Gladiolic acid, a metabolic product of Penicillium gladioli. 1. Structure

Abstract

Gladiolic acid, C11H10O5, a weakly anti-bacterial but strongly antifungal metabolic product of P. gladioli, may be represented by the tautomeric structural formulae 4-methoxy-5-methyl-o-phthalaldehyde-3-carboxylic acid (in the keto form) and 4-formyl-3-hydroxy-7-methoxy-6-methyl-phthalide (in the lactol form). The structures of a number of derivatives and degradation products of gladiolic acid were established and the synthesis of 4-methoxy-benzene-l,2,3,5-tetracarboxylic acid is reported. Three impurities, an acid, C11H12O5, a lactone, C11H10O4 and a phenolic compound, C10H10O3, were isolated from the crude gladiolic acid and their respective structural relationships to gladiolic acid established. The structural relationship of the phenol C10H10O3 to mycophenolic acid gives the gladiolic acid series of compounds a definite place in the general picture of the metabolic products of the fungi.