Quinolizidine mass spectra

Albertidine, isolated from Leontice Albertii Rgl. (196,197), is a crystalline, optically active tribase. There are IR absorption bands for a trani-quinolizidine system at 2750 and 2793 cm and a six-membered lactam carbonyl at 1640 cm The absorption in the fingerprint region is similar to that of matrine. The mass spectrum of albertidine is characterized by ion peaks at miz 247 (M -1), 219, 205, 192, 177, 150, 137, 98, and 96 which are typical for matrine alkaloids (209). On the basis of spectroscopic data and taking into account the tranj-quinolizidine band in the IR spectrum, the probable structure 182, with rings A/B-trans, was proposed. 

Epidemethoxyabresoline (70) shows a mass spectrum similar to that of its stereoisomer 68. The absence of Bohlmann bands and the NMR chemical shift of H-l at S 4.0 ppm demonstrate the presence of cw-quinolizidine system. 

A mtyor alkaloid (251F) in the small Colombian poison frog Minyabates bombetes was unusual in exhibiting a base peak at an odd mass (mh 111) in its mass spectrum (151). It was clearly unrelated to other dendrobatid alkaloids and appears to be unique to this species. The structure of alkaloid 251F has been elucidated by nuclear magnetic resonance and FTIR spectroscopy (752) it is a cyclopenta[7>]quinolizidine as shown in XI. 

Nitraramine and A-hydroxynitraramine were isolated from Nitraria schoberi (194,195). There are active hydrogen absorption bands in the IR spectrum of nitraramine at 3280 and 3530 cm- and a low intensity band at 1660 cm" (double bond). Acetylation of nitraramine (171) gave A-acetyl and A,0-diacetyl derivatives. Hydrogenation over Adams catalyst in acetic acid gave di-hydronitraramine (172) and dihydrodesoxynitraramine (173) (Scheme 30). The presence of peaks typical for quinolizidine alkaloids in the mass spectra of 171-... 

Neosophoramine was isolated from Sophora alopecuroides L. (191,207,222,223). There are no rons-quinolizidine bands in the IR spectrum, but there is a lactam carbonyl absorption band at 1650 cm. The MS spectrum is characterized by peaks of the molecular ions M (244) and M - 1 (243) and by ion peaks at miz 215, 149, 136, and others, typical for matrine alkaloids containing an a-pyiidine ring. A comparative study of UV, IR, H-NMR, and mass spectroscopic data of neosophoramine (194), sophoramine (195), and iso-sophoramine (196) showed that these alkaloids differ mainly in the configuration... 

The Structural identification of (-)-6a-hydroxylupanine was based on the analysis of its spectral data and is in full agreement with the C15H24N2O4 molecular formula determined by HRMS [219]. The mass fragments at m/z 247 [M-OH] and m/z 246 [M-H20] suggested the presence of a hydroxyl substituent, further confirmed by an IR absorption band at 3400 cm". Further analysis of the IR spectrum also provided evidence for the quinolizidine nucleus (2860, 2810 and 2750 cm, tram Bohlmann absorption bands) and the oxo substituent (1640 cm, lactam group). 

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