Keoxifene has been synthesized using the following process: A portion of 6-methanesulfonyloxy-2-(4-methanesulfonyloxyphenyl)-3-[4-(2-pipendinoethoxy)benzoyl]benzo[b]thiophene hydrochloride (I) was combined with denatured alcohol and 5N sodium hydroxide, and stirred under a nitrogen atmosphere. The reaction mixture was evaporated to dryness under vacuum, and the residue dissolved in water and washed with diethyl ether. The water layer was degassed under vacuum, and then nitrogen was bubbled through it to remove all traces of ether. The mixture was then acidified with 1N hydrochloric acid, and then made basic with excess sodium bicarbonate The precipitate was collected by filtration and washed with cold water to obtain crude product, which was purified on a column of silica gel. The column was eluted first with 700 ml of 5% methanol in chloroform, followed by 1l of 10% methanol in chloroform. The impurities came off first, and the product-containing fractions were combined and evaporated under vacuum to obtain a yellow oil. The oil was dissolved in acetone seeded and chilled in a freezer to obtain the purified product.

The synthesis of radiolabeled raloxifene has been reported: The esterification of 3,5-dibromo-4-hydroxybenzoic acid (I) with methanol/HCl gives the corresponding methyl ester (II), which is condensed with 1-(2-chloroethyl)piperidine (III) by means of K2CO3 in DMF yielding 3,5-dibromo-4-[2-(1-piperidyl)ethoxy]benzoic acid methyl ester (IV). The hydrolysis of (IV) with NaOH in methanol affords the corresponding free acid (V), which by treatment of SOCl2 in toluene is converted to the acyl chloride (VI). The Friedel-Crafts condensation of (VI) with 6-methoxy-2-(4-methoxyphenyl)benzo[b]thiophene (VII) by means of AlCl3 in dichloromethane gives [3,5-dibromo-4-[2-(1-piperidinyl)ethoxy]phenyl]-[6-methoxy-2-(4-methoxy phenyl)benzo[b]thien-3-yl]methanone (VIII), which is demethylated with AlCl3 and ethylmercaptane to dibromoraloxifene (IX). Finally, this compound is submitted to hydrogenolysis with tritium over Pd/C in methanol.

The two major metabolites of raloxifene, the glucuronide conjugates (VI) and (VIII) are synthesized as follows: The partial silylation of raloxifene (I) with tert-butyldimethylsilyl chloride (TBDMS-Cl) by means of dimethylaminopyridine (DMAP) in THF/DMF gives a mixture of the monosilylated compounds (II) and (III), which are separated by chromatography. Compounds (II) and (III) are independently condensed with methyl 1,2,3,4-tetra-O-acetyl-D-glucuronate (IV) by means of BF3.OEt2 in dichloromethane yielding protected glucuronides (V) and (VII), respectively. Finally, both compounds are deprotected by a treatment first with LiOH in dioxane to hydrolyzed the ester groups, and then with tetrabutylammonium fluoride in THF to eliminate the silyl groups, thus obtaining the desired metabolites (VI) and (VIII), respectively.

The two major metabolites of raloxifene, the glucuronide conjugates (VI) and (VIII) are synthesized as follows: The partial silylation of raloxifene (I) with tert-butyldimethylsilyl chloride (TBDMS-Cl) by means of dimethylaminopyridine (DMAP) in THF/DMF gives a mixture of the monosilylated compounds (II) and (III), which are separated by chromatography. Compounds (II) and (III) are independently condensed with methyl 1,2,3,4-tetra-O-acetyl-D-glucuronate (IV) by means of BF3.OEt2 in dichloromethane yielding protected glucuronides (V) and (VII), respectively. Finally, both compounds are deprotected by a treatment first with LiOH in dioxane to hydrolyzed the ester groups, and then with tetrabutylammonium fluoride in THF to eliminate the silyl groups, thus obtaining the desired metabolites (VI) and (VIII), respectively.

Two related new syntheses of raloxifene have been described: 1) The acylation of N-(6-methoxy-1-benzothiophen-2-yl)-N,N-dimethylamine (I) with 4-fluorobenzoyl chloride (II) by heating at 100 C in chlorobenzene gives the 3-acyl derivative (III), which is condensed with 4-methoxyphenylmagnesium bromide (IV) in THF yielding 3-(4-fluorobenzoyl)-6-methoxy-2-(4-methoxyphenyl)-1-benzothiophene (V). The condensation of (V) with 1-(2-hydroxyethyl)piperidine (VI) by means of NaH in DMF affords the ether (VII), which is finally demethylated with AlCl3 and ethanethiol. 2) The intermediate (III) can also be condensed first with 1-(2-hydroxyethyl)piperidine (VI) by means of NaH as before giving the piperidinoethyl ether (VIII), which is then condensed with the Grignard reagent (IV) affording the previously reported ether (VII).

Keoxifene has been synthesized using the following process: A portion of 6-methanesulfonyloxy-2-(4-methanesulfonyloxyphenyl)-3-[4-(2-pipendinoethoxy)benzoyl]benzo[b]thiophene hydrochloride (I) was combined with denatured alcohol and 5N sodium hydroxide, and stirred under a nitrogen atmosphere. The reaction mixture was evaporated to dryness under vacuum, and the residue dissolved in water and washed with diethyl ether. The water layer was degassed under vacuum, and then nitrogen was bubbled through it to remove all traces of ether. The mixture was then acidified with 1N hydrochloric acid, and then made basic with excess sodium bicarbonate The precipitate was collected by filtration and washed with cold water to obtain crude product, which was purified on a column of silica gel. The column was eluted first with 700 ml of 5% methanol in chloroform, followed by 1l of 10% methanol in chloroform. The impurities came off first, and the product-containing fractions were combined and evaporated under vacuum to obtain a yellow oil. The oil was dissolved in acetone seeded and chilled in a freezer to obtain the purified product.