Hydroxylated Analogues of ATP-Sensitive Potassium Channel Openers Belonging to the Group of 6- and/or 7-Substituted 3-Isopropylamino-4H-1,2,4-benzothiadiazine 1,1-Dioxides: Toward an Improvement in Sulfonylurea Receptor 1 Selectivity and Metabolism Stability

Diversely substituted 3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides are known to be potent K-ATP channel openers, with several drugs being selective for the SUR1/Kir6.2 channel subtype. This work examined the biological activity, tissue selectivity, and in vitro metabolic stability of hydroxylated analogues of 3-isopropylaminobenzothiadiazine dioxides. Because of the presence of a chiral center, the R and S isomers were prepared separately and characterized. R isomers were systematically found to be more potent and more selective than S isomers on pancreatic tissue (compared to vascular smooth muscle tissue), leading to compounds with an improved sulfonylurea receptor 1 (SUR1) selectivity. An in vitro metabolic study revealed that 7-chloro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide (1a) was rapidly biotransformed and led in part to a mixture of the corresponding (R)- and (S)-3-(1-hydroxy-2-propyl)amino-substituted derivatives. Radioisotopic experiments characterized one of the most potent and SUR1-selective enantiomers, (R)-7-chloro-3-(1-hydroxy-2-propyl)amino-4H-1,2,4-benzothiadiazine 1,1-dioxide 13a, as being a K-ATP channel opener. Moreover, 13a exhibited an enhanced metabolic stability. Such a compound can be considered as a new lead candidate displaying improved physicochemical (hydrosolubility) and pharmacological (tissue selectivity) properties as well as improved metabolic stability compared to its nonhydroxylated counterpart, 1a.