AR-42 (HDAC-42) 1MG. AR-42 (HDAC-42), CAS Number: 935881-37-1, Molecular Formula: C18H20N2O3, Molecular Weight: 312. 36, Purity: greater than or equal to 98% by HPLC, Appearance: Crystalline solid, Synonym: S)-N-hydroxy-4-(3-methyl-2-phenylbutanamido)benzamide, Size: 1MG