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.     

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.     

The IBR5 phosphatase promotes Arabidopsis auxin responses through a novel mechanism distinct from TIR1-mediated repressor degradation

Background  

In Arabidopsis, INDOLE-3-BUTYRIC ACID RESPONSE5 (IBR5), a putative dual-specificity protein phosphatase, is a positive regulator of auxin response. Mutations in IBR5 result in decreased plant height, defective vascular development, increased leaf serration, fewer lateral roots, and resistance to the phytohormones auxin and abscisic acid. However, the pathways through which IBR5 influences auxin responses are not fully understood.     

The human MSH5 (MutS Homolog 5) protein localizes to mitochondria and protects the mitochondrial genome from oxidative damage

MutS homologs play a central role in maintaining genetic stability. We show that MSH5 (MutS Homolog 5) is localized into the mitochondria of germ and somatic cells. This protein binds to mtDNA and interacts with the Twinkle helicase and the DNA polymerase gamma. hMSH5 stimulates mtDNA repair in response to DNA damage induced by oxidative stress. Furthermore, we observed a subsarcolemmal accumulation of hMSH5 in COX negative muscle fibers of patients presenting a mitochondrial myopathy. We report a novel localization for hMSH5 suggesting that this protein may have functions other than those known in meiotic recombination.     

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).     

Effectiveness of ph gene in inducing homoeologous chromosome pairing in agrotricum

Summary We observed pairing, when the ph gene was present, between wheat (Triticum aestivum L. em. Thell.) chromosome 4B, and an Agropyron intermedium (Host) Beauv. chromosome (Ai) carrying a gene resistant to wheat streak mosaic (WSM). In a monosomic addition polyhaploid [2n = 22 = 19' + 5B' (ph) + 4B' + Ai'], we recorded an average of 4.1 bivalents and 0.3 trivalents per cell. Induced homoeologous pairing was most effective when both 5B chromosomes carrying ph gene were present. Our data suggest that chromosome 4B of wheat and the Agropyron chromosome (Ai) carrying a gene for resistance to WSM are homoeologous and that it is possible to use either ph mutant or nullisomic 5B stock to induce genetic recombination between the two chromosomes.Contribution No. 1657-j, Kansas State Agric. Expt. Sta., Manhattan, KS. The research is partially supported by a grant from Kansas Wheat Commission     

Conformations of cyclic 3',5'-nucleotides. Effect of the base on the synanti conformer distribution

The furanose and the phosphate rings of cyclic 3′,5′-nucleotides are locked in the ₄T³ and chair conformations respectively. The only variable which shows major conformational flexibility in these molecules is the rotation about the glycosyl bond which describes the orientation of the base relative to the sugar-phosphate bicyclic system. The glycosyl torsion angle has been analyzed for cyclic nucleotides with different purine and pyrimidine bases by use of conformational energy calculations. The results indicate that all the pyrimidine bases, U, T and C show a very strong energetic preference for the anti range of conformations. The calculations predict that among cyclic 3′,5′-purine nucleotides cyclic GMP and cyclic IMP favor the syn conformation to the anti by 95:5 and 70:30 respectively, while cyclic AMP shows a preference for the anti conformation to syn by 70:30. Thus the purines show a greater probability for the syn conformation than the pyrimidines in cyclic 3′,5′-nucleotides.     

Conformation and Antiherpes Activity of 3′- and 5′-Azido and Amino Analogs of 5-Methoxymethyl-2′-Deoxyuridine

Abstract

The molecular conformations of 3′- and 5′-azido and amino derivatives of 5-methoxymethyl-2′-deoxyuridine, 1, were investigated by nmr. The glycosidic conformation of 5-methoxymethyl-5′-amino-2′,5′-dideoxy-uridine, 5 had a considerable population of the syn form. The 5′-derivatives show a preference for the S conformation of the furanose ring as in 1. In contrast, the 3′-derivatives show preference for the N conformation. For 5-methoxymethyl-3′-amino-2′,3′-dideoxyuridine, 3, the shift towards the N state is pH dependent. The preferred conformation for the exocyclic (C4′,C5′) side chain is g⁺ for all compounds except 5 which has a strong preference for the t rotamer (79%). Compounds 1, 3 and 5 inhibited growth of HSV-1 by 50% at 2, 18 and 70 μg/ml respectively, whereas 2 and 4 were not active up to 256 μg/ml (highest concentration tested). The compounds were not cytotoxic up to 3,000 μM.     

Growth of selected fungi on leaf-protein supernatant

Summary Some 19 strains ofAspergillus niger,A. oryzae, andPaccilomyces spp. are tested for their ability to grow on the supernatant remaining after the expressed juice from sugar beet tops and meadow grass has been heat-treated to precipitate crude leaf protein, and supplemented as required by glucose or ammonium sulphate. With effective strains ofA. niger,A. oryzae,P. elegans orP. variotii and an optimized carbohydrate/nitrogen ratio, over 70% of the organic content of the supernatant is rapidly converted into mycelial biomass of high protein content.     

Crown gall transformation of lentil (Lens culinaris Medik.) with virulent strains of Agrobacterium tumefaciens

Summary Four diverse strains of Agrobacterium tumefaciens (C58, Ach5, GV3111, and A281) were capable of inducing tumors at a high frequency on inoculated stems of lentil (Lens culinaris Medik. cultivar Laird) in vivo, and on excised shoot apices in vitro. GV3111 and Ach5 produced the largest and heaviest tumors in vivo, while A281 produced the heaviest tumors in vitro. Tumor formation and opine production are indicative of plant cell transformation and tumors produced appropriate opines: nopaline (C58), octopine (Ach5 and GV3111), and agropine and mannopine (A281). Southern analysis of DNA from a tumor line produced by strain C58 showed that a T-DNA fragment had been transferred into the lentil genome.     

Synthesis of Some Novel 1-(5-Thio-ß-D-glucopyranosyl)-6-azauracil Derivatives - Thiosugar Nucleosides

Abstract

The chemical syntheses of 1-(2,3,4,6-tetra-0-acety]-5-thio-β-D-glucopyranosyl)-6-azauracil (4) and the 5-bromo analogue 6 are described. Deblocking of 4 and 6 with sodium methoxide afforded the free nucleosides 5 and 7, respetively. Treatment of 6 with benzylmercaptan in basic medium led to the formation of 6-benzylthio-1-((2,3,4,6-tetra-0-acetyl-5-thio-β-D-glucopyranosyl)-6-azauracil (8), in good yield, which was deblocked to 9 on treatment with sodium methoxide. Reaction of 6 with benzlamine gave 5-benzylamino-1-(5-thio-β-D-glucopyranosyl)-6-azauracil (10).     

Spectrophotometric titrations of ferricytochrome C with ferrohexacyanide in the pH range 5 to 7

Spectrophotometric titrations were conducted on the system horse heart ferricytochromec plus ferrohexacyanide in the pH range 5 to 7 and at temperatures 8, 18, 22 and 28°C. A difference extinction coefficient for reducedvs. oxidized cytochromec at 550 nm of 21 mmol^–1cm^–1 was used in part of the evaluations. On the assumption that only one electron-transferlinked proton dissociation is effective for both ferro- and ferricytochromec in this pH range, various possible models are developed with only three conforming with the experimental pH dependence of the spectrophotometric equilibrium constant. The data conform best to a model with protonic dissociation constants between pH 5 and 7 such that the reduced cytochromec species is at least a factor of 3 more acidic than the one for oxidized cytochromec (with pK_H 6). This interpretation holds least for the data at 22°C, which points to a structural rearrangement at about this temperature (Czerlinski and Bracokova, 1973; Zabinski and Czerlinski, 1974; Zabinski, et al., 1974). While the extinction coefficient of ferrocytochromec shows no significant change with pH and temperature, the one for ferricytochromec does: it is about 5% larger at pH 5 than at pH 7 (550 nm). Graphs for the absorption change of ferricytochromec (pH 7 as reference) document the details over the wavelength range 500 to 750 nm.     

Towards a classification ofE. coli ribosomal proteins: A hypothetical ‘small ribosome’ as a primitive protein-synthesizing apparatus

Homologies were searched among the published primary sequences of 51E. coli ribosomal proteins, partly by eye and partly by computer-assisted methods. By employing Moore and Goodman's alignment statistics for evaluating homology levels, 33 out of these 51 ribosomal proteins has been classified into 9 homology groups, some of which being yet tentative and remaining to be further analyzed. Taking it into consideration that most ribosomal protein genes are clustered atstr-stc region,rif region and several other regions, these results strongly suggest that most or all of the contemporary ribosomal proteins must have evolved by repeated gene duplications ofvery few (oronly one) primitive ancestral ribosomal protein gene(s). Thus it is most reasonable to propose that a small ribosome consisting of very few (or only one) ribosomal protein(s) must have existed as a primitive protein-synthesizing apparatus.     

Synthesis and Biological Activity of C-Acyclic Nucleosides of Imidazo [1,5-a]-1,3,5-Triazines

Abstract

C-acyclic nucleoside analogues of inosine and guanosine 8-[(RS)-2,3-dihydroxypropyl] imidazo [1,5-a]-1,3,5-triazin-4 (3H)-ones 6a, c, d were synthesized. The route involved the cyclization-rearrangement of 5-acylamino-5-allyl-6-amino-4,5-dihydropyrimidin-4-ones 4a-c to 8-allylimidazo [1,5-a]-1,3,5-triazin-4 (3H) ones 5a-c. 5a was transformed selectively into 5d by reductive desulfurization with highly deactivated Raney nickel. The poorly soluble compounds 5b and 5c were converted to N-2-acetylated 5f and 5g. Osmium tetroxide hydroxylation of 5d, f, g gave 6a, c, d. None of the newly synthesized C-acyclic nucleoside derivatives showed an appreciable antiviral or antitumor cell activity.     

Nucleosides,I Ribosylation of 8-Substituted Theophylline Derivatives

Abstract

The attempted ribosylation reaction of 8-nitro-theophylline (2) with 1-o-acetyl-2, 3, 5-tri-o-benzoyl-D-ribo-furanose (5) failed to give any nucleoside product, whereas the reaction of 8-chlorotheophylline (3) with 5 afforded the 8-chloro-7-(2,3,5-tri-o-benzoyl) β-D-ribofuranosyltheophylline (6) in good yield. The product 6 reacted with benzylamine producing the 8-benzylamino-7-(2, 3, 5-tri-O-benzoyl) β-D-ribo-furanosyltheophylline (10), which could also be synthesised by ribosylation of 8-benzylaminotheophylline (8) with 5. Debenzoylation of 6 and 10 gave the corresponding 7-β-D-ribofuranosyltheophylline nucleosides (7) and (11), respectively. Compound 7 could be converted into 11 by reaction with benzylamine. The newly synthesised compounds have been characterised by elemental analysis, ¹H-NMR and UV spectra.     

3′-3′,3′-5′ and 5′-5′ TpT-Amides: Synthesis,Characterization and Alkaline Hydrolysis

Abstract

A simple procedure is described for the preparation of the title compounds 1, 8 and 9. 3′-3′ or 3′-5′ or 5′-5′ TpT was reacted with a twofold molar excess of TPS in anhydrous DMF, at room temperature, for 5 min, followed by a 1 min in situ treatment of the reaction mixture with excess 7.0 N NH₄OH, at 0°C. The alkaline hydrolysis of 1, 8 and 9 proceeds without the assistance of 3′- and 5′-hydroxyl groups resulting in equimolar mixtures of thymidine (4) and thymidine 3′-phosphoramidate (6) (for the 3′-3′ isomer) or thymidine 5′-phosphoramidate (7) (for the 5′-5′ isomer) or 6 and 7 in equal quantities (for the 3′-5′ isomer).     

Molecular cloning and expression of s-(2-aminoethyl)-L-cysteine resistant aspartokinase gene ofCorynebacterium glutamicum

Summary A 2.9 kb DNA fragment encoding s-(2-aminoethyl)-l-cysteine (AEC) resistant aspartokinase ofCorynebacterium glutamicum was cloned on theC. glutamicum/E. coli shuttle vector pECCG117. A recombinant plasmid, designated pAK12, conferred the AEC resistance, the ability to excrete lysine and threonine, and the 3–5 fold increased specific activity of aspartokinase to host strain.     

Synthesis and Antiviral Activity of 5′-O-Sulfamoyluridine Derivatives

Abstract

A series of 5′-O-[[[[(alkyl)oxy]carbonyl] amino] sulfonyl] uridines have been synthesized by reaction of cyclohexanol, palmityl alcohol, 1,2-di-O-benzoylpropanetriol and 2,3,4,6-tetra-O-benzoyl-L-glucopyranose with chlorosulfonyl isocyanate and 2,3′-O-isopropylidene-uridine. Another series of 5′-O-(N-ethyl and N-isopropylsulfamoyl) uridines have been prepared by reaction of 2′,3′-O-isopropylidene and 2′,3′-di-O-acetyluridine with N-ethylsulfamoyl and N-isopropylsulfamoyl chlorides. All compounds were tested against HSV-2, VV, SV and ASFV viruses. 2′,3′-Di-O-acetyl-5′-O-(N-ethyl and N-isopropylsulfamoyl) uridine showed significant activities against HSV-2. 5′-O-[[[[(2,3,4,6-Tetra-O-benzoyl-β-L-glucopyranosyl)oxy]carbonyl]amino] sulfonyl]-2′,3′-O-isopropylideneuridine was very active against ASFV.     

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).