- Chiral recognition of amino-acid esters by a glucose-derived macrocyclic receptor
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We report a glucose-based crown ether capable of chiral recognition of a wide range of amino-acid methyl esters in aqueous environments. The enantioselectivities towards amino-acids with extended hydrophobic side chains displayed by the glucose-derived ma
- Dominique, Pit,Schnurr, Martin,Lewandowski, Bartosz
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supporting information
p. 3476 - 3479
(2021/04/12)
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- The building blocks of cellulose: The intrinsic conformational structures of cellobiose, its epimer, lactose, and their singly hydrated complexes
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A combination of vibrational spectroscopy conducted under molecular beam conditions and quantum chemical calculation has established the intrinsic three-dimensional structures of the cellulose disaccharide and, focusing on the critical β1,4-linkage at the nonreducing end of the growing cellulose polymer, its C-4′ epimer. Left to their own devices they both adopt a cis (anti-φ/syn-ψ) glycosidic configuration, supported in the epimer by strong, cooperative inter-ring hydrogen bonding. In the cellulose disaccharide, however, where the OH-4′(Glc) group is equatorial, the cooperativity is reduced and the corresponding inter-ring hydrogen bonding is relatively weak. The cis conformational preference is still retained in their singly hydrated complexes. In the cellulose disaccharide insertion of the water molecule at the favored binding site between OH-4′ and the neighboring hydroxyl group OH-6′ promotes a structural reorganization to create a configuration that parallels that of its unhydrated epimer and greatly strengthens the inter-ring hydrogen bonding. In the C-4′ epimer, the axial orientation of OH-4′ blocks this binding site and the bound water molecule simply adds on at the end of the (OH-O)n chain, which has a negligible effect on the (already strong) inter-ring bonding. The implications of these results are discussed with respect to the structure and insolubility of native cellulose polymers.
- Cocinero, Emilio J.,Gamblin, David P.,Davis, Benjamin G.,Simons, John P.
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supporting information; experimental part
p. 11117 - 11123
(2009/12/03)
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- Novel cyclic phosphate-linked oligosaccharides (CyPLOSs) covalently immobilized on solid supports for potential cation scavenging
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For potential cation scavenging both from water and from organic solvents, here we propose a synthetic procedure for functionalization of a Tentagel solid support with novel cyclic phosphate-linked oligosaccharide (CyPLOS) analogues. To establish the feas
- D'Onofrio, Jennifer,Coppola, Cinzia,Fabio, Giovanni Di,De Napoli, Lorenzo,Montesarchio, Daniela
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p. 3849 - 3858
(2008/02/13)
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- Efficient formation and cleavage of benzylidene acetals by sodium hydrogen sulfate supported on silica gel
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NaHSO4SiO2 was used as an efficient heterogeneous catalyst for both the formation and the cleavage of benzylidene acetals. This catalyst is compatible with many functional or protective groups. Under different solvent systems, either the formation or the cleavage of benzylidene acetals was carried out smoothly in excellent yields and with good chemoselectivity. Georg Thieme Verlag Stuttgart.
- Niu, Youhong,Wang, Ning,Cao, Xiaoping,Ye, Xin-Shan
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p. 2116 - 2120
(2008/02/09)
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- Novel amphiphilic cyclic oligosaccharides: Synthesis and self-aggregation properties
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(Chemical Equation Presented) Novel amphiphilic cyclic disaccharide analogues, in which the saccharide units are connected through stable phosphodiester linkages (CyPLOS, Cyclic Phosphate-Linked Oligosaccharides) and decorated with long lipophilic tentacl
- Coppola, Cinzia,Saggiomo, Vittorio,Di Fabio, Giovanni,De Napoli, Lorenzo,Montesarchio, Daniela
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p. 9679 - 9689
(2008/03/27)
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- Biomimetic synthesis of the novel 1,4-dioxanyloxy fragment of silvestrol and episilvestrol
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The biomimetic synthesis of the 1,4-dioxanyloxy fragment of silvestrol (1) and episilvestrol (2) from d-glucose is described. The biomimetic synthesis of the 1,4-dioxanyloxy fragment of silvestrol (1) and episilvestrol (2) from d-glucose is described. Cro
- Sous, Mariana El,Rizzacasa, Mark A.
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p. 293 - 295
(2007/10/03)
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- Stereospecific synthesis of β-D-allopyranosides by dihydroxylation of β-D-erythro-2,3-dideoxyhex-2-enopyranosides
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The synthesis of 4,6-O-benzylidene-β-D-erythro-2-3-dideoxyhex-2-enopyranosides and their osmium and ruthenium catalysed dihydroxylation reactions have been investigated. These reactions have been shown, for a range of monosaccharides and a disaccharide, to proceed stereospecifically to give β-D-allopyranosides in moderate to excellent yield.
- Murphy, Paul V,O'Brien, Julie L,Smith III, Amos B
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p. 327 - 335
(2007/10/03)
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- Regioselective Lipase-catalysed acylation of 4,6-O-benzylidene-α- and - β-D-pyranoside derivatives displaying a range of anomeric substituents
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The application of Lipase enzymes to effect regioselective C-3-O- acylation of 4,6-O-benzylidene-β-D-gluco- and -galactopyranosides displaying a range of anomeric substituents, and C-2-O-acylation of phenyl 4,6-O- benzylidene-α-D-glucopyranoside and ethyl 4,6-O-benzylidene-1-thio-α-D- glucopyranoside is reported. In particular this method has allowed introduction of a variety of acyl protecting groups at the C-3 hydroxyl group of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside 11.
- Gridley, Jonathan J.,Hacking, Andrew J.,Osborn, Helen M. I.,Spackman, David G.
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p. 14925 - 14946
(2007/10/03)
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- Asymmetric hydrogenation - Influence of the structure of carbohydrate derived catalysts on the relative enantioselectivity Q(H/Me) regarding acid and ester substrates and its inversion - Selectivity increase in water by amphiphiles
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4,6-O-Benzylidene protected 2,3-bis(O-diphenylphosphino)-D-glycopyranoside rhodium(I) chelate precatalysts 1-4 e,f showed for the hydrogenation of methyl (Z)2-N-acylamidoacrylates 6-8 a stepwise decrease of the enantioselectivity with increasing number of axially oriented hexopyranoside substituents. The decrease is even stronger for the analogous substrate acids 6h-8h resulting in an unusual low relative enantioselectivity Q = q(H)/q(Me) of 0.3 for the precatalysts 4e and 4f. Deprotected, 4,6-OH-group bearing catalysts 1-4 g,h generally show smaller differences of %ee in methanol or benzene, however, not in water. Under addition of amphiphiles a in comparison with blanks b the relative enantioselectivity Q = q(a)/q(b) clearly increases for both groups of catalysts in most cases to Q-values between 3 up to 8 - independent of a neutral or ionic nature of the amphiphile.
- Selke, Ruediger,Ohff, Manuela,Riepe, Andreas
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p. 15079 - 15102
(2007/10/03)
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