Chemical Protein Synthesis by Chemoselective α‐Ketoacid–Hydroxylamine (KAHA) Ligations with 5‐Oxaproline

The chemical synthesis of proteins from unprotected peptide segments uses KAHA ligation with 5-oxaproline, which is incorporated readily into peptides by solid-phase peptide synthesis. Ligation of such protein segments in aqueous buffers with an α-ketoacid peptide gives an α-homoserine residue at the ligation site. The new ligation is used for the synthesis of two proteins, prokaryotic-ubiquitin like protein (Pup) and probable cold shock protein A (cspA; see scheme). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.