A New and Convenient Route to Optically Active 2‐Phosphoryl‐3‐oxo‐5‐alkyl/‐aryltetrahydrofurans and Their Reactions

The two enantiomers of 4‐hydroxy‐2‐oxo‐4‐alkyl/‐arylalkylphosphonates were prepared chemoenzymatically and converted to chiral 2‐phosphoryl‐3‐oxo‐5‐alkyl/‐aryl tetrahydrofurans using an intramolecular O−H insertion reaction catalyzed by rhodium( II ) acetate. The potential biological activity of the resulting tetrahydrofurans is of much interest. The presence of the β‐ketophosphonate skeleton in these heterocycles allowed their use as substrate in the cyclic Horner−Wadsworth−Emmons reaction with aldehydes or ketones furnishing chiral α,β‐unsaturated ketones − a new class of building block in organic synthesis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)