Tetrazoleacetic acid derivatives having aldose reductase inhibitory activity

Abstract: A tetrazoleacetic acid derivative represented by the following general formula (I): [in Formula (I), R₁ represents a hydrogen atom or an alkyl group; R₂ represents a hydrogen atom, an alkyl group, an aralkyl group, a halogen atom, a haloalkyl group, a hydroxyl group, an alkoxy group, an alkoxyalkyl group, an amino group, an aryl group, an alkyl or aryl thio group, an alkyl or aryl carbonylamino group, an alkyl or aryl sulfonylamino group, an alkyl or aryl aminosulfonyl group, an alkyl or aryl sulfonyl group or an alkyl or aryl sulfinyl group; and X represents -O- or -S- ] except for [5-(2-thienyl)tetrazol-1-yl] acetic acid, [5-(2-furyl)tetrazol-1-yl] acetic acid and ethyl esters thereof, or a salt thereof shows excellent aldose reductase inhibitory activity, has low toxicity to organisms and is quite effective as an essential component of a preventive medicine and/or remedy for diabetic complications.

Description: The present invention relates to compounds having aldose reductase inhibitory activity and more specifically to tetrazoleacetic acid derivatives and aldose reductase inhibitors which comprise the tetrazoleacetic acid derivative as an effective component and which are effective as a preventive medicine and/or remedy for diabetic complications as well as a method for alleviating or reducing diabetic complications. It has been known that aldose reductase inhibitors are effective for prevention and/or treatment of diabetic complications. This is detailed in the article of Dr. Tsuyoshi TANIMOTO [Division of Biological Chemistry and Reference Standards, National Institute of Hygienic Sciences] (see Farumashia, 1988, 24 , No. 5, pp. 459-463). This article discloses the chemical structures and 50% inhibitory concentrations (IC 50 ) of representative aldose reductase inhibitors such as Alrestatin, Tolrestat, 4-Isopropyl-BPOC, Sorbinil, M-79175, Alconil, ADN-138, Epalrestat, CT-112 and Statil. Compounds represented by the following general formula (III): [in Formula (III), R 1 represents a hydrogen atom or a group: -A-COOR 5 (wherein A represents an alkylene group having 1-4 carbon atoms and R 5 represents a hydrogen atom or a lower alkyl group) and R 2 , R 3 and R 4 may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a phenyl group, a phenoxy group, a nitro group, a residue represented by the formula: - NHCOCOOR 6 (wherein R 6 represents a hydrogen atom or a lower alkyl group) or a residue represented by the following formula: (wherein A and R 5 are the same as those defined above)] having aldose reductase inhibitory activity are disclosed in Japanese Patent Unexamined Publication No. Hei 4-270271. [5-(2-thienyl)tetrazol-1-yl] acetic acid and ethyl ester thereof as well as [5-(2-furyl)tetrazol-1-yl] acetic acid and ethyl ester thereof are reported in an article of A. K. Zorenzen, Acta Chem. Scand., 1972, 26 , p. 541. However, this article only discloses a method for preparing these substances, but there is no disclosure about the biological activity thereof. Accordingly, an object of the present invention is to provide compounds which show excellent aldose reductase inhibitory activity, have low toxicity to organisms and are quite effective as a preventive medicine and/or remedy for diabetic complications and more specifically to provide novel tetrazoleacetic acid derivatives. Another object of the present invention is to provide an aldose reductase inhibitor which comprises the tetrazoleacetic acid derivative as an effective component and which is effective as a preventive medicine and/or remedy for diabetic complications. According to an aspect of the present invention, there are provided novel tetrazoleacetic acid derivatives represented by the following general formula (I): [in Formula (I), R 1 represents a hydrogen atom or an alkyl group; R 2 represents a hydrogen atom, an alkyl group, an aralkyl group, a halogen atom, a haloalkyl group, a hydroxyl group, an alkoxy group, an alkoxyalkyl group, an amino group, an aryl group, an alkyl or aryl thio group, an alkyl or aryl carbonylamino group, an alkyl or aryl sulfonylamino group, an alkyl or aryl aminosulfonyl group, an alkyl or aryl sulfonyl group or an alkyl or aryl sulfinyl group; and X represents -O- or -S- ] except for [5-(2-thienyl)tetrazol-1-yl] acetic acid, [5-(2-furyl]tetrazol-1-yl] acetic acid and ethyl esters thereof, or a salt thereof. According to another aspect of the present invention, there is provided a pharmaceutical composition having aldose reductase inhibiting activity which comprises a tetrazoleacetic acid derivative represented by the following general formula (II): [in Formula (II), R 1 represents a hydrogen atom or an alkyl group; R 2 represents a hydrogen atom, an alkyl group, an aralkyl group, a halogen atom, a haloalkyl group, a hydroxyl group, an alkoxy group, an alkoxyalkyl group, an amino group, an aryl group, an alkyl or aryl thio group, an alkyl or aryl carbonylamino group, an alkyl or aryl sulfonylamino group, an alkyl or aryl aminosulfonyl group, an alkyl or aryl sulfonyl group or an alkyl or aryl sulfinyl group; and X represents -O- or -S-] or a salt thereof and a pharmaceutical acceptable carrier. According to a further aspect of the present invention, there is provided a tetrazoleacetic acid derivative represented by the general formula (II) for use in a method for alleviating or reducing diabetic complications. The tetrazoleacetic acid derivatives and the aldose reductase inhibitor as well as their use for alleviating diabetic complications according to the present invention will hereunder be explained in more detail. First, each substituent in Formulae (I) and (II) will be explained in detail. The term "alkyl", taken alone or as part of another group (e.g. aralkyl) comprises alkyl residues having 1 to 8,preferably 1 to 6 and especially 1 to 4 carbon atoms. Similarily the term "aryl" comprises aryl residues having 6 to 10 carbon atoms. The alkyl group represented by R 1 or R 2 is, for instance, methyl, ethyl, propyl, isopropyl, butyl, isobutyl or t-butyl group; the aralkyl group includes, for instance, phenylpropyl and benzyl group; examples of the alkoxy groups are methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy and t-butoxy groups; examples of the alkoxyalkyl groups are methoxymethyl and butoxymethyl groups; the haloalkyl groups are, for instance, mono-, di- or tri-haloalkyl groups such as chloromethyl, bromomethyl, fluoromethyl and chlorobutyl groups; the alkyl or aryl thio groups are, for instance, methylthio, ethylthio, butylthio and phenylthio groups; the alkylaminosulfonyl groups include, for instance, mono- or di-alkylaminosulfonyl groups such as methylaminosulfonyl, ethylaminosulfonyl, propylaminosulfonyl and butylaminosulfonyl groups; the alkyl or aryl sulfonylamino groups are, for instance, methylsulfonylamino, ethylsulfonylamino, butylsulfonylamino and phenylsulfonylamino groups; examples of the alkyl or aryl carbonylamino groups are methylcarbonylamino, ethylcarbonylamino, propylcarbonylamino and phenethylcarbonylamino groups; examples of the alkyl or aryl sulfonyl groups are methylsulfonyl, ethylsulfonyl, butylsulfonyl and piperidinosulfonyl groups; and examples of the alkylsulfinyl groups are methylsulfinyl, ethylsulfinyl and butylsulfinyl groups. These substituents may be present on any position on the furan or thiophene ring. In addition, salts of the foregoing compounds represented by Formulae (I) and (II) wherein R 1 is a hydrogen atom are pharmaceutically acceptable ones and typical examples thereof include inorganic salts such as alkali metal salts (for instance, sodium salts and potassium salts), alkaline earth metal salts (for instance, calcium salts and magnesium salts) and ammonium salts; and organic salts such as organic amine salts (for instance, triethylamine salts, pyridine salts and ethanolamine salts) and salts with basic amino acids, for instance, arginine. The aldose reductase inhibitors (pharmaceutical compositions) according to the present invention comprise , as an essential component, at least one compound represented by the foregoing general formula (II) and are effective as preventive medicines and/or remedies for diabetic complications. It has been known that the term "diabetic complications" means a variety of pathema such as peripheral disorder, retinopathy, nephrosis, cataract and keratopathy. These diseases or disorders are triggered by hyperglycemia resulted from the diabetic disease, that the production of sorbitol in the polyol metabolic pathway is correspondingly abnormally accelerated and that, as a result, a large amount of sorbitol is accumulated within cells. This leads to the onset of these diseases. The aldose reductase inhibitors of the present invention can suppress the sorbitol-production through strong inhibition of the activity of the aldose reductase which catalyzes the sorbitol-production in the foregoing polyol metabolic pathway and thus show excellent preventive and/or treating effects for these various diabetic complications. The dose of the compounds of Formulae (I) and (II) is appropriately determined depending on the conditions or symptoms of patients to be treated, but in general ranges from 1 to 1,000 mg per day for adult which is administered at one time or over several times. The compounds may be administered through any route for medication such as oral administration, subcutaneous injection, intravenous injection and local administration. The aldose reductase inhibitors of the present invention may usually comprise, in addition to the foregoing compounds as the essential components, pharmaceutically acceptable carriers, vehicles and other additives. The inhibitors of the invention may be used in any dosage form such as tablets, powder, fine particles, granules, capsules, pills, liquid preparations, solutions and suspensions for injection and eye drops. Then methods for preparing the compounds (I) as the essential components, conditions therefor or the like will be detailed below with reference to the following reaction schemes. Reaction Scheme 1: Preparation of Tetrazole Ring Reaction Scheme 2: Conversion of R 1 Into Hydrogen Atom The reaction scheme 1 shows the tetrazole ring formation reaction in which N-aryloylaminoalkyl carboxylate is reacted with a chlorinating agent such as phosphorus pentachloride, thionyl chloride or thionyl chloride/N,N-dimethylformamide to obtain a corresponding imidoyl chloride compound and then the product is reacted with sodium azide to obtain an intended compound of Formula (I). The reaction for obtaining the imidoyl chloride can be carried out in an organic solvent such as benzene, toluene or methylene chloride. In general, the reaction is preferably performed at a temperature of not more than room temperature. In the subsequent cyclization reaction, it is preferred to use sodium azide in an amount of 2 to 6 times that of the imidoyl chloride as an intermediate. The cyclization reaction is in general performed at room temperature in N,N-dimethylformamide. The reaction scheme 2 means that the compounds of Formula (I) in which R 1 is a hydrogen atom may be prepared by hydrolysis of the carboxylic acid ester obtained in the reaction scheme 1. The hydrolysis can be performed in the presence of a base such as sodium hydroxide or potassium hydroxide or an acid such as hydrochloric acid, sulfuric acid, acetic acid or trifluoroacetic acid. The compounds of Formula (I) prepared according to the foregoing method are separated and purified by a chemical operation commonly employed such as extraction, recrystallization and/or column chromatography and the products thus separated and purified are used as essential components for the aldose reductase inhibitors of the present invention. The present invention will hereinafter be described in more detail with reference to the following non-limitative working Examples and the effects practically achieved by the present invention will also be discussed in detail with reference to Test Examples. Example 1 (1-1) preparation of methyl [5-(2-thienyl)tetrazol-1-yl] acetate: To a solution of 1 g (5.02 mM) of N-(2-thenoyl)glycine methyl ester in 15mℓ of anhydrous methylene chloride, there was slowly added 1.5 g (7.2 mM) of phosphorus pentachloride at room temperature with stirring, the resulting mixture was stirred for additional 30 minutes and the reaction solution was concentrated at 40 ° C under reduced pressure. The resulting residue was dissolved in 5 mℓ of N,N-dimethylformamide. The solution was dropwise added to a suspension of 1.6 g (24.6 mM) of sodium azide in 3 mℓ of N,N-dimethylformamide at room temperature over 30 minutes with stirring. After the dropwise addition and agitation for additional 30 minutes at room temperature, the mixture was poured into ice-water and extracted with ethyl acetate. The organic phase obtained was washed with water, dried over anhydrous sodium sulfate and then concentrated under reduced pressure. The resultant residue was subjected to silica gel column chromatography (eluent: ethyl acetate/benzene =1/20) for separation and purification to thus give 0.59 g (yield 52.4%) of methyl [5-(2-thienyl)tetrazol-1-yl] acetate. M.P. = 73 - 74° C N.M.R. (CDCℓ 3 ) δ ppm: 3.84 (s, 3H); 5.34 (s, 2H); 7.24 (dd, 1H, J = 5.20, 3.60 Hz); 7.58 (dd, 1H, J = 3.60, 1.20 Hz); 7.65 (dd, 1H, J = 5.20, 1.20 Hz). I.R. ν KBr (cm -1 ): 3400, 1730, 1650, 1540, 1370, 1230. Mass: m/z 224 [M + ] The following compounds were prepared in the same manner used in Example (1-1): (1-2) methyl [5-(3-methyl-2-thienyl)tetrazol-1-yl ] acetate (yield 51.1%) Starting material: N-(3-methyl-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.43 (s, 3H); 3.80 (s, 3H); 5.25 (s, 2H); 7.07 (d, 1H, J = 5.0 Hz); 7.52 (d, 1H, J = 5.0 Hz). I.R. ν NaCl (cm -1 ): 3100, 2950, 1760, 1440, 1220, 1000. Mass: m/z 238 [M + ] (1-3) methyl [5-(4-methyl-2-thienyl)tetrazol-1-yl ] acetate (yield 48.8%) Starting material: N-(4-methyl-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.34 (s, 3H); 3.83 (s, 3H); 5.33 (s, 2H); 7.22 (d, 1H, J = 1.2 Hz); 7.41 (d, 1H, J = 1.2 Hz). I.R. ν NaCl (cm -1 ): 3090, 2950, 1740, 1580, 1440, 1240. Mass: m/z 238 [M + ] (1-4) methyl [5-(5-methyl-2-thienyl)tetrazol-1-yl ] acetate (yield 50.1%) Starting material: N-[5-methyl-2-thenoyl)glycine methyl ester M.P. = 88 - 89° C. N.M.R. (CDCℓ 3 ) δ ppm: 2.57 (s, 3H); 3.83 (s, 3H); 5.32 (s, 2H); 6.87∼6.89 (m, 1H); 7.36∼7.39 (m, 1H). I.R. ν KBr (cm -1 ): 3440, 1750, 1580, 1510, 1430, 1260, 1230, 1100. Mass: m/z 238 [M + ] (1-5) methyl [5-(3-thienyl)tetrazol-1-yl] acetate (yield 52%) Starting material: N-(3-thenoyl)glycine methyl ester M.P. = 106 - 107° C. N.M.R. (CDCℓ 3 ) δ ppm: 3.84 (s, 3H); 5.27 (s, 2H); 7.48 (dd, 1H, J=5.01, 1.20 Hz); 7.56 (dd, 1H, J=5.01, 2.80 Hz); 8.25 (dd, 1H, J=2.80, 1. 20Hz) I.R. ν KBr (cm -1 ): 3100, 1760, 1580, 1440, 1360, 1230. Mass: m/z 224 [M + ] (1-6) methyl [5-(2-furyl)tetrazol-1-yl] acetate (yield 24%) Starting material: N-(2-furoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 3.79 (s, 3H); 5.49 (s, 2H); 6.66 (dd, 1H, J=3.60, 2.01 Hz); 7.36 (dd, 1H, J=3.60, 0.80 Hz); 7.64 (dd, 1H, J=2.01, 0.80Hz) I.R. ν NaCl (cm -1 ): 3120, 3000, 2950, 1750, 1620, 1520, 1440, 1220, 1010. Mass: m/z 208 [M + ] (1-7) methyl [5-(3-furyl)tetrazol-1-yl] acetate (yield 30%) Starting material: N-(3-furoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 3.84 (s, 3H); 5.24 (s, 2H); 6.81 (bs, 1H); 7.63 (bs, 1H); 7.96 (bs, 1H) I.R. ν NaCl (cm -1 ): 3140, 2950, 1750, 1440, 1220. Mass: m/z 208 [M + ] (1-8) methyl [5-(5-ethyl-2-thienyl)tetrazol-1-yl] acetate (yield 44.0%) Starting material: N-[5-ethyl-2-thenoyl)glycine methyl ester M.P. = 45 - 46° C. N.M.R. (CDCℓ 3 ) δ ppm: 1.36 (t, 3H, J=7.70Hz); 2.91 (dq, 2H, J=7.70, 0. 80Hz); 3.83 (s, 3H); 5.32 (s, 2H); 6.91 (dt, 1H, J=3.60, 0.80Hz); 7.40 (d, 1H, J=3.60Hz) I.R. ν KBr (cm -1 ): 2960, 1760, 1580, 1510, 1430, 1270, 1220, 1100, 1000, 820. Mass: m/z 252 [M + ] (1-9) methyl [5-(5-benzyl-2-thienyl)tetrazol-1-yl ] acetate (yield 38.0%) Starting material: N-[5-benzyl-2-thenoyl)glycine methyl ester M.P. = 71 - 72° C. N.M.R. (CDCℓ 3 ) δ ppm: 3.80 (s, 3H); 4.20 (s, 2H); 5.29 (s, 2H); 6.91 (dt, 1H, J=4.01, 1.20Hz); 7.23∼7.38 (m, 5H); 7.39 (d, 1H, J=4.01Hz) I.R. ν KBr (cm -1 ): 3000, 1740, 1580, 1510, 1460, 1420, 1380, 1270, 1240, 800. Mass: m/z 314 [M + ] (1-10) methyl [5-(5-methylthio-2-thienyl)tetrazol-1-yl ] acetate (yield 66%) Starting material: N-[5-methylthio-2-thenoyl)glycine methyl ester M.P. = 64 - 65° C. N.M.R. (CDCℓ 3 ) δ ppm: 2.60 (s, 3H); 3.84 (s, 3H); 5.31 (s, 2H); 7.07 (d, 1H, J=4.00Hz); 7.45 (d, 1H, J=4.00Hz) I.R. ν KBr (cm -1 ): 3470, 1750, 1580, 1480, 1440, 1410, 1360, 1260, 1220, 1100, 990, 790. Mass: m/z 270 [M + ] (1-11) methyl [ 5-(5-bromo-2-thienyl)tetrazol-1-yl] acetate (yield 55.0%) Starting material: N-[5-bromo-2-thenoyl)glycine methyl ester M.P. = 45 - 46 °C. N.M.R. (CDCℓ 3 ) δ ppm: 3.84 (s, 3H); 5.30 (s, 2H); 7.19 (d, 1H, J=4.90Hz); 7.30 (d, 1H, J=4.90Hz) I.R. ν KBr (cm -1 ): 3450, 1740, 1580, 1490, 1440, 1400, 1270, 1240, 1100, 980, 800. Mass: m/z 303 [M + ] (1-12) methyl [5-(2-methyl-3-thienyl)tetrazol-1-yl ] acetate (yield 49.7%) Starting material: N-(2-methyl-3-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.58 (s, 3H); 3.80 (s, 3H); 5.12 (s, 2H); 6.99 (d, 1H, J=5.20Hz); 7.27 (d, 1H, J=5.20Hz) I.R. ν NaCl (cm -1 ): 2950, 1750, 1580, 1500, 1440, 1260, 1220. Mass: m/z 238 [M + ] (1-13) methyl [5-(5-bromomethyl-2-thienyl)tetrazol-1-yl] acetate (yield 50.9%) Starting material: N-(5-bromomethyl-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.49 (s, 3H); 3.85 (s, 3H) ; 5.30 (s, 2H); 7.26∼7.36 (m, 2H). I.R. ν NaCl (cm -1 ): 2950, 1760, 1580, 1500, 1440, 1270, 1220, 1000, 800. Mass: m/z 317 [M + ] (1-14) methyl [5-(5-phenyl-2-thienyl)tetrazol-1-yl ] acetate (yield 47.1%) Starting material: N-(5-phenyl-2-thenoyl)glycine methyl ester M.P. = 133 - 134° C. N.M.R. (CDCℓ 3 ) δ ppm: 3.85 (s, 3H); 5.38 (s, 2H); 7.39 (d, 1H, J=3.80Hz); 7.40∼7.48 (m, 3H); 7.55 (d, 1H, J=3.80Hz); 7.63∼7.66 (m, 2H). I.R. ν KBr (cm -1 ): 3440, 1760, 1580, 1480, 1420, 1220, 750. Mass: m/z 300 [M + ] (1-15) methyl [5-(3-methylcarbonylamino-2-thienyl)tetrazol-1-yl] - acetate; (yield 16.2%) Starting material: N-(3-methylcarbonylamino-2-thenoyl)glycine methyl ester M.P. = 35 - 36° C. N.M.R. (CDCℓ 3 ) δ ppm: 2.31 (s, 3H); 3.84 (s, 3H); 5.45 (s, 2H); 7.56 (d, 1H, J=5.20Hz); 8.34 (d, 1H, J=5.20Hz). I.R. ν KBr (cm -1 ): 3240, 1750, 1580, 1490, 1440, 1220, 1180, 930, 750. Mass: m/z 281 [M + ] (1-16) methyl [5-(3-propylcarbonylamino-2-thienyl)tetrazol-1-yl] - acetate; (yield 22.4%) Starting material: N-(3-propylcarbonylamino-2-thenoyl)glycine methyl ester M.P. = 92 - 93° C. N.M.R. (CDCℓ 3 ) δ ppm: 1.04 (t, 3H, J=7.3Hz); 1.76∼1.90 (m, 2H); 2.51 (t, 3H, J=7.30Hz); 3.84 (s, 3H); 5.46 (s, 2H); 7.56 (d, 1H, J=5.50Hz); 8.37 (d, 1H, J=5.50Hz); 10.75 (bs, 1H). I.R. ν KBr (cm -1 ): 3270, 2940, 1740, 1680, 1580, 1440, 1380, 1260, 1240, 1100, 760. Mass: m/z 309 [M + ] (1-17) methyl [5-(3-phenethylcarbonylamino-2-thienyl)tetrazol-1-yl] acetate; (yield 28.5%) Starting material: N-(3-phenethylcarbonylamino-2-thenoyl)glycine methyl ester M.P. = 96 - 97° C. N.M.R. (CDCℓ 3 ) δ ppm: 2.85 (t, 2H, J=7.70Hz); 3.11 (t, 2H, J=7.70Hz); 3.82 (s, 3H); 5.43 (s, 2H); 7.18∼7.30 (m, 5H); 7.55 (d, 1H, J=5.50Hz); 8.34 (d, 1H, J=5.50Hz); 10.75 (bs, 1H). I.R. ν KBr (cm -1 ): 3300, 1760, 1700, 1580, 1440, 1390, 1220, 1100. Mass: m/z 371 [M + ] (1-18) methyl [5-(5-methyl-2-furyl)tetrasol-1-yl ] acetate; (yield 34.1%) Starting material: N-(5-methyl-2-furoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.39 (d, 3H, J=0.98Hz); 3.80 (s, 3H); 5.45 (s, 2H); 6.25 (dq, 1H, J=3.66, 0.98Hz); 7.23 (d, 1H, J=3.66Hz). I.R. ν NaCl (cm -1 ): 3120, 2950, 1740, 1620, 1570, 1440, 1220, 1020, 790. Mass: m/z 222 [M + ] (1-19) methyl [5-(5-butyl-2-furyl)tetrazol-1-yl] acetate; (yield 27.2%) Starting material: N-(5-butyl-2-furoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 0.95 (t, 3H, J=7.33Hz); 1.31∼1.45 (m, 2H); 1.57∼1.70 (m, 2H); 2.70 (t, 2H, J=7.57Hz); 3.79 (s, 3H); 5.45 (s, 2H); 6.24 (d, 1H, J=3.66Hz); 7.24 (d, 1H, J=3.66Hz). I.R. ν NaCl (cm -1 ): 2950, 1760, 1620, 1560, 1440, 1220, 1020, 790. Mass: m/z 264 [M + ] (1-20) methyl [5-(5-bromo-2-furyl)tetrazol-1-yl] acetate; (yield 34%) Starting material: N-(5-bromo-2-furoyl)glycine methyl ester M.P. = 106 - 107° C N.M.R. (CDCℓ 3 ) δ ppm: 3.84 (s, 3H); 5.45 (s, 2H); 6.58 (d, 1H, J=3.54Hz); 7.31 (d, 1H, J=3.54Hz). I.R.ν KBr (cm -1 ): 3100, 3000, 1730, 1620, 1520, 1440, 1280, 1100, 1000, 780. Mass: m/z 287 [M + ] (1-21) methyl [5-[5-methylthio-2-furyl)tetrazol-1-yl ] acetate; (yield 29%) Starting Material: N-(5-methylthio-2-furoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.48 (s, 3H); 3.82 (s, 3H); 5.47 (s, 2H); 6.55 (d, 1H, J=3.66Hz); 7.32 (d, 1H, J=3.66Hz). I.R. ν NaCl (cm -1 ): 3100, 2950, 1750, 1610, 1500, 1440, 1220, 1100, 1010, 780. Mass: m/z 254 [M + ] (1-22) methyl [5-(2-bromo-3-furyl)tetrazol-1-yl] acetate; (yield 27.4%) Starting material: N-(2-bromo-3-furoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 3.81 (s, 3H); 5.23 (s, 2H); 6.70 (d, 1H, J=2.20Hz); 7.52 (d, 1H, J=2.20Hz). I.R. ν NaCl (cm -1 ): 3150, 2950, 1750, 1620, 1530, 1440, 1220, 960. Mass: m/z 287 [M + ] (1-23) methyl [5-(2-(oct-4-yl]-3-furyl] tetrazol-1-yl ] acetate; (yield 60.4%) Starting material: N- [2(-oct-4-yl)-3-furoyl ] glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 0.82 (t, 6H, J=7.20Hz); 1.10∼1.27 (m, 6H); 1.52∼1.70 (m, 4H); 3.25∼3.31 (m, 1H); 3.81 (s, 3H); 5.16 (s, 2H); 6.40 (d, 1H, J=2.20Hz); 7.48 (d, 1H, J=2.20Hz). I.R. ν NaCl (cm -1 ): 2950, 2850, 1750, 1620, 1530, 1440, 1220, 1000, 960. Mass: m/z 320 [M + ] (1-24) methyl [5-(2-methylthio-3-furyl)tetrazol-1-yl ] acetate; (yield 57.1%) Starting material: N- [2-methylthio-3-furoyl)glycine methyl ester M.P. = 71 - 72° C N.M.R. (CDCℓ 3 ) δ ppm: 2.51 (s, 3H); 3.78 (s, 3H); 5.25 (s, 2H); 6.65 (d, 1H, J=2.20Hz); 7.63 (d, 1H, J=2.20Hz). I.R. ν NaCl (cm -1 ): 3150, 2950, 1750, 1600, 1530, 1430, 1220, 960, 740. Mass: m/z 254 [M + ] (1-25) methyl [5-(3-methylsulfonylamino-2-thienyl)tetrazol-1-yl] acetate: (yield 36.8%) Starting material: N-(3-methylsulfonylamino-2-thenoyl)glycine methyl ester M.P. = 154 - 155 ° C N.M.R. (CDCℓ 3 ) δ ppm: 3.01 (s, 3H); 3.78 (s, 3H); 5.38 (s, 2H); 7.52 (d, 1H, J=5.61Hz); 7.55 (d, 1H, J=5.61Hz); 9.92 (bs, 1H). I.R. ν KBr (cm -1 ): 3150, 3100, 1740, 1560, 1370, 1220, 1150, 760. Mass: m/z 317 [M + ] (1-26) methyl [5-(3-butylsulfonylamino-2-thienyl)tetrasol-1-yl ] acetate: (yield 74.4%) Starting material: N-(3-butylsulfonylamino-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 0.87 (t, 3H, J=7.32Hz); 1.35∼1.44 (m, 2H); 1.57∼1.75 (m, 2H); 3.14 (t, 2H, J=7.94Hz); 3.84 (s, 3H); 5.45 (s, 2H); 7.54 (d, 1H, J=5.49Hz); 7.62 (d, 1H, J=5.49Hz); 9.98 (bs, 1H). I.R. νN a Cℓ (cm -1 ): 3100, 1750, 1560, 1370, 1220, 1150. Mass: m/z 359 [M + ] (1-27) methyl [5-(3-phenylsulfonylamino-2-thienyl)tetrazol-1-yl] acetate: (yield 82.4%) Starting material: N-(3-phenylsulfonylamino-2-thenoyl)glycine methyl ester M.P. = 124 - 125 °C N.M.R. (CDCℓ 3 ) δ ppm: 3.72 (s, 3H); 5.23 (s, 2H); 7.31∼7.47 (m, 5H); 7.53 (d, 1H, J=5.62Hz); 7,58∼7.91 (m, 2H); 10.16 (bs, 1H). I.R. ν KBr (cm -1 ): 3120, 2950, 1750, 1560, 1520, 1430, 1380, 1240, 1160, 760, 580. Mass: m/z 379 [M + ] (1-28) methyl [5-(2-methyl-3-furyl)tetrazol-1-yl ] acetate: (yield 40.0%) Starting material: N-(2-methyl-3-furoyl)glycine methyl ester M.P. = 54.5-56° C N.M.R. (CDCℓ 3 ) δ ppm: 2.58 (s, 3H); 3.82 (s, 3H); 5.19 (s, 2H); 6.44 (d, 1H, J= 2.00Hz); 7.45 (d, 1H, J=2.00Hz). I.R. ν KBr (cm -1 ): 3410, 3150, 1760, 1620, 1540, 1460, 1370, 1230. Mass: m/z 222 [M + ] (1-29) methyl [5- [5-(N-methyl-N- [2-(methoxymethoxy)ethyl)-aminosulfonyl ] -2-thienyl] tetrazol-1-yl ] acetate: (yield 82.4 %) Starting material: N- [5- [N'-methyl-N'- [2-(methoxymethoxy)ethyl ) - aminosulfonyl) -2-thenoyl] glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.77 (s, 3H); 3.14 (t, 2H, J=5.37Hz); 3.32 (s, 3H); 3.59 (t, 2H, J=5.37Hz); 3.72 (s, 3H); 4.56 (s, 2H); 5.21 (s, 2H); 7.25 (d, 1H, J= 5.13Hz); 7.71 (d, 1H, J=5.13Hz). I.R. ν KBr (cm -1 ): 2950, 1750, 1440, 1350, 1220, 1150, 1040, 750, 710. Mass: m/z 405 [M + ] Example 2 (2-1) [5-(2-thienyl)tetrazol-1-yl] acetic acid 0.5 g (2.2mM) of methyl [5-(2-thienyl)tetrazol-1-yl] acetate obtained in Example (1-1) was dissolved in 3 mℓ of methanol, 1mℓ of a 4N aqueous sodium hydroxide solution was added to the resulting solution at room temperature and the mixture was refluxed with heating for one hour. After cooling the mixture to room temperature, it was diluted with water, then impurities were removed with ethyl acetate and the aqueous phase was separated. The aqueous phase was acidified with hydrochloric acid, crystals precipitated out were filtered off, washed with water and recrystallized from a 50% ethanol-water mixture to give 0.39 g (yield 84.4%) of [5-(2-thienyl)tetrazol-1-yl] acetic acid. M.P. = 129 - 130° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 4.9∼6.2 (br, 1H); 5.30 (s, 3H); 7.27∼7.33 (m, 1H); 7.61 (dd, 1H, J=3.60, 1.20Hz); 7.68 (dd, 1H, J= 3.60, 1.20Hz). I.R. ν KBr (cm -1 ): 3380, 1730, 1580, 1350, 1250. Mass: m/z 210 [M + ] The following compounds were prepared in the same manner used in Example (2-1): (2-2) [5-(3-methyl-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 78%) Starting Material: methyl [5-(3-methyl-2-thienyl)tetrazol-1-yl ] acetate M.P. = 165 - 166° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.42 (s, 3H); 3.70 (bs, 1H); 5.20 (s, 2H); 7.06 (d, 1H, J=5.2Hz); 7.53 (d, 1H, J=5.2Hz). I.R. ν KBr (cm -1 ): 3100, 2500, 1720, 1570, 1510, 1420, 1220. Mass: m/z 224 [M + ] (2-3) [5-(4-methyl-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 76%) Starting Material: methyl [5-(4-methyl-2-thienyl)tetrazol-1-yl ] acetate M.P. = 154 - 155° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.34 (s, 3H); 5.29 (bs, 3H); 7.22 (d, 1H, J=1.2Hz); 7.41 (d, 1H, J=1.2Hz). I.R. ν KBr (cm -1 ): 3500, 2550, 1730, 1520, 1450, 1270, 1240, 1120. Mass: m/z 224 [M + ] (2-4) [5-(5-methyl-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 82%) Starting Material: methyl [5-(5-methyl-2-thienyl)tetrazol-1-yl ] acetate M.P. = 150 - 151° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.58 (s, 3H); 5.28 (s, 2H); 5.90 (bs, 1H); 6.88∼6.92 (m, 1H); 7.39∼7.42 (m, 1H). I.R. ν KBr (cm -1 ): 3400, 2990, 1730, 1580, 1520, 1440, 1260, 1240, 1000. Mass: m/z 224 [M + ] (2-5) [5-(3-thienyl)tetrazol-1-yl] acetic acid (yield = 71%) Starting Material: methyl [5-(3-thienyl)tetrazol-1-yl] acetate M.P. = 172 - 173° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 3.33 (bs, 1H); 5.58 (s, 2H); 7.57-(dd, 1H, J=5.20, 1.20Hz); 7.85 (dd, 1H, J=5.20, 2.80Hz); 8.25 (dd, 1H, J=2.80, 1.20Hz). I.R. ν KBr (cm -1 ): 3380, 3120, 1730, 1580, 1280. Mass: m/z 210 [M + ] (2-6) [5-(2-furyl)tetrazol-1-yl] acetic acid (yield = 21%) Starting Material: methyl [5-(2-furyl)tetrazol-1-yl] acetate M.P. = 157 - 158° C (decomposition) N.M.R. (CDCℓ 3 -DMSO-d 6 ) δ ppm: 4.79 (bs, 1H); 5.45 (s, 2H); 6.81 (dd, 1H, J=3.60, 1.60Hz); 7.37 (d, 1H, J=3.6Hz); 8.08 (d, 1H, J=1.70Hz). I.R. ν KBr (cm -1 ): 3010, 2970, 2520, 1730, 1620, 1520, 1220, 1020. Mass: m/z 194 [M + ] (2-7) [5-(3-furyl)tetrazol-1-yl] acetic acid (yield = 30%) Starting Material: methyl [5-(3-furyl)tetrazol-1-yl] acetate M.P. = 150 - 151° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 3.33 (bs, 1H); 5.56 (s, 2H); 7.00 (bs, 1H); 7.97 (bs, 1H); 8.46 (bs, 1H). I.R. ν KBr (cm -1 ): 3370, 2430, 1720, 1620, 1350, 1240. Mass: m/z 194 [M + ] (2-8) [5-(5-ethyl-2-thienyl)tetrazol-1-yl] acetic acid (yield = 82%) Starting Material: methyl [5-(5-ethyl-2-thienyl)tetrazol-1-yl] acetate M.P. = 131 - 138° C N.M.R. (DMSO-d 6 ) δ ppm: 1.36 (dt, 3H, J=7.70, 1.20Hz); 2.93 (q, 2H, J=7.70Hz); 3.28 (bs, 1H); 5.28 (s, 2H); 6.92 (dd, 1H, J=3.60, 1.20Hz); 7.41 (dd, 1H, J=3.60, 1.20Hz). I.R. ν KBr (cm -1 ): 3490, 2950, 1740, 1580, 1500, 1410, 1220, 1110, 800. Mass: m/z 238 [M + ] (2-9) [5-(5-benzyl-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 77%) Starting Material: methyl [5-(5-benzyl-2-thienyl)tetrazol-1-yl ] acetate M.P. = 148 - 149° C N.M.R. (DMSO-d 6 ) δ ppm: 4.02 (s, 2H); 4.70 (bs, 1H); 5.25 (s, 2H); 6.92 (dd, 1H, J=3.60, 0.80Hz); 7.23∼7.38 (m, 5H); 7.41 (d, 1H, J=3.60). I.R. ν KBr (cm -1 ): 2950, 1750, 1580, 1510, 1430, 1230. Mass: m/z 300 [M + ] (2-10) [5-(5-methylthio-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 67%) Starting Material: methyl [5-(5-methylthio-2-thienyl)tetrazol-1-yl] acetate M.P. = 179° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.61 (s, 3H); 5.34 (s, 2H); 7.10 (d, 1H, J=4.01Hz); 7.49 (d, 1H, J=4.01Hz). I.R. ν KBr (cm -1 ): 3400, 1730, 1570, 1480, 1410, 1210. Mass: m/z 256 [M + ] (2-11) [5-(5-bromo-2-thienyl)tetrazol-1-yl] acetic acid (yield = 67%) Starting Material: methyl [5-(5-bromo-2-thienyl)tetrazol-1-yl] acetate M.P. = 200° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 5.30 (S, 2H); 6.63 (bs, 1H); 7.19 (d, 1H, J=4.01Hz); 7.34 (d, 1H, J=4.01Hz). I.R. ν KBr (cm -1 ): 3100, 2900, 1730, 1580, 1490, 1440, 1400, 1280, 1260, 1100, 980, 880, 800. Mass: m/z 289 [M + ] (2-12) [5-(2-methyl-3-thienyl)tetrazol-1-yl ] acetic acid (yield = 62%) Starting Material: methyl [5-(2-methyl-3-thienyl)tetrazol-1-yl] acetate M.P. = 144° C (decomposition). N.M.R. (DMSO-d 6 ) δ ppm: 2.57 (S, 3H); 5.08 (s, 2H); 7.06 (d, 1H, J=5.20Hz); 7.27 (d, 1H, J=5.20Hz). I.R. ν KBr (cm -1 ): 2900, 1740, 1570, 1440, 1400, 1340, 1260, 1220. Mass: m/z 224 [M + ] (2-13) [5-(5-bromomethyl-2-thienyl)tetrazol-1-yl] acetic acid (yield = 66%) Starting Material: methyl [5-(5-bromomethyl-2-thienyl)tetrazol-1-yl] acetate M.P. = 192° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.49 (s, 3H); 4.62 (bs, 1H); 5.28 (s, 2H); 7.39∼7.41 (m, 2H). I.R. ν KBr (cm -1 ): 3000, 1740, 1500, 1240, 1140. Mass: m/z 303 [M + ] (2-14) [5-(5-phenyl-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 66%) Starting Material: methyl [5-(5-phenyl2-thienyl)tetrazol-1-yl ] acetate M.P.: 210° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 4.03 (bs, 1H); 5.36 (s, 2H), 7.36∼7.48 (m, 3H); 7.42 (d, 1H, J=4.01Hz); 7.58 (d, 1H, J=4.01Hz),7.64∼7.67 (m, 2H). I.R. ν KBr (cm -1 ): 3000, 1730, 1580, 1480, 1430, 1240, 1110, 760. Mass: m/z 286 [M + ] (2-15) [5-(3-methoxy-2-thienyl)tetrazol-1-yl] acetic acid (yield = 72.1%) Starting Material: methyl [5-(3-methoxy-2-thienyl)tetrazol-1-yl] acetate M.P.: 234° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 3.94 (s, 3H); 5.36 (s, 2H); 6.95 (d, 1H, J=5.50Hz); 7.55 (d, 1H, J=5.50Hz). I.R. ν KBr (cm -1 ): 3110, 2950, 1740, 1580, 1520, 1440, 1250, 1200, 1070, 800, 750. Mass: m/z 240 [M + ] (2-16) [5-(3-butoxy-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 65.6%) Starting Material: methyl [5-(3-butoxy-2-thienyl)tetrazol-1-yl ] acetate M.P.: 197 - 198° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 0.95 (t, 3H, J=7.30Hz); 1.34∼1.41 (m, 2H); 1.70∼1.81 (m, 2H); 4.13 (t, 2H, J=6.60Hz); 4.80 (bs, 1H); 5.35 (s, 2H); 6.94 (d, 1H, J=5.50Hz); 7.54 (d, 1H, J=5.50Hz). I.R. ν KBr (cm -1 ): 3500, 2950, 1730, 1570, 1510, 1400, 1250, 1200, 1070, 800, 750. Mass: m/z 282 [M + ] (2-17) [5-(3-methylcarbonylamino-2-thienyl)tetrazol-1-yl] acetic acid; (yield = 55.1%) Starting Material: methyl [5-(3-methylcarbonylamino-2-thienyl)tetrazol-1-yl ] acetate M.P.: 221° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.92 (s, 3H); 3.80∼4.80 (br, 1H); 5.42 (s, 2H); 7.59 (d, 1H, J=5.40Hz); 8.28 (d, 1H, J=5.40Hz). I.R. ν KBr (cm -1 ): 3250, 2920, 1740, 1650, 1580, 1440, 1390, 1240, 1220, 1110, 760. Mass: m/z 267 (M + ] (2-18) [5-(3-propylcarbonylamino-2-thienyl)tetrazol-1-yl] acetic acid; (yield = 69.6%) Starting Material: methyl [5-(3-propylcarbonylamino-2-thienyl)tetrazol-1-yl ] acetate M.P.: 192° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 1.03 (t, 3H, J=7.30Hz); 1.74∼1.88 (m, 2H); 2.49 (t, 2H, J=7.30Hz); 4.40∼5.60 (br, 1H); 5.41 (s, 2H); 7.59 (d, 1H, J=5.50Hz); 8.30 (d, 1H, J=5.50Hz); 10.74 (bs, 1H). I.R. ν KBr (cm -1 ): 3310, 2960, 1720, 1590, 1530, 1440, 1180, 760. Mass: m/z 295 [M + ] (2-19) [5-(3-phenethylcarbonylamino-2-thienyl)tetrazol-1-yl ] acetic acid; (yield = 59.7%) Starting Material: methyl [5-(3-phenethylcarbonylamino-2-thienyl) tetrazol-1-yl] acetate M.P.: 178° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.83 (t, 2H, J=7.70Hz); 3.09 (t, 2H, J=7.70Hz); 4.22 (bs, 1H); 5.39 (s, 2H); 7.18∼7.30 (m, 5H); 7.60 (d, 1H, J=5.50Hz); 8.27 (d, 1H, J=5.50Hz); 10.72 (bs, 1H). I.R. ν KBr (cm -1 ): 3450, 2920, 1740, 1640, 1580, 1440, 1400, 1220, 1110. Mass: m/z 357 [M + ] (2-20) [5-(5-butyl-2-thienyl)tetrazol-1-yl] acetic acid (yield = 89%) Starting Material: methyl [5-(5-butyl-2-thienyl)tetrazol-1-yl] acetate M.P.: 103 - 104° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 0.95 (t, 3H, J=7.33Hz); 1.35∼1.49 (m, 2H); 1.65∼1.76 (m, 2H); 2.89 (t, 2H, J=7.33Hz); 5.27 (s, 2H); 6.89 (d, 1H, J=3.66Hz); 7.41 (d, 1H, J=3.66Hz). I.R. ν KBr (cm -1 ): 2920, 1730, 1580, 1520, 1420, 1220, 800. Mass: m/z 266 [M + ] (2-21) [5-(5-phenylpropyl-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 89.8%) Starting Material: methyl [5-(5-phenylpropyl-2-thienyl)tetrazol-1-yl ] acetate M.P.: 85 - 86° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 2.06 (quint., 2H, J=7.57Hz); 2.71 (t, 2H, J=7.57Hz); 2.91 (t, 2H, J=7.57Hz); 4.98 (bs, 1H); 5.28 (s, 2H); 6.91 (d, 1H, J=3.80 Hz); 7.18∼7.33 (m, 5H); 7.42 (d, 1H, J=3.80Hz). I.R. ν KBr (cm -1 ): 2920, 1720, 1580, 1510, 1420, 1220, 1130, 800. Mass: m/z 328 [M + ] (2-22) [5-(5-methoxymethyl-2-thienyl)tetrazol-1-yl] acetic acid (yield = 48.9%) Starting Material: methyl [5-(5-methoxymethyl-2-thienyl)tetrazol-1-yl ] acetate M.P.: 124 - 125° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 3.43 (S, 3H); 4.67 (d, 2H, J=0.73Hz); 5.29 (s, 2H); 7.10 (dt, 1H, J=3.66, 0.73Hz); 7.49 (d, 1H, J=3.66Hz). I.R. ν KBr (cm -1 ): 2900, 1740, 1580, 1420, 1220, 1020, 800. Mass: m/z 254 [M + ] (2-23) [5-(5-butoxymethyl-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 82.3%) Starting Material: methyl [5-(5-butoxymethyl-2-thienyl)tetrazol-1-yl ] acetate M.P.: 67 - 68° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 0.93 (t, 3H, J=7.20Hz); 1.38∼1.47 (m, 2H); 1.55∼1.66 (m, 2H); 3.54 (t, 2H, J=6.47Hz); 4.67 (d, 2H, J=0.73Hz); 4.07 (s, 2H); 5.27 (s, 2H); 7.07 (d, 1H, J=3.79Hz); 7.47 (d, 1H, J=3.79Hz). I.R. ν KBr (cm -1 ): 2950, 1730, 1580, 1420, 1230, 1090, 800. Mass: m/z 296 [M + ] (2-24) [5-(2-bromo-3-thienyl)tetrazol-1-yl] acetic acid (yield = 48.9%) Starting Material: methyl (5-(2-bromo-3-thienyl)tetrazol-1-yl] acetate M.P.: 145 - 146° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 4.56 (bs, 1H); 5.10 (s, 2H); 7.12 (d, 1H, J=5.18Hz); 7.47 (d, 1H, J=5.18Hz). I.R. ν KBr (cm -1 ): 2950, 1740, 1570, 1440, 1220, 1000, 800, 720. Mass: m/z 289 [M + ] (2-25) [5- (2-(oct-4-yl)-3-thienyl] tetrazol-1-yl ] acetic acid (yield = 80.6%) Starting Material: methyl [5- [2-(oct-4-yl]-3-thienyl] tetrazol-1-yl] acetate M.P.: 79 - 80° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 0.78∼0.84 (m, 6H); 1.13∼1.25 (m, 6H); 1.45∼1.71 (m, 4H); 3.15∼3.22 (m, 1H); 5.00 (s, 2H); 7.01 (d, 1H, J=5.37Hz); 7.36 (dd, 1H, J=5.37, 0.73Hz). I.R. ν KBr (cm -1 ): 2900, 1740, 1570, 1440, 1220, 720. Mass: m/z 322 [M + ] (2-26) [5-(2-methylthio-3-thienyl)tetrazol-1-yl ] acetic acid (yield = 75.3%) Starting Material: methyl [5-(2-methylthio-3-thienyl)tetrazol-1-yl] acetate M.P.: 134 - 135° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 2.51 (s, 3H); 5.14 (s, 2H); 7.18 (d, 1H, J=5.50Hz); 7.47 (d, 1H, J=5.50Hz). I.R. ν KBr (cm -1 ): 3100, 2900, 1730, 1550, 1440, 1220, 800. Mass: m/z 256 [M + ] (2-27) [5-(5-methyl-2-furyl)tetrazol-1-yl ] acetic acid (yield = 42.7%) Starting Material: methyl [5-(5-methyl-2-furyl)tetrazol-1-yl ] acetate M.P.: 150 - 151° C (decomposition) N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 2.41 (s, 3H); 5.40 (s, 2H); 6.23 (dd, 1H, J=3.42, 0.98Hz); 7.20 (d, 1H, J=3.42Hz). I.R. ν KBr (cm -1 ): 3500, 3100, 1720, 1570, 1440, 1240, 800. Mass: m/z 208 [M + ] (2-28) [5-(5-butyl-2-furyl)tetrazol-1-yl] acetic acid (yield = 63.4%) Starting Material: methyl [5-(5-butyl-2-furyl)tetrazol-1-yl] acetate M.P.: 109 - 110°C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 0.95 (t, 3H, J=7.20Hz); 1.32∼1.46 (m, 2H); 1.62∼1.73 (m, 2H); 2.72 (t, 2H, J=7.56Hz); 5.40 (s, 2H); 6.24 (d, 1H, J=3.42Hz); 7.19 (d, 1H, J=3.42Hz). I.R. ν KBr (cm -1 ): 2900, 1740, 1560, 1450, 1200, 800. Mass: m/z 250 [M + ] (2-29) [5-(5-bromo2-furyl)tetrazol-1-yl] acetic acid (yield = 73.6%) Starting Material: methyl [5-(5-bromo-2-furyl)tetrazol-1-yl] acetate M.P.: 159 - 160° C (decomposition) N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 5.41 (s, 2H); 6.60 (d, 1H, J=3.66Hz); 7.27 (d, 1H, J=3.66Hz). I.R. ν KBR (cm -1 ): 3150, 3000, 1730, 1600, 1420, 1200, 740. Mass: m/z 273 [M + ] (2-30) [5-(5-methylthio-2-furyl)tetrazol-1-yl ] acetic acid (yield = 42.3%) Starting Material: methyl [5-(5-methylthio-2-furyl)tetrazol-1-yl] acetate M.P.: 160.5 - 161.5° C (decomposition) N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 2.51 (s, 3H); 5.43 (s, 2H); 6.55 (d, 1H, J=3.66Hz); 7.28 (d, 1H, J=3.66Hz). I.R. ν KBR , (cm -1 ) : 3100, 3000, 1730, 1620, 1500, 1440, 1210, 1200, 800. Mass: m/z 240 [M + ] (2-31) [5-(2-bromo-3-furyl)tetrazol-1-yl] acetic acid (yield = 60.5%) Starting Material: methyl [5-(2-bromo-3-furyl)tetrazol-1-yl] acetate M.P.: 138 - 139° C (decomposition) N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 5.17 (s, 2H); 4.33 (bs, 1H); 6.74 (d, 1H, J=2.20Hz); 7.54 (d, 1H, J=2.20Hz). I.R. ν KBr (cm -1 ): 3100, 3000, 1720, 1620, 1520, 1440, 1260, 1100, 1010, 930. Mass: m/z 273 [M + ] (2-32) [5-(2-methylthio-3-furyl)tetrazol-1-yl ] acetic acid (yield = 78%) Starting Material: methyl [5-(2-methylthio-3-furyl)tetrazol-1-yl] acetate M.P.: 120 - 122° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 2.53 (s, 3H); 4.09∼4.65 (br, 1H); 5.43 (s, 2H); 6.71 (d, 1H, J=1.95Hz); 7.67 (d, 1H, J=1.95Hz). I.R. ν KBr (cm -1 ): 3300, 3150, 2950, 1730, 1590, 1440, 1220, 960, 810, 740. Mass: m/z 240 [M + ] (2-33) [5-(2-phenylthio-3-thienyl)tetrazol-1-yl ] acetic acid (yield = 67.6%) Starting Material: methyl [5-(2-phenylthio-3-thienyl)tetrazol-1-yl] acetate M.P.: 133 - 134° C (decomposition) N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 5.50 (s, 2H); 7.23∼7.29 (m, 6H); 7.59 (d, 1H, J=5.30Hz). I.R. ν KBr (cm -1 ): 3100, 3000, 1720, 1570, 1480, 1430, 1390, 1260, 870, 730. Mass: m/z 318 [M + ] (2-34) [5-(5-phenylthio-2-thienyl)tetrazol-1-yl ] acetic acid (yield = 61.0%) Starting Material: methyl [5-(5-phenylthio-2-thienyl)tetrazol-1-yl] acetate M.P.: 125 - 126° C (decomposition) N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 3.37 (bs, 1H); 5.29 (s, 2H); 7.27∼7.38 (m, 6H); 7.51 (d, 1H, J=3.90Hz). I.R. ν KBr (cm -1 ): 3000, 1730, 1580, 1480, 1430, 1410, 1220, 1130, 800, 730. Mass: m/z 318 [M + ] (2-35) [5- [5-(N,N-diethylaminosulfonyl]-2-thienyl] tetrazol-1-yl acetic acid (yield = 80.0%) Starting Material: methyl [5- [5-(N,N-diethylaminosulfonyl)-2-thienyl ] tetrazol-1-yl ] acetate M.P.: 134 - 135° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 1.01 (t, 6H, J=7.08Hz); 3.10 (q, 4H, J=7.08Hz); 3.32 (bs, 1H); 5.25 (s, 2H); 7.23 (d, 1H, J=5.13Hz); 8.18 (d, 1H, J=5.13Hz). I.R. ν KBr (cm -1 ): 3100, 2970, 1740, 1410, 1360, 1220, 1150, 940, 700, 590. Mass: m/z 333 [M + ] (2-36) [5- [5-(N,N-dibutylaminosulfonyl)-2-thienyl] tetrazol-1-yl acetic acid (yield = 61.0%) Starting Material: methyl [5- [5-(N,N-dibutylaminosulfonyl)-2-thienyl ] tetrazol-1-yl ] acetate N.M.R. (CDCl 3 ) δ ppm: 0.79 (t, 6H, J=7.32Hz); 1.09∼1.23 (m, 4H); 1.30∼1.41 (m, 4H); 2.87 (t, 4H, J=7.57Hz); 5.14 (s, 2H); 7.11 (d, 1H, J=5.12Hz); 7.61 (d, 1H, J=5.12Hz). I.R. ν NaCl (cm -1 ): 2950, 1740, 1340, 1220, 1150. Mass: m/z 401 [M + ] (2-37) [5-(5-piperidinosulfonyl-2-thienyl)tetrazol-1-yl ] acetic acid; (yield = 55.0%) Starting Material: methyl [5-(5-piperidinosulfonyl-2-thienyl)tetrazol-1-yl ] acetate M.P.: 143 - 146° C N.M.R. (CDCl 3 ) δ ppm: 1.38∼1.39 (m, 2H); 1.48∼1.58 (m, 4H); 2.86 (t, 4H, J=5.37Hz); 5.15 (s, 2H); 7.16 (d, 1H, J=5.13Hz); 7.66 (d, 1H, J=5.13Hz). I.R. ν KBr (cm -1 ): 3450, 2950, 1735, 1340, 1230, 1160. Mass: m/z 357 [M + ] (2-38) [5- [2-(N,N-diethylaminosulfonyl ] -3-thienyl)tetrazol-1-yl] acetic acid; (yield = 66.1%) Starting Material: methyl [5- [2-(N,N-diethylaminosulfonyl]-5-trimethylsilyl-3-thienyl) tetrazol-1-yl ] acetate M.P.: 128.5 - 130° C N.M.R. (CDCl 3 ) δ ppm: 1.00 (t, 6H, J=7.08Hz); 3.00 (q, 4H, J=7.08Hz); 5.13 (s, 2H); 7.10 (d, 1H, J=4.88Hz); 7.62 (d, 1H, J=4.88Hz). I.R. ν KBr (cm -1 ): 2950, 1740, 1340, 1220, 1140. Mass: m/z 331 [M + ] (2-39) [5-(3-methylsulfonylamino-2-thienyl)tetrazol-1-yl] acetic acid; (yield = 36.8%) Starting Material: methyl [5-(3-methylsulfonylamino-2-thienyl) tetrazol-1-yl ] acetate M.P.: 154 - 155° C N.M.R. (CDCl 3 ) δ ppm: 3.01 (s, 3H); 3.78 (s, 3H); 5.38 (s, 2H); 7.53 (d, 1H, J=5.61Hz); 7.62 (d, 1H, J=5.61Hz); 9.92 (bs, 1H). I.R. ν KBr (cm -1 ): 3150, 3100, 1740, 1560, 1370, 1330, 1220, 1150, 760. Mass: m/z 303 [M + ] (2-40) [5-(3-butylsulfonylamino-2-thienyl)tetrazol-1-yl ] acetic acid; (yield = 74.4%) Starting Material: methyl [5-(3-butylsulfonylamino-2-thienyl) tetrazol-1-yl ] acetate M.P.: 158 - 159° C (decomposition) N.M.R. (CDCl 3 ) δ ppm: 0.87 (t, 3H, J=7.32Hz); 1.35∼1.44 (m, 2H); 1.75∼1.85 (m, 2H); 3.14 (t, 2H, J=7.95Hz); 3.84 (s, 3H); 5.45 (s, 2H); 7.54 (d, 1H, J=5.49Hz); 7.62 (d, 1H, J=5.49Hz); 9.98 (bs, 1H). I.R. ν KBr (cm -1 ): 3100, 2950, 1750, 1560, 1370, 1220, 1150. Mass: m/z 345 [M + ] (2-41) [5-(3-phenylsulfonylamino-2-thienyl)tetrazol-1-yl] acetic acid; (yield = 82.4%) Starting Material: methyl [5-(3-phenylsulfonylamino)-2-thienyl) tetrazol-1-yl ] acetate M.P.: 124 - 125° C N.M.R. (CDCl 3 ) δ ppm: 3.72 (s, 3H); 5.23 (s, 2H); 7.31∼7 .47 (m, 5H); 7.53 (d, 1H, J=5.62Hz); 7.58∼7.91 (m, 2H); 10.16 (bs, 1H). I.R. ν KBr (cm -1 ): 3120, 2950, 1750, 1560, 1520, 1430, 1380, 1240, 1160, 760, 580. Mass: m/z 365 [M + ] (2-42) [5-(3-hydroxy-2-thienyl)tetrazol-1-yl] acetic acid (yield = 73.6%) Starting Material: methyl [5-(3-hydroxy-2-thienyl)tetrazol-1-yl] acetate M.P.: 199 - 200° C (decomposition) N.M.R. (CDCl 3 ) δ ppm: 4.36 (bs, 1H); 5.38 (s, 2H); 6.87 (d, 1H, J=5.37Hz); 7.45 (d, 1H, J=5.37Hz); 10:23(bs, 1H). I.R. ν KBr (cm -1 ): 3450, 2850, 1720, 1440, 1230, 1120, 1010, 750. Mass: m/z 226 [M + ] (2-43) [5-(2-methylsulfinyl-3-thienyl)tetrazol-1-yl ] acetic acid; (yield = 20.4%) Starting Material: methyl [5-(2-methylsulfinyl-3-thienyl)tetrazol-1-yl ] acetate M.P.: 144 - 145° C N.M.R. (CDCl 3 + DMSO-d 6 ) δ ppm: 3.08 (s, 3H); 5.15 (d, 1H, J=17.82Hz); 5.30 (d, 1H, J=17.82Hz); 7.34 (d, 1H, J=5.12Hz); 7.81 (d, 1H, J=5.12Hz). I.R. ν KBr (cm -1 ): 3100, 2900, 1700, 1570, 1420, 1300, 1260, 1220, 1000, 760. Mass: m/z 272 [M + ] (2-44) [5-(2-methylsulfonyl-3-thienyl)tetrazol-1-yl ] acetic acid; (yield = 76.1%) Starting Material: methyl [5-(2-methylsulfonyl-3-thienyl)tetrazol-1-yl ] acetate M.P.: 135 - 136° C N.M.R. (CDCl 3 + DMSO-d 8 ) δ ppm: 3.32 (bs, 1H); 3.48 (s, 3H); 5.37 (s, 2H); 7.40 (d, 1H, J=5.13Hz); 8.32 (d, 1H, J=5.13Hz). I.R. ν KBr (cm -1 ): 3500, 3100, 3000, 1720, 1310, 1140, 950, 760. Mass: m/z 288 [M + ] (2-45) [5-(3-amino-2-thienyl)tetrazol-1-yl] acetic acid, hydrochloride; (yield = 76.1%) Starting Material: methyl [5-(3-methylcarbonylamino-2-thienyl)tetrazol-1-yl ] acetate M.P.: 258° C (decomposition) N.M.R. (DMSO-d 6 ) δ ppm: 2.34 (bs, 1H); 5.17 (s, 2H); 7.02 (d, 1H, J=5.50Hz); 7.59 (d, 1H, J=5.50Hz); 11.01 (bs, 1H). I.R. ν KBr (cm -1 ): 3240, 3160, 1700, 1590, 1530, 1380, 1040, 770. (2-46) [5- [5- [N-methyl-N-(2-hydroxyethyl)aminosulfonyl] -2-thienyl] tetrazol-1-yl ] acetic acid; (yield = 76.1%) Starting Material: methyl [5- [5- [N-methyl-N- [2-(methoxyethoxy)-ethyl ] aminosulfonyl ] -2-thienyl] -tetrazol-1-yl] acetate N.M.R. (CD 3 OD) δ ppm: 2.77 (s, 3H); 3.07 (t, 2H, J=5.61Hz); 3.60 (t, 2H, J=5.61Hz); 5.24 (s, 2H); 7.26 (d, 1H, J=5.13Hz); 8.02 (d, 1H, J=5.13Hz). I.R. ν NaCl (cm -1 ): 3450, 2950, 1740, 1440, 1350, 1150, 1040, 590. Mass: m/z 347 [M + ] Example 3 (3-1) methyl [5-(2-thienyl)tetrazol-1-yl] acetate To a solution of 500 mg (2.51 mM) of N-(2-thenoyl)glycine methyl ester in 5mℓ of anhydrous methylene chloride, there were added, at room temperature, 185 mg (2.53 mM) of anhydrous N,N-dimethylformamide and 418 mg (3. 51 mM) of thionyl chloride and then the mixture was refluxed for one hour. The reaction solution was concentrated at 40° C under reduced pressure and the resulting residue was dissolved in 5m ℓ of anhydrous N,N-dimethylformamide. The resulting solution was dropwise added to a suspension of 410 mg (6.3 mM) of sodium azide in 3mℓ of anhydrous N,N-dimethylformamide at a temperature of the suspension ranging from 5 to 10° C over 30 minutes with stirring. After the dropwise addition, the reaction mixture was stirred for additional 30 minutes at room temperature, poured into ice-water and extracted with ethyl acetate. The organic phase obtained was washed with water, dried over anhydrous sodium sulfate and then concentrated under reduced pressure. The resultant residue was recrystallized from ethyl acetate/n-hexane to give 395 mg (yield 70.2%) of methyl [5-(2-thienyl)tetrazol-1-yl] acetate. The results of the instrumental analysis of this product are consistent with those for the product obtained in Example (1-1). (3-2) ethyl [5-(3-thienyl)tetrazol-1-yl] acetate To a solution of 1 g (4.69 mM) of N-(3-thenoyl)glycine methyl ester in 10 m ℓ of anhydrous methylene chloride, there were added, at room temperature, 350 mg (4.79 mM) of anhydrous N,N-dimethylformamide and 800 mg (6.72 mM) of thionyl chloride and then the mixture was refluxed for one hour. The reaction solution was concentrated at 40° C under reduced pressure and the resulting residue was dissolved in 10 mℓ of anhydrous N,N-dimethylformamide. The resulting solution was dropwise added to a suspension of 800 mg (12.3 mM) of sodium azide in 5 mℓ of anhydrous N,N-dimethylformamide at a temperature of the suspension ranging from 5 to 10 ° C over 30 minutes with stirring. After the dropwise addition, the reaction mixture was stirred for additional 30 minutes at room temperature, poured into ice-water and extracted with ethyl acetate. The organic phase obtained was washed with water, dried over anhydrous sodium sulfate and then concentrated under reduced pressure. The resultant residue was recrystallized from ethyl acetate/n-hexane to give 730 mg (yield 65.3%) of ethyl [5-(3-thienyl)tetrazol-1-yl] acetate. M.P.: 69.5 - 70.5°C N.M.R. (CDCℓ 3 ) δ ppm: 1.27 (t, 3H, J = 7.25 Hz); 4.26 (q, 2H, J=7.25Hz); 5.25 (s, 2H); 7.48 (dd, 1H, J=5.20, 1.21Hz); 7.55 (dd, 1H, J=5.20, 2.82Hz); 7.84 (dd, 1H, J=2.82, 1.21Hz). I.R. ν KBr (cm -1 : 3100, 2970, 2950, 1740, 1570, 1440, 1370, 1210, 880. Mass: m/z 238 [M + ] The following compounds were prepared in the same manner as described above. (3-3) methyl [5-(3-methoxy-2-thienyl)tetrazol-1-yl] acetate (yield = 12%) Starting Material: N-(3-methoxy-2-theonyl)glycine methyl ester M.P.: 121 - 122° C N.M.R. (CDCℓ 3 ) δ ppm: 3.76 (s, 3H); 3.90 (s, 3H); 5.34 (s, 2H); 6.97 (d, 1H, J= 5.64Hz); 7.54 (d, 1H, J=5.64Hz). I.R. ν KBr (cm -1 ): 3100, 2950, 1760, 1580, 1520, 1400, 1240, 1220, 1070, 760. Mass: m/z 254 [M + ] (3-4) methyl [5-(3-butoxy-2-thienyl)tetrazol-1-yl ] acetate (yield = 13%) Starting Material: N-(3-butoxy-2-theonyl)glycine methyl ester M.P.: 62 - 62.5° C N.M.R. (CDCℓ 3 ) δ ppm: 0.88 (t, 3H, J=7.26Hz); 1.28∼1.39 (m, 2H); 1.59∼1.70 (m, 2H); 3.66 (s, 3H); 4.04 (t, 2H, J=6.85Hz); 5.34 (s, 2H); 6.84 (d, 1H, J=5.64Hz); 7.45 (d, 1H, J=5.64Hz). I.R. ν KBr (cm -1 ): 3100, 2950, 1760, 1580, 1510, 1400, 1240, 1220, 1050, 750. Mass: m/z 296 [M + ] (3-5) methyl [5-(5-butyl-2-thienyl)tetrasol-1-yl] acetate (yield = 63.8%) Starting Material: N-[5-butyl-2-thenoyl)glycine methyl ester M.P.: 58 - 59° C N.M.R. (CDCℓ 3 ) δ ppm: 0.95 (t, 3H, J=7.32Hz); 1.37∼1.46-(m, 2H); 1.65∼1.76 (m, 2H); 2.88 (t, 2H, J=7.32Hz); 3.83 (s, 3H); 5.32 (s, 2H); 6.89 (d, 1H, J=3.66Hz); 7.38 (d, 1H, J=3.66Hz). I.R. ν KBr (cm -1 ): 2950, 1740, 1580, 1520, 1440, 1380, 1220, 1100, 1000, 800. Mass: m/z 280 [M + ] (3-6) methyl [5-(5-phenylpropyl-2-thienyl)tetrazol-1-yl ] acetate (yield = 74.1%) Starting Material: N-(5-phenylpropyl-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 2.06 (quint., 2H, J=7.57Hz); 2.71 (t, 2H, J=7.57Hz); 2.91 (t, 2H, J=7.57Hz); 3.83 (s, 3H); 5.31 (s, 2H); 6.90 (dt, 1H, J=3.72, 0.73Hz); 7.18∼7.34 (m, 5H); 7.40 (d, 1H, J=3.72Hz). I.R. ν NaCl (cm -1 ): 2920, 1750, 1580, 1500, 1440, 1220, 1100, 700. Mass: m/z 342 [M + ] (3-7) methyl [5-(5-methoxymethyl-2-thienyl)tetrazol-1-yl] acetate (yield = 72.5%) Starting Material: N-(5-methoxymethyl-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 3.44 (s, 3H); 3.84 (s, 3H); 4.67 (d, 2H, J=0.73Hz); 5.33 (s, 2H); 7.10 (dt, 1H, J=3.66, 0.73Hz), 7.48 (d, 1H, J=3.66Hz). I.R. ν NaCl (cm -1 ): 2950, 1750, 1580, 1440, 1360, 1220, 1000, 800. Mass: m/z 268 [M + ] (3-8) methyl [5-(5-butoxymethyl-2-thienyl)tetrazol-1-yl ] acetate (yield = 68.9%) Starting Material: N-(5-butoxymethyl-2-thenoyl)glycine methyl ester M.P.: 48 - 49° C N.M.R. (CDCℓ 3 ) δ ppm: 0.93 (t, 3H, J=7.21Hz); 1.33∼1.45 (m, 2H); 1.56∼1.66 (m, 2H); 3.54 (t, 2H, J=6.74Hz); 3.83 (s, 3H); 4.70 (d, 2H, J=0.73Hz); 5.33 (s, 2H); 7.07 (dt, 1H, J=3.72, 0.73Hz); 7.46 (d, 1H, J=3.72Hz). I.R. ν KBr (cm -1 ): 2950, 2850, 1740, 1580, 1420, 1230, 1100, 800. Mass: m/z 310 [M + ] (3-9) methyl [5-(2-bromo-3-thienyl)tetrazol-1-yl] acetate (yield = 45.9%) Starting Material: N-(2-bromo-3-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 3.76 (s, 3H); 5.17 (s, 2H); 7.10 (d, 1H, J=5.73Hz); 7.48 (d, 1H, J=5.73Hz). I.R. ν NaCl (cm -1 ): 3100, 2950, 1750, 1580, 1430, 1220, 1000. Mass: m/z 303 [M + ] (3-10) methyl [5- [2-(oct-4-yl]-3-thienyl] tetrazol-1-yl ] acetate (yield = 35.5%) Starting Material: N- [2-(oct-4-yl)-3-thenoyl] glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 0.78∼0.85 (m, 6H); 1.11∼1.26 (m, 6H); 1.50∼1.67 (m, 4H); 3.12∼3.18 (m, 1H); 3.81 (s, 3H); 5.05 (s, 2H); 6.93 (d, 1H, J=5.37Hz); 7.36 (d, 1H, J=5.37Hz). I.R. ν NaCl : (cm -1 ): 2950, 2850, 1760, 1440, 1220. Mass: m/z 336 [M + ] (3-11) methyl [5-(2-methylthio-3-thienyl)tetrazol-1-yl ] acetate (yield = 70.8%) Starting Material: N-(2-methylthio-3-thenoyl)glycine methyl ester M.P.: 90 - 91° C N.M.R. (CDCℓ 3 ) δ ppm: 2.47 (s, 3H); 3.75 (s, 3H); 5.20 (s, 2H); 7.15 (d, 1H, J=5.37Hz); 7.46 (d, 1H, J=5.37Hz). I.R. ν KBr (cm -1 ): 3110, 2920, 1750, 1550, 1420, 1220, 1100. Mass: m/z 270 [M + ] (3-12) methyl [5-(2-phenylthio-3-thienyl)tetrazol-1-yl ] acetate (yield = 78.6%) Starting Material: N-(2-phenylthio3-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 3.73 (s, 3H); 5.10 (s, 2H); 7.21∼7.27 (m, 6H); 7.55 (d, 1H, J=5.37Hz). I.R.ν NaCl (cm -1 ): 3100, 2950, 1750, 1570, 1480, 1440, 1360, 1220, 1000. Mass: m/z 332 [M + ] (3-13) methyl [5-(5-phenylthio-2-thienyl)tetrazol-1-yl ] acetate (yield = 70.8%) Starting Material: N-[5-phenylthio-2-thenoyl)glycine methyl ester M.P.: 102 - 103° C N.M.R. (CDCℓ 3 ) δ ppm: 3.82 (s, 3H); 5.30 (s, 2H); 7.26∼7.37 (m, 6H); 7.49 (d, 1H, J=3.91Hz). I.R. ν KBr (cm -1 ): 2900, 1750, 1570, 1480, 1430, 1410, 1360, 1220, 1100, 800. Mass: m/z 332 [M + ] (3-14) methyl [5- [5-(N,N-diethylaminosulfonyl)-2-thienyl) tetrazol-1-yl] acetate; (yield = 72.5%) Starting Material: N- [5-(N′,N′-diethylaminosulfonyl]-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 1.08 (t, 6H, J=7.20Hz); 3.07 (q, 4H, J=7.20Hz); 3.72 (s, 3H); 5.23 (s, 2H); 7.22 (d, 1H, J=5.12Hz); 7.67 (d, 1H, J=5.12Hz). I.R. ν NaCl (cm -1 ): 3100, 2950, 1750, 1610, 1440, 1350, 1220, 1150, 940, 700. Mass: m/z 347 [M + ] (3-15) methyl [5- [5-(N,N-dibutylaminosulfonyl)-2-thienyl] tetrazol-1-yl] acetate; (yield = 68.9%) Starting Material: N- [5-(N′,N′-dibutylaminosulfonyl]-2-thenoyl)glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 0.86 (t, 6H, J=7.32Hz); 1.33∼1.37 (m, 4H); 1.40∼1.48 (m, 4H); 2.04 (t, 4H, J=7.32Hz); 3.71 (s, 3H); 5.23 (s, 2H); 7.22 (d, 1H, J=5.25Hz); 7.67 (d, 1H, J=5.25Hz). I.R. ν NaCl (cm -1 ): 2950, 1760, 1360, 1220, 1150. Mass: m/z 415 [M + ] (3-16) methyl [5-(5-piperidinosulfonyl-2-thienyl)tetrazol-1-yl ] acetate; (yield = 45.9%) Starting Material: N-(5-piperidinosulfonyl-2-thenoyl]glycine methyl ester M.P.: 133 - 135° C N.M.R. (CDCℓ 3 ) δ ppm: 1.04∼1.53 (m, 2H); 1.59∼1.68 (m, 4H); 2.92 (t, 4H, J=5.25Hz); 3.71 (s, 3H); 5.23 (s, 2H); 7.26 (d, 1H, J=5.13Hz); 7.72 (d, 1H, J=5.13Hz). I.R. ν KBr (cm -1 ): 3100, 2950, 1760, 1340, 1220, 1150, 940, 710, 590. Mass: m/z 371 [M + ] (3-17) methyl [5- [2-(N,N-diethylaminosulfonyl]-5-trimethylsilyl-3-thienyl ] tetrazol-1-yl ] acetate; (yield = 75.4%) Starting Material: N- [2-(N′,N′-diethylaminosulfonyl]-5-trimethylsilyl-3-thenoyl ] glycine methyl ester N.M.R. (CDCℓ 3 ) δ ppm: 0.37 (s, 9H); 1.08 (t, 6H, J=7.20Hz); 3.06 (q, 4H, J=7.08Hz); 3.71 (s, 3H); 5.21 (s, 2H); 7.24 (s, 1H). I.R. ν NaCl (cm -1 ): 2950, 1760, 1440, 1350, 1250, 1220, 1140, 1000, 840, 700. Mass: m/z 431 [M + ] (3-18) methyl [5-(3-hydroxy-2-thienyl)tetrazol-1-yl] acetate (yield = 54.0%) Starting Material: N-(3-hydroxy-2-thenoyl)glycine methyl ester M.P. = 141 - 142° C N.M.R. (CDCℓ 3 ) δ ppm: 3.84 (s, 3H); 5.38 (s, 2H); 6.95 (d, 1H, J=5.37Hz); 7.46 (d, 1H, J=5.37Hz); 10.12 (bs, 1H). I.R. ν KBr (cm -1 ): 3100, 1760, 1740, 1530, 1220, 1000. Mass: m/z 240 [M + ] The compounds prepared in the foregoing Examples are listed in the following Table I. As has been explained above in detail, the aldose reductase inhibitor of the present invention shows excellent aldose reductase inhibitory effect and has low toxicity. Therefore, it can be used as a medicine for preventing and/or treating mammaliansinclusive of has suffering from diabetic complications such as neural disorders, nephrosis, cataract and retinopathy with safety. The effects and toxicity of the aldose reductase inhibitor according to the present invention will be detailed below with reference to the following Test Examples. Test Example 1: Test for Examining Aldose Reductase Inhibitory Effect (i) Methodology Six-weeks-old male SD rats were anesthetized with ether and killed. Then their crystalline lenses were immediately removed and stored at -80° C. The lenses were homogenized in 3 volumes of 135 mM sodium potassium phosphate buffer (pH 7.0) and centrifuged at 30,000 rpm for 30 minutes. The resulting supernatant was dialyzed overnight against 0.05 M sodium chloride solution to obtain an aldose reductase solution. All operations were conducted at 4° C and the enzyme solution was stored at -80 ° C. The activity of aldose reductase was determined according to a partially modified method of J.H. Kinoshita et al. (J. Biol. Chem., 1965, 240 , p. 877). More specifically, 0.1 ml of DL-glyceraldehyde (final concentration: 10 mM) was added to 0.9 ml of 100 mM sodium potassium phosphate buffer (pH 6.2) which contained lithium sulfate (final concentration: 400 mM), reduced nicotinamide adenine dinucleotide phosphate (final concentration: 0.15 mM), the enzyme solution, and the compound to be evaluated (final concentration: 10 - 6 M, 10 - 7 M or 10 - 8 M), and then the reaction was conducted at 30° C for 5 minutes. During the reaction, the change in the absorbance at 340 nm with time was monitored. The maximum reducing rate of the absorbance (U) during the reaction was determined. By subtracting, from this value, the maximum reducing rate (U 0 ) at 340 nm of the reaction solution before the addition of the substrate (DL-glyceraldehyde), the reaction rate ( V = U - U 0 ) was calculated as a true reaction rate in the presence of the compound to be tested. The same procedure was repeated except for the absence of the compound to be tested. A true reaction rate (V 0 ) in case the enzyme was not inhibited was calculated ( V 0 = U'- U 0 ' ). The aldose reductase inhibitory activity of the test compounds was determined according to the following formula: Rate of Inhibition (%) = (V 0 - V)/V 0 X 100 For comparison, the same tests were conducted using a known aldose reductase inhibitor: ONO-2235 [ (E)-3-carboxymethyl-5 [ (2E)-methyl-3-phenylpropenylidene ] rhodan] . (ii) Results The results thus obtained are summarized in the following Table II. As seen from Table II, the compounds of the present invention tested show aldose reductase inhibitory effect identical to or superior to those attained by the known inhibitor ONO-2235. Compound Tested (Ex. No.) IC 50 (10 - 8 )M Compound Tested (Ex. No.) IC 50 (10 - 8 )M 1-5 95 2-23 2.5 1-7 74 2-24 3.8 1-27 23 2-26 3.1 2-1 1.6 2-27 15 2-2 1.8 2-28 13 2-3 2.4 2-29 16 2-4 2.3 2-30 11 2-5 2.1 2-31 8.5 2-6 6.0 2-32 3.5 2-7 3.0 2-33 2.4 2-8 2.1 2-34 2.6 2-9 2.0 2-35 39 2-10 2.0 2-36 8.5 2-11 1.9 2-37 23 2-12 3.0 2-38 46 2-13 2.5 2-39 2.8 2-14 2.1 2-40 1.6 2-15 2.9 2-41 2.3 2-16 3.1 2-42 2.0 2-17 2.8 2-43 30 2-18 2.0 2-44 52 2-19 2.4 3-2 58 2-20 2.3 3-5 18 2-21 2.8 3-11 38 2-22 3.1 ONO-2235 2.2 Test Example 2: Test on the Effect of Inhibiting the Accumulation of Sorbitol in Sciatic Nerve (i) Methodology Groups of 6 to 8-weeks-old Sprague-Dawley male rats (4 animals per group) were fasted for 18 hours and streptozotocin was injected through the tail vein in a dose of 60 mg/kg to thus obtain diabetic rats. Immediately after the administration of the streptozotocin, each compound to be tested was orally administered to these rats in the form of a suspension at a dose of 10 mg/kg, 30 mg/kg and 50 mg/kg (each was suspended in a 0.5% sodium carboxymethyl cellulose solution) twice a day (9 o'clock in the morning and 5 o'clock in the afternoon) for 5 days. During the test, the rats took diet and drank water freely. 4 Hours after the final administration of the drug in the 5th day's morning (9 o'clock in the morning), the rats were sacrificed and then the sciatic nerve thereof was removed to determine the amount of sorbitol accumulated therein. The results are expressed in the percentage obtained while the value obtained on the control to which any drug was not administered is defined to be 100. (ii) Test Results The results of the test are listed in the following Table III. These results indicate that the compounds of the present invention show high inhibitory effect as compared with those for the known aldose reductase inhibitor ONO-2235. Compound Tested (Ex. No.) Rate of Inhibition of Sorbitol Accumulation (%) 10 mg/kg 30 mg/kg 50 mg/kg 2-1 68 89 --- 2-2 62 93 --- 2-5 73 90 --- 2-7 46 77 --- ONO-2235 0 0 40 Test Example 3: Acute Toxicity Test (i) Methodology Each compound to be tested was suspended to 0.5% sodium carboxymethyl cellulose solution and the resulting suspension was orally administered to 6-weeks-old male MCH mice (5 animals per test group). The 50% lethal dose (LD 50 ; mg/kg) was evaluated from the mortality rate (%) observed 14 days after the administration of the compound. The mice took diet and drank water freely during the test. (ii) Results The results obtained are summarized in the following Table IV. As seen from Table IV, the compounds of the present invention which were subjected to the foregoing test show LD 50 of not less than 3,000 mg/kg. Compound Tested (Ex. No.) LD 50 (mg/kg) 2-1 > 3,000 2-5 > 3,000 2-7 > 3,000

Claims: Tetrazoleacetic acid derivatives represented by the following general formula (I): [in Formula (I), R 1 represents a hydrogen atom or an alkyl group; R 2 represents a hydrogen atom, an alkyl group, an aralkyl group, a halogen atom, a haloalkyl group, a hydroxyl group, an alkoxy group, an alkoxyalkyl group, an amino group, an aryl group, an alkyl or aryl thio group, an alkyl or aryl carbonylamino group, an alkyl or aryl sulfonylamino group, an alkyl or aryl aminosulfonyl group, an alkyl or aryl sulfonyl group or an alkyl or aryl sulfinyl group; and X represents -O- or -S-] except for [5-(2-thienyl)tetrazol-1-yl] acetic acid, [5-(2-furyl)tetrazol-1-yl] acetic acid, [5-(5-bromo-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylthio-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylsulfonyl-2-furyl)-tetrazol-1-yl]acetic acid and ethyl esters thereof, [5-(5-phenyl-2-furyl)tetrazol-1-yl]acetic acid and C 1 to C 3 alkyl esters thereof, or a salt thereof. The tetrazoleacetic acid derivative of claim 1 wherein, in the general formula (I), the alkyl group represented by R 1 or R 2 is a methyl, ethyl, propyl, isopropyl, butyl, isobutyl or t-butyl group ; the aralkyl group is a benzyl or phenylpropyl group; the alkoxy group is a methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy or t-butoxy group ; the alkoxyalkyl group is a methoxymethyl or butoxymethyl group; the haloalkyl group is a mono-, di- or tri-haloalkyl group; the alkyl or aryl thio group is a methylthio, ethylthio, butylthio or phenylthio group ; the alkylaminosulfonyl group is a mono- or di-alkylaminosulfonyl group; the alkyl or aryl sulfonylamino group is a methylsulfonylamino, ethylsulfonylamino, butylsulfonylamino or phenylsulfonylamino group ; the alkyl or aryl carbonylamino group is a methylcarbonylamino, ethylcarbonylamino, propylcarbonylamino or phenethylcarbonylamino group ; the alkyl or aryl sulfonyl group is a methylsulfonyl, ethylsulfonyl, butylsulfonyl or piperidinosulfonyl group ; and the alkylsulfinyl group is a methylsulfinyl, ethylsulfinyl or butylsulfinyl group . The tetrazoleacetic acid derivative of claim 2 wherein the haloalkyl group is a chloromethyl, bromomethyl, fluoromethyl or chlorobutyl group ; and the alkylaminosulfonyl group is a methylaminosulfonyl, ethylaminosulfonyl, propylaminosulfonyl or butylaminosulfonyl group . The tetrazoleacetic acid derivative of claim 1 wherein the salt of the compound represented by Formula (I) wherein R 1 is a hydrogen atom is an alkali metal salt , alkaline earth metal salt , ammonium salt , organic amine salt or a salt with a basic amino acid . The tetrazoleacetic acid derivative of claim 4 wherein the alkali metal salt is a sodium salt or a potassium salt; the alkaline earth metal salt is a calcium salt or a magnesium salt; the organic amine salt is a triethylamine salt, a pyridine salt or an ethanolamine salt; and the basic amino acid salt is an arginine salt. The tetrazoleacetic acid derivative of claim 1 wherein, in the foregoing Formula (I), R 1 is a hydrogen atom and X is an oxygen or sulfur atom. A pharmaceutical composition having aldose reductase inhibiting activity comprising a tetrazoleacetic acid derivative according to any one of claims 1 to 6 including [5-(2-thienyl)tetrazol-1-yl] acetic acid, [5-(2-furyl)tetrazol-1-yl] acetic acid, [5-(5-bromo-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylthio-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylsulfonyl-2-furyl)-tetrazol-1-yl]acetic acid and ethyl esters thereof and C 1 to C 3 alkyl esters of [5-(5-phenyl-2-furyl)tetrazol-1-yl]acetic acid, and salts thereof and a pharmaceutically acceptable carrier. The composition of claim 7 which is in the form of tablets, powder, fine particles, granules, capsules, pills, liquid preparations, solutions or suspensions for injection or eye drops. A tetrazoleacetic acid derivative according to any one of claims 1 to 6 including [5-(2-thienyl)tetrazol-1-yl] acetic acid, [5-(2-furyl)tetrazol-1-yl] acetic acid, [5-(5-bromo-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylthio-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylsulfonyl-2-furyl)-tetrazol-1-yl]acetic acid and ethyl esters thereof and C1 to C3 alkyl esters of [5-(5-phenyl-2-furyl)tetrazol-1-yl]acetic acid and salts thereof for use as a medicament. A tetrazoleacetic acid derivative according to any one of claims 1 to 6 including [5-(2-thienyl)tetrazol-1-yl] acetic acid, [5-(2-furyl)tetrazol-1-yl] acetic acid, [5-(5-bromo-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylthio-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylsulfonyl-2-furyl)-tetrazol-1-yl]acetic acid and ethyl esters thereof and C1 to C3 alkyl esters of [5-(5-phenyl-2-furyl)tetrazol-1-yl]acetic acid and salts thereof for use in a method for alleviating or reducing diabetic complications. The use of a tetrazoleacetic acid derivative according to any one of claims 1 to 6 including [5-(2-thienyl)tetrazol-1-yl] acetic acid, [5-(2-furyl)tetrazol-1-yl] acetic acid, [5-(5-bromo-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylthio-2-furyl)tetrazol-1-yl]acetic acid, [5-(5-phenylsulfonyl-2-furyl)-tetrazol-1-yl]acetic acid and ethyl esters thereof, [5-(5-phenyl-2-furyl)tetrazol-1-yl]acetic acid and C1 to C3 alkyl esters and salts thereof, acid and salts thereof for preparing a medicament for alleviating or reducing diabetic complications.

Inventors: AGATA MITSUZI, GOTO MASAYOSHI, HORIO YOSHIHIRO, INUKAI SINJI, OOTAKE YASUHIRO, SAWAKI SHOHEI, UMEZAWA MANAMI, AGATA, MITSUZI, GOTO, MASAYOSHI, HORIO, YOSHIHIRO, INUKAI, SINJI, OOTAKE, YASUHIRO, SAWAKI, SHOHEI, UMEZAWA, MANAMI
Applicants: WAKAMOTO PHARMA CO LTD, WAKAMOTO PHARMACEUTICAL CO., LTD.
Application year: 1990
Main classification: C07D409
IPC codes: C07D409, A61P27, A61P3, C07D405, A61P25, A61K31, C07D257, A61P13, A61P15