Synthesis of 1-β-D-(5-Deoxy-5-iodoarabinofuranosyl)-2-nitroimidazole (β-IAZA): A Novel Marker of Tissue Hypoxia

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The present work describes the synthesis of the β-isomer of 1-α-D-(5-deoxy-5-iodoarabinofuranosyl)-2-nitroimidazole (IAZA). Radioiodinated IAZA (¹²³I-IAZA) has been extensively studied as a radiopharmaceutical for the diagnosis of regional and/or focal tissue hypoxia in a variety of clinical pathologies. The β-anomer of IAZA, 1-β-D-(5-deoxy-5-iodoarabinofuranosyl)-2-nitroimidazole (β-IAZA, 1), was synthesized via an unconventional route starting from 1-β-D-(ribofuranosyl)-2-nitroimidazole (AZR), with a change of configuration at the C-2′-position to afford 1-β-D-(arabinofuranosyl)-2-nitroimidazole (β-AZA, 7). Nucleophilic iodination of the 5′-O-toluenesulfonyl-2′,3′-di-O-acetyl precursor of β-AZA, 9, followed by deprotection, afforded 1 in satisfactory yield. β-IAZA (1) was also synthesized from 7 using molecular iodine and triphenylphosphine.