STUDIES ON PAF ANTAGONISTIC BICYCLO(3,2,1) OCTANOID NEOLIGNANS FROM PIPER KADSURA

As a continuation of our previous report dealing with the structures of novel neolignans from Piper kadsura (Choisy)Ohwi, two other new bicyclo (3, 2, 1) octanoid neolignans, named kadsurenin K and kadsurenin L, were isolated. On the basis of spectral analysis and chemical derivatization, their structures were established as 7R, 8R, 3' R, 5' R- △^8'- 3, .5' - dimethoxy- 4- hydroxy-2' ,3' ,4', 5'-tetrahydro-2', 4'-oxo-7. 3', 8. 5'-neolignan and 7R, 8R, 3' 8, 4' R, 5' R-△^8'- 3, 4, 5'-trimethoxy-4'-acetoxy-2', 3', 4', 5'-tetrahydro-2'-oxo-7. 3', 8. 5'-neolignan respectively. Kadsurenin B and kadsurenin C were known compounds. In ³H--PAF receptor binding assay, kadsurenin B, C, K and L demonstrated significant PAF--antagonistic activity.