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Kinetic Resolution of the Racemic 2‐Hydroxyalkanoates Using the Enantioselective Mixed‐Anhydride Method with Pivalic Anhydride and a Chiral Acyl‐Transfer Catalyst
Author(s) -
Shiina Isamu,
Nakata Kenya,
Ono Keisuke,
Sugimoto Masuhiro,
Sekiguchi Akihiro
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902257
Subject(s) - kinetic resolution , pivalic acid , chemistry , moiety , enantioselective synthesis , organic chemistry , catalysis , maleic anhydride , reagent , acid anhydride , alcohol , copolymer , polymer , epoxy
A variety of optically active 2‐hydroxyalkanoates and the corresponding 2‐acyloxyalkanoates are produced by the kinetic resolution of racemic 2‐hydroxyalkanoates by using achiral 2,2‐diarylacetic acid with hindered carboxylic anhydrides as the coupling reagents. The combined use of diphenylacetic acid, pivalic anhydride, and (+)‐( R )‐benzotetramisole (( R )‐BTM) effectively produces ( S )‐2‐hydroxyalkanoates and ( R )‐2‐acyloxyalkanoates from the racemic 2‐hydroxyalkanoates ( s ‐values=47–202). This protocol directly provides the desired chiral 2‐hydroxyalkanoate derivatives from achiral diarylacetic acid and racemic secondary alcohols that do not include the sec ‐phenethyl alcohol moiety by using the transacylation process to generate the mixed anhydrides from the acid components with bulky carboxylic anhydrides under the influence of the chiral acyl‐transfer catalyst. The transition state that provides the desired ( R )‐2‐acyloxyalkanoate from ( R )‐2‐hydroxyalkanoate included in the racemic mixture is disclosed by DFT calculations, and the structural features of the transition form are also discussed.