Oxindoles, carbolines from

Oxindoles, carbolines from, 133 cyclization of derivatives of, 95 3,3-spiro-, 167, 168... 

Mitraphylline and rhynchophylline undergo characteristic fragmentation processes on electron impact, hence their mass spectra are markedly different from those of the tetrahydro-/3-carboline alkaloids in general, and of the heteroyohimbine alkaloids (e.g., ajmalicine) in particular. Consequently, the mass spectra of the oxindole alkaloids promise to be very valuable in the structural elucidation of new members of this subgroup the structure of one such base, carapanaubine, a constituent of Aspidosperma carapanauba M. Pichon, has already been elucidated by this method, and the structure deduced has subsequently been confirmed by partial synthesis from isoreserpiline (82). 

A new simple oxindole alkaloid, (-)-horsfiline (57) was obtained from Horsfieldia superba (Myristicaceae), in addition to the known alkaloids 6-methoxy-2-methyl-l,2,3,4-tetrahydro-P-carboline (58) and 5-methoxy-A, -dimethyltryptamine [59]. Horsfiline is a simple spiro-pyrrolidinyloxindole, its structure was deduced from spectral data (MS NMR) as well as by partial synthesis from 58 via oxidation with Pb(OAc)4 to the acetoxyindolenine 59, followed by acid catalysed rearrangement (MeOH/AcOH) to ( )-horsfiline (Scheme 2) [59]. 

---