PR-D-92-EA was tested on isolated guinea pig ileum and rat stomach strips for activity against mediators probably released after allergen antibody union. It antagonized the response produced by histamine, bradykinin, serotonin, prostaglandin E2, prostaglandin F_2αand slow-reacting substance of anaphylaxis (SRS-A). The concentrations which blocked 50% of the response were 150, 145, 92, 70, 47, and 32 μg/ml, respectively. This compound may be useful in the treatment of allergic conditions.

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.

In Gegenwart von Natriumhydrid kondensieren die 2‐Acetyl‐3‐hydroxy‐dibenzopyrane (I) mit Diethylcarbonat (II) zu Benzopyrano‐benzopyranen (III), die in Tabellen aufgeführt werden.