Synthesis and anti-HCV activity of β-d-2′-deoxy-2′-α-chloro-2′-β-fluoro and β-d-2′-deoxy-2′-α-bromo-2′-β-fluoro nucleosides and their phosphoramidate prodrugs

We report herein the synthesis and evaluation of a series of β-d-2′-deoxy-2′-α-chloro-2′-β-fluoro and β-d-2′-deoxy-2′-α-bromo-2′-β-fluoro nucleosides along with their corresponding phosphoramidate prodrugs. Key intermediates, lactols 11 and 12, were obtained by a diastereoselective fluorination of protected 2-deoxy-2-chloro/bromo-ribonolactones 7 and 8. All synthesized nucleosides and prodrugs were evaluated with a hepatitis C virus (HCV) subgenomic replicon system.     

Synthesis and evaluation of 5′-modified thymidines and 5-hydroxymethyl-2′-deoxyuridines as Mycobacterium tuberculosis thymidylate kinase inhibitors

We report the synthesis of 5′-modified thymidines (16, 18, 21, 23) and 5,5′-bis-substituted 2′-deoxyuridine analogues (30, 47) as inhibitors of thymidine monophosphate kinase of Mycobacterium tuberculosis (TMPKmt). These analogues were evaluated for their capacity to inhibit TMPKmt and solely two 5′-modified thymidines were found to possess moderate inhibitory activity. In addition, a feasibility study of protecting groups for the 5-CH₂OH moiety of 2′-deoxyuridines is described that enables to introduce the desired 5′-modification.     

Synthesis and anti-CVB3 activity of 4-amino acid derivative substituted pyrimidine nucleoside analogues

Seven novel 4-amino acid derivative substituted pyrimidine nucleoside analogues were designed, synthesized, and tested for their anti-CVB3 activity. Initial biological studies indicated that among these 4-amino acid derivative substituted pyrimidine nucleoside analogues, 4-N-(2′-amino-glutaric acid-1′-methylester)-1-(2′- deoxy-2′-β-fluoro-4′-azido)-furanosyl-cytosine 2 exhibited the most potent anti-CVB activity (IC₅₀ = 9.3 μM). The cytotoxicity of these compounds has also been assessed. The toxicity of compound 2 was similar to that of ribavirin.     

Synthesis of 3′,4′-difluoro-3′-deoxyribonucleosides and its evaluation of the biological activities: Discovery of a novel type of anti-HCV agent 3′,4′-difluorocordycepin

Upon reacting 3′,4′-unsaturated cytosine (8 and 9) and adenine nucleosides (13 and 14) with XeF₂/BF₃·OEt₂, the respective novel 3′,4′-difluoro-3′-deoxyribofuranosyl nucleosides (10–12 and 15–18) could be obtained. Formation of anti-adducts (11, 16 and 18) revealed that the fluorination involved oxonium ions as incipient intermediates. TBDMS-protected 3′,4′-unsaturated adenosine provided the β-face adducts as sole stereoisomers whereas α-face-selectivity was observed with the TBDPS-protected adenosine 14. The evaluation of the novel 3′-deoxy-3′,4′-difluororibofuranosylcytosine-(19–21) and adenine nucleosides (22–25) against antitumor and antiviral activities revealed that 3′,4′-difluorocordycepin (24) was found to possess anti-HCV activity. The SI of 24 was comparable to that of the anti-HCV drug ribavirin. However, sofosbuvir, FDA-approved novel anti-HCV drug, showed better SI value. Our finding revealed that the introduction of the fluoro-substituent into the 4′-position of cordycepin derivatives decreased the cytotoxicity to the host cell with retention of the antiviral activity.     

Triethylated chromones with substituted naphthalenes as tubulin inhibitors

Previously synthesized 2-(benzo[b]thiophene-3′-yl)-6,8,8-triethyldesmosdumotin B (1, TEDB-TB) and 2-(naphth-1′-yl)-6,8,8-triethyldesmosdumotin B (2) showed potent activity against multiple human tumor cell lines, including a multidrug-resistant (MDR) subline, by targeting spindle formation and/or the microtubule network. Consequently, ester analogues of hydroxylated naphthyl substituted TEBDs (3–5) were prepared and evaluated for their effects on tumor cell proliferation and on tubulin assembly. Among all new compounds, compound 6, a 4′-acetoxynaphthalen-1′-yl derivative, displayed the most potent antiproliferative activity (IC₅₀ 0.2–5.7 μM). Selected analogues were confirmed to be tubulin assembly inhibitors in cell-free and cell-based assays using MDR tumor cells. The new analogues partially inhibited colchicine binding to tubulin, suggesting their binding mode would be different from that of colchicine. This observation was supported by computational docking model analyses. Thus, the newly synthesized triethylated chromones with esterified naphthalene groups have good potential for development as a new class of mitotic inhibitors that target tubulin.     

Synthesis,thymidine phosphorylase,angiogenic inhibition and molecular docking study of isoquinoline derivatives

Isoquinoline analogues (KA-1 to 16) have been synthesized and evaluated for their E. coli thymidine phosphorylase inhibitory activity. Except compound 11, all other analogs showed outstanding thymidine inhibitory potential ranging in between 4.40 ± 0.20 to 69.30 ± 1.80 µM when compared with standard drug 7-Deazaxanthine (IC₅₀ = 38.68 ± 4.42 µM). Structure Activity Relationships has been established for all compounds, mainly based on substitution pattern on phenyl ring. All analogs were characterized by various spectroscopic techniques such as ¹H NMR, ¹³C NMR and EI-MS. The binding interactions of isoquinoline analogues with the active site of TP enzyme, the molecular docking studies were performed. Furthermore, the angiogenic inhibitory potentials of isoquinoline analogues (KA-1-9, 14, 12 and 16) were determined in the presence of standard drug Dexamethasone based on percentage inhibitions at various concentrations. Herein this work analogue KA-12, 14 and 16 emerged with most potent angiogenic inhibitory potentials among the synthesized analogues.     

5-thio-D-ribopyranose : Part III. Conformational equilibria in the methyl D-ribopyranosides,their 1-thio, 5-thio,and 1,5-dithio analogues,and the related triacetates

Conformational equilibria have been estimated by n.m.r. spectroscopy for the methyl 2,3,4-tri-O-acetyl-α- and -β-D-ribopyranosides (1′a and 1′b), their 1-thio (2′a, 2′b), their 5-thio (3′a, 3′b), and their 1,5-dithio (4′a, 4′b) analogues. Only 1′b shows a preference for the 1C conformation; the others favour the C1 form to various extents. These results are discussed in terms of polar and steric effects. Similar estimations have been made on the unacetylated D-ribopyranosides (1–4) and, where a definite conformational assignment is possible, these follow the same trend as the triacetates (1′–4′). These results are compared, where possible, with the results of X-ray crystallographic studies.     

l-like 3-deazaneplanocin analogues: Synthesis and antiviral properties

The potent antiviral properties of 3-deazaneplanocin, 3-deaza-isoneplanocins (1) and recently discovered l-like carbocyclic nucleosides (2, 3 and 4) prompted us to pursue rationally conceived l-like 3-deazaneplanocin analogues. The synthesis of those analogues including l-like 3-deazaneplanocin (5), l-like 3-bromo-3-deazaneplanocin (6), and l-like 5′-fluoro-5′-deoxy-3-deazaneplanocin (7), was accomplished from a common intermediate, (−)-cyclopentenone (8). Antiviral analysis found 5 and 6 to display favorable activity against the Ebola virus, as expected for 3-deazaadenine carbocyclic nucleosides. Compound 5 also showed activity against arenaviruses, including Pinchinde and Tacaribe.     

Concise syntheses and HCV NS5B polymerase inhibition of (2′R)-3 and (2′S)-2′-ethynyluridine-10 and related nucleosides

(2′R)-Ethynyl uridine 3, and its (2′S)-diastereomer 10, are synthesised in a divergent fashion from the inexpensive parent nucleoside. Both nucleoside analogues are obtained from a total of 5 simple synthetic steps and 3 trivial column chromatography purifications. To evaluate their effectiveness against HCV NS5B polymerase, the nucleosides were converted to their respective 5′-O-triphosphates. Subsequently, this lead to the discovery of the 2′-β-ethynyl 18 and -propynyl 20 nucleotides having significantly improved potency over Sofosbuvir triphosphate 24.     

A new synthesis of 4′-resveratrol esters and evaluation of the potential for anti-depressant activity

The 4′-ester analog of the disease preventative resveratrol 1 (RV), 4′-acetyl-RV 2 along with 4′-pivaloate 13 and benzoate 14 RV were synthesized. The previously developed palladium catalyzed decarbonylative Heck coupling was used to assemble the stilbene core together with 3,5-dibenzyl protected phenol intermediates that allowed for efficient coupling and deprotection using boron trifluoride etherate. Studies with Long-Evans rats were performed to establish safety, toxicity, and behavioral parameters. In addition, the Porsalt forced-swim test was used to demonstrate anti-depressant activity.     

Synthesis and activity of substituted heteroaromatics as positive allosteric modulators for α4β2α5 nicotinic acetylcholine receptors

The design and synthesis of a series of substituted heteroaromatic α4β2α5 positive allosteric modulators is reported. The optimization and development of the heteroaromatic series was carried out from NS9283, and several potent analogues, such as 3-(5-(pyridin-3-yl)-2H-tetrazol-2-yl)benzonitrile (5k) and 3,3′-(2H-tetrazole-2,5-diyl)dipyridine (12h) with good in vitro efficacy were discovered.     

Synthesis of 1′,2′-methano-2′,3′-dideoxynucleosides as potential antivirals

The synthesis of constrained nucleosides has become an important tool to understand the SAR in the interaction between biological and synthetic nucleotides in the context of antisense oligonucleotide therapy. The incorporation of a cyclopropane into a furanose ring of a nucleoside induces some degree of constrain without affecting significantly the steric environment of a nucleoside. Here, we report a new, short and stereocontrolled synthesis of two constrained nucleosides analogues, 1′,2′- methano-2′,3′-dideoxyuridine 9, and the corresponding cytidine analog 12. X-ray crystallography revealed that the furanose ring in the constrained uridine and cytidine analogues was flattened with virtual loss of pseudorotation. The phosphoramidate esters of the novel constrained uridine and cytidine nucleosides, intended as prodrugs, were tested in cell-based assays for viral replication across the herpes virus family and HIV inhibition courtesy of Merck laboratories, Rahway. They were also tested in antiproliferative assays against colorectal and melanoma cell lines. Unfortunately, none of the compounds showed activity in these assays.     

7-Methylguanosine monophosphate analogues with 5′-(1,2,3-triazoyl) moiety: Synthesis and evaluation as the inhibitors of cNIIIB nucleotidase

The hydrolysis of nucleoside 5′-monophosphates to the corresponding nucleosides and inorganic phosphate is catalysed by 5′-nucleotidases, thereby contributing to the control of endogenous nucleotide turnover and affecting the fate of exogenously delivered nucleotide- and nucleoside-derived therapeutics in cells. A recently identified nucleotidase cNIIIB shows preference towards 7-methylguanosine monophosphate (m⁷GMP) as a substrate, which suggests its potential involvement in mRNA degradation. However, the extent of biological functions and the significance of cNIIIB remains to be elucidated. Here, we synthesised a series of m⁷GMP analogues carrying a 1,2,3-triazole moiety at the 5′ position as the potential inhibitors of human cNIIIB. The compounds were synthesised by using the copper-catalysed azide-alkyne cycloaddition (CuAAC) between 5′-azido-5′-deoxy-7-methylguanosine and different phosphate or phosphonate derivatives carrying terminal alkyne. The analogues were evaluated as cNIIIB inhibitors using HPLC and malachite green assays, demonstrating that compound 1a, carrying a 1,2,3-triazoylphosphonate moiety, inhibits cNIIIB activity at micromolar concentrations (IC₅₀ 87.8?±?7.5?µM), while other analogues showed no activity. In addition, compound 1d was identified as an artifical substrate for ^HscNIIIB. Further characterization of inhibitor 1a revealed that it is poorly recognised by other m⁷G-binding proteins, eIF4E and DcpS, indicating its selectivity towards cNIIIB. The first inhibitor (1a) and unnatural substrate (1d) of cNIIIB, identified here, can be used as molecular probes for the elucidation of biological roles of cNIIIB, including the verification of its proposed function in mRNA metabolism.     

Novel 4,4′-diether-2,2′-bipyridine cisplatin analogues are more effective than cisplatin at inducing apoptosis in cancer cell lines

The synthesis and characterization of dichloro(4,4′-bis[methoxy]-2,2′-bipyridine)platinum (1) and dichloro(4,4′-bis[3-methoxy-n-propyl]-2,2′-bipyridine)platinum (2) are described. As analogues to CDDP, these 4,4′-disubstituted 2,2′-bipyridine complexes exhibit decreased EC₅₀ values of 10–100 times in cancer cell lines of the lung, prostate, and melanoma with several combinations of complex and cell line less than 10 μM. Flow cytometry data indicate ‘blocks’ of MDA-MD-435 cycle by 1 (G2/M) and 2 (S). Observed cell survival trends in the presence of 1, 2 under ionizing radiation mimic those of CDDP. Preliminary structure activity relationships are discussed for the 4,4′-substitutions made on the bipyridine ring.     

Synthesis of purine and pyrimidine 2′-deoxynucleosides from a 1,2-dithio sugar precursor

9-(2-S-Ethyl-2-thio- and α-D-mannofuranosyl)adenine (8α and 8β) were synthesized from ethyl 3,5,6-tri-O-acetyl-2-S-ethyl-1,2-dithio-α-D-mannofuranoside (1) by bromination followed by coupling of the resultant bromide (2) with 6-benzamido-(chloromercuri)purine. The 2-chloro analogues (10α and 10β) of 8α and 8β were obtained by way of a fusion reaction between 1,3,5,6-tetra-O-acetyl-2-S- ethyl-2-thio-α-D-mannofuranose (5) and 2,6-dichloropurine. Fusion of the bromide 2 with 2,4-bis(trimethylsilyloxy)pyrimidine and its 5-methyl derivative led to 1-(2-S- ethyl-2-thio-β-D-mannofuranosyl)uracil (16) and its thymine analogue (15). The action of Raney nickel led to rapid dechlorination of 10α and 10β, and all of the 2′-thio-nucleosides underwent desulfurization to give the corresponding 2′-deoxynucleosides. Sequential periodate oxidation-borohydride reduction converted the hexofuranosyl nucleosides into their pentofuranosyl analogues. Thus prepared were 9-(2-deoxy-α-and β-D-arabino-hexofuranosyl)adenine (11α and 11β) and their 2-deoxy-D-threo-pentofuranosyl counterparts (6α and 2′-deoxy-3′-epiadenosine, 6β), and 1-(2-deoxy- β-D-arabino-hexofuranosyl)-thymine (17) and -uracil (18) and their 2-deoxy-D-threo-pentofuranosyl counterparts (3′-epithymidine, 21, and 2′-deoxy-3′-epiuridine, 20). Detailed n.m.r.-spectral correlations are described for the series, and various derivatives of the nucleosides are reported.     

New glycosides from the leaves and rattan stems of Schisandra chinensis

Two new glycosides, vanillic acid 4-O-β-d-(6′-O-(Z)-2′'-methylbut-2′'-enoate)glucopyranoside (1), p-methoxycarvacrol-6-O-β-d-glucopyranoside (2), along with two known analogues (3-4), were isolated from the leaves and rattan stems of Schisandra chinensis. The structures of these isolates were determined by UV, HRESIMS, 1D and 2D NMR spectral analyses.     

Monohydroxycarotenoids from diphenylamine-inhibited cultures of Rhodospirillum rubrum

The monohydroxycarotenoids formed by diphenylamine-inhibited cultures of Rhodospirillum rubrum have been investigated. Nine have been isolated and identified as 1-hydroxy-1,2-dihydrophytofluene (1), 1-Hydroxy-1,2,7′,8′,11′,12′-hexahydrolycopene (2), chloroxanthin (3), 1-methoxy-1′-hydroxy-1,2,1′,2′-tetrahydrophytofluene (4a), 1′-hydroxy-3,4,1′,2′,11′,12′-hexahydrospheroidene (5, 1′-hydroxy-3,4,1′,2′-tetrahydrospheroidene (6, 1′-hydroxy 1′,2′-dihydrospheroidene (7), rhodovibrin (8a) and monodeme thylated spirilloxanthin (9). 4a, 5 and 6 are novel carotenoids, and a definite structure has been assigned to 2 for the first time; the structure of 1 has been amended. The possible role of these carotenoids in spirilloxanthin biosynthesis is discussed.     

Synthesis and anticancer activity of novel quinoline–docetaxel analogues

A series of novel quinoline–docetaxel analogues (6a–6g, 13a–13g) were designed and synthesized by introducing bioactive quinoline scaffold to C2′-OH of docetaxel. The anticancer activities of these novel analogues were investigated against different human cancer cell lines including Hela, A549, A2780, MCF-7 and two resistant strains A2780-MDR and MCF-7-MDR. The data showed these analogues possessed similar to better cytotoxicity than docetaxel. Compound 6c was found to be the most potent one, and its IC₅₀ value against MCF-7-MDR was 8.8 nM (IC₅₀ of docetaxel was 180 nM). The work indicated that the introduction of quinolyl group in docetaxel could enhance cytotoxicity and reduce drug-resistance.     

Synthesis and anti-hepatitis C virus (HCV) activity of 3′-C-substituted-methyl pyrimidine and purine nucleosides

On the basis of potent anti-hepatitis C virus (HCV) activity of 2′-C-hydroxymethyladenosine, 3′-C-substituted-methyl-ribofuranosyl pyrimidine and purine nucleosides were designed and synthesized from d-xylose. Among compounds tested, all adenine analogues, 4a, 4d, and 4g showed significant anti-HCV activity in a replicon-based cell assay irrespective of the substituent (Y = OH, N₃, or F) at the 3′-C-substituted methyl position, among which 4g (Y = N₃) was the most potent, but it is also cytotoxic. This study guarantees the 3′-C-substituted-methyl nucleoside serves as a new template for the development of new anti-HCV agents.     

Synthesis,cytotoxicity against human oral cancer KB cells and structure–activity relationship studies of trienone analogues of curcuminoids

A general method for the synthesis of substituted (1E,4E,6E)-1,7-diphenylhepta-1,4,6-trien-3-ones, based on the aldol condensations of substituted 4-phenylbut-3-en-2-ones and substituted 3-phenylacrylaldehydes, was achieved. The natural trienones 4 and 5 have been synthesized by this method, together with the trienone analogues 9–20. These analogues were evaluated for their cytotoxic activity against human oral cancer KB cell line. The structure–activity relationship study has indicated that the analogues with the 1,4,6-trien-3-one function are more potent than the curcuminoid-type function. Analogues with meta-oxygen function on the aromatic rings are more potent than those in the ortho- and para-positions. Free phenolic hydroxy group is more potent than the corresponding methyl ether analogues. Among the potent trienones, compounds 11, 18 and 20 were more active than the anticancer drug ellipticine. All compounds were also evaluated against the non-cancerous Vero cells and it was found that compounds 11, 12 and 17 were much less toxic than curcumin (1); they showed high selectivity indices of 35.46, 33.46 and 31.68, respectively. These analogues are regarded as the potent trienones for anti-oral cancer study.