Synthesis of a metabolite of metoclopramide and its detection in human urine.

The synthesis of 2-(4-amino-5-chloro-2-methoxybenzamido)acetic acid 2, a metabolite of metoclopramide 1, has been accomplished through the coupling of 4-amino-5-chloro-2-methoxybenzoic acid 4 with glycine benzyl ester followed by a catalytic hydrogenation. Such a metabolite could not be detected directly in the human urines but only after its transformation into the corresponding methyl ester 6. Compound 6 was prepared both by condensing acid 4 with glycine methyl ester and by reacting acid 2 with diazomethane. HPLC analyses of biological samples were therefore performed after treatment with diazomethane. In five healthy volunteers, the percentage of 6 spanned the range 0.6-1.2%.