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