Chiral analysis of synthetic peptides: high performance liquid chromatography of diastereoisomeric carbamoyl esters derived from N-terminal cleavage

A cleavage routine for chiral analysis has revealed that the N-terminal residue in model dipeptides, after derivatisation with a chiral isocyanate reagent, can be cleaved off as the N-carbamoyl ester under relatively mild conditions (MeOH/SOCl2/60 °C for 3 h) free from inherent problems of racemisation. The diastereoisomeric carbamoyl amino acid esters produced can be separated and identified by HPLC. The methodology has been optimised for a number of representative amino acids, including tyrosine, histidine, methionine and tryptophan which have side-functions capable of complicating the procedure.