The reaction of 3-bromopropanol (I) with thiourea in refluxing water gives 3-sulfanylpropanol (II), which is cyclized with 2-phenylacetaldehyde (III) by means of p-toluenesulfonic acid in refluxing toluene yielding 2-benzyl-1,3-oxathiane (IV). The reductive cleavage of (IV) with Ca in liquid ammonia affords 3-(2-phenylethoxy)propanethiol (V), which is condensed with bromoacetic acid by means of NaH in DMF providing 2-[3-(2-phenylethoxy)propylsulfanyl]acetic acid (VI). The oxidation of (VI) with potassium peroxymonosulfate (oxone) gives the corresponding sulfonylacetic acid (VII), which is condensed with benzothiazolone (VIII) by means of DCC, HOBT and triethylamine in DMF yielding the correponding amide (IX). Finally, this compound is reduced with borane/THF yielding the target compound.
The reaction of 3-bromopropanol (I) with thiourea in refluxing water gives 3-sulfanylpropanol (II), which is cyclized with 2-phenylacetaldehyde (III) by means of p-toluenesulfonic acid in refluxing toluene yielding 2-benzyl-1,3-oxathiane (IV). The reductive cleavage of (IV) with Ca in liquid ammonia affords 3-(2-phenylethoxy)propanethiol (V), which is condensed with bromoacetic acid by means of NaH in DMF providing 2-[3-(2-phenylethoxy)propylsulfanyl]acetic acid (VI). The oxidation of (VI) with potassium peroxymonosulfate (oxone) gives the corresponding sulfonylacetic acid (VII).The condensation of sulfonylacetic acid (VII) with dimethoxybenzothiazole derivative (X) by means of DCC, HOBT and triethylamine in DMF gives the corresponding amide (XI), which is reduced with borane/THF yielding intermediate (XII). Finally, this compound is demethylated with concentrated HBr or HCl.
The target compound can also be obtained by reductocondensation of benzothiazolone (VIII) with aldehyde (XIII) by means of sodium cynonoborohydride.