Total Synthesis of 3,6‐Dimethoxy‐17β‐Acetyl‐1,3,5(10),6,8‐Estrapentaene

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Abstract
A Friedel‐Crafts reaction of 2,8‐dimethoxynaphthalene with β‐methyltricarballylic acid anhydride (I) gave the ketoacid (IId), which upon catalytic hydrogenation and cyclization with hydrogen fluoride afforded the tricyclic ketone (V). Addition of methyl acrylate yielded the tetracyclic ester (VI), which was dehydrated and then decarboxylated at carbon 15. The reactions could be controlled to produce either the 17α‐ or the 17β epimers (IX) and (X). Their hydrogenation furnished the 14β, 17α‐ and 14α, 17β isomers (XII) and (XIb), respectively. The latter was transformed into the 17β‐acetyl derivative (XIe).