3-Alkylpiperidine alkaloids biogenesis

The motuporamines are considered as manzamine-related alkaloids owing to their structural relationship with manzamine C (57), the simplest alkaloid of this family of compounds. Baldwin and Whitehead have proposed a plausible biogenesis for these 3-alkylpiperidine alkaloids, suggesting that they could be formed from three basic building blocks ammonia, a C3 unit, and a Cio unit [54]. The motuporamines, which contain a spermidine-like side chain instead of the alkylated p-carboline substructure of manzamine C, appear to be biogenetically derived from the same precursors, ammonia, acrolein, and a long-chain dialdehyde involved in the Baldwin-Whitehead pathway (Scheme 9.2). 

A proposed biogenesis for the formation of monomeric, dimeric and oligomeric 3-alkylpiperidine alkaloids. The proposal is based on Baldwin and Whitehead s proposed biogenesis for the manzamines [58]. 

As outlined above, the Baldwin and Whitehead proposal for the biogenesis of the manzamines has provided a mechanistic framework that can be used to formulate rather detailed step by step hypotheses for the formation of all known 3-alkylpiperidine alkaloids. Figure 3.11 shows an overall scheme for the biogenesis of the 3-alkylpiperidine alkaloids that incorporates elements of all of the individual proposals that have been put forth to date. 

Scheme 2 Proposed biogenesis of dimeric bis-3-alkylpiperidine macrocyclic alkaloids.

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