(2S,4S)-4-Nitrobenzyl 2-(dimethylcarbamoyl)-4-mercaptopyrrolidine-1-carboxylate;side chain for meropenem;(2s,4s)-2-(dimethylaminocarbonyl)-4-mercapto-1-(p-nitrobenzyloxycarbonyl)-1-pyrrolidine;(2s-cis)-2-[(dimethylamino)carbonyl]-4-mercapto-1-pyrrolidinecOpen