The bakers' yeastreduction of trifluoroacetyl derivatives was examined in the presence of various esters of methanethiosulfonate. The yeastreduction of 4-bromo-4′-trifluoroacetylbiphenyl using the cyclohexylmethyl methanethiosulfonate resulted in the R product with the highest enantiomeric excess of 96% ee, which is compared with the reduction without the additive to give the corresponding alcohol
Structural effects of the oxazaborolidine derived from L-threonine in the reduction of (trifluoroacetyl)biphenyl derivatives with catecholborane
作者:Tamotsu Fujisawa、Yoshio Onogawa、Makoto Shimizu
DOI:10.1016/s0040-4039(98)01237-4
日期:1998.8
The reduction of (trifluoroacetyl)biphenyl derivatives with catecholborane as a stoichiometric reductant in the presence of the oxazaborolidine catalyst derived from L-threonine in dichloromethane-toluene at -90 degrees C proceeds to give the corresponding alcohols in high yields with high enantioselectivity: The distinctive feature of this oxazaborolidine exists in the five-membered ring covered with the t-butyldimethylsiloxy group. (C) 1998 Elsevier Science Ltd. All rights reserved.
Asymmetric reductions of (trifluoroacetyl)biphenyl derivatives with bakers' yeast and with Geotrichum candidum acetone powder
The bakers' yeast reduction of (trifluoroacetyl)biphenyl derivatives produces (R)-trifluoromethyl biphenylyl carbinols in high enantioselectivity, whereas the reduction of the same derivatives with Geotrichumcandidumacetonepowder gives the corresponding (S)-carbinols in excellent yields and enantioselectivity.