Mandelic acid, chromatographic studies

The chromatographic behavior of mandelic acid and its esters was studied in reversed-phase HPLC (RP-HPLC) with a-, p-, y-, and permethylated-) -CyD as additive to the mobile phase. It was found that native CyDs do not recognize enantiomers of esters although they form relatively stable 1 1 complexes with them. Estimated stability constants for these guests are presented in Table 5.1 [43]. 

Epichlorohydrin-cross-linked cyclohexa- and cyclohepta-amylose gels have been used for the chromatographic resolution of racemic mandelic acid and its derivatives. Modified cyclohepta-amylose bound the L-(- -)-isomers preferentially, and resolved D,L-methyl mandelate to give the D-(—)-isomer of 100% optical purity in the first fraction. Cross-linked cyclohexa-amylose bound D-(—)-isomers more strongly than L-(-t-)-isomers, resolving D,L-methyl mandelate to a smaller extent than cross-linked cyclohepta-amylose. Binding was studied quantitatively by the equilibrium method. 

The chromatographic efficiency of these polymers was studied with DL-mandelic acid (I) resp. with DL-2-phenyl glycine (20). As it can be seen in Table II the resolution efficiency of the adsorbants (AOP) in the COOH-form showed the following order 6 (phenyl) <... 

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