Piperidine alkaloids nomicotine

Physiology biosynthesis Like the tropane alkaloids, T. a. are formed in the roots and transported to the aboveground parts for storage by the plant s phloem system. In some sorts of tobacco plants a part of the nicotine is demethylated to nomicotine during transport to the shoot. Nomicotine and anabasine are often the main alkaloids in the so-called nicotine-poor tobacco plant types. The T. a. are formed biogenetically from nicotinic acid, made available via the pyridine nucleotide cycle (see nicotinamide), and a pyrrolidine or piperidine building block (figure). In the case of nicotine, like for the tropane alkaloids, Al-methylpyr-roline is an intermediate, in the biosynthesis of anabasine the intermediate is a piperidine derived from the amino acid lysine (see piperidine alkaloids). 

Nicotine in tobacco is always accompanied by three other prominent alkaloids nomicotine, (S)-2-(3-pyridyl)pyrrolidone, anatabine, (S)-2-(pyrid-3-yl)-l,2,5,6-tertrahydropyridine and anabasine, (S)-2-(pyrid-3-yl)piperidine (10-7). Apart from these main alkaloids, more than 20 other minor tobacco alkaloids (10-8) have been identihed. 

Pyridine alkaloids are compounds with a pyridine nucleus and a pyrrohdine or piperidine unit. The pyrrohdine ring appears in nicotine and the piperidine ring in anahasine. Typical alkaloids from this group are nomicotine and anatahine. The a of pyridine alkaloids is nicotinic acid, the j8 is dihydronicohnic acid, the q> is 1,2-dihydropyridine (Figure 61). The A is nicotine and its P is nomicotine. ... 

Nomicotine, an organocatalyst studied by Dickerson and co-workers (Entry 5 [52, 58d], Appendix 7.B), reinforces the important principle that even catalysts from Nature can present problems when it comes to toxicity. The family of nicotinic receptor agonists (Figure 7.9) contains several chiral pyrrolidines and piperidines with the potential to act as asymmetric aldol catalysts. Nomicotine, which can be isolated from plants such as tobacco, or readily synthesized by demethylation of the maj or tobacco alkaloid nicotine, was investigated in some depth as an aldol catalyst by Dickerson and Janda in 2002 [52]. 

Pyridine, piperidine and pyrrolidone alkaloids Arg, Lys, Orn, nicotinic acid Tobacco leaves Nicotine, nomicotine, anatabine, anabasine... 

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