A CONVENIENT ACCESS TO BETA-GLYCOSIDES OF N-ACETYLLACTOSAMINE

Iodoacetoxylation of anosyl)-1,5-anhydro-2-deoxy-D-arabino-hex-1-enito l (hexa-O-acetyllactal) and the corresponding hexa-O-benzoyl derivativ e, gave the alpha-1,2-trans 1-O-acetyl-2-deoxy-2-iodo adducts with hig h stereoselectivity and good yields. These were treated with an excess of trimethylsilyl azide in the presence of trimethylsilyl trifluorome thanesulfonate affording the corresponding alpha-1,2-trans 2-deoxy-2-i odoglycosyl azides. In the presence of an alcohol, a Staudinger reacti on at the anomeric azide ledin situ to an iminophosphorane which rearr anged with elimination of iodine at C-2. The aziridine intermediate th us obtained reacted with a suitable alcohol to afford the correspondin g lactosamine beta-glycosides. The reaction occurred with double inver sion of configuration at C-1 and C-2. Deprotection of the amine functi onality and further transformation into the acetamido derivatives coul d be achieved without isolation of the intermediates. (C) 1997 Elsevie r Science Ltd.