Novel Carbocyclic Nucleosides Containing A Cyclobutyl Ring. Guanosine and Adenosine Analogues

Abstract

(1R,cis)-2-(3-Amino-2,2-dimethylcyclobutyl)ethanol (4) was used as a precursor in the synthesis of cyclobutyl nucleoside analogues containing guanine, 8-azaguanine, adenine or 8-azaadenine. All the compounds were evaluated as antiviral agents in a variety of assay systems. Some activity was noted for compound 13, 17, 19 and 20 against vaccinia virus and for compounds 11, 12, 13, 17, 19 and 20 against herpes simplex virus, at concentrations that were up to 10-fold below the cytotoxic concentrations for the host cells.     

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).     

Synthesis,cyclooxygenase inhibition and anti-inflammatory evaluation of new 1,3,5-triaryl-4,5-dihydro-1H-pyrazole derivatives possessing methanesulphonyl pharmacophore

A new series of 1,3,5-triaryl-4,5-dihydro-1H-pyrazole derivatives 13a–p were synthesized via aldol condensation of 3/4-nitroacetophenones with appropriately substituted aldehydes followed by cyclization of the formed chalcones with 4-methanesulfonylphenylhydrazine hydrochloride. All the synthesized compounds were evaluated for their cyclooxygenase (COX) inhibition, anti-inflammatory activity and ulcerogenic liability. All compounds were more potent inhibitors for COX-2 than COX-1. While most compounds showed good anti-inflammatory activity, compounds 13d, 13f, 13k and 13o were the most potent derivatives (ED₅₀?=?66.5, 73.4, 79.8 and 70.5?μmol/kg, respectively) in comparison with celecoxib (ED₅₀?=?68.1?μmol/kg). Compounds 13d, 13f, 13k and 13o (ulcer index?=?3.89, 4.86, 4.96 and 3.92, respectively) were 4–6 folds less ulcerogenic than aspirin (ulcer index?=?22.75) and showed approximately ulceration effect similar to celecoxib (ulcer index?=?3.35). In addition, molecular docking studies were performed for compounds 13d, 13f, 13k and 13o inside COX-2 active site which showed acceptable binding interactions (affinity in kcal/mol ?2.1774, ?6.9498) in comparison with celecoxib (affinity in kcal/mol ?6.5330).     

Reaction of Astaxanthin with Peroxynitrite

The in vitro reactivities of astaxanthin toward peroxynitrite were investigated and the reaction products after scavenging with peroxynitrite were analyzed in order to determine the complete mechanism of this reaction. A series of carotenoids, 13-apo-astaxanthinone (1), 12′-apo-15′-nitroastaxanthinal (2), 12′-apo-astaxanthinal (3), 10′-apo-astaxanthinal (4), 9-cis-14′-s-cis-15′-nitroastaxanthin (5), 14′-s-cis-15′-nitroastaxanthin (6), 13-cis-14′-s-cis-15′-nitroastaxanthin (7), 10′-s-cis-11′-cis-11′-nitroastaxanthin (8), 13,15,13′-tri-cis-15′-nitroastaxanthin (9), 9-cis-astaxanthin (10), and 13-cis-astaxanthin (11), were isolated from the reaction products of carotenoids with peroxynitrite. Our previous studies achieved for the first time the isolation of nitro derivatives from the reaction of astaxanthin with peroxynitrite. Here we identify the major remaining reaction products of this reaction and investigate the stabilities of the nitro astaxanthins.     

Synthesis,physiochemical property and antimicrobial activity of novel quaternary ammonium salts

Twenty-four novel 5-phenyl-1,3,4-oxadiazole-2-thiol (POT) analogues, benzo[d]oxazole-2-thiol, benzo[d]thiazole-2-thiol and 5-methyl-1,3,4-thiadiazole-2-thiol-substituted N,N-bis(2-hydroxyethyl) quaternary ammonium salts (QAS) (5a-d, 6a-d, 7a-d, 10a-d, 13a-d, 16a-d) were prepared and characterised by FTIR, NMR and elemental analysis. Part of target compounds (5d, 6d, 7d, 10d, 13d, 16d) displayed potent antimicrobial effect against ten common pathogens (S. aureus, α-H-tococcus, β-H-tococcus, E. coli, P. aeruginosa, Proteus vulgaris, Canidia Albicans, Cytospora mandshurica, Physalospora piricola, Aspergillus niger) and had relatively low cytotoxity against two human cell lines (HaCat and LO2). TEM and SEM images of E. coli and S. aureus morphologies treated with 7d showed that the antibacterial mechanism might be the QAS fixing on cell wall surfaces and puncturing to result in the release of bacterial cytoplasm. This study provides new information of QAS, which could be used to design novel antimicrobial agents applied in clinic or agriculture.     

Clinical and prognostic effects of CDKN2A,CDKN2B and CDH13 promoter methylation in ovarian cancer: a study using meta-analysis and TCGA data

Abstract

Background: Promoter methylation of tumour suppressor genes (TSGs) CDKN2A, CDKN2B and CDH13 has been reported in ovarian cancer. However, the clinicopathological characteristics and prognostic role of CDKN2A, CDKN2B and CDH13 promoter methylation in ovarian carcinoma remained unclear.

Methods: The pooled odds ratio (OR) or hazard ratios (HRs) with their 95% confidence intervals (95% CIs) were calculated in this meta-analysis. The Cancer Genome Atlas data were obtained to confirm the role of CDKN2A, CDKN2B and CDH13 methylation in ovarian cancer.

Results: CDKN2A, CDKN2B and CDH13 promoter methylation was higher in ovarian cancer than in normal ovarian tissues. CDH13 promoter methylation was correlated with tumour histology (serous vs. non-serous type: OR?=?0.33, p?=?0.031). CDKN2A promoter methylation was not linked to overall survival (OS), but it was correlated with a poor prognosis in progression-free survival (HR?=?1.55, p?=?0.004). TCGA data showed no correlation between CDKN2A, CDKN2B and CDH13 methylation and OS as well as disease-free survival (DFS).

Conclusions: CDKN2A, CDKN2B and CDH13 promoter methylation may correlate with the increased risk of ovarian cancer. CDKN2A promoter methylation may be an independent prognostic biomarker for predicting progression-free survival.     

Reaction of Retinol with Peroxynitrite

The reactivity of retinol with peroxynitrite, which is a strong oxidant and has been reported to induce several biological damages, was investigated. 13-cis-14-nitroretinol (1), 13-trans-14-nitroretinol (2), 13-apo-β-carotenone (3), retinal (4), 11,14-epoxyretinol (5), and 11,15-epoxyretinol (6) were identified as reaction products of retinol with peroxynitrite. From these results, it was observed that retinol can undergo a nitration reaction with peroxynitrite. Furthermore, the formation mechanisms of 1, 2, and 3 from retinol with peroxynitrite are discussed.     

Biotransformation of 5α-hydroxycaryophylla-4(12),8(13)-diene with Cunninghamella elegans and Rhizopus stolonifer

Abstract

Biotransformation of 5α-hydroxycaryophylla-4(12),8(13)-diene (1) was studied with Cunninghamella elegans and Rhizopus stolonifer. Incubation of 1 with C. elegans gave regioselective oxidative addition (hydration) and isomerization at the C-4(12) exocyclic double bond and hydroxylation at C-3 and C-15, and thus provided two polar metabolites, (3Z),8(14)-caryophylladiene-5α,(11R)-15-diol (2) and 3β,4β,5α-trihydroxycaryophylla-8(13)-ene (3). Incubation of 1 with R. stolonifer gave a transannular cyclization reaction and afforded 2β-methoxyclovan-9-one (4), clovan-2β-ol-9-one (5) and 8-methoxycaryolane-5α,13β-diol (6). Compounds 3 and 6 are new compounds described here for the first time; their structures were deduced with the help of different spectroscopic techniques.     

Synthesis of bis-amino acid derivatives by Suzuki cross-coupling,Michael addition and substitution reactions

Several bis-amino acids were prepared using a bis-Suzuki coupling (compounds 4–8, 10), a sequential Michael addition and bis-Suzuki coupling (compounds 12, 13) and a Michael addition followed by a substitution reaction (compounds 18, 19). Thus, the pure stereoisomer of the methyl esters of N-(tert-butoxycarbonyl)-β-bromodehydroaminobutyric acid and dehydrophenylalanine and of N-benzyloxycarbonyl-β-bromodehydroaminobutyric acid were reacted with 1,4-phenylene-bis-boronic acid or 9,9-dioctyl-9H-fluorene-2,7-bis-boronic acid using modified Suzuki coupling conditions. The corresponding bis-dehydroamino acid derivatives were obtained in good to high yields maintaining the stereochemistry of the starting materials. This reaction was also applied successfully to a brominated dehydrodipeptide and 1,4-phenylene-bis-boronic acid showing that it could be used to create cross-links in peptide chains. An N,N-diacyldehydroalanine derivative was used in a sequential Michael addition and bis-Suzuki coupling giving a p-terphenyl bis-amino acid and a fluorenyl bis-amino acid in good yields. Two bis-α,β-diamino acids were obtained by a Michael addition of 1,2,4-triazole to the methyl esters of N-(4-toluenesulfonyl), N-(tert-butoxycarbonyl) dehydroamino acids followed by treatment with ethylenediamine.     

Inhibition of human cytochromes P450 2A6 and 2A13 by flavonoids,acetylenic thiophenes and sesquiterpene lactones from Pluchea indica and Vernonia cinerea

The human liver cytochrome P450 (CYP) 2A6 and the respiratory CYP2A13 enzymes play role in nicotine metabolism and activation of tobacco-specific nitrosamine carcinogens. Inhibition of both enzymes could offer a strategy for smoking abstinence and decreased risks of respiratory diseases and lung cancer. In this study, activity-guided isolation identified four flavonoids 1–4 (apigenin, luteolin, chrysoeriol, quercetin) from Vernonia cinerea and Pluchea indica, four hirsutinolide-type sesquiterpene lactones 5–8 from V. cinerea, and acetylenic thiophenes 9–11 from P. indica that inhibited CYP2A6- and CYP2A13-mediated coumarin 7-hydroxylation. Flavonoids were most effective in inhibition against CYP2A6 and CYP2A13, followed by thiophenes, and hirsutinolides. Hirsutinolides and thiophenes exhibited mechanism-based inhibition and in irreversible mode against both enzymes. The inactivation kinetic K_I values of hirsutinolides against CYP2A6 and CYP2A13 were 5.32–15.4 and 0.92–8.67 µM, respectively, while those of thiophenes were 0.11–1.01 and 0.67–0.97 µM, respectively.     

Labdane diterpenoids from Aframomum sceptrum: NMR study and antiparasitic activities

Two novel labdane diterpenoids, 15ξ-methoxy-labdan-8(17),11(E),13(14)-trien-15,16-olide (1) and 12(S)-hydroxy-15ξ-methoxy-labdan-8(17),13(14)-dien-15,16-olide (2) were isolated from the rhizomes of Aframomum sceptrum K. Schum (Zingiberaceae). Their structures were established on the basis of their spectroscopic data. Stigmast-4-en-6β-ol-3-one and caryophylene oxide were also obtained. In vitro trypanocidal and leishmanicidal activities of labdanes 1 and 2 were evaluated. Compound 2 exhibited activity similar to that of reference drugs against Leishmania donovani.     

Biotransformation of gallic acid by <Emphasis Type="Italic">Beauveria sulfurescens</Emphasis> ATCC 7159

Preparative-scale fermentation of gallic acid (3,4,5-trihydroxybenzoic acid) (1) with Beauveria sulfurescens ATCC 7159 gave two new glucosidated compounds, 4-(3,4-dihydroxy-6-hydroxymethyl-5-methoxy-tetrahydro-pyran-2-yloxy)-3-hydroxy-5-methoxy-benzoic acid (4), 3-hydroxy-4,5-dimethoxy-benzoic acid 3,4-dihydroxy-6-hydroxymethyl-5-methoxy-tetrahydro-pyran-2-yl ester (7), along with four known compounds, 3-O-methylgallic acid (2), 4-O-methylgallic acid (3), 3,4-O-dimethylgallic acid (5), and 3,5-O-dimethylgallic acid (6). The new metabolite genistein 7-O-β-D-4″-O-methyl-glucopyranoside (8) was also obtained as a byproduct due to the use of soybean meal in the fermentation medium. The structural elucidation of the metabolites was based primarily on 1D-, 2D-NMR, and HRFABMS analyses. Among these compounds, 2, 3, and 5 are metabolites of gallic acid in mammals. This result demonstrated that microbial culture parallels mammalian metabolism; therefore, B. sulfurescens might be a useful tool for generating mammalian metabolites of related analogs of gallic acid (1) for complete structural identification and for further use in investigating pharmacological and toxicological properties in this series of compounds. In addition, a GRE (glucocorticoid response element)-mediated luciferase reporter gene assay was used to initially screen for the biological activity of the 6 compounds, 2–6 and 8, along with 1 and its chemical O-methylated derivatives 9–13. Among the 12 compounds tested, 11–13 were found to be significant, but less active than the reference compounds of methylprednisolone and dexamethasone.     

Microwave-assisted synthesis and bioevaluation of new sulfonamides

In this study, 4-[5-(4-hydroxyphenyl)-3-aryl-4,5-dihydro-1H-pyrazol-1-yl]benzenesulfonamide derivatives (8-14) were synthesized for the first time by microwave irradiation and their chemical structures were confirmed by ¹H NMR, ¹³C NMR and HRMS. Cytotoxic activities and inhibitory effects on carbonic anhydrase I and II isoenzymes of the compounds were investigated. The compounds 9 (PSE?=?4.2), 12 (PSE?=?4.1) and 13 (PSE?=?3.9) with the highest potency selectivity expression (PSE) values in cytotoxicity experiments and the compounds 13 (Ki?=?3.73?±?0.91?nM toward hCA I) and 14 (Ki?=?3.85?±?0.57?nM toward hCA II) with the lowest Ki values in CA inhibition studies can be considered as leader compounds for further studies.     

In vitro antimicrobial studies of new benzimidazolium salts and silver N-heterocyclic carbene complexes

A series of new benzimidazolium salts (1a–g) were synthesized from the reaction of 1-(4-vinylbenzyl)benzimidazole with various alkyl halides. These salts were used to synthesize silver N-heterocyclic carbene (Ag-NHC) complexes (2a–f). The thirteen compounds were characterized by FT-IR, NMR (¹H and ¹³C) spectroscopic methods and an elemental analysis technique. These selected candidates were tested for their in vitro antimicrobial activities. Antibacterial and antifungal results indicated that the new salts, and particularly their silver complexes, were found to be strongly effective against seven Gram (?) bacterial strains, three Gram (+) bacterial strains and one yeast (Candida albicans).     

Minor diterpenoid glycosides from the leaves of Stevia rebaudiana

From the commercial extract of the leaves of Stevia rebaudiana, three new diterpenoid glycosides were isolated besides eight known steviol glycosides including stevioside, rebaudiosides A–F and dulcoside A. The structures of the three compounds were identified as 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-kaur-16-en-18-oic acid-(6-O-β-d-xylopyranosyl-β-d-glucopyranosyl) ester (1), 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-17-hydroxy-kaur-15-en-18-oic acid β-d-glucopyranosyl ester (2), and 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-17-oxo-kaur-15-en-18-oic acid β-d-glucopyranosyl ester (3) on the basis of extensive NMR and MS spectral studies. Another known diterpenoid glycoside, 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-kaur-15-en-18-oic acid β-d-glucopyranosyl ester (4) was also isolated and its complete NMR spectral assignments were made on the basis of COSY, HSQC and HMBC spectral data.     

Alkyl phenols and saponins from the roots of Labisia pumila (Kacip Fatimah)

Recently, there is a remarkable boom in the sales of Labisia pumila (Kacip Fatimah) in the Malaysian market, as an extract of the plant is used to gain energy and libido as well as to treat many other ailments. A chemical analysis of its roots was undertaken and three metabolites, demethylbelamcandaquinone B (1), fatimahol (2), and dexyloprimulanin (3) together with 21 known compounds including epoxyoleanane glycosides, alkenated phenolics, cerebroside, glycerogalactolipids, and lipids were isolated and identified. Structure elucidation was achieved by spectroscopic and chemical studies. The MeOH extract of KF and compounds 12 and 13 exhibited moderate in vitro antibacterial activity.     

Screening of free radical scavengers from Erigeron breviscapus using on-line HPLC-ABTS/DPPH based assay and mass spectrometer detection

Erigeron breviscapus is a well-known traditional Chinese herbal medicine. In this study, on-line HPLC-ABTS/DPPH assay coupled with MS detection were applied to screen and identify the free radical scavengers in 70% methanol extracts of E. breviscapus. Using on-line HPLC-ABTS-MS and HPLC-DPPH-MS assay, 13 radical scavengers (including 4-O-caffeoylquinic acid (4-CQA) (1), 9-caffeoyl-2,7-anhydro-2-octulosonic acid (9-COA) (2), 3-caffeoyl-2,7-anhydro-3-deoxy-2-octulopyranosonic acid (3-CDOA) (3), erigeside I (4), quercetin-3-O-glucuronide (5), eriodictyol-7-O-glucuronide (6), scutellarin (7), 1,4-di-O-caffeoylquinic acid (1,4-di-CQA) (8), 3,5-di-CQA (9), 1-malonyl-3,5-di-CQA (10), erigoster B (11), 4,5-di-CQA (12) and 4,9-di-CDOA (13)) and 9 radical scavengers (including 1, 4, 7, 8, 9, 10, 11, 12 and 13) were discovered, respectively. Furthermore, the anti-oxidative activities of 4 compounds, including 7, 9, 11 and 12 were evaluated. Reverse anti-oxidative activity order of scutellarin and 3,5-di-CQA was observed in on-line HPLC-ABTS assay and on-line HPLC-DPPH assay. To validate their anti-oxidative activities, the off-line ABTS and DPPH assays were performed. Given sufficient reaction time, 3,5-di-CQA showed higher activity than scutellarin, which was consistent with the order obtained in on-line HPLC-ABTS assay. These results revealed that on-line HPLC-ABTS assay is a more sensitive method for screening and determining free radical scavengers, especially more suitable for those compounds with slower reaction kinetics.     

The synthesis of 2-nitroaryl-1,2,3,4-tetrahydroisoquinolines, nitro-substituted 5,6-dihydrobenzimidazo[2,1-a]isoquinoline N-oxides and related heterocycles as potential bioreducible substrates for the enzymes NAD(P)H: quinone oxidoreductase 1 and E. coli nitroreductase

A series of 2-nitroaryl-1,2,3,4-tetrahydroisoquinolines 10 and nitro-substituted 5,6-dihydrobenzimidazo[2,1-a]isoquinoline N-oxides 11 have been synthesised and evaluated as potential bioreducible substrates for the enzymes NAD(P)H: quinone oxidoreductase 1 (NQO1) and Escherichia coli nitroreductase (NR). Also prepared and evaluated were 2-(3,5-dinitropyridin-2-yl)-1,2,3,4-tetrahydroisoquinoline 12 and 5,6-dihydro-10-nitropyrido[3″,2″:4′,5′]imidazo[2′,1′-a]isoquinoline 12-oxide 13. Both compounds 10b and 13 were reduced faster by human NQO1 than by CB-1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide].     

Synthesis of 2′-Deoxy[5′-13C]Ribonucleotides and HMQC-Noesy NMR Study of the Dickerson's Dodecamer with 13C-Labeling at the 5′ Positions

Abstract

In addition to the synthesis of 2′-deoxy[5′-¹³C]ribonucleosides (6) via the D-[5-¹³C]ribose derivative (4), the construction of the corresponding dodecanucleotide with the Dickerson's sequence and its HMQC-NOESY NMR analysis are described.     

1,5-Anhydro-2-Deoxy-D-Altritol Oligonucleotides as Conformationally Restricted Analogues of Rna

Abstract

As part of a project concerning the investigation of new hexitol nucleic acids (HNA), the 1,5-anhydro-2-deoxy-D-altritol nucleoside building blocks with a uracil, cytosine, adenine and guanine base moiety were synthesized. The uracil analogue was used for the automated synthesis of corresponding oligonucleotides. Hybridization capabilities of these altritol nucleic acids (ANA) are illustrated by the Tm values obtained for the (a ^hU)₁₃/(dA)₁₃ duplex.