The unique spiro-biflavonoid structure of larixinol ( l a ) is described and a suggested pathway of biogenesis from dihydrokaempferol is proposed.Larix gmelini (Rupr) Rupr is an important coniferous species of Northern China. During an investigation of the proanthocyanidins of the bark1 a unique spiro-biflavonoid (la) was isolated (0.15%) together with the flavan-3-ols, (-)epicatechin, (+)-catechin, and (-)-epiafzelechin (2). The spiro compound was identical in all respects with the substance larixinol isolated from Larix sibirica by Chumbalov and his colleagues2 and for which they proposed the structure (3). Larixinol, C30H22010,t m.p. 208-210 "C, [a]D2' -151" (Me2C0, c l.O), RF 0.83 (BusOH-HOAC-H~O, 14: 1 : 5, Whatman No 2) formed a hexa-acetate (lb) on treatment with acetic anhydride-pyridine, m.p. 255-257 " c , [a]D2' +33.3" t Accurate analytical data (C,H) were obtained for all compounds described in the text.
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