text:  α @-@ <unk> with <unk> has been widely implemented in total synthesis . It is a key step in both the <unk> <unk> total synthesis and the <unk> <unk> total synthesis . Additionally , <unk> implemented the transformation in his synthesis of the <unk> @-@ <unk> ( <unk> 1 @,@ 7 @-@ <unk> [ 5 @.@ 5 ] <unk> @-@ 3 @-@ <unk> ) System of <unk> acid . 
  