Synthesis and structure-activity relationships in a series of ethenesulfonamide derivatives, a novel class of endothelin receptor antagonists

In the previous paper, we described a series of the 2-arylethenesulfonamide derivatives, a novel class of ETA-selective endothelin (ET) receptor antagonists, including the compounds 1a, b. Compound 1a showed excellent oral antagonistic activities and pharmacokinetic profiles, and the monopotassium salt of 1 (YM-598 monopotassium) is in clinical trials. In this paper, we wish to report the investigation of the further details of structure-activity relationships (SARs) of the 2-phenylethenesulfonamide region in 1a. It was found that methyl substitutions at the 2-, 4- and 6-positions of the phenyl group in 1a led to the discovery of the ET(A)/ET(B) mixed antagonist (6s) with an IC50 of 2.2 nM for the ET(A) receptor. We also found that introduction of an ethyl group to the 1-position of the ethenyl group in 1a gave the ET(A) selective antagonist (6u) with an oral endothelin antagonistic activity in rats.

Ethenesulfonamide and ethanesulfonamide derivatives, a novel class of orally active endothelin-A receptor antagonists

In the previous paper, we described a series of 2-phenylethenesulfonamide derivatives, a novel class of ET(A)-selective endothelin (ET) receptor antagonists, including the 2-methoxyethoxy derivative 2a and the 2-fluoroethoxy derivative (2b). In this paper, we wish to report further details of structure-activity relationships (SARs) of the two regions of the molecule in compound 2b, which were the alkoxy region at the 6-position of the core pyrimidine ring and the 2-phenylethenesulfonamide region. In these modifications, replacement of the 2-fluoroethoxy group with a methoxy group (6e) and replacement of the 2-phenylethenesulfonamide group with a 2-(pyridin-3-yl)ethenesulfonamide group (6l) or 2-phenylethanesulfonamide group (6q) were well tolerated both in the ET(A) binding affinity and ET(A) selectivity. Among them, compound 6e showed further improvement in oral activity compared to 2b. After oral administration, compound 6e inhibited the big ET-1 induced pressor response in conscious rats at 0.3mg /kg with a duration of >6.5h. Compound 6e also exhibited a potent antagonistic activity in the pithed rats.

Comparison of the angiotensin II type 1-receptor antagonist YM358 and the angiotensin-converting enzyme inhibitor enalapril in rats with cardiac volume overload

We evaluated the effects of chronic oral administration of an angiotensin II type 1 (AT1)-receptor antagonist YM358 and an angiotensin converting enzyme inhibitor enalapril on hemodynamics and cardiac hypertrophy in rats with volume overload-induced heart failure. We assessed changes of cardiac hemodynamics and cardiac hypertrophy at 2 and 4 weeks after administration of YM358 (3, 30 mg/kg per day) or enalapril (30 mg/kg per day) in abdominal aortocaval shunt rats. YM358 (30 mg/kg) attenuated increases of left ventricle (LV)/body weight (BW), left atrium (LA)/BW, right ventricle (RV)/BW and heart/BW ratios, but did not affect cardiac hemodynamics in shunt rats. Enalapril also reduced the increased LV/BW and heart/BW ratios together with significant reductions of systolic blood pressure, left ventricular systolic pressure and the first derivative of left ventricular pressure. These data suggest that the effects on attenuation of the development of cardiac hypertrophy are not different for YM358 and enalapril, although the effects on cardiac hemodynamics are different for the same dosages. The attenuating action of YM358 on cardiac hypertrophy was independent of the action on hemodynamics and indicated the direct action of the AT1 receptor on the heart.

Ethenesulfonamide derivatives, a novel class of orally active endothelin-A receptor antagonists

In the present article we wish to report the discovery of a novel class of ET(A)-selective endothelin (ET) receptor antagonists through the modification of the ET(A)/ET(B) non-selective antagonist, Ro47-0203 (Bosentan, 1). Replacement of the benzenesulfonamide group of 1 with a 2-phenylethenesulfonamide group gave compound 5a and resulted in improvement in ET(A)-selectivity. Optimization of the alkoxy side chain attached to the core pyrimidine ring yielded the 2-fluoroethoxy derivative (5n) with further improvement of ET(A)-selectivity. [IC50=2.1 nM for ET(A) receptor, ET(B)/ET(A) ratio=1200]. After oral administration, compound 5n inhibited the big ET-1 induced pressor response in pithed rats with a DR2 value of 2.6 mg/kg and also exhibited a potent antagonistic activity in conscious rats.

Novel potassium channel activators. III. Synthesis and pharmacological evaluation of 3,4-dihydro-2H-1,4-benzoxazine derivatives: modification at the 2 position

A new series of 3,4-dihydro-2H-1,4-benzoxazine derivatives, where various substituents were introduced into one of the geminal dimethyl groups at the 2 position, were synthesized and their potassium channel-activating activity was evaluated. Introduction of a hydroxyl group, as in compound 5, resulted in good solubility in water and a long duration of action compared with the parent compound 1. Introduction of a nitrato group, as in compound 8, produced typical nitrate activity such as exhibited by nitroglycerine in addition to potassium channel-activating activity. X-ray structural analysis of compound 5 showed that the sum of the bond angles around the N atom at the 4 position was 357.8 degrees, suggesting that the N atom had an approximately sp2-like planar bond configuration.

Effects of YM358, an angiotensin II type 1 (AT1) receptor antagonist, and enalapril on blood pressure and vasoconstriction in two renal hypertension models

The effects of the angiotensin II type 1 receptor antagonist YM358 on blood pressure were compared to those of the angiotensin converting enzyme inhibitor enalapril in one-kidney, one-clip renal hypertensive rats (1K1C RHR), two-kidney, one-clip renal hypertensive rats (2K1C RHR) and normotensive rats (NTR). Additionally, the local drug actions in peripheral tissues were investigated using isolated mesenteric arteries from these rats. In 2K1C RHR, YM358 and enalapril produced a long-lasting hypotensive effect in a dose-dependent manner. In 1K1C RHR, YM358 (30 mg/kg) also produced an antihypertensive effect, whereas enalapril (30 mg/kg) had no effect. Administration of YM358, but not enalapril, to 1K1C RHR, 2K1C RHR and NTR did not affect heart rate. In isolated mesenteric arteries from 1K1C RHR and 2K1C RHR, angiotensin II (Ang II), angiotensin I (Ang I) and tetradecapeptide (TDP), a physiologically active renin substrate, produced concentration-dependent vasoconstriction. YM358 (10(-7) M) inhibited the vasoconstricting responses to Ang II, Ang I and TDP in isolated mesenteric arteries. In contrast, enalaprilat (10(-7) M), an active metabolite of enalapril, did not completely inhibit the response to Ang I and TDP. These results indicate that YM358 has higher efficacy than enalapril for the treatment of hypertension.

Novel potassium channel openers. Part 4: transformation of the 1,4-benzoxazine skeleton into 1,4-benzothiazine, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroquinoxaline, indoline, and 1,5-benzoxazepine

As part of a search for a new potassium channel opener, the 1,4-benzoxazine skeleton derived from the benzopyran skeleton of cromakalim, was transformed into other fused rings such as 1,4-benzothiazine, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroquinoxaline, indoline, and 1,5-benzoxazepine. The 1,4-benzothiazine derivative displayed approximately 20 times more potent vasorelaxant activity than cromakalim.

Novel potassium channel activators. II. Synthesis and pharmacological evaluation of 3,4-dihydro-2H-1,4-benzoxazine derivatives: modification of the aromatic part

Three new series of analogues related to 3,4-dihydro-2H-1,4-benzoxazine derivative 1a were synthesized and evaluated for their potassium channel activating activity. In the first series I, where the 6,7-positions were disubstituted, it was found that an electron-withdrawing substituent was preferable at the 6 position, but either an electron-withdrawing or releasing substituent without bulkiness was tolerated at the 7 position. In the second series II, where several heterocycles were introduced into the 6,7-positions, the oxadiazole derivative 6 showed more potent activity than cromakalim. In the third series III, where the benzene ring was replaced by a pyridine ring, borane complex 16 had equivalent activity to cromakalim. Especially, compound 6 showed a potent hypotensive effect with a long duration of action in the spontaneous hypertensive rat and had a lesser increasing effect on intracranial pressure in dogs than 1a and levcromakalim, showing a good profile as an antihypertensive agent.

Studies on nonpeptide angiotensin II receptor antagonists. IV. Synthesis and biological evaluation of 4-acrylamide-1H-imidazole derivatives

A novel series of nonpeptide angiotensin II antagonists containing the acrylamide group at the 4-position of the imidazole ring was synthesized and their antagonistic activity was examined by functional assay in rabbit aorta. The acrylamide group was selected as a large lipophilic surrogate for the chloro group of EXP3174. A structure-activity relationship study of the acrylamide moiety has shown that substitution at the 4-position with the N-methyl-3,3-dimethylacrylamide group resulted in the optimal compound, 2-butyl-4-[(3,3-dimethylacryloyl)methyl-amino]-1-[[2'-(1H-tetra zol-5- yl)biphenyl-4-yl]methyl]-1H-imidazole-5-carboxylic acid (1), which was superior to EXP3174 in vitro. Since 1 showed only poor activity against angiotensin II-induced pressor response in rats after oral administration, the carboxylic acid function of 1 was converted into prodrug esters (13). Among these, the 1-[(ethoxycarbonyl)oxy]ethyl ester (13a) showed the most potent and longest-lasting activity when given orally to rats. When administered orally to conscious furosemide-treated dogs, 13a showed an approximately 3-fold increased hypotensive activity in comparison with DuP 753. These data suggest that 13a may be an useful agent for the treatment of angiotensin II-dependent diseases, such as hypertension.

Studies on nonpeptide angiotensin II receptor antagonists. III. Synthesis and biological evaluation of 5-alkylidene-3,5-dihydro-4H-imidazol-4-one derivatives

5-Alkylidene-3,5-dihydro-4H-imidazol-4-one derivatives were synthesized and evaluated for activity as angiotensin II receptor antagonists. Substitutions at C-2 and C-5, respectively, with a propyl group and a 1-methylethylidene group resulted in the optimal compound, 3,5-dihydro-5-(1-methylethylidene)-2-propyl-3-[[2'-(1H-tetrazol - 5-yl)biphenyl-4-yl]methyl]-4H-imidazol-4-one (2b), with a pA2 value of 8.85 in rabbit aorta. When administered orally to rats, 2b showed a greater inhibitory effect on angiotensin II-induced pressor response than DuP 753. Compound 2b also showed a good antihypertensive effect when administered orally to conscious sodium-depleted spontaneously hypertensive rats, with a duration of action of 24 h. These data suggest that 2b may be a useful agent for the treatment of angiotensin II-dependent diseases such as hypertension.

Enhancement of tissue-type plasminogen activator-induced thrombolysis and prevention of reocclusion by combination with a humanized anti-glycoprotein IIb/IIIa monoclonal antibody, YM337, in a rhesus monkey model of coronary thrombosis

We examined the effect of a humanized anti-glycoprotein IIb/IIIa monoclonal antibody, YM337, on thrombolysis with tissue-type plasminogen activator in a copper coil-induced coronary thrombosis model in rhesus monkeys. Fifty minutes after the formation of an occlusive thrombus, a test drug was administered by either i.v. bolus injection followed by continuous infusion (YM337, 0.25 mg/kg + 1.5 microg/kg/min) or i.v. bolus injection (aspirin, 17 mg/kg). Sixty minutes after induction of the occlusive thrombus, thrombolysis was initiated with tPA at a total dose of 0.5 mg/kg intravenously administered over 60 min, with 10% given as an initial bolus. The median time to reperfusion was significantly shortened by YM337 [saline, 60 min (n = 5); aspirin, 45 min (n = 5); YM337, 30 min (n = 5)]. The incidence of reocclusion was significantly decreased by YM337 (saline, 4/4; aspirin, 5/5; YM337, 1/5), and the median time to reocclusion was significantly prolonged by YM337 [saline, 30 min (n = 4); aspirin, 30 min (n = 5); YM337, 180 min (n = 5)]. YM337 significantly reduced the thrombus protein content at the end of experiment. ADP-induced platelet aggregation was completely inhibited by YM337. These results suggest that YM337 may be of clinical value as an adjunctive agent in thrombolytic therapy for patients with acute myocardial infarction.

Studies on nonpeptide angiotensin II receptor antagonists. II. Synthesis and biological evaluation of 5H-pyrazolo[1,5-b][1,2,4]triazole derivatives with a C-linked oxygen functional group at the 6-position

2,7-Diethyl-5H-pyrazolo[1,5-b][1,2,4]triazole derivatives were synthesized and evaluated for activity as angiotensin II receptor antagonists. Replacement of the C-6 hydrogen with C-linked oxygen functional groups led to derivatives with increased in vitro activities. Among these compounds, 2,7-diethyl-5-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H- pyrazolo[1,5-b][1,2,4]triazole-6-carboxylic acid (2d) showed potent, insurmountable antagonism, but had poor oral potency against angiotensin II-induced pressor response in rats. In order to improve the oral activity, the carboxylic acid function of 2d was converted into a double ester. This modification afforded (+/-)-1-[(ethoxycarbonyl)oxy]ethyl 2,7-diethyl-5-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H- pyrazolo[1,5-b][1,2,4]-triazole-6-carboxylate (2f), which was orally active in rats, and produced a dose-dependent decrease in blood pressure when administered orally to conscious furosemide-treated dogs, with ca. 3-fold increased potency in comparison with the parent C-6 hydrogen compound.

Synthesis and biological evaluation of phenylacetyl derivatives having low central nervous system permeability as potent and selective M2 muscarinic receptor antagonists

A series of phenylacetyl derivatives containing the 5,10-dihydro-11H-dibenzo[b,e,][1,4]diazepin-11-one or 5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one skeleton was prepared and evaluated for their binding affinities to muscarinic receptors in vitro and for antagonism of bradycardia, salivation and tremor in vivo. Among them, compounds 56 and 66 had high affinity for M2 muscarinic receptors in the heart (pKi = 8.7 and 8.9, respectively) with low affinity for M3 muscarinic receptors in the submandibular gland. A structure-activity relationship (SAR) study suggested that the high M2 selectivity over the M3 muscarinic receptors of 56 may be attributed to the direction of the carboxamide carbonyl group. In in vivo studies, 56 and 66 antagonized oxotremorine-induced bradycardia in rats on both intravenous and oral administration, and their heart rate increasing effect in dogs with nocturnal bradycardia was about 3-fold greater than that of AF-DX 116. Furthermore, they had almost no influence on oxotremorine-induced tremor in mice, presenting no evidence of central transfer.

Nonpeptide arginine vasopressin antagonists for both V1A and V2 receptors: synthesis and pharmacological properties of 2-phenyl-4'-[(2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl)carbonyl]benzanil ide derivatives

A series of compounds structurally related to 4'-[(2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl)carbonyl]benzanili de was synthesized and demonstrated to have arginine vasopressin (AVP) antagonist activity for both V1A and V2 receptors. The introduction of a phenyl or a 4-substituted phenyl group into the ortho position of the benzoyl moiety resulted in an increase in both binding affinity and antagonistic activity. The 2-(4-methylphenyl) derivative (1g) exhibited high antagonistic activities for both V1A (8.6-fold) and V2 (38-fold) receptors and high oral activity (8.6-fold) compared with the 2-methyl lead compound (1a). Detail of the synthesis and the pharmacological properties of this series are presented.

Antihypertensive activity of a nonpeptide angiotensin II receptor antagonist, YM358, in rats and dogs

The antihypertensive activity of YM358, 2,7-diethyl-5-[[2'-(1 H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H-pyrazolo[1,5-b][1,2,4]tri azole potassium salt monohydrate, a new nonpeptide angiotensin II receptor antagonist, was characterized in rats and dogs. In conscious rats, YM358 after a single oral administration (1-30 mg/kg) lowered blood pressure. The rank order of hypotensive potency of YM358 in conscious rats was 2-kidney, 1-clip renal hypertensive rats > spontaneously hypertensive rats > normotensive rats on the basis of maximum hypotension. YM358 also caused decreases in blood pressure in 2-kidney, 1-clip renal hypertensive dogs and furosemide-treated dogs. Repeated administration of YM358 to 2-kidney, 1-clip renal hypertensive rats for 28 days produced a stable and long-lasting antihypertensive effect without influencing circadian blood pressure and heart rate rhythms. No reflex tachycardia was observed in any animals of either species treated with YM358. Therefore, the pharmacological profile of this compound indicates that YM358 has potential as a useful antihypertensive agent.

Pharmacological profile of YM358, a novel nonpeptide angiotensin AT1 receptor antagonist

The pharmacological profile of YM358, 2,7-diethyl-5-[[2'-(1 H-tetrazol-5-yl)biphenyl-4-yl]methyl]-5H-pyrazolo[1,5-b][1,2,4]tri azole potassium salt monohydrate, a novel non-peptide angiotensin AT1 receptor antagonist, was studied in vitro and in vivo. YM358 competed with [125I][Sar1, Ile8]angiotensin II for angiotensin AT1 receptors in rat liver membranes. YM358 displayed competitive kinetics and the pKi value was calculated as 8.79. In contrast, YM358 had little effect on the binding of [125I][Sar1, Ile8]angiotensin II to the angiotensin AT2 receptor in bovine cerebellum. In isolated rabbit aorta, YM358 produced a parallel rightward shift in the concentration-response curve for angiotensin II with a pA2 value of 8.82. YM358 had no effect on the contraction induced by KCl, norepinephrine, serotonin, histamine, prostaglandin F2alpha or endothelin-1 even at 10(-5) M. On the basis of pKi values in the binding assay and pA2 values in the isolated tissues, YM358 was approximately 3-10 times more potent than losartan in antagonizing angiotensin AT1 receptors. In pithed rats, intravenous administration of YM358 inhibited an increase in mean blood pressure induced by intravenous infusion of angiotensin II in a dose-dependent manner. In conscious normotensive rats, YM358 at 3-30 mg/kg p.o. inhibited the angiotensin II-induced pressor response in a dose-dependent manner. YM358 at 30 mg/kg caused maximum and complete inhibition 30 min after dosing, and inhibition lasted more than 24 h. These results demonstrate that YM358 is a potent, AT1-selective and competitive nonpeptide angiotensin receptor antagonist. Moreover, YM358 is both orally active and long-lasting. This pharmacological profile suggests that YM358 would be suitable for the treatment of cardiovascular disorders such as hypertension and chronic heart failure.

Synthesis of novel succinamide derivatives having a 5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one skeleton as potent and selective M2 muscarinic receptor antagonists. II

A series of succinamide derivatives containing the 5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one skeleton (6a-z) was prepared and evaluated for binding affinity to muscarinic receptors in vitro and for antagonism of bradycardia and salivation in vivo in comparison with AF-DX 116 (1a). Structure-activity relationships (SAR) studies in vitro indicated that the 4-(4-alkyl-1-piperazinyl)benzylamino moiety plays a crucial role in enhancing the affinity for M2 muscarinic receptors. Compound 6y, containing a 4-(4-isopropyl-1-piperazinyl)benzylmethylamino moiety, exhibited the highest affinity for M2 muscarinic receptors (pKi = 9.2), being 200 times as potent as 1a, and compound 6u, containing a 4-(4-ethyl-1-piperazinyl)benzylethylamino moiety, showed the highest selectivity for M2 over M3 muscarinic receptors (M3/M2 ratio = 320). Both 6y and 6u antagonized the oxotremorine-induced bradycardia in rats after intravenous or oral administration. Oral evaluation in conscious dogs showed that the efficacy for increasing the heart rate was at least 3-fold greater than that of 1a.

Synthesis of novel succinamide derivatives having the 5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one skeleton as potent and selective M2 muscarinic receptor antagonists. I

A series of 5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one derivatives containing the succinamide skeleton has been synthesized and evaluated for M1, M2 and M3 muscarinic receptor binding affinities (in vitro) and M2 and M3 muscarinic receptor antagonistic activities (in vivo). Some of them showed higher and more selective binding affinities for M(2) muscarinic receptors than that of AF-DX 116. Among them, 11-[3-[N-[2-(N-benzyl-N- methylamino)ethyl]-N-ethylcarbamoyl]propionyl]-5,11-dihydro-6H-pyr ido [2,3-b][1,4]benzodiazepin-6-one (68) was found to be the most potent and selective M2 muscarinic receptor antagonist in vitro. This compound also strongly inhibited the oxotremorine-induced bradycardia after intravenous administration and showed 130-fold selectivity for M2 muscarinic receptors over M3 muscarinic receptors in vivo.

Novel 5-hydroxytryptamine (5-HT3) receptor antagonists. Synthesis and structure-activity relationships of 9-methyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indol-4-one derivatives

Novel 9-methyl-4,9-dihydrothiopyrano[2,3-b]indol-4-one derivatives 2b-e, 3-methylene-9-methyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indol-4-on e derivatives 3b-e and 9-methyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indol-4-one derivatives 4a-e were prepared. The 5-hydroxytryptamine (5-HT3) receptor-antagonistic activities of these compounds were evaluated by using the von Bezold-Jarisch reflex test (B. J. reflex, rats) and the contractile response to 5-HT in the isolated distal colon (guinea pig). The 5-ethyl-4-imidazolyl derivative 4d was found to be 79 times more potent than ondansetron 1 in the B. J. reflex test (ID50 = 0.048 microgram/kg, i.v.), and the 5-methyl-4-imidazolyl derivative 4c was found to be 126 times more potent than 1 in the colonic contraction (IC50 = 0.0062 microM) assay.

Synergistic effect of aurintricarboxylic acid and triflavin in a photochemically induced thrombosis model in rats

We report here the synergistic antithrombotic effect of aurintricarboxylic acid in combination with a snake venom-derived disintegrin, triflavin, in a photochemically induced thrombosis model in rats. The time to initiation of thrombus was prolonged by i.v. bolus injection of aurintricarboxylic acid at 10 mg/kg. In contrast, time to occlusion was dose-dependently prolonged by both agents, this prolongation being significant with aurintricarboxylic acid at 10 mg/kg i.v. and with triflavin at more than 3 mg/kg i.v. Interestingly, the combination of aurintricarboxylic acid at 3 mg/kg i.v. and triflavin at 1 mg/kg i.v. prolonged not only the initiation of thrombus, but also the time to occlusion.

Novel 5-hydroxytryptamine (5-HT3) receptor antagonists. III. Pharmacological evaluations and molecular modeling studies of optically active 4,5,6,7-tetrahydro-1H-benzimidazole derivatives

The R- and S-enantiomers of the 4,5,6,7-tetrahydro-1H-benzimidazole derivatives 3-8 were prepared by optical resolution. Each R-isomer, except for 3, was almost two orders of magnitude more potent than its S-isomer as a 5-hydroxytrptamine (5-HT3) receptor antagonist, as judged from they effect on the von Bezold-Jarisch reflex (B. J. reflex) in rats, the contraction of isolated guinea-pig colon and the receptor-binding affinity. The (--)-(R)-5-[(1-methyl-1H-indol-3-yl)carbonyl] derivative 6R.HCl (ramosetron = YM060) and (--)-(R)-5-[(1-indolinyl)carbonyl] derivative 4R.HCl (YM114 = KAE-393) given p.o. were hundreds of times more potent than 1 (ondansetron) and 2 (granisetron) in their inhibitory effects on cisplatin-induced emesis in ferrets and restraint stress-induced increases in fecal pellet output in rats. Three-dimensional molecular modeling studies suggested that the 'chiral selection' of the enantiomers might be influenced by the steric repulsion between the aromatic ring part and the conformationally restricted 4,5,6,7-tetrahydro-1H-benzimidazole ring in "equatorial-twist" conformation. In our pharmacophore model for the 5-HT3 receptor antagonist, a basic center exists at the left side of the aromatic-carbonyl plane when viewing from the aromatic part with the carbonyl oxygen atom upwards, whereas the "handedness" is ambiguous in the previously proposed model.

Novel 5-hydroxytryptamine (5-HT3) receptor antagonists. I. Synthesis and structure-activity relationships of conformationally restricted fused imidazole derivatives

We prepared a novel series of conformationally restricted fused imidazole derivatives 4b, 4c and 4d (possessing 4,5,6,7-tetrahydroimidazo[4,5-c] pyridine and substituted 4,5,6,7-tetrahydro-1H-benzimidazole for 4b, 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine for 4c and 5,6,7,8-tetrahydroimidazo[1,5-a]pyridine for 4d as a basic amine part and (2-methoxyphenyl)aminocarbonyl group as an aromatic-carbonyl part). Their activities were then evaluated as an 5-hydroxytryptamine (5-HT3) receptor antagonist which may be useful for the treatment of irritable bowel syndrome (IBS) as well as for nausea and vomiting associated with cancer chemotherapy. The most potent compound was N-(2-methoxyphenyl)-4,5,6, 7-tetrahydro-1H-benzimidazole-5-carboxamide 14 in this series with an ID50 value of 0.32 microgram/kg on the von Bezold-Jarisch reflex in rats and an IC50 value of 0.43 microM on the isolated colonic contraction in guinea pig, approximately ten and two times more potent than ondansetron 1, respectively. The structure activity relationships (SAR) study suggested that the high potency of 14 may be attributed to the suitable position and direction of the N-C-N centroid in the conformationally restricted imidazole ring against the planar (2-methoxyphenyl)aminocarbonyl part in the binding of 14 to the receptor.

Novel 5-hydroxytryptamine (5-HT3) receptor antagonists. II. Synthesis and structure-activity relationships of 4,5,6,7-tetrahydro-1H-benzimidazole derivatives

A novel series of 4,5,6,7-tetrahydro-1H-benzimidazole derivatives 4,5,6 and 7 was prepared and evaluated for activities as 5-hydroxytryptamine (5-HT3) receptor antagonists which may be useful for the treatment of irritable bowel syndrome (IBS) as well as nausea and vomiting associated with cancer chemotherapy. These compounds were designed by modifying the aromatic-carbonyl part of N-(2-methoxyphenyl)-4,5,6,7-tetrahydro-1H-5-benzimidazolylcarboxamide 3, leaving the imidazole moiety unchanged as the amine part. The indole derivatives 7d, g, h and indolizine derivatives 7k, l were found to be highly potent on the von Bezold-Jarisch (B.J.) reflex test with ID50 values of below 0.1 microgram/kg, and the indoline derivative 6c, indole derivatives 7a, d, g, benzofurane derivative 7j and indolizine derivative 7k were observed to be very potent on the colonic contraction with IC50 values of below 0.1 microM. In particular, 7l was the most potent on the B.J. reflex (ID50 = 0.018 microgram/kg), approximately 200 and 50 times more potent than ondansetron 1 and granisetron 2, and 7k was the most potent on the colonic contraction (IC50 = 0.011 microM), approximately 70 and 6 times more potent than 1 and 2, respectively.

Biochemical characterization of a new disintegrin, flavostatin, isolated from Trimeresurus flavoviridis venom

We biochemically characterized a new disintegrin, flavostatin, isolated from Trimeresurus flavoviridis venom. Flavostatin inhibited ADP-, collagen-, and thrombin receptor agonist peptide-induced platelet aggregation in human platelet-rich plasma (IC50 range: 59 to 111 nM) and blocked the binding of biotinylated human fibrinogen to purified GPIIb/IIIa with an inhibitory potency 31,000-fold higher than that of Arg-Gly-Asp-Ser (RGDS). Flavostatin strongly inhibited high-shear-stress-induced platelet aggregation in platelet-rich plasma (PRP) with an IC50 value of 188 nM. Fluorescein isothiocyanate (FITC)-conjugated flavostatin saturably bound to unstimulated and ADP-stimulated washed platelets with high affinity (Kd values: 38 and 21 nM, respectively); the corresponding number of binding sites was 86460 and 79192 per platelet. In competition experiments with several glycoprotein IIb/IIIa antagonists, the binding of FITC-conjugated flavostatin to platelets was completely inhibited by ReoPro, triflavin, TP9201, MK383 and GR144053, but not by YM207, YM337 and B6A3.

Novel potassium channel activators: synthesis and structure-activity relationship studies of 3,4-dihydro-2H-1,4-benzoxazine derivatives

Strong potassium channel-activating effects were found among a series of novel 4-substituted 3,4-dihydro-2H-1,4-benzoxazine derivatives. The key step in preparation was the nucleophilic substitution of 3,4-dihydro-2H-1,4-benzoxazine (3) with activated halogenopyridines, such as halogenopyridine N-oxides (15a--c) and the borane adduct (15d) of 4-bromopyridine. Structure-activity relationship studies identified 2-(3,4-dihydro-2,2-dimethyl-6-nitro-2H-1,4-benzoxazin-4-yl)pyridin e-1-oxide (16a: YM934) as the optimal compound. This compound (16a) showed a more potent oral antihypertensive effect than cromakalim in conscious spontaneously hypertensive rats.

Purification of a chitooligosaccharidolytic beta-N-acetylglucosaminidase from Bombyx mori larvae during metamorphosis and the nucleotide sequence of its cDNA

Three beta-N-acetylglucosaminidase (catalyzing hydrolysis of p-nitrophenyl-beta-D-GlcNAc) were purified from the integument tissue of Bombyx mori larvae during metamorphosis into pupae. The largest enzyme (66 kDa by SDS-PAGE, 126 kDa by gel-filtration chromatography) reacted with chitooligosaccharides to produce GlcNAc. A full-length cDNA encoding this chitooligosaccharidolytic beta-GlcNAcase was isolated. Based on the amino acid sequence deduced from the nucleotide sequence, the pre-beta-GlcNAcase was found to consist of 596 amino acid residues including a characteristic signal peptide of 23 residues and have an M(r) of 68,212. Homoloyg search and limited proteolytic digestion showed that the enzyme has a C-terminal 58-kDa catalytic domain very similar to that of human lysosomal beta-hexosaminidase that is responsible for hydrolyzing gangliosides. Two other enzymes (composed of 58-kDa and 48-kDa polypeptides, respectively) did not hydrolyze chitooligosaccharides, and were not proteolytic fragments from the largest enzyme judged by amino acid sequencing analyses. Natural substrates for the beta-GlcNAcases are unknown.

Antisecretory and antiulcer effects of YM020, a new H+,K(+)-ATPase inhibitor, in rats and dogs

We examined the effects of YM020 (3-cyanomethyl-2-methyl-8-[(3-methyl-2-butenyl)oxy]-imidazo[1,2- a]pyridine), a novel H+,K(+)-ATPase inhibitor, on gastric acid secretion and experimental gastroduodenal lesions in rats and dogs. Intraduodenal, subcutaneous and oral YM020 inhibited basal gastric acid secretion in pylorus-ligated rats with ED50 values of 9.1, 9.1 and 9.5 mg/kg, respectively. Oral pretreatment with YM020 5 hr before ligation still suppressed acid secretion, with a potency a little less than that of omeprazole. In anesthetized dogs, intravenous YM020 inhibited histamine-, methacholine- and pentagastrin-induced gastric acid secretion with ED50 values of 0.05, 0.01 and 0.08 mg/kg, respectively. In Heidenhain pouch dogs, although oral YM020 (3 mg/kg) inhibited histamine-induced acid secretion, acid output returned to control levels faster than in dogs treated with omeprazole. Oral YM020 inhibited the formation of water-immersion restraint stress-, indomethacin-, absolute ethanol-, 0.7 N hydrochloric acid- and cysteamine-induced gastric or duodenal lesions with ED50 values of 2.9, 4.3, 2.0, 11.7 and 8.4 mg/kg, respectively. Moreover, subcutaneous YM020 also suppressed the formation of ethanol- and HCl-induced gastric lesions. These results suggest that YM020 has an antisecretory effect almost the same as or 2 to 3 times weaker than those of omeprazole and that its duration is not as long as that of omeprazole in rats and dogs. Furthermore, YM020 possesses a cytoprotective effect and the mechanism of YM020 may be different to that of omeprazole.

Pharmacological properties of YM-26365, a low molecular weight, orally active renin inhibitor

This report describes the pharmacological properties of a novel renin inhibitor (YM-26365: (3R)-3-[3-[(1S)-1-cyclohexylmethyl-2-hydroxy-3- [(1-methyl-5-tetrazolyl)thio]propyl]ureido]-1-methyl-5-phenyl- 2,3-dihydro-1H-1,4-benzodiazepin-2-one) with molecular weight 577 and no peptide bonds. YM-26365 inhibited human plasma renin with an IC50 value of 2.9 x 10(-6) M, but did not affect plasma renin from dogs, rabbits, and rats at 10(-4) M. YM-26365 inhibited not only human renin, but also cathepsin D with an IC50 value of 1.7 x 10(-5) M. This compound competitively inhibited the reaction between recombinant human renin and N-acetyl tetradecapeptide with a Ki value of 1.1 x 10(-6) M. In pithed spontaneously hypertensive rats, YM-26365 at 10 mg/kg i.v. significantly antagonized the pressor response to recombinant human renin, but did not affect responses to angiotensin II, angiotensin I, norepinephrine, or arginine vasopressin. Similarly, oral administration of YM-26365 (10 and 30 mg/kg) to pithed spontaneously hypertensive rats caused a shift to the right of the recombinant human renin dose-pressor response curve. Systemic bioavailability as determined on the basis of the ratio of the total area under the plasma concentration-time curve after 3 mg/kg i.v. and 30 mg/kg orally to rats was 9.6%. These results demonstrate that YM-26365 is a weak but orally absorbed, low molecular weight renin inhibitor.

Potassium channel-opening and vasorelaxant profiles of a novel compound YM099 in rat isolated portal vein and rabbit isolated aorta

The potassium channel-opening and vasorelaxant profiles of YM099, a newly synthesized benzoxadiazol derivative K channel opener, were evaluated in vitro. In the rat isolated portal vein, YM099 and a benzopyran derivative K channel opener levcromakalim concentration-dependently inhibited the frequency of spontaneous rhythmic contractions, with IC50 values of 104 and 38 nM, respectively. In the rabbit isolated aorta, YM099 (10(-7)-3 x 10(-5) M) and levcromakalim (10(-7)-3 x 10(-5) M) also concentration-dependently relaxed the contractions induced by 20 mM KCl, but they were ineffective against the contractions induced by 50 mM KCl. These effects of YM099 and levcromakalim were competitively antagonized by a K channel blocker glibenclamide (10(-7)-3 x 10(-6) M). In the rabbit isolated aorta, YM099 (3 x 10(-8)-3 x 10(-6) M), but not the calcium antagonist nifedipine (10(-8)-3 x 10(-6) M), relaxed the contractions induced by norepinephrine (10(-6) M) or prostaglandin F2 alpha (3 x 10(-6) M). These vasorelaxant effects of YM099 were also antagonized by glibenclamide. In conclusion, YM099 is a potent vascular smooth muscle-relaxant agent and possesses a vasorelaxant effect different from that of nifedipine. These effects of YM099 may be mediated, like those of levcromakalim, by the opening of glibenclamide-sensitive K channels.

The cloning of size-heterogeneous, Y-specific repetitive DNAs and their clinical application

Four Y-specific DNAs of different sizes were isolated by screening a human Y-chromosome gene-library. After determining their structural characteristics, the possibility for their clinical application was examined. The results are as follows: 1. The 4 cloned DNAs had inserts of 3.3, 2.0, 1.9 and 1.4 kb; they were subcloned into plasmid pUC19, and designated pKY-2, pKY-3, pKY-4 and pKY-5, respectively. 2. All four clones hybridized specifically with the Y-specific 3.5 kb DNA but not with female DNA. However, they did not cross-hybridize with the 2.1 kb fragment known to be another Y-specific repetitive DNA of human genomes. 3. The newly cloned probes were applied to the detection of Y-specific DNA in abnormal Y-chromosomes [Turner Syndrome (45, X/46, X, -X, + marker), 46, XY-female, mosaicism (46, XY/47, XYY), 46, XX-male and super male (47, XYY)]. 4. Since the newly cloned DNAs did not hybridize with other eukaryotic genome DNAs such as monkey, rat, mouse, chicken, frog, or fish, their human gene specificities were confirmed.

Structural study of histamine H2-receptor antagonists. Five 3-[2-(diamino-methyleneamino)-4-thiazolylmethylthio]propionamidine and -amide derivatives

(1) N2-Cyano-3-[2-(diaminomethyleneamino)-4- thiazolylmethylthio]propionamidine monohydrate, C9H13N7S2.H2O, Mr = 301.39, P1, a = 11.089 (4), b = 9.130 (6), c = 7.033 (5) A, alpha = 100.99 (6), beta = 83.86 (5), gamma = 86.80 (7) degrees, V = 692.9 (6) A3, Z = 2, Dm = 1.443 (2), Dx = 1.444 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 34.86 cm-1, F(000) = 316, T = 293 K, R = 0.043 for 2219 reflections. (2) 3-[2-Diaminomethyleneamino)-4- thiazolylmethylthio]-N2-sulfamoylpropionamidine (famotidine) hydrochloride, C8H15N7O2S3.HCl, Mr = 373.90, Cc, a = 15.205 (3), b = 14.442 (3), c = 9.262 (1) A, beta = 124.00 (5) degrees, V = 1686.1 (7) A3, Z = 4, Dm = 1.470 (2), Dx = 1.473 g cm-3, mu(Cu K alpha) = 56.09 cm-1, F(000) = 776, T = 293 K, R = 0.036 for 1411 reflections. (3) 3-[2-(Diaminomethyleneamino)-4-thiazolylmethylthio]-propi ona mide, C8H13N5OS2, Mr = 259.35, P2(1)2(1)2(1), a = 5.472 (1), b = 18.260 (5), c = 11.890 (3) A, V = 1188.0 (5) A3, Z = 4, Dm = 1.448 (1), Dx = 1.450 g cm-3, mu(Cu K alpha) = 39.26 cm-1, F(000) = 544, T = 293 K, R = 0.036 for 1260 reflections.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on histamine H2 receptor antagonists. 2. Synthesis and pharmacological activities of N-sulfamoyl and N-sulfonyl amidine derivatives

A series of N-sulfamoyl and N-sulfonyl amidines have been prepared and tested in vitro for H2 antihistamine activity on guinea pig atrium. In addition, several selected compounds were assessed as inhibitors of gastric acid secretion induced by histamine in anesthetized dogs. Structure-activity relationship studies showed that those compounds containing 2-[(diaminomethylene)amino]thiazole exhibited potent H2-receptor antagonist activity. Introduction of alkyl or aralkyl groups to the terminal nitrogen of the sulfamoyl moiety reduced biological activities. Sulfamoyl amidines were more potent in both tests than sulfonyl amidines. Of these compounds, 3-[[[2-[(diaminomethylene)amino]-4-thiazolyl]methyl]thio]- N2-sulfamoylpropionamidine (2e, famotidine) showed extremely high potency in both assays and was selected for clinical trials as an antiulcer agent. Acid-catalyzed hydrolysis of famotidine gave the sulfamoyl amide 6 at room temperature and the carboxylic acid 7 at elevated temperatures. 15N NMR spectrum showed that famotidine in solution existed in only one of several possible tautomers derived from the amidine and the guanidine moieties. Nitrosation of famotidine was performed under mild condition and proved to occur on the 5-position of the thiazole ring.

On the structure-activity relationship of histamine H2-receptor antagonists based on the X-ray crystal structures and 1H-NMR spectra of amidine derivatives

The conformation of six amidine compounds, which possess a common 3-[(4-thiazolyl)methylthio]propionylamidine framework but exhibit different activities as histamine H2-receptor antagonists, have been subjected to both single crystal X-ray structural and 1H-NMR analyses. The X-ray studies suggest a correlation between antagonist activity and the relative spatial orientation of the thiazolyl and amidine nitrogen atoms. This correlation is supported by a comparison of the conformations observed for the amidines with those of other H2-receptor antagonists and reveal that a folded conformation, specifically the NH...N intramolecular hydrogen-bonded configuration, is important for antagonist activity. The 1H-NMR measurements on the active amidine compounds show that the intramolecular NH...N bond is likely to be present in solution.

Simultaneous separation and sensitive determination of free fatty acids in blood plasma by high-performance liquid chromatography

The quantitative determination of saturated and unsaturated fatty acids (ranging from acetic acid to lignoceric acid) in biological samples is presented. The secondary amine group of 5-(dimethylamino)-1-naphthalenesulponyl-semipiperazide (dansyl-semipiperazide) reacts with the carboxyl group of the fatty acids to form an amide linkage in order to obtain fluorescent derivatives of the acids. The fluorescent derivatives are analysed by high-performance liquid chromatography (HPLC) using an internal standard.

Histamine H2 receptor antagonists. 1. Synthesis of N-cyano and N-carbamoyl amidine derivatives and their biological activities

A large number of N-cyano amidine derivatives were prepared as potential histamine H2 receptor antagonists and evaluated for their inhibitory action on histamine-stimulated chronotropic response of isolated right atria from guinea pigs. Several selected compounds were assessed as inhibitors of gastric acid secretion induced by histamine in anesthetized dogs. Of these compounds, furan (8c) and [(diaminomethylene)amino]thiazole derivatives (16c) were found to be more potent than cimetidine in both assays. In contrast to the guanidine series, methyl substitution at the terminal nitrogen of the cyano amidines was detrimental to the activities. Furthermore, acid hydrolysis of the cyano amidines gave carbamoyl amidines, which proved to be more active than the cyano amidines, the converse of the case for guanidines. 3-[[[2-[(Diaminomethylene)amino]-4- thiazolyl]methyl]thio]-N'-carbamoylpropionamidine (16d) was the most potent of all the compounds tested and was approximately 30 times more active in vitro and 50 times more active in vivo than cimetidine.

Anticholinesterase action of a bromine compound isolated from human cerebrospinal fluid

L-1- Methylheptyl -gamma- bromoacetoacetate was found to be a competitive inhibitor of the acetylcholinesterases (electric eel, Ki = 17.2 microM; rat brain, Ki = 32.6 microM) and of butyrylcholinesterase (horse serum, Ki = 1.2 microM). The L-isomer was a more effective inhibitor than the D-isomer. The bromine atom at the gamma-position of the acidic moiety, the specific length of the carbon chain constituting the secondary alcohol moiety, and the presence of the ketone radical at the acidic moiety of the ester were necessary for the anticholinesterase action. 1- Methylheptyl -gamma- bromoacetoacetate formed a complex with acetylcholinesterase or butyrylcholinesterase without hydrolysis of its own molecule.

Microdetermination of 1-Methylheptyl gamma-bromoacetoacetate in human blood

One of the authors reported previously on the presence of 1-methylheptyl gamma-bromoacetoacetate (MHBAA) in human cerebrospinal fluid. In this work, a microdetermination of MHBAA in human blood plasma was developed. The sulfhydryl group of 5-(dimethylamino)-1-naphthalene-sulfonyl L-cysteine (DANSYL L-cysteine) reacted with Br at the gamma-position of MHBAA to form a thioether bond, and a fluorescent derivative was obtained. The fluorescent derivative was separated by TLC. Quantitative determination of MHBAA was done by the radiodilution method combined with fluorometry. It was shown that MHBAA exists in human blood plasma at a concentration of several hundred pmol per ml.

Ribulose-peptide in human semen: II. Synthesis

In order to study the metabolism of a naturally occurring peptide containing D-ribulose in the semen, a pathway of D-ribulose synthesis from radioactively labeled glucose was analyzed. Semen obtained from ten healthy adults was used in this study. The seminal fluid of each person sampled was divided into two equal parts and each one was incubated with glucose-1-14C or glucose-6-14C at room temperature for 1 hr. The rate of incorporation into ribulose from glucose-6-14C was higher than that of glucose-1-14C. This suggests that the ribulose in semen might be converted from glucose through the pentose-phosphate cycle, and incorporated into the ribulose-peptide through an unknown pathway. Incorporation of the labelled 14C was also found in all of the amino acids which were detected in the acid hydrolysate of the ribulose-peptide.

Ribulose-peptide in human semen: I. Isolation

A substance apparently related to a compound consisting of phospho-peptide and ribulose-peptide in the yolk of chick embryos was isolated from acid soluble fractions of human semen by means of Dowex 1 (OH) form column chromatography. The treated precipitate of human semen was examined with an analytical ultracentrifuge by means of synthetic boundary cells and found to be a single component. The sedimentation coefficient was 0.80. The sugar component in the precipitate was identified as ribulose by paper chromatography, color reaction, absorption spectrum of the reaction product in the orcinol, and enzymatic analysis. Amino acids detected in the acid hydrolysate of the precipitate were lysine, histidine, arginine, aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, isoleucine, and leucine. From the above, this substance was determined to be a ribulose-peptide.