| 摘要 |
The invention relates to compounds of the formula: <IMAGE> I wherein R is hydrogen or lower alkyl, R1, R2, R3 and R4, independently, are hydrogen, lower alkyl, lower alkenyl, cycloalkyl or phenyl unsubstituted or substituted by up to 3 substituents independently selected from lower alkyl, lower alkoxy or halogen, or R1 and R2 taken together with the carbon atom are alkylene of 2 to 5 carbon atoms unsubstituted or substituted by lower alkyl, and n is an integer of from 0 to 3, and, when R1 is different from R2 and/or when R3 is different from R4, enantiomers, diastereomers and racemates thereof and, when R is hydrogen, salts thereof with pharmaceutically acceptable bases. The compounds of formula I and, when R is hydrogen, pharmaceutically exceptable salts thereof are useful as bronchopulmonary agents, for example, in the relief of asthma and allergic reactions.
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