22α-hydroxy-23-ketone moieties characteristic of brassinolide and its congeners, has been developed. The key step is the coupling of a steroidal C-22 aldehyde with an anion derived from a specially synthesized thioacetal-containing chiral synthon. The cathasterone and cryptolide side chains are prepared by reductive or hydrolytic thioketal removal, respectively. The brassinolide side chain is obtained by DIBAL-H
Stereoselective synthesis of α-methyl and α-alkyl ketones from esters and alkenes<i>via</i>cyclopropanol intermediates
作者:Maryia V. Barysevich、Volha V. Kazlova、Aliaksandr G. Kukel、Aliaksandra I. Liubina、Alaksiej L. Hurski、Vladimir N. Zhabinskii、Vladimir A. Khripach
DOI:10.1039/c8cc00888d
日期:——
undergo Kulinkovich hydroxycyclopropanation with good diastereoselectivity. For the isomerization of the resulting cyclopropanols to diastereomerically enriched α-methyl ketones, a new mild regioselective method has been developed. A sequence of stereoselective cyclopropanation and cyclopropanol ring opening was successfully employed for the construction of the C20 stereocenter in steroids.
The development and use of a general route to brassinolide, its biosynthetic precursors, metabolites and analogues
作者:A. L. Hurski、Yu. V. Ermolovich、V. N. Zhabinskii、V. A. Khripach
DOI:10.1039/c4ob02197e
日期:——
A new method for the construction of steroid sidechains through the addition of lithium salts of dithianes to a C-22 aldehyde was developed. An efficient one-pot procedure for the preparation of a suitable C-22 aldehyde from commercial epibrassinolide in three steps in 86% isolated yield was described. Enantioselective hydroxymethylation of isovaleraldehyde and Kulinkovich cyclopropanation of silylated