Abstract: Process for the preparation of a 3,6'-di-N-Acyl-1-[L-(-)-4-Acylamino-2-hydroxybutyryl] kanamycin A, wherein Acyl is a N-protecting acylating group, which comprises reacting kanamycin A with an aluminum salt in an inert organic solvent, treating the aluminum complex thus obtained with a N-acylating agent and acidifiying the reaction mixture, as such or after having removed the complexing aluminum in basic medium and isolated the 3,6'-di-N-Acyl-kanamycin A, to pH 6, treating the protonated 3,6'-di-N-Acyl-kanamycin A, in form of a salt thereof, with an active derivative of L-(-)-4-Acyl-amino-2-hydroxybutyric acid, wherein Acyl is a N-protecting group preferably identical with that which protects the amino groups in the positions 3 and 6' of kanamycin A, and isolating the product thus obtained by simple correction of the pH.

Abstract: The 6-[D(-)-alpha(4-ethyl-2,3-dioxopiperazin-1-ylcarbonylamino)-alphaphenylace tamido]penicillanic acid and the salts thereof are prepared by synthetizing the novel intermediates, thioesters of D(-)-alpha-(4-ethyl-2,3-dioxopiperazin-1-ylcarbonylamino)-alpha-phenylacet ic acid, with mercaptoheterocycles and by converting them into the desired compound by reaction with 6-amino-penicillanic acid.