Design and synthesis of novel 7-heterocycle-6-trifluoromethyl-3-oxoquinoxaline-2-carboxylic acids bearing a substituted phenyl group as superior AMPA receptor antagonists with good physicochemical properties

We describe the design, synthesis, and physicochemical and biological properties of a novel series of 7-heterocycle-6-trifluoromethyl-3-oxoquinoxaline-2-carboxylic acids bearing a substituted phenyl group joined through a urethane or urea linkage to the heterocycle at the 7 position. Introduction of the trifluoromethyl group at the 6 position conferred good biological activity, including neuroprotective effects, as well as good physicochemical properties. In terms of alpha-amino-3-hydroxy-5-methylisoxazole propionate receptor (AMPA-R) affinity, a urea linkage was equivalent to a urethane linkage and a pyrrole ring at the 7 position reduced affinity in comparison with an imidazole ring. Among this series, compound 14h (KRP-199), which has a 4-carboxyphenyl group joined through a urethane linkage to a 7-imidazolyl heterocycle, was found to possess high potency and selectivity for the AMPA-R in vitro and to exhibit good neuroprotective effects in vivo. Furthermore, the compound showed good physicochemical properties, including stability to LIGHT and good solubility in aqueous solutions.