This invention relates to compounds of general formula (I), wherein R1, R2, R3, R4 and R5 are as defined in the specification intermediates used in their preparation, preparation processes and use thereof. The present invention produces new harmine derivatives with enhanced antitumor activity and lower nervous system toxicity by structurally modification of the parent structure of β-carboline of harmines at position 1, 2, 3, 7 and 9. The compounds of the present invention can be prepared easily with high yield. They can be used in manufacture of a variety of antitumor medicines and medicines used in treatment of tumor diseases in combination of light or radiation therapy.
