Heterocyclic compounds, intermediates thereof and elastase inhibitors

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, R1 and R2 are the same or different and each is a lower alkyl group, R3 and R4 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 R5 is 2-benzoxazolyl, trifluoromethyl, benzylaminocarbonyl, etc.