Pyridine group alkaloids

Pyridine Group. Piperine, Piperovatine, Leucenol, Mimosine, Alkaloids of Ricinus communis, Foenugrec, vy eca Nut, Hemlock, Lobelia, Tobacco (Nicotiana spp.). Anabasis aphylla, Pomegranate Root Bark. ... 

The alkaloid nicotine is present in tobacco, Nicotiana tabacum. In discussing the derivatives of pyridine it was stated (p. 858) that the e/a-mono-carboxy acid of pyridine is known as nicotinic acid and that it is obtained by the oxidation of the alkaloid nicotine. Therefore the alkaloid undoubtedly contains the pyridine group. It has been synthesized by Pictet and its constitution established as a pyridine derivative of methyl pyrrolidine. This constitution was first suggested by... 

In 1931 Ing pointed out that formula (II) and (III) do not contain methyl or potential methyl groups in j ositions 6 and 8 which they occupy in cytisoline. Further, a partially reduced quinoline ought to oxidise easily to a benzenecarboxylic acid and so far the only simple oxidation, products recorded from cytisine were ammonia, oxalic acid and isovaleric acid. Distillation of cytisine with zinc dust or soda-lime yields pyrrole and pyridine, but no quinoline. On these grounds Ing suggested that cytisine should be formulated without a quinoline nucleus, and that the reactions which indicate the presence of an aromatic nucleus in the alkaloid can be accounted for by an a-pyridone ring. This a-pyridone nucleus can... 

Nearly all of the microbial and mammalian transformation studies with this group of alkaloids have been focused on nicotine. Microorganisms have been used to resolve racemic nicotine to make available unnatural (/ )-(+)-nicotine for biological evaluation. Highly significant work has detailed the mechanism of nicotine oxidation in mammals, and has resulted in the identification of reactive intermediates formed as the alkaloid is transformed by hepatic monooxygenases. The chemistry and pharmacology of the pyridine alkaloids is discussed by Strunz and Findlay in Volume 26 of this treatise. 

Another directing group whose value and effectiveness is greatly enhanced in the pyridine series is the a-aminoalkoxide group derived by addition of a lithioamine to an aldehyde (see Section LB.Lb). Aldehyde 237 was converted to 238, and thence to an intermediate 239 in the synthesis of the alkaloid maxonine, by this method (Scheme 115). ... 

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. ... 

Compounds belonging to this group of alkaloids are sourced from the Celas-traceae and Hippocrateaceae families and contain the sesquiterpene nucleus. More than 220 alkaloids are known in this groups. Sesquiterpene pyridine... 

The biotoxicity of pyridine alkaloids is well studied and the toxicity of nicotine is one of the best examples of the very active alkaloids study area. Aydos et al." have studied 20 rats injected daily with nicotine at doses 0.4 mg 100 of body weight during 3 months and made comparisons to a control group of 20 rats. The researchers concluded that ultra-structural alternations in rats exposed to nicotine occurred. 

Table VII lists the important IR peaks given for the alkaloids isolated. The noreugenin moiety contributes peaks at 1550, 1660, and about 3300 cm for the C=C, C=0, and OH groups, respectively. In the pyridine-noreugenin congeners an additional band due to the lactone C=0 is seen at about 1750...

The pyridine-noreugenin compounds 18, 29, 13, and 32 show characteristic downfield aromatic protons between 8 8.0 and 9.5, and the quaternary nitrogen alkaloids 31 and 32 exhibit a distinct iV-methyl singlet at 8 4.3. The chemical shift of the iV-methyl group in the other alkaloids which contain it is influenced by the substituents on the adjacent carbon atoms. Thus in rohitukine (17), where the adjacent groups are both methylene, the signal is seen at 8 2.21 whereas in N-methylschumannificine (26) (where a CHOH is adjacent) it is seen at 8 2.95 and in (V-methylanhydroschumannificine (28) (where HC=CR3 is adjacent) it is seen as far downfield as 8 3.14. 

---