Prenylated flavanones from the twigs of Dorstenia mannii

Investigation of the twigs of Dorstenia mannii gave 6,8-diprenyl-5,7,3'4'-t etrahydroxyflavanone and four new prenylated flavanones, named dorsmanins E -H and characterized as 5,6-7,8-bis-(2,2-dimethylchromano)-3',4'-dihydroxyf lavanone, 7,8-[2 "-(1-hydroxy-1-methylethyl)-dihydrofurano]-6-prenyl-5,3',4 '-trihydroxyflavanone, 6,7-[2 "-(1-hydroxy-1-methylethyl)dihydrofurano]-8-p renyl-5,3',4'-trihydroxyflavanone and 6-prenyl-8-(2-hydroxy-3-methylbut-3-e nyl)-5,7,3',4'-tetrahydroxyflavanone, respectively, on the basis of spectra l analysis and chemical evidence for the chromano derivative. (C) 1999 Else vier Science Ltd. All rights reserved.