Microbiological desymmetrization of difficult-to- reduce bulky-bulky ketones

Abstract This report presents the desymmetrization of prochiral bulky-bulky pyrimidine bases in the presence of commercial or home-made enzyme preparations as biocatalysts. Based on the experiments carried out, it was shown that commonly used baker’s yeast is a catalyst for 1N- and 3N-phenacyl derivatives of trimethyleneuracils. The substrate concentration and pH of the reaction medium were important for the selectivity and efficiency of the process. 1N derivatives were reduced with the highest degree of enantiomeric purity and a moderate degree of conversion for a substrate concentration of 5×10-4 mol/dm3, in a solution with pH 7.0 and 5.0. In the case of 3N-phenacyl derivatives for a concentration of 1×10-3 mol/dm3 in a solution with pH 6.0 and 7.0. Biotransformations catalyzed by Saccharomyces cerevisiae provided the corresponding (R)- or (S)-products with high optical purity (up to 99% ee).