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A cyclistation reaction of the D-allo- and D-altro isomers of 2-(2, 4:3, 5'-di-O-benzylidenepentitol-1-yl)pyridine derivatives to afford the corresponding substituted 2-(D-ribofuranosyl) pyridine-C-nucleosides, was investigated. The latter compounds were obtained in good yield (90%) if the reaction was performed in 1 N HCI. The structures were confirmed by 13C-NMR studies and an HPLC method with was developed specifically for a determination of their purity. All compounds were evaluated for biological activity in a variety of antiviral and antitumor cell systems in vitro.

Eight new 5-heteroaromatic substituted analogues of 2'-deoxyuridine have been synthesized and evaluated for their inhibitory properties against a panel of different viruses. Several analogues containing a substituted thiophene moiety proved to be highly selective against herpes simplex virus type 1 (HSV-1).

Diethyl and dibutyl α-anilinobenzylphosphonates and [α-(4-benzeneazoanilino)benzyl]-phosphonates and their new palladium(II) halide complexes were evaluated for their cytostatic and antiviral activity in different cell systems.

The bis-pivaloyloxymethyl(POM)- and diphenyl-ester prodrugs of the broad spectrum antiviral agent 9-(2-phosphonylmethoxyethyl)adenine (PMEA) have been evaluated in vivo for antiviral efficacy upon oral administration in severe combined immune deficiency (SCID) mice infected with Moloney murine sarcoma virus (MSV). Oral bis (POM)-PMEA proved highly efficient in delaying MSV-induced tumor formation and associated death, its effect being equal to that of subcutaneous PMEA at an equimolar dose. Compared to bis(POM)-PMEA, oral diphenyl-PMEA had lower antiviral efficacy, whereas PMEA as such was poorly effective when administered orally. Our studies indicate that bis(POM)-PMEA must have a favorable oral bioavailability and justify its clinical investigation as an oral prodrug of PMEA in the treatment of HIV infections.

The nucleoside analogue 2',3'-dideoxyadenosine (ddA), the phosphonate isostere of 2',3'-dideoxy-2',3'-didehydro-adenosine (d4A) 5'-monophosphate (d4API), and the acyclic nucleoside phosphonates PMEoA, PMEA, FPMPA and PMPA are potent and selective antiretroviral agents. We found that these compounds are recognized as substrates by the PRPP synthetases from E. coli, rat liver and human erythrocytes, as their monophosphate and triphosphate form in the reverse and forward reaction, respectively. In particular, ddA-5'-monophosphate (ddAMP) and ddA-5'-triphosphate proved to be excellent substrates for the enzymes. D4API was a relatively good substrate of the rat liver and human erythrocyte PRPP synthetases. The acyclic nucleoside phosphonates were rather poor substrates, as evident from their low Vmax values. None of the PRPP synthetases are found to act stereospecifically: they recognized both the S- and R-enantiomers of FPMPA and PMPA in a comparably efficient manner. Our data indicate that PRPP synthetase may recognize a much broader range of adenine nucleotide analogues than previously thought.

A number of oligodeoxynucleotides containing thymine bases linked to the deoxyribose in the α-configuration have been synthesized. In view of the possible activity of α-origomers as antisense compounds against HIV replication, the effects of α-thymidylate oligomers (α-dTn, n=1-1-16) in a poly (A)-directed HIV reverse transcriptase (RT) reaction were investigated. No priming activity could be detected with the α-dT oligomers at concentrations up to 100 μM. However, in the presence of the natural β-dT12-18 primer, 50% inhibition of RT activity was achieved at a concentration of about 1 μM with the α-dT oligomers containing ≥ 10 monomer units. The kinetics of RT inhibition by the α-decamer was found to be competitive with respect to the natural primer, β-dT10.

The total synthesis of 3-chloro-4-(D-ribofuranosyl)-pyridine and 3-(D-ribo-furanosyl)-2-pyridone was elaborated using the appropriate lithiopyridines and 2,4:3,5-di-O-benzylidene-aldehydo-D-ribose. The conformation of these compounds was investigated by 360 MHz 1H-NMR. The compounds were evaluated as α,β-mixtures for their antiviral and cytostatic properties. However, no significant biological activity was found.

HHV-6 was evaluated in vitro for its susceptibility to a broad range of nucleoside analogues. PFA and several acyclic nucleoside phophonates emerged as the most potent inhibitors of HHV-6 replication as monitored by a newly developed immunofluorescence / flow cytometric assay as well as by microscopical evaluation of their inhibitory effect on HHV-6-induced cytopathogenicity.

Combinations of high concentrations of AZT with BVDU, acyclovir (ACV) or ganciclovir (GCV) show antagonism against TK+ HSV-1, but not TK+ VZV strains, in cell cultures. When BVDU and AZT were used in combination against TK- HSV-1, TK- HSV-2 and TK- VZV strains, a pronounced inhibition of viral replication was observed. This potentiating effect was not seen if AZT was combined with ACV or GCV.

To assess the structure-activity relationship for antiviral activity, a series of 3'-deoxy-3'-N-functionalized thymidine analogues were synthesized. Several of these thymidine analogues show moderate in vitro activity against HIV-1 and HIV-2.

9-(2-Phosphonylmethoxyethyl)adenine (PMEA), the prototype compound of a well-defined structural class of potent and selective anti-retroviral agents, was found to be endowed with long-lasting and dose-dependent differentiation-inducing properties in human erythroleukemia K562 cell cultures.

In order to study the influence of the position of both the carbamoyl and the D-ribofuranosylmoiety on the biological activity of pyridine-C-nucleosides, the 2-carbamoyl-5-P-D-ribofuranosylpyridine was synthesized.

2-(2-Deoxy-D-erythro-pent-1-enofuranosyl)pyridine and its methyl analogues have been prepared by treatment of the corresponding 2',3'-O-isopropylidene-D-ribofuranosyl derivatives with several bases such as sodium amide, tert.BuOK, EtONa, lithium tetramethylpiperidide (LTMP) and phenyl lithium (PhLi). PhLi and tert.BuOK gave the best results. The products thus obtained showed cytostatic activity against human tumor cell lines, in particular MT-4, a human T-lymphocyte cell line. No antiviral activity was noted at subtoxic concentrations.

The reaction between 3-bromo-5-chloromethylpyridine hydrochloride (4) with the mono sodium salt of ethylene glycol was investigated. 3-Bromo-5-(2-hydroxyethoxymethyl)-pyridine (5) was synthesized and converted to the 3-carboxy analogue using butyllithium and CO2. Subsequent treatment with diazomethane and ammonolysis gave the corresponding acyclic nicotinamide C-nucleosides. The latter compounds were converted into the thioamide analogues by reaction with Lawesson's reagent. The pyridine N-oxide derivatives were obtained by treatment with peracetic acid or hydrogen peroxide. All compounds were identified with the aid of 1H- and 13C-NMR and mass spectrometry. The acyclic pyridine C-nucleosides were evaluated against a number of viral strains and cancer cell lines but no significant biological activity was found.

Members of a new class of carbonucleoside analogues (OTC, one two substituted carbonucleosides) were synthesized and evaluated against HIV.

Several new prodrugs of 5-fluoro-2'-deoxyuridine 5'-monophosphate and 3',5'-cyclic monophosphate were synthesized and their antitumor activities were evaluated in vitro.

The synthesis of the α- and β-anomers of 2',3'-dideoxy-3'-fluoro-2-thiouridine and 2',3'-dideoxy-3'-fluoro-2-thiothymidine via Lewis acid catalysed nucleoside condensation is described. High resolution 1H NMR data, solution conformations and biological properties are also presented.

AbstractThe bis(S-pivaloyl-2-thioethyl) phosphotriesters of Ara-C and Ara-A were synthesized as potential bioreversible mononucleotide prodrugs. Some N- and O-acylated derivatives were also prepared with the aim to modify the lipophilicity of the title pronucleotides. Compounds were tested for their antitumor/antiviral activity against a variety of tumor cells and viruses.