1,4-DIHYDROPYRIDINE DERIVATIVES USEFUL AGAINST TUMOUR CELLS

Compounds of formula 1 Formula 1 and pharmaceutically acceptable salts thereof, wherein each of R1,R2,R3,R4 and R5 independently represents a hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, a hydroxy group, a lower alkyloxy group having 1 to 3 carbon atoms, or a nitro group, or two substituents adjacent to each other on the benzene ring are combined together to form an alkylenedioxy group having 1 to 3 carbon atoms; at least one of R6 and R7 represents an alkyloxycarbonyl group or an alkylaminocarbonyl group in which the alkyl moiety has a nitrogen-containing substituent and where only one of R6 and R7 represents an alkyloxycarbonyl group or an alkylaminocarbonyl group in which the alkyl group has a nitrogen-containing substituent, the other is an alkyloxycarbonyl group; each of R8 and R9 independently represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms; n represents an integer of 2 to 9; X represents a methylene group or oxygen atom, wherein the methylene is optionally substituted with a lower alkyl group having 1 to 5 carbon atoms, or a lower alkyloxy group having 1 to 5 carbon atoms; and, R10 represents an aryl group or an aralkyl group, wherein the aryl moiety in the aryl group and aralkyl group is optionally substituted with a substituent selected from a halogen atom, a lower alkyl group having 1 to 5 carbon atoms, a lower alkyloxy group having 1 to 5 carbon atoms, a hydroxy group an aryl group, an aryloxy group, an aralkyl group, or an aralkyloxy group, or two substituents adjacent to each other on the benzene ring are combined together to form an alkylenedioxy group having 1 to 3 carbon atoms are effective at reducing the resistance of cancer cells which have acquired resistance to chemotherapeutic agents used in cancer treatment.