Novel Series of [ddN]-[TSAO-T] Heterodimers as Potential Bi-Functional Inhibitors of HIV-1 RT. Studies in the Linker and ddN Region

Abstract

Novel series of [ddN]-(CH₂)_n-[TSAO-T] heterodimers have been prepared and tested for their anti-HIV-1 and HIV-2 activity. The most active compound of this series was the [d4T]-(CH₂)₃-[TSAO-T] heterodimer (EC₅₀ = 0.018 ± 0.03 μM).     

Synthesis and Anti‐HIV Activity of [ddN]‐[ddN] Dimers and Benzimidazole Nucleoside Dimers

In an attempt to combine the HIV‐inhibitory capacity of different 2′,3′‐dideoxynucleoside (ddN) analogs, we have designed and synthesized several dimers of [AZT]‐[AZT] and [AZT]‐[d4T]. In addition, we also synthesized the dimers of 1‐(1H‐benzimidazol‐1‐yl)‐1‐deoxy‐β‐D ‐ribofuranose. The in vitro anti‐HIV activity of these compounds on a pseudotype virus, pNL4‐3.Luc.R‐E‐, in the 293T cells has been determined. Among these compounds, 2,2′‐(propane‐1,3‐diyl)bis[1‐(β‐D ‐ribofuranosyl)‐1H‐benzimidazole] ( 3 ) showed the highest anti‐HIV activity with similar effect as AZT.     

Synthesis and antitumor activity of some indeno[1,2-b]quinoline-based bis carboxamides

A series of bis(11-oxo-11H-indeno[1,2-b]quinoline-6-carboxamides) linked through the 6-carboxamides were prepared by coupling the requisite acid imidazolides with various diamines. Compounds with mono-cationic linker chains were more potent cytotoxins than the corresponding monomer in a panel of rodent and human cell lines, while those with the dicationic linker chains (CH2)2NR(CH2)2NR(CH2)2 and (CH2)2NR(CH2)3NR(CH2)2 showed extraordinarily high potencies (for example, IC50s of 0.18-1.4 nM against human Jurkat leukemia; up to 1000-fold more potent than the parent monomer). As seen previously in the monomeric series, small, lipophilic 4-substituents significantly increased potency in cell culture. The dimeric compounds were all slightly to significantly more potent in the mutant JL(A) and JL(D) cell lines that under-express topo II, suggesting that this enzyme is not their primary target. An 11-imino-linked dimer was much less active, and an asymmetric indeno[1,2-b]quinoline-6-carboxamide/naphthalimide dimer was less active than the comparable symmetric bis(indeno[1,2-b]quinoline-6-carboxamide). Selected analogues were active against sub-cutaneously implanted colon 38 tumors in mice, giving growth delays comparable to that of the clinical topo I inhibitor irinotecan at up to 10-fold lower doses. These compounds form an interesting new class of putative topo I inhibitors.     

Thiolate exchange in [TmR]ZnSR' complexes and relevance to the mechanisms of thiolate alkylation reactions involving zinc enzymes and proteins

The zinc and cadmium thiolate complexes [TmBut]MSCH2C(O)N(H)Ph (M = Zn, Cd) may be obtained via treatment of the respective methyl complex [TmBut]MMe with PhN(H)C(O)CH2SH. The molecular structure of [TmBut]ZnSCH2C(O)N(H)Ph has been determined by X-ray diffraction, thereby demonstrating the presence of an intramolecular N-H S hydrogen bond between the amide N-H group and thiolate sulfur atom. [TmBut]ZnSCH2C(O)N(H)Ph mimics the function of the Ada DNA repair protein by undergoing alkylation with MeI to give [TmBut]ZnI and MeSCH2C(O)N(H)Ph. A series of crossover experiments and 1H NMR magnetization transfer studies establish that thiolate exchange between [TmR]ZnSR' derivatives is facile in this system, an observation that supports the previous suggestion that the alkylation of [TmPh]ZnSCH2C(O)N(H)Ph by MeI may proceed via a sequence that involves dissociation of [PhN(H)C(O)CH2S]-.     

Development of novel mixed-ligand oxotechnetium [SNS/S] complexes as potential 5-HT1A receptor imaging agents

The "3 + 1" ligand system [SN(R)S/S combination] was applied in order to synthesize neutral mixed-ligand oxotechnetium complexes of the general formula 99mTcO[SN(R)S]/[S] as potential 5-HT1A receptor imaging agents. The complexes are carrying the 1-(2-methoxyphenyl)piperazine moiety, a fragment of the true 5-HT1A antagonist WAY 100635, either on the monodentate ligand [S] or on the tridentate ligand [SN(R)S]. The complexes MO[EtN(CH2CH2S)2] [o-MeOC6H4N(CH2CH2)2NCH2CH2S] (3), MO[o- MeOC6H4N(CH2CH2)2N(CH2)3N(CH2CH2S)2][PhS] (6) and MO[o-MeOC6H4N(CH2CH2)2N(CH2)3N(CH2CH2S)2] [PhCH2CH2S] (9), where M = 99mTc, were prepared at tracer level using 99mTc glucoheptonate as precursor. For structural characterization, the analogous oxorhenium (M = Re, 1, 4 and 7, respectively) and oxotechnetium (M = 99gTc, 2, 5 and 8, respectively) complexes were prepared by ligand exchange reactions. All products were characterized by elemental analysis and spectroscopic methods. Complexes 1, 4 and 7 were further characterized by crystallographic analysis. For 1, the coordination geometry about rhenium can be described as trigonally distorted square pyramidal (tau = 0.36), while for 4 and 7, as distorted trigonal bipyramidal (tau = 0.66 and tau = 0.61, respectively). The coordination sphere about oxorhenium in all complexes is defined by the SNS donor atom set of the tridentate ligand and the sulfur atom of the monodentate coligand. The structure of the 99mTc complexes 3, 6 and 9 was established by comparative HPLC using authentic oxorhenium and oxotechnetium samples. The binding affinity of oxorhenium compounds for the 5-HT1A receptor subtype was determined in rat brain hippocampal preparations (IC50 = 6-31 nM). Preliminary tissue distribution data in healthy mice revealed the ability of all three 99mTc complexes to cross the intact blood-brain barrier (0.49-1.15% ID at 1 min p.i.). In addition, complexes 6 and 9 showed significant brain retention. These promising results have demonstrated that the SNS/S mixed-ligand system can be used in the development of 99mTc complexes as potential 5-HT1A receptor imaging agents.     

Radiosynthesis of [11C]BBAC and [11C]BBPC as potential PET tracers for orexin2 receptors

Radiosynthesis of [N-methyl-(11)C](S)-N-([1,1'-biphenyl]-2-yl)-1-(2-((1-methyl-1H-benzo[d]imidazol-2-yl)thio)acetyl)pyrrolidine-2-carboxamide ([(11)C]BBAC or [(11)C]3) and [N-methyl-(11)C] (S)-N-([1,1'-biphenyl]-2-yl)-1-(3-(1-methyl-1H-benzo[d]imidazol-2-yl)propanoyl)pyrrolidine-2-carboxamide ([(11)C]BBPC or [(11)C]-4), two potential PET tracers for orexin2 receptors are described. Syntheses of non-radioactive standards 3, 4 and corresponding desmethyl precursors 1, 2 were achieved from common intermediate (S)-2-([1,1'-biphenyl]-2-yl)-1-(pyrrolidin-2-yl)ethanone. Methylation using [(11)C]CH(3)OTf in the presence of base in acetone afforded [(11)C]3 and [(11)C]4 in 30±5% yield (EOS) with >99 % radiochemical purities with a specific activity ranged from 2.5±0.5 Ci/μmol (EOB). The logP of [(11)C]3 and [(11)C]4 were determined as 3.4 and 2.8, respectively. The total synthesis time was 30 min from EOB. However, PET scans performed in a rhesus monkey did not show tracer retention or appropriate brain uptake. Hence [(11)C]3 and [(11)C]4 cannot be used as PET tracers for imaging orexin2 receptors.     

Design and synthesis of spiro[indole-thiazolidine]spiro[indole-pyrans] as antimicrobial agents

A series of novel spiro[indole-thiazolidine]spiro[indole-pyran] derivatives were synthesized from N-(bromoalkyl)indol-2,3-diones via monospiro-bisindole intermediates; the two indole nuclei being connected via N-(CH(2))(n)-N linker. Synthesized compounds were evaluated for their antimicrobial activities in vitro against three Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Staphylococcus epidermis), four Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumonia) as well as four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, and Candida albicans) using Cup plate method. Bis spiro-indoles exhibited stronger antibacterial and antifungal efficiency than their corresponding mono spiro-indoles. Compound 10e, the most active derivative was shown to inhibit the growth of all bacterial strains and two fungal strains (A. niger and C. albicans).     

Psi[CH2O] pseudodipeptide synthesis. An improved approach which allows absolute configuration determination

An improved way to obtain psi[CH2O] pseudodipeptide units is proposed, involving an intramolecular Williamson's reaction, with displacement of bromine by an alkoxide, instead of the classical intermolecular one. Until now, psi[CH2O] pseudodipeptide synthesis done by this new method, has used a protected form of the amino alcohol hydroxyl group to prepare the acyclic precursor. In the present paper, the use of an active ester of the brominated carboxylic acid avoids this protection step. The pseudodipeptides AcGly psi[CH2O]-D,L-Ala-OH and Ac-Ser(Bzl) psi [CH2O]-D,L-Ala-OH were obtained in high yields, through a delta-lactam intermediate, which furthermore allows the determination of the absolute configuration of compounds using HPLC and appropriate nuclear magnetic resonance (NMR) techniques.     

Glass-capillary-gas chromatography/mass spectrometry data of mono- and polyhydroxylated benz[a]anthracene. Comparison with benz[a]anthracene metabolites from rat liver microsomes

By means of glass-capillary-gas chromatography all possible benz[a]anthracene metabolites formed by rat liver microsomes (phenols, dihydrodiols, dihydrodiol enols and tetrahydrotetrols) can be separated. Mass spectra of their trimethylsilyl ethers show intense molecule ions and, in most cases, characteristic fragments. K-Region diols and their secondary oxidation products can be recognized by the ratio (m/e 147) (m/e 191) greater than 1, whereas the ratio is inverse in all other dihydrodiol trimethylsilyl ethers investigated. With the exception of 1,2-dihydrobenz[a]anthracene-1,2,3-triol all vicinal dihydrodiol enols investigated exhibit an intense elimination of the fragment CH = CH-OSiMe3 according to m/e 379. The conformation of vicinal tetrahydrobenz[a]anthracenetetrols possibly can be distinguished by the intensity of m/e 380 (M - 240) since only in those possessing two or more subsequent Me3SiO groups in the same conformation intense elimination of Me3Si-O-CH = CH-O-SiMe3 is observed. Retention times and mass spectrometric data of a series of synthetic benz[a]anthracene derivatives are presented as a base for the identification of benz[a]anthracene metabolites in biological systems.     

(+)-3-[2-(Benzo[b]thiophen-2-yl)-2-oxoethyl]-1-azabicyclo[2.2.2]octane as potent agonists for the alpha7 nicotinic acetylcholine receptor

A series of 3-substituted 1-azabicyclo[2.2.2]octanes was discovered as the alpha7 nicotinic acetylcholine (alpha7) receptor agonists. It was found that (+)-3-[2-(benzo[b]thiophen-2-yl)-2-oxoethyl]-1-azabicyclo[2.2.2]octane (+)-15b has potent agonistic activity for the alpha7 receptor.     

HIV protease (HIV PR) inhibitor structure-activity-selectivity, and active site molecular modeling of high affinity Leu [CH(OH)CH2]Val modified viral and nonviral substrate analogs.

This report details the structure-activity relationships of the HIV gag substrate analog Val-Ser-Gln-Asn-Leu psi[CH(OH)CH2]Val-Ile-Val (U-85548E), an inhibitor exhibiting subnanomolar affinity towards HIV type-1 aspartic proteinase (HIV-1 PR). Our data show that the P1-P2' tripeptidyl sequence provides the minimal chemical determinant for HIV-1 PR binding. We describe the structure-activity properties of Leu psi[CH(OH)CH2]Val substitution in other peptidyl ligands of nonviral substrate origin (e.g., angiotensinogen, insulin and pepstatin). Furthermore, the aspartic proteinase selectivities of a few key compounds are summarized relative to evaluation against human renin, human pepsin, and the fungal enzyme, rhizopuspepsin. These studies have led to the rational design of nanomolar potent inhibitors of both HIV-1 and HIV-2 PR. Finally, a 2.5 A resolution X-ray crystallographic structure of U-85548E complexed to synthetic HIV-1 PR dimer (Jaskolski et al., Biochemistry 30, 1600 [1991]) provided a 3-D picture of the inhibitor bound to the enzyme active site, and we performed computer-assisted molecular modeling studies to explore the possible binding modes of the above series of Leu psi[CH(OH)CH2]Val substituted HIV-1 PR inhibitors.     

Synthesis and binding characteristics of [3H] H-Tyr-Ticpsi[CH2-NH] Cha-Phe-OH, a highly specific and stable delta-opioid antagonist.

Substitution of the Phe3 aromatic ring in H-Tyr-Ticpsi[CH2-NH]Phe-Phe-OH with cyclohexylalanine (Cha) has been reported to result in a compound, H-Tyr-Ticpsi[CH2-NH]Cha-Phe-OH (TICP[psi]), showing substantially increased delta-opioid antagonist potency and high delta selectivity. TICP[psi] was radiolabeled by catalytic tritiation of its precursor Tyr(3',5'-I2)1TICP[psi]. Binding characteristics of the new tritiated pseudopeptide were determined using the radioligand binding assay in rat brain membranes. On the basis of the results of saturation binding studies performed at 25 degrees C, an equilibrium dissociation constant (Kd) of 0.35 nM and a receptor density (Bmax) of 112 fmol/mg protein were calculated. This new tritiated ligand exhibits high affinity for delta-opioid receptors, whereas its binding to mu and kappa receptors is weak. A study of [H3]TICP[psi] binding displacement by various receptor-selective opioids showed the following rank order of potency: delta > kappa = mu. These receptor binding characteristics of the ligand, together with its high specific radioactivity (41.3 Ci/mmol) and stability, makes it a useful tool for labeling delta-opioid receptors, both in vitro and in vivo.     

Synthesis of naphtho[2,3-a]phenoxazinium chlorides: structure-activity relationships of these heterocycles and benzo[a]phenoxazinium chlorides as new antimicrobials

Synthesised functionalised naphtho[2,3-a]phenoxazinium chlorides revealed great fluorescence with maximum emission wavelengths between 630 and 676 nm, in ethanol and water at physiological pH. Naphtho[2,3-a]phenoxazines, as well as a series of benzo[a]phenoxazines, were evaluated against Saccharomyces cerevisiae, in a broth microdilution assay. This family of compounds exhibited antifungal activity depending both on the substituents of the heterocycle nucleus as well as on its size. The best activities were obtained for four-ring systems, and particularly for 5,9-diaminobenzo[a]phenoxazines with R=Me, R(1)=H and R(2)=Et. As for R(3) substitution, the greatest efficiency was obtained for R(3)=(CH(2))(3)Cl, with a MIC of 3.75 microM. The linkage of different amino acids to the functional group of the 5-amino position of diaminobenzo[a]phenoxazinium moiety resulted in compounds with diverse antimicrobial efficiencies, depending on the polar character of the amino acid, on its linkage position and on the size of the alkyl chain linker.     

Synthesis of some new [1,2,4]triazolo[3,4-b][1,3,4]thiadiazines and [1,2,4]triazolo[3,4-b][1,3,4] thiadiazoles starting from 5-nitro-2-furoic acid and evaluation of their antimicrobial activity

New series of fused 1,2,4-triazoles such as, 6-(aryl)-3-(5-nitrofuran-2-yl)-5,6-dihydro-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 4-8, 6-(alkyl/aryl amino)-3-(5-nitrofuran-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 9-13 and 6-(4-substituted phenyl)-3-(5-nitrofuran-2-yl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines 14-18 have been synthesized via the reaction of 4-amino-5-(5-nitrofuran-2-yl)-4H-1,2,4-triazole-3-thiol 3 with various reagents such as hetero aromatic aldehydes, alkyl/aryl isothiocyanates and 4-substituted phenacyl bromides, respectively. The structures of the newly synthesized compounds have been confirmed on the basis of elemental analysis and spectral studies. The newly synthesized triazolo derivatives have been investigated for their in vitro antibacterial activity. Most of the tested compounds showed interesting antibacterial activity against Staphylococcus aureus. Furthermore, the most potent antibacterial compounds 11-13 were evaluated for their in vitro cytotoxic activity against human cancer cell lines. It was found that compounds 11 and 13 showed higher cytotoxicity against Hep-G2 cell line as compared to standard.     

Solvent free microwave synthesis and evaluation of antimicrobial activity of pyrimido[4,5-b]- and pyrazolo[3,4-b]quinolines

A series of 2-oxopyrimido[4,5-b]-, 2-thio[4,5-b]-, 1-(p-tosyl)pyrazolo[3,4-b]- and 1-(2',4'-dinitrophenyl)pyrazolo[3,4-b]-quinolines have been synthesized in good to excellent yields by environmentally benign solvent free microwave-induced techniques involving the condensation of 2-chloro-3-formylquinolines with urea, thiourea, p-toluenesulfonylhydrazide and 2,4-dinitrophenylhydrazine, respectively, using PTSA as a catalyst. All the synthesized compounds were evaluated for their antibacterial and antifungal activities. Most of the compounds showed the best activity against Escherichia coli and Pseudomonas aeruginosa.     

Specific, uncompetitive inhibition of beta-galactosidases by a 5,6-isopropylidenedioxyfuro[2,3-d]isoxazole-3-methanol derivative

(-)-(3aS,5S,6S.6aR)-3a,5,6,6a-Tetrahydro-5,6-isopropylide nedioxyfuro [2,3-d]isoxazole-3-methanol ((-)-5) has been tested toward 25 glycohydrolases and found to inhibit beta-galactosidase from Aspergillus niger (Ki = 18 microM) and that from Aspergillus orizae (Ki = 72 microM). Hydrolysis of the acetonide or exchange of CH2OH group for a CHO, CH2OMe or a CH2OMOM group suppresses the inhibitory activity.     

Chemistry of the diazeniumdiolates. I. Structural and spectral characteristics of the [N(O)NO]- functional group.

Ions of structure X[N(O)NO]-, examples of which have seen increasing use as probes for studying the biology of nitric oxide (NO) over the past decade, have a varied chemical history spanning nearly two centuries. Nevertheless, they have not been widely appreciated for their physicochemical similarities. Here we begin a series of systematic inquiries into the fundamental chemistry of such compounds aimed at identifying both the characteristics that justify considering them as a group and the factors that contribute to observed differences in their physicochemical properties. In the present paper, X-ray structures in which X is SO3- (1), O- (2), Ph (3), and Et2N (5), as well as that of the gem-disubstituted carbon derivative CH2[N(O)NO]2-(2) (4), are compared. All their O-N-N-O systems are essentially planar, with cis oxygens and an N-N linkage exhibiting considerable double-bond character. The ultraviolet spectrum of the isolated chromophore consists of a relatively intense ( approximately 6-10 mM(-1) x cm(-1) per [N(O)NO]- group) absorption at 248-250 nm (for 2 and 5) that is red shifted by through-space Stark interactions (e.g., by approximately 10 nm in 1 and 4) as well as by conjugative interaction with X (lambda(max) = 284 nm for 3). Infrared and Raman spectra for the widely used pharmacological probe 5 were determined, with analysis of vibrational modes being aided by comparison with the spectra of the [15N(O)15NO]- isotopomer and density functional theory calculations at the B3LYP/6-311++G** level. To address confusion that has arisen in the literature resulting from rather widespread use of differing trivial designations for this class of compounds, a unifying nomenclature system is recommended in which compounds containing the [N(O)NO]- moiety are named as diazeniumdiolates. It is hoped that these and other efforts to understand and predict the physicochemical similarities and differences among different members of the diazeniumdiolate class will aid in reaping their full potential in the area of rational drug design.     

Synthesis and Anti-HIV-1 Activity of 4- and 5-Substituted 1,2,3-Triazole-TSAO Derivatives

Abstract

Several 4- or 5-monosubstituted and 4,5-disubstituted 1,2,3-triazole analogues of the anti-HIV-1 lead compound [1-[2′,5′-bis-O-(tert-butyldimethylsilyl)-β-D-ribofuranosyl]thymine]-3′-spiro-5″-(4″-amino-1″,2″-oxathiole-2″,2″-dioxide) (TSAO-T) have been prepared and evaluated for their inhibitory effect against HIV-1-induced cytopathicity.     

Synthesis and anticonvulsant activity of 7-alkoxyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinolines

A series of 7-alkoxyl-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline derivatives was synthesized using 6-hydroxy-3,4-dihydro-1H-quinolin-2-one as a starting material. Their anticonvulsant activities were evaluated by the maximal electroshock test (MES test) and the subcutaneous (s.c.) pentylenetetrazol test (scMet test), and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). MES and scMet tests show that 7-(4-fluorobenzyloxy)-4,5-dihydro-[1,2,4]triazolo[4,3-a]quinoline 4l was found to be the most potent with ED50 value of 11.8 and 6.7 mg kg(-1) and protective index (PI = TD50/ED50) value of 4.6 and 8.1, respectively.