are n n 39 dibenzylethylenediamine chloroprocaine choline diethanolamine dicyclohexylamine ethylenediamine n methylglucamine and procaine see for example berge s m et al 34 pharmaceutical salts 34 journal of pharmaceutical science 1977 66 1 19 the base addition salts of said acidic compounds are prepared by contacting the free acid form with a sufficient amount of the desired base to produce the salt in the conventional manner certain of the compounds of the present invention can exist in unsolvated forms as well as solvated forms including hydrated forms in general the solvated forms including hydrated forms are equivalent to unsolvated forms and are intended to be encompassed within the scope of the present invention certain of the compounds of the present invention possess one or more chiral centers and each center may exist in the r or s configuration the present invention includes all enantiomeric and epimeric forms as well as the appropriate diastereomeric mixtures thereof the compounds of formula i are valuable antagonists of endothelin the tests employed indicate that compounds of the invention possess endothelin antagonist activity thus the compounds were tested for their ability to inhibit 125 i et 1 125 i endothelin 1 binding in a receptor assay selected compounds were also tested for antagonist activity by inhibition of et 1 stimulated arachidonic acid release and et 1 stimulated vasoconstriction the following testing procedures were used doherty a m et al 34 design of c terminal peptide antagonists of endothelin structure activity relationships of et 1 16 21 d his 16.