An organocatalytic domino Michael addition strategy: construction of bispiro[oxindole-thiazolidinone-hexahydroxanthone]s with five contiguous stereocenters

We herein report a highly efficient strategy for the stereoselective synthesis of structurally complex bispiro[oxindole-thiazolidinone-hexahydroxanthone]s. This squaramide-catalyzed domino Michael addition afforded these products in good to excellent yields with excellent stereoselectivities bearing five contiguous stereocenters with two spiroquaternary stereocenters. Meanwhile, both gram-scale synthesis and further transformation experiments have been also demonstrated.