Construction of spiro-fused 2-oxindole/α-methylene- γ-butyrolactone systems with extremely high enantioselectivity via indium-catalyzed amide allylation of N-methyl isatin.

A remarkably effective method allowing an extremely high enantioselective synthesis of the spiro-fused 2-oxindole/α-methylene-γ-butyrolactones is described. The key strategy lies in the use of indium-catalyzed asymmetric amide allylation of N-methyl isatin with functionalized allylstannanes, which can lead to the antineoplastic spirocyclic lactones in almost enantiopure forms.