A Novel Method for the In situ Generation of Alkoxydialkylboranes and Their Use in the Selective Preparation of 1,3-<i>syn</i>Diols
作者:Kau-Ming Chen、Karl G. Gunderson、Goetz E. Hardtmann、Kapa Prasad、Oljan Repic、Michael J. Shapiro
DOI:10.1246/cl.1987.1923
日期:1987.10.5
An in situ method for generating Et2BOCH3 from triethylborane and methanol without using any other catalysts is described. Using the Et2BOCH3 thus generated as a chelating agent, syn 1,3-diols are prepared in ≥ 98% stereochemical purity by reducing β-hydroxyketones with sodium borohydride.
A convenient stereoselective synthesis of 5-hydroxy-3-oxoesters and 3-hydroxy-5-oxoesters
作者:Anna Żądło-Dobrowolska、Joerg H. Schrittwieser、Barbara Grischek、Dominik Koszelewski、Wolfgang Kroutil、Ryszard Ostaszewski
DOI:10.1016/j.tetasy.2017.05.005
日期:2017.6
A biocatalytic approach was employed for the asymmetric reduction of sterically demanding ketones to prepare 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates. Screening a collection of microorganisms led to the identification of stereocomplementary microbial strains that provide access to both enantiomers of 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). Moreover, the application of Saccharomyces cerevisiae gave two diastereomers of 3,5-dihydroxy-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). The applicability of the identified strains was demonstrated by transforming the obtained dihydroxy ester into the chemically valuable lactone (4S,6R)-tetrahydro-4-hydroxy-6-phenyl-pyran-2-one. (C) 2017 Elsevier Ltd. All rights reserved.
A Concise Total Synthesis of Diospongins A and B
作者:Gowravaram Sabitha、Pannala Padmaja、Jhillu S. Yadav
DOI:10.1002/hlca.200890242
日期:2008.12
The totalsynthesis of the diarylheptanoids (−)-diospongin A (1) and B (2) was achieved stereoselectively via the δ-lactone intermediate 6. The key reactions involved are a stereoselective reduction of β-keto ester and the Horner–Wadsworth–Emmons and intramolecular oxy-Michael reactions.