The stability of pseudopeptides bearing sulfoximines as chiral backbone modifying element towards proteinase K

Incorporation of sulfoximines as backbone modifying element results in two new pseudopeptide bonds which display enhanced (bond A) and strongly reduced reactivity (bond B) towards hydrolysis by Proteinase K.

Metal-catalyzed asymmetric oxidations

Recent advances in enantioselective metal-catalyzed oxidations are presented. Two transformations are discussed in detail: (a) asymmetric Baeyer-Villiger reactions of racemic and prochiral cyclic ketones giving optically active lactones, and (b) sulfide oxidations affording enantiomerically enriched sulfoxides. For both reactions, new metal/ligand combinations have been introduced which allow catalysis of these reactions with high enantioselectivities. For some substrates, the ee-values are above 90%. As previously demonstrated, sulfoxides can be iminated to give the corresponding sulfoximines. Under appropriate reaction conditions, this transformation is stereospecific and enantiopure sulfoximines are obtained. These highly oxidized sulfur reagents have now been modified to give beta-amino acid analogues which may be incorporated into peptides. Two variants have been realized: either the sulfoximine-containing pseudo-amino acids are connected with standard alpha-amino acids to give mixed pseudopeptides, or the sulfoxime units are mutually attached to give homooligomers, which can be regarded as beta-peptide analogues.

Simultaneous and combinatorial chemical synthesis techniques for the generation and screening of molecular diversity

By skillful 'mixing and sorting', thousand millions of different compounds, so-called molecular repertoires or molecular libraries, can be produced and screened for biological activity in a very short time. Today, both sophisticated as well as surprisingly simple procedures for simultaneous and combinatorial chemical synthesis open fascinating new perspectives for basic research, biotechnology and drug development. This contribution will give a brief survey of current strategies in the chemical synthesis of oligonucleotide and peptide repertoires with special emphasis on techniques employing membrane-type solid supports developed in this laboratory.