Chemical Synthesis of a Glycoprotein Having an Intact Human Complex-Type Sialyloligosaccharide under the Boc and Fmoc Synthetic Strategies

Abstract

The chemical synthesis of complex glycoproteins is an ongoing challenge in protein chemistry. We have examined the synthesis of a single glycoform of monocyte chemotactic protein-3 (MCP-3), a CC-chemokine that consists of 76 amino acids and one N-glycosylation site. A three-segment native chemical ligation strategy was employed using unprotected peptides and glycopeptide. Importantly, the synthesis required the development of methods for the generation of sialylglycopeptide-alphathioesters. For the sialylglycopeptide-alphathioester segment, we examined and successfully implemented approaches using Fmoc-SPPS and Boc-SPPS. To avoid use of hydrogen fluoride, the Boc approach utilized minimal side chain protection and direct thiolysis of the resin bound peptide. Using these strategies, we successfully synthesized a glycoprotein having an intact and homogeneous complex-type sialyloligosaccharide.

Chemoenzymatic synthesis of glycopeptides and glycoproteins through endoglycosidase-catalyzed transglycosylation

“…Recent work has also demonstrated that when combined with native chemical ligation, this approach is appropriate for constructing some large N-glycopeptides and even selected glycoproteins. [21][22][23] Nevertheless, a potential problem of this approach is that the bulky glycans attached in the building block may result in low-yield coupling in solid-phase or solution-phase peptide synthesis, and the O-glycosidic linkages in the oligosaccharide moiety are susceptible to acidic hydrolysis under strong acidic conditions (e.g., TFA or HF treatment) required for final global deprotection and release of peptide from the resin.…”

Studies on the Precise Chemical Synthesis of Human Glycoproteins

“…34 The strategy employed three-segment coupling by NCL at the 11 and 36 cysteine sites. In terms of oligosaccharide, biantennary sialyloligosaccharide 39 or 40 was used and the sialylglycopeptide-α-thioester 37 was prepared by both the Fmoc and Boc conditions.…”

Misfolded Glycoproteins as Probes for Analysis of Folding Sensor Enzyme UDP-Glucose

“…To obtain homogeneous glycoproteins, chemical synthesis has become an alternative method because of its dramatic advance in recent years (34)(35)(36)(37). Therefore, we examined the first chemical Fig.…”