نتایج جستجو برای: stereoelectronic effects
تعداد نتایج: 1544327 فیلتر نتایج به سال:
The bioactive amino monosaccharide D-glucosamine has been generated in the gas phase via laser ablation of D-glucosamine hydrochloride. Three cyclic α-(4)C1 pyranose forms have been identified using Fourier transform microwave techniques. Stereoelectronic hyperconjugative forces - essentially linked with the anomeric or gauche effect - and cooperative OH···O, OH···N and NH···O chains, extended ...
The reaction course of the selenation-oxidation-elimination sequence carried out from cis-4-benzyloxy-1,2-epoxycyclohexane (cis-1) is studied. Contrary to literature precedents, this transformation leads to an unexpected diastereomeric cyclohexenol, whose formation can be interpreted by stereoelectronic grounds. In addition, the base induced rearrangement of cis-1 with lithium amide bases is al...
This paper reports the in vitro trypanocidal activity evaluation of new carbohydrazide derivatives from 3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine, substituted at C-6 position by phenyl, methyl or trifluoromethyl group. These compounds were evaluated in order to identify the antiparasitic profile against trypomastigote and amastigote forms of Trypanosoma cruzi. The 4-carbohydrazide derivative...
Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F∙∙∙HO intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction co...
The unexpected ability of arylzinc reagents bearing electron-donating substituents to react in a Friedel-Crafts fashion (cine) with electrophiles like perpivaloylated glucoside bromide and benzhydryl bromides in competition with organometallic coupling (ipso) is shown. The stereoelectronic factors required to promote the cine reactivity versus the classical ipso, and the mechanism of this alter...
The first examples of amino acid (Ser/Thr)-sp(2)-iminosugar glycomimetic conjugates featuring an α-O-linked pseudoanomeric linkage are reported. The key synthetic step involves the completely diastereoselective α-glycosylation of Ser/Thr due to strong stereoelectronic and conformational bias imposed by the bicyclic sp(2)-iminosugar scaffold. Mucin-related glycopeptides incorporating these motif...
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