148.5 g 4,7,10,13-tetraoxahexadecane-1,16-dinitrile (U.S. Patent No.
2,401,607) was added to a solution of 232 g (2.45 mol) concentrate sulfuric
acid in 290 ml absolute ethanol at 15°C. The mixture was heated at reflux for
15 hours, cooled and poured into 1000 g ice and 250 g ammonium sulfate. It
was extracted with methylene chloride, dried and a solvent was removed in
vacuum. The residue was distilled to give 4,7,10,13-tetraoxahexadecane-1,16-
dicarbonic acid dimethyl ester; BP: 190°-195°C/0.005 mm Hg.
1 mol above prepared diester was saponificated with equivalent of NaOH in
water. The reaction mixture was heated for 90 minutes. On cooling it was
extracted with ether and the water layer was evaporated to dryness. The
residue was washed with acetone. The obtained disodium salt of 4,7,10,13-
tetraoxahexadecane-1,16-dicarbonic acid (yield 100%; MP: 102°-104°C) was
acidified with calculated quantity of HCl to give the dicarbonic acid. The
solvent was evaporated to dryness. Acetone was added to the residue for
removing a by-product (sodium chloride) by filtration. Acetone was evaporated
and the residue was extracted with ether, dried and evaporated. The residual
liquid was 4,7,10,13-tetraoxahexadecane-1,16-dicarbonic acid.
100 ml thionyl chloride was cautious added to 56 g above prepared diacid and
heated at 40°-50°C and excess thionyl chloride was distilled in vacuum. The
residue was the 4,7,10,13-tetraoxahexadecane-1,16-dicarbonic acid
dichloride. The desired iodoxamic acid was prepared from above dichloride
and 3-amino-2,4,6-trijode benzoic acid, in dimethylacetamide
Endobil (Bracco Industria Chimica S.p.A.,Italy); Endomirabil (Bracco Industria Chimica S.p.A.,
Italy); Videocolangio (Bracco Industria Chimica S.p.A.,
Italy).
