Asymmetric base hydrolysis of α-chiral esters with synthetic small-molecule catalysts is described. Quaternary ammonium salts derived from quinine were used as chiral phase-transfer catalysts to promote the base hydrolysis of N-protected aminoacid hexafluoroisopropyl esters in a CHCl3/NaOH (aq) via dynamic kinetic resolution, providing the corresponding products in moderate to good yields (up to 99%)
Dynamic Kinetic Resolution of N-Benzoyl-DL-Amino Acids via Peptide Bond Forming Reactions
作者:Toshifumi Miyazawa、Takashi Hamada
DOI:10.2174/092986610790963582
日期:2010.4.1
Dynamic kinetic resolution (DKR) was demonstrated in the carbodiimide-mediated couplings of N-benzoyl-DLamino acids with L-amino acid esters: the yields of the D-L-peptides significantly exceeded 50% in some cases. NBenzoyl- DL-t-leucine afforded the D-L-peptide almost exclusively (up to 96% yield) in the reaction with methyl Lprolinate, which is the most efficient DKR obtained in the field of amino acids and derivatives.
Structural optimization of thiourea-based bifunctional organocatalysts for the highly enantioselective dynamic kinetic resolution of azlactones
作者:Albrecht Berkessel、Santanu Mukherjee、Thomas N. Müller、Felix Cleemann、Katrin Roland、Marc Brandenburg、Jörg-M. Neudörfl、Johann Lex
DOI:10.1039/b607574f
日期:——
describes the synthesis of a library of structurally diverse bifunctionalorganocatalysts bearing both a quasi-Lewis acidic (thio)urea moiety and a Bronsted basic tertiary amine group. Sequential modification of the modular catalyst structure and subsequent screening of the compounds in the alcoholytic dynamickineticresolution (DKR) of azlactones revealed valuable structure-activity relationships. In particular
Enantioselective Organocatalytic Addition of Oxazolones to 1,1-Bis(phenylsulfonyl)ethylene: A Convenient Asymmetric Synthesis of Quaternary α-Amino Acids
作者:Andrea-Nekane R. Alba、Xavier Companyó、Guillem Valero、Albert Moyano、Ramon Rios
DOI:10.1002/chem.200903025
日期:2010.5.10
A new, easy, and highlyenantioselective method for the synthesis of quaternary α‐alkyl‐α‐aminoacids 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‐aminoacid derivatives with complete C4 regioselectivity and with excellent yields and enantioselectivities
Palladium-Catalyzed Asymmetric Benzylation of Azlactones
作者:Barry M. Trost、Lara C. Czabaniuk
DOI:10.1002/chem.201302390
日期:2013.11.4
Asymmetric benzylation of prochiral azlactone nucleophiles enables the catalytic introduction of a benzyl group towards the synthesis of α,α‐disubstituted amino acids. Herein, we report an enantioselective palladium‐catalyzed process using chiral bis(diphenylphosphinobenzoyl)diamine (dppba) ligands. Naphthalene‐ and heterocycle‐based methyl carbonates react with a number of azlactones derived from