Practical stereoselective synthesis of beta-branched alpha-amino acids through efficient kinetic resolution in the phase-transfer-catalyzed asymmetric alkylations.
Phase-transfer-catalyzed alkylation of glycinate Schiff base with racemic secondary alkyl halides proceeded with excellent levels of syn- and enantioselectivities under the influence of chiral quaternary ammonium bromide 1d and 18-crown-6. The alkylation product can be selectively converted to the corresponding anti isomer, allowing the preparation of all the stereoisomers of beta-alkyl-alpha-amino acid derivatives, an extremely valuable chiral building block.
Ooi
Takashi
T
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
Kato
Daisuke
D
Inamura
Koji
K
Ohmatsu
Kohsuke
K
Maruoka
Keiji
K
D000478:Alkylation; D000597:Amino Acids, Branched-Chain / Q000138:chemical synthesis* / Q000737:chemistry; D001966:Bromine / Q000737:chemistry; D002384:Catalysis; D004980:Ethane / Q000737:chemistry; D005461:Fluorine / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D044367:Phase Transition; D013237:Stereoisomerism
D000597:Amino Acids, Branched-Chain; D005461:Fluorine; D004980:Ethane; D001966:Bromine