Cyclization of 3-methoxy-Δ1,3,5,(10)-8,14-secoestratriene-14,17-dione

Depending on the conditions, 3-methoxy-Δ1,3,5(10)-8,14-secoestratriene-14,17-dione (III) under the influence of acid agents is cyclized to estradiol, equilenol, 18-norequilenane, and cyclopentanophenanthrene derivatives. As a result, the spatial factor determines the course of the reaction even if the Δ9(11)-double bond, which activates the H atoms at C7, is absent.