Synthesis and antiinflammatory activities of 3-(3,5-di-tert-butyl-4-hydroxybenzylidene)pyrrolidin-2-ones

In Silico Analysis: Anti-Inflammatory and α-Glucosidase Inhibitory Activity of New α-Methylene-γ-Lactams

The research about α-methylene-γ-lactams is scarce; however, their synthesis has emerged in recent years mainly because they are isosters of α-methylene-γ-lactones. This last kind of compound is structurally most common in some natural products' nuclei, like sesquiterpene lactones that show biological activity such as anti-inflammatory, anticancer, antibacterial, etc., effects. In this work, seven α-methylene-γ-lactams were evaluated by their inflammation and α-glucosidase inhibition. Thus, compounds 3-methylene-4-phenylpyrrolidin-2-one (1), 3-methylene-4-(p-tolyl)pyrrolidin-2-one (2), 4-(4-chlorophenyl)-3-methylenepyrrolidin-2-one (3), 4-(2-chlorophenyl)-3-methylenepyrrolidin-2-one (4), 5-ethyl-3-methylene-4-phenylpyrrolidin-2-one (5), 5-ethyl-3-methylene-4-(p-tolyl)pyrrolidin-2-one (6) and 4-(4-chlorophenyl)-5-ethyl-3-methylenepyrrolidin-2-one (7) were evaluated via in vitro α-glucosidase assay at 1 mM concentration. From this analysis, 7 exerts the best inhibitory effect on α-glucosidase compared with the vehicle, but it shows a low potency compared with the reference drug at the same dose. On the other side, inflammation edema was induced using TPA (12-O-tetradecanoylphorbol 13-acetate) on mouse ears; compounds 1-7 were tested at 10 µg/ear dose. As a result, 1, 3, and 5 show a better inhibition than indomethacin, at the same doses. This is a preliminary report about the biological activity of these new α-methylene-γ-lactams.

Synthesis and In Vitro Biological Evaluation of p-Carborane-Based Di-tert-butylphenol Analogs

Targeting inflammatory mediators and related signaling pathways may offer a rational strategy for the treatment of cancer. The incorporation of metabolically stable, sterically demanding, and hydrophobic carboranes in dual cycloxygenase-2 (COX-2)/5-lipoxygenase (5-LO) inhibitors that are key enzymes in the biosynthesis of eicosanoids is a promising approach. The di-tert-butylphenol derivatives R-830, S-2474, KME-4, and E-5110 represent potent dual COX-2/5-LO inhibitors. The incorporation of p-carborane and further substitution of the p-position resulted in four carborane-based di-tert-butylphenol analogs that showed no or weak COX inhibition but high 5-LO inhibitory activities in vitro. Cell viability studies on five human cancer cell lines revealed that the p-carborane analogs R-830-Cb, S-2474-Cb, KME-4-Cb, and E-5110-Cb exhibited lower anticancer activity compared to the related di-tert-butylphenols. Interestingly, R-830-Cb did not affect the viability of primary cells and suppressed HCT116 cell proliferation more potently than its carbon-based R-830 counterpart. Considering all the advantages of boron cluster incorporation for enhancement of drug biostability, selectivity, and availability of drugs, R-830-Cb can be tested in further mechanistic and in vivo studies.

A Rare Alder-ene Cycloisomerisation of 1,6-Allenynes

Thermally induced cycloisomerization reactions of 1,6-allenynes gives α-methylene-γ-lactams via intramolecular Alder-ene reactions. The mechanism is supported by computational and deuterium labeling studies. This thermal, non-radical method enables the discovery of a hitherto unknown route that proceeds via a divergent mechanism distinct from the previous [2+2] cycloisomerization manifold.

Anticancer potential of novel α,β-unsaturated γ-lactam derivatives targeting the PI3K/AKT signaling pathway

Six recently synthesized alkyl (Z)-2-(2-oxopyrrolidin-3-ylidene)acetates were evaluated for their potential as cytotoxic and anticancer agents. All compounds were tested in the ERα positive MCF-7, triple negative MDA-MB-231, and Her2⁺ SKBR-3 breast cancer cell lines. The most lipophilic derivatives, bearing the 4-isopropylphenyl (2) or 4-tert-butylphenyl (3) group at the γ-lactam nitrogen, proved to be cytotoxic against all the cancer cell lines tested (IC₅₀ values ranging from 18 to 63 μM), exerting their greatest activity in SKBR-3 cells, with IC₅₀ values of 33 and 18 μM, respectively. Biological studies showed that the cytotoxic effects of 2 and 3 are accompanied by apoptotic death in breast cancer cells, and both compounds showed no significant toxicity on healthy cells (e.g., MCF-10A) and red blood cells. An in-depth mechanistic study based on molecular biology, immunoblotting analysis and in silico docking calculations suggested that α,β-unsaturated γ-lactam derivatives could interfere with the functioning of PI3K and PDK-1, two key enzymes in the PI3K/AKT signaling pathway, whose overactivation is related to the regulation of cell growth and survival in several malignancies.

Synthesis, biological evaluation and docking study of 1,3,4-thiadiazole-thiazolidinone hybrids as anti-inflammatory agents with dual inhibition of COX-2 and 15-LOX

Selective inhibition of both cyclooxygenase-2 (COX-2) and 15-lipooxygenase (15-LOX) may provide good strategy for alleviation of inflammatory disorders while minimizing side effects associated with current anti-inflammatory drugs. The present study describes the synthesis, full characterization and biological evaluation of a series of thiadiazole-thiazolidinone hybrids bearing 5-alk/arylidene as dual inhibitors of these enzymes. Our design was based on merging pharmacophores that exhibit portent anti-inflammatory activities in one molecular frame. 5-(4-hydroxyphenyl)-1,3,4-thiadiazol-2-amine (3) was efficiently synthesized, chloroacetylated and cyclized to give the key 4-thiazolidinone (5). Knovenagel condensation of 5 with different aldehydes afforded the final compounds 6a-m, 7, 8 and 9. These compounds were subjected to in vitro COX-1/COX-2, 15-LOX inhibition assays. Compounds (6a, 6f, 6i, 6l, 6m and 9) with promising potency (IC₅₀ = 70-100 nM) and selectivity index (SI = 220-55) were further tested for in vivo anti-inflammatory activity and effect on gastric mucosa. The most promising compound (6l) inhibits COX-2 enzyme at a nanomolar concentration (IC₅₀ = 70 nM, SI = 220) with simultaneous inhibition of 15-LOX (IC₅₀ = 11 µM). These results are comparable to the potency and selectivity of the standard drugs of both enzymes; celecoxib (COX-2 IC₅₀ = 49 nM, SI = 308) and zileuton (15-LOX IC₅₀ = 15 µM) in one construct. Interestingly three compounds (6a, 6l and 9) exhibited equivalent to or even higher than that of celecoxib in vivo anti-inflammatory activity at 3 h interval with good GIT safety profile. Molecular docking study conferred binding sites of these compounds on COX-2 and 15-LOX. Such type of compounds would represent valuable leads for further investigation and derivatization.

Biologically active γ-lactams: synthesis and natural sources

The γ-lactam moiety is present in a large number of natural and non-natural biologically active compounds. The range of biological activities covered by these compounds is very broad. Functionalized γ-lactams are thus of high interest and have great potential in medicinal chemistry. This review provides a description of the title compounds by focusing on their synthesis, natural sources and biological activities.

5-membered cyclic hydroxamic acids as HDAC inhibitors

The new histone deacylases inhibitors (HDACi) were synthesized in the class of 5-membered cyclic hydroxamic acids (5-CHA), showing medium size CHA as a new Zn-binding group. New reaction sequence was proposed for the synthesis of 5-membered alkylidene-cyclic-hydroxamic acids starting from butyrolactone. Compound 10c showed low µM activity on HeLa cell extracts. From these results, cyclic hydroxamic acids will be further investigated to find more potent compounds.

Synthesis and pharmacological activities of some new triazolo- and tetrazolopyrimidine derivatives

A new series of fused triazolo- and tetrazolopyrimidine derivatives 2-14 were synthesized and their anti-inflammatory and ulcerogenic activities were evaluated. The pharmacological screening showed that many of these obtained compounds have good anti-inflammatory activities, comparable to the reference drug. The toxicity of the compounds was also assayed via the determination of their LD50 values. The structures of newly synthesized compounds were confirmed by IR, 1H-NMR, MS spectral data and elemental analysis.

Pharmacokinetic, distribution, metabolism, and excretion of (Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) in Sprague-Dawley rats

(Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) is an imidazolone COX/5-LOX inhibitor, which has excellent anti-inflammatory activity with an improved gastrointestinal safety profile. The purpose of this study was to evaluate the in vivo absorption, distribution, metabolism, and excretion of ZLJ-601 in Sprague-Dawley rats. After intravenous or intragastric administration to rats, the concentration of ZLJ-601 in plasma, bile, urine, feces and various types of tissues was detected by LC-MS. We also conducted the identification of metabolites using tandem mass spectrometry. After the intravenous administration, the t(1/2) ranged from 38.71 to 42.62 min and the AUC increased in a dose-proportional manner. After oral dosing, the plasma level of ZLJ-601 peaked at 28.33 min, having a C(max) value of 0.26 mg/l, and the bioavailability was only 4.92%. The highest tissue concentration of ZLJ-601 was observed in lung and kidney, but it was not found in brain. The majority of unchanged ZLJ-601 was excreted in urine (∼35.87%) within 36 h. Two main metabolites are the hydroxylation product and the glucuronide conjugate of the hydroxylation product.

Natural and synthetic α-methylenelactones and α-methylenelactams with anticancer potential

α-Methylene-γ- and δ-lactones, as well as α-methylene-γ- and δ-lactams, are plant-derived compounds often used in traditional medicine for the treatment of inflammatory diseases. In recent years, the anticancer properties of these compounds and the molecular mechanisms of their action have been studied extensively. In the search for modern anticancer drugs, various synthetic analogs of α-methylene-γ- and δ-lactones and lactams have been synthesized and tested for their cytotoxic activity. In this review, we give a brief description of the occurrence and biological activity of such compounds isolated from plants and their diverse synthetic analogs.

Design, synthesis and pharmacobiological evaluation of novel acrylic acid derivatives acting as lipoxygenase and cyclooxygenase-1 inhibitors with antioxidant and anti-inflammatory activities

A series of novel acrylic acid derivatives bearing at the 3 position thienyl, furfuryl and 3,5-ditert-butyl-4-hydroxyphenyl substituents have been designed, synthesized and tested as potential dual lipoxygenase/cyclooxygenase-1 (LOX/COX-1) inhibitors and as antioxidant and anti-inflammatory agents. Some compounds have shown moderate antioxidant and COX-1 inhibitory activities, very good anti-inflammatory activity and an inhibition of soybean lipoxygenase (LOX) higher than caffeic acid. In particular, compound 4I disclosed a moderate in vitro LOX inhibition with an IC(50) = 100 μM whereas compounds 1I and 2II exhibited the best, albeit poor, activity as COX-1 inhibition (75% inhibition at 100 μM). Good radical scavenging properties were shown by compounds 4I, 3I and 1II. Docking simulations performed on LOX inhibitor 4I and COX-1 inhibitor 1I indicated that hydrophobic key interactions may govern the enzyme-inhibitor binding.

Synthesis and biological activities of new substituted thiazoline-quinoline derivatives

5-Acyl-8-hydroxyquinoline-2-(3'-substituted-4'-aryl-2,3-dihydrothiazol-2'-ylidene)hydrazones, 5a-e to 10a-c, were prepared by the reaction of appropriate 5-acyl-8-hydroxyquinoline-4-substituted thiosemicarbazones 3a-e and phenacyl bromides 4a-e. Structures of the new compounds were verified on the basis of spectral and elemental analyses. Twenty-eight new compounds were tested for their possible antimicrobial activities. Most of the tested compounds showed weak to moderate antibacterial activity against most of the bacterial strains used in comparison with gatifloxacin as a reference drug. The test compounds showed weak to moderate antifungal activity against tested fungi in comparison with ketoconazole as a reference drug. On the other hand, the newly synthesized compounds were tested for their anti-inflammatory effects and most of them showed good to excellent anti-inflammatory activity compared to indomethacin. Moreover, ulcerogenicity and the median lethal dose (LD(50)) of the most active anti-inflammatory compounds 6b and 9e were determined in mice; they were non-toxic at doses up to 400 mg kg(-1) after i.p. administration.

Multiplicity of diverse heterocycles from polymer-supported alpha-acylamino ketones

Polymer-supported alpha-acylamino ketones were transformed to seven types of structurally unrelated heterocyclic compounds. Syntheses involved variety of chemical routes and comprised diverse chemistries (C-C, C=C, C-N, C=N, and C-O bond formations). Different sizes of heterocycles (4-, 5-, 6-, and 7-membered rings) were prepared, including dihydro-pyrrol-2-ones, pyrazin-2-ones, dihydro-triazepin-6-ones, morpholin-3-ones, imidazoles, beta-lactams, and isoquinolin-1-ones. Further elaboration to fused ring systems was also documented.

Synthesis and pharmacological activities of some condensed 4-chloro-2,2-dialkyl chromene-3-carbaldehyde derivatives

Some new hydrazono 5a,b, thiosemicarbazono 6a-c, and oximo chromenes 7a-c were prepared via the reaction of the corresponding beta-chlorocarbaldehyde 3 with hydrazine, aromatic hydrazine, thiosemicarbazide and hydroxylamine hydrochloride, respectively. In addition, ether derivatives 8a-h were prepared from the corresponding aldoximes 7a-c. The new products were tested for anti-inflammatory and ulcerogenic score activities compared to indomethacin.

Synthesis, X-ray Structure, and Pharmacological Activity of Some 6,6-Disubstituted Chromeno[4,3-b]- and Chromeno- [3,4-c]-quinolines

Some chromeno[4,3-b]quinolines 4a-i were obtained from beta-chloro carboxyaldehydes 3a-c with different aniline derivatives namely, aniline, 4-fluoroaniline, and 2-aminophenol. Surprisingly, 3a-c reacted with 2-aminothiophenol and afforded the chromeno[3,4-c]quinoline derivatives 5a-c. Single-crystal X-ray diffraction studies of 4e and 5b provided good support for the established structure. Compounds 4b and 5b showed significant anti-inflammatory and ulcerogenic score activities compared to that of indomethacin.

Short stereoselective synthesis of alpha-substituted gamma-lactams

A concise, stereoselective synthesis of alpha-substituted gamma-lactams is reported. gamma-Lactam scaffolds 2 and 3, possessing an Evans' chiral auxiliary and two types of N substituents, were successfully alkylated with different electrophiles to give alpha-substituted gamma-lactams with reasonable diastereoselectivities. The use of a masked carboxymethyl function off the lactam nitrogen provided a convergent means to alpha-substituted gamma-lactam dipeptide isosteres.

Synthesis and biological evaluation of acyclic triaryl (Z)-olefins possessing a 3,5-di-tert-butyl-4-hydroxyphenyl pharmacophore: Dual inhibitors of cyclooxygenases and lipoxygenases

A new class of regioisomeric acyclic triaryl (Z)-olefins possessing a 3,5-di-tert-butyl-4-hydroxyphenyl (DTBHP) 5-lipoxygenase (5-LOX) pharmacophore that is vicinal to a para-methanesulfonylphenyl cyclooxygenase-2 (COX-2) pharmacophore were designed for evaluation as selective COX-2 and/or 5-LOX inhibitors. The target compounds were synthesized via a highly stereoselective McMurry olefination cross-coupling reaction. This key synthetic step afforded a (Z):(E) olefinic mixture with a predominance for the (Z)-olefin stereoisomer. Structure-activity studies for the (Z)-1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-(4-methanesulfonylphenyl)-1-phenylalk-1-ene regioisomers showed that COX-1 inhibition decreased, COX-2 inhibition increased, and the COX-2 selectivity index (SI) increased as the chain length of the alkyl substituent attached to the olefinic double bond was increased (Et-->n-butyl-->n-heptyl). In this group of compounds, inhibition of both 5-LOX and 15-LOX was dependent upon the length of the alkyl substituent with the hex-1-ene compound 9c having a n-butyl substituent exhibiting potent inhibition of both 5-LOX (IC50=0.3 microM) and 15-LOX (IC50=0.8 microM) relative to the inactive (IC50>10 microM) Et and n-heptyl analogs. Compound 9c is of particular interest since it also exhibits a dual inhibitory activity against the COX (COX-1 IC50=3.0 microM, and COX-2 IC50=0.36 microM, COX-2 SI=8.3) isozymes. A comparison of the relative inhibitory activities of the two groups of regioisomers investigated shows that the regioisomers in which the alkyl substituent is attached to the same olefinic carbon atom (C-2) as the para-methanesulfonylphenyl moiety generally exhibit a greater potency with respect to COX-2 inhibition. The 4-hydroxy substituent in the 3,5-di-tert-butyl-4-hydroxyphenyl moiety is essential for COX and LOX inhibition since 3,5-di-tert-butyl-4-acetoxyphenyl derivatives were inactive inhibitors. These structure-activity data indicate acyclic triaryl (Z)-olefins constitute a suitable template for the design of dual COX-2/LOX inhibitors.

Synthesis of 5-Phenyl-1-(3-pyridyl)-1H-1,2,4-triazole-3-carboxylic Acid Derivatives of Potential Anti-inflammatory Activity

A series of 5-phenyl-1-(3-pyridyl)-1H-1,2,4-triazole-3-carboxylic acid derivatives 4-10 were synthesized by rearrangement of 4-(3-pyridyl)-hydrazono-2-phenyl-2-oxazolin-5-one 3 in the presence of different nucleophiles to afford derivatives 4, 7, and 8, while hydroxamic acid derivative 6 was prepared from reaction of methyl ester 4 with hydroxylamine hydrochloride. Semicarbazide 9 and thiosemicarbazide 10, derivatives of the 5-phenyl-1-(3-pyridyl)-1H-1,2,4-triazole-3-carboxylic acid, were synthesized via hydrazide 8 with potassium cyanate and appropriate isothiocyanate, respectively. The structures of the synthesized compounds were confirmed by elemental analyses, IR, (1)H-NMR, and mass spectra. The results of the anti-inflammatory activity of the synthesized derivatives showed that most of the tested compounds 4-10 showed significant inhibition against carrageenan-induced rat paw edema in albino rats. Derivatives 4 and 8 showed promising results and were found to be equipotent or more potent than Indomethacin and Celecoxib as reference drugs at two dose levels, 5 and 10 mg/kg, and they have no ulcerogenic activity.

[Studies on the new antiarthritic drug candidate S-2474]

Various 1,2-isothiazolidine-1,1-dioxide (gamma-sultam) derivatives containing an antioxidant moiety, 2,6-di-tert-butyl-phenol substituent, were prepared. Some compounds that have a lower alkyl group at the 2-position of the gamma-sultam skeleton showed potent inhibitory effects on both cyclooxygenase (COX)-2 and 5-lipoxygenase (5-LO), as well as production of interleukin-1 (IL-1) in in vitro assays. They also proved to be effective in several animal arthritic models without any ulcerogenic activities. Among these compounds, (E)-(5)-(3,5-di-tert-butyl-4-hydroxybenzylidence)-2-ethyl-1,2- isothiazolidine-1,1-dioxide (S-2474) was selected as an antiarthritic drug candidate. The structure-activity relationships examined and some pharmacological evaluations are described. Furthermore, we have developed an efficient and E-selective synthesis of S-2474, in which alpha-methoxy-p-quinone methide is used as a key intermediate. alpha-Methoxy-p-quinone methide was revealed to be equivalent to a p-hydroxy-protected benzaldehyde. It reacts smoothly with alpha-sulfonyl carbanion to give 1,6-addition intermediates, which can be further processed to provide S-2474 directly in the presence of a base. This procedure gives S-2474 as an almost single isomer on the benzylidene double bond in excellent yield and thus is a very practical method adaptable to large-scale synthesis. The detailed mechanistic aspects are studied and discussed.

Short synthesis of tert-butyl-hydroxylated 3,5-di-tert-butyl-4-hydroxybenzaldehyde: Synthesis of tert-butyl-hydroxylated S-2474

We have developed a very short synthesis of tert-butyl-hydroxylated di-tert-butyl-4-hydroxybenzaldehyde in which the HBr-DMSO system is used as an effective oxidant (overall yield of 45% for the entire four-step process from 2-tert-butyl-p-cresol). We also accomplished the synthesis of a major metabolite of the antiarthritic drug candidate S-2474.

Structure-based design of a parallel synthetic array directed toward the discovery of irreversible inhibitors of human rhinovirus 3C protease

Utilizing the tools of parallel synthesis and structure-based design, a new class of Michael acceptor-containing, irreversible inhibitors of human rhinovirus 3C protease (HRV 3CP) was discovered. These inhibitors are shown to inhibit HRV-14 3CP with rates of inactivation ranging from 886 to 31 400 M(-1) sec(-1). These inhibitors exhibit antiviral activity when tested against HRV-14 infected H1-HeLa cells, with EC(50) values ranging from 1.94 to 0.15 microM. No cytotoxicity was observed at the limits of the assay concentration. A crystal structure of one of the more potent inhibitors covalently bound to HRV-2 3CP is detailed. These compounds were also tested against HRV serotypes other than type 14 and were found to have highly variable activities.

Effects of S-2474, a novel nonsteroidal anti-inflammatory drug, on amyloid beta protein-induced neuronal cell death

1. The accumulation of amyloid beta protein (Abeta) in the brain is a characteristic feature of Alzheimer's disease (AD). Clinical trials of AD patients with nonsteroidal anti-inflammatory drugs (NSAIDs) indicate a clinical benefit. NSAIDs are presumed to act by suppressing inhibiting chronic inflammation in the brain of AD patients. 2. In the present study, we investigated effects of S-2474 on Abeta-induced cell death in primary cultures of rat cortical neurons. 3. S-2474 is a novel NSAID, which inhibits cyclo-oxygenase-2 (COX-2) and contains the di-tert-butylphenol antioxidant moiety. S-2474 significantly prevented neurons from Abeta(25 - 35)- and Abeta(1 - 40)-induced cell death. S-2474 ameliorated Abeta-induced apoptotic features such as the condensation of chromatin and the fragmentation of DNA completely. 4. Prior to cell death, Abeta(25 - 35) generated prostaglandin D(2) (PGD(2)) and free radicals from neurons. PGD(2) is a product of cyclo-oxygenase (COX), and caused neuronal cell death. 5. S-2474 significantly inhibited the Abeta(25 - 35)-induced generation of PGD(2) and free radicals. 6. The present cortical cultures contained little non-neuronal cells, indicating that S-2474 affected neuronal survival directly, but not indirectly via non-neuronal cells. Both an inhibitory effect of COX-2 and an antioxidant effect might contribute to the neuroprotective effects of S-2474. 7. In conclusion, S-2474 exhibits protective effects against neurotoxicity of Abeta. Furthermore, the present study suggests that S-2474 may possess therapeutic potential for AD via ameliorating degeneration in neurons as well as suppressing chronic inflammation in non-neuronal cells.

6-Benzylidenethiazolo[3,2-b]-1,2,4-triazole-5(6H)-ones substituted withibuprofen: synthesis, characterization and evaluation of anti-inflammatory activity

In this study, the synthesis of 3-[1-(4-(2-methylpropyl)phenyl)ethyl]-1,2,4-triazole-5-thione (2) and its condensed derivatives 6-benzylidenethiazolo[3,2-b]-1,2, 4-triazole-5(6H)-ones (2a-u) are described. The structures of the compounds were elucidated by spectral and elemental analysis. In the pharmacological studies, anti-inflammatory activities of these compounds have been screened. Among the compounds examined, the compounds 2 and 2g possessed the most prominent and consistent activity. In gastric ulceration studies the synthesized compounds were generally found to be safe at a 200 mg/kg dose level.

Novel antiarthritic agents with 1,2-isothiazolidine-1,1-dioxide (gamma-sultam) skeleton: cytokine suppressive dual inhibitors of cyclooxygenase-2 and 5-lipoxygenase

Various 1,2-isothiazolidine-1,1-dioxide (gamma-sultam) derivatives containing an antioxidant moiety, 2,6-di-tert-butylphenol substituent, were prepared. Some compounds, which have a lower alkyl group at the 2-position of the gamma-sultam skeleton, showed potent inhibitory effects on both cyclooxygenase (COX)-2 and 5-lipoxygenase (5-LO), as well as production of interleukin (IL)-1 in in vitro assays. They also proved to be effective in several animal arthritic models without any ulcerogenic activities. Among these compounds, (E)-(5)-(3,5-di-tert-butyl-4-hydroxybenzylidene)-2-ethyl-1, 2-isothiazolidine-1,1-dioxide (S-2474) was selected as an antiarthritic drug candidate and is now under clinical trials. The structure-activity relationships (SAR) examined and some pharmacological evaluations are described.

Structure-based design, synthesis, and biological evaluation of irreversible human rhinovirus 3C protease inhibitors. 1. Michael acceptor structure-activity studies

The structure-based design, chemical synthesis, and biological evaluation of peptide-derived human rhinovirus (HRV) 3C protease (3CP) inhibitors are described. These compounds incorporate various Michael acceptor moieties and are shown to irreversibly bind to HRV serotype 14 3CP with inhibition activities (kobs/[I]) ranging from 100 to 600 000 M-1 s-1. These inhibitors are also shown to exhibit antiviral activity when tested against HRV-14-infected H1-HeLa cells with EC50's approaching 0.50 microM. Extensive structure-activity relationships developed by Michael acceptor alteration are reported along with the evaluation of several compounds against HRV serotypes other than 14. A 2.0 A crystal structure of a peptide-derived inhibitor complexed with HRV-2 3CP is also detailed.