Resolution of Racemates by Enantioselective Extraction

Easy protonation of tinchona alkaloids (ionic character) together with the possibility of modification of their lipophilicity makes this class of compounds interesting candidates for the enantioselective extraction. A pioneering work in this 

Very efficient enantioseparation of racemic DNB-leucine 23 exploiting an extraction with a mechanistically designed quinine 1-adamantylcarbamate 24 bearing a highly hydrophobic side arm has been reported by Lindner and coworkers. The most efficient extraction was achieved with aqueous ammonium acetate buffer/dodecane solvent system. After back-extraction of the organic phase with 1 M H3PO4 solution, the preferentially complexed S-enantiomer of 23 

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