CHEMOSYSTEMATICS OF BRYOPHYTES .39. PRENYL BIBENZYLS FROM THE LIVERWORT RADULA-KOJANA

Fourteen new bibenzyl derivatives have been isolated from the liverwort Radula kojana together with two previously known bis(bibenzyls) and their structures characterized by spectral and chemical evidence. Seven new bibenzyls, 3,5-dihydroxy-2-(3-methyl-2-butenyl)-, 3-methoxy-5-hydroxy-2-(3-methyl-2-butenyl)-, 3-hydroxy-5-methoxy-2-(3-methyl-2-butenyl)- and 2-geranyl-3,5-dihydroxybibenzyls, 2,2-dimethyl-7-methoxy-5-(2-phenylethyl)-,2,2-dimethyl-5-methoxy-7-(2-phenylethyl)- and 2-methyl-2-(4-methyl-3-pentenyl)-7-methoxy-5-(2-phenylethyl) chromenes have been synthesized from pinosylvin and its dimethyl ether. 3,5-Dihydroxy-2-(3-methyl-2-butenyl)- and 2-geranyl-3,5-dihydroxybibenzyls showed 5-lipoxygenase and calmodulin inhibitory activity. Radula kojana belonging to the subgenus Odontoradula is chemically different from species of the subgenera Radula and Cladoradula as it produces chromene derivatives (six-membered) and the latter two genera elaborate dihydrooxepins (seven-membered) and benzofurans with a propenyl group (five-membered). Our chemical results support the modern classification of Radula species.