Potassium Carbonate → 2,4,6-triiodo-N,N'-dimethylisophthalamide

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A slurry of glucosamine (0.591 g.; 0.0033 mole) and potassium carbonate (1.242 g.; 0.009 mole) in dimethylformamide (30 ml.) was heated rapidly to 75° C. (to dissolve the glucosamine) and quickly cooled in an ice bath to 25° C. 2,4,6-Triiodo-5-isocyanato-N,N'-dimethylisophthalamide (IV; 1.83 g.; 0.003 mole) dissolved in dimethylformamide (9 ml.) was added dropwise over a five minute period. After being stirred overnight at room temperature, the reaction mixture was filtered and concentrated to a foam under reduced pressure employing a 50° C. water bath. The residue was dissolved in water (24 ml.), and the aqueous solution was adjusted to pH 1 with concentrated hydrochloric acid. The solution was extracted with aqueous 90% phenol (4×10 ml.). The combined phenolic layers were washed with water (4×10 ml.), diluted with ether (120 ml.) and extracted with water (4×10 ml.). The combined aqueous extracts were washed with chloroform-isopropyl alcohol (3/1; 10×40 ml., contact time 15 min.). The aqueous solution was evaporated under reduced pressure at 40° C. (water bath) to give 5-{3-[3-D-gluco-2-deoxy-3,4,5,6-tetrahydroxy-1-oxohexyl)]ureido}-2,4,6-triiodo-N,N'-dimethylisophthalamide (V) as a colorless foam, 1.3 g. (55% yield), m.p. 175°-230° C. (dec.). The infrared and nuclear magnetic resonance spectra were consistent with the assigned structure. The material was homogeneous by thin-layer chromatography (chloroform-methanol-trimethylamine, 65:35:5; and ethanol-concentrated ammonium hydroxide, 50:50), and the aqueous solubility was determined to be 2.7-8% depending upon the method employed.

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