Synthesis of enantiopure 2,7-diaryl-1,6-dioxaspiro[4.4]nonanes via enantioselective reduction of prochiral γ-nitroketones by diisopinocampheylchloroborane (DIP-C1™)
摘要:
The enantioselective reduction of gamma-nitroketones 1-4 and gamma-nitrodiketones 5-6 by the chiral reducing agent (+)- or (-)-diisopinocampheylchloroborane (DTP-Cl(TM)) afforded respectively nitroalcohols 7-9 with e.e.'s ranging from 33 to 86% and nitrodiols 11-12 with complete diastereoselectivity and e.e. > 95 %. Nitrodiols (1S,7S)-11 and (1S,7S)-12 were then used as chiral precursors for the synthesis of the enantiopure 2,7-diphenyl- and 2,7-di-(2'-methoxyphenyl)-2,6-dioxaspiro[4.4]nonanes, 21 and 22, as EE/ZZ mixtures. Copyright (C) 1996 Elsevier Science Ltd
Microbial biotransformations in water/organic solvent system. Enantioselective reduction of aromatic β- and γ-nitroketones
摘要:
The production of single enantiomers of gamma- and beta-nitroalcohols by microbial bioreduction has been studied. A restricted screening among 14 yeasts was performed using 1-phenyl-4-nitro-1-butanone 1 as substrate. Pichia minuta (CBS 1708) and Pichia etchellsii (CBS 2011) gave the highest enantiopreference for (S)-alcohol 3 formation (e.e. 85% and 80%, respectively), while Kluyveromyces marxianus (CBS 397) was the only strain able to preferentially furnish the (R) enantiomer (e.e. 70%). These three microorganisms, along with baker's yeast, were then employed in reactions performed in water/organic solvent systems using different solvents (hexane, benzene and dibutyl ether) affording alcohol 3 in high enantiomeric excesses (>95-97%). These strains were also employed to reduce 1-phenyl-3-nitro-1-propanone 2, maintaning the same stereobias observed with gamma-nitroketone 1 and showing high enantioselectivity in both simple aqueous (>85-97%) and biphasic media (>97%). (C) 1998 Elsevier Science Ltd. All rights reserved.
Baker's yeast reduction of prochiral γ-nitroketones: Enantioselective synthesis of (S)-4-nitroalcohols
作者:Antonio Guarna、Ernesto G. Occhiato、Laura M. Spinetti、Maria E. Vallecchi、Dina Scarpi
DOI:10.1016/0040-4020(94)01056-6
日期:1995.2
The baker'syeastreduction of seven different prochiral nitroketones 1a-g occurred on the re face of the carbonyl group, thus affording the (S)-nitroalcohols 2a-g, with different level of enantioselectivity (e.e. 15–99%). The best results (e.e. = 99%) were achieved when the substituent R is markedly different from the nitroalkyl group [e.g. 1a (R = Me) and 1e (R = o-MeO-C6H4)]. The e.e. and the configuration
Baker的七个不同的前手性硝基酮酵母还原1A-G上发生了重新羰基的面,由此提供第(小号)-nitroalcohols 2A-G ,具有不同水平的对映选择性(EE 15-99%)。当取代基R与硝基烷基显着不同时(例如1a(R = Me)和1e(R = o -MeO-C 6 H 4)),可获得最佳结果(ee = 99%)。通过相应的Mosher酯的NMR研究确定了生物产物的ee和构型,在一种情况下(2d)的化学相关性。还描述了从2d开始的光学活性内酯7和吡咯烷11的合成。
Lyophilised yeasts: easy-to-handle biocatalysts for stereoselective reduction of ketones
作者:Francesco Molinari、Raffaella Gandolfi、Raffaella Villa、Ernesto G Occhiato
DOI:10.1016/s0957-4166(99)00379-1
日期:1999.9
The use of lyophilised yeasts as biocatalysts for the reduction of carbonyl compounds has been studied. First, a comparison of the performances of fresh and lyophilised cells of seven yeasts was performed using ethyl acetoacetate and acetophenone as typical substrates. Lyophilised cells gave from low to high conversions but, with a few exceptions, always good enantioselectivity, and they were then employed for the reduction of structurally different carbonyl compounds. Highly enantioselective reduction of carbonyls was often achieved, even with aromatic ketones. Both enantiomers of the alcohols were, in most cases, obtained with high enantiomeric excess by simply choosing a suitable yeast. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.
Selectivity of Daucus carota roots and baker’s yeast in the enantioselective reduction of γ-nitroketones
作者:Dina Scarpi、Ernesto G. Occhiato、Antonio Guarna
DOI:10.1016/j.tetasy.2005.03.002
日期:2005.4
The enantioselective reduction of a series of aromatic gamma-nitroketones was achieved by using Daticus carota roots in water, which afforded the corresponding (S)-alcohols with ees ranging from 73% to 100%. A comparison of these results with the data obtained by reducing the same substrates with baker's yeast resulted in D. carota always being more enantioselective than baker's yeast, although a lower number of substrates were reduced. The possible influence of the aromatic ring substituents on the reaction outcome is also discussed. (c) 2005 Elsevier Ltd. All rights reserved.