Solid-phase synthesis of bis-2-imidazolidinethiones from resin-bound tripeptides.

The exhaustive reduction of resin-bound tripeptides with borane afforded three secondary amines and one primary amine. The treatment of the solid-support polyamines with thiocarbonyldiimidazole afforded, following cleavage of the solid support, the corresponding bis-cyclic thiourea in good purity and yield.