63 ユウポラウラミンの簡易合成(口頭発表の部)

概要

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6-Methoxy-5-methylbenzo[h]pyrrolo[4,3,2-de]quinolin-4(51-)-one (eupolauramine) (1) is a structually unusual azaphenanthrene alkaloid isolated from Eupomatia laurina. In this paper we have described the 9-steps total synthesis of 1 in 34% overall yield using new methods recently developed in our laboratory. The key steps are involving (1) the first example of new application of an intramolecular aromatic substitution with a N-methoxy-N-acylnitrenium ion to the synthesis of a natural product bearing nitrogen heterocyclic rings (step d), (2) the direct regiospecific introduction of a methoxy group into the para-position of N-methoxy function (step e), (3) the aromatization of dihydrocarbostyril moiety in the presence of other functional groups to quinoline moiety via thiolactam formation followed by the desulfurization and simultaneously occurring dehydrogenation with Raney Ni (step f and g), and (4) nitration of the compound (26) labile to oxidation by using Cu(NO_3)_2・2H_2O in the presence of ascorbic acid (step h). This methodology will be useful not only for the synthesis of azaphenanthrene skeleton but also other nitrogen heterocyclic rings, which will offer a new route for the synthesis of natural products bearing nitrogen heterocyclic rings.
天然有機化合物討論会の論文
1988-09-26