The equimolar reactions of N-protected amino acids, amino acids or amino acid esters with oxallates (1a-1e) having active ester groups in the presence of pyridine in acetonitrile afforded the corresponding dipeptides via active esters in good yields. ... Hutinec A. , Rupčić R. , Ćaleta I. , Oršulić M. ... Sheikh MC , Takagi S. , Yoshimura T. , Morita H. ... Bailén MA , Chinchilla R. , Dodsworth DJ , Nájera C.