title: Stereoselective Organocatalytic Synthesis of Oxindoles with Adjacent Tetrasubstituted Stereocenters.
abstract: Oxindoles with adjacent tetrasubstituted stereocenters were obtained in high yields and stereoselectivities by organocatalyzed conjugate addition reactions of monothiomalonates (MTMs) to isatin-derived N-Cbz ketimines. The method requires only a low catalyst loading (2 mol %) and proceeds under mild reaction conditions. Both enantiomers are accessible in good yields and excellent stereoselectivities by using either Takemoto's catalyst or a cinchona alkaloid derivative. The synthetic methodology allowed establishment of a straightforward route to derivatives of the gastrin/cholecystokinin-B receptor antagonist AG-041R.
authors.affiliation: ETH Zurich, Laboratory for Organic Chemistry, D-CHAB, Vladimir-Prelog-Weg 3, 8093 Zurich (Switzerland) http://www.wennemers.ethz.ch.
authors.forename: Oliver D
authors.initials: OD
authors.lastname: Engl
authors.affiliation: ETH Zurich, Laboratory for Organic Chemistry, D-CHAB, Vladimir-Prelog-Weg 3, 8093 Zurich (Switzerland) http://www.wennemers.ethz.ch.
authors.forename: Sven P
authors.initials: SP
authors.lastname: Fritz
authors.affiliation: ETH Zurich, Laboratory for Organic Chemistry, D-CHAB, Vladimir-Prelog-Weg 3, 8093 Zurich (Switzerland) http://www.wennemers.ethz.ch. Helma.Wennemers@org.chem.ethz.ch.
authors.forename: Helma
authors.initials: H
authors.lastname: Wennemers
keywords: asymmetric synthesis; enantioselectivity; heterocycles; organocatalysis; synthetic methods