Effect of the presence of a free hydroxyl group on the enantiodiscrimination properties of cholic acid based CSPs bearing 2-naphthylcarbamate and 3,5-dinitrophenylcarbamate moieties in the HPLC resolution of racemic compounds

Two new chiral selectors, obtained by derivatizing two of the three hydroxyl groups of cholic acid with 2-naphthylisocyanate and 3,5-dinitrophenylisocyanate, have been prepared and linked to silica gel to obtain chiral stationary phases (CSPs) for the HPLC separation of enantiomers. The enantiodiscriminating capability of the two CSPs has been compared to that of the analogous CSP obtained from an exhaustively derivatized cholic acid based selector, in order to establish the effect of the presence of a free hydroxyl group on the enantiodiscrimination properties of this kind of selector. The chromatographic results demonstrate that the enantioselectivity of these selectors strongly depends on the position of the hydroxyl group on the cholestanic backbone.

Figure optionsDownload as PowerPoint slide

N-Allyl-N′-methyl-3-acetyl-7-oxo-12-hydroxycholan-24-amideC30H47NO5[α]D20=+17.3 (c 0.99, CH2Cl2)Source of chirality: natural source

N-Allyl-N′-methyl-3-acetyl-7-oxo-12-(3,5-dinitrophenyl)carbamoyloxycholan-24-amideC37H50N4O10[α]D21=+63.1 (c 1, CH2Cl2)Source of chirality: natural source

N-Allyl-N′-methyl-3-acetyl-7-hydroxy-12-(3,5-dinitrophenyl)carbamoyloxycholan-24-amideC37H52N4O10[α]D20=+56.4 (c 0.99, CH2Cl2)Source of chirality: natural source

N-Allyl-N′-methyl-3-acetyl-7-(2-naphthyl)carbamoyloxy-12-(3,5-dinitrophenyl)carbamoyloxycholan-24-amideC48H59N5O11[α]D20=+87.1 (c 0.97, CH2Cl2)Source of chirality: natural source

N-Allyl-N′-methyl-3-hydroxy-7-(2-naphthyl)carbamoyloxy-12-(3,5-dinitrophenyl)carbamoyloxycholan-24-amideC46H57N5O10[α]D18=+93.4 (c 0.98, CH2Cl2)Source of chirality: natural source