Asymmetric Metal-Templated Approach to Amino Acids with a CF3-Containing 3,2’-Pyrrolidinyl Spirooxindole Core via a Michael/Mannich [3+2]-Cycloaddition ReactionстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 15 февраля 2024 г.
Аннотация:We report here a practical protocol for the asymmetric synthesis of AAs with a CF3-containing 3,2’-pyrrolidinyl spirooxindole skeleton with three defined carbon stereocenters via a sequential Michael/Mannich [3+2]-cycloaddition reaction. The coupling of a robust and stereochemically stable chiral dehydroalanine Ni(II) complex with various N-2,2,2-trifluoroethylisatin ketimines in the presence of triethylamine afforded a library of single diastereomeric complexes with a 3,2’-pyrrolidinyl spirooxindole moiety in 36–71% yields. In particular, the change of base to LiOH allowed to obtain predominantly the Michael addition product in 76% yield. Finally, the decomposition of the obtained Ni(II) complexes with 3N HCl provided the target complex AA with a 3,2’-pyrrolidinyl spirooxindole core and (2S,4R)-2,4-diamino-5,5,5-trifluoropentanoic acid – an (S)-norvaline derivative, together with easy recovery of the chiral auxiliary ligand for the synthesis of the starting dehydroalanine complex.