Trinoranastreptene 1 from the cultured cells of the liverwort, Calypogeia granulata Inoue l is a novel tricyclic trinor-sesquiterpene which has an unprecedented tricyclo [5.3. 0 1* 6.0] decane ring system. Its structure was determined by detailed NMR analysis, and it turned out to be identical with or antipodal to clavukerin B from the Okinawan soft coral (stolonifer) Clauularia KoeZZikeri 2