Chiralm selective chromatography

D. Kozma ed. Handbook of Optical Resolutions via Diastereomeric Salt Formation. CRC Handbooks, 2001.Z Juvancz, G. Seres Appendix

Definition of chirality

• Chiral molecules are asymmetric.

• Enantiomers or optical isomers are mirror image of each others, but they are not same.

• Diastereomeric molecules are not

• mirror images, but they have same constitutions.

Central chirality with for different substituents.

Enantiomers

Kajtár M., Változatok négy elemre, Gondolat, 1984.

DNS molecules

Application of chiral selective analysis

Checking the chiral selective synthesis:Pharmaceutical, pesticide industry

Metabolite research: (pl. Warfarin, Ibuprofen, pheromonos)

Adulteration, bacterial infectiouns: ( pl. wine, essential oils)

Racemisation: (pl. heat treatment, age determination)

Different effects of enantiomeric pharmaceuticals

Share of enantiomeric pure pharmceuticals

Different odor of enatiomers

Three point interaction is necessary for the chiral recognation I.

V.R. Meyer, M. Rais,Chirality1 (1989) 167.

Two point interactions are not enough II.

V.R. Meyer, M. Rais, Chirality 1 (1989) 167.

Certain rigidity is necessary for chiral recognition

V.R. Meyer, M. Rais,Chirality1 (1989) 167.

Interaction points can be surface or axis

π acid - π base, and h_bridge are the key interactions.

Working theory of chiral stationer phase, (CSP)

C. Welch et al., Review of Stereochemistry

Working theory of chiral mobile phase addtitive (CMA)

C. Welch et al., Review of Stereochemistry

General rules of chiral selective chromatography

• Rigid structure offers high selectivity.• Flexible structure offer broad selectivity range.• Most of the separation bases on three point

interaction.• Functional groups close to asymmetric center

improves the resolution.• Repulsion interactions have a big role.• Low analysis temperature improves the separations.

Temeperature dependence of chiral chromatography

ln α = S+- (S0sm)/R - H+- (H0

sm)/RT +- : difference between the two isomers (+and -)

sm: difference between two phases (stationary and mobile).

Generally the low analysis temperature improve the separation.

Using high efficiency stationary phase, 0,1kJ/mol (α: 1,01) energy difference is enough between the enantiomers for Rs 1.5 resolution value.

Importance of minor first elution order

Most frequently used CSP are cyclodextrin based molecules

.

Shape of derivatized a CD

The direction and length of bonds are differents..

Reason of good chiral recognation properties of cyclodextrins

• There are several chiral center in a CD

• The surrounding of chiral centers are of uniform in a glucose unit.

• The shape of glucose units are different

• Substituted derivates are bunch of isomers

• The chiral recognition depends on the type of substituents

• The selectivity can depend on the ionized state

• Cyclodextrins have flexible structure (induce fit)

Cyclodextrins can separate even the functionless hydrocarbons enantiomers

Selecticvity vs. Concetration of chiral selector

The acharial silicone matrix offers a good efficiency.

Selecticvity vs. Concetration of chiral selector

Low analysis temperature results in high selectivity

Cyclic derivatives give high selectivity

Separation of enetiomers of essential aminoacids with Chirasil-Val

Orginal CSP ImprovedCSP

Chiral selective HPLC

Most frequently used CSps in

Key interaction of polysaccharide CSps

H-bridge ands π- π interactions

Selectivity depend on the substitution of cellulose

Cyclodextrin CSp in HPLC

Cyclodextris as CMAs (

Methylated cyclodexrin CMAs

Pirkle type CSP

Separation with π base CSP

Vancomycin, antibiotic CSP

Separation with Vancomycin CSP

Chiral separation in CE

Neutral selector can not separate neutral molecules.The oppositely charged selector and sample offer high resolution.Separation has maximum value in the function of the selector concentration.

Separation vs. concentration of selector

High selectivity with oppositelly charged sample and selector

Used chiral selectors in CE

Separations of pyretroic acids

Chiral separation with β-HDMACD

0,5 mMol concentration of selectror is enough for baseline separation.

Chiral selective separation of

γ-PhoCD reversed migration orders TRIMEB

Dual CD seletor system

min2 4 6 8 10 12 14

mAU

-20

-10

0

10

20

30

min2 4 6 8 10 12 14

mAU

-20

-10

0

10

20

30

min2 4 6 8 10 12 14

mAU

-20

-10

0

10

20

30

min 5 10 15 20 25

mAU

-10 -5 0 5

10 15 20

50 mM acetic acid / TRIS; pH 5.0

+ 1 mM MACD50 mM acetic acid / TRIS; pH 5.0

50 mM acetic acid / TRIS; pH 5.0

+ 10 mM PMMACD

50 mM acetic acid / TRIS; pH 5.0 + 1 mM MACD + 10 mM PMMACD

Kass : 100 – 370 M-1

Kass : 1.3 – 70 M-1

mecoprop, 2,4-DP, 3ClPPA

Fenoprop

4MePPA

PPA

R. Iványi et al.

The selectivity of ionizable CDs depend on their ionized states

Partially filling technique

No EOF (acrylamide coated column).The sample and selector migrate in opposite directions.The selector nigrates away, when the sample reaches the detector windows.

Vancomicine selector

Chiral selector with chiral MKEC agent

Chips chiral separation

Designed for Martian space rockett

EKC

Chiral CEC

Monolit CSP selector