Constituents of Dragon's blood. Part I. Structure and absolute configuration of new optically active flavans

Abstract

Dragon's blood resin has yielded six new natural substances, (2S)-5-methoxy-6-methylflavan-7-ol (1), (2S)-5-methoxyflavan-7-ol (2), the quinone methides nordracorhodin (6) and nordracorubin (10), 2,4-dihydroxy-5-methyl-6-methoxychalcone (7), and 2,4-dihydroxy-6-methoxychalcone (8). Their structures have been determined by physical methods and chemical interconversions. The absolute 2S configuration for flavans (1) and (2) has been established by comparison of c.d. data with those for synthetic (2R)-flavan-7-ol (14).