Synthesis of chiral 18-crown-6 ethers containing lipophilic chains and their enantiomeric recognition of chiral ammonium picrates

Four new chiral 18-crown-6 ethers have been prepared to be used in enantiomeric recognition and extraction. The influence of the lipophilic character and bulkiness of the substituents on the complexation of different chiral ammonium picrates in CD3CN has been evaluated. Racemic aqueous solutions of the ammonium salts have been enriched in one enantionter after extraction experiments, and the enantiomeric excesses have been calculated. (c) 2005 Elsevier Ltd. All rights reserved.