A convenient access to β-glycosides of N-acetyllactosamine

Article abstract of DOI:10.1016/S0008-6215(96)00263-7

Iodoacetoxylation of 3,6-di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-1,5-anhydro -2-deoxy-D-arabino-hex-1-enitol (hexa-O-acetyllactal) and the corresponding hexa-O-benzoyl derivative, gave the α-1,2-trans 1-O-acetyl-2-deoxy-2-iodo adducts with high stereoselectivity and good yields. These were treated with an excess of trimethylsilyl azide in the presence of trimethylsilyl trifluoromethanesulfonate affording the corresponding α-1,2-trans 2-deoxy-2-iodoglycosyl azides. In the presence of an alcohol, a Staudinger reaction at the anomeric azide led in situ to an iminophosphorane which rearranged with elimination of iodine at C-2. The aziridine intermediate thus obtained reacted with a suitable alcohol to afford the corresponding lactosamine β-glycosides. The reaction occurred with double inversion of configuration at C-1 and C-2. Deprotection of the amine functionality and further transformation into the acetamido derivatives could be achieved without isolation of the intermediates.