2-<3-benzyl-6-oxo-2-thia-4,7-diaza-(1R,5R)-bicyclo-<3,2,0>-hept-3-en-7-yl>-t-butyl acetate

2-((2R,3R)-4-Oxo-3-phenylacetylamino-azetidin-2-ylsulfanyl)-malonic acid dimethyl ester