Synthesis of a new 125I-labeled tyrosine methyl ester conjugate of adenylyl-(2′-5′)-adenylyl-(2′-5′)-[2′,3′-di-O-(2-carboxyethyl)ethylidene]adenosine

A novel 125I-labeled conjugate of 2′,5′-oligoadenylate trimer for radioimmuno assay of 2′,5′-oligoadenylates have been obtained by the reaction of adenylyl-(2′-5′)-adenylyl-(2′-5′)-[2′,3′-di-O-(2-carboxyethyl)ethylidene]adenosine (1) with tyrosine methyl ester followed by iodination of intermediate 2 with 125I in the presence of chloramine-T. 125I-labeled conjugate 3 was isolated by column chromatography on a TSK-gel HW-40 in 73% yield. Specific activity for the synthesized conjugate was approximately 1760 Ci/mmol.