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■ Selective Acetylation of Berbin-8-one. Synthesis of 2-Methoxyberbine

Jean-Francois Stambach* and Louis Jung

*Laboratoire de Chimie Thérapeutique, U.F.R. des Sciences Pharmaceutiques, Université Louis Pasteur, 74, route du Rhin, BP 24, 67401 ILLKIRCH Cedex, France

Abstract

In the presence of excess aluminum chloride, berbin-8-one (1) could be selectively acetylated at the C-2 position to give 2-acetylberbin-8-one (2) in good yield. In fact this exclusive orientation was due to a complex between the amide carbonyl and the Lewis acid which deactivated the aromatic ring D for electrophilic substitution. Further chemical degradation of the acetyl group afforded the corresponding phenol derivative (3) which was converted to 2-methoxyberbin-8-one (4). Reduction of this latter gave finally 2-methoxyberbine (5). Spectral data comparison of compound (4) and 3-methoxyberbin-8-one permitted us to conclude unambiguously in favour of the C-2 orientation of the acetylation.