1 H NMR ( 300 MHz , CD 3 OD ) : δ 7 . 53 ( d , J = 8 . 1 Hz , 2 H ) , 7 . 01 ( d , J = 8 . 4 Hz , 2 H ) , 4 . 10 - 4 . 21 ( m , 1 H ) , 3 . 90 ( s , 1 H ) , 3 . 82 ( s , 1 H ) , 3 . 69 - 3 . 64 ( m , 7 H ) , 2 . 78 - 2 . 76 ( m , 4 H ) , 0 . 95 ( s , 9 H ) , 0 . 91 ( s , 9 H ) ;