Asymmetric Addition Reactions with Optimized Selenium Electrophiles

Abstract

Abstract:The synthesis of various nonracemic diselenides by different methods is described. These diselenides are precursors for optically active selenium electrophiles. Their facial selectivity upon addition to styrene was investigated with respect to the chiral moiety neighboring the selenium. Diselenides 1 i, 1 n, and 1 v yielded addition products 7 with diastereomeric excesses up to 95 YO. Some diselenides, intermediates, and products of the addition reaction were investigated by "Sc NMR spectroscopy.

Glutathione Peroxidase-like Activities of Oxygen-Containing Diselenides

“…In the course of our studies concerning asymmetric reactions with chiral selenium electrophiles, a series of new diselenides containing an oxygen as heteroatom in close proximity to selenium were prepared [10]. The asymmetric induction observed was investigated in detail and is due to an interaction between the oxygen and the selenium [11].…”

“…We were interested to evaluate the GPx-like activity for the oxygen-containing diselenides 1 -8 ( Figure 1). The antioxidant properties (GPx activities) and the pro-oxidant properties (glutathione oxidase [GOx] activities) were investigated (Table 1) The diselenides were prepared by short synthetic sequences as described [10]. The GPx activities were measured with the protocol of Paglia et al using the glutathione reductase coupled assay with either hydrogen peroxide or tert-butyl hydroperoxide as oxidant [12].…”

New and Efficient Chiral Selenium Electrophiles

“…The selectivities of the reactions described were all determined from NMR spectra of the crude reaction mixtures and HPLC of radical cleavage products, as described earlier. [4] …”

Stereoselective addition reactions with chalcogen electrophiles

“…The corresponding selenium electrophile has already been proven to be difficult to react. 15 In conclusion, we have shown that disulfides and a ditelluride could be prepared in analogy to the diselenides investigated earlier. The generation of the corresponding electrophiles is possible using the disulfide precursors, although the reaction yields as well as the observed selectivities are disappointingly low.…”