(5S,4S,3R)-N-tert-butyloxycarbonyl-5-tert-butyldimethylsiloxymethyl-4-difluoromethyl-3-(tert-butyldimethylsiloxy)pyrrolidin-2-one

(5S,4R,3R)-N-tert-butyloxycarbonyl-5-tert-butyldimethylsiloxymethyl-4-difluoromethyl-3-(tert-butyldimethylsiloxy)pyrrolidin-2-one

(2S,3R,4S,5S)-N-tert-butyloxycarbonyl-2-acetyloxy-3-tert-butyldimethylsilyloxy-4-difluoromethyl-5-(tert-butyldimethylsiloxymethyl)pyrrolidine

(2S,3R,4R,5S)-N-tert-butyloxycarbonyl-2-acetyloxy-3-tert-butyldimethylsilyloxy-4-difluoromethyl-5-(tert-butyldimethylsiloxymethyl)pyrrolidine

(2S,3S,4R)-N-tert-butyloxycarbonyl-4-benzoyloxy-3-difluoromethyl-2-(tert-butyldiphenylsiloxymethyl)pyrrolidine