A stereoselective chemoenzymatic synthesis of all fourstereoisomers of tert-butyl 6-chloro-3,5-dihydroxy-hexanoate (6a) is presented. The key step of the sequence is a highly regio- and enantioselective single-site reduction of tert-butyl 6-chloro-3,5-dioxohexanoate (1a) by two enantiocomplementary biocatalysts. Alcohol dehydrogenase from Lactobacillus brevis (recLBADH) afforded a 72% yield of enantiopure
Asymmetric Total Synthesis of (−)-Callystatin A Employing the SAMP/RAMP Hydrazone Alkylation Methodology
作者:Jose L. Vicario、Andreas Job、Michael Wolberg、Michael Müller、Dieter Enders
DOI:10.1021/ol0256116
日期:2002.3.1
[structure: see text] The asymmetrictotalsynthesis of (-)-callystatin A has been achieved. The key steps generating the stereogenic centers rely on the asymmetric alpha-alkylation of aldehydes or ketones exploiting the SAMP/RAMPhydrazone alkylation methodology, as well as an enzymatic enantioselective reduction of a 3,5-dioxocarboxylate. For the construction of the alkene moieties, highly selective