The optimization of a series of fused β‐homophenylalanine inhibitors of dipeptidyl peptidase‐4 (DPP‐4) is described. Modification on the P2‐binding moiety of 6 (IC50 = 10 nM) led to the discovery of β‐homophenylalanine derivatives containing pyrrolidin‐2‐ylmethyl amides. The introduction of a sulfamine in the meta position of the phenyl ring improved the potency against DPP‐4 (6–12‐fold increase).