Strategies to single-step edit the core skeleton of structurally complex compounds still remains highly desirable but challenging. Herein an unexpected discovery to access natural product dehydrocostus lactone/parthenolide-inspired bispiro[oxindole-oxazinane] hybrids enabled by formal oxygen atom insertion into a carbon–nitrogen bond as a skeletal-editing step is described. These structurally diverse and medicinally important products containing up to six adjacent stereocentres including two quaternary spiro-stereocentres were smoothly afforded with excellent results in two steps. It is noteworthy that such a protocol represents the first example of the skeletal editing of a pyrrolidine skeleton to a 1,2-oxazinane skeleton and expands the applicability scope of “single-atom” skeletal-editing technologies.