Chiral substituted glycidic esters have been prepared from their corresponding chalcones via a two step procedure consisting of an asymmetric epoxidation mediated by a poly-L-leucine polymer, followed by a previously unreported Baeyer-Villiger oxidation. The regioselectivity of this latter procedure was found to depend on the aryl substituent.
The chiral phenyl-substttuted glycidic ester is an important synthetic intermediate in organic synthesis. From this key intermediate a variety of other chiral compounds (eg. acids, amides, etc.) can be easily prepared.' During a recent investigation on the preparation of another important chiral synthon, the epoxyketone, it became apparent that the glycidtc esters can be prepared from this precursor in a direct fashion.
Asymmetric epoxidation of chafcones have been reported using a triphasic system of H202/NaOH, an organic solvent, and a polyamino acid2 or via asymmetric catafysis.3 The yields and optical purity of the resulting epoxides have varied from poor to excellent, depending on the conditions and method used.
We herein report an extension of the Julia method that affords chiral epoxyketones in good yields and optical