Protease catalysis mediated by a substrate mimetic: A novel enzymatic approach to the synthesis of carboxylic acid amides

We present a protease-based method for the coupling of non-coded and non-am ino-acid-derived amines with carboxy components. The key feature of this ap proach is the combination of the substrate-mimetic strategy with the abilit y of the cysteine protease clostripain to accept a wide spectrum of amines. Firstly, we tested the use of the 4-guanidinophenyl ester leaving group to mediate acceptance of noncoded and non-amino-acid-derived acyl residues. T his employed beta-amino acid and simple carboxylic acid moieties as acyl do nors, and several amino acid and peptide units as acyl accepters. The study was completed by the use of non-amino-acid-derived acyl accepters comprisi ng simple amines, amino alcohols, and diamines. The results indicate that t he approach presented is a useful strategy for the synthesis of peptide iso steres, peptide analogues, and organic amides. These last open a new range of synthetic applications of proteases completely beyond peptide synthesis, achieving efficient and selective acylations of non-amino-acid-derived ami nes under extraordinarily mild reaction conditions.