نتایج جستجو برای: stereoelectronic effect
تعداد نتایج: 1641819 فیلتر نتایج به سال:
in this research, we report the results of dft calculations using xc-hybrid functional, b3lyp and employ nbo interpretation to investigate the stereoelectronic effects. electrostatic and steric impacts on the conformational properties of 1,2-difluorodiazene (1), 1,2-dichlorodiazene (2) and 1,2-dibromodiazene (3) are also studied. factors determining the thermodynamically stable molecular struct...
Correction for ‘Stereoelectronic power of oxygen in control chemical reactivity: the anomeric effect is not alone’ by Igor V. Alabugin et al. , Chem. Soc. Rev. 2021, DOI: 10.1039/d1cs00386k.
In previous work, we demonstrated that 4-fluoroproline residues can contribute greatly to the conformational stability of the collagen triple helix, and that this stability arises from stereoelectronic effects that fix the pucker of the pyrrolidine ring and thereby preorganize the backbone properly for triple-helix formation. Here, we take a reciprocal approach, demonstrating that the steric ef...
According to a prevailing theory, (2S,4R)-4-hydroxyproline (Hyp) residues stabilize the collagen triple helix via a stereoelectronic effect that preorganizes appropriate backbone torsion angles for triple-helix formation. This theory is consistent with the marked stability that results from replacing the hydroxyl group with the more electron-withdrawing fluoro group, as in (2S,4R)-4-fluoroproli...
A plausible route for the spontaneous synthesis of an activated ribonucleotide that is poised for polymerization has been put forth (Powner et al. (2009) Nature, 459, 239-242). A key step in this route necessitates the regioselective phosphorylation of the secondary alcohol on C(3') of an anhydroarabinonucleoside in the presence of the primary alcohol on C(5'). Here, we propose that this regios...
Stable and easy-to-handle zwitterions containing carbanion and pyridinium moieties were synthesized, and their structural studies by both X-ray crystallography and theoretical methods revealed the stereoelectronic effect in the zwitterionic 'C(-)-C-N(+)' system.
Anomeric O-alkylation/arylation is applied to the synthesis of 2-deoxy-beta-glycosides. Treatment of lactols with NaH in dioxane followed by the addition of electrophiles leads to the formation of 2-deoxy-beta-glycosides in high yield and high selectivity. The high beta-selectivity observed here demonstrates a powerful stereoelectronic effect for the stereoselective formation of acetals under k...
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