Highly enantioselective reduction of β,β-disubstituted aromatic nitroalkenes catalyzed by Clostridium sporogenes

This is the first report of the use of Clostridium sporogenes extracts for enantioselective reduction of C = C double bonds of beta,beta-disubstituted (1) and alpha,beta-disubstituted nitroalkenes (3). Crude enzyme preparations reduced aryl derivatives la-e and 1h, in 35-86% yield with >= 97% ee. Reduction of (E)- and (Z)-isomers of 1c gave the same enantiomer of 2c (>= 99% ee). In contrast, alpha,beta-disubstituted nitroalkene 3a was a poor substrate, yielding (S)-4a in low yield (10-20%), and the ee (30-70% ee) depended on NADH concentration. An efficient synthesis of a library of nitroalkenes I is described.