Syntheses of radiolabeled ABT-578 for ADME studies

Several isotopomers of ABT-578 (I, II, III, and IV) were prepared starting from different labeled precursors: [5'-3H]-tetrazole (1), [5'-14C]-tetrazole (2), [40-3H]rapamycin (3), and [2,11,31-3H]rapamycin (4). It was shown that the tritium label at the 40 position of rapamycin is lost during an attempted synthesis of [40-3H]ABT-578 (III). Copyright © 2006 John Wiley & Sons, Ltd.