Cephalosporin C was first isolated from Cephalosporium acremonium in 1953 by Newton and Abraham, Oxford University. The core structure of cephalosporin is a fused β-lactam-dihydrothiazine system. The importance of the cephalosporin family in modern medicine is due to its resistance to β-lactamase and its versatility for producing semi-synthetic derivatives through which the spectrum of action has been extended from broad Gram-positive activity to include some Gram-negative organisms. The Cephalosporin Metabolite Set contains important examples of generations I to IV, as well as the key synthetic intermediate, 7-amino-3-cephem-4-carboxylic acid.