This study describes a non-conventional approach to the synthesis of 1--D-[2-deoxy-2-iodoarabinofuranosyl]-2-nitroimidazole (-2-IAZA), a positional and configurational isomer of 1--D-[5-deoxy-5-iodoarabinofuranosyl]-2-nitroimidazole (IAZA). [123I]IAZA, a radiopharmaceutical used clinically to image regional tissue hypoxia in a number of pathologies, is synthesized by coupling the appropriately protected 1--halo arabinofuranoside, with azomycin, with retention of configuration. To circumvent participation of the C-2 protecting group, which prevents -anomer formation during coupling, the riboside 1--D-(ribofuranosyl)-2-nitroimidazole (AZR) was elaborated to 1--D-(3,5-tetraisopropyldisylyloxy-2-O-trifluoromethanesulfonylribofuranosyl)-2-nitroimidazole. Nucleophilic displacement of the 2-O-trifluoromethanesulfonyl leaving group by iodide results in inversion of configuration at the ribosyl C-2-position, thereby affording silylated arabinofuranosyl-2-IAZA, which was desilylated under neutral conditions to afford -2-IAZA.
Tehran University of Medical Sciences
Synthesis of b-azomycin nucleosides: 1-(b-D-2-iodo-2-deoxyarabinofuranosyl)-2-nitroimidazole, a novel marker of tissue hypoxia
Authors: Kumar P, Wiebe LI, Beiki D, Ohkura K, Seki KI,
Tetrahedron Lett, Vol.43, No., 2002,Page:4427-4429