Hypatulins A and B, Meroterpenes from Hypericum patulum.

Two novel prenylated benzophenone related meroterpenes, hypatulins A (1) and B (2), were isolated from the leaves of Hypericum patulum. The structures of 1 and 2 were assigned by spectroscopic analysis, chemical conversion, and calculations of the ECD (electron circular dichroism) spectra. Hypatulin A (1) had a unique densely substituted tricyclic octahydro-1,5-methanopentalene core, while hypatulin B (2) possessed a bicyclo[3.2.1]octane moiety. Hypatulin A (1) exhibited antimicrobacterial activity against Bacillus subtilis. A possible biogenetic pathway of the new meroterpenes 1 and 2 from a prenylated benzophenone was presented.