Synthesis of 5-amino-1-(5-deoxy-beta-D-ribofuranosyl)imidazole-4-carboxamide and related 5'-deoxyimidazole ribonucleosides.

5-Amino-1-(beta-D-ribofuranosyl)imidazole-4-carboxamide (1, AICA ribonucleoside) was converted in two steps to 5-amino-1-(5-deoxy-5-iodo-2,3-O-isopropylidene-beta-D-ribofuranosyl)imidazole-4-carboxamide (3) which was hydrogenated in the presence of Pd/C to yield 5-amino-1-(5-deoxy-2,3-O-isopropylidene-beta-D-ribofuranosyl)imidazole-4-carboxamide (4). The dehydration of 4 yielded 5-amino-1-(5-deoxy-2,3-O-isopropylidene-beta-D-ribofuranosyl)imidazole-4-carbonitrile (7). The compounds 3, 4, and 7 were deblocked with formic acid to furnish 5-amino-1-(5-deoxy-5-iodo-beta-D-ribofuranosyl)imidazole-4-carboxamide (6). 5-amino-1-(5-deoxy-beta-D-ribofuranosyl)imidazole-4-carboxamide (5), and 5-amino-1-(5-deoxy-beta-D-ribofuranosyl)imidazole-4-carbonitrile (8), respectively. Compound 8 was acetylated and then deaminated to give 1-(2,3-di-O-acetyl-5-deoxy-beta-D-ribofuranosyl)imidazole-4-carbonitrile (11). The compounds 8 and 11 were converted into 5-amino-1-(5-deoxy-beta-D-ribofuranosyl)imidazole-4-thiocarboxamide (9) and 1-(5-deoxy-beta-D-ribofuranosyl)imidazole-4-thiocarboxamide (12), respectively. The synthesis of 1-(5-deoxy-beta-D-ribofuranosyl)imidazole-4-carboxamide (13) was achieved for the first time by the treatment of 11 with hydrogen peroxide in the presence of ammonium hydroxide. The compounds were tested for antibacterial, antifungal, and antiviral activity, with 5 and 6 significantly inhibitory to Staphylococcus aureus.     

Synthesis and biological activity of nucleosides and nucleotides related to the antitumor agent 2-beta-D-ribofuranosylthiazole-4-carboxamide

Phosphorylation of 2-beta-D-ribofuranosylthiazole-4-carboxamide (1) provided the 5'-phosphate 2, which was converted to the corresponding 5'-triphosphate 4 and the cyclic 3',5'-phosphate 5. Treatment of 2-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)thiazole-4-carbonitrile (6) with NH3-NH4Cl provided 2-beta-D-ribofuranosylthiazole-4-carboxamidine hydrochloride (7), and treatment with H2S-pyridine provided the corresponding 4-thiocarboxamide 9. Compound 9 was treated with ethyl bromopyruvate, followed by treatment with methanolic ammonia, to yield 2'-(2-beta-D-ribofuranosylthiazol-4-yl)thiazole-4'-carboxamide (11). 5'-Phosphate 2 was cytotoxic to L1210 cells in culture and significantly effective against the intraperitoneally implanted murine leukemias in mice. Amidine 7 was slightly toxic to L1210 in culture and inhibitory to purine nucleoside phosphorolysis. The cyclic 3',5'-phosphate 5 was less effective than the corresponding 5'-phosphate 2 or the parent nucleoside 1 as an antitumor agent.     

New imidazole-5-carbohydroxamic acids with biological activity

A series of 1-benzyl-2-arylthio (or heteroarylthio)-5-imidazolecarbohydroxamic acids (Va-e) was prepared starting from the corresponding imidazole-5-carboxylic acids IIIa-e via acid chlorides IVa-e. Tests of biological activity showed that compounds Va-e are fairly active against Escherichia coli and Candida albicans.     

Synthesis and biological activity of 6-azacadeguomycin and certain 3,4,6-trisubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides

Several 3,4,6-trisubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides were prepared and tested for their biological activity. High-temperature glycosylation of 3,6-dibromoallopurinol with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose in the presence of BF3 X OEt2, followed by ammonolysis, provided 6-amino-3-bromo-1-beta-D-ribofuranosylpyrazolo-[3,4-d]pyrimidin-4(5H)-on e. Similar glycosylation of either 3-bromo-4(5H)-oxopyrazolo [3,4-d]pyrimidin-6-yl methyl sulfoxide or 6-amino-3-bromopyrazolo [3,4-d]pyrimidin-4(5H)-one, and subsequent ammonolysis, also gave 7a. The structural assignment of 7a was on the basis of spectral studies, as well as its conversion to the reported guanosine analogue 1d. Application of this glycosylation procedure to 6-(methylthio)-4(5H)-oxopyrazolo[3,4-d]pyrimidine-3-carboxamide gave the corresponding N-1 glycosyl derivative. Dethiation and debenzoylation of 16a provided an alternate route to the recently reported 3-carbamoylallopurinol ribonucleoside thus confirming the structural assignment of 16a and the nucleosides derived therefrom. Oxidation of 16a and subsequent ammonolysis afforded 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-carboxamide. Alkaline treatment of 15a gave 6-azacadeguomycin. Acetylation of 15a, followed by dehydration with phosgene, provided the versatile intermediate 6-amino-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-4(5H)-oxopyrazolo [3, 4-d]pyrimidine-3-carbonitrile. Deacetylation of 19 gave 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-carbonitrile. Reaction of 19 with H2S gave 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-thiocarboxamide. All of these compounds were tested in vitro against certain viruses and tumor cells. Among these compounds, the guanosine analogues 7a and 20a showed significant activity against measles in vitro and were found to exhibit moderate antitumor activity in vitro against L1210 and P388 leukemia. 6-Azacadeguomycin and all other compounds were inactive against the viruses and tumor cells tested in vitro.     

Synthesis and biological activity of some 4-substituted pyrimidines and fused pyrimidines

The synthesis of 4-beta-cyanoethylthiopyrimidine 2 and 4-chloropyrimidine 8a was chieved from 4-mercapto-5-acetylpyrimidine (1a). Also the synthesis of thienopyrimidine-7,7-dioxide 6, 4-arylaminopyrimidines 9a-e, 4-alkoxypyrimidines 11a, b, pyrimidoquinazoline 10, thienopyrimidines 19a, b and tetrazolopyrimidine 18 was described.     

Synthesis and biological activity of certain derivatives of oxazinomycin and related oxadiazole nucleosides

Oxazinomycin was converted into 2',3',5'-tri-O-acetyloxazinomycin (2) and 2',3'-O-isopropylideneoxazinomycin (3), respectively. Compound 3 was iodinated and reduced to provide 5'-deoxy-2',3'-O-isopropylideneoxazinomycin (5) which, after acid hydrolysis, provided 5'-deoxyoxazinomycin (6). Alternatively, the iodination of oxazinomycin followed by catalytic hydrogenation also provided 6. Oxazinomycin was treated with 2-acetoxybenzoyl chloride to provide 3'-O-acetyl-2'-chloro-2'-deoxyoxazinomycin (8) which, after reduction with tributyltin hydride, provided 3'-O-acetyl-2'-deoxyoxazinomycin (9). Oxazinomycin was also converted into oxazinomycin 5'-phosphate (10) and into O4,2'-anhydrooxazinomycin (11). 1,2,4-Oxadiazole-3,5-dione (12) was glycosylated to provide 2-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-1,2,4-oxadiazole-3,5-dione (13) which, after deacetylation, provided 2-beta-D-ribofuranosyl-1,2,4-oxadiazole-3,5-dione (14). Similarly, 12 provided 2-(2-deoxy-beta-D-erythro-pentofuranosyl)-1,2,4-oxadiazole-3,5-dione (17); 14 was also converted into the corresponding 2',3'-O-isopropylidene derivative 15. Compound 14 showed significant antiviral activity against herpes simplex virus type 1, in vitro.     

Synthesis and biological activity of some 8-substituted selenoguanosine cyclic 3',5'-phosphates and related compounds.

8-Bromoguanosine cyclic 3',5'-monophosphate, 8-bromoguanosine 5'-monophosphate, and 8-bromoguanosine served as intermediates for the chemical synthesis of a series of 8-substituted seleno cyclic nucleotides, nucleotides, and their nucleosides. Selenourea was found to be a useful reagent in synthesizing these seleno-substituted nucleoside, nucleotide, and cyclic nucleotide. A nucleic acid analyzer was used to study the hydrolysis of these cyclic nucleotides by phosphodiesterase. It was found that all of the 8-substituted selenoguanosine cyclic 3',5'-phosphates synthesized, except 8-MeSe-cGMP, were resistant to hydrolyze by phosphodiesterase. These 8-substituted seleno cyclic GMP derivatives showed some antitumor activities against murine leukemic cells (L5178Y) in vitro and in vivo.     

Synthesis and biological evaluation of some N4-substituted 5-nitroisatin-3-thiosemicarbazones

A series of 5-nitroisatin-3-thiosemicarbazones 2a–2l was synthesised and evaluated for selected biological activities. The brine shrimp lethality bioassay was carried out to study their in vitro cytotoxicity potential and besides, their antifungal, phytotoxic and urease inhibitory effects were also investigated. Only compound 2j proved to be active in the brine shrimp assay exhibiting LD₅₀ value 1.16?×?10^?3?M. Compounds 2a and 2d displayed moderate antifungal activity (50 and 40%, respectively) against M. canis. Similarly, compound 2l exhibited moderate activity (40%) against the fungal strain, A. flavus. In phytotoxicity assay, all the synthesised compounds including the reference point 2m showed weak to moderate (20–60%) activity at the highest tested concentrations (1,000?μg and 500?μg/ml, respectively). In urease inhibition assay, compounds 2a, 2i and 2k proved to be potent inhibitors demonstrating pronounced inhibition with IC₅₀ values 0.440, 0.901 and 27.880?μM, respectively. These compounds may act as leads for further studies.     

Synthesis and biological activity of N6-(n-alkylureido)purine ribonucleosides and their 5'-phosphates

Syntheses and biological activities of 12 N6-(n-alkylureido)purine ribonucleosides (alkyl chain length of 1--10, 16, and 18 carbons) and three N6-(n-alkylureido)purine ribonucleoside 5'-phosphates (chain length of 4, 9, and 10 carbons) are described. The N6-(n-alkylureido)purine ribonucleosides were prepared by a reaction of (2',3',5'-tri-O-acetyl-beta-D-ribofuranosyl)-9H-purine-6-carbamate and n-alkylamine in refluxing pyridine. The 5'-nucleotides were prepared by direct phosphorylation of the corresponding ribonucleoside with phosphorus oxychloride and triethyl phosphate. Some N6-(n-alkylureido)purine ribonucleosides (n-octyl, n-nonyl, and n-decyl) and their nucleotides showed a marked antiproliferative activity against L-1210 cells in culture.     

Synthesis and antibacterial activity of some imidazole-5-(4H)one derivatives

In the present study, several substituted oxazolones were synthesized by condensation of benzoylglycine with different aldehydes. From such oxazolones, substituted imidazolones were synthesized by condensation with ethylenediamine, urea and 4-N,N-dimethylaminoaniline. All these synthesized compounds produced significant antibacterial activities. Furthermore, compounds containing -CH(2)CH(2)NH(2), -CONH(2) and -C(6)H(4)-N(CH(3))(2) groups as substitutents on the imidazolones were found to be potent antibacterial agents. Thus, among the twelve compounds, 1-(2-aminoethyl)-2-phen yl-4-(4-(dimethylamino)benzylidene)imidazole-5-(4H)one (4d), 1-carboxamido-2-phenyl-4-(4-(dimethylamino)benzylidene)imidazole-5-(4H)one (4e) and 1-(4-(N,N-dimethylamino)phenyl)-2-phenyl-4-(4-(dimethylamino)benzylidene)imidazole-5-(4H)one (4f) were found to have a significant higher antibacterial activity than the other substituted imidazolones. Compound 4e was the most active one in this series.