title: Enantioselective Pictet-Spengler Reactions of Isatins for the Synthesis of Spiroindolones.
abstract: The condensation cyclization between isatins and 5-methoxy tryptamine catalyzed by chiral phosphoric acids provides spirooxindole tetrahydro-β-carboline products in excellent yields (up to 99%) and enantioselectivity (up to 98:2 er). A comparison of catalysts provides insight for the substrate scope and factors responsible for efficient catalytic activity and selectivity in the spirocyclization. Chiral phosphoric acids with different 3,3'-substitution on the binaphthyl system and opposite axial chirality afford the spiroindolone product with the same absolute configuration.
authors.affiliation: Department of Chemistry, University of California, One Shields Ave, Davis, California 95616, United States.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Badillo
authors.forename: Abel
authors.initials: A
authors.lastname: Silva-García
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Shupe
authors.forename: James C
authors.initials: JC
authors.lastname: Fettinger
authors.forename: Annaliese K
authors.initials: AK
authors.lastname: Franz