| 摘要 |
The present invention relates to a heterocyclic compound of the following formula (I-a), its ester, or a salt thereof, and a human neutrophilic elastase inhibitor containing the same as the active ingredient, etc.wherein A and B are the same or different and each is a lower alkylene group being optionally substituted by an oxo group, D is a heteromonocyclic or heterobicyclic group being optionally substituted by an oxo group, R<1 >and R<2 >are the same or different and each is a lower alkyl group, R<3 >and R<4 >are different from each other, and each is a hydrogen atom or a hydroxy group, or both combine together to form an oxo group, and R<5 >is 2-benzoxazolyl, trifluoromethyl, benzylamino-carbonyl, etc.
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