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Asymmetric 1,4‐Addition of Oxazolones to Nitroalkenes by Bifunctional Cinchona Alkaloid Thiourea Organocatalysts: Synthesis of α,α‐Disubstituted α‐Amino Acids
Author(s) -
Alemán José,
Milelli Andrea,
Cabrera Silvia,
Reyes Efraim,
Jørgensen Karl Anker
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200802030
Subject(s) - thiourea , bifunctional , chemistry , cinchona , organocatalysis , amino acid , organic chemistry , optically active , michael reaction , enantioselective synthesis , catalysis , biochemistry
An easy and simple synthetic approach to optically active α,α‐quaternary α‐amino acids using asymmetric organocatalysis is presented. The addition of oxazolones to nitroalkenes catalyzed by thiourea cinchona derivatives provides the corresponding α,α‐quaternary α‐amino acid derivatives with good yields, excellent diastereoselectivities (up to 98 % dr ), and from moderate to good enantioselectivities (up to 92 % ee ). The reaction can be performed on a large scale. The optically active oxazolone–nitroalkene addition products can be opened in a one‐pot reaction to the corresponding ester–amide derivatives. Additional transformations are also presented, such as the synthesis of amino esters, amino acids, and transformation into 3,4‐disubstituted pyrrolidin‐2‐ones.