Chemistry of the indoleninones. II. Isolation from the hypobranchial glands of marine molluscs of 6-Bromo-2,2-dimethylthioindolin-3-one and 6-\Bromo-2-methylthioindoleninone as alternative precursors to Tyrian purple

6-Bromo-2-methylthioindoleninone and 6-bromo-2,2-dimethylthioindolin-3- one have been isolated from ether extracts of Dicathais orbita Gmelin. Both compounds are derived from the absolute precursor sodium tyrindoxyl sulphate. Isolation of the compounds from certain other species of molluscs is reported.