Use of dichlorophthaloyl (DCPhth) group as an amino protecting group in oligosaccharide synthesis

As an alternative to phthaloyl (Phth) group, 4,5-dichlorophthaloyl (DCPhth) group was investigated as an amino protecting group to prove it to be useful for the synthesis of B-glycosides of 2-acetamido-2-deoxy glucose (GlcNAc). DCPhth was introduced onto the C-2 nitrogen of glucosamine to give 2, which was further transformed into mono-and di-and trisaccharide derivatives which constitute basic structural units of asparagine linked glycoprotein oligosaccharides. DCPhth group proved to have sufficient stability under the standard conditions of protecting group manipulations (e.g. deacetylation, benzylation, benzylidenation), and Lewis acid-, silver salt-and iodonium ion-promoted glycosylation. Removal of DCPhth group was smoothly performed by using ethylenediamine in alcoholic solvent under substantially milder conditions required for deprotection of Phth. (C) 1998 Elsevier Science Ltd. All rights reserved.