New dimeric anthracenyl-derived Cinchona quaternary ammonium salts as phase-transfer catalysts for the asymmetric synthesis of α-amino acids
摘要:
New dimeric cinchonidine- and cinchonine-derived ammonium salts which incorporate a dimethylanthracenyl bridge have been prepared and used as phase-transfer catalysts in the asymmetric alkylation of N-(diphenylmethylene)glycine esters in good yields and tip to 90% ee. (C) 2002 Elsevier Science Ltd. All rights reserved.
Oxygen Alkylation of Schiff Base Derivatives of Amino Acids
作者:Martin J. O'Donnell、Gwendolyn K. Cook、David B. Rusterholz
DOI:10.1055/s-1991-26625
日期:——
Higher imine esters 1a-h and 7a-b of amino acids and dipeptides are prepared in 68-91% yield by saponification of the benzophenone Schiff base methyl esters 3a-d and 6 using phase-transfer techniques followed by O-alkylation with an alkyl halide. The procedure occurs with retention of configuration at the α-carbon except with phenylglycine derivatives.
Chiroptical properties and applications in PTC of new dendritic cinchonidine-derived ammonium salts
作者:Gabriela Guillena、Robert Kreiter、Rob van de Coevering、Robertus J.M. Klein Gebbink、Gerard van Koten、Patricia Mazón、Rafael Chinchilla、Carmen Nájera
DOI:10.1016/j.tetasy.2003.08.030
日期:2003.11
Chiral nanosize molecules, derived from cinchonidine and Fréchet dendriticwedges up to generation three, have been synthesized. The chiroptical properties, optical rotation and circular dichroism of these systems have been studied. These chiraldendritic molecules have been used as phase transfer catalysts in the alkylation of a glycine imine ester, showing a promising level of asymmetric induction
Polymer-Supported Cinchona Alkaloid-Derived Ammonium Salts as Recoverable Phase-Transfer Catalysts for the Asymmetric Synthesis of α-Amino Acids
作者:Rafael Chinchilla、Patricia Mazón、Carmen Nájera
DOI:10.3390/90500349
日期:——
of polymer-supported chiral ammonium salts which have been employed as phase-transfercatalysts in the asymmetric benzylation of an N-(diphenylmethylene)glycine ester. These new polymeric catalysts can be easily recovered by simple filtration after the reaction and reused. The best ee's were achieved when Merrifield resin-anchored cinchonidinium ammonium salts were employed.
Polystyrene-AnchoredCinchona Ammonium Salts: Easily Recoverable Phase-Transfer Catalysts for the Asymmetric Synthesis ofα-Amino Acids
作者:Rafael Chinchilla、Patricia Mazón、Carmen Nájera
DOI:10.1002/adsc.200404093
日期:2004.8
cross-linked polystyrene (Merrifield resin) or grafted polystyrene (SynPhaseTM Lanterns) affording polymer-supported chiral ammonium salts which are employed as phase-transfercatalysts in the asymmetric alkylation of N-(diphenylmethylene)glycine esters. These new polymeric catalysts can be easily recovered after the reaction by simple filtration and reused.
Unexpected metal base-dependent inversion of the enantioselectivity in the asymmetric synthesis of α-amino acids using phase-transfer catalysts derived from cinchonidine
作者:Patricia Mazón、Rafael Chinchilla、Carmen Nájera、Gabriela Guillena、Rob Kreiter、Robertus J.M. Klein Gebbink、Gerard van Koten
DOI:10.1016/s0957-4166(02)00611-0
日期:2002.10
dNew cinchonidinium salts bearing a 3,5-dialkoxybenzyl group show an alkaline metal base-dependent reversal of enantioselectivity when used as phase-transfer catalysts in the asymmetric alkylation of N-(diphenylmethylene)glycine isopropyl ester with benzyl bromide. The use of potassium hydroxide as base in this alkylation reaction afforded the (S)-enantiomer, whereas using sodium hydroxide under the same conditions afforded the corresponding (R)-enantiomer. (C) 2002 Elsevier Science Ltd. All rights reserved.