Selective histone deactylase 6 inhibitors

A compound having Formula I:

• wherein
• A is aryl, heteroaryl, or C1-C8 alkyl, any of which is optionally substituted with one or more groups chosen from acetyl, C1-C5 alkyl, amino, —NR6R7, —C(O)NR6R7, C1-C4 alkoxy, C1-C4 alkylhydroxy, C5-C6 cycloalkyl, C5-C6 heterocycloalkyl, aryl, heteroaryl, halo, hydroxy, thiol, cyano, or nitro;
• and
• R1 is hydrogen and R2 is C1-C8 alkyl, C1-C8 alkenyl, C1-C8 alkynyl, C1-C8 haloalkyl, C5-C6 cycloalkyl, C5-C6 heterocycloalkyl, C1-C3 alkylaryl, aryl, C1-C3 alkylheteroaryl, or heteroaryl, any of which is optionally substituted with acetyl, C1-C5 alkyl, amino, —NR6R7, —C(O)NR6R7, C1-C4 alkoxy, C1-C4 alkylhydroxy, C5-C6 cycloalkyl, C5-C6 heterocycloalkyl, aryl, heteroaryl, carbonyl, halo, hydroxy, thiol, cyano, or nitro;
• and
• R6 and R7 are independently H, C1-C4 alkyl, or are joined such that together they form an alkylene bridge comprising 4 or 5 atoms so that a 5 or 6-membered ring is formed with the nitrogen;
• or a pharmaceutically acceptable salt or hydrate thereof.