Bisabosquals, novel squalene synthase inhibitors. II. Physico-chemical properties and structure elucidation.

The squalene synthase inhibitor bisabosqual A was isolated from the culture broth of Stachybotrys sp. RF-7260, and its structure was determined on the basis of spectroscopic methods including detailed 2D NMR analyses. The structures of bisabosquals B, C and D isolated from Stachybotrys ruwenzoriensis RF-6853 were determined by spectroscopic methods and chemical reactions. The absolute stereochemistry of bisabosquals A, B and D was determined by X-ray crystallographic analysis. They have novel cis-fused tetracyclic structures with a bisabolane-type sesquiterpene and phenol moieties.