Velpatasvir Intermediate-I S,S-Isomer

n-boc-cis-4-cyano-d-prolinemethylester ; (2r,4s)-1-tert-butyl 2-methyl 4-cyanopyrrolidine-1,2-dicarboxylate ; cis-n-boc-4-cyano-l-proline methyl ester, 97% ; 1-tert-butyl 2-methyl (2s,4s)-4-cyanopyrrolidine-1,2-dicarboxylate ; 1,2-pyrrolidinedicarboxylicacid, 4-cyano-, 1-(1,1-dimethylethyl) 2-methyl ester, (2s,4s)- ; 1-o-tert-butyl 2-o-methyl (2s,4s)-4-cyanopyrrolidine-1,2-dicarboxylate ; (2s,4s)-4-cyano-1,2-pyrrolidinedicarboxylic acid 1-(tert-butyl) 2-methyl ester ; boc-cis-4-cyano-l-proline methyl ester ; (2s,4s)-1-boc-4-azidopyrrolidine-2-carboxylic acid methylester ; (2s,4s)-1-tert-butyl 2-methyl 4-cyanopyrrolidine-1,2-dicarboxylate ; n-boc-cis-4-cyano-l-proline methyl ester