Pyrimidine derivatives

A compound represented by the formula (I):

• wherein
• R1 is (1) lower alkyl which may have 1 to 3 substitutents independently selected from the group consisting of halogen, amino, and cyano, (2) C6 to C12 aromatic group which may have 1 to 3 substituents independently selected from the group consisting of lower alkyl, halogen, amino, and cyano, or (3) C1 to C6 lower alkyl substituted by C6 to C12 aromatic group which may have 1 to 3 substituents independently sel-ected from the group consisting of lower alkyl, halo-gen, amino, and cyano;
• R2 and R3 each is independently (1) hydrogen, (2) lower alkyl which may have 1 to 3 substituents independently selected from the group consisting of halogen, amino, and cyano, or (3) C6 to C12 aromatic group which may have 1 to 3 substituents independently selected from the group consisting of lower alkyl, halogen, amino, and cyano;
• R4 is (1) hydro-gen, (2) lower alkyl, or a cation capable of forming a non-toxic pharmaceutically acceptable salt;
• X is sulfur, oxygen, or sulfonyl, or imino which may be substituted by formyl, acetyl, propionyl, butyryl, isobutyryl, vale-ryl, isovaleryl, amino substituted by sulfonyl or alkyl-sulfonyl, and sulfonyl substituted by alkyl, amino or alkylamino, the dotted line represents the presence or absence of a double bond, or the corresponding ring-closed lactone.