Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1997-09-02
1999-09-07
Wilson, James O.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536 179, 536 187, 536 20, 536 30, 536 45, 536 51, 536 53, 536 553, 536 56, 536112, 536124, 536126, 536127, C07H 100
Patent
active
059489049
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of aromatic carbamoyl-substituted polysaccharide derivatives which find utility as support materials for the chromatographic separation of enantiomers.
In Chemistry Letters, pp. 739-742 (1984), Y.Okamoto et al describe a separation material suitable for chromatography, which material consists of a macroporous silica gel coated with cellulose triacetate or cellulose tribenzoate. This support material is expensive. In addition, only the cellulose derivative layer is available for the separation of the enantiomers so that the separation capacity is not entirely satisfactory.
In J. of Chromatography, 351, pp. 346-350 (1986), K. -H. Rimbock propose using as stationary phase powdered microcrystalline tribenzoyl cellulose obtained by simple precipitation from a solution. The separation capacity of the powdered material is insufficient. Furthermore, the particle size and the outer particle shape cannot be controlled when this process is used.
EP-A-0 025 639 discloses a process for the preparation of spherical porous cellulose particles. In this process, an organic solution of cellulose triacetate containing a long-chain alcohol is suspended, with stirring, in an aqueous phase containing a high molecular weight surfactant, typically polyvinyl alcohol or gelatin. After removal of the organic solvent, the cellulose triacetate particles so obtained are isolated and purified and then saponified. Our own tests showed that the cellulose triacetate particles obtained according to this process have only a small specific surface area and only low separating power for enantiomers when used as stationary phase in liquid chromatographic processes.
EP-A-0 316 270 discloses finely particulate cellulose esters of aromatic or aromatic-aliphatic carboxylic acids in the form of essentially round partially crystalline particles, which may indeed be used as stationary phase in chromatographic processes, in particular for the separation of enantiomers, but which are not suitable for all compound classes.
EP-A-0 157 364, EP-A-0 147 801 and EP-A-0 157 356 disclose polysaccharide carbamates which are suitable for separating enantiomers, but in the case of said polymers it has to be taken into consideration that they can be used only after being applied to a support, typically silica gel.
EP-A-0 527 236 discloses aromatic and araliphatic polysaccharide carbamates which are used as stationary phase for the chromatographic separation of enantiomers. It is emphasized that the materials so obtained can be used as such without being applied to a support. However, extensive experiments on our part showed that the materials so obtained cannot be used according to the indicated conditions for the chromatographic separation of enantiomers.
The invention relates to a process for the preparation of polysaccharide-N-arylcarbamates in suitable form as supports for chromatography, which process comprises adding to polysaccharide carbamates, which may be substituted in the aryl moiety, a N-aryl-1-lower-alkylcarbamate-containing solution of an organic solvent, with vigorous stirring, until the polysaccharide derivative is completely dissolved and then adding thereto an aqueous solution containing a high molecular weight surfactant and, with continued stirring, removing the organic solvent from the emulsion so obtained and isolating the solid particles and washing and drying them.
The polysaccharide particles are obtained in a particle size of 5-150 .mu.m and, in particular, of 10-30 .mu.m in rounded or also in irregular shape.
The specific surface area is preferably 1-100 m.sup.2 /g, but particularly preferably 3-35 m.sup.2 /g.
The specific surface area can be influenced by the reaction conditions, typically by the choice of solvent and by the way in which the reaction is carried out, e.g. by the rate of addition, stirring and evaporation, as well as by the ratios of solvent, water and high molecular weight surfactant.
High molecular weight surfactants are preferably polyvinyl alcohol or carboxymethyl
REFERENCES:
patent: 4861872 (1989-08-01), Okamoto et al.
patent: 5354852 (1994-10-01), Ikeda
Kalinchak Stephen G.
Novartis AG
Wilson James O.
Wissing William K.
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