Generalizing a Ligation\nSite at the <i>N</i>‑Glycosylation Sequon for Chemical\nSynthesis of <i>N</i>‑Linked Glycopeptides and Glycoproteins

Chemical synthesis can generate homogeneous glycoproteins\nwith\nwell-defined and modifiable glycan structures at designated sites.\nThe precision and flexibility of the chemical synthetic approach provide\na solution to the heterogeneity problem of glycopeptides/glycoproteins\nobtained through biological approaches. In this study, we reported\nthat the conserved <i>N</i>-glycosylation sequon (Asn-Xaa-Ser/Thr)\nof glycoproteins can serve as a general site for performing Ser/Thr\nligation to achieve <i>N</i>-linked glycoprotein synthesis.\nWe developed an N + 2 strategy to prepare the corresponding glycopeptide\nsalicylaldehyde esters for Ser/Thr ligation and demonstrated that\nSer/Thr ligation at the sequon was not affected by the steric hindrance\nbrought about by the large-sized glycan structures. The effectiveness\nof this strategy was showcased by the total synthesis of the glycosylated\nreceptor-binding domain (RBD) of the SARS-CoV-2 spike protein.