A physico-chemical information rich library of 256 N-protected dipeptides is described. This library has been constructed using a factorial design in the principal properdes of the amino acids. These compounds represent a data set of diverse physical properties which can be screened against a variety of protein substrates in binding assays in the search for micromolar chemica1 leads for drug design. The concept is supported by the design of CCK-A and -B non-peptide ligands from the dipeptide lead Boc-Trp-Phe-NH,, a no-conti~~ dipeptide fragment of CCK.