Elsevier

Steroids

Volume 13, Issue 1, January 1969, Pages 11-20
Steroids

Novel A-nor sterols: Synthesis and stereochemistry

https://doi.org/10.1016/S0039-128X(69)80056-5Get rights and content

Abstract

A new and simple method of synthesis of A-nor sterols having a tertiary hydroxyl group allylic to an exocyclic methylene is described consisting of utilization of the Eschenmoser Fragmentation of αβ-epoxy ketones and the Stork Ring-closure of acetylenic ketones. 4β,5β-epoxycholestan-3-one gave 3-methylene-A-nor-cholestan-5β-ol together with 3-methyl-A-nor-cholest-3-ene (III). The structure of the former was established by NMR, IR and by allylic isomerization. The stereochemistry at the 5 position was established by correlation with the diol and the minor epoxide obtained from III and to which configurations were assigned using NMR data. Exclusive formation of cis-hydrindane brings forth an unsuspected stereoselectivity in the Stork Ring-closure. The 17 β-hydroxyandrostane analogue was prepared via the pyranyl ether. With the hydroxyl unprotected the sole product in the Stork reduction was III (R = OH).

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