- Photorelease of Pyridines Using a Metal-Free Photoremovable Protecting Group
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The photorelease of bioactive molecules has emerged as a valuable tool in biochemistry. Nevertheless, many important bioactive molecules, such as pyridine derivatives, cannot benefit from currently available organic photoremovable protecting groups (PPGs). We found that the inefficient photorelease of pyridines is attributed to intramolecular photoinduced electron transfer (PET) from PPGs to pyridinium ions. To alleviate PET, we rationally designed a strategy to drive the excited state of PPG from S1 to T1 with a heavy atom, and synthesized a new PPG by substitution of the H atom at the 3-position of 7-dietheylamino-coumarin-4-methyl (DEACM) with Br or I. This resulted in an improved photolytic efficiency of the pyridinium ion by hundreds-fold in aqueous solution. The PPG can be applied to various pyridine derivatives. The successful photorelease of a microtubule inhibitor, indibulin, in living cells was demonstrated for the potential application of this strategy in biochemical research.
- Dong, Zaizai,Fang, Xiaohong,Kou, Xiaolong,Tan, Weihong,Tang, Xiao-Jun,Wu, Yayun,Zhang, Zhen,Zhao, Rong,Zhou, Wei
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supporting information
p. 18386 - 18389
(2020/08/24)
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- An Approach to Nonsymmetric Bis(tertiary phosphine oxides) Comprising Heterocyclic Fragments via the Pd-Catalyzed Phosphorylation
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Nonsymmetric tertiary phosphine oxides with different five- and six-membered heterocyclic fragments such as pyridine, 2,2′-bipyridine, 1,10-phenantroline, quinoline, imidazole, and thiazole were synthesized in good yields via the successive introduction of phosphine oxide groups into the initial dihalogenated heterocycles by means of Pd-catalyzed phosphorylation reaction. The synthesis of pyridine-type compounds is hindered by competing double coupling, while for five-membered heterocycles the principal difficulty is the dehalogenation. Both side processes were successfully suppressed by the use of an excess of a dihalide (which can be easily recovered during the product purification step), proper phosphine ligand for palladium, and nonpolar solvent such as toluene.
- Zakirova, Gladis G.,Mladentsev, Dmitrii Yu.,Borisova, Nataliya N.
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supporting information
p. 1833 - 1837
(2020/09/21)
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- ANTIBACTERIAL AGENTS: ARYL MYXOPYRONIN DERIVATIVES
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The invention provides compounds of formula la, lb and Ic: [Formula Ia, Ib, and Ic] and salts thereof, wherein variables are as described in the specification, as well as compositions comprising a compound of formula Ia-Ic, methods of making such compounds, and methods of using such compounds, e.g., as inhibitors of bacterial RNA polymerase and as antibacterial agents.
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Page/Page column 117
(2014/01/09)
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- HETEROARYL COMPOUNDS AND METHODS OF USE THEREOF
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Provided herein are heteroaryl compounds, methods of their synthesis, pharmaceutical compositions comprising the compounds, and methods of their use. In one embodiment, the compounds provided herein are useful for the treatment, prevention, and/or management of various disorders, such as CNS disorders and metabolic disorders, including, but not limited to, e.g., neurological disorders, psychosis, schizophrenia, obesity, and diabetes
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Page/Page column 103
(2011/12/14)
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- Preparatory study for the synthesis of the starfish alkaloid imbricatine. Syntheses of 5-arylthio-3-methyl-L-histidines
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Chiral syntheses of 3-methyl-5-(phenylthio)-L-histidine (8a) and 3-methyl-5-(1-naphthalenylthio)-L-histidine (8b), selected as models for the asteroid alkaloid imbricatine (7), have been accomplished through a 10-step route starting from 4(5)-bromoimidazole (9). The key steps involved were methylation of 9, hydroxymethylation of 4-bromo-1-methyl-1H-imidazole (11), replacement of the 4-bromo group by an arylthio group in the aldehyde 14, and introduction of a chiral α-amino acid moiety into the chlorides 17a and 17b by the 'bis-lactim ether' method. The synthesis of the 4-(4-methoxybenzyl)thio analogue 17c, carried out in a similar manner, concluded formal syntheses of ovothiols A and C (1 and 3).
- Ohba,Mukaihira,Fujii
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p. 1784 - 1790
(2007/10/02)
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- SYNTHESIS OF 5-ARYLTHIO-3-METHYL-L-HISTIDINE, A MODEL FOR THE STARFISH ALKALOID IMBRICATINE
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Syntheses of 3 methyl-5-phenylthio-L-histidine (8a) and 3-methyl-5-(1-naphthyl)thio-L-histidine (8b), selected as models for the asteroid alkaloid imbricatine (7), have now become feasible through a 10-step route starting from 4(5)-bromoimidazole (9).The key steps involve replacement of the 4-bromo group by an arylthio group in the aldehyde (14) and construction of the L-alanine moiety in the chlorides (17a,b) by the "bis-lactim ether" method.
- Ohba, Masashi,Mukaihira, Takafumi,Fuji, Tozo
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- Alkylation, Acylation and Silylation of Azoles
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Performing alkylation, acylation and silylation reactions in separate deprotonation and nucleophilic displacement steps allows for better control of reaction conditions and facilitates problem handling in these processes.In the alkylation of azoles the alkylating agents and solvents possess individual reaction capabilities which seem to be approximately additive.Monoalkylation occurs if the sum of the normalized reaction potentials is equal or larger than the pKa value of the azole.Dialkylation is avoided by keeping the sum of the normalized reaction potentials below the pKa value of the alkylazole.The applicability of these principles is demonstrated by the development of effective procedures for the methylation, benzylation, acetylation, methoxycarbonylation and trimethylsilylation of azoles.
- Begtrup, Mikael,Larsen, Peter
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p. 1050 - 1057
(2007/10/02)
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- A General Route to 4-Substituted Imidazoles
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Literature routes to di(imidazol-4-yl)methanol (1a) dinitrate and tri(imidazol-4-yl)methanol (2a) trihydrochloride were improved to give 32 and 16percent overall yields, respectively; but we failed to synthesize bis- (1b) and tris-(1-methylimidazol-4-yl)methanol (2b) by the methylation of the corresponding N-methoxymethyl compounds (3; x=2 and x=3).Attempted 4-lithiation of the 1,2,5-protected imidazole (4a) with BuLi-TMEDA failed, giving after hydrolysis 1-methyl-5-trimethylsilylimidazole (4b); similar failures were observed for 2,5-dicarboxy-1-methylimidazole, which after metallation with BuLi-TMEDA and hydrolysis afforded 1-methylimidazole-5-carboxylic acid (5).Our attempts to obtain 4-bromo-1-methylimidazole (10a) and 4-bromo-1-ethylimidazole suitable for a halogen-lithium exchange or for Grignard reaction also failed.Attempted selective lithiation of 2-phenylthio-1-tritylimidazole (16) at the 4-position, then theatment with ethyl formate, led only to a mixture of 4- and 5-substituted products in very low yield, and 1-diethoxymethyl-2-phenylthioimidazole (18) was unstable and difficult to purify. 4-Bromoimidazole with two mol equiv. of t-butyl-lithium gives 1,4-dilithioimidazole, which is now shown to provide a general route to 4-substituted imidazoles.
- Katritzky, Alan R.,Slawinski, Jaroslaw J.,Brunner, Frederic,Gorun, Sergiu
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p. 1139 - 1145
(2007/10/02)
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- INTRODUCTION OF SUBSTITUENTS INTO 5-MEMBERED AZA-HETEROAROMATICS
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With emphasis on mono- and regio-selectively, methods for introduction of substituents at nitrogen and carbon atoms of 5-membered aza-heteroaromatics have been developed.The methods involve application of activation and of assistant groups for direction and protection.Activation has been achieved by the use of quaternary azolium ions and azol-N-oxides as reactive intermediates.If necessary, the N-oxides were further activated by alkylation or acylation.
- Begtrup, Mikael
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p. 573 - 598
(2007/10/02)
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- Metal-Halogen Exchange Reactions of Mono- and Poly-halogenoimidazoles
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4(5)-Bromoimidazole gave a mixture of 4- and 5-bromo-1-methylimidazole on treatment with 1 or 2 mol equiv. of n-butyl-lithium in ether or THF under various reaction conditions followed by addition of dimethyl sulphate. 5-Iodo and 2,4,5-tribromo-1-methylim
- Iddon, Brian,Lim, Bee Lan
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p. 735 - 739
(2007/10/02)
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- Metallation and Metal-Halogen Exchange Reactions of Imidazoles
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Some reactions (reagents in parentheses) are reported of 1-ethoxymethyl-2-phenylthioimidazol-5-yl-lithium 2S2>, 1-ethoxymethyl-5-methylthio-2-phenylthioimidazol-4-yl-lithium (Me2S2, HCONMe2, CO2), 4,5-dibromo-1-ethoxymethylimid
- Iddon, Brian,Lim, Bee Lan
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p. 1095 - 1097
(2007/10/02)
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