Biosynthesis of reticuline

Abstract

The incorporation of tyrosine, dopa, dopamine, and 4-hydroxy- and 3,4-dihydroxy-phenylpyruvic acids into reticuline in Litsea glutinosa has been studied, and it has been demonstrated that dopa and dopamine contribute only to the formation of the phenethylamine portion; the benzylic portion is biosynthesized from 3,4-dihydroxyphenylpyruvic acid not derived from dopa. Tyrosine and 4-hydroxy- and 3,4-dihydroxy-phenylpyruvic acids participate in the formation of both halves of reticuline. Tracer experiments have shown the intermediacy of norlaudanosoline-1-carboxylic acid, norlaudanosoline, and didehydronorlaudanosoline in the biosynthesis of reticuline. Incorporation studies with (±)-4'-O-methylnorlaudanosoline, (±)-laudanosoline, (±)-6-O-methylnorlaudanosoline, and (±)-nor-reticuline have demonstrated that O-methylation prededes N-methylation and that there is no rigid selectivity of O-methylation in the biosynthesis of reticuline.