Macrocyclic phosphonate I is prepd.; while in D2O soln. I binds b-amino alcs. with little selectivity, I incorporated into a stearic acid monolayer binds noradrenaline at least ten times more strongly than other catecholamines and binds b-amino alc. substrates much more strongly than in soln. I is prepd. from 4-ethynylbenzoic acid, 2,5-bis(chloromethyl)-p-xylene, and 1,3-bis(aminomethyl)benzene in a longest linear sequence of eight steps. Addn. of noradrenaline to I suspended in a stearic acid monolayer on water leads to the formation of visible domains by Brewster angle microscopy and significant changes in the pressure-area isotherm of the monolayer; the changes upon addn. of b-amino alcs. differ significantly between noradrenaline and other catecholamines such as adrenaline and dopamine and between noradrenaline and either atenolol or propanolol. Noradrenaline can thus be detected at micromolar concns. by I incorporated into a stearic acid monolayer.