117(P-50) フェナジン類の新規合成法(ポスター発表の部)

概要

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Naturally occurring phenazines have attracted considerable attention because of their interesting biological activities. One of the most promising methods for synthesizing polysubstituted phenazines developed by Holliman and co-workers was the reductive cyclization of o-nitrodiphenylamines (Method C). However, the yield was poor when competitive cyclization occurred. Recently, N-arylation has become more accessible owing to the advent of a new methodology developed by Hartwig and Buchwald. Here, we report on the use of the new method to synthesize phenazines using sequential palladium-mediated aniline arylation. Our method is based on the regiospecific bromination of o-nitrodiphenylamine 3, which is obtained from o-bromonitrobenzene 1 and aniline 2 by aniline arylation, to give bromide 4 (Method A), which is also obtained from 1 and o-bromoaniline 5 (Method B). Subsequent chemoselective reduction of the nitro group on 4 followed by the Hartwig-Buchwald aniline arylation affords the target phenazine. For the total synthesis of benthocyanin A, a powerful radical scavenger from the mycelium of Streptomyces prunicolor, and of phenazostatin A, a new neuronal cell protecting substances from the culture broth of Streptomyces sp. 833, we adapted the new methods to construct phenazines.
天然有機化合物討論会の論文
2000-10-01