Nils Gunnar Johansson

Inhibition of Influenza Virus Ribonucleic Acid Polymerase by Ribavirin Triphosphate

Ribavirin 5′-triphosphate (RTP), derived from the broad-spectrum antiviral compound ribavirin (Virazole), can selectively inhibit influenza virus ribonucleic acid polymerase in a cell-free assay. Ribavirin and its 5′-monophosphate have no effect on the polymerase. The inhibition is competitive with respect to adenosine 5′-triphosphate and guanosine 5′-triphosphate. RTP also inhibits ApG- and GpC-stimulated influenza virus ribonucleic acid polymerase. Since ribavirin is phosphorylated in the cell, the inhibition of influenza multiplication in the cell may also be caused by RTP.

Characterization of N7 and N9 alkylated purine analogues by 1H and 13C NMR

Abstract The Use of 1 H and 13 C NMR for differentiating N7 and N9 alkylated guanine derivatives is described.

An analysis of the inhibition of replication of HIV and MuLV by some 3'-blocked pyrimidine analogs.

Some 3-blocked pyrimidine analogs were synthesized and tested as inhibitors of replication of human immunodeficiency virus (HIV) and Moloney-murine leukemia virus (MuLV). The analogs were of 3 kinds: (1) analogs of 3-azido-3-deoxythymidine (AZT) in which the C-5 CH3 of the base was exchanged for H (AZU) or C2H5 (AZEU); (2) 3-fluoro-3-deoxythymidine (FLT) and analogs thereof, in which the C-5 CH3 of the base was exchanged for H (FLU), C2H5 (FLEU) or nC3H7 (FLPU); (3) the threo analogs of AZT (AZT increases) and AZU (AZU increases). All analogs were less active inhibitors of HIV replication than AZT, except FLT, which was as active as AZT. The 3-fluoro analogs and AZEU did not inhibit MuLV replication at non-cytotoxic concentrations. Oral administration of FLT to MuLV-infected mice result in antiviral effects only at toxic drug levels. AZU and FLU were less potent inhibitors of HIV replication than AZT or FLT, but the 2-deoxy uridine analogs were less cytotoxic to human embryonic fibroblasts than the thymidine analogs. The 5-triphosphates of AZU, AZT, AZEU, FLT and FLEU were tested as inhibitors of the HIV- and MuLV-reverse transcriptases. Ranking of the Ki/Km values for HIV-RT resulted in the following order of potency of the 5-triphosphates AZT = FLT greater than AZU greater than AZEU greater than FLEU. The 5-triphosphates of AZEU, FLT and FLEU did not inhibit the MuLV-RT, which explains, in part, the lack of effect of these analogs against MuLV replication. The threo forms (azido up) of AZU and AZT were less active inhibitors of HIV replication than the erythro forms (azido down). A 15N-NMR and 1H-NMR study showed that the furanose moieties of analogs with the azido function up assume a conformation distinct from that of the analogs with azido down. This is due to intramolecular stabilisation of the N conformer in the threo (up) diastereomer, due to interaction of the azido functions with the nucleobase and possibly the OH group of C-5 of the furanose. As discussed, this conformation might explain the decreased biological activity of threo forms compared with the erythro forms.

Studies on the Alkylation of Derivatives of Guanines

Abstract The synthesis of some N7- and N9-substituted guanine analogs was investigated. The influence of the base, the alkylating agent and of the type of derivatization of the purine moiety on the relative formation of the N7 and N9 isomers was studied.

Regioselective alkylation of 6-(β-methoxyethoxy)guanine to give the 9-alkylguanine derivative

Abstract In the presence of lithium hydride 6-(β-methoxyethoxy)guanine reacts regioselectively with 4-bromobutyl acetate to give the 9-alkylguanine derivative.

The use of 15N-NMR spectroscopy for assigning the structures of isomeric N7- and N9-substituted purines

An 15N-NMR study has shown a considerable difference in electronic structures between the isomeric N7 and N9 substituted purines. A comparison of 15N chemical shifts amongst the seven pairs of N7 and N9 isomers has revealed that (1) the N3 resonances are shielded by 18–20 ppm in an N9 isomers; (2) the amino nitrogens at the C-2 or at C-6 positions are always shielded by 3–4 ppm in the N7 isomers; (3) the N7 chemical shifts in the N7 isomers are always more shielded by 6–7 ppm than the N9 resonances in the N9 isomers. It has a also been found by protonation studies that the N9 of the N7 isomer is much more basic than the N7 of the N9 isomer.

Preclinical Evaluation of 1H-Benzylindole Derivatives as Novel Human Immunodeficiency Virus Integrase Strand Transfer Inhibitors

ABSTRACT We have identified 1H-benzylindole analogues as a novel series of human immunodeficiency virus (HIV) integrase inhibitors with antiretroviral activities against different strains of HIV type 1 (HIV-1), HIV-2, and simian immunodeficiency virus strain MAC251 [SIV(MAC251)]. Molecular modeling and structure-activity relationship-based optimization resulted in the identification of CHI/1043 as the most potent congener. CHI/1043 inhibited the replication of HIV-1(IIIB) in MT-4 cells at a 50% effective concentration (EC50) of 0.60 μM, 70-fold below its cytotoxic concentration. Equal activities against HIV-1(NL4.3), HIV-2(ROD), HIV-2(EHO), and SIV(MAC251) were observed. CHI/1043 was equally active against virus strains resistant against inhibitors of reverse transcriptase or protease. Replication of both X4 and R5 strains in peripheral blood mononuclear cells was sensitive to the inhibitory effect of CHI/1043 (EC50, 0.30 to 0.38 μM). CHI/1043 inhibited integrase strand transfer activity in oligonucleotide-based enzymatic assays at low micromolar concentrations. Time-of-addition experiments confirmed CHI/1043 to interfere with the viral replication cycle at the time of retroviral integration. Quantitative Alu PCR corroborated that the anti-HIV activity is based upon the inhibition of proviral DNA integration. An HIV-1 strain selected for 70 passages in the presence of CHI/1043 was evaluated genotypically and phenotypically. The mutations T66I and Q146K were present in integrase. Cross-resistance to other integrase strand transfer inhibitors, such as L-708,906, the naphthyridine analogue L-870,810, and the clinical drugs GS/9137 and MK-0518, was observed. In adsorption, distribution, metabolism, excretion, and toxicity studies, antiviral activity was strongly reduced by protein binding, and metabolization in human liver microsomes was observed. Transport studies with Caco cells suggest a low oral bioavailability.

Synthesis and antiviral activity of various 5-substituted 2'-deoxyuridines and -cytidines

Abstract 5-Cyclopropyl-2′-deoxycytidine and some 5-aryl-2′-deoxyuridines and -cytidines have been prepared and their inhibition of HIV have been tested.

Conformations of Acyclonucleosides: Crystal Structure of 9-(4-Hydroxybutyl)Guanine, an Analogue of Acyclovir

Abstract 9-(4-Hydroxybutyl)guanine is an analogue of acyclovir in which the ether oxygen is replaced by a methylene group. Crystals of the monohydrate belong to the monoclinic space group P21/n with a = 4.350 (1), b = 10.859 (1), c = 23.684 (4) A, β = 90.65 (1)°. X-ray intensity data were measured with a diffractometer and the structure was determined by direct methods. Least-squares refinement converged at R = 0.055 for 1982 reflections. The side chain is fully extended and almost perpendicular to the guanine base.

An 15n-nmr study of isomeric n1 and n3 substituted 7-methyl-10-oxo-9,10-dihydro pyrimido[l,2-a]purines and 9-oxo-8,9-dihydro-5-alkyl-imidazo[1,2-a] purines in neutral and acidic medium.

Abstract An 15N-NMR study in neutral and acidic solutions of isoaeric N1 and N3 substituted 7-methy1-10-oxo-9,10-dihydro-pyrimido[l,2-a]purines, 4 and 5 , and 9-oxo-8,9-dihydro-5-alkyl-imidazo[l,2-a] purines, 6 and 7 respectively, have shown the electronic implications of building an additional six-membered ring with two double bonds, as in 4 and 5 , and a five-membered ring with one double bond, as in 6 and 7 , involving 1-NH and exocyclic 2-NH2 substituent of the guanine moiety 1a . The ease of formation of N1 or N3 protonated species and the magnitude of their 15N chemical shifts in compounds 4 to 7 have established that the π-electron rich imidazole system is more deactivated 1n pyrimido[l,2-a]purine derivatives, 4 and 5 , than in the imidazo[l,2-a]purines 6 and 7 . It has also emerged that the N3 of N1 isomers, 5 and 7 , are more strongly protonated than the N1 of N3 isomers 4 and 6 . A consideration of 2JN8(N9)H7(H8) and the resonances of N9(N8) and N5 in compounds 4 to 1 has shown that the N5,N9-fused six-membered ring of the pyrimido[1,2-a ] purines is π-electron deficient and is not coplanar with the rest of the molecule while the geometry of the N5,N8-fused five-membered ring of the imidazo[l,2-a] purines allows the participation of the N5 ione pair to activate the imidazole system as the exocyclic 2-NH2 or 2-NHCOR groups of N9-substituted guanine moiety.