β-l-Rhamnosylation and β-d-Mannosylation Mediated by 4--Ester Groups in a Weakly Nucleophilic Environment.

-4--Acyl group directed β-rhamnosylation and β-mannosylation are achieved in a carborane or BARF anion formed weakly nucleophilic environment with the assistance of a 2,3-orthocarbonate group. The 4--acyl group plays a critical role in directing the β-selectivity, and the weakly coordinating anion is essential to amplify this direction. The orthocarbonate group could be readily removed with 1,3-propanediol in the presence of BF·EtO.

Reinvestigation of ,-Diacetylimido-Protected 2-Aminothioglycosides in -Glycosylation: Intermolecular Hydrogen Bonds Contributing to 1,2-Orthoamide Formation.

,-Diacetylimido protection of 2-aminoglycosides is an elegant strategy but has had limited applications due to unexpected side reactions in glycosylation. We found that high acid concentrations could diminish the side reactions. We observed intermolecular hydrogen bonding among alcohols and acids could disrupt.