(+)-(2S,3S)-3-O,N-dibenzylhydroxyl-2-hydroxymethyl-5-oxopyrrolidine

(2R,5S,6S)-6-(N-benzyloxycarbonyl-2-aminomethyl)-8-oxo-2-phenyl-1-aza-3-oxa-bicyclo[3.3.0]octane

(2R,5S,6R)-6-(N-benzyloxycarbonyl-2-aminomethyl)-8-oxo-2-phenyl-1-aza-3-oxa-bicyclo[3.3.0]octane

7-ethyloxycarbonyl-6-cyano-8-oxo-2-phenyl-1-aza-3-oxa-bicyclo[3.3.0]octane

(2S,3S,4S)-4-Benzyl-3-tert-butoxycarbonylmethyl-4-ethoxycarbonyl-2-hydroxymethyl-5-oxopyrrolidine