Syntheses and bio-evaluation of radioiodinated organic compounds for application in the nuclear medicine field

Abstract

Malignant melanoma (skin cancer) is a common tumour and its frequency is increasing in the general population, the incidence varying with geographical region (John et al., 1993). It is estimated that the mortality rate worldwide has doubled over the past 20 years due to this tumour. In this study radioiodine-labelled chemical compounds, [1231]-ME-BA and [1231]-E-BA, having different chemical structures, were prepared. These compounds were evaluated by means of their tumour uptake and compared with the control compound [1231]-PAB. The bromobenzamide derivatives were synthesized according to various standard methods. The tri-n-butyltin precursors were synthesized from the bromo compounds by a slight modification of the published procedure (Moreau et al., 1998). "Cold" I-ME-BA and 1-E-BA standards were prepared from their tributyltin derivatives in modest yields of 27% and 23% respectively, by reaction with Nal in the presence of chloramine-T as an oxidizing agent. 1-PAB was prepared by condensing 4-iodobenzoic acid with 1-(2-aminoethyl) piperidine via its SOCh generated benzoylchloride, and subsequent silica gel purification to afford a purified product in a modest yield (30%). [1231]-ME-BA, [1231]-E-BA and [123l]-P AB were prepared from their tributyltin derivatives in moderate to high yields (67- 88%) and high radiochemical purity (84-99%) by reaction with Na123I in the presence of chloramine-T as an oxidizing agent. Both [1231)-E-BA and [1231)-ME-BA bound with low affinity to sigma-receptors of the G 11 cells, whereas the [1 231)-PAB bound with high affinity. However, (123!)-E-BA bound slightly better than (123l)-ME-BA.