As a model metathesis, calicheamicin was treated with excess dibenzyl trisulfide (35 equivalents) in deuteurated DMF (Figure ). Excess dibenzyl trisulfide was used to drive the equilibrium in favor of the benzyl calicheamicin trisulfide derivative. Analysis by 1 H NMR revealed clean conversion to the benzylated calicheamicin product and the MeS3Bn co-product over a period of 10 minutes (S203-S208). The calicheamicin derivative was precipitated and triturated with pentane.