The hydroxyethylene dipeptide isosteres l-682,679, l-684,414, l-685,434, and l-685,458 were synthesized in a few steps by a sequence involving an allyltrichlorostannane coupling with an α-amino aldehyde, followed by hydroboration of the corresponding 1,2-syn and 1,2-anti amino alcohols to give the diols, lactonization under TPAP conditions, lactone opening, and peptide coupling with the desired amine or dipeptide amide. The present synthetic approach represents a practical entry to a large range of other dipeptide isosteres.