Antiallergic agents. 2. N-(1H-tetrazol-5-yl)-6-phenyl-2-pyridinecarboxamides

A new series of N-(1H-tetrazol-5-yl)-6-phenyl-2-pyridinecarboxamides was prepared to determine the effects of substituents on the benzene and pyridine rings on antiallergic activity in the rat passive cutaneous anaphylaxis (PCA) assay after oral administration. One member of this series, N-(1H-tetrazol-5-yl)-4-methyl-6-[4-(methylamino)-phenyl]-2- pyridinecarboxamide (231), has an ED50 value of 0.8 mg/kg po and is 85 times more potent than disodium cromoglycate (DSCG) on intravenous administration. Further evaluation of 231 as a clinically useful antiallergic agent is in progress.     

5-Isoquinolinesulfonamide derivatives. 1. Synthesis and vasodilatory activity of N-(2-guanidinoethyl)-5-isoquinolinesulfonamide derivatives

Two novel series of N-(2-guanidinoalkyl)-5-isoquinolinesulfonamides, 2 and 3, were prepared. Many of the compounds possessed vasodilatory activity when injected locally into the femoral artery of dogs. The most potent compound, 1-amidino-4-(5-isoquinolylsulfonyl)-1,4-perhydrodiazepine, 33, was comparable to diltiazem, which is used clinically as a vasodilator.     

N-4-Substituted 1-(2-arylethyl)-4-piperidinyl-N-phenylpropanamides, a novel series of extremely potent analgesics with unusually high safety margin.

The intravenous analgesic activity and toxicity of a novel series of N-[4-substituted 1-(2-arylethyl)-4-piperidinyl]-N-phenylpropanamides was studied in rats. Onset, potency and duration of analgesic action were assessed in the tail withdrawal test and compared with the activity of fentanyl, (+)-cis-3-methylfentanyl (R 26 800), morphine, and pethidine. All compounds studied were found to be extremely potent analgesics characterized by an unusually high safety margin. Methyl 4-[N-(1-oxopropyl)-N-phenyl-amino]-1-(2-phenylethyl)-4-piperidinecarboxylate (R 31 833; lowest ED50 = 0.00032 mg/kg) is the most potent compound (10 031 times morphine). cis-Methyl 3-methyl-4-[N-(1-oxopropyl)-N-phenylamino]-1-(2-phenylethyl)-4-piperidine carboxylate (R 32 792) is the longest acting compound (more than 8 h at 4 times the lowest ED50) and N-[4-(1-oxopropyl)-1-[2-(2-thienyl)ethyl]-4-piperidinyl]-N-phenylpropanamide (R 33 352) is the shortest acting compound (0.74 h at 4 times the lowest ED50) of the 4-substituted fentanyl derivatives. N-[4-(Methoxymethyl)-1-[2-(2-thienyl)ethyl]-4-piperidinyl]-N-phenylpropanamide (R 30 730) was selected for further investigation. R 30 730 has a rapid onset of action and is 4521 times more potent than morphine at the time of peak effect; it has a relatively short duration of action comparable to that of fentanyl and its safety margin (LD50/lowest ED50 = 25 211) is unusually high.     

Substituted arylmethyl phenyl ethers. 1. A novel series of 5-lipoxygenase inhibitors and leukotriene antagonists

A series of new substituted arylmethyl phenyl ethers has been prepared. These compounds were tested as inhibitors of 5-lipoxygenase (5-LO) in rat neutrophils, in vitro antagonists of leukotriene-induced contraction of guinea pig (GP) lung parenchymal strips, and inhibitors of slow reacting substance of anaphylaxis (SRS-A) mediated bronchospasm in the GP in vivo. Most representatives of this new class of potential antiallergic/antiinflammatory agents showed potent inhibition of 5-LO activity in rat PMNs. The most potent compound, 2-[[3-(1-hydroxyhexyl)phenoxy]-methyl]quinoline (33), had an I50 of 0.12 microM in the rat PMN 5-LO assay and an I50 of 3.6 microM in the leukotriene-induced contraction of GP lung parenchymal strips, and it also showed 91% inhibition of SRS-A-mediated bronchospasm in the GP in vivo at 10 mg/kg, administered intraduodenally. Some of the compounds in this series were also leukotriene antagonists in vitro, and several of them showed in vivo activity against SRS-A-mediated bronchospasm in the GP.     

New N-(pyridin-4-yl)-(indol-3-yl)acetamides and propanamides as antiallergic agents

A series of new N-(pyridin-4-yl)-(indol-3-yl)alkylamides 44-84 has been prepared in the search of novel antiallergic compounds. Synthesis of the desired ethyl (2-methyindol-3-yl)acetates 1-4 was achieved by indolization under Fischer conditions; Japp-Klingemann method followed by 2-decarboxylation afforded the ethyl (indol-3-yl)alkanoates 17-25. Amidification was successfully carried out by condensation of the corresponding acids or their N-aryl(methyl) derivatives with 4-aminopyridine promoted by 2-chloro-1-methylpyridinium iodide. Efforts to improve the antiallergic potency of the title series by variation of the indole substituents (R1, R2, R) and the length of the alkanoic chain (n = 1, 2, 3) led to the selection of N-(pyridin-4-yl)-[1-(4-fluorobenzyl)indol-3-yl]acetamide 45, out of 41 compounds.This amide was 406-fold more potent than astemizole in the ovalbumin-induced histamine release assay, using guinea pig peritoneal mast cells, with an IC50 = 0.016 microM. Its inhibitory activity in IL-4 production test from Th-2 cells was identical to that of the reference histamine antagonist (IC50 = 8.0 microM) and twice higher in IL-5 assay: IC50 = 1.5 and 3.3 microM, respectively. In vivo antiallergic activity evaluation confirmed efficiency of 45 in sensitized guinea pig late phase eosinophilia inhibition, after parenteral and oral administration at 5 and 30 mg/kg, respectively. Its efficiency in inhibition of microvascular permeability was assessed in two rhinitis models; ovalbumin and capsaicin-induced rhinorrhea could be prevented after topical application of submicromolar concentrations of 45 (IC50 = 0.25 and 0.30 microM); and it also exerted significant inhibitory effect in the first test after iv and oral administration, with ID50 = 0.005 and 0.46 mg/kg.     

Synthesis and in vitro opioid receptor functional antagonism of analogues of the selective kappa opioid receptor antagonist (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic)

In previous structure-activity relationship (SAR) studies, we identified (3 R)-7-hydroxy- N-((1 S)-1-{[(3 R,4 R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic, 1) as the first potent and selective kappa opioid receptor antagonist from the trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine class of opioid antagonist. In the present study, we report the synthesis and in vitro opioid receptor functional antagonism of a number of analogues of 1 using a [ (35) S]GTPgammaS binding assay. The results from the studies better define the pharmacophore for this class of kappa opioid receptor antagonist and has identified new potent and selective kappa antagonist. (3 R)-7-Hydroxy- N-[(1 S,2 S)-1-{[(3 R,4 R)-4-(3-hydroxyphenyl)-3,4-dimethylpiperidin-1-yl]methyl}-2-methylbutyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxamide ( 3) with a K e value of 0.03 nM at the kappa receptor and 100- and 793-fold selectivity relative to the mu and delta receptors was the most potent and selective kappa opioid receptor antagonist identified.     

Synthesis and antiallergy activity of N-[2-(dimethylamino)ethyl]-4-aryl-1-piperazinecarboxamide derivatives

A series of N-[2-(dimethylamino)ethyl]-4-aryl-1-piperazinecarboxamides was synthesized and evaluated for antiallergy activity. Several derivatives had activity in the passive foot anaphylaxis (PFA) assay, an IgE-mediated model useful in the detection of compounds possessing antiallergic activity, but no derivative tested had activity at 10 mg/kg in the guinea pig anaphylaxis (GPA) assay. One analogue, N-[2-(dimethylamino)ethyl]-4-(4-fluorophenyl)-1-piperazinecarboxamide , had an IC50 = 310 nM for inhibition of tritiated mepyramine binding to H1 histaminic receptors isolated from guinea pig cerebral cortex.     

Synthesis and neuroleptic activity of benzamides. Cis-N-(1-benzyl-2-methylpyrrolidin-3-yl)-5-chloro-2-methoxy-4-(methylamino)benzamide and related compounds

Three series of benzamides of N,N-disubstituted ethylenediamines (linear alkane-1,2-diamines), 1-substituted 2-(aminomethyl)pyrrolidines, and 1-substituted 3-aminopyrrolidines (cyclic alkane-1,2-diamines) were designed and synthesized as potential neuroleptics. All target compounds were evaluated for their inhibitory effects on apomorphine-induced stereotyped behavior in rats, and a good correlation between structure and activity was found throughout the series. In the linear series (analogues of metoclopramide), introduction of a benzyl group on the terminal nitrogen, rather than an ethyl group, and a methyl group on the p-amino group of metoclopramide both enhanced the activity. The resulting N-[2-(N-benzyl-N-methylamino)ethyl]-5-chloro-2-methoxy-4-(methylamino) benzamide(23) was about 15 times more active than metoclopramide. In the cyclic series, particularly among the benzamides of 1-benzyl-3-aminopyrrolidine, most of the compounds tested were more active than the corresponding linear benzamides. cis-N-(1-Benzyl-2-methylpyrrolidin-3-yl)-5-chloro-2-methoxy-4-(methylamino) benzamide (YM-09151-2, 55) was the most active among all of the compounds tested, being 13 and 408 times more potent than haloperidol and metoclopramide, respectively. Moreover, compound 55 exhibited a fairly high ratio of antistereotypic activity to cataleptogenicity compared with haloperidol and metoclopramide. It is expected that compound 55 may be used as a potent drug with few side effects in the treatment of psychosis.     

Synthesis and antimicrobial activity of 7 alpha-methoxypyrimidinyl-ureidocephalosporins

The synthesis of a series of 7 alpha-methoxy-7-[(R)-2-[3-[5-pyrimidinyl]ureido]-2-(4-hydroxyphenyl) acetamido]-3-cephem-4-carboxylates 2 is described. 7-[(R)-2-[3-[2-(p-Aminosulfonyl)-anilino-4-hydroxy-5-pyrimidinyl]ureido- 2-(4-hydroxyphenyl)acetamido]-7 alpha-methoxy-3-[(1-methyl-1H-tetrazol-5 -yl)thio]methyl-3-cephem-4-carboxylic acid, sodium salt (2k, UG-FA 132), has exhibited a broad range of antimicrobial activity. UG-FA 132 is highly active against Gram-positive and Gram-negative organisms, including Pseudomonas and lactamase producers, and shows potent activity against anaerobes. The high efficacy of UG-FA 132 was confirmed by in vivo experiments in mice.     

Synthesis of 2-(2,3-dihydro-2-oxo-1,3,4-oxadiazol-5-yl) benzo heterocycles. A novel series of orally active antiallergic agents

A series of new 2-(2,3-dihydro-2-oxo-1,3,4-oxadiazol-5-yl) benzo heterocycles has been prepared. These compounds were tested as inhibitors of antigen-induced release of histamine (AIR) in vitro from rat peritoneal mast cells (RMC) and as inhibitors of IgE-mediated rat passive cutaneous anaphylaxis in the rat (PCA). Most of this new class of antiallergic agents showed good activity in the RMC assay. The most potent compound, 3-chloro-2-(2,3-dihydro-2-oxo-1,3,4-oxadiazol-5-yl)benzo[b]thiophe ne (6t), with an I50 value of 0.2 microM, is 15 times more potent than disodium cromoglycate (DSCG) in the RMC assay. Many compounds were orally active in the PCA test, and several of these compounds showed higher potency when given in this way to that shown by DSCG when given intraperitoneally.     

Indazolinones, a new series of redox-active 5-lipoxygenase inhibitors with built-in selectivity and oral activity.

Since the hypothetical mechanisms of hydroperoxydation of arachidonic acid by, respectively, 5-lipoxygenase (5-LPO) and cyclooxygenase (CO) involve a redox cycle, a compound which reduces 5-LPO and CO to their inactive state would give a nonselective inhibitor of both enzymes. Structural modifications of such a compound could be expected to give improved potency and selectivity for 5-LPO and oral activity. Such an approach has led to the discovery of 1,2-dihydroindazol-3-ones which are potent 5-LPO inhibitors with various degrees of selectivity. Structure-activity relationship studies indicated that while N-1,N-2-unsubstituted and N-1-substituted derivatives are orally inactive, N-2-alkyl derivatives are orally active and inhibit both 5-LPO and CO. In contrast, N-2-benzyl derivatives are selective for 5-LPO but possess only weak oral activity. Further structural modifications have identified ICI 207968 [1,2-dihydro-2-(3-pyridylmethyl)-3H-indazol-3-one, 21a] which combines potent oral activity and high selectivity. Methemoglobin (MHb) induction by 21a in dog blood precluded its development for clinical use. Attempts at dissociating 5-LPO inhibitory properties and MHb formation showed that MHb formation in vitro seemed to be related to the redox potential of the compounds whereas 5-LPO inhibition was not. This study led to a series of 4-(N-n-pentylcarbamoyl)indazolinones which maintained in vitro 5-LPO potency but did not induce MHb.     

TSAO analogues. Stereospecific synthesis and anti-HIV-1 activity of 1-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro -5'- (4'-amino-1',2'-oxathiole 2',2'-dioxide) pyrimidine and pyrimidine-modified nucleosides.

Several analogues of a new lead for anti-HIV-1 agents [1-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-thymine] -3'-spiro-5'-(4'-amino-1',2'-oxathiole 2',2'-dioxide) (TSAO) modified at positions N-3, O-4 and C-5 of the thymine moiety, have been prepared and evaluated as inhibitors of HIV-1 replication. A new stereoselective synthetic procedure is described. Reaction of 1,2-di-O-acetyl-5-O-benzoyl-3-C-cyano-3-O-mesyl-D-ribofuranose with pyrimidine bases, followed by treatment with Cs2CO3 afforded stereoselectively, beta-D-ribofuranosyl-3'-spiro nucleosides. 2',5'-O-Deacylation and subsequent treatment with tert-butyldimethylsilyl chloride gave the TSAO derivatives. Only those analogues having a tBDMSi group at both the C-5' and C-2' positions of the ribose moiety showed potent anti-HIV-1 activity. The activity ranged from 0.060 microM to 1.0 microM. Introduction of an alkyl or alkenyl function at N-3 of the thymine ring markedly decreased cytotoxicity without affecting the antiviral activity. While markedly active against HIV-1, the TSAO derivatives had no activity against HIV-2 or SIV. They represent the first example of nucleoside analogues with an intact ribose moiety that discriminate between HIV-1 and other retroviruses.     

Studies on antianaphylactic agents. 7. Synthesis of antiallergic 5-oxo-5H-[1]benzopyrano[2,3-b]pyridines

5-Oxo-5H-[1]benzopyrano[2,3-b]pyridine-3-carboxylic acids 23 and their tetrazole analogues 24 were synthesized from 4-oxo-4H-1-benzopyran-3-carbonitriles 3 or 2-amino-4-oxo-4H-1-benzopyran-3-carboxaldehydes 4. When administered intravenously, they exhibited antiallergic activity in a reaginic PCA test in rats. In the carboxylic acid series, the activity was influenced by the substituents at the 2-position and increased substantially in the following order: Me, OMe less than NH2 less than OH, H less than NHOMe. On the other hand, in the tetrazole series, 2-unsubstituted derivatives showed the highest activity. Regardless of the kinds of substituents at positions 2 and 3, compounds bearing an alkyl group, especially an isopropyl group at the 7-position, were superior in activity to the corresponding unsubstituted compounds. Among these alkyl derivatives, 3-carboxylic acid derivatives, i.e., 23c (7-ethyl), 23g (2-amino-7-isopropyl), 23r [2-(methoxyamino)-7-isopropyl], and a 3-tetrazole derivative 24c (7-isopropyl), were 41-184 times as potent as disodium cromoglycate. They also exhibited remarkable activity when administered orally; clinical studies on 23g (AA-673) are in progress.     

Highly selective kappa-opioid analgesics. 3. Synthesis and structure-activity relationships of novel N-[2-(1-pyrrolidinyl)-4- or -5-substituted-cyclohexyl]arylacetamide derivatives

This paper describes the chemical synthesis, mu/kappa opioid receptor selectivity and analgesic activity of 14 novel N-[2-(1-pyrrolidinyl)-4- or -5-substituted-cyclohexyl]arylacetamide derivatives. The prototype kappa-selective agonist, PD117302 (trans-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzo[b]thiophene-4- acetamide, 2) has been regio- and stereoselectively substituted in the C-4 and C-5 positions of the cyclohexyl ring with the methyl ether and spiro tetrahydrofuran groups. It is observed that optimal mu/kappa-receptor selectivity is obtained when the oxygen atom of the methyl ether or the tetrahydrofuran ring is joined to the equatorial C-4 position. Hence, (-)-(5 beta,7 beta,8 alpha)-N-methyl-N-[7-(1-pyrrolidinyl)-1- oxaspiro[4.5]dec-8-yl]benzo[b]furan-4-acetamide monohydrochloride (21) has exceptionally high kappa opioid receptor affinity and selectivity in vitro (kappa Ki = 0.83 nM, mu/kappa ratio = 1520) is the most potent kappa-selective analgesic ever reported. Compound 21 is 25 times more potent than morphine and 17 times more potent than U-62066 (spiradoline, 19) when assayed by the rat paw pressure test by intravenous administration (MPE50 = 0.024, 0.6, and 0.4 mg/kg, respectively).     

Synthesis and anticonvulsant properties of new N-[(4-arylpiperazin-1-yl)-methyl] derivatives of 3-aryl pyrrolidine-2,5-dione and 2-aza-spiro[4.4]nonane-1,3-dione

A series of N-[(4-arylpiperazin-1-yl)-methyl] derivatives of 3-arylpyrrolidine-2,5-dione and 2-aza-spiro[4.4]nonane-1,3-dione were synthesized and tested for anticonvulsant activity in the maximum electroshock seizure (MES) and metrazole seizure threshold (sc.MET) tests. The most potent in the series were N-[[4-(3-chlorophenyl)-piperazin-1-yl]-methyl]-3-(2-chlorophenyl)-pyrrolidine-2,5-dione (ED50=14.18 mg/kg) and N-[[4-(2-methoxyphenyl)-piperazin-1-yl]-methyl]-3-(3-bromophenyl)-pyrrolidine-2,5-dione (ED50=33.64 mg/kg). Structures of the novel compounds were confirmed by elemental and spectral analyses.     

Synthesis and 5-HT1A/5-HT2A receptor activity of N-(4-arylpiperazin-1-yl)alkyl derivatives of 2-azaspiro([4.4]nonane and [4.5]decane-1,3-dione

Two series of N-[(4-arylpiperazin-1-yl)-alkyl]-2-azaspiro[4.4]nonane (5-10) and [4.5]decane-1,3-dione (11-16) derivatives were synthesized and their serotonin 5-HT1A and 5-HT2A receptor affinities were determined. Compounds with the methylene spacer (5-7 and 11-13) exhibited low 5-HT1A/5-HT2A receptor affinity, in contrast to their ethylene analogues regarded as potent 5-HT1A ligands, especially those containing a cyclohexane moiety (14-16; Ki = 5.1, 2.7 and 4.3 nM, respectively) in the 3-position of the pyrrolidine-2,5-dione ring. Moreover, derivatives with 3-chloro substituent (10 and 14) showed distinct affinity for 5-HT2A receptors. The functional activity of compounds 10, 14, 15 and 16 was tested in vivo in the commonly used animal models. In those experiments, the tested compounds showed features of agonists of pre- and postsynaptic (14), agonists of presynaptic and antagonists of postsynaptic (10, 15), or agonists of postsynaptic (16) 5-HT1A receptors. Additionally, 10 and 16 exhibited properties of potential 5-HT2A receptor antagonists. The above results suggested a crucial role of the spacer between the amide fragment and 4-arylpiperazine moiety, as well as of the size of the cycloalkyl ring at the 3-position of pyrrolidine-2,5-dione ring in functional 5-HT1A/5-HT2A properties.     

Antiallergy agents. 1. 1,6-Dihydro-6-oxo-2-phenylpyrimidine-5-carboxylic acids and esters.

The synthesis of some 1,6-dihydro-6-oxo-2-phenylpyrimidine-5-carboxylic acids and esters with potent oral and intravenous antiallergic activity against passive cutaneous anaphylaxis in the rat is described. Requirements for high activity include a free NH group in the pyrimidinone nucleus and a small to medium size ortho alkoxy or alkenyloxy group on the phenyl ring. It is suggested that in the case of the highly active compounds hydrogen bonding occurs between a nitrogen of the pyrimidine ring and the ethereal oxygen. The nature of this bonding and its possible contribution to an optimum configuration for the molecules is discussed.     

Synthesis and structure-affinity relationships of 1-[omega-(4-aryl-1-piperazinyl)alkyl]-1-aryl ketones as 5-HT(7) receptor ligands

Structural requirements for 5-HT(7) receptor affinity and selectivity over that for the 5-HT(1A) receptor were studied on a series of 1-[omega-(4-aryl-1-piperazinyl)alkyl]-1-aryl ketones. The presence of a hydroxy or methoxy substituent on aryl ketone moiety, alkyl chain length, and the nature of N-1-piperazine substituent were explored. 6-[4-(3-Benzisoxazolyl)-1-piperazinyl]-1-(2-hydroxyphenyl)-1-hexanone (40) and its methoxy analogue 43 exhibited high 5-HT(7) receptor affinities (Ki = 2.93 nM and 0.90 nM, respectively) and agonist properties when tested for 5-HT(7) receptor-mediated relaxation of substance P-induced guinea-pig ileum contraction.     

Antiallergic agents. 3. N-(1H-tetrazol-5-yl)-2-pyridinecarboxamides

A series of N-tetrazolylpyridinecarboxamides was prepared and evaluated for antiallergic activity by the passive cutaneous anaphylaxis (PCA) assay. From the structure-activity relationships (SAR) of this class of compounds, it was revealed that the N-tetrazolylcarbamoyl group as an acidic functionality is required to be at the 2-position of the pyridine nucleus and that the phenyl group as a subtituent is not necessarily required for activity. 6-Methyl-N-(1H-tetrazol-5-yl)-2-pyridinecarboxamide (36) showed good oral activity and low toxicity.     

Novel 4-alkyl-1-arylpiperazines and 1,2,3,4-tetrahydroisoquinolines containing diphenylmethylamino or diphenylmethoxy fragment with differentiated 5-HT1A/5-HT2A/D2 receptor activity

Two series of 4-alkyl-1-arylpiperazines (1-4) and 1,2,3,4-tetrahydroiso-quinolines (5, 6) with diphenylmethylamino (series a) or diphenylmethoxy (series b) fragment were synthesized in order to obtain potential ligands of 5-HT1A and/or 5-HT2A and dopamine D2 receptors. Four new arylpiperazines (1a, 3a, 1b, 3b) were found to demonstrate high 5-HT1A receptor affinity (Ki = 1.5-35 nM); among them, 3a exhibited satisfactory 5-HT2A receptor affinity (Ki = 74 nM). Only compounds 1b and 2b showed moderate affinity for D2 receptor sites (Ki = 123 and 128 nM, respectively). Compounds 1a, 3a, 1b and 3b were investigated in vivo to determine their functional activity at 5-HT1A receptors; additionally, 3a was tested for 5-HT2A receptor activity. Derivatives 1a, 1b and 3b produced effects characteristic of antagonists of postsynaptic 5-HT1A receptors. Moreover, 1b exhibited features of an agonist of presynaptic 5-HT1A receptors, while 3a behaved like a partial agonist of postsynaptic 5-HT1A sites. The latter derivative may also be classified as a 5-HT2A receptor antagonist. Thus, novel potent 5-HT1A receptor ligands were successfully obtained, and the most promising compound 3a showed mixed 5-HT1A/5-HT2A receptor activity in in vitro and in vivo tests.