A stereoselective entry into a new class of pentacyclic estrogens is illustrated for the parent cycloprop[8,14]-8 alpha-estra-1,3,5(10)-triene-3,17 beta-diol (3). Moreover, a high degree of regiocontrol in acid-promoted cyclopropane ring opening, 11-->15, offers an attractive, unprecedented access to 8-methyl 19-nor-8 alpha-steroids.
A stereoselective entry into a new class of pentacyclic estrogens is illustrated for the parent cycloprop[8,14]-8 alpha-estra-1,3,5(10)-triene-3,17 beta-diol (3). Moreover, a high degree of regiocontrol in acid-promoted cyclopropane ring opening, 11-->15, offers an attractive, unprecedented access to 8-methyl 19-nor-8 alpha-steroids.