1 H NMR ( 300 MHz , CDCl 3 ) δ 4 . 71 ( brs , 1 H ) , 3 . 69 - 3 . 77 ( m , 1 H ) , 3 . 40 - 3 . 68 ( m , 3 H ) , 3 . 30 ( d , J = 10 . 2 Hz , 1 H ) , 3 . 01 - 3 . 25 ( m , 3 H ) , 2 . 88 ( brs , 1 H ) , 2 . 47 - 2 . 77 ( m , 2 H ) , 2 . 19 - 2 . 31 ( m , 1 H ) , 1 . 48 ( s , 18 H ) , 1 . 45 ( s , 9 H ) , 1 . 00 ( s , 3 H ) ;