Synthesis and biological activity of pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one derivatives: in silico approach

Xanthine oxidase (XO) is responsible for the pathological condition called gout. Inhibition of XO activity by various pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidine-4-one derivatives was assessed and compared with the standard inhibitor allopurinol. Out of 10 synthesized compounds, two compounds, viz. 3-amino-6-(2-hydroxyphenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one (3b) and 3-amino-6-(4-chloro-2-hydroxy-5-methylphenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one (3g) were found to have promising XO inhibitory activity of the same order as allopurinol. Both compounds and allopurinol inhibited competitively with comparable Ki (3b: 3.56?µg, 3g: 2.337?µg, allopurinol: 1.816?µg) and IC₅₀ (3b: 4.228?µg, 3g: 3.1?µg, allopurinol: 2.9?µg) values. The enzyme–ligand interaction was studied by molecular docking using Autodock in BioMed Cache V. 6.1 software. The results revealed a significant dock score for 3b (?84.976?kcal/mol) and 3g (?90.921?kcal/mol) compared with allopurinol (?55.01?kcal/mol). The physiochemical properties and toxicity of the compounds were determined in silico using online computational tools. Overall, in vitro and in silico study revealed 3-amino-6-(4-chloro-2-hydroxy-5-methylphenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2–a]pyrimidin-4-one (3g) as a potential lead compound for the design and development of XO inhibitors.     

Solution NMR Conformational Analysis of the Potent Equilibrative Sensitive (ES) Nucleoside Transporter Inhibitor,S 6-(4-Nitrobenzyl)mercaptopurine Riboside (NBMPR)

Abstract

High resolution NMR analysis involving one-dimensional (1-D) ¹H and nuclear Overhauser (NOE) difference spectroscopy was applied to solutions of NBMPR in DMSO-d ₆. Coupling constants were obtained at different temperatures between 285 and 353 K, and used to analyze the rotamer preferences about the C-4′-C-5′ bond. The results revealed a rotamer distribution about the χ tortion angle that favors the high-anti range, a preponderance of the γ⁺ rotamer (at ～64 %) with respect to the γ torsion angle, and a higher population of the south (S) conformer, which was favored by as little as the 4 % to as much as 31 % over the north (N) conformer as calculated by the program PSEUROT 6.2. The high-anti glycosidic torsion orientation appears to be the major conformational difference between the solution structure of NBMPR determined in this study and the structure previously observed in the solid state.     

The crystal structure of d-glucose 6-(sodium hydrogen-phosphate)

The title compound, when recrystallised from water, is monoclinic, space group P2₁, with a = 5.774(4), b = 7.189(5), c = 12.69(1) Å, β = 106.66(5)°, and Z = 2. The crystal structure was determined from three-dimensional X-ray diffraction data taken on an automatic diffractometer with CuKα, and refined by least-squares techniques to R = 0.034 for 977 reflexions. The pyranose ring adopts the ⁴C₁ conformation. The conformation about the exocyclic C-5-C-6 bond is gauche-trans [the torsion angles O-6-C-6-C-5-O-5 and O-6-C-6-C-5-C-4 are 64.2(8) and ?175.6(7)°, respectively], which is significantly different from the gauche-gauche geometry in d-glucose 6-(barium phosphate). The phosphate ester bond, P-O-6, is 1.584(3) Å. All of the oxygen-bonded hydrogen atoms are involved in intermolecular hydrogen-bonds.     

Synthesis of 2-Bromomethyl-3-Hydroxy-2-Hydroxymethyl-Propyl Pyrimidine and Theophylline Nucleosides Under Microwave Irradiation. Evaluation of Their Activity Against Hepatitis B Virus

Alkylation of 2-methylthiopyrimidin-4(1H)-one (1a) and its 5(6)-alkyl derivatives 1b–d as well as theophylline (7) with 2,2-bis(bromomethyl)-1,3-diacetoxypropane (2) under microwave irradia-tion gave the corresponding acyclonucleosides 1-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]-2-methyl-thio pyrmidin-4(1H)-ones 3a–d and 7-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]theophylline (8), which upon further irradiation gave the double-headed acyclonucleosides 1,1 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis[(2-(methylthio)-pyrimidin-4(1H)-ones] 4a–c, and 7,7 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis(theophylline) (9). The deacetylated derivatives were obtained by the action of sodium methoxide. The activity of deacetylated nucleosides against Hepatitis B virus was evaluated. Compound 5b showed moderate inhibition activity against HBV with mild cytotoxicity.     

Novel 1,5-diphenyl-6-substituted 1H-pyrazolo[3,4-d]pyrimidin-4(5H)-ones induced apoptosis in RKO colon cancer cells

Novel 1,5-diphenyl-6-substituted-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-ones were synthesized and characterized. All compounds were screened for their anti-proliferative activities in five different cancer cell lines. The results showed that compounds 7a and 7b comprising aminoguanidino or guanidino moiety at position 6 inhibited proliferation of RKO colon cancer cells with IC₅₀ of 8 and 4?μM, respectively. Compounds 7a and 7b induced apoptosis in RKO cells, which was confirmed by TUNEL and annexin V-FITC assays. Flow cytometric analysis indicated that compounds 7a and 7b arrested RKO cells in the G1 phase and the most active compound 7b increased levels of p53, p21, Bax, ERK1/2 and reduced levels of Bcl2 and Akt. Compound 7b also activates release of cytochrome c, which is consistent with activation of caspase-9. Additionally, compound 7b increased caspase-3 activity and cleaved PARP-1 in RKO cells. Collectively, these findings could establish a molecular basis for the development of new anti-cancer agents.     

Synthesis of new pyridothienopyrimidinone derivatives as Pim-1 inhibitors

Four series of pyridothienopyrimidin-4-one derivatives were designed and prepared to improve the pim-1 inhibitory activity of the previously reported thieno[2,3-b]pyridines. Significant improvement in the pim-1 inhibition and cytotoxic activity was achieved using structure rigidification strategy via ring closure. Six compounds (6c, 7a, 7c, 7d, 8b and 9) showed highly potent pim-1 inhibitory activity with IC₅₀ of 4.62, 1.18, 1.38, 1.97, 8.83 and 4.18?μM, respectively. Four other compounds (6b, 6d, 7b and 8a) showed moderate pim-1 inhibition. The most active compounds were tested for their cytotoxic activity on three cell lines [MCF7, HCT116 and PC3]. Compounds 7a [the 2-(2-chlorophenyl)-2,3-dihydro derivative] and 7d [the 2-(2-(trifluoromethyl)-phenyl)-2,3-dihydro derivative] displayed the most potent cytotoxic effect on the three cell lines tested consistent with their highest estimated pim-1 IC₅₀ values.     

Design, synthesis and in vitro evaluation of novel chroman-4-one, chroman, and 2H-chromene derivatives as human rhinovirus capsid-binding inhibitors

As part of an effort to generate broad-spectrum inhibitors of rhinovirus replication, novel series of (E)-3-[(E)-3-phenylallylidene]chroman-4-ones 1a–e, (E)-3-(3-phenylprop-2-yn-1-ylidene)chroman-4-ones 2a and 2b, (Z)-3-[(E)-3-phenylallylidene]chromans 3a–e, and (E)-3-(3-phenylprop-1-en-1-yl)-2H-chromenes 4a–d were designed and synthesized. All the compounds were tested in vitro for their efficacy against infection by human rhinovirus (HRV) 1B and 14, two representative serotypes for rhinovirus group B and A, respectively. Most of the analogues were found to be potent and selective inhibitors of both HRVs, although HRV 1B was generally more susceptible than HRV 14. Mechanism of action studies of (E)-6-chloro-3-(3-phenylprop-1-en-1-yl)-2H-chromene 4b, the most potent compound on HRV 1B infection, suggested that 4b behaves as a capsid-binder probably acting at the uncoating level.     

Design and synthesis of (5-amino-1, 2, 4-triazin-6-yl)(2-(benzo[d] isoxazol-3-yl) pyrrolidin-1-yl)methanone derivatives as sodium channel blocker and anticonvulsant agents

Abstract

A series of novel (5-amino-3-substituted-1, 2, 4-triazin-6-yl) (2-(6-halo-substituted benzo[d]isoxazol-3-yl) pyrrolidin-1-yl) methanone 5a–5r was synthesized. Their anticonvulsant activities were evaluated by the maximal electroshock (MES) test and neurotoxicity was evaluated by the rotorod test. The MES test showed that (5-amino-3-phenyl-1, 2, 4-triazin-6-yl)(2-(6-fluorobenzo[d]isoxazol-3-yl) pyrrolidin-1-yl) methanone 5c was found to be the most potent compound with ED₅₀ value of 6.20?mg/kg (oral/rat) and a protective index (PI?=?ED₅₀/TD₅₀) value of >48.38, which was much higher than the PI of the reference drug phenytoin. To explain the possible mechanism of action of selected derivatives 5b, 5c, 5i and 5o, their influence on sodium channel was evaluated in vitro.     

Phosphoralaninate Pronucleotides of Pyrimidine Methylenecyclopropane Analogues of Nucleosides: Synthesis and Antiviral Activity

The Z- and E-thymine and cytosine pronucleotides 3d, 4d, 3e, and 4e of methylenecyclopropane nucleosides analogues were synthesized, evaluated for their antiviral activity against human cytomegalovirus (HCMV), herpes simplex virus 1 and 2 (HSV-1 and HSV-2), varicella zoster virus (VZV), Epstein-Barr virus (EBV), human immunodeficiency virus type 1 (HSV-1), and hepatitis B virus (HBV) and their potency was compared with the parent compounds 1d, 2d, 1e, and 2e. Prodrugs 3d and 4d were obtained by phosphorylation of parent analogues 1d or 2d with reagent 8. A similar phosphorylation of N⁴-benzoylcytosine methylenecyclopropanes 9a and 9b gave intermediates 11a and 11b. Deprotection with hydrazine in pyridine–acetic acid gave pronucleotides 3e and 4e. The Z-cytosine analogue 3e was active against HCMV and EBV. The cytosine E-isomer 4e was moderately effective against EBV.     

Design,Synthesis, and Antiviral Evaluation of 2-Deoxy-D-Ribosides of Substituted Benzimidazoles as Potential Agents for Human Cytomegalovirus Infections

Abstract

Stereoselective glycosylation of 2,5,6-trichlorobenzimidazole (1b), 2-bromo-5,6-dichlorobenzimidazole (1c), 5,6-dichlorobenzimidazole (1d), 5,6-dichlorobenzimidazole-2-thione (1e), 5,6-dichloro-2-(methylthio)benzimidazole (1f), 2-(benzylthio)-5,6-dichlorobenzimidazole (1g), and 2-chloro-5,6-dimethylbenzimidazole (1h) with 2-deoxy-3,5-di-O-p-toluoyl-α-D-erythro-pentofuranosyl chloride was achieved to give the desired β nucleosides 2b-h. Subsequent deprotection afforded the corresponding free β-D-2-deoxyribosides 3b-h. The 2-methoxy derivative 3i was synthesized by the treatment of 2b with methanolic sodium methoxide. Displacement of the 2-chloro group of 2b with lithium azide followed by a removal of the protective groups gave the 2-azido-5,6-dichlorobenzimidazole derivative (5). The 2-amino derivative (6) was obtained by hydrogenolysis of 5 over Raney nickel. 5,6-Dichloro-2-isopropylamino-1-(2-deoxy-β-D-erythro-pentofuranosyl)benzimidazole (10) was prepared using 2′-deoxyuridine (7), N-deoxyribofuranosyl transferase and 1d followed by functionalization of the C2 position. Antiviral evaluation of target compounds established that compounds 3b and 3c were active against human cytomegalovirus (HCMV) at non-cytotoxic concentrations. The activity of these 2-deoxy ribosides, however, was less than the activity of the parent riboside, 2,5,6-trichloro-1-β-D-ribofuranosylbenzimidazole (TCRB). Compared to TCRB, 3b and 3c were somewhat more cytotoxic and active against herpes simplex virus type 1. Compounds 3d-i with other substituents in the 2-position were inactive against both viruses and non-cytotoxic. In contrast, compounds with amine substituents in the 2-position (5, 6, 10) were active against HCMV albeit less so than TCRB. These results establish that 2-deoxy-D-ribosyl benzimidazoles are less active against the DNA virus HCMV than are the corresponding D-ribosides.     

Regioselective Synthesis of Indazole N 1‐ and N 2‐(β‐d‐Ribonucleosides)

The regioselective synthesis of 4‐nitroindazole N ¹‐ and N ²‐(β‐d‐ribonucleosides) (8, 9, 1b and 2b) is described. The N ¹‐regioisomers are formed under thermodynamic control of the glycosylation reaction [fusion reaction or Silyl Hilbert‐Johnson glycosylation for 48 h (66%)], while the kinetic control (Silyl Hilbert‐Johnson glycosylation for 5 h) afforded only the N ²‐isomer (64%). The structures of the nucleosides 1b and 2b were assigned by single crystal X‐ray analyses. The 4‐amino‐N ¹‐(β‐d‐ribofuranosyl)‐1H‐indazole (3b) was obtained from the nitro nucleoside 1b by catalytic hydrogenation. Compound 3b shows fluorescence while the 4‐nitroindazole nucleosides 1b and 2b do not possess this property.     

Production of a co-polyester of 3-hydroxybutyric acid and 3-hydroxyvaleric acid from succinic acid by Rhodococcus ruber: biosynthetic considerations

The biosynthesis of the 3-hydroxyvalerate (3HV) monomer of polyhydroxyalkanoate by Rhodococcus ruber from succinic acid was investigated using nuclear magnetic resonance analysis. Polymer produced from [2,3-¹³C]- and [1,4-¹³C]succinate showed that the C-1-C-2 and C-4-C-5 fragments of 3HV were derived from carbons 2 and 3 of succinate, essentially without bond cleavage, and carbon 3 of 3HV was derived from a carboxyl carbon of succinate. Using [1,2-¹³C]succinate it was demonstrated that the C-1-C-2 bond of succinate was cleaved during polymer biosynthesis. Methylmalonyl-coenzyme A (CoA) mutase activity was detected in cell-free extracts of R. ruber by enzyme assay and HPLC analysis of reaction products. A pathway, involving the known methylmalonyl-CoA pathway for propionate formation in Propionibacteria, followed by the established pathway for PHA biosynthesis from propionyl-CoA and acetyl-CoA, is proposed for the biosynthesis of 3HV from succinate by R. ruber. Correspondence to: A. J. Anderson     

Synthesis of Certain Acyclic Nucleoside Analogs of 1,2,4-Triazolo[3,4-f][1,2,4]triazine and Pyrimido[5,4-d]pyrimidine

Abstract

Synthesis of 2-penten-1-yl (8a) and ganciclovir analog (8b) of 1,2,4-triazolo[3,4-f][1,2,4]triazine was accomplished by the ring annulation of the corresponding hydrazides (6a and 6b), which in turn was obtained by the dehydrative coupling of 4 with 5a or 5b. Base catalysed ring expansion of N9-alkylpurine-6-carbonitriles (10a 10c 10e) provided the acyclic analogs of 4-aminopyrimido-[5,4-d]pyrimidines (13a 13d 13e). Debenzylation of 13e afforded the ganciclovir analog (13f) of 4-amino-8-(β-D-ribofuranosylamino)-pyrimido[5,4-d]pyrimidine. However, compound 10b did not undergo the expected rearrangement but resulted in the formation of the methyl formimidate derivative (12).     

Pyrazolo[3,4-d)Pyrimidine 2′-Deoxyribo and 2′,3′-Dideoxyribo-Furanosides: Synthesis and Application to Oligonucleotide Chemistry

Abstract

The synthesis of pyrazolo[3,4-d]pyrimidine 2′-deoxyribo-nucleosides with various substituents at C-4 and C-6 (1 4) is described employing either liquid-liquid or solid-liquid phase-transfer glycosylation. From 1a (Z⁸C⁷A_d) and 2b (Z⁸C⁷G_d) the phosphoramidites 12a, b and 15a, b were synthesized. They were used in automated solid-phase synthesis resulting in the oligonucleotides 16 - 25. Deoxygenation (3′-OH) of 1a and 2b yielded pyrazolo[3,4-d]-pyrimidine 2′,3′-dideoxynucleosides isosteric to ddA, ddG, and ddI.     

Amyloglucosidase-catalyzed synthesis of eugenyl and curcuminyl glycosides

Glycosylation of the phenolic hydroxyl group of the phenyl propanoid systems, eugenol 1 and curcumin 2, using an amyloglucosidase from Rhizopus and a β-glucosidase from sweet almonds together with carbohydrates (d-glucose 3, d-mannose 4, maltose 5, sucrose 6 and d-mannitol 7) in di-isopropyl ether produced glycosides at 7–52% yields in 72 h. Spectral studies indicated that the reaction occurred between the phenolic OH groups and C-1 and/or 6-O-groups of the carbohydrates with curcumin exhibiting bis glycosylation.     

Synthesis of new thieno[2,3-b]pyridine derivatives as pim-1 inhibitors

Three series of 5-bromo-thieno[2,3-b]pyridines bearing amide or benzoyl groups at position 2 were prepared as pim-1 inhibitors. All the prepared compounds were tested for their pim-1 enzyme inhibitory activity. Two compounds (3c and 5b) showed moderate pim-1 inhibitory activity with IC₅₀ of 35.7 and 12.71?μM, respectively. Three other compounds (3d, 3g and 6d) showed poor pim-1 inhibition. The most active compounds were tested for their cytotoxic activity on five cell lines [MCF7, HEPG2, HCT116, A549 and PC3]. Compound 3g was the most potent cytotoxic agent on almost all the cell lines tested.     

Synthesis and potential antitumor activity of 7-(4-substituted piperazin-1-yl)-4-oxoquinolines based on ciprofloxacin and norfloxacin scaffolds: in silico studies

The potential antitumor activities of a series of 7-(4-substituted piperazin-1-yl)fluoroquinolone derivatives (1–14a,b) using ciprofloxacin and norfloxacin as scaffolds are described. These compounds exhibit potent and broad spectrum antitumor activities using 60 human cell lines in addition to the inherent antibacterial activity. Compounds 1a, 2a, 3b, 6b and 7a were found to be the most potent, while 2b, 5b, and 6a were found to have an average activity. The results of this study demonstrated that compounds 1a, 2a, 3b, 6b and 7a (mean GI₅₀; 2.63–3.09?µM) are nearly 7-fold more potent compared with the positive control 5-fluorouracil (mean GI₅₀; 22.60?µM). More interestingly, compounds 1a, 2a, 3b, 6b and 7a have an almost antitumor activity similar to gefitinib (mean GI₅₀; 3.24?µM) and are nearly 2-fold more potent compared to erlotinib (mean GI₅₀; 7.29?µM). In silico study and ADME-Tox prediction methodology were used to study the antitumor activity of the most active compounds and to identify the structural features required for antitumor activity.     

Hydroxylation of (+)-menthol by Macrophomina phaseolina

Abstract

Biotransformation of (+)-menthol with Macrophomina phaseolina led to hydroxylations at C-1, C-2, C-6, C-7, C-8 and C-9, with the C-8 position being preferentially oxidized. The resulting metabolites were identified as 8-hydroxymenthol (2), 6R-hydroxymenthol (3), 1R-hydroxymenthol (4), 9-hydroxymenthol (5), 2R,8-dihydroxymenthol (6), 8S,9-dihydroxymenthol (7), 6R,8-dihydroxymenthol (8), 1R,8-dihydroxymenthol (9) and 7,8-dihydroxymenthol (10). Metabolites 6–10 are described here for the first time. Their structures were characterized by spectroscopic analysis.     

Design,synthesis and anticancer evaluation of novel pyrazole,pyrazolo[3,4-d]pyrimidine and their glycoside derivatives

The chalcone derivatives 3a,b were cyclized upon reaction with thiourea to give the pyrazolo[3,4-d]pyrimidine derivatives 5a,b. Condensation of 5a,b and their hydrazide derivatives 8a,b with cyclic and acyclic glucose gave the condensed S- and N-glycosides 7a,b and 9a,b, respectively. Reaction of 3b with ethyl cyanoacetate followed by reaction with cyclic glucose afforded a mixture of the O- and/or N-glycoside isomers 12 and 13, respectively. The pyrazolo[3,4-c]pyrazole derivative 14 was also obtained from the reaction of 3b with hydrazine hydrate. A number of the synthesized compounds were screened for their antitumor activity against three different tumor cell lines HEPG2 (liver), HCT116 (colon) and MCF-7 (breast) with a docking study against CDK2.     

On the soybean type-I lipoxygenase-mediated conversion of linoleic acid into (S) 2-nonen-4-olide

(S) 2-nonen-4-olide3 of 0.5ee is obtained upon steam distillation from linoleic acid1 treated with oxygen at pH 9.6 in the presence of soybean type-I lipoxygenase; the two enantiomers of 2-nonen-4-olide obtained from [12, 13-²H₂]1 were shown by multidimensional GC/MS to contain both 70% d₂ and 30% d₁ species