An approach for preparing 3,3-disubstituted oxindole from acyclic tetrasubstituted aldehyde: Total synthesis of (-)-coerulescine & (-)-coixspirolactam A

Abstract

(-)-Coerulescine 7 and (-)-coixspirolactam A 8, two naturally occurring compounds characterized by an all-carbon quaternary center containing spirooxindole, have been synthesized asymmetrically. The key feature of their total synthesis involves a novel rational construction of the chiral 3,3-disubstituted oxindole core from the acyclic tetrasubstituted aldehyde. The latter scaffold was prepared in very good enantioselectivity up to 91% (after recrystallization) from the ethyl-2-(2-nitrophenyl)acrylate 1 by exploring both intermolecular and intramolecular Pd- mediated asymmetric allylic alkylation.