(S,5R,6R)-6-[[(2R)-2-Carboxy-2-(3-thienyl)acetyl]amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic-13C3 Acid DSodiumSalt; 6-[D-(-)-α-Carboxy-3-thienylacetamido]penicillanic-13C3 Acid DSodiumSalt; [S-[2α,5α,6 βS*)]]-6-[(Carboxy-3-thienylacetyl)amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic-13C3 Acid DSodiumSalt; AB 2288-13C3; 6-D(-)-(α-Carboxy-3-thienylacetamido)penicillanic-13C3 Acid DSodiumSalt; BRL 2288-13C3; DSodium