Asymmetric Alkylation Of Glycine Derivatives Research Articles

The asymmetric alkylation reaction of glycine derivatives catalyzed by the novel chiral phase transfer catalysts

Herein a new series of chiral phase transfer catalysts derived from the cinchona alkaloids were synthesized and applied in the asymmetric alkylation of glycine derivatives with high yields and moderate to excellent ee values (39.5–99.7%).

ChemInform Abstract: Asymmetric Amino Acid Synthesis by the Asymmetric Alkylation of Glycine Derivatives with Chiral Spiro‐Type and Simplified Phase‐Transfer Catalysts

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Copper-Catalyzed Asymmetric Alkylation of Glycine Derivatives

Copper-Catalyzed Asymmetric Alkylation of Glycine Derivatives

両親媒性高分子を利用する高分子固定化型不斉触媒の創製

The heterogeneous chiral catalysts for the synthesis of optically active compounds have been energetically developed mainly due to their easy separation and recycle use. However, the supported catalysts sometimes lead to negative effects both on the reactivity and the enantioselectivity. Design of the polymer–support is important issue to develop essentially useful polymeric chiral catalyst. We have designed novel polymer–immobilized chiral catalysts based on the use of amphiphilic polymer support. For example, polymers having quaternary ammonium sulfonate pendant groups were efficiently used as suitable polymer support of the chiral catalyst for the reactions in aqueous solution. By using of the amphiphilic polymer–immobilized chiral catalyst, asymmetric transfer hydrogenation in water smoothly occurred to give the corresponding optically active alcohol with positive effect on the enantioselectivity. When the enantiopure quaternary ammonium sulfonate was introduced into polymer, asymmetric alkylation of glycine derivatives can be catalyzed by the chiral ammonium polymer. Chiral quaternary ammonium cation was attached to polymeric sulfonate anion through ionic bonding. This immobilization method using ionic bond is substantially useful since any type of chiral quaternary ammonium structure can be immobilized into polymer without any additional chemical modification on the catalyst molecule.

Design of Chiral Phase Transfer Catalyst with Conformationally Fixed Biphenyl Core: Application to Asymmetric Alkylation of Glycine Derivatives.

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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 tert-butyl ester with excellent enantioselectivity. In particular, catalyst ( S)- 1b was found to exhibit the unique temperature effect on the enantioselectivity, and asymmetric alkylation of glycine derivatives at room temperature gave higher enantiomeric excess than that at 0 °C. In addition, the catalyst ( S)- 2 exhibited the high catalytic performance (0.01–1 mol %) in the asymmetric alkylation of N-(diphenylmethylene)glycine tert-butyl ester and N-( p-chlorophenylmethylene)alanine tert-butyl ester compared to the existing chiral phase-transfer catalysts, thereby allowing to realize a general and useful procedure for highly practical enantioselective synthesis of structurally diverse natural and unnatural α-alkyl-α-amino acids as well as α,α-dialkyl-α-amino acids. This approach is successfully applied to the short asymmetric synthesis of cell adhesion BIRT-377.

Design of Chiral Phase Transfer Catalyst with Conformationally Fixed Biphenyl Core: Application to Asymmetric Alkylation of Glycine Derivatives

Chiral phase transfer catalysts (S)-1a and (S)-1b with a conformationally fixed biphenyl core were conveniently prepared from the known (S)-6,6‘-dimethylbiphenyl-2,2‘-diol 2 in five steps. These catalysts, (S)-1a and (S)-1b, are readily applicable to asymmetric alkylation of glycine derivatives with excellent enantioselectivity. In particular, catalyst (S)-1b was found to exhibit a unique temperature effect on the enantioselectivity, and asymmetric alkylation of glycine derivatives at room temperature gave a higher ee than that at 0 °C.

Dramatic Rate Enhancement of Asymmetric Phase‐Transfer‐Catalyzed Alkylations

The intervention of crown ethers or achiral quaternary ammonium salts as achiral phase-transfer catalysts (PTCs, see scheme) in a chiral PTC system leads to dramatic rate enhancements in the asymmetric alkylation of glycine derivatives.

Spiro Crown Ethers Bearing (S)-1,1’-Spirobiindanes as Chiral Backbones

The synthesis of spiro chiral crown ethers ((S)-1a) and ((S)-1b) has been achieved. The combination of (S)-1a and KOH promoted the asymmetric alkylation of glycine derivative (2) with moderate enantioselectivity.