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1.
3,5-Di-O-acetyl-6,7-dideoxy-1,2-O-isopropylidene-β-L-ido- and α-d-gluco-hept-6-ynofuranose were separately deacetonated, and the products acetylated, to give the 1,2,3,5-tetra-O-acetyl analogs (2 and 6). Fusion of compounds 2 and 6 with 2,6-dichloropurine under acid catalysis produced 2,6-dichloro-9-(2,3,5-tri-O-acetyl-6,7-dideoxy-α-L-ido-hept-6-ynofuranosyl)-9H-purine (3) and its β-d-gluco analog 7, respectively. Methanolic ammonia converted 3 in good yield into 2-chloro-9-(6,7-dideoxy-α-L-ido-hept-6-ynofuranosyl)-6-methoxy-9H-purine. Treatment of compound 3 with mesityl nitrile oxide gave a “double-headed nucleoside” analog. Upon treatment with phenyl azide, the d-gluco derivative 7 produced another “double-headed nucleoside”. Fusion of 2 and 6 with p-nitrophenol yielded the respective p-nitrophenyl glycosides. The stereochemistry and regiospecificity of the reactions were verified spectroscopically.  相似文献   

2.
(2′,3′-O-Isopropylidene-5′-uridyl) 4-(2,3,4,6-tetra-O-acetyl-β-d-glycopyranosyl)allophanates were obtained in the reactions of 2′,3′-O-isopropylidene-uridine and O-peracetylated β-d-gluco-, galacto- and xylopyranosylamines, and OCNCOCl. 2,3,4,6-Tetra-O-acetyl-β-d-glucopyranosyl isocyanate and N-(2′,3′-O-isopropylidene-5′-uridyl)urea gave 1-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-5-(2′,3′-O-isopropylidene-5′-uridyl)biuret. Deprotection of the β-d-gluco configured allophanate and biuret was carried out by standard methods.  相似文献   

3.
O-Peracetylated methyl 3-(d-glycopyranosylthio)propanoates of β-d-gluco, and α- and β-d-galacto configurations were oxidized to the corresponding S,S-dioxides (sulfones) by Oxone® or MCPBA. Oxidation of the β-d-gluco derivative with H2O2/Na2WO4 gave the corresponding S-oxide (sulfoxide). DBU-induced elimination of methyl acrylate from the β-d-gluco and β-d-galacto configured S,S-dioxides (sulfones) gave O-peracetylated β-d-glycopyranosyl-1-C-sulfinates which, on treatment with H2NOSO3H, furnished the corresponding β-d-glycopyranosyl-1-C-sulfonamides. Radical-mediated bromination of the protected methyl 3-(β-d-glycopyranosylthio)propanoate S,S-dioxides gave mixtures of 1-C- and 5-C-bromoglycosyl compounds. Similar brominations of the O-peracetylated β-d-glycopyranosyl-1-C-sulfonamides resulted in the formation of α-d-glycopyranosyl bromides and 1-C- and 5-C-bromoglycosyl sulfonamides. A rationale for these observations was proposed. Methyl 3-(β-d-glucopyranosylthio)propanoate, its S,S-dioxide, and β-d-glucopyranosyl-1-C-sulfonamide proved inefficient when tested as inhibitors of rabbit muscle glycogen phosphorylase b.  相似文献   

4.
Glycosyl 1,2,3-triazoles with α-d-gluco, β-d-gluco, α-d-galacto, β-d-galacto and β-2-acetamido-2-deoxygluco (GlcNAc) stereochemistry were prepared by reaction of the corresponding azides with vinyl acetate under microwave irradiation. The deprotected glucosyl and galactosyl triazoles did not display inhibitory activity against the tested glycosidases at 1 mM. Of the four fungal glycosidases evaluated, GlcNAc-triazole was found to be hydrolyzed by Talaromyces flavus CCF 2686 β-N-acetylhexosaminidase. β-GlcNAc-triazole was furthermore established to act as a strong ligand of rat and human natural killer cell activating receptors.  相似文献   

5.
《Carbohydrate research》1986,148(2):279-285
2,3,4,6,1′,3′,4′-Hepta-O-benzylsucrose, obtained by acid-catalysed hydrolysis of the 6′-O-trityl derivative, was oxidised with the Pfitzner-Moffatt reagent and the product was alkylated with methylmagnesium iodide. Removal of the protecting groups then gave a mixture of diastereomers, namely 7-deoxy-β-d-altro and -α-l-galacto-hept-2-ulofuranosyl α-d-glucopyranoside. Application of this reaction sequence to 2,3,4,1′,3′,4′,6′-hepta-O-benzylsucrose afforded β-d-fructo-furanosyl 7-deoxy-dl-glycero-α-d-gluco-heptopyranoside.  相似文献   

6.
O-Peracetylated 1-(β-d-glucopyranosyl)-5-phenylbiuret was prepared in the reaction of O-peracetylated β-d-glucopyranosylisocyanate and phenylurea. The reaction of O-peracetylated N-β-d-glucopyranosylurea with phenylisocyanate furnished the corresponding 1-(β-d-glucopyranosyl)-3,5-diphenyl- as well as 3-(β-d-glucopyranosyl)-1,5-diphenyl biurets besides 1-(β-d-glucopyranosyl)-3-phenylurea. O-Peracetylated 1-(β-d-glucopyranosyl)-5-(β-d-glycopyranosyl)biurets were obtained in one-pot reactions of O-peracetylated β-d-glucopyranosylamine with OCNCOCl followed by a second glycopyranosylamine of β-d-gluco, β-d-galacto and β-d-xylo configurations. O-Acyl protected 1-(β-d-glucopyranosyl)-3-(β-d-glycopyranosylcarbonyl)ureas were obtained from the reaction of β-d-glucopyranosylisocyanate with C-(glycopyranosyl)formamides of β-d-gluco and β-d-galacto configurations. The O-acyl protecting groups were removed under acid- or base-catalyzed transesterification conditions, except for the N-acylurea derivatives where the cleavage of the N-acyl groups was faster than deprotection. Some of the new compounds exhibited moderate inhibition against rabbit muscle glycogen phosphorylase b and human salivary α-amylase.  相似文献   

7.
When kept at 105° for 2.5 h, weakly alkaline, syrupy d-erythrose was readily converted into a mixture containing mainly d-glycero-tetrulose, the previously unknown β-d-altro-l-glycero-3-octulofuranose (2), and α-d-gluco-l-glycero-3-octulopyranose, which were isolated as the corresponding acetates. Treatment of 2 with Dowex 50 (H+) resin yielded 3,8-anhydro-β-d-altro-l-glycero-octulopyranose, identified as its acetate. Previous discrepancies in the [α]d values for d-erythrose appear partly to originate in the self-aldol reaction. The dimerisation of d-erythrose 4-phosphate is also described.  相似文献   

8.
3,4,5,6,7-Penta-O-acetyl-1,2-dideoxy-1-nitro-d-gluco- and -d-galacto-hept-1-enitol and 3,4,5,6-tetra-O-acetyl-1,2-dideoxy-1-nitro-d-xylo-hex-1-enitol react with 3-aminocrotonic esters, yielding mixtures of the epimeric Michael adducts. These are thermally stable, and do not cyclize to pyrroles. The structures, configurations, and conformations of these compounds were established on the basis of their spectroscopic and X-ray crystallographic data. The intramolecularly bonded, (Z) configuration was deduced for all of them. Mild hydrolysis of adducts with acid yields the corresponding 2-(nitromethylpolyacetoxyalkyl)acetoacetates.  相似文献   

9.
Oxidative dimerization of 7,8-dideoxy-1,2:3,4-di-O-isopropylidene-d-glycero-α-d-galacto-oct-7-ynopyranoside (1) gave a high yield of the diyne 2, readily reduced by lithium aluminum hydride to the trans,trans-diene (4). The structures of 2 and 4 were established spectroscopically and by degradation of 4 to d-glycero-d-galacto-heptitol (perscitol). A mixture of the alkyne 1 and its 7-epimer 10 was readily oxidized by dimethyl sulfoxide-acetic anhydride to the 6-ketone 11, and the 8-alkene analog was similarly prepared from the alkenes derived from 1 and 10. Likewise, oxidation of 6,7-dideoxy-1,2-O-isopropylidene-α-d-gluco(and β-L-ido)-hept-6-enopyranose gave the corresponding 5-ketone. The acetylenic ketone 11 gave a crystalline oxime and (2,4-dinitrophenyl)hydrazone, the latter being accompanied by the product of attack of the reagent at the acetylene terminus (C-8). Previous work had shown that formyl-methylenetriphenylphosphorane did not convert 1,2:3,4-di-O-isopropylidene-6-aldehydo-α-d-galacto-hexodialdo-1,5-pyranose into the corresponding C8 unsaturated aldehyde, although the latter was obtainable via1 and 10 by an ethynylation-hydroboration sequence. The Wittig route with formylmethylenetriphenylphosphorane is shown to be satisfactory for obtaining C7 unsaturated aldehydes from 3-O-benzyl-1,2-O-isopropylidene-5-aldehydo-α-d-xylo-pentodialdo-1,4-furanose (22) and the 3-epimer of 22, respectively. These reactions provide convenient access to higher-carbon sugars and chiral dienes for synthesis of optically pure products of cyclo-addition reactions.  相似文献   

10.
Treatment of methyl β-d-ribofuranoside with acetone gave methyl 2,3-O-isopropylidene-β-d-ribofuranoside (1, 90%), whereas methyl α-d-ribofuranoside gave a mixture (30%) of 1 and methyl 2,3-O-isopropylidene-α-d-ribofuranoside (1a). On oxidation, 1 gave methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside (2), whereas no similar product was obtained on oxidation of 1a. Ethynylmagnesium bromide reacted with 2 in dry tetrahydrofuran to give a 1:1 mixture (95%) of methyl 6,7-dideoxy-2,3-O-isopropylidene-β-d-allo- (3) and -α-l-talo-hept-6-ynofuranoside (4). Ozonolysis of 3 and 4 in dichloromethane gave the corresponding d-allo- and l-talo-uronic acids, characterized as their methyl esters (5 and 6) and 5-O-formyl methyl esters (5a and 6a). Ozonolysis in methanol gave a mixture of the free uronic acid and the methyl ester, and only a small proportion of the 5-O-formyl methyl ester. Malonic acid reacted with 2 to give methyl 5,6-dideoxy-2,3-O-isopropylidene-β-d-ribo-trans-hept-5-enofuranosiduronic acid (7).  相似文献   

11.
2,6-Anhydro-3-deoxy-aldehydo-d-lyxo-hept-2-enose (7) 2,6-anhydro-3-deoxy-d-lyxo-hept-2-enitol (8) were synthesized as half-chair analogs of d-galactal (1). As 1 is a strong inhibitor of, as well as a substrate for, β-d-galactosidase from Escherichia coli, the same properties were expected for 7 and 8; however, both were ineffective. This result, together with those of other authors, allows speculative conclusions on the tight binding of 1 to the enzyme only, when water or an alcohol is bound as a co-substrate.  相似文献   

12.
The reactivity of N-(2-aminophenyl)-d-glycero-d-gulo-heptonamide (adgha), with the group 12 cations, Zn(II), Cd(II), and Hg(II), was studied in DMSO-d6 solution. The studied system showed a selective coordination to Hg(II), and the products formed were characterized by 1H and 13C NMR in DMSO-d6 solution and fast atom bombardment (FAB+) mass spectra. The expected coordination compounds, [Hg(adgha)](NO3)2 and [Hg(adgha)2](NO3)2, were observed as unstable intermediates that decompose to bis-[2-(d-glycero-d-gulo-hexahydroxyhexyl)-benzimidazole-κN]mercury(II) dinitrate, [Hg(ghbz)2](NO3)2. The chemical transformation of the complexes was followed by NMR experiments, and the nature of the species formed is sustained by a theoretical study done using DFT methodology. From this study, we propose the structure of the complexes formed in solution, the relative stability of the species formed, and the possible role of the solvent in the observed transformations.  相似文献   

13.
Lipopolysaccharide (LPS) of Haemophilus influenzae comprises a conserved tri-l-glycero-d-manno-heptosyl inner-core moiety (l-α-d-Hepp-(1→2)-[PEtn→6]-l-α-d-Hepp-(1→3)-[β-d-GlcIp-(1→4)]-l-α-d-Hepp-(1→5)-α-Kdop) to which addition of β-d-Glcp to O-4 of GlcI in serotype b strains is controlled by the gene lex2B. In non-typeable H. influenzae strains 1124 and 2019, however, a β-d-Galp is linked to O-4 of GlcI. In order to test the hypothesis that the lex2 locus is involved in the expression of β-d-Galp-(1→4-β-d-Glcp-(1→ from HepI, lex2B was inactivated in strains 1124 and 2019, and LPS glycoform populations from the resulting mutant strains were investigated. Detailed structural analyses using NMR techniques and electrospray-ionisation mass spectrometry (ESIMS) on O-deacylated LPS and core oligosaccharide material (OS), as well as ESIMSn on permethylated dephosphorylated OS, indicated both lex2B mutant strains to express only β-d-Glcp extensions from HepI. This provides strong evidence that Lex2B functions as a galactosyltransferase adding a β-d-Galp to O-4 of GlcI in these strains, indicating that allelic polymorphisms in the lex2B sequence direct alternative functions of the gene product.  相似文献   

14.
An approach to stereoselective synthesis of α- or β-3-C-glycosylated l- or d-1,2-glucals starting from the corresponding α- or β-glycopyranosylethanals is described. The key step of the approach is the stereoselective cycloaddition of chiral vinyl ethers derived from both enantiomers of mandelic acid. The preparation of 1,5-anhydro-4,6-di-O-benzyl-2,3-dideoxy-3-C-[(2,3,4,6-tetra-O-benzyl-β-d-glucopyranosyl)methyl]-l-arabino-hex-1-enitol, 1,5-anhydro-4,6-di-O-benzyl-2,3-dideoxy-3-C-[(2,3,4,6-tetra-O-benzyl-β-d-glucopyranosyl)methyl]-d-arabino-hex-1-enitol, and 1,5-anhydro-4,6-di-O-benzyl-2,3-dideoxy-3-C-[(2,3,4-tri-O-benzyl-α-l-fucopyranosyl)methyl]-d-arabino-hex-1-enitol serves as an example of this approach.  相似文献   

15.
《Carbohydrate research》1986,146(1):73-88
Although the known ring-opening with sodium azide in 2,3-anhydro-4,6-O-benzylidene-α-d-allopyranosyl 2,3-anhydro-4,6-O-benzylidene-α-d-allopyranoside gave mainly symmetrical 2-azido-4,6-O-benzylidene-2-deoxy-α-d-allopyranosyl 2-azido-4,6-O-benzylidene-2-deoxy-α-d-allopyranoside (2), the unsymmetrical 2,3′-diazido isomer 3 having the α-d-altro, α-d-gluco configuration was shown to be a second product that can be conveniently isolated on a preparative scale. The ditriflate 4 derived from 3 was subjected to regioselective displacement in the altro moiety with sodium azide, followed by displacement with sodium benzoate in the gluco moiety, to give a 2,3,3′-triazide having the α-d-manno, α-d-manno configuration. Alternatively, 4 was subjected to displacement first with benzoate and then with azide, thus providing the regioisomeric 2,3,2′-triazide of the same configuration. The ditriflate obtained from 2 furnished the corresponding 2,3,2′,3′-tetraazido derivative. Minor proportions of elimination products also arose in these reactions. The protected azido sugars were converted by standard methods into the 2,3,2′- and 2,3,3′-triamino derivatives and the 2,3,2′,3′-tetraamino derivative of α-d-mannopyranosyl α-d-mannopyranoside.  相似文献   

16.
The kinetics of CO2 and SO2 uptake by a coordinate ion, cis-[Cr(C2O4)(L-L)(OH2)2]+, where L-L stands for a bidentate sugar ligand, methyl 3-amino-2,3-dideoxy-α-d-arabino-hexopyranoside has been studied, over temperature ranges of 5 - 25 and 5 - 20 °C for CO2 and SO2, respectively. Investigations were carried out using stopped-flow spectrophotometry in the range of 340-700 nm. Results of the kinetic measurements obtained for both gases were compared. The kinetics and mechanisms of the reactions were suggested and ΔH values for both processes were determined.  相似文献   

17.
The Streptomyces coelicolor A3(2) gene SCI11.14c was overexpressed and purified as a His-tagged protein from heterologous host, Streptomyces lividans. The purification procedure resulted in 34.1-fold increase in specific activity with an overall yield of 21.4%. Biochemical and physical properties of the purified enzyme were investigated and it was shown that it possesses (aryl)esterase and a true lipase activity. The enzyme was able to hydrolyze p-nitrophenyl-, α- and β-naphthyl esters and poly(oxyethylene) sorbitan monoesters (Tween 20–80). It showed pronounced activity towards p-nitrophenyl and α- and β-naphthyl esters of C12–C16. Higher activity was observed with α-naphthyl esters. The enzyme hydrolyzed triolein (specific activity: 91.9 U/mg) and a wide range of oils with a preference for those having higher content of linoleic or oleic acid (C18:2; C18:1, cis). The active-site serine specific inhibitor 3,4-dichloroisocoumarin (DCI) strongly inhibited the enzyme, while tetrahydrofurane and 1,4-dioxane significantly increased (2- and 4- fold, respectively) hydrolytic activity of lipase towards p-nitrophenyl caprylate. The enzyme exhibited relatively high temperature optimum (55 °C) and thermal stability. CD analysis revealed predominance of α-helical structure (54% α-helix, 21% β-sheet) and a Tm value at 66 °C.  相似文献   

18.

Background

(5R?) and (5S?) diastereomers of 1-[2-deoxy-β-d-erythro-pentofuranosyl]-5-hydroxyhydantoin (5-OH-dHyd) and 1-[2-deoxy-β-d-erythro-pentofuranosyl]-5-hydroxy-5-methylhydantoin (5-OH-5-Me-dHyd) are major oxidation products of 2′-deoxycytidine and thymidine respectively. If not repaired, when present in cellular DNA, these base lesions may be processed by DNA polymerases that induce mutagenic and cell lethality processes.

Methods

Synthetic oligonucleotides that contained a unique 5-hydroxyhydantoin (5-OH-Hyd) or 5-hydroxy-5-methylhydantoin (5-OH-5-Me-Hyd) nucleobase were used as probes for repair studies involving several E. coli, yeast and human purified DNA N-glycosylases. Enzymatic reaction mixtures were analyzed by denaturing polyacrylamide gel electrophoresis after radiolabeling of DNA oligomers or by MALDI-TOF mass spectrometry measurements.

Results

In vitro DNA excision experiments carried out with endo III, endo VIII, Fpg, Ntg1 and Ntg2, show that both base lesions are substrates for these DNA N-glycosylases. The yeast and human Ogg1 proteins (yOgg1 and hOgg1 respectively) and E. coli AlkA were unable to cleave the N-glycosidic bond of the 5-OH-Hyd and 5-OH-5-Me-Hyd lesions. Comparison of the kcat/Km ratio reveals that 8-oxo-7,8-dihydroguanine is only a slightly better substrate than 5-OH-Hyd and 5-OH-5-Me-Hyd. The kinetic results obtained with endo III indicate that 5-OH-Hyd and 5-OH-5-Me-Hyd are much better substrates than 5-hydroxycytosine, a well known oxidized pyrimidine substrate for this DNA N-glycosylase.

Conclusions

The present study supports a biological relevance of the base excision repair processes toward the hydantoin lesions, while the removal by the Fpg and endo III proteins are effected at better or comparable rates to that of the removal of 8-oxoGua and 5-OH-Cyt, two established cellular substrates.

General significance

The study provides new insights into the substrate specificity of DNA N-glycosylases involved in the base excision repair of oxidized bases, together with complementary information on the biological role of hydantoin type lesions.  相似文献   

19.
Addition of 3,6-di-tert-butyl-o-benzoquinone (3,6-DBBQ) to SnCl2 in THF leads to the oxidation of Sn(II) to Sn(IV) with formation of catecholate complex (3,6-DBCat)SnCl2 · 2THF (1), where 3,6-DBCat is 3,6-di-tert-butyl-catecholate dianion. The reaction of 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone (IBQ-Pri) also proceeds on the oxidative-addition mechanism yielding bis-iminosemiquinonato species (ISQ-Pri)2SnCl2(2), where ISQ-Pri is anion-radical 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzosemiquinolate. The complexes have been characterized by IR, X-band EPR, 1H NMR (for 1) spectroscopy and magnetochemistry (for 2). X-ray analysis data show the distorted octahedral environment of tin(IV) for both complexes. Complex 1 is diamagnetic (ground state S = 0), while 2 has triplet ground state (S = 1, biradical). Catecholate complex 1 is able to be a spin trap for different organic radicals.  相似文献   

20.
The new aryl phosphinites PPh2OR (R = 2,4,6-Me3C6H2, 1; R = 2,6-Ph2C6H3, 2) have been prepared from chlorodiphenylphosphine and the corresponding phenols. In these ligands, the ortho-positions of the aromatic phosphite function are blocked by methyl and phenyl substituents, which allows coordination to metal centres without ortho-metallation. Thus, reaction with [PdCl2(cod)] leads to the complexes trans-[PdCl2(PPh2OR)2] (R = 2,4,6-Me3C6H2, 3; R = 2,6-Ph2C6H3, 4), while the reaction with [Rh2(CO)4Cl2] gives trans-[Rh(CO)Cl(PPh2OR)2] (R = 2,4,6-Me3C6H2, 5; R = 2,6-Ph2C6H3, 6). The single-crystal X-ray structure analyses of 3 and 5 confirm the trans-coordination of the new ligands in these square-planar complexes.  相似文献   

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