An object of the present invention is to provide compounds which have antitumor activity and do not change cytomorphosis. Disclosed are compounds represented by formula (I) and a pharmaceutically acceptable salts and solvates thereof and pharmaceutical compositions comprising said compounds: wherein X and Z each independently represent CH or N; R1 to R3 represent H, substituted alkoxy, unsubstituted alkoxy or the like; R4 represents H; R5 to R8 represent H, halogen, alkyl, alkoxy, alkylthio, nitro, or amino, provided that R5 to R8 do not simultaneously represent H; R9 and R10 represent H, alkyl, or alkylcarbonyl; and R11 represents alkyl, alkenyl, alkynyl, or aralkyl.