A new lignan, (-)-berchemol, from Berchemia racemosa.

A new tetrahydrofuranoid lignan, named (-)-berchemol (1), mp 188-189 °C, [α] D -7.9°, C20H24O7, was isolated together with a known lignan, (-)-secoisolariciresinol, from the stems of Berchemia racemosa SIEB. et ZUCC. (Rhamnaceae). The relative stereostructure of 1 was elucidated on the basis of chemical evidence, and spectroscopic and X-ray analysis. The absolute configuration of 1 was determined by comparison of its circular dichroism spectrum...