Enantioselective construction of a quaternary asymmetric carbon center: a versatile synthesis of .alpha.-alkyl .alpha.-amino acids
TL;DR: Alkylation enantioselective des dianions derives des monoesters chiraux d'acides maloniques monosubstitues avec des halogenures d'alkyles as discussed by the authors.
Abstract: Alkylation enantioselective des dianions derives des monoesters chiraux d'acides maloniques monosubstitues avec des halogenures d'alkyles
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TL;DR: Asymmetric Michael reaction of 2-cyanopropionates with vinyl ketones or acrolein in the presence of 0.1-1 mol% of a rhodium catalyst prepared in situ from RhH(CO)(PPh3)3 and a trans-chelating chiral diphosphine ligand (S,S)-(R,R)-PhTRAP in benzene at 3-5°C gave optically active Michael adducts with high enantiomeric excesses (83-93% ee) in high yields RE
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TL;DR: An efficient access to configurationally stable α,α-disubstituted α-amino aldehydes, oxazolidinones, and α amino acids has been presented in this article.
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TL;DR: In this paper, an enantioselective synthetic method for the construction of a quaternary carbon center from malonates via phase-transfer catalytic (PTC) alkylation has been developed.
Abstract: A novel enantioselective synthetic method for the construction of a quaternary carbon center from malonates via phase-transfer catalytic (PTC) alkylation has been developed. The asymmetric α-alkylation of diphenylmethyl tert-butyl α-alkylmalonates with alkylating agents under phase-transfer catalysis conditions (aq 50% KOH, toluene, 0°C) in the presence of (S,S)-3,4,5-trifluorophenyl-NAS bromide (8) as PTC catalyst afforded the corresponding α,α-dialkylmalonates in high chemical (up to 99%) and optical yields (up to 97% ee) which could be readily converted to versatile chiral intermediates. Notably, the direct double α-alkylations of diphenylmethyl tert-butyl malonate also provided the corresponding α,α-dialkylmalonates without loss of enantioselectivity. The synthetic potential of this method has been demonstrated by the preparation of α,α-dialkylamino acid and oxindole systems.
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