Biosynthesis of Lobinaline

The biosynthesis of lobinaline (1) in intact plants of Lobelia cardinalis L. was studied by tracer methods. The incorporation data are consistent with the view that the alkaloid is formed by dimerization of α-phenacylpiperidine (3), whose piperidine nucleus is derived from lysine via a nonsymmetrical intermediate, and whose sidechain originates, as an intact C 6 –C 2 unit, from phenylalanine via cinnamic acid.