Water-based carbodiimide mediated synthesis of polysaccharide-amino acid conjugates: Deprotection, charge and structural analysis

Fazilet Gürer, Rupert Kargl, Matej Bračič, Damjan Makuc, Martin Thonhofer, Janez Plavec, Tamilselvan Mohan*, Karin Stana Kleinschek*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We report here a one-step aqueous method for the synthesis of isolated and purified polysaccharide-amino acid conjugates. Two different types of amino acid esters: glycine methyl ester and L-tryptophan methyl ester, as model compounds for peptides, were conjugated to the polysaccharide carboxymethylcellulose (CMC) in water using carbodiimide at ambient conditions. Detailed and systematic pH-dependent charge titration and spectroscopy (infrared, nuclear magnetic resonance: 1H, 13C- DEPT 135, 1H- 13C HMBC/HSQC correlation), UV–vis, elemental and ninhydrin analysis provided solid and direct evidence for the successful conjugation of the amino acid esters to the CMC backbone via an amide bond. As the concentration of amino acid esters increased, a conjugation efficiency of 20–80% was achieved. Activated charcoal aided base-catalyzed deprotection of the methyl esters improved the solubility of the conjugates in water. The approach proposed in this work should have the potential to tailor the backbone of polysaccharides containing di- or tri-peptides.

Original languageEnglish
Article number118226
JournalCarbohydrate Polymers
Volume267
DOIs
Publication statusPublished - 1 Sep 2021

Keywords

  • Amino acids
  • Carbodiimide
  • Charges
  • Conjugates
  • Deprotection
  • NMR
  • Polysaccharide

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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