1) The reaction of dimethyl sulfate (I) with dimethyl sulfide (II) by means of sodium methoxide in acetonitrile gives dimethyl (methylene)-lambda4-sulfane (III), which, without isolation, is condensed with benzo[b]thiophene-5-carbaldehyde (IV) in the same solvent to yield 2-(benzo[b]thiophen-5-yl)oxirane (V) (1). The reaction of (V) with 2-(dimethylamino)ethanol (VI) by means of potassium tert-butoxide in hot DMSO (1, 2), or hot DMF (3) affords (?-1-(benzo[b]thiophen-5-yl)-2-[2-(diethylamino)ethoxy]ethanol (racemic T-588) (VII), which is submitted to optical resolution first by treatment with acetic anhydride in refluxing toluene to give the corresponding acetate (VIII), and then by reaction of (VIII) with D-dibenzoyltartaric acid (IX) in ethyl acetate/acetone/water followed by fractionated crystallization of the resulting salt to yield the D-dibenzoyltartrate salt of the (R)-isomer (X). Finally, (X) is deacetylated with sodium methoxide in methanol and salified with ethanolic hydrochloric acid.

1) The reaction of dimethyl sulfate (I) with dimethyl sulfide (II) by means of sodium methoxide in acetonitrile gives dimethyl (methylene)-lambda4-sulfane (III), which, without isolation, is condensed with benzo[b]thiophene-5-carbaldehyde (IV) in the same solvent to yield 2-(benzo[b]thiophen-5-yl)oxirane (V) (1). The reaction of (V) with 2-(dimethylamino)ethanol (VI) by means of potassium tert-butoxide in hot DMSO (1, 2), or hot DMF (3) affords (?-1-(benzo[b]thiophen-5-yl)-2-[2-(diethylamino)ethoxy]ethanol (racemic T-588) (VII), which is submitted to optical resolution first by treatment with acetic anhydride in refluxing toluene to give the corresponding acetate (VIII), and then by reaction of (VIII) with D-dibenzoyltartaric acid (IX) in ethyl acetate/acetone/water followed by fractionated crystallization of the resulting salt to yield the D-dibenzoyltartrate salt of the (R)-isomer (X). Finally, (X) is deacetylated with sodium methoxide in methanol and salified with ethanolic hydrochloric acid.

2) The condensation of aldehyde (IV) with bromoform by means of LiOH in hot dioxane/water gives (?-2-(benzo[b]thiophen-5-yl)-2-hydroxyacetic acid (XI), which is submitted to optical resolution by fractional crystallization of its 2(R)-aminobutanol salt in isopropanol and acidification with HCl to yield (R)-(-)-2-(benzo[b]thiophen-5-yl)-2-hydroxyacetic acid (XII). The cyclization of (XII) with acetone and concentrated H2SO4 affords (R)-(-)-5-(benzo[b]thiophen-5-yl)-2,2-dimethyl-1,3-dioxolan-4-one (XIII), which, by treatment with methanol and H2SO4, is converted into (R)-(-)-2-(benzo[b]thiophen-5-yl)-2-hydroxyacetic acid methyl ester (XIV). The protection of the OH group of (XIV) with dihydropyran (DHP) and pyridinium p-toluenesulfonate (Pyr稵sOH) affords the corresponding tetrahydropyranyl ether (XV), which is reduced with NaBH4 in ethanol, giving (R)-(-)-2-(benzo[b]thiophen-5-yl)-2-(tetrahydropyranyloxy)ethanol (XVI). Finally, this compound is condensed with 2-(diethylamino)ethyl chloride (XVII) by means of NaOH and tetrabutylammonium hydrogensulfate in toluene/water, followed by acidification with HCl. 3) The (R)-dioxolane (XIII) can also be obtained as follows: The racemic hydroxyacetic acid (XI) is cyclized with acetone and H2SO4 as before, giving the racemic dioxolane (XVIII). This compound is dissolved in hot (50 C) tert-amyl alcohol along with 1,8-diazabicyclo[5.4.0]-7-undecene (DCU); this solution is then seeded with a suspension of the (R)-(-)-isomer (XIII) in the same solvent and is slowly cooled at 25 C; a 81% yield of pure crystals of (R)-(-)-isomer (XIII) is obtained. This procedure allows for improving the yields by recovering the unused (S)-(+)-isomer.

1) The reaction of dimethyl sulfate (I) with dimethyl sulfide (II) by means of sodium methoxide in acetonitrile gives dimethyl (methylene)-lambda4-sulfane (III), which, without isolation, is condensed with benzo[b]thiophene-5-carbaldehyde (IV) in the same solvent to yield 2-(benzo[b]thiophen-5-yl)oxirane (V) (1). The reaction of (V) with 2-(dimethylamino)ethanol (VI) by means of potassium tert-butoxide in hot DMSO (1, 2), or hot DMF (3) affords (?-1-(benzo[b]thiophen-5-yl)-2-[2-(diethylamino)ethoxy]ethanol (racemic T-588) (VII), which is submitted to optical resolution first by treatment with acetic anhydride in refluxing toluene to give the corresponding acetate (VIII), and then by reaction of (VIII) with D-dibenzoyltartaric acid (IX) in ethyl acetate/acetone/water followed by fractionated crystallization of the resulting salt to yield the D-dibenzoyltartrate salt of the (R)-isomer (X). Finally, (X) is deacetylated with sodium methoxide in methanol and salified with ethanolic hydrochloric acid.

1) The reaction of dimethyl sulfate (I) with dimethyl sulfide (II) by means of sodium methoxide in acetonitrile gives dimethyl (methylene)-lambda4-sulfane (III), which, without isolation, is condensed with benzo[b]thiophene-5-carbaldehyde (IV) in the same solvent to yield 2-(benzo[b]thiophen-5-yl)oxirane (V) (1). The reaction of (V) with 2-(dimethylamino)ethanol (VI) by means of potassium tert-butoxide in hot DMSO (1, 2), or hot DMF (3) affords (?-1-(benzo[b]thiophen-5-yl)-2-[2-(diethylamino)ethoxy]ethanol (racemic T-588) (VII), which is submitted to optical resolution first by treatment with acetic anhydride in refluxing toluene to give the corresponding acetate (VIII), and then by reaction of (VIII) with D-dibenzoyltartaric acid (IX) in ethyl acetate/acetone/water followed by fractionated crystallization of the resulting salt to yield the D-dibenzoyltartrate salt of the (R)-isomer (X). Finally, (X) is deacetylated with sodium methoxide in methanol and salified with ethanolic hydrochloric acid.

1) The reaction of dimethyl sulfate (I) with dimethyl sulfide (II) by means of sodium methoxide in acetonitrile gives dimethyl (methylene)-lambda4-sulfane (III), which, without isolation, is condensed with benzo[b]thiophene-5-carbaldehyde (IV) in the same solvent to yield 2-(benzo[b]thiophen-5-yl)oxirane (V) (1). The reaction of (V) with 2-(dimethylamino)ethanol (VI) by means of potassium tert-butoxide in hot DMSO (1, 2), or hot DMF (3) affords (?-1-(benzo[b]thiophen-5-yl)-2-[2-(diethylamino)ethoxy]ethanol (racemic T-588) (VII), which is submitted to optical resolution first by treatment with acetic anhydride in refluxing toluene to give the corresponding acetate (VIII), and then by reaction of (VIII) with D-dibenzoyltartaric acid (IX) in ethyl acetate/acetone/water followed by fractionated crystallization of the resulting salt to yield the D-dibenzoyltartrate salt of the (R)-isomer (X). Finally, (X) is deacetylated with sodium methoxide in methanol and salified with ethanolic hydrochloric acid.

2) The condensation of aldehyde (IV) with bromoform by means of LiOH in hot dioxane/water gives (?-2-(benzo[b]thiophen-5-yl)-2-hydroxyacetic acid (XI), which is submitted to optical resolution by fractional crystallization of its 2(R)-aminobutanol salt in isopropanol and acidification with HCl to yield (R)-(-)-2-(benzo[b]thiophen-5-yl)-2-hydroxyacetic acid (XII). The cyclization of (XII) with acetone and concentrated H2SO4 affords (R)-(-)-5-(benzo[b]thiophen-5-yl)-2,2-dimethyl-1,3-dioxolan-4-one (XIII), which, by treatment with methanol and H2SO4, is converted into (R)-(-)-2-(benzo[b]thiophen-5-yl)-2-hydroxyacetic acid methyl ester (XIV). The protection of the OH group of (XIV) with dihydropyran (DHP) and pyridinium p-toluenesulfonate (Pyr稵sOH) affords the corresponding tetrahydropyranyl ether (XV), which is reduced with NaBH4 in ethanol, giving (R)-(-)-2-(benzo[b]thiophen-5-yl)-2-(tetrahydropyranyloxy)ethanol (XVI). Finally, this compound is condensed with 2-(diethylamino)ethyl chloride (XVII) by means of NaOH and tetrabutylammonium hydrogensulfate in toluene/water, followed by acidification with HCl. 3) The (R)-dioxolane (XIII) can also be obtained as follows: The racemic hydroxyacetic acid (XI) is cyclized with acetone and H2SO4 as before, giving the racemic dioxolane (XVIII). This compound is dissolved in hot (50 C) tert-amyl alcohol along with 1,8-diazabicyclo[5.4.0]-7-undecene (DCU); this solution is then seeded with a suspension of the (R)-(-)-isomer (XIII) in the same solvent and is slowly cooled at 25 C; a 81% yield of pure crystals of (R)-(-)-isomer (XIII) is obtained. This procedure allows for improving the yields by recovering the unused (S)-(+)-isomer.