Ring expansion of azetidinium ylides: rapid access to the pyrrolizidine alkaloids turneforcidine and platynecine.
[reaction: see text] Azetidinecarboxylate esters react readily with metallocarbenes in an inter- or intramolecular fashion to generate azetidinium ylides. Efficient [1,2]-shift by the ester-substituted carbon furnishes ring-expanded pyrrolidine products. In the case of substrate 1, this provides access to the pyrrolizidine alkaloids turneforcidine and platynecine via a high-yield, five-step sequence starting with readily available methyl 1-benzylazetidine-2-carboxylate.
Vanecko
John A
JA
Department of Chemistry, University of Utah, Salt Lake City, 84112-0850, USA.
West
F G
FG
D001384:Azetidines / Q000737:chemistry*; D003500:Cyclization; D006574:Heterocyclic Compounds, 2-Ring / Q000138:chemical synthesis*; D015394:Molecular Structure; D011763:Pyrrolizidine Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry
D001384:Azetidines; D006574:Heterocyclic Compounds, 2-Ring; D011763:Pyrrolizidine Alkaloids; C443726:turneforcidine; C494063:platynecine