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Quaternized α,α'-Amino Acids via Curtius Rearrangement of Substituted Malonate-Imidazolidinones.

Maheswara Rao GokadaRoger HunterAna AndrijevicWade F PetersenSauvik SamantaGerhard VenterSophie Rees-Jones
Published in: The Journal of organic chemistry (2017)
An efficient synthesis protocol is presented for accessing quaternized α-amino acids in chiral, nonracemic form via diastereoselective malonate alkylation followed by C- to N-transposition. The key stereodifferentiating step involves a diastereoselective alkylation of an α-monosubstituted malonate-imidazolidinone, which is followed first by a chemoselective malonate PMB ester removal and then a Curtius rearrangement to provide the transposition. The method demonstrates a high product ee (89-99% for eight cases) for quaternizing a range of proteinogenic α-amino acids. The stereogenicity in targets 5a-i supports previous conclusions that the diastereoselective alkylation step proceeds via an α-substituted malonate-imidazolidinone enolate in its Z-configuration, with the auxiliary in an s-transC-N conformation.
Keyphrases
  • amino acid
  • molecular docking
  • randomized controlled trial
  • ionic liquid
  • molecular dynamics simulations
  • mass spectrometry
  • capillary electrophoresis