The present invention relates to a novel compound of general formula (I) and its pharmaceutically acceptable acid addition salt, and process for the preparation thereof, which have strong antitumor activities and very low toxicity, wherein R1 and R2 are independently hydrogen, C1-C4 alkyl, C1-C4 alkylcarboxyl, C1-C4 alkylcarbonyl, C1-C4 alkoxy, C1-C4 hydroxyalkyl, C1-C4 aminoalkyl or C1-C4 hydroxyiminoalkyl, or R1 and R2 are fused to form C3-C4 unsaturated ring; R3, R4, R5, R6 and R7 are independently hydrogen, halogen, hydroxy, nitro, amino, C1-C4 alkyl, C1-C4 alkylcarboxyl, C1-C4 alkylcarbonyl, C1-C4 alkoxy or C1-C4 thioalkoxy; R8 is C1-C4 alkyl; Y is oxygen, sulphur, amino, substituted amino or C1-C4 thioalkyl; Z is C1-C4 alkoxy, C1-C4 alkyl, C1-C4 alkylamino or C1-C4 thioalkoxy; X1 and X2 are independently carbon or nitrogen; and -N--C- and -C--Y- may form a single bond or a double bond provided that if -N--C- forms a single bond, -C--Y- forms a double bond, and if -C--Y- forms a single bond, -N--C- forms a double bond and R8 is nonexistent.