The structure of hallachrome: 7-hydroxy-8-methoxy-6-methyl-1,2-anthraquinone

Abstract

The epidermal pigment of the marine worm Halla parthenopeia, originally considered to be an indolequinone derivative and later an aminoquinonesulphonic acid, has been isolated in crystalline form and identified as 7-hydroxy-8-methoxy-6-methyl-1,2-anthraquinone (III) from its chemical and spectral properties. The arrangement of the substituents is proposed on the basis of nuclear Overhauser effect experiments on hallachrome itself and the identification of a previously unknown 9,10-anthraquinone derivative (1,2,7-trihydroxy-8-methoxy-6-methyl-9,10-anthraquinone), obtained from hallachrome leucotriacetate by oxidation with chromic acid.