1,4-Chirality transfer via the ester enolate Claisen rearrangements in the preparation of (25R)- and (25S)-cholestenoic acids

Yurii V Ermolovich; Vladimir N Zhabinskii; Vladimir A Khripach

doi:10.1016/j.steroids.2013.03.006

1,4-Chirality transfer via the ester enolate Claisen rearrangements in the preparation of (25R)- and (25S)-cholestenoic acids

Steroids. 2013 Jul;78(7):683-92. doi: 10.1016/j.steroids.2013.03.006. Epub 2013 Apr 9.

Authors

Yurii V Ermolovich¹, Vladimir N Zhabinskii, Vladimir A Khripach

Affiliation

¹ Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str. 5/2, 220141 Minsk, Belarus.

PMID: 23583600
DOI: 10.1016/j.steroids.2013.03.006

Abstract

Two variants of the Claisen rearrangement were evaluated for a stereoselective construction of a C-25 stereogenic center in cholestenoic acids based on 1,4-chirality transfer. Johnson orthoester Claisen rearrangement of (22R)- and (22S)-propargyl enol ethers proceeded in a highly stereoselective manner to give (25R)- and (25S)-isomeric allenes. The stereochemical outcome of the Ireland-Claisen rearrangement of 22-allylic alcohols was dependent on the configuration of the C-22 hydroxyl group and the geometry of the enol ether. The latter could be controlled by the solvent (THF or a mixture of THF/HMPA) chosen for the generation of silyl enolate.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

4-Aminopyridine / analogs & derivatives
4-Aminopyridine / chemistry
Cholestenes / chemistry*
Hempa / chemistry
Molecular Structure
Stereoisomerism

Substances

Cholestenes
cholestenoic acid
4-Aminopyridine
Hempa
4-dimethylaminopyridine