Development of a photoaffinity label for respiratory syncytial virus inhibitors

The syntheses of tritiated and radio‐iodinated respiratory syncytial virus inhibitor photoaffinity labels are reported. 3 H‐1‐Isopropyl‐3‐(1‐[2‐(3‐methyl‐3H‐diazirin‐3‐yl)‐ethyl]‐1H‐benzoimidazol‐2‐yl)methyl)‐1,3‐dihydrobenzoimid‐azol‐2‐one ( 1 ), was prepared in two steps by the initial tritiation of N ‐isopropenyl‐2‐benzimidazolone followed by coupling to 2‐chloromethyl‐1‐[2‐(3‐methyl‐3H‐diazirin‐3‐yl)ethyl]‐1H‐benzoimidazole. The mono and diiodo‐radio‐iodinated derivatives of 1‐(4‐hydroxybenzyl)‐3‐(1‐[2‐(3‐methyl‐3H‐diazirin‐3‐yl)‐ethyl]‐2,3‐dihydro‐1H‐benzo‐imidazol‐2‐ylmethyl)‐1,3‐dihydro‐benzoimidazol‐2‐one ( 2, 3 ), were prepared by the radio‐iodination of the corresponding phenol with Na 125 I and iodogen. Copyright © 2003 John Wiley & Sons, Ltd.