<(R)-N-p-nitrobenzyloxycarbonylpyrrolidin-2-yl>carbothioic S-acid

(3S,4R)-3-<(1R)-(tert-butyldimethylsiloxy)ethyl>-4-<(2R)-N-p-nitrobenzyloxycarbonylpyrrolidin-2-yl>carbonylthioazetidin-2-one