Piperidinium cation

Pyridine is a base (pATa pyridinium cation 5.2), but it is a considerably weaker base than a typical non-aromatic heterocyclic amine such as piperidine (pATa piperidinium cation 11.2). This is because the lone pair electrons in pyridine are held in an sp orbital. The increased character of this orbital, compared with the sp orbital in piperidine, means... 

Alkaloids with the piperidine nucleus, such as pelletierine (Punica grana-tum), lobelanine Lobelia inflata) and piperine Piper nigrum), have a typical biosynthesis pathway. It starts with L-lysine and continues via cadaverine (biogenic amine), A -piperideine and A -piperidinium cations and lobelanine, to be synthesized as lobeline. Piperine is synthesized from A -piperideine via piperidine (Figure 49). For the transformation from A -piperideine to A -piperideine cation, the residue from acetyl-CoA is needed, together with SAM activity in the transformation to lobelanine. Piperine is synthesized from piperidine through the formation of amide. 

In the case of protein amino acid-derived alkaloids, the second obligatory intermedia is synthesized from the obligatory intermedia by chemical reactions. In the pelletierine synthesis pathway started with L-lysine, the second obligatory intermedia is A -piperidinium cation. It is formed by a Maimich reaction from A -piperidine (obligatory intermedia) and COSCoA. The second obligatory intermedia, by hydrolysis decarboxylation, produces pelletierine. 

This allows an aldol-type reaction with the A-methylpyrrolinium cation, and finally dehydrogenation of the dihydropyridine ring back to a pyridine gives nicotine. Nornicotine is derived by oxidative demethylation of nicotine. Anaba-sine is produced from nicotinic acid and lysine via the A1 -piperidinium cation in an essentially analogous manner (Figure 6.32). A subtle anomaly has been exposed in that a further Nicotiana alkaloid anatabine appears to be derived by... 

It has been found that water as a solvent accelerates the indium-mediated Barbier-type allylation and benzylation of / ,7-unsaturated piperidinium cation generated from / ,7-unsaturated a-methoxy-A-methoxycarbonylpiperidine, whereas a ring-opened allylated product has been obtained in a case using /3,7-saturated a-methoxy-A-meth-oxycarbonylpiperidine. Other solvents than water result in low yield of the allylated and benzylated products, suggesting that water is essential to generate the piperidinium intermediate from /3,7-unsaturated a-methoxy-A-methoxycarbonylpiperidine (Scheme 85).319... 

Scheme 5.61. A piperidinium cation containing transition state analogue was used as the hapten to elicit Ab72D4. Aldol reaction catalyzed by Ab72D4. BSA = bovine serum albumin.

Salt 26 is monoclinic, space group PZnc, Z = 4. The thiatriazine ring is planar, the piperidinium cation is in a chair conformation, and ionic fragments in the crystal are joined into a three-dimensional (3-D) structure by strong hydrogen bonds <2002RJ01702>. 

Fang S, Zhang Z, Jin Y, Yang L, Hirano S, Tachibana K, Katayama S (2011) New functionalized ionic liquids based on pyrrolidinium and piperidinium cations with two ether groups as electrolytes for lithium battery. J Power Sources 196(13) 5637-5644... 

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