Aiming at restricting the conformational freedom of tryptophan-containing peptide ligands, we designed a THBC (tetrahydro-beta-carboline)-DKP (diketopiperazine)-based peptidomimetic scaffold capable of arranging in an unusual alpha-turn conformation. The synthesis is based on a diastereoselective Pictet-Spengler condensation to give the THBC core, followed by an intramolecular lactamization to complete