1: (L)-leucine methyl ester hydrochloride With triethylamine in tetrahydrofuran T=20°C; 2: N-Cbz-L-proline p-toluene thiol ester With N,O-bis-(trimethylsilyl)-acetamide in ethanol T=40°C; 48 h;

1: C7H15NO2*(x)ClH With triethylamine in tetrahydrofuran T=20°C; 2: N-Cbz-L-proline p-toluene thiol ester With bis-trimethylsilyl ether T=40°C; 27 h; Ionic liquid;