The present invention relates to compounds represented by formula (I), or isomers, prodrugs, pharmaceutically acceptable salts, solvates or hydrates thereof: in which each substituent of formula (I) is as defined in the specification. The present invention also relates to preparation methods of compounds represented by formula (I), a pharmaceutical composition comprising compounds represented by formula (I) and usage of compounds represented by formula (I) for treating chronic neurodegenerative diseases such as Alzheimer's disease and other diseases induced by aggregation or deposition of ²-amyloid peptide.