Coupling strategies in solid-phase synthesis of glycopeptides

Area of Science:

• Glycopeptide synthesis
• Immunology
• Organic chemistry

Background:

• N-glycosylation is crucial for protein function and immune recognition.
• Synthesizing glycosylated peptides presents challenges in solid-phase peptide synthesis (SPPS).
• Understanding the impact of N-glycosylation on T-cell responses requires reliable synthesis methods.

Purpose of the Study:

• To develop and optimize solid-phase synthesis of N-glycosylated asparaginyl peptides [Asn(GlcNAc)].
• To evaluate the impact of protecting group strategies on coupling efficiency.
• To prepare glycopeptides for investigating N-glycosylation's role in immune recognition of viral glycoproteins.

Main Methods:

• Solid-phase peptide synthesis (SPPS) utilizing various protecting groups on the glycosylated asparagine residue.
• Coupling of Fmoc-Asn(GlcNAc)-OH with O-unprotected saccharides.
• Synthesis of T-cell epitopic peptides from pigeon cytochrome c and rabies virus N-protein.

Main Results:

• Coupling rates decreased with larger protected carbohydrate moieties.
• Using O-unprotected saccharides, specifically Fmoc-Asn(GlcNAc)-OH, yielded acceptable coupling rates.
• Achieved comparable coupling efficiencies to conventional SPPS, even for difficult sequences.

Conclusions:

• Fmoc-Asn(GlcNAc)-OH is an effective reagent for synthesizing N-glycosylated peptides.
• This method facilitates the preparation of glycopeptides for immunological studies.
• The synthesized glycopeptides will aid in probing the effects of N-glycosylation on immune recognition.