The constitution of carviolin: a colouring matter of Penicillium carmino-violaceum Biourge

IT has recently been shown [Hind, 1940] that P. carmino-violaceum Biourge produces two pigments, which were named carviolin (C06H1206) and carviolacin (C20H607).These compounds are polyhydroxyanthraquinones and each contains a methyl ether group.From a study of the properties of carviolin, and from analogy with other mould anthraquinones [Raistrick, 1938] this compound appeared to be a methyl ether of a tetrahydroxy-fl-methylanthraquinone.Further examination of the chemical properties of the pigment has in fact, revealed that it is a methyl ether of co-hydroxyemodin.This conclusion was arrived at from a consideration of the following properties of carviolin.(1) It is well known that oxidation of oc-hydroxyanthraquinones with Pb304 or MnO2 in conc.H2S04, followed by reduction of the product in aqueous solution with SO2, introduces a hydroxyl group in the p-position to the oc- hydroxyl group already in the molecule.Treatment of carviolin after this manner gave a compound having the absorption bands of a 1:4:5:8-tetrahydroxyanthraquinone.This result could only be expected from a compound having oc-hydroxyl groups in both benzene nuclei.In view of the fact that all mould anthraquinones so far identified have been derivatives of 1:8-dihydroxyanthraquinone, it was thought probable that this might also apply to carviolin.(2) Treatment with HBr in boiling glacial acetic acid solution gave a mono- bromo derivative of the demethylated pigment.The bromine atom was removed from the molecule by boiling for a short time with aqueous silver acetate, indicating the presence of a -CH20H or a -CH2OMe grouping in the carviolin molecule.It is a necessary corollary of (1) that this grouping must be in the fl-position.