Stereochemistry of the Black Tea Pigments Theacitrins A and C
Yosuke Matsuo, Keita Okuda, Hitomi Morikawa, Ryosuke Oowatashi, Yoshinori Saito, Takashi Tanaka
Journal of Natural Products
Theacitrins A–C are yellow pigments of black tea that are produced by oxidative coupling of gallocatechins, i.e., flavan-3-ols with pyrogallol-type B-rings. However, their stereostructures have not yet been determined. In this study, DFT calculations of NMR chemical shifts of theacitrin C (1) and TDDFT calculations of the ECD spectra of theacitrinin A (5), a degradation product of theacitrin C (1), were used to determine the stereostructure of the theacitrins. Furthermore, the preparation of theacitrins A (4) and C (1) by enzymatic oxidation of an epigallocatechin (7) and epigallocatechin-3-O-gallate (2) mixture confirmed their structural relationship.
Circular dichroism, Absolute configuration, Natural products, Pharmaceutical