Organocatalytic Asymmetric Michael Addition of Oxazolones to Arylsulfonyl Indoles: Facile Access to syn-Configured α,β-Disubstituted Tryptophan Derivatives

• Published in: European journal of organic chemistry Vol. 2013; no. 3; pp. 456 - 459
• Main Authors: Cai, Chang-Wu, Zhu, Xing-Li, Wu, Song, Zuo, Zong-Le, Yu, Liang-Liang, Qin, Da-Bin, Liu, Quan-Zhong, Jing, Lin-Hai
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.01.2013; WILEY‐VCH Verlag; Wiley
• Subjects: Asymmetric synthesis; Chemistry; Chemistry, Organic; Enantioselectivity; Heterocycles; Michael addition; Organocatalysis; Physical Sciences; Science & Technology; Michael addition; Heterocycles; GENERATED IN-SITU; Enantioselectivity; ENANTIOSELECTIVE SYNTHESIS; BETA-SUBSTITUTED TRYPTOPHANS; 3-(1-ARYLSULFONYLALKYL) INDOLES; ALPHA-AMINO-ACIDS; CARBONYL-COMPOUNDS; ACTIVATING PROPERTIES; Organocatalysis; STEPHACIDIN-B; Asymmetric synthesis; THIOUREA CATALYSTS; FRIEDEL-CRAFTS REACTION
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201201335

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.