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Definitive assignment of the 13C NMR signals of the indole C-3 and C-3a carbons of the ajmaline, picraline and sarpagine alkaloids

✍ Scribed by M. S. Morales-Ríos; P. Joseph-Nathan

Publisher: John Wiley and Sons
Year: 1989
Tongue: English
Weight: 212 KB
Volume: 27
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260270212

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✦ Synopsis

Comparison of a 'H coupled natural abundance "C NMR spectrum of l-oxo-1,2,3,4-tetrahydrocarbazole with a single-frequency experiment in which the hydrogens three bonds away from C-3 (indole numbering) were irradiated allowed the unambiguous distinction of the C-3 and C-3a signals. The results can be extrapolated for the assignment of the same signals in the ajmaline, picraline and sarpagine alkaloids, which also contain a carbonyl group as the substituent at the C-2 position of the indole skeleton. The effect of this carbonyl group on the chemical shifts of the beozenoid carbons is also discussed.

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