Piperidine alkaloids contain the piperidine nucleus. The structural development of this group of alkaloids in synthesis is presented in Figure 52. Here a is L-lysine and ft is cadaverine. The basic ring of ft is the same as in a, although the activity of PLP reduces carbon dioxide. The ft is biogenic amine, neither a stable nor a poisonous compound
By oxidative deamination, in which diamine oxidase (DAO) is active together with Schiff base formation, the ft converts into The ^ is A^piperideine, which can not be substituted by other compounds, although several hypothetical obligatory intermedia such as glutardialdehyde and 5-aminopentanal have been proposed225. In the case of piperidine alkaloids, these hypothetical substitutes of ^ are ruled out. ^ has slowly changed the basic ring, but it is no longer piperidine. The deeper change in the ring occurs in the next reaction, the Mannich Reaction (MR), the result of which is x. For this purpose, the nucleophilic acetoacetyl-CoA with (—) is used for (+) closing the ring. In this case, the intermolecular Mannich reaction is under question. Subsequently, x, which is A^piperidinium cation, has a ring similar to piperidine, though not identical. Only after hydrolysis and decarboxylation will the compound be A (pelletierine) with the piperidine nucleus. By the activity of SAM, A is converted to P, which is N-methylpelletierine. P can be converted by the intramolecular Mannich reaction to the next postcursor, Pj, which is pseudopelletierine. Other postcursors of pelletierine are possible,
N - methylpelletierine
Pseudopelletierine Figure 52. Structural development of piperidine alkaloids.
for example anaferine, in the intermolecular Mannich reaction. True piperidine alkaloids have one-cycle compounds with the C5N nucleus.
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