Novel benzothiazole and antirheumatic agent comprising it as an active ingredient

A benzothiazole of the following formula ##STR1## in which R represents a methyl, methoxy, carboxyl or methoxycarbonyl group. The compound is useful for treating rheumatic arthritis.

This invention relates to a novel benzothiazole and an antirheumatic agent 
comprising it as an active ingredient. 
More specifically, it relates to a benzothiazole represented by the 
following formula 
##STR2## 
in which R represents a methyl, methoxy, carboxyl or methoxycarbonyl 
group, and an antirheumatic agent comprising it as an active ingredient. 
Rheumatoid arthritis (RA for short) is a systemic inflammatory disease 
characterized by destructive, deformative and non-suppurative articular 
changes that become chronic with time. It is thought that RA is closely 
related to hereditary or environmental factors and caused by chronic 
inflammation due to an immune disorder triggered by viral infection. 
Treatment of RA has previously been performed mainly by symptomatic 
therapy with non-steroidal anti-inflammatory agents. Recently a therapy 
close to casual therapy by which the immune disorder is suppressed by an 
immunomodulatory effect has attracted attention. An example of a drug 
belonging to this type is lobenzarit disodium 
[N-(2-carboxyphenyl)-4-chloroanthranilic acid disodium salt, see Progress 
in Drug Research, 24, 185-186, edited by Ernst Jucker, published by 
Birkhauser Verlag (1980)]. 
##STR3## 
J. Med. Chem., 1986, 29, 820-825 describes 
5-acetoxy-2-(4-methylphenyl)benzothiazole (compound A), 
6-acetoxy-2-(4-methylphenyl)benzothiazole (compound B) and 
7-acetoxy-2-(4-methylphenyl)benzothiazole (compound C) but does not 
describe their pharmacological activity. 
It is an object of this invention to provide a novel antirheumatic agent. 
Another object of this invention is to provide a novel antirheumatic agent 
of the type which serves as an RA treating agent with immunomodulatory 
effect. 
Still another object of this invention is to provide a novel benzothiazole 
used as an active ingredient in the antirheumatic agent of this invention, 
and an intermediate thereof. 
Further objects of the invention along with its advantages will become 
apparent from the following description. 
According to this invention, the objects and advantages of the invention 
are achieved firstly by a benzothiazole represented by the folllowing 
formula 
##STR4## 
in which R represents a methyl, methoxy, carboxyl or methoxycarbonyl 
group. 
The benzothiazole of formula (I) includes 
4-acetoxy-2-(4-methylphenyl)benzothiazole, 
4-acetoxy-2-(4-methoxyphenyl)benzothiazole, 
4-(4-acetoxybenzothiazol-2-yl)benzoic acid, and 
methyl 4-(4-acetoxybenzothiazol-2-yl)benzoate. 
The benzothiazole of formula (I) of this invention can be produced by 
reacting a compound of the following formula 
##STR5## 
in which R is as defined, with an acetylating agent such as acetic 
anhydride or acetyl chloride in a customary manner. 
Specifically, the compound (I) can be produced by reacting the compound 
(II) with the acetylating agent in an amount of 1.0 equivalent or more per 
equivalent of the compound (II) in the absence of solvent or in an inert 
organic solvent such as pyridine or dichloromethane, as required in the 
presence of a base such as pyridine or 4-dimethylaminopyridine, at a 
temperature from room temperature to a temperature under refluxing 
conditions for 1 to 3 hours. 
The compound (II) used as the starting material in the above method is a 
novel compound which can be produced, for example by the following scheme. 
##STR6## 
In the above scheme, R' represents a methyl, methoxy or methoxycarbonyl, 
and R is as defined. 
Specifically, the compound (III) is reacted with thionyl chloride in the 
presence of a catalytic amount of N,N-dimethylformamide (DMF) to form the 
acid chloride, and it is then reacted with o-anisidine to obtain the 
compound (IV). Subsequently, the action of a Lawesson's reagent 
[2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide] on 
the compound (IV) yields the compound (V) which is then reacted with 
potassium ferricyanide in the presence of potassium hydroxide to give the 
compound (VI). Action of boron tribromide on the compound (VI) gives the 
compound (II). 
When R in formula (II) is a methyl group, it is preferred to use aluminum 
iodide in the presence of a catalytic amount of tetra-n-butylammonium 
iodide in the above final step instead of using boron tribromide. When R 
in formula (II) is a carboxyl group, it is preferred to use hydrobromic 
acid (47%) in the above final step (see Examples given hereinbelow). 
The benzothiazole of this invention strongly suppresses the development of 
rat adjuvant arthritis, which is an animal model of RA, on the basis of 
their immunomodulatory effect, and yet has low toxicity. Accordingly, the 
benzothiazole of this invention is useful as an antirheumatic agent. 
For use in the treatment of RA, the benzothiazole of this invention is 
usually applied as an orally administrable agent. 
Oral dosage forms include, for example, solid formulations such as tablets, 
granules, powders and capsules, and liquid formulations such as syrups. 
The solid formulations are prepared by using ordinary drug additives such 
as lactose, corn starch, crystalline cellulose, carboxymethyl cellulose 
calcium, hydroxypropyl cellulose and magnesium stearate. The capsules may 
be obtained by filling the granules or powders so prepared in suitable 
capsules. The syrups may be obtained by dissolving or suspending the 
compound of this invention in an aqueous solution containing sugar, ethyl 
p-hydroxybenzoate or propyl p-hydroxybenzoate, for example. 
The dosage of the compound of this invention can be varied according to the 
condition, age, etc. of the patient, but is usually 0.1 to 15.0 mg/kg per 
day for adults. This dosage is administered once or in two or three 
divided portions a day. 
The pharmacological activity of the compounds of this invention will be 
described. 
The compound of this invention showed clearly stronger suppressive effect 
on the development of rat adjuvant arthritis, an animal model of RA, than 
lobenzarit disodium and the compounds A, B and C mentioned above (see Test 
Example 1). 
From the following facts (i) and (ii), the suppressive effect of the 
compound of this invention on the development of adjuvant arthritis is 
considered to be based not on anti-inflammatory effect but on 
immunomodulatory effect. 
(i) The compound of this invention, like lobenzarit disodium, shows no 
effect on rat carrageenin-induced paw edema, a model of acute 
inflammation, and on rat mustard-induced paw edema, a model of subacute 
inflammation (in either case, no effect in a dose of 100 mg/kg). 
(ii) Effect on cellular immunity was studied using delayed-type 
hypersensitivity as an index. The compound of this invention, like 
lobenzarit disodium, suppresses an abnormally enhanced immune reaction, 
but shows no effect on a normal immune reaction (see Test Example 2). 
The compound of this invention showed lower toxicity than lobenzarit 
disodium (see Test Example 3). 
Hence, the benzothiazole of this invention strongly suppresses the 
development of adjuvant arthritis on the basis of their immunomodulatory 
effect and has low toxicity. Hence the benzothiazole of this invention is 
useful as an antirheumatic agent. 
TEST EXAMPLE 1 
Effect on the Development of Adjuvant Arthritis Test Compounds 
(1) The compounds of Examples 5 to 8 (invention) 
(2) Compounds A, B and C (comparison; described in the above-cited 
reference) 
(3) Lobenzarit disodium (comparison) 
Method 
Fischer male rats (8 weeks old; body weight 120-180 g) were grouped so that 
the average of body weights among the groups were nearly the same. Then, 
0.1 ml of complete adjuvant obtained by suspending Mycobacterium butyricum 
(Difco Laboratories) in paraffin oil in a concentration of 6 mg/ml was 
injected into the footpad of the right hind paw to induce adjuvant 
arthritis. 
Each of the test compounds was dissolved or suspended in a 1% gum arabic 
solution, and administered orally once a day on six days a week over a 
period of three weeks starting from the day of the adjuvant injection. The 
group administered with a 1% gum arabic solution instead of the test 
compound was served for a control. The volumes of both hind paws were 
measured plethysmographically by displacement of water at various times 
after injection of the adjuvant, and the percent paw edema inhibition was 
calculated from the following equation. 
##EQU1## 
E.sub.exp : the percent paw edema in rats treated with the test compound 
E.sub.cont : the mean of percent paw edema in rats of the control group 
The percent paw edema was calculated from the following equation. 
##EQU2## 
V.sub.post : the paw volume after treatment with the adjuvant V.sub.pre : 
the paw volume before treatment with the adjuvant 
Results 
Table 1 shows percent paw edema inhibitions by the compounds calculated 21 
days after injection of the adjuvant. 
TABLE 1 
______________________________________ 
Paw edema inhibition 
Test Dose (%, mean .+-. standard error) 
compound (mg/kg) N Treated paw 
Non-treated paw 
______________________________________ 
Example 
5 100 24 31.8 .+-. 3.9 
32.0 .+-. 7.7 
6 100 24 24.7 .+-. 3.7 
27.4 .+-. 10.8 
7 100 24 29.9 .+-. 2.9 
38.5 .+-. 6.0 
8 100 24 29.3 .+-. 3.6 
28.6 .+-. 8.8 
Com- A 100 16 12.9 .+-. 4.4 
4.5 .+-. 11.7 
pound B 100 8 -7.6 .+-. 8.8 
4.4 .+-. 14.2 
C 100 24 16.6 .+-. 4.1 
8.9 .+-. 10.4 
Lobenzarit 
50 16 6.3 .+-. 5.3 
-9.0 .+-. 12.0 
disodium 100 12* 15.1 .+-. 6.6 
-1.7 .+-. 11.4 
______________________________________ 
*Four animals out of 16 could not be included in the data because of deat 
during the test. 
Table 1 showed that the compound of this invention had a clear inhibitory 
effect on edema of the rat hind paws treated or non-treated with the 
adjuvant, and this effect was evidently stronger than those of lobenzarit 
disodium and the compounds A, B and C. 
TEST EXAMPLE 2 
Effect on Delayed-Type Hypersensitivity (DTH) 
(A) Effect on a normal immune reaction 
Test Compounds 
(1) the compound of Example 5 (invention) 
(2) Lobenzarit disodium (comparison) 
Method 
BALB/c male mice (8 weeks old) were sensitized by injection into the tail 
vein with 0.2 ml of 5.times.10.sup.6 /ml sheep red blood cells (SRBC). 
Three days after the sensitization, 0.05 ml of 8.times.10.sup.9 /ml SRBC 
was injected into the footpad of the right hind paw for elicitation of 
DTH. Footpad thickness was measured immediately before and 24 hours after 
the elicitation with a dial thickness gauge. The level of DTH was 
expressed as footpad swelling (mm) at 24 hour. The inhibition (%) of 
footpad swelling was calculated from the following equation. 
The test compound was dissolved or suspended in a 1% gum arabic solution, 
and administered orally once a day over a period of 7 days starting from 
four days before the sensitization. To a control group, a 1% gum arabic 
solution was administered instead of the test compound. 
##EQU3## 
T.sub.exp : the mean of the footpad swelling in mice treated with the test 
compound 
T.sub.cont : the mean of the footpad swelling in mice of the control group 
Results 
The results are shown in Table 2. 
TABLE 2 
______________________________________ 
Footpad swelling (.times. 10.sup.-2 mm, 
mean .+-. standard error) 
[Footpad swelling 
inhibition, %] 
Dose Compound of Lobenzarit 
(mg/kg) N Example 5 disodium 
______________________________________ 
1 7 59 .+-. 5 [0.0] 
67 .+-. 2 [4.3] 
3 7 63 .+-. 6 [-6.8] 
64 .+-. 5 [8.6] 
10 7 57 .+-. 6 [3.4] 
76 .+-. 6 [-8.6] 
30 7 64 .+-. 6 [-8.5] 
65 .+-. 4 [7.1] 
100 7 53 .+-. 4 [10.2] 
65 .+-. 5 [7.1] 
-- 7 59 .+-. 6 [--] 
70 .+-. 2 [--] 
______________________________________ 
Table 2 showed that the compound of this invention, like lobenzarit 
disodium,did not inhibit footpad swelling at any doses, and consequently 
did not affect DTH in a normal immune reaction. 
(B) Effect on an enhanced immune reaction 
Test compounds 
Same as in (A) above. 
Method 
Cyclophosphamide (75 mg/kg) was administered intraperitoneally to BALB/c 
male mice (8 weeks old), and four days later, the mice were sensitized by 
injection into the tail vein with 0.2 ml of 5.times.10.sup.7 /ml SRBC. 
Three days after the sensitization, 0.05 ml of 8.times.10.sup.9 /ml SRBC 
was injected into the footpad of the right hind paw for elicitation of 
DTH. Twenty four hours later, footpad swelling (mm) was measured in the 
same way as in (A) above, and the inhibition (%) of footpad swelling was 
calculated from the following equation. 
The test compound was dissolved or suspended in a 1% gum arabic solution, 
and administered orally once a day over a period of 7 days starting from 
four days before the sensitization (immediately after administration of 
cyclophosphamide). To a control group, a 1% gum arabic solution was 
administered instead of the test compound. The group, administered with 
physiological saline instead of cyclophosphamide and a 1% gum arabic 
solution instead of test compound respectively, was served for a normal 
group. 
##EQU4## 
T.sub.cont : the mean of the footpad swelling in mice of the control group 
T.sub.exp : the mean of the footpad swelling in mice treated with the test 
compound 
T.sub.nor : the mean of the footpad swelling in mice of the normal group. 
Results 
The results are shown in Table 3. 
TABLE 3 
______________________________________ 
Footpad swelling (.times. 10.sup.-2 mm, 
mean .+-. standard error) 
Dose [Footpad swelling 
(mg/kg) inhibition, %] 
Cyclo- Test Compound of 
Lobenzarit 
phosphamide 
compound N Example 5 disodium 
______________________________________ 
75 1 7 37 .+-. 5* [57.1] 
47 .+-. 3 [20.0] 
75 3 7 35 .+-. 1** [66.7] 
43 .+-. 3 [40.0] 
75 10 7 31 .+-. 3** [85.7] 
53 .+-. 3 [-10.0] 
75 30 7 33 .+-. 2** [76.2] 
41 .+-. 3* [50.0] 
75 100 7 37 .+-. 4* [57.1] 
41 .+-. 3* [50.0] 
-- -- 7 28 .+-. 2*** [--] 
31 .+-. 2*** [--] 
75 -- 7 49 .+-. 3 [--] 
51 .+-. 4 [--] 
______________________________________ 
*P &lt; 0.05, significantly different from the control group (ttest). 
**P &lt; 0.01, significantly different from the control group (ttest). 
***P &lt; 0.001, significantly different from the control group (ttest). 
Table 3 showed that the compound of this invention at any doses inhibited 
footpad swelling significantly, and consequently inhibited DTH in an 
enhanced immune reaction. This effect was evidently stronger than that of 
lobenzarit disodium. 
TEST EXAMPLE 3 
Acute Toxicity 
Test Compounds 
(1) The Compounds of Examples 5 to 8 (invention) 
(2) Lobenzarit diodium (comparison) 
Method 
ddY male mice (body weight about 23 g) were fasted overnight, and the test 
compound dissolved or suspended in a 1% gum arabic solution administered 
orally. From the number of mice died within a week, the LD.sub.50 value 
was calculated by the probit method. 
Results 
The results are shown in Table 4. 
TABLE 4 
______________________________________ 
Test compound N LD.sub.50 (mg/kg) 
______________________________________ 
Example 5 5 &gt;3,000 
6 5 &gt;3,000 
7 5 2,020 
8 5 &gt;3,000 
Lobenzarit disodium 
5 593 
______________________________________ 
The dosage of the benzothiazole of this invention can alleviate, improve or 
resolve the symptoms of the patient with RA. 
The following Examples further illustrate the present invention 
specifically.

EXAMPLE 1 
4-Hydroxy-2-(4-methylphenyl)benzothiazole 
(1) 4-Methyl-2'-methoxybenzanilide 
A catalytic amount of DMF (ca. 0.5 ml) was added to a mixture of 33.0 g of 
p-methylbenzoic acid and 80 ml of thionyl chloride, and the mixture was 
refluxed for 3 hours. After the reaction, the reaction mixture was dried 
under reduced pressure. The residue was dissolved in 40 ml of 
tetrahydrofuran, and added dropwise to a solution of 29.8 g of o-anisidine 
in 190 ml of pyridine at 5.degree. to 10.degree. C. After stirring the 
mixture at room temperature for 1 hour, it was poured into 2.5 liters of 
water. The precipitated crystals were collected by filtration, washed with 
water and dried. Recrystallization from cyclohexane gave 50.5 g of 
4-methyl-2'-methoxybenzanilide. mp 72.5.degree.-74.5.degree. C. 
(2) 4-Methyl-2'-methoxybenzothioanilide 
The 4-methyl-2'-methoxybenzanilide (50.0 g) obtained in (1) was dissolved 
in 200 ml of toluene, and 46.1 g of Lawesson's reagent was added. The 
mixture was refluxed for 1 hour. After the reaction, the reaction mixture 
was cooled to about 50.degree. C., and 200 ml of water was added. The 
mixture was further refluxed for 2 hours. The organic layer was separated, 
washed with water and dried over anhydrous magnesium sulfate. The solvent 
was evapoated under reduced pressure. The residue was recrystallized from 
methanol and then cyclohexane to give 31.9 g of 
4-methyl-2'-methoxybenzothioanilide. mp 91.0.degree.-93.0.degree. C. 
(3) 2-(4-Methylphenyl)-4-methoxybenzothiazole 
Potassium hydroxide (21.8 g) and 64.0 g of potassium ferricyanide were 
dissolved in 2.5 liters of water, and with stirring, 25.0 g of 
4-methyl-2'-methoxybenzothioanilide obtained in (2) was added, and the 
mixture was stirred at room temperature for 6 hours. After the reaction, 
the crystals were collected by filtration, washed with water and dried. 
Recrystallization from cyclohexane gave 13.9 g of 
2-(4-methylphenyl)-4-methoxybenzothiazole. mp 98.0.degree.-100.0.degree. 
C. 
(4) 4-Hydroxy-2-(4-methylphenyl)benzothiazole 
Aluminum powder (1.4 g) and 10.9 g of iodine were added to 50 ml of 
benzene. The mixture was refluxed in a stream of nitrogen until the color 
of iodine disappeared. A solution of 11.4 g of 
2-(4-methylphenyl)-4-methoxybenzothiazole obtained in (3) and 31 mg of 
tetra-n-butylammonium iodide in 100 ml of benzene was added dropwise. The 
mixture was refluxed for 7 hours, and then poured into 200 ml of water, 
extracted with ethyl acetate three times, and dried over anhydrous 
magnesium sulfate. The solvent was evaporated under reduced pressure. The 
residue was washed with a small amount of chloroform, and recrystallized 
from acetonitrile to give 7.8 g of 
4-hydroxy-2-(4-methylphenyl)benzothiazole. mp 163.5.degree.-165.5.degree. 
C. 
EXAMPLE 2 
4-Hydroxy-2-(4-methoxyphenyl)benzothiazole 
(1) 4-Methoxy-2'-methoxybenzothioanilide 
4-Methoxy-2'-methoxybenzanilide (29.5 g) [Bull. Soc. Chim. France, 1964, 
(5), 924-935] was dissolved in 150 ml of toluene, and 25.6 g of Lawesson's 
reagent was added. The mixture was refluxed for 4.5 hours. After the 
reaction, the solvent was evaporated under reduced pressure. The residue 
was subjected to silica gel column chromatography [eluted with 
cyclohexane/ethyl acetate (7/1, v/v)] to give 26.5 g of 
4-methoxy-2'-methoxybenzothioanilide. 
A portion of this product was recrystallized from cyclohexane to give a 
product having a melting point of 84.5.degree. to 86.5.degree. C. 
(2) 4-Methoxy-2-(4-methoxyphenyl)benzothiazole 
Potassium hydroxide (20.8 g) and 61.2 g of potassium ferricyanide were 
dissolved in 2.4 liters of water, and with stirring, 25.4 g of 
4-methoxy-2'-methoxybenzothioanilide obtained in (1) was added. The 
mixture was stirred at room temperature for 10 hours. After the reaction, 
the crystals were collected by filtration, washed with water and dried. 
The crystals were subjected to silica gel column chromatography [eluted 
with cyclohexane/ethyl acetate (7/1, v/v)]. Recrystallization from 
cyclohexane gave 12.0 g of 4-methoxy-2-(4-methoxyphenyl)benzothiazole. mp 
86.0.degree.-88.0.degree. C. 
(3) 4-Hydroxy-2-(4-methoxyphenyl)benzothiazole 
The 4-methoxy-2-(4-methoxyphenyl)benzothiazole (9.0 g) obtained in (2) was 
dissolved in 15 ml of dichloromethane, and a solution of 8.7 g of boron 
tribromide in 15 ml of dichloromethane was added dropwise to the solution. 
The mixture was stirred at room temperature for 2 hours, and then poured 
into 200 ml of ice water, followed by extraction with chloroform three 
times. The extract was dried over anhydrous magnesium sulfate, and the 
solvent was evaporated under reduced pressure. The residue was subjected 
to silica gel column chromatography (eluted with chloroform) to give 4.2 g 
of 4-hydroxy-2-(4-methoxyphenyl)benzothiazole. 
A portion of this product was recrystallized from cyclohexane and ethyl 
acetate to give a product having a melting point of 128.0.degree. to 
130.0.degree. C. 
EXAMPLE 3 
4-(4-Hydroxybenzothiazol-2-yl)benzoic acid 
(1) 4-Methoxycarbonyl-2'-methoxybenzanilide 
A catalytic amount of DMF (ca. 0.5 ml) was added to a mixture of 102.4 g of 
p-methoxycarbonylbenzoic acid and 160 ml of thionyl chloride, and the 
mixture was refluxed for 1.5 hours. After the reaction, the reaction 
mixture was dried under reduced pressure. The residue was dissolved in 90 
ml of tetrahydrofuran, and the solution was added dropwise at 
5.degree.-10.degree. C. to a solution of 70.0 g of o-anisidine in 440 ml 
of pyridine. The mixture was stirred at room temperature for 2 hours, and 
then poured into 4 liters of water. The crystals that precipitated were 
collected by filtration, washed with water and dried to give 160.8 g of 
4-methoxycarbonyl-2'-methoxybenzanilide. 
A portion of the product was recrystallized from cyclohexane and ethyl 
acetate to give a product having a melting point of 119.0.degree. to 
121.0.degree. C. 
(2) 4-Methoxycarbonyl-2'-methoxybenzothioanilide 
The 4-methoxycarbonyl-2'-methoxybenzanilide (123.2 g) obtained in (1) was 
dissolved in 400 ml of toluene, and 96.1 g of Lawesson's reagent was 
added. The mixture was refluxed for 2 hours. After the reaction, the 
reaction mixture was hot-filtered. The filtrate was left to stand until it 
cooled to room temperature. The precipitated crystals were collected by 
filtration and washed with a small amount of benzene to give 69.2 g of 
4-methoxycarbonyl-2'-methoxybenzothioanilide. 
A portion of this product was recrystallized from cyclohexane and ethyl 
acetate to give a product having a melting point of 105.0.degree. to 
107.0.degree. C. 
(3) 4-(4-Methoxybenzothiazol-2-yl)benzoic acid and methyl 
4-(4-methoxybenzothiazol-2-yl)benzoate 
Potassium hydroxide (52.2 g) and 230.0 g of potassium ferricyanide were 
dissolved in 3 liters of water, and with stirring, 70.0 g of 
4-methoxycarbonyl-2'-methoxybenzothioanilide obtained in (2) was added. 
The mixture was stirred at room temperature for 3.5 hours. After the 
reaction, the crystals were collected by filtration, washed with water, 
dried and subjected to silica gel column chromatography [eluted with 
benzene/ethyl acetate (97/3, v/v)]. Recrystallization from cyclohexane 
gave 13.1 g of methyl 4-(4-methoxybenzothiazol-2-yl)benzoate. mp 
165.0.degree.-167.0.degree. C. 
The filtrate from which the crystals were collected by filtration after the 
reaction was acidified with concentrated hydrochloric acid. The 
precipitated crystals were collected by filtration, washed with water and 
dried to give 31.0 g of 4-(4-methoxybenzothiazol-2-yl)benzoic acid. 
A portion of the product was recrystallized from dioxane to give a product 
having a melting point of 289.0.degree. to 291.0.degree. C. 
(4) The 4-(4-hydroxybenzothiazol-2-yl)benzoic acid 
4-(4-Methoxybenzothiazol-2-yl)benzoic acid (7.8 g) obtained in (3) was 
added to 180 ml of hydrobromic acid (47%), and the mixture was refluxed 
for 27 hours. After the reaction, the mixture was poured into 180 ml of 
water. The crystals were collected by filtration, washed with water, 
dried, and then further washed with chloroform. Recrystallization from 
dioxane gave 7.0 g of 4-(4-hydroxybenzothiazol-2-yl)benzoic acid. 
A portion of the product was subjected to silica gel column chromatography 
[eluted with chloroform/methanol (98/2, v/v)], and recrystallized from 
isopropanol and then from dioxane to give a product having a melting point 
of 290.0.degree. to 302.0.degree. C. (decomp.). 
EXAMPLE 4 
Methyl 4-(4-hydroxybenzothiazol-2-yl)benzoate 
The methyl 4-(4-methoxybenzothiazol-2-yl)benzoate (11.3 g) obtained in 
Example 3 (3) was dissolved in 200 ml of dichloromethane, and a solution 
of 9.5 g of boron tribromide in 80 ml of dichloromethane was added 
dropwise to the solution. The mixture was stirred at room temperature for 
2.5 hours, then poured into 300 ml of ice water, extracted with chloroform 
three times, and dried over anhydrous magnesium sulfate. The solvent was 
evaporated under reduced pressure. The residue was subjected to silica gel 
column chromatography (eluted with chloroform), and the solvent was 
evaporated under reduced pressure. The residue was washed with a small 
amount of chloroform, and recrystallized from ethyl acetate to give 3.6 g 
of methyl 4-(4-hydroxybenzothiazol-2-yl)benzoate. mp 
215.degree.-219.0.degree. C. 
EXAMPLE 5 
4-Acetoxy-2-(4-methylphenyl)benzothiazole 
The 4-hydroxy-2-(4-methylphenyl)benzothiazole (5.8 g) obtained in Example 1 
was added to 58 ml of acetic anhydride and refluxed for 3 hours. After the 
reaction, the reaction mixture was dried under reduced pressure. The 
residue was washed with a small amount of cyclohexane, and recrystallized 
from cyclohexane to give 4.8 g of 
4-acetoxy-2-(4-methylphenyl)benzothiazole. 
mp 110.0.degree.-113.0.degree. C. 
NMR (CDCl.sub.3, .delta. ppm): 2.42(3H, s), 2.48(3H, s), 7.20(1H, dd), 
7.28(2H, d), 7.36(1H, dd), 7.76(1H, dd), 7.96(2H, d). 
Elemental analysis value (for C.sub.16 H.sub.13 NO.sub.2 S) Calculated (%) 
C, 67.82; H, 4.62; N, 4.94. Found (%) C, 68.11; H, 4.58; N, 5.07. 
EXAMPLE 6 
4-Acetoxy-2-(4-methoxyphenyl)benzothiazole 
The 4-hydroxy-2-(4-methoxyphenyl)benzothiazole (4.0 g) obtained in Example 
2 was added to 40 ml of acetic anhydride, and the mixture was refluxed for 
1 hour. After the reaction, the reaction mixture was dried under reduced 
pressure. The residue was washed with a small amount of cyclohexane, and 
recrystallized from cyclohexane and ethyl acetate to give 4.0 g of 
4-acetoxy-2-(4-methoxyphenyl)benzothiazole. 
mp 121.5.degree.-124.5.degree. C. 
NMR (CDCl.sub.3, .delta. ppm): 2.48(3H, s), 3.82(3H, s), 6.94(2H, d), 
7.16(1H, dd), 7.30(1H, dd), 7.70(1H, dd), 7.98(2H, d). 
Elemental analysis value (for C.sub.16 H.sub.13 NO.sub.3 S) Calculated (%) 
C, 64.20; H, 4.38; N, 4.68. Found (%) C, 64.29; H, 4.43; N, 4.59. 
EXAMPLE 7 
4-(4-Acetoxybenzothiazol-2-yl)benzoic acid 
The 4-(4-hydroxybenzothiazol-2-yl)benzoic acid (6.9 g) obtained in Example 
3 was dissolved in 15 ml of pyridine, and 2.6 g of acetic anhydride was 
added dropwise. The mixture was stirred at room temperature for 2 hours, 
and 160 ml of cyclohexane was added. The precipitated crystals were 
collected by filtration, washed with cyclohexane and then diethyl ether, 
and recrystallized from acetonitrile to give 4.0 g of 
4-(4-acetoxybenzothiazol-2-yl)benzoic acid. 
mp 229.0.degree.-233.0.degree. C. 
NMR (DMSO-d.sub.6, .delta. ppm): 2.48(3H, s), 7.38(1H, dd), 7.54(1H, dd), 
8.0-8.3(5H, m), 12.8-13.6(1H, bs). 
Elemental analysis value (for C.sub.16 H.sub.11 NO.sub.4 S) Calculated (%) 
C, 61.33; H, 3.54; N, 4.47. Found (%) C, 61.38; H, 3.41; N, 4.32. 
EXAMPLE 8 
Methyl 4-(4-acetoxybenzothiazol-2-yl)benzoate 
The methyl 4-(4-hydroxybenzothiazol-2-yl)benzoate (2.5 g) obtained in 
Example 4 was added to 30 ml of acetic anhydride, and the mixture was 
refluxed for 2 hours. After the reaction, the reaction mixture was dried 
under reduced pressure. The residue was washed with a small amount of 
cyclohexane, and recrystallized from cyclohexane and ethyl acetate to give 
2.3 g of methyl 4-(4-acetoxybenzothiazol-2-yl)benzoate. 
mp 143.5.degree.-145.5.degree. C. 
NMR (CDCl.sub.3, .delta. ppm): 2.50(3H, s), 3.94(3H, s), 7.20(1H, dd), 
7.38(1H, dd), 7.74(1H, dd), 8.0-8.2(4H, m). 
Elemental analysis value (for C.sub.17 H.sub.13 NO.sub.4 S) Calculated (%) 
C, 62.37; H, 4.00; N, 4.28. Found (%) C, 62.32; H, 3.98; N, 4.34. 
EXAMPLE 9 
Preparation of tablets: 
______________________________________ 
Recipe 
Ingredient Amount (g) 
______________________________________ 
4-Acetoxy-2-(4-methyl- 
500 
phenyl)benzothiazole 
(compound of Example 5) 
Lactose 700 
Crystalline cellulose 
400 
Carboxymethyl cellulose 
150 
calcium 
Hydroxypropyl cellulose 
30 
Magnesium stearate 20 
Total 1,800 
______________________________________ 
Procedure 
The compound of Example 5, lactose and crystalline cellulose were uniformly 
mixed. Hydroxypropyl cellulose was dissolved in 600 g of purified water, 
and the solution was added to the above mixture. They were kneaded, and 
the kneaded mixture was passed through a crusing-granulating machine (2 mm 
screen) and then dried for 20 minutes by a fluidized bed granulator 
(80.degree. C.). Crystalline cellulose, carboxymethyl cellulose calcium 
and magnesium stearate were added and mixed. The mixture was tableted to 
give tablets (180 mg tablets, diameter 8 mm) each containing 50 mg of the 
compound of Example 5. 
EXAMPLE 10 
Preparation of a powder: 
______________________________________ 
Recipe 
Ingredient Amount (g) 
______________________________________ 
4-Acetoxy-2-(4-methoxy- 
100 
phenyl)benzothiazole 
(compound of Example 6) 
Lactose 600 
Corn starch 290 
Magnesium stearate 10 
Total 1,000 
______________________________________ 
Procedure 
The above ingredients were fully mixed to form a uniform mixed powder to 
obtain a powder containing 100 mg of the compound of Example 6 as an 
active ingredient per gram. 
EXAMPLE 11 
Preparation of granules: 
______________________________________ 
Recipe 
Ingredient Amount (g) 
______________________________________ 
4-(4-Acetoxybenzothiazol-2- 
100 
yl)benzoic acid (compound 
of Example 7) 
Lactose 400 
Corn starch 280 
Crystalline cellulose 
200 
Hydroxypropyl cellulose 
20 
Total 1,000 
______________________________________ 
Procedure 
The compound of Example 7, lactose, corn starch and crystalline cellulose 
were uniformly mixed. A solution of hydroxypropyl cellulose in 400 g of 
purified water was added to the mixture, and they were kneaded. The 
kneaded mixture was passed through an extrusion granulator (0.8 mm 
screen), and dried in a fluidized bed granulator at 80.degree. C. for 20 
minutes. The granules wee sieved by a 14-mesh sieve to obtain granules 
containing 100 mg of the compound of Example 7 per gram. 
EXAMPLE 12 
Preparation of capsules agents: 
______________________________________ 
Recipe 
Ingredient Amount (g) 
______________________________________ 
Methyl 4-(4-Acetoxybenzothia- 
500 
zol-2-yl)benzoate 
(compound of Example 8) 
Lactose 970 
Crystalline cellulose 
600 
Corn starch 400 
Magnesium stearate 30 
Total 2,500 
______________________________________ 
Procedure 
The above ingredients were fully mixed, and filled in No. 3 hard capsules 
to prepare a capsular agent containing 50 mg of the compound of Example 8 
as an active ingrediet per capsule (250 mg).