Synthesis of Phostones via the Palladium-Catalyzed Ring Opening of Epoxy vinyl phosphonates.

The reaction of epoxy aldehydes with tetraethyl methylenediphosphonate gave gamma,delta-epoxy vinyl phosphonates. The palladium-catalyzed addition of primary alcohols gave the monoprotected diols as single diastereoisomers. The trans- and cis-epoxides lead to opposite (syn and anti) diastereoisomers of the addition products. The alkene of the vinyl phosphonates was subjected to hydrogenation, and the resulting saturated phosphonates underwent base-catalyzed cyclization to give phostones with a very high diastereoselectivity in the formation of the new chiral center at the phosphorus atom.