SYNTHESIS OF THE C1-C6 KETO-ACID SYNTHON OF THE EPOTHILONES Field of the Invention The present invention relates to the synthesis of chemical compounds useful in the formation of epothilones. More specifically, the present invention is directed to methods for synthesizing chemical precursor compounds for use in epothilone synthesis. The present invention is also directed to chemical compounds and intermediates formed through the methods of the present invention.

Background of the Invention Since their discovery in 1993, epothilones A-D have evoked strong interest from the scientific community because of their anticancer activity. For example, epothilones A and B of formula: R R s s , OH OH N 6'C N 111, "-- /,. oh 0 1 3 56 N 1 3 56 . 0 OH oh Epothilone A, R = H Epothilone C, R = H Epothilone B, R = Me Epothilone D, R = Me appear to possess identical modes of action to paclitaxel (taxol), but are a thousand- fold more active than paclitaxel in cancerous cells that have acquired multiple drug resistance (MDR). They also have the advantage of better solubility than paclitaxel, and can be obtained in multigram quantities.

Because of these advantages, there is great interest in providing routes for the synthesis of epothilones. There is also great interest in synthesizing analogs and derivatives of the epothilones for further study in cancer research. As described in U. S. Patent Application No. 09/981,312 entitled"Synthesis of Epothilones and Related Analogs" (U. S. Publication No. US 2002/0091269 A1) and in PCT Application No. PCT/US01/32225 of the same title (PCT Publication No. WO 02/30356 A2), one strategy for the total synthesis of epothilones includes construction of a C1-C6 synthon, such as a keto-acid of formula: which undergoes aldol condensation with an aldehyde to set important stereochemical features of the epothilone architecture. One important stereochemical aspect of the C1-C6 synthon in particular is the 3S stereochemistry of the OX group, where X can be H or a protecting group, such as the tert- butyldimethylsilyl, t-BuMe2Si, or ether.

Accordingly, it is desirable to provide an efficient process for forming the C1- C6 synthon and analogs, derivatives and stereoisomers thereof for use in the synthesis of epothilones. The key for preparation of the C1-C6 synthon is to introduce a hydroxyl group at the C-3 position in an optically pure form. There remains a need for chemosynthetic approaches that will provide an efficient route to forming the C1-C6 synthon having the desired C-3 stereochemistry and variations in the substituents thereof for use in epothilone synthesis. The present invention is directed to meeting this need.

Summary of the Invention According to the present invention then, new and useful methods are provided for producing keto-acid synthons useful in the synthesis of epothilones and analogs and derivatives thereof.

In a broad generalized form, the method of producing keto-acid synthons according to the present invention comprises performing an aldol condensation of a first aldehyde of this general formula: with a carbonyl compound in the form of a ketone or a second aldehyde having a generalized formula: thereby to form a first compound having a generalized formula: and thereafter converting the first compound to a protected keto-acid synthon of generalized formula : When reference is made to compounds throughout this disclosure, possible Rx contemplated hereby are set forth in the following Table 1: TABLE 1 Rx GROUPS CONTEMPLATED Ri-R7 H, methyl or optionally substituted n-alkyl, s-alkyl, t-alkyl, E or Zalkenyl, terminal alkenyl, alkynyl, aryl, alkylaryl, alkenylaryl, alkynylaryl, alkylheteroaryl, alkenylheteroaryl, alkynylheteroaryl, cycloalkyl, alkylheterocyclic, alkenylheterocyclic, alkynylheterocyclic, heteroalkyl, heteroalkenyl, heteroalkynyl, primary alkylamines, secondary alkylamines, tertiary alkylamines, alkyl sulfides, alkylethers, hydroxyalkyls, alkylthiols and other functional groups known in the art Rs may be any of the functional groups listed above for R1-R7 ; it may specifically be a TBS protecting group Rs and Rio may be any of the functional groups listed above for R1-R7 ; and, in some instances, may be connected to form a cyclic structure R11-R14 H, methyl, or optionally substituted n-alkyl, s-alkyl, t-alkyl, E or Z alkenyl, terminal alkenyl, alkynyl, aryl, alkylaryl, alkenylaryl, alkynylaryl, alkylheteroaryl, alkenylheteroaryl, alkynylheteroaryl, cycloalkyl, alkylheterocyclic, alkenylheterocyclic, alkynylheterocyclic, heteroalkyl, heteroalkenyl, heteroalkynyl, primary alkylamines, secondary alkylamines, tertiary alkylamines, alkyl sulfides, alkylethers, hydroxyalkyls, alkylthiols and other functional groups known in the art Pis and R16 may be any of the functional groups listed above for Rr1-R14 ; each may specifically be a TBS or TMS protecting group Ria may be any of the functional groups listed above for Rn-Rie ; it may specifically be a TBS protecting group R19-CH3,-CH2R4, or-CH=C (R6) (R7), H R20 carbonyl group, =CH2, a protected ketal, or a protected alcohol As contemplated, the first aldehyde may have any of the following four formulas : In these examples, R20 (shown in the general formula above) may be a carbonyl group, a double-bonded =CH2 group, a protected ketal, or a protected alcohol, respectively.

As mentioned above, the carbonyl compound may be either a ketone or aldehyde. For example, when R19 is-CH3,-CH2R4, or-CH=C (R6) (R7), the carbonyl compound is a ketone having the formula When R19 is H, the carbonyl compound is an aldehyde of formula Upon aldol condensation of the first aldehyde with the carbonyl compound, the first compound is formed. The conversion of this first compound to the protected keto- acid synthon may be accomplished by forming at least one intermediate compound.

A first exemplary embodiment of the present invention contemplates aldol condensation of the first aldehyde with the carbonyl compound that is a ketone to ultimately form a protected keto-acid synthon through various routes. Additionally, the present invention contemplates a second alternative embodiment where aldol condensation of the first aldehyde occurs with an aldehyde to ultimately form a protected keto-acid synthon.

One route, with respect to the first exemplary embodiment of the present invention, includes performing an aldol condensation of a first aldehyde of formula: with a carbonyl compound that is a ketone of formula : thereby to form a first compound having a formula: Catalyzed cyclization of the first compound may thereafter be performed to form a respective first intermediate compound having a formula: The hydroxyl group of the first intermediate compound may then be protected with a protecting group, R8, to form a respective second intermediate having a formula : Finally, oxidative cleavage of the second intermediate may then be performed to form the respective protected keto-acid synthon having a formula: As should be appreciated, the respective diastereomers of the first compound formed by the aldol condensation of the first aldehyde and carbonyl compound may also be formed. The respective diastereomers of the first compound have the formulas : These diastereomers may similarly be converted to the protected keto-acid synthon by first performing catalyzed cyclization of these diastereomers to form a respective first intermediate compound having a formula: The hydroxyl group of the respective first intermediate compounds may then be protected with a protecting group, R8, to form a respective second intermediate having a formula : Finally, oxidative cleavage of the second intermediate may then be performed to form the respective protected keto-acid synthon having a formula: For the sake of clarity and simplicity, the various compounds of route one can be summarized with a scheme that adopts generalized formulas that serve as a representative for each compound and its diastereomer. Accordingly, the aldol condensation of the aldehyde and ketone shown above form a first compound of the general formula : Cyclizing the first compound form a first intermediate compound having the general formula : Protecting the hydroxyl group of the first intermediate compound is protected provides the second intermediate compound of the general formula : Thereafter, oxidative cleavage of the second intermediate compound provides the keto-acid synthon having the generalized formula : which was also shown above with reference to the broad generalized method.

A second route, with respect to the first exemplary embodiment of the present invention comprises performing an aldol condensation of a first aldehyde that is a ketal aldehyde of formula: with a carbonyl compound that is a ketone having the formula : thereby to form a first compound having a formula: The hydroxyl group of the first compound may then be protected with a protecting group, R8, to form a respective first intermediate compound having the formula: Oxidation and deketalization of the first intermediate compound may then be performed to form a respective protected keto-acid having the formula : The step of oxidation and deketalization may include a first step of performing oxidation of the first intermediate compound thereby to form a resepctive second intermediate compound having the formula : and then a second step of performing deketalization of the second intermediate compound to form the respective protected keto-acid.

Similar to the method described with respect to the first route, the respective diastereomers of the first compound may also be formed by the aldol condensation according to the second route. The respective diasteromers of the first compound have the formulas : These diastereomers may then be converted to protected keto-acid synthons by thereafter, protecting the hydroxyl group with a protecting group, R8, to form a respective first intermediate compound having a formula: Oxidation and deketalization of the first intermediate compound may then be performed to form the respective protected keto-acid synthon having the formula : Again, the oxidation and deketalization may include a first step of performing oxidation of the first intermediate compound thereby to form a respective second intermediate compound having the formula: and then a second step of performing deketalization of the second intermediate compound to form the respective protected keto-acid.

Again, for the sake of clarity and simplicity, the various compounds of route two can be summarized with generalized formulas that serve as a representative for each compound and its diastereomer. Accordingly, the aldol condensation of the aldehyde and ketone shown above form a first compound of the general formula: The first and second intermediate compounds formed during the method according to route 2 can be generally represented by the following respective formulas: first intermediate compound second intermediate compound A third route of the first exemplary embodiment of the present invention comprises performing an aldol condensation of a ketal aldehyde of formula: with a carbonyl compound that is a methyl ketone of formula thereby to form a first compound having a formula : The respective hydroxyl groups of the first compound may then be protected with a protecting group, R8, to form a respective first intermediate compound having a formula : The first intermediate compound may then be converted to a respective second intermediate compound having a formula : Finally, deketalization of the second intermediate compound may be performed to form the respective protected keto-acid having a formula: Here again, the diastereomers of the first compound formed according to the third route may be used to ultimately provide the protected keto-acid synthon. The respective diastereomers of the first compound have the formulas: These diastereomers may then be converted to protected keto-acid synthons by thereafter, protecting the respective hydroxyl group with a protecting group, R8, to form a respective first intermediate compound having a formula: The first intermediate compound may then be converted to a respective second intermediate compound having a formula : Finally deketalization of the second intermediate compound may then be performed to form the respective protected keto-acid having a formula : Here again, for the sake of both clarity and simplicity, the various compounds of route three can be summarized with respective general formulas that serve as a representative for each compound and its diastereomer. Here, aldol condensation of the aldehyde with the ketone form a first compound of the general formula : Further, the first intermediate compound and the second intermediate compound, which are formed according to the scheme of route three, can be represented with the following generalized formulas, respectively : Rs R1 o A aj, R3 HO X9Rs Q ORg p 0 0 Rs Rs ho R R2 R2 and first intermediate compound second intermediate compound A fourth route, with respect to the first exemplary embodiment of the present invention, provides a further method for producing a keto-acid synthon useful in the synthesis of epothilones and analogs and derivatives thereof, comprising performing an aldol condensation of an olefinic-aldehyde of formula: with a ketone of formula : thereby to form a first compound having a formula : The respective hydroxyl groups of the first compound may then be protected with a protecting group, R8 to form a respective intermediate compound having a formula: Dual oxidative cleavage of the double bonds of the intermediate compound may then be performed to form the respective protected keto-acid having a formula : The diastereomers of the first compound formed according to the fourth route may be used to ultimately provide the protected keto-acid synthon. The respective diastereomers the first compound have the formulas These diastereomers may then be converted to protected keto-acid synthons by thereafter, protecting the respective hydroxyl groups with a protecting group, R8, to form a respective intermediate compound having a formula: Dual oxidative cleavage of the double bonds of the first intermediate compound may then be performed to form the respective protected keto-acid having a formula: The various compounds of route four can be summarized with respective general formulas that serve as a representative for each compound and its diastereomer. Here, the first compound and the intermediate compound have the following respective general formulas: first compound intermediate compound A fifth route, with respect to the first exemplary embodiment of the present invention, for producing a keto-acid synthon according to the present invention comprises performing an aldol condensation of a protected alcohol-aldehyde synthon of formula: with a methyl ketone of formula : thereby to form a first compound having a formula: The respective hydroxyl groups of the first compound may then be protected with a protecting group, R8 to form a respective first intermediate compound having a formula : The first intermediate compound may then be converted to a respective second intermediate compound having a formula: The second intermediate compound may then be deprotected and oxidized to form the respective protected keto-acid synthon of formula: The diastereomers of the first compound formed according to the fifth route may also be used to ultimately provide the protected keto-acid synthon. The respective diastereomers of the first compound formed by the fifth route have the formulas These diastereomers may then be converted to protected keto-acid synthons by thereafter, protecting the respective hydroxyl groups with a protecting group, R8, to form a respective first intermediate compound having a formula : The first intermediate compound may then be converted to a respective second intermediate compound having a formula : The second intermediate compound may then be deprotected and oxidized to form the respected protected keto-acid synthon of formula: With respect to route five of the first exemplary embodiment, the various compounds can be summarized with respective general formulas that serve as a representative for each compound and its diastereomer. Here, the first compound can be represented with the general formula : The first and second intermediate compounds can be represented by the following respective general formulas : first intermediate compound second intermediate compound With respect to the first exemplary embodiment, the conversion of the first intermediate compound to the second intermediate compound may be accomplished by haloform reaction, enol ether oxidation, or benzylidene ketone oxidation. The step of enol ether oxidation may include enolization of the first intermediate compound to form an oxidizable silyl enol ether intermediate of formula : which may then be oxidized to the second intermediate compound. The step of benzylidene ketone oxidation may include aldol condensation with benzaldehyde to form a respective benzylidene ketone of formula : which may then be oxidized to the second intermediate compound.

A second exemplary embodiment of the present invention comprises performing a crossed aldol condensation of an aldehyde of formula : with an aldehyde of formula : thereby to form a first compound having a formula : The respective hydroxyl groups may then be protected with a protecting group, R8, to form a respective intermediate compound having a formula : An aldehyde to carboxylic acid oxidation may then be performed to form the respective protected keto-acid synthon having a formula: The diastereomers of the first compound formed according to the second exemplary embodiment of the present invention may also be used to ultimately provide the protected keto-acid synthon. The respective diastereomers have the formulas These diastereomers may then be converted to protected keto-acid synthons by thereafter protecting the respective hydroxyl group with a protecting group, R8, to form a respective intermediate compound having a formula selected from: An aldehyde to carboxylic acid oxidation may then be performed to form the respective protected keto-acid synthon having a formula : Similar to the routes shown above with respect to the first exemplary embodiment, the various compounds associated with the scheme according to the second exemplary embodiment can be summarized with respective generalized formulas that serve as a representative for each compound and its diastereomer for the sake of clarity and simplicity. Accordingly, the step of crossed aldol condensation provides a first compound having the general formula : Further, the intermediate compound and its respective diastereomers that may be formed during the process of arriving at the synthon is represented with the general formula : With respect to the second exemplary embodiment of the present invention, when the protected alcohol-aldehyde is an enantiomerically pure compound of formula: the first compound may have a formula : and the respective diastereomer may have a formula : In the above each of the above methods described, the aldol condensations may be performed in the presence of a catalyst, such as a chiral amine base, which may be D-prolin or L-proline, or racemic proline, for example. The aldehydes may be reacted with the ketones in the presence of a solvent such as DMSO. The ketone may specifically be 4-aryl but-3-ene-2-one, methyl ketone or acetone. The catalyzed cyclization may be performed with a secondary amine, such as pyrrolidine, piperidene, or morpholine, in THF, benzene or other solvents. The steps of protecting the hydroxyl group may be accomplished by reacting the second compound with R8X, imidazole and DMF at room temperature for a time period such as 72 hours. The hydroxyl may be specifically protected with a tert-butyidimethylsilyl (TBS) protecting group, such that R8 is t-BuMe2Si, or with other protecting groups as known in the art. The steps of oxidation/oxidative cleavage may be accomplished with RuCI3/NalO4 ; or 03/Jones oxidation; or 03, low temperature, Me2S workup; or Ru04. The haloform reaction may be accomplished, for example, by Br2 or 12/NaOH/Dioxane/H20, 0°C. The deketalization reactions may be performed, for example, by reaction with aqueous mineral acid in a suitable organic solvent such as tetrahydrofuran, or through other methods such as sequestering the alcohol corresponding to the ketalizing reagent.

Additionally, the present invention is also directed to chemical compounds useful in the synthesis of epothilones and analogs and derivatives thereof and to methods for forming each of these chemical compounds, as illustrated in the individual steps of the above-described methods. The chemical compounds of the present invention comprise compounds having formulas selected from: wherein Ri-Rio are as above.

Finally, the present invention provides a method for use in producing epothilones and analogs and derivatives thereof. The method comprises performing an aldol condensation of a first compound having the formula: with a second compound of the formula : and stereoisomers thereof, thereby to form a third compound of the formula : and stereoisomers thereof.

Thereafter macrolactonization of the third compound may be performed to form a fourth compound of the formula : 14 R13 Rys N \ R S wherein Z is selected from is and' ; and stereoisomers thereof, wherein Ri-R3, R5 and R8 are as above and R11-R16 and R18 are each individually selected from H, methyl, or optionally substituted n-alkyl, s- alkyl, t-alkyl, E or Z alkenyl, terminal alkenyl, alkynyl, aryl, alkylaryl, alkenylaryl, alkynylaryl, alkylheteroaryl, alkenylheteroaryl, alkynylheteroaryl, cycloalkyl, alkylheterocyclic, alkenylheterocyclic, alkynylheterocyclic, heteroalkyl, heteroalkenyl, heteroalkynyl, primary alkylamines, secondary alkylamines, tertiary alkylamines, alkyl sulfides, alkylethers, hydroxyalkyls, alkylthiols and other functional groups known in the art. In one particular embodiment, Ri, R2, R3, R11, R13, and R14 may each specifically be methyl ; R5 and R12 may each specifically be H; R8 and R18 may each specifically be a TBS protecting group; and R15 and R16 may each specifically be a TBS or TMS protecting group.

These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed decription of the exemplary embodiments of the present invention when taken together with the accompanying drawings, in which: Brief Description of the Drawings Figure 1 is a diagram of an exemplary synthetic route for forming epothilones ; Figure 2 is a diagram of a generalized reaction according to the present invention to produce a protected keto-acid synthon; Figure 3 (a) is a diagram of chemical reaction Scheme I-a according to the present invention; Figure 3 (b) is a diagram of chemical reaction Scheme l-ß according to the present invention; Figure 4 (a) is a diagram of chemical reaction Scheme ll-oc according to the present invention; Figure 4 (b) is a diagram of chemical reaction Scheme II- according to the present invention; Figure 5 (a) is a diagram of chemical reaction Scheme III-a according to the present invention; Figure 5 (b) is a diagram of chemical reaction Scheme III-ß according to the present invention; Figure 6 (a) is a diagram of chemical reaction Scheme IV-oc according to the present invention; Figure 6 (b) is a diagram of chemical reaction Scheme IV-ß according to the present invention; Figure 7 is a diagram of an exemplary aldol condensation reaction according to the present invention; Figure 8 is a diagram of an exemplary cyclization reaction according to the present invention; Figure 9 is a diagram of an exemplary hydroxyl protection reaction according to the present invention; Figure 10 is a diagram of an exemplary oxidative cleavage reaction according to the present invention; Figure 11 (a) is a diagram showing an exemplary selective formation of enantiomers using D-Proline or L-Proline, and optional formation of diastereomers thereof; Figure 11 (b) is a diagram showing an exemplary selective formation of the reverse enantiomers of Figure 10 (a), and optional formation of diastereomers thereof; Figure 11 (c) is a diagram showing an exemplary formation of a racemic mixture of the enantiomers of Figures 10 (a) and 10 (b) using racemic proline, and optional formation of diastereomers thereof; Figure 12 (a) is a diagram showing an exemplary synthesis of epothilones using a syn-a compound formed according to the methods of the present invention; Figure 12 (b) is a diagram showing an exemplary synthesis of epothilones using an anti-a compound formed according to the methods of the present invention; Figure 12 (c) is a diagram showing an exemplary synthesis of epothilones using a syn-ß compound formed according to the methods of the present invention; Figure 12 (d) is a diagram showing an exemplary synthesis of epothilones using an anti- compound formed according to the methods of the present invention; Figure 13 (a) is a diagram showing an alternative exemplary synthesis of epothilones using a syn-a compound formed according to the methods of the present invention; Figure 13 (b) is a diagram showing an alternative exemplary synthesis of epothilones using an anti-a compound formed according to the methods of the present invention; Figure 13 (c) is a diagram showing an alternative exemplary synthesis of epothilones using a syn-ß compound formed according to the methods of the present invention; Figure 13 (d) is a diagram showing an alternative exemplary synthesis of epothilones using an anti-p compound formed according to the methods of the present invention; Figure 14 is a diagram showing a generalized reaction scheme for forming the ketal starting compounds of Schemes ll-oc and II- (3 and Schemes III-a and III-ß ; Figure 15 is a diagram showing an exemplary synthesis of a ketal starting compound for use in Schemes ll-oc and ll-ß and Schemes III-oc and III-ß ; Figure 16 (a) is a diagram of chemical reaction Scheme V-a according to the present invention; Figure 16 (b) is a diagram of chemical reaction Scheme V-ß according to the present invention; Figure 17 (a) is a diagram of chemical reaction Scheme VI-a according to the present invention; Figure 17 (b) is a diagram of chemical reaction Scheme Vt- (3 according to the present invention; Figure 18 is a diagram showing the stereoisomers resulting from the aldol condensation reactions of Figures 16 (a) and (b) utilizing an enantiomerically pure protected alcohol aldehyde ; Figure 19 is a diagram of exemplary enol ether oxidations for use with Schemes III-a and III-ß ; Figure 20 is a diagram of exemplary benzylidene ketone oxidations for use with Schemes III-oc and III-P ; Figure 21 is a diagram of exemplary enol ether oxidations for use with Schemes VI-a and Vl-p ; and Figure 22 is a diagram of exemplary benzylidene ketone oxidations for use with Schemes Vl-oc and VI-P.

Detailed Description of the Invention The present invention provides new compounds useful in forming a C1-C6 keto-acid synthon for use in synthesizing epothilones and methods for forming these synthons. As shown in Figure 1, epothilone compounds such as Epothilane A or Epothilone B may be synthesized by, in part, reacting a C1-C6 keto-acid synthon of the epothilone, or analogs or derivatives thereof, with another compound. Such methods for synthesizing epothilones and related analogs and derivatives are described more thoroughly, for example, in U. S. Patent Application No. 09/981, 312 entitled"Synthesis of Epothilones and Related Analogs" (U. S. Publication No. US 2002/0091269 A1) and in PCT Application No. PCT/US01/32225 of the same title (PCT Publication No. WO 02/30356 A2). In particular, the present invention provides a method for constructing the key C-3 chiral center of such a keto-acid synthon.

Figure 2 shows a generalized method for forming the C1-C6 keto-acid compound. In its broad form, the method includes performing an aldol condensation of a first aldehyde with either a ketone or a second aldehyde, and further transformations of the product thereof so as to arrive at a keto-acid useful in the synthesis of epothilones. The ordinarily skilled artisan will appreciate that the carbons numbered 2,3 and 4 in Figure 2 are stereocenters such that numerous stereoisomers may be formed by the method of the present invention. Furthermore, when there is not a double bond between C5 and R20, the 5 carbon is also a stereocenter, further increasing the number of possible stereoisomers.

Figures 3 (a) and (b) through 6 (a) and (b), and 17 (a) and (b) provide several generalized reaction schemes (Schemes l-x through IV-a ; I-ß through IV-ß ; and VI-a and VI-P) for forming the C1-C6 keto-acid synthon of the epothilones according to the present invention involving the aldol condensation of a ketone. Figure 16 (a) and (b) provide a generalized reaction scheme (Schemes V-a and V-0) for forming the C1-C6 keto-acid synthon of the epothilones according to the present invention involving the aldol condensation of an aldehyde. As apparent from Figures 3 (a) and (b) through 6 (a) and (b), 16 (a) and (b), and 17 (a) and (b) the aldol condensation is followed by further transformations of the product thereof, to arrive at a protected keto-acid synthon of formula : wherein R1 through Rio in Figures 2,3 (a) and (b) through 6 (a) and (b), 16 (a) and (b) and 17 (a) and (b) (Schemes I-a through Vl-a and l-ß through Vu-0) are each individually selected from H or optionally substituted n-alkyl, s-alkyl, t-alkyl, E or Z alkenyl, terminal alkenyl, alkynyl, aryl, alkylaryl, alkenylaryl, alkynylaryl, <BR> <BR> <BR> alkylheteroaryl, alkenylheteroaryl, alkynylheteroaryl, cycloalkyl, alkylheterocyclic, alkenylheterocyclic, alkynylheterocyclic, heteroalkyl, heteroalkenyl, heteroalkynyl, primary alkylamines, secondary alkylamines, tertiary alkylamines, alkyl sulfides, alkylethers, hydroxyalkyls, alkylthiols and other functional groups known in the art.

Additionally, in Figures 4 and 5, acetals exist when Rg and Rio are not connected to one another. Common acetals for a hindered system such as these would be a dimethylacetal. However, Rg and Rio may be optionally connected to form cyclic ketals. For example, Rg and RIO may both be-CH2-and be connected through a single bond to specify a 1, 3-dioxolane. This ketal, prepared from ethylene glycol, acid and the ketone, is commonly referred to as an ethylene ketal. In a number of embodiments, various ones of R1 through Rio may each be H, methyl or protecting groups such as TBS or TMS.

Notably, the methods of the present invention involve the selective resolution of diastereomers through the use of either D-proline or L-prolin to provide high enantiomeric excesses, as illustrated for example in Figures 11 (a) and (b). In particular, the present invention provides either the syn-a or syn-, adducts having the desired 3S or 3R stereochemistry of the epothilones. For a particular set of reactants, experimental observation is used to determine which stereoisomer is produced by each form of proline. For example, as shown in Figure 11 (a), D-prone may produce the syn-a product and L-prolin the syn-, 8 product for a given set of reactants of Formulas A and B. Conversely, as shown in Figure 11 (a), L-prolin may produce the syn-a product and D-prolin the syn-/ ? product for a given set of reactants of Formulas A and B, depending upon the substituents thereof. As further shown in Figures 11 (a) and (b), the enantiomers may be converted to their respective anti-a and anti- diastereomers in the presence of LDA at room temperature. As illustrated in Figure 11 (c), use of racemic proline provides a racemic mixture of the enantiomers, which may each be further converted to their diastereomers in the presence of LDA at room temperature, as shown.

It should be appreciated that in the below-described processes of Schemes I- a through VI-a and l-ß through Vl-ß, the several R groups can be varied and diastereomeric products obtained. Clearly, the use of variations of the ketones or aldehydes as starting materials is possible leading to production of synthons for construction of analogs of Epothilones in which R1 through Rio are varied as required to achieve goals of enhanced potency, delivery, bioavailability, metabolic stability, reduced side-effects and other important pharmaceutical properties for the treatment of proliferative disorders such as, but not limited to, cancer. Once incorporated into the total synthesis, the resulting analogs of epothilones A-D, for example, are useful for Structure-Activity Relationship (SAR) studies, and these SAR or QSAR (Quantitative Structure-Activity Relationship) tools can be useful in drug design efforts.

It should further be noted that when R5 is H in the formulas of the present invention, the 2-carbon is not a stereocenter, such that the possible stereoisomers are then limited. For example, the formulas: are equivalent structures when R5 is H, and both could be represented as formula : as would be understood by the ordinarily skilled artisan. Similarly, the formulas : are equivalent structures when R5 is H, and both could be represented as formula : as would also be understood by the ordinarily skilled artisan. Additionally, when the R1 and R2 groups are the same, the 4-carbon is not a stereocenter, as would be further understood by the ordinarily skilled artisan. For example, when R5 is H and R1 and R2 are both methyl, the 3-carbon is the only stereocenter in the keto-acid, such that the only enantiomers are of formula : which can be resolved through the use of either D-prolin or L-proline as described herein.

Further, it would be understood that, for the sake of clarity and simplicity, a compound and its stereoisomers and diastereomers can be collectively represented with a structural formula. For example, the synthons that are produced according to the present invention have the formulas : Each synthon may be collectively represented with the following general formula : The use of a general formula can also represent various compounds and intermediate compounds, which are also discussed herein.

In the examples below, reactions requiring anhydrous conditions were performed with the usual precautions for rigorous exclusion of air and moisture.

Tetrahydrofuran was distilled from sodium benzophenone ketyl prior to use. Thin layer chromatography (TLC) was performed on precoated silica gel 60 F254 plates from EM reagents and visualized with a 254-nm UV light. Flash chromatography was carried out on silica gel 60 (E. M. Merck, particle size 0.040-0. 063 mm, 230-400 mesh ASTM).'H NMR and 13C NMR spectra were recorded on a Bruker DPX 400 at 400 MHz and 100MHz, respectively. The chemical shifts were reported in parts per million (ppm) downfield from tetramethylsilane, and J-values were in Hz. IR spectra were obtained on an ATI Mattson FT/IR spectrometer. Mass spectra were recorded on a Bruker BioApex FTMS system. All mass spectral data were uncorrected. When necessary, chemicals were purified according to the reported procedures.

The starting aldehyde and ketone compounds of the present invention are readily obtained from commercial suppliers or formed according to methods known in the art from compounds readily obtained from commercial suppliers. For example, to make keto-aldehyde A, an a-substituted or unsubstituted aldehyde may be converted to its enamine by routine chemistry (See, Carey and Sundberg, Advanced Organic Chemistry, Book B, 3rd Edition, 2001), and then trapped by an electrophilic acid chloride. Both aldehyde and acid chlorides are commercially available or made by routine methods known in the art. For the component ketone B, again, routine chemistry may be employed to prepare those that are not commercially available.

Thousands of ketones are commercially available, as are acid and aldehyde precursors to compounds A and B. It should be appreciated that the various R groups herein, such as R1 through R5 in compounds A and B for example, encompass the numerous variations of such commercially available compounds or compounds prepared as described above from such commercially available precursors or by methods further known in the art.

1. Schemes I-a and l-ß As shown in Scheme I-a of Figure 3 (a) and Scheme 1-0 of Figure 3 (b), and as exemplified in Figures 7 through 10, the present invention provides a generalized method for synthesizing a keto-acid for use in synthesizing epothilones, as follows.

A. Aldol Condensation In Scheme I-a, an aldehyde of formula : (a pivaldehyde-like substance) is first reacted with a ketone of formula : such as acetone by direct aldol reaction under catalysis by a specific enantiomer of proline (either D-prolin or L-proline) to form a first compound shown here as a diketoalcohol of formula : Csyn-&alpha; in chiral form with high enantiomeric (R5 = H) and diastereomeric (R5 not = H) excesses. As further shown in Figure 3 (a), the Csyn-&alpha; enantiomer may be further converted to the Canti-&alpha; diastereomer, if desired, in the presence of LDA at room temperature. As illustrated in Figure 3 (b) (Scheme 1-0), the other enantiomer of proline may be used to provide the Csyn-a enantiomer or Canti-p diastereomer, if desired. In both cases, the formation of the Canti diastereomer may provide either a mixture of syn and anti aldol adducts, or syn adducts can be epimerized to anti by warming, as addressed for example in"The Aldol Addition Reaction", Heathcock, Clayton H. , Dep. Chem. , Univ. California, Berkeley, CA, USA. Editor (s): Morrison, James D. Asymmetric Synth. (1984), 3,111-212. Publisher: Academic, Orlando, Fla., which provides a general reference to syn-anti aldols, mixtures, interconversions, predictions and so on.

The various formulas for the diketoalcohol shown in Figures 3 (a) and 3 (b) can be collectively represented with the following general formula : An exemplary reaction is provided in Figure 7 for compounds wherein R1 = R2 = R3 = methyl group; and R4 = R5 = H in the formulas of Figure 3 (a). Here, the 24 hour reaction of D-prolin (35 mol %) in DMSO/acetone with the ketolaldehyde of formula: 0 0 Formula 1 H furnished the (-)-4S-4-hydroxy-5, 5-dimethyl-2, 6-octanedione aldol product of formula : 0 OH 0 Formula 2 v in 75% yield and with better than 99% enantiomeric excesses (Mosher ester analysis). In addition, 1. 9% of cyclization product of formula: 0 tj Formula 3 Ho was obtained. If the reaction time was extended from 24h to 72h, the yield of cyclization product increased from 1.9% to 10%.

Here, a mixture of D-proline (2.0 g, 0.35 mmol) in anhydrous acetone (50 mL) and anhydrous DMSO (200 mL) was stirred at room temperature for 15 min. At this time, the aldehyde of Formula 1 was added and the mixture stirred at room temperature for 24 hours. Saturated aqueous ammonium chloride (250 mL) was added and the reaction mixture was extracted with ethyl acetate (3X200 mL). The combined organic phase was dried over anhydrous sodium sulfate, filtered and the solvent was evaporated. The residue was subjected to flash chromatography (silica gel, EtOAc: hexanes 1: 1) providing Formula 2 (7.0 g, 75 %) and Formula 3 (160 mg, 1.9 %) as colorless oils. For Formula 2, Rf = 0.53 (silica gel, 50% ethyl acetate in hexane); [a] 25D-48. 8 (c = 1.2, CHCI3) ; IR (thin film) Vmax 3493,2975, 2940,2857, 1704,1701, 1469,1366, 1099, 970 cm-1; 1H NMR (400 MHz, CDCl3) # 4. 02 (m, 1H, CHOH), 3.46 (s, 1H, O, 2.35-2. 28 (m, 4H, CHCH2CO, CH3CH2CO), 1.95 (s, 3H, CH3CO), 0.90, 0.87 (2s, 6H, C (CH3) 2), 0.76 (t, J = 6.8 Hz, 3H, CH2CH3) ; 13C NMR (100 MHz, CDCl3) # 215.9, 209.0, 71.7, 51.0, 45.1, 31.0, 30.4, 20.8, 19.5, 7.5 ; ESI+ HRMS m/z 209. 1108, M+Na+ calcd for C1oH1803Na 209.1154.

The Mosher ester was synthesized as follows : Into a flask, 2 (37.2 mmg, 0.2 mmol), R- (+)-a-methoxy-a-trifluromethylphenylacetic acid (MPTA, 56.2 mg, 0.24 mmol), DCC (53.6 mg, 0.26 mmol), DMAP (6.1 mg, 0.05 mmol) and dichloromethane (5 mL) were added in order. The mixture was stirred at room temperature for 24 hours and directly subjected to flash chromatography (silica gel, 40 % ethyl acetate in hexanes) to give the Mosher ester, which was analyzed by nmr for its enantiomeric purity.

B. Cyclization Next, intramolecular closure of the diketoalcohol with a secondary amine, such as pyrrolidine, piperidene or morpholine, in a solvent such as dichloromethane, THF or benzene furnishes a first intermediate compound in the form of an enone of formula : as shown in Figures 3 (a) and (b). The first intermediate compound can be collectively represented with the general formula: An exemplary reaction is provided in Figure 8 for compounds wherein R1 = R2 = R3 = methyl group; and R4 = R5 = H in the formulas of Figure 3 (a). Here, treatment of the diketo-alcohol of Formula 2: 0 OH 0 Formula 2 with pyrrolidine in dichloromethane at ambient temperature produced the (-)-5S-3- ethyl-4, 4-dimethyl-5-hydroxycyclohex-2-enone compound of Formula 3: 0 o Formula 3 HO in 76% yield (based on converted Formula 2).

To the solution of Formula 2 (2. 90 g, 15.6 mmol) in anhydrous dichloromethane (10 mL) at room temperature was added pyrrolidine (0.111 g, 1.56 mmol). The solution was stirred at room temperature for 3 hours and then concentrated on the rotary evaporator at room temperature. The residue was directly purified by flash chromatography (silica gel, 40 % ethyl acetate in hexanes). The product of Formula 3 was obtained as a colorless oil (1.16 g, 76 %, based on converted Formula 2), and 1.20 g of Formula 2 was recovered; Rf = 0.32 (silica gel, 50% ethyl acetate in hexane); [a] 25o-17. 8 (c= 0.70, CHC13) ; IR (thin film) vmax 3430, 2971,2938, 2881,1666, 1647,1610, 1468, 1417, 1362, 1283,1047, 863 cm'H NMR (400 MHz, CDCl3) 5 5.61 (s, 1H, CH=C), 4.16 (s, 1H, OH), 3.70-3. 60 (m, 1H, CHOH), 2.47-2. 29 (m, 2H, HOCHCH2), 2.10 (q, 2H, J= 6.8 Hz, CH2CH3), 1.01, 0.96 (2s, 6H, C (CH3) 2), 0.89 (t, J= 6.8 Hz, 3H, CH2CH3) ; 13C NMR (100 MHz, Ceci3) 6 198.4, 173.5, 122.8, 73.7, 42.4, 41.1, 24.7, 23.9, 20.3, 11.3. ESI+ HRMS m/z 151. 1104, M-H2O+H+ cacld for C10H15O 151.1123.

C. Hvdroxvl Protection As further shown in Figures 3 (a) and (b), the enone is then protected on the hydroxyl group to form a second intermediate compound in the form of an ether of formula: The second intermediate compounds can be collectively represented with the general formula : Various appropriate hydroxyl protecting groups and their protection/deprotection procedures are described, for example, in Greene et al., Protective Groups in Organic Synthesis, 3rd Ed. , John Wiley & Sons, 1999, p. 779.

An exemplary reaction is provided in Figure 9 for compounds wherein R1 = R2 = R3 = methyl group; R4 = R5 = H; and R8 = tert-butyldimethylsilyl (TBS) in the formulas of Figure 3 (a). Here, protection of the compound of Formula 3 as the (-)- 5S-3-ethyl-4, 4-dimethyl-5- (fert-butyidimethylsilyl) oxycyclohex-2-enone TBS ether of formula: 0 Formula 4 TBSOX/ could be readily achieved in 81% unoptimized yield using the Corey method with TBSCI and imidazole.

To a solution of tert-Butyldimethylsilylchloride (0.247 g, 1.65 mmol) at 0 °C was added a solution of Formula 3 (0.180 g, 1.07 mmol) and imidazole (0.146 g, 2.14 mmol) in DMF (0.8 mL). The ice bath was removed and the solution was stirred at room temperature for 72 hours until all of the starting material had disappeared by TLC. The mixture was directly subjected to flash chromatography to give Formula 4 as a colorless oil (0.255 g, 81 %); Rf = 0.88 (silica gel, 50% ethyl acetate in hexane); [a] 25D-7. 7 (c= 0.58, CHC13) ; IR (thin film) vmax 2957, 2931,2884, 2857,1673, 1614, 1471,1256, 110,1079, 837,776 cm'H NMR (400 MHz, CDC13) 6 5.62 (s, 1H, CH=C), 3.65 (dd, 1 H, J = 9.6, 4.4 Hz, 1H, CHOH), 2.39 (dd, J = 16.4, 4.4 Hz, 1H, HOCHCH2), 2.08 (dd, J = 16.4, 9.6 Hz, 1 H, HOCHCH2), 2. 10 (q, 2H, J = 6.0 Hz, CH2CH3), 0.98, 0.0. 93 (2s, 6H, C (CH3) 2), 0.89 (t, J = 6.0 Hz, 3H, CH2CH3), 0.70 (s, 9H, SiC (CH3) 3), -0. 11, -0. 12 (2s, Si (CH3) 2); 13C NMR (100 MHz, CDC13) 5 197.2, 172.2, 123.2, 74.7, 43.2, 41.7, 25.5, 24.8, 23.7, 20.5, 17.7, 11. 6, -3.7,-4. 4; D. Oxidative Cleavage Finally, as shown in the last step of each of Figures 3 (a) and 3 (b), the oxidative cleavage of the ether can be accomplished in a number of ways, such as RuCI3/NalO4 ; 03/Jones oxidation; 03, low temperature, Me2S workup; or Ru04, affording the target keto-acid synthon (a common C1-C6 synthon for total synthesis of the epothilones) of formula: in high overall yield utilizing simple reagents. In certain cases, the conditions must be adjusted to accommodate reactive protecting groups, e. g. not all conditions will work on the first try and require some amount of optimization for each case. This aspect of conducting organic synthesis is well known to those practiced in the art. Thus, while a para-methoxybenzyl ether (PMB) at R8 may be easily installed, its stability to highly oxidizing conditions is questionable. Thus, milder reagents, conditions, stoichiometry, temperature, solvents and so on, might have to be adjusted to optimize oxidation of a compound similar to Formula 4 having a PMB ether instead of a TBS ether, to furnish a ketoacid such as a compound similar to Formula 5, below, having PMB instead of TBS. Here again, the keto-acid synthon can be collectively represented with the general formula: An exemplary reaction is provided in Figure 10 for compounds wherein Ri = R2 = R3 = methyl group; R4 = R5 = H; and R8 = tert-butyidimethylsilyl (TBS) in the formulas of Figure 3 (a). The double-bond of Formula 4 is smoothly cleaved to the desired (-)-3S-3- (tert-butyldimethylsilyl) oxy-4, 4-dimethyl-5-oxo-heptanoic acid of formula : O OTBS O Formula 5 HO X e v in 67% yield by the Sharpless method employing NalO4 and RuCI3 in CCI4/CH3CN/H20 (1: 1: 1.6).

Here, sodium periodate (1.18 g, 5.5 mmol) was added into the solution of the enone of Formula 4 (282mg, 1.0 mmol) in CCI4 (1.8 mL) and CH3CN (1.8 mL).

Under vigorous magnetic stirring, RuCI3 (2.9 mL, 9.28 mM in distilled H20, 0.027 mmol) was added and stirring was continued for about 1 hour until the starting material had disappeared by TLC. Water was gradually added until the separated Na103 dissolved and the mixture was then extracted with ethyl acetate (3X5 mL).

The combined organic phase was dried over anhydrous Na2SO4, filtered, and the solvent was then rotary evaporated. The residue was subjected to flash chromatography (silica gel, 50 % ethyl acetate in hexanes) to give 5 (0.202 g, 67 %) as a colorless oil. [a] 25D-15. 8 (c4. 7, CHCI3) ; 1H NMR (400 MHz, CDCI3) 5 10.51 (s, 1H, COOH), 4.45 (dd, 1H, J = 6.8, 3.6Hz, SOCH), 2.62-2. 42 (m, 3H, CH2CH3, CH2COOH), 2.34, 2.30 (dd, J = 6.8 Hz, 16 Hz, SiOCHCH2), 1.12, 1.06 (2s, 6H, 2CH3), 0.98 (t, 3H, J = 7.2 Hz, CH2CH3), 0.83 (s, 9H, SiC (CH3) 3), 0.036, 0.017 (s, 6H, Si (CH3) 2); 13C NMR (100 MHz, CDCI3) 5 215.4, 178.5, 73.7, 52.7, 39.5, 31.9, 26.1, 21.1, 20.7, 18.3, 7.9,-4. 2, -4.7.

The keto-acid of Formula 5 thus obtained had a negative sign of optical rotation ([a] D25 =-15. 8 (c 4.7, CHC13) ; while 5 prepared by a literature method showed [a] D25 =-15 (c 0.56, CHC13). Further, 5 had identical H'and C13 NMR spectra compared to literature values. This result confirmed that the absolute configuration at the chiral center of the compound of Formula 2 was 3S. While none of the steps have been optimized, the overall yield for the four-step process described with respect to Figures 6 through 10 is 24%. The use of commercially available D-proline to construct the chiral center of Formula 5 under very mild reaction conditions provided an economical and practical method for its construction.

Exemplary starting compounds for use in the present invention further include compounds of Formula B in schemes l-oc and l-ß wherein R5 is a thiomethyl, methyl or ether functionality (such as 0-methyl, O-ethyl or the like). R4 may further be a vinyl group. For example, Formula B may be mesitylene oxide (4-methylpent-3-ene- 2-one).

II. Schemes li-a and II-ß An alternative generalized approach is shown as Scheme ll-a and Scheme II- in Figures 4 (a) and (b), respectively.

A. Aldol Condensation Here, the ketone group of the aldehyde is protected as a ketal or acetal of some variety, of formula : As shown in Figure 14, compounds of formula G can be formed indirectly by oxidative cleavage (for example, by 03 or catalytic Os04, Na104, aqueous ethanol) of the terminal double bond of a ketalized a, oc-disubstituted-ß, y-unsaturated ketone, such as of formula : which can be obtained by protecting a ketone of formula : as a ketal. Ketal formation normally can be done using ethylene glycol, benzene, and catalytic p-TSA with a Dean-Stark apparatus, as known in the art. Various appropriate ketal protecting groups and their protection/deprotection procedures are described, for example, in Green et al., Protecting Groups in Organic Synthesis, cited above.

An exemplary formation of a compound according to Formula G is shown in Figure 15. Here, a compound of formula : Formula 6 (Ri = R2 = R3 = methyl in AA of Figure 14) is protected as a ketal of formula: Formula 7 (Ri = R2 = R3 = methyl ; R9-Rio are collectively O-CH2-CH2-O in BB of Figure 14). To a solution of Formula 6 (12.6g, 100 mmol) in 300 ml of benzene was added diethylene glycol (12. 4g, 200 mmol) and pyridinium p-toluene sulfonate (1 g), and the mixture was refluxed, using a Dean-Stark apparatus, for 30 hours. The reaction mixture was washed with sodium bicarbonate, water and brine and dried over anhydrous sodium sulfate. Evaporation of the solvent afforded the crude product, which was distilled under reduced pressure to give the pure ketal of Formula 7 (11.7 g, 69%).

Next, Formula 7 undergoes oxidative cleavage to provide the aldehyde of formula: Formula 8 (Ri = R2 = R3 = methyl ; Rg-Rio are collectively O-CH2-CH2-O in G of Figure 14).

Ozone was bubbled through a solution of Formula 7 (11.05 g, 65 mmol) in methanol (30 ml) at-78°C until the solution became slightly blue in color. Excess ozone was flushed out with a stream of argon and to the crude ozonide was added dimethyl sulfide (15 ml). The reaction mixture was allowed to warm to room temperature.

After stirring for 3 hours, water was added, and the solution was extracted with ethyl acetate. The organic layer was washed with water and brine and dried over anhydrous sodium sulfate. Evaporation of the solvent gave the crude product, which was purified by column chromatography (silica gel, 3% ethyl acetate in hexanes) to afford the pure aldehyde of Formula 8 (7.93 g, 71 %).

As shown in Figures 4 (a) and (b), formula G allows for aldol condensation with a keto component of formula: such as 4-aryl but-3-ene-2-one, to give a first compound of formula : depending on which enantiomer of proline (D-or L-proline) is used. The first compound may optionally be converted to its respective diastereomer lanti-a or lanti-a in the presence of LDA at room temperature, as illustrated in Figures 4 (a) and 3 (b) and as described above with respect to Schemes I-&alpha; and l-ß. This aldol condensation may be performed under the same reaction conditions and utilizing the same reagents as given above for the aldol condensation step of Schemes l-oc and l-ß (for example, D-proline/DMSO/rt, 24hours). The first compound shown illustrated in Figures 4 (a) and 4 (b) can be collectively represented with the general formula : ' The enone starting material H is again either easily prepared by those skilled in the art, or commercially available. Many low molecular weight enones are used as polymer monomers and a large industry exists in the synthesis of compounds such as methyl vinyl ketone, methyl acrylate, acrylic acid, acrylonitrile, and so on.

B. Hvdroxvl Protection The first compound or its diastereomer is then protected as a first intermediate compound of formula: This hydroxyl protection may be performed under the same reaction conditions and utilizing the same reagents as given above for the hydroxyl protection step of Schemes and l-ß (for example, R8X/Imidazole/DMF/rt, 72 hours). The first intermediate compound can be collectively represented with the general formula: C. Oxidation and Deketalization The final keto-acid of formula : can be obtained as shown in Figures 4(a) and (b) after oxidation of the first intermediate compound in the form of protected enone, to a second intermediate compound of formula: and a deketalization step. Here, the second intermediate compound can be collectively represented with the general formula : The oxidation of the second compound may be performed under the same reaction conditions and utilizing the same reagents as given above for the oxidative cleavage step of Schemes l-oc and t-p (for example, RuCI3/NalO4 or O3/Jones oxidation, or Ru04). Enones such as Jsyn-&alpha;, Jsyn-ß, Janti-&alpha; and/or Janti-p overoxidize upon ozonolysis or other oxidation conditions/reagents, leading to loss of the entire double bond and its substituents, and replacing the bond to the enone carbonyl with a hydroxyl group, thereby leaving a carboxylic acid at the position of the enone.

The deketalization step may be performed under conditions known in the art, such as using dilute aqueous mineral acid (such as 1 N HCI) in solvent such as THF and water, stirring at room temperature, or through other methods known in the art such as sequestering the alcohol corresponding to the ketalizing reagent (such as ethylene glycol in many cases shown herein). These methods are greatly expounded upon in Greene et al., Protective Groups in Organic Synthesis, cited above; or Pearson et al., Handbook of Reagents for Organic Synthesis: Activating Agents and Protecting Groups (1999), p. 513.

In some instances, the oxidation can be combined with the deketalization step to go directly from the second compound to the keto-acid in a one pot procedure.

Ill. Schemes III-a and III-a Another alternative approach is shown as Schemes III-a and III-ß in Figures 5 (a) and (b).

A. Aldol Condensation Here, the ketal aldehyde of formula : is employed for aldol condensation with a methyl ketone of formula: forming a first compound of formula : depending upon which enantiomer of proline is used. This aldol condensation may be performed under the same reaction conditions and utilizing the same reagents as given above for the aldol condensation step of Schemes and l-ß (for example, D- proline/DMSO/rt, 24hours). As further shown in Figures 5 (a) and 4 (b) and as discussed above with respect to previous schemes, the diastereomers Nanti-a and Nantj may be formed in the presence of LDA at room temperature. The first compound shown in Figures 5 (a) and (b) can be collectively represented with the general formula: B. Hvdroxvl Protection These adducts (syn or anti) can be protected at the hydroxyl group as a first intermediate compound of formula: This hydroxyl protection may be performed under the same reaction conditions and utilizing the same reagents as given above for the hydroxyl protection step of Scheme I (for example, R8X/Imidazole/DMF/rt, 72 hours). The first intermediate compound can be collectively represented with the formula : C. Haloform Reaction, Enol Ether Oxidation or Benzvlidene Ketone Oxidation The first intermediate compound may be subjected to a haloform reaction to convert the methyl ketone to a carboxylic acid. In this instance, there is no competition for enolization of the terminal ketone, nor for intramolecular cyclization and subsequent halogenations. Thus, after protection of the first compound, the first intermediate compound undergoes the haloform reaction cleanly providing a second intermediate compound of formula Ksyna or Kanti-a ; or for the other enantiomer of prolin, Ksyn-ß or Kanti-p : Here, the haloform reaction may be performed under conditions known in the art, such as a bromoform reaction (for example, Br2/NaOH/Dioxane/H20, 0°C) or an iodoform reaction (for example, 12/NaOH/Dioxane/H20, 0°C). Here, the second intermediate compound can be collectively represented with the general formula: Two alternatives to the haloform reaction are shown in Figures 19 and 20. In one alternative, as shown in Figure 19, enolization of the first intermediate compound to form an oxidizable-silyl enol ether intermediate (for example, TBSOTf/Et3N/CH2CI2,-78 °C to room temperature, see Tetrahedron. Lett. , 1984, 5953), followed by oxidation, forms the second intermediate compound. In a second alternative, as shown in Figure 20, aldol condensation of the first intermediate compound with benzaldehyde to form a benzylidene ketone (for example, DBU/THF, room temperature), followed by oxidation, also forms the second intermediate compound.

D. Deketalization As further shown in Figures 5 (a) and (b), the third compound only requires deketalization to arrive at the keto-acid products of formula Fsyn-&alpha;, Fanti-&alpha;, Fsyn-ß, or Fanti-p, respectively. The deketalization step may be performed as described above with respect to Schemes lu-oc and ii- (for example, 1 N HCI/THF/H20, r. t.).

IV. Schemes IV-a and IV-ß A final alternative approach shown as Schemes IV-a and Il- (3 in Figures 6 (a) and (b) is a streamlined approach.

A. Aldol Condensation The olefinic-aldehyde of formula : undergoes aldol condensation with the ketone of formula : to furnish the syn adduct of a first compound of formula : depending upon the enantiomer of proline used. This aldol condensation may be performed under the same reaction conditions and utilizing the same reagents as given above for the aldol condensation step of Scheme I (for example, D- proline/DMSO/rt, 24hours). In addition, the anti adduct diastereomers Santi-a and Santj may be formed in the presence of LDA at room temperature, as described above. The first compound shown in Figures 6 (a) and (b) can be collectively represented with the general formula: B. Hydroxyl Protection Now, protection with nearly any choice of protecting groups is possible, affording the oxidation precursors, or the intermediate compound, of formula: This hydroxyl protection may be performed under the same reaction conditions and utilizing the same reagents as given above for the hydroxyl protection step of Schemes I-&alpha; and I-P (for example, R8X/Imidazole/DMF/rt, 72 hours). The intermediate compound can be collectively represented with the general formula : C. Oxidative Cleavage As further shown in Figures 6 (a) and (b), upon dual oxidative cleavage of the double bonds of the above oxidation precursors, the keto-acid of formula Fsyn-a7 Fant a, Fsyn-p, or Fantj ß, respectively, is unveiled in a convenient three step process.

The oxidative cleavage may be performed under the same reaction conditions and utilizing the same reagents as given above for the oxidative cleavage step of Scheme I (for example, RuCI3/Na1O4 or O3/Jones oxidation, or Ru04) or for oxidation of the complex enone in Scheme II.

V. Schemes V-a and V-ß A further alternative approach is shown as Schemes V-a and V- in Figures 16 (a) and (b).

A. Aidol Condensation This method comprises performing a crossed aldol condensation of an aldehyde of formula : with an aldehyde of formula : thereby to form a first compound having a formula: which may optionally be converted to a respective diastereomer having a formula : in the presence of LDA at room temperature.

The aldehyde of formula DD may be a compound such as acetaldehyde, propionaldehyde or other appropriate compound. The use of propionaldehyde, for example, works well to provide final acids having R5 = Me. Other R5 groups may be substituted by using other aldehydes of formula DD, as would be appreciated by the ordinarily skilled artisan. The first compound shown in Figures 16 (a) and (b) can be collectively represented with the general formula: B. Hydroxyl Protection Thereafter, the hydroxyl group of the first compound or its diastereomer may be protected with a protecting group to form an intermediate compound having a formula selected from: This hydroxyl protection may be performed under the same reaction conditions and utilizing the same reagents as given above for the hydroxyl protection step of Scheme I (for example, R8X/Imidazole/DMF/rt, 72 hours). The intermediate compound can be collectively represented with the general formula : C. Oxidation An aldehyde to carboxylic acid oxidation may then be performed on the intermediate compound thereby to form the keto-acid having a formula : The oxidation may be performed under the same reaction conditions and utilizing the same reagents as given above for the oxidative cleavage step of Scheme I (for example, RuCI3/NalO4 or O3/Jones oxidation, or Ru04) or for oxidation of the complex enone in Scheme II.

VI. Schemes Vl-oc and Vu-0 An additional approach is shown as Schemes Vl-oc and Viz in Figures 17 (a) and (b). As shown here, it is possible to utilize a reduced keto-aldehyde synthon in its protected version for the aldol condensations and provides alterations in diastereoselectivity. Ultimately, the alcohol can be oxidized back to the ketone before aldol reaction with a larger epothilone aldehyde segment (as discussed with respect to Figures 12 (a) through (d) and 13 (a) through (d), below).

A. Aldol Condensation An aldol condensation is performed between a protected alcohol-aldehyde synthon of formula : with a methyl ketone of formula : thereby to form a first compound having a formula: which may optionally be converted to a respective diastereomer having a formula: in the presence of LDA at room temperature. The first compound shown in Figures 17 (a) and (b) can be collectively represented with the general formula: As shown in Figure 18, when the protected alcohol-aldehyde is an enantiomerically pure compound of formula : the first compound may have a formula : and the respective diastereomer may have a formula : B. Hydroxyl Protection The hydroxyl group of the first compound or its diastereomer may be protected with a protecting group to form a first intermediate compound having a formula : This hydroxyl protection may be performed under the same reaction conditions and utilizing the same reagents as given above for the hydroxyl protection step of Scheme I (for example, R8X/Imidazole/DMF/rt, 72 hours). The first intermediate compound may be collectively represented with the general formula : C. Haloform Reaction, Enol Ether Oxidation or Benzvlidene Ketone Oxidation The first intermediate compound may be subjected to a haloform reaction to convert the methyl ketone to a carboxylic acid. In this instance, there is no competition for enolization of the terminal ketone, nor for intramolecular cyclization and subsequent halogenations. Thus, after protection of the first compound, the first intermediate compound undergoes the haloform reaction cleanly providing a second intermediate compound of formula KKsyn-a or KKanti-a; or for the other enantiomer of proline, KKsyn-or KKantiC13 Here, the haloform reaction may be performed under conditions known in the art, such as a bromoform reaction (for example, Br2/NaOH/Dioxane/H20, 0°C) or an iodoform reaction (for example, I2/NaOH/Dioxane/H2O, 0°C). The second intermediate compound may be collectively represented with the formula: Two alternatives to the haloform reaction are shown in Figures 21 and 22. In one alternative, as shown in Figure 21, enolization of the first intermediate compound to form an oxidizable silyl enol ether intermediate (for example, TBSOTf/Et3N/CH2CI2,-78 °C to rt, see Tetrahedron. Lett., 1984, 5953), followed by oxidation, forms the second intermediate compound. In a second alternative, as shown in Figure 22, aldol condensation of the first intermediate compound with benzaldehyde to form a benzylidene ketone (for example, DBU/THF, rt), followed by oxidation, also forms the second intermediate compound D. Deprotection and Oxidation The third compound may then be deprotected and oxidized to form the keto- acid of formula: The deprotection step may be performed as described above with respect to the deketalization step of Schemes li-a and ll-ß (for example, 1 N HCI/THF/H20, r. t.).

The oxidation may be performed under the same reaction conditions and utilizing the same reagents as given above for the oxidative cleavage step of Scheme I (for example, RuCI3/Na104 or O3/Jones oxidation, or Ru04) or for oxidation of the complex enone in Scheme II.

VII. Epothilone Synthesis It should now be appreciated that the keto-acid synthons formed according to the methods of the present invention may be incorporated into various routes for epothilone synthesis. For example, as shown in Figures 12 (b) and 12 (b), a keto-acid synthon of formula: *anti-a or analogs, derivatives or stereoisomers thereof (including Fsyn. af Fsyn p and Fantj ß, as shown in Figures 12 (a) and 13 (a), 12 (c) and 13 (c), and 12 (d) and 13 (d), respectively), may undergo aldol condensation with a second compound selected from the formulas: and stereoisomers thereof. Here, the aldol condensation may be performed, for example, under conditions a) 2LDA/-40°C ; b) TBSOTf ; c) silica gel, as reported in U. S. Patent Application No. 09/981,312 entitled"Synthesis of Epothilones and Related Analogs" (U. S. Publication No. US 2002/0091269 A1) and in PCT Application No. PCT/US01/32225 of the same title (PCT Publication No. WO 02/30356 A2). This second compound can be collectively represented with the formula : wherein Z is selected from The resulting product in the form of a third compound has a formula selected from: and stereoisomers thereof undergoes macrolactonization. The macrolactonization may be performed, for example, under conditions of OsPhCOCt/pyridine/DMAP, again as reported in U. S. Patent Application No. 09/981, 312 entitled"Synthesis of Epothilones and Related Analogs" (U. S. Publication No. US 2002/0091269 A1) and in PCT Application No. PCT/US01/32225 of the same title (PCT Publication No. WO 02/30356 A2). The third compound can be collectively represented as: wherein Z is selected from The macrolactonization step forms an epothilone compound, or analogs or derivatives thereof, having a formula selected from: and stereoisomers thereof, wherein R1-R3, R5 and R8 are as above and Rn-Rie and Ris are each individually selected from H or optionally substituted n-alkyl, s-alkyl, t- alkyl, E or Z alkenyl, terminal alkenyl, alkynyl, aryl, alkylaryl, alkenylaryl, alkynylaryl, alkylheteroaryl, alkenylheteroaryl, alkynylheteroaryl, cycloalkyl, alkylheterocyclic, alkenylheterocyclic, alkynylheterocyclic, heteroalkyl, heteroalkenyl, heteroalkynyl, primary alkylamines, secondary alkylamines, tertiary alkylamines, alkyl sulfides, alkylethers, hydroxyalkyls, alkylthiols and other functional groups known in the art.

In one particular embodiment, R1, R2, R3, R11, R13, and R14 may each specifically be methyl ; R5 and R12 may each specifically be H; R8 and Ris may each specifically be a TBS protecting group; and R15 and R16 may each specifically be a TBS or TMS protecting group. The epothilone compound can be collectively represented as: wherein Z is selected from This compound may be further modified as known in the art, again such as taught for example in U. S. Patent Application No. 09/981,312 entitled"Synthesis of Epothilones and Related Analogs" (U. S. Publication No. US 2002/0091269 A1) and in PCT Application No. PCT/US01/32225 of the same title (PCT Publication No. WO 02/30356 A2).

It should be appreciated that keto-acid synthons of formula Fsyn-a, Fsyn-p and Fantj may be substituted for the keto-acid synthon Fanti-a in the above-described exemplary epothilone synthesis to provide epothilones of formula W, Z, W", Z", W"' and Z"', and stereoisomers thereof, as shown in Figures 12 (a) and 13 (a), 12 (c) and 13 (c), and 12 (d) and 13 (d), respectively.

Vl. Chemical Compounds and Production Methods Finally, it should be appreciated that the present invention is also directed to novel chemical compounds disclosed herein that are useful in the synthesis of epothilones and analogs and derivatives thereof. For example, the present invention provides compounds having the following formulas: wherein Ri-Rio are as defined above.

Additionally, the present invention provides methods for forming each of these chemical compounds, as illustrated in the individual steps of the above-described methods.