Azapeptides represent a class of peptidomimetics and exhibit important utilizations in drug discovery. Diversity-oriented synthesis of azapeptides is challenging due to the complexity of hydrazine chemistry and peptide coupling. Here we report an improved procedure of submonomer azapeptide synthesis by selective alkylation of semicarbazone using various alcohols mediated by the Mitsunobu reaction. The effectiveness of this new strategy was further proved by synthesizing a series of azapeptidomimetics of angiotensin 1–7.