The B-lactam structure is derived from two covalently bonded amino acid residues; cysteine and valine. This forms via a tripeptide intermediate where the third amino acid is replaced by the variable r-group SH H2N HN HN OH Cysteine β- actam structure ValineThe β-lactam structure is derived from two covalently bonded amino acid residues; cysteine and valine. This forms via a tripeptide intermediate where the third amino acid is replaced by the variable R-group