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Paper | Regular issue | Vol 75, No. 6, 2008, pp.1329-1354
Published online, 26th February, 2008
DOI: 10.3987/COM-07-11276
Synthesis of the Diazatricyclic Core of Madangamines via Cyclic N,O-Acetalization-Bridgehead Reduction

Yuta Yoshimura, Takahiko Kusanagi, Chihiro Kibayashi, Naoki Yamazaki,* and Sakae Aoyagi*

*School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan

Abstract

A new approach to synthesize the diazatricyclic core of the madangamine alkaloids is described. The synthesis involves intramolecular N,O-acetalization of the keto-aminophenol which enables rapid construction of the 2-azabicyclo[3.3.1]nonane skeleton. Reductive C-O bond cleavage of the N,O-acetal has been accomplished by using AlH3 as the source of nucleophilic hydrogen as well as the Lewis acid character. This strategy also demonstrates the utility of such approach in the stereoselective construction of the central 2,6-diazatricyclo[6.2.2.04,9]dodecane core with a quaternary carbon center at C-4 found in the madangamine alkaloids.