CAS No:19379-33-0 ||Chemical Formula:C16H19N3O4S ||Molecular Weight:349.405 ||Exact Mass:349.10963 || Chemical Formula: C16H19N3O4S|(2S,5R,6R)-6-((S)-2-amino-2-phenylacetamido)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid http://www.pipitech.com/ampicillin-Impurity-b.html