A new bifunctional amino acid chelator targeting the glucose transporter

The coupling reactions of d-glucosamine, 1,3,4,6-tetra-O-acetylglucosamine, and 4-aminophenyl-galactopyranosine with N,N-bis(quinolinoyl)aminovaleric acid (L1) provided a series of conjugates containing a potentially tridentate donor group terminus linked to a sugar moiety, L2′, L2 and L3, respectively. Reactions of the ligands with [NEt4]2[Re(CO)3Br3] in refluxing methanol provided the rhenium complexes [Re(CO3)(L1)]Br (ReL1), [Re(CO)3(L2)]Br (ReL2), [Re(CO)3(L2′)]Br (ReL2′) and [Re(CO)3(L3)]Br (ReL3). The ligands and complexes were characterized by elemental analyses, 1H and 13C NMR, mass spectroscopy and, in the case of L1 and ReL1, by X-ray crystallography. The rhenium complexes exhibit fluorescence emissions with long lifetimes, large Stokes shifts, and moderate quantum yields.