A CONVENIENT SYNTHESIS OF BIFUNCTIONAL CHELATING-AGENTS BASED ON DIETHYLENETRIAMINEPENTAACETIC ACID AND THEIR COORDINATION CHEMISTRY WITH YTTRIUM(III)

The bifunctional chelating agents N,N,N',N",N"-pentakis(carboxymethyl)-1-[(4-aminophenyl)methyl]diethylenetriamine and N,N,N',N",N"-pentakis(carboxymethyl)-1-[(4-aminophenyl)methyl]-4-methyldiethylenetriamine were prepared in six-step syntheses in overall yields of 38% and 31%, respectively. The use of bromoacetate esters in the synthesis allowed large-scale flash chromatographic purification of reaction products. The synthesis of N,N,N',N",N"-pentakis(carboxymethyl)-1-[(4-aminophenyl)methyl]-4-methyldiethylenetriamine resulted in a mixture of two diastereomers. Chelation of yttrium(III) with these bifunctional chelating agents resulted in 1:1 chelates. In the case of N,N,N',N",N"-pentakis (carboxymethyl)-1-[(4-aminophenyl)methyl]diethylenetriamine, two diastereomers were observed upon chelation, as expected. In the case of N,N,N',N",N"-pentakis(carboxymethyl)-1-[(4-aminophenyl)methyl]-4-methyldiethylenetriamine, only three of the four anticipated diastereomers were observed.