Molecular structures of two bicyclo-(3.2.1)-octanoid neolignans from Piper kadsura

Abstract

The molecular structures of two bicyclo-(3.2.1)-octanoid neolignans, kadsurenin C ( 1) and kadsurenin H ( 2), have been determined by single-crystal X-ray analysis. Compound 1 represents a (8,5′.7,3′)-neolignan and compound 2 a (8,1′.7,3′)-neolignan. They differ from each other in regard to the fusion mode of the pair of lignan units, the substituent pattern and the conformation of the bridged ring system. The marked differences of their three-dimensional structures are considered to be responsible for the significantly different levels of Platelet Activating Factor antagonistic activity.