Synthesis of norcantharidin-dimer derivatives

We use one molecule of ethylene diamine as a connecting arm to combine two molecules of 5,6-dehydronorcantharidin. Then, ten novel norcantharidin derivatives were synthesized in a single step by the [3 + 2] 1,3-dipolar cycloaddition reaction with oxime or hydrazone in the presence of chloramine-T, which is simpler than the conventional method.