Cinchonan-type selectors

The favorable effect of the introduction of a carbamate moiety into the cinchonan selectors was already proven by the prototype cinchonan carbamate CSPs (type I and type II) (Figure 1.9) [30], which showed enhanced enantioselectivities and a widened application range as compared to the CSPs with native cinchona alkaloid selectors and those reported earlier in the literature. 

FIGURE 1.9 Selection of cinchonan carbamate CSPs that have been prepared in the course of selector optimization studies (type I prototype type II, O-9-linked thiol-silica supported prototype type III, C-ll-linked thiol-silica supported CSPs type IV, dimeric selectors). (Adapted from M. Lammerhofer and W. Lindner, J. Chromatogr. A, 741 33 (1996) W. Lindner et al., PCT/EP97/02888, US 6,313,247 B1 (1997) P. Franco et ah, J. Chromatogr. A, 869 111 (2000) C. Czerwenka et ah. Anal. Chem., 74 5658 (2002).)... 

Moreover, it could be figured out that an effective means to modulate the stereorecognition capabilities of the cinchonan selector motif may be via the carbamate residue. It offers a way of straightforward introduction of bulky alkyl substituents, which may affect the accessibility of active binding sites and/or lead to additional supportive Van der Waals-type interactions. 

Laemmerhofer, M., Lindner,W. Quinine and quinidine derivatives as chiral selectors. I. Brush type chiral stationary phases for high-performance liquid chromatography based on cinchonan carbamates and their application as chiral anion exchangers, J. Chromatogr. A, 1996, 741, 33-48. 

---