Indole alkaloids mass spectra

Erysophorine (13) was isolated from the water-soluble extract of the seeds of E. arborescens Roxb. (37). The molecular formula C32H38N304.CI was established by analysis. The mass spectrum of 13 gave no molecular ion but exhibited fragments consistent with a 1,6-diene Erythrina alkaloid and a carboxylated indole-3-alkylamine. Erysophorine appeared to be a combined alkaloid, and its UV spectrum was similar to that of an equimolar mixture... 

The closure of a bond between positions 12 and 19, presumably involved in the natural synthesis of aspidospermine-type alkaloids from quebrachamine, has been shown (18) to occur during the zinc dust distillation of the latter when a compound IX was isolated whose mass spectrum was exactly comparable with that of the indolenine VII, except for the 30-unit shift in the indole-containing fragments (Table V). Substance IX has subsequently been found in nature (Section II, E). 

The vast majority of indole alkaloids contain a tryptamine unit in which Nb is linked to the j9-position of the indole nucleus by an ethylene chain. On biogenetic grounds and also from the mass spectral similarity with aspidospermine (II), it is reasonable to expect this feature in the aspidofractinine-type alkaloids. Furthermore, in kopsine lactam A (CLXXV), in which C-ll is substituted by the C-3 bridge and C-10 has been oxidized (five-membered lactam), the residual hydrogen atom on C-ll shows as a singlet (2.82 S) in the NMR-spectrum and C-12 is therefore quaternary. 

Only one bisindole alkaloid, nitaphylline (313), was isolated from Kopsia teoi which otherwise provided a large number of new indoles. Nitaphylline [155,186] was shown to be a bisindole constituted from union of two kopsingine moieties. The mass-spectrum showed a molecular ion at m/z 910 with a significant peak at ndi 455 suggesting symmetrical cleavage of... 

Paucivenine (268), an amorphous alkaloid of M. balansae var. paucivenosus, contains indole, indoline, and saturated ester chromophores, and in its mass spectrum exhibits peaks characteristic of eburnane and tabersonine (both of which could be generated by transfer of H-2 to C-16 with fission of the 16-16 bond) together with peaks reminiscent of tabersonine. On the basis of these data. 

Nitaphylline (572), was the only bisindole isolated from Kopsia teoi which otherwise provided a large number of new indole alkaloids. The mass spectrum... 

In the spectrum of des-Af-methyl-a-obscurine, a similar mechanism (Equation 9.49) can explain the loss of the —CH2—CHfCHj)—CH2— bridge plus a hydrogen atom to form the (M — 57) ion. The (M — C4H8) is of much lower abundance than the (M — C4H9)". (The mass spectra of nicotine, indole alkaloids, and strychnine are shown in Figure 5.1, Unknown 6.3, and Figure 3.28.)... 

Membership to the condylocarpine rather than to the akuammicine group was established by mass spectral examination of the dihydro derivative (CCXXIV-B). The spectrum paralleled that of condylocarpine except in that the s peak appeared at m/e 257 (227 + 30 due to the aromatic methoxyl), while the indolic peaks were also shifted upward by 30 mass units. The UV-spectra of CCXXIV-B and its V-acetyl derivative, CCXXIV-C, corresponded to those of la,l,2,3,4,4a-hexahydro-7-methoxycarbazole and its iV-acetyl derivative, respectively (120a), thus placing the methoxyl group in the 11 position (condylocarpine numbering). The alkaloid CCXXIV-A may thus be formulated as 11-methoxy-14,19-dihydrocondylocarpine (48). 

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