1,3,4-oxadiazole derivative compounds as histone deacetylase 6 inhibitor, and pharmaceutical composition comprising the same

A 1,3,4-oxadiazole derivative compound represented by a following formula I, optical isomer thereof or pharmaceutically acceptable salt thereof:

• wherein,
• X, Y and Z are each independently CR3 or N;
• L is —(C1-C6 alkylene)-, —(C2-C6 alkenylene)-, —(C═O)—(C1-C4 alkylene)-, —(C═O)O—(C1-C4 alkylene)-, —(C═O)NH—(C1-C4 alkylene)-, —O(C═O)—(C1-C4 alkylene)- or a single bond, wherein at least one H of —(C1-C6 alkylene)-, —(C2-C6 alkenylene)-, —(C═O)—(C1-C4 alkylene)-, —(C═O)O—(C1-C4 alkylene)-, —(C═O)NH—(C1-C4 alkylene)- and —O(C═O)—(C1-C4 alkylene)- may be substituted with aryl or heteroaryl;
• R1 is hydrogen, —C1-C6 alkyl, —C2-C6 alkenyl, —C3-C8 cycloalkyl, heterocycloalkyl, benzyl, aryl, heteroaryl or —NR4R5, wherein at least one H of aryl or heteroaryl may be substituted with —C1-C6 alkyl, —C2-C6 alkenyl, —C1-C6 haloalkyl, —C1-C6 aminoalkyl, —C1-C6 hydroxyalkyl, —C1-C6 alkoxy, hydroxy, cyano, halo, nitro, —CF2H, —CF3, —NR6R7, —C(═O)—R8 or —S(═O)2—R9;
• R2 is —CF2H or —CF3;
• R3 is hydrogen, halo or —C1-C6 alkyl;
• R4 to R7 are each independently H or —C1-C6 alkyl;
• and
• R8 and R9 are each independently H, OH or —C1-C6 alkyl.