Synthesis of 12,13-didehydroprostaglandin J2 methyl ester

Abstract

A new class of prostanoid has been synthesized. The carboxylic acid ester (3) is an analogue of prostaglandin J₂ and contains an allene moiety at C₁₂. The novel compound (3) is available from 7-chloronorbornadiene (5) in a route which has two key steps. The first is the reaction of (5) with an alkynyl Grignard reagent to give the dienyne (7). The second is the regioselective epoxidation of the dienyne (7), rearrangement of the epoxide (8) to give the aldehyde (9), followed by an oxa-Cope rearrangement; the derived enol (10) was hydrolysed to give the useful prostaglandin synthon (14) directly.