There is provided a novel compound that inhibits interaction between murine double minute 2 (Mdm2) protein and p53 protein and exhibits anti-tumor activity. The present invention provides an imidazothiazole derivative represented by the following formula (1) having various substituents that inhibits interaction between Mdm2 protein and p53 protein and exhibits anti-tumor activity:
wherein R
1
, R
2
, R
3
, R
4
, and R
5
in the formula (1) each has the same meaning as defined in the specification.