Functionalization of Lupane with Chromium(VI) Oxide. A Remark on the Structure of Clerodone

Abstract

The reaction of lupane (1) with chromium oxide gave lup-2-en-1-one (3), lupan-12-one (2), lupan-16-one (isolated after hydride reduction as lupan-16α-ol (4)), and lup-18-en-21-one (5) in low yields. The same oxidation of 3β,28-dimethoxylupane (11) afforded no products of functionalization in non-activated positions; only products of oxidation of the 3β-methoxy group and of the oxidation cleavage of the A ring were obtained, viz. 28-methoxylupan-3β-ol formate (12), 28-methoxylupan-3-one (14), and 28-methoxy-2-norlupane-1,3-dioic anhydride (13). The structure of the compounds obtained was confirmed by their 1H NMR, 13C NMR, and mass spectra. The lupan-12-one (2) prepared is not identical with clerodone, whose isolation from Clerodendron infortunatum BHAT. was described in 1965 and to which the structure of lupan-12-one was then ascribed.