Kinetic resolution of racemic l-cyano-l-methylalkyl and alkenyl acetates has been achieved on incubation with Pichia mist IAM 4682, which -hydrolyzed selectively the (RI-enantianer, leaving behind the (S)-enantianer intact. The chiral l-cyano-lmethyl-5-hexenyl acetate thus obtained was converted to (S)-(-)-frontalin via unsaturated diol.
The enzymatic kinetic resolution of cyanohydrin acetates is unique because hydrolyzed cyanohydrin can be easily converted to starting ketone simply by controlling the pH of the medium. ') Thus, in principle, one mole of chiral cyanohydrin acetate can be obtained from one mole of racemate without any tedious racemization process. This reaction provides a convenient tool for the synthesis of optically active compounds. Although some methods have been disclosed for the preparation of chiral aldehyde cyanohydrins including biochemical, 2, catalytic3) and diastereoselective reactions,l) relatively few reports have been demonstrated so far on the synthesis of ketone cyanohydrins. 5) As these canpounds are considered to be useful in organic synthesis, we tried to obtain them via microbial kinetic resolution of the corresponding acetates.
We have already reported that esterases of Candida trooicalis6) and bacillus coasulans7) are effective to the enantioselective hydrolysis of a number of cyanohydrin carboxylates. Thus, we first tested these strains to the kinetic resolution of l-cyano-I-methyldecyl acetate (4d) as the representative substrate. Unfortu-