A series of growth hormone secretagogues (GHSs) based on 2, 3-dihydroisothiazole has been synthesized in the search for a potential treatment of growth hormone deficiency or frailty in the elderly. This paper describes the evaluation of the SAR of the benzyl-d-Ser- aminoisobutyric acid dipeptide fragment. Introduction of substituents in the peptide backbone and in the phenyl ring has been investigated, as well as replacements for the ...