The first totalsynthesis of (+)-conagenin, a novel immunomodulator produced by Streptomyces roseosporus, has been achieved in highly stereo- and enantioselective manner. The carboxylic acid moiety was synthesized starting with asymmetric aldol reaction of propiophenone with acetaldehyde followed by in situ syn-selective NaBH4 reduction. The amino acid moiety was synthesized based upon Et2AlCl catalyzed
作者:Daniela Acetti、Elisabetta Brenna、Claudio Fuganti、Francesco G. Gatti、Stefano Serra
DOI:10.1002/ejoc.200901006
日期:2010.1
Reduction of β-hydroxy ketones to the corresponding 1,3-diols by baker'syeast was investigated, in order to develop methods for simultaneous control over the configurations of multiple stereogenic centres. The reactions were found to be enantiospecific and generally characterised by good diastereoselectivity. Substrates with a substituent at the carbon atom in the α position were also considered.
Diastereoisomers (1S,2R,3S)-, (1R,2R,3S)-, (IR,2S,3S)- and (1S,2S,3S)-2-methyl-1-phenyl-1,3-butanediols were prepared by simple and convenient strategies using two different chemo-enzymatic approaches for the reduction of racemic 2-methyl-1-phenyl-1, 3-butanedione, both involving in situ racemization. The first method comprised a one-pot microbial reduction coupled with a chemical reduction, while in the second method, stepwise chemo-enzymatic reductions were performed. (c) 2006 Elsevier Ltd. All rights reserved.