TANDEM ASYMMETRIC SYNTHESES FROM ACHIRAL PRECURSORS - ASYMMETRIC HOMOGENEOUS REDUCTION OF BISDEHYDRODIPEPTIDES

Sequential asymmetric syntheses on an achiral substrate with two proch iral centers is a direct route to products with two asymmetric centers . The product distribution is discussed as a function of the various s tereoselectivities. After a general presentation of double asymmetric syntheses, the specific case of asymmetric hydrogenation of some achir al bisdehydrodipeptides is considered. When the chiral ligand of the r hodium catalyst was dipamp, very high diastereoselectivities and enant ioselectivities with respect to resulting dipeptides could be achieved .