Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/33269
Title: Guanidine Catalyzed Enantioselective Mannich Reaction: Towards the Synthesis of ?-Amino Acids
Authors: PAN YUANHANG
Keywords: decarboxylation, guanidine, Mannich reaction, amination, fluorocarbon nucleophile, organocatalysis
Issue Date: 6-Aug-2011
Source: PAN YUANHANG (2011-08-06). Guanidine Catalyzed Enantioselective Mannich Reaction: Towards the Synthesis of ?-Amino Acids. ScholarBank@NUS Repository.
Abstract: Due to the low reactivity of simple esters, using them as nucleophiles in direct asymmetric transformations is a long standing challenge in synthetic organic chemistry. Nature approaches this difficulty through a decarboxylative mechanism in polyketide biosynthesis. Inspired by nature, we developed chiral bicyclic guanidine catalyzed enantioselective biomimetic decarboxylative C-C and C-N bond formation reactions (up to 90% yield, up to 98% ee). These highly enantioselective decarboxylative Mannich and amination reactions utilized malonic acid half thioesters as simple ester surrogates. This methodology provided the synthetic route towards both beta-amino acid and alfa-amino acid derivatives. Mechanistically, based on the experimental studies and theoretical calculations, we proposed that the nucleophilic addition precedes decarboxylation. In addition, we also developed a highly enantio- and diastereoselective guanidine-catalyzed Mannich reaction with alfa-fluoro-beta-keto acyloxazolidinone as the fluorocarbon nucleophile (up to 99% yield, up to 99:1 dr, up to >99% ee). alfa-Fluoro-beta-amino acid derivatives with chiral fluorinated carbon were obtained via selective deacylation or decarboxylation reaction.
URI: http://scholarbank.nus.edu.sg/handle/10635/33269
Appears in Collections:Ph.D Theses (Open)

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