text:  The success of the <unk> <unk> as a tool in organic synthesis stems from the utility and <unk> of <unk> as both motifs in natural products ( including <unk> , the <unk> , and a <unk> of <unk> ) and as useful synthetic <unk> for total synthesis . The reaction has been used in several total syntheses and several reviews have been published . 
  