The esterification of N-methylpyrrol-2-carboxylic acid (I) with NaH and methyl iodide in DMF gives methyl N methylpyrrol 2 carboxylate (II), which is condensed with acetonitrile by means of NaH in DMF yielding 3-(1-methyl-2-pyrrolyl)-3-oxopropionitrile (III). The reaction of (III) with phenylisocyanate (IV) by means of triethylamine in toluene affords 2-cyano-3-(1-methyl-2-pyrrolyl)-3-oxo-N-phenylpropionamide (V), which is finally treated with triethanolamine (VI) in hot ethanol.
The reaction of acid (I) with SOCl2 in ethyl ether containing triethylamine gives the corresponding acyl chloride (VII), which is condensed with ethyl cyanacetate (VIII) by means of NaH in glyme yielding ethyl 2-cyano-3-(1-methyl-2-pyrrolyl)-3-oxopropanoate (IX). The reaction of (IX) with aniline (X) in refluxing xylene affords the corresponding anilide (V) already obtained.
The synthesis of [14C]-labeled prinomide has been described: The carboxylation of 1-methylpyrrole (I) with 14CO2 and butyllithium in THF gives labeled 1-methylpyrrole-2-carboxylic acid (II), which is esterified with diazomethane to the methyl ester (III). The reaction of (III) with acetonitrile by means of NaH in DMF affords 3-(1-methylpyrrol-2-yl)-3-oxopropanenitrile (IV) labeled in the carbonyl group. Finally, this compound is condensed with phenylisocyanate (V) by means of triethylamine in toluene, affording the prinomide labeled in the carbonyl group. The condensation of unlabeled (IV) with (V) labeled in the phenyl ring yields the corresponding prinomide labeled in the aromatic ring.