Purine Nucleoside 3′,5′-Cyclic Monophosphates as Hormonal Modulators of Cellular Proliferation,Metastases and Lymphocyte Response

Abstract

A review of the potential role of cAMP and cGMP as hormonal regulators of tumor cell proliferation, metastases and lymphocyte activation reveals that several synthetic purine nucleoside 3′,5′-cyclic monophosphates are more potent and more selective in modulating certain specific responses than the parent natural cyclic nucleotides. cAMP derivatives have been prepared which will temporarily restore transformed cells to the normal phenotype. cAMP analogs may well be found which will selectively inhibit tumor metastases. Certain cGMP analogs could selectively stimulate the lymphocyte response toward the destruction of tumor cells. The synthesis of new cyclic nucleotides should provide unique nontoxic agents that could combat neoplasia on a hormonal basis.     

Synthesis of Pyrazolo[3, 4-d]Pyrimidine Ribonucleoside 3′, 5′-Cyclic Phosphates Related to cAMP,cIMP and cGMP1

Abstract

The synthesis of pyrazolo[3,4-d]pyrimidine ribonucleoside 3′, 5′-cyclic phosphates related to cAMP, cIMP and cGMP has been achieved for the first time. Phosphorylation of 4-amino-6-methylthio-1-β-D-ribo-furanosylpyrazolo[3,4-d]pyrimidine (1) with POCl₃ in trimethyl phosphate gave the corresponding 5′-phosphate (2a). DCC mediated intramolecular cyclization of 2a gave the corresponding 3′, 5′-cyclic phosphate (3a), which on subsequent dethiation provided the cAMP analog 4-amino-1-β-D-ribofuranosylpyrazolo[3, 4-d]pyrimidine 3′, 5′-cyclic phosphate (3b). A similar phosphorylation of 6-methylthio-1-β-D-ribofuranosylpyrazolo[3, 4-d]pyrimidin-4(5H)-one (5), followed by cyclization with DCC gave the 3′, 5′-cyclic phosphate of 5 (9a). Dethiation of 9a with Raney nickel gave the cIMP analog 1-β-D-ribofuranosylpyrazolo[3, 4-d]pyrimidin-4(5H)-one 3′, 5′-cyclic phosphate (9b). Oxidation of 9a with m-chloroperoxy benzoic acid, followed by ammonolysis provided the cGMP analog 6-amino-1-β-D-ribofuranosylpyrazolo [3, 4-d] pyrimidin-4(5H)-one 3′, 5′-cyclic phosphate (7). The structural assignment of these cyclic nucleotides was made by UV and H NMR spectroscopic studies.     

Cyclic AMP Diphenyl Phosphoric Mixed Anhydride: Synthesis,P NMR Characterization and Reaction with Dimethylamine

Abstract

Phosphorus diastereoisomers, R _p and S _p of p¹-adenosine cyclic 3′, 5′ P² -diphenylpyrophosphate (cyclic AMP diphenylphosphoric mixed anhydride) (1) were prepared from adenosine cyclic 3′, 5′-monophosphate (cyclic AMP) and diphenyl phosphorochloridate and characterized by ³¹p NMR. The synthesis preferentially gave R _p-1. Reaction of 1 with dimethylamine resulted in the formation of a (～ 3:1) mixture of adenosine cyclic 3′,5′-N, N-dimethylphosphoramidate and diphenyl-N, N-dimethylphosphoramidate and occurred with inversion of configuration at cyclic AMP phosphorus.     

Targets for the Antiviral and Antitumor Activities of Nucleoside,Nucleotide and Oligonucleotide Analogues

Abstract

The following targets can be considered in the development of antiviral agents: (i) DNA polymerase via dThd kinase, (ii) S-adenosylhomocysteine hydrolase; and in the development of antitumor agents: (iii) dTMP synthetase and (iv) protein synthesis via the 2–5A pathway.     

Studies on the Dehydration of New 2- (Pentitol-1-YL) Pyridines Having D-Gulo,D-IDO,and L-Manno Configurations

Abstract

Fusion of 2-trimethylsilylpyridine and tetra-O-acetyl-aldehydo-D-xylose or 2,3:4,5-di-O-isopropylidene-aldehydo-L-arabinose led, after removing of the protecting groups, to 2-(pentitol-1-yl)pyridines of D-gulo and D-ido or L-manno configurations. Dehydration of the sugar-chain with D-gulo and D-ido configurations gave the corresponding 2′,5′-anhydro derivatives, whereas 2-(5-O-isopropyl-L-manno-pentitol-1-yl)-pyridine was the only compound formed by dehydration of the sugar-chain with L-manno configuration. Structural proofs are based on ¹H and ¹³C NMR spectra.     

Conformation of Diastereomers of Adenosine Cyclic 3′, 5′-Phosphorothioate

Abstract

¹H and ³¹P NMR spectra of cAMP (1) and both diastereomers of cAMPS (2 and 3) were compared with these of structurally related bicyclic phosphate 4 and phosphorothioates 5 and 6. Conformational analysis was also performed by NMR techniques for bicyclic phosphoranilidates 7 and 8 and (Rp)-cdAMP anilidate (9). Chair conformation is predominant for all investigated compounds 1–8, while the phosphoranilidate 9 exists in solution in chair-twist equilibrium. Thus, antagonistic properties of (Rp)-cAMPS with respect to cAMP are inferred by the change in the overall molecular shape caused by the presence of the bulky sulfur atom in the equatorial position of the cAMPS molecule.     

Synthesis of Certain 5′-Substituted Derivatives of Ribavirin and Tiazofurin

Abstract

The synthesis of several 5′-substituted derivatives of ribavirin (1) and tiazofurin (3) are described. Direct acylation of 1 with the appropriate acyl chloride in pyridine-DMF gave the corresponding 5′-O-acyl derivatives (4a-h). Tosylation of the 2′, 3′-O-isopropylidene-ribavirin (6) and tiazofurin (11) with p-toluenesulfonyl chloride gave the respective 5′-O-p-tolylsulfonyl derivatives (7a and 12a), which were converted to 5′-azido-5′-deoxy derivatives (7b and 12b) by reacting with sodium/lithium azide. Deisopropylidenation of 7b and 12b, followed by catalytic hydrogenation afforded 1-(5-amino-5-deoxy-β-D)-ribofuranosyl)-1, 2, 4-triazole-3-carboxamide (10b) and 2 - (5 -amino- 5-deoxy- β-D-ribofuranosyl) thiazole-4-carboxamide (16), respectively. Treatment of 6 with phthalimide in the presence of triphenylphosphine and diethyl azodicarboxylate furnished the corresponding 5′-deoxy-5′-phthaloylamino derivative (9). Reaction of 9 with n-butylamine and subsequent deisopropylidenation provided yet another route to 10b. Selective 5′-thioacetylation of 6 and 11 with thiolacetic acid, followed by saponification and deisopropylidenation afforded 5′-deoxy-5′-thio derivatives of 1-β-D-ribofuranosyl-1, 2, 4-triazole-3-carboxamide (8a) and 2-β-D-ribofuranosylthiazole-4-carboxamide (15), respectively.     

Synthetic Studies on the Isomeric N -Methyl Derivatives of C-Ribavirin

Abstract

The syntheses of all three of the mono-N-methy1 derivatives of C-ribavirin (3-β-D-ribofuranosyl-1, 2, 4-triazole-5-carboxamide, 2) have been accomplished. Reaction of 1-(β-D-ribofuranosyliminomethyl)-2-methyl-hydrazine ( 7 ) with ethyl oxamate (8) in boiling ethanol gave the N′-methyl-C-ribavirin ( 3 ). A similar treatment of β-D-ribofuranosyl-1-carboximidic acid methyl ester ( 6 ) with N′-methyloxamic hydrazide ( 10 ) furnished the N²-methyl-C-ribavirin ( 4 ). Direct methylation of unprotected 2 with methyl iodide in the presence of potassium carbonate in dimethyl sulfoxide gave N ⁴-methyl isomer ( 5 ) as the major product. Structural assignments of 3 , 4 , and 5 were based on the unequivocal synthetic sequences, ¹H and ¹³C NMR data and confirmed by single crystal X-ray diffraction analysis.     

Morphometric analysis of autophagy-related structures in Saccharomyces cerevisiae

When macroautophagy (autophagy) is induced by nutrient starvation or rapamycin treatment, Atg (autophagy-related) proteins are assembled at a restricted region close to the vacuole. Subsequently, the phagophore expands to form a closed autophagosome. In Saccharomyces cerevisiae cells overexpressing precursor Ape1 (prApe1), a specific autophagosome cargo protein, the phagophore can be visualized as a cup-shaped structure labeled with green fluorescent protein (GFP)-tagged Atg8. Previously, our group has shown that the maximum length of GFP-Atg8-labeled structures reflects the magnitude of bulk autophagy. In that study, the morphological parameters of the autophagy-related structures were extracted manually, requiring a great deal of time. Moreover, only well-expanded phagophores were subjected to further analysis. Here we report Qautas (Quantitative autophagy-related structure analysis system), a high-throughput and comprehensive system for morphological analysis of autophagy-related structures using a combination of image processing and machine learning. We describe both the manual method and Qautas in detail.     

Nucleosides,XLVI1 Syntheses and Reactions of 6- and 7-p-Chlorophenyllumazine Nucleosides

Abstract

The syntheses of 6-(4) and 7-p-chlorphenyl-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-lumazine (6), was well as the debenzoylation to the corresponding free nucleosides 5 and 7, were improved. Thiation of 4 and 6 by P₄S₁₀ led in excellent yields to 4-thiolumazine nucleosides (8, 10) which could be deblocked to 9 and 11 and converted on treatment with ammonia into the isopterin-N-1- ribofuranosides 13 and 14. 2,2′-Anhydro-nucleoside formation worked well with 5 and 7 respectively to give 15 and 16, which formed on acid hydrolysis the 6- and 7-substituted 1-β-D-arabinofuranosyl-lumazines 18 and 19. The new nucleosides have been characterized by UV and ¹H-NMR spectra.     

Synthesis of Brunfelsamidine Ribonucleoside and Certain Related Compounds by the Stereospecific Sodium Salt Glycosylation Procedure

Abstract

A synthesis of 2,4-dideazaribavirin ( 2 ), brunfelsamidine ribonucleoside ( 8c ) and certain related derivatives are described for the first time using the stereospecific sodium salt glycosylation procedure. Glycosylation of the sodium salt of pyrrole-3-carbonitrile ( 4 ) with 1-chloro-2, 3-O-t-isopropylidene-5-O-t-butyldimethylsilyl-α-D-ribofuranose ( 5 ) gave exclusively the corresponding blocked nucleoside ( 6 ) with β-anomeric configuration, which on deprotection provided 1-β-D-ribofuranosylpyrrole-3-carbonitrile ( 7 ). Functional group tranformation of 7 gave 2 , 8c and related 3-substituted pyrrole ribonucleosides. These compounds are devoid of any significant antiviral/antitumor activity invitro.     

Synthetic Nucleosides and Nucleotides. XX1. Synthesis of Various 1-β-D-Xylofuranosyl-5-Alkyluracils and Related Nucleosides

Abstract

Treatment of D-xylose (1) with 0.5% methanolic hydrogen chloride under controlled conditions followed by benzoylation and acetolysis afforded crystalline 1-O-acetyl-2, 3, 5-tri-O-benzoyl-α-D-xylofuranose (4) in good yield. Coupling of 4 with 2, 4-bis-trimethylsilyl derivatives of 5-alkyluracils (methyl, ethyl, propyl and butyl) (5a-5d), 5-fluorouracil (5e) and uracil (5f) in acetonitrile in the presence of stannic chloride gave 1-(2,3,5-tri-O-benzoyl-β-D-xylofuranosyl)-nucleosides (6a-6f). Saponification of 6 with sodium methoxide afforded 1-β-D-xylofuranosyl-5-substituted uracils (7a-7f). Condensation of 4 with free adenine in similar fashion and deblocking gave carcinostatic 9-β-D-xylofuranosyladenine (7g).     

New Acyclic C-Nucleosides of the Imidazole

Abstract

Acid catalyzed isomerization of 1-aryl-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-2-imidazolines (4) yields 1-aryl-4-(D-galacto-pentitol-1-yl)imidazoles (8) which can be also obtained by reductive desulphuration of 1-aryl-2-benzylthio-4-(D-galacto-pentitol-1-yl)imidazoles (6). Compounds (4) were obtained by desulphuration with Raney nickel from 1-aryl-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-imidazolidine-2-thiones (1) or 1-aryl-2-benzylthio-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-2-imidazolines (2).     

Preparation of New Glycoheptofurano[2,1-d]Imidazolidine-2-Thiones., Isomerizations to Acyclic-Sugar C-Nucleoside Analogues of Imidazole

Abstract

1-Methyl- and 1-aryl-(1,2-dideoxy-D-glyofurano)[2,1-d]-imidazolidine-2-thiones having the configurations β-D-glycero-L-gluco (4), β-D-glycero-D-ido (5—8), α-D glycerol-D-galacto (9—10) and β-D-glycero-D-talo (11, 12) are prepared by reaction of 2-amino-2-deoxy-aldoses with methyl and aryl isothiocyanates. 1-Aryl-(1,2-dideoxy–β-D-glycero-L-gluco-heptofurano)[2,1-d]imidazolidine-2-thiones (1—3) have been converted into 1-aryl-4-(D-galacto-pentitol-1-yl)-4-imidazo-line-2-thiones (24—26) by acid catalysed isomerization.     

Improved and Reliable Synthesis of 3′‐Azido‐2′,3′‐dideoxyguanosine Derivatives

An improved synthesis of N²‐protected‐3′‐azido‐2′,3′‐dideoxyguanosine 20 and 23 is described. Deoxygenation of 2′‐O‐alkyl (and/or aryl) sulfonyl‐5′‐dimethoxytritylguanosine coupled with [1,2]‐hydride shift rearrangement gave protected 9‐(2‐deoxy‐threo‐pentofuranosyl)guanines ( 10 , 12 and 16 ). This rearrangement was accomplished in high yield with a high degree of stereoselectivity using lithium triisobutylborohydride (l‐Selectride®). Compounds 10 , 12 and 16 were transformed into 3′‐O‐mesylates ( 18 and 21 ), which can be used for 3′‐substitution. The 3′‐azido nucleosides were obtained by treatment of 18 and 21 with lithium azide. This procedure is reproducible with a good overall yield.     

Synthesis of (R - and (S)-1-[[2-Hydroxy-1-(aminomethyl)ethoxy]methyl]-5- benzyluracil,Potent Inhibitors of Uridine Phosphorylase

Abstract

Optically pure (R)- and (S)-1-[[2-hydroxy-1-(aminomethyl) ethoxy]methyl]-5-benzyluracil [(R)-AHPBU and (S)-AHPBU, respectively], two potent uridine phosphorylase inhibitors, have been synthesized via multi-step syntheses starting from independent chiral compounds. The activity of (R)-AHPBU, (S)-AHPBU, and (R,S-AHPBU which have been previously synthesized, on the inhibition of uridine phosphorylase from Sarcoma-180 cells has been studied and compared. The K. values for (R,S)-, (R)- and (S)-AHPBU were determined to be 15·2.3, 17·2.7 and 16·2.0 nM, respectively. This indicates that (R) and (S) optical enantiomers have the same affinity for binding to uridine phosphorylase. These acyclic pyrimidine amino nucleoside analogues represent a new class of potent uridine phosphorylase inhibitors, which has a bulky hydrophobic substituent at the 5-position in the uracil base, yet has remarkably high water solubility.     

A New Synthesis of 7-Methyl-8-Oxoguanosine

Abstract

A new, facile synthesis of 7-methyl-8-oxoguanosine is reported. 2-Chloro-7-methylpurine-6, 8-dione (5) was silylated with hexamethyldi-silazane and the silylated intermediate, 6, glycosylated with 1-0-acetyl-2, 3, 5-tri-0-benzoyl-D-ribofuranose to yield 2-chloro-7-methyl-9-(2′, 3′,-5′-tri-0-benzoyl-β-D-ribofuranosyl) purin-6, 8-dione (8). Deprotection of 8 with sodium hydroxide in aqueous methanol gave 2-chloro-7-methyl-9-(β-D-ribofuranosyl) purine-6,8-dione (9), which was aminated with liquid ammonia or methanolic ammonia to yield 7-methyl-8-oxoguanosine (3).     

Synthesis and Biological Evaluation of 1,2-Disubstituted Carbonucleosides of 6-Substituted Purine and 8-Azapurine

Abstract

A series of new one two subtituted carbonucleoside analogues (OTC), with the purine and 8-azapurine base linked through a methylene group at the cyclopentane ring, were synthesized and evaluated for their activity against a number of viruses and tumor cells in vitro.     

Nucleosides. 131. The Synthesis of 5-(2-Chloro-2-Deoxy-β-D-arabino-Furanosyl)Uracil. Reinterpretation of Reaction of ψ-Uridine With α-Acetoxyisobutyryl Chloride. Studies Directed Toward the Synthesis of 2′-Deoxy-2′-Substituted Arabino-Nucleosides. 2

Abstract

Treatment of ψ-uridine (3) with α-acetoxyisobutyryl chloride in acetonitrile gave, after deprotection, a mixture of four products: 5-(2-chloro-2-deoxy-β-D-arabinofuranosyl)uracil (10a), its 3′-chloro xylo isomer (11a), 2′-chloro-2′-deoxy-ψ-uridine (9a) and 4,2′-anhydro-ψ-uridine (8a). Each component was isolated by column chromatography. Compound 9 was converted to the known 1,3-dimethyl derivative 2 by treatment with DMF-dimethylacetal. Treatment of 10 and 11 with NaOMe/MeOH afforded the same 4,2′-anhydro-C-nucleoside 8. The 1,3-dimethyl analogues of 10 and 11, however, were converted to 2′,3′-anhydro-1,3-dimethyl-ψ-uridine (13) upon base treatment. The epoxide 13 was also prepared in good yield by treatment of 10 and 11 with DMF-dimethylacetal.     

Synthesis and X-Ray Crystal Structure of 3-Amino-1-β-D-Ribofuranosyl-s-Triazolo[5, 1-c]-s-Triazole

Abstract

The first chemical synthesis of 3-amino-1-β-D-ribofuranosyl-s-triazolo[5,1-c]-s-triazole (6) is described. Direct glycosylation of 3-amino-5(7)H-s-triazolo[5,1-c]-s-triazole (2) with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose (3) in the presence of TMS-triflate gave 3-amino-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-s-triazolo[5, 1-c]-s-triazole (4) which, on ammonolysis, gave 6. The absolute structure of 6 is determined by X-ray diffraction techniques employing Mo Kα radiation. The structure is solved by direct methods and refined to the R value of 0.044 by using a full-matrix least-squares method. The sugar of 6 has a ³T₂ configuration. The torsion angles about the C5′–C4′ bond are both gauche and the torsion angle about the glycosidic bond is in the anti range. Each azole ring of the aglycon is planar and the dihedral angle between the planes of the rings is 3.6°.