Rhenium tricarbonyl core complexes of thymidine and uridine derivatives

Thymidine and uridine were modified at the C2′ and C5′ ribose positions to form amine analogues of the nucleosides (1 and 4). Direct amination with NaBH(OAc)₃ in DCE with the appropriate aldehydes yielded 1-{5-[(bis(pyridin-2-ylmethyl)amino)methyl]-4-hydroxytetrahydrofuran-2-yl} -5-methyl-1H-pyrimidine-2,4-dione (L1), 1-{5-[(bis(quinolin-2-ylmethyl)amino) methyl]-4-hydroxytetrahydrofuran-2-yl}-5-methyl-1H-pyrimidine-2,4-dione (L2), and 1-[3-(bis(pyridin-2-ylmethyl)amino)-4-hydroxy-5-(hydroxymethyl) tetrahydrofuran-2-yl]-1H-pyrimidine-2,4-dione (L5), while standard coupling procedures of 1 and 4 with 5-(bis(pyridin-2-ylmethyl)amino)pentanoic acid (2) and 5-(bis(quinolin-2-ylmethyl)-amino)pentanoic acid (3) in the presence of HOBT-EDCI in DMF provided a second novel series of bifunctional chelators: 5-(bis(pyridin-2-ylmethyl)amino)pentanoic acid [(3-hydroxy-5-(5-methyl-4-oxo-3, 4-dihydro-2H-pyrimidin-1-yl)tetrahydrofuran-2-yl)methyl] amide (L3), 5-(bis(quinolin-2-ylmethyl)amino)pentanoic acid [(3-hydroxy-5-(5-methyl-4-oxo-3, 4-dihydro-2H-pyrimidin-1-yl)tetrahydrofuran-2-yl)methyl] amide (L4), 5-(bis(pyridin-2-ylmethyl)amino)pentanoic acid [2-(2,4-dioxo-3,4-dihydro-2H- pyrimidin-1-yl)-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-3-yl] amide (L6), and 5-(bis(quinolin-2-ylmethyl)amino)pentanoic acid [2-(2,4-dioxo-3,4-dihydro-2H- pyrimidin-1-yl)-4-hydroxy-5-(hydroxy-methyl)tetrahydrofuran-3-yl] amide (L7). The rhenium tricarbonyl complexes of L1-L4, L6, and L7, [Re(CO) ₃(LX)]-Br (X = 1-4, 6, 7: compounds 5-10, respectively), have been prepared by reacting the appropriate ligand with [NEt₄][Re(CO) ₃Br₃] in methanol. The ligands and their rhenium complexes were obtained in good yields and characterized by common spectroscopic techniques including 1D and 2D NMR, HRMS, IR, cyclic voltammetry, UV, and luminescence spectroscopy and X-ray crystallography. The crystal structure of complex 6·0.5NaPF₆ displays a facial geometry of the carbonyl ligands. The nitrogen donors of the tridentate ligand complete the distorted octahedral spheres of the complex. Crystal data: monoclinic, C2, a = 24.618(3) Å, b = 11.4787(11) Å, c = 15.5902(15) Å, β = 112.422(4)°, Z= 4, D_calc = 1.562 g/cm³.