Evaluation of a series of 3, 4-dihydro-2H-l-benzopyran-2-carboxylic acids linked to the 2- hydroxyacetophenone pharmacophore present in the standard peptidoleukotriene antagonist FPL 55712 (1) has led to the discovery of Ro 23-3544 (7), an antagonist possessing greater potency and duration of action vs LTD4 than the standard (aerosol route of administration, guinea pig bronchoconstriction model). Interestingly, this compound ...