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
✍ Scribed by Mohamed I. M. Tahir; Nicholas H. Rees; Stephen J. Heyes; Andrew R. Cowley; Keith Prout
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 964 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0899-0042
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
3α,12α‐Dihydroxy‐5β‐cholan‐24‐oic acid (deoxycholic acid DCA) is able to discriminate between the R‐ and S‐enantiomers of camphorquinone and endo‐(+)‐3‐bromocamphor and select only the S‐enantiomers from a racemic mixture. DCA forms novel well ordered 1:1 adducts with (1__S__)‐(+)‐camphorquinone and (1__S__)‐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 (1__S__)‐(+)‐camphorquinone, DCA forms a 2:1 adduct with (1__R__)‐(−)‐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 ^13^C CP/MAS NMR are reported. Cocrystallizing DCA with (1__R__)‐endo‐(+)‐3‐bromocamphor gives the free guest and a glassy solid. Chirality, 2008. © 2008 Wiley‐Liss, Inc.