Solid-phase synthesis of O-sulfated glycopeptide by the benzyl-protected glycan strategy
摘要:
To expand the repertoire of our benzyl-protection strategy for solid-phase glycopeptide synthesis, an C-sulfated glycopeptide was chosen as the synthetic target. Trisaccharyl serine derivatives (Gal beta 1-4-GlcNAc beta 1-2-Many alpha 1-3-Ser) carrying (4-methoxyphenyl)methyl (MPM) groups at either 3-O or 6-O of the Gal residue were prepared through three stereoselective glycosylations. Cleavage of MPM followed by reaction with Me3N center dot SO3 efficiently afforded 3-O- and 6-O-sulfo-glycoserines, respectively. A preliminary debenzylation Study using the sulfated glycoserines revealed that the sulfate groups persisted under 'low-acidity TfOH' conditions, when using a limited amount of TfOH and extending the reaction period. The 3-O-sulfo-glycoserine was then introduced into an icosapeptide modeled after an alpha-dystroglycan fragment by a combination of automated and manual solid-phase peptide synthesis procedures. The synthesized glycopeptide was successfully debenzylated by the low-acidity TfOH cocktail with slight damage to the sulfate functionality. (C) 2009 Elsevier Ltd. All rights reserved.