Hydrochloric Acid → DO2A

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Reaction Steps

20 g (0.074 mol) of 12-oxo-1,4,7,10-tetraazabicyclo[8.2.2]tetradecane-4-acetic acid, prepared as described in example 5, are dissolved in 88.8 g of 10% NaOH. The solution is refluxed overnight, then cooled and acidified to pH 12 by addition of conc. HCl. The resulting solution is percolated on a column containing 600 ml of anionic exchanger resin IRA420 (Rohm & Haas), which is washed repeatedly with water, then eluted with 1N HCl. The fractions containing the product are combined and concentrated at reduced pressure to a volume of about 500 mL. The solution is percolated on a column containing 2 L of polyvinylpyridine resin (PVP), eluting with water, the fractions containing the desalted product are collected, combined and concentrated to dryness under vacuum. The crude solid is recrystallized from methanol/acetone=8/2, finally dried in a static drier at 50° C. under vacuum. 18.5 g (0.064 mol) of 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid are obtained.

Provenance & Evidence