Enzymatic reduction method for the preparation of compounds useful for preparing taxanes

A method for the enzymatic reduction of a compound of the formula I or a salt thereof:

• ##STR21## to form a compound of the formula II or a salt thereof:
• ##STR22## where W is
• (a) --NHR.sup.3 ;
• or
• (b) --N.sub.3 ;
• R.sup.1 is aryl;
• R.sup.2 is
• (a) hydrogen;
• or
• (b) R.sup.4, where R.sup.4 is (i) alkyl;
• (ii) aryl;
• (iii) cycloalkyl;
• (iv) alkenyl;
• (v) alkynyl;
• or (vi) cycloalkenyl, wherein the ring portion of said cycloalkyl and cycloalkenyl groups consists of 1 to 3 rings and 3 to 7 carbons per ring;
• and
• R.sup.3 is
• (a) --C(O)--OR.sup.4, where R.sup.4 is alkyl;
• or
• (b) --C (O)--R.sup.4, where R.sup.4 is aryl;
• where, with respect to the chiral center marked with an asterisk, said compound of the formula I or salt thereof is employed as a starting material as a single isomer or as a mixture of both R and S isomers,
• comprising the step of contacting said compound of the formula I or salt thereof with an enzyme or microorganism which catalyzes said reduction, and effecting said reduction, thereby obtaining said compound of the formula II or salt thereof,
• (1) wherein said enzyme or microorganism is a microorgsnism selected from the genera consisting of Candida, Rhodococcus, Saccharomyces, Hansenula, Pseudomonas, Nocardia, Mortierella, Penicillium, Cunninghamella, Geotrichum, Pichia, Aspergillus, and Mucor, or is an enzyme obtained therefrom, or
• (2) wherein said enzyme is selected from the group consisting of L-2-hydroxy isocaproate dehydrogenase, lactic acid dehydrogenase, .beta.-hydroxyhutyrate dehydrogenase, glucose dehydrogenase, alcohol dehydrogenase, glycerol dehydrogenase, formate dehydrogenase, pyruvate dehydrogenase and hydroxy steroid dehydrogenase.