Abstract
“Laccaic acid”, isolated from stick lac, is a mixture of anthraquinone pigments, at least one of which contains about 2% nitrogen. This fraction has been isolated as a pure homogeneous compound, and a structure is proposed. A second major constituent contains no nitrogen. By the methylation of the mixed laccaic acids and of the mixed xantholaccaic acids obtained by purpurin → xanthopurpurin reduction a series of ether-esters have been prepared, and the structures of some of them have been elucidated, mainly on the basis of NMR data. When the nitrogenous constituent, laccaic acid A, is methylated by dimethyl sulphate and potassium carbonate in acetone, the main product involves cyclization of a 2-phenylanthraquinone to a brazanquinone. It is very probable that the second major constituent is an intermolecular or intramolecular carbonate of a polyhydroxy-2-phenyl-anthraquinone; during its methylation also a brazanquinone is formed, but as a minor product.
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