Aryloxyalkyloxy- and aralkyloxy-4-hydroxy-3-nitrocoumarins which inhibit histamine release in the rat and also antagonize the effects of a slow reacting substance of anaphylaxis.

The syntheses and structure--activity relationships of a number of 4-hydroxy-3-nitrocoumarins, which are both antagonists of a slow reacting substance of anaphylaxis and potent inhibitors of antigen-induced histamine release in the rat, are described. Most active among these are 7-[3-(4-acetyl-3-hydroxy-2-n-propylphenoxy(-2-hydroxypropoxy] derivatives having hydrogen or lower alkyl substituents at the C-8 position of the coumarin ring, 168, 171, 173, and 174.