Synthesis of glycopyranosylphosphonate analogues of certain natural nucleoside diphosphate sugars as potential inhibitors of glycosyltransferases

The synthesis of alpha-D-glucopyranosyl-, alpha-D-galactopyranosyl-, and alpha-D-mannopyranosylphosphonate is described. Condensation of tris(trimethylsilyl) phosphite with 2,3,4,6-tetrakis-O-(phenylmethyl)-1-O-acetyl-alpha-D-glucopyranose generated 2,3,4,6-tetrakis-O-(phenylmethyl)-alpha-D-glucopyranosylphosphonic acetic anhydride (13). The benzyl blocking groups were removed by catalytic hydrogenation, and the anhydride bond was cleaved by alkaline hydrolysis to obtain alpha-D-glucopyranosylphosphonate (15). alpha-D-Galactopyranosylphosphonate (17) and alpha-D-mannopyranosylphosphonate (19) were also similarly synthesized. The anomeric configuration of 15 was assigned by single-crystal X-ray analysis, and the structural assignments of 17 and 19 were made on the basis of comparative NMR spectral studies. Compound 15 was then coupled with adenosine 5'-phosphoric di-n-butylphosphinothioic anhydride in dry pyridine to give adenosine 5'-phosphoric alpha-D-glucopyranosylphosphonic anhydride (23). Similarly, uridine 5'-phosphoric alpha-D-galactopyranosylphosphonic anhydride (24) and guanosine 5'-phosphoric alpha-D-mannopyranosylphosphonic anhydride (25) were synthesized from 17 and 19, respectively. With ovalbumin as an acceptor for [3H]galactose, provided by UDP-[3H]galactose, only uridine 5'-phosphoric alpha-D-galactopyranosylphosphonic anhydride (24) was shown to inhibit glycoprotein beta-D-galactosyltransferase (EC 2.4.1.38), with an apparent Ki equal to 165 microM. Even though these ionic compounds hardly penetrate the cell membrane, preliminary in vitro antitumor screening shows that compounds 23 and 25 are slightly active against human B-lymphoblastic leukemia and human T-lymphoblastic leukemia. None of these compounds show any antiviral activity.     

Glycoconjugates, products of uridine derivatives phosphitylation and oxidation as glycosyltransferases potential inhibitors

The title compounds, variously protected 5'-uridine derivatives connected with 1-thiosugar with thio-phosphoesters fragment (17-22) were synthesized in sequence of reactions: phosphitylation--reaction of 5'-hydroxyl group of selectively protected nucleoside with a phosphitylating agent (N,N-diisopropyl chlorophosphoamidite), connection an phosphoroamidites with 2-bromoethanol or 3-bromopropanol and secondary oxidation with sulfur presence and finally condensation reaction of obtained products with 1-thiosugar. Received glycoconjugates (17-22) had a structure which mimic to structure of natural glycosyltransferases substrates.     

Synthesis of certain thiaxanthones as potential schistosomicidal agents

Twenty nine substituted thiaxanthone derivatives were synthesized for schistosomicidal evaluation. The compounds, 1-morpholino-4-methyl-6-nitrothiaxanthone and 1-(2-diethyl-aminoethylamino)-4-methyl-6-nitrothiaxanthone dipicrate were found to possess promising schistosomicidal activity againstSchistosoma mansoni in mice.     

Synthesis of new nucleoside phosphoraziridines as potential site-directed antineoplastic agents

With the aim of increasing the selectivity of the 2,2-dimethylphosphoraziridine type antitumor agents toward the intracellular site of DNA synthesis, a series of new compounds was synthesized in which the reactive bis(2,2-dimethyl-1-aziridinyl)phosphinyl (2,2-DMAP) group was linked through a carbamate or amide linkage to thymidine or cytosine nucleoside moieties. The 3'- and 5'-(2,2-DMAP)carbamates of thymidine (1 and 2) were found to be highly unstable, therefore the corresponding O-acetyl derivatives 5 and 6 were prepared by reacting 5'- and 3'-acetylthymidine, respectively, with dichloroisocyanatophosphine oxide followed by the addition of 2,2-dimethylaziridine and triethylamine. The 3'- and 5'-(2,2-DMAP)amides of thymidine 14 and 15 were prepared by reacting the appropriate thymidinylamines with bis(2,2-dimethyl-1-aziridinyl)phosphinyl chloride (17). The N4-(2,2-DMAP)amides of cytidine, 2'-deoxycytidine, and cytosine arabinoside (18, 19, and 20, respectively) were prepared by reacting the hydrochlorides of the O-peracetylated cytosine nucleosides with triethylamine and POCl3 and, subsequently, with 2,2-dimethylaziridine and triethylamine, to give the corresponding N4-(2,2-DMAP)cytosine nucleoside peracetates 21, 22, and 23, respectively, which were then deacetylated by aminolysis. However, the peacetate intermediates were found to be more stable and, probably for the same reason, also more active against P388 leukemia in mice than the deacetylated products. Particularly, 22 and 23 showed sufficient activity in this in vivo assay system to warrant further evaluation. The relationships between the antitumor activities, the chemical alkylating activities, and the cholinesterase inhibitory activities of these agents are discussed.     

Synthesis and evaluation of 5-amino-1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine and certain related nucleosides as inhibitors of purine nucleoside phosphorylase

The 5-amino and certain related derivatives of the powerful purine nucleoside phosphorylase (PNPase) inhibitor 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine (TCNR,3) have been prepared and evaluated for their PNPase activity. Acetylation followed by dehydration of 5-chloro-1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (4a) gave 5-chloro-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-1,2,4-triazole-3- carbonitrile (5). Ammonolysis of 5 furnished 5-amino-1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine (5-amino-TCNR, 6), the structure of which was assigned by single-crystal X-ray analysis. Acid-catalyzed fusion of methyl 5-chloro-1,2,4-triazole-3-carboxylate (7a) with 5-deoxy-1,2,3-tri-O-acetyl-D-ribofuranose (8) gave methyl 5-chloro-1-(2,3-di-O-acetyl-5-deoxy-beta-D-ribofuranosyl)- 1,2,4-triazole-3-carboxylate (9a) and the corresponding positional isomer 9b. Transformation of the functional groups in 9a afforded a route to 5'-deoxyribavirin (9i). Compound 9a was converted in four steps to 5-amino-1-(5-deoxy-beta-D-ribofuranosyl)-1,2,4-triazole-3- carboxamidine (5'-deoxy-5-amino-TCNR, 9g). Similar acid-catalyzed fusion of 1,2,4-triazole-3-carbonitrile (7b) with 8 and ammonolysis of the reaction product 9h gave yet another route to 9i. Treatment of 9h with NH3/NH4Cl furnished 1-(5-deoxy-beta-D-ribofuranosyl)- 1,2,4-triazole-3-carboxamidine (5'-deoxy-TCNR, 9k). The C-nucleoside congener of TCNR (3-beta-D-ribofuranosyl- 1,2,4-triazole-5-carboxamidine, 12) was prepared in two steps from 3-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)- 1,2,4-triazole-5-carbonitrile (10) by conventional procedure. 5-Amino-TCNR (6) displayed a more potent, high-affinity inhibition than TCNR, with a Ki of 10 microM. In contrast, 5'-deoxy-5-amino-TCNR (9g) was a significantly less potent inhibitor of PNPase, compared to 5'-deoxy-TCNR (Ki = 80 and 20 microM, respectively). Neither the C-nucleoside congener of TCNR (12) nor that of ribavirin were found to inhibit inosine phosphorolysis.     

Synthesis of certain mercapto-and aminopyrimidine derivatives as potential antimicrobial agents

Reaction of ethyl 4-chloro-2-phenylpyrimidine-4-carboxylate (4) with 5-chloro-2-methylthiophenol or 3-aryl-4-phenyl-1,2,4-triazole-5-thiol yielded the corresponding thioethers (5) and (8a, b), respectively. Careful alkaline hydrolysis of (5) yielded the corresponding carboxylic acid (6). Reaction of (4) withp-aminoacetophenone yielded compound (10) which was reacted with certain aromatic aldehydes to afford the α, β-unsaturated ketones (11a–d). Condensation of (11a–d) with malononitrile or phenylhydrazine yielded the 2-amino-3-cyanopyridines (12a–f) or the 2-pyrazolines (13a, b), respectively. Seven representative compounds were tested for theirin vitro antimicrobial activity against some pathogenic micro-organisms, some of them were proved to be active.     

Synthesis of certain 2-aminoadamantane derivatives as potential antimicrobial agents

N-(2-Adamantyl)-N'-(5-arylhydrazono-6-methyl-4-oxopyrimidin-2-yl) guanidines (IIIa, b), 2-(2-adamantyl-amino)-4-amino-s-triazine (IVa) and its 6-chloromethyl derivative (IVb) were prepared by cyclization of 1-(2-admantyl) biguanide HCl (I) with ethyl 2-arylhydrazono-3-oxobutyrates (II), ethyl formate and ethyl chloroacetate, respectively. Where 1-(2-adamantyl)-3-(4, 5-dioxo-2-imidazolidinylidene) guanidine (V) was used as intermediate for the synthesis of amides (VIIa, b), hydrazide (VIII) and azomethine derivatives (IXa, b) of alkyl 2-(2-adamantyl-amino)-4-amino-s-triazine-6-carboxylates (VI a, b). The antimicrobial testing of the prepared compounds proved that compound IXb was the most active. It showed a marked bacteriostatic effect againstStaphylococcus aureus andBacillus subtilis.     

Synthesis of certain 2-aminoadamantane derivatives as potential antimicrobial agents

1-(2-Adamantyl-3-(5-arylhydrazono-6-methyl-4-oxopyrimidin -2-yl)guanidines, 2-(2-adamantylamino)-4-amino-s-triazine and its 6-chloromethyl derivative were prepared by cyclization of 1-(2-adamantyl)biguanide.HCl with ethyl 2-arylhydrazono-3-oxobutyrates, ethyl formate and ethyl chloroacetate, respectively. 1-(2-damantyl)-3-(4,5-dioxo-2-imidazolidinylidene)guanidine was used as intermediate for the synthesis of amides, hydrazide and azomethine derivatives of alkyl 2-(2-adamantylamino)-4-amino-s-triazine-6-carboxylates. The antimicrobial testing of the prepared compounds proved that an azomethine derivative was the most active. It showed a marked bacteriostatic effect against Staphylococcus aureus and Bacillus subtilis.     

Synthesis of alkylamides of dipeptides as potential plasmin inhibitors

Four dipeptide alkylamides with general formula H-D-Phe-L-Lys-NH-X, where X = cyclohexyl, - (CH2)5NH2, -(CH2)2-OH and hexyl were obtained. Effect of these compounds on amidolytic and fibrinolytic activity of plasmin was examined.     

Synthesis of certain thiosemicarbazide and triazole derivatives as potential antimicrobial agents

Two novel series of thiosemicarbazide derivatives were synthesized: 2-[4-(substituted thiocarbamoylhydrazinocarbonyl) phenoxymethyl]-1H-benzimidazoles and 1-benzyl-2-[4-(substituted thiocarbamoylhydrazinocarbonyl) phenoxymethyl]-1H-benzimidazoles, and cyclised to 2-[4-(4-substituted-4H-1,2,4-triazole-5-thion-3-yl)phenoxymethy ]-1H-benzimidazoles and 1-benzyl-2-[4-(4-substituted-4H-1,2,4-triazole-5- 5-thion-3-yl)phenoxymethyl]-1H-benzimidazoles, respectively. The antimicrobial activity of the prepared compounds was tested.     

Synthesis of benzylamides of dipeptides as potential inhibitors of plasmin

Four benzylamides of dipeptides with the general formula: X-L-Lys-NH-CH2-C6H5, where X = L-or D-Leu and L-or D-Phe were prepared as potential inhibitors of plasmin. All of them influenced on the fibrynolytic activity of plasmin, but only D-Leu-L-Lys-NH-CH2-C6H5 inhibited the amidolytic activity of this enzyme. None of the tested compounds was an inhibitor of thrombin in an amidolytic test.     

Synthesis and antiviral activity of certain nucleoside 5'-phosphonoformate derivatives

(Ethoxycarbonyl)phosphonic dichloride (3) was synthesized by chlorination of bis(trimethylsilyl) (ethoxycarbonyl)phosphonate with thionyl chloride. Adenosine 5'-(ethoxycarbonyl)phosphonate (4), guanosine 5'-(ethoxycarbonyl)phosphonate (5), 2'-deoxyadenosine 5'-(ethoxycarbonyl)phosphonate (18) and 2'-deoxyguanosine 5'-(ethoxycarbonyl)phosphonate (19) were synthesized by coupling of compound 3 with adenosine, guanosine, 2'-deoxyadenosine, and 2'-deoxyguanosine, respectively. Alkaline treatment of 4, 5, 18, and 19 gave the corresponding adenosine 5'-(hydroxycarbonyl)phosphonate (14), guanosine 5'-(hydroxycarbonyl) phosphonate (15), 2'-deoxyadenosine 5'-(hydroxycarbonyl)phosphonate (20), and 2'-deoxyguanosine 5'-(hydroxycarbonyl) phosphonate (21). Treatment of 4 and 5 with methanolic ammonia resulted in the production of adenosine 5'-(aminocarbonyl)phosphonate (12) and guanosine 5'-(aminocarbonyl)phosphonate (13), respectively. The nucleotide analogue 20 exhibited the most potent antiviral activity of this group of nucleotide tested in vitro and was most active against herpes viruses especially HSV-2. The nucleotide analogue 21 had lower, but significant, activity against HSV-2. All of the compounds tested were nontoxic to confluent Vero cells at concentrations as high as 5000 microM.     

8-Aza-immucillins as transition-state analogue inhibitors of purine nucleoside phosphorylase and nucleoside hydrolases

The 8-aza-immucillins (8-aza-9-deazapurines linked from C9 to C1 of 1,4-dideoxy-1,4-iminoribitol) have been designed as transition-state analogues of the reactions catalyzed by purine nucleoside phosphorylase and nucleoside hydrolases. Syntheses of the 8-aza-immucillin analogues of inosine and adenosine are described. They are powerful inhibitors of the target enzymes with equilibrium dissociation constants as low as 42 pM.     

Synthesis of bridged catechol-homocysteine derivatives as potential inhibitors of catechol O-methyltransferase

Catechol derivatives, covalently joined to homocysteine by sulfide or sulfonium linkages, were synthesized as potential catechol O-methyltransferase multisubstrate inhibitors which might bridge the enzymatic binding sites for the catechol substrate and the amino acid portion of the methyl donor S-adenosylmethionine. These compounds were found to be less effective inhibitors than the product inhibitor S-adenosylhomocysteine.     

Synthesis of phenothiazine derivatives as potential inhibitors of phospholipase C.

In order to study the structure-activity relationships of phenothiazine derivatives inhibiting phosphatidylinositol-specific phospholipase C (PI-PLC), the synthesis of some phenothiazine amide, amine and ester derivatives was performed mainly by reacting 10H-phenothiazine-10-propanoyl chloride with some amines and alcohols; the resulting amides were reduced with borane to yield the corresponding amines. Starting from 2-chloro and 2-trifluoromethyl-10H-phenothiazine-10-propanoyl chloride two amides were synthesized. The inhibiting activity on PI-PLC from human platelets is reported.     

Acyclic nucleoside analogues as inhibitors of Plasmodium falciparum dUTPase

We report the discovery of novel uracil-based acyclic compounds as inhibitors of deoxyuridine 5'-triphosphate nucleotidohydrolase (dUTPase), an enzyme involved in nucleotide metabolism that has been identified as a promising target for the development of antimalarial drugs. Compounds were assayed against both P.falciparum dUTPase and intact parasites. A good correlation was observed between enzyme inhibition and cellular assays. Acyclic uracil derivatives were identified that showed greater or similar potency and in general increased selectivity compared to previously reported inhibitors. The most active compound reported here against the P. falciparum enzyme had a K(i) of 0.2 microM. Molecular modeling studies provided a good rationale for the observed activities. Preliminary ADME studies indicated that some of the lead compounds are drug-like molecules. These compounds are useful tools for further investigating P. falciparum dUTPase for the development of much-needed novel antimalarial drugs.     

Synthesis and biological activity of certain nucleoside and nucleotide derivatives of pyrazofurin

A number of nucleoside and nucleotide derivatives of 4-hydroxy-3-beta-D-ribofuranosylpyrazole-5-carboxamide (pyrazofurin, 1) were prepared and tested for their antiviral and cytostatic activity in cell culture. Treatment of 1 with benzyl bromide gave 4-O-benzylpyrazofurin (4). Methylation of 4 with CH2N2 and subsequent removal of the benzyl group by catalytic hydrogenation provided 1-methylpyrazofurin (8). Direct methylation of 1 with CH3I furnished 4-O-methylpyrazofurin (6). Dehydration of the pentaacetylpyrazofurin (9) with phosgene furnished 4-acetoxy-3-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-1-acetylpyrazol e-5-carbonitrile (10). A similar dehydration of the precursor tetraacetyl derivative of 4 gave the corresponding carbonitrile, which on deprotection and subsequent treatment with hydroxylamine furnished 4- (benzyloxy)-3-beta-D-ribofuranosylpyrazole-5-carboxamidoxime (13). Treatment of the tetraacetyl derivative of 4 with Lawesson's reagent and subsequent deacetylation furnished a mixture of 4- (benzyloxy)-3-beta-D-ribofuranosylpyrazole-5-thiocarboxamide (15) and the corresponding nitrile derivative (16). Phosphorylation of unprotected 4 with POCl3 and subsequent debenzylation of the intermediate 17 gave pyrazofurin 5'-phosphate (18), which provided the first chemical synthesis of 18. Similar phosphorylation of 4 with POCl3 and quenching the reaction mixture with either EtOH or MeOH, followed by debenzylation, furnished the 5'-O-(ethyl phosphate) (19b) and 5'-O-(dimethyl phosphate) (20b) derivatives of pyrazofurin. DCC-mediated cyclization of 17, followed by debenzylation, gave pyrazofurin 3',5'-(cyclic)phosphate (21b). The NAD analogue 23b was also prepared by the treatment of 17 with an activated form of AMP in the presence of AgNO3. The structural assignment of 7,8, and 20a were made by single-crystal X-ray analysis, and along with pyrazofurin, their intramolecular hydrogen bond characteristics have been studied. All of these compounds were tested in Vero cell cultures against a spectrum of viruses. Compounds 18 and 23b were active at concentrations very similar to pyrazofurin but are less toxic to the cells than pyrazofurin. Compounds 19b, 20b, and the 3',5'-(cyclic)phosphate 21b are less active than 1. Compounds 18, 19b, 20b, and 23b also exhibited significant inhibitory effects on the growth of L1210 and P388 leukemias and Lewis lung carcinoma cells in vitro, whereas B16 melanoma cells were less sensitive to growth inhibition by these compounds. Pyrazofurin derivatives modified at the 1-, 4-, or 5-position showed neither antiviral nor cytostatic activity in cell culture.     

Synthesis of some substituted quinazolinediones as potential inhibitors of smooth muscle contraction

3-Substituted 2,4(1H,3H)-quinazolinediones were prepared from the corresponding N-substituted 2-aminobenzamides by treatment with ethyl chloroformate and KOH in ethanol. Also, a series of 3-substituted and 1-methyl-3-substituted 2,4(1H,3H)-quinazolinediones were synthesized by the reaction of 1-methyl-1,4-dihydro- and 1,4-dihydro-2,4-dioxo-3(2H)-quinazolineacetic acid with the corresponding N-substituted piperazines. The 13C NMR spectra and mass spectra of the compounds were measured and signals were assigned. Some of the compounds showed inhibitory action on contractile function of smooth muscle.