(5S)-1-(2,2-dimethylpropionyl)-3,3-dimethyl-5-trityloxymethylpyrrolidin-2-one

(5S)-(-)-5-tert-butyldimethylsiloxymethyl-3,3-dimethyl-1-(propionyl)-pyrrolidin-2-one

(5S)-5-tert-butyldimethylsiloxymethyl-1-(2,2-dimethylpropionyl)-3,3-dimethylpyrrolidin-2-one

(S)-(N-benzyloxycarbonyl)-(4,4-dimethylpyrrolidin-2-yl)methan-1-ol

(5S)-(-)-3,3-dimethyl-5-triphenylmethoxymethyl-1-propionyl-pyrrolidin-2-one