Structure of pilosanones A and B: novel diterpenoids with a bicyclo[5.4.0.]undecane skeleton from Portulaca pilosa L.

Pilosanones A (1) and B (2), the major diterpenoid constituents of Portulaca pilosa l., have been assigned structures with a novel bicyclo[5.4.0.]undecane skeleton on the basis of detailed spectroscopic analyses, and their significance in the biosynthesis and the chemosystematics of Portulaca plants is suggested.