Synthesis of novel D- and L-3'-deoxy-3'-C-hydroxymethyl nucleoside with exocyclic methylene as potential ribonucleotide reductase inhibitor

D- and L-3'-Deoxy-3'-C-hydroxymethyl thymidine substituted with exocyclic methylene at 2'-position were synthesized, starting from D- and L-xylose as potential ribonucleotide reductase inhibitor, respectively, but they were found to be inactive against several tumor cell lines.     

Synthesis of 3'-deoxy-3'-C-hydroxymethyl analogues of tiazofurin and ribavirin

On the basis of potent biological activity of 3'-branched-3'-deoxynucleoside analogues, novel ribavirin and tiazofurin derivatives with 3'-C-hydroxymethyl substituent were synthesized, starting from D-xylose.     

Synthesis and characterization of a ribavirin-3'',5''-phosphate pentadecamer homoribopolymer bearing a 5''-amino tether group and a 3''-thymidine.

The synthesis of a pentadecamer of the 5'-phosphate of the antiviral nucleoside ribavirin (1'-beta-D-ribofuranosyl-1H-1,2,4-triazole-3-carboxamide) has been achieved. This homoribopolymer is terminated at the 5'-position with an (6-aminohexyl)phosphate group to permit conjugation to a carrier and at the 3'-position by a thymidine-5'-phosphate. The synthesis was accomplished using the methyl phosphoramidite approach to oligoribonucleotides. The homoribopolymer was insensitive to ribonuclease A but was sensitive to ribonuclease T2 digestion.     

Synthesis and monoamine transporter affinity of 2beta-carbomethoxy-3beta-(2''-, 3''- or 4''-substituted) biphenyltropanes

A series of 11 novel 3beta-substituted biphenyltropanes was synthesized and evaluated by selective radioligand binding assays for affinity to monoamine transporters. Both 5-HTT potency and selectivity for 5-HTT over DAT was greatest with electron withdrawing group at the 3'-position.     

Exploring the potential of 3'-O-carboxy esters of thymidine as inhibitors of ribonuclease A and angiogenin

In this study, compounds with a carboxy ester in lieu of the phosphate ester at the 3'-position have been employed to inhibit the ribonucleolytic activity of ribonuclease A (RNase A). Phosphates at the 3'-position of pyrimidine bases are well-known inhibitors of the protein. We have investigated the inhibition of RNase A by 3'-O-carboxy esters of thymidine. The compounds behave as competitive inhibitors with inhibition constants ranging from 42 to 95 microM. The mode of inhibition has also been confirmed by (1)H NMR studies of the active site histidines of RNase A. Docking studies have further substantiated the experimental results. The compounds are also found to inhibit the ribonucleolytic activity of angiogenin, a homologous protein and potent inducer of blood vessel formation.     

Synthesis of a highly active new anti-HIV agent 2',3'-didehydro-3'-deoxy-4'-ethynylthymidine

Compounds having methyl, vinyl, and ethynyl groups at the 4'-position of stavudine (d4T: 2',3'-didehydro-3'-deoxythymidine) were synthesized. The compounds were assayed for their ability to inhibit the replication of HIV in cell culture. The 4'-ethynyl analogue (15) was found to be more potent and less toxic than the parent compound stavudine.     

Synthesis and biological evaluation of 3'-carboranyl thymidine analogues

Boron neutron capture therapy (BNCT) is a chemoradio-therapeutic method for the treatment of cancer. It depends on the selective targeting of tumor cells by boron-containing compounds. One category of BNCT agents with potential to selectively target tumor cells may be thymidine derivatives substituted at the 3'-position with appropriate boron moieties. Thus, several thymidine analogues were synthesized with a carborane cluster bound to the 3'-position either through an ether or a carbon linkage. The latter are the first reported carborane-containing nucleosides in which the carboranyl entity is directly linked to the carbohydrate portion of the nucleoside by a carbon-carbon bond. Low but significant phosphorylation rates in the range of 0.18% that of thymidine were observed for the carbon-linked 3'-carboranyl thymidine analogues in phosphoryl transfer assays using recombinant preparations of thymidine kinases 1 (TK1) and thymidine kinases 2 (TK2). Some of the ether-linked 3'-carboranyl thymidine analogues appeared to be slightly unstable under acidic as well as phosphoryl transfer assay conditions and were, if at all, poor substrates for TK1.     

In vitro inhibition of carrot chalcone synthase by 3'-nucleotidase: the role of the 3'-phosphate group of malonyl-coenzyme A in flavonoid biosynthesis

In mixing experiments with extracts derived from two cell lines of Daucus carota tissue cultures with and without chalcone synthase activity, strong inhibition of chalcone synthase (CHS) became obvious. This inhibition was due to the presence of a heatlabile protein in extracts from cells devoid of CHS activity. This protein was partially purified and identified as 3'-nucleotidase (EC 3.1.3.6). Inhibition was also observed in the presence of purified 3'-nucleotidase from Lolium multiflorum. The phosphate group in the 3'-position of adenosine, a part of the CoA thioester substrates of CHS, was hydrolyzed by this enzyme. The dephosphorylated form of malonyl-CoA was no longer a substrate, whereas 4-coumaryl-3'-dephospho-CoA as well as 4-coumaryl-CoA was still able to act as a primer for the CHS reaction. Further studies showed that malonyl-3'-dephospho-CoA was an efficient CHS inhibitor. On the other hand, CoA-SH lost its inhibitory activity after dephosphorylation in the 3'-position. These results are discussed with respect to the mechanism of chalcone synthesis.     

Synthesis and anti-HIV activity of 4'-cyano-2',3'-didehydro-3'-deoxythymidine

A new anti-HIV agent 4'-cyano-2',3'-didehydro-3'-deoxythymidine (9) was synthesized by allylic substitution of the 3',4'-unsaturated nucleoside 14, having a leaving group at the 2'-position, with cyanotrimethylsilane in the presence of SnCl4. Evaluation of the anti-HIV activity of 9 showed that this compound is much less potent than the recently reported 2',3'-didehydro-3'-deoxy-4'-(ethynyl)thymidine (1).     

Triplex-forming ability of modified oligonucleotides

We present our studies on the ability of several different nucleotide analogs as triplex-forming oligonucleotides. The modifications tested include 4'-C-hydroxymethyl, LNA, 2'-amino-LNA and N2'-functionalized 2'-amino-LNA. Triplexes containing monomers of N2'-glycyl-functionalized 2'-amino-LNA are particularly stable.     

Synthesis of 3'-acetamidoadenosine derivatives as potential A3 adenosine receptor agonists

On the basis of high binding affinity of 3'-aminoadenosine derivatives 2b at the human A3 adenosine receptor (AR), 3'-acetamidoadenosine derivatives 3a-e were synthesized from 1,2:5,6-di-O-isopropylidene-D-glucose via stereoselective hydroboration as a key step. Although all synthesized compounds were totally devoid of binding affinity at the human A3AR, our results revealed that 3'-position of adenosine can only be tolerated with small size of a hydrogen bonding donor like hydroxyl or amino group in the binding site of human A3AR.     

Synthesis of 2-C-hydroxymethylribofuranosylpurines as potent anti-hepatitis C virus (HCV) agents

On the basis of potent anti-HCV activity of 2'-C-methyladenosine, novel 2'-C-hydroxymethyladenosine analogues 2a-c were synthesized from d-ribose in order to lead to favorable interaction with HCV polymerase. Among compounds tested, adenosine derivative 2a exhibited potent anti-HCV activity, indicating that the hydroxyl group of 2'-C-hydroxymethyl substituent led to favorable interaction with HCV polymerase.     

C-C bond formation at the 3'-position of nucleosides by the use of their enol esters

Nucleosides having an enol ester structure in the sugar portion were synthesized and their reaction with several types of electrophiles were carried out. This furnished a new method for constructing C-C bond at the 3'-position.     

Synthesis and properties of oligonucleotides containing 2'-pyrenylalkyluridine.

The synthesis, binding and fluorescence properties of oligonucleotides containing the uridine modified at the 2'-position by a pyrene group using different length of linker arm have been described. It is demonstrated that the oligonucleotides possessing a C3-amide group at the 2'-position display an enhanced signal of the pyrene monomer fluorescence upon binding to DNA segments.     

Synthesis and biological evaluation of novel D-2'-azido-2',3'-dideoxyarabinofuranosyl-4'-thiopyrimidines and purines

Novel D-2'-azido-2',3'-dideoxyarabinofuranosyl-4'-thiopyrimidines and purines have been synthesized, starting from L-xylose via azidation at the 2'-position as a key step. Most of the final nucleosides exhibited toxicity-dependent anti-HIV-1 activity, among which D-alpha-adenine analogue was found to be the most cytotoxic.     

Anti-AIDS agents. Part 62: anti-HIV activity of 2'-substituted 4-methyl-3',4'-di-O-(-)-camphanoyl-(+)-cis-khellactone (4-methyl DCK) analogs

Four 4-methyl-3',4'-di-O-(-)-camphanoyl-(+)-cis-khellactone (4-methyl DCK) analogs (7a-d) with different alkyl substituents at the 2'-position were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. 2'-Methyl-2'-ethyl-4-methyl DCK (7b) was more potent (EC(50)=0.22 microM, TI>175) than the other three compounds (7a, 7c, and 7d), but significantly less potent than 4-methyl DCK (2, EC(50)=0.0059 microM, TI>6600). The bioassay results indicated that the 2'-substituents had a strong effect on the anti-HIV activity, and gem-dimethyl substitution at the 2'-position was greatly preferable to larger alkyl substituents or hydrogen atoms.     

Antitumour benzothiazoles. Part 20: 3'-cyano and 3'-alkynyl-substituted 2-(4'-aminophenyl)benzothiazoles as new potent and selective analogues

The synthesis of a new series of antitumour 2-(4-aminophenyl)benzothiazole analogues, substituted in the 3'-position by cyano or alkynyl groups, is described. Several of the analogues, notably the 5-fluorinated compounds 7c and 9c, were found to possess potent in vitro activity against MCF-7 and MDA 468 human cancer cell lines. More comprehensive in vitro analysis (NCI 60-cell line) established compound 7c as a particularly potent and selective 2-(4-aminophenyl)benzothiazole analogue.     

Relationship between mutagenic potency in Salmonella typhimurium and chemical structure of amino- and nitro-substituted biphenyls

All positional isomers of mononitro- and monoaminobiphenyls and those of dinitro-, diamino- and aminonitrobiphenyls, which have one substituent on each benzene ring, were assayed for mutagenicity in Salmonella typhimurium by the Ames method. The results suggest that the structural requirements favoring mutagenic activity are the presence of substituents at the 4-position and their absence at the 2'-position. The introduction of an amino group to the 3'- or 4'-position of 4-nitrobiphenyl or a nitro group to 3'- or 4'-position of 4-aminobiphenyl enhanced the mutagenicity. Among the mutagenic compounds, 4-nitro analogues were mutagenic in strains TA98 and TA100 in the absence of a microsomal metabolic activation system. Strain TA98NR was not reverted by the direct-acting mutagens, whereas strain TA98/1,8-DNP6 was as revertible as strain TA98; these results suggest that the direct-acting mutagenicity involves the reduction of the nitro group by bacterial nitroreductase but does not involve specific esterification enzymes.     

The 3'-amido and 5'-amido analogues of adenosine 3':5'-monophosphate; interaction with cAMP-specific proteins.

The sensitivity for recognition of adenosine 3:5'-monophosphate (cAMP) by its coordinate proteins towards chemical changes in the six-membered cyclic phosphate ring has been investigated. A comparison of the interaction parameters of the 3' and 5'-amido analogues (I, II) and of unsubstituted cAMP has been made using two different protein kinases and the phosphodiesterase from bovine heart. Binding affinity and the capacity of the amido analogues to stimulate the phosphotransferase activity of the kinases is greatly reeuced relative to cAMP, the 3'-position being more sensitive towards the modification than the 5'-position. The coordinate noncyclic derivatives, 3'-deoxy-3'-amino-5'-AMP (IV) and 5'-deoxy-5'-amino-3'-amp (iii), were also tested. Surprisingly activity towards protein kinases was found to be considerable for the 5'-deoxy-5'-amino-3'-AMP (III), while the 3'-deoxy-3'-amino-5'-AMP (IV) is practically inactive. A possible reason for this is that the noncylic 5'-analogue (III) may be able to assume a cyclic structure maintained by internal salt formation. The phosphodiesterase splits both cyclic amido analogues but with reduced rates compared to that of natural cAMP. Kinetic data obtained from different methods reveal a stronger affinity for the 5'-analogue (I) than the 3'-analogue (II) for the active site, although the reaction rate at saturated substrate concentration is significantly higher with II than with I. The properties of the amido and the noncyclic amino analogues are discussed with available data from chemotaxis of the cellular slime moulds. Furthermore data of the respective methylene cyclic derivatives are used for a more comprehensive comparison. The above is interpreted in terms of the electronic features of the substitutions and of the changes in bond distances or angles upon replacement of O by NH or CH2 in the cyclic phosphate ring (obtained from X-ray work).     

Synthesis of 5-chloro-1-(2,3-dideoxy-3-fluoro-beta-D-glycero-hex-2- enopyranose-4-ulosyl)uracil as potential anticancer/antiviral agent

Peracetylated alpha-D-glucose was coupled with silylated 5-chlorouracil. The product (2) was deacetylated and 4',6'-hydroxyls were then protected with 4',6'-O-isopropylidene group. Fluorine was introduced at the 3'-position, followed by acetylation, deprotection, tritylation, oxidation and deritylation of subsequent compounds gave the target compound (10).