The Use of Esters of Simple Ketoximes in Peptide Synthesis

A number of esters of carbobenzoxyamino acids with acetoxime, cyclopentanonoxime and cyclohexanonoxime have been synthesized by direct condensation using dicyclohexylcarbodiimide. These esters are stable and crystalline solids (including carbobenzoxy-serine, -threonine and-nitroarginine) and react readily with amino acid esters or peptide esters in the presence of acid catalyst such as acetic acid, formic acid or phenylacetic acid. Because of the easy availability and the water solubility of the simple ketoximes, these active esters should be useful for the peptide synthesis.