Aufspaltung des Laevoglykosans mit Titantetrachlorid

Ein neuer Zugang zu Glycopeptiden

“…Die auf diesem Wege erhaltenen 2,2-Bis(trifluormethyl)-1,3-oxazolidin-5-one sind unter Feuchtigkeitsausschluû im Kühlschrank über Monate lagerbar. [15] Die Hexafluoraceton(HFA)-geschützten Aminosäuren 5 ± 8 wurden mit 2,3,4,6-Tetra-O-acetyl-a-d-glucopyranosylbromid/Hg(CN) 2 nach Helferich, [16] mit Penta-O-acetyl-b-d-glucopyranose/BF 3 nach Paulsen [17] und mit 2,3,4,6-Tetra-Oacetyl-b-d-glucopyranosyltrichloracetimidat nach Schmidt [18] umgesetzt. Die guten Ausbeuten an b-d-Glc-(HFA)-Xaa (Tabelle 1) deuten darauf hin, daû die neue Schutzgruppenstrategie für alle drei Glycosylierungsverfahren erfolgreich eingesetzt werden kann.…”

Synthesis of Ether- and Imino-Linked OctylN-Acetyl-5a′-carba-β-lactosaminides and -isolactosaminides: Acceptor Substrates for α-(1→3/4)-Fucosyltransferase, and Enzymatic Synthesis of 5a′-Carbatrisaccharides

“…These antigens include sialyl Lewis x, which is a tumor-associated structure and a ligand of E-selectin-me-been considered as substrates and inhibitors for the Lewis α-(1Ǟ3/4)-fucosyltransferase available from human milk. Zemplén de-O-acetylation [8] of 9, followed by benzylidenation with benzaldehyde in the presence of moieties of the true substrates 1 and 2 are replaced by etherand imino-linked 5a-carba-β--galactopyranose residues, zinc chloride, gave the (R)-4,6-O-benzylidene derivative [9] 10 in 88% yield. [4] There is interest in developing assays for monitoring enzyme activity and specific fucosyltransferase inhibitors which prevent the synthesis of these antigens.…”

“…Epimerization at C-4Ј was also carried out by S N 2 reaction of the 4Ј,6Ј-dimesylate 31 with an acetate ion, giving the triacetate 32 (82%) having a 5aЈ-carba-β--galactopyranose residue. De-O-acetylation [8] gave the free carbadisaccharide 5. De-O-acetylation [8] gave the free carbadisaccharide 5.…”

Synthesis and Glycosidase Inhibitory Activity of Five Stereoisomers of 5-Amino-5-C-methyl-1,2,3,4-cyclopentanetetrol

“…[8] Some nitromational feature of the transition state mannopyranosyl alkanes and alkanols have successfully been applied [9] [10] in cation predicted in hydrolysis of mannopyranosides, it the reaction of glutaraldehyde, producing some unaccessible seemed rather difficult to correlate the structures of the branched-chain aminocyclitols. Deseveral glycosidases, only 1-and 1-(1,2,3,5/4) (2), and O-acetylation of the compounds under Zemplén con-(1,2,3,4,5/0) isomers (3) have been shown to be weak inhibiditions [12] led to a separable mixture of products, and, after tors of Jack beans α-mannosidase (IC 50 ϭ 1Ϫ10 ϫ 10 Ϫ5 ).silica gel chromatography, three stereoisomers of the 5-acet-In fact, compounds 2 and 3 are likely to resemble mannosamido-5-C-methyl-1,2,3,4-cyclopentanetetrol derivatives 9, tatin A in configurations the all-cis relationships of the 10, and 11 were obtained in 16, 10, and 1% yields, respecamino and consecutive three hydroxy groups, suggesting tively, based on the inositol derivative used [13] . Recently, Winkler rived by treatment of -1,2-O-cyclohexylidene-myo-inosiand his coworkers [4] have proposed adequate corretol [11] with excess of sodium metaperiodate has been carried lationship by comparing the structures of some α-mannoout for synthesis of the target compounds.…”

“…In the present study, nitro known potent inhibitors conformationally to the postulated aldol cyclization between nitroethane and a dialdehyde destructure of mannopyranosyl cation [3] . Deseveral glycosidases, only 1-and 1-(1,2,3,5/4) (2), and O-acetylation of the compounds under Zemplén con-(1,2,3,4,5/0) isomers (3) have been shown to be weak inhibiditions [12] led to a separable mixture of products, and, after tors of Jack beans α-mannosidase (IC 50 ϭ 1Ϫ10 ϫ 10 Ϫ5 ). No cyclization sidase inhibitors to their flap up mannopyranosyl cation product was formed when sodium methoxide, sodium hymodel.…”