Polysaccharide derivatives as separating agents

Details Polysaccharide derivatives as separating agents Polysaccharide derivatives as separating agents

1991-01-18

1993-04-13

Brown, Johnnie R.

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

540357, 540362, 544246, 549401, 549512, 568336, 568808, 568730, C07D20508, C07D48700

Patent

active

052024334

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a new polysaccharide derivative which is extremely useful as a functional material for optical resolution. Particularly, the present invention relates to a new polysaccharide derivative having an asymmetric carbon atom group, and a separating agent comprising said polysaccharide derivative. Further, the present invention relates to a process for the separation of .beta.-lactam stereoisomers.


BACKGROUND ART

Derivatives prepared by reacting polysaccharides with achiral compounds are known. These derivatives have a structure wherein an achiral group is bonded to a stereoregular polymer chain, so that they can discriminate the asymmetry of various racemic modifications when used as column packings for liquid chromatography. However, they are apt to fail in discriminating the asymmetry of some racemic modifications of compounds having complicated structures such as those having two asymmetric centers in the same molecule or those having various functional groups in their asymmetric centers.
The present invention aims at providing a polysaccharide derivative and a separating agent having a higher asymmetry discriminating power, which are prepared by reacting a polysaccharide with a chiral compound to thereby regulate the configurations of both the backbone chain and the side chain.
.beta.-Lactams are important substances as raw materials for the preparation of various drugs including antibiotics. The separation of a .beta.-lactam into respective stereoisomers is essential because the action of such a drug on a living organism is, in many cases, different depending upon the kind of stereoisomer used in the preparation thereof, like in the case of thalidomide [see G. Blaschke, Angew. Chem. Int. Ed. Engl., 19, 13 (1980)].
Known processes for preparing a .beta.-lactam stereoisomer include asymmetric synthesis, diastereomer process and chromatographic process. Among these processes, the chromatographic process has advantages in that a high-purity stereoisomer can be obtained and continuous operation because possible by employing Sorbex techniques. However, none of the columns which have been used for the separation of .beta.-lactam stereoisomers exhibit a sufficiently high separating power and, therefore, the separation of same .beta.-lactams has been impossible as yet.


DISCLOSURE OF INVENTION

Under these circumstances, the present invention relates to a new polysaccharide derivative prepared by replacing some or all of the hydrogen atoms of the hydroxyl and/or amino groups of a polysaccharide with one or more atomic groups represented by the following formula (1), (2) or (3), and to a separating agent comprising said polysaccharide derivative as the main component: ##STR2## wherein the number of carbon atoms constituting R is 1 to 30 and R is a group having at least one asymmetric carbon atom.
The degree of replacement with the above atomic groups is at least 30%, preferably at least 50%, still preferably at least 85%.
It has now been found that .beta.-lactams can be efficiently separated into respective stereoisomers by using a separating agent comprising the above polysaccharide derivative as the main component.
The polysaccharide derivative of the present invention has a chiral side chain and can resolve a racemic mixture. The resolving power of the derivative can be exhibited not only by itself but also when it is supported on a carrier.
The present invention also provides a process for separating a racemic mixture, particularly a compound represented by the following general formula (4), into respective stereoisomers by using a separating agent comprising the above polysaccharide derivative as the main component: ##STR3## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each a hydrogen atom or a substituent having 1 to 30 carbon atoms, with the proviso that if R.sub.1 and R.sub.2 are the same, R.sub.3 and R.sub.4 are different from each other and if R.sub.3 and R.sub.4 are the same, R.sub.1 and R.sub.2 are different from each other.
In the above general f

REFERENCES:
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patent: 4892659 (1990-01-01), Shibata et al.
patent: 4912094 (1990-03-01), Myers et al.
patent: 4912205 (1990-03-01), Okamoto et al.
patent: 4976952 (1990-12-01), Lang et al.
patent: 5041226 (1991-08-01), Shibata et al.

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