- Role of solvent, pH, and molecular size in excited-state deactivation of key eumelanin building blocks: Implications for melanin pigment photostability
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Ultrafast time-resolved fluorescence spectroscopy has been used to investigate the excited-state dynamics of the basic eumelanin building block 5,6-dihydroxyindole-2-carboxylic acid (DHICA), its acetylated, methylated, and carboxylic ester derivatives, and two oligomers, a dimer and a trimer in the O-acetylated forms. The results show that (1) excited-state decays are faster for the trimer relative to the monomer; (2) for parent DHICA, excited-state lifetimes are much shorter in aqueous acidic medium (380 ps) as compared to organic solvent (acetonitrile, 2.6 ns); and (3) variation of fluorescence spectra and excited-state dynamics can be understood as a result of excited-state intramolecular proton transfer (ESIPT). The dependence on the DHICA oligomer size of the excited-state deactivation and its ESIPT mechanism provides important insight into the photostability and the photoprotective function of eumelanin. Mechanistic analogies with the corresponding processes in DNA and other biomolecules are recognized.
- Gauden,Pezzella,Panzella,Neves-Petersen,Skovsen,Petersen,Mullen,Napolitano,D'Ischia,Sundstr?m
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Read Online
- A Bu4N[Fe(CO)3(NO)]-Catalyzed Hemetsberger–Knittel Indole Synthesis
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The nucleophilic Fe complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) catalyzes the direct intramolecular amination of aryl vinyl azides to give the corresponding indole derivatives in good to excellent yields.
- Baykal, Aslihan,Plietker, Bernd
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supporting information
(2020/02/20)
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- A Bioinspired Synthesis of Polyfunctional Indoles
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Polyfunctional indoles bearing substituents at C5 and C6 are prevalent in natural products, pharmaceuticals, agrochemicals, and materials. Owing to the remoteness of the C5 and C6 positions, indoles of this family can be difficult to prepare, and often require multistep syntheses. Herein, we describe a concise process that converts simple derivatives of tyrosine into 5,6-difunctionalized indoles by direct oxidation of C?H, N?H, and O?H bonds. Our work draws inspiration from the biosynthetic polymerization of tyrosine to make melanin pigments, but makes an important departure to provide well-defined indole heterocycles.
- Huang, Zheng,Kwon, Ohhyeon,Huang, Haiyan,Fadli, Aziz,Marat, Xavier,Moreau, Magali,Lumb, Jean-Philip
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supporting information
p. 11963 - 11967
(2018/09/11)
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- Ligand-free copper-catalyzed one-pot synthesis of indole-2-carboxylic esters
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A simple, efficient, and facile synthetic route for the preparation of indole-2-carboxylic esters was described. The cascade reactions of 2-bromobenzaldehyde and glycine ester hydrochloride were promoted by Cu 2O and a base to provide the corresponding products in good yields. Commercially available, inexpensive substrates and reagents were employed under mild reaction conditions in this one-pot operation, which is complementary to existing methods for access to 2-substituted indoles. A simple, efficient, and facile synthetic route to indole-2-carboxylic esters through copper-catalyzed one-pot cascade reactions of commercially available, inexpensive 2-bromobenzaldehyde and glycine ester hydrochloride without the use of any external ligand under mild conditions is reported. Copyright
- Zhu, Zhiqiang,Yuan, Jiangjun,Zhou, Yirong,Qin, Yang,Xu, Jingshi,Peng, Yiyuan
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supporting information
p. 511 - 514
(2014/02/14)
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- Ligand-Free Copper-Catalyzed One-Pot Synthesis of Indole-2-carboxylic Esters
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A simple, efficient, and facile synthetic route for the preparation of indole-2-carboxylic esters was described. The cascade reactions of 2-bromobenzaldehyde and glycine ester hydrochloride were promoted by Cu2O and a base to provide the corresponding products in good yields. Commercially available, inexpensive substrates and reagents were employed under mild reaction conditions in this one-pot operation, which is complementary to existing methods for access to 2-substituted indoles.
- Zhu, Zhiqiang,Yuan, Jiangjun,Zhou, Yirong,Qin, Yang,Xu, Jingshi,Peng, Yiyuan
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supporting information
p. 511 - 514
(2015/10/05)
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- CuI-catalyzed intramolecular cyclization of 3-(2-aminophenyl)-2- bromoacrylate: Synthesis of 2-carboxyindoles
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A new approach was described for the synthesis of substituted 2-carboxyindole using 3-(2-aminophenyl)-2-bromo-acrylates through a CuI-catalyzed intramolecular coupling. The reactions were mild, rapid and with good to excellent yields.
- Xiao, Xiong,Chen, Tian-Qi,Ren, Jiangmeng,Chen, Wei-Dong,Zeng, Bu-Bing
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supporting information
p. 2056 - 2060
(2014/04/03)
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- Synthesis of symmetrical and unsymmetrical diindolylmethanes via acid-catalysed electrophilic substitution reactions
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A range of activated indole-2-carboxylate derivatives was prepared via the Hemetsberger indole synthesis. Vilsmeier formylation was explored to establish regioselectivity and to prepare a range of new indole carbaldehydes. The indole aldehydes were reduce
- Bingul, Murat,Cheung, Belamy B.,Kumar, Naresh,Black, David StC.
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p. 7363 - 7369
(2017/09/12)
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- Iron(II) triflate as a catalyst for the synthesis of indoles by intramolecular C-H amination
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A practical iron-catalyzed intramolecular C-H amination reaction and its application in the synthesis of indole derivatives are presented. As a catalyst, commercially available iron(II) triflate is used.
- Bonnamour, Julien,Bolm, Carsten
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supporting information; experimental part
p. 2012 - 2014
(2011/06/28)
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- Concise, efficient and practical assembly of bromo-5,6-dimethoxyindole building blocks
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A concise, efficient and simple route to a series of bromoindole building blocks is described. The synthetic routes are highlighted by purification-free preparation of o-nitrocinnamate intermediates and clean, modified Cadogan indole syntheses. The scope of this indole synthesis has been explored and expanded through the use of a range of solvents and easily removable phosphine reagents.
- Huleatt, Paul B.,Lau, Jacelyn,Chua, Sheena,Tan, Yun Lei,Duong, Hung Anh,Chai, Christina L.L.
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p. 1339 - 1342
(2011/03/22)
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- [Fe(F20TPP)Cl] catalyzed intramolecular C-N bond formation for alkaloid synthesis using aryl azides as nitrogen source
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The syntheses of alkaloids including indoles, indolines, tetrahydroquinolines, dihydroquinazolinones and quinazolinones have been accomplished in moderate to excellent yields via [Fe(F20TPP)Cl] catalyzed intramolecular C-N bond formation using aryl azides as nitrogen source.
- Liu, Yungen,Wei, Jinhu,Che, Chi-Ming
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supporting information; experimental part
p. 6926 - 6928
(2010/11/16)
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- Tandem palladium-catalyzed N,C-coupling/carbonylation sequence for the synthesis of 2-carboxyindoles
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(Chemical Equation Presented) Tandem palladium-catalyzed N,C-coupling/carbonylation, under 10 aim of carbon monoxide and at 110 °C, is a novel and efficient method for the preparation of 2-carboxyindoles. The catalyst system tolerates a variety of functional groups, and the noted indoles were obtained in good isolated yields.
- Vieira, Tiago O.,Meaney, Laura A.,Shi, Yong-Ling,Alper, Howard
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supporting information; experimental part
p. 4899 - 4901
(2009/05/31)
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- Expedient routes to valuable bromo-5,6-dimethoxyindole building blocks
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The synthesis of 3-, 4-, 7-bromo and 4,7-dibrominated 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) derivatives is reported. Hemetsberger and Bartoli indole syntheses were investigated and expedient routes to the desired compounds were developed. These indoles are valuable substrates for elaboration using transition metal-mediated cross-coupling chemistry.
- Huleatt, Paul B.,Choo, Sze Shiong,Chua, Sheena,Chai, Christina L.L.
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p. 5309 - 5311
(2008/12/22)
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- Intramolecular C-H amination reactions: Exploitation of the Rh 2(II)-catalyzed decomposition of azidoacrylates
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Rhodium(II) perfluorobutyrate-mediated decomposition of vinyl azides provides a new, mild entry into Rh2(II) nitrenoid chemistry. This methodology allows rapid access to a variety of complex, functionalized N-heterocycles in two steps from commercially available starting materials. Copyright
- Stokes, Benjamin J.,Dong, Huijun,Leslie, Brooke E.,Pumphrey, Ashley L.,Driver, Tom G.
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p. 7500 - 7501
(2008/02/09)
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- Hyperbranched molecular structures with potential antiviral activity: Derivatives of 5,6-dihydroxyindole-2-carboxylic acid
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In the search of new HIV-1 integrase (IN) inhibitors, we synthesized a series of multimeric 5,6-dihydroxyindole-2-carboxylic acid (DHICA) derivatives. Preliminary results indicate that hyperbranched architectures could represent a peculiar molecular requi
- Sechi, Mario,Casu, Fabio,Campesi, Ilaria,Fiori, Stefano,Mariani, Alberto
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p. 968 - 977
(2007/10/03)
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- CBI analogues of the duocarmycins and CC-1065
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An extensive series of CBI analogues of the duocarmycins and CC-1065 exploring substituent effects within the first indole DNA binding subunit is detailed. In general, substitution at the indole C5 position led to cytotoxic potency enhancements that can be ≧1000-fold providing simplified analogues containing a single DNA binding subunit that are more potent (IC50=2-3 pM) than CBI-TMI, duocarmycin SA, or CC-1065. The increases in cytotoxicity correlate well with accompanying increases in the rate and efficiency of DNA alkylation. This effect is more pronounced with the CBI versus DSA or CPI based analogues. Moreover, this effect is largely insensitive to the electronic character of the C5 substituent but is sensitive to the size, rigid length, and shape (sp, sp2, sp3 hybridization) of this substituent consistent with expectation that the impact is due simply to its presence.
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- Effects of indole fatty alcohols on the differentiation of neural stem cell derived neurospheres
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In a search for inducers of neuronal differentiation to treat neurodegenerative diseases such as Alzheimer's disease, a series of indole fatty alcohols (IFAs) were prepared, 13c (n = 18) was able to promote the differentiation of neural stem cell derived neurospheres into neurons at a concentration of 10 nM. Analysis of the expression of the Notch pathway genes in neurospheres treated during the differentiation phase with 13c (n = 18) revealed a significant decrease in the transcription of the Notch 4 receptor.
- Coowar, Djalil,Bouissac, Julien,Hanbali, Mazen,Paschaki, Marie,Mohier, Eliane,Luu, Bang
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p. 6270 - 6282
(2007/10/03)
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- 1,3-Diaryl-2-carboxyindoles as potent non-peptide endothelin antagonists
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Endothelin-1 is a potent vasoconstrictor that is thought to be involved in many human disease states. We have developed a series of indole non-peptide endothelin antagonists including PD 159110 (31), and ET(A) selective antagonist, and PD 159020 (37), a non-selective ET(A)/ET(B) antagonist. The discovery, synthesis, and structure-activity relationships of this series of compounds are described.
- Bunker, Amy M.,Edmunds, Jeremy J.,Berryman, Kent A.,Walker, Donnelle M.,Flynn, Michael A.,Welch, Kathy M.,Doherty, Annette M.
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p. 1061 - 1066
(2007/10/03)
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- The synthesis of roeharmine and (-)-1,2,3,4-tetrahydroroeharmine
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The total synthesis of roeharmine 1 as well as an enantiospecific synthesis of (-)-1,2,3,4-tetrahydroroeharmine 2 has been achieved via the Pictet-Spengler reaction as a key step. The optical rotation of synthetic (- )-2 was found to be higher than that reported for the natural product. A possible mechanism for the racemization of 2 upon exposure to acid has been proposed and serves as a warning to alkaloid chemists who isolate ring-A alkoxylated indole alkaloids under acidic conditions.
- Sreenivasa Reddy,Cook, James M.
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p. 5413 - 5416
(2007/10/02)
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