Azapeptides, Automated on a Standard Synthesizer

Summary. Chemists in the Department of Chemistry at North Carolina State University in the United States reported in the Journal of Peptide Science, published online on 9 October, an automated version of the submonomer method for making azapeptides. Azapeptides are peptide analogues in which one or more amino acid residues are replaced by aza-amino acids, built here directly on the solid-phase resin. In the submonomer route each aza-amino acid is assembled in several on-resin steps: semicarbazone incorporation, alkylation, deprotection and semicarbazide acylation. The team adapted all of these steps for use on a commercially available peptide synthesizer.

Research context (RUO). The authors identify three requirements for making the procedure run on the instrument: a stable isocyanate precursor for installing the semicarbazone, reagents that remain stable in DMF (dimethylformamide), and elimination of the cooling steps. Using their optimized automated procedure, they synthesized more than 30 azapeptides. The paper is a synthetic methods report and describes no biological testing. For laboratories that prepare peptide analogues, it shows that a multistep on-resin modification that is usually carried out by hand can be moved onto standard synthesis hardware, provided the reagents chosen tolerate the instrument's conditions. The abstract does not compare yields or purities with the manual method, so readers interested in those figures should consult the full paper.