SYNTHESIS AND CHARACTERIZATION OF SCHIFF-BASE CHELATES OF TETRAMIC ACIDS AS NMR CONTRAST AGENTS FOR MICRO IMAGING

Novel Cu(II) complexes derived from N,N'-ethylene-bis-(1 ',5',5'-trime thyltetramic acid-3'-acetiminato)copper (II) aCu [1] were evaluated as contrast agents for NMR microscopy and therefore tested for penetrati on into living cells (Xenopus laevis oocytes). By in vitro H-1 NMR rel axation (T-1) and atomic absorption spectroscopy measurements (AAS) we confirmed, that independent of the complex isomers (Z/Z, Z/E, E/E, E/ Z) compounds with alkyl substituents in R(1) - R(5) exclusively were a ble to penetrate the plasma membranes. It is noteworthy that compounds containing the tetramic acid moieties from both a penetrating and a n on-penetrating complex most likely were accumulated in the plasma memb rane and/or plasma membrane-associated vesicles, which was concluded f rom in vitro NMR measurements combined with AAS trace analyses. In thi s context the crystal and molecular structure of the 'chimerical' C17H 22N4O4Cu . 3H(2)O kCu . 3H(2)O were determined by x-ray analysis. The x-ray structural parameters are discussed in detail.