CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. Patent application Serial Number 07/451,675 filed December 14, 1989 which is incorporated herein by reference.

Background of the Invention The present invention relates to a process for the production of hydantoins and glycines. More particularly, the invention relates to a process for the preparation of 5-(4'- hydroxyphenyl)hydantoin and p-hydroxyphenylglycine, in particular D-p-hydroxyphenylglycine from 4-hydroxyacetophenone.

5-(4'-Hydroxyphenyl)hydantoin is an important intermediate in the production of D-4-hydroxyphenylglycine which is employed for preparing semi-synthetic penicillins and cephalosporins. It is known that 5-(4'-hydroxyphenyl)hydantoin may be synthesized by the reaction of 4-hydroxybenzaldehyde, ammonium bicarbonate and sodium cyanide according to Bucherer-Berg's method. However, this method requires the use of dangerous sodium cyanide, and further, the obtained crude hydantoin may contain large quantities of by-products caused by the oxidative side reaction of the phenol nucleus under an alkaline condition or may be colored.

U.S. Patent 4,230,869 provides a process for preparing 5-(4'- hydroxyphenyl)hydantoin by reacting glyoxyliσ acid, urea and phenol in the presence of an acid. One disadvantage of this method is the requirement of heating to 40°C to 100°C to drive the reaction. 5-(4 ^, -hydroxyphenyl)hydantoins have also been prepared by reacting allantoin with phenol in the presence of acids as taught in Japanese Kokai 78/112874.

In the prior art, D-4-hydroxyphenylglycine has been generally prepared by chemically subjecting DL-4-hydroxyphenylglycine to optical resolution. However, such a process has the disadvantage that DL-4-hydroxyphenylglycine must be converted to derivatives such as esterification and acylation products prior to subjecting it to optical resolution, or resolving reagents are required, and also process steps are required for racemizing the residual L- form.

It is also known in the art that D-4-hydroxyphenylglycine may be prepared by the enzymatic or alkali hydrolysis of 5-(4'- hydroxypheny1)hydantoin. In this regard one may refer to Takehashi, Microbial Production of D-p-Hvdroxyphenylσlvcine. Prog. Ind. Microbiol. 24(Biotechnol. Amino Acid Prod.) 269-79 (1986) and U.S. Patent 4,436,510 which are incorporated herein by reference.

In U.S. Patent 3,094,741, which is incorporated herein by reference, it is disclosed that DL-5-(4-hydroxyphenyl)hydantoin can be almost quantitatively converted to D-N-carbamoyl-(4- hydroxyphenyl)glycine by causing cells or treated cells of specific microorganisms to act on the hydantoin in an aqueous medium at pH 7 to 10. D-N-carbamoyl-(4-hydroxyphenyl)glycine can be converted into D-4-hydroxyphenylglycine in high yields, for

instance by reacting it with an equimolar amount of nitrous acid in the presence of a strong acid.

The method of preparing the foregoing hydantoin and glycine compounds according to the present invention proceeds according to an improved method commencing with a hydroxyaromatic ketone, specifically 4-hydroxyacetophenone. The process is a one pot, two step reaction which commences by first anhydrously mixing 4- hydroxyacetophenone, a C^ to C5 alkyl nitrite, a C5 or less secondary alcohol, and anhydrous hydrogen chloride to form an intermediate; and then reacting the intermediate with urea, water and concentrated hydrochloric acid to thereby produce 5-(4'-hydroxyphenyl)hydantoin. Without being restricted to a particular theory, it is hypothesized that the reaction proceeds as follows.

The 4-hydroxyacetophenone (I) , which is present in solution initially, undergoes acid catalyzed tautomerization to the enol form (II) in the presence of the HCl. The enol then reacts with a nitrosonium ion (N0+) to form the alpha nitroso-4- hydroxyacetophenone (III) . (Ill) undergoes an acid catalyzed tautomerization yielding alpha-oximino-4-hydroxyacetophenone (IV) . The nitrosonium ion comes from the nitrosyl chloride which is generated from the reaction of HCl with isopropyl nitrite

(IPN + HCl > IPA + N0C1) . (IV) then undergoes a solvolysis reaction with the isopropanol solvent forming the diisopropyl

acetal of 4-bydroxyphenylglyoxaldehyde (V) . In the presence of water the acetal (V) undergoes hydrolysis yielding 4-hydroxyphenylglyoxaldehyde (VI) which condenses with urea to form the pinacol (VII) which in the presence of acid undergoes a pinacol rearrangement yielding the hydantoin (VIII) . None of these intermediates are isolated in the reaction and many are only present as equilibrium mixtures which are shifted forward as the result of product formation.

Step 1:

Step 2:

Summary of the Invention The invention provides a method for producing 5-(4'- hydroxyphenyl)hydantoin which comprises:

i) anhydrously admixing 4-hydroxyacetophenone, a C^ to C ₅ alkyl nitrite, a C ₅ or less secondary alcohol, and anhydrous hydrogen chloride to form an intermediate; and then ii) reacting said intermediate with urea, water and concentrated hydrochloric acid to thereby produce 5-(4'- hydroxyphenyl)hydantoin.

The invention also provides a method for producing p-hydroxyphenylglycine which comprises:

i) anhydrously admixing 4-hydroxyacetophenone, a C^ to C5 alkyl nitrite, a C ₅ or less secondary alcohol, and anhydrous hydrogen chloride to form an intermediate; and then ii) reacting said intermediate with urea, water and concentrated hydrochloric acid to thereby produce 5-(4'- hydroxyphenyl)hydantoin; and then iii) hydrolyzing 5-(4'-hydroxyphenyl)hydantoin to thereby produce p-hydroxyphenylglycine.

The invention further provides a method for producing D-p-hydroxyphenylglycine which comprises:

i) anhydrously admixing 4-hydroxyacetophenone, a C to C5 alkyl nitrite, a C5 or less secondary alcohol, and anhydrous hydrogen chloride to form an intermediate; and then ii) reacting said intermediate with urea, water and concentrated hydrochloric acid to thereby produce 5-(4'- hydroxypheny1)hydantoin; and then iii) hydrolyzing 5-(4'-hydroxyphenyl)hydantoin to thereby produce p-hydroxyphenylglycine; and then iv) optically resolving p-hydroxyphenylglycine to produce D-p-hydroxyphenylglycine.

The invention still further provides a method for producing D-p-hydroxyphenylglycine which comprises:

i) anhydrously admixing 4-hydroxyacetophenone, a C^ to C ₅ alkyl nitrite, a C ₅ or less secondary alcohol, and anhydrous hydrogen chloride to form an intermediate; and then ii) reacting said intermediate with urea, water and concentrated hydrochloric acid to thereby produce 5-(4'- hydroxyphenyl)hydantoin; and then iii) enzymatically hydrolyzing 5-(4'-hydroxyphenyl)hydantoin to thereby form D-5-(4'-hydroxyphenyl)hydantoic acid, and then iv) decarbamoylating D-5-(4'-hydroxyphenyl)hydantoic acid to thereby form D-p-hydroxyphenylglycine.

Detailed Description of the Preferred Embodiment In the practice of the present invention, one begins the two step procedure of producing 5-(4'-hydroxyphenyl)hydantoin by reacting a composition which is broadly composed of 4-hydroxyacetophenone, a C;L to C ₅ alkyl nitrite, a C ₅ or less secondary alcohol, and anhydrous hydrogen chloride to form an intermediate.

The composition uses a C- to C ₅ alkyl nitrite component, which is most preferably isopropyl nitrite or t-butyl nitrite. This component is preferably present in the composition in an amount of from about 1 to about 3 mole equivalents of the amount of 4-hydroxyacetophenone, more preferably from about 1 to about 2.5 mole equivalents and most preferably from about 1 to about 2.0 mole equivalents.

The composition then contains a C ₅ or less secondary alcohol. In the most preferred embodiment this component is isopropyl alcohol or sec-butyl alcohol. It is preferably present in a large excess of that amount required for the reaction or from about 2 to about 10 times the weight of the 4-hydroxyacetophenσne or more preferably from about 2 to about 5 times the weight of the 4-hydroxyacetophenone.

The composition then contains anhydrous hydrogen chloride. Theoretically, it is should be present in at least a catalytic amount, however, it is preferably present in the composition in

an amount of from about 0.1 to about 6 mole equivalents of the amount of 4-hydrσxyacetophenone, more preferably from about 0.1 to about 3 mole equivalents and most preferably from about 0.1 to about 2 mole equivalents.

It presently appears that the components of the first reaction step may be combined in any order. The first reaction step is exothermic and requires no heating to drive the reaction. The reaction may be cooled to a convenient working temperature. In the preferred embodiment, the first step is conducted at a temperature of from about -10°C to about 50°C, or more preferably from about 0°C to about 40°C or most preferably from about 0°C to about 25°C.

In the preferred embodiment, the first step is conducted for from about 1 hour to about 24 hours, or more preferably from about 1 hour to about 8 hours, and most preferably from about 1 hour to about 4 hours.

In the second reaction step, the intermediate resulting from the first step is reacted with urea, water and aqueous concentrated hydrochloric acid to thereby produce 5-( '-hydroxyphenyl)- hydantoin.

In the preferred embodiment, the urea is present in an amount of from about 1 to about 4 mole equivalents of the amount of

4-hydroxyacetophenone, more preferably from about 1 to about 3 mole equivalents and most preferably from about 1 to about 2 mole equivalents.

In the preferred embodiment, the water is present in the mixture in a large excess of that amount required for the reaction, preferably from about 0.1 to about 3 times the weight of the alcohol, or more preferably from about 0.5 to about 2.5 times the weight of the alcohol, and,most preferably about 0.5 to about 1.5 times the weight of the alcohol.

In the preferred embodiment, the concentrated hydrochloric acid is theoretically present in at least a catalytic amount, however, it is preferably present in the composition in an amount of from about 0.1 to about 8 mole equivalents of the amount of 4-hydroxyacetophenone, more preferably from about 0.1 to about 4 mole equivalents and most preferably from about 0.1 to about 2 mole equivalents.

It additionally appears that the components of the second reaction step may be combined in any order. The second reaction step does require heating to drive the reaction. In the preferred embodiment, the second step is conducted at a temperature of from about 40°C to about 100°C, or more preferably from about 50°C to about 100°C, and most preferably from about 50°C to the reflux temperature of the solution.

In the preferred embodiment, the second step is conducted for from about 0.5 hour to about 24 hours, or more preferably from about 0.5 hour to about 8 hours, and most preferably from about 1 hour to about 5 hours.

In the preparation of p-hydroxyphenylglycine, the thusly prepared 5-(4'-hydroxyphenyl)hydantoin is hydrolyzed. Methods of hydrolysis are known in the art per. se. The hydrolysis may be conducted by reacting the crude 5-(4'-hydroxyphenyl)hydantoin with an aqueous sodium hydroxide solution containing hydroxylamine yielding 5-(4'-hydroxyphenyl)hydantoic acid. Upon treatment with nitrous acid, p-hydroxyphenylglycine is formed.

Resolution

There are many optical resolution techniques known in the art whereby a racemic mixture of DL-p-Hydroxyphenylglycine can be resolved to D-p-Hydroxyphenylglycine. Such may be performed with d-3-bromocamphor-3-sulfonic acid; aromatic sulfonic acids, such as benzenesulfonic acid, o-toluenesulfonic acid, p- toluenesulfonic acid, p-ethylbenzenesulfonic acid, sulfosalicylic acid, and 2-naphthol~6-sulfonic acid; and (+)- phenylethanesulfate. In an alternative method, DL-5-(4- hydroxyphenyl)hydantoin can be converted into D-N-carbamoyl-(4- hydroxyphenyl)glycine, i.e. D-( -hydroxyphenyl)hydantoic acid and the latter is then decarbamoylated into D-4-hydroxyphenylglycine.

It is known from U.S. Patent 3,094,741, that DL-5-(4- hydroxyphenyl)hydantoin can be converted into D~N-carbamoyl-(4- hydroxyphenyl)glycine by causing cells or treated cells of specific microorganisms to act on the hydantoin in an aqueous medium at pH 7 to 10. D-N-carbamoyl-(4-hydroxyphenyl)glycine can be converted into D-4-hydroxyphenylglycine by decarbamoylation by reacting D-N-carbamoyl-(4-hydroxyphenyl)glycine with an equimolar amount of nitrous acid in the presence of a strong acid.

A racemic mixture of p-hydroxyphenylhydantoin may be converted to D-p-hydroxyphenylglycine according to the method of Takahashi, S. "Microbial Production of D-p-Hydroxyphenylglycine", Prog. Ind. Microbiol., 24 (Biotechnol. Amino Acid Prod.), 269-279 (1986), which is incorporated herein by reference.

Transformation of p-hvdroxyphenylhydantoin into N-Carbamoyl-D- hydroxyphenylqlycine (D-hydroxyphenylhvdantoic acid)

Enzyme preparation

For the industrial production of D-p-hydroxyphenylglycine, the microorganism employed in the asymmetric hydrolysis of p-hydroxyphenylhydantoin is selected from wild strains by examining the hydantoinase activity and its stereoselectivity. Such microorganisms can be found in a wide range of genera, high activity is especially found in bacteria. Cells with high

hydantoinase activity can be obtained by culturing the microorganism in a medium supplemented by pyri idine base or their metabolites such as uracil, thymine, or Beta-alanine as the inducer. The accumulation of hydantoinase in cells is further increased, when a metal ion such as manganese, nickel, or magnesium is added in the medium together with the inducer.

Asymmetric hydrolysis of p-hydroxyphenyl hydantoin In the reaction of the asymmetric hydrolysis of p-hydroxyphenylhydantoin, racemic p-hydroxyphenyl hydantoin can be completely transformed into N-carbamoyl-D-p- hydroxyphenylglycine by the action of microbial hydantoinase. Generally hydantoins are readily racemized in dilute alkaline solution through the mechanism of base catalysis. In practice, p-hydroxyphenyl hydantoin undergoes spontaneous racemization very easily under mild conditions such as those of the enzymatic reaction. In the reaction system of the asymmetric hydrolysis of p-hydroxyphenylhydantoin, only D-form p-hydroxyphenylhydantoin is susceptible to the enzymatic hydrolysis. Unreactive L-p- hydroxyphenylhydantoin undergoes rapid spontaneous racemization in the same system. However, the N-carbamoyl-D-p- hydroxyphenylglycine formed is never racemized under these conditions. Consequently, in this system, the enzymatic hydrolysis of the hydantoin ring and chemical racemization of the substrate proceed simultaneously, so that DL~p-hydroxyphenyl

15

hydantoin can be completely transformed into D-form N-carbamoyl- p-hydroxyphenylglycine.

The microorganism is employed in a form of cultured broth, with intact cells or treated cells used as an enzyme for the hydrolysis. In many cases, the smooth reaction can be performed by using the cultured broth as is. The high concentration of the substrate DL-p-hydroxyphenylhydantoin is available to the reaction depending upon the activity of microorganism used. A large portion of p-hydroxyphenylhydantoin is present in suspended form, since the solubility of p-hydroxyphenylhydantoin in water is very low (50-75 mM) . However, the substrate is successively dissolved in the progress of the reaction in alkaline pH. It is preferable to maintain the pH by adding alkaline solution successively, since the pH is lowered in the course of hydrolysis and the drop in pH will result in lowering the reaction rate. It is also effective to cover the reaction mixture with an inert gas such as nitrogen to avoid oxidative side reaction of phenol nucleus. Under these optimum conditions, the yield of N- carbamoyl-D-p-hydroxyphenylglycine formed is almost quantitative.

Decarbamoylation of N-Carbamoyl-D-p-hydroχyphenylqlycine N-Carbamoyl-D-p-hydroxyphenylglycine produced by the enzymatic hydrolysis can be readily converted into

D-p-hydroxyphenylglycine by decarbamoylation with nitrous acid under acidic conditions. The principle of this oxidative reaction

is based on the Van Slyke determination, and the reaction seems to be a consecutive reaction as follows. With respect to the stereochemistry of the reaction, the retention of the configuration is achieved, completely. Therefore, optically pure D-p-hydroxyphenylglycine can be readily obtained in good yield. The decarbamoylation is preferably carried out by reacting N- carbamoyl-D-p-hydroxyphenylglycine with an approximately equimolar nitrous acid in an aqueous medium in the presence of a strong mineral acid such as sulfuric or hydrochloric acid. It is convenient to employ a water-soluble salt of nitrous acid such as sodium nitrite or potassium nitrite. Since this decarbamoylation is an exothermic reaction and generates large quantities of gas (N ₂ and CO2) , an aqueous solution of nitrous acid is added gradually to the reaction medium with agitation to perform the smooth reaction. The reaction temperature is usually kept below 20°C in order to avoid a side reaction such as the further degradation of D-p-hydroxyphenylglycine into 4-hydroxymandelic acid and others. Under these optimum conditions, the yield of D- p-hydroxyphenylglycine from N-carbamoyl-D-p-hydroxyphenylglycine is almost quantitative. A chemico-enzymatic process, attractive from economical and technical standpoints, was developed for the production of D-p-hydroxyphenylglycine. In the first step of the process, DL-p-hydroxyphenylhydantoin is synthesized. In the second step, DL-p-hydroxyphenyl hydantoin is completely hydrolyzed into N-carbamoyl-D-p-hydroxyphenylglycine by microbial hydantoinase. In the third step, N-σarbamoyl-D-p-

hydroxyphenylgjycine is then transformed into D-p- hydroxyphenylglycine by chemical reaction. This simplified process provides high optically pure D-p-hydroxyphenylglycine in high yield.

The following non-limiting examples serve to illustrate the invention.

Example 1 A 250 ml three neck round bottom flask is charged with 100 ml isopropanol and sparged with HCl for 5 minutes. Then 20 g of 4-hydroxyacetophenone are added forming a red solution. The flask is then fitted with a thermowell, a reflux condenser and an addition funnel containing 22 ml of crude isopropyl nitrite and 20 ml isopropanol. The reflux condenser is fitted with a oil filled U-tube and the contents heated with a water bath to 40°C. The contents of the addition funnel are added dropwise over a one hour period while the temperature is held between 40 - 50°C. The contents are held at 50°C for 4 hours and then allowed to stand at room temperature overnight. The next morning 18 g of urea are slurried with 20 ml water and then added to the flask followed by 18 ml of concentrated HCl. The contents are refluxed for 5 hours and then allowed to stand overnight. The next day the solids are filtered, washed with 100 ml water and then dried in a vacuum oven at 60°C overnight yielding 18 g of light yellow solids. HPLC analysis reveals that the solids are about 56%

5-( '-hydroxyphenyl)hydantoi .

Example 2 A 2000 ml three neck round bottom flask is charged with 500 ml isopropanol and gently sparged with HCl for 5 minutes. Then 100 g of 4-hydroxyacetophenone are added and dissolved with stirring. The flask is then fitted with a thermowell, a reflux condenser and an addition funnel containing 110 ml of crude isopropyl nitrite and 110 ml isopropanol. An ice bath is placed around the flask and the contents of the addition funnel added dropwise while stirring over a 1 hour period. The temperature is held between 4 - 8°C during the addition. After the addition is complete the contents are sparged with HCl for 5 minutes and then allowed to stand stirring at room temperature for 1.5 hours. Then a slurry of 90 g urea and 100 ml water are added to the flask followed by 90 ml concentrated HCl. The contents are then refluxed for 1.5 hours and allowed to stand overnight at room temperature. The next day the slurry is cooled to 5°C and filtered. The solids are then dried on a rotovap at 60°C for 1 hour yielding 85 g of solids which prove to be about 72% 5-(4'-hydroxyphenyl)hydantoin by HPLC.

Example 3 A 500 ml three neck round bottom flask is fitted with a thermowell, a reflux condenser (capped with an oil filled U-

tube), and an addition funnel. The flask is charged with 100 ml of 13.5% HCl/isopropanol solution and 40 g 4-hydroxyacetophenone. The addition funnel is charged with 36 ml of crude isopropyl nitrite and 36 ml isopropanol. An ice bath is placed around the stirred flask and the contents of the addition funnel added dropwise over a 2 hour period while holding the temperature between 0 - 10°C. After the addition is complete the contents are allowed to stir at room temperature for 2 hours. Then 40 g of urea are dissolved in 40 ml water and added to the flask followed by 20 ml of concentrated HCl. The contents are then refluxed for 1 hour and allowed to stand stirring at room temperature overnight. The next day the slurry is cooled to 5°C, filtered and washed with 100 ml cold water. The solids are dried on the rotovap at 60°C for 2 hours yielding 25.5 g of material which proves to be about 70% 5-(4'-hydroxyphenyl)hydantoin by HPLC.

Example 4 A 500 ml three neck round bottom flask is fitted with a thermowell, a reflux condenser (capped with an oil filled U- tube) , and an addition funnel. The flask is charged with 25 ml of 28.3% HCl/isopropanol solution, 50 ml isopropanol, and 40 g 4-hydroxyacetophenone. The addition funnel is charged with 36 ml of crude isopropyl nitrite and 36 ml isopropanol. The flask contents are stirred and cooled with an ice bath while the

contents of the addition funnel are added dropwise over a 2 hour period. During the addition the temperature is held between 5 - 10°C. The contents are then allowed to stand stirring at room temperature for 2 hours. Next 40 g of urea are dissolved in 80 ml of water and added to the flask followed by 25 ml concentrated HCl. The contents are refluxed for 2 hours and during this time 125 ml of distillate removed. The slurry is cooled to 5°C and the solids filtered and washed with 100 ml cold water. After drying in the rotovap at 60°C for 2 hours, 38.7 g of material is realized. HPLC analysis reveals that the material is 68.8% 5-(4'-hydroxyphenyl)hydantoin.

Example 5 A 250 ml round bottom flask is fitted with a thermowell, a reflux condenser (capped with an oil filled U-tube) , and an addition funnel. The flask is charged with 25 ml of 28.3% HCl/isopropanol solution, 57 ml isopropanol, and 20 g 4-hydroxyacetophenone. The addition funnel is charged with 20 ml t-butyl nitrite. A water bath is placed around the flask and the contents stirred while the t-butyl nitrite is added in 2-3 ml portions over a 30 minute period and the temperature held between 20 - 0°C. The contents are allowed to stir at room temperature for 30 minutes and an additional 4 ml of crude t-butyl nitrite added followed by 25 ml of 28.3 HCl/isopropanol solution. The contents of the flask are allowed to stand stirring at room temperature over the weekend.

Then 20 g of urea are added and allowed to stir for 10 minutes. Next, 50 ml of water and 15 ml concentrated HCl are added and the contents refluxed for 4 hours. After refluxing, the slurry is cooled to 5°C and the solids filtered and washed with 25 ml cold water. The solids are dried overnight in the vacuum oven at 60°C yielding 15.3 g of material that proves to be about 74% 5-(4'-hydroxyphenyl)hydantoin.

Example 6 A 250 ml round bottom flask is fitted with a thermowell, a reflux condenser (capped with an oil filled U-tube) , and an addition funnel containing 18 ml of crude isopropyl nitrite. The flask is charged with 25 ml of 28.3 HCl/isopropanol solution, 57 ml isopropanol, and 20 g 4-hydroxyacetophenone. The contents of the flask are stirred and a water bath placed around the flask. Then the contents of the addition funnel are added into the flask in 2-3 ml portions over a 30 minute period while the temperature is held between 20-30°C. The contents are allowed to stand stirring at room temperature for 30 minutes and an additional three 3 ml portions of isopropyl nitrite are added. The contents are then allowed to stir overnight at room temperature and the next day 20 g of urea are added. After stirring for 10 minutes, 50 ml of water and 15 ml concentrated HCl are added. The contents are then refluxed for 4 hours. The resulting slurry is cooled to 5°C with an ice bath and the solids filtered and washed with 25 ml

cold water. The wet cake is then recrystallized from acetic acid yielding 9.3 g of substantially pure 5-(4'-hydroxyphenyl)hydantoin by HPLC analysis.

Example 7 A 500 ml three neck round bottom flask is fitted with a thermowell, an addition funnel, and a reflux condenser (capped with an oil filled U-tube) . The flask is charged with 50 ml of isopropanol, 50 ml of 25% HCl/isopropanol solution, and 40 g

4-hydroxyacetophenone. The contents are cooled in an ice bath and 62 ml of crude isopropyl nitrite placed in the addition funnel. The contents of the addition funnel are added dropwise to the flask over a 60 minute period while stirring and holding the temperature between 0 - 10°C. The contents are then allowed to stand stirring at room temperature overnight. The next day 40 g of urea are dissolved in 100 ml of water and added to the flask. After stirring for 15 minutes, 20 ml of concentrated HCl is added to the flask and the contents refluxed for 4 hours. During this time 100 ml of distillate is removed from the flask. After the reflux is ccmpleted, the contents are cooled to 5°C and the slurry filtered. The solids are washed with 25 ml of cold water and dried overnight in a vacuum oven at 60°C yielding 38 g of solids which proves to be 72.3% 5-( '-hydroxyphenyl)hydantoin by HPLC analysis.

Example 8 A 250 ml round bottom flask is fitted with a thermowell, an addition funnel, and a reflux condenser (capped with an oil filled U-tube). The flask is charged with 57 ml isopropanol, 25 ml of 28.3% HC3./isopropanol solution and 20 g

4-hydroxyacetophenone. The addition funnel is charged with 20 ml of t-butyl nitrite and the contents of the flask stirred. The contents of the additional funnel are added to the stirred flask in 2-3 ml portions over a 30 minute period while the temperature is held between 20 - 40°C. After the addition is complete the contents are allowed to stand stirring at room temperature for 30 minutes, then an additional 4 ml of t-butyl nitrite are added followed by 25 ml of 28.3% HCl/isopropanol solution. The contents are allowed to stand stirring over the weekend at room temperature. Then 20 g of urea are added to the flask and the contents stirred for 10 minutes at which time 50 ml of water, and 15 ml of concentrated HCl are added to the flask. The contents are refluxed for 4 hours and then cooled to 5°C and the slurry filtered. The solids are washed with 25 ml of cold water and dried in a vacuum over at 60°C overnight yielding 15.3 g of material which proves to be 73.5% 5-(4'-hydroxyphenyl)hydantoin by HPLC analysis.

Example 9 p-Hydroxyphenylqlvcine

A 250 ml round bottom flask is charged with 10 g of crude 5-(4'- hydroxyphenyl)hydantoin (ca. 74.5% pure). 8 g NaOH, 5 g hydroxylamine sulfate, and 100 ml of water. The contents are stirred to dissolve the solids and then brought to reflux. After refluxing for 30 minutes the solution is hot filtered through a pad of Celite. Then 60 ml of concentrated HCl are added to the filtrate and the solution cooled in a ice bath. The cold slurry is filtered and the solids washed with 50 ml of cold water. The solids are dried in a vacuum oven at 60°C overnight yielding 6.0 g of essentially pure 5-(4'-hydroxyphenyl)hydantoic acid. A 2 g sample of the 5-(4'-hydroxyphenyl)hydantoic acid is dissolved in 20 ml of concentrated hydrochloric and cooled in an ice bath. Over a 45 minute period 6.5 g of 10% aqueous sodium nitrite solution is added dropwise to the flask (while still in the ice bath) . The contents are allowed to stand for 1 hour in the ice bath and then concentrated on the rotovap at 75°C. The pH is then adjusted to 4 with concentrated ammonium hydroxide. The slurry is cooled in an ice bath and then filtered. The solids are washed with 30 ml of cold water and dried in an oven at 145°C for 1 hour yielding 1.3 g of material which proves (via HPLC) to be ca. 65.1% p-hydroxyphenylglycine and ca. 27.9% unreacted 5-(4'-hydroxyphenyl)hydantoic acid.

Example 10 Preparation of p-Hydroxyphenγlhvdantoic Acid

25

Crude 5-(p-hydroxyphenyl)hydantoin (85.6 g) is placed in a 1- liter round bottom flask with 4/g hydroxyla ine sulfate, 1 g a ₂ S ₂ 4, 60 g NaOH, and 300 ml H ₂ 0. The contents are refluxed for 1 hour and then cooled in an ice bath. Then 125 ml cold concentrated HCl are added. The solids are filtered and washed with 200 ml H ₂ 0. The solids are dried in a vacuum oven at 60°c over the weekend yielding 58.8 g of ca. 95% pure p- hydroxyphenylhydantoic acid (by HPLC analysis) .

Example 11 Hydrolysis of p-Hvdroxyphenylhvdantoic Acid p-Hydrcxyphenyl hydantoic acid (19 g) is dissolved in 200 ml of cold concentrated HCl in a 500 ml flask. The flask is cooled in an ice bath and a solution of 6.5 g NaN0 ₂ in 56 ml H ₂ 0 is added dropwise ever a 45 minute period while the temperature is held between 0-8°C. The solution is allowed to stand stirring in the ice bath for 2 1/2 hours and then stand at room temperature overnight. The next day the pH is adjusted to ^" 5 with concentrated NH OH. The solution is concentrated on a rotovap to ^" 250 ml. The slurry is cooled in an ice bath and then filtered. The solids are washed with 2-25 ml portions of ice water. The solids are then placed in a round bottom flask with 700 ml water and 1 g activated carbon. The contents are stirred and refluxed for 30 min, and then hot filtered through a pad of Celite. The solution is concentrated on a rotovap to ^" 350 ml (the cloud

point) and then cooled in an ice bath. The white solids are filtered and washed with 50 ml ice water. After drying in a vacuum oven (60°c) over the weekend 6.2 g of white needles with a mp 222°C is obtained. HPLC analysis reveals the sample is 99.8% pure p-hydroxyphenylglycine.

REFERENCE EXAMPLE 1 D-Hydroxyphenylglycine may be resolved according to the method described in Ya ada, et al, "Preparation of D-p- Hydroxyphenylglycine. Optical Resolution of DL-p- Hydroxyphenylglycine with d-3-Bromocamphor-8-Sulfonic Acid", Agric. Biol. Chem. 43(2), 395-396, 1979, which is incorporated herein by reference.

D-camphor ([a]j ₎ ° - 44.0°, c=7.5), in ethanol is prepared as follows: Bromine (320 g) is added dropwise to d-camphor (304 g) at 80°C over a period of three hours under stirring and the liquified reaction mixture is kept at the same condition for 3 hours. After hydrogen bromide is released by bubbling, the reaction mixture is poured into ice water (3 liters) and the resulting precipitate is recrystallized from ethanol (230 mol) to give d-3-bromocamphor (302 g) , mp 76°C [a] ² ₎ ⁰ - 134° (c=10, EtOH). d-3-bromocamphor (231 g) is dissolved in chloroform (400 ml) and chlorosulfonic acid (233 g) are added dropwise to this solution over 1 hour at 50°C. The reaction mixture is refluxed for 12

hours and poured into iced water (1 liter) . The layer and washings are neutralized with Ca(0H) ₂ (120 g) , and precipitated CaS0 ₄ is filtered off. To the filtrate (NH ₄ ) ₂ C0 ₃ (128 g) are added and the precipitated CaC0 ₂ is removed. The filtrate is concentrated and crystallized crude ammonium d-bromocamphor sulfonic acid (152 g) is recrystallized from water (270 ml) to give ammonium d-bromocamphor sulfonic acid (102 g) , p. 270-272°C(dec) , [a]g° -85.3° (c=2, water), lit. [a] ² , ² -85.3° (c=4, water), [a] _D ° -84.5° (c=1.6, water). Calculated for NH ₄ C ₁₀ H _L4 θ ₂ 4SBr: C, 36.59: II, 5.53: N, 4.27. Ammonium d- bromoca phor sulfonic acid obtained above is passed through Amberlite IR-120, and the effluent is concentrated to dryness and used as free d-bromocamphor sulfonic acid monohydrate. Analysis: All samples are dried overnight in vacuo at 40°C. Melting points are measured with a Yamato MP-21 melting point apparatus in an unsealed capillary tube and are unσorrected. Optical rotations are measured with a Perkin-El er 141 automatic polarimeter.

Optical Resolution of DL-p-hvdroxyphenylqlycine with d-3- bromocamρhor-3-sulfonic acid.

A mixture of DL-hydroxyphenylglycine (30.0 g) and d-bromocamphor sulfonic acid monohydrate (59.1 g) is dissolved in water (290 ml) at 95°C and stirred at 25°C for 2 hours. The precipitated crystals are filtered, washed with a small amount of cold water and dried to give crude D-p-hydroxyphenylglycine'd-bromocamphor sulfonic acid (40.2 g) , [a]g ³ -4.9° (c=l, IN HCl). The crude

salt (40.0 g) is recrystallized from 0.5° d-bromocamphor sulfonic acid aqueous solution (300 ml) to give D-p- hydroxyphenylglycine-d-bromocamphor sulfonic acid (35.5 g) , [a]g ³ -2.9°, (c=l, IN HCl), mp 243-245°C (dec). Analysis - Found: C, 45.17; H, 5.11; N, 2.93; S, 6.94. The product is optically and chemically pure. The specific rotation of a mixture of DL-p- hydroxyphenylglycine and equivalent amount of d-bromocamphor sulfonic acid is [ajf _j ³ -54.7° (c=l, IN HCl) and that of authentic DL-p-hydroxyphenylglycine is [a] ² _; ³ -2.9° (c=l, IN HCl).

Preparation of D-p-Hydroxyphenylqlycine

The pure D-p-hydroxyphenylglycine'd-bromocamphor sulfonic acid (30.0 g) obtained above is dissolved in water (250 ml) at 95°C. The solution is adjusted at pH 6 with 2N NaOH (ca. 31 ml) , concentrated to about 70 g and stirred at 5°C for 2 hours. The precipitated crystals are filtered, washed with water and dried to give D-p-hydroxyphenylglycine (9.6 g) , [a]j) ⁵ -158.3° (c=l, IN HCl). Analysis - Found C, 57.70; H, 5.41, N, 8.33 calculated for C ₆ H ₉ NO, C, 57.48; H, 5.43, N, 8.38°.

Recovery of Optically Pure L-p-Hydroxyphenylqlvcine After the separation of less soluble D-p-hydroxyphenylglycine*d- bromocamphor sulfonic acid in the above resolution process, the mother liquor is adjusted at pH 6 with 2N NaOH, concentrated to about 130 g and stirred at 5°C for 2 hours. The precipitated crystals are filtered, washed with water, and dried to give

dried to give optically impure L-p-hydroxyphenylglycine (12.6 g)

[a] ² ₎ ⁵ -129.3° (C=l, IN HCl).

Racemization of optically impure L-p-Hydroxyphenylglvcine Optically impure L-p-hydroxyphenylglycine (10.0 g) obtained by the above procedure is dissolved in 2N HCl (30 ml) . The mixture is heated in an autoclave at 140°C for 12 hours. After the reaction, the mixture is adjusted at pH 6 with 2N NaOH and is stirred at 5°C for 2 hours. The precipitated crystals are filtered, washed with water and dried to give DL-p- hydroxyphenylglycine (9.2 g) , [a] ² , ⁵ -0.0° (c=l, IN HCl). The racemized p-hydroxyphenylglycine can be reused for resolution.

Reuse of d-3-bromocamphor-8-sulfonic acid

The sodium salt of d-bromocamphor sulfonic acid contained in the mother liquor after the separation of D- and L-p- hydroxyphenylglycine can be reused as a resolving agent by addition of an equivalent amount of hydrochloric acid. In the mother liquor, after the separation of D-p-hydroxyphenylglycine (9.6 g) in the preceding procedure, DL-p-hydroxyphenylglycine (9.1 g) and 2N HCl (31 ml) are added. The mixture is heated at 95°C for dissolution and stirred at 25°C for 2 hours. The precipitated crystals are filtered, washed with a small amount of cold water, and dried a give crude D-p-hydroxyphenylglycine* - bromocamphor sulfonic acid (14.7 g) [a] ² , ⁵ -3.9° (c=l, IN HCl).

90/06062

30

REFERENCE EXAMPLE 2 Optical Resolution of DL-p-hydroxyphenylqlvcine The following resolution method is suggested by Yamada, et al, "Preparation of D-p-hydroxyphenylglycine: Optical Resolution of DL-p-hydroxyphenylglycine By Preferential Crystallization Procedure", Λgric. Biol. Chem., 42(8), 1521-6, 1978, which is incorporated herein by reference.

In this example, D-, L-, and DL-p-hydroxyphenylglycine manufactured by Tanabe Seiyaku Co. Ltd. are used. Aromatic sulfonic acids, i.e. benzenesulfoniσ acid, o-toluenesulfonic acid, p-toluenesulfoniσ acid, p-ethylbenzenesulfonic acid, sulfosalicylic acid, and 2-naphthol-6-sulfonic acid are obtained from Tokyo Kasei Kogyo Co., Ltd. All samples are dried overnight in vacuo at 0°C. Melting points are measured with a Yamato MP- 21 melting point apparatus in an unsealed capillary tube and are uncorrected. Infrared spectra of samples are determined in KBr with a Shimazu infrared spectrophotometer. Model IR-27G. Optical rotations are measured with a Perkin-Elmer 141 automatic polarimeter. Elemental analyses are performed by using a Perkin- Elmer 240 elemental analyzer. Solubility is determined by approaching saturation equilibrium from the both sides of undersaturation and supersaturation. Solute concentration is measured with a Karl Zeiss immersion refractometer.

Preparation of aromatic sulfona es of p-hvdroxyphenylrlycine Aromatic sulfonates of p-hydroxyphenylglycine are prepared from p-hydroxyphenylglycine and an equimolar amount or a slight excess of the corresponding aromatic sulfonic acids in aqueous solution. In the case of DL-p-hydroxyphenylglycine*o-toluenesulfonic acid, a mixture of DL-p-hydroxyphenylglycine (200.0 g) and 1.05 equimolar amount of o-toluenesulfonic acid'2H ₂ 0 (261.6 g) are dissolved in water (800 ml) by heating, treaLed with charcoal and cooled in a refrigerator. The resulting precipitates and the second crop obtained by concentration of the mother liquor to about a half volume are collected, washed with cold water and dried. The total yield of DL-p-hydroxyphenylglycine*o- toluenesulfoniσ acid is 393.5 g (96.9%). The products are almost pure and can be used for optical resolution without further purification. D-and L-p-hydroxyphenylglycine*o-toluenesulfonic acid are prepared in the same way. The racemic modi ications and the optically active isomers of p- hydroxyphenylglycine'benzenesulfonic acid, p- hydroxyphenylglycine*p-toluenesulfonic acid, p- hydroxyphenylglyσine* -ethylbenzenesulfonic acid, p- hydroxyphenylglycine*εul osalicylic acid ^* H ₂ 0, and p- hydroxyphenylglycinG*2~naphthol-6-sulfonlc acid are similarly prepared as above in a high yield (85-95%) . For elemental analysis and determination of properties, p- bydroxypheny glycine*o-toluenesulfonic acid, p-

hydroxyphenylglycine*sulfosalicylie acid*H ₂ 0, and p- hydroxyphenylglycine*2-naphthol-6-sulfonic acid are recrystallized from water, p- hydroxyphenylglycine*benzenesulfonic acid, p- hydroxyphenylglycine*p-toluenesulfonic acid, and p- hydroxyphenylglyσin *p-ethylbenzenesulfonic acid are recrystallized from aqueous solutions of 0.5 M benzenesulfonic acid, 0.5 M p-toluenesulfonic acid, and 3 M p- ethylbenzenesulfonic acid, respectively.

Optical resolution

Optical resolution of the aromatic sulfonates of DL-p- hydroxyphenylglycine by the preferential crystallization procedure is carried out in the usual manner. In the case of DL- p-hydroxyphenylglycine-o-toluenesulfonic acid, DL-p- hydroxyphenylglycine*o-toluenesulfonic acid (24.00 g) and D-p- hydroxyphenylglycine*o-toluenesulfonic acid (2.50 g) are dissolved in water (100 ml) at an elevated temperature. The solution is cooled to 30°C, seeded with D-p- hydroxyphenylglycine*o-toluenesulfonic acid (0.10 g) , and stirred at the same temperature. By refractometric and polarimetric measurements of the liquid phase, it is observed that preferential crystallization of D-p-hydroxyphenylglycine*o- toluenesul.Conic acid remain in the solution. After 70 min, the precipitated crystals are collected by filtration, washed with a small amount of cold water, and dried to give D-p-

hydroxyphenylglycine*o-toluenesulfonic acid (5.30 g) , [a]^ ⁵ - 64.6° (c=l, water), optical purity 97.0%. In order to adjust the concentration of DL-p-hydroxyphenylglycine*o-toluenεsulfonic acid in the mother liquor to the same as that in the previous operation, DL-p-hydroxyphenylglycine*o-toluenesulfonic acid (5.38 g) and a small amount of water are added to the mother liquor after the separation of D-p-hydroxyphenylglycine ^• o- toluenesulfonic acid. Amounts of the added DL-p- hydroxyphenylglycine are calculated from the analyses of the solution. Thus, the composition of the solution is the same as that in the initial state except that the solution contained the L-isomer in excess. By seeding this supersaturated solution with L-p-hydroxyphenylglycine"o-toluenesulfonic acid (0.10 g) , preferential crystallization of L-p-hydroxyphenylglycin *o~ toluenesulfonic acid is carried out in the same manner as described above. By repeating these procedures, D- and L- isomers are successively obtained. Other sulfonates of DL-p- hydroxyphenylglycine can also be resolved in the same manner as described above.

Purification of optically impure D-p-hvdroxyphenylqlycine O- toluenesulfonic acid

The optical isomers obtained by the above procedure are practically pure. However, if further optical purification is required, it can be performed as follows. Optically crude D-p- hydroxyphenylglycine-o-toluenesulfonic acid (20.00 g, optical

purity 82.3%) is mixed with water (28.8 ml) for 20 hours at 20°C. The residual crystals are collected by filtration, washed with a small amount of cold water, and dried to give optically pure D-p- hydroxyphenylglycine*o-toluenesulfonic acid (16.20 g) , the yield being 98.4% based on D-isomer in the original optically crude D- p-hydroxyphenylglycine*o-toluenesulfonic acid.

Preparation of optically active D-p-hydroxyphenylqlycine From the optically pure sulfonates of p-hydroxyphenylglycine obtained above, optically pure p-hydroxyphenylglycine is obtained by neutralization with alkali or by use of ion exchange resins. In the case of p-hydroxyphenylglycine*o-toluenesulfonic acid, optically pure D-p-hydroxyphenylglycine-o-toluenesulfonic acid (14.00 g) is dissolved, in water (40 ml) at an elevated temperature and treated with charcoal. The solution is adjusted to pH 6 with 5 N sodium hydroxide and allowed to stand in a refrigerator overnight. The resulting precipitate is collected, washed with water, and dried to give D-p-hydroxyphenylglycine (5.82 g) , [a]g ⁵ -158.4° (c=l, N-HCl) . Anal. Calculated for C ₈ H ₉ N0 ₃ :C, 57.48; H,5.43;N,8.38. Found: C,57.63; H,5.63; N, 8.29.

Preparation of DL-p-hydroxyphenylglycine*o-toluenesulfonic acid by using recovered o-toluenesulfonic acid

To the mother liquor obtained after the separation of D-p- hydroxyphenylglycine in the above experiment, DL-p-

35 bydroxyphenylglycine (5.82 g) is added with 12 N IICl (3.5 ml) and dissolved by heating. The solution is concentrated to about 40 g, and cooled in a refrigerator. The resulting precipitates and the second crop obtained by concentration to about 13 g are collected, washed with cold water, and dried. The total yield of DL-p-hydroxyphenylglycine.o-toluenesulfonic acid is 12.10 g, [a] ^ - 11.3° (c=l, water). The product could be reused for resolution.

Racemization of optically active p-hvdroxyphenylglvcine.o- toluenesulfonic acid

A mixture of L-p-hydroxyphenylglycine*o-tolueneεulfσnic acid(4.00 g) and water (4 ml) is heated at 140°C for 12 hr in a sealed tube. The rate of racemization is as follows: 4 hours, 74.3%; 8 hours, 93.0%; 10 hours, 95.3%; 12 hours, 96.3%. The reaction mixture is cooled to 5°C. The resulting precipitates and the second crop obtained by concentration are collected, washed with cold water, and dried. The total yield of DL-p- hydroxyphenylglycine-o-toluenesulfonic acid is 3.4 g (85.0%), [ ] ² / ⁵⁵ - 1.8° (c=l, water). Anal. Found: C, 53.06; H, 5.08; N,4.11. The product itself could be reused for the resolution step.

REFERENCE EXAMPLE 3 This example demonstrates the optical resol'.ition of

D-hydroxyphenylglycine according to the method described in Hongo, et al, "Asymmetric Transformation of DL-p- Hydroxyphenylglycine by a Combination of Preferential Crystallization and Simultaneous Racemization of the o- Toluenesulfonate", Bull. Chem. Soc. Japan, 58, 433-436 (1985) which is incorporated herein by reference. Optically active and racemic hydroxyphenylglycine is used. o-toluenesulfonic acid, salicylaldehyde, and other chemicals are obtained from Tokyo Kasei Kogyo Co., Ltd. Optically active and racemic hydroxyphenylglycineO-toluenesulfonic acid are prepared in a mannsr described in the above example. All samples are dried overnight in vacuo at 40°C. Optical rotation is measured with a Perkin-Elmer 141 automatic polarimeter. The water content of samples is determined by the Karl-Fischer's method.

Racemization of L-hydroxyphenylglycine*o-toluenesulfonic acid A mixture of L-hydroxyphenylglycine*o-toluenesulfonic acid (50 mg) , DL-hydroxyphenylglycine (5 mg) , salicylaldehyde (3 ul) , and acetic acid containing 5% water (5 ml) is heated in a sealed tube at 100°C for 1 hour or 3 hours. After the reaction mixture is diluted with 1 M hydrochloric acid (5 ml (IM = 1 mol dm" ³ ) ) , the optical rotation is measured. The racemization degree is calculated in the same way as described in the previous example. The effect of DL-hydroxyphenylglycine or salicylaldehyde in acetic acid containing water and the effect of the reaction temperature are noted.

Crystallization of DL-hydroxyphenylglycine'o-Toluenesulfonic acid from Racemizinα Solution

A mixture of DL-hydroxyphenylglycine-o-toluenesulfonic acid (3.8 g) , DL-hydroxyphenylglycine (0.2 g) , and salicylaldehyde (0.25 ml) is dissolved in acetic acid (20 ml) containing 5% water, under reflux and maintained at 100°C. The solution is seeded with finely pulverized crystals of DL-hydroxyphenylglycine*o- toluenesulfonic acid (10 mg) and stirred for 5 h at the same temperature. The precipitated crystals are quickly separated by filtration, washed with a small amount of acetic acid, and dried to give DL-hydroxyphenylglycine*o-toluenesulfonic acid (0.92 g) crystallized from racemizing solution. The melting point (213- 215°C,dec) and IR-spectrum of the DL-hydroxyphenylglycine*o- toluenesulfonic acid are identical with those of racemic mixture of DL-hydroxyphenylglycine-o-toluenesulfonic acid shown in the previous example.

Stability of Crystalline D-hydroxyphenylqlycine-o- Toluenesulfonic acid under Conditions for Racemization A mixture of DL-hydroxyphenylglycine*o-toluenesulfonic acid (1.0 g) , DL-hydroxyphenylglycine (40 mg) , and salicylaldehyde (50 mg) is dissolved in acetic acid containing 2% water under reflux to prepare a solution saturated with DL-hydroxyphenylglycine*o- toluenesulfonic acid at 100°C. To the saturated solution

maintained at 100°C. , crystals of D-hydroxyphenylglycine*o- toluenesulfonic acid (2.0 g) are added. The heterogeneous reaction mixture is stirred for 5 hours at the same temperature. The insoluble crystals are quickly separated by filtration, washed with a small amount of acetic acid, and dried. The insoluble crystals prove to be optically pure D- hydroxyphenylglycine*o-toluenesulfonic acid (1.9 g) , [ajf^-θδ.δ ⁰ (c=l,water) .

Asymmetric Transformation

Batch Transformation: A mixture of DL-hydroxyphenyIglycine*o- toluenesulfonic acid (3.8 g) , DL-hydroxyphenylglycine (0.2 g) , salicylaldehyde (0.25 ml) and acetic acid (20 ml) containing 5% water is heated under reflux until a complete solution occurs and is maintained at 100°C. The supersaturated solution is seeded with finely pulverized crystals of D-hydroxyphenylglycine*o- toluenesulfonic acid (0.2 g) and stirred for 2 hours at the same temperature. The precipitated crystals are quickly separated by filtration, washed with a small amount of acetic acid, and dried to give D-hydroxyphenylglycine*o-toluenesulfonic acid (0.85 g) , [a]f) ⁵ -66.6° (c=l, water), optical purity 100%. Subtracting 0.2 g of seeded D-hydroxyphenylglycine-o-toluenesulfonic acid, 0.65 g of pure D-hydroxyphenylglycine*o-toluenesulfonic acid is obtained. After the separation of D-hydroxyphenylglycine ^• o- toluenesulfonic acid, the filtrate is stirred at 20°C. for 2 hours and the precipitated crystals are collected by filtration

to give DL-hydroxyphenylglycine-o-toluenesulfonic acid (2.66 g) , [a]5 ⁵ +0.6° (c=l, water). The mother liquor does not show any optical rotation. Therefore, the whole reaction mixture becomes 17.1% enantiomeric excess.

Continuous Transformation: A mixture of DL- hydroxyphenylglycine*o-toluenesulfonic acid(19.0 g) a d aqueous 95% (v/v) acetic acid (100 ml) in a three-necked flask fitted with a mechanical stirrer and a condenser is heated under reflux until complete solution occurs. Then the flask is placed in an oil bath controlled at 100°C. Salicylaldehyde (1.24 ml) is added to the solution and DL-hydroxyphenylglycine (51.0 g) is suspended therein. After 20 minutes, into the heterogeneous reaction mixture are added under stirring finely pulverized crystals of D- hydroxyphenylglycine*o-toluenesulfonic acid (2.0 g) as seed crystals. To this is poured a solution consisting of o- toluenesulfonic acid dihydrate (62.5 g) and acetic anhydride (62.5 ml) at the rate cf 5.0 ml/h by a Micro Feeder JP-W (Furue Science Co., Ltd.) _* At 5 hours and 20 hours after the addition of the seed crystals, 1.3 ml and 0.7 ml of salicylaldehyde are added to the mixture, respectively. The mixture is stirred at the same temperature for a total of 30 hours. The precipitated crystals are quickly collected by filtration, washed with a small amount of acetic acid, and dried to give D- hydroxypheny glycine-o-toluenesulfonic acid (82.8 g) , [ajf) ⁵ - 64.9° (c=l, water) , optical purity 97.4%. After the separation of

D-hydroxyphenylglycine-o-toluenesulfonic acid, the filtrate is stirred for 2 hours at room temperature and the precipitated crystals are collected by filtration to recover DL- hydroxyphenylglycine-o-toluenesulfonic acid (18.2 g) , [a]fj ⁵ 0.0° (c=l, water) . The filtrate does not show any optical rotation. The change in the composition of both enantiomers by the reaction is noted.

Preparation of D-hydroxyphenylglycine

The D-hydroxyphenylglycine*o~toluenesulfonic acid (82.0 g) , obtained above is dissolved in water (230 ml) at an elevated temperature and is treated with charcoal. The solution is adjusted to PH 6 with 5 M sodium hydroxide and allowed to stand in a refrigerator overnight. The resulting precipitates are collected, washed with water, and dried to give D- hydroxyphenylglyσine (34.0 g) , [a] _D ⁵ -158.2° (c=l, M-HCl) .

Reference Example 4 D-hydroxyphenylglycine may be resolved as follows according to U.S. Patent 4,415,504, which is incorporated herein by reference.

(1) DL-hydroxyphenylglycine HCL (10.0 g) is reacted with (- )-phenylethanesulf e NH ₄ (9.98 g) in water (10 ml) to form two diastereomers of DL-hydroxyphenylglycine (-τ-)-phenylethanesulfate. DL-hydroxyphenylglycine (0.82 g) is added to the reaction mixture

and the mixture is heated in an autoclave at 140° _c for 12 hours. After completion of the reaction, 50% aqueous solution of (+)- phenylethanesulfate (1.8 g) and water (10 ml) are added to the reaction mixture and the mixture is stirred at room temperature for 1 hour. The crystals thus formed are filtered off and dried to give D-hydroxyphenylglycine (+)-phenylethanesulfate (17.73 9) • [a]g ⁵ -76.5° (c=l, CH ₃ 0H) , Optical purity 97.3%.

(2) Methanol (44 ml.) is added to D-hydroxyphenylglycine (+)- phenylethanesulfate prepared in the above (1) (14.5 g) and an aqueous sodium hydroxide solution is added to the mixture with stirring to adjust pH to 6. The mixture is stirred at room temperature for 2 hours and filtered to give D- hydroxyphenylglycine (6.5 g) . [a]f) ⁵ -158.0°(c=l,1 N HCl). Optical purity 99.8%.

REFERENCE EXAMPLE 5 According to U.S. Patent 4,094,741, DL-5-(4- hydrox henyl)hydantoin may be converted to D-(4- hydroxyphenyl)glycine as follows.

A liquid medium is prepared containing the following components,

100 ml portions of this medium are poured into 500 ml shaking flasks and are steam sterilized at 120°C for 10 minutes. To each flask is added 300 mg of sterilized DL-5-(2- ethylthioethyl)hydantoin under sterile conditions. The thus obtained mixtures are employed as culture media. Each of the following microorganisms, which are previously cultured on an agar bouillon slant at 33°C for 24 hours, is inoculated into each culture medium and is cultured at 33°C for 22 hours with shaking.

TABLE

Amount of obtained cyclohexyl amine salt of N-carb¬ amoyl-2-(4-

Strain N-carbamoyl-2- Conver- hydroxy- (4-hydroxyphenyl sion pheny1)- glycine mg/m (mol%) glycine (mg)

Pseudomonas Striata 4.5 82 655 IFO 12996*

Corynebacterium 3.0 55 491 sepedonicum IFO 3306*

Aerobacter cloacae 1.5 27 249 IAM 1221*

Agrobacterium 0.9 16 123 rhizogenes IFO 13259*

Control 0.0

*Catalog number of strains deposited at:

IFO - Institute for Fermentation, Osaka, Japan

IAM - Institute for Applied Microbiology, Univ. of Tokyo, Japan

Cells are separated from each cultured broth and washed with a

0.9% saline water solution. The cells are collected again by centrifugation and then suspended into 33 ml of 0.9% saline water. Each of the thus obtained suspensions is employed as a component of the mixture described below.

Mixture Components

(1) 500 mg of DL-5-(4-hydroxyphen l)hydantoin

(2) 67 ml of 0.1 M NH4CI-NH4OH buffer solution of pH 9.5

(3) 33 ml of cell suspension

The hydrolysis reaction of DL-5-(4-hydroxyphenyl)hydantoin is carried out in a 300 ml ground stopper Erlenmeyer flask at 31°C for 40 hours with mild shaking, respectively. During the reaction, the pH of the reaction mixture is maintained at 9.5 with 2N KOH. After completion of the reaction, the produced N-carbamoyl-2-(4-hydroxyphenyl)glycine is colorimetrically determined. After completion of the reaction, the reaction mixture is centrifuged and 2 ml of the supernatent solution is taken out. The supernatent solution is color-developed with 0.5 ml of a 5% solution of p-dimethylaminobenzaldehyde in 211 hydrochloric acid. The amount of N-carbamoyl-2-(4- hydroxyphenyl)glycine is σolorimetrically determined by measuring

the absorbance at 420 nm. The amounts of N-carbamoyl-2-(4- hydroxyphenyl)glycine produced in the reaction mixtures and the conversions from DL-5-(4-hydroxyphenyl)hydantoin are shown in the above Table.

The supernatent solution obtained by centrifuging the reaction mixture is lyophilized, and the residue is extracted with ethanol. After removing insoluble materials by filtration, to the ethanol solution is added ethyl acetate in the weight ration of ethyl acetate to ethanol of 2:1, and further added about 1.5 equivalents of dicyclohexylamine to give a white precipitate of dicyclohexylamine salt of N-carbamoyl-2~(4- hydroxypheny1)glycine. The white precipitate is taken out and caused to react with 1.1 equivalents of sodium nitrite in an aqueous medium under acidic conditions with hydrochloric acid at room temperature for 1 hour. Then the resulting reaction mixture is passed through a column of strongly acidic cation exchange resin of H-type (commercially available as Amerlite IR-120B from Rohm & Haas) to adsorb the produced 2-(4-hydroxyphenyl)glycine on the resin. After eluting with 1.5 NH ₄ OH, crystalline 2-(4- hydroxyphenyl)glycine is isolated by concentrating the elute under reduced pressure. These procedures are repeated on each reaction mixture. The infrared spectra and Rf values by silica gel thin layer chromatography (solvent: n-butanol/acetic acid/water = 4/1/1) of the thus obtained crystals agree with those of an authentic sample, and also the found data of the

elementary analysis agree with the calculated value. Further, the specific rotary power of each crystal falls within the range of [a] ² ₎ ⁰ = -161.8° to [ a] ² ₎ ⁰ = -158.5° (c=0.5, IN HCl) and approximately agree with the value for D-(-)-2-(4- hydroxypheny1)glycine, [a]f _j ⁴ = -159.1° (c= 1, IN IICl) described in Japanese disclosure 56946/1974. It is confirmed that the described reaction products are D-(-)-2-(4-hydroxyphenyl)glycine of high purity.

REFERENCE EXAMPLE 6 According to U.S. Patent 4,094,741, DL-5-(4- hydroxyphenyl)hydantoin may be converted to D-(-)-Il-carbamoyl-2- (4-hydroxyphenyl)glycine as follows.

A culture medium of pH 7.0 containing the following components is prepared, and 90 ml thereof is placed in a 500 ml shaking flask and is steam sterilized at 120°C for 10 minutes.

Medium Components Meat extract 2.0% Glycerol 1.0%

Hydantoin 0.1%

To the flask is add the cultured broth obtained previously by culturing Pseudomonas striata IFO 12996 in 10 ml of the same

liquid medium as above in a test tube at 33°C for 24 hours, and the culture is carried out at 33°C for 20 hours with shaking. Cells are separated from the resulting cultured broth by centrifugation and washing with 100 ml of 0.9% saline water. The cells are collected again by centrifugation to give 2.62 g of the intact cells. The thus obtained intact cells are suspended into 10.4 ml of 0.9% saline water and thereto are added 1.0 g of acrylamide and 105 mg of N,N'-methylenebis(acrylamide) and further added 1.3 ml of a 5% aqueous solution of dimethyla inopropionitrile and 1.3 ml of a 2.4% aqueous solution of ammonium persulfate. The resulting mixture is shaken. The mixture gels after several minutes. The mixture is further maintained at 36°C for 30 minutes to complete the reaction. To the obtained gel containing cells is added a small amount of 0.9% saline water and the gel is crushed in a mortar and the resulting granules are washed with 0.9% saline water to give 2.5 g of immobilized cells. A 200 ml four neck flask equipped with a stirrer is charged with 2.0 g of DL-5-( -hydroxyphenyl)hydantoin and 80 ml of deionized water. To this flask is added a 2N solution of NaOH to adjust the liquid to pH 7.0 and further added are the immobilized cells suspended in 110 ml of deionized water. After adjusting the mixture to pH 8.7, the reaction is carried out at 36°C with mild agitation. During the reaction, the pH of the reaction mixture is maintained at pH 8.7 with a 21! aqueous solution of NaOH. The reaction is approximately completed in 15 hours. At that time, the total volume of the reaction mixture is

47 200 ml. The amount of D-(-)~N-carbamoyl-2-(4- hydroxyphenyl)glycine produced in the reaction mixture is 10.4 mg/ml and the conversion from DL-5-(4-hydroxyphenyl)hydantoin is 98% by mole.