Incensfuran: isolation, X-ray crystal structure and absolute configuration by means of chiroptical studies in solution and solid state

A new cembrane diterpene named incensfuran (1), biogenetically derived from incensole (2), was isolated from crude extracts of the Boswellia papyrifera Hochst. The structure of incensfuran (1) was elucidated by 1D and 2D NMR study, and its absolute configuration was determined by single crystal X-ray diffraction analysis and electronic and vibrational circular dichroism spectroscopy (ECD, VCD). Moreover semisynthesis of incensfuran (1) was achieved after treatment of incensole (2) with BF3·OEt2. In addition epoxidation of incensfuran (1) provided expoxide analog 3 with 80% yield.