Imidazole. The amino acid histidine contains an imidazole ring, and that tiny five-membered structure helps enzymes move protons, bind metals, and perform some of biology's most precise chemistry.
Now take that same type of ring and add one bromine atom. You get 4-bromo-1H-imidazole. For a synthetic chemist, that bromine is like a removable construction marker. The imidazole ring is the part you want to keep.
Global Chemical Database