Synthetic study of peptidoglycan partial structures. Synthesis of tetrasaccharide and octasaccharide fragments

Partial structures of peptidoglycan, a potent immunostimulating glycoconjugate of bacteria, were synthesized for precise biological studies. A key disaccharide glucosaminyl-beta (1-4)-muramic acid was prepared by stereoselective glycosylation of a N-Troc (Troc = 2,2,2-trichloroethoxycarbonyl) muramic acid acceptor with a N-Troc-glucosaminyl trichloroacetimidate. The disaccharide was converted to either a disaccharide acceptor or a donor. They were then coupled together by the same glycosylation method to give a tetrasaccharide in a good yield. Octasaccharide was also obtained in a good yield in a similar manner. N-Acetylation and coupling with the dipeptide moiety of L-alanyl-D-isoglutamine followed by deprotection afforded the repeating peptidoglycan tetrasaccharide and octasaccahride peptide conjugates for the first time. (C) 2001 Elsevier Science Ltd. All rights reserved.