DPPA-promoted decarbonylation of a N-Cbz-(D,L)-pipecolinic acid derivative: An easy entry to [4.5]spirolactams and [4.5]spirolactones. Total synthesis of (±)-δ-coniceine

Article abstract of DOI:10.1016/S0040-4039(00)73161-3

The synthesis of 6-benzyloxycarbonyl-1-oxa-6-azaspiro[4.5]decane 2-one 7a and 6-benzyloxycarbonyl-1,6-diazaspiro[4.5]decane-2-one 7b from (D,L)-pipecolinic acid is described. The extremely clean decarboxylation of the α-substituted amino acid 9d promoted by diphenylphosphorazidate (DDPA) is the key step of our strategy. The total synthesis of (±)-δ-coniceine (16) from the enamine ester 10a has been succesfully achieved.