Quinolizidine alkaloids, mass spectra

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-... 

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. 

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. 

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... 

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