Antiallergic 9-oxo-11-hydroxy-5H,9H-[2]benzopyrano[4,3-g][1]benzopyrans.

The synthesis and properties of the title compounds 1 are described. Several of these compounds, in addition to being potent inhibitors of the passive cutaneous anaphylaxis reaction of rats against egg albumin challenge, significantly block the effects of several mediators of anaphylaxis in isolated smooth muscle preparations. An improved procedure for the isolation and partial purification of SRS-A from chopped guinea pig lung tissue is also described.