title: Native chemical ligation in dimethylformamide can be performed chemoselectively without racemization.
abstract: Native chemical ligation of unprotected peptides in organic solvents has been previously reported as a fast, efficient, and suitable method for coupling of hydrophobic peptides. However, it has not been determined whether the reaction can be carried out without possible side reactions or racemization. Here, we present a study on the chemoselectivity of this method by model reactions designed to test the reactivity of Arg and Lys side chains as well as that of α-amino groups. A possible racemization of the C-terminal amino acid of the N-terminal peptide was also investigated. The results show that ligation in organic solvents can be conducted chemoselectively without side reactions with other nucleophilic groups. Furthermore, no racemization of the C-terminal amino acid was observed if both educts were added simultaneously. Thus, native chemical ligation can be performed either in aqueous buffer systems or in organic solvents paving the way for the synthesis of larger hydrophobic peptides and/or membrane proteins.
authors.affiliation: Max Planck Institute of Molecular Physiology, Otto Hahn Str. 11, 44227, Dortmund, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Dittmann
authors.forename: Muheeb
authors.initials: M
authors.lastname: Sadek
authors.forename: Ralf
authors.initials: R
authors.lastname: Seidel
authors.forename: Martin
authors.initials: M
authors.lastname: Engelhard
mesh_terms: D004126:Dimethylformamide / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D010455:Peptides; D012997:Solvents; D004126:Dimethylformamide