نتایج جستجو برای: mechanisms of cis and trans beta lactam ring formation
تعداد نتایج: 24118100 فیلتر نتایج به سال:
The mitochondrial metabolism of 5-enoyl-CoAs, which are formed during the beta-oxidation of unsaturated fatty acids with double bonds extending from odd-numbered carbon atoms, was studied with mitochondrial extracts and purified enzymes of beta-oxidation. Metabolites were identified spectrophotometrically and by high performance liquid chromatography. 5-cis-Octenoyl-CoA, a putative metabolite o...
The structure and solution conformation of meropenem was examined by using 1H and 13C NMR spectroscopy and nuclear Overhauser enhancement experiments. Similar to the X-ray crystal structure, the close spacing of 1 beta-methyl substituent to the beta-lactam ring and the accessible conformation of C-2 side chain in relation to the carbapenem skeleton was confirmed. The structure of the primary me...
Gabapentin is currently used as a therapeutic agent against epilepsy as well as neuropathic pain. In contrast to gabapentin, its derivative gabapentin-lactam has a pronounced neuroprotective activity. We have studied in cultured hippocampal neurons whether gabapentin-lactam has also neurotrophic effects. Gabapentin-lactam enhanced the formation of dendritic filopodia, which are necessary for sy...
SnBr(4)-promoted oxonium-Prins cyclizations to form 2,3-disubstituted tetrahydrofurans (THFs) are reported. In the absence of an internal nucleophile, the carbocation intermediates are trapped by bromide to give 2,3-cis- and 2,3-trans-configured products; two variations with intramolecular trapping are also reported. One of these allows a single-step stereocontrolled synthesis of the core 2,3-c...
In the present study, theoretical chemical reactivates Photo isomerization in Cis-Retinal as a Natural Photo switch in Vision. DFT hybrid functional, B3LYP and, post-HF method, were the theoretical methods applied utilizing G09 software. 6-31G+ (d,p) basis set employed for structural optimizations, and single point computations performed using B3LYP/6-31G+(d,p). The isomers cis molecule retinal...
The title compound, digoxigenone, C(23)H(30)O(5)·H(2)O, was biotransformed from digoxigenin. In the crystal, inter-molecular O-H⋯O hydrogen bonds contribute to the formation of a three-dimensional supra-molecular structure. The title compound has three fused six-membered rings (A,B,C) and two non-fused five-membered rings (D,E). As in other structures, compound nucleus has a cis-trans-cis confo...
The analysis of beta-carotene and lycopene, the two predominant carotenoids in human serum and tissues, was extended to the level of geometrical (cis-trans) isomers by using an improved reversed-phase HPLC methodology. We separated five geometrical isomers of beta-carotene and seven of lycopene in human serum and tissues. 13-cis-beta-Carotene was identified as the predominant cisisomer in human...
Abstract Background and purpose: Escherichia Coli is one of the most common pathogens associated with nosocomial infection. Increasing use of beta Lactam Antibiotics in treatment of bacterial infections resulted in increments of drug resistance of such bacteria that is caused due to the production of B-lactamase enzymes. The beta lactamase – producing bacteria especially E.coli which is resi...
The experimental results of the reaction of C60 with carbonyl ylides generated from trans-epoxides, which afforded cis-products exclusively or predominantly, can be explained well by computational investigation of the proposed reaction mechanism. Our theoretical calculations demonstrate that only cis-carbonyl ylides can be formed directly from trans-epoxides, in compliance with the Woodward-Hof...
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