N-terminal substituent and side-chain influences on the chemical shifts of protons in model dipeptide systems

Abstract

¹ H Chemical shift values of ester methyls in model dipeptide esters have been shown to be sensitive to (a) the nature and configuration of the constituent amino acids and (b) the spatial distance between the N-terminal aryl group and the ester protons. Chemical shift differences have been rationalised in terms of shielding effects as calculated from space-filling models and tables of ‘ring current’ effects.