Synthesis of biantennary complex-type nonasaccharyl asn building blocks for solid-phase glycopeptide synthesis

J Org Chem. 2011 Jul 1;76(13):5229-39. doi: 10.1021/jo200149d. Epub 2011 Jun 10.

Abstract

The biantennary complex-type N-glycans bearing LacNAc and LacdiNAc as the nonreducing end motif were synthesized in a protected form suitable to use in the Fmoc solid-phase peptide synthesis studies. Two approaches for the nonasaccharide synthesis were examined by taking advantage of the highly β-selective glycosylation with GlcNTCA (N-phenyl)trifluoroacetimidate. An earlier approach, which involved the reaction of the trisaccharide donor (Gal-GlcNTCA-Man) and trisaccharide acceptor (Man-GlcNPhth(2)-N(3)), produced a mixture of nonasaccharide isomers. On the other hand, mannosylation of the trisaccharide acceptor (Man-GlcNPhth(2)-N(3)) stereoselectively afforded the known pentasaccharide (Man(3)-GlcNPhth(2)-N(3)), which was reacted with the disaccharyl glycosyl donor (Gal-GlcNTCA or GalNTCA-GlcNTCA) to produce the desired nonasaccharide as a single stereoisomer. Selective dephthaloylation followed by N-acetylation furnished the GlcNAc(2) functionality. The resulting nonasaccharyl azides were condensed with Fmoc-Asp(OPfp)-OBu(t) or Fmoc-Asp(OPfp)-OPac in the presence of Ph(CH(3))(2)P and HOOBt. Finally, the Zn reduction and cleavage of the tert-butyl ester or Zn reduction alone produced the targeted nonasaccharyl Asn building blocks.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbohydrate Conformation
  • Carbohydrate Sequence
  • Glycopeptides / chemical synthesis*
  • Glycopeptides / chemistry
  • Molecular Sequence Data
  • Polysaccharides / chemical synthesis*
  • Polysaccharides / chemistry
  • Stereoisomerism

Substances

  • Glycopeptides
  • Polysaccharides