Antimicrobial activity of some 2-amino-5-subsituted pyridine derivatives

A series of 2-amino-5-substituted pyridine derivatives were prepared and evaluated against phytopathogenic fungi and bacteria under laboratory conditions. Position 4 on the pyridine ring has notable fungicidal and bactericidal activity, greater than position 3 and/or position 6. Reaction of 1-hydroxymethyl benzotriazole with the amino group of the pyridine ring gave better fungicidal activity than substitution on the carbon of the pyridine ring (compound 4 versus 1c). Replacing the benzotriazole moiety with thiophenol exhibited the strongest fungicidal and bactericidal activity in this series (compound 3).     

Synthesis and inhibitory activity of benzoic acid and pyridine derivatives on influenza neuraminidase

Based upon the activity and X-ray crystallographic studies of tri-substituted benzene derivatives containing carboxylic acid, acetamido and guanidine groups, we investigated the effect of the fourth substituent to fulfill the fourth pocket of neuraminidase enzyme. The groups selected as fourth substituents were hydroxymethyl, hydroxyethyl, oxime and amino. These tetra-substituted benzene derivatives were synthesized and evaluated for neuraminidase inhibitory activity. All these compounds were found to have poorer IC(50) values than the tri-substituted compounds. Further, benzene ring was replaced by pyridine ring and di, tri and tetra-substituted pyridine derivatives were synthesized. The activity of the pyridine derivatives was comparable to benzene derivatives. The fourth substituent seems to disturb the binding of the other three substituents, so the activity is reduced as compared to tri-substituted benzene and pyridine derivatives.     

Structural requirements of some sulphonamides that possess an antifertility activity in male rats

Sulphonamides with different chemical structures were synthesized and these 13 compounds together with 7 commercially available sulpha drugs were tested for antifertility activity by natural mating in male rats. All compounds were given daily by gastric intubation at doses of 125, 150, 250 or 450 mg/kg for 6 weeks. Sulphapyridine caused a dose-related and reversible reduction in fertility at doses between 125 and 450 mg/kg. At the high dose, fertility was reduced to 25.9% of control at 5 weeks after treatment, and complete recovery occurred by 3 weeks after drug withdrawal. This activity was abolished when the pyridine ring was substituted by other heterocyclic rings, except sulphachloropyridazine which had only weak activity. Replacement of the pyridine ring by a hydrogen atom or short aliphatic chains preserved or even enhanced the potency. Thus, sulphanilamide, N1-methylsulphanilamide or N1-diethylsulphanilamide produced a marked but reversible reduction in fertility. Removal or substitution of the N4-amino group on the benzene ring of sulphapyridine with a methyl group destroyed the activity. However, the bromo or nitro analogue (at the para- but not the meta-position of the benzene ring) still possessed some activity. N4-Acetyl derivatives of sulphapyridine, sulphanilamide, and N1-diethylsulphanilamide were as potent as their parent compounds. These results suggest that the presence of pyridine or other heterocyclic rings is not necessary for the antifertility activity of sulphonamide compounds. However, the N4-amino group is indispensable. In addition, acetylation of this amino group does not change the potency. The prototype of the antifertility sulphonamides therefore seems to be sulphanilamide.     

Barrier to rotation and conformation of the -NR2 group in cytosine and its derivatives. Part II. Experimental and theoretical dipole moments of methylated cytosines.

The dipole moments of several cytosine, methylaminocytosine and dime-thylaminocytosine derivatives with and without an ortho methyl group were determined experimentally in dioxane and benzene. Calculations of total energies and dipole moments were performed by the CNDO/2 and INDO methods for sp2 and sp3 hybridization of exocyclic nitrogen for different values of rotational angle phiC-N. Comparison of the experimental dipole moments with those calculated for the energy minima suggests that the conformation of the dimethylamino group is not planar and differs from that found in cytosine. 1,5,7-Trimethylcytosine, with the dipole moment of 7 Deby units, was considered to be the model compound which closely reproduces the dipole moment of cytosine.     

Synthesis of 1-(2-hydroxy-3-methoxypropyl)uracils and their activity against L1210 and macrophage raw 264.7 cells

The title compounds were obtained from appropriate 5-substituted uracil derivatives and 1,2-oxy-3-methoxypropane in the presence of sodium hydride. Under similar conditions 5-iodouracil gave 2-methoxymethyl-2,3-dihydro-oxazolo[3,2-c]pyrimidine-5,7-dione as a result of intramolecular cine type nucleophilic substitution. Cytotoxicity of 1-(2-hydroxy-3-methoxypropyl)-5-substituted uracil derivatives against L1210 and macrophage RAW 264.7 cells in vitro was examined.     

Combining the tail and the ring approaches for obtaining potent and isoform-selective carbonic anhydrase inhibitors: Solution and X-ray crystallographic studies

5-(3-Tosylureido)pyridine-2-sulfonamide and 4-tosylureido-benzenesulfonamide (ts-SA) only differ by the substitution of a CH by a nitrogen atom, but they have very different inhibitory properties against the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). By means of X-ray crystallography on the human CA II adducts of the two compounds these differences have been rationalized. As all sulfonamides, the two compounds bind in deprotonated form to the Zn(II) ion from the enzyme active site and their organic scaffolds extend throughout the cavity, participating in many interactions with amino acid residues and water molecules. However the pyridine derivative undergoes a tilt of the heterocyclic ring compared to the benzene analog, which leads to a very different orientation of the two scaffolds when bound to the enzyme. This tilt also leads to a clash between a carbon atom from the pyridine ring of the first inhibitor and the OH moiety of Thr200, leading to less effective inhibitory properties of the pyridine versus the benzene sulfonamide derivative. Indeed, ts-SA is a promiscuous, low nanomolar inhibitor of 7 out of 10 human (h) CA isoforms, whereas the pyridine sulfonamide is a low nanomolar inhibitor only of the tumor-associated hCA IX and XII, being less effective against other 9 isoforms. Thus, a difference of one atom (N vs CH) in two isostructural sulfonamides leads to drastic differences of activity, phenomenon understood at the atomic level through the high resolution crystallographic structure and kinetic measurements reported in the paper. Combining the tail and the ring approaches in the same chemotype leads to isoform-selective, highly effective sulfonamide CA inhibitors.     

Binding of adenosine 3',5'-monophosphate dependent protein kinase regulatory subunit to immobilized cyclic nucleotide derivatives.

Several cyclic nucleotide derivatives with aminoalkyl side chains attached to the purine ring were synthesized and their interactions with adenosine 3',5'-monophosphate (cAMP) dependent protein kinase were studied before and after immobilization to CNBr-activated Sepharose 4B. The soluble N6-substituted derivatives were as effective as cAMP itself in activating protein kinase and were more effective than 8-substituted cAMP derivatives, whereas the 2-substituted cAMP derivatives and the cGMP derivatives were the least effective. All of the synthetic derivatives tested were poor substrates for beef heart phosphodiesterase being hydrolyzed at rates less than 2% for that of cAMP itself. Utilizing methodology developed to evaluate the affinity of protein kinase for immogilized cyclic nucleotides it was found that all of the immobilized cyclic nucleotides interacted with protein kinase in a biospecific manner as judged by the following criteria: (1) the immobilized cyclic nucleotides competed with cAMP for the binding sites on protein kinase; (2) the analogous spacer-arm did not compete; and (3) the effects of enzyme concentration, MgATP, and cleavage of the cyclic phosphate ring on the interactions of protein kinase with the immobilized cyclic nucleotides were the same as previously shown for free cAMP. In addition, the immobilized ligands were bound with the same order of effectiveness as the analogous soluble ligand. The observed Ka for the activation of 0.005 muM protein kinase by N6-H2N(CH2)2-cAMP was increased from 0.23 to 3 muM by the process of immobilization. This increase was unaffected by the coupling density and spacer-arm length. The observed Kb for 0.10 muM protein kinase binding to immobilized N6-H2N(CH2)2-cAMP was increased as the molecular sieving exclusion limit of the matrix used was decreased indicating that at least part of this decrease in apparent affinity upon immobilization is due to exclusion of the enzyme from a portion of the matrix and therefore of the immobilized ligand molecules.     

Different Binding Mode in AT and GC Sequences for Unfused-Aromatic Dications

Abstract

We have previously synthesized a 2,5-diphenylfuranamidine dication (4) and presented evidence that this compound binds to AT sequences in DNA by a minor-groove interaction mode but binds to GC sequences by intercalation (1,2). To probe these sequence-dependent binding modes in more detail, and particularly to obtain additional evidence for the binding mode in GC rich sequences, we have synthesized and studied the DNA complexes of 1–3 which have the furan ring of 4 replaced by 2,6-substituted pyridine (1), pyrimidine (2), or triazine (3) ring systems. The three compounds with a six-membered central ring system bind to AT DNA sequences more weakly than the furan compound, but retain the minor-groove binding mode. The pyridine and pyrimidine derivatives bind to GC sequences of DNA more strongly than the furan, but the triazine derivative binds more weakly. The aromatic proton signals of 1–3, as previously observed with 4 shift upfield by approximately 0.5 ppm or greater on complex formation with polyd(G-C)₂. This and other spectroscopic as well as viscosity and kinetics results indicate that 1–4 bind to GC sites in DNA by intercalation. A nonclassical intercalation model, with the twisted-unfused, aromatic ring system intercalated into an intercalation site of matching structure can explain all of our and the literature results for the GC binding mode of these unfused, aromatic compounds.     

Effect of novel N-aryl sulfonamide substituted 3-morpholino arecoline derivatives as muscarinic receptor 1 agonists in Alzheimer's dementia models

A series of novel, potent, and selective muscarinic receptor 1 agonists (M1 receptor agonists) that employ a key N-substituted morpholine Arecoline moiety has been synthesized as part of research effort for the therapy of Alzheimer’s diseases. The ester group of arecoline (which is reported as muscarinic agonist) has been replaced by N-substituted morpholine ring. The structure–activity relationship reveals that the electron donating 4-substituted sulfonyl derivatives (9a, 9b, 9c, and 9e) on the nitrogen atom of the morpholine ring increases the affinity of M1 receptor binding 50- to 80-fold greater than the corresponding arecoline. Other derivatives also showed considerable M1 receptor binding affinity.     

Inhibition of copper amine oxidases by pyridine-derived aldoximes and ketoximes

The reactions of pea diamine oxidase (PSAO) and 2-phenylethylamine oxidase from Arthrobacter globiformis (AGAO) with pyridine-derived oximes were studied. Pyridine carbaldoximes and alkyl pyridyl ketoximes act as strong non-competitive inhibitors of the enzymes. The inhibition constants K(i) of these compounds vary between 10(-4) and 10(-5) M, for AGAO and some of the studied oximes were found even micromolar K(i) values. The presence of pyridine moiety in the studied compounds has remarkable influence on the inhibition potency. Elementary oximes lacking the heterocyclic ring, i.e., aliphatic (acetone oxime), alicyclic (cyclohexanone oxime) and aromatic (benzaldoxime), are considerably weaker non-competitive inhibitors (K(i) similar to 10(-3) or 10(-2) M). The position of the pyridine ring substitution by -C(R)=NOH group does not play a significant role for the inhibition potency of the studied oxime compounds. If the pyridine nitrogen is quaternised (in hydroxyiminomethyl-1-methylpyridinium iodides), the compound looses its inhibitory properties. Extended length of alkyl substituents on the ketoxime group of alkyl pyridyl ketoximes increases the K(i) value. The enzyme-bound copper represents one of possible target sites for pyridine-derived oxime inhibitors. The addition of an alkyl pyridyl ketoxime or a pyridine carbaldoxime to a native PSAO sample perturbs the absorption spectrum of the enzyme (by an absorption increase in the region 300-400 nm) that is not observed in the spectrum of reacted PSAO apoenzyme. However, an additional formation of hydrogen bonds with amino acid side-chains at the active site should be considered, namely for 3- and 4-substituted pyridine derivatives.     

QSARs of some novel isosteric heterocyclics with antifungal activity

QSAR analysis of a set of previously synthesized 2,5,6-trisubstituted benzoxazole, benzimidazole and 2-substituted oxazolo(4,5-b)pyridine derivatives tested for growth inhibitory activity against Candida albicans, was performed by using the computer-assisted multiple regression procedure. The activity contributions for either heterocyclic ring systems or substituent effects of these compounds were determined from the correlation equation and the predictions for the lead optimization were described. The resulting QSAR revealed that the oxazolo(4,5-b)pyridine ring system with the substitution of a benzyl moiety at position 2 was the most favourable structure among the heterocyclic nuclei. Moreover, the fifth position in the fused ring system is found more significant than the other positions in improving the activity.     

Antifungal effect of 4-arylthiosemicarbazides against Candida species. Search for molecular basis of antifungal activity of thiosemicarbazide derivatives

The in vitro antifungal potency of six series of 4-arylthiosemicarbazides was evaluated. Two isoquinoline derivatives with an ortho-methoxy or ortho-methyl group at the phenyl ring were the most potent antifungal agents. Molecular modeling studies and docking of all 4-arylthiosemicarbazides into the active sites of sterol 14α-demethylase (CYP51), topoisomerase II (topo II), L: -glutamine: D: -fructose-6-phosphate amidotransferase (GlcN-6-P), secreted aspartic proteinase (SAP), N-myristoyltransferase (NMT), and UDP-N-acetylmuramoyl-L: -alanine:D: -glutamate ligase (MurD) indicated the importance of both structural and electronic factors in ligand recognition and thus for the antifungal effectiveness of 4-arylthiosemicarbazides. A possible antifungal target was identified (NMT) and isoquinoline-thiosemicarbazides showed more favorable affinity than the native ligand.     

Synthesis and biological evaluation of aroylguanidines related to amiloride as inhibitors of the human platelet Na(+)/H(+) exchanger

Pyridine and benzene bioisosteres of amiloride were synthesized and evaluated for their inhibitory potency against the sodium-hydrogen exchanger (NHE) involved in intracellular pH regulation. The inhibition of NHE was determined by using the platelet swelling assay (PSA) in which the swelling of human platelets was induced by their incubation in an acid buffer (pH 6.7). Additionally, the inhibitory potency of the most active compounds was assessed by measuring the inhibition of the EIPA-sensitive (22)Na(+) uptake (UIA) by human platelets after intracellular acidosis. The results indicated that several benzene derivatives and compounds bearing an carbonylguanidine moiety in the meta position of the pyridine nitrogen were much more potent than amiloride (PSA:IC(50)=43.5 microM; UIA:IC(50)=100.1 microM), but less than EIPA, a pyrazine NHE inhibitor (PSA:IC(50)=0.08 microM; UIA:IC(50)=0.5 microM). In both biological assays (2-amino-5-bromo-pyridine-3-carbonyl)guanidine (32) was the most active molecule (PSA: IC(50)=0.8 microM, UIA : IC(50)=0.8 microM). Our investigations demonstrated that the replacement of the pyrazine ring of amiloride by a pyridine or a phenyl ring improved the NHE inhibitory potency (phenyl >pyridine >pyrazine).     

SYNTHESIS OF 1-(2-HYDROXY-3-METHOXYPROPYL)URACILS AND THEIR ACTIVITY AGAINST L1210 AND MACROPHAGE RAW 264.7 CELLS

ABSTRACT

The title compounds were obtained from appropriate 5-substituted uracil derivatives and 1,2-oxy-3-methoxypropane in the presence of sodium hydride. Under similar conditions 5-iodouracil gave 2-methoxymethyl-2,3-dihydro-oxazolo[3,2-c]pyrimidine-5,7-dione as a result of intramolecular cine type nucleophilic substitution. Cytotoxicity of 1-(2-hydroxy-3-methoxypropyl)-5-substituted uracil derivatives against L1210 and macrophage RAW 264.7 cells in vitro was examined.     

8-Substituted derivatives of adenosine 3',5'-cyclic phosphate require an unsubstituted 2'-hydroxyl group in the ribo configuration for biological activity.

Derivatives of adenosine 3',5'-cyclic phosphate (cAMP) with modifications in both the 2' and the 8 positions were synthesized and their enzymic activities as activators of cAMP-dependent protein kinase and as substrates for and inhibitors of cAMP phosphodiesterases were determined. Three types of derivatives were investigated: 8-substituted derivatives of O2'-Bt-cAMP, 8-substituted derivatives of 9-beta-D-arabinofuranosyladenine 3',5'-cyclic phosphate (ara-cAMP), and 8-substituted derivatives of 8,2'-anhydro-9-beta-D-arabinofuranosyladenine 3,'5'-cyclic phosphate (8,2'-anhydro-cAMP). The 8-substituted O2'-Bt-cAMP derivatives were synthesized by acylation of the preformed 8-substituted cAMP (8-HS-cAMP, 8-MeS-cAMP, and 8-PhCH2S-cAMP). 8-Br-O2'-tosyl-cAMP was sued as an intermediate for the preparation of 8,2'-anhydro-cAMP derivatives (8-HO-, 8-SH-, 8-H2N-, and 8-H3 CHN derivatives of 8,2'-anhydro-cAMP). 8-Substituted ara-cAMP derivatives were obtained by ring opening of 8-HO-8,2'-anhydro-cAMP with H+/H2O, NH3/MeOH, or MeONa/MeOH (to yield the 8-HO-, 8-H2N-, and 8-MeO-ara-cAMP derivatives). All of these doubly modified derivatives of cAMP are less than one-hundredth as active as cAMP at activating protein kinase and did not serve as substrates for the phosphodiesterase. These data show that the general inactivity of 2' derivatives of cAMP with kinase was not overcome by addition of an 8-substituent, even though many 8-substituted derivatives of cAMP activate the kinase more efficiently than does cAMP itself. In addition they show that while 2'-modification were tolerated by the phosphodiesterase, addition of an 8-substituent countermanded the allowable 2'-modification. The 8-substituted derivates of 02'-Bt-cAMP were found in general to be slightly better inhibitors of phosphodiesterase than the parent compounds containing no o2'-Bt substitution. As a group, the 8-substituted ara-cAMP derivatives were poorer inhibitors of phosphodiesterase than 8-substituted cAMP derivatives while the 8,2'-anhydro-cAMP derivatives were much poorer inhibitors than the 8-substituted ara-cAMP derivatives.     

A density functional theory study on the kinetics and thermodynamics of N-glycosidic bond cleavage in 5-substituted 2'-deoxycytidines

B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d) density functional theory calculations were employed to explore the kinetics and thermodynamics of gas-phase N-glycosidic bond cleavage induced by nucleophilic attack of C1' with a hydroxide ion in 5-substituted 2'-deoxycytidines. The results showed that, among the 5-substituted 2'-deoxycytidine derivatives examined [XdC, where X = H (dC), CH(3) (medC), CH(2)OH (hmdC), CHO (fmdC), COOH (cadC), F (FdC), or Br (BrdC)], fmdC and cadC exhibited the lowest energy barrier and largest exothermicity for N-glycosidic bond cleavage. These results paralleled previously reported nucleobase excision activities of human thymine DNA glycosylase (hTDG) toward duplex DNA substrates harboring a thymine and 5-substituted cytosine derivatives when paired with a guanine. Our study suggests that the inherent chemistry associated with the nucleophilic cleavage of N-glycosidic bond constitutes a major factor contributing to the selectivity of hTDG toward 5-substituted dC derivatives. These findings provided novel insights into the role of TDG in active cytosine demethylation.     

Selective inhibition of thromboxane synthetase by pyridine and its derivatives

Pyridine and some derivatives inhibit the conversion of prostaglandin endoperoxide to thromboxane catalyzed by thromboxane synthetase of human platelet microsomes. The structure-activity relationship of pyridine derivatives was investigated. Substitution of pyridine at position 2 either by an alkyl or an aryl group abolishes the inhibitory power of pyridine. Substitution at position 3 or 4 with a hydrophobic chain was found to increase the inhibitory potency, with 3-substituted pyridines being the most potent inhibitors. Inhibition by pyridine and its active derivatives appears to be selective for thromboxane synthetase since other enzymes in the arachidonic acid catabolic pathway were not affected. Kinetic studies indicate that inhibition as examined with hexylnicotinate is of the noncompetitive type.     

Synthesis of glycosides in which the aglycon is an N-(Hydroxymethyl)amino-1,3,5-triazine derivative

The synthesis of analogues of the anti-tumour drug 2-[N-(hydroxymethyl)methylamino]-4,6-bis (dimethylamino)-1,3,5-triazine (HMPMM) in which the OH or a dimethylamino group is replaced by a carbohydrate has been explored. Triazinyl β-glycosides were readily prepared by reaction of sugars with trimethyl-triazinylammonium salts. These were made with one or two methylamino groups on the triazine for reaction with formaldehyde to give the cytotoxic NMeCH2OH group. However, reaction of the triazinyl glycosides with formaldehyde gave complex intractable mixtures. When the carbohydrate portion was changed to the fully protected 2,3,4,6-tetra-O-acetyl glucose a good yield of the 2-[N-(hydroxymethyl)methylamino]-4-(dimethylamino)-1,3,5-triazin-2-yl tetra-O-acetyl β-glucoside was obtained. However, de-acetylation using sodium methoxide also removed the N–CH2OH group. We are investigating protection of the base-sensitive N–CH2OH group as trialkylsilyl and benzyl ethers and are looking at de-acetylation methods that are more selective. We have prepared glycosides in which the sugar is joined through the oxygen of the NMeCH2OH group. Coupling of acetobromoglucose with HMPMM catalysed by silver salts was not successful. Although methyl and cyclohexyl derivatives of HMPMM may be produced in high yields by reaction of HMPMM with methyl and cyclohexyl alcohols under acidic catalysis, production of glycosides in this way gave poor yields. MNDO calculations on reactions of HMPMM helped us devise improved reaction conditions for the condensation of 2,3,4,6-tetra-O-acetyl glucose with HMPMM and its derivatives. The best procedure to generate one of the target glycosides is to react 2,3,4,6-tetra-O-acetyl glucose and formaldehyde with 2-methylamino- 4,6-bis(dimethylamino)-1,3,5-triazine. The β-glycoside product was de-acetylated using potassium carbonate in dry methanol. Abbreviations: HMM, hexamethylmelamine (2) or 2,4,6-tris(dimethylamino)-1,3,5-triazine; HMPMM, hydroxymethylpentamethylmelamine or 2-[N-(hydroxymethyl)-methylamino]-4,6-bis(dimethylamino)-1,3,5-triazine; PMM, Pentamethylmelamine or 2-methylamino-4,6-bis(dimethylamino)-1,3,5-triazine; TBMS, t-Butyldimethylsilyl; p-TSA, p-Toluenesulphonic acid This revised version was published online in November 2006 with corrections to the Cover Date.     

Design and synthesis of 4H-3-(2-phenoxy)phenyl-1,2,4-triazole derivatives as benzodiazepine receptor agonists

A series of new 5-substituted analogues of 4H-3-(2-phenoxy)phenyl-1,2,4-triazole and its chlorinated derivatives was designed and prepared. Conformational analysis and superimposition of energy minima conformers of the compounds on estazolam, a known benzodiazepine receptor agonist, revealed that the main proposed benzodiazepine pharmacophores were well matched. Rotarod and pentylenetetrazole-induced lethal convulsion tests showed that the introduction of an amino group in position 5 of 1,2,4-triazole ring especially in chlorinated derivatives had the best effect which was comparable with diazepam.     

The square conformation of phenylglycine-incorporated ascidiacyclamide is stabilized by CH/π interactions between amino acid side chains

We designed a phenylglycine (Phg)-incorporated ascidiacyclamide (ASC) analogue, cyclo(-Phg-oxazoline-d-Val-thiazole-Ile-oxazoline-d-Val-thiazole- ([Phg]ASC), with the aim of stabilizing the square conformation of ASC through interactions between amino acid side chains. X-ray diffraction analysis showed that [Phg]ASC has a square structure, similar to ASC, in which the sec-butyl group of Ile and the benzene ring of Phg are in close proximity. Consistent with that finding, 1H NMR experiments revealed significant high-field shifts in the sec-butyl group of Ile, which suggests a potential for CH/π interactions between the sec-butyl group of Ile and the benzene ring of Phg. The CD spectra of [Phg]ASC were less affected by TFE titration or increasing temperature than those of ASC. In addition, [Phg]ASC showed approximately three times greater toxicity toward HL-60 cells than ASC. Thus the potently cytotoxic conformation of [Phg]ASC may be stabilized by CH/π interactions between the side chains of the Ile and Phg residues.