Synthetic studies on terpenoids. Part XVII. Synthetic approaches to hirsutic acid

Abstract

Stereoselective syntheses of some potential intermediates for hirsutic acid (6β,6aβ-epoxy-2,3,3aα,3b,4,5,6,6a,7,7aα-decahydro-5β-hydroxy-2β.3bβ-dimethyl-4-methylene-1H-cyclopenta[a]pentalene-2-carboxylic acid)(I), viz. methyl 3-methyl-6-oxo-cis-bicyclo[3.3.0]octane-3-carboxylate (XVa and b), methyl 1,2,3,3aα,8,8aα-hexahydro-6-methoxy-2β-methylcyclopent[a]indene-2-carboxylate (XXV), and methyl 1,2,3,3aα,8,8aα-hexahydro-6-methoxy-2β-methoxycarbonylmethylcyclopent[a]indene-2-carboxylate (XXIX) are reported.