Efficient multigram synthesis of the bifunctional chelating agent (S)-1-p-isothiocyanatobenzyl-diethylenetriaminepentaacetic acid [correction of diethylenetetraminepentaacetic acid].

We have developed and optimized the synthesis of the title compound, eliminating all HPLC purifications prior to the final product. The yield (and scale) of the synthesis was increased from 19% (200 mg) to 75% (26 g).