Diastereoselective Intramolecular Ester Transfer Reaction ofN-Alkenylcar­bamate Derivatives Mediated by Zirconocene-Butene Complex: Preparation of α,γ-Disubstituted γ-Aminobutyric Acid (GABA) Derivatives and 2,4-Di­substituted Pyrrolidine Derivatives

Abstract

D i a s t e r e o s e l e c t i v e I n t r a m o l e c u l a r E s t e r T r a n s f e r R e a c t i o n o f N -A l k e n y l c a r b a m a t e D e r i v a t i v e s Abstract: Zirconium-mediated diastereoselective alkene-carbonyl coupling reactions of N-alkenylcarbamate derivatives are reported. The present alkene-carbonyl coupling reactions using chiral tertbutyl 3-butenylcarbamates having a substituent at the homoallylic position proceeded in a highly diastereoselective manner to give a-methyl-g-substituted g-aminobutyric acid (GABA) derivatives. Iodination of the intermediary zirconium species gave the a-iodomethylated g-aminobutyrates, which were, in turn, converted to the 5-substituted pyrrolidine-3-carboxylate having cis stereochemistry.