New syntheses of the Amaryllidacaea alkaloids vasconine, assoanine, oxoassoanine, pratosine and ismine by radical cyclisation

Ana M. Rosa, Ana M. Lobo, Paula S. Branco, Sundaresan Prabhakar, Margarida Sá-da-Costa

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

N-(2-bromo-4,5-dimethoxybenzyl)-N-(2'-β-hydroxyethylphenyl)amine when subjected to the action of AIBN and tri-n-butyltin hydride (TBTH) in benzene, under reflux, yielded the corresponding β-4-phenanthridinylethyl alcohol. While reduction of the tetracyclic quaternary salt obtained by treatment of this alcohol with PBr3 gave assoanine, its oxidation with alkaline ferricyanide led to a separable mixture of pratosine and oxoassoanine, its oxidation with alkaline ferricyanide led to a separable mixture of pratosine and oxoassoanine. The σ radical, similarly generated from 2-bromo-4,5-methylenedioxybenzyl-2'-aminophenylether, afforded the biphenyl alcohol, N-norismine.

Original languageEnglish
Pages (from-to)299-306
Number of pages8
JournalTetrahedron
Volume53
Issue number1
DOIs
Publication statusPublished - 6 Jan 1997

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