Effects of the incorporation of IBTM β-turn mimetics into the dipeptoid CCK1 receptor agonist PD 170292

Replacement of the 2-Adoc- -αMeTrp residue in the non-selective CCK1 receptor agonist PD 170292 by the Z-(2R,5R,11bS)-IBTM skeleton, able to fix a type II β-turn-like conformation, led to a conformationally restricted dipeptoid analogue, namely 3a, which exhibited a notable increase in the CCK1 selectivity and antagonist properties.