Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1999-11-18
2001-10-02
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S656000, C210S198200, C210S502100, C204S601000, C204S605000, C204S606000
Reexamination Certificate
active
06296768
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the development of novel separating materials for high performance liquid chromatography (HPLC), liquid chromatography (LC), thin layer chromatography (TLC), capillary electrophoretic chromatography (CCE) and counter-current chromatographic processes, which essentially comprise amine-bearing support materials and functionalised cyclodextrins (CD) chemically bonded via a urethane linkage. More significantly, our procedure affords materials in which the cyclodextrins are bonded to the support with well defined chemical structure and good experimental reproducibility.
BACKGROUND OF THE INVENTION
The applicability of cyclodextrins in chromatographic separation and purification processes were previously described at length in reviews by W. L. Hinze,
Separation and Purification Methods
, 1981, 10(2), 159-237; Y. Kawaguchi, et al.,
Anal. Chem
., 1983, 55, 1852; D. M. Armstrong, et al.,
Anal. Chem
., 1985, 57, 234 and S. Li, et al.,
Chem. Rev
., 1992, 92, 1457. Chromatographic separation on chiral stationary phases (CSP) is also the most convenient analytical method for the determination of enantiomeric purity (see for example S. G. Allenmark,
Chromatographic Enantioseparations: Methods and Applications
, 2nd ed., Prentice Hall, N.J., 1991). In recent years, tremendous research efforts were made in bonding cyclodextrins to solid matrices, such as silica gel, via amino or amido linkages. However, these bonds were inherently unstable to hydrolysis, thus placing severe limitations on their use in aqueous media. Alternative approaches for immobilizing CD using hydrolytically more stable ether linkages (U.S. Pat. No. 4,539,399) or carbamic acid moieties (U.S. Pat. No. 503,898) were also investigated. However, in all these approaches, arising from the presence of multiple hydroxy moieties in the CD starting materials, regioselective derivatisation of cyclodextrin cannot be readily effected. Thus, reaction may take place on the 2, 3 or 6- position of cyclodextrin and may result in mixtures of multi-functionalised CDs instead of the desired regiodefined compound.
It was often reported that derivatized CD stationary phases show definite enantioselectivity for a variety of compounds while pristine cyclodextrin bonded LC stationary phases depict low enantioselectivity. Thus, as an example, enantioselectivity of the materials were generally increased with increasing degree of derivatisation of the —OH groups on CD with carbamate groups on cyclodextrin as of an increasing surface concentration of the functionalised cyclodextrin immobilized on the support materials (D. W. Armstrong et al.,
Anal Chem
., 1990, 62, 1610; T. Hargitai et al.,
J. Chromatogr
., 1993, 628, 11; T. Hargitai, et al.,
J. Liq. Chromatogr
., 1993, 16(4), 843). In order to maximise the extent of cyclodextrin derivatisation, large molar excesses of derivatizing reagents under vigorous conditions were often used. However, as the derivatisation processes invariably involved the prior immobilization of underivatised cyclodextrin on the support material followed by functionalisation procedures involving solid-liquid phases, partial derivatisation of the hydroxyl groups of the cyclodextrin usually resulted with large, sterically encumbered substituents consistently having a lower extent of derivitisation. In addition, these methods did not give good reproducibility or uniformity of product with the consequence that separation of enantiomers may vary from batch to batch of the obtained CD-based CSP.
OBJECTIVES AND BRIEF SUMMARY OF THE INVENTION
One objective of this invention is the obtainment of novel and improved CSP materials comprising a support and completely regiodefined derivatised cyclodextrin chemically bonded via single or double urethane linkage(s), universally applicable in HPLC, LC, TLC and CCE. Application in counter-current chromatographic processes would thus afford a viable and efficient means into bulk/ industrial scale enantioseparation, which would be of interest particularly to pharmaceutical firms involved in enantioseparation of racemic chiral drugs.
Another objective of the invention is to derive methodologies for the preparation of materials mentioned above. These and other objectives will become apparent or will be highlighted in the ensuing description.
The present invention is based on the almost quantitative reaction of pre-synthesized regiodefined perfuctionalized monoazidocyclodextrin with primary amines based on an extended application of the Staudinger reaction which we have investigated. In addition, application of existing synthetic strategies (G. Wenz,
Angew. Chem. Int. Ed. Eng
., 1994, 33, 803 and references therein) into regiodefined disulphonated CDs, often referred to as capped cyclodextrins, can likewise afford regiodefined diazido perfunctionalised CDs suitable for reaction with amines. When aminized silica gel was used in place of the primary amine under similar conditions, the perfunctionalized mono- (or di-)azidocyclodextrin could be immobilized onto the surface of silica gel easily via stable urethane linkage(s), usually adopted in Pirkle-typed or protein-based CSPs (N.Oi, et al.,
J. Chromatogr
., 1983, 111, 257; W. H. Pirkle,
J. Chromatogr
., 1985, 322, 295; W. H. Pirkle,
J. Liq. Chromatogr
., 1986, 9, 443; C. J. Welch,
J. Chromatogr
. A, 1994, 666, 3; W. H. Pirkle, et al.,
J. Am. Chem. Soc
., 1989, 111, 9222; A. M. Dyas,
Recent Advances in Chiral Separations
, Plenum Press, New York, 1991). Furthermore, when perfunctionalized mono- or diazidocyclodextrins are reduced into the corresponding perfunctionalized mono- or diamino cyclodextrins, the latter can be easily anchored onto the surface of the support by suitable coupling reagents via urethane or amido linkages.
The invention therefore relates to a separating material used in chromatography, essentially comprising a support material and regiodefined perfunctionalized cyclodextrins chemically bonded to this support and characterized by a bonding via single or double urethane moieties. The invention also relates to a process for the production of this separating material in which the perfunctionalized mono-(or di)azidocyclodextrin is:
a. coupled directly to any support which is carrying free —NH
2
groups on the surface of the support.
b. reacted with any alkenyl amines to give the corresponding perfunctionalized cyclodextrin with mono- (or di)alkenyl substituted side chain(s) via urethane linkage(s) and then allowing this derivative to be hydrosilylized with HSiR
n
X
3−n
(where R and X are alkyl, alkyloxy, aryl or halide) and thereafter effecting an immobilization onto the surface of a support material.
c. reacted with any aminosilanes containing at least one further reactive group to afford the corresponding cyclodextrin-silane derivative. The resulting cyclodextrin-silane derivative is treated with silica gel to afford the perfunctionalized cyclodextrin bonded silica gel.
d. reduced to perfunctionalized mono- or diaminocyclodextrin and then anchored onto the surface of a support via coupling reagents.
Support which can be employed are silica gel or any alternative inorganic materials such as Al
2
O
3
, TiO
2
or ZiO
2
or synthetic polymer supports, preferably incorporating existing free NH
2
group on the surface. The support employed of choice is silica gel, which is commercially available in a wide range of different shapes and sizes.
REFERENCES:
patent: 4539399 (1985-09-01), Armstrong
patent: 4867884 (1989-09-01), Rendleman
patent: 5104547 (1992-04-01), Cabrera et al.
patent: 5198429 (1993-03-01), Konig
patent: 5294341 (1994-03-01), Fukazawa
patent: 5639824 (1997-06-01), Okamoto
Hinze et al.,Cyclodextrins in Chromatography, pp. 159-227 (1982).
Kawaguchi et al.,Anal. Chem., vol. 55, pp. 1852-1857 (1983).
Armstrong et al.,Anal. Chem., vol. 57, pp. 234-237 (1985).
Li et al.,Chem. Rev., vol. 92, pp. 1457-1470 (1992).
Allenmark,Chromatographic Enantioseparation: Methods and Applications, Second Edition, pp. 110-113 (1991).
Armstrong et al.,Anal. Chem., vol. 6
Ching Chi Bun
Ng Siu Choon
Zhang Lifong
National University of Singapore
Therkorn Ernest G.
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