Reduction of Vulpinic Acid

Abstract

Acid product was obtained by the reduction of pulvinic anhydride (II) with Pd-coal as a cataylst but it did not solidify. Heating this product with acetic anhydride resulted in the formation of carboxycornicular lactone (IV), yellow needles, m.p. 218-9°, and vacuum distillation gave cornicular lactone (V), pale yellow leaflets, m.p. 136-6.5°. It follows, therefore, that this reduction product is dihydropulvinic acid (III). Methyl ester of (IV), yellow needles, m.p. 170-2°, gave, by reduction with PtO₂, methyl diphenyladipiate, colorless leaflets m.p. 139-141°, and methyl tetrahydrocarboxy-cornicular lactone (VIII), white needles, m.p. 136°. Catalytic reduction of (V) with PtO₂ resulted in obtaining α, δ-diphenylbutane-α-carboxylic acid (IX), colorless needles, m.p. 77-8°, cyclohexylphenyl-valerolactone (X), white needles, m.p. 66-7°, and α, δ-diphenyl-γ-valerolactone (XI), colorless needles, m.p. 67-9°. On the other hand, α, δ-diphenyl-γ-valerolactone of m.p. 72° is obtained by the catalytic reduction of α-phenyl-γ-benzyl-Δα, β-crotonlactone, colorless needles, m.p. 86-9°, with PtO₂, or by the reduction of dihydrocorniculic acid. The above valerolactone was found to be identical with (IX) when fused with it.