Metal-catalyzed asymmetric oxidations

Recent advances in enantioselective metal-catalyzed oxidations are presente d. Two transformations are discussed in detail: (a) asymmetric Baeyer-Villi ger reactions of racemic and prochiral cyclic ketones giving optically acti ve lactones, and (b) sulfide oxidations affording enantiomerically enriched sulfoxides, For both reactions, new metal/ligand combinations have been in troduced which allow catalysis of these reactions with high enantioselectiv ities. For some substrates, the ee-values are above 90%. As previously demo nstrated, sulfoxides can be iminated to give the corresponding sulfoximines . Under appropriate reaction conditions, this transformation is stereospeci fic and enantiopure sulfoximines are obtained. These highly oxidized sulfur reagents have now been modified to give beta-amino acid analogues which ma y be incorporated into peptides. Two variants have been realized: either th e sulfoximine-containing pseudo-amino acids are connected with standard alp ha-amino acids to give mixed pseudopeptides, or the sulfoxime units are mut ually attached to give homooligomers, which can be regarded as beta-peptide analogues. (C) 1999 John Wiley & Sons, Inc.