The biosynthesis of decodine (7) and decinine (9), Lythraceae alkaloids containing a trans-fused quinolizidine nucleus, was studied in intact plants of Decodonverticillatus (L.) Ell. Nonrandom incorporation of radioactivity from 14C-labelled samples of lysine, cadaverine, and Δ1-piperideine was demonstrated by partial degradation. Pelletierine did not serve as a precursor of the alkaloids. It was also shown, by means of 3H,14C-labelled tracers, that the alkaloids are derived from L-lysine whereas pipecolic acid, which is present in the plant, is derived from D-lysine.

Two fragments derived from phenylalanine (l), one a c&3 unit, the other probably a c& unit, are incorporated into the Lythraceae alkaloid, decodine (2).ACTIVITY from @14C]phenylalanine (1) enters the two predicted positions (0) of the phenylquinolizidine alkaloid cryogeninel [an isomer of 0-methyl-1 ',2'-dehydro-(2) J This observation was consistent with the four hypothe~es~l-~ summarized in ref. 4, which have been advanced to account for the origin of this group of alkaloids, but did not distinguish among them. In all these hypotheses an intact

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