Enantioselective photocycloaddition mediated by chiral Brønsted acids: asymmetric synthesis of the rocaglamides.

Enantioselective syntheses of methyl rocaglate and the related natural products rocaglamide and rocaglaol are outlined. The approach involves enantioselective [3 + 2] photocycloaddition promoted by chiral Brønsted acids (TADDOLs) to afford an aglain precursor followed by a ketol shift/reduction sequence to the rocaglate core.