Biologically active peptides have significant therapeutic potential but face serious limitations, especially for oral dosing. Our group at Merck adopted a structure/conformation/activity strategy based on native peptide structure to address these challenges. This article covers two key research areas: design and synthesis of dipeptide lactams as conformational constraints for peptides, and development of cyclic hexapeptide somatostatin agonists. For dipeptide lactams, we established synthetic methods (intramolecular acylation, alkylation, condensation) to produce optically pure products, applied them to C3 symmetric cyclic hexapeptides (δ-lactam analogues retained activity) and luteinizing hormone-releasing hormone (LH-RH), yielding an analogue with 8.9-fold higher in vitro potency and 2.4-fold higher in vivo potency than native LH-RH. For cyclic hexapeptide somatostatin agonists, we designed analogues (e.g., compound 37 with Phe-Pro scaffold) showing 1.74 times somatostatin's potency in growth hormone release assays, developed an improved NaHCO3-mediated cyclization protocol (77% yield, minimal racemization, scalable to 100 g), constructed a conformational model (type II′ β-turn for Phe-D-Trp-Lys-Thr, type VI β-turn with cis Phe-Pro for Thr-Phe-Pro-Phe), and validated it via N-methylation (activity consistent with predictions) and constraint studies (Cys-Cys replacement retained activity, lactam constraints with trans amide were inactive). These results demonstrate the utility of dipeptide lactams and conformational modeling in developing potent, stable peptide analogues for therapeutic use.