Acyclic Nucleosides other than Acyclovir as Potential Antiviral Agents

Synthesis of New 7-Alkylated Theophyllines by Chemical Modification of Dyphylline

Chemical modification of the propyl side chain of 7-(2,3-dihydroxyprop-1-yl)theophylline led to a variety of hetero-cyclic compounds linked to the theophylline by a methylene group.

A facile synthesis and anti-avian influenza virus (H5N1) screening of some novel pyrazolopyrimidine nucleoside derivatives

Treatment of 5-amino-1-(9-methyl-5,6-dihydronaphtho[1',2':4,5]thieno[2,3-d]pyrimidin-11-yl)-1H-pyrazole-4-carbonitrile (1) with formic acid afforded pyrazolo[3,4-d]pyrimidin-4-one derivative 2. The sodium salt of the latter compound (generated in situ) was treated with some alkyl halides to afford the corresponding N-substituted compounds 3-7. The siloxy derivative 8 (generated also in situ from 2) was ribosylated and glycosylated to yield compounds 9 and 11, respectively. Deprotection of compounds 9 and 11 in methanolic ammonia produced the free nucleosides 10 and 12, respectively. Moreover, the prepared compounds were tested for antiviral activity against H5N1 virus [A/chicken/Egypt/1/2006] and some of them revealed moderate results compared with the other tested compounds.

Synthesis and in vitro antitumor activity of new substituted thiopyrimidine acyclic nucleosides and their thioglycoside analogs

Some new thiopyrimidine acyclic nucleosides and thioglycoside derivatives 3a-c, 4a-c, 6a,b, and 7a,b were synthesized. The cytotoxicity and antitumor evaluation of all prepared compounds have been tested in vitro against Ehrlich's ascites carcinoma cell line and their activity against glutathione peroxidase and catalase were reported. The role of the prepared compounds as free radical regulators and the therapeutic antitumor effect of a balanced generation of free radicals are discussed. Compounds 2, 3b, 3c, 4a, and 4c inhibited significantly in a dose dependent manner the growth of Ehrlich ascites carcinoma cells while the other compounds did not show any antitumor activity even at higher concentrations.

Microwave-assisted synthesis of acyclic C-nucleosides from 1,2- and 1,3-diketones

A simple, rapid and regioselective approach for the synthesis of C-acyclic nucleosides 3, 4, 6, and 9 of dihydropyrimidine, imidazole and indeno[1,2-b]pyridine-9-one derived from 1,2- and 1,3-diketones was performed. By using DMF or pyridine as solvent or bentonite clay as a support, in the presence of TMSTf, ZnCl(2), NH(4)OAc, or NH(4)NO(3), all the desired products were obtained within 5-25 minutes under microwave irradiation (MWI). Acid hydrolysis of 6 and 9 afforded the free acyclic C-nucleosides 7 and 10, respectively. Upon treatment with NaOMe under MWI, 3 and 14 rearranged to the C-nucleoside 4 and 16.

Microwave-assisted synthesis and anti-HIV activity of new acyclic C-nucleosides of 3-(D-ribo-tetritol-1-yl)-5-mercapto-1,2,4-triazoles. Part 1

Microwave-assisted synthesis of novel acyclic C-nucleosides of 6-alkyl/aryl-3-(1,2-O-isopropylidene-D-ribo-tetritol-1-yl)[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles (5-12) and the 6-aryl-thiomethyl analogues 25-27 has been described. Deblocking of 5-12 and 25-27 afforded the free acyclic C-nucleosides 13-20, and 28-30, respectively. All of the synthesized compounds showed no inhibition against HIV-1 and HIV-2 replication in MT-4 cells. However, 6-(3,4-dichlorophenyl)-3-(1,2-O-isopropylidene-D-ribo-tetritol-1-yl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole (6) is a potent inhibitor, in vitro, of the replication of HIV-2. These results suggest that compound 6 should be considered as a new lead in the development of antiviral agent.

Synthesis and activity against HBV of novel Tetra-seconucleoside analogues of dyphlline having the acyclic chains of ACV and HBG

Selective alkylation of dyphylline (1) with (2-acetoxyethoxy)methyl bromide (2a) or 4-acetoxybutyl bromide (2b) afforded 3'-O-[(acetoxyethoxy)methyl]dyphylline (3a) and 3'-O-(4-acetoxybutyl)-dyphylline (3b), respectively. A trans esterification process rather than alkylation of the dihydroxy-propyl side chain in 1 had taken place during the reaction with 2-p-toluoyloxy)ethyl chloride (5) to afford the respective 3'-toluoyloxy derivative 7 and not the anticipated 3'-O-[(p-toluoyloxy)ethyl]-dyphylline (6). Deacylation of 3a,b and 7 afforded 4a,b and 1, respectively. Viral screening of selected compounds against HBV has been investigated.

New acyclic quinoxaline nucleosides. Synthesis and anti-hiv activity

A series of acyclonucleosides substituted 1-(4,5-dihydroxypentyl) (13-8) and 2-(4,5-dihydroxypentyloxy)quinoxalines (19-24) were synthesized by the sharpless asymmetric dihydroxylation of the derivatives 1-6 and 7-12, respectively. Treatment of the quinoxaline base 26 with (R)-2,2-dimethyl-1,3-dioxolan-4-ylmethyl-p-toluenesulfonate (27) in the presence of NaH/DMF furnished 28. Acid hydrolysis of 28 gave 1-(2,3-dihydroxypropyl)-6,7-dimethyl-quinoxaline-2-one (29). Alternatively, 29 was prepared by sharpless dihydroxylation of 30. All the compounds were evaluated for their in vitro anti-HIV-1 and HIV-2 in MT-4 cell and found inactive, except 29, which showed inhibition of HIV-1 with EC50 value of 0.15 +/- 0.1 microg/ml and a therapeutic index (SI) of 73.

First synthesis of double headed 1,3,4-oxadiazino[6,5-b]indole acyclo C-nucleosides

Condensation of 1,3-dihydro-2,3-dioxo-2H-indoles (la-c) with galactaric acid bis hydrazide (2) gave the corresponding galactaric acid bis[2-(1,2-dihydro-2-oxo-3H-indol-3-ylidene)hydrazides] (3a-c). Acetylation of the latter compounds with acetic anhydride in the presence of pyridine at ambient temperature gave the 2,3,4,5-tetra-O-acetylgalactaric acid bis[2-(1,2-dihydro-2-oxo-1-substituted-3H-indol-3-ylidene)hydrazides] (4b-d). Heterocyclization of the tetra-O-acetates 4b-d by heating with thionyl chloride afforded the double headed acyclo C-nucleosides: 1,2,3,4-tetra-O-acetyl- 1,4-bis[9-substituted-1,3,4-oxadiazino[6,5-b]indol-2-yl-1-ium]-galacto-tetritol dichlorides (5b-d). Structures of the prepared compounds were elucidated from their spectral properties.

Synthesis and structural characterization of 1-(d-glycosyloxy)phthalazines

Coupling of the trimethylsilyl derivative of (2H)phthalazin-1-one with 1,2,3,4,6-penta-O-acetyl-alpha-D-glucopyranose and 1,2,3,4,6-penta-O-acetyl-alpha-D-galactopyranose in the presence of stannic chloride gave the respective glycosides, 2-(per-O-acetyl-D-glycosyloxy)phthalazines, which upon deacetylation gave the respective unprotected analogues. Under the same conditions 1,2,3,5-tetra-O-acetyl-beta-D-ribofuranose gave 1-(2,3,5-tri-O-acetyl-alpha-D-ribofuranosyloxy)phthalazine. Electrospray mass spectrometry aided the structural characterization of this series of 1-(D-glycosylyloxy)phthalazines. Low energy collisionally-induced dissociation tandem mass spectrometry of the protonated molecules confirmed the MS fragmentation routes and the structural identities of this novel series of glycosides.

Synthesis of double headed imidazoline acyclo C-nucleosides: 1,4-bis[1-amino-5-oxo-4-substituted(imidazolin-2-yl)]galacto-tetritols

Condensation of 2,3,4,5-tetra-O-acetyl-galactaroyl dichloride (1) with two equivalents of the alpha-amino esters 2a-c gave the corresponding 2,3,4,5-tetra-O-acetyl-galactaric acid diamides 3a-c. Heterocyclization of 3a-c by heating with hydrazine hydrate took place with concomitant de-O-acetylation of the polyacetoxyalkyl chain to give 1,4-bis[1-amino-5-oxo-4-substituted(imidazolin-2-yl)] galacto-tetritols (5a-c) and not the theoretically possible 1,2,4-triazinones 4 as indicated by spectral data. Compounds 5a-c readily reacted with p-nitrobenzaldehyde to give the corresponding p-nitrobenzylideneamino derivatives 6a-c. Acetylation of 5a-c afforded the 2,3,4,5-tetra-O-acetyl-1,4-bis[1-acetamido-5-oxo-4-substituted(imidazolin-2-yl)]galacto-tetritols (7a,b,d). De-O-acetylation of 7a,b,d gave 1,4-bis[1-acetamido-5-oxo-4-substituted (imidazolin-2-yl)]galacto-tetritols (8a-c).

Synthesis and biological evaluation of some acyclic alpha-(1H-pyrazolo-[3,4-d]pyrimidin-4-yl)thioalkylamide nucleosides

The chemical synthesis of some acyclic alpha-(1H-pyrazolo[3,4-d]pyrimidin-4-yl)thioalkylamide nucleosides (10-12)a-c is described. The treatment of IH-pyrazolo[3,4-d]pyrimidin-4-thione 1 with compounds 2a-c gave, regioselectively, ethyl alpha-(1H-pyrazolo[3,4-d]pyrimidin-4-yl)thioalkylates 3a-c, respectively. These heterocycles were alkylated, separately, with alkylating agents 4, 5 and 6 to give, regioselectively, the N1-acyclic nucleosides (7-9)a-c which were deprotected to afford the desired products (10-12)a-c. All synthetic compounds were characterized on the basis of their physical and spectroscopic properties. The products (10-12)a-c were evaluated for their inhibitory effects against the replication of HIV-1 (III(B)), HIV-2 (ROD), various DNA viruses, a variety of tumor-cell lines and M. tuberculosis. No marked biological activity was found.

Synthesis and biological activity of 4-substituted 1-[1-(2-hydroxyethoxy)-methyl-1,2,3-triazol-(4 & 5)-ylmethyl]-1H-pyrazolo[3,4-d]pyrimidines

The chemical synthesis of some 4-substituted 1-[1-(2-hydroxyethoxy)-methyl-1,2.3-triazol-(4 and 5)-ylmethyl]-1-H-pyrazolo[3,4-d]pyrimidines 12a,b, 13a,b and 14-23 as acyclic nucleosides is described. Treatment of (2-acetoxyethoxy)methylbromide with sodium azide afforded (2-acetoxyethoxy)methylazide 9. The heterocycles 6a,b were alkylated, separately, with propargyl bromide to obtain. regioselectively, 4-(methyl and benzyl)thio-1-(prop-2-ynyl)-1H-pyrazolo[3,4-d]pyrimidines 7a,b. These N-alkylated products were condensed with compound 9 via a 1,3-dipolar cycloaddition reaction to obtain, after separation and deprotection, 1,4- and 1,5-regioisomers 12a,b and 13a,b. The deprotected acyclic nucleosides 12a and 13a served as precursors for the preparation of 4-amino (14 and 15), 4-methylamino (16 and 17). 4-benzylamino (18 and 19), 4-methoxy (20 and 21) and 4-hydroxy (22 and 23) analogues. Compounds 7a,b and all deprotected acyclic nucleosides were evaluated for their inhibitory effects against the replication of HIV-(IIIB) and HIV-2(ROD) in MT-4 cells and for their anti-tumor activity. No marked activity was found. However, initial evaluation of 6a,b, 7a,b. 12a,b, 13a,b and 14-23 showed that compound 7b has marked activity against M. tuberculosis.

Synthesis and biological activities of new carbaacyclonucleosides and 1'-oxaacyclonucleosides related to clitocine

We describe the synthesis of two series of acyclonucleosides:carbaacyclonucleosides and 1'-oxaacyclonucleosides which possess the same aglycone as clitocine 3 which is a natural nucleoside exhibiting interesting biological properties. These compounds have been obtained by condensation of 4-aminobutanol or 3-silyloxypropoxyamine with 4,6-dichloro-5-nitropyrimidine. Structural modifications have been made on the heterocyclic base and the side chain to enhance their potential activity. All these compounds have been tested against different viruses: HIV-1, HSV-1, HSV-2, CMV, VZV, EBV. The carbaacyclonucleoside 10 was associated with an anti-EBV activity (EC50 = 0.86 microg/mL).

Potential antiviral agents. Part II. Synthesis and antiviral evaluation of pyrazinones substituted with acyclic chains

The synthesis of a series of 4'-substituted hydroxybutyl pyrazine analogues of the anti-herpes compound, acyclovir, is described. The compounds were characterized with 1H and 13C nmr, mass and IR spectroscopy. Antiviral (HSV-1, CMV, Cox B4, HIV-1) properties of these compounds were examined. None of these compounds were active against these viruses.

Synthesis and antiviral evaluation of pyrazinones substituted with acyclic chains

The synthesis of a series of pyrazine analogues of the anti-herpes compound, acyclovir is described. These syntheses were accomplished by various methods: in the presence of a Lewis acid or NaH for hydroxyethoxymethyl and hydroxybutyl groups or by sequential oxidation/reduction of 1-(beta-D-ribofuranosyl)-2-pyrazinones for 2',3'-acyclonucleosides. Antiviral (HSV-1, CMV, Cox B4, HIV-1) properties of these compounds were determined.

Thiazolo[4,5-d]pyrimidines. Part II. Synthesis and anti-human cytomegalovirus activity in vitro of certain acyclonucleosides and acyclonucleotides derived from the guanine analogue 5-aminothiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione

The synthesis and in vitro antiviral activity of certain hydroxyalkoxymethyl, hydroxyalkyl, hydroxyalkenyl and phosphonoalkenyl derivatives of the guanine congener 5-aminothiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione are reported. The compounds of this study were selected for their structural similarity to acyclonucleosides with known anti-herpesvirus activity. 5-Amino-3-[(Z)-4-hydroxy-2-buten-1-yl]thiazolo[4,5-d]pyrimidine-2, 7(3H,6H)- dione was the only member of the series to display significant in vitro activity against human cytomegalovirus (HCMV); however, this compound did not inhibit other herpesviruses, human immunodeficiency virus type 1 or murine cytomegalovirus. It was found to have a cytotoxicity profile similar to that of ganciclovir (DHPG). The antiviral effect was found to be sensitive to the initial viral input and the time of addition during the virus replication cycle. Significantly, the compound was found to have equal anti-HCMV activity, against standard virus strains, to DHPG, but also showed potent activity against DHPG-resistant virus strains, except for a strain mutated in the UL97 (phosphotransferase) gene.