Dihydroflavonols from Lannea coromandelica

The dihydroflavonols, (2R,3S)-(+)-3',5-dihydroxy-4',7-dimethoxydihydroflavo nol and (2R,3R)-(+)-4',5,7-trimethoxydihydroflavonol were isolated from the stem bark of Lannea coromandelica. along with the known (2R,3R)-(+)-4',7-d i-O-methyldihydroquercetin, (2R,3R)-(+)-4',7-di-O-methyldihydrokaempferol a nd (2R,3R)-(+)-4'-O-methyldihydroquercetin. All five compounds were isolate d for the first time from the genus Lannea; furthermore, (2R,3S)-(+)-3',5-d ihydroxy-4',7-dimethoxydihydroflavonol, was a rare cis-type isomer. The str uctures of all compounds were elucidated by spectroscopic methods including 2D NMR and CD analysis. (C) 2000 Elsevier Science Ltd. All rights reserved .