(+/-)-trans-2-(3-Methoxy-5-methylsulfonyl-4-propoxyphenyl)-5-(3,4,5- trimethoxyphenyl)tetrahydrofuran (L-659,989), a novel, potent PAF receptor antagonist

The title compound, L-659,989, is a highly potent, competitive, and selective antagonist of the binding of [3H]PAF to its receptors in platelet membranes from rabbits and humans. It exhibits equilibrium inhibition constants for PAF binding of 1.1 nM (rabbit) to 9.0 nM (human), values that are at least 1-2 orders of magnitude lower than those of other PAF antagonists tested. L-659,989 potently inhibits PAF-induced aggregation of rabbit platelets and degranulation of rat (ED50 4.5 nM) and human (ED50 10 nM) neutrophils. L-659,989 inhibits PAF-induced extravasation and lysosomal enzyme release in rats, and is active orally in female rats (ED50 0.2 mg/kg) with an extraordinary oral duration of action of 12 to 16 hours at 1.0 mg/kg p.o.     

Novel (S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acids: peroxisome proliferator-activated receptor γ selective agonists with protein-tyrosine phosphatase 1B inhibition

A novel series of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and (S)-2-[(2E,4E)-hexadienoyl]-7-(2-{5-methyl-2-[(1E)-5-methylhexen-1-yl]oxazol-4-yl}ethoxy)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (14i) was identified as a potent human peroxisome proliferator-activated receptor γ (PPARγ) selective agonist (EC(50)=0.03 μM) and human protein-tyrosine phosphatase 1B (PTP-1B) inhibitor (IC(50)=1.18 μM). C(max) after oral administration of 14i at 10mg/kg was 2.2 μg/ml (4.5 μM) in male SD rats. Repeated administration of 14i and rosiglitazone for 14 days dose-dependently decreased plasma glucose levels, ED(50)=4.3 and 23 mg/kg/day, respectively, in male KK-A(y) mice. In female SD rats, repeated administration of 14i at 12.5-100mg/kg/day for 28 days had no effect on the hematocrit value (Ht) and red blood cell count (RBC), while rosiglitazone significantly decreased them from 25mg/kg/day. In conclusion, 14i showed about a fivefold stronger hypoglycemic effect and fourfold or more weaker hemodilution effect than rosiglitazone, indicating that 14i is 20-fold or more safer than rosiglitazone. Compound 14i is a promising candidate for an efficacious and safe anti-diabetic drug targeting PPARγ and PTP-1B.     

Synthesis and SAR of benzyl and phenoxymethylene oxadiazole benzenesulfonamides as selective beta3 adrenergic receptor agonist antiobesity agents

Benzyl and phenoxymethylene substituted oxadiazoles are potent and orally bioavailable beta3 adrenergic receptor (AR) agonists. The 4-trifluormethoxy substituted 5-benzyl oxadiazole 5f has an EC50 of 8 nM in the beta3 AR agonist assay with 100-fold selectivity over beta1 and beta2 AR binding inhibition activity. Its oral bioavailability in dogs is 30 +/- 4%, with a half-life of 3.8 +/- 0.4 h. In the anesthetized rhesus, 5f evoked a dose-dependent glycerolemia (ED50Gly = 0.15 mg/kg). Under these conditions a heart rate increase of 15% was observed at a dose level of 10 mg/kg.     

L-663,536 (MK-886) (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2 - dimethylpropanoic acid), a novel, orally active leukotriene biosynthesis inhibitor

L-663,536 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2, 2-dimethylpropanoic acid) is a potent inhibitor of leukotriene (LT) biosynthesis in intact human polymorphonuclear leukocytes (PMN) (IC50, 2.5 nM). Similarly, L-663,536 inhibited A23187-induced LTB4 formation by rat peripheral blood and elicited PMN. At concentrations where inhibition of leukotriene biosynthesis occurred in human whole blood (1.1 microM), no effect was seen on cyclooxygenase or 12-lipoxygenase, an effect also observed in washed human platelets. The compound had no effect on rat or porcine 5-lipoxygenase indicating that L-663,536 is not a direct 5-lipoxygenase inhibitor. When administered in vivo L-663,536 was a potent inhibitor of antigen-induced dyspnea in inbred rats pretreated with methysergide (ED50, 0.036 mg/kg p.o.) and of Ascaris-induced bronchoconstriction in squirrel monkeys (1 mg/kg p.o.). The compound inhibited leukotriene biosynthesis in vivo in a rat pleurisy model (ED50, 0.2 mg/kg p.o.), an inflamed rat paw model (ED50, 0.8 mg/kg), a model of leukotriene excretion in rat bile following antigen provocation, and a model in the guinea-pig ear where leukotriene synthesis was induced by topical challenge with ionophore A23187 (ED50, 2.5 mg/kg p.o. and 0.6 micrograms topically). The results indicate that L-663,536 is a potent inhibitor of leukotriene biosynthesis both in vitro and in vivo indicating that the compound is suitable for studying the role of leukotrienes in a variety of pathological situations.     

Design, synthesis, and biological evaluation of linear 1-(4-, 3- or 2-methylsulfonylphenyl)-2-phenylacetylenes: a novel class of cyclooxygenase-2 inhibitors

A group of regioisomeric 1-(methylsulfonylphenyl)-2-phenylacetylenes possessing a COX-2 SO(2)Me pharmacophore at the para-, meta- or ortho-position of the C-1 phenyl ring, in conjunction with a C-2 phenyl or substituted-phenyl ring substituent (3-F, 3-OMe, 3-OH, 3-OAc, 4-Me), were designed for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. These target linear 1,2-diarylacetylenes were synthesized via a palladium-catalyzed Sonogashira cross-coupling reaction followed by oxidation of the respective 1-(methylthiophenyl)-2-phenylacetylene intermediate. In vitro COX-1/COX-2 isozyme inhibition structure-activity studies identified 1-(3-methylsulfonylphenyl)-2-(4-methylphenyl)acetylene (12d) as a potent COX-2 inhibitor (IC(50) = 0.32 microM) with a high COX-2 selectivity index (SI > 320) comparable to the reference compound rofecoxib (COX-2 IC(50) = 0.50 microM; COX-2 SI > 200). A molecular modeling study where (12d) was docked in the binding site of COX-2 showed that the MeSO(2) COX-2 pharmacophore was positioned in the vicinity of the secondary COX-2 binding site near Val(523). The 1-(4-methylsulfonylphenyl)-2-(3-acetoxyphenyl)acetylene (11f, COX-1 IC(50) = 1.00 microM; COX-2 IC(50) = 0.06 microM; COX-2 SI = 16.7) and 1-(3-methylsulfonylphenyl)-2-(3-acetoxyphenyl)acetylene (12f, COX-1 IC(50) = 6.5 microM; COX-2 IC(50) = 0.05 microM; COX-2 SI = 130) regioisomers exhibited comparable COX-2 inhibition, and moderately lower selective COX-2 selectivity, relative to the reference drug celecoxib (COX-1 IC(50) = 33.1 microM; COX-2 IC(50) = 0.07 microM; COX-2 SI = 472). The most potent anti-inflammatory agent 1-(3-methylsulfonylphenyl)-2-(4-methylphenyl)acetylene (12d) exhibited moderate oral anti-inflammatory activity (ED(50)= 129 mg/kg) at 3 h postdrug administration relative to the reference drug celecoxib (ED(50) = 10.8 mg/kg) in a carrageenan-induced rat paw edema assay. The structure-activity data acquired indicate that the acetylene moiety constitutes a suitable scaffold (template) to design novel acyclic 1,2-diarylacetylenes with selective COX-2, or dual COX-1/COX-2, inhibitory activities.     

Synthesis and anticonvulsant activity of new N-Mannich bases derived from 5-cyclopropyl-5-phenyl- and 5-cyclopropyl-5-(4-chlorophenyl)-imidazolidine-2,4-diones

Synthesis, physicochemical and anticonvulsant properties of new N-Mannich bases derived from 5-cyclopropyl-5-phenyl- and 5-cyclopropyl-5-(4-chlorophenyl)-imidazolidine-2,4-diones have been described. Initial anticonvulsant screening was performed using intraperitoneal (ip.) maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The neurotoxicity was determined applying the rotarod test. The in vivo results in mice showed that all compounds were effective especially in the MES screen. The quantitative evaluation after oral administration in rats showed that the most active was 5-cyclopropyl-5-phenyl-imidazolidine-2,4-dione (1) with ED(50) values of 5.76 mg/kg (MES) and 57.31 mg/kg (scPTZ). This molecule was more potent than phenytoin and ethosuximide which were used as reference antiepileptic drugs. Additionally compound 1 with ED(50) of 26.06 mg/kg in psychomotor seizure test (6-Hz) in mice showed comparable activity to new generation anticonvulsant - levetiracetam.     

Synthesis of celecoxib analogs that possess a N-hydroxypyrid-2(1H)one 5-lipoxygenase pharmacophore: biological evaluation as dual inhibitors of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity

A hitherto unknown class of celecoxib analogs was designed for evaluation as dual inhibitors of the 5-lipoxygenase/cyclooxygenase-2 (5-LOX/COX-2) enzymes. These compounds possess a SO(2)Me (11a), or SO(2)NH(2) (11b) COX-2 pharmacophore at the para-position of the N(1)-phenyl ring in conjunction with a 5-LOX N-hydroxypyrid-2(1H)one iron-chelating moiety in place of the celecoxib C-5 tolyl group. The title compounds 11a-b are weak inhibitors of the COX-1 and COX-2 isozymes (IC(50)=7.5-13.2 microM range). In contrast, the SO(2)Me (11a, IC(50)=0.35 microM), and SO(2)NH(2) (11b, IC(50)=4.9 microM), compounds are potent inhibitors of the 5-LOX enzyme comparing favorably with the reference drug caffeic acid (5-LOX IC(50)=3.47 microM). The SO(2)Me (11a, ED(50)=66.9 mg/kg po), and SO(2)NH(2) (11b, ED(50)=99.8 mg/kg po) compounds exhibited excellent oral anti-inflammatory (AI) activities being more potent than the non-selective COX-1/COX-2 inhibitor drug aspirin (ED(50)=128.9 mg/kg po) and less potent than the selective COX-2 inhibitor celecoxib (ED(50)=10.8 mg/kg po). The N-hydroxypyridin-2(1H)one moiety constitutes a novel pharmacophore for the design of cyclic hydroxamic mimetics capable of chelating 5-LOX iron for exploitation in the design of 5-LOX inhibitory AI drugs.     

Design, synthesis, and biological evaluation of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides as cyclooxygenase isozyme inhibitors

A group of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides, possessing either a F or a substituted-phenyl ring substituent (4-F, 2,4-F2, 4-SO2Me, 4-OCHMe2) attached to its C-4 or C-6 position, was prepared using a palladium-catalyzed Suzuki cross-coupling reaction for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. Although N-acetyl-3-carboxymethyl-6-fluorobenzenesulfonamide [14, COX-1 IC50 = 2.26 microM; COX-2 IC50 = 0.012 microM; COX-2 selectivity index (SI) = 188] and N-acetyl-3-carboxymethyl-6-(4-isopropoxyphenyl)benzenesulfonamide (20c, COX-1 IC50 >100 microM; COX-2 IC50 = 0.15 microM; COX-2 SI >667) exhibited potent in vitro COX-2 inhibitory activity and high COX-2 selectivity, both compounds were inactive anti-inflammatory agents in a carrageenan-induced rat paw edema assay. In contrast, the less potent and less selective COX-2 inhibitors N-acetyl-2-carboxymethyl-4-fluorobenzenesulfonamide (12, COX-1 IC50 = 4.25 microM; COX-2 IC50 = 0.978 microM; COX-2 SI = 4.3), N-acetyl-2-carboxymethyl-4-(2,4-difluorophenyl)benzenesulfonamide (17c, COX-1 IC50 = 1.02 microM; COX-2 IC50 = 1.00 microM; COX-2 SI = 1.02), and N-acetyl-3-carboxymethyl-6-(4-methanesulfonylphenyl)benzenesulfonamide (20e, COX-1 IC50 = 0.109 microM; COX-2 IC50 = 1.14 microM; COX-2 SI = 0.095) exhibited moderate anti-inflammatory activity where a 75 mg/kg oral dose reduced inflammation 26%, 14%, and 20%, respectively, at 3 h postdrug administration relative to the reference drug aspirin where a 50 mg/kg oral dose reduced inflammation by 25% at 3 h postdrug administration.     

Discriminative stimulus properties of the serotonergic agent 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)

Using a two-lever drug discrimination procedure, six rats were trained to discriminate 0.5 mg/kg of racemic 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) from saline. Once trained, the animals demonstrated a dose-related decrease in discriminative performance upon administration of lower doses of DOI (ED50 = 0.16 mg/kg). DOI-stimulus generalization occurred with the putative 5-HT2 agonist DOM (ED50 = 0.49 mg/kg), but not with the 5-HT1A agonist 8-OH DPAT, or the 5-HT1B agonist TFMPP. Furthermore, the DOI stimulus could be antagonized by pretreatment of the animals with the 5-HT2 antagonist ketanserin. The present results, coupled with the prior demonstration that DOI possesses a significant affinity and selectivity for 5-HT2 binding sites, suggest that the discriminative stimulus effects of DOI may be 5-HT2-mediated.     

Synthesis and anticonvulsant activity of new N-Mannich bases derived from 3-(2-fluorophenyl)- and 3-(2-bromophenyl)-pyrrolidine-2,5-diones. Part II

Synthesis and anticonvulsant activity of new N-Mannich bases of 3-(2-fluorophenyl)- and 3-(2-bromophenyl)-pyrrolidine-2,5-diones have been described. Initial anticonvulsant screening was performed in mice after intraperitoneal administration in the maximal electroshock seizure test (MES) and subcutaneous pentylenetetrazole seizures test (scPTZ). The neurotoxicity was determined applying the rotarod test. The in vivo results in mice showed that majority of compounds were effective in the MES test. Only seven molecules showed protection in the scPTZ test. The quantitative evaluation in the MES seizures after oral administration into rats showed that the most active were 1-[{4-(4-fluorophenyl)-piperazin-1-yl}-methyl]-3-(2-bromophenyl)-pyrrolidine-2,5-dione (14) with ED(50) of 7.4mg/kg and 1-[{4-(3-bromophenyl)-piperazin-1-yl}-methyl]-3-(2-bromophenyl)-pyrrolidine-2,5-dione (16) with ED(50) of 26.4mg/kg. These molecules were more potent and also less neurotoxic than phenytoin which was used as reference antiepileptic drug.     

4-Phenyl-4-[1H-imidazol-2-yl]-piperidine derivatives, a novel class of selective delta-opioid agonists

A novel series of 4-phenyl-4-[1H-imidazol-2-yl]-piperidine derivatives has been prepared and their synthesis described herein. In vitro affinities for delta-, mu-, and kappa-opioid receptors, as well as the functional activity in the [(35)S]GTPgammaS assay are reported. The most potent and selective delta-opioid agonist 18a exhibited a K(i) of 18 nM, and was >258-fold and 28-fold selective over mu- and kappa-receptors, respectively; the compound is a full agonist with an EC(50) value of 14 nM.     

Synthesis of new 4-[2-(4-methyl(amino)sulfonylphenyl)-5-trifluoromethyl-2H-pyrazol-3-yl]-1,2,3,6-tetrahydropyridines: a search for novel nitric oxide donor anti-inflammatory agents

A group of 4-[2-(4-methyl(amino)sulfonylphenyl)-5-trifluoromethyl-2H-pyrazol-3-yl]-1,2,3,6-tetrahydropyridines possessing a variety of substituents (Me, CO2Et, H, N=O) attached to the 1,2,3,6-tetrahydropyridyl N(1)-nitrogen atom were synthesized and evaluated as anti-inflammatory agents. Structure-activity relationship data showed that the N-methyl-1,2,3,6-tetrahydropyridyl moiety is a suitable bioisosteric replacement for the tolyl moiety in celecoxib. The most potent compound 4-[5-(1-methyl-1,2,3,6-tetrahydropyridin-4-yl)-3-trifluoromethylpyrazol-1-yl]benzenesulfonamide (ED(50)=61.2 mg/kg po) exhibited an anti-inflammatory activity between that of the reference drugs celecoxib (ED(50)=10.8 mg/kg po) and aspirin (ED(50)=128.7 mg/kg po). The synthesis of model hybrid nitric oxide donor N-diazen-1-ium-1,2-diolate derivatives of 4-[2-(4-methyl(amino)sulfonylphenyl)-5-trifluoromethyl-2H-pyrazol-3-yl]-1,2,3,6-tetrahydropyridines requires further investigation since the reaction of 1,2,3,6-tetrahydropyridines with nitric oxide furnished the undesired N-nitroso-1,2,3,6-tetrahydrohydropyridyl product rather than the desired N-diazen-1-ium-1,2-diolate-1,2,3,6-tetrahydropyridyl product.     

Blockade of N-methyl-D-aspartate induced convulsions by 1-aminocyclopropanecarboxylates

1-Aminocyclopropanecarboxylic acid is a potent and selective ligand for the glycine modulatory site on the N-methyl-D-aspartate receptor complex. This compound blocks (ED50 234 mg/kg) the convulsions and deaths produced by N-methyl-D-aspartate (125 mg/kg) in a dose dependent fashion. In contrast, 1-aminocyclopropanecarboxylic acid does not protect mice against convulsions induced by pentylenetetrazole (80 mg/kg), strychnine (2 mg/kg), bicuculline (6 mg/kg), or maximal electroshock (50 mA, 0.2 s), and does not impair motor performance on either a rotarod or horizontal wire at doses of up to 2 g/kg. The methyl- and ethyl- esters of 1-aminocyclopropanecarboxylic acid are 5- and 2.3-fold more potent, respectively, than the parent compound in blocking the convulsant and lethal effects of N-methyl-D-aspartate. However, these esters are several orders of magnitude less potent (IC50 greater than 40 microM) than 1-aminocyclopropanecarboxylic acid as inhibitors of strychnine-insensitive [3H] glycine binding, indicating that conversion to the parent compound may be required to elicit an anticonvulsant action. These findings suggest that 1-aminocyclopropanecarboxylates may be useful in the treatment of neuropathologies associated with excessive activation of N-methyl-D-aspartate receptor coupled cation channels.     

Human beta3 adrenergic receptor agonists containing imidazolidinone and imidazolone benzenesulfonamides

The cyclopentylpropylimidazolidinone L-766,892 is a potent beta3 AR agonist (EC50 5.7 nM, 64% activation) with 420- and 130-fold selectivity over binding to the beta1 and beta2 ARs, respectively. In anesthetized rhesus monkeys, L-766,892 elicited dose-dependent hyperglycerolemia (ED50 0.1 mg/kg) with minimal effects on heart rate.     

L-770,644: a potent and selective human beta3 adrenergic receptor agonist with improved oral bioavailability.

L-770,644 (9c) is a potent and selective agonist of the human beta3 adrenergic receptor (EC50 = 13 nM). It shows good oral bioavailability in both dogs and rats (%F = 27), and is a full agonist for glycerolemia in the rhesus monkey (ED50 = 0.21 mg/kg). Based on its desirable in vitro and in vivo properties, L-770,644 was chosen for further preclinical evaluation.     

Biological characterization of 10-(2-propynyl) estr-4-ene-3, 17-dione (MDL 18,962), an enzyme-activated inhibitor of aromatase

MDL 18,962 was shown to be a highly specific, potent (Ki = 3-4 nM), enzyme-activated inhibitor of aromatase with minimal intrinsic endocrine properties. The affinity of MDL 18,962 was higher for human and baboon placental aromatase than for rhesus placental or rodent ovarian aromatase. These species differences necessitated the development of a novel model of peripheral aromatase utilizing human enzyme. Human choriocarcinoma trophoblast xenografts in athymic nude mice were used for pharmacologic and pharmacokinetic evaluation of MDL 18,962. The ED50 for inhibition of aromatase activity in these trophoblast tumors at 6 h post-treatment was 1.4 mg/kg, s.c. and 3.0 mg/kg, oral. Preliminary results indicated that the ED50 for inhibition of peripheral aromatization of androgen by MDL 18,962 in female baboons was 0.01 mg/kg, i.v. and 4 mg/kg, oral.     

Synthesis and 5-hydroxytryptamine (5-HT) activity of 2,3,4,4a-tetrahydro-1H-pyrazino[1,2-a]quinoxalin-5-(6H)ones and 2,3,4,4a,5,6-hexahydro-1H-pyrazino[1,2-a]quinoxalines

A series of 2,3,4,4a-tetrahydro-1H-pyrazino[1,2-a]quinoxalin-5-(6H)ones and 2,3,4,4a,5,6-hexahydro-1H-pyrazino[1,2-a]quinoxalines was shown to exhibit 5-HT2C agonist binding and functional activity. Compound 21R inhibited food intake over 2 h in fasted, male Sprague Dawley rats with ED50 values of 2 mg/kg (i.p.) and 10 mg/kg (p.o.).     

3,7-Dimethyl-1-propargylxanthine: a potent and selective in vivo antagonist of adenosine analogs

3,7-Dimethyl-1-propargylxanthine (DMPX), a caffeine analog that exhibits in vitro selectivity for A2-adenosine receptors, compared to A1-adenosine receptors, has now been investigated with respect to in vivo potency and selectivity. DMPX potently and selectively blocked the actions of the potent A2 adenosine agonist, 5'-N-ethylcarboxamidoadenosine (NECA), in DBA/2 mice, compared to blockade of the same responses elicited by the selective A1-adenosine agonist, N6-cyclohexyladenosine (CHA). DMPX was 57-fold more potent versus NECA-induced hypothermia than versus CHA-induced hypothermia and 11-fold more potent versus NECA-induced behavioral depression than versus CHA-induced behavioral depression. The hypothermia is mediated by peripheral receptors, based on blockade by 8-(p-sulfophenyl)theophylline (PSPT), while the behavioral depression is centrally mediated, based on lack of blockade by PSPT. DMPX was 28- and 15-fold more potent than caffeine in blocking peripheral and central NECA-responses, respectively. DMPX was equipotent with caffeine versus CHA-induced hypothermia and 2.5-fold more potent than caffeine versus CHA-induced behavioral depression. The motor stimulating potency of DMPX (ED50 10 mumol/kg) was slightly greater than caffeine.     

Resolution, configurational assignment, and enantiopharmacology of 2-amino-3-[3-hydroxy-5-(2-methyl-2H- tetrazol-5-yl)isoxazol-4-yl]propionic acid, a potent GluR3- and GluR4-preferring AMPA receptor agonist

We have previously shown that (RS)-2-amino-3-[3-hydroxy-5-(2-methyl-2H-tetrazol-5-yl)isoxazol -4-yl] propionic acid (2-Me-Tet-AMPA) is a selective agonist at (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors, markedly more potent than AMPA itself, whereas the isomeric compound 1-Me-Tet-AMPA is essentially inactive. We here report the enantiopharmacology of 2-Me-Tet-AMPA in radioligand binding and cortical wedge electrophysiological assay systems, and using cloned AMPA (GluR1-4) and kainic acid (KA) (GluR5, 6, and KA2) receptor subtypes expressed in Xenopus oocytes. 2-Me-Tet-AMPA was resolved using preparative chiral HPLC. Zwitterion (-)-2-Me-Tet-AMPA was assigned the (R)-configuration based on an X-ray crystallographic analysis supported by the elution order of (-)- and (+)-2-Me-Tet-AMPA using four different chiral HPLC columns and by circular dichroism spectra. None of the compounds tested showed detectable affinity for N-methyl-D-aspartic acid (NMDA) receptor sites, and (R)-2-Me-Tet-AMPA was essentially inactive in all of the test systems used. Whereas (S)-2-Me-Tet-AMPA showed low affinity (IC(50) = 11 microM) in the [(3)H]KA binding assay, it was significantly more potent (IC(50) = 0.009 microM) than AMPA (IC(50) = 0.039 microM) in the [(3)H]AMPA binding assay, and in agreement with these findings, (S)-2-Me-Tet-AMPA (EC(50) = 0.11 microM) was markedly more potent than AMPA (EC(50) = 3.5 microM) in the electrophysiological cortical wedge model. In contrast to AMPA, which showed comparable potencies (EC(50) = 1.3-3.5 microM) at receptors formed by the AMPA receptor subunits (GluR1-4) in Xenopus oocytes, more potent effects and a substantially higher degree of subunit selectivity were observed for (S)-2-Me-Tet-AMPA: GluR1o (EC(50) = 0.16 microM), GluR1o/GluR2i (EC(50) = 0.12 microM), GluR3o (EC(50) = 0.014 microM) and GluR4o (EC(50) = 0.009 microM). At the KA-preferring receptors GluR5 and GluR6/KA2, (S)-2-Me-Tet-AMPA showed much weaker agonist effects (EC(50) = 8.7 and 15.3 microM, respectively). It is concluded that (S)-2-Me-Tet-AMPA is a subunit-selective and highly potent AMPA receptor agonist and a potentially useful tool for studies of physiological AMPA receptor subtypes.     

Novel 6-aryl-1,4-dihydrobenzo[d]oxazine-2-thiones as potent,selective, and orally active nonsteroidal progesterone receptor agonists

The functional activity of 6-aryl benzoxazinone-based progesterone (PR) antagonists changed to PR agonism when the 2-carbonyl group was replaced by a 2-thiocarbonyl moiety. Based on this finding novel 6-aryl benzoxazine-2-thiones were synthesized and evaluated as PR agonists in various in vitro and in vivo assays. Several analogues had sub-nanomolar in vitro potency and showed excellent oral activities in rats. Compounds 15 and 29 had similar potencies to medroxyprogesterone acetate (MPA) in the in vitro T47D alkaline phosphatase assay and in vivo rat decidualization model. In contrast to MPA, 29 was highly selective (>500-fold) for PR over glucocorticoid and androgen receptors.