Stereoselective Synthesis of 1,2‐<i>Cis O</i>‐Linked Glycosyl Amino Acids via Additive‐Modulation for Glycopeptide Synthesis

A highly stereoselective strategy to facilitate the synthesis of 1,2-cis-O-linked glycosyl amino acids was established via a additive-modulated trichloroacetimidate glycosylation approach. This mild and practical protocol demonstrates broad applicability with diverse glycosyl donors, including D-gluco-, D-galacto-, 2-deoxy-2-azido-D-gluco-, 2-deoxy-2-azido-D-galacto-, D-xylo-, L-fuco-pyranosyl and L-arabinofuranosyl trichloroacetimidates, and orthogonally protected amino acids such as Ser, Thr, Tyr, and 4-hydroxyproline (Hyp) as acceptors. These 1,2-cis linked glycosyl amino acids serve as valuable building blocks for glycopeptide synthesis via solid-phase peptide synthesis (SPPS), offering significant potential for advancing glycoprotein research.