5-Substituted-3-(alkoxycarbonyl)alkyl-hydantoin derivatives were prepared by mechanochemistry from amino esters or dipeptides, via a 1,1'-carbonyldiimidazole-mediated one-pot/two-step cyclization reaction involving amino acid unsymmetrical urea A and carboxy-imidazolyl-dipeptide ester B intermediates. Comparative experiments in solution were also performed. The successful preparation of an antibacterial agent precursor was also investigated.