Polysaccharide derivative, process for producing the same, and separating agent

A particulate aromatic or araliphatic carbamate of a polysaccharide having a mean particle diameter of 1 to 200 .mu.m and a specific surface area of 0.5 to 300 m.sub.2 /g is prepared by first dissolving an aromatic or araliphatic carbamate of a polysaccharlde in an organic solvent, adding a hydrocarbon having 4 to 22 carbon atoms in an amount of 0 to 0.5 time by volume of that of the organic solvent, gradually adding the resultant solution to a sufficiently agitating aqueous surfactant solution, removing the organic solvent while continuing the agitation, isolating solid particles, and washing and drying the solid particles. The particulate aromatic or araliphatic carbamate of a polysaccharide has an excellent capability of resolution and, as such, can be used as a stationary phase of preparative liquid chromatography without being supported on a support.

FIELD OF INDUSTRIAL APPLICATION 
The present invention relates to a polysaccharide derivative, a process for 
producing the same, and a separating agent. 
PRIOR ART 
It is known that a packing material for liquid chromatography wherein use 
is made of a stationary phase comprising a silica gel and, supported 
thereon, an ester of a polysaccharide and a carbamate has an excellent 
capability of optical resolution (see Japanese Patent Publication-A No. 
289601/1990 ). The silica gel used as a support, however, is very 
expensive. A process for producing a particulate cellulose ester of an 
aromatic or araliphatic carboxylic acid is well known in the art (see 
Japanese Patent Publication-A No. 152101/1989). However, a particulate 
aromatic or araliphatic carbamate of a polysaccharide has not been 
produced because the production thereof was difficult due to the 
limitation of the solubility and the solvent therefor. 
DISCLOSURE OF THE INVENTION 
The present inventors have made extensive studies with a view to solving 
the above-described problems and, as a result, have found that a 
particulate aromatic or araliphatic carbamate of a polysaccharide can be 
easily prepared, has an excellent capability of resolution because it is 
in the particulate form, particularly has a separation factor larger than 
that of the carbamate carried on a support, and is suitable for use in 
preparative liquid chromatography, thus accomplishing the present 
invention. 
Accordingly, the present invention provides a polysaccharide derivative 
comprising a particulate aromatic or arallphatic carbamate of a 
polysaccharide having a mean particle diameter of 1 to 200 .mu.m and a 
specific surface area of 0.5 to 300 m.sup.2 /g, a process for producing 
the same, and a separating agent comprising said polysaccharide derivative 
for use in the separation of racemic compounds and structural isomer 
mixtures, particularly a separating agent for use as a stationary phase in 
chromatography. 
In the present invention, the mean particle diameter of the polysaccharide 
derivative is 1 to 200 .mu.m, although it depends upon the application, 
preferably 3 to 20 .mu.m for analytic applications and 10 to 200 .mu.m for 
preparative applications. It is possible to attain a very narrow mean 
particle diameter range by fractionation through the use of a conventional 
method, for example, sedimentation, sifting or centrifugation by means of 
a cyclone. 
The specific surface area of the polysaccharide derivative according to the 
present invention is 0.5 to 300 m.sup.2 /g, preferably 1 to 80 m.sup.2 /g. 
The particle is spherical or crushed in its shape, preferably spherical. 
The surface of the particle may be porous or non-porous, preferably porous 
for the purpose of increasing the absorption area and improving the 
performance of separation. The particle diameter distribution is 
preferably narrow when the particle is used as a separating agent for 
chromatography. 
The aromatic or arallphatic carbamate of a polysaccharide of the present 
invention is derived from an lsocyanate represented by the following 
formulas (1) or (2): 
EQU R-N=C=O(1) 
EQU R-X-N=C=O(2) 
(wherein R stands for a monovalent aromatic hydrocarbon group which may 
have a heteroatom and may be unsubstltuted or substituted with at least 
one member selected from the group consisting of a hydrocarbon group 
having 1 to 12 carbon atoms and optionally a heteroatom, a cyano group, a 
halogen atom, a hydroxy group, a nitro group, an amino group and a 
di(C.sub.1 to C.sub.8 alkyl) amino group; and 
X stands for a divalent hydrocarbon group which has 1 to 4 carbon atoms and 
which may have a double bond or a triple bond). 
Examples of the monovalent aromatic hydrocarbon group represented by the R 
include groups such as phenyl, naphthyl, phenanthryl, anthracyl, indenyl, 
indanyl, furyl, thionyl, pyrryl, benzofuryl, benzthionyl, indyl, pyridyl, 
pyrimidyl, quinolinyl and isoquinolinyl. 
Examples of the substituents of the monovalent aromatic hydrocarbon group 
represented by the R include an alkyl group having 1 to 12 carbon atoms, 
an alkoxy group having 1 to 12 carbon atoms, an alkylthio group having 1 
to 12 carbon atoms, a cyano group, a halogen atom, an acyl group having 1 
to 8 carbon atoms, an acyloxy group having 1 to 8 carbon atoms, a hydroxy 
group, an alkoxycarbonyl group having 1 to 12 carbon atoms, a nitro group, 
an amino group and a di(C.sub.1 to C.sub.8 alkyl)amino group. 
X is a dlvalent hydrocarbon group having 1 to 4 carbon atoms and may have a 
double bond or a triple bond. Examples of X include methylene, ethylene, 
ethylidene, ethenylene, ethynylene, 1,2-or 1,3-propylene and 1,1- or 
2,2-propylidene. 
In the present invention, although the polysaccharide may be any of 
naturally occurring polysaccharides, synthetic polysaccharides and 
naturally occurring modified polysaccharides as far as they are optically 
active, it is preferably a polysaccharlde having a highly regular bonding 
form. Examples of the polysaccharlde include .beta.-1,4-glucan (cellulose 
), .alpha.-1,4-glucan (amylose, aminopectin or cyclodextrin), 
.alpha.-1,6-glucan (dextran), .beta.-1,6-glucan (pustulan), 
.beta.-1,3-glucan (for example, curdlan, schizophyllan or the like), 
.alpha.-1,3-glucan, .beta.-1,2-glucan (crown gall polysaccharide ), 
.beta.-1,4-galactan, .beta.-1,4mannan, .alpha.-1,6-mannan, 
.beta.-1,2-fructan (inulin), .beta.-2,6fractan (levan), .beta.-1,4-xylan, 
.beta.-1,3-xylan, .beta.-1,4chitosan, .beta.-1,4-N-acetylchitosan 
(chitin), pullulan, agarose and alginic acid, and still preferred examples 
of the polysaccharide include cellulose, amylose, .beta.-1,4-chitosan, 
.beta.-1,4-mannan, .beta.-1,4-xylan, inulin, chitin, chitosan and curdlan 
which enable polysaccharides having a high purity to be easily prepared. 
The number-average degree of polymerization of the polysaccharide (the 
average number of the pyranose or furanose rings contained in its 
molecule) is 5 or more, preferably 10 or more. Although the upper limit of 
the number-average degree of polymerization is not crucial, the upper 
limit is preferably 500 or less from the viewpoint of handleability. 
The aromatic or arallphatic carbamate of a polysaccharlde to be used in the 
present invention can be produced from an lsocyanate represented by the 
formulas (1) or (2) and a polysaccharlde by a conventional method. 
The percentage introduction of the substituent of the polysaccharlde is 10 
to 100%, preferably 80 to 100%. 
The particulate aromatic or araliphatic carbamate of a polysaccharide 
having a mean particle diameter of 1 to 200/.mu.m and a specific surface 
area of 0.5 to 300 m.sup.2 /g according to the present invention can be 
prepared by first dissolving an aromatic or araliphatic carbamate of a 
polysaccharide in an organic solvent, adding a hydrocarbon having 4 to 22 
carbon atoms in an amount of 0 to 0.5 by volume of that of the organic 
solvent, gradually adding the resultant solution to a sufficiently 
agitated aqueous surfactant solution, removing the organic solvent while 
continuing the agitation, isolating solid particles, and washing and 
drying the solid particles. 
In the above-described method, the particle diameter of the resultant 
polysaccharlde derivative varies depending upon the ratio of the amount of 
the organic solvent to the amount of the aqueous solution, the 
concentration of the polysaccharlde derivative, the rate of addition of 
the organic solvent, and the shapes of the vessel and the stirring blade, 
when the agitation rate is 10 to 1000 rpm, preferably 100 to 500 rpm. 
Although the organic solvent is not particularly limited as far as it can 
dissolve the polysaccharide carbamate, an organic solvent which is 
insoluble in water is particularly preferred. Even if the organic solvent 
is one which is soluble in water, it can be used after being mixed with an 
solvent which is insoluble in water. 
The amount of the hydrocarbon to be added to a solution of a polysaccharide 
derivative in an organic solvent is 0 to 0.5 by volume, preferably 0.1 to 
0.3 by volume of that of the organic solvent. The number of carbon atoms 
of the hydrocarbon is 2 to 22, preferably 4 to 10. Examples of the 
hydrocarbon include butane, pentane, heptane, hexane, octane, nonane and 
decane. 
The ratio of the total volume of the organic solvent, polysaccharlde 
derivative and hydrocarbon to that of the aqueous surfactant solution is 
preferably 1 : 10 to 1 : 1. 
In the present invention, the term "surfactant" refers to an acid, a 
dibasic acid, a tribasic acid, a tetrabasic acid or a hemlester or salt 
thereof, preferably an alkyl sulfate having 4 to 18 carbon atoms, 
particularly preferably a lauryl sulfate. 
The particulate polysaccharlde derivative thus prepared according to the 
present invention is useful as a separating agent for separating a racemic 
mixture, a structural isomer mixture, particularly as a packing material 
for gas chromatography and liquid chromatography. 
EFFECT OF THE INVENTION 
The polysaccharide derivative of the present invention is very useful as 
functional material, particularly useful for separating a racemic mixture 
and a structural isomer mixture. Since the polysaccharide derivative of 
the present invention is particulate, it is not necessary to use an 
expensive supporting material (silica gel) and it can be produced in a 
large quantity at a low cost. Further, when the surface of the particle is 
made porous, the separation factor can be increased through an increase in 
the specific surface area of the particle, which enables the separation to 
be conducted at a high efficiency and a high profitability.

EXAMPLES 
The present invention will now be described in more detail with reference 
to the following Examples, though it is not limited to these Examples 
only. 
EXAMPLE 1 
8.7 g of cellulose-3,5-dimethylphenylcarbamate was dissolved in 300 ml of 
mesityl oxide. The resultant solution was gradually added in portions to 
600 ml of a 0.75% aqueous sodium lauryl sulfate solution being agitated at 
about 400 rpm. The reaction system was heated to 90.degree. C. and 
evacuated while continuing the agitation at the same rate. 250 ml of 
distilled water was added in the course of the above procedure to distill 
away mesityl oxide. The residue was isolated by filtration and washed with 
distilled water and ethanol. The resultant powder was dried in vacuo at 
140.degree. C. for 16 hr. The yield of the resultant powder was 8.1 g 
(93%). The powder was classified by sifting and sedimentation to prepare a 
spherical particle having a diameter of 3 to 6 .mu.m and a specific 
surface area of 3.4 m.sup.2 /g (BET method). 
EXAMPLE 2 
The powder prepared In the Example 1 was packed in a column having an inner 
diameter of 4.6 mm and a length of 125 mm, and the separation of various 
racemic compounds listed in Table 1 was conducted by HPLC. The results are 
given in Table 1. 
EXAMPLE 3 
10.0 g of cellulose-3,5-dlmethylphenylcarbamate was dissolved in a mixed 
solvent comprising 250 ml of mesityl oxide and 50 ml of acetone, and 50 ml 
of n-nonane was added thereto. The resultant solution was gradually added 
in portions to 600 ml of a 0.75% aqueous sodium lauryl sulfate solution 
being agitated at about 400 rpm. The reaction system was heated to 
90.degree. C. and evacuated while continuing the agitation at the same 
rate. 200 ml of distilled water was added in the course of the above 
procedure to distil away mestyl oxide and acetone. The residue was 
isolated by filtration and washed with distilled water and ethanol. The 
resultant powder was dried in vacuo at 140.degree. C. for 16 hr. The yield 
of the resultant powder was 7.83 g (78.3%). The powder was classified by 
sifting and sedimentation to prepare a spherical particle having a 
diameter of 3 to 8 .mu.m and a specific surface area of 4.8 m.sup.2 /g 
(BET method). 
EXAMPLE 4 
The powder prepared in Example 3 was packed in a column having an inner 
diameter of 4.6 mm and a length of 100 mm, and the separation of various 
racemic compounds listed in Table 1 was conducted by HPLC. The results are 
given in Table 1. 
EXAMPLE 5 
10.0 g of cellulose-3,5-dlmethylphenylcarbamate was dissolved in a mixed 
solvent comprising 250 ml of mesityl oxide and 50 ml of acetone, and 50 ml 
of n-nonane was added thereto. The resultant solution was gradually added 
in portions to 600 ml of a 0.75% aqueous sodium lauryl sulfate solution 
being agitated at about 200 rpm. The reaction system was heated to 
90.degree. C. and evacuated while continuing the agitation at the same 
rate. 200 ml of distilled water was added in the course of the above 
procedure to distil away mesityl oxide and acetone. The residue was 
isolated by filtration and washed with distilled water and ethanol. The 
resultant powder was dried in vacuo at 140.degree. C. for 16 hr. The yield 
of the resultant powder was 8.46 g (84.6%). The powder was classified by 
sifting and sedimentation to prepare a spherical particle having a 
diameter of 12 to 30 .mu.m and a specific surface area of 1.2 m.sup.2 /g 
(BET method). 
EXAMPLE 6 
10.0 g of amylose-3,5-dlmethylphenylcarbamate was dissolved in a mixed 
solvent comprising 300 ml of chloroform and 6 ml of N,N-dimethylacetamide, 
and 40 ml of n-heptane was added thereto. The resultant solution was 
gradually added in portions to 600 ml of a 0.75% aqueous sodium lauryl 
sulfate solution being agitated at about 400 rpm. The reaction system was 
heated to 60.degree. C. and evacuated while continuing the agitation at 
the same rate to distil away the organic solvent. The residue was isolated 
by filtration and washed with distilled water and ethanol. The resultant 
powder was dried in vacuo at 90.degree. C. for 20 hr. The yield of the 
resultant powder was 9.41 g (94.1%). The powder was classified by sifting 
and sedimentation to prepare a spherical particle having a diameter of 3 
to 6 .mu.m and a specific surface area of 4.3 m.sup.2 /g (BET method). 
EXAMPLE 7 
The powder prepared in Example 6 was packed in a column having an inner 
diameter of 4.6 mm and a length of 125 mm, and the separation of various 
racemic compounds listed in Table 1 was conducted by HPLC. The results are 
given in Table 1. 
TABLE 1 
______________________________________ 
Ex. 2 Ex. 4 Ex. 7 
racemic compd. 
k.sub.1 ' 
.alpha. k.sub.1 ' 
.alpha. 
k.sub.1 ' 
.alpha. 
______________________________________ 
t-stilbene oxide 
5.41 1.76 1.20 2.64 1.76 2.92 
Troger's base 
7.15 1.28 1.84 1.21 1.82 1.69 
benzoin 15.19 1.58 3.61 1.69 12.95 
1.32 
phenyl vinyl 
12.89 1.25 2.69 1.41 4.93 1.0 
sulfoxide 
trifluoroanthryl- 
15.76 2.47 2.97 3.52 4.63 1.39 
ethanol 
______________________________________ 
mobile phase: hexane/2-propanol=9/1 
flow rate: 0.5 ml/min 
temp.: room temp. 
The HPLC used was one (pump: 880-PU, detector: 875-UV) manufactured by 
Japan Spectroscopic Co., Ltd. 
In the table, the volumetric ratio (k.sub.1 ') and the separation factor 
(.alpha.) are defined by the following equations: 
##EQU1## 
EXAMPLE 8 
10 g of cellulose tris(phenylcarbamate) was dissolved in a mixed solvent 
comprising 250 ml of mesityl oxide and 50 ml of acetone, and 50 ml of 
n-nonane was added thereto. The mixture was agitated until the opaque 
solution turned transparent. The solution was gradually added in portions 
to 600 ml of a 0.75% aqueous sodium lauryl sulfate solution being agitated 
at about 400 rpm. The reaction system was heated to 40.degree. C. and 
evacuated while continuing the agitation at the same rate to distil away 
the organic solvent. The residue was isolated by filtration and washed 
with distilled water and ethanol. The resultant powder was dried in vacuo 
at 140.degree. C. for 19 hr. The yield of the resultant powder was 7.2 g 
(72%). The powder was classified by sifting and sedimentation to prepare a 
spherical particle having a diameter of 6 to 15 .mu.m and a specific 
surface area of 5.4 m.sup.2 /g (BET method ). 
EXAMPLE 9 
The powder prepared in Example 8 was packed in a column having an inner 
diameter of 4.6 mm and a length of 125 mm, and the separation of various 
racemic compounds listed in Table 2 was conducted by HPLC. The results are 
given in Table 2. 
TABLE 2 
______________________________________ 
Ex. 9 
racemic compd. k.sub.1 ' 
.alpha. 
______________________________________ 
t-stilbene oxide 6.13 1.40 
phenyl vinyl sulfoxide 
58.32 1.15 
2,2,2-trifluoro-1-(9- 
9.95 1.36 
anthryl)-ethanol 
______________________________________ 
mobile phase: hexane/2-propanol=9/1 
flow rate: 0.5 ml/min 
temp.: room temp. 
The HPLC used was one (pump: 880-PU, detector: 875-UV) manufactured by 
Japan Spectroscopic Co., Ltd. 
EXAMPLE 10 
10 g of cellulose tris(phenylcarbamate) was dissolved in a mixed solvent 
comprising 250 ml of methylene oxide and 10 ml of acetone, and the 
resultant solution was gradually added in portions to 600 ml of a 0.75% 
aqueous sodium lauryl sulfate solution being agitated at about 400 rpm. 
The reaction system was heated to 45.degree. C. while continuing the 
agitation at the same rate to distil away the organic solvent. The residue 
was isolated by filtration and washed with distilled water and ethanol. 
The resultant powder was dried in vacuo at 80.degree. C. for 20 hr. The 
yield of the resultant powder was 9.4 g (94%). The powder was classified 
by sifting and sedimentation to prepare a spherical particle having a 
diameter of 10 to 30 .mu.m.