(2S,5R,6S)-6-(hydroxymethyl)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid
(2S,5R,6S)-7-keto-3,3-dimethyl-6-methylol-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid