Triethylamine → 3,6-Bis(carboxymethyl)-9-(10-carboxydecylcarbamoylmethyl)-3,6,9-triazaundecanedioic acid

Participants

Reaction Steps

15.33 g (38 mmol) of N3-(2,6-dioxomorpholinoethyl)-N6-(ethoxy-carbonylmethyl)-3,6-diazaoctanedioic acid (Example 13a of EP 0331 616) is suspended in dimethylformamide (DMF) and mixed in an ice bath with 21.07 ml (152 mmol) of triethylamine and 7.65 g (38 mmol) of 11-aminoundecanoic acid. The temperature is allowed to increase to room temperature and the reaction solution is stirred overnight. After completion of the reaction, the possibly still slightly cloudy solution is filtered and the filtrate is concentrated by evaporation in a vacuum. The residue is absorptively precipitated with ether and then recrystallized from water (17.8 g). The ethyl ester is dissolved in 2 N NaOH and is adjusted to pH 7 after 3 hours by adding Amberlite® IR 120 (H+). The ion exchange material is suctioned off, the filtrate is freeze-dried (20.1 g) and then added to H2O/methanol (2:1) on 100 ml of Amberlite® IR 120 (H+) and the acid eluate is concentrated by evaporation and recrystallized from water.

Provenance & Evidence