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Communication | Regular issue | Vol 55, No. 12, 2001, pp.2269-2272
Published online, 1st January, 1970
DOI: 10.3987/COM-01-9344
Enantioselective Synthesis of (S)-2,3,9,10,11-Pentamethoxyhomoprotoberberine, and (S)-O-Methylkreysigine Using an Asymmetric Addition to an Isoquinoline Ring

Kazuhiro Nagata, Takashi Itoh, Keiko Kameoka, Michiko Miyazaki, and Akio Ohsawa*

*School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan


Total synthesis of (S)-2,3,9,10,11-pentamethoxyhomoprotoberberine (7) was carried out using an asymmetric nucleophilic addition of a silyl enol ether to 5,8-dibromo-6,7-dimethoxyisoquinoline (1) in the presence of an acid chloride derived from alanine. The addition proceeded in high diastereoselectivity to give a 1-substituted 1,2-dihydroisoquinoline (2), which was converted to the target alkaloid in short steps. One of the intermediates was readily transformed to a product (8) which was known as a precursor for synthesis of O-methylkreysigine (9).