Spectral evidence for the structure of three flavanotropolones related to theaflavin, an orange-red pigment of black tea

Abstract

Conclusive spectral evidence for the structure of categallin (V), pyrogallin (VI), and erycetin (VIII), three flavanotropolones related to theaflavin (I) and purpurogallin (IX), is presented. The synthetic, chromatographic, and spectroscopic data for four simpler hydroxybenzotropolones are also recorded and discussed.