Benzopyrans as openers of potassium channels.

THIS invention relates to compounds of formula (I) and pharmaceutically acceptable salts thereof, wherein the dashed line represents a covalent bond OPTIONAL; X is O, NH, SO a direct bond; {R} Sup.3 is hydroxy when the line INTERMITTENT NO represents a covalent bond YR} {Sup.3 LINE IS ABSENT WHEN THE INTERMITTENT represents a covalent bond; {R} Sup.4 ES (A), when X is O, a group of formula (I), (B), when X is O, NH OS, optionally substituted by hydroxyphenyl, (C) a heterocyclic ring of 4 A 7 members OPCIONALEMENTE unsubstituted, or (D), when X is NH, a group of formula (II). The compounds are useful for treating RELATED DISEASES WITH ALTERED OR TONE SMOOTH MUSCLE MOVEMENT.