Stereoselective synthesis of functionalized quaternary stereocenters, naturally occurring tetronic acids and (-)-(R,R)-L-factor

Manchoju, Amarender (2018) Stereoselective synthesis of functionalized quaternary stereocenters, naturally occurring tetronic acids and (-)-(R,R)-L-factor. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The enantioselective synthesis of functionalized, acyclic, quaternary stereocenter- containing building blocks was achieved from diastereomerically pure alkylidenemorpholinones by employing Suzuki-Miyaura cross-coupling and Prins reactions as the key steps. In a separate approach, the enantioselective conjugate addition of a variety of 3-alkyl-and/or 3-aryl tetronic acids or 3-alkyl-and/or 3-aryl tetramic acids to α,β-unsaturated systems catalyzed by chiral aminothioureas, aminosquaramides and cinchona alkaloids was examined. These studies provided the quaternary stereocenter-containing furan-2,4-diones and pyrrolidine-2,4-diones with moderate enantiomeric excess. A variety of 3-aryl tetronic acids were synthesized by employing an undirected, intermolecular C−H functionalization reaction of arenes with 3-diazofuran-2,4-dione as the key step. This method was applied in the synthesis of a series of biologically active, naturally occurring 3-aryl-5-arylidene tetronic acid derivatives such as pulvinic acids and pulvinones. A concise synthesis of (-)-(R,R)-L-factor was achieved in four steps by using an organocatalytic asymmetric direct vinylogous aldol reaction of -crotonolactone and hexanal as the key step.

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