Three Dimeric Anthracene Derivatives From Bulbine Abyssinica.
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From the fruits of Bulbine abyssinica three new dimeric anthracene derivatives, (P)-8,9,10,80-tetrahydroxy-3,30-dimethyl[10,70-bianthracene]-1,4,90,100-tetraone (trivial name abyquinone A), (10R)-1,4,8,10,80-pentahydroxy-3,30-dimethyl-[10,70-bianthracene]-9,90,100(10H)-trione (trivial name abyquinone B), and (10R)-30,40-dihydro-1,4,8,30,80,90-hexahydroxy-3,30-dimethyl-[10,70-bianthracene]-9,10(10H,20H)-dione (trivial name abyquinone C) were isolated. Despite their structural differences, these three compounds are connected to each other by the apparently biomimetic conversion of abyquinone C (a preanthraquinonylanthrone with two stereogenic centers) into B (an anthraquinonylanthrone with one stereogenic center) and finally into A (an axially chiral bianthraquinone) under mild conditions, involving a highly efficient center-to-axis chirality transfer. In addition, the known anthraquinones islandicin and chrysophanol were identified. The structures were determined on the basis of spectroscopical evidences, chemical transformations, and quantum chemical CD calculations.
CitationYenesew, A. 2005. Three dimeric anthracene derivatives from Bulbine abyssinica. . Tetrahedron . 61:2667-2674.
University of NairobiDepartment of Chemestry