The use of a dipeptide library as the source of a micromolar chemical lead compound for the human tachykinin NK3 receptor is described. The screening of a dipeptide library through a cloned human NK3 receptor binding assay resulted in the identification of Boc (S) Phe (S) PheNH2 (1), which has subsequently been developed, following a'peptoid'design strategy, into a series of high-affinity NK3 receptor selective antagonists. The structure-activity ...