Synthesis of Glycosaminoglycan Oligosaccharides− An Unexpected Inhibitory Effect of a RemoteN-Acetyl Group upon Trichloroacetimidate-Mediated Couplings
due to the presence of the N-acetyl group, which inhibits the trichloroacetimidate-mediated glycosylation, since the analogous reaction proceeds smoothly once the N-acetyl group has been replaced by an azide. In the latter case, we show that the careful optimisation of the solvent system is a powerful way to obtain high yields and α-stereoselectivity in coupling reactions of 1 with the 4-OH of a GlcUA