isobutyryloxymethyl (5R,6S,7S)-7-[(R)-1-tert-butyldimethylsilyloxymethyl]-5-methyl-4,8-dioxo-1-aza-3-thia-bicyclo-[4.2.0]octan-2-carboxylate (HCID 131718995)|Huagongshe