Highly Diastereo- and Enantioselective Aza-Mannich Addition of Oxazolones to N-Boc Protected alpha-Amido Sulfones Catalyzed by Bifunctional Thiourea-modified Cinchona Alkaloid

摘要

A diastereo- and enantioselective aza-Mannich addition of oxazolones to alpha-amino sulfones catalyzed by tertiary amine-1-phenylethyl thiourea based on cinchona structure has been developed. The reaction afforded the azlactone adducts bearing quaternary and tertiary stereogenic centers with high yields (up to 98 %) and moderate to excellent diastereo- and enantioselectivities (up to >99 : 1 dr and 96 % ee). The absolute configuration of a product was assigned by X-ray crystal structural analyses and a plausible reaction mechanism was proposed.