RESUMO
[structure: see text] The Cinchona alkaloid-derived quaternary ammonium salts containing 2'-N-oxypyridine and 2'-cyanobenzene moieties were prepared and evaluated as phase-transfer catalysts in the enantioselective alkylation of glycine imine ester 1. The N-oxypyridine and cyanobenzene moieties might play an important role to form a rigid conformation by coordinating with H(2)O via hydrogen bonding leading to high enantioselectivity (97 approximately >99% ee), which provides evidence of an electronic factor for the high enantioselective catalytic efficiency in phase-transfer alkylation.
Assuntos
Alcaloides de Cinchona/química , Alquilação , Catálise , Eletroquímica , Estrutura Molecular , EstereoisomerismoRESUMO
A new Merrifield-resin-derived glycinimine tert-butyl ester (9) was prepared and applied to the enantioselective synthesis of non-natural alpha-amino acids. High enantioselectivities (86 to >99% ee) were accomplished by employing the aldimine linker under phase-transfer alkylation conditions, using 50% aqueous CsOH in toluene/chloroform (7:3) at 0 degrees C in the presence of N-(9-anthracenylmethyl)-O(9)-allylcinchonidium bromide (10 mol %).
Assuntos
Aminoácidos/síntese química , Reagentes de Ligações Cruzadas/química , Iminas/química , Alquilação , Catálise , Conformação Molecular , EstereoisomerismoAssuntos
Chalconas/química , Alcaloides de Cinchona/química , Compostos de Epóxi/síntese química , Tensoativos/química , Catálise , Chalcona/análogos & derivados , Chalcona/síntese química , Chalcona/química , Compostos de Epóxi/química , Hexoses/química , Modelos Moleculares , Estrutura Molecular , Octoxinol/química , Poloxaleno/química , Polietilenoglicóis/química , Polissorbatos/química , EstereoisomerismoRESUMO
Systematic investigations to develop an efficient enantioselective synthetic method for alpha-alkyl-alanine by catalytic phase-transfer alkylation were performed. The alkylation of 2-naphthyl aldimine tert-butyl ester, 1E, with RbOH and O(9)-allyl-N-2',3',4'-trifluorobenzylhydrocinchonidinium bromide, 6, at -35 degrees C showed the highest enantioselectivities, up to 96% ee.
RESUMO
[structure: see text] Various N-benzylcinchonidinium salts were prepared to study electronic factors in the catalytic enantioselective phase-transfer alkylation of glycine anion equivalent. An ortho-fluoro substituent on the benzyl group in the quaternary ammonium salt dramatically increased the enantioselectivity in the alkylation. O(9)-Allyl-N-2',3',4'-trifluorobenzylhydrocinchonidinium bromide (27), which gave the highest enantioselectivity of the catalysts studied, was used to prepare 12 alpha-alkylated amino acid derivatives in 94 approximately >99% ee.