EDC·HCl (EDC, EDAC or EDCI) is a water-soluble carbodiimide coupling reagent that can be used in aqueous phase to facility the activation of a carboxyl group. It also simplifies the purification of the coupling reaction as the byproduct from EDC is also water soluable which makes it more convenient to be removed. EDC is often used in combination with HOBt or HOSu.