A carbene insertion route to β-lactam fused cyclic enediynes

A new methodology has been developed for the synthesis of biologically important β-lactam fused enediynes 1 and 2. The key step is the successful insertion of the carbene generated from the diazo enediynes 3 and 4. The result is in sharp contrast to the fate of the carbene generated from acyclic enediyne 5 in which case the rearrangement product 6 and the dimer 7 were obtained.