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Abstract
Betulin–allobetulin transformation is effected with ferric nitrate or ferric chloride adsorbed onto silica gel or alumina, in excellent yields. In addition, allobetulin can be converted to allobetulone with silica adsorbed ferric nitrate or to 19β,28- epoxy-A-neo-18α-olean-3(5)-ene and 19β,28-epoxy-A-neo-5β-methyl-25-nor-18α-olean-9-ene with silica or alumina adsorbed ferric chloride.
ACKNOWLEDGMENTS
We thank Jimmy Bouchard, Bruce Black, and Brian Dawson for their assistance in the NMR experiments. The financial support of the Fondation de l'UQAC is gratefully acknowledged. SL thanks PAIR, Bourse Paul-Émile-Boulet, and Association des diplômé (e)s et ami(e)s de I'UQAC for graduate scholarships.
