Preparation of chiral amino esters by asymmetric phase-transfer catalyzed alkylations of Schiff bases in a ball mill.
The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase-transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75 %. Because an equimolar amount of starting material was used, purification was greatly simplified.
Institut des Biomolécules Max Mousseron, UMR 5247 Université Montpellier 1-CNRS, Place Eugène Bataillon, 34095 Montpellier cedex 05, France.
Pierrick
P
Nun
Violaine
V
Pérez
Monique
M
Calmès
Jean
J
Martinez
Frédéric
F
Lamaty
D000478:Alkylation; D000596:Amino Acids / Q000737:chemistry*; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry; D004952:Esters; D005998:Glycine / Q000737:chemistry*; D015394:Molecular Structure; D012545:Schiff Bases; D013237:Stereoisomerism
D000596:Amino Acids; D002930:Cinchona Alkaloids; D004952:Esters; D012545:Schiff Bases; C041622:cinchonidine; D005998:Glycine