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A variety of imidazo[1,5-a]-1,3,5-triazine derivatives carrying C-, O-, and S-benzyl and/or 4-methylbenzyl groups were synthesized and examined for their inhibitory effects on the replication of ortho- and paramyxoviruses. The key compounds 8-R-2-thioxo-2,3-dihydroimidazo [1,5-a]-1,3,5-triazin-4(1H)-ones 3a,b,d were synthesized by chlorotrimethylsilane/HMDS-effected cyclization--rearrangement of the corresponding 6-amino-5-(formylamino)-5-R-2-mercaptopyrimidin-4(5H)-ones 2a,b,d (R = benzyl, 4-methylbenzyl and 5-(benzyloxy)pentyl). Compounds 3a,b were further transformed into 4-thiones 5a,b and 4-dimethylamino derivatives 7a,b. Preparation of S-methyl, S-benzyl, and S-(4-methylbenzyl) derivatives 12-19 was carried out by the treatment of thioxo compounds 3b,d, 5b, and 8b in an alcohol/potassium carbonate system with methyl iodide or the appropriate aralkyl bromide. Simultaneous presence of the benzyl and thio structural units was found to be indispensable for any selective biological activity. Some 2-thio substituted compounds were specifically inhibitory to some viruses, e.g., 8-(4-methylbenzyl)-2-[(4-methylbenzyl) thio]imidazo[1,5-a]-1,3,5-triazin-4-one (13) and 8-[5-(benzyloxy)pentyl]-2-[(4-methylbenzyl)thio]imidazo [1,5-a]-1,3,5-triazin-4-one (15) inhibited influenza A virus at a concentration of 4.1 and 5.3 microM, and 2-(benzylthio)-6, 8-dimethylimidazo[1,5-a]-1,3,5-triazin-4-one (16) and 6, 8-dimethyl-2-[(4-methylbenzyl)thio]imidazo[1,5-a]1,3, 5-triazin-4-one (17) inhibited respiratory syncytial virus at a concentration of 21.9 and 15.7 microM, respectively, that is, at concentrations that were 20-50-fold lower than the cytotoxic concentrations. Compound 13 was inhibitory to respiratory syncytial virus at a concentration of 1.4 microM, that is, at a concentration that was 180-fold lower than the cytotoxic concentration to MDCK or Vero cells but only 7-fold lower than the cytotoxic concentration to HeLa cells. The 4-thiones 5a,b were nonselectively inhibitory to ortho-and paramyxoviruses at concentrations that coincided with their cytotoxic concentrations.

A series of novel 1,2,4-triazole derivatives has been designed and synthesized. All of the new compounds were evaluated for their anti-HIV activities in MT-4 cells. Three of them showed moderate activities against wild-type HIV-1 with an EC50 ranging from 17.4 μM to 4.87 μM. Among the active compounds, 3-((4-(3,4-dimethoxybenzylideneamino)- 5-(furan-2-yl)-4H-1,2,4-triazol-3-ylthio)methyl)benzonitrile (4d) was identified as the promising compound (EC50 = 17.4 μM, SI =13). However, no compound displayed inhibitory activity against HIV-2. Keywords: HIV-1, AIDS, NNRTIs, Triazoles, Synthesis, Anti-HIV-1 activity, NNRTIs, LC Autosampler Device, heterocyclic scaffold, Nexus 470FT-IR

We have recently reported the discovery of an entirely new category of potent antivaricella-zoster virus agents based on novel deoxynucleoside analogues bearing unusual fluorescent bicyclic furo base moieties. Initial studies revealed an absolute requirement of a long alkyl side-chain, with an optimal length of C8-C10, for antiviral activity. However, the impact of this requirement on the physical properties of these compounds is high: inherent lipophilicity and extremely poor aqueous solubility, which may limit the use of these nucleosides as drugs. In order to address this issue, we have now prepared a new series of analogues, bearing ether and glycol type side-chains, designed to improve the aqueous solubility of the compounds. Synthesis of target nucleosides involved Pd-catalysed coupling of terminal alkynes with 5-iodo-2'-deoxyuridine. The 5-alkynyl nucleosides thus obtained were then treated with copper (I) iodide to produce the desired bicyclic analogues. As anticipated, the new compounds exhibited a dramatic increase in aqueous solubility, although antiviral activity was significantly reduced. A possible correlation between antiviral activity and overall compound lipophilicity is discussed.

Abstract The synthesis of β-L-thrco-, α-L-threo, β-D-erythro and α-D-erythro-apiofuranosylcytidine and their biochemical properties are reported.

9-R-[2-(Phosphonomethoxy)propyl]-adenine (tenofovir) is an acyclic nucleoside phosphonate with antiviral activity against human immunodeficiency virus type 1 (HIV-1) and hepatitis B virus (HBV). Tenofovir is not orally bioavailable but becomes orally active against HIV-1 infection as the disoproxil ester (tenofovir disoproxil fumarate [Viread]). We have developed an alternative strategy for promoting the oral availability of nucleoside phosphonate analogs which involves esterification with a lipid to form a lysolecithin mimic. This mimic can utilize natural lysolecithin uptake pathways in the gut, resulting in high oral availability. Since the mimic is not subject to cleavage in the plasma by nonspecific esterases, it remains intact in the circulation and facilitates uptake by target cells. Significant drops in apparent antiviral 50% effective concentrations (EC(50)s) of up to 3 logs have been observed in comparison with non-lipid-conjugated parent compounds in target cells. We have applied this technology to tenofovir with the goal of increasing oral availability, decreasing the apparent EC(50), and decreasing the potential for nephrotoxicity by reducing the exposure of the kidney to the free dianionic tenofovir. Here we report that, in vitro, the hexadecyloxypropyl ester of tenofovir, CMX157, is 267-fold more active than tenofovir against HIV-1 and 4.5-fold more active against HBV. CMX157 is orally available and has no apparent toxicity when given orally to rats for 7 days at doses of 10, 30, or 100 mg/kg/day. Consequently, CMX157 represents a second-generation tenofovir analog which may have an improved clinical profile.