1 H - NMR ( CDCl 3 ) : 8 . 066 ( s , 1 H ) , 6 . 648 ( d , 1 H , J = 10 Hz ) , 6 . 167 ( s , 1 H ) , 5 . 525 ( d , 1 H , J = 10 Hz ) , 4 . 827 ( s , 2 H ) , 2 . 401 ( br , 1 H ) , 2 . 132 ( s , 3 H ) , 1 . 399 ( s , 6 H ) .