Discrimination of Chiral Guests by Chiral Channels: Variable Temperature Studies by SXRD and Solid State 13C NMR of the Deoxycholic Acid Complexes of Camphorquinone and Endo-3-Bromocamphor

• Main Authors: Mohamed I. M., Tahir, Nicholas, H. Rees, Stephen, J. Heyes, Andrew, R. Cowley, Keith, Prout
• Format: Article
• Language: English; English
• Published: Wiley-Blackwell 2008
• Online Access: http://psasir.upm.edu.my/id/eprint/5809/1/Discrimination%20of%20Chiral%20Guests%20by%20Chiral%20Channels.pdf; http://psasir.upm.edu.my/id/eprint/5809/; http://dx.doi.org/10.1002/chir.20561

3a,12a-Dihydroxy-5b-cholan-24-oic acid (deoxycholic acid DCA) is able to discriminate between the R- and S-enantiomers of camphorquinone and endo-(1)-3-bromocamphor and select only the S-enantiomers from a racemic mixture. DCA forms novel well ordered 1:1 adducts with (1S)-(1)-camphorquinone and (1S)-endo-(-)-3-bromocamphor, both of which have been characterized by single crystal X-ray diffraction SXRD). When DCA is cocrystallized with (RS)-camphorquinone and (RS)-endo-3-bromocamphor,1:1 adducts of the S-enantiomers are produced together with crystals of the free racemic guest. In contrast, in the absence of (1S)-(1)-camphorquinone, DCA forms a 2:1 adduct with (1R)-(2)-camphorquinone. In this 2:1 adduct the guest is disordered at ambient temperature and undergoes a phase change in the region 160–130 K similar to that observed for the ferrocene adduct, but with only partial ordering of the guest. The SXRD structure of the low temperature form and the variable temperature 13C CP/MAS NMR are reported. Cocrystallizing DCA with (1R)-endo-(1)-3-bromocamphor gives the free guest and a glassy solid.