Optical resolution with tribenzoyl-b-1,4-chitosan

A separation agent essentially comprises an aliphatic or aromatic ester of a polysaccharide, except for cellulose acetate and an aromatic ester of cellulose. It is useful for separation of various chemical substances, especially optical resolution of optical isomers.

The invention relates to a sepaaration agent which essentially comprises an 
aromatic carboxylic acid ester of a polysaccharide. It is useful for 
separation of various chemical substances, especially optical resolution 
of optical isomers. 
The resolving agent of the present invention can be used for separation of 
all sorts of chemical substances, particularly for optical resolution of 
them. 
It has been well known that optical isomers of a chemical compound have 
effects different from each other in vivo generally. Therefore, it is 
important to obtain optically pure compounds for the purposes of improving 
medicinal effects per unit dose of them and removing adverse reactions 
thereof and damages from them in medical, agriculture and biochemical 
fields. A mixture of optical isomers has been optically resolved by 
preferential crystallization or diastereomer process. However, varieties 
of compounds capable of being optically resolved by these processes are 
limited and these processes require a long time and much labor. Under 
these circumstances, development of a technique of conducting the optical 
resolution by an easy chromatographic process has eagerly been demanded. 
The above-mentioned object of the present invention is attained by a 
resolving agent contaaining an aromatic carboxylic acid ester of a 
polysaccharide as an effective component. 
The resolving agent of the invention exhibits preferably different powers 
of absorbing different optical isomers of a given compound. 
The term "polysaccharides" herein involves any optically active 
polysaccharide selected from the group consisting of synthetic, natural 
and modified natural polysaccharides. Among them, those having highly 
regular linkages are preferred. Examples of them include 
.beta.-1,4-glucans (celluloses), .alpha.-1,4-glucans (amylose and 
amylopectin), .alpha.-1,6-glucan (dextran), .beta.-1,6-glucan (pustulan), 
.beta.-1,2-glucan (Crown gall polysaccharide), .beta.-1,4-galactan, 
.beta.-1,4-mannan, .alpha.-1,6-mannan, .beta.-1,2-fructan (inulin), 
.beta.-2,6-fructan (levan), .beta.-1,4-xylan, .beta.-1,3-xylan, 
.beta.-1,4-chitosan, .beta.-1,4-N-acetylchitosan (chitin), pullulan, 
agarose and alginic acid. Still preferred ones are those capable of easily 
yielding highly pure polysaccharides, such as cellulose, aamylose, 
.beta.-1,4-chitosan, chitin, .beta.-1,4-mannan, .beta.-1,4-xylan, inulin, 
and curdlan. 
These polysaccharides have a number-average degree of polymerization 
(average number of pyranose or furanose rings in the molecule) of at least 
5, preferably 10. Though there is provided no upper limit of the degree of 
polymerization, it is preferably 500 or less from the viewpoint of the 
ease of handling. 
The term "aromatic carboxylic acids" herein refers to those having an 
aromatic ring having 6 to 20 carbon atoms or a heteroaromatic ring having 
4 to 20 carbon atoms. Preferred aromatic carboxylic acids are those having 
carboxyl groups directly bonded with the aromatic or heteroaromatic ring. 
They may have further a substituent bonded with the ring. 
In the polysaccharide, the hydroxyl groups other than those forming the 
linkage bond with the aabove-mentioned carboxylic acid may be present in 
the form of free hydroxyl groups or they may be esterified, etherified or 
carbamoylated so far as the resolving ability of the resolving agent is 
not damaged. 
The esterification for forming the fatty acid esters of the polysaccharides 
used in the present invention may be conducted by a known process for the 
esterification of cellulose or amylose (see, for example, "Dai-Yuki 
Kagaku" 19, `Tennen Kobunshi Kagaku I` published by Asakura Book Store, p. 
124). For example, generally used esterfying agents are anhydrides and 
halides of corresponding carboxylic acids, particularly acid chlorides. It 
is preferred to use a tertiary amine base or Lewis acid as the catalyst. 
The reaction solvent may be any solvent so far as it does not inhibit the 
esterification reaction, such as pyridine or quinoline which acts also as 
the base. Frequently, a catalyst such as 4-(N,N-dimethylamino)pyridine is 
effective in accelerating the reaction. 
Further, a corresponding carboxylic acid combined with a dehydrating agent 
may also be reacted with the polysaccharide to obtain the ester. 
Since most of the polysaccharides used as the starting material have a low 
reactivity, it is preferable that, they are activated by 
dissolution/reprecipitation or dissolution/freeze drying treatment or by 
using a reaction solvent in which the polysaccharides are soluble. 
The resolving agent of the present invention is used for the purpose of 
resolving compounds and optical isomers thereof generally according to a 
chromatographic method such as gas, liquid or thin layer chromatographic 
method. Further, the resolving agent may be used in membrane resolution 
method. 
In using the resolving agent of the present invention in the liquid 
chromatography, there may be employed a method wherein the powdered 
resolving agent is packed in a column, a method wherein a capillary column 
is coated with the resolving agent, aa method wherein a capillary is made 
form the resolving agent to use the inner wall thereof and a method 
wherein the resolving agent is spun and bundled up to form a column. Among 
them, the method wherein the powdered resolving agent is employed is most 
general. 
The separation agent of the invention is preferaably used in the form of 
powder. It is obtained by crushing the agent or forming it into spherical 
beads. The particle size which varies depending on the size of a column or 
plate used is 1 .mu.m to 10 mm, preferably 1 to 300 .mu.m. The particles 
are preferably porous. 
It is preferred to support the resolving agent on a carrier so as to 
improve the resistance thereof to pressure or prevent swelling or 
shrinkage thereof due to solvent exchange and from the viewpoint of the 
number of theoretical plates. The suitable size of the carrier which 
varies depending on the size of the column or plate used is generally 1 
.mu.m to 10 mm, preferably 1 to 300 .mu.m. The carrier is preferably 
porous and has an average pore diameter of 10 .ANG. to 100 .mu.m, 
preferably 50 to 50,000 .ANG.. The amount of the resolving agent to be 
supported is 1 to 100 wt. %, preferably 5 to 50 wt. %, based on the 
carrier. 
The resolving agent may be supported on the carrier by either chemical or 
physical means. The physical means include one wherein the resolving agent 
is dissolved in a suitable solvent, the resulting solution is mixed with a 
carrier homogeneously and the solvent is distilled off by means of a 
gaseous stream under reduced pressure or heating and one wherein the 
resolving agent is dissolved in a suitable solvent, the resulting solution 
is mixed homogeneously with a carrier and the mixture is dispersed in a 
liquid incompatible with said solvent by stirring to diffuse the solvent. 
The resolving agent thus supported on the carrier may be crystallized, if 
necessary, by heat treatment or the like. Further, the state of the 
supported resolving agent and accordingly its resolving power can be 
modified by adding a small amount of a solvent thereto to temporarily 
swell or dissolve it and then distilling the solvent off. 
Both porous organic and inorganic carriers may be used, though the latter 
is preferred. The suitable porous organic carriers are those comprising a 
high molecular substance such as polystyrene, polyacrylamide or 
polyacrylate. The suitable porous inorganic carriers are synthetic or 
natural products such as silica, alumina, magnesia, titanium oxide, glass, 
silicate or kaolin. They may be surface-treated so as to improve their 
affinity for the resolving agent. The surface treatment may be effected 
with an organosilane compound or by plasma polymerization. 
In using the resolving agent of the present invention in the resolution of 
compounds or optical isomers, the resolving characteristics thereof may 
vary sometimes depending on physical properties thereof such as molecular 
weight, crystallinity and orientation, even though they are chemically 
similar. Therefore, the resolving characteristics of the resolving agent 
may be altered according to the use thereof by suitably selecting the 
solvent used in that step or by physical treatments such as heat 
treatment, etching or swelling with the liquird after said step in any of 
the above-mentioned processes. 
In liquid or thin layer chromatography, any developer may be used except 
those in which the resolving agent is soluble or which are reactive with 
the resolving agent. In case the resolving agent has been bound to the 
carrier by the chemical process or it has been insolubilized by 
crosslinking, any solvent other than a reactive liquid may be used. As a 
matter of course, it is preferred to select the developer after 
examination of various developers, since the resolving characteristics of 
chemical substances or optical isomers vary depending on the developer 
used. 
In the thin layer chromatography, a layer having a thickness of 0.1 to 100 
mm and comprising the resolving agent in the form of particles of about 
0.1 .mu.m to 0.1 mm and, if necessary, a small anount of a binder is 
formed on a supporting plate. 
In the membrane resolution process, the resolving agent is used in the form 
of a hollow filament or film. 
The resolving agent of the present invention containing the aromatic ester 
of the polysaccharide as the effective component is effective for the 
resolution of various compounds. Particularly, it is quite effective for 
the resolution of optical isomers which are quite difficult to resolve. 
Either one of the optical isomers to be resolved is selectively adsorbed 
on the resolving agent. 
The separation agent according to the invention is useful to the optical 
resolution as above shown. In addition, it serves for separation of 
geometrical isomers and polymers having different molecular weight ranges 
from each other. They have not easily been separated in the state of prior 
arts.

The following examples will further illustrate the present invention, which 
by no means limit the invention. In the examples, the terms are defined as 
follows: 
##EQU1## 
SYNTHESIS EXAMPLE 1 
10 g silica beads (LiChrospher SI 1000; a product of Merck & Co.) was 
placed in a 200 ml round-bottom flask with a side arm. After vacuum-drying 
in an oil bath at 120.degree. C. for 3 h, N.sub.2 was introduced therein. 
100 ml of toluene which had been preliminarily distilled in the presence 
of CaH.sub.2 was added to the silica beads. 3 ml of 
diphenyldimethoxysilane (KBM 202; a product of Shin'etsu Kagaku Co., Ltd.) 
was added to the mixture and they were stirred together and then reacted 
at 120.degree. C for 1 h. After distilling off 3 to 5 ml of toluene, the 
reaction was carried out at 120.degree. C. for 2 h. The mixture was 
filtered through a glass filter, washed with 50 ml of toluene three times 
and then with 50 ml of methnol three times and dried in vacuum at 
40.degree. C. for 1 h. 
About 10 g of the silica beads were placed in the 200 ml round-bottom flask 
with a side arm. After vacuum drying at 100.degree. C. for 3 h, the 
pressure was returned to the atmospheric pressure and the mixture was 
cooled to room temperature. Then N.sub.2 was introduced therein. 100 ml of 
distilled toluene was added to the dried silica beads. 1 ml of 
N,O-bis(trimethylsilyl)acetamide (a trimethylsilylating agent) was added 
thereto and the mixture was stirred to effect the reaction at 115.degree. 
C. for 3 h. The reaction mixture was collected with a glass filter, washed 
with toluene and dried under vacuum for about 4 h. 
SYNTHESIS EXAMPLE 2 
10 g of silica beads (LiChrospher SI 1000; a product of Merck & Co.) was 
placed in a 200 ml round-bottom flask with a side arm. After vacuum-drying 
in an oil bath at 120.degree. C. for 3 h, N.sub.2 was introduced therein. 
100 ml of toluene which had been priliminarily distilled in the presence 
of CaH.sub.2 was added to the silica beads. 3 ml of 
diohenyldimethoxysilane (KBM 202; a product of Shin'etsu Kagaku Co., Ltd.) 
was added to the mixture and they were stirred together and then reacted 
at 120.degree. C. for 1 h. After distilling off 3 to 5 ml of toluene, the 
reaction was carried out at 120.degree. C. for 2 h. The mixture was 
filtered through a glaass filter, washed with 50 ml of toluene three times 
aand then with 50 ml of methanol three times and dried in vacuum at 
40.degree. C. for 1 h. 
About 10 g of the silica beads were placed in the 200 ml round-bottom flask 
with a side arm. After vacuum drying at 100.degree. C. for 3 h, the 
pressure was returned to the atmospheric pressure and the mixture was 
cooled to room temperature. Then N.sub.2 was introduced therein. 100 ml of 
distilled toluene was added to the dried silicaa beads. 1 ml of 
N,O-bis(trimethylsilyl)acetamide (a trimethylsilylating agent) was added 
thereto and the mixture was stirred to effect the reaaction at 115.degree. 
C. for 3 h. The reaction mixture was filtered through a glass filter, 
washed with toluene and dried under vacuum for about 4 h. 
SYNTHESIS EXAMPLE 3 (Synthesis of .beta.-1,4-mannan Tribenzoate) 
Albumens of seeds of ivory palm were treated by a process disclosed in 
literature [see G. O. Aspinall et al., "J. Chem. Soc.", 3184 (1953)] to 
obtain mannan B from a high molecular weight fraction. 1.5 g of powder of 
mannan B was mixed with 70 ml of dehydrated pyridine, 7.7 ml of dehydrated 
triethylamine and 50 mg of 4-dimethylaminopyridine. 10.7 ml of benzoyl 
chloride was added thereto under stirring. The reaction was carried out at 
100.degree. C. for 5 h. After cooling, the product was added to 400 ml of 
ethanol under stirring to form a precipitate, which was filtered through a 
glass filter and washed thoroughly with ethanol. After vacuum drying, the 
product was dissolved in 30 ml of methylene chloride and the insoluble 
matter was removed. The product was reprecipitated from 400 ml of ethanol. 
The precipitate was collected by filtration, washed with ethanol, 
dehydrated and dried. 
The product was dissolved in methylene chloride. The solution was applied 
to a common salt tablet and dried. The infrared absorption spectrum of the 
product had the following characteristics absorption bands: 
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3070 cm.sup.-1 : stretching vibration of 
aromatic C--H, 
1730 cm.sup.-1 : stretching vibration of 
C.dbd.O of carboxylic acid 
ester, 
1605, 1495, 1455 cm.sup.-1 : 
skeletal vibration due 
to stretching of carbon 
and carbon in the benzene 
ring, 
1270 cm.sup.-1 : stretching vibration of 
C--O of ester, 
1030 to 1200 cm.sup.-1 : 
stretching vibration of 
C--O--C of mannan, and 
690 to 900 cm.sup.-1 : 
out-of-plane deformation 
vibration of benzene ring. 
______________________________________ 
Substantially no absorption at around 3450 cm.sup.-1 due to OH of mannan 
was observed. This fact suggested that the product substantially comprised 
a trisubstituted compound. In the proton NMR spectrum determined in 
CDCl.sub.3, the characteristic absorptions were as follows: 
6.8 to 8.4 ppm: proton of benzene ring, 
2.8 to 6.0 ppm: protons of mannan ring and methylene in position 6. 
The ratio of these absorption intensities was 15:7. 
SYNTHESIS EXAMPLE 4 (Synthesis of Tribenzoyl-.beta.-1,4-chitosan) 
10 g of purified chitosan was dissolved in 1000 ml of water containing 40 
ml of conc. hydrochloric acid. The solution was kept at 73.degree. C. for 
5 h. The solution was concentrated by means of a rotary evaporator and 
then neutralized with 27 ml of aqueous ammonia (28%) to precipitate 
chitosan. The precipitate was collected by filtration, washed with water, 
ethanol and then ether each twice and dried in vacuo. Yield: 9.71 g. 
1.0 g of obtained chitosan was dissolved in 30 ml of water containing 0.5 
ml of conc. hydrochloric acid. The solution was freeze-dried. 30 ml of 
pyridine, 0.05 g of 4-dimethylaminopyridine, 8 ml of triethylamine and 10 
ml of benzoyl chloride were added to the residue and the mixture was kept 
at 100.degree. to 105.degree. C. under stirring for 7 h. The resulting 
suspension was added to ethanol to form a precipitate, which was filtered, 
washed with ether and then with dichloromethane and dried in vacuo. Yield: 
3.0 g. In the I.R. spectrum, two carbonyl stretching vibrations were 
observed at 1720 and 1660 cm.sup.-1. this fact suggested that the product 
was tribenzoylchitosan. 
EXAMPLE 1 
1.2 g of .beta.-1,4-mannan tribenzoate obtained in Synthesis Example 3 was 
dissolved in a mixture of 12.5 g of dischloromethane and 3.5 ml of 
acetone. 6.4 g of the silica gel particles obtained in Synthesis Example 2 
were impregnated with the solution. the solvent was distilled off under 
reduced pressure to obtain a powdery, supported material. 
EXAMPLE 2 
1.2 g of tribenzoylchitosan obtained in Synthesis Example 4 was dissolved 
in a mixture of 5 ml of dichloromethane and 4.5 of dichloroacetic acid. 
The solution was filtered. 3.2 g of the silica gel obtained in Synthesis 
Example 1 was impregnated with 7.5 ml of the solution. The vessel was 
heated with hot water under reduced pressure realized by means of a vacuum 
pump to remove the solvent. A powdery, supported material was thus 
obtained. 
APPLICATION EXAMPLE 1 
The silica beads carrying mannan tribenzoate obtained in Example 1 were 
packed in a stainless steel column having a length of 25 cm and an inner 
diameter of 0.46 cm by slurry process. The high performance liquid 
chromatograph used was TRIROTAR-SR (a product of Japan Spectroscopic Co., 
Ltd.) and the detector was UVIDEC-V. The results of the resolution of 
2-phenylcyclohexanone are shown in Table 1. 
TABLE 1 
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capacity 
Resolution 
Rate of 
ratio factor separation 
Flow rate 
Racemates 
k.sub.1 ' 
k.sub.2 ' 
.alpha. Rs ml/min 
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##STR1## 
3.80 4.02 1.06 0.5 0.5 
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Solvent: hexane/2propanol (9:1) 
APPLICATION EXAMPLE 2 
The silica beads carrying tribenzoylchitosan obtained in Example 2 were 
suspended in methanol. The suspension was packed in a stainless steel 
column having a length of 25 cm and an inner diameter of 0.46 cm by slurry 
process. The high performance liquid chromatograph used was TRIROTAR-SR (a 
product of Japan Spectroscopic Co., Ltd.) and the polarimeter was DIP-181 
(a product of Japan Spectroscopic Co., Ltd.). The results of the 
resolution of racemic compounds are shown in Table 2. 
In the determination effected by using the polarimeter as the detector of 
the high performance chromatograph, the terms were defined as follows: 
##EQU2## 
TABLE 2 
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Flow rate 
racemates l.sub.1 ' 
l.sub.2 ' 
.beta. 
(ml/min) 
______________________________________ 
1.56 1.88 1.21 1.0 
______________________________________ 
Solvent: hexane/2propanol (9:1) 
SYNTHESIS EXAMPLE 5 (Synthesis of .beta.-1,4-xylan benzoate) 
5.0 g of xylan (a product of Tokyo Kasei Co.) was dispsersed in 10 ml of 
water. A 30% aqueous sodium hydroxide solution was added to the dispersion 
under cooling with ice until xylan had been dissolved to form a 
transparent solution. The solution was added to 150 ml of methanol 
containing 3 ml of acetic acid to form a precipitate, which was filtered 
and washed with methanol. About a half of the precipitate was suspended in 
a mixture of 40 ml of benzene and 40 ml of pyridine. Benzene was distilled 
off from the reaction system through a 20 cm column. 20 ml of benzoyl 
chloride was added thereto and the mixture was kept at 90.degree. C. for 
10 h. The mixture was cooled and then added to 500 ml of ethanol to form a 
precipitate, which was filtered, washed and dried. The product was 
dissolved in dichloromethane. An insoluble matter was removed by 
filtration. Dichloromethane was distilled off under reduced pressure to 
obtain xylan dibenzoate. In the I.R. absorption spectrum of this product, 
the absorption due to the stretching vibration of OH was weak. 
EXAMPLE 3 
1.2 g of .beta.-1,4-xylan dibenzoate obtained in Synthesis Example 5 was 
dissolved in 7.5 ml of dichloromethane. The solution was filtered through 
a glass filter (G2) and the filtrate was mixed with 3.4 g of the silica 
beads obtained in Synthesis Example 2. The solvent was distilled off under 
reduced pressure to obtain a powdery, supported material. 
APPLICATION EXAMPLE 3 
The results of the optical resolution of racemic compounds conducted with 
the supported material obtained in Example 3 under the same conditions as 
in Application Example 1 are shown in Table 3. 
TABLE 3 
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capacity ratio 
Resolution factor 
racemates k.sub.1 ' 
k.sub.2 ' 
.alpha. 
______________________________________ 
##STR2## 1.75(+) 2.04(-) 1.17 
##STR3## 4.91(-) 5.74(+) 1.17 
______________________________________ 
Eluent: hexane/2propanol (9:1) 
Flow rate: 0.5 ml/min 
SYNTHESIS EXAMPLE 6 
20 g of purified chitosan (a product of Kyowa Kasei Co.) was dispersed in 1 
ml of water. 40 ml of conc. hydrochloric acid was added slowly to the 
dispersion to dissolve chitosan. The resulting solution was kept at 
80.degree. C. for 5 h and then cooled. The solids suspended therein was 
filtered out. The filtrate was concentrated to a volume of 200 ml means of 
a rotary evaporator. The liquid was made alkaline with excess aqueous 
ammonia. Chitosan having a reduced molecular weight was thus precipitated. 
After collection, the product was washed with water and then ethanol and 
dried. 1.0 g of the resulting chitosan was dispersed in 10 ml of water. 
Hydrochloric acid was added in portions to the dispersion until a solution 
was obtained. The solution was added to 60 ml of methanol containing 3 ml 
of aqueous ammonia (28%) to precipitate chitosan. After filtration, the 
product was washed with methanol twice and then with ether twice. Chitosan 
containing the solvent was added to 60 ml of pyridine. A part (about 30 
ml) of pyridine was distilled off. 10 ml of benzoyl chloride was added 
dropwise to the obtained chitosan-containing pyridine and the mixture was 
kept at 80.degree. C. to 90.degree. C. for 8 h. A suspension thus formed 
was added to cooled methanol to form a precipitate. After filtration, the 
product was washed with methanol, acetone and dichloromethane and then 
dried. 
EXAMPLE 4 
1.05 g of tribenzoylchitosan obtained in Synthesis Example 6 was dissolved 
in a mixture of 4.0 ml of dichloromethane, 3.0 ml of trifluoroacetic acid 
and 0.5 ml of benzoyl chloride. The solution was mixed with 3.2 g of the 
silica beads obtained in Synthesis Example 2. The solvent was distilled 
off under reduced pressure to obtain a powdery, supported material. 
APPLICATION EXAMPLE 4 
The optical resolution of racemic compounds was conducted with the 
supported material obtained in Example 4 in the same manner as in 
Application Example 1. The results are shown in Table 4. It was noted that 
Troger's bases which could not be resolved with cellulose tribenzoate were 
resolved. 
TABLE 4 
__________________________________________________________________________ 
capacity ratio 
Resolution factor 
racemates k.sub.1 ' 
k.sub.2 ' 
.alpha. 
__________________________________________________________________________ 
##STR4## 1.71(-) 
1.85(+) 
1.08 
##STR5## 1.31(+) 
1.61(-) 
1.23 
##STR6## 3.93(-) 
4.28(+) 
1.09 
##STR7## 6.64 7.28 1.10 
##STR8## 14.6(+) 
15.9(-) 
1.09 
__________________________________________________________________________ 
Eluent: hexane/2propanol (9:1) 
Flow rate: 0.5 ml/min. 
SYNTHESIS EXAMPLE 7 (Synthesis of Mannan A Tribenzoate) 
Albumens of seeds of ivory palm were treated by a process disclosed in 
literature [see G. O. Aspinall et al., "J. Chem. Soc.", 3184 (1953)] to 
obtain mannan A from a low molecular weight fraction. 
1.5 g of mannan A was dipersed in a solution comprising 70 ml of pyridine, 
7.7 ml of triethylamine and 50 mg of 4-dimethylaminopyridine. 10.7 ml of 
benzoyl chloride was added to the dispersion and the reaction was carried 
out at 100.degree. C. for 5 h. After cooling, the reaction mixture was 
added to ethanol to form a precipitate, which was washed thoroughly with 
ethanol and dried. The dried sample was dissolved in methylene chloride. 
The solution was filtered through a glass filter (G3). The filtrate was 
added to ethanol to form a precipitate, which was washed thoroughly with 
ethanol and dried. 
EXAMPLE 5 
1.2 g of mannan A tribenzoate obtained in Synthesis Example 7 was dissolved 
in 7.5 ml of dichloromethane. The solution was filtered through a glass 
filter (G-2). The filtrate was mixed thoroughly with 3.4 g of the silica 
beads obtained in Synthesis Example 2. The solvent was distilled off under 
reduced pressure to obtain a powdery, supported material. 
APPLICATION EXAMPLE 5 
The optical resolution of racemic compounds of 
.gamma.-phenyl-.gamma.butyrolactone was conducted with the supported 
material obtained in Example 5in the same manner as in Application Example 
1. The resolution factor (.alpha.) was 1.22 [(+) compound being eluted 
first]. The flow rate was 0.5 ml/min. 
SYNTHESIS EXAMPLE 8 (Synthesis of dextran tribenzoate) 
3.0 g of dextran (a product of Nakai Kagaku Yakuhin Co. having a molecular 
weight of 50,000 to 70,000) was dissolved in 10 ml of water. Pyridine was 
added to the solution to precipitate dextran. Pyridine was removed by 
decantation. Additional 20 ml of pyridine was added and then removed by 
the decantation. The addition and decantation of pyridine were repeated 
three times. Then, 30 ml of pyridine and 20 ml of benzoyl chloride were 
added thereto and the mixture was kept at 70.degree. C. for 10 h. After 
cooling, pyridinium chloride and unreacted dextran were removed by means 
of a glass filter (G-2). The filtrate was concentrated under reduced 
pressure. Methanol was added thereto to precipitate dextran tribenzoate, 
which was filtered, washed with methanol and dried. In the I.R. absorption 
spectrum of the product, the absorption due to stretching vibration of OH 
was weak. This fact suggested that the product was a trisubstituted 
compound. 
EXAMPLE 6 
1.2 g of dextran tribenzoate obtained in Synthesis Example 8 was dissolved 
in 7.5 ml of dichloromethane. The solution was mixed thoroughly with 3.6 g 
of the silica gel obtained in Synthesis Example 2. The solvent was 
distilled off under reduced pressure to obtain a powdery, supported 
material. 
APPLICATION EXAMPLE 6 
The optical resolution of trans-stilbene oxide was conducted with the 
supported material obtained in Example 6 in the same manner as in 
Application Example 1. The resolution factor was 1.18. The enantiomer 
having (-) optical rotation was eluted first. The eluent was 
hexane-2-propanol (9:1). The flow rate was 0.5 ml/min.