Photoaffinity analog of herbicide inhibiting cellulose biosynthesis: Synthesis of [³H]‐2,6‐dichlorophenylazide

The compound 2,6‐dichlorobenzonitrile (dichlobenil, DCB) is known to be a reversible inhibitor of in vivo cellulose biosynthesis in higher plants and algae. We now report the synthesis of 2,6‐dichlorophenylazide (DCPA) with a non‐exchangeable tritium label of high specific activity. We have shown this compound to compete with DCB in binding to cotton fiber extracts, and to specifically label a low molecular weight protein in this extract on irradiation with UV light.