Effect of structural modification of enol-carboxamide-type nonsteroidal antiinflammatory drugs on COX-2/COX-1 selectivity

Clinically approved small-molecule drugs for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a persistent autoimmune ailment that is typified by the development of pannus, proliferation of synovial lining cells, microvascular neogenesis, infiltration of interstitial inflammatory cells, and destruction of cartilage and bone tissue. The disease not only imposes physical pain and economic burden on patients, but also results in a significant decline in their quality of life, rendering it a leading cause of disability. General treatment and drugs are commonly employed to alleviate the condition and symptoms of RA. Cyclooxygenase (COX), janus kinase (JAK), glucocorticoid receptor (GR) et al. have been identified as the main therapeutic targets for RA. This article provides a comprehensive review of the clinical applications and synthetic routes of 26 representative drugs for the treatment of RA, with the aim of facilitating the discovery of more effective new drugs for the treatment of this debilitating disease.

Do NSAIDs used prior to standard inferior alveolar nerve blocks improve the analgesia of mandibular molars with irreversible pulpitis? An umbrella review

INTRODUCTION

The aim of the present umbrella review was to answer the following question: "Does the use of NSAIDs as premedication increase the efficacy of the standard inferior alveolar nerve block on teeth with symptomatic irreversible pulpitis?"

MATERIAL AND METHODS

Systematic reviews with and without meta-analyses that evaluated the influence of premedication on anesthetic efficacy of the inferior alveolar nerve in symptomatic irreversible pulpitis of mandibular molars were searched in six electronic databases (MEDLINE/PubMed, Scopus, Web of Science, Cochrane Library, EMBASE, and Grey Literature Reports), without the restriction of language or year of publication. A Measurement Tool to Assess systematic Reviews (AMSTAR 2) was used to evaluate the quality of the included studies.

RESULTS

Twelve systematic reviews were included. Only one did not perform a meta-analysis. The AMSTAR 2 overall confidence ranged from very low to high. In general, the main findings of the systematic reviews were that non-steroidal anti-inflammatory drugs (e.g., ibuprofen, oxicam, diclofenac, association of ibuprofen with acetaminophen, and ketorolac) increased the success rate of the inferior alveolar nerve block.

CONCLUSIONS

From the "very low" to "high"-quality evidence available, this umbrella review concluded that NSAIDs as premedication acts through cyclooxygenase pathways and block the synthesis of specific prostaglandins that complicate the mechanism of action of the anesthesia, improving its success rate.

CLINICAL RELEVANCE

Non-steroidal anti-inflammatory drugs can increase the success rate of the anesthetic technique of inferior alveolar nerve block efficacy in situations of mandibular molars with symptomatic irreversible pulpitis.

Application and synthesis of thiazole ring in clinically approved drugs

The development of heterocyclic derivatives has progressed considerably over the past few decades, and many new agents of synthetic and natural origin have been produced. Among heterocyclic compounds, thiazole is a unique five-membered heterocyclic motif characterized by nitrogen and sulfur atoms, which is widely used as an important core skeleton in a variety of pharmaceutically important compounds due to their diverse biological activities, such as antibacterial, antivirus, and antifungal. To the best of our knowledge, more than 90 thiazole-containing derivatives have been currently under clinical investigation, and some thiazole analogs have been approved to treat various diseases. As the potentially privileged scaffolds, thiazole derivatives can be further extensively explored to search for new drugs characterized by improved therapeutic efficacy and similar biological targets. This review aims to outline the applications and synthetic routes of some representative thiazole-containing drugs approved in the clinic, which may guide medicinal researchers to rationally design more effective thiazole-containing drug candidates.

Synthesis of Isoquinolone, 1,2-Benzothiazine, and Naphtho[1',2':4,5]imidazo[1,2-a]pyridine Derivatives via Rhodium(III)-Catalyzed (4 + 2) Annulation

In this study, we report a novel and efficient synthetic method to construct isoquinolone scaffold via the Rh(III)-catalyzed (4 + 2) annulation of benzamide with an unreported coupling reagent methyl 2-chloroacrylate. Accordingly, other valuable 1,2-benzothiazine and naphtho[1',2':4,5]imidazo[1,2-a]pyridine derivatives are also obtained through a similar synthetic protocol. Thus, our developed method is highlighted by high yield and reaction versatility.

Rhodium(III)-catalyzed cascade C-H functionalization/annulation of sulfoximines with iodonium ylides for the synthesis of cyclohexanone-1,2-benzothiazines

A highly efficient Rh(III)-catalyzed cascade C-H activation/annulation of sulfoximines with iodonium ylides under metal-oxidant-free conditions has been reported. The fused cyclohexanone-1,2-benzothiazine scaffold is readily achieved with a one-pot process in this reaction. This protocol exhibits good functional group tolerance and moderate to excellent yields. Additionally, the olefination of the target product illustrates the promising usefulness of this strategy.

Structurally Diverse Synthesis of Five-, Six-, and Seven-Membered Benzosultams through Electrochemical Cyclization

We have developed a metal- and oxidant-free approach to structurally diverse synthesis of benzosultams from aryl sulfonamides through an electrochemical cyclization. Upon variation of the ortho substituent on aryl sulfonamides, five-, six-, and seven-membered benzosultams were efficiently assembled in an atom- and resource-economic manner. The generality of the process is demonstrated by the formation of five- to seven-membered cyclic products from 42 substrates bearing substituents with different electronic effects and steric hindrance.

Assembly of Benzothiazine and Triazole in a Single Molecular Entity: Synthesis of -Oxicam Derived Novel Molecules as Potential Antibacterial/ Anti-cancer Agents

BACKGROUND

Benzothiazine derivatives, because of their various biological activities have attracted particular attention in Med Chem and drug discovery efforts. The synthetic modifications of 1,2-benzothiazine 1,1-dioxides have been undertaken in order to explore and identify novel compounds or new analogues possessing promising biological activities. In our effort we have designed -oxicam derived bezothiazine-1,2,3-triazole derivatives as potential antibacterial agents.

METHODS

These compounds were synthesized via a multi-step sequence involving the Cu catalyzed azide- alkyne cycloaddition (CuAAC) as a key step. The CuAAC proceeded at room temperature in DMF to afford 26 novel molecules in good (70-90%) yields.

RESULTS

All these compounds were tested for their antibacterial properties against four strains of bacterial microorganisms and subsequently cytotoxic properties against lung and colon cancer cell lines. The compound 4e showed activities against majority of the bacterial species used (nearly comparable to amoxicillin, ciprofloxacin and ofloxacin against P. vulgaris) whereas 4d and 4f showed cytotoxicities selective towards cancer cells.

CONCLUSION

The present bezothiazine-1,2,3-triazole framework represents a new template for the identification of novel and potent antibacterial/anticancer agents.

Designing around Structural Alerts in Drug Discovery

Cumulative research over several decades has implicated the involvement of reactive metabolites in many idiosyncratic adverse drug reactions (IADRs). Consequently, "avoidance" strategies have been inserted into drug discovery paradigms, which include the exclusion of structural alerts and possible termination of reactive metabolite-positive compounds. Several noteworthy examples where reactive metabolite-related liabilities have been resolved through structure-metabolism studies are presented herein. Considerable progress has also been made in addressing the limitations of the avoidance strategy and further refining the process of managing reactive metabolite issues in drug development. These efforts primarily stemmed from the observation that numerous drugs, which contain structural alerts and/or form reactive metabolites, are devoid of ADRs. The Perspective also dwells into an analysis of the structural alert/reactive metabolite concept with a discussion of risk mitigation tactics to support the progression of reactive metabolite-positive drug candidates.

Classification of Cyclooxygenase-2 Inhibitors Using Support Vector Machine and Random Forest Methods

This work reports the classification study conducted on the biggest COX-2 inhibitor data set so far. Using 2925 diverse COX-2 inhibitors collected from 168 pieces of literature, we applied machine learning methods, support vector machine (SVM) and random forest (RF), to develop 12 classification models. The best SVM and RF models resulted in MCC values of 0.73 and 0.72, respectively. The 2925 COX-2 inhibitors were reduced to a data set of 1630 molecules by removing intermediately active inhibitors, and 12 new classification models were constructed, yielding MCC values above 0.72. The best MCC value of the external test set was predicted to be 0.68 by the RF model using ECFP_4 fingerprints. Moreover, the 2925 COX-2 inhibitors were clustered into eight subsets, and the structural features of each subset were investigated. We identified substructures important for activity including halogen, carboxyl, sulfonamide, and methanesulfonyl groups, as well as the aromatic nitrogen atoms. The models developed in this study could serve as useful tools for compound screening prior to lab tests.

SAR and QSAR models of cyclooxygenase-1 (COX-1) inhibitors

Cyclooxygenase-1 (COX-1) is one isoform of COX, and it is a main target of nonsteroidal anti-inflammatory drugs (NSAIDs). It is important to develop efficient and selective COX-1 inhibitors. In this work, 12 classification models for 1530 cyclooxygenase-1 (COX-1) inhibitors were built by support vector machine (SVM), decision tree (DT) and random forest (RF) methods. The best classification model (model 1A) was built by SVM with MACCS fingerprints. The classification accuracies for the training and test sets were 99.67% and 97.39%, respectively. The Matthews correlation coefficient (MCC) of the test set was 0.94. We also divided the 1530 COX-1 inhibitors into nine subsets according to their different scaffolds using Kohonen's self-organizing map (SOM). In addition, six quantitative structure-activity relationship (QSAR) models for 181 COX-1 inhibitors whose IC₅₀ were measured by enzyme immunoassay were built by multiple linear regression (MLR) and SVM. The best QSAR model (model 5A) was built by SVM with CORINA Symphony descriptors. The correlation coefficients of the training and test sets are 0.93 and 0.84, respectively. The models built in this study can be obtained from the authors.

Synthesis, characterization, monoamine oxidase inhibition, molecular docking and dynamic simulations of novel 2,1-benzothiazine-2,2-dioxide derivatives

In this research work, we report the synthesis and biological evaluation of two new series of 1-benzyl-4-(benzylidenehydrazono)-3,4-dihydro-1H-benzo[c] [1,2]thiazine 2,2-dioxides and 1-benzyl-4-((1-phenylethylidene)hydrazono)-3,4-dihydro-1H-benzo[c][1,2]thiazine 2,2-dioxides. The synthetic plan involves the mesylation of methyl anthranilate with subsequent N-benzylation of the product. The methyl 2-(N-benzylmethylsulfonamido)benzoate was subjected to cyclization reaction in the presence of sodium hydride to obtain 1-benzyl-1H-benzo[c][1,2]thiazin-4(3H)-one 2,2-dioxide which was treated with hydrazine hydrate to get corresponding hydrazone precursor. Finally, the titled compounds were obtained by reaction of hydrazone with various substituted aldehydes and ketones. The synthesized derivatives were subjected to carry out their inhibition activities against monoamine oxidases along with modelling investigations to evaluate their binding interactions and dynamic stability during the docking studies. The inhibition profile of potent compounds was found as competitive for both the isozymes. The compounds were more selective inhibitors of MAO-A as compared to MAO-B. Moreover, drug likeness profile of the derivatives was evaluated to have an additional insight into the physicochemical properties. The molecular dynamic simulations predicted the behaviour of amino acids with the active site residues.

Synthesis and Antimicrobial Activity of 1,2-Benzothiazine Derivatives

A number of 1,2-benzothiazines have been synthesized in a three-step process. Nine chalcones 1–9 bearing methyl, fluoro, chloro and bromo substituents were chlorosulfonated with chlorosulfonic acid to generate the chalcone sulfonyl chlorides 10–18. These were converted to the dibromo compounds 19–27 through reaction with bromine in glacial acetic acid. Compounds 19–27 were reacted with ammonia, methylamine, ethylamine, aniline and benzylamine to generate a library of 45 1,2-benzothiazines 28–72. Compounds 28–72 were evaluated for their antimicrobial activity using broth microdilution techniques against two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative bacteria (Proteus vulgaris and Salmonella typhimurium). The results demonstrated that none of the compounds showed any activity against Gram-negative bacteria P. vulgaris and S. typhimurium; however, compounds 31, 33, 38, 43, 45, 50, 53, 55, 58, 60, 63 and 68 showed activity against Gram-positive bacteria Bacillus subtilis and Staphylococcous aureus. The range of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was 25–600 µg/mL, though some of the MIC and MBC concentrations were high, indicating weak activity. Structure activity relationship studies revealed that the compounds with a hydrogen atom or an ethyl group on the nitrogen of the thiazine ring exerted antibacterial activity against Gram-positive bacteria. The results also showed that the compounds where the benzene ring of the benzoyl moiety contained a methyl group or a chlorine or bromine atom in the para position showed higher antimicrobial activity. Similar influences were identified where either a bromine or chlorine atom was in the meta position.

Synthesis of novel 1-substituted triazole linked 1,2-benzothiazine 1,1-dioxido propenone derivatives as potent anti-inflammatory agents and inhibitors of monocyte-to-macrophage differentiation

Compounds12g,12iand12lmodulate pro-inflammatory cytokine production by inhibiting monocyte differentiation.

Oxicams, a class of nonsteroidal anti-inflammatory drugs and beyond

Oxicams are a class of nonsteroidal anti-inflammatory drugs (NSAIDs) structurally related to the enolic acid class of 4-hydroxy-1,2-benzothiazine carboxamides. They are used clinically to treat both acute and chronic inflammation by inhibiting the activity of the two cyclooxygenase (COX) isoforms, COX-1 and COX-2. Oxicams are structurally distinct from all other NSAIDs, exhibiting a novel binding pose in the COX active site. The 4-hydroxyl group on the thiazine ring partners with Ser-530 via hydrogen bonding while two coordinated water molecules mediate a polar interaction between the oxicam and COX. The rotation of Leu-531 in the complex opens a new pocket, which is not used for binding other NSAIDs to the enzyme. This structure provides the basis for understanding documented structure-activity relationships within the oxicam class. In addition, from the oxicam template, a series of potent microsomal prostaglandin E synthase-1 (mPGES-1) inhibitors represents a new direction for drug development. Here, we review the major route of oxicam synthesis and structure-activity for COX inhibition, as well as recent advances in oxicam-mediated mPGES-1 inhibition.

Oxicams bind in a novel mode to the cyclooxygenase active site via a two-water-mediated H-bonding Network

Oxicams are widely used nonsteroidal anti-inflammatory drugs (NSAIDs), but little is known about the molecular basis of the interaction with their target enzymes, the cyclooxygenases (COX). Isoxicam is a nonselective inhibitor of COX-1 and COX-2 whereas meloxicam displays some selectivity for COX-2. Here we report crystal complexes of COX-2 with isoxicam and meloxicam at 2.0 and 2.45 angstroms, respectively, and a crystal complex of COX-1 with meloxicam at 2.4 angstroms. These structures reveal that the oxicams bind to the active site of COX-2 using a binding pose not seen with other NSAIDs through two highly coordinated water molecules. The 4-hydroxyl group on the thiazine ring partners with Ser-530 via hydrogen bonding, and the heteroatom of the carboxamide ring of the oxicam scaffold interacts with Tyr-385 and Ser-530 through a highly coordinated water molecule. The nitrogen atom of the thiazine and the oxygen atom of the carboxamide bind to Arg-120 and Tyr-355 via another highly ordered water molecule. The rotation of Leu-531 in the structure opens a novel binding pocket, which is not utilized for the binding of other NSAIDs. In addition, a detailed study of meloxicam·COX-2 interactions revealed that mutation of Val-434 to Ile significantly reduces inhibition by meloxicam due to subtle changes around Phe-518, giving rise to the preferential inhibition of COX-2 over COX-1.

1,5-Rhodium shift in rearrangement of N-arenesulfonylazetidin-3-ols into benzosultams

Benzosultams are synthesized in an enantiopure form starting from α-amino acids through a rhodium-catalyzed rearrangement reaction of N-arenesulfonylazetidin-3-ols. Mechanistically, this reaction involves C-C bond cleavage by β-carbon elimination and C-H bond cleavage by a 1,5-rhodium shift.

Pharmacokinetics and milk secretion of gabapentin and meloxicam co-administered orally in Holstein-Friesian cows

Management of neuropathic pain in dairy cattle could be achieved by combination therapy of gabapentin, a GABA analog and meloxicam, an nonsteroidal anti-inflammatory drug. This study was designed to determine specifically the depletion of these drugs into milk. Six animals received meloxicam at 1 mg/kg and gabapentin at 10 mg/kg, while another group (n=6) received meloxicam at 1 mg/kg and gabapentin at 20 mg/kg. Plasma and milk drug concentrations were determined over 7 days postadministration by HPLC/MS followed by noncompartmental pharmacokinetic analyses. The mean (±SD) plasma C(max) and T(max) for meloxicam (2.89±0.48 μg/mL and 11.33±4.12 h) were not much different from gabapentin at 10 mg/kg (2.87±0.2 μg/mL and 8±0 h). The mean (±SD) milk C(max) for meloxicam (0.41±80.16 μg/mL) was comparable to gabapentin at 10 mg/kg (0.63±0.13 μg/mL and 12±6.69 h). The mean plasma and milk C(max) for gabapentin at 20 mg/kg p.o. were almost double the values at 10 mg/kg. The mean (±SD) milk to plasma ratio for meloxicam (0.14±0.04) was lower than for gabapentin (0.23±0.06). The results of this study suggest that milk from treated cows will have low drug residue concentration soon after plasma drug concentrations have fallen below effective levels.

Structural alert/reactive metabolite concept as applied in medicinal chemistry to mitigate the risk of idiosyncratic drug toxicity: a perspective based on the critical examination of trends in the top 200 drugs marketed in the United States

Because of a preconceived notion that eliminating reactive metabolite (RM) formation with new drug candidates could mitigate the risk of idiosyncratic drug toxicity, the potential for RM formation is routinely examined as part of lead optimization efforts in drug discovery. Likewise, avoidance of "structural alerts" is almost a norm in drug design. However, there is a growing concern that the perceived safety hazards associated with structural alerts and/or RM screening tools as standalone predictors of toxicity risks may be over exaggerated. In addition, the multifactorial nature of idiosyncratic toxicity is now well recognized based upon observations that mechanisms other than RM formation (e.g., mitochondrial toxicity and inhibition of bile salt export pump (BSEP)) also can account for certain target organ toxicities. Hence, fundamental questions arise such as: When is a molecule that contains a structural alert (RM positive or negative) a cause for concern? Could the molecule in its parent form exert toxicity? Can a low dose drug candidate truly mitigate metabolism-dependent and -independent idiosyncratic toxicity risks? In an effort to address these questions, we have retrospectively examined 68 drugs (recalled or associated with a black box warning due to idiosyncratic toxicity) and the top 200 drugs (prescription and sales) in the United States in 2009 for trends in physiochemical characteristics, daily doses, presence of structural alerts, evidence for RM formation as well as toxicity mechanism(s) potentially mediated by parent drugs. Collectively, our analysis revealed that a significant proportion (∼78-86%) of drugs associated with toxicity contained structural alerts and evidence indicating that RM formation as a causative factor for toxicity has been presented in 62-69% of these molecules. In several cases, mitochondrial toxicity and BSEP inhibition mediated by parent drugs were also noted as potential causative factors. Most drugs were administered at daily doses exceeding several hundred milligrams. There was no obvious link between idiosyncratic toxicity and physicochemical properties such as molecular weight, lipophilicity, etc. Approximately half of the top 200 drugs for 2009 (prescription and sales) also contained one or more alerts in their chemical architecture, and many were found to be RM-positive. Several instances of BSEP and mitochondrial liabilities were also noted with agents in the top 200 category. However, with relatively few exceptions, the vast majority of these drugs are rarely associated with idiosyncratic toxicity, despite years of patient use. The major differentiating factor appeared to be the daily dose; most of the drugs in the top 200 list are administered at low daily doses. In addition, competing detoxication pathways and/or alternate nonmetabolic clearance routes provided suitable justifications for the safety records of RM-positive drugs in the top 200 category. Thus, while RM elimination may be a useful and pragmatic starting point in mitigating idiosyncratic toxicity risks, our analysis suggests a need for a more integrated screening paradigm for chemical hazard identification in drug discovery. Thus, in addition to a detailed assessment of RM formation potential (in relationship to the overall elimination mechanisms of the compound(s)) for lead compounds, effects on cellular health (e.g., cytotoxicity assays), BSEP inhibition, and mitochondrial toxicity are the recommended suite of assays to characterize compound liabilities. However, the prospective use of such data in compound selection will require further validation of the cellular assays using marketed agents. Until we gain a better understanding of the pathophysiological mechanisms associated with idiosyncratic toxicities, improving pharmacokinetics and intrinsic potency as means of decreasing the dose size and the associated "body burden" of the parent drug and its metabolites will remain an overarching goal in drug discovery.

Changes in Tissue Substance P Levels in Patients With Carpal Tunnel Syndrome

BACKGROUND:

Although carpal tunnel syndrome (CTS) is the most common entrapment neuropathy in adults, its etiology is not completely known. Chronic inflammation, fibrosis of the transverse carpal ligament (TCL), and altered sensory response contribute to the symptoms.

OBJECTIVE:

Because substance P (SP) is known to be involved in neuropathic pain, chronic inflammation, and fibrosis, the present study evaluated changes in SP levels in patients with CTS.

METHODS:

TCL, median nerve adventitia, and synovial connective tissue of the middle flexor digitorum superficialis tendon samples from patients (n = 42) with CTS and healthy control subjects (n = 13) who were operated on for hand wounds were obtained at surgery. A group of these patients with CTS (n = 9) had received meloxicam treatment for 10 days before surgery. A 2-step acetic acid extraction was used to determine changes in SP levels in free nerve endings (neuronal) and in nonneuronal cells.

RESULTS:

Changes in SP levels were observed in both neuronal and nonneuronal tissues. SP levels increased in extracts of the TCL and synovial connective tissue of the middle flexor digitorum superficialis tendon but not in the median nerve adventitia of patients with CTS. Meloxicam pretreatment increased SP levels in nonneuronal components of the TCL.

CONCLUSION:

These findings suggest that SP contributes to the pain and inflammation associated with CTS. Further studies are required to evaluate the therapeutic potentials of SP receptor (NK1R) antagonists in CTS.

Handling reactive metabolite positives in drug discovery: What has retrospective structure-toxicity analyses taught us?

Because of the inability to predict and quantify the risk of idiosyncratic adverse drug reactions (IADRs) and because reactive metabolites (RMs) as opposed to the parent molecules from which they are derived are thought to be responsible for the pathogenesis of some IADRs, procedures (RM trapping/covalent binding) are being incorporated into the discovery screening funnel early-on to assess the risk of RM formation. Utility of the methodology in structure-toxicity relationships and scope in abrogating RM formation at the lead optimization stage are discussed in this article. Interpretation of the output from RM assessment assays, however, is confounded by the fact that many successfully marketed drugs are false positives. Therefore, caution must be exercised in deprioritizing a compound based on a positive result, so that the development of a useful and potentially profitable compound won't be unnecessarily halted. Risk mitigation strategies (e.g., competing detoxication pathways, low daily dose, etc.) when selecting RM positives for clinical development are also reviewed.

Structure-based design, synthesis, and biological evaluation of indomethacin derivatives as cyclooxygenase-2 inhibiting nitric oxide donors

Indomethacin, a nonselective cyclooxygenase (COX) inhibitor, was modified in three distinct regions in an attempt both to increase cyclooxygenase-2 (COX-2) selectivity and to enhance drug safety by covalent attachment of an organic nitrate moiety as a nitric oxide donor. A human whole-blood COX assay shows the modifications on the 3-acetic acid part of the indomethacin yielding an amide-nitrate derivative 32 and a sulfonamide-nitrate derivative 61 conferred COX-2 selectivity. Along with their respective des-nitrate analogs, for example, 31 and 62, the nitrates 32 and 61 were effective antiinflammatory agents in the rat air-pouch model. After oral dosing, though, only 32 increased nitrate and nitrite levels in rat plasma, indicating that its nitrate tether served as a nitric oxide donor in vivo. In a rat gastric injury model, examples 31 and 32 both show a 98% reduction in gastric lesion score compared to that of indomethacin. In addition, the nitrated derivative 32 inducing 85% fewer gastric lesions when coadministered with aspirin as compared to the combination of aspirin and valdecoxib.

A remarkable accelerating effect of Ag-salt on intramolecular cyclization of o-(1-alkynyl)benzenesulfonamides

Herein, we report transition metal-catalyzed intramolecular cyclization of o-(1-alkynyl)benzenesulfonamides to afford 3-substituted benzothiazines regioselectively via a C-N bond forming reaction and Cu-catalyzed sequential C-N and C-C bond formation leading to the corresponding 3,4-disubstituted derivatives.

Versatile access to C-4-substituted 2-amino-1,3-azoles from hydropyridines in oxidative conditions

[Chemical reaction: see text] Various substituted 2-aminotetrahydroazolopyridines and 2-aminohexahydroazolopyridines have been prepared by bromine-mediated addition of protected guanidine or urea to hydropyridine derivatives. The pH-dependent regioselective cleavage of the resulting aminal function led to the 2-aminoazole products III. The yields of the bicycles of type II, and their conversion into azoles III depends on the electronic properties of the substituents on the nitrogen of the tetrahydopyridine.

Evaluation of 2 celecoxib derivatives: analgesic effect and selectivity to cyclooxygenase-2/1

AIM

To evaluate the analgesic effects of 2 celecoxib derivatives and their inhibitory effects on cyclooxygenase (COX).

METHODS

Four antinociceptive assays were used: the acetic acid-induced writhing test, hot plate test, hot tail-flick test and formalin test. Three doses were used in the analgesic assays and ED50 values were calculated. For the selectivity assay, macrophages were incubated with test compounds at various concentrations and then stimulated with calcimycin or lipopolysaccharide (LPS). The amounts of 6-keto-prostaglandin F1alpha(6-keto-PGF1alpha) and prostaglandin E2 (PGE2) in the supernatant were examined by radioimmunoassay (RIA). The selectivity of the test compounds was expressed as the IC(50,COX-1)/IC(50,COX-2) value.

RESULTS

Celecoxib and its 2 derivatives had a significant analgesic effect. The ED50 values of celecoxib, PC-406 and PC-407 were 94.2, 67.9, and 63.3 mg/kg, respectively, for the acetic acid-induced writhing test; 104.7, 89.1, and 30.0 mg/kg, respectively, for the hot tail-flick response test; 60.7, 56.7, and 86.2 mg/kg, respectively, for the hot plate response test; 67.1, 55.8, and 68.8 mg/kg, respectively, for the formalin-induced response. That is, the ED50 of PC-406 was the lowest for the formalin and hot plate tests, which focus on changes above the spinal cord level; however, the ED50 of PC-407 was lowest for the tail-flick and writhing tests, which focus on changes at the spinal cord level. Celecoxib and PC-407 inhibited COX-1 with IC50 values of 39.8 and 27.5 nmol/L, respectively. PC-406 inhibited COX-1 with an IC50 value of more than 1000 nmol/L. The IC50 values for the effect of celecoxib, PC-406 and PC-407 on COX-2 were 4.8, 8.9, and 1.9 nmol/L respectively. The IC(50, COX-1)/IC(50,COX-2) ratios for celecoxib and PC-407 were 8.3 and 14.4, respec-tively. For PC-406, the ratio was greater than 112.2.

CONCLUSION

Derivatives of celecoxib via substitution with an isopropyl or naphthyl group at the 5 position in the pyrazole ring still have analgesic effects and the ability to selectively inhibit COX-2. Substitution with a naphthyl group may have more effect on the peripheral pain pathway, whereas substitution with an isopropyl group may have more effect on the central pain pathway. This phenomenon occurs partly because substitution with an isopropyl group is more beneficial for COX-2 selectivity than is substitution with a naphthyl group.