Synthesis of a 6-azaspiro[4.5]decane related to halichlorine and the pinnaic acids

Article abstract of DOI:10.1016/S0040-4039(99)01815-8

Sulfone 15, derived from D-glutamic acid, and aldehyde 23, made by diastereoselective alkylation, were linked and elaborated into enamine sulfone 33. This underwent 5-exo radical cyclization to 34, which was desulfonylated to (-)-35, a compound that represents the spirobicyclic core of halichlorine.