Mass spectrometry of bis‐quinolizidine alkaloids: Lactams of sparteine and α‐isosparteine

Abstract

The mass spectral fragmentations of 2-oxosparteine (lupanine), 2-oxo-a-isosparteine (a-isolupanine), 15-oxosparteine, 17-oxosparteine and 10-oxosparteine (aphylline) are reinvestigated and discussed. Fragmentation pathways, elucidation of which were assisted by accurate mass measurements and metastable transitions, are proposed. The fragmentation assignments are not consistent with those previously reported in the literature. Many fragment species of the same m/z (low-resolution spectra) are composed of two or three fragment ions of Merent elemental compositions (high-resolution spectra). The obtained data create a safe basis for distinguishing structural and stereo isomers.

Mass spectrometry of bis-quinolizidine alkaloids: 2- and 17-alkyl-substituted derivatives of sparteine and lupanine

“…On the basis of the low‐resolution EI mass spectra, exact mass determinations (Tables 1 and 2) and CAD B / E as well as B 2 / E linked scan spectra (Figs 2 and 3), the principal mass spectral fragmentation routes of compounds 1–3 are interpreted as shown in Scheme , and those of 4 and of 5 and 6 as in Schemes and 3 respectively. It should be pointed out that only the fragmentation pathways have been confirmed by B / E and B 2 / E linked scan spectra and that many of the cyclic ion structures shown in Schemes are conjectural, similarly to those discussed previously in the literature 1–10. The common feature of the mass spectral fragmentation of molecular ions of 1–6 is the cleavage of N1–C10, C6–C7, C9–C10 (ring B), C9–C11, C7–C17 (ring C) as well as C17–R (RCH 3 , i ‐C 3 H 7 ) (ring C) and C2–CH 3 (ring A) bonds of the skeleton of sparteine.…”

“…The main characteristic of the mass fragmentation of the molecular ions of these compounds is the dependence of the mass decomposition of the bis‐quinolizidine skeleton on the stereochemistry of the A/B and C/D ring junctions 5. As a continuation of our study of the mass fragmentation of lactams of sparteine and α‐isosparteine,6, 7 multiflorine and its derivatives,8 13‐keto‐ and hydroxy‐substituted derivatives of sparteine and lupanine9 and 2‐ and 15‐substituted derivatives of sparteine and 2‐ (or 14‐) dehydrosparteine,10 it seemed reasonable to extend our investigation to 2‐ and 17‐alkyl‐substituted derivatives of sparteine and lupanine. The purpose of this study was to explain the mass fragmentation of 2‐methylsparteine (1), 2,17‐dimethylsparteine (2), 2‐methyl‐17‐isopropylsparteine (3), 2‐methyl‐17‐oxosparteine (4), 2‐oxo‐17‐methylsparteine (17‐methyllupanine) (5) and 2‐oxo‐17‐isopropylsparteine (17‐isopropyllupanine) (6).…”

Differentiation between isomeric 2‐thionosparteine and 15‐thionosparteine on the basis of electron ionization mass spectra

“…The fragmentation pathways of compounds (1) and (2) All the fragment species in 1 and 2 are composed of one fragment ion, in contrast to those in the oxo analogues. 12 The mass fragmentation of the molecular ions proceeds by elimination of the ž SH radical and also by the cleavages of Csp 3 -Csp 3 , Csp 3 -Csp 2 , Csp 3 -N bonds of rings A, B, C and D of the sparteine skeleton. The principal mass fragmentation pathways of the isomeric 2thionosparteine (1) and 15-thionosparteine (2) (the thiolactam groups are located in the external rings: A in 1 and D in 2) are very similar, but differ in the abundance of the main fragment ions ( Table 1).…”

Mass Spectrometry of Bis-quinolizidine Alkaloids: Differentiation of Stereoisomers and Metamers Using ESI and FAB Mass Spectrometry

“…[1][2][3][4][5][6] The stereochemical effects that are encountered with dissociations of stereoisomers incorporating saturated heterocyclic rings are due to the spatial relationship of chemical bonds to be broken or formed. The basic bis-quinolizidine system sparteine consists of four rings, two of which (A=B) form a double-chair system of trans-quinolizidine that is relatively resistant (for thermodynamic reasons) to conformational-configurational changes.…”