Structure of Aurasperone C

Aurasperone C (III) shows properties closely related to those of aurasperone B (II) and gave dianhydro compound (V) on hydrochloric acid treatment. Partial methylation of (V) with methyl iodide afforded a monomethyl ether identical with aurasperone A (I).

NMR studies, including solvent induced methoxyl shifts, indicate the structure of (III) to be 2,2′-dimethyl-2,2′,5,5′-,8-pentahydroxy-6,6′,8-trimethoxy-7,10′-bi[2,3-dihydro-4H-naphtho[2,3b]pyran-4-one], in which the 8-methoxyl of aurasperone B is replaced by a hydroxyl group.