8-Aza-1-deazapurine Nucleosides as Antiviral Agents

Abstract

2′,3′-Dideoxy-8-aza-1-deazaadenosine (21) and its α-anomer (20) were synthesized via glycosylation of 7-chloro-3H-1,2,3-triazolo[4,5-b]pyridi-ne with 2,3-dideoxy-5-O-[(1, 1)-dimethylethyl)diphenylsilyl]-D-glycero-o-pen-tofuranosyl chloride. The reaction gave a mixture of α- and β-anomers of N³-, N⁴- and N¹-glycosylated regioisorners (12–15). The α- and β-anomers of the N⁴-glycosylated isomer 26 and 27 were also synthesized through the glycosylation of 8-aza-1-deazaadenine with 1-acetoxy-2,3-dideoxy-5-O-f(1,1-di-methylethyl)dimethylsilyl]-D-glycero-pentouranose. These dideoxynucleo-sides and a series of previously synthesized 8-aza-1-deazapurine nucleosidcs were tested for activity against several DNA and RNA viruses, HIV-1 included. The α- and β-anomers of 7-chloro-3-(2-deoxy-D-erythro-pentofuranosyl)-3H-1,2,3-triazolo[4,5-b]pyridine (3a and 4) showed activities against Sb-1 and Coxs viruses. The α- and β-anomers of 2′,3′-dideoxy-8-aza-1-deazaadenosine (20 and 21) were found active as inhibitors of adenosine deaminase.     

N6-Alkylthiomethyl and N6-Arylthiomethyl Derivatives of Adenosine and Their Cytokinin Activity

Five new derivatives of adenosine, N⁶-[(1-methylethyl)thiomethyl]-(1), N⁶-methyithiomethyl-(2), N⁶-phenylthiomethyl-(3), N⁶-[(3-amino-3-carboxypropyl)thiomethyl]-(4), and N⁶-[(2-amino-2-carboxyethyl)thiomethyl]adenosine (5), were synthesized and their cytokinin activity was tested in the Amaranthus betacyanin assay and the soybean callus growth.

1, 2, and 3 were active in the former assay and all five compounds were active in the latter assay. The activities of the compounds were, however, weaker than those of the reference derivatives, in which Sulfides were replaced by methylenes, N⁶-isopentyl-, N⁶-n-propyl-, N⁶-benzyl-, and N⁶-(5-amino-5-carboxypentyl)adenosine. This fact indicates that the sulfide structure introduced into the N⁶-side chains had the effect of reducing cytokinin activity.     

Interaction of (2′ -5′) and (3′ -5′) Linked 2-Aminoadenylyl-3-aminoadenosines with Polyuridylic Acid

Abstract

2′-5′ and 3′-5′ linked 2-aminoadenylyl-2-aminoadenosines [(2′-5′)n²Apn²A (1) and (3′-5′)n²Apn²A (2)] were synthesized by condensation of 5′-O-monomethoxytrityl-N ² N ⁶-dibenzoyl-2-aminoadenosine and N ²,N ⁶,2′,3′-O-tetrabenzoyl-2-aminoadenosine 5′-phosphate using dicyclohexylcarbodiimide (DCC). The conformational properties of these dimers 1 and 2 were examined by UV, NMR and CD spectroscopy. The results reveal that the 2′-5′-isomer 1 takes a stacked conformation, which contains a larger base-base overlap and is more stable against thermal perturbation with respect to the 3′-5′-isomer 2. Interactions of 1 and 2 with polyuridylic acid (Poly (U)) were also examined by Tm, mixing curves, UV and CD spectra. Both the dinucleoside isomers 1 and 2 formed a complex of 1 : 2 stoichiometry with poly(U), which was much more stable than that of the corresponding ApA isomer     

A Functional Screening of Adenosine Analogues at the Adenosine A2B Receptor: A Search for Potent Agonists

Abstract

Various adenosine analogues were tested at the adenosine A_2B receptor. Agonist potencies were determined by measuring the cyclic AMP production in Chinese Hamster Ovary cells expressing human A_2B receptors. 5′-.N-Substituted carboxamidoadenosines were most potent. 5′-N-Ethylcarboxamidoadenosine (NECA) was most active with an ECso value of 3.1 μM. Other ribose modified derivatives displayed low to negligible activity. Potency was reduced by substitution on the exocyclic amino function (N⁶) of the purine ring system. The most active N⁶-substituted derivative N⁶-methyl-NECA was 5 fold less potent than NECA. C8-and most C2-substituted analogues were virtually inactive. 1-Deaza-analogues had a reduced potency, 3-and 7-deazaanalogues were not active.     

Ribosylation of the Base Residue of Inosine Derivatives by Phase-Transfer Catalysis

Abstract

Reaction of 2′,3′,5′-O-silylated inosine derivative 1 with 2, 3-O-isopropylidene-5-O-tritylribosyl chloride (3) in a two-phase (CH₂Cl₂-aq. NaOH) system in the presence of Bu₄NBr gave three products, i. e., 6-O-α-, 6-O-β-, and N ¹-β-isomers of glycosides 4, 5a, and 5b. A similar PTC reaction of 1 with 2, 3, 5-tri-O-benzylribosyl bromide (9) gave four regio- and stereo-isomers involving the N¹-β-glycoside 10. Reaction of 1 with 2, 3, 5-tri-O-benzoylribosyl bromide (11) afforded three products involving the desired N¹-β-glycoside 12b, which could be deprotected to give N ¹-ribosylinosine (15b) as a useful intermediate for the synthesis of cIDPR.

     

An Improved Synthesis of N6-(6-Aminohexyl)FAD

Abstract

We report an improved synthesis of N ⁶-(6-aminohexyl)FAD (1) using an efficient one-pot conversion of inosine to the N-trifluoroacetyl protected N ⁶-(6-aminohexyl)adenosine 3. The 5′-O-phosphorylated AMP derivative 4, activated as the imidazolide, was coupled with commercial sodium riboflavin phosphate by using 18-crown-6 in DMF.     

Synthesis of Methylenecyclobutyl- and Cyclobutenyl Adenine,Potent Antiviral Carbocyclic Analogues of Oxetanocin A

Abstract

9-Cyclobutyladenines bearing both methylene and hydroxymethyl groups, 3 and 4, were prepared by dehydration of carbocyclic oxetanocin A (1a). Introduction of a double bond into cyclobutane ring was achieved by allylic oxidation of N ⁶-benzoyl-9-[3-methylenecyclobutyl]adenine (12), which after several steps, afforded 9-[3-(hydroxy-methyl)-2-cyclobutenyl)adenine (5).     

Chemical Synthesis of Cap Analogues: P1,P2-Dinucleoside-5′-diphosphates

Abstract

A procedure was developed for the chemical synthesis of P¹,P²-dinucleoside-5′-diphosphates (N₁(5′)pp(5′)N₂) on a nanomolar scale Reaction conditions for activating purine-5′-monophosphates (pA, pG, and pm⁷G) by 1,1′-carbonyldiimidazole were studied and optimized in respect to solvents and amount of activating reagent used. Various dinucleoside-5′-diphosphates were synthesized in 62-98% yield by incubating activated and non-activated purine-5′-monophosphates. Two unexpected by-products were formed by competition reactions: the imidazolidate of the non-activated nucleotide and the corresponding symmetrically substituted dinucleoside-5′-diphosphate. A mechanism is proposed to explain the observed side reactions.     

Improved Targeting of the Flanks of a DNA Stem Using α-Oligodeoxynucleotides.-The Enhanced Effect of an Intercalator

Abstract

2′-Deoxy-5′-0-(4,4′-dimethoxytrityl)-5-methyl-N ⁴-(1-pyrenylmethyl)-α-cytidine (5) was prepared by reaction of 1-pyrenylmethylamine with an appropriate protected 4-(l,2,4-triazolyl)-α-thymidine derivative 3 which was synthesized from 5-O-DMT protected α-thymidine 1. Aminolysis of 3 afforded 3′-O-acetyl-2′-deoxy-5′-O-(4,4′-dimethoxytrityl)-5-methyl-α-cytidine (8). Benzoylation of 8 and removal of acetyl afforded N ⁴-benzoyl-2-deoxy-5–0-(4,4′-dimethoxytrityl)-5-methyl-α-cytidine (10). The amidites of compounds 5and 10 were prepared and used in α-oligonucleotide synthesis. DNA three-way junction (TWJ) is stabilized when an α-ODN is used for targeting the dangling flanks of the stem in a DNA hairpin. Further stabilization of the TWJ is observed when 5 is inserted into the α-ODN at the junction region.

     

Facile Synthesis of N-(1-Alkenyl) Derivatives of 2,4-Pyrimidinediones

Abstract

N-(1-alkenyl) derivatives of 2,4-pyrimidinediones (6–9) were prepared in a one pot synthesis from aldehydes and the nucleobases using trimethylsilyl trifluoromethanesulfonate (TfOTMS) as coupling reagent. Presilylation of the above nucleobases, and N ⁶-benzoyladenine, with excess N,O-bis(trimethylsilyl)acetamide (BSA) followed by addition of one mol eq. TfOTMS yielded the N-(1-trimethylsilyloxyalkyl) derivatives 1–5.     

Uptake,translocation, and metabolite partitioning of14C-labeled metribuzin in plant growth-regulated soybean (Glycine max)

Plant growth regulator (PGR) application decreased uptake of 10^–6 M¹⁴C-labeled metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one) into leaf interveinal areas of 21-day-old soybean seedlings. BAS 140 810, (N-allyl-N-2-(2,4,6-trichlorophenoxy)ethyl-piperidinium-bromide), as a seed treatment or 10^–6 M triapenthenol or RSW 0411 (B-(cyclohexalmethylene)-gamma-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol) in nutrient solution slowed interveinal unloading of metribuzin and altered metabolite pools. Stems and roots of PGR-treated plants exhibited significantly greater water-soluble metabolite pools than untreated controls. TLC metabolite identification indicated an increase in metribuzin conjugates. This may contribute to the mode of action involved in the apparent safening mechanism. Furthermore, floating leaf disk studies with metribuzin showed plant growth regulation figured prominently in safening against the cessation of oxygen evolution.     

A Simple Synthesis of N4 -(6-Aminohexyl)-2′-Deoxy-5′-O-(4,4′-Dimethoxytrityl)Cytidine

Abstract

The title compound was synthesized by a transamination reaction between N⁴ -benzoyl-2′-deoxy-5′-O-(4,4′-dimethoxytrityl)cytidine and hexane-1,6-diamine in the presence of 1,5,7-triazabicyclo(4.4.0)dec-5-ene (TBD).     

Synthesis of novel selenium containing sulfa drugs and their antibacterial activities

Synthesis of 3-[4-(N-substituted sulfamoyl)phenyl]-3,4-dihydro-4-oxo-7,9-dimethylpyri-do[3′,2′:4,5]selenolo[3,2-d]pyrimidines,7-[4-(N-substituted sulfamoyl)phenyl]-7,8-dihydro-8-oxo-3,4-diphenylpyrimido[4′,5′:4,5]selenolo [2,3-c]pyridazines and 1-[4-(N-substituted sulfamoyl)phenyl]-1,11-dihydro 11-oxo-4-methylpyrimido[4′,5′:4,5]selenolo[2,3-b]quinolines is reported. 4-Amino-N-pyrimidine-2-ylbenzene sulfonamide (a), 4-amino-N-(2,6-dimethylpyrimidin-4-yl)benzene sulfonamide (b), N-[(4-aminophenyl)sulfonyl] acetamide (c) with N-ethoxymethyleneamino of selenolo pyridine, selenolo pyridazine and selenolo quinoline derivatives respectively were obtained starting from 1-amino-N ⁴-substituted sulfanilamides. Spectroscopic data (IR, ¹H NMR, ¹³C NMR and Mass spectral) confirmed the structure of the newly synthesized compounds. Substituted pyrimidines, pyridazines and quinolines were screened for antibacterial activity against gram-positive and gram-negative bacteria. Selenolo derivative of N-[(4-aminophenyl)sulfonyl] acetamide (substitutent of sulfacetamide c) showed strong bactericidal effect against all the tested organisms. Selenolo[3,2-d]pyrimidin (substitutent a) showed a good bactericidal effect against Serratia marcescens, Staphylococcus aureus and Escherichia coli. Compounds selenolo[2,3-c]pyridazine (substitutent b), selenolo[2,3-b]quinoline(substitutents c)) exhibited a moderate bactericidal effect against Serratia marcescens. None of the synthesized seleno pyridazines has a considerable antimicrobial activity against the tested organisms. The minimum inhibitory concentration (MIC) of the most active compound-3-[4-(N-acetyl sulfamoyl)phenyl]-3,4-dihydro-4-oxo-7,9-dimethylpyrido[3′,2′:4,5]selenolo [3,2-d]pyrimidine was 10 mg ml⁻¹.     

Synthesis and bioactivity of 5-(1-aryl-1H-tetrazol-5-ylsulfanylmethyl)-N-xylopyranosyl-1,3,4-oxa(thia)diazol-2-amines

A series of new N′-[N-(2,3,4-tri-O-acetyl-β-d-xylopyranosyl)thiocarbamoyl]-2-[(1-aryl-1H-tetrazol-5-yl)sulfanyl]acetohydrazides 5a–5e were synthesized rapidly in high yields from 2-(1-aryl-1H-tetrazol-5-ylsulfanyl)acetohydrazides 3a–3e and 2,3,4-tri-O-acetyl-β-d-xylopyranosyl isothiocyanate 4, then 5a–5e were converted to a series of new 5-(1-aryl-1H-tetrazol-5-ylsulfanylmethyl)-N-(2,3,4-tri-O-acetyl-β-d-xylopyranosyl)-1,3,4-oxadiazole-2-amines 6a–6e and 5-(1-aryl-1H-tetrazol-5-ylsulfanylmethyl)-N-(2,3,4-tri-O-acetyl-β-d-xylopyranosyl)-1,3,4-thiadiazole-2-amines 7a–7e, respectively under mercuric acetate/alcohol system or acetic anhydride/phosphoric acid system, then deacetylated in the solution of CH₃ONa/CH₃OH. All of the novel compounds were characterized by IR, ¹H NMR, ¹³C NMR, MS and elemental analysis. The structures of compounds 2e, 3e, 5a and 5c have been determined by X-ray diffraction analysis. Some of the synthesized compounds displayed PTP1B inhibition and microorganism inhibition.     

EFFICIENT METHODS FOR THE SYNTHESIS OF [2-15N]GUANOSINE AND 2′-DEOXY[2-15N]GUANOSINE DERIVATIVES

The nucleophilic addition–elimination reaction of 2′,3′,5′-tri-O-acetyl-2-fluoro-O ⁶-[2-(4-nitrophenyl)ethyl]inosine (8) with [¹⁵N]benzylamine in the presence of triethylamine afforded the N ²-benzyl[2-¹⁵N]guanosine derivative (13) in a high yield, which was further converted into the N ²-benzoyl[2-¹⁵N] guanosine derivative by treatment with ruthenium trichloride and tetrabutyl-ammonium periodate. A similar sequence of reactions of 2′,3′,5′-tri-O-acetyl-2-fluoro-O ⁶-[2-(methylthio)ethyl]inosine (9) and the 6-chloro-2-fluoro-9-(β-D-ribofuranosyl)-9H-purine derivative (11), which were respectively prepared from guanosine, with potassium [¹⁵N]phthalimide afforded the N ²-phthaloyl [2-¹⁵N]guanosine derivative (15; 62%) and 9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-6-chloro-2-[¹⁵N]phthalimido-9H-purine (17; 64%), respectively. Compounds 15 and 17 were then efficiently converted into 2′,3′,5′-tri-O-acetyl[2-¹⁵N]guanosine. The corresponding 2′-deoxy derivatives (16 and 18) were also synthesized through similar procedures.     

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.     

Process Development for the Synthesis of 5′-O-(4,4′-Dimethoxytrityl)-N 2-isobutyryl-2′-O-(2-methoxyethyl)-guanosine—A Potential Precursor for the Second Generation Antisense Oligonucleotides: An Improved Process for the Preparation of 2′-O-Alkyl-2,6-diaminopurine Riboside

Abstract

An efficient four step process for the preparation of 5′-O-(4,4′-dimethoxytrityl)-N ²-isobutyryl-2′-O-(2-methoxyethyl)-guanosine 1 was developed. Direct 2′-O-alkylation of 2,6-diaminopurine riboside 2 was accomplished via inexpensive and commercially available reagents such as KOH, DMSO and alkyl halides at room temperature in 4–6 hrs. Pure 2′-O-(2-methoxyethyl)-DAPR 3 was isolated by crystallization from methanol. Enzymatic deamination of 3 followed by selective N ²-isobutyrylation and 5′-O-dimethoxytritylation furnished desired 1 in high yield and purity. Fully optimized four step synthetic process has been scaled up to the pilot plant level.     

Design,Synthesis, and Anti-Tumor Activity of 4′-Thionucleosides as Potent and Selective Agonists at the Human A3 Adenosine Receptor

On the basis of potent and selective binding affinity of Cl-IB-MECA to the human A₃ adenosine receptor, its 4′-thioadenosine derivatives were efficiently synthesized starting from D-gulonic γ -lactone. Among compounds tested, 2-chloro-N ⁶-(3-iodobenzyl)- and 2-chloro-N ⁶-methyl-4′ -thioadenosine-5′ -methyluronamides (7a and 7b) exhibited nanomolar range of binding affinity (K _i = 0.38 nM and 0.28 nM, respectively) at the human A₃AR. These compounds showed anti-growth effects on HL-60 leukemia cell, which resulted from the inhibition of Wnt signaling pathway.     

Synthesis and Anti-HIV Activity of 5-Fluorocytallene: N-Dimethylaminomethylene as a Facilitating Group in Acetylene → Allene Isomerization

Abstract

The synthesis and biological activity of 5-fluorocytallene (3a) is described. 5-Fluorocytosine (4) was alkylated with 1-benzoyloxy-4-bromo-2-butyne (5) to give N¹-(4-benzoyloxy-2-butyn-1-yl)-5-fluorocytosine (6). Debenzoylation led to N¹-(4-hydroxy-2-butyn-1-yl)-5-fluorocytosine (7a). The latter compound was transformed to the N⁴-dimethylaminomethylene derivative 8 which was isomerized in situ to the corresponding allene 9. Deprotection afforded 5-fluorocytallene (3a). Compound 3a suppressed the infectivity and replication of both laboratory and primary HIV-1 strains in vitro at nontoxic concentrations.     

Nucleosides and Nucleotides. 192. Toward the Total Synthesis of Cyclic ADP-Carbocyclic-Ribose. Formation of the Intramolecular Pyrophosphate Linkage by a Conformation-Restriction Strategy in a Syn-form Using a Halogen Substitution at the 8-Position of the Adenine Ring

Abstract

The synthesis of cyclic ADP-carbocyclic-ribose (2), as a stable mimic for cyclic ADP-ribose, was investigated. Construction of the 18-membered backbone structure was successfully achieved by condensation of the two phosphate groups of 19, possibly due to restriction of the conformation of the substrate in a syn-form using an 8-chloro substituent at the adenine moiety. SN2 reactions between an optically active carbocyclic unit 8, which was constructed by a previously developed method, and 8-bromo-N ⁶-trichloroacetyl-2′,3′-O-isopropylideneadenosine 9c gave N-1-carbocyclic derivative, which was deprotected to give 5′,5′-diol derivatives 18. When 18 was treated with POCl₃ in PO(OEt)₃, the bromo group at the 8-position was replaced to give N-1-carbocyclic-8-chloroadenosine 5′,5′-diphosphate derivative 19 in 43% yield. Treatment of 19 with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride gave the desired intramolecular condensation product 20 in 10% yield. This is the first chemical construction of the 18-membered backbone structure containing an intramolecular pyrophosphate linkage of a cADPR-related compound with an adenine base.