Solid-Phase Synthesis of trisubstituted 2-imidazolidones and 2-imidazolidinethiones

An efficient method for the solid-phase synthesis of 1,3,4-trisubstituted-2 -imidazolidones and 1,3,4-trisubstituted-2-imidazolidinethiones from reduce d N-acylated dipeptides is described. The complete reduction of the amide b onds of an N-acylated dipeptide with borane in THF results in two secondary and one tertiary amine. Reaction of the resulting resin-bound polyamine 4 with carbonyldiimidazole or thiocarbonyldiimidazole affords, respectively, cyclic ureas 6 and cyclic thioureas 7 in high yield and purity. Details on the selection of the building blocks and characterization of the controls f or the libraries' synthesis will be presented. These procedures have also b een used to generate parallel arrays and mixture-based combinatorial librar ies of cyclic ureas and thioureas.