The synthesis of two 14C‐labeled forms of prinomide, compounds 7 and 10, and the synthesis of a 14C‐labeled form of its hydroxy metabolite are described. Compound 7 was synthesized by the reaction of phenyl isocyanate and 1‐methyl‐β‐oxo‐pyrrole‐2‐propanenitrile‐carbonyl‐14C (6), which was synthesized in three steps from 1‐methylpyrrole and 14CO2. Cpmpound 10 was synthesized by the reaction of 8, the unlabeled form of the above ketonitrile, and ring‐labeled phenyl isocyanate (9), which was synthesized in three steps from benzene‐14C. The 14C‐labeled form of the hydroxy metabolite 14 was synthesized by reaction of 4‐methoxyphenyl isocyanate and the 14CN‐labeled ketonitrile 12, followed by demethylation with boron tribromide. Labeled ketonitrile 12 was synthesized from 1‐methylpyrrole, by reaction with chloroacetonitrile, followed by replacement of the chlorine atom by a 14CN group. Copyright © 1990 John Wiley & Sons, Ltd.
