PURE ENANTIOMERS FROM SIMPLE, SYMMETRICAL DIENOPHILES

Starting from p-benzoquinone or 2-cyclopentene-1, 4-dione as dienophil es and the enantiomerically pure dienes 1a and 1b, high pressure cyclo additions led to chiral adducts. These were transformed in a regiosele ctive manner to generate well defined stereogenic centres. A remarkabl y efficient electron density directed regioselectivity was discovered with 18c and 18d.