Synthesis of 125I‐lamivudine and 125I‐lamivudine‐ursodeoxycholic acid codrug

The preparation of 125 I‐lamivudine ( 125 I‐3TC) and 125 I‐lamivudine‐ursodeoxycholic acid codrug ( 125 I‐3TC‐UDCA), suitable for comparative biodistribution studies, is described. The synthesis of the unlabeled precursor 3TC‐UDCA proceeds in an 11.6% yield, and the radiolabelling yields for 125 I‐3TC and 125 I‐3TC‐UDCA were 89 and 92%, respectively. The final products are radiochemically pure (greater than 98%).