Synthesis and biological evaluation of novel benzyl-substituted (S)-phenylalanine derivatives as potent dipeptidyl peptidase 4 inhibitors

Novel benzyl-substituted (S)-phenylalanine derivatives 6a and 6g showed potent DPP-4 inhibitory activity with IC50 values of 9.39 and 3.79 nM, respectively, which was significantly superior to that of lead compound 1.