Studies in the biochemistry of micro-organisms. 82. Ustic acid, a metabolic product of Aspergillus ustus (Bainier) Thom & Church

Abstract

A new, colorless, crystalline mold metabolic product, ustic acid, C11H12O7, was isolated from culture filtrates of 4 different strains of A. ustus which were grown on Raulin-Thom soln. Ustic acid was shown to be 2,4-dihydroxy-5-methoxybenzoic acid with an unbranched side chain -C3H5O2 in position 6. The most favored structure for this side chain is - CHOH.CO.CH3, though many of the properties of ustic acid are as well illustrated by the side chains -CO.CHOH.CH3, -C(OH) = C(OH).CH3,CH.C.(OH).CH3, L. o 1 -C(OH).CH.CH3 or by equilibrium mixtures of 2 or more of these 5 tautomers, depending on the exptl. conditions obtained when any particular test is carried out. The close structural relationship existing between ustic acid and a number of other mold metabolic products and lichen acids is pointed out.