1: (-)-methyl (1S,2S,3R,4R)-3-[(1S)-1-(acetylamino)-2-ethylbutyl]-4-amino-2-hydroxycyclopentanecarboxylate hydrochloride With sodium hydroxide in N,N-dimethyl-formamide T=0°C; 2 h; 2: chloroformamidine hydrochloride in N,N-dimethyl-formamide T=0 - 20°C; 24.5 h; 3: With sodium hydroxide in water; N,N-dimethyl-formamide pH=8.3 - 8.5;