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Summary. rac-2-Acetoxy-1,1-dimethyl-1-sila-cyclohexane (rac-2) was synthesized by esterification of rac-1, 1-dimethyl-1 ~sila-cyclohexan-2-ol (rac-1) with acetic anhydride. Enantioselective hydrolysis of rac-2 in aqueous solution, catalysed by a crude Iipase preparation of Candida cylindracea (EC 3.1.1.3), led to the formation of (S)-1 (95% ee). Enantioselective transesterification of rac-1 with triacetin in isooctane, catalysed by the same enzyme preparation, yielded (S)-2 (95% ee), which was separated by chromatography from non-reacted (R)~1 (96% ee). Recrystallization led to an improvement of the enantiomeric purity of (R)-1 and (S)-1 up to >98% ee. Thus the enantiomers of rac-1 were prepared (100 mg scale) with high enantiomeric purities by the use of two different types of enzyme-catalysed reaction.

Abstract(R)-1,1-Dimethyl-1-sila-cyclohexan-2-ol [(R)-2] was prepared by enantioselective microbial reduction of 1,1-dimethyl-1-sila-cyclohexan-2-one (1) with growing cells of the yeast Kloeckera corticis (ATCC 20109). At a substrate concentration of 0.5 g/1 (temperature 27° C, incubation time 16 h), (R}-2 was obtained on a preparative scale in 60% yield and with an enantiomeric purity of 92% ee. Repeated recrystallization of the biotransformation product from n-hexane raised the enantiomeric purity to 99% ee.