Two Furanharzianones with 4/7/5/6/5 Ring System from Microbial Transformation of Harzianone

Furanharzianones A and B (<b>2</b> and <b>3</b>), two new harziane-type diterpenoids with a tetrahydrofuran and unusual 4/7/5/6/5 ring system, were obtained from the microbial transformation of harzianone (<b>1</b>) by a bacterial strain <i>Bacillus</i> sp. IMM-006. The structures, including the stereochemistry, of the two new compounds were elucidated by extensive spectroscopic analysis. The absolute configuration of <b>2</b> was unambiguously determined by single-crystal X-ray diffraction. In addition, a plausible bioconversion pathway was proposed.