Elsevier

Tetrahedron

Volume 32, Issue 10, 1976, Pages 1085-1095
Tetrahedron

Imidazole alkaloids of Macrorungia longistrobus: Revised structures and total syntheses

https://doi.org/10.1016/0040-4020(76)85030-2Get rights and content

Abstract

By total synthesis, it was shown that the imidazole alkaloids dehydroisolongistrobine and isolongistrobine possess structures 1 and 2, respectively, rather than the structures proposed by Arndt, Eggers and Jordaan in 1969. Reaction of methyl 1-methylimidazole-5-carboxylate with phenylsulfonylmethyl magnesium bromide provided a β-ketosulfone which was alkylated with o-nitrobenzyl bromide to provide 6. In the key step, amino alcohol 10 and tetrahydroquinoline 8 were obtained through aluminum amalgam reduction of 6. 8 was converted to isomacrorine 12. 10 could be converted to 1 by a three-step sequence; 2 was obtained from 10 by acylation with 4-pentenoyl chloride, oxidation, and osmium tetroxide catalyzed periodate cleavage of the vinyl group. Comparison of samples of synthetic alkaloids 1 and 2 with the corresponding alkaloids from natural sources showed that the natural and synthetic samples of each were identical.

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    Based on M.A. Wuonola, Ph.D. Thesis, Harvard University (1973).

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