Migrated Lupane Derivatives. Boron Trifluoride Etherate-catalyzed Backbone Rearrangement of 3α,4α- and 3β,4β-Epoxy-<i>D</i>:<i>A</i>-friedo-18β,19α<i>H</i>-lupanes and Solvent Effects
Backbone rearrangements of 3α,4α- and 3β,4βepoxy-D:A-friedo-18β,19αH-lupanes catalyzed by borontrifluoride etherate gave 18β,19αH-lup-12-en-3-ols, lup-18-en-3-ols, and lup-19-en-3-ols, besides known D:B-friedo-18β,19αH-lup-5-en-3-ols and -5(10)-en-3-ols. D:B-Friedo-18β,19αH-lup-l(10)-en-3α-ol and 3β,10β-epoxy-D:B-friedo-18β,19αH-lupane were also obtained from α- and β-epoxides, respectively. Solvent effects