Structure–activity relationships of some opiate glycosides

A number of analogues of morphine-6-glucuronide 1 have been prepared and evaluated as potential analgesic agents by competitive μ-receptor binding assay and in vivo antinociceptive activity. The analogues show variation in the nature of the carbohydrate residue, the N-substituent, the O(3)-substituent and saturation of the 7,8-double bond compared to 1. In general, only the 6β-glucoside or β-glucuronide carbohydrate residues showed potent agonism; other modified carbohydrates were less active or exhibited potential antagonism. Variations in N-substituent led to either reduced agonism (N–H) or potential antagonism [N-allyl, N-(cyclopropyl)methyl]; a polar N-substituent, carboxymethyl, failed to bind. Saturation of the 7,8-double bond led to increased agonism compared to the parent compound in all three examples studied.