New Alkoxypyridine-sulfonamides: Synthesis, Biological Evaluation, and Physicochemical Properties

As a further phanmacomodulation of benzamide derivatives, two structural modifications were introduced by synthesizing pyridinesulfonamides 5 and 6 (Scheme). The pharmacological profile of substituted benzamides such as metoclopramide (2) is not retained in the pyridine-sulfonarm'des 6: the latter have very low toxicity but do not exhibit any affinity for D2 and 5-HT2 receptors, and gastrointestinal prokinetic activity is weak (Table 3), Lipophilicity does not seem to be a determining factor for this lack of activity. A conformational analysis shows that the sulfonamide group in 6 is rather unfavorable for an intramolecular H-bond formation when compared to the carboxamide group of, e.g., 2. Nevertheless, the interaction remains possible and leads to a stable conformation (Fig. 1, Table 5.) Moreover, the sp3 character of the sulfonamide N-atom of 6 modifies the relative spatial orientation of one substituent in relation to each of the others. This feature seems to be more important for the observed very low activity than the H-bond formation itself.