융점 199 - 200 ℃; 순도 99 . 3 % ( HPLC ) ; 1 H NMR ( DMSO - d 6 , ppm ) δ 2 . 27 ( s , 6 H ) , 3 . 54 ( s , 3 H ) , 4 . 49 ( s , 1 H ) , 7 . 55 ( m , 2 H ) , 8 . 0 ( m , 2 H ) , 8 . 97 ( s , 1 H ) , 11 . 91 ( brs , 1 H )