Piperidine carboxamide compound, preparation method, and use thereof

A method for treating drug-resistant tumors wherein the drug-resistant tumor is drug-resistant breast cancer, which comprises administering to a subject in need of such treatment a therapeutically effective amount of the compound of formula

• wherein:
• A represents CH2, S, O,
• wherein “” terminal is attached to R2;
• R1 represents aryl, aromatic heterocyclyl, arylalkyl, or aromatic heterocyclylalkyl, wherein said aryl, aromatic heterocyclyl, arylalkyl, or aromatic heterocyclylalkyl is unsubstituted or substituted with one or two substituents independently selected from the group consisting of halogen, nitro, hydroxy, amino, cyano, alkyl, alkoxy, alkylthio, alkylamino, cycloalkoxy, cycloalkylthio, cycloalkylamino, alkenyl and alkynyl;
• R2 represents hydrogen, alkyl, cycloalkyl, substituted cycloalkyl, alkoxy, alkoxycarbonyl, alkanoyl, substituted alkanoyl, aliphatic heterocyclyl, substituted aliphatic heterocyclyl, aliphatic heterocyclylalkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, arylsulfonyl, substituted arylsulfonyl, arolyl, substituted arolyl, aromatic heterocyclyl, substituted aromatic heterocyclyl, aromatic heterocyclylalkyl, aromatic heterocyclylsulfonyl, aromatic heterocyclylacyl;
• wherein the substituent includes alkyl, halogen, nitro, cyano, amino, hydroxy, alkoxy, mono(C1-C6)alkylamino, di(C1-C6)alkylamino, C2-C6alkenyl, C2-C6alkynyl, C1-C6haloalkyl, C1-C6haloalkoxy, aromatic heterocyclylalkyl,
• R3 represents hydrogen, C1-C3alkyl, or C3-C6cycloalkyl;
• or a pharmaceutically acceptable salt or a solvate thereof.