ENANTIOSEPARATION OF BETTI BASE ANALOGS
555
TABLE 4. Thermodynamic parameters, DH8, DS8*, D(DH8), D(DS8), D(DG8), and correlation coefficients (R2)
of analytes 1A, 1L, and 2A on IP-CF6 CSP
Correlation
2DH8
2DS8*
coefficient
2D(DH8)
2D(DS8)
2D(DG8)298 K
Analyte
Stereoisomer
(kJ mol2)
(J mol21 K21
)
(R2)
(kJ mol21
)
(J mol21 K21
)
(kJ mol21
)
Tiso (8C)
1A
1
2
1
2
1
2
12.4
15.6
13.0
15.8
20.5
23.4
30.4
40.5
29.2
36.9
57.3
65.9
0.9903
0.9929
0.9977
0.9982
0.9969
0.9981
3.2
10.1
7.7
0.2
45
1L
2A
2.8
2.9
0.5
0.3
87
58
8.6
Chromatographic conditions: column, IP-CF6; mobile phase, n-heptane/IPA/TFA 5 70/30/0.1 (v/v/v); R2, correlation coefficient of van’t Hoff plot, ln k 2 1/T
curves; flow rate, 0.5 ml min21; and detection, 215 nm.
8. Lu YP, Nikolovska-Coleska Z, Fang XL, Gao W, Shangary S, Qiu S, Qin
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In summary, the complex formation that involved multiple
intermolecular interactions between the analyte and the CSP
was generally exothermic, and the corresponding entropic
contribution was also negative. As it is evident from the
9. Sztojkov-Ivanov A, Szatma´ri I, Pe´ter A, Fu¨lo¨p F. Structural and tempera-
D(DG8) data, the separations for the investigated analytes on
this CSP were enthalpically favored. However, the exact chi-
ral recognition mechanism on IP-CF6 is not yet clear. Fur-
ther investigations are needed to clarify the effects of acidic/
alcoholic modifiers and interactions governing the chiral rec-
ognition.
ture effects in the high-performance liquid chromatographic enantiosepa-
ration of 1-(a-aminobenzyl)-2-naphthol and 2-(a-aminobenzyl)-1-naphthol
analogs. J Sep Sci 2005;28:2505–2510.
10. Sztojkov-Ivanov A, To´th D, Szatma´ri I, Fu¨lo¨p F, Pe´ter A. High-perform-
ance liquid chromatographic enantioseparation of 1-(aminoalkyl)-2-naph-
thol analogs on polysaccharide-based chiral stationary phases. Chirality
2007;19:374–379.
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CONCLUSIONS
The direct separations of 27 1- and 2-naphthol (Betti base)
analogs were performed in normal-phase mode on a newly
developed CSP containing IP-CF6 as chiral selector. Applying
n-heptane/alcoholic modifier/acidic modifier mobile-phase
system, IPA and t-BuOH as alcoholic modifier and TFA as
acid seemed to be most effective in the enantioseparation.
By variation of the nature and concentration of the alcoholic
and acidic modifiers in most cases, baseline resolution was
achieved for the majority of the investigated analytes. Prob-
ably because of the steric effect, the 1-naphthol and sterically
more constrained analogs exhibited larger retention factors,
separation factors, and resolutions. On the basis of thermo-
dynamic data, the separation proved to be enthalpically
favored. The elution sequence was reversal compared to
results obtained on polysaccharide-based CSPs.
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Chirality DOI 10.1002/chir