Organocatalytic asymmetric michael addition of oxazolones to arylsulfonyl indoles: Facile access to syn-configured α,β-disubstituted tryptophan derivatives

Abstract

Enantioselective Michael addition of oxazolones to in situ generated vinylogous imine intermediates is reported. A series of optically active 3-alkylindole derivatives with adjacent quaternary and tertiary stereocenters was obtained. The resulting adducts can readily be converted into syn-configured α,β-disubstituted tryptophan derivatives without compromising the stereoselectivities. Organocatalytic asymmetric Michael addition of oxazolones 2 to vinylogous imine intermediates generated in situ from arylsulfonyl indoles 1 is described. This protocol provides facile access to optically active 3-indolyl derivatives with good results. The resulting adducts can be easily converted into syn-α,β-disubstituted tryptophan derivatives without compromising the stereoselectivities. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.