Sulfoxi mines

Consequently, compounds such as 96 having a suitable donor atom X in the appropriate position became desirable targets. In particular, phosphino sulfoxi-mine 97 appeared attractive because other P,N-ligands had already been applied successfully in various catalyses [76, 77]. 

The reaction proceeds stereospecifically, giving sulfoximines from the corresponding enantiomerically enriched sulfoxides without racemization. The NH-sulfoxi-mines can then be obtained after Boc cleavage with trifluoroacetic acid. Bolm et al. applied this reaction in the synthesis of sulfoximines having a benchrotene skeleton (Scheme 3.55) [171]. 

In the original publication lithiated sulfoximines should have been referred to as lithiated (S)-sulfoxi mines and not (R)-lithiated sulfoximines. 

Another efficient process has been described for the silylcyanation of aldehydes in the presence of salen-titanium alkoxide complexes [86]. When a chiral C2 symmetric bis(dihydrooxazole)-Mg complex is employed with aldehydes as substrates, both excellent chemical yields and enantiomeric excesses are obtained [87]. Chiral titanium complexes are also derived from optically active sulfoxi-mines and a titanium alkoxide precursor [88]. 

Aryl chlorides were found to successfully couple with methyl phenyl sulfoxi-mines in a series of experiments reported by Harmata s group [129]. Using palladium acetate and binap with a large excess of aryl chlorides as coupling partners and cesium carbonate as the base, yields between 10-94% were obtained after one or two 1.5-h irradiation periods at 135 °C. Switching to an aryl triflate and use of an excess of the sulfoximines (5 equiv.) furnished an impressive 94% yield (Scheme 15.63). 

The role of GSH in the in-vivo reduction of V(V) to V(IV) was examined by EPR in a study by Lu, Fantus and coworkers [65]. The results of this experiment are shown in Figure 8. In insulin-resistant adipocytes (with naturally lower GSH coneentrations, Resistant in Fig. 8) or in cells pretreated with buthionine sulfoxi-mine (BSO, a GSH-synthase inhibitor, GSH-synthase inhibited in Fig. 8), showed inereased sensitivity to vanadate-stimulated phosphorylation of insulin reeeptors. This result was consistent with EPR speetra showing a decreased intra-eellular eoneentration of vanadyl ions that do not promote phosphorylation. Addition of N-aeetylcysteine, a precursor of GSH synthesis, to the incubating cells, restored the amount of EPR-detected vanadyl ion within the cells to control levels (eompare Resistant + NAC to Resistant in Fig. 8). 

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