A new isolate, Rhodotorula sp. AS2.2241, capable of reducing acetophenone and α-bromoacetophenone with high stereoselectivity, was further studied to exploit its potential in the asymmetric reduction of silicon-containing ketones to silyl alcohols. After encapsulation, the cells were used in an aqueous or an aqueous/organic solvent biphasic system for the asymmetric reduction of cetyltrimethylsilane (ATMS) to prepare (−)-1-trimethylsilylethanol [(−)-TMSE]. It has been found that higher product yield and product enantiomeric excess could be achieved with immobilized cells in an aqueous/organic solvent biphasic system. For optimization of the reaction, various influential variables, such as the volume ratio of the aqueous phase to the organic phase, the hydrophobicity of the organic solvent, reaction temperature, buffer pH of the aqueous phase and the shaking speed, were examined with respect to the initial reaction rate, the product yield and the enantiomeric excess (e.e.) of TMSE formed. All the factors mentioned above had influences on the reaction to some extent. Isooctane was found to be the most suitable organic phase for the reaction. The optimum volume ratio of the aqueous phase to the organic phase, reaction temperature, buffer pH and shaking speed were 1/1, 40℃, 6.5 and 150 rpm, respectively under which the product yield and the product enantiomeric excess were as high as 99 and 90%, which are much higher than those previously obtained by enantioselective reduction of acylsilanes.

The enantioselective synthesis of (R)-2-trimethylsilyl-2-hydroxyl-ethylcyanide with (R)-oxynitrilase from defatted almond meal in a biphasic system was successfully performed. The influences of some factors on the reaction were investigated systematically. Diisopropyl ether was found to be the best for this reaction among all the organic solvents explored. The optimal aqueous phase content, concentrations of crude enzyme, acetyltrimethylsilane, acetone cyanohydrin, shake speed, buffer pH, reaction temperature were 13% (v/v), 5% (w/v), 0.02M, 0.04M, 150rpm, 5.0, 40℃, respectively, under which the initial reaction rate, substrate conversion and product e.e. were 5.87mmol/lh, 99.5 and 99.0%.

Synthesis of optically active organosilyl alcohol via asymmetric reduction of prochiral acyl silane with immobilized Saccharomyces cerevisiae type II (a mutant from S. cerevisiae by UV irradiation treatment, named UVSC II) cells compared to free UVSC Ⅱcells was studied. It has been found that higher yield and enantiomeric excess (e.e.) of the product could be achieved with immobilized UVSC Ⅱ cells. To further enhance the product yield and the product e.e., an aqueous/organic biphasic system was used as the reaction medium. The influence of various factors, such as shake speed, organic solvent, volume ratio of water phase to organic phase, buffer pH of water phase, reaction temperature and substrate concentration, was systematically studied and the reaction conditions were optimized with respect to the initial reaction rate, the product yield and the product e.e. All the above-mentioned factors had effect on the reaction to some extent. n-Hexane was found to be the best organic solvent. The optimum shake speed, volume ratio of water phase to organic phase, buffer pH, reaction temperature and substrate concentration were 150rpm, 1/2, 8.0, 30℃ and 42mM, espectively, under which the product yield and the product e.e. were as high as 97.4 and 95.4%.

The enantioselective esterification of racemic 1-trimethylsilylethanol with acids actalyxed by lipase in organic solvent was successfully performed. The influence of some factors on the reaction was investigate. Among the four lipases explores, Candida rugosa lipase (CRL) showed the highest activity and enantioselectivity. Octanoc acid was the best acyl donor among the eleven acids studied and n-hexane was the most suitable medium for the reaction. The optimum shaking rate and temperature were found to be 150r·min-1 and 20℃ to 30℃, respectively. The enantiomeric excess of the remaining (S)-(-)-1-trimethylsilylethanol was 93% when substrate conversion was 53% upon incubation of the reaction mixture at 30℃, 150r·min-1 for 12h.