Helisterculins A and B, two new (7.5 ',8.2 ')-neolignans, and helisorin, the first (6.4 ',7.5 ',8.2 ')-neolignan, from the Indonesian medicinal plantHelicteres isora

During a chemical study of Indonesian medicinal plants, we examined the con stituents of fruits of Helicteres isora L. (Sterculiaceae),one of the famou s Jamu medicines. From a water extract of the fruits, we isolated three new neolignans, helisterculins A (1) and B (2) and helisorin (3), and elucidat ed their structures by spectral analyses. Helisterculins A (1) and B (2) ar e (7.5',8.2')-neolignans with a bicyclo[2.2.2]octene C-framework, while hel isorin (3) is a (6.4',7.5',8.2') -neolignan with a very rare 4,4a,9,9a-tetr ahydro-3,9-methano-3H-fluorene C-framework. The natural product with the la tter C-framework has no literature precedent. The neolignans 1-3 showed wea k inhibitory activity against reverse transcriptase from avian myeloblastos is virus.