A Novel Norclerodane Diterpenoid from the Roots of Croton crassifolius.

A chemical investigation of Croton crassifolius afforded a novel norclerodane diterpenoid (1) with an unprecedented six-membered oxygen ring between C-1 and C-12, together with three known compounds. The structure of the new compound was elucidated based on spectroscopic (IR, 1D, and 2D NMR) and HR-ESI-MS techniques. This report describes the first example of a natural norclerodane with a 4H-chromene ring system.