A new approach to the side chain formation of 24-alkyl-22-hydroxy steroids: Application to the preparation of early brassinolide biosynthetic precursors
作者:Alaksiej L. Hurski、Vladimir N. Zhabinskii、Vladimir A. Khripach
DOI:10.1016/j.steroids.2012.03.010
日期:2012.6
introduction of the 22-hydroxyl group has been achieved by epoxidation of the Delta(22)-double bond, nucleophilic opening of the intermediate mesyl epoxide with sodium sulfide, and desulfurization of the formed tetrahydrothiophenes with Raneynickel.
The putativeintermediates in brassinolide biosynthesis, 22α-hydroxycampesterol 1, 6-deoxocathasterone and its 6α-hydroxylated compound 3, as well as cathasterone 4, are synthesized from a known (22E,24S)-6β-methoxy-3α,5-cyclo-5α-ergost-22-ene 5.
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.