Synthesis and in vitro anti-mycobacterial activity of 5-substituted pyrimidine nucleosides

Mycobacterium tuberculosis and Mycobacterium avium infections cause the two most important mycobacterioses, leading to increased mortality in patients with AIDS. Various 5-substituted 2′-deoxyuridines, uridines, 2′-O-methyluridine, 2′-ribofluoro-2′-deoxyuridines, 3′-substituted-2′,3′-dideoxy uridines, 2′,3′-dideoxyuridines, and 2′,3′-didehydro-2′,3′-dideoxyuridines were synthesized and evaluated for their in vitro inhibitory activity against M. bovis and M. avium. 5-(C-1 Substituted)-2′-deoxyuridine derivatives emerged as potent inhibitors of M. avium (MIC₉₀ = 1–5 μg/mL range). The nature of C-5 substituents in the 2′-deoxyuridine series appeared to be a determinant of anti-mycobacterial activity. This new class of inhibitors could serve as useful compounds for the design and study of new anti-tuberculosis agents.     

Synthesis and biological evaluation of methanesulfonamide analogues of rofecoxib: Replacement of methanesulfonyl by methanesulfonamido decreases cyclooxygenase-2 selectivity

A new group of 3-(4-substituted-phenyl)-4-(4-methylsulfonamidophenyl)-2(5H)furanones in which the methylsulfonyl (MeSO(2)) COX-2 pharmacophore present in rofecoxib was replaced by a methanesulfonamido (MeSO(2)NH) moiety, and where the substituent at the para-position of the C-3 phenyl ring was simultaneously varied (H, F, Cl, Br, Me, OMe), were evaluated to determine the combined effects of steric and electronic substituent properties upon COX-1 and COX-2 inhibitory potency and COX isozyme selectivity. Structure-activity relationship (SAR) studies showed that compounds having a neutral (H), or electronegative halogen (F, Cl, Br), substituent at the para-position of the C-3 phenyl ring inhibited both COX-1 and COX-2 with COX-2 selectivity indexes in the 3.1-39.4 range. In contrast, compounds having an electron-donating Me or OMe substituent were selective inhibitors of COX-2 (COX-1 IC(50)>100 microM). These SAR data indicate the 3-aryl-4-(4-methylsulfonamidophenyl)-2(5H)furanone scaffold provides a suitable template to design COX inhibitors with variable COX-2 selectivity indexes.     

Synthesis and SAR of heteroaryl-phenyl-substituted pyrazole derivatives as highly selective and potent canine COX-2 inhibitors

The discovery of heteroaryl-phenyl-substituted pyrazole derivatives as canine selective COX-2 inhibitors is described. Structure-activity relationship (SAR) studies of this class of compounds led to the identification of compound 1 which demonstrated a canine whole blood COX-2 inhibitory IC50 of 12 nM and selectivity ratio of COX-1/COX-2 greater than 4000-fold.     

Selective addressing of heteroditopic ligands by iron(II) and platinum(II)

The heteroditopic ligand 4′-(4,7,10-trioxadec-1-yn-10-yl)-2,2′:6′,2″-terpyridine, 2, contains an N,N′,N″-donor metal-binding domain that recognizes iron(II), and a terminal alkyne site that selectively couples to platinum(II). This selectivity has been used to investigate routes to the formation of heterometallic systems. The single crystal structures of ligand 2 and the complex [Fe(2)₂][PF₆]₂ are reported.     

Synthesis and biological evaluation of 3-heteroaryloxy-4-phenyl-2(5H)-furanones as selective COX-2 inhibitors

A series of 3-heteroaryloxy4-phenyl-2-5H)-furanones were prepared and evaluated for their potency and selectivity as COX-2 inhibitors. This led to the identification of L-778,736 as a potent, orally active and selective inhibitor of the COX-2 enzyme.     

Conjugation position of quercetin glucuronides and effect on biological activity

Quercetin glycosides are common dietary antioxidants. In general, however, potential biological effects of the circulating plasma metabolites (e.g., glucuronide conjugates) have not been measured. We have determined the rate of glucuronidation of quercetin at each position on the polyphenol ring by human liver cell-free extracts containing UDP-glucuronosyltransferases. The apparent affinity of UDP-glucuronosyltransferase followed the order 4′- > 3′- > 7- > 3, although the apparent maximum rate of formation was for the 7-position. The 5-position did not appear to be a site for conjugation. After isolation of individual glucuronides, the inhibition of xanthine oxidase and lipoxygenase were assessed. The K_i for the inhibition of xanthine oxidase by quercetin glucuronides followed the order 4′- > 3′- > 7- > 3-, with quercetin-4′-glucuronide a particularly potent inhibitor (K_i = 0.25 μM). The glucuronides, with the exception of quercetin-3-glucuronide, were also inhibitors of lipoxygenase. Quercetin glucuronides are metabolites of quercetin in humans, and these compounds can retain some biological activity depending on conjugation position at expected plasma concentrations.     

Synthesis and biological evaluation of 1,3-diphenylprop-2-yn-1-ones as dual inhibitors of cyclooxygenases and lipoxygenases

A new class of 1,3-diphenylprop-2-yn-1-ones possessing a p-MeSO2 COX-2 phamacophore on the C-3 phenyl ring was designed for evaluation as dual inhibitors of cyclooxygenase (COX) and lipoxygenase (LOX). Among the group of compounds evaluated, 1-(4-fluorophenyl)-3-(4-methanesulfonylphenyl)prop-2-yn-1-one (11j) exhibited excellent COX-2 inhibitory potency (COX-2 IC50 = 0.1 microM) and selectivity (SI = 300), whereas 1-(4-cyanophenyl)-3-(4-methanesulfonylphenyl)prop-2-yn-1-one (11d) exhibited an optimal combination of COX and LOX inhibition (COX-2 IC50 = 1.0 microM; COX-2 SI = 31.5; 5-LOX IC50 = 1.0 microM; 15-LOX IC50 = 3.2 microM).     

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.     

Synthesis and cyclooxygenase inhibition of various (aryl-1,2,3-triazole-1-yl)-methanesulfonylphenyl derivatives

A series of 1,4- and 1,5-diaryl substituted 1,2,3-triazoles was synthesized by either Cu(I)-catalyzed or Ru(II)-catalyzed 1,3-dipolar cycloaddition reactions between 1-azido-4-methane-sulfonylbenzene 9 and a panel of various para-substituted phenyl acetylenes (4-H, 4-Me, 4-OMe, 4-NMe₂, 4-Cl, 4-F). All compounds were used in in vitro cyclooxygenase (COX) assays to determine the combined electronic and steric effects upon COX-1 and COX-2 inhibitory potency and selectivity. Structure-activity relationship studies showed that compounds having a vicinal diaryl substitution pattern showed more potent COX-2 inhibition (IC₅₀ = 0.03–0.36 μM) compared to their corresponding 1,3-diaryl-substituted counterparts (IC₅₀ = 0.15 to >10.0 μM). In both series, compounds possessing an electron-withdrawing group (Cl and F) at the para-position of one of the aryl rings displayed higher COX-2 inhibition potency and selectivity as determined for compounds containing electron-donating groups (Me, OMe, NMe₂). The obtained data show, that the central carbocyclic or heterocyclic ring system as found in many COX-2 inhibitors can be replaced by a central 1,2,3-triazole unit without losing COX-2 inhibition potency and selectivity. The high COX-2 inhibition potency of some 1,2,3-triazoles having a vicinal diaryl substitution pattern along with their ease in synthesis through versatile Ru(II)-catalyzed click chemistry make this class of compounds interesting candidates for further design and synthesis of highly selective and potent COX-2 inhibitors.     

KMI-008, a novel beta-secretase inhibitor containing a hydroxymethylcarbonyl isostere as a transition-state mimic: design and synthesis of substrate-based octapeptides

A novel class of substrate-based β-secretase (BACE1) inhibitors containing a hydroxymethylcarbonyl (HMC) isostere was designed and synthesized. Phenylnorstatine [(2R,3S)-3-amino-2-hydroxy-4-phenylbutyric acid; Pns] was an effective transition-state mimic at the P₁ position. Structure–activity relationships (SARs) of the P₃–P₃′ positions of BACE1 inhibitors were studied.     

Synthesis and opioid activity of N,N-dimethyl-Dmt-Tic-NH-CH(R)-R' analogues: acquisition of potent delta antagonism

N,N-Dimethylation of the H-Dmt-Tic-NH-CH(R)-R′ series of compounds produced no significant affect on the high δ-opioid receptor affinity (K_i=0.035–0.454 nM), but dramatically decreased that for the μ-opioid receptor. The effect of N-methylation was independent of the length of the linker (R); however, the bioactivities were affected by the chemical composition of the third aromatic group (R′): phenyl (Ph) (5′–8′) elicited a greater reduction in μ-affinity (40–70-fold) compared to analogues containing 1H-benzimidazole-2-yl (Bid) (9-fold). The major consequences of N,N-dimethylation on in vitro bioactivity were: (i) a loss of δ-agonism coupled with the appearance of potent δ antagonism (4′–7′) (pA₂=8.14–9.47), while 1 exhibited only a 160-fold decreased δ agonism (1′) and the δ antagonism of 8 enhanced >10-fold (pA₂=10.62, 8′); and (ii) a consistent loss of μ-affinity resulted in enhanced δ-opioid receptor selectivity. With the exception of compound 1′, the change in the hydrophobic environment at the N-terminus and formation of a tertiary amine by N,N-dimethylation in analogues of the Dmt-Tic pharmacophore produced potent δ-selective antagonists.     

Design and synthesis of 1,3-diarylurea derivatives as selective cyclooxygenase (COX-2) inhibitors

A group of 1,3-diarylurea derivatives, possessing a methylsulfonyl pharmacophore at the para-position of the N-1 phenyl ring, in conjunction with a N-3 substituted-phenyl ring (4-F, 4-Cl, 4-Me, 4-OMe), were designed and synthesized for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. In vitro COX-1/COX-2 isozyme inhibition structure-activity studies identified 1-(4-methylsulfonylphenyl)-3-(4-methoxyphenyl) urea (4e) as a potent COX-2 inhibitor (IC(50)=0.11 microM) with a high COX-2 selectivity index (SI=203.6) comparable to the reference drug celecoxib (COX-2 IC(50)=0.06 microM; COX-2 SI=405). The structure-activity data acquired indicate that the urea moiety constitutes a suitable scaffold to design new acyclic 1,3-diarylurea derivatives with selective COX-2 inhibitory activity.     

Crystal structure of phosphodiesterase 4D and inhibitor complex(1)

Cyclic nucleotide phosphodiesterases (PDEs) regulate physiological processes by degrading intracellular second messengers, adenosine-3′,5′-cyclic phosphate or guanosine-3′,5′-cyclic phosphate. The first crystal structure of PDE4D catalytic domain and a bound inhibitor, zardaverine, was determined. Zardaverine binds to a highly conserved pocket that includes the catalytic metal binding site. Zardaverine fills only a portion of the active site pocket. More selective PDE4 inhibitors including rolipram, cilomilast and roflumilast have additional functional groups that can utilize the remaining empty space for increased binding energy and selectivity. In the crystal structure, the catalytic domain of PDE4D possesses an extensive dimerization interface containing residues that are highly conserved in PDE1, 3, 4, 8 and 9. Mutations of R358D or D322R among these interface residues prohibit dimerization of the PDE4D catalytic domain in solution.     

Further farnesyl-homogentisic acid derivatives from Otoba parvifolia

The seeds of Otoba parvifolia contain three novel compounds apparently derived from homogentisic acid, rel-(1′R,5′R)-2-(1′-farnesyl-5′-hydroxy-2′-oxocyclohex-3′-en-1′-yl)-acetic acid and its acetate as well as rel-(1′R,4′S,5′R)-2-(1′-farnesyl-4′,5′-dihydroxy-2′-oxocyclohexan-1′-yl)-acetic acid δ-lactone. The structure of an additional isolate, previously described as 2-(1′-farnesyl-2′-hydroxy-5′-oxocyclohex-3′-en-1′-yl)-acetic acid γ-lactone was revised to rel-(1′R,5′R)-2-(1′-farnesyl-5′-hydroxy-2′-oxocyclohex-3′-en-1′-yl)-acetic acid δ-lactone.     

Synthesis, molecular modelling and enzymatic evaluation of (+/-)3,5-diphenyl-2-thioxoimidazolidin-4-ones as new potential cyclooxygenase inhibitors

A series of substituted (+/-)3,5-diphenyl-2-thioxoimidazolin-4-ones was synthesized in order to design new type-2 cyclooxygenase (COX-2) inhibitors. This study has led to molecules which completely inhibit human recombinant COX-2 at 50 microM. Molecular modelling highlighted drug interactions with the active site of both cyclooxygenases and suggested modifications to enhance the selectivity of the compounds. In human blood, COX-2 expression was then induced by LPS, and the inhibitory potency of these drugs was disappointing. This weak activity was attributed to a poor aqueous stability of these imidazolidinones substituted by two aryl in position 3 and 5 (15 min < t(1/2) < 130 min). The improvement of the stability of this heterocycle could generate a novel template to treat COX-associated diseases such as arthritis, rheumatoid polyarthritis and cancer.     

A novel series of highly selective inhibitors of MMP-3

The design and synthesis of a series of highly selective hydroxamate inhibitors of stromelysin-1 (MMP-3) is described. Substitution of a 4-biaryl piperidine sulfonamide core, which binds at the S1′ subsite of MMP-3, was optimised to give potent inhibitors of MMP-3, with greater than 300-fold selectivity over MMP-1, MMP-2, MMP-9 and MMP-14. Compounds 26 and 27 were identified as having the best balance of pharmacology and properties required for topical drug delivery.     

Chiral macrocyclic compounds from lactose derivatives

The reaction of benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-isopropylidene-β-lactoside with 1,11-ditosyloxy-3,6,9-trioxaundecane gave benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-isopropylidene-3,2′-O--(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (2, 47%). Acid hydrolysis of 2 and condensation of the product with 1,14-ditosyloxy-3,6,9,12-tetra-oxatetradecane afforded benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-(3,6,9,12-tetraoxa-tetradecane-1,14-diyl)-3,2′-O-(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (29%). Similarly, the reaction of benzyl 2,6,2′,4′,6′-penta-O-benzyl-β-lactoside with Ts[OCH₂CH₂]₄OTs gave benzyl 2,6,2′,4′,6′-penta-O-benzyl-3,3′-O-(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (78%). ¹H-N.m.r. spectroscopy has been used to study the formation of host-guest complexes with some of these macrocyclic compounds and benzyl ammonium thiocyanate.     

Radioimmunoassays of 3,4,5-trimethoxyphenethylamine (mescaline) and 2,5-dimethoxy-4-methylphenyl-isopropylamine(DOM)

Mescaline (3,4,5-trimethoxyphenethylamine) and N-succinylmescaline were coupled to human serum albumin with carbodiimide. DOM (2,5-dimethoxy-4-methylphenylisopropylamine) was linked to human serum albumin by reaction with glutaraldehyde. These conjugates were used for immunization of rabbits. Derivatives of mescaline [N-(3′,4′,5′-trimethoxyphenethyl)-4-hydroxyphenylacetamide] and of DOM [N-(2′,5′-dimethoxy-4′-methylphenylisopropyl)-4-hydroxyphenylacetamide], which could be iodinated to high specific activity, were synthesized. The antibodies bound specifically to these iodinated compounds. In competition experiments with a mescaline antiserum, 6 pmoles of mescaline inhibited 50%; with a DOM antiserum, 50% inhibition was observed with 118 pmoles of DOM. Thus, 100 pg of mescaline and 2 ng of DOM can be detected. The specificity of both antibodies is such that structurally related molecules, such as p-methoxy-phenethylamine or 3-methoxytyramine, are several orders of magnitude less effective as inhibitors than the parent molecules. With the use of antimescaline, it was determined that mescaline administered intravenously to rabbits disappeared rapidly from the circulation. The acid was identified as the major metabolite in the serum and urine of these animals.     

Isolation, structural elucidation, and partial synthesis of lutein dehydration products in extracts from human plasma

All-E-(3R,6′R)-3-hydroxy-3′,4′-didehydro-β,γ-carotene (anhydrolutein I) and all-E-(3R,6′R)-3-hydroxy-2′,3′-didehydro-β,ε-carotene (2′,3′-anhydrolutein II) have been isolated and characterized from extracts of human plasma using semipreparative high-performance liquid chromatography (HPLC) on a C₁₈ reversed-phase column. The identification of anhydroluteins was accomplished by comparison of the UV-Vis absorption and mass spectral data as well as HPLC-UV-Vis-mass spectrometry (MS) spiking experiments using fully characterized synthetic compounds. Partial synthesis of anhydroluteins from the reaction of lutein with 2% H₂SO₄ in acetone, in addition to anhydrolutein I (54%) and 2′,3′-anhydrolutein II (19%), also gave (3′R)-3′-hydroxy-3,4-dehydro-β-carotene (3′,4′-anhydrolutein III, 19%). While anhydrolutein I has been shown to be usually accompanied by minute quantities of 2′,3′-anhydrolutein II (ca. 7–10%) in human plasma, 3′,4′-anhydrolutein III has not been detected. The presence of anhydrolutein I and II in human plasma is postulated to be due to acid catalyzed dehydration of the dietary lutein as it passes through the stomach. These anhydroluteins have also been prepared by conversion of lutein diacetate to the corresponding anhydrolutein acetates followed by alkaline hydrolysis. However, under identical acidic conditions, loss of acetic acid from lutein diacetate proceeded at a much slower rate than dehydration of lutein. The structures of the synthetic anhydroluteins, including their absolute configuration at C(3) and C(6′) have been unambiguously established by ¹H NMR and in part by ¹³C NMR, and circular dichroism.