K-Oxyma: a Strong Acylation-Promoting, 2-CTC Resin-Friendly Coupling Additive

Here we present a new formulation of the recently introduced OxymaPure additive for peptide bond formation, in which the N-hydroxylamine group is replaced by a potassium salt. The complete suppression of its acidity converts K-Oxyma into the most suitable coupling choice when peptides are assembled on highly acid-labile solid-supports. The coupling efficiency and diminished prospects for epimerization are conserved relative to OxymaPure. In addition, K-Oxyma displays excellent solubility in a variety of organic solvents and undergoes safer decomposition than classical 1-hydroxybenzotriazole additives.