Condensed thiadiazole derivative, method of its production, and use thereof

Abstract: (1) a compound represented by the following formula(I): wherein R represents a hydrocarbon group or heterocyclic group which may be substituted for; the ring A represents a pyridine ring having a substituent or a thiazole ring which may be substituted for; or a pharmaceutically acceptable salt thereof, and a method of its production, and (2) an endothelin receptor antagonist, an cathepsin B inhibitor or a bone resorption suppressor comprising as an active ingredient a compound represented by the following formula (I'): wherein R has the same definition as in term (1); the ring A' represents a pyridine ring or thiazole ring which may be substituted for; or a pharmaceutically acceptable salt thereof.

Description: The present invention relates to new compounds useful as exhibiting endothelin receptor antagonistic action, cathepsin B inhibiting action and bone resorption inhibitory action, a method of their production and use thereof. Although various peptides have been reported as exhibiting endothelin receptor antagonistic action, there have been reported no non-peptide compounds but anthraquinone derivatives (the official gazette of EP Publication No. 405421 A). Osteoporosis is a pathologic state or disease involving any symptom or risk due to quantitative reduction in bone exceeding a certain degree. Major symptoms are spinal kyphosis, and fractures of dorsolumbar bone and vertebral centra, femoral neck, lower end of radius, ribs, upper end of humerus, and other bones. In bone tissue, bone destruction occurs constantly with a good balance between bone formation and resorption; osteoblasts and osteoclasts play key roles in bone formation and bone resorption, respectively. If bone resorption surpasses bone formation as a result of the deterioration of the bone destruction balance, a quantitative reduction in bone occurs. Also, inflammatory joint diseases such as chronic rheumatoid arthritis involve accentuated bone resorption, posing a major clinical problem. Drugs suppressing bone resorption are therefore expected to serve well in the prevention and treatment of osteoporosis and inflammatory joint diseases such as chronic rheumatoid arthritis. Traditionally, bone resorption inhibitory agents such as estrogens'and calcitonin have been used to treat osteoporosis. To treat inflammatory joint diseases chemotherapeutically, there have been used steroids such as cortisone and other adrenocortical hormones, non-steroidal anti-inflammatory agents such as aspirin, piroxicam and indomethacin, aurothiomalate and other gold agents, antirheumatic agents such as chloroquine preparations and D-penicillamine, anti-gout agents such as colchicine, and immunosuppressants such as cyclophosphamide, azathioprine, methotrexate and levamisole. However, these therapeutic agents fail to have a satisfactory effect in some cases, due to limitation on the subject or to uncertain efficacy. There is therefore a need of a new preventive/therapeutic method for accentuated bone resorption. It has recently been suggested that cathepsin B, a lysosome cysteine protease, is involved in joint destruction due to inflammatory joint disease [Biochemical Pharmacology, 44 , 1201 (1992)]. Also, cathepsin B is thought of as causing intractable muscle collapsing diseases such as myodystrophy and vacuolar distal myopathy. It is also among the enzymes involved in the formation of senile plaques in the brain of patients with Alzheimer's disease. Cathepsin B inhibitors are therefore expected to be useful against these diseases. Traditionally, leupeptin, antipain etc., and epoxysuccinic acid derivatives such as those disclosed in Japanese Patent Unexamined Publication Nos. 304074/1990, 304075/1990 and 304085/1990 are known to exhibit cathepsin B inhibitory action. On the other hand, among condensed thiadiazole derivatives having a sulfonylimino group are 2-sulfonylimino-2H-[1, 2, 4]thiadiazolo[2, 3- a ]pyrimidine and triazine derivatives, which are known to serve as herbicides (see Japanese Patent Unexamined Publication Nos. 263185/1987 and 10795/1988 and EP-A-0 239 064). Also, Japanese Patent Unexamined Publication No. 246389/1985 describes a 2-sulfonylimino-2H-[1, 2, 4]thiadiazolo[2, 3- a ]pyrimidine derivative, a compound exhibiting platelet aggregation inhibitory and cardiotonic actions, represented by the following formula: wherein R represents a lower alkyl group or a phenyl group which may be substituted for by a lower alkyl group or halogen. Chem. Abs. Vol 114, 1991, 23848 u discloses 2-aroyliminobenzothiazolo-[3,2-b]-1,2,4-thiadiazolines. However, none of these reports discloses endothelin receptor antagonistic action, cathepsin B inhibiting action and bone resorption inhibitory-action. OBJECT OF THE INVENTION The present invention aims at providing new thiadiazole derivatives useful as exhibiting endothelin receptor antagonistic action, cathepsin B inhibiting action and bone resorption inhibitory action, a method of their production and use thereof. Through intensive investigations from the above viewpoint, the present inventors found that a new condensed thiazole derivative exhibits excellent endothelin receptor antagonistic action, potent cathepsin B inhibiting action and potent bone resorption inhibitory action, and developed the present invention. Accordingly, the present invention provides: (1) A compound represented by one of the following formulae: wherein R is a hydrocarbon group selected from a linear or branched alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, cycloalkadienyl group, and aryl group, or a heterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl; R 1 , R 2 , R 3 and R 4 independently represent (1) hydrogen, (2) halogen, (3) a hydroxyl group which may be substituted, (4) an amino group which may be substituted, or the two substituents on the nitrogen atom of the amino group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having C 1-6 alkyl group, an aralkyl group, or an aryl group at the 4-position, (5) a thiol group which may be substituted, (6) a carboxyl group which may be esterified, (7) a hydrocarbon group selected from a linear or. branched alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, cycloalkadienyl group, and an aryl group or (8) a heterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl; and the adjoining two substituents of R 1 , R 2 , R 3 , and R 4 may cooperate to form a ring selected from : said rings may be substituted by one or two methyl, ethyl and propyl group at any possible positions; at least one of R 1 , R 2 , R 3 , and R 4 is different from hydrogen; R 5 and R 6 independently represent hydrogen, halogen, a carboxyl group which may be esterified, a hydrocarbon group selected from a linear or branched alkyl group, alkenyl group, alkynyl group, cycloalkyi group, cycloalkenyl group, cycloalkadienyl group, and aryl group or a heterocyclic group selected from furyl, thienyl, pyridyl, pyrimidmyl, indolyl, isoindolyl, azetidinyl, oxazetanyl, thietanyl, pyrrolidinyl, tetrahydrofuryl, thiolanyl, piperidyl, tetrahydropyranyl, morpholinyl, thiomorpholinyl and piperazinyl; the adjoining substituents R 5 and R 6 may cooperate to form a ring selected from : Said rings may be substituted by one or two methyl, ethyl and propyl group at any possible positions ; if R, R 1 , R 2 , R 3 , R 4 , R 5 or R 6 represents a hydrocarbon group as mentioned above, it may be optionally substituted by (1) cycloalkyl, (2) aryl, (3) aromatic heterocyclic group selected from furyl, thienyl,pyridyl and pyrimidinyl, (4) acyl groups, (5) carboxyl which may be esterified, (6) amino which may be substituted, or the two substituents on the nitrogen atom of the ammo group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1 -C 6 alkyl group, an aralkyl group, or an aryl group at the 4-position, (7) carbamoyl which may be substituted, or the two substituents on the nitrogen atom of the carbamoyl group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1-6 alkyl group, an aralkyl group, or an aryl group at the 4-position, (8) hydroxyl which may be substituted, (9) thiol which may be substituted, (10) sulfo, (11) cyano, (12) nitro, or (13) halogen; in case that said hydrocarbon group is an alicyclic hydrocarbon group or an aryl group, further examples of substituents include C 1-6 alkyl groups C 2-6 alkenyl groups, C 2-6 alkinyl groups and aralkyl groups; further, in case that said hydrocarbon group is an aryl group, two adjoining hydroxyl groups, which may be substituted for, on the aryl group may cooperate therewith to form a heterocyclic ring of the following formula: ; of the substituents in the hydrocarbon group which may be substituted for, each of C 1-6 alkyl groups and aryl groups may have additional one or two of halogens, carboxyl groups which may be esterified including methoxycarbonyl, ethoxycarbonyl and propoxycarbonyl and carbamoyl groups which may be substituted for at any possible positions by C 1-3 alkyls which may be substituted for by an alkoxycarbonyl selected from ethoxycarbonyl, methoxycarbonyl, propoxycarbonyl, and phenyls which may be substituted for by a C 1-3 alkyl or halogen; if R, R 1 , R 2 , R 3 , R 4 , R 5 or R 6 represents a heterocyclic group as mentioned above, it may be optionally substituted by (1) C 1-6 alkyl, (2) C 2-6 alkenyl, (3) C 2-6 alkynyl, (4) cycloalkyl, (5) aryl, (6) aromatic heterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl, (7) aralkyl, (8) acyl, (9) carboxyl which may be esterified, (10) amino which may be substituted, or the two substituents on the nitrogen atom of the amino group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1 -C 6 alkyl group, an aralkyl group, or an aryl group at the 4-position, (11) carbamoyl which may be substituted, or the two substituents on a nitrogen atom of the carbamoyl group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1 -C 6 alkyl group, an aralkyl group, or an aryl group, (12) hydroxyl which may be substituted, (13) thiol which may be substituted, (14) sulfo, (15) cyano group, (16) nitro, or (17) halogen; wherein the aryl group of the aralkyl group may have one or two substituents at any possible positions selected from C 1 -C 6 alkyl groups, C 2 -C 6 alkenyl groups, C 2 -C 6 alkynyl groups, cycloalkyl groups, aryl groups, aromatic heterocyclic groups selected from furyl, thienyl, pyridyl and pyrimidinyl, aralkyl groups, amino groups which may be substituted, acyl groups, carbamoyl groups which may be substituted, hydroxyl groups which may be substituted, carboxyl groups which may be esterified, thiol groups which may be substituted, sulfo groups, cyano groups, nitro groups and halogens ; wherein the substituents of the hydroxyl group, amino group, thiol group and carbamoyl group which may be substituted are selected from C 1 -C 6 alkyl, cycloalkyl group, aryl group, aromatic heterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl, aralkyl, acyl group or carboxyl group which may be esterified, wherein the acyl groups are selected from a C 1-6 alkanoyl group, a C 2-6 alkenoyl group, a cycloalkanecarbonyl group, an alkanesulfonyl group, an aroyl group, an arylalkanoyl group, an arylalkenoyl group, an arenesulfonyl group, an aromatic heterocyclic carbonyl group selected from furoyl, thenoyl, nicotinoyl, isonicotinoyl, pyrrolecarbonyl, oxazolecarbonyl, imidazolecarbonyl and pyrazole carbonyl, and an aromatic heterocyclic C 1-6 alkanoyl group, the aromatic heterocyclic C 1-6 alkanoyl group being selected from thienylacetyl, thienylpropanoyl, furylacetyl, thiazolylacetyl, 1,2,4-thiadiazolylacetyl and pyridylacetyl; the substituents in the carbamoyl group which may be substituted for in the substituent for the hydrocarbon group which may be substituted for may be a tetrahydronaphthyl which may have one or two C 1-3 alkyls at any possible positions; of the substituents in the carbamoyl group which may be substituted for, C 1-6 alkyls, cycloalkyl groups and aryl groups may have at any possible positions one or two of carboxyl groups which may be esterified, cycloalkyl groups and hydroxyl groups which may be substituted for; in case that the' substituents in the carbamoyl group which may be substituted for is a cycloalkyl group or an aryl group, said substituent may have C 1-3 alkyl groups which may be substituted by a phosphono group which may be esterified including ethylphosphono, diethylphosphono, methylphosphono or dimethylphosphono groups and a carboxyl group which may be esterified; two of the substituents in the carbamoyl group which may be substituted for may cooperate with the adjacent nitrogen atom to form a heterocyclic ring: which may have 1 to 2 substituents at any possible positions selected from C 1-6 alkyl groups, carboxyl groups which may be esterified, hydroxyl groups which may be substituted for and carbamoyl groups which may be substituted for; or a pharmaceutically acceptable salt thereof. (2) A method of producing a compound as defined in (1), by cyclizing a compound represented by the following formulae: wherein R, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 have the same definitions as mentioned in (1). (3) An endothelin receptor antagonist comprising as an active ingredient a compound as defined in (1). (4) A cathepsin B inhibitor comprising as an active ingredient a compound as defined in (1). (5) A bone resorption suppressor comprising as an active ingredient a compound as defined in (1). (6) Use of a compound represented by the formulae (I) and (II) as defined in (1) or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for therapeutic application as an endothelin receptor antagonist. (7) Use of a compound represented by the formulae (I) and (II) as defined in (1) or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for therapeutic application as a cathepsin B inhibitor. (8) Use of a compound represented by the formulae (I) and (II) as defined in (1) or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for therapeutic application as a bone resorption suppressor. (9) Use of a compound represented by the formulae (I) and (II) as defined in (1) or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for prevention and treatment of osteoporosis, inflammatory joint diseases, myodystrophy, vacuolar distal myopathy and Alzheimer's disease. Such pharmaceutically acceptable salts include salts with inorganic base, salts with organic base, salts with inorganic acid, salts with organic acid and salts with basic or acidic amino acid. Preferable salts with inorganic base include alkali metal salts such as sodium salt, alkaline earth metal salts such as calcium salt and magnesium salt, aluminum salt, and ammonium salt. Preferable salts with organic base include salts with trimethylamine, triethylamine, pyridine, picoline, ethanolamine, diethanolamine, triethanolamine, dicyclohexylamine and N, N'-dibenzylethylenediamine. Preferable salts with inorganic acid include hydrochloride, hydrobromate, nitrate, sulfate and phosphate. Preferable salts with organic acid include formate, acetate, trifluoroacetate, fumarate, oxalate, tartrate, maleate, citrate, succinate, malate, methanesulfonate, benzenesulfonate and p-toluenesulfonate. Preferable salts with basic amino acid include salts with arginine, lysine and ornithine. Preferable salts with acidic amino acid include aspartate and glutamate. Terms used in the present specification are described below. The term "lower" means 1 to 6 carbon atoms, unless otherwise stated, and a "hydrocarbon group" is an aliphatic chain hydrocarbon group, alicyclic hydrocarbon group, or aryl group. Aliphatic chain hydrocarbon groups include linear or branched aliphatic hydrocarbon groups, such as alkyl groups, alkenyl groups and alkinyl groups, with preference given to lower alkyl groups, lower alkenyl groups and lower alkinyl groups. Preferable lower alkyl groups include C 1-6 alkyls such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 1-ethylpropyl, hexyl, isohexyl, 1, 1-dimethylbutyl, 2, 2-dimethylbutyl, 3, 3-dimethylbutyl and 2-ethylbutyl, with preference given to methyl, ethyl, propyl, isopropyl, butyl and isobutyl. Preferable lower alkenyl groups include C 2-6 alkenyls such as vinyl, allyl, isopropenyl, 1-propenyl, 2-methyl-1- propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-ethyl-1-butenyl, 3-methyl-2-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 4-methyl-3-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl and 5-hexenyl, with preference given to vinyl, allyl, isopropenyl and 2-methyl-1-propenyl. Preferable lower alkinyl groups include C 2-6 alkinyls such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, 1-hexynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl and 5-hexynyl, with preference given to ethynyl, 1-propynyl, and 2-propynyl. Alicyclic hydrocarbon groups are saturated or unsaturated alicyclic hydrocarbon groups such as cycloalkyl groups, cycloalkenyl groups and cycloalkadienyl groups. Preferable cycloalkyl groups include C 3-6 cycloalkyls such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, and cycloheptyl, cyclooctyl, bicyclo[2, 2, 1]heptyl, bicyclo[2, 2, 2]octyl, bicyclo[3, 2, 1]octyl, bicyclo[3, 2, 2]nonyl, bicyclo[3, 3, 1]nonyl, bicyclo[4, 2, 1]nonyl and bicyclo[4, 3, 1]decyl. Preferable cycloalkenyl groups include 2-cyclopenten-1-yl, 3-cyclopenten-1-yl, 2-cyclohexen-1-yl and 3-cyclohexen-1-yl. Preferable cycloalkadienyl groups include 2, 4-cyclopentadien-1-yl, 2, 4-cyclohexadien-1-yl and 2, 5-cyclohexadien-1-yl. Aryl groups are monocyclic or condensed polycyclic aromatic hydrocarbon groups. Preferable aryl groups include phenyl, naphthyl, anthryl, phenanthryl and acenaphthylenyl, with preference given to phenyl, 1-naphthyl, 2-naphthyl and others. Acyl groups are aliphatic acyl groups such as alkanoyl groups, alkenoyl groups, cycloalkanecarbonyl groups and alkanesulfonyl groups, aromatic acyl groups such as aroyl groups, arylalkanoyl groups, arylalkenoyl groups and allenesulfonyl groups, aromatic heterocyclic carbonyl groups, and aromatic heterocyclic alkanoyl groups. Alkanoyl groups are alkylcarbonyl groups. Preferable alkanoyl groups include lower alkanoyl groups such as formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, pivaloyl and hexanoyl. Alkenoyl groups are alkenylcarbonyl groups. Preferable alkenoyl groups include lower alkenoyl groups such as acryloyl, methacryloyl, crotonoyl and isocrotonoyl. Cycloalkanecarbonyl groups are cycloalkylcarbonyl groups. Preferable cycloalkanecarbonyl groups include cyclopropanecarbonyl groups, cyclobutanecarbonyl groups, cyclopentanecarbonyl groups and cyclohexanecarbonyl groups. Alkanesulfonyl groups are alkylsulfonyl groups. Preferable alkanesulfonyl groups include lower alkanesulfonyl groups such as mesyl, ethanesulfonyl and propanesulfonyl. Aroyl groups are arylcarbonyl groups. Preferable aroyl groups include benzoyl, p-toluoyl, 1-naphthoyl and 2-naphthoyl. Arylalkanoyl groups are alkylcarbonyl groups substituted for by an aryl group. Preferable arylalkanoyl groups include aryl lower alkanoyl groups such as phenylacetyl, phenylpropionyl, hydroatropoyl and phenylbutyryl. Arylalkenoyl groups are alkenylcarbonyl groups substituted for by an aryl group. Preferable arylalkenoyl groups include,aryl lower alkenoyl groups such as cinnamoyl and atropoyl. Arenesulfonyl groups are arylsulfonyl groups. Preferable arenesulfonyl groups include benzenesulfonyl groups and p-toluenesulfonyl groups. The carboxyl group which may be esterified is a lower alkoxycarbonyl group or an aryloxycarbonyl group. Preferable carboxyl groups which may be esterified include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, phenoxycarbonyl and 1-naphthoxycarbonyl. Example substituents in the amino group which may be substituted for include lower alkyl groups, cycloalkyl groups, aryl groups, aromatic heterocyclic groups, aralkyl groups, acyl groups, and carboxyl groups which may be esterified. Also, the two substituents on a nitrogen atom may cooperate therewith to form a cyclic amino group. Examples of such cyclic amino groups include 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl, and 1-piperazinyl having a lower alkyl group, an aralkyl group, an aryl group at the 4-position. Substituents in the carbamoyl group which may be substituted for include the same substituents as those specified for the amino group which may be substituted for. Substituents for the hydroxyl group which may be substituted for, and for the thiol group which may be substituted for, include the same substituents as those specified for the amino group which may be substituted for. Preferable halogens include fluorine, chlorine, bromine and iodine, with preference given to fluorine, chlorine, bromine and others. The aralkyl group is an alkyl group having a substituent aryl group (arylalkyl group). Said aryl group may have one or two substituents at any possible positions. Such additional substituents include C 1 -C 6 alkyl groups, C 2 -C 6 alkenyl groups, C 2 -C 6 alkinyl groups, cycloalkyl groups, aryl groups, aromatic heterocyclic groups, aralkyl groups, amino groups which may be substituted for, acyl groups, carbamoyl groups which may be substituted for, hydroxyl groups which may be substituted for, carboxyl groups which may be esterified, thiol groups which may be substituted for, sulfo groups, cyano groups, nitro groups and halogens, with preference given to halogens and C 1 -C 6 alkyl groups, more preferably C 1-3 alkyls such as methyl, ethyl and propyl. Preferable aralkyl groups include benzyl, phenethyl, 3-phenylpropyl, (1-naphthyl) methyl and (2-naphthyl) methyl, with preference given to benzyl, phenetyl and others. With respect to the above formula, the hydrocarbon group represented by R, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 which may be substituted for, is exemplified by aliphatic hydrocarbon groups, alicyclic hydrocarbon groups and aryl groups, with preference given to aliphatic hydrocarbon groups and aryl groups. It is preferred that the aliphatic hydrocarbon group contains carbon atoms of less than 10, preferably less than 8. This hydrocarbon group may have 1 or more, preferably 1 to 3 substituents at any possible positions. The heterocyclic group represented by R, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 may have 1 or more, preferably 1 to 3 substituents at any possible positions. The aryl group in said hydrocarbon group may be a partially reduced one, such as tetrahydro-2-naphthyl. The acyl group in the substituent for the hydrocarbon group which may be substituted for may be an arenesulfinyl resulting from reduction of arenesulfonyl, such as a benzenesulfinyl group or a p-toluenesulfinyl group. The carboxyl group which may be esterified in the substituent for the hydrocarbon group which may be substituted for may be an aryl lower alkoxycarbonyl, such as benzyloxycarbonyl, phenylethoxycarbonyl or phenylpropoxycarbonyl. Of the substituents in the hydrocarbon group which may be substituted for, the substituent in the hydroxyl group which may be substituted for may be a halogen. Of the substituents in the hydroxyl group which may be substituted for, lower alkyls may have 1 to 2 aryl groups which may be substituted for at any possible positions. Examples of the substituents in the. aryl group which may be substituted for include halogens and C 1-3 alkyls. Rings formed by the adjoining substituents include the following: with preference given to the following: Said ring may have one or two substituents at any possible positions. Such substituents include methyl, ethyl and propyl. The present invention also provides a method of producing a compound as defined in claim 1, by cyclizing a compound represented by the following formulae: wherein R, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 have the same definitions as mentioned above. Cyclization of the compound represented by formula III or IV is achiebed by carrying out dehydrogenation under oxidative conditions. This cyclizing reaction is carried out without being affected by the substituent in the pyridine ring or thiazole ring. This reaction is carried out by keeping compound III or IV in combination with oxidant. Example oxidants include halogens such as iodine and bromine, N-halogenosuccinic imides such as N-chlorosuccinic imide and N-bromosuccinic imide, hypochlorites such as sodium hypochlorite, potassium hypochlorite and calcium hypochlorite, and sulfonyl halides such as methanesulfonyl chloride and sulfuryl chloride, with preference given to bromine and sulfuryl chloride. Although the amount of oxidant used for this cyclizing reaction can be chosen as appropriate to complete the reaction, theoretically, it is sufficient to use it at not lower than 0.5 mol, preferably 0.5 to 3 mol per mol of the starting material compound III or IV. This reaction is generally carried out in an inert solvent. Such solvents include water, alcohols such as methanol, ethanol and propanol, aromatic hydrocarbons such as benzene, toluene, xylene, nitrobenzene and chlorobenzene, hydrocarbon halides such as dichloromethane, chloroform and carbon tetrachloride, and aliphatic carboxylic acids such as formic acid and acetic acid. These solvents may be used singly or in combination at any ratio as necessary. Reaction temperature can be chosen over the range of from about -50 to 100°C, being preferably about 0 to 50°C. Reaction time is normally about 0.1 to 50 hours, preferably 0.2 to 5 hours. Provided that either of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is a substituent having a free carboxyl group (e.g., carboxylic acid, acetic acid, propionic acid), compound (I) or (II) can be converted to the corresponding amide derivative by reaction with an amine derivative which may be substituted for or a salt thereof. This reaction can be carried out by a known method. For example, a reactive derivative of compound (I) or (II), such as one reactive with acid anhydride, acid chloride, imidazolide or diethylphosphocyanide, is reacted with an amine derivative or s salt thereof. Of these methods, the most convenient is the use of acid chloride. The reaction is preferably carried out in a common solvent (e.g., dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, water, or a mixture thereof) in the presence of a base (e.g., triethylamine, N-methylmorpholine, sodium hydrogen carbonate, potassium carbonate). Reaction temperature is about -50 to 100°C, and reaction time is about 0.1 to 10 hours. The amount of amine derivative or salt thereof used is 1 to 2 mol per mol of compound (I). Provided that either of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is a substituent having a free hydroxyl group (e.g., hydroxymethyl, hydroxyethyl, hydroxypropyl), compound (I) or (II) can be converted to the corresponding ester derivative by reaction with a carboxylic acid derivative. This reaction can be carried out by a known method. Such methods include the method wherein compound (I) or (II) and a carboxylic acid derivative are directly condensed together in the presence of a condensing agent such as dicyclohexylcarbodiimide, and the method wherein compound (I) or (II) and a reactive derivative of carboxylic acid derivative, such as acid anhydride, acid chloride or imidazolide are reacted. Of these methods, the most convenient is the use of acid anhydride or acid chloride. When using an acid anhydride, the reaction is preferably carried out in a common solvent (e.g., dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, water, or a mixture thereof) in the presence of a base (e.g., triethylamine, N-methylmorpholine, sodium hydrogen carbonate, potassium carbonate). Pyridine may be used both as a solvent and as a base. When using an acid chloride,the reaction is preferably carried out in a common solvent (e.g., dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, water, or a mixture thereof) in the presence of a base (e.g., triethylamine, N-methylmorpholine, sodium hydrogen carbonate, potassium carbonate). For all these reactions, reaction temperature is about -50 to 100°C, and reaction time is about 0.1 to 10 hours. The amount of acid anhydride or acid chloride used is 1 to 2 mol per mol of compound (I). A compound represented by formula (III) or (IV) is produced by reaction of a compound represented by the following formula (V) or (VI): wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 have the same definitions as above, and a compound represented by the following formula (VII): R-SO 2 NCS wherein R has the same definition as above. This reaction is normally carried out in an inert solvent. Examples of such solvents include aromatic hydrocarbons such as benzene, toluene and xylene, hydrocarbon halides such as dichloromethane, chloroform and carbon tetrachloride, ethers such as ethyl ether, dioxane and tetrahydrofuran, nitriles such as acetonitrile and propionitrile, esters such as ethyl acetate, ketones such as acetone and 2-butanone, and amides such as N, N-dimethylformamide. These solvents may be used singly or in combination in any ratio as necessary. Reaction temperature can be chosen over the range of from about 0 to 200°C, being preferably about 10 to 100°C. Reaction time is normally about 0.1 to 50 hours, preferably 0.2 to 5 hours. The amount of compound (VII) used is 1 to 3 mol per mol of compound (V) or (VI). A compound represented by formula (VII) can be produced by heating a compound represented by the following formula (VIII): R-SO 2 NHCS 2 R' wherein R has the same definition as above, and R' represents a lower alkyl group, at 130 to 180°C in a high boiling solvent such as xylene or o-chlorobenzene for about 1 to 4 hours. A compound represented by formula (III) or (IV) can also be produced by heating compound (V) or (VI) and compound (VIII) at 130 to 180°C in a high boiling solvent such as xylene or o-chlorobenzene for about 1 to 4 hours. A compound represented by formula (III) or (IV) can also be produced by reaction of a compound represented by the following formula (IX) or (X): wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 have the same definition as above, and a compound represented by the following formula (XI) R-SO 2 NH 2 wherein R has the same definition as above, in an inert solvent (e.g., benzene, toluene, xylene, dioxane, N,N-dimethylformamide, or a mixture thereof) in the presence of a base (e.g. triethylamine, N-methylmorpholine, sodium hydrogen carbonate, potassium carbonate), Compounds represented by formula (I) or (II) thus produced can be isolated and purified by known means of fractional purification such as concentration, concentration under reduced pressure, solvent extraction, crystallization, recrystallization, re-dissolution and chromatography, Compound (V) and (VI), used for these production methods can be produced by, or in accordance with, the methods described in Chemical Abstracts, 53 , 14089e (1959), Chemical Abstracts, 105 , 221003s (1986), European Journal of Medicinal Chemistry, 16 , 355 (1981), and Shin Jikken Kagaku Koza , 14 , " Yuki Kagobutsu no Gosei to Hanno IV " (1978), for instance. Compound (V) can be produced by, or in accordance with, the method described in Chemische Berichte, 99 , 2885 (1966), for instance. Compounds (IX) and (X) can be produced by, or in accordance with, the method described in Organic Synthesis Collective Volume III, 735 (1955), for instance. Compound (VII) can be produced by, or in accordance with, the method described in the Journal of Organic Chemistry 28 , 3537 (1963) and Chemical Abstracts, 74 , 22502v (1971), for instance. Since the compound represented by formula (I) or (II) or pharmaceutically acceptable salt thereof exhibits endothelin antagonistic action, it can be used as a pharmaceutical for mammals (e.g., humans, mice, rats, cats, dogs, rabbits, bovines, swine) to treat and prevent various diseases caused by endothelin. For example, said compound can be used as a vasodilator to treat hypertension such as peripheral circulatory failure, heart diseases such as angina pectoris, myocardosis, arteriosclerosis and myocardial infarction, Raynaud's syndrome, cerebral vascular spasm, cerebral ischemia, cerebral apoplectic attacks such as late cerebral vascular spasm following subarachnoid bleeding, bronchial asthma, acute renal failure and endotoxin shock, or a therapeutic drug for chronic nephritis. Since the compound represented by the formula (I) or (II) or pharmaceutically acceptable salt thereof exhibits excellent bone resorption inhibitory action, as well as potent cathepsin B inhibiting action, it can be used as a pharmaceutical for mammals (e.g., humans, mice, rats, cats, dogs, rabbits, bovines, swine) to treat and prevent diseases involving accentuated bone resorption and diseases caused by accentuated cathepsin B activity such as chronic rheurmatoid arthritis and metabolic bone diseases. The compound represented by formula (I) or (II) or pharmaceutically acceptable salt thereof can be administered orally or parenterally in the form of solid preparations such as tablets, capsules, granules and powders or liquid preparations such as syrups and injections, in pharmaceutically acceptable carriers. Pharmaceutically acceptable carriers are various organic or inorganic carrier materials commonly used as preparation materials, which are formulated as excipients, lubricants, binders and disintegrating agents in solid preparations, or as solvents, dissolution aids, suspending agents, isotonizing agents, buffers and analgesics in liquid preparations. Also, preparation additives such as preservatives, antioxidants, coloring agents and sweeteners may be used as necessary. Preferable excipients include lactose, sucrose, D-mannitol, starch, crystalline cellulose and light silicic anhydride. Preferable lubricants include magnesium stearate, calcium stearate, talc and colloidal silica. Preferable binders include binding cellulose, sucrose, D-mannitol, dextrin, hydroxypropyl cellulose, hydroxypropylmethyl cellulose and polyvinylpyrrolidone. Preferable disintegrating agents include starch, carboxymethyl cellulose, carboxymethyl cellulose calcium, sucrose calmelose sodium and carboxymethyl starch sodium. Preferable solvents include water for injection, alcohol, propylene glycol, macrogol, sesame oil and corn oil. Preferable dissolution aids include polyethylene glycol, propylene glycol, D-mannitol, benzyl benzoate, ethanol, tris-aminomethane, cholesterol, triethanolamine, sodium carbonate and sodium citrate. Preferable suspending agents include surfactants such as stearyltriethanolamine, sodium lauryl sulfate, laurylaminopropionic acid, lecithin, benzalkonium chloride, benzethonium chlorine and glycerol monostearate, and hydrophilic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose sodium, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose. Preferable isotonizing agents include sodium chloride, glycerol and D-mannitol. Preferable buffers include phosphate, acetate, carbonate and citrate buffers. Preferable analgesics benzyl alcohol. Preferable preservatives include p-oxybenzoates, chlorobutanol, benzyl alcohol, phenethyl alcohol, dehydroacetic acid and sorbic acid. Preferable antioxidants include sulfites and ascorbic acid. The compound represented by formula (I) or (II) or pharmaceutically acceptable salt thereof can be used safely with low toxicity (no deaths occurred in mice given a 300 mg/kg dose of the compound obtained in Example 83 below). Although the daily dose varies depending on the condition and weight of the patient, kind of the compound, route of administration and other factors, it is administered parenterally, specifically subcutaneously, intravenously, intramuscularly or rectally at about 0.05 to 100 mg/kg/day, preferably 0.5 to 50 mg/kg/day in an endothelin receptor antagonist, about 0.1 to 100 mg/kg/day, preferably 1 to 50 mg/kg/day in a cathepsin B inhibitor and about 1 to 200 mg/kg/day, preferably 5 to 100 mg/kg/day in a bone resorption suppressor, respectively. For use as an oral agent, it is desirable to administer it at about 0.1 to 500 mg/kg/day, preferably 0.5 to 200 mg/kg/day in an endothelin receptor antagonist, about 1 to 500 mg/kg/day, preferably 10 to 300 mg/kg/day in a cathepsin B inhibitor and about 5 to 1000 mg/kg/day, preferably 10 to 300 mg/kg/day in a bone resorption suppressor, respectively. The bioactivities of the compound represented by formula (I) or (II) or pharmaceutically acceptable salt thereof are described below. Test 1 Inhibition of endothelin-1 binding to endothelin receptor (a) Preparation of rabbit ventricular microsomal fraction Rabbit ventricular microsomal fraction was prepared by the method described in Methods in Enzymology, 109 , 513 with a slight modification. The cardiac ventricular muscle excised from a 2 to 2.5 kg rabbit was minced in solution A (20 mM NaHCO 3 , 0.1 mM phenylmethylsulfonyl fluoride (PMSF)) and then homogenized using a Polytron PT-20, and centrifuged at 1500 × g for 15 minutes. The supernatant was centrifuged at 45000 × g for 15 minutes. The resulting sediment was suspended in solution B (50 mM Tris-HCl, pH 7.4, 0.1 mM PMSF) and then re-centrifuged at 45000 × g for 15 minutes. The sediment was again suspended in solution B and then centrifuged at 45000 × g for 15 minutes. The sediment was re- suspended in solution B, and the suspension was frozen with liquid nitrogen and stored at -80°C. This series of operations was performed at 4°C. Protein contents was determined by Lowry's method. (b) 125 I-endothelin binding test To 250 µl of a reaction solution (50 mM Tris-HCl, pH 7.4, 0.2% BSA (bovine serum albumin)), supplemented with 6 × 10 -11 M 125 I-endothelin-1 (Amersham Japan) 50 µl of the ventricular microsomal fraction (20 µg) and a sample were added, followed by incubation at 37°C for 90 minutes. The reaction mixture was then filtered through a GF/B glass filter (Millipore Japan), and the filter was washed with a 40-fold (12 ml) of the reaction solution. The radioactivity of the 125 I-endothelin on the glass filter was determined using a gamma-ray counter. Nonspecific binding was defined as the amount of 125 I-endothelin in the presence of 4x10 -7 M unlabelled endothelin-1 and was less than 8% of total binding. The specific binding was calculated as total binding minus nonspecific binding. Non-specific binding accounted for not higher than 8% of the total binding. The inhibitory rate of the compound is expressed as the concentration (IC 50 M) required to cause a 50% reduction in the specific binding. The results are given in Table 1. Test compound IC 50 value (M) 12 6.5 × 10 -6 13 5.9 × 10 -6 14 8.8 × 10 -6 20 3.0 × 10 -6 23 2.5 × 10 -6 24 2.5 × 10 -6 26 4.0 × 10 -6 73 7.3 × 10 -6 82 7.5 × 10 -6 83 6.0 × 10 -6 99 2.1 × 10 -6 104 2.7 × 10 -6 106 4.2 × 10 -6 111 6.1 × 10 -6 112 5.2 × 10 -6 114 3.8 × 10 -6 Note: The above test compound numbers correspond to Examples below. Test 2 Inhibitory action on endothelin-1-induced constriction in swine coronary artery After fat tissue removal, the swine left coronary arterial anterior descending branch (LAD) was isolated and vascular rings were prepared. These arterial rings kept at 37°C, were suspended in a 20 ml organ chamber filled with Krebs solution being aerated with 95% O 2 /5% CO 2 gas. Two grams of the tension was applied. After equilibration for 1 hr, 60 mMKCl was applied to condition the coronary rings. The test compound was tested for inhibition of the constriction induced by endothelin-1 (3 × 10 -9 M) by adding the test compound when the maximum of endothelin-1 induced constriction was reached. Activity is expressed as percent relaxation of the maximum constriction induced by endothelin-1. The results are given in Table 2. The developed tension of rings was reached isometrically. % Relaxation Test compound Concentration (M): 1×10 -5 3 ×10 -5 1 X 10 -4 12 14 - 62 13 56 - 78 20 11 - 68 24 37 - 99 111 40 78 - 112 35 83 - 114 44 75 - Note: The above test compound numbers correspond to Examples below. The results from the above bioassays demonstrate that the compound represented by formula (I) or the salt thereof exhibits endothelin-1 antagonistic action. Test 3 Determination of cathepsin B inhibitory activity Cathepsin B (produced by Sigma) was diluted with 100 mM sodium acetate buffer (pH 5.5) to a concentration of 30 µg/ml. To 1 µl of this enzyme dilution, 46 µl of diluent, 2 µl of 0.1 M DTT and 25 µl of activator/buffer (340 mM sodium acetate, 60 mM acetic acid, 4 mM EDTA disodium salt, pH 5.5) were added. To this mixture, a 1 µl sample, diluted to 10 -3 M with dimethylsulfoxide (DMSO), and 25 µl of 20 µM Z-Phe-Arg-NH-Mec (enzyme substrate solution) were added. After the mixture was incubated at 37°C for 20 minutes, 100 µl of a stop solution (100 mM sodium monochloroacetate, 30 mM sodium acetate, pH 4.3) was added. The reaction was carried out on a 96-well fluoroplate (produced by Labo-Systems). After the reaction was stopped, the absorbance of free aminomethyl-coumarin was determined by excitation at 365 nm and emission at 450 nm, using Fluorescence Concentration Analyzer (produced by Baxter). One µl of sample-free DMSO was added for control, and the absorbance from reaction of this control was defined as 100% activity. For samples of under 10% residual activity, further dilutions were assayed for residual activity as described above to obtain the IC 50 value. The results are given in Table 3. Compound (Example No.) Cathepsin B Inhibitory Activity [IC 50 (M)] 25 1.2 × 10 -6 31 2.9 × 10 -6 34 9.3 × 10 -6 96 1.9 × 10 -6 98 3.5 × 10 -6 108 1.1 × 10 -6 Test 4 Inhibition of bone resorption The inhibitory effect of compound on bone resorption was measured by the method of Rais 3 [Journal of Clinical Investigation, 44 , 103-116 (1965)]. Specifically, one Sprague-Dawley rat, at 19 days of gestation, was given 50 µCi of 45 Ca (calcium isotope, in CaCl 2 solution) by subcutaneous injection. On the following day, fetal rats were aseptically taken out, both forearm bones (radius and ulna) were cut out from the body of each fetus, and connective tissue and cartilages were removed to maximum possible extent, to yield prepare bone culture samples. Each bone fragment was incubated at 37°C for 24 hours in 0.6 ml of BGJ b medium (Fitton-Jackson modification, produced by GIBCO Laboratories, United States) containing 2 mg/ml bovine serum albumin, after which it was cultured in the same medium as above but containing a 10 µg/ml compound for two more days. 45 Ca radioactivity in the medium and 45 Ca radioactivity in the bone were then measured, and the percent ratio of 45 Ca released from the bone to the medium was calculated using the following equation: For control, bone fractions from fetuses of the same litter were cultured for two days in the absence of the test compound. The mean ± standard deviation for the values from five bone fragments in each group were calculated, and their percent ratios to the control were calculated. The results are given in Table 4. Compound (Example No.) Inhibition of Bone Resorption [ 45 Ca released (percent ratio to control)] 25 72 34 75 65 74 94 76 96 81 98 87 108 85 111 75 115 85 Examples The present invention is hereinafter described in more detail by means of the following reference examples and working examples, which are not to be construed as limitative. Figures for melting point were obtained by the hot plate method and remain uncorrected. In the description below, Me, Et, Ph, Bz and Ac represent a methyl group, an ethyl group, a phenyl group, a benzyl group and an acetyl group, respectively. Reference Example 1 A mixture of methyl 4-methylphenylsulfonyldithiocarbamate (2.60 g) and xylene (20 ml) was refluxed with heating for 4.5 hours. After solvent removal, the residue was dissolved in acetone (20 ml), and 2-amino-4, 6-dimethylpyridine (1.22 g) was added, followed by stirring at room temperature for 30 minutes. The separating crystal was collected by filtration and recrystallized from ethyl acetate-chloroform-methanol to yield 1-(4, 6-dimethyl-2-pyridyl)-3-(4-methylphenyl) sulfonyl-2-thio urea (2.96 g, yield 88%) as a light yellow needle. Melting point: 167 to 168°C (decomposed) Elemental analysis (for C 15 H 17 N 3 O 2 S 2 ): Calculated (%): C, 53.71; H, 5.11; N, 12.53 Found (%): C, 53.49 ; H, 5.09 ; N, 12.29 Reference Examples 2 through 78 The compounds listed in Tables 5 through 12 were obtained in the same manner as in Reference Example 1. Example 1 To a mixture of 1-(4,6-dimethyl-2-pyridyl)-3-(4-methylphenyl) sulfonyl-2-thiourea (2.90 g) and chloroform (50 ml), sulfuryl chloride (1.28 g) was added. After being stirred at room temperature for 15 minutes, the mixture was refluxed with heating for 30 minutes. The reaction mixture was concentrated, and the resulting crystal was collected by filtration and suspended in water. After pH adjustment to 7 by the addition of saturated aqueous sodium bicarbonate, the suspension was stirred at room temperature for 1 hour. The separating crystal was collected by filtration and recrystallized from chloroform-methanol to yield 5, 7-dimethyl-2-(4-methylphenyl) sulfonylimino-2H-[1, 2, 4]thiadiazolo[2, 3- a ]pyridine (2.40 g, yield 83%) as a colorless needle. Melting point: 228 to 229°C (decomposed) Elemental analysis (for C 15 H 15 N 3 O 2 S 2 ): Calculated (%): C, 54.03 ; H, 4.53 ; N, 12.60 Found (%): C, 54.00 ; H, 4.50 ; N, 12.40 Examples 2 through 19 The compounds listed in Tables 13 and 14 were obtained in the same manner as in Example 1. Example 20 To a mixture of 1-[5-ethyl-4-(5, 6, 7, 8-tetrahydro-2-naphthyl)-2-thiazolyl]-3-(4-methylphenyl) sulfonyl-2-thiourea (1.40 g) and chloroform (10 ml), sulfuryl chloride (420 mg) was added. After being stirred at room temperature for 2 hours, the reaction mixture was concentrated, the residue was treated with ethanol, and the resulting crystal was collected by filtration and recrystallized from dichloromethane-ethanol to yield 5-ethyl-2-(4-methylphenyl) sulfonylimino-6-(5, 6, 7, 8-tetrahydro-2-naphthyl)-2H-thiazolo[3, 2- b ][1, 2, 4]thiadiazole (1.00 g, yield 72%) as a colorless needle. Melting point: 151 to 152°C Elemental analysis (for C 23 H 23 N 3 O 2 S 3 ): Calculated (%): C, 58.82; H, 4.94; N, 8.95 Found (%): C, 58.85; H, 4.85; N, 8.97 Examples 21 through 83 The compounds listed in Tables 15 through 20 were obtained in the same manner as in Example 20. Example 84 A mixture of 2-[2-(4-methylphenyl) sulfonylimino-6-(5,6,7,8-tetrahydro-2-naphthyl)-2H-thiazolo[3, 2- b ][1,2, 4]thiadiazol-5-yl]ethanol (500 mg), acetic anhydride (1 ml) and pyridine (5 ml) was stirred at room temperature for 1 hour. The reaction mixture was added to water, and the resulting crystal was collected by filtration and washed with water. The obtained crystal was subjected to silica gel chromatography and eluted with ethyl acetate-hexane (1:1, v/v). The separating crystal was recrystallized from dichloromethane-methanol to yield 2-[2-(4-methylphenyl)sulfonylimino-6-(5, 6, 7, 8-tetrahydro-2-naphthyl)-2H-thiazolo [3, 2- b ][1, 2, 4]thiadiazol-5-yl]ethyl acetate (355 mg, yield 65%) as a colorless needle. Melting point: 126 to 127°C Elemental analysis (for C 25 H 25 N 3 O 4 S 3 ): Calculated (%): C, 56.90; H, 4.78; N, 7.96 Found (%): C, 56.69; H, 4.78; N, 7.95 Example 85 3-[4-(5-Methyl-2-(4-methylphenyl) sulfonylimino-2H-thiazolo[3,2- b ][1,2, 4]thiadiazol-6-yl]phenyl]propionic acid (500 mg) was dissolved in tetrahydrofuran (10 ml). To this solution were added dimethylformamide (one drop) and oxalyl chloride (160 mg) at room temperature. After mixture stirring for 2 hours, the solvent was distilled off. The residue was dissolved in dichloromethane (10 ml), and a solution of 3,4-(dimethoxy) aniline (165 mg) and triethylamine (110 mg) in dichloromethane (5 ml) was added. After stirring at room temperature for 1 hour, the reaction mixture was washed with 2 N hydrochloric acid and water, and dried (magnesium sulfate), after which the solvent was distilled off. The residue was subjected to silica gel chromatography and eluted with ethyl acetate-chloroform (1:1, v/v) to yield a crystal of N-(3, 4-dimethoxyphenyl)-3-[4-[5-methyl-2-(4-methylphenyl) sulfonylimino-2H-thiazolo[3,2-b][1,2, 4]thiadiazol-6-yl]phenyl]propionamide (425 mg, yield 65%). This product was recrystallized from dichloromethane-ethanol to yield a colorless prismatic crystal. Melting point: 203 to 204°C Elemental analysis (for C 29 H 28 N 4 O 5 S 3 0.5H 2 O): Calculated (%): C, 56.38; H, 4.73; N, 9.07 Found (%): C, 56.42; H, 4.75; N, 8.95 Examples 86 and 87 The compounds listed in Table 21 were obtained in the same manner as in Example 85. Reference Examples 79 through 95 The compounds listed in Tables 22 and 23 were obtained in the same manner as in Reference Example 1. Reference Example 96 A mixture of N-[4-(4-cyclohexylphenyl)-5-methyl-2-thiazolyl]thiourea (1.00 g), 4-methoxy-2,6-dimethylphenylsulfonamide (1.30g), potassium carbonate (500 mg) and xylene (40 ml) was refluxed with heating for 2 hours. After ethyl acetate (200 ml) was added, the mixture was washed with 2 N-hydrochloric acid and water and dried (magnesium sulfate), after which the solvent was distilled off. The residue was subjected to silica gel chromatography and eluted with methanol-chloroform (5:95, v/v) to yield a crystal of 1-[4-(4-cyclohexylphenyl)-5-methyl-2-thiazolyl]-3-(4-methoxy-2,6-dimethylphenylsulfonyl)-2-thiourea (890 mg, yield 56%). This product was recrystallized from dichloromethane-methanol to yield a colorless prismatic crystal. Melting point: 177 to 178°C Elemental analysis (for C 26 H 31 N 3 O 3 S 3 ): Calculated (%): C, 58.89; H, 5.90; N, 7.93 Found (%) : C, 58.55; H, 5.89; N, 7.93 Reference Examples 97 through 105 The compounds listed in Table 24 were obtained in the same manner as in Reference Example 96. Examples 88 through 117 The compounds listed in Tables 25 through 27 were obtained in the same manner as in Example 20. Example 118 A crystal of N-[2-(3-indolyl)ethyl]-2-(4-methylphenyl)sulfonylimino-6-(5,6,7,8-tetrahydro-2-naphthyl)-2H-thiazolo[3,2- b ][1,2,4]thiadiazol-5-ylacet-amide (195 mg, yield 20%) was obtained in the same manner as in Example 85. This product was recrystallized from chloroform-methanol to yield a colorless prismatic crystal. Melting point: 210 to 211°C Elemental analysis (for C 33 H 31 N 5 O 3 S 3 ·0.5H 2 O): Calculated (%):C, 60.90; H, 4.96; N, 10.76 Found (%):C, 61.09; H, 4.91; N, 10.66 Formulation Examples (A) An endothelin receptor antagonist comprising as an active ingredient the compound represented by the formula (I) of the present invention or a pharmaceutically acceptable salt thereof can be used in accordance with, for example, the following formulations. 1. Capsules (1) the compound of Example 23 10 mg (2) lactose 90 mg (3) fine crystalline cellulose 70 mg (4) magnesium stearate 10 mg one capsule 180 mg (1), (2), (3) and a half of (4) are mixed and granulated. To the granules is added the remainder of (4), and the whole is filled into gelatin capsules. 2. Tablets (1) the compound of Example 23 10 mg (2) lactose 35 mg (3) corn starch 150 mg (4) fine crystalline cellulose 30 mg (5) magnesium stearate 5 mg one tablet 230 mg (1), (2), (3), two thirds of (4) and a half of (5) are mixed and granulated. To the granules are added the remainders of(4) and (5), followed by subjecting the granules to compression molding. 3.Injections (1) a sodium salt of the compound of Example 39 10 mg (2) inositol 100 mg (3) benzyl alcohol 20 mg one ampoule 130 mg (1), (2) and (3) are dissolved in distilled water for injection to make the whole volume 2 ml, which is filled into an ampoule. The whole process is conducted under sterile conditions. (B) A cathepsin B inhibitor comprising as an active ingredient the compound represented by the formula (I) of the present invention or a pharmaceutically acceptable salt thereof can be used in accordance with, for example, the following formulations. 1.Capsules (1) the compound of Example 25 10 mg (2) lactose 90 mg (3) fine crystalline cellulose 70 mg (4) magnesium stearate 10 mg one capsule 180 mg (1), (2), (3) and a half of (4) are mixed and granulated. To the granules is added the remainder of (4), and the whole is filled into gelatin capsules. 2. Tablets (1) the compound of Example 25 10 mg (2) lactose 35 mg (3) corn starch 150 mg (4) fine crystalline cellulose 30 mg (5) magnesium stearate 5 mg one tablet 230 mg (1), (2), (3), two thirds of (4) and a half of (5) are mixed and granulated. To the granules are added the remainders of (4) and (5), followed by subjecting the granules to compression molding. 3. Injections (1) a sodium salt of the compound of Example 39 10 mg (2) inositol 100 mg (3) benzyl alcohol 20 mg one ampoule 130 mg (1), (2) and (3) are dissolved in distilled water for injection to make the whole volume 2 ml, which is filled into an ampoule. The whole process is conducted under sterile conditions. (C) A bone resorption suppressor comprising as an active ingredient the compound represented by the formula (I) of the present invention or a pharmaceutically acceptable salt thereof can be used in accordance with, for example, the following formulations. 1. Capsules (1) the compound of Example 25 10 mg (2) lactose 90 mg (3) fine crystalline cellulose 70 mg (4) magnesium stearate 10 mg one capsule 180 mg (1), (2), (3) and a half of (4) are mixed and granulated. To the granules is added the remainder of (4), and the whole is filled into gelatin capsules. 2.Tablets (1) the compound of Example 25 10 mg (2) lactose 35 mg (3) corn starch 150 mg (4) fine crystalline cellulose 30 mg (5) magnesium stearate 5 mg one tablet 230 mg (1), (2), (3), two thirds of (4) and a half of (5) are mixed and granulated. To the granules are added the remainders of (4) and (5), followed by subjecting the granules to compression molding. 3. Injections (1) a sodium salt of the compound of Example 39 10 mg (2) inositol 100 mg (3) benzyl alcohol 20 mg one ampoule 130 ms (1), (2) and (3) are dissolved in distilled water for injection to make the whole volume 2 ml, which is filled into an ampoule. The whole process is conducted under sterile conditions.

Claims: A compound represented by one of the following formulae: wherein R is a hydrocarbon group selected from a linear or branched alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, cycloalkadienyl group, and aryl group, or a heterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl; R 1 , R 2 , R 3 and R 4 independently represent (1) hydrogen, (2) halogen, (3) a hydroxyl group which may be substituted, (4) an amino group which may be substituted, or the two substituents on the nitrogen atom of the amino group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having C 1-6 allyl group, an aralkyl group, or an aryl group at the 4-position, (5) a thiol group which may be substitued, (6) a carboxyl group which may be esterified, (7) a hydrocarbon group selected from a linear or branched alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, cycloalkadienyl group, and an aryl group or (8) a hoterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl; and the adjoining two substituents of R 1 , R 2 , R 3 , and R 4 may cooperate to form a ring selected from : Said rings may be substituted by one or two methyl, ethyl and propyl group at any possible positions at least one of R 1 , R 2 , R 3 , and R 4 is different from hydrogen; R 5 and R 6 independently represent hydrogen, halogen, a carboxyl group which may be esterified, a hydrocarbon group selected from a linear or branched alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, cycloalkadienyl group, and aryl group or a heterocyclic group selected from furyl, thienyl, pyridyl, pyrimidinyl, indolyl, isoindolyl, azetidinyl, oxazetanyl, thietanyl, pyrrolidinyl, tetrahydrofuryl, thiolanyl, piperidyl, tetrahydropyranyl, morpholinyl, thiomorpholinyl and piperazinyl; the adjoining substituents R 5 and R 6 may cooperate to form a ring selected from: Said rings may be substituted by one or two methyl, ethyl and propyl group at any possible positions ; if R, R 1 , R 2 , R 3 , R 4 , R 5 or R 6 represents a hydrocarbon group as mentioned above, it may be optionally substituted by (1) cycloalkyl, (2) aryl, (3) aromatic heterocyclic group selected from furyl, thienyl,pyridyl and pyrimidinyl, (4) acyl groups, (5) carboxyl which may be esterified, (6) amino which may be substituted, or the two substituents on the nitrogen atom of the amino group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1 -C 6 alkyl group, an aralkyl group, or an aryl group at the 4-position. (7) carbamoyl which may be substituted, or the two substituents on the nitrogen atom of the carbamoyl group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1-6 alkyl group, an aralkyl group, or an aryl group at the 4-position, (8) hydroxyl which may be substituted, (9) thiol which may be substituted, (10) sulfo, (11) cyano, (12) nitro, or (13) halogen; in case that said hydrocarbon group is an alicyclic hydrocarbon group or an aryl group, further examples of substituents include C 1-6 alkyl groups C 2-6 alkenyl groups, C 2-6 alkinyl groups and aralkyl groups; further, in case that said hydrocarbon group is an aryl group, two adjoining hydroxyl groups, which may be substituted for, on the aryl group may cooperate therewith to form a heterocyclic ring of the following formula: ; of the substituents in the hydrocarbon group which may be substituted for, each of C 1-6 alkyl groups and aryl groups may have additional one or two of halogens, carboxyl groups which may be esterified including methoxycarbonyl, ethoxycarbonyl and propoxycarbonyl and carbamoyl groups which may be substituted for at any possible positions by C 1-3 alkyls which may be substituted for by an alkoxycarbonyl selected from ethoxycarbonyl, methoxycarbonyl, propoxycarbonyl, and phenyls which may be substituted for by a C 1-3 alkyl or halogen; if R, R 1 , R 2 , R 3 , R 4 , R 5 or R 6 represents a heterocyclic group as mentioned above, it may be optionally substituted by (1) C 1-6 alkyl, (2) C 2-6 alkenyl, (3) C 2-6 alkynyl, (4) cycloalkyl, (5) aryl, (6) aromatic heterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl, (7) aralkyl, (8) acyl, (9) carboxyl which may be esterified, (10) amino which may be substituted, or the two substituents on the nitrogen atom of the amino group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1 -C 6 alkyl group, an aralkyl group, or an aryl group at the 4-position, (11) carbamoyl which may be substituted, or the two substituents on a nitrogen atom of the carbamoyl group may cooperate therewith to form a cyclic amino group selected from 1-azetidinyl, 1-pyrrolidinyl, piperidino, morpholino, 1-piperazinyl and 1-piperazinyl having a C 1 -C 6 alkyl group, an aralkyl group, or an aryl group, (12) hydroxyl which may be substituted, (13) thiol which may be substituted, (14) sulfo, (15) cyano group, (16) nitro, or (17) halogen ; wherein the aryl group of the aralkyl group may have one or two substituents at any possible positions selected from C 1 -C 6 alkyl groups, C 2 -C 6 alkenyl groups, C 2 -C 6 alkynyl groups, cycloalkyl groups, aryl groups, aromatic heterocyclic groups selected from furyl, thienyl, pyridyl and pyrimidinyl, aralkyl groups, amino groups which may be substituted, acyl groups, carbamoyl groups which may be substituted, hydroxyl groups which may be substituted, carboxyl groups which may be esterified, thiol groups which may be substituted, sulfo groups, cyano groups, nitro groups and halogens ; wherein the substituents of the hydroxyl group, amino group, thiol group and carbamoyl group which may be substituted are selected from C 1 -C 6 alkyl, cycloalkyl group, aryl group, aromatic heterocyclic group selected from furyl, thienyl, pyridyl and pyrimidinyl, aralkyl, acyl group or carboxyl group which may be esterified, wherein the acyl groups are selected from a C 1-6 alkanoyl group, a C 2-6 alkenoyl group, a cycloalkanecarbonyl group, an alkanesulfonyl group, an aroyl group, an arylalkanoyl group, an arylalkenoyl group, an arenesulfonyl group, an aromatic heterocyclic carbonyl group selected from furoyl, thenoyl, nicotinoyl, isonicotinoyl, pyrrolecarbonyl, oxazolecarbonyl, imidazolecarbonyl and pyrazole carbonyl, and an aromatic heterocyclic C 1-6 alkanoyl group, the aromatic heterocyclic C 1-6 alkanoyl group being selected from thienylacetyl, thienylpropanoyl, furylacetyl, thiazolylacetyl, 1,2,4-thiadiazolylacetyl and pyridylacetyl; the substituents in the carbamoyl group which may be substituted for in the substituent for the hydrocarbon group which may be substituted for may be a tetrahydronaphthyl which may have one or two C 1-3 alkyls at any possible positions; of the substituents in the carbamoyl group which may be substituted for, C 1-6 alkyls, cycloalkyl groups and aryl groups may have at any possible positions one or two of carboxyl groups which may be esterified, cycloalkyl groups and hydroxyl groups which may be substituted for; in case that the substituents in the carbamoyl group which may be substituted for is a cycloalkyl group or an aryl group, said substituent may have C 1-3 alkyl groups which may be substituted by a phosphono group which may be esterified including ethylphosphono, diethylphosphono, methylphosphono or dimethylphosphono groups and a carboxyl group which may be esterified; two of the substituents in the carbamoyl group which may be substituted for may cooperate with the adjacent nitrogen atom to form a heterocyclic ring: which may have 1 to 2 substituents at any possible positions selected from C 1-6 alkyl groups, carboxyl groups which may be esterified, hydroxyl groups which may be substituted for and carbamoyl groups which may be substituted for; or a pharmaceutically acceptable salt thereof. The compound according to claim 1 wherein the alkyl group is C 1-6 alkyl, the alkenyl group is C 2-6 alkenyl and the alkynyl group is C 2-6 alkynyl. The compound according to claim 1, wherein the aryl group is phenyl, naphthyl or tetrahydro-2-naphthyl. A method of producing a compound as defined in claim 1, by cyclizing a compound represented by the following formulae: wherein R, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 have the same definitions as mentioned in claim 1. The method according to claim 4, wherein the alkyl group is C 1-6 alkyl, the alkenyl group is C 2-6 alkenyl and the alkynyl group is C 2-6 alkynyl. The method according to claim 4, wherein the aryl group is phenyl, naphthyl or tetrahydro-2-naphtyl. Compound as defined in anyone of claims 1 to 3 for use as a medicament. An endothelin receptor antagonist comprising as an active ingredient a compound as defined in anyone of claims 1 to 3. A cathepsin B inhibitor comprising as an active ingredient a compound as defined in anyone of claims 1 to 3. A bone resorption suppressor containing as an active ingredient a compound as defined in anyone of claims 1 to 3. Use of a compound represented by the formulae (I) and (II) as defined in anyone of claims 1 to 3 or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for therapeutic application as an endothelin receptor antagonist. Use of a compound represented by the formulae (I) and (II) as defined in anyone of claims 1 to 3 or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for therapeutic application as a cathepsin B inhibitor. Use of a compound represented by the formulae (I) and (II) as defined in anyone of claims 1 to 3 or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for therapeutic application as a bone resorption suppressor. Use of a compound represented by the formulae (I) and (II) as defined in anyone of claims 1 to 3 or a pbarmaoeutically acceptable salt thereof, for the manufacture of a medicament for prevention and treatment of osteoporosis, inflammatory joint diseases, myodystrophy, vacuolar distal myopathy and Alzheimer's disease.

Inventors: FUJISAWA YUKIO, MIZOGUCHI JUNJI, MOMOSE YU, SOHDA TAKASHI, TERASHITA ZEN-ICHI, FUJISAWA, YUKIO, MIZOGUCHI, JUNJI, MOMOSE, YU, SOHDA, TAKASHI, TERASHITA, ZEN-ICHI
Applicants: TAKEDA CHEMICAL INDUSTRIES LTD, TAKEDA CHEMICAL INDUSTRIES, LTD.
Application year: 1993
Main classification: C07D513
IPC codes: C07D513