A Concise Synthesis of Turneforcidine via a Metalloiminium Ion Cyclization Terminated by the 2-(Methylthio)-3-(trimethylsilyl)-1-propenyl Moiety
摘要:
[GRAPHICS]A concise synthetic route to racemic turneforcidine (1) is described that relies on the stereocontrolled cyclization of the 2-(methylthio)-3-(trimethylsilyi)-1-propenyl bearing imine 5 in the presence of TiCl4.
Necine bases of pyrrolizidine alkaloids, turneforcidine, hastanecine, and platynecine are synthesized from ethyl 1-hydroxy-2,3,5,6-tetrahydro-1H-pyrrolizine-7-carboxylate in racemic form.
Ring Expansion of Azetidinium Ylides: Rapid Access to the Pyrrolizidine Alkaloids Turneforcidine and Platynecine
作者:John A. Vanecko、F. G. West
DOI:10.1021/ol050915o
日期:2005.7.1
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.
Novel synthesis of the pyrrolizidine skeleton by sulfenocycloamination. Total synthesis of (.+-.)-retronecine and (.+-.)-turneforcidine