A Threonine‐Forming Oxazetidine Amino Acid for the Chemical Synthesis of Proteins through KAHA Ligation

Abstract

a-Ketoacid-hydroxylamine (KAHA) ligation allows the coupling of unprotected peptide segments through the chemoselective formation of an amide bond. Currently,t he most widely used variant employs a5 -membered cyclic hydroxylamine that forms ah omoserine ester as the primary ligation product. In order to directly form amide-linked threonine residues at the ligation site,w ep repared an ew 4membered cyclic hydroxylamine building block. This monomer was applied to the synthesis of wild-type ubiquitinconjugating enzyme UbcH5a (146 residues) and Titin protein domain TI I27 (89 residues). Both the resulting UbcH5a and the variant with two homoserine residues showed identical activity to ar ecombinant variant in aubiquitination assay.

Integration of C-Acylation in the Solid-Phase Synthesis of Peptides and Peptidomimetics Employing Meldrum’s Acid, Phosphorus, and Sulfur Ylides

“…In addition, small proteins and variants thereof have been synthesized through α-Ketoacidhydroxylamine (KAHA) ligations including C-terminal modifications of the Ubiquitin-fold modifier 1 (UFM1), glucagonlike peptide-1 (GLP-1), variants of interleukin-2 (IL-2), ubiquitinconjugating enzyme 9 (Ubc9), ubiquitin-conjugating enzyme H5a (UbcH5a), the Titan protein domain, human insulin variants, derivatives of interferon-induced transmembrane protein 3 nitrophorin and others (Scheme 30). [67][68][69][70][71][72][73][74][75][76][77] Fmoc or Boc Scheme 32. Synthesis of epoxides from aldehydes by C-C bond formation using selenium ylides 79…”

“…Scheme 30. Synthesis of small proteins and natural cyclopeptides based on C-acylation of sulfur ylides[67][68][69][70][71][72][73][74][75][76][77] 4 Miscellaneous ylides as acyl anion equivalents Besides phosphorus and sulfur ylides, ammonium ylides were reported to behave as acyl anion equivalents that undergo reactions with active electrophiles leading to new C-C bonds. Wang et.…”

“…Scheme 30 Synthesis of small proteins and natural cyclopeptides based on C-acylation of sulfur ylides[67][68][69][70][71][72][73][74][75][76][77] …”

Diverse protein manipulations with genetically encoded glutamic acid benzyl ester

“…sortase, lipoic acid ligase, transglutaminase and butelase 1), 4 the use of elaborately designed chemical reagents to react with rare residues ( e.g. Cys, Met and N-terminal residues), 5 ligand-directed protein labelling, 6 and protein synthesis via expressed protein ligation, 7 native chemical ligation, 8 or most recently KAHA ligation, 9 etc. These technologies have significantly advanced our capabilities in functionalizing proteins with photophysical probes 2 b ,4 a ,4 c and bioorthogonal handles, 10 preparing proteins with post-translational modifications, 11 as well as producing high-quality biologics.…”

Revealing the function of HMGB1 N-terminal acetylation by a protein semi-synthesis approach

“…Alternatively, advances in chemoselective peptide ligation chemistry enable peptide chemical synthesis to readily reach the protein domains comprising of 100-300 amino acid residues in general. [3][4][5][6][7][8][9] In brief, side chain unprotected short peptides (less than 50 amino acids) obtained from solid phase peptide synthesis (SPPS) are chemoselectively merged specifically at C-and N-termini via multiple chemical ligations. Along this line, the modified amino acids are used as the building blocks during SPPS with which to incorporate unnatural moieties into the polypeptide sequences, followed by protein refolding to generate functional synthetic biologics.…”