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Search for "labeling experiments" in Full Text gives 37 result(s) in Beilstein Journal of Organic Chemistry.
Enantioconvergent catalysis
Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192
- . Deuterium labeling experiments have shown that the hydrogenation reaction occurs only on the chiral keto tautomer, and therefore the catalyst selects one enantiomer of the substrate when the reduction takes place. Enantioconvergent methods are not limited to carbon stereocenters. An exceptional example of
Recent highlights in biosynthesis research using stable isotopes
Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271
- Jan Rinkel Jeroen S. Dickschat Kekulé-Institute of Organic Chemistry and Biochemistry, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany 10.3762/bjoc.11.271 Abstract The long and successful history of isotopic labeling experiments within natural products research has both changed and deepened our
- a special emphasis on mechanistic surprises. Keywords: biosynthesis; enzyme mechanisms; isotopes; labeling experiments; natural products; Introduction This year may be seen as the 80th anniversary of using isotopes in biosynthetical and biochemical research. Since the first experiments performed
- of the metabolite did not prove to be suitable for broader applications, and therefore, after the discovery of the isotopes by Frederick Soddy, for which he was awarded the Nobel prize in 1921, the first labeling experiments using isotopes quickly changed the way of investigating metabolic pathways
Facile synthesis of 1-alkoxy-1H-benzo- and 7-azabenzotriazoles from peptide coupling agents, mechanistic studies, and synthetic applications
Beilstein J. Org. Chem. 2014, 10, 1919–1932, doi:10.3762/bjoc.10.200
- synthesis of 1-alkoxy-1H-benzo[d][1,2,3]triazoles. Three possible mechanisms for the reaction of BOP with oxygen nucleophiles. Possible products in the [18O]-labeling experiments. Two possible products from the reaction of At-OTs with MeOH. Synthesis of acyclic nucleoside-like compounds. Formation of Bt-OR
New developments in gold-catalyzed manipulation of inactivated alkenes
Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294
- substituted N- or O-heterocycles in high yields (Scheme 33) [76]. Deuterium labeling experiments unambiguously demonstrated the anti-functionalization of the double bond and the use of neutral gold complexes suggested that [Au(I)] oxidation took place prior of C–X bond formation. The same team also reported
The myxocoumarins A and B from Stigmatella aurantiaca strain MYX-030
Beilstein J. Org. Chem. 2013, 9, 2579–2585, doi:10.3762/bjoc.9.293
- . erecta Pd e21 using isotope-labeling experiments that revealed its precursor molecules to be glucose-derived erythrose-4-phosphate (10) and phosphoenol-pyruvate (11, Scheme 1). Due to the observed scrambling of the expected labeling pattern in 13, its biosynthesis has to proceed via a symmetrical
The chemistry of isoindole natural products
Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243
- subdivided into cytochalasins [41] (phenylalanine), chaetoglobosins [45][46] (tryptophan), aspochalasins [47] (leucine), pyrichalasins [48] (tyrosine) or alachalasins [49][50] (alanine). The biosynthesis of cytochalasans was established on the basis of various isotope labeling experiments using cytochalasin
- relationship between these three classes [87][96]. The biosynthesis of aristolochic acid I (117) was elucidated via labeling experiments and is depicted in Scheme 14 [97][98][99][100]. First, two molecules of the amino acid L-tyrosine (98) are transformed to (R)-orientaline (121) in a similar fashion as
Gold-catalyzed cyclization of allenyl acetal derivatives
Beilstein J. Org. Chem. 2013, 9, 1751–1756, doi:10.3762/bjoc.9.202
- deuterium labeling experiments supports a 1,4-hydride shift of the resulting allyl cationic intermediates because a complete deuterium transfer is observed. We tested the reaction on various acetal substrates bearing a propargyl acetate, giving 4-methoxy-5-alkylidenecyclopent-2-en-1-ones 4 via a degradation
- the product without deuterium content (Scheme 2, reaction 2). The results of these labeling experiments reveal a 1,4-hydrogen shift [20][21][22] in the d1-1a→d1-4a transformation. Scheme 3 shows a plausible mechanism to rationalize the transformation of the allenyl acetal 1e into the observed
- % yields. Conclusion In summary, we report a gold-catalyzed transformation of allenyl acetals 1 into 5-alkylidenecyclopent-2-en-1-ones 4. Our deuterium labeling experiments support a 1,4-hydride shift for the resulting allyl cation because of a complete deuterium transfer. This observation excludes the
True and masked three-coordinate T-shaped platinum(II) intermediates
Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153
- filled by an agostic interaction prior to the C–H bond activation. Intermediate 53 evolves through a σ-CAM process, whereas intermediate 54 undergoes oxidative addition and reductive elimination processes. The release of methane and dimethylsulfide yields 55. Further studies including labeling
- experiments support the reversibility of these “rollover” reactions. The highly unsaturated species 55 is still reactive and can coordinate and decompose XMe2 molecules (X = S [128] and O [129]) and dehydrogenate alkanes [130]. Finally
Chemical–biological characterization of a cruzain inhibitor reveals a second target and a mammalian off-target
Beilstein J. Org. Chem. 2013, 9, 15–25, doi:10.3762/bjoc.9.3
- ., cathepsin B) and/or other cytosolic nucleophiles (e.g., glutathione). This possibility is supported by our competitive labeling experiments (Figure 6) and by in vitro studies employing physiological concentrations of glutathione (Supporting Information File 1). With regard to the inhibitor chemotypes
Identification and isolation of insecticidal oxazoles from Pseudomonas spp.
Beilstein J. Org. Chem. 2012, 8, 749–752, doi:10.3762/bjoc.8.85
- A and B. Labeling experiments confirmed their structures and gave initial evidence for a novel biosynthesis pathway of these natural oxazoles. In order to confirm their structure, they were synthesized, which also allowed tests of their bioactivity. Additionally, the bioactivities of the synthesis
- characteristic fragment ion of 130 m/z [M + H]+ (Supporting Information File 1, Figure S2), and labeling experiments (Supporting Information File 1, Figure S3) enabled the elucidation of this ion as 3-methylidene-3H-indolium (Figure 1). In order to determine the genus of the producing strain PB22.5, we sequenced
- produces compounds 3–6 but not 1 and 2. Furthermore two novel oxazole derivatives named labradorin 3 (7, 268.4 m/z [M + H]+, C17H20N2O) and labradorin 4 (8, 283.2 m/z [M + H]+, C18H22N2O) were detected, but they could not be isolated due to their very low production. Labeling experiments were performed in
Recent advances in the gold-catalyzed additions to C–C multiple bonds
Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103
- sp3-hybridized C–H bond can be achieved by undergoing 1,3-addition to a vinyl–carbenoid intermediate [142]. The bicyclo[3.2.1]oct-6-en-2-ones 265 and 267 could be synthesized stereoselectively by this method. Deuterium labeling experiments indicated the cyclization involved an unprecedented 1,3
- via oxidative gold catalysis and provided expedient access to various substituted N- or O-heterocycles (344–351) (Scheme 57). Deuterium labeling experiments were carried out to unveil the reaction mechanism. The results established the anti nature of the alkene functionalization and the indispensable
When gold can do what iodine cannot do: A critical comparison
Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97
- selectivity and 90% yield (Scheme 9a) [91]. Labeling experiments showed that the proposed mechanism where the cation is trapped by the nucleophile and subsequent loss of the proton and protodemetallation is viable. A more elaborate study of 5-endo hydroxy- and alkoxycyclizations of 1,5-enynes was described by
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