Sequential One-Pot Synthesis of Dipeptides through the Transient Formation of CDI-N--Protected alpha--Aminoesters: The synthesis of dipeptides through a sequential one-pot procedure from commercially available protected amino acids is described. The transformation relies on the use of in situ generated transiently CDI-protected alpha-amino esters (CDI, e.g. N,N’-carbonyldiimidazole). In addition of being a highly atom-economical process, the couplings take place under very mild and neutral conditions without adding a base to the reaction medium. This protocol provides a concise and less costly route to dipeptide derivatives (12 examples, up to 87% yield) and is compatible with commonly used N-urethane protecting groups. Moreover, no epimerization was detected even when sensitive Boc-Cys(Bn)-OH was used.