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001-es BibID:	BIBFORM022185
Első szerző:	Szilágyi László (vegyész)
Cím:	Non-conventional glycosidic linkages : syntheses and structures of thiooligosaccharides and carbohydrates with three-bond glycosidic connections / László Szilágyi, Oscar Varela
Dátum:	2006
ISSN:	1385-2728 1875-5348
Megjegyzések:	Thiooligosaccharides display inhibitory activity against glycoside hydrolases and they constitute a valuable tool for structural biology. The construction of the interglycosidic linkage, in which the oxygen atom is replaced by sulfur, usually involves one of the following reactions: i) nucleophilic displacement of good leaving groups in a carbohydrate moiety by a sugar thiol, ii) Michael and Michael-type additions of sugar thiols to unsaturated acceptors, iii) ring-opening of aziridines and oxiranes by thiosugars, iv) enzyme-catalyzed couplings of thiosugar moieties. The application of these reactions for the syntheses of thiooligosaccharides are surveyed, and the biological activities of the resulting products briefly described. Carbohydrate structures incorporating three-bond glycosidic linkages with two heteroatoms are uncommon in Nature. The -N-O- interglycosidic bond in the oligosaccharide part of enediyne antibiotics is partly responsible for their potent antitumor activities. The disulfide bond which plays an essential role in proteins has recently been introduced as an interglycosidic connecting motif. The sulfenamide functionality is the sulfur analog of the hydroxylamine type glycosidic linkages in calicheamicins. Novel glycosylation strategies have recently been developed by taking advantage of unconventional, three-bond glycosidic linkages to construct neoglycoproteins and other glycoconjugates which are increasingly important tools in glycobiology and drug discovery. To explore conformational preferences and molecular flexibility in these structures NMR spectroscopy, chiroptical methods and X-ray crystallography are being used, supplemented by molecular modelling calculations. The structural features will be briefly discussed with relevance to biological interactions such as enzyme binding.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban circular dichroism (CD) NOE measurements bovine serum albumin disulfide glycosidic linkages deprotonation
Megjelenés:	Current Organic Chemistry. - 10 : 14 (2006), p. 1745-1770. -
További szerzők:	Varela, Oscar
Internet cím:	Intézményi repozitóriumban (DEA) tárolt változat DOI
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001-es BibID:	BIBFORM001239
Első szerző:	Uhrig, María Laura
Cím:	Synthesis of non-glycosidic 4,6'-thioether-linked disaccharides as hydrolytically stable glycomimetics / María Laura Uhrig, László Szilágyi, Katalin E. Kövér, Oscar Varela
Dátum:	2007
ISSN:	0008-6215
Megjegyzések:	Michael addition of 1,2:3,4-di-O-isopropylidene-6-thio-alpha-D-galactose (2) to 2-propyl 6-O-acetyl-3,4-dideoxy-alpha-D-glycerohex-3-enopyranosid-2-ulose (1) afforded, as the major diastereoisomer, 2-propyl 6-O-acetyl-3-deoxy-4-S-(6-deoxy-1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranos-6-yl)-4-thio-alpha-D-threo-hexopyranosid-2-ulose (3,91% yield). Reduction of the carbonyl group of 3, followed by O-deacetylation gave the two epimers 7 (alpha-D-lyxo) and 8 (alpha-D-xylo) in a 1:2 ratio. On removal of the protecting groups of 8 by acid hydrolysis, formation of an 1,6-anhydro bridge was observed in the 3-deoxy-4-thiohexopyranose unit (10). The free nonglycosidic thioether-linked disaccharide 3-deoxy-4-S-(6-deoxy-alpha,beta-D-galactopyranos-6-yl)-4-thio-alpha,beta-D-xylo-hexopyranose (11) was obtained by acetolysis of 10 followed by O-deacetylation. A similar sequence starting from the enone 1 and methyl 2,3,4-tri-Obenzoyl-6-thio-alpha-D-glucopyranoside (12) led successfully to 2-propyl 3-deoxy-4-S-(methyl 6-deoxy-alpha-D-glucopyranos-6-yl)-4-thio-alpha-D-lyxo-hexopyranoside (17) and its alpha-D-xylo analog (19, major product). In this synthetic route, orthogonal sets of protecting groups were employed to preserve the configuration of both reducing ends and to avoid the formation of the 1,6-anhydro ring.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban thioether-linked disaccharide analogues sugar enones Michael addition 4,6'-Thioether-linked sugars
Megjelenés:	Carbohydrate research. - 342 (2007), p. 1841-1849. -
További szerzők:	Kövér Katalin, E. (1956-2023) (vegyész) Varela, Oscar Szilágyi László (1941-) (vegyész)
Internet cím:	DOI elektronikus változat elektronikus változat
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