1994 Volume 42 Issue 9 Pages 1745-1749
Double bond migration on the 22(17→28)abeo-lupane skeleton was investigated using 28-p-toluenesulfonyloxy-lupane (4) and its 20(29)-ene derivative (7) as starting materials. In the case of 4, the double bond, formed between C-17 and C-28 after elimination of the p-toluenesulfonyloxy group followed by E-ring expansion, migrated to C-13 and C-18 under acidic conditions. In the case of 7, the double bond, formed after the elimination and the E-ring expansion, migrated in response to migration of the other double bond, 20(29)-ene, under acidic conditions. First, 20(29)-ene migrated to 19-ene (9), and then 17(28)-ene migrated to 13(18)-ene to form a conjugated 13 (18), 19-diene (10). Further migration proceeded to give an equilibrium mixture of 17α-H-11, 13(18)-diene (11), 12, 17-diene (12) and 17β-H-11, 13(18)-diene (13) in a ratio of 3 : 3 : 5.
