Enantioselective Organocatalytic Addition of Oxazolones to 1,1‐Bis(phenylsulfonyl)ethylene: A Convenient Asymmetric Synthesis of Quaternary α‐Amino Acids |
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Authors: | Andrea‐Nekane R. Alba Xavier Companyó Guillem Valero Albert Moyano Prof. Dr. Ramon Rios Dr. |
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Affiliation: | 1. Department of Organic Chemistry, Universitat de Barcelona, Faculty of Chemistry, Martí i Franquès 1‐11, 08028 Barcelona (Spain), Fax: (+34)?9333‐97‐878;2. Department of Organic Chemistry, Universitat de Barcelona, Faculty of Chemistry, Martí i Franquès 1‐11, 08028 Barcelona (Spain), Fax: (+34)?9333‐97‐878Dr. Ramon Rios is an ICREA Researcher at Universitat de Barcelona and an ICC‐UB Researcher |
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Abstract: | A new, easy, and highly enantioselective method for the synthesis of quaternary α‐alkyl‐α‐amino acids based on organocatalysis is reported. The addition of oxazolones to 1,1‐bis(phenylsulfonyl)ethylene is efficiently catalyzed by simple chiral bases or thioureas. The reaction affords α,α‐disubstituted α‐amino acid derivatives with complete C4 regioselectivity and with excellent yields and enantioselectivities. This methodology is complementary to previously reported enantioselective approaches to quaternary α‐amino acids and allows the synthesis of α‐phenyl‐α‐alkyl‐α‐amino acids and α‐tert‐butyl‐α‐alkyl‐α‐amino acids. It has distinct advantages in terms of operational simplicity, enviromentally friendly conditions, and suitability for large‐scale reactions. |
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Keywords: | amino acids Michael addition organocatalysis oxazolones stereoselectivity |
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