Rhenium and 99m-technetium complexes of monosaccharide based tripodal triamines as potential radio imaging agents

Abstract

A synthetic pathway to new sugar containing tripodal triamines of the TAME type (1,1,1-tris(aminomethyl)ethane) is presented. The tripodal bromo substituted precursors Ac₃Xyl-O-CH₂C(CH₂Br)₃, Ac₄Glc-O-CH₂C(CH₂Br)₃ and Ac₄Gal-O-CH₂C(CH₂Br)₃ (2a–c) were obtained by glycosidation reaction of the fully acetylated glycopyranosides with pentaerythritol tribromide. Nucleophilic substitution to the corresponding azides with sodium azide and deprotection of the sugars, followed by hydrogenation reaction in the presence of PtO₂ leads to the triamines Xyl-O-CH₂C(CH₂NH₂)₃, Glc-O-CH₂C(CH₂NH₂)₃ and Gal-O-CH₂C(CH₂NH₂)₃ (5a–c). The triamines form complexes of the type [Re(CO)₃L]Cl (6a–c). The precursors as well as the final ligands and complexes were characterized by elemental analysis, IR and NMR spectroscopy as well as mass spectrometry. The synthesis of the analogous radiolabelled ^99mTc complex with galactosyl appendage 7c (L = Gal-O-CH₂C(CH₂NH₂)₃) was achieved for 5c and its stability over a period of 24 h could be verified by HPLC analysis, confirming the significant stability of 7c against histidine exchange.