The present invention relates to a compound represented by Formula [I]: ##STR00001## wherein X is O, S, NH or CH.sub.2; Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4 and Y.sub.5, which may be identical or different, are each CH or N; however, at least one of Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4 and Y.sub.5 is N; Z.sub.1 and Z.sub.2, which may be identical or different, are each CH or N; n is an integer from 1 to 3; R.sub.1 is a C.sub.3-C.sub.8 cycloalkyl group, a C.sub.6-C.sub.10 aryl group, an aliphatic heterocyclic ring or an aromatic heterocyclic ring, or a bicyclic aliphatic saturated hydrocarbon group; R.sub.2 and R.sub.3, which may be identical or different, are each a hydrogen atom, a lower alkyl group, a lower alkenyl group, a C.sub.3-C.sub.8 cycloalkyl group, a C.sub.6-C.sub.10 aryl group, an aromatic heterocyclic ring, or the like; and R.sub.4 is a hydrogen atom, a lower alkyl group, a C.sub.3-C.sub.6 cycloalkyl group or the like, or a pharmaceutically acceptable salt or ester thereof, and a selective inhibitor against Cdk4 and/or Cdk6 or an anticancer agent containing the compound or a pharmaceutically acceptable salt or ester thereof.