PROCESS FOR PRODUCING 5-HYDROXYBENZO [b]THIOPHENE-3-CARBOXYLIC ACID DERIVATIVES

Abstract: Benzothiophenecarboxylic acid derivatives of the formula (I) which are useful as starting materials for producing drugs, and a process for preparing 5-hydroxybenzo[b]thiophene-3-carboxylic acid derivatives of the formula (VI) which are specific PGD 2 antagonists.

Description: TECHNICAL FIELD The present invention relates to 5-hydroxybenzo[b]thiophene-3-carboxylic acid derivatives which are key starting materials for producing compounds useful in the field of pharmaceuticals. BACKGROUND ART Hydroxybenzo[b]thiophene-3-carboxylic acid derivatives of the general formula (I): wherein R is hydrogen or a hydroxy-protecting group are important starting materials in the synthesis of pharmacologically active compounds. For example, a compound of the formula (I) is essential in the synthesis of benzothiophenecarboxamide derivatives of the general formula (VI): wherein R is as defined above and X is hydrogen or alkyl. The benzothiophenecarboxamide derivatives are specific antagonists of PGD 2 and known to be useful as drugs in the treatment of various diseases related to mast cell dysfunction caused by excessive production of PGD 2 , for example, systemic mastocytosis, disorder of systemic mast cell activation, tracheal contraction, asthma, allergic rhinitis, allergic conjunctivitis, urticaria, injury due to ischemic reperfusion, inflammation, and atopic dermatis (WO97/00853, PCT/JP97/04527 (WO98/25919)). Among compounds of the formula (VI), a compound wherein OR is a 5-hydroxy and X is hydrogen (hereinafter, referred to as "Compound A") has especially high antagonistic effect on PGD 2 , showing an excellent anti-nasal occlusion activity, and is envisaged to be a promising drug for treating nasal occlusion. WO97/02269 discloses condensed thiazole derivatives having 5-HT Receptor Affinity, which are useful for the treatment of central nervous disorders. DISCLOSURE OF THE INVENTION A process for preparing the above-mentioned compounds is illustrated by the following reaction scheme (WO98/25919) : In order to clinically apply Compound A widely, it is essential to establish a process for preparing a starting material, the compound (I), which process is safe, efficient and industrially applicable. However, it is difficult to synthesize benzothiophene derivatives having a 5-hydroxyl group like the compound (I) and there have been no methods industrially applicable so far. The existing methods involve various complicated processes and are inefficient and of low yield. For example, there have been methods wherein 5-acetoxybenzo[b]thiophene is brominated to yield 3-bromo-5-acetoxybenzo[b]thiophene, which in turn is reprotected at the 5-acetoxy group with a benzyl group to yield 3-bromo-5-benzyloxybenzo[b]thiophene, which is followed by metallization with magnesium, introduction of carbon dioxide and removal of the benzyl group (J. Chem. Soc. (C).1967, 1899-1905); or 5-bromobenzo[b]-thiophene is subjected to a Friedel-Crafts reaction to yield 3-acetyl-5-bromobenzo[b]thiophene, which is followed by oxidation with sodium hypochlorite to yield 5-bromobenzo[b]thiophene-3-carboxylic acid (Nippon-Kagaku Zasshi vol. 86, No. 10, 1067-1072(1965), J. Chem. Soc. (C). 1967, 2084-2089). 5-Hydroxybenzo[b]thiophene-3-carboxylic acid or 5-acetoxybenzo[b]thiophene-3-carboxylic acid are then synthesized starting from the reaction products above. However, a starting material such as 5-hydroxybenzo[b]thiophene or 5-bromobenzo [b] thiophene is not commercially available and had to be synthesized from an appropriate reagent (e.g., J. Am. Chem. Soc., 57, 1611 (1935), J. Heterocyclic Chem., 25, 1271 (1988)) in all cases, which has made the synthetic process longer and complex. The present invention solves the problems of the existing methods and provides a method for the preparation of the compounds of the formula (I), which method is industrially applicable, efficient and safe. Thus, the present invention provides a process for preparing a compound of the formula (I): wherein R is hydrogen or a hydroxy-protecting group, or a reactive derivative thereof comprising subjecting 4-mercaptophenol to reactions for introduction of a propargyl group and protection of the hydroxyl group to yield a compound of the formula (II) wherein R 1 is a hydroxy-protecting group; oxidizing the compound (II) to yield a compound of the formula (III): wherein R 1 is a hydroxy-protecting group; subjecting the compound (III) to a thermal rearrangement reaction to yield a compound of the formula (IV): wherein R 1 is as defined above; and subjecting the compound (IV) to stepwise oxidation of the hydroxymethyl group and optionally deprotection. THE BEST EMBODIMENT FOR PRACTISING THE INVENTION The terms used herein are defined below. The term "hydroxy-protecting group" means alkyl, alkoxyalkyl, acyl, aralkyl, alkylsulfonyl, arylsulfonyl, alkyl-substituted silyl, alkoxycarbonyl, aryloxycarbonyl, aralkyloxycarbonyl or tetrahydropyranyl. The term "alkyl" means C 1 -C 20 linear or branched alkyl, particularly, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl, and C 1 -C 6 alkyl is preferred. The term "alkoxy" means C 1 -C 6 linear or branched alkoxy, particularly, methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentyloxy, i-pentyloxy, neopentyloxy, s-pentyloxy, t-pentyloxy, n-hexyloxy, neohexyloxy, i-hexyloxy, s-hexyloxy and t-hexyloxy, and C 1 -C 3 alkoxy is preferred. The term "alkoxyalkyl" means alkyl group substituted by alkoxy group, including methoxymethyl, ethoxymethyl, methoxyethoxymethyl, ethoxyethyl and methoxypropyl. The term "acyl" means C 1 -C 11 acyl derived from aliphatic carboxylic acid or aromatic carboxylic acid. Examples of aliphatic carboxylic acid-derived acyl include acetyl, chloroacetyl, trichloroacetyl, propionyl, butyryl and valeryl, and examples of aromatic carboxylic acid-derived acyl include benzoyl, p-nitrobenzoyl, p-methoxybenzoyl, p-bromobenzoyl, toluoyl and naphthoyl. The term "aryl" means e.g. phenyl, naphthyl or polycyclic aromatic hydrocarbon group. In addition, aryl may be substituted by the following substituents: Examples of substituents include alkyl such as methyl, ethyl, n-propyl, isopropyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl or tert-pentyl, lower alkoxy such as methoxy or ethoxy, halogen such as fluoro, chloro, bromo or iodo, nitro, hydroxy, carboxy, cyano, sulfonyl, amino, lower alkylamino such as methylamino, dimethylamino, ethylmethylamino or diethylamino. The aryl group may have one or more substituents at any possible position. Specific examples of aryl include 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 4-pentylphenyl, 4-carboxyphenyl, 4-acetylphenyl, 4-(N,N-dimethylamino)phenyl, 4-nitrophenyl, 4-hydroxyphenyl, 4-methoxyphenyl, 4-fluorophenyl, 4-chlorophenyl and 4 iodophenyl. The aryl group in the "aralkyl", "arylsulfonyl", "aryloxycarbonyl" or "aralkyloxycarbonyl" described below may have similar substituents as defined above. The term "aralkyl" means an alkyl group substituted by an aryl group, and includes benzyl, 4-methylbenzyl, 4-methoxybenzyl, 3,4-dimethoxybenzyl, naphthylmethyl, and phenethyl. The term "alkylsulfonyl" means a sulfonyl group substituted by an alkyl group, and includes methanesulfonyl and ethanesulfonyl. The term "arylsulfonyl" means a sulfonyl group substituted by aryl group, and includes benzenesulfonyl and p-toluenesulfonyl. The term "alkyl-substituted silyl" means mono-, di- or tri-alkyl-substituted silyl, for example, methylsilyl, dimethylsilyl, trimethylsilyl, and t-butyldimethylsilyl. The term "alkoxycarbonyl" means e.g. methoxycarbonyl, isopropoxycarbonyl, and t-butoxycarbonyl. The term "aryloxycarbonyl" means e.g. phenoxycarbonyl. The term "aralkyloxycarbonyl" means e.g. benzyloxycarbonyl. Although all the above-mentioned hydroxy-protecting groups are preferred as the hydroxy-protecting group shown by R 1 or R in the respective formulae above, aryl sulfonyl is more preferred and benzenesulfonyl is particularly preferred among them. The method of the present invention is described below in more detail. When a substituent(s) possibly interfering the reaction is present, it can be appropriately protected and then deprotected at a desired stage. Such protection or deprotection can be accomplished by a procedure known in the art. Process I Wherein R and R 1 are as defined above. Step 1 This step relates to the introduction of a propargyl group at the mercapto group of 4-mercaptophenol (1) and protection of the hydroxyl group. The introduction of a propargyl group is accomplished by using a propargyl halide such as propargyl bromide or propargyl chloride in the presence of a basic agent. The reaction can be accomplished within several tens of minutes to several hours at room temperature by employing, as a basic agent, an inorganic base such as potassium carbonate or sodium carbonate, or an organic base such as triethylamine, pyridine or 4-dimethylaminopyridine in a solvent such as acetone, ethyl acetate, tetrahydrofuran or acetonitrile. When a strong base such as potassium hydroxide or sodium hydroxide is used, it can also be accomplished in a two-layer solvent system such as toluene-water or xylene-water. The protection of the hydroxyl group may be conducted using an ordinary hydroxy-protecting group in a conventional manner. Preferred protecting groups to be used in the present method are those which do not undergo changes during the oxidative reactions in the 2nd and 4th steps of the present process and the 2nd step of Process II below for the preparation of the compound of the formula (VI) and also during the Wittig reaction of the 3rd step of said Process, and can be easily deprotected in the 4th step to give leaving groups which are easily separable from, for example, Compound A for purification thereof, which corresponds to a compound of the formula (VI) wherein OR is 5-hydroxy, X is hydrogen and the double bond is in the Z-configuration. Examples of such a hydroxy-protecting group include alkyl, alkoxyalkyl, acyl, aralkyl, alkylsulfonyl, arylsulfonyl, alkyl-substituted silyl, alkoxycarbonyl, aryloxycarbonyl, aralkyloxycarbonyl or tetrahydropyranyl. Considering the requirements that a protecting group should survive during the Wittig reaction conducted under strongly basic conditions, be easily deprotected, for example, in the 4th step for the preparation of Compound A, and be separable from Compound A, arylsulfonyl is more preferred and benzenesulfonyl is particularly preferred. The benzenesulfonyl group is relatively stable to bases in anhydrous solvents and, upon deprotection, gives benzenesulfonic acid which is water-soluble and is easily separated from the final product of the formula (VI). The protection and deprotection can be carried out by methods known in the art. For example, in the case of the benzenesulfonyl group, the introduction of the benzenesulfonyl group is carried out in a manner similar to that for the introduction of a propargyl group by using benzenesulfonyl chloride. Step 2 This step relates to the oxidation of the compound (II). There have been known oxidizing methods which use, for instance, aqueous hydrogen peroxide - acetic acid (J. Am, Chem. Soc., 87, 1109-1114 (1965)), aqueous hydrogen peroxide - titanium(III) chloride (Synthesis 1981, 204-206), m-chloroperbenzoic acid (Org. Synth., 64, 157-163 (1985)), or sodium metaperiodate (J. Org. Chem., 27, 282-284 (1962)). In the present step, it is preferred to use a slight excess amount of 30 % aqueous hydrogen peroxide in an alcoholic solvent such as ethanol, methanol, isopropanol or tert-butanol solution containing formic acid. The reaction is accomplished within several tens of minutes to several hours under cooling or at room temperature. Step 3 This step relates to the conversion of the compound (III) into the hydroxymethyl compound (IV) by a thermal rearrangement reaction. The thermal rearrangement reaction in this step is carried out according to the method described in J. C. S. Chem. Communication., 1974, 848-849. Examples of preferred solvents for this reaction include dioxane, 1,2-dimethoxyethane, propyl acetate and 3-pentanone. The reaction is accomplished by refluxing in a solvent for several hours followed by adding to the resultant intermediate an acid (e.g. p-toluenesulfonic acid, methanesulfonic acid or sulfuric acid). Step 4 This step relates to the oxidation of the compound (IV) to provide a carboxylic acid (I). The oxidation can be carried out either directly or in a stepwise manner. Examples of the oxidizing agent for converting an aromatic primary alcohol to the corresponding carboxylic acid directly include chromic acids (Synthesis. 1986, 285-288), potassium permanganate (J. Org. Chem., 18, 806-809 (1953)) and ruthenium oxides (J. C. S. Chem. Communication., 1979, 58-59)). However, these methods have disadvantages not only in the yield but also in the following matters. For instance, the reaction time is long, a detoxification treatment of the oxidizing agent is needed following the reaction, the reagents are unstable and/or they involve complicated operations. On the contrary, in some cases, a stepwise oxidation wherein a primary alcohol is oxidized to an aldehyde and then to a carboxylic acid may be of advantage with regard to yield. In general, the oxidation of an alcohol to an aldehyde has been carried out using an oxidizing agent of the chromic acid series, for example, Jones reagents (J. Org. Chem., 40, 1664-1665 (1975)), Collins reagents (J. C. S. Chem. Communication., 1972 1126)), pyridinium chlorochromate (Tetrahedron Lett., 2647-2650 (1975)). There are also known methods which use manganese dioxide (Helv. Chim. Acta., 39, 858-862 (1956)) or dimethyl sulfoxide (Swern oxidation, J. Org. Chem., 43, 2480-2482 (1978)). However, these existing methods have disadvantages. For example, chromic acids are toxic to the human body and must be detoxified after use. Further, the Swern oxidation using dimethyl sulfoxide-oxalyl chloride is not suited for large scale production because it is accompanied by the generation of carbon monoxide which is harmful to workers and sulfurous odor and also it must be carried out at low temperature, for example, between -50°C and -78°C. Alcohol (IV) can be converted into aldehyde (IV') almost quantitatively by a method wherein an alcohol (IV) is oxidized with an oxidizing reagent such as a halo oxoacid in the presence of e.g. 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (referred to as 'TEMPOs") according to the description in the literature (e.g., J. Org. Chem., 52, 2559-2562 (1987)), whereby the problems of the existing methods are solved. Examples of usable TEMPOs include 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and 4-cyano-2,2,6,6-tetramethylpiperidine-1-oxyl. Examples of usable halo oxoacids include sodium hypochlorite, sodium hypobromite, sodium bromite and higher bleaching powder. A solution of an oxidizing agent may be adjusted to, for example, pH 8.5 to 9.5 with a mineral acid such as sodium hydrogen carbonate, hydrogen chloride or sulfuric acid. Alternatively, a solution of an oxidizing agent may be added in the presence of sodium hydrogen carbonate. The reaction can be accomplished within several minutes to several tens of minutes at a temperature from ice-cooling to room temperature in a solvent such as ethyl acetate, acetonitrile or dichloromethane. When the reaction solution containing the resultant aldehyde (IV') is acidified and sodium chlorite and aqueous hydrogen peroxide are added thereto, the aldehyde is converted into carboxylic acid under ice-cooling within several tens of minutes to several hours. If desired, the product may be further subjected to the deprotection of the 5-hydroxy-protecting group and/or conversion into reactive derivatives at the 3-carboxyl group. Such 'reactive derivatives" include the corresponding acid halides (e.g., chloride, bromide, iodide), acid anhydrides (e.g. mixed acid anhydride with formic acid or acetic acid), activated esters (e.g., succinimide ester), and includes acylating agents generally used for the acylation of amino groups. For example, to obtain acid halides, a carboxylic acid is reacted with thionyl halide (e.g., thionyl chloride), phosphorous halide (e.g.,phosphorous trichloride, phosphorous pentachloride), oxalyl halide (e.g., oxalyl chloride), according to a known methods (e.g., Shin-jikken Kagaku Koza, vol. 14, p.1787 (1978); Synthesis 852-854 (1986); Shin-jikken Kagaku Koza vol. 22, p. 115 (1992)). Process II, mentioned above, is illustrated below. Process II is not a process of the present invention, but requires the compound of formula I as a starting material. Process II wherein R and X are as defined above and the double bond represents the E- or Z-configuration. Step 1 This step relates to the preparation of a compound of the formula (IX) by reacting a compound of the formula (I) or a reactive derivative thereof with a compound of the formula (V') or its salt in a manner similar to that described in Process III above. The preparation of some of the compounds of the formula (V') is described in Chem. Pharm. Bull. Vol.37, No. 6 1524-1533 (1989). Step 2 This step relates to the preparation of an aldehyde of the formula (X) by oxidizing a compound of the formula (IX). The reaction can be carried out for several hours under cooling or at room temperature using an oxidizing agent selected from the chromic acid series such as Jones reagents, Collins reagents, pyridinium chlorochromate, pyridinium dichromate or dimethyl sulfoxide-oxalyl chloride in a solvent such as a chlorinated hydrocarbon (e.g. chloroform or dichloromethane), an ether (e.g. ethyl ether or tetrahydrofuran), acetone or benzene. Step 3 This step relates to the formation of a double bond by reacting a compound of the formula (X) with an ylide (Ph 3 P=CH(CH 2 ) 3 COOH). The reaction for providing a double bond can be carried out in a conventional manner for the Wittig reaction. The ylides used in the reaction can be synthesized, in the presence of a base, by treating a phosphonium salt which has been synthesized from triphenylphosphine and an alkyl halide having a desired alkyl group to be condensed, for example, 5-bromopentanoic acid. Examples of bases include dimsyl sodium, dimsyl potassium, sodium hydride, n-butyl lithium, potassium t-butoxide and lithium diisopropylamide. The reaction is accomplished within several hours at room temperature in a solvent such as ether, tetrahydrofuran, n-hexane, 1,2-dimethoxyethane or dimethyl sulfoxide. Step 4 In this step, a compound (VI) wherein R is a hydroxy-protecting group is optionally deprotected to give compound (VI-1). The reaction can be carried out in a conventional manner using a catalyst such as hydrochloric acid, sulfuric acid, sodium hydroxide, potassium hydroxide or barium hydroxide. The reaction is accomplished within several tens of minutes to several hours with heating in a solvent such as methanol-water, ethanol-water, acetone-water or acetonitrile-water, preferably dimethyl sulfoxide-water. The following Examples are provided to further illustrate the present invention in more detail and should not be interpreted in any way as to limit the scope thereof. The abbreviations used in the Examples have the following meanings: Ph: phenyl Ac: acetyl TEMPO: 2,2,6,6-tetramethylpiperidine-1-oxyl Example 1 (1) Step 1: 4-(2-Propyn-1-ylthio)phenyl benzenesulfonate (2) 4-Mercaptophenol (1) (37.85 g, 300 mmol) and propargyl bromide (42.82g, 360 mmol) were dissolved in ethyl acetate (757 ml). To the solution was added dropwise triethylamine (42.5g, 420 mmol) over 25 minutes with stirring and under ice-cooling. After stirring for another 1.5 hours at the same temperature, triethylamine (42.5g, 420 mmol) was added in one portion, and benzenesulfonyl chloride (63.58g, 360 mmol) was added dropwise over 20 minutes. After keeping 1 hour at the same temperature, the cooling bath was removed and the mixture was stirred for 30 minutes at room temperature and partitioned into two layers by adding ice-water (500ml) and 2N hydrochloric acid (110 ml). The aqueous layer was extracted with ethyl acetate (200 ml). The combined organic layer was washed with water, dried over anhydrous magnesium sulfate, and then the solvent was distilled off under reduced pressure to provide 100.04g of the title compound (2) as an oil. Crude yield: 109%. IR (CHCl 3 ); 3306, 3071, 3031, 3019, 3009, 1585, 1486,1449, 1378 cm -1 1 H NMRδ (CDCl 3 ), 300MHz; 2.23 (1H, t, J=2.7Hz), 3.56 (2H, d, J=2.7Hz), 6.94 and 7.34 (each 2H, each d, J=8.7Hz), 7.51-7.56 (2H, m), 7.68 (1H, m), 7.82-7.85 (2H, m) (2) Step 2: 4-(2-Propyn-1-ylthio)phenyl benzenesulfonate (3) The compound (2) (60.8g, 183 mmol) prepared in step (1) above was dissolved in formic acid (30.4 ml) and methanol (122 ml), and 31% aqueous hydrogen peroxide (26.29g, 240 mmol) was then added. After 3.5 hours, ice-water (240 ml) was added and the mixture was extracted with ethyl acetate (2 x 300 ml). The combined organic layer was washed with 5% aqueous sodium carbonate and water, dried over anhydrous magnesium sulfate and the solvent was then distilled off under reduced pressure to provide 65.47g of the title compound (3) as an oil. Crude yield: 117%. IR (CHCl 3 ); 3305, 3066, 3032, 3012, 1586, 1486, 1449, 1382 cm -1 1 H NMR6(CDCl 3 ) , 300MHZ; 2.34 (1H, t, J=3.9Hz), 3.58 and 3.68 (each 1H, each dd, J =3.9 and 23.7Hz), 7.18 and 7.67 (each 2H, each d, J=9.9Hz), 7.51-7.59 (2H, m), 7. 66 (1H, m), 7.82-7.87 (2H, m) (3) Step 3: 5-Benzenesulfonyloxy-3-hydroxymethylbenzo[b]thiophene (4) The compound (3) (65.47g, 183 mmol) obtained in (2) above was dissolved in 1,2-dimethoxyethane (1.6L) and the solution was refluxed for 4 hours. To the solution were added water (64 ml) and p-toluenesulfonic acid monohydrate (19.2g, 100 mmol) and refluxing was continued for 2 hours. The reaction mixture was concentrated under reduced pressure. After water (200 ml) was added to the resulting oil, the mixture was extracted with ethyl acetate (300 ml). The organic layer was washed with aqueous sodium hydrogen carbonate and water, dried over anhydrous magnesium sulfate and then the solvent was distilled off under reduced pressure to provide 60.18g of the title compound (4) as an oil. Crude yield: 103%. IR (CHCl 3 ); 3609, 3067, 3033, 3013, 2935, 2878, 1589, 1566, 1449, 1435, 1376 cm -1 1 H NMR δ (CDCl 3 ), 300MHz; 4.78 (2H, d, J=0.9Hz), 6.98 (1H, dd, J=2.4 and 8.7Hz), 7.26 (1H, s), 7.43-7.45 (2H, m), 7.50-7.55 (2H, m), 7.66 (1H, m), 7.73 (1H, d, J=8.7Hz), 7.83-7.86 (2H, m) (4) Step 4: 5-Benzenesulfonyloxybenzo[b]thiophene-3-carboxylic acid (6) The compound (4) (51.26g, 155 mmol) prepared in (3) above was dissolved in acetonitrile (1.54L), and TEMPO (2, 2, 6, 6-tetramethylpiperidine-l-oxyl, 250 mg, 0.01 eq.) was added thereto. To the mixture was added dropwise 0.81 N aqueous sodium hypochlorite, which had been prepared by diluting 1.63 N aqueous sodium hypochlorite (150ml) with water (75 ml), adjusting to pH 8.6 with 1 N sulfuric acid, and adjusting to the total volume to 300ml, over 15 minutes, while maintaining the inner temperature between -1°C and 8°C. After stirring for 25 minutes at this temperature, 1 N aqueous sodium sulfite (32 ml) was added. Subsequently, 79% sodium chlorite (27.48g, 240 mmol) and 31% aqueous hydrogen peroxide (23.26g, 212 mmol) were added under ice-cooling. The cooling bath was removed and the mixture was stirred for 2 hours. The reaction mixture was diluted with water (1.5L), adjusted to pH 3 with 1 N hydrochloric acid and the deposited crystals were filtered, and washed twice with water (200 ml), acetonitrile (50 ml) to provide 32.4g of crude crystals. The crude crystals (32.4g) were suspended in acetonitrile (224 ml), refluxed for 15 minutes and cooled on ice. The crystals were filtered and washed with acetonitrile (65 ml) to provide 26.79g of the title compound (6). Yield: 51.7%, mp 202-203°C. IR (Nujol): 3102, 2925, 2854, 2744, 2640, 2577, 1672, 1599, 1558, 1500, 1460, 1451 cm -1 NMR δ (CDCl 3 ), 300MHz; 7.16 (1H, dd, J=2.7 and 9.0Hz), 7.55-7.61 (2H, m), 7.73 (1H, m), 7.81 (1H, d, J=9.0Hz), 7.90-7.94 (2H, m), 8.16 (1H, d, J=2.7Hz), 8.60 (1H, s) Elemental Analyses for C 15 H 10 O 5 S 2 Calculated (%) C, 53.88; H, 3.01; S, 19.18 Found (%) C, 53.73; H, 3.24; S, 19.09

Claims: A process for preparing a compound of the formula (I): wherein R is hydrogen or a hydroxy-protecting group, or a reactive derivative thereof, which comprises subjecting 4-mercaptophenol to reactions for introduction of a propargyl group and protection of the hydroxyl group to yield a compound of the formula (II): wherein R 1 is a hydroxy-protecting group; oxidizing the compound (II) to yield a compound of the formula (III): wherein R 1 is a hydroxy-protecting group; subjecting the compound (III) to a thermal rearrangement reaction to yield a compound of the formula (IV): wherein R 1 is as defined above; and subjecting the compound (IV) to stepwise oxidation of the hydroxymethyl group and optionally deprotection. The process of claim 1, wherein the hydroxy-protecting group represented by R 1 is alkyl, alkoxyalkyl, acyl, aralkyl, alkylsulfonyl, arylsulfonyl, alkyl-substituted silyl, alkoxycarbonyl, aryloxycarbonyl, aralkyloxycarbonyl or tetrahydropyranyl, wherein each alkyl moiety is a C 1 -C 20 linear or branched alkyl, each alkoxy moiety is a C 1 -C 6 linear or branched alkoxy, each acyl moiety is a C 1 -C 11 acyl derived from aliphatic carboxylic acid and each aralkyl moiety is a C 1 -C 20 linear or branched alkyl substituted with an aryl group. The process of claim 1, wherein the hydroxy-protecting group represented by R 1 is arylsulfonyl.

Inventors: HIRAMATSU YOSHIHARU, HONMA TSUNETOSHI, HIRAMATSU, YOSHIHARU, HONMA, TSUNETOSHI
Applicants: SHIONOGI & CO, SHIONOGI & CO., LTD.
Application year: 1999
Main classification: C07D333
IPC codes: C07D333