Synonyms: Pyridinium,4-[[(2R,4S)-4-[[(4R,5S,6S)-2-carboxy-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-en-3-yl]thio]-2-pyrrolidinyl]methyl]-1-methyl-,chloride (9CI); Pyridinium, 4-[[4-[[2-carboxy-6-(1-hydroxyethyl)-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-en-3-yl]thio]-2-pyrrolidinyl]methyl]-1-methyl-,chloride, [4R-[3(2R*,4S*),4a,5b,6b(R*)]]-; 1-Azabicyclo[3.2.0]heptane, pyridiniumderiv.; FR 21751