1 H NMR ( 300 MHz , CDCl 3 ) δ 6 . 42 ( t , 1 H , J = 1 . 2 Hz ) , 5 . 78 ( m , 1 H ) , 5 . 36 ( s , 1 H ) , 4 . 93 ( td , 2 H , J = 18 . 9 , 31 . 2 Hz ) , 4 . 69 ( d , 1 H , J = 18 . 9 Hz ) , 3 . 21 ( q , 1 H , J = 7 . 5 Hz ) , 2 . 87 ( m , 1 H ) , 2 . 48 ( m , 1 H ) , 1 . 99 ( m , 2 H ) , 1 . 74 ( m , 2 H )