New Synthesis of Columbianetin and Related Coumarins

Abstract

2,4-Dihydroxy-3-(3-methyl-2-butenyl)benzaldehyde was obtained from 2,4-dihydroxybenzaldehyde with either 3-hydroxy-3-methyl-1-butene or 1-bromo-3-methyl-2-butene. Oxidation of the product in neutral medium with m-chloroperoxybenzoic acid gave (±)-2,3-dihydro-2-(1-hydroxy-1-methylethyl)-4-hydroxybenzofuran-5-aldehyde, whose condensation product with malonic acid was (±)-3-carboxy-columbianetin. Oxidation in acidic medium gave (±)-2,2-dimethyl-3,5-dihydroxybenzopyran-6-aldehyde, whose condensation product with malonic acid was (±)-3-carboxylomatin. (±)-Columbianetin and (±)-lomatin were obtained by decarboxylation.