Synthesis of 24-Noroleanolic Acid Derivatives

Epoxidation of 2-cyano-2,3-seco-24-nor-4(23)-ene derivatives of oleanolic acid with m-chloroper­oxy­benzoic acid, followed by treatment of the resulting epoxides with boron trifluoride–diethyl ether complex, afforded new 24-noroleanane derivatives whose structure was determined using two-dimensional NMR correlation techniques (1H–1H COSY, 1H–1H NOESY, 1H–13C HSQC, 1H–13C HMBC). Depending on the conditions, the reaction of methyl 2-cyano-2,3-seco-24-norolean-4(23)-ene-28-oate with m-chloroperoxybenzoic acid may be regioselective with the formation of 4(23)-epoxy or 12-oxo derivative, as well as allylic oxidation product of the isopropenyl moiety.