Geissovelline, C23H30N2O4, is a new dihydroindole alkaloid from the bark extract of Brazilian Geissospermum vellosii. Based on the chemistry of the unusual functional groups, e.g., a tertiary nitrogen which interacts transannularly with an α,β-unsaturated ketone carbonyl, structure 3 is proposed for geissovelline and is supported by complete analyses of proton and carbon-13 nmr spectra of deacetylgeissovelline (28). The reactions of this alkaloid are unparalleled. Deacetylgeissovelline is readily pyrolyzed to 1-ethyl-6,7-dimethoxycarbazole. Lead tetraacetate oxidation of deacetylgeissovelline prior to pyrolysis, on the other hand, leads to compound 6. © 1973, American Chemical Society. All rights reserved.