New Approach for Complete Reversal of Enantioselectivity Using a Single Chiral Source

Obtaining both enantiomers of a given compound in high enantiomeric excess is an attractive and important challenge, because it is often the case that each enantiomer exhibits different bioactivity. This review summarizes some approaches to realize complete reversal of enantioselectivity by changing various reaction conditions. Our new approach to achieve reversal of enantioselection in the enantioselective addition of diketene to aldehydes, affording optically active 5-hydroxy-3-keto esters in high optical yield using, Schiff bases that contain an oxazoline moiety derived from L-serine, is also described.