On the Synthesis of Hypericin by Oxidative Trimethylemodin Anthrone and Emodin Anthrone Dimerization: Isohypericin

Article abstract of DOI:10.1007/BF00811548

The base catalyzed oxidative dimerization of emodin anthrone exclusively yields hypericin.However, on oxidative dimerization of trimethylemodin anthrone a mixture of hexamethylhypericin and hexamethylisohypericin was obtained.Chromatographic separation of the hexabenzoyl derivatives was achieved, and by saponification about equal amounts of hypericin and isohypericin were produced.Isohypericin could be characterized for the first time by its spectroscopic data and its protonation and deprotonation pK_a and pK_a^* values. Keywords.Trimethylemodin anthrone; Emodin anthrone; Hypericin; Isohypericin; Spectroscopic properties; pK_a-values; Synthesis.