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A Unified Route to the Welwitindolinone Alkaloids: Total Syntheses of (−)-N-Methylwelwitindolinone C Isothiocyanate, (−)-N-Methylwelwitindolinone C Isonitrile, and (−)-3-Hydroxy-N-methylwelwitindolinone C Isothiocyanate

Author:
Allan, Kevin M., Kobayashi, Kenichi, Rawal, Viresh H.
Source:
Journal of the American Chemical Society 2012 v.134 no.3 pp. 1392-1395
ISSN:
1520-5126
Subject:
alkaloids, chlorination, desulfurization, isothiocyanates, nuclear magnetic resonance spectroscopy, oxidation, spectral analysis, vinyl chloride
Abstract:
As part of a comprehensive strategy to the welwitindolinone alkaloids possessing a bicyclo[4.3.1]decane core, we report herein concise asymmetric total syntheses of (−)-N-methylwelwitindolinone C isothiocyanate (2a), (−)-N-methylwelwitindolinone C isonitrile (2b), and (−)-3-hydroxy-N-methylwelwitindolinone C isothiocyanate (3a) from a common tetracyclic intermediate. The crucial vinyl chloride moiety was installed through electrophilic chlorination of a hydrazone, but only after adjustment of reactivity to circumvent a facile skeletal rearrangement. Selective desulfurization and oxidation of 2a provided access to 2b and 3a, respectively. Notably, this work provides corrected ¹H and ¹³C NMR spectral data for 3a.
Agid:
5386129