RSS-Feed abonnieren
PDF herunterladen
DOI: 10.1055/s-2005-869889
Asymmetric PTC for Preparation of a-Amino Acids
Rezensent(en): Yasuhiro Uozumi, Yoichi M. A. Yamada, Naoshi FukuyamaSeoul National University, Korea
Highly Enantioselective Phase-Transfer Catalytic Alkylation in the Preparation of Non-Natural α-Amino Acids via Solid Phase Synthesis Using Aldimine Linker
J. Org. Chem. 2005, 70: 1904-1906
Publikationsverlauf
Publikationsdatum:
20. Juli 2005 (online)
Key words
aldimine linker - phase-transfer catalysts - alkylation
Significance
A polystyrene resin-bound phenylmethyleneglycinimine tert-butyl ester was prepared from a Merrifield resin in two steps. The polymer-bound glycinimine was alkylated with alkyl halides (e.g., hexyl bromide, allyl bromide, propargyl bromide, benzyl bromide, etc.) in the presence of 10 mol% of a cinchona-derived phase transfer catalyst and 50% aqueous CsOH in toluene/chloroform at 0 °C, for four days to give the corresponding non-natural α-amino acids in 50-82% yields with up to 99% ee. Eleven examples of the alkylation are shown.
Comment
This method is very useful to construct the chiral non-natural α-amino acids library for combinatorial synthesis.