Sumatranins A–J: Lignans with Immunosuppressive Activity from <i>Cleistanthus sumatranus</i>

Abstract

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