Fluorenylmethoxycarbonyl‐Protected O ‐Glycosyl‐ N ‐methyl Amino Acids: Building Blocks for the Synthesis of Conformationally Tuned Glycopeptide Antigens

Peptide antibiotics often contain N ‐methylated amino acids. These N ‐methylamino components enhance the metabolic stability and strongly influence the conformational behavior of these peptide drugs. N ‐Methyl‐ O ‐glycosyl amino acids, in particular, threonine and serine derivatives, are unknown so far. Fmoc‐protected N ‐methyl‐ O ‐glycosyl‐threonine and ‐serine building blocks, including sialyl T N antigens, have been synthesized for the first time by converting the Fmoc‐protected O ‐glycosyl amino acids or their tert ‐butyl esters into the corresponding oxazolidinones followed by reductive ring‐opening. These new components are considered interesting for the construction of modified mucin glycopeptide anti‐tumor vaccines with extended biological half‐life.