Synthesis and Antiviral Evaluation of Some Novel Tricyclic Pyrazolo[3,4‐b]indole Nucleosides

Novel pyrazolo[3,4‐b]indole nucleoside analogs were synthesized from the corresponding 3‐formyl‐2‐chloroindole and 3‐cyano‐2‐chloroindole nucleosides by treatment with hydrazine. Very few examples of pyrazolo[3,4‐b]indole heterocycles have been published in the literature and this is the first synthesis of nucleoside analogs containing this heterocycle. These new pyrazolo[3,4‐b]indole nucleosides were active against human cytomegalovirus and herpes simplex virus type 1, but this activity was not well separated from cytotoxicity.     

Synthesis and Biological Activity of Bimorpholine and its Carbanucleoside

A new enantiomerically pure carbacyclic nucleoside analogue with bimorpholine as a nonaromatic nucleobase was synthesized. The nucleoside analogue and bimorpholine were tested for cytotoxicity using an MTT assay and the xCELLigence System. Both assays revealed that compound 3 was highly cytotoxic at a 50 μM concentration while the cytotoxic effect of compound 1 was much less prominent. No antiretroviral activity was detected for this compound. In contrast, it acted as a potent inhibitor of hepatitis C virus (HCV) replication. Most likely this effect originates largely from the cytotoxicity of the compound; however, it is possible that a specific mechanism of HCV inhibition also exists.     

Synthesis of Novel Peptidyl Adenosine Antibiotic Analogs

A small library of peptidyl adenosine antibiotic analogs was synthesized, under the Pilot Scale Library Program of the NIH Roadmap initiative, from 2′,3′-O-isoproylideneadenosine-5′-carboxylic acid 2 in excellent yield. The coupling of the amino terminus of L-2-aminophenylbutyric methyl ester to a free 5′-carboxylic acid moiety of 2 followed by sodium hydroxide treatment led to carboxylic acid analog 4. Hydrolysis of this latter gave unprotected nucleoside analog 5. Intermediate 4 served as the precursor for the preparation of novel peptidyl adenosine analogs 6–18 in good yields and high purity through peptide coupling reactions to diverse amine derivatives. No marked anticancer and antimalaria activity was noted on preliminary cellular testing; however these analogs should be useful candidates for other types of biological activity.     

Synthesis of Branched-Chain and Bicyclic Thiosugar Nucleosides

Abstract

The synthesis of strategically protected nucleosides bearing β-mercaptoethyl chains at the α-C-3′ position from 1,2-di-O-acetyl-2′-S-acetyl-5-t?butyldiphenylsilyl-3-deoxy-3-C-(2′-mercaptoethyl)-α-D-ribofuranose 1 is described. It was found that treatment of the 5-O-methanesulfonyl sugar 19 or nucleoside 5 with either benzylmercaptan or methoxide resulted in rapid cleavage of the thiolester followed by intramolecular cyclization. This was used to prepare the novel trans?fused oxathiahydrindane nucleosides 7 and 27 as well as the cAMP analogue 29.     

Synthesis of a Non-Hydrolyzable Dinucleoside Analogue

Abstract

A non-hydrolyzable dinucleoside analogue 31, which bears an internucleoside thioether linkage, was prepared from the branched-chain nucleoside precursors 26 and 28. Previous attempts to form the sulfide by the displacement of a 5′-mesyl group by thiol gave unsatisfactory results. In the course of preparing 28, it was found that the Vorbruggen coupling of 5-thiosugar 8 and persilylated base results in competing thiopyranone enol acetate formation.     

Synthesis and biological activity of bimorpholine and its carbanucleoside

A new enantiomerically pure carbacyclic nucleoside analogue with bimorpholine as a nonaromatic nucleobase was synthesized. The nucleoside analogue and bimorpholine were tested for cytotoxicity using an MTT assay and the xCELLigence System. Both assays revealed that compound 3 was highly cytotoxic at a 50 μM concentration while the cytotoxic effect of compound 1 was much less prominent. No antiretroviral activity was detected for this compound. In contrast, it acted as a potent inhibitor of hepatitis C virus (HCV) replication. Most likely this effect originates largely from the cytotoxicity of the compound; however, it is possible that a specific mechanism of HCV inhibition also exists.     

Design and Synthesis of Acyclic Nucleoside Analogs with Chlorinated Imidazo[1,2-a]pyridine Bases

Abstract

A series of acyclic C-nucleoside analogs of 2,6-dichloro- and 2,6,7-trichloroimidazo[1,2-a]pyridine were synthesized and tested for antiviral activity. The appropriate hydroxymethyl-substituted heterocycles were treated successively with thionyl chloride, an appropriate nucleophile, then diisopropylethylamine to obtain the desired acyclic nucleoside analogs. These compounds were evaluated for activity against human cytomegalovirus and herpes simplex virus, type 1. Two of the dichloro analogs, but none of the trichloro analogs demonstrated slight antiviral activity (IC₅₀'s = 20–45 µM) at non-cytotoxic concentrations.     

Synthesis of cyclobutane nucleoside analogues 3: Preparation of carbocyclic derivatives of oxetanocin

Abstract

A synthesis of cyclobutene nucleoside analogs in which the nucleobase is tethered by a methylene group is described. The coupling of 6-chloropurine with 3-hydroxymethyl-cyclobutanone proceeds via its triflate to give both N-7 and N-9 regioisomers with relative yields corresponding to the calculated charge distribution of the 6-chloropurinyl anion. The stereoselective reduction of the N-alkylated ketones yielded quantitatively one stereoisomer in each case. The structural assignments were based on spectroscopic data and single crystal X-ray diffraction. Attempts to photoexcite the N-7 and N-9 ketones in order to promote ring-expansion did not ensue. Preliminary evidence suggests a photodecarbonylation to cyclopropanes took place.     

Synthesis and triplex forming ability of conformationally locked oligonucleotides containing unnatural nucleobases: efficient recognition of a C.G interruption.

In order to develop a novel nucleoside analogue which recognizes C.G interruption in homopurine.homopyrimidine DNA, we designed and synthesized a conformationally locked nucleoside analogue, 1-(2-O,4-C-methylene-beta-D-ribofuranosyl)pyridin-2-one (4), and introduced it into a triplex-forming oligonucleotide (TFO). On melting temperature (Tm) measurements, the unprecedented C.G base recognition ability of 4 was observed.     

Tandem Radical Cyclization-Oxygenation of 6-(2,2-Di-bromovinyl)-1-(2-deoxy-d-erytho-pent-1-enofuranosyl)-uracil: Synthesis of Anomeric Spiro Nucleosides Having Arabino and Ribo Configurations

Abstract

Radical-mediated 5-exo-trig cyclization of 6-(2,2-dibromovinyl)-1-(2-deoxy-D-erythro-pent-1-enofuranosyl)uracil, when carried out in the presence of oxygen, furnished an anomeric spiro nucleoside having arabino-configuration. The corresponding ribofuranosyl analogue was also synthesized via the 2′-keto derivative.

     

Synthesis and anti-HCV activity of a new 2'-deoxy-2'-fluoro-2'-C-methyl nucleoside analogue

2'-Deoxy-2'-fluoro-2'-C-methyl nucleoside analogue 4 was designed and synthesized. Initial biological studies indicated that this compound showed promising activity against HCV replication.     

Short Synthesis and Antiviral Activity of Acyclic Phosphonic Acid Nucleoside Analogues

An efficient route for synthesizing novel allylic and cyclopropanoid phosphonic acid nucleoside analogues is described. The condensation of the bromine derivatives 6 and 18 with nucleoside bases (A, U, T, C, G) under standard nucleophilic substitution and deprotection conditions, afforded the target phosphonic acid nucleoside analogues. These compounds were evaluated for their antiviral properties against various viruses. Cyclopropanoid phosphonic adenine nucleoside analogue 23 showed significant anti-HIV activity.     

Fluoride,beryllium and ADP combine as a ternary complex in aqueous solution as revealed by a multinuclear NMR study

Different kinds of nucleotide binding enzymes are sensitive to fluoroberyllate complexes (BeF.) and fluoroaluminate complexes (AlF_y). It has been hypothesized that the effects of these fluorometals are related to the generation at a nucleotide binding site of a pseudo nucleoside triphosphate, consisting of a fluorometal moiety bound to the phosphate group of a molecule of nucleoside diphosphate (Bigay et al. 1985; Lunardi et al. 1985). In order to establish whether ternary complexes comprising ADP, beryllium and fluoride can exist in slightly alkaline solution in the absence of enzyme, we have carried out a multinuclear (³¹P, ⁹Be and ^t9F) NMR study. In preliminary experiments, pyrophosphate (PPi) was substituted for ADP and taken as a simpler analog of nucleoside diphosphate. In the absence of fluoride, three types of PPi-Be complexes were generated: two of these were bidentate chelates with either one or two pyrophosphate molecules bound per beryllium; the third one was a monodentate complex. It is probable that the same types of combination exist between the polyphosphate chain of ADP and Be. In the presence of fluoride, both ADP and PPi combined with beryllium to form ternary complexes. These complexes consisted of monofluoroberyllate(-BeF) or difluoroberyllate (-BeF,) bound to the two phosphates of one molecule of ADP or PPi as a bidentate chelate. We failed to observe the formation of complexes between ADP and trifluoroberyllate (-BeF₃). The relevance of this study to the biological effects of fluoride and beryllium on various enzymic reactions is discussed.Abbreviations PPi pyrophosphate - AMP adenosine -5-monophos-phate - ADP adenosine- 5-diphosphate - ADPS adenosine-5-O-(2-thiodiphosphate) - Ap²A P1,p²-di(adenosine-5)pyrophosphate - F₁-ATPase catalytic sector (soluble) of the beef heart mitochondrial ATPase complex - Tris tris(hydroxymethyl)aminomethane Offprint requests to: J.-L. Girardet     

Development of a Nucleoside Analog UV Light Sensor

Abstract

Conjugation of the photosensitive nucleoside ( E )-5-(2-methoxycarbonylethenyl)cytidine to biotin provided a means to attach this analogue to microparticles for dosimetry applications that require uv sensor mobility.     

Bacterial Synthesis of Nucleotides

The synthesis of inosinic acid from inosine and p-nitrophenylphosphate by the partially purified enzyme, nucleoside phosphotransferase, prepared from Escherichia coli (B-25) is described.

The results presented in this paper represent that the nucleotide, inosinic acid, synthesized by the nucleoside phosphotransferase of E. coli, used as an example of bacterial enzymes, is not always 5′-isomer and that most of inosinic acid synthesized are 3′(& 2′)-isomer, together with a small amount of 5′-isomer. It was pointed out that cupric ion accelerated both the synthesis of inosinic acid and the liberation of p-nitrophenol, and that the nucleoside phosphotransferase and the phosphatase may be different from each other.     

Synthesis of Novel Difluoro-Cyclopropyl Guanine Nucleosides and Their Phosphonate Analogues as Potent Antiviral Agents

The synthesis of new rigid guanine analogues with anti-HIV-1 and anti-herpes viral activities is described. The phosphonate of difluorocyclopropane nucleoside analogue 26 exhibits in vitro anti-HIV-1 activity similar to that of PMEA in MT-4 cells. Further, analogue 20 shows moderate anti-HCMV activity in MRC cells.     

Synthesis of 5′-Ethynyl-2′-deoxynucleoside Analogues as Building Block for Antisense Oligonucleotide

Abstract

New nucleosides and nucleoside analogue dimers were prepared using 5′-ethynyl-2′-deoxynucleoside as starting material.     

Synthesis of β-Hydroxyphosphonate and 1,2-Dihydroxy Acyclic Nucleoside Analogs via 1,3-Dipolar Cycloaddition Strategy

A convenient synthetic approach toward nucleoside analogs where β-hydroxyphosphonate- or 1,2-dihydroxy units are connected to the nucleic acid base through a triazole spacer is discussed.     

Efficient Pyrimidine N‐1‐Alkylation via Activation of Electron Rich Olefins with Oxoammonium Salts: Synthesis of Methoxy TEMPO Substituted Pyrimidine Nucleoside Analogs

Our work outlines the use of oxoammonium salts in a formal 1,2 addition process to olefins giving nucleoside analogs as products. Specifically, oxoammonium salts can be added to a solution of olefin and silylated heterocycle to give Methoxy TEMPO substituted nucleoside analogs after hydrolytic workup and chromatographic purification.     

Synthesis and Structural Analysis of Oxadiazole Carboxamide Deoxyribonucleoside Analogs

Two novel C-linked oxadiazole carboxamide nucleosides 5-(2′-deoxy-3′,5′-β-D-erythro-pentofuranosyl)-1,2,4-oxadiazole-5-carboxamide (1) and 5-(2′-deoxy-3′,5′-β-D-erythro-pentofuranosyl)-1,2,4-oxadiazole-3-carboxamide (2) were successfully synthesized and characterized by X-ray crystallography. The crystallographic analysis shows that both unnatural nucleoside analogs 1 and 2 adapt the C2′-endo (“south”) conformation. The orientation of the oxadiazole carboxamide nucleobase moiety was determined as anti (conformer A) and high anti (conformer B) in the case of the nucleoside analog 1 whereas the syn conformation is adapted by the unnatural nucleoside 2. Furthermore, nucleoside analogs 1 and 2 were converted with high efficiency to corresponding nucleoside triphosphates through the combination chemo-enzymatic approach. Oxadiazole carboxamide deoxyribonucleoside analogs represent valuable tools to study DNA polymerase recognition, fidelity of nucleotide incorporation, and extension.