STUDIES ON THE BLUE PIGMENTS PRODUCED FROM GENIPIN AND METHYLAMINE .2. ON THE FORMATION MECHANISMS OF BROWNISH-RED INTERMEDIATES LEADING TOTHE BLUE PIGMENT FORMATION

The mechanisms of the formation of brownish-red pigments having a 2-me thyl-4-carbomethoxy-2-pyrindine nucleus as a basic skeleton by reactio n of genipin with methylamine under an atmosphere of inert gas are dis cussed based on the isolation of -methyl-4-carbomethoxy-8-hydroxymethy l-2-pyrindine as a precursor and on comparisons of the results obtaine d from the reactions of genipin congeners and methylamine. The origin of the extra methyl group at C-6 in the structures of some of the brow nish-red pigments was clarified to be the carbon atom of the hydroxyme thyl group at C-8 of genipin by using deuterium-labelled genipin.