- Effect of ionic liquids as additives in the catalytic properties of different immobilized preparations of Rhizomucor miehei lipase in the hydrolysis of peracetylated lactal
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The addition of small amount of different ionic liquids modified the activity and regioselectivity of different immobilized preparations of R. miehei lipase catalyzing the hydrolysis of hexa-O-acetyl lactal in aqueous media. ILs with [emim] as cation and different anions were first evaluated affecting in a different manner depending on the immobilized preparation used. The enzymatic activity of RML immobilized on octyl-agarose or CNBr-agarose decreased in the following order: NO3-≈ BF4- > MeOSO3- > PF6-, whereas when RML was immobilized on Q-Sepharose, the enzymatic activity decreased in a different order: MeOSO3- > PF6- > BF4- > NO3-. Using [bdmim], the activity of octyl-RML and CNBr-RML preparations resulted higher in the presence of PF6- than BF4-, 6-fold for octyl-RML and 2-fold for CNBr-RML if compared with the enzyme activity without additive. In both preparations the enzyme was completely regioselective in the presence of the IL hydrolyzing at C-3 position in 99% yield. The modification of the cation in the IL did not affect to the activity of Q-RML with BF4- or decreased the activity with PF 6-, although affected to the regioselectivity producing another undesired product, a bihydrolized product in 20-25% yield. In this case, the addition of [emim][MeOSO3] caused the best increment in the activity for this RML biocatalyst, 2-fold with only 8% of bihydrolized production.
- Filice, Marco,Guisan, Jose M.,Palomo, Jose M.
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experimental part
p. 1365 - 1369
(2010/10/01)
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- A highly convergent synthesis of an N-linked glycopeptide presenting the H-type 2 human blood group determinant
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The total synthesis of an H-type blood group determinant in a model biological setting is described. The construct is comprised of a high mannose core structure with projecting lactose spacers, culminating in a two-copy presentation of the H-type blood group determinant itself. Key reactions that were used in this construction include sulfonamidohydroxylation (see 15→18) and benzoate-directed glycosylation via an activated thiophenyl donor (see 34→36). Another key strategic element involved the epimerization of an interior core glucoside to reach the β-mannoside (see 37→38) required in the ring C sugar of the high mannose core.
- Wang, Zhi-Guang,Warren, J. David,Dudkin, Vadim Y.,Zhang, Xufang,Iserloh, Ulrich,Visser, Michael,Eckhardt, Matthias,Seeberger, Peter H.,Danishefsky, Samuel J.
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p. 4954 - 4978
(2007/10/03)
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- Iterative synthesis of Leishmania phosphoglycans by solution, solid-phase, and polycondensation approaches without involving any glycosylation
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A general strategy (solution, solid-phase, and polycondensation) for the synthesis of antigenic phosphoglycans (PG) of the protozoan parasite Leishmania is presented. Phosphoglycans constitute the variable structural and functional domain of major cell-su
- Ruhela, Dipali,Vishwakarma, Ram A.
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p. 4446 - 4456
(2007/10/03)
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- Toward fully synthetic homogeneous glycoproteins: A high mannose core containing glycopeptide carrying full h-type2 human blood group specificity
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Blood typing with the ABO classification is based on cell-surfacse glycoproteins. In a significant step toward the synthesis of these compounds, the laboratory synthesis of a fully functional N-linked glycopeptide featuring H-type blood group determinants 1 is described.
- Wang, Zhi-Guang,Zhang, Xufang,Visser, Michael,Live, David,Zatorski, Andrzej,Iserloh, Ulrich,Lloyd, Kenneth O.,Danishefsky, Samuel J.
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p. 1728 - 1732
(2007/10/03)
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- Synthesis of the tetrasaccharide cap domain of the antigenic lipophosphoglycan of Leishmania donovani parasite
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In this paper we report a new synthesis of the immunologically important tetrasaccharide terminal cap domain [Galp(1-4)-β-[Manp-(1-2)-α-Manp-(1-2)-α]-Manp] of lipophosphoglycan (LPG); the major cell surface GPI molecule and key virulence factor of the protozoan parasite Leishmania donovani. The synthetic approach provided a short convergent route for the LPG cap motif from lactose and mannose starting materials. The synthesis was then applied for the preparation of a radiolabelled cap epitope for macrophage receptor binding and immunological studies. (C) 2000 Elsevier Science Ltd.
- Upreti,Ruhela,Vishwakarma
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p. 6577 - 6584
(2007/10/03)
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- Synthesis of the phosphodisaccharide repeat of antigenic lipophosphoglycan of Leishmania donovani parasite
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Synthesis of the immunologically important and structurally unusual phosphodisaccharide repeat unit (Galp1,4β-Manp-1α-phosphate) of the lipophosphoglycan cell surface GPI molecule of the protozoan parasite Leishmania donovani has been carried out using la
- Upreti, Mani,Vishwakarma, Ram A.
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p. 2619 - 2622
(2007/10/03)
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- Glycosyltransferase-catalysed Stereoselective Glycosidation of Monosaccharide-based Glycosidase Inhibitors: a New Approach to the Synthesis of Sequence-specific Glycosidase Inhibitors
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β-1,4-Galactosyltransferase was used as catalyst for galactosidation of 5-thioglucose, glucal and 1-deoxynojirimycin to form the corresponding β-1,4-galactosides as potential sequence-specific glycosidase inhibitors.
- Gautheron-Le Narvor, Christine,Wong, Chi-Huey
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p. 1130 - 1131
(2007/10/02)
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- Synthesis of Novel Disaccharides Based on Glycosyltransferases: β1,4Galactosyltransferase
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β1,4Galactosyltransferase and β-galactosidase have been investigated with regard to their acceptor specificity and used in the synthesis of galactosides using 5-thioglucose, deoxyazaglucose, glucal, modified N-acetylglucosamine and glucose derivatives as acceptors.
- Wong, Chi-Huey,Krach, Thomas,Narvor, Christine Gautheron-Le,Ichikawa, Yoshitaka,Look, Gary C.,et al.
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p. 4867 - 4870
(2007/10/02)
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- Probing the Acceptor Specificity of β-1,4-Galactosyltransferase for the Development of Enzymatic Synthesis of Novel Oligosaccharides
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β-1,4-Galactosyltransferase has been investigated with regard to its acceptor specificity and used in the synthesis of galactosides with 5-thioglucose, glucal, deoxynojirimycin, modified N-acetylglucosamine, and glucose derivatives as acceptors. The galactoside products are potentially useful as endoglycosidase or glycosyltransferase inhibitors or as intermediates for the synthesis of complex oligosaccharides. The conformation of each enzyme product has been investigated with NMR; all arc shown to possess similar glycosidic torsional angles based on a significant NOE between H-1 of Gal and H-4 of the acceptor. Comparison of the transferase reactions with the β-1,4-galactosidase-catalyzed galactosyl transfer reactions indicates that the transferase reactions provide exclusively a β-1,4-glycosidic linkage while the galactosidase reactions predominantly form a β-1,6-glycosidic linkage.
- Wong, Chi-Huey,Ichikawa, Yoshitaka,Krach, Thomas,Narvor, Christine Gautheron-Le,Dumas, David P.,Look, Gary C.
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p. 8137 - 8145
(2007/10/02)
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