1: (S)-2-{2-[(E)-Hydroxyimino]-3-phenyl-propionylamino}-3-phenyl-propionic acid methyl ester With methanesulfonic acid; zinc in tetrahydrofuran T=25°C; 8 h; 2: di-tert-butyl dicarbonate With sodium hydrogencarbonate in water T=25°C; 1 h;