(S,S)-1-(tert-Butoxycarbonyl)-3-Hydroxypyrrolidine-2-carboxylic acid methyl Ster; (S,S)-N-(tert-Butyloxycarbonyl)-3-hydroxy-2-pyrrolidinecarboxylic acid methyl Ster; (S,S)-N-tert-Butoxycarbonyl-3-hydroxy-2-pyrrolidinecarboxylic acid methyl Ster; N-(tert-Butoxycarbonyl)-(S)-hydroxy-L-proline methyl Ster; tert-Butyl methyl (S,S)-3-hydroxypyrrolidine-1,2-dicarboxylate;