Anomeric oxidation

Aldonolactones are commercially available at low cost, when compared to most of the common monosaccharides. They are typically synthesized by selective anomeric oxidation of unprotected aldoses with bromine [6]. Usually the thermodynamically more stable five-membered lactone (y-lactone) predominates over the six-membered form, with the exception of o-gluconolactone, which crystallizes as the 1,5-pyranolactone (5-lactone) [7] (Scheme 1). Another method for the preparation of sugar lactones is the dehydrogenation of unprotected or partially... 

The synthesis of (+)-nojirimycin (1) from tetra-O-benzyl-D-glucopyranose (11) as depicted in Scheme 10 °° was found to be unreliable. Compound 11 underwent anomeric oxidation with DMSO-AC2O to afford tetra-0-benzyl-D-glncono-l,5-lactone (52) in 84% yield, which was treated with liquid ammonia solntion in the presence of trace amounts of Amberlite IR-120 (H+) resin in dioxane to give the glnconolactam 53 (50%). Treatment of 53 with sodinm borohydride followed by removal of the benzyl protecting groups afforded... 

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