Gd(III) complexes of poly(hydroxymethyl)substituted derivatives of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid

Gd(III) complexes of 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic a cid bearing two and four hydroxymethyl moieties on the cyclen ring were pre pared to be studied as low toxicity MRI contrast agents. The key intermedia tes in the syntheses of the two ligands are the corresponding bis and tetra substituted cyclen derivatives. Bis(hydroxymetyl)cyclen was obtained accord ing the so-called 'crab-like' cyclization procedure. Photoelectron transfer -induced tetramerization of (R)-2-(benzyloxymethyl)-N-(benzyl) aziridine st ereoselectively led to homochiral tetra(hydroxymethyl)cyclen. The X-ray cry stal structure of the latter compound unambiguously proved the alike stereo chemical configuration of the four stereogenic carbon atoms in the cyclen r ing. Carboxymethylation of the cyclen derivatives followed by complexation with either GdCl3 or Gd(OAc)(3) afforded the target complexes. (C) 2001 Els evier Science B.V. All rights reserved.