Lanthanide(III) complexes of DOTA-glycoconjugates:: A potential new class of lectin-mediated medical imaging agents

The synthesis and characterization of a new class of DOTA (1,4,7,10-tetrakis(carboxymethyl)-1,4,7,10-tetraazacyclododecane) monoamide-linked glycoconjugates (glucose, lactose and galactose) of different valencies (mono, di and tetra) and their Sm-III, Eu-III and Gd-III complexes are reported. The H-1 NMR spectrum of Eu-III-DOTALac(2) shows the predominance of a single structural isomer of square antiprismatic geometry of the DOTA chelating moiety and fast rotation about the amide bond connected to the targeting glycodendrimer. The in vitro relaxivity of the Gd-III-glycoconjugates was studied by H-1 nuclear magnetic relaxation dispersion (NMRD), yielding parameters close to those reported for other DOTA monoamides. The known recognition of sugars by lectins makes these glycoconjugates good candidates for medical imaging agents (MRI and gamma scintigraphy).