Patent ID: 8846749

Claim:
A method for reducing resistance of a subject to an anticancer drug, comprising administering at least one of a compound represented by formula I or a pharmaceutically acceptable salt thereof: wherein X represents —S— or —O—; R 1 represents —CH 2 —CH(OH)—CH 2 Cl, —CH 2 —CH(OH)—CH 2 OH, —CH 2 —CH(SH)—CH 2 Cl, —CH 2 —CH(SH)—CH 2 OH, R 2 represents hydrogen, —OH, (C 1 -C 4 )alkoxy, and R 3 , R 4 , R 5 , and R 6 each independently represent H or (C 1 -C 4 )alkoxy, or alternatively R 3 and R 4 , R 4 and R 5 , or R 5 and R 6 represent —CH═CH—CH═CH—.