BF3–methanol as a cyclization/cleavage/conversion reagent for suppression of amino acid racemization in Edman sequencing and l-configuration determination method

A modified Edman procedure using phenylisothiocyanate (PITC) and boron trifluoride (BF3)–methanol for amino acid sequencing and d / l configuration determination was developed. The utilization of BF3–methanol solution resulted in the direct generation of phenylthiohydantoin (PTH)-amino acids from phenylthiocarbamoyl (PTC)-peptide excluding the extraction step after cyclization/cleavage reaction. BF3–methanol as a cyclization/cleavage/conversion reagent in the Edman sequencing procedure afforded a great suppression of the racemization of liberated PTH-amino acids avoiding the extraction step.