Total synthesis of 12-methyl-19-nor-steroids

Abstract

The reaction of 6-methoxy-1-tetralone with the Grignard reagent from 1-bromopropene gave a mixture of allylic alcohols which could be condensed with 2-methylcyclopentane-1,3-dione, in the presence of acetic acid, to yield two isomeric 12-methylestra-1,3,5(10),8,14-pentaenes (VIa) in the ratio ca. 5 : 1, albeit in a combined yield of less than 10%. Subsequent chemical transformations and an X-ray analysis of a derivative showed that the major isomer had the C-12 and -13 methyl groups in a trans-arrangement.