On the synthesis of protopine alkaloids
Yasuhiro Wada1, Harumi Kaga, Shiho Uchiito
1Laboratory of Organic Synthesis, Division of Molecular Chemistry, School of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Abstract:
For the synthesis of protopine alkaloids, we studied a reaction sequence based on a ring enlargement of indeno[2,1-a][3]benzazepines by a singlet oxygen oxygenation, followed by conversion of an amide carbonyl group of the resultant 10-membered keto-lactam to a methylene group, which is the last step for completion of the synthesis. The key substances, indeno[2,1-a][3]benzazepines, were prepared by Bischler-Napieralski cyclization of alkoxy-substituted 1-(2-bromobenzyl)-3-benzazepin-2-ones. Steric effects of the substituents in this synthesis were examined.
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