| abstract |
A compound of the formula (I): n n nwherein R 1 is hydroxy and the like; R 2 is optionally substituted lower alkyl and the like; R 3 is hydrogen atom and the like; R 4 is optionally substituted arylene and the like; R 5 is —C≡C— and the like; R 6 is optionally substituted naphtyl and the liken nits optically active substance, its prodrug, their pharmaceutically acceptable salt, or solvate thereof. |