2′-(E)-O-p-coumaroylgalactaric acid and 2′-(E)-O-feruloylgalactaric acid in citrus

2′-(E)-O-p-Coumaroyl- and 2′-(E)-O-feruloylgalactaric acids, hitherto unknown in nature, have been isolated and identified from orange peel.     

5′-O-[N-(Amnoacyl)Sulfamoyl]Nucleosides. Synthesis and Antiviral and Cytostatic Activities

Abstract

5′-O-[N-(Aminoacyl)sulfamoyl]-uridines and -thymidines 4a-12a and 4b-12b have been synthesized and tested against Herpes Simplex virus type 2 (HSV-2) and as cytostatics. Condensation of 2′,3′-O-isopropylidene-5′-O-sulfamoyluridine and 3′-O-acetyl-5′-O-sulfamoylthymidine with the N-hydroxysuccinimide esters of Boc-L-Ser(Bzl), (2R, 3S)-3-benzyloxycarbonylamino-2-hydroxy-4-phenylbuta-noic acid [(2R, 3S-N-Z-AHPBA], (2R, 3S) and (2S, 3R)-N-Boc-AHPBA gave 4a,b-7a,b, which after removal of the protecting groups provided 1Oa,b-12a,b. A study of the selective removal of the O-Bzl protecting group from the L-Ser derivatives 4a,b, without hydrogenation of the pyrimidine ring, has been carried out. Only the fully protected uridine derivatives 4a-7a did exhibit high anti-HSV-2 activity, and none of the synthesized compounds showed significant cytostatic activity against HeLa cells cultures.     

Synthesis and Biological Effects of 5′-Deoxy-5′-(Cyclo-Propylmethylthio)Adenosine

Abstract

A novel synthesis of the nucleoside analog, 5′-deoxy-5′-(cyclopropylmethylthio)adenosine (CPMTA, 1) has been developed. CPMTA is a closely related structural analog of 5′-deoxy-5′-(isobutylthio)-adenosine (SIBA, 2), which has been widely studied and shown to exert a multitude of biological effects. The in vitro and in vivo antitumor (L1210 leukemia) activity of CPMTA has been found to be comparable to that of SIBA, whereas its in vitro antiviral (HSV and VSV) activity is diminished. These agents are being developed as inhibitors of methylation and/or polyamine synthesis.     

Template-directed oligomerization of 5′-deoxy-5′-nucleosideacetic acid derivatives

5-Deoxy-5-nucleosideacetic acids II–V are isostructural analogues of nucleotides with a carboxylate group in the place of the 5-phosphate group. We have studied their oligomerization in aqueous solution using a water-soluble carbodiimide as the condensing agent in the presence or absence of an appropriate polynucleotide template. Condensation of adenylic acid analogues IIa, IIIa, and Va in the presence of polyuridylic acid were found to be the most efficient reactions. Cyclization of the activated monomers to lactones and the insolubility of the oligomers in aqueous solution were found to be obstacles to the efficient formation of long oligomers.     

Synthesis and antibacterial activity of 5′-tetrachlorophthalimido and 5′-azido 5′-deoxyribonucleosides

Reported is an efficient synthesis of adenyl and uridyl 5′-tetrachlorophthalimido-5′-deoxyribonucleosides, and guanylyl 5′-azido-5′-deoxyribonucleosides, which are useful in solid-phase synthesis of phosphoramidate and ribonucleic guanidine oligonucleotides. Replacement of 5′-hydroxyl with tetrachlorophthalimido group was performed via Mitsunobu reaction for adenosine and uridine. An alternative method was applied for guanosine which replaced the 5′-hydroxyl with an azido group. The resulting compounds were converted to 5′-amino-5′-deoxyribonucleosides for oligonucleotide synthesis. Synthetic intermediates were tested as antimicrobials against six bacterial strains. All analogs containing the 2′,3′-O-isopropylidine protecting group demonstrated antibacterial activity against Neisseria meningitidis, and among those analogs with 5′-tetrachlorophthalimido and 5′-azido demonstrated increased antibacterial effect.     

Synthesis of 5′-Fluoro-5′-deoxy-and 5′-Amino-5′-Deoxytoyocamycin and Sangivamycin and Some Related Derivatives

Abstract

A series of 5′-substituted analogs of toyocamycin were prepared by condensation of silylated 4-amino-6-bromo-5-cyanopyrrolo[2,3-d]pyrimidine with protected 5-azido-5-deoxy- or 5-fluoro-5-deoxyribofuranose followed by debromination and deblocking. Alternatively, 5′-azido-5′-deoxytoyocamycin was prepared by azidation of toyocamycin. Conversion of the 5-nitrile function of the toyocamycin derivatives into a carboxamide or a thiocarboxamide gave the corresponding analogs of sangivamycin or thiosangivamycin while reduction of the 5′-azido-5′-deoxy nucleosides provided 5′-amino-5′-deoxy derivatives.     

Polynucleotides. LII1 Synthesis and properties of poly(2′-deoxy-2′-fluoroadenylic acid)

2′-Deoxy-2′-fluoroadenosine was chemically transformed to its 5′-diphosphate and polymerized with polynucleotide phosphorylase to give poly(2′-deoxy-2′-fluoroadenylic acid) [poly(Af)]. Polymerization proceeded smoothly as in the case of poly(A) and the yield of the polymerization was 55%. The UV absorption spectra of poly(Af) closely resembled those of poly(A) and the hypochromicity was 32% at pH 7.0. The CD profile at 25° and neutrality showed similar pattern to that of other poly(2′-deoxy-2′-halogenoadenylic acids) with somewhat larger [θ] values both in the positive and negative maxima. Acid titration of poly(Af) showed a transition point at pH 5.2 and the Tm of the acid form was 37° which was significantly lower than that of poly(A), but similar to that of poly(2′-azido-2′-deoxyadenylic acid). Poly(Af) formed 1:1 and 1:2 complexes with poly-(U) having Tm of 49° and 62° at 0.04M and 0.15M Na⁺ concentration, respectively. Poly(Af) also formed a 1:2 complex with poly(I) and its Tm was 36° at 0.05M Na⁺ concentration. These data showed that poly(Af) has rather similar properties to those of poly(A), but not to poly(dA).     

The 5′-Nor Aristeromycin Analogues of 5′-Deoxy-5′-Methylthioadenosine and 5′-Deoxy-5′-Thiophenyladenosine

To extend the potential of 5′-noraristeromycin (and its enantiomer) as potential antiviral candidates, the enantiomers of the carbocyclic 5′-nor derivatives of 5′-methylthio-5′-deoxyadenosine and 5′-phenylthio-5′-deoxyadenosine have been synthesized and evaluated. None of the compounds showed meaningful antiviral activity.     

Amino acid activation with adenosine 5′-phosphorimidazolide

Summary Amino acids are activated by reaction with adenosine 5-phosphorimidazolide in aqueous imidazole buffers. If adenosine 5-(O-methylphosphate), an analogue of the 3-terminus of t-RNA is present, 2(3)-O-aminoacyladenosine 5-(O-methylphosphate) is formed. Fifteen percent of this compound accumulated at pH 5.8, but less was formed at higher pHs. The highest efficiency of utilization of ImpA attained in our experiments was about 24%. Analogous reactions occured with several other amino acids, including a number that have functional side-chains.Abbreviations pA adenosine 5-monophosphate - MepA adenosine-5-(O-methylphosphate) - ImpA adenosine-5-phosphorimidazolide - A adenosine - MepA-ala 2(3)-O-alanyl-adenosine-5-(O-methylphosphate) - ala-N-pA adenylyl-(5 N)-alanine - ImH imidazole - DKP diketopiperazine     

Structural and thermodynamic analysis of the conformational states of self-complementary hexanucleotides 5′-d(GCATGC) and 5′-d(GCTAGC) in Aqueous Solution

The conformational states of hexanucleotides 5′-d(GCATGC) and 5′-d(GCTAGC) capable of forming hairpins in aqueous solution were studied by 1D and 2D ¹H NMR and molecular dynamics. The equilibrium thermodynamic parameters were determined for the formation of duplexes and hairpins, and the spatial structures were computed for the GCATGC and GCTAGC conformers. The mobility of the hexamer constituents was evaluated by nanosecond molecular dynamics simulation. The possible causes of the observed difference in the thermodynamic stability of the duplex and the hairpin are discussed.     

Enzymatic Synthesis of Bis(5′-Nucleosidyl) Tetra- and Triphosphates

The total fraction of aminoacyl-tRNA synthases from Escherichia coli has been shown to catalyze the synthesis of the bis(5′-nucleosidyl) oligophosphates Ap₄AZT, Ap₄d4T, Ap₄3TC, and Ap₄ACV, as well as Ap₃AZT and Ap₃d4T, from [α-³²P]ATP and the corresponding nucleoside-5′-tri(or di)phosphate. The resulting compounds, characterized by HPLC, are resistant to alkaline phosphatase. Ap₄AZT, Ap₄d4T, and Ap₄3TC are formed with approximately equal efficiency, whereas the efficiencies of the synthesis of Ap₄ACV, Ap₃AZT, and Ap₃d4T are three- to fivefold lower.     

Semi-rational chemical modification of endoinulinase by pyridoxal 5′-phosphate and ascorbic acid

It is important to improve the quality of the enzyme inulinase used in industrial applications without allowing the treatment to have any adverse effects on enzyme activity. We achieved preferential chemical modification of the non-catalytic domain of endoinulinase (EC 3.2.1.7) to enhance the thermostability of the enzyme. We used pyridoxal 5′-phosphate (PLP) to modify the more accessible lysine residues at the surface of endoinulinase and then performed a necessary step of reduction with ascorbate. Endoinulinase was incubated in the presence of PLP at various concentrations; this step was followed by reduction of the resulting Schiff base and dialysis. The effects of different PLP concentrations and incubation times on enzyme modification were evaluated. Enzyme deactivation was observed immediately after treatment, even at low PLP concentrations, while reactivation was observed for samples treated with low PLP concentrations after a period of time. Structural analysis revealed that the α-helix content increased from 13.60% to 17.60% after applying the modification strategy; consequently, enzyme stabilization was achieved. The melting temperature (T_m) of the modified enzyme increased from 64.1 °C to 72.2 °C, and a comparative study of thermal stability at 25 °C, 45 °C, and 50 °C for 150 min confirmed that the enzyme was stabilized because of increase in its half-life (t_1/2) after PLP modification/ascorbate reduction. The modification process was optimized to achieve the optimum mole ratio for the PLP/endoinulinase (1.37). Excess moles of the modifier are thought to be responsible for enzyme deactivation through unwanted/nonspecific and noncovalent interactions, and the optimization ensured that there was no excess modifier after the desired covalent reaction was complete.     

Stereocontrolled Facile Synthesis and Biological Evaluation of (3′S) and (3′R)-3′-Amino (and Azido)-3′-Deoxy Pyranonucleosides

This article describes the synthesis of (3 ′S) and (3 ′R)-3 ′-amino-3 ′-deoxy pyranonucleosides and their precursors (3 ′S) and (3 ′R)-3 ′-azido-3 ′-deoxy pyranonucleosides. Azidation of 1,2:5,6-di-O-isopropylidene-3-O-toluenesulfonyl-α-D-allofuranose followed by hydrolysis and subsequent acetylation afforded 3-azido-3-deoxy-1,2,4,6-tetra-O-acetyl-D-glucopyranose, which upon coupling with the proper silylated bases, deacetylation, and catalytic hydrogenation, obtained the target 3 ′-amino-3 ′-deoxy-β-D-glucopyranonucleosides. The desired 1-(3 ′-amino-3 ′-deoxy-β-D-allopyranosyl)5-fluorouracil was readily prepared from the suitable imidazylate sugar after azidation followed by a protection/deprotection sequence and reduction of the unprotected azido precursor. No antiviral activity was observed for the novel nucleosides. Moderate cytostatic activity was recorded for the 5-fluorouracil derivatives.     

Stereospecific assignment of H5′ and H5″ in a (5′R)-/(5′S)-deuterium- labeled DNA decamer for3 JHH determination and unambiguous NOE assignments

The stereoselective deuterium labeling at the 5' methylene protons of the ribose ring recently developed by Kawashima et al. [1995, Tetrahedron Lett., 36, 6699–6700] enabled the assignment of pro-R and pro-S protons at the 5' position. The deuterium-labeled nucleotides, [(5'S)-²H]- and [(5'R)-²H]-diastereomers, in an approximate ratio of 2:1, were incorporated in the decamer 5'-d(GCATTAATGC)-3'. Thus, both pro-R and pro-S methylene proton signals without geminal coupling appeared in the NOESY and DQF-COSY spectra. Complete stereospecific assignments and simplified spin systems enabled the determination of 15 ³J coupling constants between H4' and H5'/H5", and the unambiguous assignment of 135 NOESY cross peaks originating from H4'/H5'/H5" resonances.     

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).     

Enantiospecific Synthesis of 5′-Noraristeromycin and its 7-Deaza Derivative and A Formal Synthesis of (-)-5′-Homoaristeromycin

Abstract

Beginning with the treatment of the diacetate of cis-3,5-cyclopentenediol (5) with Pseudomonas cepacia lipase, (-)-5′-noraristeromycin (1) and (-)-7-deaza 5′-noraristeromycin (3) have been prepared. Subjecting 5 to treatment with porcine liver esterase led to an efficient preparation of a substituted cyclopentane precursor which, following literature precedence, can be converted into (-)-5′-homoaristeromycin (4).     

The kinetics and mechanism of the reaction of 2′-deoxy-5′-guanosinemonophosphoric acid and the diaqua form of cis-platin

2′-Deoxy-5′-guanosinemonosphoric acid (B) reacts with cis-[Pt(NH₃)₂(OH₂)₂]²⁺ in two steps to form the cis-[Pt(NH₃)₂B₂]^y+ ion. In the first step 2′-d-5′- GMPH₂ reacts some ten times faster than 5′-GMPH₂ does. Rate constants, ΔH^#, ΔS^# and ΔV^# are very similar for the two bases in the second reaction. It is proposed that the product in the first step contains no water and is cis-[Pt(NH₃)₂B]^x+ in which the nucleobase is bidentate bonding through both N(7) of guanine and an oxygen atom of the phosphate group.