<p>SUMMARY Novel bicycloester derivatives and pharmaceutically acceptable salts thereof have high DPP-IV inhibitory activity. SOLVING MEANS The novel bicycloester derivatives are represented by the general formula (1):
Pharmaceutically acceptable salts thereof are also included (Example: (2S,4S)-1-[[N-(4-ethoxycarbonylbicyclo[2.2.2]oct-1-yl)amino]acetyl]-4-fluoropyrrolidine-2-carbonitrile)).</p>
