Derivatization for the separation of enantiomers

The requirement that a reagent be chiral in order to exert differential action upon a pair of enantiomers is normally met in one of two ways (1) treatment of the mixture with a conventional derivatizing agent and separating the products on a suitable chiral stationary phase (2) treatment of the mixture with a chiral derivatizing agent and separating the products on a conventional stationary phase. 

For preparation of diastereomeric esters from a racemic acid mixture, there is the classic naturally occurring alcohol, (-)-menthol, or, if greater volatility is sought, optically active 2-butanol. (-I- )-3-Methyl-2-butanol reportedly leads to good separation of diastereomeric esters from amino acids, hydroxy acids and branched acids 

Where resolution of a particular amino acid via the JV-fluoroacyl (+ )-2-alkyl ester is not feasible, an alternative strategy involves the formation of a diastereomeric acyl dipeptide ester mixture through condensation with a second, chiral amino acid unit 

Employment of a chiral acylating agent is another possibility resolution of 

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