Structural and Kinetic Considerations for the Application of the Traceless Staudinger Ligation to Future F-18 Radiolabeling Using XRD and F-19 NMR

摘要

A 4-fluorobenzoate-functionalized phosphane was synthesized and reacted with different azides using the traceless Staudinger ligation as a representative sample reaction for future radiolabeling purposes with short-lived radionuclides like fluorine-18. For this purpose, the reaction rate was evaluated at different temperatures. The effect of starting material concentrations and the influence of the steric effect coming from the applied azides were investigated. F-19 NMR was used to determine the reaction half-live ((1/2)) and the reaction rate constant (k(obs)) of this ligation under mild reaction conditions in a water-acetonitrile mixture. Furthermore, the phosphane key compound 1 (orthorhombic, space group Pna2(1), a = 18.6363(9), b = 8.3589(4), c = 18.5480(9) angstrom, V = 2889.4(2) angstrom(3), Z = 8, D-obs = 1.277 g/cm(3)), which acts as starting material for all subsequent syntheses, and the fluorine-containing phosphane 3 (monoclinic, space group P2(1)/c, a = 8.321(2), b = 16.160(4), c = 14.940(4) angstrom, = 99.51(1)degrees, V = 1981.4(8) angstrom(3), Z = 4, D-obs = 1.342 g/cm(3)) were analyzed by single-crystal XRD.