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

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 (LGal-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.