Synthesis and antimicrobial evaluation of quaternary salts of 4-phenyl-1,2,3,6-tetrahydropyridine and 3,6-dimethyl-6-phenyl-tetrahydro-2H-1,3-oxazine.

Fifteen predominantly alkyl bromide quaternary salts of 1-substituted 4-phenyl-1,2,3,6-tetrahydropyridine and 10 from 3,6-dimethyl-l-phenyltetrahydro-2H-1,3-oxazine were synthesized. None was effective against the parasitic protozoan Eimeria tenella and the helminth trichostrongyle nematode. Nearly all inhibited Gram-positive and Gram-negative bacteria; maximum efficiency was obtained with nonyl through dodecyl bromide salt derivatives. Antifungal effectiveness paralleled these results. The oxazinium salt analogs were inhibitory in an in vitro peridontal microorganism screen. The decyl bromide derivative at 0.05% in drinking water prevented dental plaque and reduced calculus deposition in rats but not in hamsters fed cariogenic diets. A 0.01% concentration of the tetrahydropyridinium analog caused increased plaque in rats compared to nonmedicated control animals.