Cephalosporin C

Cephalosporin C is a fungal natural product in the beta-lactam antibiotic family, with formula ${\mathrm{C}}_{16}{\mathrm{H}}_{21}{\mathrm{N}}_3{\mathrm{O}}_8\mathrm{S}$. Its framework contains a strained four-membered cyclic amide fused to a sulfur-containing six-membered ring.^[ref]

For synthetic chemistry, the challenge is the combination of reactive rings, several functional groups and defined stereochemistry. Making the correct elemental formula is therefore a much weaker test than constructing the complete structure. This compound supplies a concrete example of why total synthesis needs control over connectivity and spatial arrangement together.