Optical resolution of mandelic acid derivatives by column chromatography on crosslinked cyclodextrin gels

Abstract

Crosslinked α‐ and β‐cyclodextrin gels (α‐CD‐E and β‐CD‐E) were used for the chromatographic resolution of racemic mandelic acid and its derivatives. β‐CD‐E bound L‐(+)‐isomers preferentially over D‐(−)‐isomers and resolved DL‐methyl mandelate to give a D‐(−)‐isomer of 100% optical purity in the first fraction. Mandelic acid, ethyl mandelate, and O‐methylated mandelic acid yielded resolutions of 65–83% in initial fractions. α‐CD‐E, on the contrary, bound D‐(−)‐isomers more strongly than L‐(+)‐isomers, resolving DL‐methyl mandelate to a smaller extent than β‐CD‐E. Binding of DL‐mandelic acid and DL‐methyl mandelate on β‐CD‐E was studied quantitatively by the equilibrium method. β‐CD‐E has a similar binding capacity to starch with 1:1 stoichiometry but bound much more strongly than starch. β‐CD‐E has the same mode of selectivity as starch for the asymmetric binding of the mandelic acid derivatives, but α‐CD‐E has a reverse selectivity to β‐CD‐E and starch.

Synthesis and applications of adsorbents containing cyclodextrins

“…The results were interpreted in terms of anion-exchange interaction and inclusion complexation. Nozakura et al proposed the use of these gels as stationary phases for the enantio-resolution of racemic mandelic acid and its derivatives [148]. b-ECP gels bound L-(+)-isomers in preference to D-( -)-isomers, and resolved (DL)-methyl mandelate to give a D-( -)-isomer of 100% optical purity.…”

Solid and liquid state investigations of mandelic acid cyclodextrin complexes

“…1) and its derivatives [17][18], and gave a description about the crystalline structure of the complexes [19][20]. A few authors approached the problem of complex formation from the theoretical side, with the aid of molecule-modelling [21].…”

“…According to the studied literature [17][18] they may also exist in their dissolved forms. There are no reports about the direct production of the CD complexes of mandelic acid and its derivatives, their solid state characteristics (including thermal properties).…”

Enantiomerek királis elválasztása és megkülönböztetése

“…[83] α-CD és ß-CD térhálósításával állították elő, melyeken fordított fázisú kromatográfiás módszerrel racém mandulasavat és annak észtereit és étereit választották el. Az azóta eltelt harminc évben a CD-nel foglalkozó közlemények száma évről-évre jelentősen nő.…”