Pinidine and Coniine

Pinidine and Coniine.—Pinidine (8) and the hemlock alkaloid coniine (9) are unusual among simple piperidine alkaloids in being derived exclusively from acetate units. The combination is in each case a simple linear one and proceeds either via polyketide intermediates or, arguably in the case of coniine, via the fatty acid (10). Strong evidence from tracer and enzyme studies points to (11) as an intermediate 

More positive information was obtained, however, when diethyl [l- C]malonate was fed to Pinus jeffreyi together with inactive sodium acetate. The activity at C-2 (9%) in the derived pinidine was much lower than that at C-9 (30%) from which it follows that C-2 and C-7 of pinidine (8) represent the starter acetate unit and the carboxy-function lost in the course of biosynthesis must therefore be sited as in (13) rather than as in (14). It was suggested that the failure of (13) to act as a precursor might indicate that biosynthesis only proceeds via a A -derivative of this acid. 

Coccinelline.—Coccinelline (16) is an alkaloid isolated from the defensive secretion of the Coccinellidae. [l- C]Acetate has been found to be incorporated into this arthropod alkaloid with 16% of the activity confined to C-2 plus C-10. This is consistent with derivation via the polyketide (17) (or the alternative with the carboxy-group at what becomes C-10 of coccinelline). 

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Pinidine and Coniine.—Pinidine (1) is found in various species of pine, including Firms jeffreyi. Inspection would indicate an origin similar to coniine (2) or to iV-methylpelletierine (13). Whilst the former is biosynthesised by the linear combination of four acetate units, the piperidine ring of the latter is generated from lysine and the side chain from acetate. ... 

Pinidine and Coniine Nicotiana Alkaloids yV-Methylpelletierine Lycopodium Alkaloids Lyduraceae Alkaloids Pyrrolizidine Group Tropane and Pyrrolidine Alkaloids Quinoline and Acridme Alkaloids Benzodiazepine Alkaloids Tylophora Alkaloids Cactus Alkaloids Ephedrine... 

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