Identification of two novel promelacacinidin dimers from Acacia nigrescens.

Two new flavanol-flavonol C(4)(C) to C(5)(D) linked promelacacinidin dimers were isolated from the heartwood of Acacia nigrescens. Their structures were elucidated by extensive (1)H and (13)C NMR spectroscopic studies, and the main conformational features are discussed.