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LI ET AL.
ACKNOWLEDGMENTS
The authors acknowledge the support of the National Natural
Science Foundation of China (No 21474024, 51073046) and
the Fundamental Research Funds for the Central Universities
(HEUCFT1009, HEUCF20151009). This work was also par-
tially supported by Daicel Corporation (Tokyo, Japan).
LITERATURE CITED
1. Francotte E, Lindner W (eds.). Chirality in drug research. Weinheim,
Germany: Wiley-VCH; 2006.
2. Subramanian G (ed.). Chiral separation techniques: a practical approach,
3rd ed. Weinheim, Germany: Wiley-VCH; 2007.
3. Ikai T, Okamoto Y. Structural control of polysaccharide derivatives for ef-
ficient separation of enantiomers by chromatography. Chem Rev 2009;
109: 6077–6101.
Fig. 5. Chromatograms for resolution of racemate
3
on xylan
4. Okamoto Y. Chiral polymers for resolution of enantiomers. J Polym Sci
Part A Polym Chem 2009; 47: 1731–1739.
5. Okamoto Y, Ikai T. Chiral HPLC for efficient resolution of enantiomers.
Chem Soc Rev 2008; 37: 2593–2608.
phenylcarbamates bearing 3-Cl (1b), 4-Cl (1f) and 3,5-Cl2 (1j) substituents.
Column: 25 × 0.20 cm (i.d.); eluent: hexane/2-propanol (90/10, v/v); flow rate:
0.1 mL/min.
6. Francotte E. Enantioselective chromatography as a powerful alternative for
the preparation of drug enantiomers. J Chromatogr A 2001; 906: 379–397.
7. Okamoto Y, Yashima E. Polysaccharide derivatives for chromatographic
separation of enantiomers. Angew Chem Int Ed 1998; 37: 1020–1043.
indicate that the chiral recognition ability of the xylanphenyl-
carbamates can be influenced by the nature, position, and
number of the substituents. The effect of the substituents is
similar to that of the cellulose phenylcarbamate derivatives.19
The xylan bisphenylcarbamates may have a more flexible
structure than the corresponding trisphenylcarbamates of
cellulose because of the absence of the carbamate groups
at 6-position, which can make the hydrogen bond with
the carbamate groups on a different glucose unit to fix
the polymer chain. Therefore, the structures of the xylan
phenylcarbamate derivatives may be more responsive to
the polymer dissolution solvents, suggesting that the
solvent used for coating the derivatives on silica gel may
influence the chiral recognition of the xylan-based CSPs.
On the other hand, owing to the limited set of racemates
used in this study, the conclusion might be changed. We
will go further to examine the structural influence on the
chiral recognition ability of the xylan-based CSPs including
the effect of eluents.
8. Okamoto Y, Aburatani R, Hatada K. Chromatographic chiral resolution XIV:
cellulose tribenzoate derivatives as chiral stationary phases for high-
performance liquid chromatography. J Chromatogr 1987; 389: 95–102.
9. Shen J, Ikai T, Okamoto Y. Synthesis and chiral recognition of novel am-
ylose derivatives containing regioselectively benzoate and phenylcar-
bamate groups. J Chromatogr A 2010; 1217: 1041–1047.
10. Shen J, Liu S, Li P, Shen X, Okamoto Y. Enantioseparation using ortho- or meta-
substituted phenylcarbamates of amylose as chiral stationary phases for high-
performance liquid chromatography. J Chromatogr A 2013; 1286: 41–46.
11. Shen J, Ikai T, Okamoto Y. Synthesis and application of immobilized
polysaccharide-based chiral stationary phases for enantioseparation by
high-performance liquid chromatography. J Chromatogr A 2014; 1363: 51–61.
12. Martinez SE, Lakowski TM, Davies NM. Enantiospecific analysis of 8-
prenylnaringenin in biological fluids by liquid-chromatography-
electrospray ionization mass spectrometry: application to preclinical phar-
macokinetic investigations. Chirality 2014; 26: 419–426.
13. Alanazi AM, Hefnawy MM, Al-Majed AA, Al-Suwailem AK, Kassem MG,
Mostafa GA, Attia SM, Khedr MM. HPLC-fluorescence method for the
enantioselective analysis of propranolol in rat serum using immobilized
polysaccharide-based chiral stationary phase. Chirality 2014; 26: 194–199.
14. Okamoto Y, Kawashima M, Hatada K. Useful chiral packing materials for
high-performance liquid chromatographic resolution of enantiomers:
phenylcarbamates of polysaccharides coated on silica gel. J Am Chem
Soc 1984; 106: 5357–5359.
15. Okamoto Y, Noguchi J, Yashima E. Enantioseparation on 3,5-dichloro- and
3,5-dimethylphenylcarbamates of polysaccharides as chiral stationary
phases for high-performance liquid chromatography. React Funct Polym
1998; 37: 183–188.
16. Zhang L, Shen J, Zuo W, Okamoto Y. Synthesis of chitosan 3,5-
dimethylphenyl-2-urea derivatives and their applications as chiral station-
ary phases for HPLC. J Chromatogr A 2014; 1365: 86–93.
17. Okamoto Y, Kaida Y. Resolution by high-performance liquid chromatogra-
phy using polysaccharide carbamates and benzoates as chiral stationary
phases. J Chromatogr A 1994; 666: 403–419.
CONCLUSION
Novel xylan 2,3-bisphenylcarbamate derivatives bearing
the substituents on meta- and para-positions of the phenyl
groups were synthesized and their chiral recognition abilities
were evaluated as the CSPs in HPLC using nine racemates
with a n-hexane/2-propanol (90/10, v/v) mixture as an elu-
ent. The chiral recognition abilities of these CSPs were
clearly influenced by the nature, position, and number of
the substituents. The introduction of an electron-donating
substituent is more preferable than that of an electron-
withdrawing group to improve the chiral recognition ability
of the xylan phenylcarbamate derivatives. For most of the ra-
cemates used in this study, the xylan bis(3,5-dimethyl-
phenylcarbamate) appears to show higher chiral recognition
ability than the other derivatives. Furthermore, the meta-
substituted derivatives show better resolving powers than
the para-substituted derivatives. A much higher enantios-
electivity for some racemates used in the study could be
achieved on the xylan bis(3,5-dimethylphenylcarbamate)
compared to that on the well-known cellulose tris(3,5-
dimethylphenylcarbamate), implying the superiority of the
xylan-based CSPs in the resolution of some chiral compounds
over cellulose-based analogs.
18. Yashima E, Okamoto Y. Chiral discrimination on polysaccharide deriva-
tives. Bull Chem Soc Jpn 1995; 68: 3289–3307.
19. Okamoto Y, Kawashima M, Hatada K. Controlled chiral recognition of cel-
lulose triphenylcarbamate derivatives supported on silica gel.
J
Chromatogr 1986; 363: 173–186.
20. Koller H, Rimböck KH, Mannschreck A. High-pressure liquid chromatog-
raphy on triacetylcellulose. J Chromatogr 1983; 282: 89–94.
21. Chankvetadze B, Yashima E, Okamoto Y. Chloromethylphenylcarbamate
derivatives of cellulose as chiral stationary phases for high-performance
liquid chromatography. J Chromatogr A 1994; 670: 39–49.
22. Chankvetadze B, Yashima E, Okamoto Y. Dimethyl-, dichloro-, and
chloromethylphenylcarbamates of amylose as chiral stationary phases for
high-performance liquid chromatography. J Chromatogr A 1995; 694: 101–109.
Chirality DOI 10.1002/chir