In order to distinguish between ortho-para and para-para phenol coupling in colchicine biosynthesis,[3′-O14CH3] autumnaline was converted to [14C] colchicine in seeds of Colchicum autumnale and the product was then selectively demethylated by a bacterium that exclusively demethylates C-3 of colchicine. The retention of the radioactive label in 3- demethylcolchicine indicates that biosynthesis proceeds through para-para coupling.
