The structure-activity relationship of the O-benzyl serine side chain was investigated based on the tetrazole-based growth hormone secretagogue BMS-317180 (2). The ortho position of the benzyl moiety was found to be favorable for introduction of substituents. A series of ortho-substituted compounds were synthesized with improved in-vitro and in-vivo activity. Among them, the biphenyl compound 2p shows twofold improvement in potency compared to its parent compound BMS-317180 (2).