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