New amino acid-based anionic surfactants and their use as enantiodiscriminating lyotropic liquid crystalline NMR solvents

New amino acid-based anionic surfactants have been synthesized and their use as chiral oriented NMR solvents studied. A series of sulfonated amphiphilic L-Phe or L-Ala derivatives with pentyl to tetradecyl tails were prepared by reacting the corresponding amino acid esters with o-sulfobenzoic anhydride. Their critical micelle concentrations (CMCs) range from 1.6 x 10(-5) to 1.4 x 10(-2) mol/L and depend on the alkyl chain length as well as on the nature of the amino acid block. These values are comparatively lower than those of classical surfactants such as alkylbenzenesulfonates and N-acylamino-acid carboxylates. Their use as chiral liquid crystals (CLC) for analytical purposes is reported. In particular, it is shown that aqueous solutions of these chiral sulfonates in the presence of chlorinated solvents (CHCl3, CH2Cl2, C2H2Cl4, or CCl4) provide homogeneous oriented NMR solvents able to differentiate between enantiomers of D,L-alanine-2-d(1) using proton and deuterium NMR spectroscopy. (C) 2004 Elsevier Ltd. All rights reserved.