Protecting group free glycosylation: one-pot stereocontrolled access to 1,2-trans glycosides and (1→6)-linked disaccharides of 2-acetamido sugars |
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| Authors: | Xin Qiu Anna L Garden Antony J Fairbanks |
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| Institution: | School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140 New Zealand.; Department of Chemistry, University of Otago, Dunedin 9054 New Zealand ; The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6140 New Zealand ; Biomolecular Interaction Centre, University of Canterbury, Private Bag 4800, Christchurch 8140 New Zealand |
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| Abstract: | Unprotected 2-acetamido sugars may be directly converted into their oxazolines using 2-chloro-1,3-dimethylimidazolinium chloride (DMC), and a suitable base, in aqueous solution. Freeze drying and acid catalysed reaction with an alcohol as solvent produces the corresponding 1,2-trans-glycosides in good yield. Alternatively, dissolution in an aprotic solvent system and acidic activation in the presence of an excess of an unprotected glycoside as a glycosyl acceptor, results in the stereoselective formation of the corresponding 1,2-trans linked disaccharides without any protecting group manipulations. Reactions using aryl glycosides as acceptors are completely regioselective, producing only the (1→6)-linked disaccharides.Un-protected 2-acetamido sugars are stereoselectively converted into 1,2-trans glycosides and (1→6)-linked disaccharides without any protecting groups. Reaction proceeds via intermediate oxazolines which react with acceptors under acid catalysis. |
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