6-({2'-[6-(Toluene-4-sulfonylamino)-hexanoylamino]-biphenyl-4-carbonyl}-amino)-hexanoic acid
6-({2'-[6-(4-Chloro-benzyloxycarbonylamino)-hexanoylamino]-biphenyl-4-carbonyl}-amino)-hexanoic acid
6-{[2'-(6-Benzyloxycarbonylamino-hexanoylamino)-biphenyl-4-carbonyl]-amino}-hexanoic acid