Synthesis of syn-γ-Amino-β-hydroxyphosphonates by Reduction of β-Ketophosphonates Derived from L-Proline and L-Serine

The reduction of γ-N-benzylamino-β-ketophosphonates 6 and 10, readily available from L-proline and L-serine, respectively, can be carried out in high diastereoselectivity with catecholborane (CB) in THF at -78 oC to produce the syn-γ-N-benzylamino-β-hydroxyphosphonates 11 and 13 as a single detectable diastereoisomer, under non-chelation or Felkin-Anh model control.