Biflavonoids of Calophyllum venulosum

Four new biflavonoids [pyranoamentoflavone 7,4‘‘‘-dimethyl ether ( 1 ), pyranoamentoflavone 7,4‘-dimethyl ether ( 2 ), 6‘‘-(3-methyl-2-butenyl)amentoflavone ( 3 ), and 6‘‘-(2-hydroxy-3-methyl-3-butenyl)amentoflavone ( 4 )], as well as three known biflavonoids, [pyranoamentoflavone ( 5a ), amentoflavone ( 6 ), and 2,3-dihydroamentoflavone ( 7 )] have been isolated from the leaves of Calophyllum venulosum . The structures of the new compounds were established by spectroscopic data and chemical modification.