Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1999-04-19
2001-04-17
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S656000, C210S198200, C210S502100, C096S101000, C502S404000
Reexamination Certificate
active
06217769
ABSTRACT:
TECHNICAL FIELD
This invention relates to separating agents for optical isomers, a process for producing the same, and a method for separating optical isomers. More particularly, it relates to separating agents which are useful in separating optical isomers and which are obtained by coating the surface of a polysaccharide derivative with a polymer to thereby immobilize the polysaccharide derivative on a carrier or to make the polysaccharide derivative alone solvent-resistant, a process for producing the same, and a method for separating optical isomers with the use of the same.
BACKGROUND ART
It has been well known that polysaccharides and derivatives thereof such as ester or carbamate derivatives of cellulose or amylose show a high optical resolving power. It has been also well known that chromatographic separating agents wherein these substances are physically adsorbed or held on silica gel are excellent separating agents having an optical resolving power over a wide range, a good theoretical plate number and a good durability (Y. Okamoto, M. Kawashima and K. Hatada, J. Am. Chem. Soc., 106, 5357, (1984)).
However, these separating agents can be employed only under restricted separation conditions, since polysaccharide derivatives are held on silica gel via physical adsorption and thus solvents in which the polysaccharide derivatives are soluble cannot be used as the mobile phase, etc. Also, solvents in which samples are to be dissolved are restricted. In the case of a sample having a low solubility in solvents usable as the mobile phase, there arises a serious problem particularly in chromatographic separation. Moreover, there is another inconvenience that only limited washing fluids are usable in washing away contaminants strongly adsorbed on the separating agents. Considering these points, there have been required separating agents carrying polysaccharide derivatives thereon and having a high solvent resistance.
To solve these problems, there have been developed a method wherein polysaccharide derivatives are chemically bonded directly to silica gel, a method wherein polysaccharide derivative molecules are crosslinked with each other and a method wherein a high solvent resistance is established by combining these two methods (JP-A 62-270602, JP-A 4-202141, JP-A 7-25904, JP-A 7-138301, JP-A 8-59702, WO95/18833, WO96/27615, WO97/4011 and WO97149733).
However, these techniques have the disadvantage of necessitating multi-step production processes, since unreacted hydroxyl or polyfunctional groups should be incorporated onto substituents for crosslinking or chemically bonding polysaccharide derivatives.
Accordingly, it has been required to develop separating agents for optical isomers which have the high optical resolving power inherent in polysaccharide derivatives together with a high solvent resistance and which can be produced through short process steps.
DISCLOSURE OF INVENTION
The present inventors have conducted extensive studies on separating agents for optical isomers which have the high optical resolving power inherent in polysaccharide derivatives and a high solvent resistance and which can be produced through short process steps and consequently completed the present invention.
Accordingly, the present invention provides a separating agent for optical isomers characterized in that the surface of a polysaccharide derivative supported on a carrier is coated with a polymer and a process for producing the same.
The present invention further provides a separating agent for optical isomers characterized in that the surface of a pulverized or granulated polysaccharide derivative is coated with a polymer and a process for producing the same.
The present invention furthermore provides a method for separating optical isomers characterized by using the above separating agents or the use of the above separating agents in separating optical isomers.
DETAILED DESCRIPTION OF THE INVENTION
Now, the mode for carrying out the present invention will be described in detail.
The polysaccharides to be used in the present invention may be any of synthetic polysaccharides and optionally modified natural ones, so long as they are optically active. It is preferable to use those having a regular binding mode. Examples thereof include &bgr;-1,4-glucan(cellulose), &agr;-1,4-glucan(amylose, amylopectin), &agr;-1,6-glucan(dextran), &bgr;-1,6-glucan(pustulan), &bgr;-1,3-glucan(curdlan, schizophyllan, etc.), &agr;-1,3-glucan, &bgr;-1,2-glucan(crown gall polysaccharides), &bgr;-1,4-galactan, &bgr;-1,4-mannan, &agr;-1,6-mannan, &bgr;-1,2-fructan (inulin), &bgr;-2,6-fructan (levan), &bgr;-1,4-xylan, &bgr;-1,3-xylan, &bgr;-1,4-chitosan, &agr;-1,4-N-acetylchitosan (chitin), pullulan, agarose and alginic acid. Also, starches containing amylose are included therein. Among these polysaccharides, it is preferable to use cellulose, amylose, &bgr;-1,4-xylan, &bgr;-1,4-chitosan, chitin, &bgr;-1,4-mannan, inulin, curdlan, etc. which can be easily obtained as highly pure polysaccharides, still preferably cellulose and amylose.
It is preferable that such a polysaccharide has a number-average degree of polymerization (i.e., the average number of pyranose or furanose rings per molecule) of at least 5, still preferably at least 10. From the viewpoint of handling properties, it is preferable that the number-average degree of polymerization thereof is not more than 500, though the upper limit thereof is not particularly defined.
Examples of the polysaccharide derivative to be used in the present invention include compounds prepared by introducing, into a portion of the hydroxyl groups of the above-mentioned polysaccharide, compounds having functional groups capable of reacting with the hydroxyl groups via ester, urethane or ether bonds by conventionally known methods. The compounds having functional groups capable of reacting with the hydroxyl groups may be isocyanic acid derivatives, carboxylic acids, esters, acid halides, acid amides, halides, epoxy compounds, aldehydes, alcohols and any other compounds having leaving groups. As these compounds, use can be made of aliphatic, alicyclic, aromatic and heteroaromatic ones. Among these compounds, those represented by the following general formula (I) are particularly preferable:
wherein X represents halogeno or C
1-3
alkyl; and n is a number of from 1 to 3.
Particularly preferable examples of the polysaccharide derivative to be used in the present invention include ester and carbamate derivatives of polysaccharides having at least 0.1 ester or urethane bond per monosaccharide.
As the carrier to be used in the present invention, use may be made of organic porous substrates and inorganic porous ones. It is preferred to use inorganic porous ones. Appropriate examples of the organic porous substrates include polymers comprising polystyrene, polyacrylamide, polyacrylate, etc. Appropriate examples of the inorganic porous substrates include silica, alumina, magnesia, glass, kaolin, titanium oxide, silicates and hydroxyapatite. Silica gel may be cited as a particularly preferable carrier. The particle diameter of the carrier is from 0.1 &mgr;m to 10 mm, preferably from 1 &mgr;m to 300 &mgr;m and the average pore size thereof is from 10 Å to 100 &mgr;m, preferably from 50 Å to 50,000 Å. When silica gel is employed as the carrier, it is preferable to preliminarily surface-coat the silica gel so as to exterminate the effects of the silanol remaining therein, though a non-surface-treated one may be used without any problem.
The separating agents for optical isomers according to the present invention can be produced by a process which comprises supporting a polysaccharide derivative on a carrier and then coating the surface thereof with a polymer to thereby immobilize the polysaccharide derivative on the carrier, or a process which comprises grinding or spheroidizing a polysaccharide derivative and then coating the surface thereof with a polymer.
In immobilizing the polysaccharide derivative on the carrier in the present invention, it is necessary that the polys
Okamoto Yoshio
Yashima Eiji
Daicel Chemical Industries Ltd.
Flynn ,Thiel, Boutell & Tanis, P.C.
Therkorn Ernest G.
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