{HEAD ~ The free carboxyl moiety} of the adduct is activated with a carbodiimide and a urea group is eliminated by the hydroxylimide catalyst to form {TAIL ~ an activated ester} 
{ HEAD ~ The free carboxyl moiety } of the adduct is activated with a carbodiimide and a urea group is eliminated by the hydroxylimide catalyst to form { TAIL ~ an activated ester }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL