Patent ID: 9458117
Filing Date: 2016-10-04
CPC Classification: A61K,C07D

Claim Text:
1. A process for preparing 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or a salt or a hydrate thereof and having formula (I): the process comprising the steps of: a) reacting 1,4,7,10-tetra-azacyclododecane and a halo-acetic acid with a base at a pH ≧10 so as to obtain the DOTA; b) crystallizing the DOTA obtained in step a) by adding an acid to achieve a pH ≦3, followed by a heating step and a cooling step, wherein the heating step is performed at a temperature in a range from 50° C. to 100° C. for at least 5 minutes, and the cooling step is performed at a temperature in a range from 5° C. to 25° C. for at least 5 minutes so as to obtain a raw material; c) treating the raw material obtained in step b) with a cationic resin and then desorbing the DOTA with a volatile base solution; d) further treating a solution resulting from step c) with an anionic resin; and e) washing a product produced in step d) in a two-stage wash including a first stage with a first organic volatile acid with a pKa less than 5 until the DOTA starts to be released from the anionic resin, and a second stage with an organic volatile acid with a pKa less than or equal to the pKa of the first organic volatile acid and/or with a higher concentration than the first organic volatile acid to release the DOTA from the anionic resin.