Synthesis and antiviral activity of several 2,5'-anhydro analogues of 3'-azido-3'-deoxythymidine, 3'-azido-2',3'-dideoxyuridine, 3'-azido-2',3'-dideoxy-5-halouridines, and 3'-deoxythymidine against human immunodeficiency virus and Rauscher-murine leukemia virus

Synthesis of activated 3'-amino-3'-deoxy-2-thio-thymidine, a superior substrate for the nonenzymatic copying of nucleic acid templates

We present a scalable synthesis of 3'-amino-3'-deoxy-2-thio-thymidine-5'-phosphoro-2-methylimidazolide, an activated monomer that can copy adenosine residues in nucleic acid templates rapidly without a polymerase. The sulfur atom substitution enhances the rate of template copying by 5-fold compared with the 3'-amino-3'-deoxy-T monomer, while the 3'-amino monomers exhibit a 2- to 30-fold enhancement compared with their ribonucleotide counterparts.

Alpha,beta-methylene-2'-deoxynucleoside 5'-triphosphates as noncleavable substrates for DNA polymerases: isolation, characterization, and stability studies of novel 2'-deoxycyclonucleosides, 3,5'-cyclo-dG, and 2,5'-cyclo-dT

We report synthesis and characterization of a complete set of alpha,beta-methylene-2'-dNTPs (alpha,beta-m-dNTP; N = A, C, T, G, 12-15) in which the alpha,beta-oxygen linkage of natural dNTP was replaced by a methylene group. These nucleotides were designed to be noncleavable substrates for DNA polymerases. Synthesis entails preparation of 2'-deoxynucleoside 5'-diphosphate precursors, followed by an enzymatic gamma-phosphorylation. All four synthesized alpha,beta-m-dNTPs were found to be potent inhibitors of polymerase beta, with K i values ranging 1-5 microM. During preparation of the dG and dT derivatives of alpha,beta-methylene diphosphate, we also isolated significant amounts of 3,5'-cyclo-dG (16) and 2,5'-cyclo-dT (17), respectively. These novel 2'-deoxycyclonucleosides were formed via a base-catalyzed intramolecular cyclization (N3 --> C5' and O2 --> C5', respectively). In acidic solution, both 16 and 17 underwent glycolysis, followed by complete depurination. When exposed to alkaline conditions, 16 underwent an oxidative deamination to produce 3,5'- cyclo-2'-deoxyxanthosine (19), whereas 17 was hydrolyzed exclusively to dT.

New AZT analogues having 5'-alkylsulfonyl groups: synthesis and anti-HIV activity

New derivatives of azidothymidine (AZT) substituted by alkyl and alkylsulphonyl groups at N-3 and C-5', respectively, have been synthesized. The new synthesized derivatives showed remarkable anti-HIV-1 and HIV-2 activity in MT-4 cells. Compounds 8 and 10 have IC(50) values of 0.83 and 0.31 microg/mL against HIV-1 with therapeutic index of 83 and 403, respectively, and IC(50) values of 0.93 and 0.29 microg/mL against HIV-2 with therapeutic index of 74 and 431, respectively. This means that compounds 8 and 10 were cytotoxic to MT-4 cells at CC(50) of 69.2 microg/mL and 125 microg/mL, respectively.

Synthesis of 5'-triphosphate mimics (P3Ms) of 3'-azido-3',5'-dideoxythymidine and 3',5'-dideoxy-5'-difluoromethylenethymidine as HIV-1 reverse transcriptase inhibitors

3'-Azido-3',5-dideoxythymidine 5'-phosphonate and 3',5'-dideoxy-5'-difluoromethylenethymidine 5'-phosphonate were prepared by multistep syntheses. The nucleoside 5'-phosphonates were converted to their triphosphates and triphosphate mimics (P3Ms) containing beta,gamma-difluoromethylene, beta,gamma-dichloromethylene, or beta,gamma-imodo by condensation with pyrophosphate or pyrophosphate mimics, respectively. Inhibition of HIV-1 reverse transcriptase by the nucleoside P3Ms is briefly discussed.

Assessment of anti-HIV activity of some benzimidazolylthiazoles

Benzimidazolylthiazoles 2 were synthesized by condensing 1H-benzimidazole-2-acetonitrile (1) with sulphur and isothiocyanates. The syntheses of the Schiff bases 3, thioureas 4, and thiazolopyrimido[1,6-a]benzimidazoles 5 and 6 are also described. Seven compounds were evaluated in vitro against human HIV, however, no significant activity was observed with any of these compounds.

2',5'-Bis-O-(tert-butyldimethylsilyl)-3'-spiro-5''-(4''-amino-1'',2''- oxathiole-2'',2'-dioxide)pyrimidine (TSAO) nucleoside analogues: highlyselective inhibitors of human immunodeficiency virus type 1 that are targeted at the viral reverse transcriptase

A series of pyrimidine nucleoside analogues containing [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5''-(4''-amino- 1'',2''-oxathiole-2'',2''-dioxide)]-beta-D-ribofuranose as the pentose were found to inhibit human immunodeficiency virus type 1 [HIV-1(IIIB)] replication at a concentration of 0.06-0.8 microM but were not cytotoxic at a 1000- to 10,000-fold higher concentration. These nucleoside derivatives were also effective against various other HIV-1 strains, including those resistant to 3'-azido-3'-deoxythymidine, but not against HIV-2, simian immunodeficiency virus, Moloney murine sarcoma virus, or other RNA or DNA viruses. They proved to be highly specific inhibitors of the RNA-dependent DNA polymerase function of the HIV-1 reverse transcriptase, showing no marked inhibition of the HIV-1 reverse transcriptase-associated DNA-dependent DNA polymerase activity, HIV-2 reverse transcriptase, DNA polymerase alpha, herpes simplex virus 1 DNA polymerase, or Thermus aquaticus DNA polymerase.

HIV inhibitors targeted at the reverse transcriptase

HIV inhibitors targeted at the virus-associated reverse transcriptase (RT) can be divided into two groups, depending on whether they are targeted at the substrate or nonsubstrate binding site. To the first group belong the 2',3'-dideoxynucleosides (i.e., DDC, DDI), 3'-azido-2',3'-dideoxynucleosides (i.e., AZT), 3'-fluoro-2',3'-dideoxynucleosides (i.e., FLT), 2',3'-didehydro-2',3'-dideoxynucleosides (i.e., D4C, D4T) and carbocyclic derivatives thereof (i.e., carbovir), 2'-fluoro-ara-2',3'-dideoxynucleosides, 1,3-dioxolane derivatives (i.e., 2',3'-dideoxyl-3'-thiacytidine), oxetanocin analogues and carbocyclic derivatives thereof (i.e., cyclobut-G) and the 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and 9-(3-fluoro-2-phosphonylmethoxypropyl)adenine (FPMPA) derivatives. These compounds need to be phosphorylated intracellularly to their triphosphate forms before they act as competitive inhibitors or alternate substrates (chain terminators) of HIV RT. The second group includes the tetrahydro-imidazo[4,5,l-jk][1,4]-benzodiazepin-2(1H)one (TIBO), 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)thymine (HEPT), dipyrido[3,2-b:2',3'-e]-[1,4]diazepin-6-one (nevirapine) and pyridin-2(1H)one derivatives, which interact as such, noncompetitively, with a specific allosteric binding site of HIV-1 RT. Compounds belonging to the two different groups may give rise to synergism which combined, and, likewise, viral resistance to the compounds may arise through different mutations, depending on the nature of the compounds and the group to which they belong.

Synergistic combinations and peptides in the inhibition of human immunodeficiency virus

Various combinations of inhibitors of HIV reverse transcriptase were tested for inhibition of HIV replication in order to reveal any potential synergism or antagonism. PFA, a pyrophosphate analogue, gave synergistic inhibition of HIV replication in combination with both of the thymidine analogues AZT and FLT. The combination of PFA and AZT-TP gave only additive or weakly synergistic inhibition in a reverse transcriptase enzyme assay. The combination of AZT and FLT also gave synergistic inhibition of HIV replication, whilst the combination of AZT-TP and FLT-TP gave only additive or weakly synergistic inhibition of reverse transcriptase. Thus, the synergy does not arise from effects on reverse transcriptase alone but must be owing to other, cellular factors, such as effects on nucleoside metabolism or metabolism of the analogues. The results are consistent with the hypothesis that AZT may have an alternative mechanism of inhibition other than inhibition of reverse transcriptase. The diminished cytotoxicity observed in addition to the synergistic inhibition makes these combinations attractive from the point of view of combination chemotherapy. The inhibition of HIV replication by peptides from various parts of the V3 region of gp120 whose sequences were homologous with the tryptase inhibitor trypstatin was tested. Inhibitory activity was displayed by two peptides containing cysteine in their sequence. Antibodies to two peptides containing the two conserved cysteine residues from opposite sides of the neutralizing loop of gp120 were previously associated with protection from vertical transmission of HIV. The V3 region thus seems to be important for the function of gp120 and the transmission of HIV.

Effect of 3'-deoxythymidin-2'-ene (d4T) on nucleoside metabolism in H9 cells

The effect of 3'-deoxythymidin-2'-ene (d4T) on the metabolism of exogenously supplied radiolabeled nucleosides was investigated. Following a 24-hr exposure to 250 microM d4T, we observed no significant effect on the incorporation of [3H]thymidine or [3H]deoxycytidine into DNA. In contrast, the amounts of [3H]uridine, [3H]deoxyuridine, and [3H]cytidine were significantly lower than those incorporated by control cultures. d4T had no significant effect on the incorporation of [3H]uridine or [3H]cytidine into RNA, or the incorporation of 3H-labeled amino acids into protein. In d4T-treated cells the relative proportions of [3H]dTMP, [3H]dTDP, and [3H]dTTP formed did not change but their absolute concentrations were increased. d4T significantly reduced the level of [3H]dUMP, and a parallel decrease in [3H]dTMP derived from [3H]dUMP was also evident. d4T increased the amounts of labeled deoxycytidine metabolites formed, with increased dCMP levels the most prominent. In a cell-free extract, [3H]d4T was phosphorylated at a rate of 1.6 pmol/30 min. Increasing concentrations of both thymidine and deoxyuridine inhibited the phosphorylation of [3H]d4T with IC50 values of 5.7 and 35 microM respectively. d4T was found to be a weak substrate for purified H9 cytosolic thymidine kinase (Km = 138 microM) and a weak competitive inhibitor of thymidine and deoxyuridine phosphorylation by this enzyme (Ki = 1.37 and 0.33 mM respectively).