Design and synthesis of new potassium channel activators derived from the ring opening of diazoxide: study of their vasodilatory effect, stimulation of elastin synthesis and inhibitory effect on insulin release.

Benzenesulfonylureas and benzenesulfonylthioureas, as well as benzenecarbonylureas and benzenecarbonylthioureas, were prepared and evaluated as myorelaxants on 30mMKCl-precontracted rat aortic rings. The most active compounds were further examined as stimulators of elastin synthesis by vascular smooth muscle cells and as inhibitors of insulin release from pancreaticß-cells. The drugs were also characterized for their effects on glycaemia in rats. Benzenesulfonylureas and benzenesulfonylthioureas did not display any myorelaxant activity on precontracted rat aortic rings. Such an effect could be attributed to their ionization at physiological pH. By contrast, almost all benzenecarbonylureas and benzenecarbonylthioureas displayed a myorelaxant activity, in particular the benzenecarbonylureas with an oxybenzyl group linked to the ortho position of the phenyl ring. The vasodilatory activity of the most active compounds was reduced when measured in the presence of 80mMKCl or in the presence of 30mM KCl and 10µM glibenclamide. Such results suggested the involvement, at least in part, of KATP channels. Preservation of a vasodilatory activity in rat aortic rings without endothelium indicated that the site of action of such molecules was located on the vascular smooth muscle cells and not on the endothelial cells. Some of the most active compounds also stimulated elastin synthesis by vascular smooth muscle cells. Lastly, most of the active vasorelaxant drugs, except 15k and 15t at high concentrations, did not exhibit marked inhibitory effects on the insulin releasing process and on glycaemia, suggesting a relative tissue selectivity of some of these compounds for the vascular smooth muscle.

Triphenylphosphonium salts of 1,2,4-benzothiadiazine 1,1-dioxides related to diazoxide targeting mitochondrial ATP-sensitive potassium channels.

The present work aims at identifying new ion channel modulators able to target mitochondrial ATP-sensitive potassium channels (mitoKATP channels). An innovative approach should consist in fixing a cationic and hydrophobic triphenylphosphonium fragment on the structure of known KATP channel openers. Such phosphonium salts are expected to cross the biological membranes and to accumulate into mitochondria. Previous works revealed that the presence of an (R)-1-hydroxy-2-propylamino chain at the 3-position of 4H-1,2,4-benzothiadiazine 1,1-dioxides KATP channel openers increased, in most cases, the selectivity towards the pancreatic-type (SUR1/Kir6.2) KATP channel. In order to target cardiac mitoKATP channels, we decided to introduce a triphenylphosphonium group through an ester link on the SUR1-selective (R)-7-chloro-3-(1-hydroxy-2-propyl)amino-4H-1,2,4-benzothiadiazine 1,1-dioxide. The new compounds were found to preserve an inhibitory activity on insulin secretion (SUR1-type KATP channel openers) while no clear demonstration of an impact on mitochondria from cardiomyocytes (measurement of oxygen consumption, respiratory parameters and ATP production on H9C2 cells) was observed. However, the most active (inhibition of insulin release) compound 17 was found to penetrate the cardiac cells and to reach mitochondria.

Research Advancements on Fluorinated and Non-Fluorinated 4- Phenyl(thio)ureido-Substituted 2,2-Dimethylchromans Acting as Inhibitors of Insulin Release and Smooth Muscle Relaxants.

AIMS: The present study aimed at characterizing the impact of the presence or absence of fluorine atoms on the phenyl and benzopyran rings of 4-phenyl(thio)ureido-substituted 2,2- dimethylchromans on their ability to inhibit insulin release from pancreatic ß-cells or to relax vascular smooth muscle cells. METHODS: Most compounds were found to inhibit insulin secretion and to provoke a marked myorelaxant activity. RESULTS: The lack of a fluorine or chlorine atom at the 6-position of the 2,2-dimethylchroman core structure reduced the inhibitory activity on the pancreatic endocrine tissue. One of the most active compounds on both tissues, compound 11h (BPDZ 678), was selected for further pharmacological investigations. CONCLUSION: The biological data suggested that 11h mainly expressed the profile of a KATP channel opener on pancreatic ß-cells, although a calcium entry blockade effect was also observed. On vascular smooth muscle cells, 11h behaved as a calcium entry blocker.

Modulation of the 6-position of benzopyran derivatives and inhibitory effects on the insulin releasing process.

The synthesis of different series of 4- and 6-substituted R/S-3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans is described. All of these new benzopyran derivatives were bearing, at the 4-position, a phenylthiourea moiety substituted on the phenyl ring by a meta or a para-electron-withdrawing group such as Cl or CN. The study aimed at exploring the influence of the nature of the substituent at the 6-position in order to develop new benzopyran-type K(ATP) channel activators exhibiting an improved selectivity towards the insulin secreting cells. The original compounds were examined in vitro on rat pancreatic islets (inhibition of insulin release) as well as on rat aorta rings (vasorelaxant effect) and their activity was compared to that of the reference K(ATP) channel activators (±)-cromakalim, (±)-pinacidil, diazoxide and to previously synthesized cromakalim analogues. Structure-activity relationships indicated that the inhibitory effect on the insulin secreting cells was related to the lipophilicity of the molecules and to the size of the substituent located at the 6-position. A marked inhibitory activity on the insulin secretory process was obtained with molecules bearing a bulky tert-butyloxycarbonylamino group at the 6-position (20-23). The latter compounds were found to have the same efficacy on the pancreatic endocrine tissue than some previously described molecules. Lastly, radioisotopic experiments further identified R/S-N-4-chlorophenyl-N'-(6-tert-butyloxycarbonylamino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)thiourea (23) as a K(ATP) channel opener.

Coupling of liquid chromatography/tandem mass spectrometry and liquid chromatography/solid-phase extraction/NMR techniques for the structural identification of metabolites following in vitro biotransformation of SUR1-selective ATP-sensitive potassium channel openers.

SUR1-selective ATP-sensitive potassium channel openers (PCOs) have been shown to be of clinical value for the treatment of several metabolic disorders, including type I and type II diabetes, obesity, and hyperinsulinemia. Taking into account these promising therapeutic benefits, different series of 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides structurally related to diazoxide were developed. In view of the lead optimization process of the series, knowledge of absorption, distribution, metabolism, excretion, and toxicity parameters, and more particularly the metabolic fate of these compounds, is a fundamental requirement. For such a purpose, two selected promising compounds [7-chloro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide (BPDZ 73) and 7-chloro-3-(3-pentylamino)-4H-1,2,4-benzothiadiazine 1,1-dioxide (BPDZ 157)] were incubated in the presence of phenobarbital-induced rat liver microsomes to produce expected mammal in vivo phase I metabolites. The resulting major metabolites were then analyzed by both mass spectrometry (MS) and NMR to completely elucidate their chemical structures. The two compounds were also further incubated in the presence of nontreated rats and human microsomes to compare the metabolic profiles. In the present study, the combined use of an exact mass liquid chromatography (LC)/tandem MS platform and an LC/solid-phase extraction/NMR system allowed the clarification of some unresolved structural assessments in the accurate chemical structure elucidation process of the selected PCO drugs. These results greatly help the optimization of the lead compounds.

New R/S-3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans as K(ATP) channel openers: modulation of the 4-position.

The present work aimed at exploring a series of diversely 4-arylthiourea-substituted R/S-3,4-dihydro-2,2-dimethyl-6-halo-2H-1-benzopyrans structurally related to (+/-)-cromakalim. These new compounds were examined in vitro as putative potassium channel openers (PCOs) on rat pancreatic islets (inhibition of insulin release) as well as on rat aorta rings (relaxation of aorta ring) and their activity was compared to that of the reference K(ATP) channel activators (+/-)-cromakalim, (+/-)-pinacidil, diazoxide and of previously reported cromakalim analogues. Structure-activity relationships indicated that the most pronounced inhibitory activity on the insulin secretory process was obtained with molecules bearing a strong meta- or para-electron-withdrawing group (CN or NO(2)) on the phenyl ring of the arylthiourea moiety at the 4-position of the benzopyran nucleus (compounds 12-23). Among those, R/S-6-chloro-4-(4-cyanophenylaminothiocarbonylamino)-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran (16) was found to be the most potent benzopyran-type inhibitor of insulin release ever described. Most of these original benzopyran derivatives show increased selectivity for pancreatic versus vascular tissue. Radioisotopic investigations indicated that these new compounds activated pancreatic K(ATP) channels.

2,2-Dimethyl-3,4-dihydro-2H-1,4-benzoxazines as isosteres of 2,2-dimethylchromans acting as inhibitors of insulin release and vascular smooth muscle relaxants.

The present study describes the synthesis and biological evaluation of 4-phenylureido/thioureido-substituted 2,2-dimethyl-3,4-dihydro-2H-1,4-benzoxazines as isosteres of corresponding 2,2-dimethylchromans reported to be pancreatic ß-cell KATP channel openers. The benzoxazines were found to be less active as inhibitors of the glucose-induced insulin release than their corresponding chromans, while the myorelaxant activity of some 4-arylureido-substituted benzoxazines was more pronounced than that exhibited by their chroman counterparts. The myorelaxant activity of the most potent benzoxazine 8e was further characterized on rat aortic rings precontracted by 30 mM KCl in the presence of glibenclamide (10 µM) or precontracted by 80 mM extracellular KCl. Our findings indicate that, on vascular smooth muscle cells, the benzoxazine 8e mainly behaved as a calcium entry blocker.

KATP channel openers: tissue selectivity of original 3-alkylaminopyrido- and 3-alkylaminobenzothiadiazine 1,1-dioxides.

The present study was designed to further evaluate the biological effects and tissue selectivity of new 3-alkylaminobenzo- and 3-alkylaminopyridothiadiazine 1,1-dioxides bearing identical branched alkylamino chains at the 3-position. These original compounds were compared with their parent molecules; namely the K(ATP) channel openers diazoxide and pinacidil. All tested 3-alkylamino-substituted derivatives provoked a marked, concentration-dependent inhibition of the glucose-induced insulin secretion from rat pancreatic islets. The 3-alkylaminopyridothiadiazine 1,1-dioxides evoked a weak vasorelaxant activity whilst their 7-halo-substituted benzothiadiazine counterparts elicited pronounced, concentration-dependent, relaxations of rat aortic rings. The myorelaxant effect of the different drugs was tightly correlated with their capacity to increase (86)Rb outflow ((42)K substitute) from prelabelled and perifused rat aortic rings. EC(50)/IC(50) ratios (vascular/pancreatic) revealed a pronounced selectivity of the 3-alkylaminopyridothiadiazine 1,1-dioxides towards the pancreatic endocrine tissue. Structure-activity relationships suggest that, besides the requirement of an electronegative pole at the 7-position of the heterocycle, a minimal steric hindrance confers an optimal insulin-secreting cell selectivity. Lastly, radioisotopic, electrophysiological and pharmacological investigations indicate that the marked vasorelaxant properties of the 3-alkylaminobenzothiadiazine 1,1-dioxides are related to the activation of smooth muscle K(ATP) channels.

Synthesis and activity on rat aorta rings and rat pancreatic beta-cells of ring-opened analogues of benzopyran-type potassium channel activators.

Ring-opened analogues of dihydrobenzopyran potassium channel openers (PCOs) were prepared and evaluated as putative PCOs on rat aorta rings (myorelaxant effect) and rat pancreatic beta-cells (inhibition of insulin secretion). These derivatives are characterized by the presence of a sulfonylurea, a urea or an amide function. Some compounds bearing an arylurea moiety provoked vasorelaxant effects and a marked inhibition of insulin release. Derivatives bearing a sulfonylurea or an amide function were, however, poorly active on both tissues. Structure-activity relationships and apparent tissue selectivity are discussed.

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.

Characterization and potential roles of calretinin in rodent spermatozoa.

Calretinin has been detected in various excitable cells but the presence and putative roles of such a calcium-binding protein has never been characterized in sperm. Epididymal spermatozoa were collected from C57Bl6 (wild-type, WT) or calretinin knockout (CR-/-) mice and Wistar rats. A specific staining for calretinin was detected by immunofluorescence in the principal piece of the flagellum, both in WT mouse and rat spermatozoa. Western blots confirmed the expression of calretinin in rat and WT spermatozoa as well as its absence in CR-/- mice. No significant difference was observed in the spontaneous acrosome reaction between WT and CR-/- sperm. The addition of the calcium-ionophore A-23187, Thapsigargin or Progesterone to WT or CR-/- incubated spermatozoa induced increases in the acrosome reaction but the stimulatory effects were identical in both genotypes. Motility measurements assessed by computer-assisted sperm analysis indicated that, under basal non-stimulatory conditions, CR-/- sperm exhibited a lower curvilinear velocity and a smaller lateral head movement amplitude, although no difference was observed for the beat cross frequency. After incubation with 25 mM NH4Cl, the curvilinear velocity, the amplitude of the lateral head movement and the hyperactivation were increased, while the beat cross frequency was decreased, in both genotypes. Evaluation of the in vivo fertility potential indicated that the CR-/- litter sizes were clearly reduced compared to the WT litter sizes. Our study describes, for the first time, the expression of calretinin in sperm. These data extend the potential implication of calcium-binding proteins in the sperm calcium-signaling cascade and bring new insights into the understanding of sperm physiology.

Deciphering Structure-Activity Relationships in a Series of 2,2-Dimethylchromans Acting as Inhibitors of Insulin Release and Smooth Muscle Relaxants.

4,6-Disubstituted 2,2-dimethylchromans are reported as pharmacologically active compounds that mainly target the ATP-sensitive potassium channels. The present study is an attempt to characterize the impact of the nature of substituents introduced at the 4- and 6-positions of 2,2-dimethylchromans on their capacities to inhibit insulin release from pancreatic ß-cells or to relax vascular smooth muscle cells, both biological responses that are supposed to reflect interaction with specific ion channels. From the core structure 4-amino-2,2-dimethylchroman, a progressive increase in the steric hindrance of the chemical functionalities introduced at the 4-position (amino, formamido, acetamido, arylureido/thioureido) and at the 6-position (amino, formamido, acetamido, alkoxycarbonylamino) led to a progressive magnification of the inhibitory effect on the insulin release process and, to a lesser extent, of the vasorelaxant activity. Moreover, the dextrorotatory enantiomer of 2,2-dimethylchroman compound 29 was more potent than its levorotatory counterpart for inhibiting the insulin secretory process. Additional pharmacological investigations suggested, however, that the myorelaxant activity of 11 and 15 resulted from a direct Ca2+ entry blockade.

Three-dimensional quantitative structure-activity relationships of ATP-sensitive potassium (KATP) channel openers belonging to the 3-alkylamino-4H-1,2,4-benzo- and 3-alkylamino-4H-1,2,4-pyridothiadiazine 1,1-dioxide families.

Recent studies have demonstrated that selective activation of pancreatic ATP-sensitive potassium (KATP) channels could be of clinical value in the treatment of type I and type II diabetes, obesity, and hypersinsulinemia. Taking into account these promising therapeutic opportunities, we have explored the 3-alkylamino-4H-1,2,4-pyrido- and 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide families. Among these series, numerous drugs were identified as highly potent and selective openers of either the pancreatic or the aortic KATP channels. Thanks to comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA), quantitative structure-activity relationship approaches using more than 100 compounds, pharmacophoric models explaining the activity and selectivity of the drugs have been elaborated. These models highlighted the importance of several chemical regions for KATP channel activation and could be very helpful for future improvement of drug potency, selectivity, or both. Moreover, an original CoMSIA analysis, using a selectivity index (SI) as a dependent variable, was also performed with the aim of identifying the structural parameters influencing tissue selectivity.

Design, synthesis, and pharmacological evaluation of R/S-3,4-dihydro-2,2-dimethyl- 6-halo-4-(phenylaminocarbonylamino)-2H-1-benzopyrans: toward tissue-selective pancreatic beta-cell KATP channel openers structurally related to (+/-)-cromakalim.

In the search of a novel series of benzopyrans structurally related to (+/-)-cromakalim and acting as pancreatic beta-cell potassium channel openers, several R/S-3,4-dihydro-2,2-dimethyl-6-halo-4-(phenylaminocarbonylamino)-2H-1-benzopyrans with or without a substituent on the phenyl ring in the 4-position were synthesized. Their activity on rat-insulin-secreting cells and rat aorta rings was compared to that of the K(ATP) channel activators (+/-)-cromakalim, diazoxide, (+/-)-pinacidil, and compound 4. Structure-activity relationships indicated that the most pronounced inhibitory activity on the pancreatic tissue was obtained by introducing a meta- or para-electron-withdrawing group (a chlorine atom) on the C-4 phenyl ring (drugs 37-42). Such molecules, unlike the parent compound (+/-)-cromakalim, also exhibited a high selectivity for the pancreatic tissue versus the vascular tissue. Radioisotopic and electrophysiological investigations performed with R/S-6-chloro-4-(3-chlorophenylaminocarbonylamino)-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran (38) confirmed that the drug activated pancreatic KATP channels.

4-Phenylureido/thioureido-substituted 2,2-dimethylchroman analogs of cromakalim bearing a bulky 'carbamate' moiety at the 6-position as potent inhibitors of glucose-sensitive insulin secretion.

The synthesis of 2,2-dimethylchromans bearing a 3/4-chloro/cyano-substituted phenylureido or phenylthioureido moiety at the 4-position and an alkoxycarbonylamino ('carbamate') group at the 6-position is described. These new analogs of the potassium channel opener (±)-cromakalim were further tested on rat pancreatic islets as putative inhibitors of insulin release and on rat aorta rings as putative vasorelaxants. All compounds inhibited insulin secretion and induced a myorelaxant activity. Compound 14o [R/S-N-3-cyanophenyl-N'-(6-tert-butoxycarbonylamino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)urea; BPDZ 711] emerged as the most potent inhibitor of the glucose-sensitive insulin releasing process (IC50 = 0.24 µM) and displayed selectivity towards the pancreatic endocrine tissue. Radioisotopic, fluorimetric and pharmacological investigations were performed on rat pancreatic islet and rat vascular smooth muscle cells in order to decipher its mechanism of action. Our findings suggest that the mechanism of action of 14o is rather unspecific. The compound behaves as a KATP channel opener, a Ca(2+) entry blocker, and promotes an intracellular calcium translocation.

Synthesis, characterization and biological evaluation of benzothiazoles and tetrahydrobenzothiazoles bearing urea or thiourea moieties as vasorelaxants and inhibitors of the insulin releasing process.

A series of 1,3-benzothiazoles (series I) and 4,5,6,7-tetrahydro-1,3-benzothiazoles (series II) bearing an urea or a thiourea moiety at the 2-position were synthesized and tested as myorelaxants and inhibitors of insulin secretion. Several compounds (i.e. 13u and 13v) from series I showed a marked myorelaxant activity. Benzothiazoles bearing a strong electron withdrawing group (NO2, CN) at the 6-position and an alkyl group linked to the urea or the thiourea function at the 2-position were found to be the most potent compounds. The weak vasorelaxant activity of series II compounds evidenced the necessity of the presence of a complete aromatic heterocyclic system. The myorelaxant activity of some active compounds was reduced when measured on aorta rings precontracted by 80 mM KCl or by 30 mM KCl in the presence of 10 µM glibenclamide, suggesting the involvement of KATP channels in the vasorelaxant effect. Some compounds of series I tested on rat pancreatic islets provoked a marked inhibition of insulin secretion, among which 13a exhibited a clear tissue selectivity for pancreatic ß-cells.

The novel diazoxide analog 3-isopropylamino-7-methoxy-4H-1,2,4-benzothiadiazine 1,1-dioxide is a selective Kir6.2/SUR1 channel opener.

ATP-sensitive K(+) (K(ATP)) channels are activated by a diverse group of compounds known as potassium channel openers (PCOs). Here, we report functional studies of the Kir6.2/SUR1 Selective PCO 3-isopropylamino-7-methoxy-4H-1,2,4-benzothiadiazine 1,1-dioxide (NNC 55-9216). We recorded cloned K(ATP) channel currents from inside-out patches excised from Xenopus laevis oocytes heterologously expressing Kir6.2/SUR1, Kir6.2/SUR2A, or Kir6.2/SUR2B, corresponding to the beta-cell, cardiac, and smooth muscle types of the K(ATP) channel. NNC 55-9216 reversibly activated Kir6.2/SUR1 currents (EC(50) = 16 micromol/l). This activation was dependent on intracellular MgATP and was abolished by mutation of a single residue in the Walker A motifs of either nucleotide-binding domain of SUR1. The drug had no effect on Kir6.2/SUR2A or Kir6.2/SUR2B currents. We therefore used chimeras of SUR1 and SUR2A to identify regions of SUR1 involved in the response to NNC 55-9216. Activation was completely abolished and significantly reduced by swapping transmembrane domains 8-11. The reverse chimera consisting of SUR2A with transmembrane domains 8-11 and NBD2 consisting SUR1 was activated by NNC 55-9216, indicating that these SUR1 regions are important for drug activation. [(3)H]glibenclamide binding to membranes from HEK293 cells transfected with SUR1 was displaced by NNC 55-9216 (IC(50) = 105 micromol/l), and this effect was impaired when NBD2 of SUR1 was replaced by that of SUR2A. These results suggest NNC 55-9216 is a SUR1-selective PCO that requires structural determinants, which differ from those needed for activation of the K(ATP) channel by pinacidil and cromakalim. The high selectivity of NNC 55-9216 may prove to be useful for studies of the molecular mechanism of PCO action.

4,6-Disubstituted 2,2-dimethylchromans structurally related to the K(ATP) channel opener cromakalim: design, synthesis, and effect on insulin release and vascular tone.

Five series (ureas, thioureas, carbamates, sulfonylureas, and amides) of 4,6-disubstituted-2,2-dimethylchromans structurally related to cromakalim were prepared and evaluated, as putative ATP-sensitive potassium channel activators, on rat pancreatic islets and rat aorta rings. The biological data indicate that most compounds were, like the reference molecule cromakalim, more active on the vascular smooth muscle tissue (myorelaxant effect on 30 mM KCl induced contractions of rat aorta rings) than on the pancreatic tissue (inhibition of 16.7 mM glucose induced insulin release from rat pancreatic islets). However, some drugs (8h, 8i, 9f, 9g, 9h, and 9i) markedly inhibited insulin release and exhibited an activity equivalent or greater than that of diazoxide. Compounds 9h and 9i were also found to be more active on pancreatic beta-cells than on vascular smooth muscle cells. Last, the amide 6b was selected in order to examine its mechanism of action on vascular smooth muscle cells. Pharmacological results suggest that the compound acted as a K(ATP) channel opener. In conclusion, the present data indicate that appropriate structural modifications can generate dimethylchromans with pharmacological profiles different from that of cromakalim.

3-Alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides as ATP-sensitive potassium channel openers: effect of 6,7-disubstitution on potency and tissue selectivity.

A series of 6,7-disubstituted 4H-1,2,4-benzothiadiazine 1,1-dioxides bearing a short alkylamino side chain in the 3-position were synthesized. These compounds were tested on rat pancreatic islets and on rat aorta rings. In vitro data indicated that in most cases substitution in the 6 and the 7 positions increased their activity as inhibitors of insulin secretion, while the myorelaxant potency of the drugs was maintained or enhanced according to the nature of the substituent in the 7-position. The presence of either chlorine or bromine atoms in the 6 and 7 positions did not improve the apparent selectivity of the drugs for the pancreatic tissue. By contrast, the introduction of one or two fluorine atoms, as well as the presence of a methoxy group in the 7-position, generated potent and selective inhibitors of insulin release. Radioisotopic and fluorimetric experiments performed with the most potent compound inhibiting insulin release (34, BPDZ 259, 6-chloro-7-fluoro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide) confirmed that the drug activated K(ATP) channels. 34 was found to be one of the most potent and selective pancreatic potassium channel openers yet described.

Effect on K(ATP) channel activation properties and tissue selectivity of the nature of the substituent in the 7- and the 3-position of 4H-1,2,4-benzothiadiazine 1,1-dioxides.

The present work explored 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides diversely substituted in the 7-position. Those compounds, structurally related to previously described potassium channel openers such as the benzothiadiazine dioxide BPDZ 73, were tested as putative K(ATP) channel activators on the pancreatic endocrine tissue and on the vascular smooth muscle tissue. The nature of the substituent introduced in the 7-position as well as the nature of the alkylamino side chain in the 3-position strongly affected both potency and tissue selectivity of 4H-1,2,4-benzothiadiazine 1,1-dioxides. Thus, compounds bearing in the 7-position a methyl or a methoxy group or devoid of a substituent in this position, and bearing an ethyl, an isopropyl, or a cyclobutylamino group in the 3-position were found to be potent and selective inhibitors of insulin release from rat pancreatic B-cells (i.e. 10a, 10b, 12b, 12d, 22c). In contrast, 3-alkylamino-7-trifluoromethyl- (20a-c) and 3-alkylamino-7-pentyl-4H-1,2,4-benzothiadiazine 1,1-dioxides (11a,b) expressed a marked myorelaxant activity on rat aorta ring. Among the latter compounds, the 3-alkylamino-7-pentyl derivative (11a) showed a clear selectivity for the vascular smooth muscle tissue. The present work gives new insights into the role of the substituent in both the 7- and the 3-position for the design of 4H-1,2,4-benzothiadiazine 1,1-dioxide potassium channel openers exhibiting different tissue selectivity profiles.