Condensation of diglycolic anhydride (I) with 1-amino-2-methylpropane-2-thiol (II) afforded amide (III). Subsequent nitrosation of the thiol group of (III) employing tert-butyl nitrite gave the nitrosothio derivative (IV). This was then condensed with 4-[2-(dimethylamino)ethoxy]-2-methyl-5-isopropylphenol (VI), prepared by basic hydrolysis of moxisylyte (V), and the resulting compound was finally converted to the succinate salt.
Protection of 3-methyl-3-sulfanylbutanoic acid (I) by treatment with 2,4,6-trimethoxybenzyl alcohol (II) and trifluoroacetic acid produced the trimethoxybenzyl thioether (III). Subsequent coupling of (III) with ethyl isonipecotate (IV) using EDC and DMAP gave amide (V). The ethyl ester group of (V) was then hydrolyzed to carboxylic acid (VI) by means of ethanolic NaOH. This was then condensed with 4-[2-(dimethylamino)ethoxy]-2-methyl-5-isopropylphenol (VIII), prepared by basic hydrolysis of moxisylyte (VII), and the resulting ester (IX) was deprotected with trifluoroacetic acid to give thiol (X). Finally, S-nitrosation of (X) with tert-butyl nitrite, followed by treatment with succinic acid furnished the title compound.