... N,N¢-diisopropylethylamine; DMS, dimethylsulfide; EDT,ethanedithiol; hCt, human calcitonin; MBHA, 4-methyl benzhydryl-amine resin; Mtt, 4-methyltrityl; Pip, 2-phenylisopropyl;OFm, fluoren-9-yl methylester; sCt, salmon ... in vivo hypocalcemic potencies were assessed.The novel analogues include cyclo17,21-[Asp17,D-Phe19,Lys21]hCt (2), cyclo17,21-[Asp17,Aib18,Lys21]hCt (3),cyclo17,21-[Asp17,D-Lys18,Lys21]hCt ... 836–847]. We havehypothesized that a possibly type I b turn/b sheet confor-mation in the region 1 7–21 may play an important role inhCt bioactivity. To investigate this hypothesis, analogues...