Stereoselectivity activity

With a polymer-bound chiral selenium bromide reagent, the stereoselective activation of olefins has been accomplished (entry 19) 24 Uehlin and Wirth24 found that both mesoporous silica and polystyrene-supported... 

Kinetic investigation of the deprotonation of 1 using 23 has been carried out and the reaction orders show that a stereoselecting activated complex is built from one heterodimer... 

The application of enzymes is now well documented. They are used in organic chemistry - mainly for the production of optically pure compounds - synthesis of detergents and emulsifiers, lipid modification, laundry formulations, food and beverage production etc. [1 - 6]. Due to their high chemo-, regio- and stereoselectivity, activity at ambient temperatures and pH, biocatalysts are often superior to chemical ones and this might explain that a considerable number of industrial bioprocesses have been established in recent years [2,7]. 

Although diastereoisomers, both quinine and quinidine, have similar physical properties (Fig. 18). In clinical studies, the renal clearance of quinidine was fourfold greater than that of quinine (57). No stereoselective differences in plasma protein binding were observed. The renal filtration and passive reabsorption of these two diastereoisomers should be similar since the compounds have similar octanol-water partition coefficients and pKa values (57). Therefore, stereoselective active renal secretion may be the mechanism responsible for the observed differences in the renal clearances of quinine and quinidine. 

Kinetic investigation of the deprotonation using 8 has been carried out and the reaction orders show that the stereoselecting activated complex is huilt from one heterodimer molecule and one epoxide molecule [42]. Geometry optimized structures of the stereoselecting activated complexes at the B3LYP/6-31G(d) level of theory are shown in Fig. 7. These results show that... 

Equally fast was the intuition that the formation of stereoselective active sites had to do with specific structural features of the solid catalyst surface, and the consequential decision to investigate its crystal lattice. This rapidly led to the discovery that TiQ3 is polymorphic and that the different modifications can be grouped into two classes, with fibrillar (P) and layered (a, y, 8) structures respectively [7,11,12]. Very recent quantum mechanics (QM) models of the ordered a, p, and y phases [24], in full agreement with... 

Giannini [40] and Corradini [41] were the first to extend to the new systems the crystaUochemical approach used before by Cossee and Arlman (Sect. 4). Their starting point was the identification of plausible nontrivial MgCb crystal surfaces, proposed to be 100 (with penta-coordinated Mg atoms) and 110 (with tetra-coordinated Mg atoms). According to a pirmeering paper by Corradini et al. [41], precursors of stereoselective active species would result from the epitaxial chemisorption of TiCLi... 

Acetonylthio)pyridine undergoes cycloplatination involving activation of the C-H bond of the SGH2 group." The Pt complex with an optically active sulfoxide ligand undergoes stereoselective activation of an enantiotopic G-H bond to form two diastereomeric complexes in different yields 524 and 525 (Equation (120)). 

A frontier of research in the area of Pd-mediated C—H activation lies with chemo-, regio-, and stereoselectively activating the sp hybridized carbon for subsequent functionalization. Methods have been developed to acetoxylate 3-methyl groups relative to... 

G. Jaouen and A. Meyer, Tetrahedron Letters, 1976, 3547. Stereoselective activation of benzylic protons in Cr(CO)s complexes of indanone and tetralone derivatives. 

Compared to other commonly anployed activation modes, the use of chiral iou-pairing catalysts is a complementary strategy that allows to stereoselectively activate important piochiral nucleophiles like euolates in a noncovalent fashion. Accordingly, a broad variety of fundamental enolate reactions can be controlled by using these catalysts, and a number of excellent reviews covering this topic have been published in the past [118],... 

---