An approach to the synthesis of fujenoic acid

Abstract

In experiments directed towards the total synthesis of fujenoic acid (1), the 2-(2-furyl)-6-oxobicyclo[3.2.1]octane-1-carboxylate (3b) was prepared as a key intermediate. The furyl group was designed to be transformed into ring A of fujenoic acid. In investigations of the transformation route, model compounds {the stereoisomeric dimethyl 1-methyl-7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylates (4), (5), and (12)} were examined, and it was found that diester (12) could be effectively converted into dimethyl 1,3-dimethyl-6-oxocyclohex-3-ene-1,2-dicarboxylate (18), which corresponds to ring A of fujenoic acid. The key intermediate (3b) was obtained by a Dieckmann condensation of dimethyl 6-(2-furyl)-1-methoxycarbonylmethylcyclohexane-1,3-dicarboxylate (23).