Formation of & beta;-Configured Thioglycosides of d-Glucosamine and d-Galactosamine and Synthesis of Protected Human Milk Oligosaccharides

We report on the stereoselectivemultigram scale preparationofcyclohexyl- and phenyl thioglycosides of 2-azido-2-deoxy-& beta;-d-gluco- and galactopyranosides from d-N-acetylglucosamine using a catalytic and solvent-free method. Twoof the prepared building blocks were used as key intermediates forthe synthesis of human milk oligosaccharides LNT and LNnT in theirprotected form.