Sodium Iodide → 10-(3,6-Dioxa-heptyl)-1,4,7-tris-(carboxymethyl)-1,4,7,10-tetraazacyclododecane

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Reaction Steps

3 g (8.66 mmol) of 1,4,7-tris-(carboxymethyl)-1,4,7, 10-tetraazacyclododecane is stirred in 50 ml of dimethylformamide for 10 hours with 1.83 g (10 mmol) of 1-bromo-3,6-dioxa-heptane, 100 mg of sodium iodide and 4 g of potassium carbonate at 90° C. It is concentrated by evaporation in a vacuum and the residue is spread between 100 ml of water and 50 ml of diethyl ether. The aqueous phase is adjusted to pH 2 with 5 N hydrochloric acid and evaporated to dryness. The residue is refluxed with 200 ml of methanol, the undissolved material is filtered out, evaporated to dryness in a vacuum, the residue is dissolved in 50 ml of water, adjusted to pH 2 with 5 N hydrochloric acid and the solution is put on a column with 200 ml of cation exchanger IRC 50. It is eluted first with 0.5 l of water, which is discarded. Then, it is eluted with 0.5 l of 0.5 N ammonia solution. It is evaporated almost to dryness in a vacuum, mixed with 100 ml of water and enough cation exchanger IRC 50 is added with stirring to reach pH 3.5. The solution is then filtered and freeze-dried. 2.95 g of the title compound with a water content of 3.5% is obtained.

Provenance & Evidence