Differentiating the 2,3-diols of glucopyranosides by 4,6-O-benzylidene-protected-1,2-d-glucopyranosylorthoesters strategy
摘要:
A facile and efficient method to differentiate the 2,3-diols of glucopyranosides based on 1,2-orthoesters strategy was developed. Stable thioglucosides were employed as the starting materials to prepare the corresponding 1,2-orthoesters. When treated with HCl aqueous solution and followed with Et3N, differentiation of the 2,3-diols was efficiently achieved along with the generation of a convertible anomeric hydroxyl group. In addition, an easy and practical method based on NOE was proposed to determine whether the 1,2-orthoesters were endo-type or exo-type. (C) 2011 Elsevier Ltd. All rights reserved.
Convenient Synthesis of an N-Glycan Octasaccharide of the Bisecting Type
摘要:
Convenient synthesis of an N-glycan octasaccharide (A) of the bisecting type was described. The stable and easily prepared orthoester F, 3 ''-O-chloroacetyl-4 '',6 ''-O-benzylidene-alpha-D-glucopyranose 1 '',2 ''-(chloromethyl 3',6'-di-O-benzyl-2'-deoxy-2'-phthalimido-beta-D-glucopyranosyl-(1 -> 4)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosylazide-4'-yl orthoacetate), was designed as the key intermediate with two advantages: (1) distinguishing OH-2 '' from OH-3 '' in beta-D-glucopyranoside to construct the central beta-D-mannopyranoside by inverting the configuration of OH-2 '' in beta-D-glucopyranoside and (2) distinguishing OH-4 '' and OH-6 '' from OH-3 '' in the beta-D-mannopyranoside to introduce the bisecting GlcNAc residue.