Synthesis of optically active hydroxyphosphonates

The reduction of dimenthyl ketophosphonates with sodium borohydride involves asymmetric induction at the alpha-carbon atom, resulting in a small excess of the (R)-enantiomer of the alpha-hydroxyphosphonate formed. A higher ee purity was achieved if the reduction of chiral dimenthyl ketophosphonates was carried out by the chiral complex of NaBH4-L-proline, owing to the double asymmetric induction at the a-carbon atom. The hydroxy-phosphonates obtained were isolated in a diastereomerically pure state and were transformed to the optically active, free hydroxyalkylphosphonic acids. The (R)-configuration of one of them was proved by Xray crystal structure analysis. (C) 2008 Wiley Periodicals, Inc.