Studies in the biochemistry of micro-organisms. 101. The colouring matters of species in the Aspergillus nidulans group. Part 2. Further observations on the structure of asperthecin

Abstract

Asperthecin was shown to be either 3:4: 5:6:7-pentahydrbxy-2-hydroxymethylanthraquinone or 3:4:5:7:8-penta-hydroxy-2-hydroxymethylanthraquinone. It was confirmed that full methylation of polyhydroxyanthraquinones with ethereal diazomethane is greatly facilitated by the addition of methanol to the methylation mixture. The synthesis of 4-carboxy-3:6-dimethoxyphthalic anhydride, 5-carboxy-3:4-dimethoxyphthalic acid and its anhydride and 3:4-dimethoxy-5-methylphthalic acid and its anhydride are described. 5-Carboxy-3;4-dimethoxy-phthalic anhydride was identified as an oxidation product of asperthecin tetra- and penta-methyl ethers.