Process of preparing penicillamine

In a process of preparing penicillamine or a homologue thereof by reacting together an aldehyde branched at the .alpha.-carbon atom, sulfur, and ammonia to form a thiazoline-.DELTA..sup.3, converting the thiazoline-.DELTA..sup.3 by reaction with anhydrous hydrogen cyanide to the corresponding thiazolidine-4-carbonitrile, hydrolyzing the carbonitrile with hydrochloric acid to form first the hydrochloride of the corresponding thiazolidine-4-carboxamide and then, at a higher temperature, to form the hydrochloride of the thiazolidine-4-carboxylic acid and an ammonium salt, separating the ammonium salt from the mixture and decomposing the thiazolidine-4-carboxylic acid hydrochloride by hydrolysis to form penicillamine or a homologue thereof, the improvement which consists essentially of the step of hydrolyzing the carbonitrile to the carboxamide by heating at a temperature between about 40.degree. and 70.degree. C a mixture of the carbonitrile and at least the amount of aqueous hydrochloric acid containing at least 30% by weight of hydrogen chloride that is required stoichiometrically to form the corresponding thiazolidine-4-carboxamide hydrochloride.