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One, two-disubstituted carbocyclic nucleoside analogues bearing a 2-amino-6-substituted (chloro, hydroxy or amino) purine or 8-azapurine base were prepared by constructing the base about (±)-2-aminocyclopentane methanol, and their activities against a selection of viruses and tumor cells were determined in vitro .

Nucleoside and nucleotide analogues, which are inhibitors of human immunodeficiency virus reverse transcriptase, are highly active inhibitors of visna virus replication in cell cultures. One such analogue, the acyclic nucleoside phosphonate PMEA, has also been found to have a prophylactic effect on visna virus infection in lambs. In the present study, lambs were injected subcutaneously with 10 mg/kg PMEA three times a week starting 4 weeks after inoculation with visna virus, when brain infection had been established. After 3 weeks of treatment there was a reduction in the amount of virus isolated from blood cells of PMEA-treated lambs compared to controls and during the remaining 7 months of drug treatmentthere was significantly less virus isolated from the blood cells of treated lambs than of controls. Antibody response against visna virus was also slower in the treated than in the untreated control group. On the other hand, there was no difference in the amount of virus isolated from various organs of the two groups and the severity of CNS lesions in sheep treated with PMEA for 8 months was comparable to that found in untreated controls, even though PMEA reached concentrations in the cerebrospinal fluid which were well in excess of the EC50 value of the drug for visna virus.

The acyclic nucleoside phosphonate 9-(2-phosphonyl-methoxyethyl)adenine (PMEA) is a potent and selective antiretroviral agent which is currently evaluated in its oral prodrug form, bis(POM)PMEA (adefovir dipivoxil), in phase II and III clinical trials in human hepatitis B virus (HBV)- and human immunodeficiency virus (HIV)-infected individuals, respectively. We have now found that PMEA is also a potent inhibitor of growth of the highly aggressive choriocarcinoma tumor arising from rat choriocarcinoma RCHO cells grafted under the kidney capsule of syngeneic WKA/H rats. In untreated rats, massive invasive RCHO tumors, covering the whole surface of the kidney and resulting in a marked enlargement of the kidney, were observed at day 10 after tumor cell grafting. Daily treatment with PMEA at 25 mg/kg/ day afforded a marked reduction in tumor size (i.e., smaller tumors and slight, if any, enlargement of the kidney). Increasing the PMEA dose to 50, 100 or 250 mglkglday resulted in a gradual increase of the antitumor effect of the compound. At the highest dose tested, i.e., 250 mg/kg/day, PMEA completely suppressed tumor growth. The antitumor activity of PMEA persisted for at least 10 days after termination of drug treatment. In addition, delayed treatment with PMEA at a dose of 200 mg/kg/day, started at a time point where choriocarcinoma tumors had already developed, stopped further growth and even induced regression of the tumors. PMPA, a closely related structural analogue of PMEA, failed to inhibit choriocarcinoma tumor growth. This observation points to the specificity of PMEA as an antitumor agent. In view of our findings, the therapeutic potential of PMEA for the treatment of neoplastic diseases appears to merit further investigation.

The synthesis, hydrolysis, and antiviral evaluation of novel, lipophilic cycloSal-d4TMP derivatives 3a-h of the anti-HIV dideoxynucleoside 2',3'-dideoxy-2',3'-didehydrothymidine (d4T, 1) are reported. This pro-nucleotide concept has been designed to deliver d4TMP (2) by selective chemical hydrolysis. All compounds 3a-h were synthesized using phosphorus(III) chemistry in good yields and in somewhat lower yields using phosphorus(V) chemistry starting from substituted salicyl alcohols 6a-h. The phosphotriesters 3 were obtained without stereochemical preference with respect to the configuration at the phosphorus center as 1:1 diastereomeric mixtures. However, a few of the triesters 3 could be separated into the diastereomers by means of semipreparative HPLC. In a 1-octanol/phosphate buffer mixture, all compounds 3 exhibited 9-100-fold higher lipophilicity as judged from their Pa values as compared to d4T (1). Furthermore, in hydrolysis studies 3 decomposed under mild aqueous basic conditions releasing solely d4TMP (2) and the diols 6 following the designed tandem reaction sequence. A correlation of the electronic properties introduced by the substituents and the half-lives of triesters 3 was observed. Thus, by varying the substituent, the half-lives of 3 could be adjusted over a wide range of compounds still delivering d4TMP (2) selectively. Phosphotriesters 3 exhibited considerable activity against HIV-1 and HIV-2 in wild-type human T-lymphocyte (CEM/O) cells as well as mutant thymidine kinase-deficient (CEM/TK-) cells. Surprisingly, we observed a 3-80-fold difference in antiviral activity between the two diastereomers. Our data clearly prove that the cycloSal-d4TMPs deliver exclusively the nucleotide d4TMP not only under simulated hydrolysis conditions but also under cellular conditions and thus fulfill the thymidine kinase-bypass premise. Therefore, the cycloSal-nucleotide concept is the first reported pro-nucleotide system that delivers the dideoxynucleotide by a pH-driven, chemically activated, tandem reaction without the requirement of an enzymatic contribution.

(Z) and (E)-2-(purin-9-yl/ pyrimidin-1-yl)ethylen-1-ylphosphonic acid 10–18 were synthetized by Michael addition of heterocyclic base with the diethylethynylphosphonate and deprotection of the acyclic nucleoside phosphonate with bromotrimethylsilane.

Novel chain-extended nucleoside phosphoramidates of the anti-human immunodeficiency virus (HIV) drug d4T (stavudine) have been prepared as possible membrane-permeable prodrugs of the bio-active free 5′-monophosphates. Phosphorochloridate chemistry gave the target compounds in moderate to high yields, and all materials were fully characterized by spectroscopic and analytical methods. The compounds are related to the previously reported phenyl methoxyalaninyl derivative of d4T, which was shown to be a potent and selective inhibitor of HIV. In this study theamino acid nitrogen and ester moieties were separated by methylene spacers of between two and six carbon atoms. In vitro evaluation of these compounds indicated an almost complete lack of anti-HIV activity, the compounds being several orders of magnitude less potent than the corresponding α-amino acid derivatives. The reasons for the virtual lack of anti-HIV activity appear to involve poor enzyme-mediated hydrolysis.

We report the development of a new group of nonnucleoside reverse transcriptase inhibitors (NNRTIs). One of the most active congeners of this series of 1,1,3-trioxo-2 H ,4 H -thieno[3,4- e ][1,2,4]thiadiazine (TTD) derivatives, i.e., 2-(3-fluorobenzyl)-4-cyanomethylen-1,1,3-trioxo-2 H ,4 H -thieno[3,4- e ][1,2,4]thiadiazine) (QM96639) was found to inhibit human immunodeficiency virus (HIV) type 1 [HIV-1 (III B )] replication in MT-4 cells at a concentration of 0.09 μM. This compound was toxic for the host cells only at a 1,400-fold higher concentration. The TTD derivatives proved effective against a variety of HIV-1 strains, including those that are resistant to 3′-azido-3′-deoxythymidine (AZT), but not against HIV-2 (ROD) or simian immunodeficiency virus (SIV/MAC251). HIV-1 strains containing the L100I, K103N, V106A, E138K, Y181C, or Y188H mutations in their reverse transcriptase (RT) displayed reduced sensitivity to the compounds. Their cross-resistance patterns correlated with that of nevirapine. 2-Benzyl-4-cyanomethylen-1,1,3-trioxo-2 H ,4 H -thieno[3,4- e ][1,2,4]thiadiazine (QM96521) enhanced the anti-HIV-1 activity of AZT and didanosine in a subsynergistic manner. HIV-1-resistant virus containing the V179D mutation in the RT was selected after approximately six passages of HIV-1 (III B ) in CEM cells in the presence of different concentrations of QM96521. From structure-activity relationship analysis of a wide variety of TTD derivatives, a number of restrictions appeared as to the chemical modifications that were compatible with anti-HIV activity. Modelling studies suggest that in contrast to most other NNRTIs, but akin to nevirapine, QM96521 does not act as a hydrogen bond donor in the RT-drug complex.

Ganciclovir (GCV) and its lipophilic elaidic acid ester prodrug E-GCV were evaluated for their antiherpetic, cytostatic and metabolic properties, E-GCV proved exquisitely inhibitory to the replication of herpes simplex virus type 1 (HSV-1) and HSV-2 in cell cultures (50% effective concentration (EC50): 0.002 microM). It was five- to 10-fold more effective than its parent drug GCV. E-GCV was at least 2000-fold more cytostatic to HSV-1 or HSV-2 thymidine kinase (tk) gene-transfected mammary carcinoma FM3A tk-/HSVtk+ tumor cells than to the corresponding nontransfected tumor cells. The cytostatic activity of E-GCV to the HSVtk gene-transfected tumor cells was far superior to that of GCV. Metabolic studies revealed that both GCV and E-GCV were converted to the mono-, di- and tri-phosphate derivatives of GCV to a markedly higher extent in FM3Atk-/HSV-1 tk+ cells than in wild-type FM3A/0 cells. Strikingly, mono-, di- and tri-phosphate metabolites of GCV were retained for a substantially longer time in E-GCV-treated cells (half-life approximately 50 h) than in GCV-treated cells (half-life approximately 20 h). The longer retention time of the GCV metabolites most likely explains why E-GCV is superior to GCV against herpes simplex virus replication and HSVtk gene-transfected tumor cell proliferation. Taking into account the marked stability of E-GCV in human plasma and its much higher lipophilicity than GCV, E-GCV should be considered as an effective lipophilic prodrug of GCV with a markedly enhanced cytostatic activity in HSVtk gene-transfected tumor cells compared with parental ganciclovir. Its usefulness in the combined gene/chemotherapy of HSVtk gene-transfected tumors should be further pursued.

We report the synthesis of some mercaptotriazole derivatives in an effort to discover underlying structural requirements for antiviral activity. A preliminary antiviral study was performed and the contribution of the compounds to free radical processes was investigated. Because lipophilicity influences both biological activity and antioxidant potential we calculated lipophilicity and attempted to correlate this with antioxidant activity. Treatment of the N-(aryl)piperazineacetohydrazides (compounds 1) with 2, 4-dichloro-phenylisothiocyanate gave the N-(aryl)piperazinethiosemicarbazides (compounds 2) in good yield. Cyclization of these compounds after treatment with NaOH solution provided the corresponding 5-(4-aryl-1-piperazinylmethyl)-4-(2, 4-dichlorophenyl)-4H-1, 2, 4-triazole-3-thiols (compounds 3) in good yield. Reaction of compounds 3 with 2, 4-dichloro-or 4-fluorobenzyl chloride in acetone in the presence of potassium carbonate gave the target compounds (compounds 4) in about 70% yield. The antioxidant effect of the compounds on non-enzymatic lipid peroxidation of rat hepatic microsomal membranes was studied. Most of the examined compounds were active at concentration of 0.1 mM and most were found to prevent dimethylsulphoxide oxidation moderately (20–50%) at a concentration tenfold less than that of dimethylsulphoxide. The interaction of the synthesized compounds with 1, 1-diphenyl-2-picrylhydrazyl stable free radical was also studied. Correlation was found between the two expressions of calculated lipophilicity, antioxidant activity and the lipophilicity of the synthesized compounds, and a correlation was derived between antioxidant activity and logP, which expresses the compounds’ hydrogenbonding capacity.

Purpose. To investigate the role of carrier mechanisms in: [1] the polarized transport of the bis(pivaloyloxymethyl)- [bis(POM)-] ester prodrug of the antiviral agent 9-(2-phosphonylmethoxyethyl)adenine [PMEA] and [2] the directional secretion of its metabolites.

Various carbocyclic analogues of adenosine, including aristeromycin (carbocyclic adenosine), carbocyclic 3-deazaadenosine, neplanocin A, 3-deazaneplanocin A, the 5'-nor derivatives of aristeromycin, carbocylic 3-deazaadenosine, neplanocin A and 3-deazaneplanocin A, and the 2-halo (i.e., 2-fluoro) and 6'-R-alkyl (i.e., 6'-R-methyl) derivatives of neplanocin A have been recognized as potent inhibitors of S-adenosylhomocysteine (AdoHcy) hydrolase. This enzyme plays a key role in methylation reactions depending on S-adenosylmethionine (AdoMet) as methyl donor. AdoHcy hydrolase inhibitors have been shown to exert broad-spectrum antiviral activity against pox-, paramyxo-, rhabdo-, filo-, bunya-, arena-, and reoviruses. They also interfere with the replication of human immunodeficiency virus through inhibition of the Tat transactivation process.

Purpose. To evaluate the potential of several bis-ester prodrugs of the antiviral agent 9-(2-phosphonylmethoxyethyl)adenine (PMEA, adefovir) to enhance the oral absorption of PMEA.

African buffaloes (Syncerus caffer) are reservoir hosts of Southern African Territories (SAT) foot-and-mouth disease (FMD) virus strains. In South Africa, infected buffaloes are found in the FMD-infected zone comprising the Kruger National Park (KNP) and its adjoining reserves. When these buffaloes stray into livestock areas, they pose a risk of FMD transmission to livestock. We assessed 645 records of stray buffalo events (3124 animals) from the FMD infected zone during 1998-2008 for (i) their temporal distribution, (ii) group size, (iii) age and gender composition, (iv) distance from the infected zone fence and (v) outcome reported for each event. A maximum entropy model was developed to evaluate spatial predictors of stray buffalo events and assess current disease control zones. Out of all buffaloes recorded straying, 38.5% escaped from the FMD infected zone during 2000/2001, following floods that caused extensive damage to wildlife fences. Escape patterns were not apparently influenced by season. The median size of stray groups was a single animal (IQR [1-2]). Adult animals predominated, comprising 90.4% (620/686) of the animals for which age was recorded. Of the 315 events with accurate spatial information, 204 (64.8%) were recorded within 1 km from the FMD infected zone. During late winter/spring (June-October), stray buffaloes were found significantly closer to the FMD infected zone (median = 0.3 km, IQR [0.1-0.6]). Less than 13% (40/315) of stray groups reached the FMD protection zone without vaccination, posing a higher risk of spreading FMD to these more susceptible livestock. Model outputs suggest that distance from the FMD infected zone, urban areas and permanent water sources contributed almost 85% to the spatial probability of stray buffalo events. Areas with a high probability for stray buffalo events were well covered by current disease control zones, although FMD risk mitigation could be improved by expanding the vaccination zone in certain areas.

Replication of zidovudine-resistant human immunodeficiency virus type 1 (HIV-1) strains (containing the 41 Met-->Leu and 215 Thr-->Tyr mutations in reverse transcriptase [RT]) was inhibited to a significantly greater extent by the combination of lamivudine and quinoxaline HBY 097 than by either drug alone or even fully suppressed by concomitant HBY 097 and lamivudine administration at relatively low concentrations. The virus recovered after exposure to the drug combinations individually had acquired the 103 Lys-->Arg, 138 Glu-->Lys, 184 Met-->Ile, and 189 Val-->Ile mutations in the genetic zidovudine-resistance background of zidovudine-resistant HIV-1. These mutants retained marked sensitivity to HBY 097. The genotypic zidovudine-resistance mutations were maintained in the mutant virus RT genomes, and the viruses also remained phenotypically resistant to zidovudine. Given the exquisite potency of the combination of lamivudine and HBY 097 in suppressing viral replication, this combination should be further pursued in clinical trials examining treatment of HIV-1-infected persons.

The inhibitory effects of polyanionic substances on the replication of herpes simplex virus (HSV) and other viruses were reported almost four decades ago. However, these observations did not generate much interest, because the antiviral action of the compounds was considered to be largely nonspecific. Shortly after the identification of human immunodeficiency virus (HIV) as the causative agent of the acquired immune deficiency syndrome (AIDS) in 1984, heparin and other sulfated polysaccharides were found to be potent and selective inhibitors of HIV 1 replication in cell culture. Since 1988, the activity spectrum of the sulfated polysaccharides has been shown to extend to various enveloped viruses, including viruses that emerge as opportunistic pathogens (e.g., herpes simplex virus [HSV] and cytomegalovirus [CMV]) in immunosuppressed (e.g., AIDS) patients. As potential anti-HIV drug candidates, sulfated polysaccharides offer a number of promising features. They are able to block HIV replication in cell culture at concentrations as low as 0.1 to 0.01 mu g ml(-1) without toxicity to the host cells at concentrations up to 2.5 mg ml(-1). We noted that some polysulfates show a differential inhibitory activity against different HIV strains, suggesting that marked differences exist in the tar get molecules with which polysulfates interact, They not only inhibit the cytopathic effect of HIV, but also prevent HIV induced syncytium (giant cell) formation. Furthermore, experiments carried out with dextran sulfate samples of increasing molecular weight and with sulfated cyclodextrins of different degrees of sulfation have shown that antiviral activity increases with increasing molecular weight and degree of sulfation. A sugar backbone is not strictly needed for the anti-HIV activity of polysulfates because sulfated polymers composed of a carbon-carbon backbone have also proved to be highly efficient anti-HIV agents in vitro. Other, yet to be defined, structural features may also play an important role. Sulfated polysaccharides may act synergistically with other anti-HIV drugs (e.g., azidothymidine [AZT]). They are known to lead very slowly to virus drug resistance development and they show activity against HIV mutants that have become resistant to reverse transcriptase inhibitors, such as AZT, tetrahydro-imidazo [4,5,1-jk] [1,4] benzodiazepin 2 (1H) thione (TIBO) and others. From studies on their mechanism of action we concluded that polysulfates exert their anti-HIV activity by shielding off the positively charged sites in the V3 loop of the viral envelope glycoprotein (gp120). The V3 loop is necessary for virus attachment to cell surface heparan sulfate, a primary binding site, before more specific binding occurs to the CD4 receptor of CD4(+) cells. This general mechanism also explains the broad antiviral activity of polysulfates against enveloped viruses. Variations in the viral envelope glycoprotein region may result in differences in the susceptibility of different enveloped viruses to compounds that interact with their envelope glycoproteins. The efficacy of polysulfates in the therapy and/or prophylaxis of retroviral infections and opportunistic infections remains to be demonstrated both in animal models and humans. It is important to consider not only treatment of patients who are already infected with HIV, but also prophylaxis and protection from HIV and/or other virus infections. Because (i) sexual transmission is responsible for the large majority of HIV infections worldwide; (ii) this transmission is mostly mediated via mononuclear cells that infect epithelial cells of the genital tract; and because (iii) polysulfates effectively inhibit cell-cell adhesion, polysulfates may be considered as potentially effective in a vaginal formulation to protect against HIV infection. (C) 1997 Elsevier Science Inc.

The structural features, including the absolute configuration, of the enantiomers of 1-(2′,6′-difluorophenyl)-1 H,3 H-thiazolo[3,4- a]benzimidazole (TBZ; NSC 625487), the lead compound of a new class of human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTIs), are described. Diffractometric analysis revealed that TBZ, like other NNRTIs, assumes a butterfly-like conformation in which the phenyl ring at C1 is in an orthogonal orientation relative to the thiazolobenzimidazole system, and the 2′,6′-fluorine atoms form two intramolecular hydrogen bonds with H1 and one of the methylene protons at C3, respectively. The stereochemistry in solution, as confirmed by lanthanide shift reagent-assisted ‘H NMR, paralleled the situation present in the solid state. The in vitro anti-HIV activity of the two enantiomers was also evaluated and the results obtained showed that the R-(+) is more active than the S-(−) isomer in inhibiting HIV-1 replication. Resistance and cross-resistance to other NNRTIs as well as inhibitory effects on HIV-1 reverse transcriptase activity are also reported.

Summary A number of arylazophenols 1 were converted into the corresponding mono Mannich bases 2 from which two quaternary salts 3a,b and an ester 3c were prepared. A series of bis Mannich bases 4 were also synthesized. The angles (θ) made between one of the aryl rings and the adjacent azo linkage were determined by electronic absorption spectroscopy. X-ray crystallographic data were obtained for some of the Mannich bases. The compounds were evaluated against murine P388 D1 and L1210 cells and two human T-lymphocyte (Molt 4, CEM) lines, and most of the derivatives were also screened against a panel of human tumour cell lines. A number of correlations were noted between cytotoxicity and various physicochemical constants as well as some structural features determined by X-ray crystallography. Several of the Mannich bases were shown to have mutagenic properties using the A RK mutatest; the compounds in series 2 and 4 have the ability to penetrate the central nervous system, as revealed by their anticonvulsant properties. While series 2–4 have the potential to deaminate forming ortho quinone methides which would be capable of alkylating cellular thiols, the results of stability studies suggest that the bioactivities noted were due to the molecules per se.

A new class of aminoadamantane heterocycles has been synthesized and examined for anti-HIV activity. Three compounds proved to be active against the replication of HIV-1 in MT-4 cells with an EC50 ranging from 3.6 to 75.2 mu M. No activity was noted with any of the compounds against HIV-2. (C) 1997 Elsevier Science Ltd. ispartof: Bioorg Med Chem Lett vol:7 issue:14 pages:1887-1890 status: published

The thiocarboxanilides represent a structural class of potent and selective human immunodeficiency virus type 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors. Combinations of the clinical candidate thiocarboxanilides UC-10 (oxime ether derivative) and UC-781 (pentenyloxy ether derivative) with a variety of nucleoside RT inhibitors (NRTIs) and non-nucleoside RT inhibitors (NNRTIs), two HIV protease inhibitors and one fusion/uncoating inhibitor were evaluated for their inhibitory effects on HIV-1 RT activity and HIV-1 replication in CEM cell cultures. The inhibitory activity of the NNRTIs including UC-10, UC-781, nevirapine, BHAR α-APA, 8-chloro-TIBO, MKC-442 and the quinoxaline HBY 097 against HIV-1 RT was highly dependent on the nature of the template/primer used in the HIV-1 RT reaction. However, fractionary inhibitory concentration (FIC) indexes for all drug concentrations evaluated in the combination experiments of UC-781 and the other NNRTIs fell within the range 0.5–1.5. This points to a predominantly additive effect of the thiocarboxanilides and other NNRTIs in the inhibition of HIV-1 RT. Similar FIC indexes were observed for the combination of UC-781 with the NRTI triphosphates AZT-TP, d4T-TP, ddCTP, ddATP and 3TC-TP and the NRTI diphosphate PMEApp against HIV-1 RT. All these drug combinations showed similar additive inhibitory effects on HIV-1 replication in cell culture. Also, the combinations of UC-10 or UC-781 with the protease inhibitors Ro31–8959/008 and ABT 84538.0 and the fusion/uncoating inhibitor bicyclam JM 3100 showed an additive effect (FIC within the 0.5–1.5 range). Thus, irrespective of the nature of the drugs, their combination with the thiocarboxanilides proved merely additive. In no case were antagonistic anti-HIV activity or increased cytotoxicity observed. In conclusion, thiocarboxanilides combined with a variety of clinically used anti-HIV agents result in additive anti-HIV activity.

The synthesis of lipophilic pro-nucleotides of ddAMP 2 based on cycloSal-ddAMP 3a-c is described. Phosphotriesters 3 released ddAMP 2 selectively by a controlled, chemically induced tandem reaction. CycloSal-phosphotriesters 3 exhibited antiviral activity against HIV-1/HIV-2 in CEM cells that where by a factor up to hundred higher as compared to ddA 1.

In this paper, a new method is presented to directly determine from the shape of a Ramsey pattern the real microwave level present in the cavity of a beam frequency standard. Then a new method to evaluate the atomic time of flight distribution using a regularization approach is presented. In opposition to existing methods, this approach uses only one Ramsey measurement because it allows the incorporation of the a priori information about the time of flight distribution. The validity of this method is confirmed by experimental results.

The (thio)carboxanilide derivatives are potent and selective inhibitors of HIV-1 reverse transcriptase (RT) and have a favourable antiviral activity spectrum. To understand better their mode of action, and to provide a structural basis for further improvement, models of RT complexed with four (thio)carboxanilide inhibitors (UC781, UC10, UC38 and UC84) have been constructed based on the X-ray structure of RT complexed with 9-chloro-TIBO. In the models, the protein conformation is similar to that of the RT-TIBO complex and the complexes are stabilised by hydrogen bonding between the inhibitors and the main chain oxygen of Lys101. Significant hydrophobic interactions include those with Leu100, Val106, Val179, Tyr188, Phe227, Leu234, and His235. The thiocarboxanilides UC781 and UC10 also make important hydrophobic interactions with Trp229. The models are consistent with the inhibitors' relative antiviral potencies and the observed resistance data. They further predict that mutations to Phe227, Trp229, or Leu234 might confer resistance. Since these are not observed, some constraining structural or functional role for these residues in the active enzyme is suggested.

Modified 1,2,6-thiadiazine dioxide acyclonucleosides were synthesized using the silylation method. All the compounds were tested as antiviral agents in a wide variety of assay systems. With two compounds, some activity (20, 35 and 14 μg/mL, respectively) was noted against herpes simplex virus, human cytomegalovirus and varicella-zoster virus.

From a side-by-side comparative study, the acyclic nucleoside phosphonates (R)-9-(2-phosphonylmethoxypropyl)adenine [(R)-PMPA] and 9-(2-methylidene-3-phosphonomethoxypropyl)guanine (MDL 74,968) proved more selective in their inhibitory effect on human immunodeficiency virus types 1 and 2, feline immunodeficiency virus, and Moloney murine sarcoma virus (MSV) in cell cultures than the 9-(2-phosphonylmethoxyethyl) derivatives of adenine (PMEA) and guanine (PMEG). In particular, PMEG proved quite toxic. PMEA, (R)-PMPA, and MDL 74,968 afforded a marked delay in MSV-induced tumor initiation in MSV-infected newborn NMRI mice and substantially delayed associated animal death at doses as low as 4 to 10 mg/kg of body weight. Treatment of the NMRI mice with PMEA, (R)-PMPA, and MDL 74,968 at 25 or 50 mg/kg resulted in a high percentage of long-term survivors.

Polyomavirus infections in humans are due to BK virus (BKV) and JC virus (JCV). Diseases associated with human polyomaviruses occur mostly in immunocompromised adults, e.g., progressive multifocal leukoencephalopathy (PML), caused by JCV, in AIDS patients and hemorrhagic cystitis and uretral stenosis, caused by BKV, in transplant recipients. No therapy is available for these diseases, which necessitates the development of chemical entities that are active against polyomaviruses. Several antiviral compounds were evaluated to determine their effects on the in vitro replication of mouse polyomavirus and the primate viruses simian virus 40 (SV40), SV40 PML-1, and SV40 PML-2. The activity of the different compounds was assessed by a cytopathic effect reduction assay and confirmed in a virus yield assay. Cidofovir [HPMPC; (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine] and its cyclic counterpart emerged as the most selective antipolyomavirus agents. The 50% inhibitory concentrations for HPMPC were in the range of 4 to 7 micrograms/ml, and its selectivity index varied from 11 to 20 for mouse polyomavirus and from 23 to 33 for SV40 strains in confluent cell monolayers. Cell cytotoxicity was up to 15-fold greater in growing cells. Other acyclic nucleoside phosphonates (i.e., HPMPA; [(S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine] and PMEG [9-(2-phosphonylmethoxyethyl)-guanine]) also showed some activity but had low selectivity. None of the other drugs tested against these animal viruses (i.e., acyclovir, ganciclovir, brivudine, ribavirin, foscarnet, and cytarabine) showed significant activity. Thus, HPMPC deserves further evaluation as a candidate drug for polyomavirus infections in the immunocompromised host.

We have developed a new sensitive enzyme immunoassay (EIA) and MTT (tetrazolium salt) assay for screening compounds against two variants of human herpesvirus 6 (HHV-6A, HHV-6B) and human herpesvirus 7 (HHV-7) and evaluated the anti-HHV-6 and HHV-7 activity of a series of anti-herpesvirus compounds and acyclic nucleoside phosphonate analogues. The results indicate that the pattern of activity of these compounds against these betaherpesviruses is similar to that for human cytomegalovirus (HCMV). The highest potency and selectivity against the two variants of HHV-6 and HHV-7 was demonstrated by S2242 (N7-isomer of 6-deoxy-ganciclovir). Also, ganciclovir (GCV), foscarnet, (phosphonoformic acid; PFA) and the acyclic nucleoside phosphonate analogues such as cidofovir (HPMPC) exhibited selective inhibitory activity against these viruses. Thymidine kinase (TK)-dependent drugs (acyclovir, ACV; brivudin, BVDU; and sorivudine, BVaraU) showed little, if any, activity. These results suggest a structural homology of the DNA polymerase and a lack of TK gene among these three betaherpesviruses (HHV-6, HHV-7 and HCMV). The finding that HHV-7 was highly sensitive to GCV also suggests that HHV-7 may have an HCMV-UL97-homologue gene for the phosphorylation of GCV. The present EIA method is more rapid and sensitive than the previously reported procedures and could be useful for the large-scale screening of compounds against HHV-6 and HHV-7.

The synthesis of a new pro-nucleotide approach for d4TMP 2 based on cycloSal-d4TMP 3a-d is described. Phosphotriesters 3 release d4TMP 2 selectively by a controlled, chemically induced tandem reaction. CycloSal-phosphotriesters 3 exhibited high biological activity against HIV-1/HIV-2 in CEM cells which was retained in CEM TK− cells.

N-β-D-Ribosides of agroclavine (1), elymoclavine (2), lysergene (4), lysergol (3), and 9,10-dihydrolysergol (5) were prepared by SnCl2 catalyzed ribosylation of their TMS derivatives with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose. None of the new compounds exhibited activity against HIV or other viruses tested. ispartof: Nucleos Nucleot vol:16 pages:97-106 status: published

Six new carbocyclic nucleosides were prepared by constructing a guanine (compounds 6, 8 and 10) or 8-azaguanine (compounds 7, 9 and 11) base on the amino group of (1R, cis)-3-(aminomethyl)-1,2,2-trimethylcyclopentylmethanol (2), and their activities against 13 viruses and 3 tumor cell lines were determined. Compounds 9, 10 and 11 showed activity against human immunodeficiency virus type 1 (HIV-1), and compound 11 also against vaccina virus, whereas compounds 6 and 7 showed some inhibition of tumor cell proliferation.

Bicyclic furanopyrimidines were recently discovered by us to be potent and selective inhibitors of VZV. Related studies to investigate the role of the sugar in this activity uncovered dideoxy furanopyrimidines as inhibitors of HCMV and this led to the preparation of highly modified long alkyl chain furanopyrimidines from the N- and O-alkylation of their parent bases. Herein we describe their synthesis and subsequent biological evaluation against HCMV. O-alkylated derivatives were almost invariably found to be at least equiactive with their N-alkylated counterparts. At this point, little change in activity has been found with large variation in N- and O-substituent.

The cattle tick Rhipicephalus (Boophilus) microplus is known for its invasive character and fast displacement of other species of the same subgenus. The most striking invasions were the ones observed in Ivory Coast (Madder et al. 2007, 2011) and Benin (Madder et al. 2012; De Clercq et al. 2012). Several years after being introduced through importation of exotic Brazilian cattle, R. microplus replaced local blue ticks and most importantly did not respond to the acaricide treatment becoming thus for farmers and veterinary services an uncontrollable ectoparasite affecting animal production in general, apart from being an efficient vector of Babesia bovis. Soon after its discovery in West Africa, several projects were initiated to address the issue. The TickRisk project (assessing ecological suitability for the spread of R. microplus in West Africa) (2011–2013) was implemented in Benin to determine the current spread of this species and develop habitat suitability maps of the region while the WECATiC project (assessment of emerging livestock ticks and tickborne disease threats and integrated control strategies in West and Central Africa) (2011–2014) encompasses Benin, Burkina

A high-speed HPLC gradient method for the determination of the antiviral ester prodrug bis(POM)-PMEA and its degradation products mono(POM)-PMEA and PMEA, is described. Perfusion chromatography enabled us to increase the flow rate up to 4 mL/min, resulting in high sample turn-over. Using a gradient system, the three compounds were separated from each other and the sample matrix within six minutes, while column equilibration was obtained in less than 3 minutes. Tetrabutylammonium was used as a counterion for PMEA. Notwithstanding the high flow rate, excellent reproducibility was obtained: the intraday as well as the interday precision, expressed as the relative standard deviation, for concentrations ranging from 5 to 50 μ PMEA and bis(POM)-PMEA, was lower than 5%. The applicability of the method is demonstrated by studying the temperature- and pH-dependent degradation of bis(POM)-PMEA.

The new palladium(II) halide complexes with diethyl and dibutyl esters of (α-anilino-N-benzyl)phosphonic acid and diethyl and dibutyl esters of [α-(4-benzeneazoanilino)-N-benzyl]phosphonic acid have been prepared and studied. All organophosphorus ligands form dihalide complexes, trans -Pd(L) 2 X 2 (X = Cl or Br), with monodentate N-bonded ligand through the anilinobenzyl nitrogen in (α-anilino-N-benzyl)phosphonate complexes and through the azo nitrogen in [α-(4-benzeneazoanilino)-N-benzyl]phosphonate complexes, respectively, without participation of the phosphoryl group. Azobenzene containing ligands by Ortho -metallation also form binuclear organo-palladium complexes, [Pd(LH)Cl] 2 , with the metal-metal chloro bridge. The complexes have been identified and characterized by elemental analysis, infrared and 1 H NMR, as well as by magnetic and conductometric measurements. All were tested in vitro for their cytostatic activity against KB and L1210 tumor cell lines. The results show that these complexes inhibit the multiplication of these tumor cells, but only the dichloro adduct of diethyl [α-(4-benzeneazo-anilino)-N-benzyl]phosphonate was found to have activity comparable to that of the antitumor drug cisplatin.

Novel phosphoramidate derivatives of the anti-HIV nucleoside analogue d4T were designed to act as labile membrane-soluble prodrugs of the bio-active free nucleotide d4TMP. We herein reveal the very marked dependence of the antiviral activity of these phosphoramidates upon the stereochemistry of the amino acid attached to the phosphate centre; with a strong preference for the L-stereochemistry. These phosphate triesters were shown to liberate amino acid derivatives of the nucleotide intracellularly. These novel analogues, typified by alaninyl d4T monophosphate, may act as intracellular sources of the free nucleotides. The alaninyl d4T adducts themselves exert an antiviral effect when administered extracellularly, but again with clear distinctions between the L- and D-series. This evidence indicates that extracellularly administered blocked triesters derived from L-amino acids can generate d4TMP intracellularly, by a new pathway which is highly dependent on the amino acid stereochemistry.

So324 is a 2',3'-dideoxy-2',3'-didehydrothymidine-5'-monophosphate (d4T-MP) prodrug containing at the phosphate moiety a phenyl group and the methylester of alanine linked to the phosphate through a phosphoramidate linkage. So324 has anti-HIV activity in human CEM, MT4, and monocyte/macrophage cells that is superior to that of d4T. In contrast to d4T, So324 is also able to inhibit HIV replication in thymidine kinase-deficient CEM cells. After uptake of So324 by intact human lymphocytes, d4T-MP is released and subsequently converted intracellularly to d4T-TP. In addition, accumulation of substantial amounts of a novel d4T derivative has been found. This d4T metabolite has been characterized as alaninyl d4T-MP. The latter metabolite accumulates at approximately 13- to 200-fold higher levels than d4T-TP depending the experimental conditions. Alaninyl d4T-MP should be considered as an intra- and/or extracellular depot form of d4T and/or d4T-MP. These findings may explain the superior anti-retroviral activity of So324 over d4T in cell culture.

Homo-N-nucleosides can be efficiently synthesized from 2-deoxyribose. When incorporated in an oligonucleotide, the compounds have a detrimental influence on duplex stability and on the catalytic activity of hammerhead ribozymes. However, homo-N-nucleosides with a guanine or adenine base moiety do exhibit selective antiviral activity against herpes simplex virus (HSV-1 and HSV-2).

A number of native and modified milk proteins from bovine or human sources were analyzed for their inhibitory effects on human immunodeficiency virus type 1 (HIV-1) and HIV-2 in vitro in an MT4 cell test system, The proteins investigated were lactoferrin, alpha-lactalbumin, beta-lactoglobulin A, and beta-lactoglobulin B.By acylation of the amino function of the lysine residues in the proteins, using anhydrides of succinic acid or cis-aconitic acid, protein derivatives were obtained that all showed a strong antiviral activity against human immunodeficiency virus type 1 and/or 2. The in vitro IC50 values of the aconitylated proteins were in the concentration range of 0.3 to 3 nM. Succinylation or aconitylation of alpha-lactalbumin and beta-lactoglobulin A/B also produced strong anti-HIV-2 activity with IC50 values on the order 500 to 3000 nM. All compounds showed virtually no cytotoxicity at the concentration used.Peptide-scanning studies indicated that the native lactoferrin as well as the charged modified proteins strongly bind to the V3 loop of the gp120 envelope protein, with K-d values in the same concentration range as the above-mentioned IC50. Therefore, shielding of this domain, resulting in inhibition of virus-cell fusion and entry of the virus into MT4 cells, may be the likely underlying mechanism of antiviral action.

A large variety of carboxanilide and thiocarboxanilide derivatives in which the original oxathiin or aliphatic moieties present in the prototype compounds UC84 and UC38 were replaced by an (un) substituted furanyl, thienyl, phenyl, or pyrrole entity have been evaluated for activity against wild-type human immunodeficiency virus type 1 strain IIIB [HIV-1 (IIIB)] and a series of mutant virus strains derived thereof. The mutant viruses contained either the Leu-100-->Ile, Lys-103-->Asn, Val-106-->Ala, Glu-138-->Lys, Tyr-181-->Cys, or Tyr-188-->Leu mutation in their reverse transcriptase. Several 3-(2-methylfuranyl)- and 3-(2-methylthienyl)-thiocarboxanilide ester, (thio)ether, and oxime ether derivatives showed exquisitely potent antiviral activity against wild-type HIV-1 (50% effective concentration, 0.009 to 0.021 microM). The pentenylethers of the 2-methylfuranyl and 2-methylthienyl derivatives (i.e., 313, N-[4-chloro-3-(3-methyl-2-butenyloxy)phenyl]- 2-methyl-3-furancarbothioamide or UC-781, and 314, N-[4-chloro-3-(3-methyl-2-butenyloxy)phenyl] -2-methyl-3-thiophenecarbothioamide or UC-82) proved virtually equally inhibitory for wild-type and the Ile-100, Ala-106, and Lys-138 mutant virus strains (50% effective concentration, 0.015 to 0.021 microM). Their inhibitory effect against the Asn-103 and Cys-181 reverse transcriptase mutant virus strains was decreased only four- to sevenfold compared with wildtype virus. UC-781 and UC-82 should be considered potential candidate drugs for the treatment of HIV-1-infected individuals.

1-(3′-Fluoro-2′,3′,6′-trideoxy-β-D-allofuranosyl)thymine [7] and 1-(3′-fluoro-2′,3′,6′-trideoxy-α-L-talofuranosyl) thymine [8] were synthesized starting from the corresponding 2,3′-anhydro nucleoside derivatives. The fluorine was introduced stereoselectively by opening of the anhydro bridge in the presence of HF/AIF3. The 5′-C-methyl derivatives, [7] and [8], of 3′-fluoro-3′-deoxythymidine (FLT) were evaluated for their inhibitory effect against human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2). The compounds [7] and [8] had antiviral activity which was three orders of magnitude lower than the reference compound 3′-fluoro-3′-deoxythymidine. None of the compounds showed appreciable activity against other RNA or DNA viruses at subtoxic concentrations.

We have employed the attenuated vaccine strain 17D of yellow fever virus (YFV) to evaluate the inhibitory effect of a selected series of compounds on YFV in Vero cells. Use of the vaccine strain does not require high-level microbiological containment facilities and should allow extensive screening. In addition, YFV may serve as a model for other flaviviruses including hepatitis C virus (HCV), and thus strategies for the treatment of YFV infections may apply to flavivirus infections in general. In the present study, several compounds belonging to different classes of nucleoside analogues and polyanions were evaluated for their inhibitory effect on the replication of YFV. Compounds that are targeted at: (i) IMP dehydrogenase (ribavirin, EICAR, tiazofurin, selenazofurin and mycophenolic acid), (ii) OMP decarboxylase (pyrazofurin and 6-azauridine), (iii) CTP synthetase (carbodine and cyclopentenyl cytosine), (iv) dihydrofolate reductase (methotrexate) and the (v) sulfated polymers (dextran sulfate and PAVAS) proved inhibitory to the replication of YFV. Mycophenolic acid (EC50: 0.08 microgram/ml). EICAR (EC50: 0.8 microgram/ml) and methotrexate (EC50: 0.07 microgram/ml) were the most effective. The findings that EICAR and mycophenolic acid, despite their potent anti-YFV activity, had little or no effect on the replication of the bunyavirus Punta Toro or herpes simplex virus in Vero cells, indicates that their anti-YFV activity is rather specific and does not merely result from cytotoxicity. Inhibitors of S-adenosylhomocysteine hydrolase (SAH hydrolase) and thymidylate synthase were found to be devoid of anti-YFV activity.

ROESY and NOESY NMR spectroscopic analyses of the ribofuranosyl (1a), 2′-deoxyribofuranosyl (1b), and arabinofuranosyl (1c) derivatives of 6-formyluracil in (CD3)2SO and D2O solutions have established that each exclusive 7,05′-cyclic hemiacetal diastereomer of 1a,b and the major 7,O2′-cyclic hemiacetal diastereomer of 1c possess the 7R configuration. In addition, (7R)-1c has been shown to be thermodynamically more stable than (7S)-1c, contrary to our previous indication. A new, higher yielding synthetic route to 1a has been developed, 1b has been obtained for the first time in crystalline form, the route to 1c has been modified to better accommodate large scale preparations, and a new, fourth member of this class, 6-formylthymidine (1d), has been synthesized and its solution structures in (CD3)2SO, D2O, and CD3OD have been determined. Antitumor and antiviral evaluations of 1a-c have revealed no significant levels of activity.

s A simple route towards 4,4-dihydroxymethyl-cyclohexane nucleosides has been developed. The structure of 4,4-dihydroxymethyl-1-(thymin-1-y1)-cyclohexane was confirmed by X-ray analysis. The synthesized compounds were inactive against all viruses tested.

In attempts to detect inhibitors of infectious pancreatic necrosis virus (IPNV) replication, we have evaluated, by an IPNV plaque inhibition assay, a group of compounds that have broad spectrum antiviral activity for both single- and double-stranded RNA viruses. The inosine monophosphate dehydrogenase (IMP dehydrogenase) inhibitors 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (ribavirin) and 5-ethynyl-1-beta-D-ribofuranosylimidazole-4-carboxamide (EICAR), and the orotidine monophosphate decarboxylase (OMP decarboxylase) inhibitor 4-hydroxy-3-beta-D-ribofuranosylpyrazole-5-carboxamide (pyrazofurin), were found to inhibit IPNV replication. For EICAR and pyrazofurin the concentrations that inhibited the IPNV plaque formation by 50% (EC50) were 0.01 micrograms/ml and 0.5 micrograms/ml, respectively. The cytotoxic concentrations required to reduce cell viability by 50% (CC50) were 50 micrograms/ml and 100 micrograms/ml, respectively, and the concentrations that reduced [methyl-3H] thymidine incorporation by 50% (IC50) were 0.5-1 and 50 micrograms/ml. Thus, for both compounds the IPNV-inhibitory concentration was 50-100 times lower than the concentration that affected DNA synthesis in growing cells. EICAR and pyrazofurin seem to be good candidates for further evaluation in an in vivo model of IPNV infection.

Novel phosphoramidate derivatives of the anti-HIV nucleoside analogues AZT and d4T have been prepared by phosphorochloridate chemistry. These materials are designed to act as labile membrane-soluble prodrugs of the bio-active free nucleotides. All compounds were fully characterised by a range of methods and were subjected to evaluation in vitro of their anti-HIV efficacy. A notable feature of the current study was that any attempt to replace the amino acid moiety of the phosphoramidate with a simple amine lead to a marked, virtually total loss of activity. Such simple phenyl alkylamino phosphate derivatives of either d4T or AZT inhibit HIV replication at cytotoxic concentrations and have no detectable antiviral selectivity. This clearly highlights the vital role played by the amino acid in the antiviral efficacy of the blocked phosphoramidates.

The (S)- and (R)-enantiomers of 9-(2-phosphonylmethoxypropyl) derivatives of adenine (PMPA) and 2,6-diaminopurine (PMPDAP) were evaluated for their inhibitory effect on HIV replication in several human cell systems, including natural peripheral blood lymphocytes (PBL) and freshly isolated monocyte/macrophages (M/M). The (R)-enantiomers of PMPDAP and PMPA were approximately 10-to-100-fold more effective against HIV than their (S)-enantiomeric counterparts. The antiviral efficacy of (R)-PMPA was comparable to that of the prototype acyclic nucleoside phosphonate 9-(2-phosphonylmethoxyethyl)adenine (PMEA). The most potent and selective HIV inhibitor was (R)-PMPDAP. Its 50% effective concentration ranged from 0.01 microM for HIV-1/Ba-L in M/M to 1-2.8 microM for HIV-1/IIIB and HIV-1/HE in C8166, CEM, Molt/4, MT-4 and PBL cells. Both (R)-PMPA and (R)-PMPDAP were not toxic to the host cells at 300 microM.

A series of omega-undecanoic amides of lup-20(29)-en-28-oic acid derivatives were synthesized and evaluated for activity in CEM 4 and MT-4 cell cultures against human immunodeficiency virus type 1 (HIV-1) strain IIIB/LAI. The potent HIV inhibitors which emerged, compounds 5a, 16a, and 17b, were all derivatives of betulinic acid (3beta-hydroxylup-20(29)-en-28-oic acid). No activity was found against HIV-2 strain ROD. Compound 5a showed no inhibition of HIV-1 reverse transcriptase activity with poly(C).oligo(dG) as template/primer, nor did it inhibit HIV-1 protease. Additional mechanistic studies revealed that this class of compounds interfere with HIV-1 entry in the cells at a postbinding step.

Human cytomegalovirus (CMV) infection is often associated with myelosuppression and acute inflammatory reaction in immunocompromised patients. We have previously documented that CMV exposure of bone marrow (BM) stromal cells reduces the capacity of these cells to support hematopoiesis because of a decreased production of colony- stimulating factors. This study examines the potential role of CMV on constitutive and lipopolysaccharide (LPS)-stimulated production of cytokines involved in inflammatory reaction, interleukin-6 (IL-6) and leukemia inhibitory factor (LIF) by BM stromal cells. The release of IL- 6 was already detectable 2 hours post CMV-infection (2.5-fold increase in production) and the cumulative production of IL-6 after 5 days of infection was 23 +/- 1.2 ng/mL (ninefold increase in production). CMV was also able to induce a time-dependent production of LIF that was maximal 8 hours after CMV infection (2.5-fold increase in production). Concomitantly, there was no detectable release of granulocyte colony- stimulating factor (G-CSF) and granulocyte-macrophage CSF (GM-CSF) by CMV-infected stromal cells. The similar IL-6 and LIF production in the presence of polymyxin B ruled out the possibility that this increase could be caused by contamination of the viral stock by endotoxin. In addition, ultraviolet-inactivated virus behaved similarly to live virus and caused the release of IL-6 and LIF. However, heat-inactivated CMV was unable to induce IL-6 and LIF secretion by BM stromal cells. The production of IL-6 and LIF was also evaluated after stimulation by LPS. After 5 days of CMV exposure, the LPS-stimulated production of IL-6 and LIF was significantly lower than uninfected controls. This LPS-induced release of cytokine production was found to be dependent of viral replication. The experiments have shown that CMV is a potent inducer of IL-6 and LIF with differential effect on constitutive and LPS- stimulated cytokine production by stromal cells; we suggest that CMV induction of IL-6 and LIF during the first hours of infection could play a role in CMV-induced inflammatory reaction. Moreover, our results show that human CMV can disturb the balanced cytokine network involved in the regulation of hematopoiesis.

The design, synthesis, and antiviral activities of 6'-homoneplanocin A (HNPA, 3) and its congeners having nucleobases other than adenine, such as 3-deazaadenine (4), guanine (5), thymine (6), and cytosine (7), were described. Starting from the known cyclopentenone derivative 8, the optically active (mesyloxy)cyclopentene derivative 15 was prepared, which was condensed with nucleobases then deprotected to give target compounds 3-7. Of these compounds, HNPA showed an antiviral activity spectrum that was comparable to, and an antiviral specificity that was higher than, that of neplanocin A. HNPA proved particularly active against human cytomegalovirus, vaccinia virus, parainfluenza virus, vesicular stomatitis virus, and arenaviruses, which is compatible with an antiviral action targeted at S-adenosylhomocysteine hydrolase. HNPA appears to be a promising candidate drug for the treatment of these viruses.

The syntheses and the antiviral activities of 2-halo derivatives of neplanocin A (1b,c), (6'R)-6'-C-methylneplanocin A (2b), and dehydroxymethylneplanocin A (3b,c) are described. SN2 reaction of the known cyclopentenyl units 12 and 13 with 2-haloadenines under basic conditions gave the protected carbocyclic nucleosides 14b,c and 15b,c, respectively. Starting from the cyclopentenone derivative 5, the optically active tosyloxycyclopentene derivative 11 was prepared, which was similarly condensed with 2-fluoroadenine to give the protected (6'R)-6'-C-methyl derivative 16b. Deprotection of these compounds afforded the target 2-halo derivatives of neplanocin A. Of these new compounds, 2-fluoroneplanocin A (1b) showed an antiviral potency and a spectrum that was comparable to that of neplanocin A (1a). It was particularly active against vaccinia virus, vesicular stomatitis virus, parainfluenza virus, reovirus, arenaviruses (Junin, Tacaribe), and human cytomegalovirus, i.e., those viruses that fall within the purview of the S-adenosyl-L-homocysteine hydrolase inhibitors.

Summary The dioxypyrimidine ring of 5,6-substituted 1-[(2-hydroxyethoxy)methyl]uracils is an extended ‘partial π system’ with ring distortion. PM3-MM+ geometry optimization suggested a lipophilic ‘butterfly-like’ orientation which was also found in other non-nucleoside inhibitors that interact with the HIV-1 reverse transcriptase. Multivariate QSAR has shown that discrimination between the antiviral response and undesired cytotoxicity is possible. Related to the C-6 thiophenyl ring substituents and to modifications at the C-5 position, the antiviral response depends on hydrogen-bonding forces, steric parameters, and electronic properties. The cytotoxicity depends on the lipophilicity and steric parameters.