In 100 ml of THF was dissolved 9.97 g of compound (29) and after adding slowly thereto 4.45 g of triethylamine and then 6.01 g of isobutyl chloroformate under ice-cooling, the reaction was performed under ice-cooling. To the reaction mixture was slowly added 11.37 g of 3-(2-oxo-1-pyrrolidinyl)-propylamine and then the reaction was performed for one hour under ice-cooling. Precipitates were filtered off, the filtrate was concentrated, and the residue thus formed was subjected to silica gel column chromatography. By eluting the product with ethyl acetatemethanol (4:1), 4.43 g of (S)-1-benzyloxycarbonyl-N-[3-(2-oxo-pyrrolidinyl)propyl]-2-pyrrolidine carboxamide (99) was obtained.
