A simple, one-pot amidoglycosylation method for the synthesis of 2-amino-2-deoxypyranosides was developed. Glycal 1 was activated by the reagent combination of a sulfoxide and Tf2O and reacted with an amide to give oxazoline intermediate 2, which was converted in situ to a C2-azaglycoside conjugate 3. Both the nitrogen transfer and glycosidic bond formation proceeded stereoselectively and precursors to oligosaccharides, glycopeptides, and glycolipids were obtained. Acetamidoglycosylation with glucals using N-TMS acetamide for the first time gave the naturally occurring 2-N-acetylamino-2-deoxypyranoses in a one-pot procedure. Reactions with other amides afforded C2-azasugars bearing various amido groups. The nature of sulfoxide reagents detd. the diastereoselectivity so that both glucoside and mannoside could be synthesized. Low temp. NMR spectroscopy and isotope labeling studies suggested a mechanism involving the C2-sulfonium glycosyl imidate 4 as the intermediate in the formation of oxazoline 2.
Amidoglycosylation with glycal donors
DI BUSSOLO, VALERIA
2002-01-01
Abstract
A simple, one-pot amidoglycosylation method for the synthesis of 2-amino-2-deoxypyranosides was developed. Glycal 1 was activated by the reagent combination of a sulfoxide and Tf2O and reacted with an amide to give oxazoline intermediate 2, which was converted in situ to a C2-azaglycoside conjugate 3. Both the nitrogen transfer and glycosidic bond formation proceeded stereoselectively and precursors to oligosaccharides, glycopeptides, and glycolipids were obtained. Acetamidoglycosylation with glucals using N-TMS acetamide for the first time gave the naturally occurring 2-N-acetylamino-2-deoxypyranoses in a one-pot procedure. Reactions with other amides afforded C2-azasugars bearing various amido groups. The nature of sulfoxide reagents detd. the diastereoselectivity so that both glucoside and mannoside could be synthesized. Low temp. NMR spectroscopy and isotope labeling studies suggested a mechanism involving the C2-sulfonium glycosyl imidate 4 as the intermediate in the formation of oxazoline 2.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
