Procurement of radioiodinated glucose derivative and its biological character.

Radiolabeled glucose derivatives are attracting great interest in the clinical field. Development of an analogous substrate labeled with a practical radionuclide, 123I, is most desirable, however, no radioiodine labeled glucose derivative has been reported as being chemically and biologically compatible. Thus, in the present study, a glucose derivative substituted at the C-2 position by a p-iodobenzyl group, a 2-O-(p-iodobenzyl)-D-glucose (IBG) was designed and its synthesis was carried out. A very easy and simple synthetic method was developed, and the obtained IBG showed appropriate purity and stability for its radioiodination. [125I]IBG was obtained by radioisotopic exchange reaction with high radiochemical purity and radiochemical yield, requiring no purification. The good in vivo and in vitro stability and the chemical and biological characteristic displayed by the new [125I]IBG stimulated the measurement of the brain uptake index (BUI). In the presence of glucose, brain uptake inhibition was detected, a good indication of a glucose carrier mediator for the transport of [125I]IBG through the blood-brain barrier, a similar feature to that of [14C]glucose or 3-O-[14C]methylglucose. The newly designed ligand IBG holds good promise for the study of regional cerebral glucose utilization, should the 123I become available.