- A donor-acceptor complex enables the synthesis of: E -olefins from alcohols, amines and carboxylic acids
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Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.
- Chen, Kun-Quan,Shen, Jie,Wang, Zhi-Xiang,Chen, Xiang-Yu
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p. 6684 - 6690
(2021/05/31)
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- Design of Negative and Positive Allosteric Modulators of the Cannabinoid CB2Receptor Derived from the Natural Product Cannabidiol
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Cannabidiol (CBD), the second most abundant of the active compounds found in the Cannabis sativa plant, is of increasing interest because it is approved for human use and is neither euphorizing nor addictive. Here, we design and synthesize novel compounds taking into account that CBD is both a partial agonist, when it binds to the orthosteric site, and a negative allosteric modulator, when it binds to the allosteric site of the cannabinoid CB2 receptor. Molecular dynamic simulations and site-directed mutagenesis studies have identified the allosteric site near the receptor entrance. This knowledge has permitted to perform structure-guided design of negative and positive allosteric modulators of the CB2 receptor with potential therapeutic utility.
- Navarro, Gemma,Gonzalez, Angel,Sánchez-Morales, Adrià,Casajuana-Martin, Nil,Gómez-Ventura, Marc,Cordomí, Arnau,Busqué, Félix,Alibés, Ramon,Pardo, Leonardo,Franco, Rafael
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p. 9354 - 9364
(2021/07/19)
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- Synthesis, antiepileptic effects, and structure-activity relationships of α-asarone derivatives: In vitro and in vivo neuroprotective effect of selected derivatives
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In the present study, we compared the antiepileptic effects of α-asarone derivatives to explore their structure-activity relationships using the PTZ-induced seizure model. Our research revealed that electron-donating methoxy groups in the 3,4,5-position on phenyl ring increased antiepileptic potency but the placement of other groups at different positions decreased activity. Besides, in allyl moiety, the optimal activity was reached with either an allyl or a 1-butenyl group in conjugation with the benzene ring. The compounds 5 and 19 exerted better neuroprotective effects against epilepsy in vitro (cell) and in vivo (mouse) models. This study provides valuable data for further exploration and application of these compounds as potential anti-seizure medicines.
- Zhang, Jian,Mu, Keman,Yang, Peng,Feng, Xinqian,Zhang, Di,Fan, Xiangyu,Wang, Qiantao,Mao, Shengjun
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- Aryl/heteroaryl pentafluorobenzenesulfonates (ArOPFBs): New electrophilic coupling partners for room temperature Suzuki-Miyaura cross-coupling reactions
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The first cross-coupling reaction between aryl/heteroaryl pentafluorobenzenesulfonates and aryl/heteroaryl boronic acids under mild conditions is described. The successful synthesis of highly ortho substituted biaryls and high chemoselectivity of these bench stable intermediates over tosylates, triflates, mesylates, and chlorides increases its scope as a valuable cross-coupling partner. The generality of this protocol was further extended to other boron containing nucleophiles (boronates, trifluoroborates) and alkyl boronic acids.
- Joseph, Jayan T.,Sajith, Ayyiliath M.,Ningegowda, Revanna C.,Nagaraj, Archana,Rangappa,Shashikanth, Sheena
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p. 5106 - 5111
(2015/08/06)
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- Euodenine A: A small-molecule agonist of human TLR4
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A small-molecule natural product, euodenine A (1), was identified as an agonist of the human TLR4 receptor. Euodenine A was isolated from the leaves of Euodia asteridula (Rutaceae) found in Papua New Guinea and has an unusual U-shaped structure. It was synthesized along with a series of analogues that exhibit potent and selective agonism of the TLR4 receptor. SAR development around the cyclobutane ring resulted in a 10-fold increase in potency. The natural product demonstrated an extracellular site of action, which requires the extracellular domain of TLR4 to stimulate a NF-κB reporter response. 1 is a human-selective agonist that is CD14-independent, and it requires both TLR4 and MD-2 for full efficacy. Testing for immunomodulation in PBMC cells shows the induction of the cytokines IL-8, IL-10, TNF-α, and IL-12p40 as well as suppression of IL-5 from activated PBMCs, indicating that compounds like 1 could modulate the Th2 immune response without causing lung damage.
- Neve, Juliette E.,Wijesekera, Hasanthi P.,Duffy, Sandra,Jenkins, Ian D.,Ripper, Justin A.,Teague, Simon J.,Campitelli, Marc,Garavelas, Agatha,Nikolakopoulos, George,Le, Phuc V.,De A. Leone, Priscila,Pham, Ngoc B.,Shelton, Philip,Fraser, Neil,Carroll, Anthony R.,Avery, Vicky M.,McCrae, Christopher,Williams, Nicola,Quinn, Ronald J.
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p. 1252 - 1275
(2014/03/21)
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- Methoxy-substituted stilbenes, styrenes, and 1-arylpropenes: Photophysical properties and photoadditions of alcohols
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The photochemistry of trans-stilbene and four methoxy-substituted stilbene derivatives has been investigated in a variety of solvents. The fluorescence of all five trans isomers was quenched by 2,2,2-trifluoroethanol (TFE). Upon irradiation of the five substrates in TFE, the products derived from photoaddition of the solvent were detected. Nuclear magnetic resonance spectroscopy of the products formed by irradiation in TFE-OD indicated that the proton and nucleophile are attached to two adjacent atoms of the original alkene double bond. Irradiation of the corresponding methoxy-substituted styrenes and trans-1-arylpropenes in TFE produced the analogous solvent adducts. The photoaddition of TFE proceeded with the general order of reactivity: styre > trans-1-arylpropenes > trans-stilbenes. Transient carbocation intermediates were observed following laser flash photolysis of the stilbenes in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). The results are consistent with a mechanism that involves photoprotonation of the substrates by TFE or HFIP, followed by nucleophilic trapping of short-lived carbocation intermediates. Compared to the other stilbene derivatives, trans-3,5-dimethoxystilbene displayed a large quantum yield of fluorescence and a low quantum yield of trans-cis isomerization in polar organic solvents. The unique photophysical properties of trans-3,5-dimethoxystilbene are attributed to formation of a highly polarized charge-transfer excited state (μe = 13.2 D).
- Roberts, Jeffrey C.,Pincock, James A.
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p. 1480 - 1492
(2007/10/03)
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- Suzuki reactions with B-allyl-9-borabicyclo[3.3.1]nonane (B-allyl-9-BBN)
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The mixture of borate complexes formed on treatment of B-allyl-9-BBN with KOMe readily undergoes Suzuki reactions in the presence of catalytic amounts of Pd(0) complexes, thus transferring their allyl moiety to aryl bromides, -iodides or -triflates.
- Fürstner, Alois,Seidel, Günter
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p. 161 - 162
(2007/10/03)
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- Stereoselective isomerisations of 4-(3′,5 ′-dimethoxyphenyl)-2,5-dimethyl-1,3-dioxolanes. Temperature-dependent formation of either isochromanes or dihydroisobenzofurans
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Stereoselective isomerisation of rel-(2R,4S,5R)-4-(3′,5′-dimethoxyphenyl)-2,5-dimethyl-1,3-dioxolane 7 with titanium tetrachloride affords rel-(1R,3R,4S)-4-hydroxy-6,8-dimethoxy-1,3-dimethylisochromane 19 and its C-1 epimer 20 in high yield. The former predominates at a reaction temperature of -78°C and the latter at -30°C. Similar isomerisation of the 1:1 mixture of rel-(2S,4R,5R)- and rel-(2R,4R,5R)-4-(3′,5′-dimethoxyphenyl)-2,5-dimethyl-1,3-dioxolanes 8 and 9 gives rel-(1R,3R,4R)-4-hydroxy-6,8-dimethoxy-1,3-dimethylisochromane 29 and its C-1 epimer 31, with the latter predominating at both -78 and -30°C. At 0°C, dioxolane 7 is isomerised to rel-(1S,1′R,3R)-1-(1′-hydroxyethyl)-4,6-dimethoxy-3-methyl-1,3- dihydroisobenzofuran 25 and its C-3 epimer 26 as the sole reaction products in a 10:1 ratio. Dioxolanes 8 and 9 are similarly converted into rel-(1R,1′R,3S)-1-(1′-hydroxyethyl)-4,6-dimethoxy-3-methyl-1,3- dihydroisobenzofuran 32 and its C-3 epimer 33. These furans probably arise through further isomerisation of the intermediate isochromanes at the higher reaction temperatures.
- Giles, Robin G. F.,Rickards, Rodney W.,Senanayake, Badra S.
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p. 2241 - 2248
(2007/10/03)
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- Photoinduced nucleophilic addition of ammonia and alkylamines to methoxy-substituted styrene derivatives
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The photoamination of trans-1-arylpropenes (aryl = 2-methoxyphenyl), (1), 3-methoxyphenyl (2) 3,4-dimethoxyphenyl (3), and 4-methoxyphenyl (4) with NH3, i-PrNH2, and t-BuNH2 (RNH2), in the presence of p-dicyanobenzene (p-DCB) gave 2-alkylamino-1 arylpropanes (9) and/or 2-alkylamino-1-aryl-1-(4-cyanophenyl)propanes (10). The photoaminations of 1,2-dihydro-7-methoxynaphthalenes (6-8) with RNH2 in the presence of p-DCB gave mainly 2-alkylamino-1-(4-cyanophenyl)-6-methoxy-1,2,3,4-tetrahydronaphthalene s (13). The photoamination of trans-1-(3,5-dimethoxyphenyl)propene (5) with i-PrNH2 occurred at aromatic ring to give trans-1-(2-isopropylamino-3,5-dimethoxyphenyl)propene (11). The photoaminations of 1-4 and 6-8 with NH3 in the presence of m-dicyanobenzene gave the aminated products without incorporation of cyanophenyl group. Furthermore, the addition of 1,3,5-triphenylbenzene and m-terphenyl for these reactions improved the yields of the photoaminated products.
- Yamashita,Yamashita, Toshiaki,Yasuda,Yasuda, Masahide,Isami,Isami, Toshihiro,Tanabe,Tanabe, Kimiko,Shima,Shima, Kensuke
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p. 9275 - 9286
(2007/10/02)
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- STRUCTURE-ACTIVITY RELATIONSHIPS OF PHENYLPROPANOIDS AS GROWTH INHIBITORS OF THE GREEN ALGA SELENASTRUM CAPRICORNUTUM
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Twenty-seven commercial or synthetic phenylpropanoids have been tested in broth against the unicellular alga Selenastrum capricornutum.The antialgal activity seems to be linked to the number as well as to the position of the methoxyl group in the molecule.A slight effect of the side chain substitution was also observed. Key Word Index - Selenastrum capricornutum; allelochemicals; phenylpropanoids.
- Greca, Marina Della,Monaco, Pietro,Pollio, Antonino,Previtera, Lucio
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p. 4119 - 4124
(2007/10/02)
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