The structure of pulvilloric acid

Abstract

Pulvilloric acid, from P. pulvillorum, is shown to have the quinone methide structure (4,6-dihydro-8-hydroxy-6-oxo-3-n-pentyl-3H-2-benzopyran-7-carboxylic acid). Hydrogenation of pulvilloric acid is accompanied by aromatisation of the nucleus, giving dihydropulvilloric acid which, on esterification and methylation, yields methyl di-O-methyldihydropulvillorate. Partial oxidation of the latter compound furnishes a lactone (methyl 3,4-dihydro-6,8-dimethoxy-1-oxo-3-n-pentyl-1H-2-benzopyran-7-carboxylate), while permanganate oxidation gives 3,5-dimethoxy-4-methoxycarbonylphthalic acid. On being boiled with aqueous sodium hydroxide, pulvilloric acid is degraded to 1-(3,5-dihydroxyphenyl)heptan-2-ol, the structure of which is established by reduction to 5-n-heptylresorcinol.