It has been shown that N-Phthalyl-derivatives of a-amino- acids can be converted into the corresponding diazoketones. We have applied this reaction to the preparation of the homologue of L-leucine by the Arndt-Eistert synthesis from the hitherto undescribed diazoketone of N-phthalyl-L-leucine (I), Methanolic solution of (I) heated with silver oxyde yielded the optically active ester of the homologous acid (Il), which, refluxed with hydriodic acid, gave the free, optically active B-amino acid (III)
