1: (tert-butoxycarbonyl)-L-proline pentafluorophenol ester With lithium diisopropyl amide in tetrahydrofuran T=-90°C; deprotonation; 0.333333 h; 2: acetone in tetrahydrofuran T=-90°C; cyclocondensation; 0.5 h; Further stages.;

sodium perchlorate; triethylamine in N,N-dimethyl-formamide T=20°C; Condensation; 2 h;