Enantioselective synthesis of cyclic dialkyl (3-hydroxy-1-alkenyl) phosphonates by bakerʹs yeast-mediated reduction of the corresponding enones

Cyclic dialkyl (3-oxo-1-cycloalkenyl) phosphonates were subjected to bakerʹs yeast-mediated enantioselective reductions to afford the corresponding dialkyl (3-hydroxy-1-alkenyl) phosphonates. The six- and seven-membered ring enones were reduced with moderate to good enantiomeric excesses, whereas the five-membered ring substrate always yielded the double bond reduced compound. The use of different reduction conditions did not improve the eeʹs markedly, but it was found, for the six-membered analogues, that the alkyl groups held by phosphorus influence dramatically the enantioselectivity of the reduction, leading to up to 95% enantiomeric excess.