3-[[[(2S,4S)-4-Mercapto-1-(4-nitrobenzyloxy)carbonyl-2-pyrrolidinyl]carbonyl]amino]benzoic acid

99-05-8

151072-00-3

202467-69-4

At 60 °C, m-aminobenzoic acid (9.45 g, 68.9 mmol) was dissolved in 200 g of methanol and 1 g of tributylphosphine and 400 ml of a methanolic solution of 4M HCl were added. Subsequently, 220 g of methanol solution of 4-nitrobenzyl (1S,4S)-3-oxo-2-thia-5-azabicyclo[2.2.1]heptane-5-carboxylate (19.8 g, 64.28 mmol) was slowly added. The reaction was stirred at the same temperature for 3 hours. After completion of the reaction, the slurry was cooled and filtered to obtain white crystals. The white crystals were washed with methanol and then dried under vacuum to afford 3-((2S,4S)-4-mercapto-1-(((4-nitrobenzyloxy)oxy)carbonyl)pyrrolidine-2-carboxamido)benzoic acid (127.8 g) in 97% molar yield and 99.2% HPLC purity.