  As a means for the synthesis of stereochemically challenging 2-amino sugars (e.g., 2 ), we have previously explored metallanitrene-mediated glycal amidoglycosylation, using glycal 3-carbamate starting materials and dirhodium(II) catalysts. A limitation of this method has been the formation of dihydropyranone byproducts such as 3  via a competing C3�H activation pathway. We have now established that catalysis using copper(II) complexes permits high chemoselectivity in cases where dirhodium(II) carboxylates gave substantial�or even exclusive�formation of the C3�H oxidation byproduct. The acyl nitrene precursors for the amino sugar-forming reactions can be either primary carbamates (1a ) in conjunction with iodosobenzene as the oxidant or, alternatively, N-tosyloxycarbamates (1b ). The latter starting materials remove the need for a hypervalent iodine oxidant. We have also measured an increase in the proportion of the desired amidoglycosylation product versus the dihydropyranone byproduct upon incorporation of a C3�D bond. This isotope effect is larger in a silver-catalyzed reaction compared to the rhodium-catalyzed variant.

Catalyst control and mechanistic investigations in nitrenoid-mediated amino sugar synthesis

245th National Meeting (2013)

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