No-carrier-added synthesis of meta-[131I]iodobenzylguanidine.
No-carrier-added meta-[131I]iodobenzylguanidine ([131I]MIBG) was prepared starting with two different metallated precursors. Attempted preparation of 3-(tri-n-butylstannyl)benzylguanidine was not successful. An alternate two-step strategy using 3-(tri-n-butylstannyl)benzylamine could be used to prepare radio-iodinated [131I]MIBG in an overall radiochemical yield of 30-33%. Synthesis of [131I]MIBG via the radioiododesilylation of 3-trimethylsilylbenzylguanidine was also investigated. Yields were dependent on temperature, precursor concentration, solvent and nature of the oxidant. Radiochemical yields of 90% were obtained in 5 min at room temperature using either N-chlorosuccinimide or hydrogen peroxide in trifluoroacetic acid as oxidants. The percentage of specific binding in vitro of no-carrier-added MIBG to SK-N-SH neuroblastoma cells remained constant over a 2 log activity range, while the binding of MIBG prepared by isotopic exchange dropped by a factor of seven. In normal mice, heart and adrenal uptake of no-carrier-added [131I]MIBG was found to be higher than that of [131I]MIBG prepared by isotopic exchange.
Vaidyanathan
G
G
Department of Radiology, Duke University Medical Center, Durham, NC.
Zalutsky
M R
MR
D019797:3-Iodobenzylguanidine; D000818:Animals; D003287:Contrast Media; D006801:Humans; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007462:Iodobenzenes / Q000138:chemical synthesis* / Q000378:metabolism / Q000493:pharmacokinetics; D007553:Isotope Labeling; D051379:Mice; D008807:Mice, Inbred BALB C; D009447:Neuroblastoma / Q000378:metabolism; D014407:Tumor Cells, Cultured
D003287:Contrast Media; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D019797:3-Iodobenzylguanidine