A General Synthesis of Unnatural α-Amino Acids by Iron-Catalysed Olefin-Olefin Coupling via Generated Radicalsстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 21 мая 2019 г.
Аннотация:Herein we report about the efficient and practical protocol for the asymmetric synthesis of the unnatural α-amino acids (AA) with γ-tertiary and quaternary carbon centres via selective intermolecular iron-catalysed olefin-olefin coupling of a chiral Ni(II) complex of dehydroalanine Schiff base 2 ((S)-BPB-Ni-∆-Ala) with different olefins. In all successful reactions diastereomeric nickel complexes were typically obtained in a ratio of up to dr >20:1. The desired products were isolated in 42–93% yields (18 examples). Exemplary, the three obtained Ni(II) complexes were decomposed with aqueous HCl and the
target unnatural α-amino acids isolated with excellent enantioselectivity and yields up to 83%. The chiral auxiliary (BPB = 2-(N-benzylprolyl)aminobenzophenone) was readily recycled and reused for the synthesis of starting chiral Ni(II) complex 2. The developed protocol provided a facile access to the analogues of glutamic acid, leucine and phosphinothricin.