Potential antisecretory antidiarrheals. 1. Alpha 2-adrenergic aromatic aminoguanidine hydrazones

Guanabenz, a centrally acting antihypertensive agent, has been shown to have intestinal antisecretory properties. A series of aromatic aminoguanidine hydrazones was made in an effort to separate the antisecretory and cardiovascular activities. Benzaldehyde, naphthaldehyde, and tetralone derivatives were synthesized. The compounds were evaluated in the cholera toxin treated ligated jejunum of the rat and in the Ussing chamber using a rabbit ileum preparation. A number of compounds, including members of each structural class, were active upon subcutaneous administration in the rat. Active compounds were determined to be alpha 2-adrenergic agonists by yohimbine reversals of their Ussing chamber activities. The compound displaying the best separation of activities was the aminoguanidine hydrazone of 2,6-dimethyl-4-hydroxybenzaldehyde (20).     

Anti-Helicobacter pylori agents. 4. 2-(Substituted guanidino)-4-phenylthiazoles and some structurally rigid derivatives

In order to find a new class of anti-Helicobacter pylori (H. pylori) agents, a series of 4-[(3-acetamido)phenyl]-2-(substituted guanidino)thiazoles and some structurally rigid analoges were synthesized and evaluated for antimicrobial activity against H. pylori. Among the compounds obtained, high anti-H. pyrori activities were observed in benzyl derivative 34 (MIC = 0.025 microg/mL) and phenethyl derivatives 35 and 36 (MIC = 0.037 microg/mL and 0.017 microg/mL). Though alkyl derivatives generally showed lower activity, the 2-methoxyethyl derivative 28 preserved significant activity (MIC = 0.32 microg/mL) and also exhibited more potent gastric antisecretory activity than ranitidine. Structural restriction by bridging between the thiazole and the phenyl rings with an alkyl chain did not improve the activity in this series.     

Pyridazinones. 2. Synthesis and antisecretory and antiulcer activities of thiourea and 2-cyanoguanidine derivatives

In an effort to develop new types of antiulcer agents, we synthesized a series of novel 2-[omega-(thioureido)alkyl]- and 2-[omega-(cyanoguanidino)alkyl]-3(2H)-pyridazinone derivatives. All target compounds were evaluated for gastric antisecretory activity in the pylorus-lygated rat by the method of Shay, and selected compounds were evaluated in the stress-induced ulcer test in rats. Structure-activity relationships were established. Two series of the compounds had significant activity in antisecretory and/or antiulcer tests. The molecular features essential for the activities are a thiourea group or a 2-cyanoguanidine group, a phenyl group in the C-6 position of the 3(2H)-pyridazinone ring, a four-carbon chain length between the 3(2H)-pyridazinone ring and the functional group, and a methyl group at the N-3 position of the functional group. Among them, the three thiourea derivatives (24, 26, and 38) and the six 2-cyanoguanidine derivatives (61, 62, 65, 75, 85, and 86) had the most potent antisecretory and/or antiulcer activities. These compounds are not histamine H2-receptor antagonists.     

抗疟药的研究——Ⅲ.2-(取代苯乙烯基)-4-氨基吡啶类的合成

本文报道2-(取代苯乙烯基)-4-(4′-二乙氨基-1′-甲基丁基氨基)-吡啶类的合成。动物筛选的初步结果表明:口服给药6.25mg/kg,化合物Ⅲ₂、Ⅲ₄和Ⅲ₇能完全抑制感染伯氏鼠疟原虫氯喹敏感株(Plalmodium berghei)小白鼠的原虫血症;皮下给药1.8mg/kg,化合物Ⅲ,即能达到完全抑制。     

Ester derivatives of 2,6-bis(1-pyrrolidinylmethyl)-4-benzamidophenol as short-acting antiarrhythmic agents. 1

In an effort to find a replacement for the iv antiarrhythmic drug lidocaine having reduced systemic and central nervous system effects, activity against supraventricular as well as ventricular arrhythmias, and a biological half-life of less than 15 min, derivatives of the orally active class Ic clinical agent 2,6-bis(1-pyrrolidinylmethyl)-4-benzamidophenol, 1 (ACC-9358), were synthesized and tested. Compounds with ester groups attached to the phenyl ring were either weakly active or toxic. Replacement of the formanilide function with alkyl esters afforded compounds with antiarrhythmic activity in the range of 1. When the ester carboxyl was separated from the bis(aminomethyl)phenol by methylene units, very short half-lives were observed in human blood. In general, these compounds also had low lipophilic character.     

Synthesis and pharmacological evaluation of some 3-(4-methylphenyl)-2-substituted amino-3H-quinazolin-4-ones as analgesic and anti-inflammatory agents

A variety of 3-(4-methyl phenyl)-2-substituted amino-3H-quinazolin-4-ones were synthesized by reacting the amino group of 2-hydrazino-3-(4-methyl phenyl)-3H-quinazolin-4-one with a variety of aldehydes and ketones. The starting material 2-hydrazino-3-(4-methyl phenyl)-3H-quinazolin-4-one was synthesized from 4-methyl aniline. The title compounds were investigated for analgesic, anti-inflammatory, and ulcerogenic index activities. While the test compounds exhibited significant activity, compounds Al, A2, and A3 showed more potent analgesic activity and the compound A3 showed more potent anti-inflammatory activity when compared to the reference standard diclofenac sodium. Interestingly, the test compounds showed only mild ulcerogenic potential when compared to aspirin.     

Novel bronchodilators: synthesis, transamination reactions, and pharmacology of a series of pyrazino[2,3-c][1,2,6]thiadiazine 2, 2-dioxides

The synthesis, pharmacological evaluation, and structure-activity relationships of a new class of bronchodilator agents, derivatives of pyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxides are described. The compounds were prepared by reaction of 3,4,5-triamino-1,2, 6-thiadiazine 1,1-dioxide with suitable 1,2-dicarbonyl compounds or alpha-hydroxyiminoketones and subsequent N-alkylation. A transamination procedure for synthesizing derivatives with different substituents at the 4-amino group is reported for the first time. The pyrazino[2,3-c][1,2,6]thiadiazine derivatives were screened for tracheal relaxing activity in vitro, and the active compounds were evaluated in vivo in guinea pigs as bronchodilator agents in comparison to theophylline. Among the compounds studied, the most interesting properties were displayed by the 4-amino-1-ethyl-6-methyl derivative (21). The toxicological evaluation of this derivative is also reported.     

Structure-activity relationship of imidazolidine derivatives related to clonidine at histamine H2-receptors in guinea-pig isolated atria

1 Cumulative concentration-response relationships for the chronotropic effects of histamine, oxymetazoline, clonidine and thirteen clonidine-like imidazolidine derivatives were examined in isolated spontaneously beating guinea-pig atria.

2 The following compounds induced positive chronotropic effects: histamine, clonidine (2,6-dichloro-phenyliminoimidazolidine) and the 2,6-dibromo, 2,6-dimethyl, 2,6-diethyl, 2,6-dihydroxy, 2,4,6-trimethyl, 3,4-dihydroxy and 2-methyl-5-fluoro analogues of clonidine. These compounds appeared to act as partial agonists on histamine H₂-receptors, with potencies ranging from one tenth to one hundredth and intrinsic activities from approximately 20% to 75% of those of histamine.

3 The following compounds did not induce positive chronotropic effects but rather decreased the atrial rate, usually at high concentrations: oxymetazoline and the 2,3-dichloro, 4-dichloro, 5-dichloro, 2-chloro-4-methyl, 2-methyl-5-chloro, 2,4,6-trichloro analogues of clonidine.

4 The effects of histamine were antagonized by cimetidine, the pA₂ value being 6.68 (s.e. mean = 0.16, n = 3), and also in a concentration-dependent manner by clonidine. Cimetidine antagonized the response to clonidine in a concentration-dependent manner; however, high concentrations of cimetidine depressed the maximal response to clonidine and the slope of the concentration-response curve was no longer parallel to the control curve.

5 The effects of the other compounds which induced positive chronotropic effects were also antagonized by cimetidine (1 μmol/l); however, the effect of the 3,4-dihydroxy derivative was unaffected by cimetidine (1 μmol/l) but was abolished by propranolol (0.3 μmol/l).

6 In general, phenyliminoimidazolidine derivatives with 2,6-substitution on the phenyl ring are active on histamine H₂-receptors, whereas derivatives with 2,3-, 2,4- or 2,5-substitutions are weakly active or inactive. Thus the restriction imposed on the free rotation of the phenyl ring about the carbon-imino nitrogen bond by the introduction of two ortho substituents appears to result in increased agonist activity on the histamine H₂-receptor. The introduction of substituents in the 3, 4 or 5 positions in the phenyl ring may lead to compounds sterically hindered from combining with the histamine H₂-receptor.

7 There is no apparent relationship between the activities of clonidine-like imidazolidine derivatives as agonists on histamine H₂-receptors and their hypotensive activities (as reported in the literature).

     

Bioisosterism: Interchange of 4-OH to 4-NH2 in vanillin or homovanillin ring of capsaicinoids

A series of 4-amino Capsaicin analogs 15, 17 and 19 were prepared to investigate the bioisosteric effect of 4-amino group, and all these compounds exhibited moderate or weak potency from their analgesic test. From our previous results and others, 4-hydroxyl group as well as 3-methoxy substituent could be crucial for high analgesic activity. This biological result also shows that the activity is sensitive to alkyl chain length in hydrophobic region and the phenylacetic amides 19 are more active than the corresponding urea derivatives 17.     

Antimalarial 6-aminoquinolines. VIII. 2- and 4-amino derivatives (author's transl)

Ten 2- or 4-amino derivatives 10b-I of 6-(4-diethylamino-1-methylbutylamino)-5,8-dimethoxyquinoline were synthesised with the aim of studying the influence of these substituents on antimalarial activity and toxicity of the 6-aminoquinolines. The 4-dialkylamino derivatives 10c-h were less active against P. vinckei (mouse) than 4-alkoxy derivatives. The 4-amino derivative 10b was inactive.     

Amidines and related compounds. 6. Studies on structure-activity relationships of antihypertensive and antisecretory agents related to clonidine.

Correlations of antihypertensive and antisecretory activities with various structural modifications of the antihypertensive agent clonidine (2-(2,6-dichlorophenylimino)imidazolidine) are described. Eleven chemical classes of compounds containing an "amidine" moiety were prepared in this study. The antihypertensive activity of these compounds was evaluated in metacorticoid hypertensive rats and unanesthetized neurogenic hypertensive dogs following oral administration. Antisecretory activity was evaluated in fistula rats by measuring pH and volume of gastric secretion. Two compounds, 2-(2,6-dimethylphenylimino)imidazolidine and 2-(2,6-dichlorophenylimino)pyrrolidine, are particularly effective antisecretory agents with minimal antihypertensive activity.     

Effects of the natural and unnatural isomers and degradation products of enprostil on gastric acid secretion and gastrointestinal motility in the rat

The gastric antisecretory and gastrointestinal (GI) motility activity of the natural and unnatural allenic isomers and degradation products of enprostil (methyl(+/-)-7-[(1R*,2R*,3R*)-3-hydroxy-2-[(E)-(3R*)-3-hydroxy-4-phenoxy - 1-butenyl]-5-oxocyclopentyl]-4,5-heptadienoate, RS-84135-004) were studied in the rat. The natural R-allenic isomer of enprostil was the most potent antisecretory compound. The 8-iso-enprostil, enprostil free acid, and the 5-acetylene isomer had somewhat less activity while the other compounds were relatively inactive. The natural and unnatural allenic isomers increased intestinal dye transit with the same rank potency as the gastric antisecretory activity. Enprostil, 8-iso-enprostil, prostaglandin A-enprostil and enprostil free acid, all increased intestinal dye transit.     

Modification of spectinomycin. 2. Derivatives of 4-dihydro-4-deoxy-4(R)-aminospectinomycin

Acyl derivatives 5a approximately j and alkyl derivatives 7a approximately r of 4-dihydro-4-deoxy-4(R)-aminospectinomycin (1a) were prepared and tested for antibacterial activity. Only acyl compounds derived from long chain aliphatic acids showed activity in vitro, but were inactive when tested in vivo. All alkyl derivatives were active in vitro. In vivo however only the short chain derivatives 7a approximately c were active. Compound 7b showed higher activity than spectinomycin.     

Geiparvarin analogues. 2. Synthesis and cytostatic activity of 5-(4-arylbutadienyl)-3(2H)-furanones and of N-substituted 3-(4-oxo-2-furanyl)-2-buten-2-yl carbamates

In an attempt to determine some of the structural features of geiparvarin (1) that account for its cytostatic activity in vitro, a series of geiparvarin analogues (10a-i, 1, 12, and 14-16) which contain novel modifications in the region of the olefinic double bond and of the coumarin moiety have been designed and synthesized. Among the derivatives containing a carbamate moiety, only the analogues containing a carbamate group linked to an alkyl moiety 10b-i were endowed with potent cytostatic activity, whereas the corresponding benzene derivative 10a was devoid of any antiproliferative activity. 6-Methoxygeiparvarin 101 proved equally effective as geiparvin (1), while compounds containing an additional double bond at the side chain (12 and 14-16) were invariably 5-100-fold less effective than geiparvarin. Diene derivative 15, bearing a coumarin moiety, was essentially inactive against murine (L1210, FM3A) tumor cells but exhibited good activity against human (Molt/4F, MT-4) tumor cells.     

2-Pyrrolidinylideneureas, a new class of central nervous system agents.

A series of N-aryl-N'-(1-methyl-2-pyrrolidinylidene)ureas was prepared and screened for pharmacological activity. Congeners possessing either phenyl or phenyl substituted with 4-nitro, 3-bromo, 3-chloro, 3-fluoro, and 3-methyl groups were found to demonstrate anxiolytic activity. 2,6-Disubstitution of the phenyl ring with methyl, chloro, and bromo imparted potent muscle-relaxant properties which appear to be centrally mediated. A significant separation of the anxiolytic and muscle-relaxant properties from other CNS activities, e.g., anticonvulsant, sedative, and hypnotic, was achieved.     

Anti-Helicobacter pylori agents. 5. 2-(Substituted guanidino)-4-arylthiazoles and aryloxazole analogues.

To extend the SAR study of guanidinothiazoles as a structurally novel class of anti-H. pylori agents, a series of 2-(substituted guanidino)-4-arylthiazoles and some 4-aryloxazole analogues were synthesized and evaluated for antimicrobial activity against H. pylori. Some of them were also subjected to H2 antagonist and gastric antisecretory assays. Several arylthiazoles were identified as potent anti-H. pylori agents, and of these, thienylthiazole derivative 44 exhibited the strongest activity (MIC = 0.0065 microg/mL) among the compounds obtained in our guanidinothiazole studies. Although 44 was void of H2 antagonist activity, pyridylthiazole derivative 39 had both potent anti-H. pylori and H2 antagonist activities. Thiazolylthiazole derivative 46 also showed potent anti-H. pylori activity, but the H2 antagonist activity was weak. On the other hand, no attractive activities were found in pyrimidyl, oxazolyl, isoxazolyl, imidazolyl, and oxadiazolylthiazole derivatives. The anti-H. pylori activity of the aryloxazole analogues was weaker than those of the corresponding arylthiazole derivatives, though they had potent H2 antagonist activity.     

Molecular modeling and crystallographic studies of 4-amino-N-phenylbenzamide anticonvulsants.

The molecular structures of five different MES-active N-phenylbenzamides were determined by X-ray diffraction methods, and the conformations of a series of active and inactive benzamides were analyzed by molecular mechanics calculations. The most active compounds adopt a similar, consistent conformation in both the experimentally determined crystallographic structures and in the calculated molecular mechanics structures. This conformation places one o-methyl group proximal to the NH group of the central amide plane and orients the methyl-substituted phenyl ring at an angle of 90 degrees to 120 degrees to the central amide plane. Intermolecular interactions in the crystal structures indicate that hydrogen bonding to the central amide group is the important interaction. The observed consistent conformation facilitates formation of hydrogen bonds to the carbonyl oxygen atom. The conformations of inactive compounds obstruct this interaction. These findings help to outline a model of some of the structural features which this series of benzamides must possess in order to demonstrate MES anticonvulsant activity.     

N,N-Dialkylated monophenolic trans-2-phenylcyclopropylamines: novel central 5-hydroxytryptamine receptor agonists

N,N-Dialkylated monophenolic derivatives of trans-2-phenylcyclopropylamine were synthesized and tested for central 5-hydroxytryptamine (5-HT) and dopamine (DA) receptor stimulating activity by use of a biochemical test method in rats. A hydroxy substituent in the 2- or 3-position of the phenyl ring was required for 5-HT-receptor stimulation. N,N-Diethyl or N,N-di-n-propyl substitution gave the most potent 5-HT-receptor agonists. The 4-hydroxy and 3,4-dihydroxy derivatives of trans-2-phenyl-N,N-di-n-propylcyclopropylamine were inactive at central DA and 5-HT receptors. In contrast, the corresponding 3-hydroxy derivative 18 and some of its derivatives weakly affected both DA and NE synthesis. Two of the most potent 5-HT-receptor agonists, trans-2-(2-hydroxyphenyl)-N,N-di-n-propylcyclopropylamine (8) and the 3-hydroxy isomer 18 were resolved into the enantiomers. The 1R,2S enantiomers of 8 and 18 displayed 5-HT activity, while the 1S,2R enantiomers were inactive. Compound (1R,2S)-18, but not (1R,2S)-8, weakly affected rat brain DA and NE synthesis.     

Synthesis and antiviral activity of phosphoralaninate derivatives of methylenecyclopropane analogues of nucleosides.

Phenylmethylphosphoro-L-alaninate prodrugs of antiviral Z-methylenecyclopropane nucleoside analogues and their inactive E-isomers were synthesized and evaluated for their antiviral activity against HCMV, HSV-1, HSV-2, HHV-6, EBV, VZV, HIV-1 and HBV. The adenine Z-analogue was a potent inhibitor of all these viruses but it displayed cellular toxicity. The guanine Z-derivative was active against HCMV, HBV, EBV and VZV and it was not cytotoxic. The 2,6-diaminopurine analogue was the most potent against HIV-1 and HBV and somewhat less against HHV-6, HCMV, EBV and VZV in a non-cytotoxic concentration range. The 2-amino-6-cyclopropylamino and 2-amino-6-methoxypurine prodrugs were also more active than parent analogues against several viruses but with a less favorable cytotoxicity profile. In the E-series of analogues, adenine derivative was active against HIV-1, HBV and EBV, and it was non-cytotoxic. The guanine analogue exhibited a significant effect only against HBV. The 2,6-diaminopurine E-analogue was inactive with the exception of a single EBV assay. The 2-amino-6-methoxypurine Z-methylenecyclopropane nucleoside analogue was an effective inhibitor of HCMV, MCMV and EBV. The 2,6-diaminopurine Z-prodrug seems to be the best candidate for further development.     

Enantiomeric effects of homologues of disoxaril on the inhibitory activity against human rhinovirus-14

X-ray crystallography studies of racemic 5-[7-[4-(4,5-dihydro-4-methyl-2-oxazolyl)phenoxy]heptyl]- 3-methylisoxazole bound to human rhinovirus-14 (HRV-14) indicate selective binding of the S isomer. This result correlates well with the 10-fold greater activity of the S isomer as compared to the R isomer. The enantiomeric effect on activity is explained by a hydrophobic interaction of the methyl group in the case of 2a, with a pocket formed by Leu106 and Ser107. The 4-ethyl, 4-propyl, and 4-butyloxazolinyl homologues were prepared and tested against HRV-14. All of these compounds exhibited a comparable stereochemical effect. In each case, the S isomer displayed greater levels of activity than the R. The results of energetic considerations of the oxazoline ring in an 8-A pocket bound to the HRV-14 binding site suggest that the twist angle between the oxazoline and phenyl rings resulting from hydrophobic interactions of the alkyl substituents could be one of the determining factors for biological activity.