Sumatranins A-J: Lignans with Immunosuppressive Activity from Cleistanthus sumatranus .

Chemical investigation of the twigs of Cleistanthus sumatranus (Phyllanthaceae) led to the isolation of 10 undescribed lignans, sumatranins A-J ( 1 - 10 ). Compounds 1 - 4 are unprecedented furopyran lignans characterized by a unique 2,3,3a,9a-tetrahydro-4 H -furo[2,3- b ]chromene heterotricyclic framework. Compounds 9 and 10 are rare 9'- nor -dibenzylbutane lignans. Structures were established based on analyses of spectroscopic data, X-ray crystallographic data, and experimental ECD spectra. Immunosuppressive assays revealed compounds 3 and 9 displayed moderate inhibitory effects with good selectivity indexes against LPS-induced B lymphocyte proliferation.