Carbohydrate Conjugates for Molecular Imaging and Radiotherapy: 99mTc(I) and 186Re(I) Tricarbonyl Complexes of N-(2-Hydroxybenzyl)-2-amino-2-deoxy-D-glucose

An approach to a new class of potential radiopharmaceuticals is demonstrated by the labeling of a glucosamine derivative with the tricarbonyls of 99mTc and 186Re. The proligand HL2 (N-(2ʹ-hydroxybenzyl)-2-amino-2-deoxy-d-glucose) was produced by hydrogenation of the corresponding Schiff base and reacted with [NEt4]2[Re(CO)3Br3] to form the neutral complex [(L2)Re(CO)3] in 40% yield. 1H and 13C NMR spectra indicate that the {Re(CO)3} core is bound in a tridentate fashion via the amino N, phenolato O, and C-3 hydroxyl O atoms of the ligand. At the tracer-level, labeling of HL2 with [99mTc(CO)3(H2O)3]+ and [186Re(CO)3(H2O)3]+ was achieved in aqueous conditions in 95 ± 2% and 94 ± 3% average radiochemical yields, respectively.