lysed by passing the cell suspension through a Stansted French press cell disruptor (15000 psi) for one time, followed by the removal of unbroken cells and cell debris by centrifugation (18000 g, 30 min).   Procedure for purification of his-tagged enzymes: For purification of his-tagged enzymes, the harvested cell pellets were resuspended in lysis buffer (100 mM potassium phosphate buffer, pH 8.0, 30 mM imidazole) and the cells were disrupted by using a SPX Flow Lab Homogenizer (550 bar, 5 min), followed by the removal of unbroken cells and cell debris by centrifugation (20000 g, 60 min). The supernatant was filtered and passed through a HisTrap HP affinity column (5 mL, GE Healthcare). The enzyme was eluted using a gradient flow of 30 mM to 250 mM imidazole. After desalting, the purified enzyme was stored in reaction buffer with 10% glycerol at -80 °C. 5.2 SDS-PAGE of cell-free extract, purified enzymes or whole cells used FIG. 5 depicts the SDS-PAGE of SOI cell-free extract (19.7 kDa), purified ADH9v1 (26.9 kDa), NOX (49.7 kDa), MmTA (49.6 kDa) and HnTA (35.8 kDa). FIG. 6 depicts the SDS-PAGE of E. coli (ADH9v1-NOX) (Lane 1: total cell protein and 2: soluble protein) and E. coli (SOI-MmTA-AlaDH) (Lane 3: soluble protein and 4: total cell protein). 5.3 Optimization of reactions system 5.3.1 Screening of co-solvent and buffer system for ADH9v1-catalyzed oxidation of 3a to 4a FIG. 7 depicts the results of the screening of co-solvent and amount (%v/v). Conditions: 5 mM 3a, 0.1 g/L ADH9v1, 0.1 g/L NOX, 0.1 mM NAD ⁺ , 100 mM potassium phosphate buffer, pH 8, 20 h, 30°C, 250 rpm. FIG. 8 depicts the results of the screening of buffer system and pH. Conditions: 5 mM 3a, 0.1 g/L ADH9v1, 0.1 g/L NOX, 0.1 mM NAD ⁺ , 100 mM buffer, 2%v/v DMSO, 20 h, 30°C, 250 rpm. KP = potassium phosphate, Tris = Tris-HCl buffer. 5.3.2 Screening of buffer system for MmTA or HnTA-catalyzed reductive amination of 3a to 5a FIG. 9 depicts the results of the screening of buffer system and pH for conversion of rac-2- phenylpropanal 3a to 2-phenylpropylamine 5a. Conditions: 5 mM rac-3a, 2 g _protein /L MmTA or   1 g _protein /L HnTA, 250 mM L-alanine or isopropylamine respectively, 1 mM PLP, 100 mM KP or Tris buffer, 2% DMSO co-solvent. KP = potassium phosphate buffer, Tris = Tris-HCl buffer. 5.3.3 Control reactions of 3a to investigate the formation of side product 6a. Table 2. Control reactions of 3a to investigate the formation of side product 6a. [a] General conditions: 5 mM 3a, 2%v/v DMSO, 30 °C, 250 rpm, 16 h.3a was purified by distillation prior to use. [b] The sum of detected 6a and substrate 3a is less than 50%, likely due to degradation of the aldehyde substrate into undetected products after 16 h. [c] No acid 4a detected without adding NOX and NAD ⁺ . [d] No amine 5a detected without adding L-alanine. 5.4 Specific activity measurements for SOI CFE, ADH9v1 and NOX Specific activity of SOI CFE for isomerization of 1a into 3a: 0.026 U/mg _protein Specific activity of ADH9v1 for the oxidation of 3a to 4a: 2.29 U/mg _protein Specific activity of NOX for the oxidation of NADH to NAD ⁺ : 35.8 U/mg _protein Assay conditions for SOI: 5 mM 1a, 4 g _protein /L SOI CFE, 100 mM KP buffer pH 8, 1%v/v acetonitrile co-solvent were mixed in a 2 mL Eppendorf tube (total volume = 1 mL). The reaction was shaken at 30 °C. The concentration of aldehyde 3a formed was then measured by HPLC analysis and specific activity was calculated based on the amount of 3a produced from 4 to 16 min. Assay conditions for ADH9v1: 5 mM aldehyde 3a, 1 mM NAD ⁺ , 0.01 mg/mL purified ADH9v1, 100 mM KP buffer pH 8, 2%v/v DMSO co-solvent were mixed in a cuvette (total volume = 1   mL). Initially the reaction mixture was prepared in a cuvette without the enzyme and the reaction was started upon the addition of enzyme and quickly inverting the cuvette. The increase in NADH was detected by measuring the UV absorbance at 340 nm every 1 s from 0 to 60 s, and the specific activity was calculated using the obtained slope as follows: Specific activity [μmol/min/mg] = (Slope [Abs/min] ÷ 6.22 mL/μmol/cm [molar absorptivity of NADH] × 1 cm [path length] × 1 mL [volume of reaction]) / enzyme loading [in mg]

  Assay conditions for NOX: 0.1 mM NADH, 0.001 mg/mL purified NOX, 100 mM KP buffer pH 8, were mixed in a cuvette (total volume = 1 mL). Initially the reaction mixture was prepared in a cuvette without the enzyme and the reaction was started upon the addition of enzyme and quickly inverting the cuvette. The decrease in NADH was detected by measuring the UV absorbance at 340 nm every 1 s from 0 to 60 s. Example 1. Biocatalytic conversion of racemic epoxides to (S)-2-arylpropionic acids - Example 1.1 Biotransformation of rac-1 to (S)-4 using SOI CFE, ADH9v1 and NOX General procedure: The appropriate amounts of NAD ⁺ , CFE containing SOI, purified ADH9v1 and purified NOX in 100 mM potassium phosphate buffer (pH 8) were added into a conical flask. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of substrate 1, dissolved in DMSO as a co-solvent (2%v/v). The reaction was shaken at 250 rpm and 30°C for 16 hours. For HPLC analysis, 100 μl aliquots was taken and quenched in 900 μl of solution containing 5:4 acetonitrile/ultrapure water + 0.1% TFA and 0.2 mM benzyl alcohol (internal standard). For isolation of product, 15 mL of 1 M HCl was added to quench the reaction, followed by extraction using 3×30 mL of ethyl acetate. The organic layers were combined, dried over anhydrous sodium sulfate and concentrated. Purification by silica gel column chromatography (9:1 hexanes/ethyl acetate) gave the acid product.

  Table 3. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and NAD ⁺ loading.   For 4a–4d, reactions were performed on a preparative scale, and the products 4a–4d were isolated and characterized. For 4e–4h, product conversion was determined by measuring HPLC peak area and comparing with that of synthesized standard. LC-MS was performed to confirm the mass of the product peak. Characterization data of isolated products (S)-2-phenylpropionic acid 4a: For the preparative biotransformation of 1a to (S)-4a, 30.0 mg of a colourless oil was obtained (66.7% yield, 94.7% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.27 – 7.15 (m, 5H), 3.67 (q, J = 7.2 Hz, 1H), 1.45 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 181.00, 139.88, 128.81, 127.74, 127.53, 45.51, 18.22. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₉ H ₉ O ₂ ] required 149.0608, found 149.0649. (S)-2-(2-methylphenyl)propionic acid 4b: For the preparative biotransformation of 1b to (S)-4b, 19.0 mg of a colourless oil was obtained (57.9% yield, 82.2% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.34 – 7.13 (m, 4H), 3.99 (q, J = 7.1 Hz, 1H), 2.39 (s, 3H), 1.50 (d, J = 7.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.84, 138.47, 136.05, 130.68, 127.34, 126.70, 126.60, 41.22, 19.77, 17.67. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759; found 163.0803. +87.9° (c 1.0 g/100mL, CHCl ₃ ), 96.9% ee ^{[12] [12]} C. H. Senanayake, T. J. Bill, R. D. Larsen, J. Leazer, P. J. Reider, Tetrahedron Lett.1992, 33, 5901–5904. (S)-2-(3-methylphenyl)propionic acid 4c: For the preparative biotransformation of 1c to (S)-4c, 28.5 mg of a brownish oil was obtained (86.7% yield, 90.4% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.26 – 7.20 (m, 1H), 7.16 – 7.07 (m, 3H), 3.71 (q, J = 7.1 Hz, 1H), 2.36 (s, 3H), 1.51 (d, J = 7.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 181.00, 139.83, 138.49, 128.71, 128.45, 128.30, 124.75, 45.43, 21.54, 18.22. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759, found 163.0812. +61.9° (c 0.75 g/100mL, CHCl ), Lit: ₃ +33.3° ( ^[13] c 0.75 g/100mL, CHCl ₃ ), 85% ee ^[13] F. Mandrelli, A. Blond, T. James, H. Kim, B. List, Angew. Chem. Int. Ed. 2019, 58, 11479–11482.   (S)-2-(4-methylphenyl)propionic acid 4d: For the preparative biotransformation of 1d to (S)-4d, 18.1 mg of a colourless oil was obtained (55.1% yield, 93.4% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.22 (d, J = 8.0 Hz, 2H), 7.15 (d, J = 8.0 Hz, 2H), 3.71 (q, J = 7.2 Hz, 1H), 2.34 (s, 3H), 1.50 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.96, 137.20, 136.94, 129.50, 127.59, 45.07, 21.18, 18.23. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759, found 163.0807. +46.1° (c 1.0 g/100mL, CHCl ₃ ), >95% ee ^{[14] [14]} T. Beard, M. A. Cohen, J. S. Parratt, N. J. Turner, J. Crosby, J. Moilliet, Tetrahedron Asymmetry 1993, 4, 1085–1104. - Example 1.2 Biotransformation of rac-2 to (S)-4 using SOI CFE, ADH9v1 and NOX General procedure: The appropriate amounts of NAD ⁺ , CFE containing SOI, purified ADH9v1 and purified NOX in 100 mM potassium phosphate buffer (pH 8) were added into a conical flask. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of substrate 2, dissolved in DMSO as a co-solvent (2% v/v). The reaction was shaken at 250 rpm and 30°C for 16 hours. For HPLC analysis, 100 μl aliquots was taken and quenched in 900 μl of solution containing 5:4 acetonitrile/ultrapure water + 0.1% TFA and 0.2 mM benzyl alcohol (internal standard). For isolation of product, 15 mL of 1 M HCl was added to quench the reaction, followed by extraction using 3×30 mL of ethyl acetate. The organic layers were combined, dried over anhydrous sodium sulfate and concentrated. Purification by silica gel column chromatography (9:1 hexanes/ethyl acetate) gave the acid product.

  Table 4. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and NAD ⁺ loading.   For 4a–e and 4h, reactions were performed on a preparative scale, and the products 4a–e and 4h were isolated and characterized. For 4f and 4g, product conversion was determined by measuring HPLC peak area and comparing with that of synthesized standard. LC-MS was performed to confirm the mass of the product peak. Characterization data of isolated products (S)-2-phenylpropionic acid 4a: For the preparative biotransformation of 2a to (S)-4a, 27.1 mg of a colourless oil was obtained (60.2% yield, 93.5% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.28 – 7.15 (m, 5H), 3.67 (q, J = 7.2 Hz, 1H), 1.45 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.98, 139.89, 128.81, 127.73, 127.52, 45.51, 18.22. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₉ H ₉ O ₂ ] required 149.0608, found 149.0647. (S)-2-(2-methylphenyl)propionic acid 4b: For the preparative biotransformation of 2b to (S)-4b, 21.3 mg of a colourless oil was obtained (64.9% yield, 89.8% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.35 – 7.13 (m, 4H), 4.00 (q, J = 7.1 Hz, 1H), 2.39 (s, 3H), 1.51 (d, J = 7.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 181.04, 138.46, 136.05, 130.68, 127.34, 126.70, 126.60, 41.24, 19.77, 17.66. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759, found 163.0802. ^ +87.9° (c 1.0 g/100mL, CHCl ₃ ), 96.9% ee ^[12] (S)-2-(3-methylphenyl)propionic acid 4c: For the preparative biotransformation of 2c to (S)-4c, 28.8 mg of a brownish oil was obtained (87.7% yield, 87.3% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.35 – 7.28 (m, 1H), 7.24 – 7.16 (m, 3H), 4.00 (q, J = 7.1 Hz, 1H), 2.39 (s, 3H), 1.51 (d, J = 7.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 181.04, 138.46, 136.05, 130.68, 127.34, 126.70, 126.60, 41.24, 19.77, 17.66. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759, found 163.0799. +64.0° (c 0.75 g/100mL, CHCl ₃ ), Lit: +33.3° (c 0.75 g/100mL, CHCl ₃ ), 85% ee ^[13] (S)-2-(4-methylphenyl)propionic acid 4d: For the preparative biotransformation of 2d to (S)-4d, 17.6 mg of a colourless oil was obtained (53.6% yield, 90.3% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.22 (d, J = 8.0 Hz, 2H), 7.15 (d, J = 8.0 Hz, 2H), 3.71 (q, J = 7.2 Hz, 1H), 2.34 (s, 3H), 1.51 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 181.05, 137.21, 136.93, 129.50, 127.59, 45.08, 21.18, 18.23. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₀ H ₁₁ O ₂ ] required 163.0759, found 163.0807. ^ +72.4° (c 1.0 g/100mL, CHCl ₃ ), Lit: +46.1° (c 1.0 g/100mL, CHCl ₃ ), >95% ee[ ^14]   (S)-2-(2-naphthyl)propionic acid 4e: For the preparative biotransformation of 2e to (S)-4e, 28.3 mg of a white solid was obtained (70.7% yield, 92.5% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.90 – 7.77 (m, 4H), 7.53 – 7.39 (m, 3H), 3.92 (q, J = 7.2 Hz, 1H), 1.62 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.73, 137.29, 133.54, 132.81, 128.54, 127.95, 127.75, 126.49, 126.35, 126.06, 125.83, 45.60, 18.25. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₁₃ H ₁₁ O ₂ ] required 199.0759, found 199.0800. +63.1° (c 0.65 g/100mL; ethanol), Lit: +65.0° (c 0.65 g/100mL; ethanol), 98% ee ^{[15] [15]} Z.-L. Wu, Z.-Y. Li, Tetrahedron Asymmetry 2001, 12, 3305–3312. (S)-2-(4-bromophenyl)propionic acid 4h: For the preparative biotransformation of 2h to (S)-4h, 27.0 mg of a white solid was obtained (58.9% yield, 79.5% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.46 (d, J = 8.4 Hz, 2H), 7.20 (d, J = 8.4 Hz, 2H), 3.70 (q, J = 7.2 Hz, 1H), 1.50 (d, J = 7.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.34, 138.78, 131.93, 129.50, 121.55, 44.95, 18.13. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₉ H ₈ BrO ₂ ] required 226.9708, found 226.9741. +46.9° (c 1.5 g/100mL, MeOH), 96% ee[ ^15] - Example 1.3 Biotransformation of 1a or 2a to (S)-4a using whole cells General procedure for biotransformation to (S)-4a using E. coli (SOI) and E. coli (ADH9v1-NOX): 2–5 g cdw/L E. coli (SOI) and 10 g cdw/L E. coli (ADH9v1-NOX) freshly harvested cells were added to 100 mM potassium phosphate buffer (pH 8) containing 1 mM NAD ⁺ in a baffled flask. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of 10 mM substrate 1a or 2a, dissolved in DMSO (2% v/v) or acetone (5% v/v) as a co-solvent. The reaction was shaken at 250 rpm and 30°C for 16 hours. The isolation of product is the same as in the example using SOI CFE, ADH9v1 and NOX to produce (S)-4a.   Table 5. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and cofactor loading.   Characterization data of isolated products (S)-2-phenylpropionic acid 4a: For the preparative biotransformation of 1a to (S)-4a using E. coli (SOI) and E. coli (ADH9v1-NOX) whole cells, 48.9 mg of a colourless oil was obtained (65.2%, 90.1% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.27 – 7.15 (m, 5H), 3.68 (q, J = 7.3 Hz, 1H), 1.45 (d, J = 7.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.36, 139.91, 128.83, 127.73, 45.43, 18.26. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₉ H ₉ O ₂ ] required 149.0608, found 149.0613. For the preparative biotransformation of 2a to (S)-4a using E. coli (SOI) and E. coli (ADH9v1-NOX) whole cells, 64.1 mg of a colourless oil was obtained (85.4%, 93.9% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.30 – 7.13 (m, 5H), 3.68 (q, J = 7.1 Hz, 1H), 1.45 (d, J = 7.1 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 180.92, 139.87, 128.81, 127.73, 45.49, 18.22. HRMS (ESI): m/z of [M–H] ^– calcd for [C ₉ H ₉ O ₂ ] required 149.0608, found 149.0607. Results and Discussion The study was initiated by developing the enzymatic cascade to convert racemic trans-β- methyl epoxide 1a to (S)-2-phenylpropionic acid 4a, utilizing SOI as the first enzyme to catalyze the isomerization of 1a to produce 2-phenylpropanal 3a in situ via a 1,2-methyl shift isomerization. Aldehyde 3a racemizes spontaneously and quickly in the aqueous reaction buffer via keto-enol tautomerism as the second step to allow for DKR. ADH9v1 was selected as the enzyme to catalyze the stereoselective oxidation of 3a to (S)-4a in the third reaction step based on screening (Table 6). NADH oxidase from Lactobacillus brevis (NOX) was used to regenerate NAD ⁺ and also suppress the unwanted ADH-catalyzed reductive reaction.

  Table 6. Screening of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) for the conversion of rac-3a to 4a, and ee of 4a obtained. Conditions: 10 mM rac-3a, 0.5 g/L purified ADH/ALDH, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 100 mM KP buffer pH 8.0, 2%v/v DMSO co-solvent. Conversions and ee determined by HPLC. ADH9v1: mutated alcohol dehydrogenase, EcALDH: aldehyde dehydrogenase from E. coli, HLADH: horse liver alcohol dehydrogenase, SyADH: alcohol dehydrogenase from Sphingobium yanoikuyae. The proposed cascade reaction was first demonstrated by biotransformation in vitro using a cell-free system. Since SOI is a membrane protein that is difficult to purify, cell-free extract (CFE) containing SOI was used, along with purified ADH9v1 and NOX. The specific activities of each enzyme on their respective substrates were measured and accordingly, enzyme loading of SOI CFE, ADH9v1 and NOX was set at 3 g _protein /L, 0.2 g/L and 0.2 g/L, respectively, to enable a faster oxidation of 3a to (S)-4a by ADH9v1 compared to the isomerization of 1a to 3a by SOI. The reaction system was optimized, with 0.2 mM NAD ⁺ and 2%v/v DMSO co-solvent in KP buffer (pH 8) as the best conditions. The time course of the in vitro cascade biotransformation of racemic 1a is shown in FIG. 2a. In the first 2 h, the disappearance of 1a and formation of (S)-4a was fast. Thereafter, 1a was steadily converted into (S)-4a in 87% conversion with 95% product ee over 16 h. The aldehyde intermediate 3a was kept at a low concentration throughout the course of the reaction. Since SOI can also catalyze the isomerization of α-methyl epoxides 2 to produce 2- arylpropanals 3 via a 1,2-hydride shift isomerization, the present isomerization-racemization- oxidation cascade was then applied to convert racemic 2 to (S)-4. The time course of the in vitro cascade biotransformation of racemic 2a to (S)-4a under the same cell-free conditions   (3 g _protein /L SOI CFE, 0.2 g/L ADH9v1 and 0.2 g/L NOX) is also shown in FIG. 2a. Substrate 2a was quickly consumed to produce 70% (S)-4a and 21% 3a in 1 h as a result of the SOI- catalyzed isomerization step proceeding at a faster rate than that with 1a as substrate. Over time, the remaining 3a was continuously converted to (S)-4a, which was obtained in 92% conversion and 93% ee after 16 h. DKR biotransformations with unstable 3a as substrate were known to produce acetophenone 6a as side product (up to 19%). In comparison, there was no substantial formation of side products in the present cascade reaction in initial experiments. To study this, ADH9v1-catalyzed production of (S)-4a from 3a was performed, which was either directly supplied as substrate or in situ generated from 1a or 2a using SOI (FIG. 2b). While the former produced 84% of (S)-4a with 5% of 6a, the latter produced 87–92% of (S)-4a with only a trace amount of 6a (<1 to 1%). The reduced formation of side product 6a in the reactions using SOI could be due to the low concentration of 3a maintained throughout the reaction (FIG. 2a). Furthermore, the former case showed decreased product ee (85% (S)) which is likely due to the slow racemization of 3a. The enhanced product ee when starting from 1a (95% (S)) could be attributed to some preference of SOI for the isomerization of (1R, 2R)-1a to (S)-3a over the isomerization of (1S, 2S)-1a to (R)-3a (E-value of 12). For the reaction starting from 2a, while SOI slightly prefers the isomerization of (R)-2a to (R)-3a over that of (S)-2a to (S)-3a (E-value of 1.2), (S)-4a could still be produced in high ee (93% (S)). The established cell-free cascade system was then applied to convert a range of trans-β- methyl epoxides 1b–f with various aryl substitutions to produce (S)-4b–f (Table 7). The system is able to accept substrates with 2-, 3-, or 4-methylphenyl substitutions, producing (S)-4b–d in good yields (61–87%) and ee (82–93%). Bulky substrate 1e was with a 2-naphthyl group was also well accepted, affording (S)-4e with 93% ee and 87% yield. 1f with electron-donating 4-methoxyphenyl substitution produced (S)-4f with 95% ee and 71% yield. Using the cell-free system starting from 1a–d, acids (S)-4a–d were isolated using simple purification procedures in good yields (55–87%). The cell-free cascade system was utilized to convert α-methyl epoxides 2b–f as another set of substrates to produce (S)-4b–f (Table 7). 2b–d containing 2-, 3-, or 4-methylphenyl substitutions were converted to (S)-4b–d in good conversions (76–89%) and ee (87–90%). The bulky 2-napthyl substitution in 2e was also well accepted to give (S)-4e in 93% ee and 79% yield.2g and 2h with electron-withdrawing halogen substitutions produced (S)-4g with 84% ee and 71% yield and (S)-4h with 80% ee and 98% yield, respectively. Using the cell-   free system starting from 2a–e and 2h, acids (S)-4a–e and (S)-4h were also isolated in good yields (54–88%). In general, the two different epoxide substrates 1 and 2 accepted by the cascade system provides an advantage of having additional possibility to produce the same molecule if either of the substrates is difficult to access or is not well-accepted by SOI. For example, (S)-4e, (S)-4g and (S)-4h were produced at higher conversions when starting from their corresponding α-methyl epoxide 2 compared to trans-β-methyl 1 as the former was a better substrate for the SOI-catalyzed isomerization step. In some cases, the acid product obtained from one epoxide has a higher ee than that obtained from the other, whereby the reduced ee could be caused by faster generation of the aldehyde intermediate by SOI compared to the rate of racemization and oxidation. Table 7. Biocatalytic cascade conversion of racemic epoxides 1 or 2 to (S)-4 using cell-free or whole-cell systems.   ^a) Yield and ee determined by HPLC. ^b) Isolated yield (if any) is given in parentheses. ^c) General conditions for cell-free system: 0.3–8 g _protein /L CFE containing SOI, 0.2–0.4 g/L ADH9v1, 0.2 g/L NOX, 0.2 mM NAD ⁺ , 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. ^d) General conditions for whole-cell system: 2–5 g cdw/L E. coli (SOI), 10 g cdw/L E. coli (ADH9v1-NOX), 1 mM NAD ⁺ , KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. To further demonstrate the practicality of the multi-enzymatic isomerization-racemization- oxidation cascade involving DKR, the reaction was also performed using a whole-cell system (Table 7). The use of whole cells expressing the required enzymes would simplify processes and reduce costs associated with laborious enzyme purification. Epoxide 1a was successfully converted to acid (S)-4a using 5 g cdw/L E. coli (SOI) and 10 g cdw/L E. coli (ADH9v1-NOX) in 76% conversion with 90% ee, and isolated in 65% yield. When this same condition was applied to substrate 2a, (S)-4a was produced in only 62% conversion with about 30% 2-phenylpropanol detected, presumably due to faster conversion of 2a to 3a, which was reduced by endogenous ADHs and reductases (Table 5). By reducing the loading of E. coli (SOI) to 2 g cdw/L to lower the rate of 3a generated in situ and maintaining 10 g cdw/L E. coli (ADH9v1-NOX), (S)-4a was produced in 88% conversion and 94% ee without the reduction side-product 2-phenylpropanol detected, and (S)-4a was isolated in 85% yield. The use of two different strains for this cascade allows for adjustment of the enzyme ratio for the first and third reaction step to control the flux of the cascade reaction towards high- yielding formation of the final product (S)-4a.

  Thus, the present cascade system has a broad substrate scope, being potentially useful to produce (S)-2-arylpropionic acids 4 in high yield and ee. The cascade involving the in situ generation of 3a reduced by-product formation and improved the ee of product (S)-4a, in comparison with DKR strategies using 3a as substrate. It utilizes SOI-catalyzed Meinwald rearrangement of racemic epoxides 1 or 2 for the in situ generation of 3 without the need for any co-factor, making it advantageous over other possible aldehyde-generation systems from primary alcohols or carboxylic acids which are co-factor dependent. While most of the products 4 were obtained in > 90% ee either from epoxide 1 or 2, (S)-4g and (S)-4h were obtained in 80–84% ee, which could be improved by engineering more enantioselective ADH for the oxidation. Example 2. Biocatalytic conversion of racemic epoxides to (R)-2-arylpropyl amines - Example 2.1 Biotransformation of rac-1 to (R)-5 using SOI CFE and MmTA General procedure: The appropriate amounts of L-alanine, PLP, CFE containing SOI and purified MmTA in 100 mM potassium phosphate buffer (pH 8) were added into a centrifuge tube and sealed. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of substrate 1, dissolved in DMSO as a co-solvent (2%v/v). The reaction was shaken at 250 rpm and 30°C for 16 hours. For HPLC analysis, 100 μl aliquots was taken and quenched in 900 μl of solution containing 5:4 acetonitrile/ultrapure water + 0.1% TFA and 0.2 mM benzyl alcohol (internal standard). For isolation of product, the reaction mixture was basified by adding KOH pellets until pH≥12. The product was extracted with 3×30 mL ethyl acetate, and the combined ethyl acetate layers were dried over anhydrous sodium sulfate and concentrated. Purification by silica gel column chromatography (2:1:97 MeOH/triethylamine/dichloromethane) gave the amine product.

  Table 8. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and cofactor loading.   For (R)-5a, reaction was performed on a preparative scale, and the product (R)-5a was isolated and characterized. For (R)-5b–e, product conversion was determined by measuring HPLC peak area and comparing with that of synthesized standard. Characterization data of isolated products (R)-2-phenylpropyl amine 5a: For the preparative biotransformation of 1a to (R)-5a, 30.5 mg of a colourless oil was obtained (75.2% yield, 90.8% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.37 – 7.28 (m, 2H), 7.24 – 7.17 (m, 3H), 2.95 – 2.72 (m, 3H), 2.21 (br, NH2), 1.26 (d, J = 6.5 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 144.75, 128.72, 127.48, 126.62, 49.24, 43.07, 19.44. HRMS (ESI): m/z of [M+H] ⁺ calcd for [C ₉ H ₁₄ N] required m/z 136.1121, found 136.1122. - Example 2.2 Biotransformation of rac-2 to (R)-5 using SOI CFE and MmTA General procedure: The appropriate amounts of L-alanine, PLP, CFE containing SOI and purified MmTA in 100 mM potassium phosphate buffer (pH 8) were added into a centrifuge tube and sealed. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of substrate 2, dissolved in DMSO as a co-solvent (2%v/v). The reaction was shaken at 250 rpm and 30°C for 16 hours. For HPLC analysis, 100 μl aliquots was taken and quenched in 900 μl of solution containing 5:4 acetonitrile/ultrapure water + 0.1% TFA and 0.2 mM benzyl alcohol (internal standard).

  Table 9. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and cofactor loading.   For (R)-5a–d and (R)-5g–h, product conversion was determined by measuring HPLC peak area and comparing with that of synthesized standard. - Example 2.3 Biotransformation of 1a or 2a to (R)-5a using whole cells General procedure for biotransformation to (R)-5a using E. coli (SOI-MmTA-AlaDH): 20 g cdw/L E. coli (SOI-MmTA-AlaDH) freshly harvested cells were added to 100 mM potassium phosphate buffer (pH 8) containing 50 mM L-alanine and 1 mM PLP in a centrifuge tube and sealed. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of 10 mM substrate 1a or 2a, dissolved in DMSO as a co- solvent (2% v/v). The reaction was shaken at 250 rpm and 30°C for 16 hours. The isolation of product is the same as in the example using SOI CFE and MmTA to produce (R)-5a.

  Table 10. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and cofactor loading.   Characterization data of isolated products (R)-2-phenylpropyl amine 5a: For the preparative biotransformation of 1a to (R)-5a using E. coli (SOI-MmTA-AlaDH) whole cells, 28.2 mg of a colourless oil was obtained (59.6% yield, 90.0% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.36 – 7.28 (m, 2H), 7.25 – 7.17 (m, 3H), 2.95 – 2.73 (m, 3H), 2.28 (br, NH2), 1.27 (d, J = 6.4 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 144.69, 128.74, 127.47, 126.65, 49.16, 42.96, 19.44. HRMS (ESI): m/z of [M+H] ⁺ calcd for [C ₉ H ₁₄ N] required m/z 136.1121, found 136.1122. For the preparative biotransformation of 2a to (R)-5a using E. coli (SOI-MmTA-AlaDH) whole cells, 33.5 mg of a colourless oil was obtained (61.9% yield, 90.5% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.36 – 7.28 (m, 2H), 7.25 – 7.17 (m, 3H), 2.93 – 2.67 (m, 3H), 2.00 (br, NH2), 1.26 (d, J = 6.8 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 144.86, 128.72, 127.48, 126.59, 49.34, 43.29, 19.44. HRMS (ESI): m/z of [M+H] ⁺ calcd for [C ₉ H ₁₄ N] required m/z 136.1121, found 136.1120. Results and Discussion Following the successful demonstration of the present isomerization-racemization-oxidation cascade system, (R)-2-arylpropyl amines 5 from epoxides 1 or 2 were targeted to be produced. This could be achieved by replacing the final aldehyde oxidation step in the cascade with an (R)-enantioselective amination reaction catalyzed by TA. Based on the screening of a panel of TAs available in our lab (FIG. 4), an (R)-enantioselective transaminase from Martelella mediterranea (MmTA), which showed high product ee (96%) with highest conversion, was selected to catalyze the transamination step to convert in situ generated 2-arylpropanal 3 to (R)-5. Due to the good performance of MmTA, no further screening of transaminases was performed. The isomerization-racemization-(R)-amination cascade reaction was demonstrated by biotransformation in vitro using a cell-free system. Enzyme loading of SOI CFE and purified MmTA was set at 3 g _protein /L and 3 g/L, respectively. The reaction system was optimized, with 250 mM L-alanine amine donor, 1 mM PLP and 2%v/v DMSO co-solvent in KP buffer (pH 8) as the best conditions. The time course of the in vitro cascade biotransformation of racemic epoxide 1a or 2a to (R)-5a is shown in FIG. 3a. Within 1 h, conversion of 1a to 19% amine (R)-5a and 21% aldehyde 3a was observed. The cascade reaction proceeded steadily to produce (R)-5a in 96% conversion and 90% ee over 16 h. Due to faster SOI-catalyzed   isomerization, 2a was quickly converted to produce 68% (R)-5a and 21% 3a in 1 h. The final yield of (R)-5a at 16 h was 94% with 92% ee. The amine product (R)-5a has been used in the synthesis of angiotensin receptor blockers. The advantage of in situ generation of 3a using SOI in the cascade system was also apparent for the cascade producing (R)-5a. While direct conversion of 3a using MmTA produced 94% of (R)-5a and 6% of 6a, the one-pot conversion of 1a to (R)-5a using SOI and MmTA produced (R)-5a in 96% conversion without formation of 6a. The use of 2a as substrate produced 94% of (R)-5a with some 6a (3%) (FIG.3b). The established cascade involving SOI and MmTA converted 2- and 4-methylphenyl substituted trans-β-methyl epoxides 1b and 1d into (R)-5b and (R)-5d with 62% and 77% yield respectively, with excellent ee of 94% and 93%. (R)-5e containing a bulky 2-napthyl substitution was also produced successfully from 1e, achieving 94% ee with 51% conversion. Using the cell-free system, amine (R)-5a was prepared from 1a and isolated using straightforward procedures to give 75% yield (Table 11). Using racemic α-methyl epoxides 2 as substrates under the same conditions, 2b and 2d were converted to (R)-5b and (R)-5d in 83% and 60% conversions respectively, again with high ee of 96% and 94%. While halogen-substituted epoxides 1g and 1h gave low conversions, the alternative α-methyl epoxides 2g and 2h were better substrates for SOI and were successfully converted to (R)-5g with 95% ee and 61% conversion, and (R)-5h with 94% ee and 56% conversion (Table 11). (R)-5h was used as a precursor for preparing the anti-cancer drug candidate OTS514. The isomerization-racemization-(R)-amination cascade could also be achieved using a single strain E. coli (SOI-MmTA-AlaDH) co-expressing SOI, MmTA and alanine dehydrogenase (AlaDH). (R)-5a was produced successfully from 1a in 72% conversion with 90% ee, and isolated in 60% yield. (R)-5a was also prepared from 2a in 80% conversion with 91% ee, and isolated in 62% yield (Table 11).   Table 11. Biocatalytic cascade conversion of racemic epoxides 1 or 2 to (R)-5 using cell-free or whole-cell systems. ^a) Yield and ee determined by HPLC. ^b) Isolated yield (if any) is given in parentheses. ^c) General conditions for cell-free system: 3 g _protein /L CFE containing SOI, 3 g/L MmTA, 1 mM PLP, 250 mM L- alanine, 100 mM KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. ^d) General conditions for whole-cell system: 20 g cdw/L E. coli (SOI-MmTA-AlaDH), 1 mM PLP, 50 mM L-alanine, KP buffer (pH 8), 2%v/v DMSO, 30 °C, 16 h. Thus, the present cascade system is able to convert racemic trans-β-methyl epoxides 1 or α- methyl epoxides 2 to produce six different (R)-2-arylpropyl amines 5 in high ee and good conversions, including pharmaceutically relevant molecules. The cascade system with SOI- catalyzed in situ generation of 3a from 1a eliminated the formation of by-product 6a, in comparison with DKR using unstable 3a directly as substrate. Example 3. Biocatalytic conversion of racemic epoxides to (S)-2-arylpropyl amines   Screening of 11 TAs available in our lab (FIG. 4) gave transaminase from Hyphomonas neptunium (HnTA) as the only (S)-enantioselective TA which showed high product ee (97%). HnTA, which was previously used in the direct amination of 3a to (S)-5a via DKR, was then used for the isomerization-racemization-(S)-amination cascade. No further screening of transaminases was performed. HnTA was incorporated into the cascade for the biotransformation in vitro using a cell-free system containing 3 g _protein /L SOI CFE and 3 g/L HnTA to produce (S)-5 from trans-β-methyl epoxides 1 or α-methyl epoxides 2. The optimized conditions utilized 125 mM isopropylamine as amine donor, 1 mM PLP and 2%v/v DMSO co-solvent in KP buffer (pH 7). - Example 3.1 Biotransformation of rac-1 to (S)-5 using SOI CFE and HnTA General procedure: The appropriate amounts of isopropylamine in a 1.25 M stock solution (pH 7), PLP, CFE containing SOI and purified HnTA were added to 100 mM potassium phosphate buffer (pH 7) in a centrifuge tube and sealed. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of substrate 1, dissolved in DMSO as a co-solvent (2%v/v). The reaction was shaken at 250 rpm and 30°C for 16 hours. For HPLC analysis, 100 μl aliquots was taken a nd quenched in 900 μl of solution containing 5:4 acetonitrile/ultrapure water + 0.1% TFA and 0.2 mM benzyl alcohol (internal standard). For isolation of product, the reaction mixture was basified by adding KOH pellets until pH≥12. The product was extracted with 3×30 mL ethyl acetate, and the combined ethyl acetate layers were dried over anhydrous sodium sulfate and concentrated. Purification by silica gel column chromatography (2:1:97 MeOH/triethylamine/dichloromethane) gave the amine product.

  Table 12. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and cofactor loading.   For (S)-5a, reaction was performed on a preparative scale, and the product (S)-5a was isolated and characterized. For (S)-5b–e, product conversion was determined by measuring HPLC peak area and comparing with that of synthesized standard. Characterization data of isolated products (S)-2-phenylpropyl amine 5a: For the preparative biotransformation of 1a to (S)-5a, 23.0 mg of a colourless oil was obtained (68.0% yield, 89.1% ee). ¹ H NMR (400 MHz, Chloroform-d) δ 7.36 – 7.29 (m, 2H), 7.25 – 7.17 (m, 3H), 2.96 – 2.75 (m, 3H), 2.47 (br, NH2), 1.28 (d, J = 6.2 Hz, 3H). ¹³ C NMR (101 MHz, Chloroform-d) δ 144.54, 128.78, 127.47, 126.73, 48.98, 42.63, 19.44. HRMS (ESI): m/z of [M+H] ⁺ calcd for [C ₉ H ₁₄ N] required m/z 136.1121, found 136.1123. - Example 3.2 Biotransformation of rac-2 to (S)-5 using SOI CFE and HnTA General procedure: The appropriate amounts of isopropylamine in a 1.25 M stock solution (pH 7), PLP, CFE containing SOI and purified HnTA in 100 mM potassium phosphate buffer (pH 7) were added a centrifuge tube and sealed. The reaction mixture was placed on a shaker (250 rpm, 30°C) for 5 minutes, before addition of substrate 2, dissolved in DMSO as a co-solvent (2%v/v). The reaction was shaken at 250 rpm and 30°C for 16 hours. For HPLC analysis, 100 μl aliquots was taken and quenched in 900 μl of solution containing 5:4 acetonitrile/ultrapure water + 0.1% TFA and 0.2 mM benzyl alcohol (internal standard).

  Table 13. Detailed reaction conditions including substrate concentration, reaction volume, enzyme, and cofactor loading.   For (S)-5a–d and (S)-5g–h, product conversion was determined by measuring HPLC peak area and comparing with that of synthesized standard. Results and Discussion Amine (S)-5a was produced in 84% conversion and 96% ee via SOI-catalyzed isomerization of trans-β-methyl epoxide 1a to generate 3a in situ, spontaneous racemization, and HnTA- catalyzed enantioselective amination. Using the cell-free system, amine (S)-5a was prepared from 1a with 90% ee and isolated using straightforward procedures to give 68% yield. 2a was also converted successfully to (S)-5a in 68% yield and 95% ee. While 2-methylphenyl substituted amine (S)-5b was obtained from 2b in moderate ee (79%) and 86% conversion, it could be produced in high ee (91%) and 60% conversion from 1b (Table 14). Other aryl substituted amines ((S)-5c–e, (S)-5g–h) could also be produced using this system, albeit with lower conversions and moderate ee (62–86%) due to the lower enantioselectivity of HnTA for them. Similar to the isomerization-racemization-oxidation cascades, the possibility of two types of epoxide substrates is advantageous in the isomerization-racemization-amination cascades using MmTA or HnTA. For example, the α-methyl epoxides 2g and 2h were better substrates than the corresponding trans-β-methyl epoxides to produce (R)-5g and (R)-5h respectively. Overall, the present cascade systems are potentially useful to produce a range of stereo-complementary (R)- and (S)-2-arylpropyl amines 5 in high yield and ee, by incorporating a (R)- or (S)-enantioselective TA, respectively. Table 14 Biocatalytic cascade conversion of racemic epoxides 1 or 2 to (S)-5 using cell-free system.   ^a) Yield and ee determined by HPLC. ^b) Isolated yield (if any) is given in parentheses. ^c) General conditions for cell-free system: 3 g _protein /L CFE containing SOI, 3 g/L HnTA, 1 mM PLP, 125 mM isopropylamine, 100 mM KP buffer (pH 7), 2%v/v DMSO, 30 °C, 16 h. The novel concept of one-pot cascade transformations consisting of multiple enzymatic reactions involving DKR to convert racemic substrates to produce high-value chiral chemicals in high ee and high yield was successfully proven. Unique cascade reactions of racemic epoxides to produce (S)-2-arylpropionic acids, (R)- and (S)-2-arylpropyl amines were demonstrated, consisting of SOI-catalyzed Meinwald rearrangement of racemic epoxides for in situ generation of 2-arylpropanal, spontaneous racemization of 2- arylpropanal, and ADH-catalyzed (S)-enantioselective oxidation or TA-catalyzed (R)- or (S)- enantioselective amination, respectively. High-yielding synthesis with the cascades was achieved by using isolated enzymes as well as whole-cell biocatalysts expressing the required enzymes. The cascade reactions can accept two classes of racemic methyl-substituted epoxides – trans-β-methyl epoxide or α- methyl epoxide – which are stable and easily accessible. Both racemic trans-β-methyl epoxides 1 and racemic α-methyl epoxides 2 can be accessed via well-established chemical methods. The cascade biotransformations of the racemic epoxides successfully produced (S)-arylpropionic acids, (R)-arylpropyl amines and (S)-arylpropyl amines in generally high ee and yield. These products possess various aryl group substitutions and include drug molecules and their precursors. The ee and yields of the desired products generated from the present cascade concept could be further improved by extensive screening of existing ADHs and TAs, engineering of ADH9v1, MmTA and HnTA with enhanced enantioselectivity and activity, and efficient co-factor regeneration. The substrate scope of the present cascade reactions involving DKR starting from racemic epoxides is wider than previously reported cascade biotransformations from methyl styrenes in which the enantioselectivity is determined by the styrene monooxygenase-catalyzed epoxidation step. The cascade reactions involve SOI-catalyzed redox-neutral isomerization of epoxides for the in situ generation of 2-arylpropanal intermediates, which was shown to reduce side reaction associated with aldehyde instability, when compared with DKR reactions involving direct enzymatic oxidation or amination of unstable 2-arylpropanals.   The present developed concept could contribute to the engineering of new multi-enzymatic cascade reactions involving DKR for green and sustainable synthesis of valuable chiral chemicals in high ee and yield from easily available racemic starting materials. The developed cascade reactions using cell-free or whole-cell systems are potentially useful for the practical synthesis of pharmaceutically useful (S)-2-arylpropionic acids, (R)- and (S)-2- arylpropyl amines.