Ring-c aromatic steroids. 17β-Methyl-18-norpregna-8,11,13-trienes

Abstract

Boron trifluoride–diethyl ether converts 20α,21-diacetoxy-9α,11α-epoxy-17α-hydroxypregn-4-en-3-one (18) into 20α,21-diacetoxy-17β-methyl-18-norpregna-4,8,11,13-tetraen-3-one (19). An analogous C-aromatic steroid is similarly obtained from 9α,11α-epoxy-17α-methyltestosterone (9). From (19), by modifications of ring A and the 17α-side-chain, a series of 17β-methyl C-aromatic steroids has been prepared. The 5β configuration of the 3-ketone (21), obtained stereospecifically by hydrogenation of the Δ⁴-3-ketone (19) is deduced from ¹³C and ¹H n.m.r. data. Some acid-catalysed transformations of 17α-methyl-Δ⁹⁽¹¹⁾-testosterone (1) are reported.