Synthesis of novel angiotensin converting enzyme inhibitors has been accomplished using the a-hydroxy ketomethylene dipeptide isostere as a key constituent. (2R, 5s )-2 hydroxy-5-benzamido-4-oxo-6-phenyl hexanoyl (S )-(-)-indoline-2-carboxylic acid (7) showed potent inhibitory activity against angiotensin converting enzyme. IC, = 0.09 pM.