(±)-N-Isonicotinoyl-2-amino-5-chlorobenzhydrol (1) is a rice plant growth regulator which shortens the second leaf sheaths. One of the enantiomers, (S)-1, was obtained by microbiological asymmetric reduction of 2-amino-5-chlorobenzophenone using Rhodosporidium toruloides followed by isonicotinoylation. Several substituted benzhydrol derivatives were also prepared by use of the same biological method and converted to N-isonicotinoyl compounds. The growth-regulating activities of these compounds were evaluated.
Synthesis of chiral alcohols by asymmetric reductions of various ketones including α-aminophenones
作者:Eric Brown、Antoine Lézé、Joël Touet
DOI:10.1016/0957-4166(96)00245-5
日期:1996.7
LiAlH4 previously treated with 2.5 equiv. of (S)-(+) or (R)-(-)-2-(2-isoindolinyl)butan-1-ol 1 reduced the six alpha-aminophenones 4-9 into the corresponding optically active beta-aminoalcohols 10-15 whose ee's were in the range 40-97% after chromatography and recrystallization. The asymmetric reduction of the ortho-dimethylaminobenzophenone 18, using the same reducing agents afforded the enantiomerically pure benzhydrols (R)-(-)-19 and (S)-(+)-19, respectively, and in 86-100% yields. The ortho-aminobenzhydrol (S)-(+)-20 and a-fluorenyl ethanol (R)-(+)-23 and (S)-(-)-23 were similarly obtained from the corresponding ketones 17 and 25, respectively. The latter carbinols were obtained in an enantiomerically pure state after recrystallization. Copyright (C) 1996 Elsevier Science Ltd