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001-es BibID:	BIBFORM019655
Első szerző:	Czifrák Katalin (vegyész)
Cím:	Anomeric [alpha]-azido acid (2-azido-2-deoxy-hept-2-ulopyranosonic acid) derivatives en route to peptides incorporating sugar amino acids / Katalin Czifrák, Péter Szilágyi, László Somsák
Dátum:	2005
ISSN:	0957-4166
Megjegyzések:	Per-O-acylated 2,6-anhydro-aldoheptonic acids of D-glycero-D-gulo and D-glycero-L-manno configuration obtained by nitrosation of the corresponding aldonamides were transformed into methyl-, tert-butyl-, 2,2,2-trichloroethyl-, and pentachlorophenyl esters, acid chlorides and glycinamides by standard procedures. Radical-mediated bromination either by bromine in boiling CHCl3 under illumination, or NBS in refluxing CCl4 in the presence of Bz2O2 or AIBN, or Na2S2O4?KBrO3 in CH2Cl2?water biphasic solvent mixture at rt gave axial anomers of the 2-bromides of the above esters and acid chlorides (2-bromo-2-deoxy-a-D-hept-2-ulopyranosonic acid derivatives), while a glycinamide was split along the ?H2C?NH? bond. Anomeric bromides of the glycinamides were obtained by N-acylation of a glycine ester with the pentachlorophenyl 2-bromo-2-deoxy-ulosonates. In this reaction the axial anomeric bromide proved stable. Sodium azide in DMSO or DMF was used for the substitution of the anomeric bromides. These reactions proceeded with inversion in the case of each ester and glycinamide to produce equatorial azides (2-azido-2-deoxy-beta-D-hept-2-ulopyranosonic acid derivatives). The azide substitution in 2-bromo-2-deoxy-alpha-D-galacto-hept-2-ulopyranosonic acid chloride gave 2-azido-2-deoxy-alpha-D-galacto-hept-2-ulopyranosonic acid azide with retention of the anomeric configuration. This acid azide was coupled with a glycine ester to give an axial anomeric azide. These transformations represent highly stereoselective routes to both anomers of dipeptides incorporating anomeric alpha-azido acids.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Tetrahedron: Asymmetry. - 16 : 1 (2005), p. 127-141. -
További szerzők:	Szilágyi Péter Somsák László (1954-) (vegyész)
Pályázati támogatás:	T43550 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM024653
Első szerző:	Somsák László (vegyész)
Cím:	Studies into the preparation of 1-deoxy-1-thiocyanato-D-glycopyranosyl cyanides and the anomeric effect of the thiocyanate group / László Somsák, Katalin Czifrák, Tamás Deim, László Szilágyi, Attila Bényei
Dátum:	2001
Megjegyzések:	The reaction of per-O-acetylated 1-bromo-1-deoxy-alpha-D-arabinopyranosyl cyanide with thiocyanate ions gave the corresponding 1-deoxy-1-thiocyanato-alpha- and beta-D-arabinopyranosyl cyanides. In the reaction of the per-O-acetylated 1-bromo-1-deoxy-beta-D-xylopyranosyl cyanide and its per-O-benzoylated beta-D-glucopyranosyl analogue the corresponding 2-hydroxy-glycal esters formed in addition to the anomeric pair of thiocyanato-cyanides. The formation of 2,3,4,6-tetra-O-benzoyl-alpha-D-glucopyranosyl thiocyanate was demonstrated in the reaction of benzobromoglucose with thiocyanate ions. The equilibrium constant between 2,3,4,6-tetra-O-acetyl-1-deoxy-1-thiocyanato-alpha- and beta-D-galactopyranosyl cyanides was determined. Based on this value, the equilibrium ratio for the 2,3,4,6-tetra-O-acetyl-alpha- and beta-D-galactopyranosyl thiocyanates was calculated to be 94:6, and the anomeric effect of the SCN group was estimated to exceed 3 kcal/mol. X-Ray crystallographic data support endo- and exo-anomeric effects of the SCN moiety.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Tetrahedron: Asymmetry. - 12 : 5 (2001), p. 731-736. -
További szerzők:	Czifrák Katalin (1978-) (vegyész) Deim Tamás Szilágyi László (1941-) (vegyész) Bényei Attila (1962-) (vegyész)
Internet cím:	Intézményi repozitóriumban (DEA) tárolt változat
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