Study of the full deprotection of a model peptide

Abstract

Fmoc chemistry has been used to synthesise the 2-chlorotrityl peptidyl-resin shown in the figure below, in order to study its cleavage conditions and the subsequent side products.The cleavage of the peptide, as well as the deprotection of its side chains, are practically quantitative after 30 minutes of reaction time, using 95 % TFA, 2.5 % TIPS and 2.5 Milli-Q water. The main impurity belongs to a dimer that arises from the formation of a disulphide bond between the Cys residues of two identical peptide chains. The addition of DTT to the cleavage mixture as a reducing agent does not prevent the formation of the dimer. On the other hand, using TCEP as a reducing agent minimises the formation of this side product in a very efficient way.