Advanced Organic Chemistry

Carey, Francis A.; Sundberg, Richard J.

doi:10.1007/978-1-4613-9797-7

Cited by 155 publications

(141 citation statements)

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“…This might be due to the acidic amino acids possess two carboxyl groups that can increase cross-linking between the amino acids and polyhydroxyl glucose. As well known, the carboxyl groups tend to forming esters with hydroxyls under conditions such as high temperature and low moisture 49 . In contrast, the basic amino acids (e.g.…”

Section: Resultsmentioning

confidence: 99%

Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

Wei

et al. 2014

Sci Rep

210

182

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The non-enzymatic browning, namely Maillard reaction is commonly invoked to account for abiotic chemical transformations of organic matter. Here we report a new reaction pathway via the Maillard reaction to systematically synthesize a series of nitrogen-doped carbon dots (C-dots) with superhigh quantum yield (QY) and tunable multicolor luminescent displayment. The starting materials are glucose and the serial amino acid analogues which allow systemically controlling luminescent and physicochemical properties of C-dots at will. Unexpectedly, the as-prepared C-dots possess bright photoluminescence with QY up to 69.1% which is almost the highest ever reported, favorable biocompatibility, excellent aqueous and nonaqueous dispersibility, ultrahigh photostability, and readily functionalization. We have demonstrated that they are particularly suitable for multicolor luminescent display and long-term and real-time cellular imaging. Furthermore, the methodology is readily scalable to large yield, and can provide sufficient amount of C-dots for practical demands.

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Section: Resultsmentioning

confidence: 99%

Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

Wei

et al. 2014

Sci Rep

210

182

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“…In agreement with the MS data, two hydrogens were missing from the 1 H NMR spectrum of 8 : the diagnostic B‐ring singlet of the anthracene, and one “enediyne” hydrogen, leaving a 1,2,3‐trisubstituted ring (Figure S7). We postulated, therefore, that a C–C bond formed between the enediyne and the proximal anthracene by reaction of a Bergman rearrangement radical with the anthracene at its most reactive position . Substantiating this proposal was the observation that the hydrogen at C10 was shifted downfield by about 0.7 ppm, which could result from a deshielding aromatic ring current by fixing the cycloaromatized enediyne over the anthracene A‐ring.…”

Section: Figurementioning

confidence: 99%

C−N‐Coupled Metabolites Yield Insights into Dynemicin A Biosynthesis

Cohen

Townsend

2020

ChemBioChem

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The biosynthesis of the three structural subclasses of enediyne antitumor antibiotics remains largely unknown beyond a common C16‐hexaene precursor. For the anthraquinone‐fused subtype, however, an unexpected iodoanthracene γ‐thiolactone was established to be a mid‐pathway intermediate to dynemicin A. Having deleted a putative flavin‐dependent oxidoreductase from the dynemicin biosynthetic gene cluster, we can now report four metabolites that incorporate the iodoanthracene and reveal the formation of the C−N bond linking the anthraquinone and enediyne halves emblematic of this structural subclass. The coupling of an aryl iodide and an amine is familiar from organometallic chemistry, but has little or no precedent in natural product biosynthesis. These metabolites suggest further that enediyne formation occurs early in the overall biosynthesis, and that even earlier events might convert the C16‐hexaene to a common C15 intermediate that partitions to enediyne and anthraquinone building blocks for the heterodimerization.

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“…An enzymatic acid could catalyze this step via an addition-elimination mechanism (AEM), in which a proton is added to the C5=C7 double bond and the intermediate cation loses a proton from C6 to form the product. Alternatively, the thermodynamic driving force (>6 kcal/mol as estimated from semiempirical QM calculations) could favor a 1,3-sigmatropic rearrangement (1,3-hydride shift) 21 . When conducting the reaction in D 2 O, an AEM would lead to 6D,7D-dTMP, but ESI-MS analysis ( Figure S4 ) did not indicate such product.…”

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confidence: 99%

An unusual mechanism of thymidylate biosynthesis in organisms containing the thyX gene

Koehn

Fleischmann

Conrad

et al. 2009

Nature

169

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Biosynthesis of the DNA base thymine depends on activity of the enzyme thymidylate synthase (TS) to catalyze the methylation of the uracil moiety of 2’-deoxyuridine-5’-monophosphate (dUMP). All known thymidylate synthases (TSs) rely on an active site residue of the enzyme to activate dUMP1, 2. This functionality has been demonstrated for classical TSs, including human TS, and is instrumental in mechanism-based inhibition of these enzymes. Here we report the first example of thymidylate biosynthesis that occurs without an enzymatic nucleophile. This unusual biosynthetic pathway occurs in organisms containing the thyX gene, which codes for a flavin-dependent thymidylate synthase (FDTS), and is present in several human pathogens3–5. Our findings indicate that the putative active site nucleophile is not required for FDTS catalysis, and no alternative nucleophilic residues capable of serving this function can be identified. Instead, our findings suggest that a hydride equivalent (i.e. a proton and two electrons) is transferred from the reduced flavin cofactor directly to the uracil ring, followed by an isomerization of the intermediate to form the product, 2’-deoxythymidine-5’-monophosphate (dTMP). These observations indicate a very different chemical cascade than that of classical TSs or any other known biological methylation. The findings and chemical mechanism proposed here, together with available structural data, suggest that selective inhibition of FDTSs, with little effect on human thymine biosynthesis, should be feasible. Since several human pathogens depend on FDTS for DNA biosynthesis, its unique mechanism makes it an attractive target for antibiotic drugs.

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Advanced Organic Chemistry

Cited by 155 publications

References 0 publications

Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

C−N‐Coupled Metabolites Yield Insights into Dynemicin A Biosynthesis

An unusual mechanism of thymidylate biosynthesis in organisms containing the thyX gene

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