Chloro-substituted 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides as ATP-sensitive potassium channel activators: impact of the position of the chlorine atom on the aromatic ring on activity and tissue selectivity.

The synthesis of 5-chloro-, 6-chloro-, and 8-chloro-substituted 3-alkylamino/cycloalkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides is described. Their inhibitory effect on the insulin releasing process and their vasorelaxant activity was compared to that of previously reported 7-chloro-3-alkylamino/cycloalkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides. "5-Chloro" compounds were found to be essentially inactive on both the insulin-secreting and the smooth muscle cells. By contrast, "8-chloro" and "6-chloro" compounds were found to be active on insulin-secreting cells, with the "6-chloro" derivatives emerging as the most potent drugs. Moreover, the "6-chloro" analogues exhibited less myorelaxant activity than their "7-chloro" counterparts. 8-Chloro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide (25b) and 6-chloro-3-cyclobutylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide (19e) were further identified as K(ATP) channel openers by radioisotopic measurements conducted on insulin-secreting cells. Likewise, current recordings on HEK293 cells expressing human SUR1/Kir6.2 channels confirmed the highly potent activity of 19e (EC(50) = 80 nM) on such types of K(ATP) channels. The present work indicates that 6-chloro-3-alkylamino/cycloalkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides appear to be more attractive than their previously described 7-chloro-substituted analogues as original drugs activating the SUR1/Kir6.2 K(ATP) channels.

New R/S-3,4-dihydro-2,2-dimethyl-6-halo-4-(phenylaminothiocarbonylamino)-2H-1-benzopyrans structurally related to (+/-)-cromakalim as tissue-selective pancreatic beta-cell K(ATP) channel openers.

The present work was aimed at exploring a series of R/S-3,4-dihydro-2,2-dimethyl-6-halo-4-(phenylaminothiocarbonylamino)-2H-1-benzopyrans structurally related to (+/-)-cromakalim and differently substituted at the 4- and 6-positions. The biological effects of these putative activators of ATP-sensitive potassium channels (K(ATP)) were characterized in vitro on the pancreatic endocrine tissue (inhibition of insulin release) and on the vascular smooth muscle tissue (relaxation of aorta rings). The biological activity of these new dimethylchroman derivatives was further compared to that of (+/-)-cromakalim, (+/-)-pinacidil, diazoxide and BPDZ 73. Structure-activity relationships indicated that an improved potency for the pancreatic tissue was obtained by introducing a meta- or a para-electron-withdrawing group such as a chlorine atom on the C-4 phenyl ring, independently of the nature of the halogen atom at the 6-position of the benzopyran nucleus. Most original dimethylchroman thioureas were more potent than their 'urea' homologues and even more potent than diazoxide at inhibiting insulin release. Moreover, and unlike (+/-)-cromakalim or (+/-)-pinacidil, such compounds appeared to be highly selective towards the pancreatic tissue. Radioisotopic and fluorimetric investigations indicated that the new drugs activated pancreatic K(ATP) channels. Lastly, conformational studies suggested that the urea/thiourea dimethylchromans can be regarded as hybrid compounds between cromakalim and pinacidil.