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.
Intramolecular [4 + 1] pyrroline annulation via azide-diene cycloadditions. 2. Formal stereoselective total syntheses of (.+-.)-platynecine, (.+-.)-hastanecine, (.+-.)-turneforcidine, and (.+-.)-dihydroxyheliotridane
作者:Tomas Hudlicky、Gustavo Seoane、Thomas C. Lovelace
DOI:10.1021/jo00244a047
日期:1988.4
Enantioselective synthesis of seven pyrrolizidine diols from a single precursor