was used in phase-transfer alkylations and Michael additions to afford various opticallyactive α-amino acid equivalents in up to 93% yield. Moreover, dramatic counter anion effects were observed in phase-transfer catalysis (PTC) for the first time, making it possible to further improve reactivity and selectivity. These findings validate the usefulness of three-dimensional fine-tuning of the catalyst
Design of new, chiral phase-transfer catalysts for practical, catalytic asymmetric synthesis
作者:Keiji Maruoka
DOI:10.1016/s0022-1139(01)00472-9
日期:2001.11
Structurally rigid, chiral spiro ammonium salts of type 1 derived from commercially available (S)-binaphthol have been designed as a new C2-symmetricchiralphase-transfercatalyst and successfully applied to the highly efficient, catalytic enantioselective alkylation of tert-butyl glycinate Schiff base under mild phase-transfer conditions to furnish α-alkyl-α-amino acids and α,α-dialkyl-α-amino acids with excellent
Enantioselective alkylation of alanine-derived imines using quaternary ammonium catalysts
作者:Barry Lygo、John Crosby、Justine A. Peterson
DOI:10.1016/s0040-4039(99)01836-5
日期:1999.12
alkylation of a series of alanine-derived imines is reported. Using solid as the stochiometric base such alkylations can be achieved with enantiomeric excesses up to 87% allowing rapid access to α,α-dialkyl-α-aminoacid esters.
Optically active quarternary ammonium salt with axial chirality, method for producing thereof, and application thereof for asymmetric synthesis of &agr;-amino acid
申请人:Nagase & Co., Ltd.
公开号:US06340753B1
公开(公告)日:2002-01-22
A novel optically active quarternary ammonium salt with an axial chirality is provided. The quarternary ammonium salt can act as a phase-transfer catalyst to convert glycine derivatives into optically active &agr;-amino acid derivatives by stereoselectively alkylating the glycine derivatives. Furthermore, according to the present invention, intermediates useful for producing the novel quarternary ammonium can be produced.
Convenient preparation of chiral phase-transfer catalysts with conformationally fixed biphenyl core for catalytic asymmetric synthesis of α-alkyl- and α,α-dialkyl-α-amino acids: application to the short asymmetric synthesis of BIRT-377
Chiral phase-transfer catalysts (S)-1a, (S)-1b, and (S)-2 with conformationally fixed biphenyl cores were conveniently prepared from the known, easily available (S)-6,6′-dimethylbiphenyl-2,2′-diol 3 and (S)-4,5,6,4′,5′,6′-hexamethoxybiphenyl-2,2′-dicarboxylic acid 14, respectively, in five steps. The catalysts, (S)-1a and (S)-1b are readily applicable to asymmetric alkylation of N-(diphenylmethylene)glycine