The Biosynthesis of the phenethylisoquinoline alkaloid colchicine. Early and intermediate stages

Abstract

Experiments with 14C- and 3H-labelled compounds in Colchicum byzantinum and C. autumnale show that in the early stages of biosynthesis the major pathway to colchicine (7) and demecolcine (6) is (13)→(15)→(16)→(19). Condensation of the aldehyde (19) with dopamine affords a set of phenethylisoquinolines which are precursors for the alkaloids (6) and (7) and (21) is identified as the first of these followed by (22) and then (1); (39) is by contrast also an exellent alkaloid precursor; it is deduced that neither of two phenethylisoquinolines [as (37) and (38)] which contain a side-chain double bond are involved in alkaloid biosynthesis