Pure enantiomers from simple, symmetric dienophiles

Abstract Starting from p-benzoquinone or 2-cyclopentene-1,4-dione as dienophiles and the enantiomerically pure dienes 1a and 1b , high pressure cycloadditions led to chiral adducts. These were transformed in a regioselective manner to generate well defined stereogenic centres. A remarkably efficient electron density directed regioselectivity was discovered with 18c and 18d .