IE41459B1 - Benzothiazolyl ureas and pharmaceutical compositions containing them - Google Patents

Abstract

The invention relates to novel N-2-(6-hydroxybenzothiazolyl)-Ν'-phenyl (or substituted-phenyl) ureas and a process for the preparation thereof. The ureas are useful as immune regulants. 5 The invention provides a compound of the formula z°\/\ S HO—yk/ V y Formula I wherein R is hydrogen, (C.j-C3) alkyl, (C^-C3) alkoxy or halo. 10 The invention also provides a process for preparing the compound of Formula I which comprises reacting a benzothiazole of the formula Γί>· AX Formula V with a substituted phenyl compound of the formula R —R 15 Formula VI wherein R is hydrogen, (C^-C^) alkyl, (C^-C^) alkoxy or halo; R1 and R2 are -N=C=0 or -NH2, R2 being -NH2 when R1 7 1 3 is -NCO and R being -NCO when R is -NH2; and R is ~SiCCH3)3 or R „ „ 0 V \ ” /O-NHC- and hydrolyzing the resulting compound. The invention further provides a pharmaceutical formulation containing a compound of Formula I associated with a pharmaceutically acceptable carrier therefor.

Description

The invention relates to novel N-2-(6-hydroxybenzothiazolyl)-Ν'-phenyl (or substituted-phenyl) ureas and a process for the preparation thereof. The ureas are useful as immune regulants.

The invention provides a compound of the formula z°\/\ S HO—yk/ V y Formula I wherein R is hydrogen, (C.j-C3) alkyl, (C^-C3) alkoxy or halo.

The invention also provides a process for preparing the compound of Formula I which comprises reacting a benzothiazole of the formula Γί>· AX Formula V with a substituted phenyl compound of the formula R Formula VI wherein R is hydrogen, (C^-C^) alkyl, (C^-C^) alkoxy or halo; R1 and R2 are -N=C=0 or -NH2, R2 being -NH2 when R1 1 3 is -NCO and R being -NCO when R is -NH2; and R is ~SiCCH3)3 or /O-NHC- and hydrolyzing the resulting compound.

The invention further provides a pharmaceutical formulation containing a compound of Formula I associated with a pharmaceutically acceptable carrier therefor. - 2 41459 In an embodiment of the invention a compound of Formula I in prepared by reacting 1 mole of 2-amino-6-hydroxybenzothiazole with from 1 to 2 moles of a phenyl isocyanate of the formula .·---NCO Formula II wherein R is hydrogen, (C^-CJ alkyl, (C1-C'3) alkoxy or halo; hydrolyzing any thus-obtained 6-carbamoyloxy compound of the formula R \ ·“=· \ // \ ·. .·—NH-CO-O—f « V-/ I I ,.=. R / X ;g-nh-co~nh-·. ,· Formula III wherein R lias the same meaning as hereinabove; with a base selected from alkali metal hydroxides, and carbonates, ammonium hydroxide and (C^ or C2) alkyl-substitutec1 ammonium hydroxides in an inert solvent at a temperature not higher than 100°C.

In another embodiment of the invention the compound of Formula I is prepared by reacting 2-amino6-hydroxybenzothiazole with phenylchloroformate to form a 2-phenylcarbamate, reacting the thus-formed carbamate with an excess of trimethylsilylchloride to synthesize a 6trimethylsilyloxy-2-benzothiazolylisocyanate and then treating said isocyanate with an aniline of the formula R NH -·. .· \ / •----· formula TV wherein R is hydrogen, halo, (C -cp alkyl or (Cj-Cj) alkoxy, and hydrolysing the resulting compound. 2-substituted benzimidazoles, benzothiazoles and benzoxazoles have recently been proposed for a variety of uses, mainly in the agricultural field. For example, 2-trifluoromethylbenzimidazoles are reported to be extremely active herbicides according to British Patent Specification No 1,097,561. The compounds therein disclosed are also reported to have molluscicidal, insecticidal and fungicidal properties. Other 2-substituted benzimidazoles have been found to be active coccidiostats. In particular, 2-(4thiazolyl) benzimidazole (thiabendazole) is presently being marketed as an anthelmintic. In addition, certain 2-hydroxybenzylbenzimidazoles have been revealed as having anti-viral properties (see U.S. patent 3,331,739). While the use of benzoxazoles and benzothiazoles in the above areas has not been quite as thoroughly explored as that of benzimidazoles, there is, nevertheless, considerable interest in compounds of this structure, particularly as coccidiostats.

Urea derivatives of the above classes of compounds are sparingly described in the art. N-(2-benzothiazolyl)N'-phenyl urea is described in Chem. Abs., 29, 2660; 55, 8389; 57, 801; the corresponding 4-methyl compound is described in Chem. Abs., 25, 104; 50 , 1776-1777; and the corresponding 5-methoxy derivative is described in Chem.

Abs., 52, 20673. N-(2-benzimidazolyl)-Ν'-phenyl urea is described in Beilstein, 24 (II), 62 and Chem. Abs., 15, 3077. In addition, U.S. Patent No. 3,299,085 discloses N(2-benzothiazolyl) or N-(2-benzoxazolyl)- N'-Cj-Cg aliphatic ureas as intermediates in the preparation of certain herbicides, and U.S. Patent No. 3,162,644 describes 2-benzoxazolyl ureas, useful as plant growth regulators and muscle -441459 relaxants. U.S. patents 3,399,212; 3,336,191; and 3,401,171 disclose benzimidazolyl ureas said to be anthelmintics.

Finally, South African Patent No. 68/4748 (Derwent Pharmdoc basic number 36565) discloses benzothiazolyl ureas as antiseptics in detergent compositions.

Recently, immune suppressant agents have come into prominence because of their use during transplants of organs from one human to another such as heart transplants, and in particular, kidney transplants. It is part of the defense mechanism of humans to attempt to remove foreign antigens (in this case, the transplanted organ) by the immune reaction. Thus, in all of the organ transplant operations, it has been necessary to give large doses of an immune suppressant prior to the operation and continuing thereafter in order to prevent the host from rejecting the donor organ.

The immune suppressant of choice is azathioprine, IMURAN (Registered Trade Mark) (U.S. Patent No. 3,056,785).

Belgian patent No. 744,970 granted July 27, 1970 (see also British. Patent Specification No.1,296,561 published November 15, 1972) describes the use of a number of 6-substituted-benzothiazolyl phenyl ureas including N-2-(6-methoxybenzothiazolyl)Ν'-phenyl urea. The compounds are said to be useful as immune suppressants and immune regulants.

The immune response is composed of a sequence of cellular transformations and biochemical events leading to a bimodal response to foreign substances (antigens). Cells which are to participate in the response evolve from stem cells which originate in the bone marrow and are seeded out to the peripheral lymphoid organs. Prom these latter sites, following antigenic stimulus, the body's response is mounted in the form of plasma cells (which produce antibody) and -5ύ a ό oe· specific immune lymphocytes. Antibody is released into the· circulatory system and thus may act at a distance from the producing cell (humoral immunity). Specific immune lymphocytes also enter the circulatory system and act at the site of injury (cellular immunity). The reaction of antibody vzith antigen triggers the release of histamine from basophilic leucocytes; histamine, in turn, alters the permeability of blood vessels, speeding the influx of both antibody and specific immune lymphocytes into the sites of injury. Thus, the immune response is composed of a series of biochemical events in a sequence of cells at various sites in the body. It can be altered—suppressed, in the case of the compounds herein discussed—at a number of biochemical or cellular developmental sites.

Antihistamines only affect a secondary reaction in the immune response, having no direct effect on antibodyproducing cells or specific immune lymphocytes. A number of agents, currently in use as immuno-suppressive drugs, act further back in the chain of events called herein the immune response. Certain antiinflammatory steroids, e.g., cortisone, suppress production of antibody and specific immune lymphocytes, but also radically deplete normal lymphoid tissue and have other undesirable side effects. Several antineoplastic drugs, e.g., azathioprine, cyclophosphamide, and methotrexate, are employed as immunosuppressives, but they also deplete normal lymphoid tissue and radically depress other bone-marrovz-derived cells. The general cytotoxicity of the latter drugs is to be expected in view of their having been selected on the basis of toxicity against a spectrum of cell types. -641459 In the above Formula I the term (C^-C^) alkyl comprises methyl,othy 1, n-propyl and isopropyl. Thu», l.he term (C^-C^) alkoxy includes methoxy, ethoxy, ja-propoxy and isopropoxy. The term halo includes fluoro, chloro, bromo and iodo.

Compounds illustrative of the scope of Formula I include: N-2-(6-hydroxybenzothiazolyl)-Ν'-(3-methoxyphenyl) urea N-2-(6-hydroxybenzothiazolyl)-Ν'-(2-ethylphenyl) urea N-2-(6-hydroxybenzothiazolyl)-Ν'-(4-n-propoxyphenyl) urea N-2-(6-hydroxybenzothiazolyl)-Ν'-(2-chlorophenyl) urea N-2-(6-hydroxybenzothiazolyl)-N1-(4-bromophenyl) urea N-2-(6-hydroxybenzothiazolyl)-N'-(3-fluorophenyl) urea N-2-(6-hydroxybenzothiazolyl)-Ν'-(4-iodophenyl) urea N-2-(6-hydroxybenzothiazolyl)-N' - (2-ethoxyphenyl) urea N-2-(6-hydroxybenzothiazolyl)-Ν'-(4-isopropoxyphenyl) urea N-2-(6-hydroxybenzothiazolyl)-Ν'-(4-isopropylphenyl) urea N-2-(6-hydroxybenzothiazolyl)-Ν'-(3-tolyl) urea, and N-2-(6-hydroxybenzothiazolyl)-Ν'-(4-tolyl) urea.

The compounds represented by Formula I are high-melting, white, crystalline solids, and can be prepared -7by either of the two following synthetic procedures. In both procedures, the starting material is 2-amino-6hydroxybenzothiazole prepared by condensing quinone and thiourea according to the procedure of J. Org. Chem. 35, 4103 (1970) or by demethylating 2-amino-6-methoxy-benzothiazole by the procedure of J. Hetero. Chem. 10, 769 (1973). In the first synthesis, a carbamate group is formed on the 2-amino group of the benzothiazole with a phenyl ohloroformate, for example, p-nitrophenylchloroformate. The carbamate is then reacted with trimethylsilyl chloride in accordance with the procedure of Greber and Kricheldorf, Angew. Chem. internat. Edit., 7_, 941 (1968). The trimethylsilyl group has a double function in this process. In the first place, it transforms the g-nitrophenyl carbamate group to an isocyanate group as taught by Greber and Kricheldorf (loc. cit.). In addition, the trimethylsilyl group acts as a protecting group on the free hydroxyl of the benzothiazole moiety, thus preventing a reaction between the free hydroxyl and the isocyanate formed on the thiazole moiety. The 6-hydroxybenzothiazolyl-2-isocyanate thus formed can then react readily with aniline or a suitably substituted aniline to form a urea. Addition of water to the reaction mixture serves to hydrolyze the trimethylsilyl group and thus produce the compounds of this invention having the structure of formula I above. This synthetic process is more fully illustrated in Reaction Scheme I which follows. -841458 rt ri O w ;r T I rt o ΰ T z\ \ / ·:-\ z o X N 4445© In Reaction Sequence I, the phenyl chloroformate used has been illustrated with reference to the £-nitro derivative. Other ohloroformates can, of course, be used to form carbamates with the aminohydroxybenzothiazole as, for example, the unsubstituted phenylchloroformate or a tolylohloroformate. The carbamates derived from these other chloroformates, however, require somewhat higher reaction temperatures and/or longer reaction times for the decomposition of the trimethylsilyl compound to form the benzo10 thiazolylisocyanate. In addition, in Reaction Sequence I, the silylation has been illustrated with the use of trimethylsilyl chloride. However, as pointed out by Greber and Kricheldorf (loc. cit.), either mono or bis (trimethylsilyl) acetamide can also be used to prepare the disilylated derivative.

The second synthetic procedure available for the preparation of the compounds of Formula I above involves the reaction of 1 to 2 moles Cup to a 100 percent molar excess) of a phenylisocyanate (R-CgH^-NCO) with mole of 2-amino-6-hydroxybenzo20 thiazole to produce a reaction mixture containing a 6carbamoyloxy derivative (FormulaHI) and permissibly, some of the compound of Formula I below <®—NH-CO-O Formula I :C-NH-CO-NH—< AV R Formula III -1041459 The N-2-(6-phenylcarbamoyloxybenzothiazolyi)-N'-phenyl urea (111) thus produced is treated with base in an inert solvent at a temperature not higher than 100°C. until all of the 6-phenylcarbamoyloxy group of the benzothiazolyl urea has been hydrolyzed to provide a compound of Formula X. The 6-phenylcarbamoyl compound produced in the isocyanate reaction can be hydrolyzed to the 6-hydroxy derivative either in the original reaction mixture or during an initial separation step wherein advantage is taken of the phenolic character of the 6-hydroxy group to dissolve it in base.

The base-insoluble compound is separated and then hydrolyzed by the process. It is, of course, preferable to carry out the hydrolysis step in the unseparated reaction mixture.

The 6-hydroxy urea (I) already present or produced by the hydrolytic reaction is not adversely affected under the specified hydrolysis reaction conditions.

In the reaction between the phenylisocyanate (RCgH^-NCO) and the 2-amino-6-hydroxybenzothiazole, the 2-amino group of the benzothiazolyl reacts far more rapidly than does the 6-hydroxy group. Thus, with a single mole of phenylisocyanate, the predominant reaction product will be N-2-(6-hydroxybenzothiazolyl)-Ν'-phenyl urea. The reaction between the hydroxy group and the phenylisocyanate does, however, proceed at a measurable reaction rate. Using only a single mole of isocyanate, therefore, the chief reaction product will be the urea of Formula I, as stated above but there will also be present 2-amino-6-carbamoyloxybenzothiazole, N-2-(6-carbamoyloxybenzothiazolyl)-Ν'-phenyl urea and unreacted 2-amino-6-hydroxybenzothiazole starting material. Sufficient phenylisocyanate or substituted phenylisocyanate -11- 41459 should be employed to insure that all of the 2-amino group of the benzothiazole reacts to form the corresponding urea, and preferably, a stoichiometric excess from about 25-100 percent of the isocyanate is employed. A greater than 100 percent stoichiometric excess (2 moles per mole of amino benzothiazole) is, of course, not necessary since with 2 moles of phenyl (or a substituted-phenyl) isocyanate present, all of the benzothiazole will be converted to the 6-carbamoyloxy urea (Formula III above.) If less than 2 moles, but more than 1 mole, of isocyanate is used per mole of benzothiazole, the reaction mixture will contain both the 6-hydroxy and 6-carbamoyloxy derivatives. In any case, in order to obtain a substantially quantitative yield of the desired 6-hydroxy compound, it is necessary to hydrolyze any 6-carbamoyloxy derivative produced in the isocyanate reaction using base in an inert solvent at a temperature J not higher than lOO°C. until substantially all of the 6carbamoyloxy group is hydrolyzed to the desired 6-hydroxy compound of Formula I above. Useful inert solvents include water and the lower alkanols including methanol and ethanol. Suitable bases for use in the process include alkali metal hydroxides such as potassium or sodium hydroxide; alkali metal alcoholates such as potassium ethylate and sodium methylate; alkali metal carbonates including potassium and sodium carbonate; and ammonium hydroxide, and s.ubs^itjit^d ammonium hydroxides such as triethyl ammonium hydroxide and trimethyl ammonium hydroxide The temperature of the reaction is customarily carried out at the reflux temperature of the solvent; i.e., 3o from 65°C. for methanol to 100eC. for water. As will be apparent to those skilled in the art, the higher the reflux -1241459 temperature, the shorter the time needed for the hydrolysis to proceed to completion. Likewise, the solubility of the base in the inert solvent is an important consideration with the alkali metal hydroxides, for example, being more soluble than the carbonates. Use of the hydroxides therefore requires less reaction time than use of the carbonates. Complete hydrolysis of the 6-phenylcarbamoyloxy compound usually requires from 1 to about 18 hours depending upon J solvent, base-and temperature employed, and upon the nature of the 6-phenyl (or substituted-phenyl) carbamoyloxy group.

The character of the isocyanate (R-CgH^-NCO) affects not only the rate of hydrolysis of the 6-phenyl (or substituted-phenyl) carbamoyloxy group as indicated above, but also affects the ratios of the various products of the reaction of the particular isocyanate with 2-amino6-hydroxybenzothiazole, specially the rate of urea formation compared to the rate of reaction with the 6-hydroxy group.

N-2-(6-hydroxybenzothiazolyl)-Ν'-phenyl urea and other substituted phenyl ureas represented by formula I above are useful as anti-viral agents and as immune suppressants The obvious method of preparing the compounds of Formula I above would be to demethylate the corresponding 6-methoxy ether, as with 48 percent hydrobromic acid. This procedure has been found to be inoperative in our hands and, in particular, is not at all suitable for the preparation of compounds according to formula I above wherein R is itself a methoxy group since the demethylation procedure would presumably yield hydroxy groups in both rings. Compounds according to Formula I above, however, can be demethylated by enzyme systems since they are found to be metabolic -1341459 products of the corresponding 6-methoxy compound when the latter compound is administered to rats The compounds are useful in altering the immune reaction in mammals. Thus, the compounds can be classed as g immune regulating agents by which is meant an agent which can decrease the formation of antibodies to foreign protein. This activity can thus also be characterized as antiallergic in that the allergic reaction is part of the defense mechanism of the body (the immune mechanism) against foreign antigens. (This activity is quite different from an antihistamine activity which affects only the effects of histamine released by an antibody-antigen reaction.) Although immune regulating activity was determined in mice using sheep erythrocytes as the antigen, it should be understood that the same type of activity would be shown against any foreign protein (antigen) in any species of mammal.

The ability of compounds according to the above formula to alter immune mechanisms in a host animal was measured by their activity according to the following test. Groups of five 20-gram Swiss mice were injected intraperitoneally with standardized suspensions of an antigen—in this instance sheep blood cells. The active compounds were also injected by the intraperitoneal route at various times before and/or after the injection of the red blood cells. Eight days after injection of the antigen, the mice were bled and the sera from each group pooled.

Antibody determinations were made on the serum pools by a hemagglutination pattern procedure and comparisions made between treated and control animals. In Table 1 which follows, the activity of the compounds listed therein is -14414S9 given in terms of the dose of drug necessary to suppress the hemagglutination titer in the treated mice as compared with control titers.

In the table, column 1 gives the name of the compound; column 2, the route of administration; column 3, the dose; and column 4, the level of suppression. In general, a fourfold or greater suppression of the hemagglutination titer was taken as the measure of significant immune-regulant activity.

Table 1 Name of Route of dose mg./kg. Administration x days level of N-2- (6- oral 50 x 10 8 x hydroxy- oral 25 x 10 8 x benzothiaz- oral 12.5 x 10 4 x olyl)-N'- subcutaneous 3.1 x 10 Complete phenylurea subcutaneous 1.6 x 10 16 x subcutaneous 0.8 x 10 No effect In a modification of the above procedure using an individual serum assay procedure, other compounds were tested for their immunosuppressive activity. In this later procedure, groups of ten 20 g. Swiss mice received intra7 peritoneal injections of 5 x 10 sheep red blood cells.

Each mouse in the group of ten was then given the drug under test, using several experimental dose levels, for three successive days commencing three days prior to the administration of the antigenic sheep red blood cells. An untreated control group of ten mice received only the administration vehicle and the sheep blood cells. Seven days following administration of the sheep red blood cell antigens, all of the mice were bled individually and the antibody content of the serum determined. A similar experiment was carried out in which groups of ten mice each received intravenous injections of 5 x 107 sheep red blood -1541458 cells and were then given predetermined dosages of the drug under test by the oral route on ten successive days commencing three days prior to the administration of the antigenic sheep red blood cells. Results are embodied in Table 2 below. In the table, column 1 gives the name of the compound; column 2, the dose in milligrams per kilogram by the intraperitoneal or oral route; and column 3, the logarithm to the base 2 of hemagglutinin plus or minus the standard error. -1641459 Table 2 Intraperitoneal Route Name of Compound ( Dose mg./kg.) Log? Hemagglutinin (Mean + S.E.)* 5 N-2-(6-hydroxy- 50 <3.90 + 0.53** benzothiazoly1) - 25 <3.11 + 0.11** N1-(p-methoxyphenyl) urea 12.5 <3.60 + 0.34** N-2-(6-hydroxy- 50 <3.30 + 0.15** 10 benzothiazolyl) Ν' - (o-fluoro- 25 <3.33 + 0.24** 12.5 <3.22 + 0.15** phenyl) urea N-2-(-hydroxy 50 <3.22 + 0.22** benzothiazolyl)- 25 <3.00 + 0.00** 15 Ν'—ξο—tolyl) urea 12.5 <3.70 + 0.15** Control — 6.60 + 0.48 Oral Route Name of Dose Log? Hemagglutinin Compound (mg./kg.) (Mean + S.E.)* 20 N-2- (6-hydroxy- 25 7.00 + 0.26 thiazolyl)-N'- 12.5 7.62 + 0.18 (p-methoxyphenyl) urea 6.2 6.78 + 0.22 N-2-(6-hydroxy- 25 <4.22 + 0.32** 25 benzothiazolyl) - 12.5 <4.40 + 0.43** Ν'-(o-fluoro 6.2 <6.00 + 0.44** phenyl) urea N-2- (6-hydroxy- 25 <5.78 + 0.49** benzothiazolyl) N'-(o-tolyl) urea 12.5 6.60 + 0.30** 30 6.2 7.40 + 0.22 Control — 7.50 + 0.17 *< indicates one or more sera in the group showed no detectable hemagglutinin at the lowest dilution tested. **p <0.01 - Confidence Level. 33 The compounds are useful in organ transplant operations where they can be used to prevent the host from rejecting the donor organ. In addition to their use in organ transplant operations, immune regulating agents are also useful in various diseases of little-understood etiology, denominated generically as auto-immune diseases. These diseases include: auto-immune hemolytic -1741459 anemia, idiopathic thrombocytopenic purpura, lupus erythematosus, lupoid hepatitis, lupus nephritis, glomerulonephritis, the nephrotic syndrome, Goodpasture's syndrome, Wegener's granulomatosis, schleroderma, Sezary's disease, psoriasis, uveitis,· rheumatoid arthritis, ulcerative colitis, thyroiditis and mumps orchitis. Immune suppressant agents may be more or less useful in the treatment of the above diseases depending upon the degree to which the disease is dependent upon an auto-immune mechanism.

Routes of administration include oral, intraperitoneal, topical and subcutaneous routes. For oral administration, the immune regulant can be dissolved or suspended in polyethylene glycol and mixed with corn oil, at a rate of 1-200 mg./ml. A particularly useful medium for oral administration contains 50 percent polyethylene glycol 200, 40 percent corn oil and 10 percent polyoxyethylene sorbitol monostearate. Aqueous vehicles, to which may be added surface-active agents, are also useful. For topical application, the compound is preferably administered in ethanol or in the above polyethylene glycol-corn oil-surfactant composition whereas for subcutaneous injection an isotonic solution is used. The immune-regulant is present in the particular vehicle at the rate of from 1 to 200 mg./ml.

The heterocyclic ureas useful in altering the immune response, as can be seen differ· from a majority of the known immune regulants and immunosuppressants in the mechanism of their action on the mammalian host. They do not act by directly antagonizing the action of histamine as do the anti-histamine drugs. On the other hand, they do not depress bone-marrow function as do the antineoplastic drugs -1841459 frequently used in connection with tissue transplants. The heterocyclic urea compounds more closely resemble the corticoids in their effects on the immune response, but even here there is a fundamental difference in that the corticoids deplete lymphoid tissue and the heterocyclic urea compounds do not. Thus, it is apparent that these agents function through a mechanism which neither depletes normal lymphoid mass nor depresses bone marrow, thus avoiding the major drawbacks of the currently used immunosuppressive drugs-the corticosteroids and antineoplastic drugs.

Preparation and use of the compounds are illustrated by the following specific examples: (All pKa's cited were determined in a 66 percent dimethylformamide/watcr system).

Example 1 PREPARATION OF N-2-(6-HYDROXYBENZOTHIAZOLYL)-N PHENYL UREA A slurry was prepared containing 16.7 g. of 2-amino-6-hydroxybenzothiazole hydrochloride, prepared by the method of J. Org. Chem., 35, 4103 (1970), in 300 ml. of acetone and 11 g. of potassium bicarbonate. The slurry was stirred under anhydrous conditions while 22.4 g. of p-nitrophenylchlorofopnate in 300 ml. of acetone were added thereto in dropwise fashion. The reaction mixture was stirred for about 18 hours and then poured into three liters of water. The reaction mixture was filtered, and the filter cake, comprising 2-amino-6-hydroxybenzothiazolyl-£-nitrophenyl carbamate formed in the above reaction, was washed with ether. The compound crystallized as the hemihydrate.

Analysis calculated for ci4H19N304S' 1/2 H2O Calc.: C, 51.85; H, 2.88; N, 13.33; Found: C, 51.74: H, 3.40; N, 12.74. -1941488 A slurry was prepared containing 600 mg. of the above carbamate in 25 ml. of acetone. About 0.5 ml. of aniline was added in dropwise fashion. The reaction mixture was stirred at ambient temperature while 0.3 ml. of tri5 methylsilyl chloride were added in dropwise fashion via a syringe. The resulting mixture was refluxed for about 18 hours yielding a yellow solution. The reaction mixture was cooled, poured ipto water with stirring, and then filtered. The filter cake was washed with ether and dried. The filter IQ cake comprised N-2-(6-hydroxybenzothiazolyl)-N*-phenyl urea formed in the above reaction, m.p. above 250°C. Yield=60 percent. Characteristic Mass spectral fragments at 285, 212, 192, and 166; pKa=l0.9. Analysis calculated for cx4HyyN3°2S Calc.: C, 58.93; H, 3.89; N, 14.73; Found; C, 58.34; H, 3.76; N, 13.76.

The following compounds were prepared by the above procedure: N-2-(6-hydroxybenzothiazolyl)-N'-(4-methoxyphenyl) urea; pKa=ll.l; Characteristic mass spectral fragments at 315, 192, and 166. m.p. above 250°C.

Analysis calculated for ci5Hi3N3°2S· 3/4 H2O Calc.: C, 57.88; H, 4.82; N, 13.50; Found: C, 57.42; H, 4.27; N, 13.18.

N-2-(6-hydroxybenzothiazolyl)-Ν'-(2-fluoro25 phenyl) urea. Melting point above 250°C. One spot material by thin layer chromatography. pKa=10.3; Characteristic mass spectral fragments at 303, 192, and 166.

Analysis calculated for cx4HxoFN3°2S Calc.: C, 55.44; H, 3.32; N, 13.85; Found: C, 55.28; H, 3.47; N, 13.31. -2041458 N-2- (6-hydroxybenzothiazolyl)-N'-(2-tolyl) urea. Melting point above 250C. One spot material by thin layer chromatography; pKa=10.6.

Analysis calculated for C^gH^^NgO^S Calc.: C, 57.13; H, 4.16; N, 13.33; Found: C, 56.90; H, 4.40; N, 13.37.

Example 2 ALTERNATE PREPARATION OF N-2-(6-HYDROXYBENZOTHIAZOLYL)-N'-PHENYL UREA.

A slurry of 152 g. of 2-amino-6-hydroxybenzothiazole was prepared in 3 liters of acetone. A solution of 109 g. of phenylisocyanate and 150 ml. of acetone was added thereto in dropwise fashion. After the addition had been completed, the reaction mixture was heated at refluxing temperature overnight. The reaction mixture was cooled to about 50°C. and decolorizing charcoal added. The mixture was filtered, and a second batch of 109 g. of phenylisocyanate in acetone added to the filtrate. The reaction mixture was again heated to refluxing temperature for about 2 hours. The reaction mixture was cooled, and a white solid comprising N-2-(6-phenylcarbamoyloxybenzothiazolyl)N'-phenyl urea precipitated. The precipitate was separated by filtration, and the filter cake washed with acetone. Yield=73 percent.

Analysis calculated for C2iHi5N4°3S Calc.: C, 62.52; H, 3.75; N, 13.89; S, 7.95; Found: C, 62.30; H, 3.97; N, 13.69; S, 7.76.

Melting point above 250°C.

Four grams of the above N-2-(6-carbamoyloxybenzothiazolyl)-N'-phenyl urea were dissolved in 150 ml. of anhydrous methanol. A 10 percent slurry of 0.5 g. of sodium -2141458 methylate in methanol was added with stirring. The reaction mixture was stirred at room temperature overnight. Thin layer chromatography showed that about 50 percent of the carbamoyloxy group had been removed by hydrolysis. The reaction mixture was then slowly heated, and the progress of the reaction continually checked by thin layer chromatography. After two hours of heating at about 45°C., the hydrolysis was substantially 100 percent complete. The reaction mixture was then cooled and carefully acidified to pH=4 with 10 percent aqueous hydrochloric acid. N-2(6-hydroxybenzothiazolyD-N’-phenyl urea formed in the above reaction was separated by filtration. The filter cake was washed with methanol and then ether. Examination of its NMR spectra indicated that a phenyl-carbamoyloxy group was no longer present in the molecule. This fact was further substantiated by shifts in the ultraviolet spectrum upon solution of the compound in acid and base. N-2-(6-hydroxybenzothiazolyl)-N'-phenyl urea thus prepared had the following characteristics: m.p. above 250°C.; mass spectral fragments at 205,212, 192, and 166; pKa = 10.9 (66% DMP).

Analysis Calc, for C^H^N^S: C, 58.93; H, 3.89; N, 14.73; Found : C, 58.34; H, 3.76; N, 13.76.

Example 3 A reaction mixture was prepared containing 100 mg. of N-2-(6-phenylcarbamoyloxybenzothiazolyl)-Ν'-phenyl urea, 100 mg. of sodium methylate and 25 ml. of methanol. The reaction mixture was refluxed for one-half hour, at the end of which time thin layer chromatography indicated that none of the starting material was present and that the product of -2241459 the reaction was the corresponding 6-hydroxy compound.

Further refluxing of the reaction mixture for 18 hours showed no decomposition of N-2-(6-hydroxybenzothiazolyl)N'-phenyl urea formed in the reaction.

I Example 4 Example 3 was repeated except that 20 mg. of potassium hydroxide were substituted for the sodium methylate of that example. An examination of the reaction mixture by thin layer chromatography after 6 hours indicated that the hydrolysis of the 6-phenyl-carbamoyloxy group was J incomplete. Refluxing was continued for another 12 hours, at the end of which time it was ascertained that hydrolysis - was completed and that the starting material had been entirely converted to the corresponding 6-hydroxy compound.

Example 5 The procedure of Example 2 was repeated except that about 35 mg. of the potassium carbonate were employed in place of the sodium methylate of that example. Examination of the reaction mixture at intervals indicated that 18 hours were required to hydrolyze completely the 6phenyl-carbamoyloxy group.

Example 6 The procedure of Example 6 was repeated except that 25 ml. of water were employed in place of the methanol of that example. The reaction mixture was heated slowly, and the solid starting material went into solution at about 8O'°‘c. Refluxing for one hour gave complete hydrolysis of the 6-phenylcarbamoyloxy group.

Example 7 The procedure of Example 3 was repeated except that 0.35 ml. of triethylamine were used in place of the sodium methylate of that example. Examination by thin layer chromatography indicated that the hydrolysis was complete after a 6-hour reflux.

Claims (13)

1. A compound of the formula lo wherein R is hydrogen, CC^-C^] alkyl, (C^-C^) alkoxy or halo.

2. N—2—[6-Hydroxybenzothiazolyl)-N'-phenyl urea.

3. N-2-(6-Kydroxybenzothiasolyl)-N t -(4-methoxyphenyl) urea

4. N-2-(6-Hydroxybenzothiazolyl)-N'-{2-fluorophenyl) urea.

5. N-2-(6-Hydroxybenzothiazolyl)-N*-(2-tolyl) urea.

6. A process for preparing a compound of Formula I as claimed in any one of claims 1 to 5, which comprises reacting a benzothiazolyl of the formula Formula V with a substituted phenyl compound of the formula Formula VI wherein R is hydrogen, CCj-Cj) alkyl, (C^-C 3 ) alkoxy or halo; R 1 and R 2 are -N=C=O or -NH2, R 2 being -NH2 when R 1 - 24 41459 is -NCO and R 2 -Si(CH 3 ) 3 or being -NCO when R 1 is -NH 2 ; and R 2 is \ 11 •Γ^· > - NHC- wherein R is as defined ·=· above, and hydrolyzing the resulting compound.

7. A process as in Claim 6 for preparing a compound of Formula I wherein R is hydrogen, (C^-C 3 ) alkyl, (C^-C 3 ) alkoxy or halo which comprises reacting 2-amino6-hydroxybenzothiazole with a phenylchloroformate to form a 2-phenylcarbamate, reacting the thus-formed carbamate with an excess of trimethylsilylchloride to synthesize a 6trimethylsilyloxy-2-benzothiazolylisocyanate and then treating said isocyanate with an aniline of the formula R Formula IV wherein R is hydrogen, halo, (C^-C-j) alkyl or (C^-C 3 ) alkoxy, and hydrolysing the resulting compound.

8. A process as in Claim 6 for preparing a compound of Formula I which comprises reacting 1 mole of 2-amino-6 hydroxy-benzothiazole with from 1 to 2 moles of a phenyl isocyanate of the formula Formula II wherein R is hydrogen, (C 3 -C 3 ) alkyl, (C 1 ~C 3 ) alkoxy or halo; hydrolyzing any thus-obtained 6-carbamoyloxy compound of the formula Formula III - 25 41459 wherein R has the same meaning as hereinabove; with a base selected from alkali metal hydroxides, and carbonates, ammonium hydroxide and (C^ or C 2 ) alkyl-substituted ammonium hydroxides in an inert solvent at a temperature not higher 5 than about 100°C.

9. A compound of Formula I substantially as herein described with, reference to any one of the foregoing Examples.

10. A process for preparing a compound of Formula Ϊ substantially as herein described with particular reference 10 to Example 1.

11. A process for preparing the compound of Formula X substantially as herein described with particular reference to any one of Examples 2-7.

12. A compound of formula I whenever prepared by a process 15 according to any one of claims 6 to 8, 10 or 11.

13. A pharmaceutical formulation containing a compound of formula I as claimed in any one of claims 1 to 5, 9 or 12, associated with a pharmaceutically acceptable carrier therefor.