Abstract
We have previously reported that N-(4-isopropyl-2, 2-dimethyl-3-oxo-3, 4-dihydro-2H-benzo[1, 4]oxazine-6-carbonyl)guanidine (4b) methanesulfonate salt (KB-R9032) is a potent and highly water-soluble Na/H exchange inhibitor. In a series of studies on Na/H exchange inhibitors, we designed and synthesized N-(3-oxo-3, 4-dihydro-2H-benzo[1, 4]thiazine-6-carbonyl)guanidines (5) as more potent inhibitors with high water-solubility. The design strategy for 5 was based on a quantitative structure-activity relationship (QSAR) study, involving the proportional relationship between the biological activity and hydrophobicity of the ring structure of compounds 4. As expected, compounds 5 showed more potent activity than 4. It was found by using the QSAR analysis that 4 were about five-fold more potent than 4. The increase in potency of compounds 5 well agreed with our previous QSAR analysis result. The most potent derivative was the methanesulfonate salt 5d of the 4-isopropyl derivative(IC50=0.0091μM). And in addition to the in vitro study, 5d showed significant protective activity against a rat acute myocardial infraction model.
