Models for the use of alpha-amino acids as chiral auxiliaries in asymmetric Diels-Alder reactions

  1. Bueno, M.P. 2
  2. Cativiela, C.A. 2
  3. Mayoral, J.A. 2
  4. Avenoza, A. 1
  1. 1 Universidad de Zaragoza
    info

    Universidad de Zaragoza

    Zaragoza, España

    ROR https://ror.org/012a91z28

  2. 2 Instituto de Nanociencia y Materiales de Aragón
    info

    Instituto de Nanociencia y Materiales de Aragón

    Zaragoza, España

    ROR https://ror.org/031n2c920

Revista:
Journal of Organic Chemistry

ISSN: 0022-3263

Año de publicación: 1991

Volumen: 56

Número: 23

Páginas: 6551-6555

Tipo: Artículo

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DOI: 10.1021/JO00023A020 SCOPUS: 2-s2.0-0344476083 WoS: WOS:A1991GP56900020 GOOGLE SCHOLAR

Otras publicaciones en: Journal of Organic Chemistry

Repositorio institucional: lock_openAcceso abierto Editor

Resumen

Three different models, depending on the Lewis acid used as a catalyst and the α-amino acid used as a chiral auxiliary, account for the diastereofacial selectivity obtained in reactions of cyclopentadiene with N-acryloyl derivatives of L-proline, L-phenylalanine, L-alanine, and N-methyl-L-alanine esters. For α-amino acids without an NH group and aluminum catalysts, a reactive conformer with antiplanar enoate conformation similar to those postulated for acrylates with only one center capable of coordination is proposed. These dienophiles form a chelate complex, where the acryloyl moiety is in syn conformation, with TiCl4. For α-amino acids with an NH group, a reactive intermediate with an antiplanar disposition in the acryloyl moiety and the conformation of the amino ester fixed by an intramolecular hydrogen bond accounts for the results with both kinds of catalyst. These models seem to have general application for the use of α-amino acids as chiral auxiliaries in asymmetric Diels-Alder reactions. © 1991 American Chemical Society.