Divergent synthesis of methylene lactone- and methylene lactam-based spiro compounds; Utility of amido-functionalized γ-hydroxylactam as a precursor for cytotoxic N,O– and N,N-spiro compounds
Tetsuya Sengoku, Anna Shirai, Ayaka Takano, Toshiyasu Inuzuka, Masami Sakamoto, Masaki Takahashi and Hidemi Yoda
The Journal of Organic Chemistry,  2019, 84, 12532-12541. (DOI: 10.1021/acs.joc.9b02038)

Pharmaceutically attractive methylene lactone- and methylene lactam-based spiro compounds have been synthesized by employing amido-functionalized γ-hydroxylactam as a common intermediate.