- Efficient asymmetric organocatalytic formation of erythrose and threose under aqueous conditions
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Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under aqueous conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (l)-proline yield (l)-carbohydrates, esters of (l)-leucine and (l)-alanine generate (d)-carbohydrates, offering the potential to account for the prebiotic link between natural (l)-amino acids and natural (d)-sugars.
- Burroughs, Laurence,Vale, Matthew E.,Gilks, James A. R.,Forintos, Henrietta,Hayes, Christopher J.,Clarke, Paul A.
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supporting information; experimental part
p. 4776 - 4778
(2010/09/05)
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- A class of novel conjugates of substituted purine and Gly-AA-OBzl: Synthesis and evaluation of orally analgesic activity
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Aimed at the chemotherapy of chronic pain two kinds of analgesic pharmacophores, substituted purine and Gly-AA-OBzl, were coupled via a five-step-reaction procedure and 19 novel conjugates N-[2-chloro-9- (tetrahydropyran-2-yl)-9H-purin-6-yl]-N-cyclopropylglycylamino acid benzylesters were provided. On mouse-tail flick model their in vivo analgesic activities were assayed. The results indicate that introducing Gly-OC2H 5 into the 6-position of the substituted purine leads to ambiguous increase of the analgesic activity, while introducing Gly-AA-OBzl into this position leads to significant increase of the analgesic activity.
- Kang, Guifeng,Zhao, Ming,Zhang, Xiaoyi,Peng, Li,Li, Chunbo,Mao, Wei,Ye, Weidong,Peng, Shiqi
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supporting information; experimental part
p. 6157 - 6160
(2010/12/19)
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- Synthesis and cytotoxic activities of β-carboline amino acid ester conjugates
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β-Carboline represents a class of compounds with potent anti-tumor activity by intercalating with DNA. To further enhance the cytotoxic potency and bioavailability of β-carboline, a series of novel β-carboline amino acid ester conjugates were designed and synthesized, and the cytotoxic activities of these compounds were tested using a panel of human tumor cell lines. In addition, the membrane permeability of these compounds was evaluated in vitro using a Caco-2 cell monolayer model. The β-carboline amino acid ester conjugates demonstrated improved cytotoxic activity compared to the parental β-carbolines. In particular, the Lys/Arg conjugates were the most potent analogs with an IC50 value of 4 and 1 μM against human cervical carcinoma cells. The low interaction energy of Arg conjugate based on molecular modeling may contribute to its enhanced cytotoxicity. Taken together, this study provided new insights into structure-activity relationships in the β-carboline amino acid ester conjugates and identified the β-carboline Lys/Arg conjugates as promising lead compounds for further in vivo biological and molecular evaluation.
- Zhao, Ming,Bi, Lanrong,Wang, Wei,Wang, Chao,Baudy-Floc'h, Michele,Ju, Jingfang,Peng, Shiqi
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p. 6998 - 7010
(2007/10/03)
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- Lipopeptaibol metabolites of tolypocladium geodes: Total synthesis, preferred conformation, and membrane activity
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We have synthesized by solution methods and characterized the lipopeptaibol metabolite LP237-F8 extracted from the fungus Tolypocladium geodes and five selected analogues with the Etn → Aib or Etn → Nva replacement at position 8 and/or a triple Gln → Glu(OMe) replacement at positions 5, 6, and 9 (Etn = Cα-ethylnorvaline, Aib = α-aminoisobutyric acid, Nva = norvaline). Conformation analysis, performed by FT-IR absorption, NMR, and CD techniques, strongly supports the view that the six terminally blocked decapeptides are highly helical in solution. Helix topology and amphiphilic character are responsible for their remarkable membrane activity. At position 8 the combination of high hydrophobicity and Ca tetrasubstitution, as in the Etn-containing LP237-F8 metabolite, has a positive effect on membrane interaction.
- Rainaldi, Mario,Moretto, Alessandro,Peggion, Cristina,Formaggio, Fernando,Mammi, Stefano,Peggion, Evaristo,Galvez, Jose Antonio,Diaz-de-Villegas, Maria Dolores,Cativiela, Carlos,Toniolo, Claudio
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p. 3567 - 3576
(2007/10/03)
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- The relative catalytic efficiency of β-lactamase catalyzed acyl and phosphyl transfer
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Phosphonamidates which bear a simple resemblance to penicillin type structures have been synthesised as potential inhibitors of β-lactamases: -ethyl N-(benzyloxycarbonyl) amidomethyl phosphonyl amides, PhCH2OCONHCH2P(O)(OEt)NR2, the amines HNR2 being L-proline, D-proline, L-thiazolidine, and o-anthranilic acid. The proline derivatives completely and irreversibly inactivated the class C β-lactamase from Enterobacter cloacae P99, in a time-dependent manner, indicative of covalent inhibition. The inactivation was found to be exclusive to the class C enzyme and no significant inhibition was observed with any other class of β-lactamase. The anthranilic acid derivative exhibited no appreciable inactivation of the β-lactamases. The phosphonyl proline and phosphonyl thioproline derivatives were separated into their diastereoisomers and their individual second order rate constants for inhibition were found to be 7.72 ± 0.37 and 8.3 × 10-2 ± 0.004 M-1 s-1 for the L-proline derivatives, at pH 7.0. The products of the inhibition reaction of each individual diastereoisomer, analyzed by electrospray mass spectroscopy, indicate that the more reactive diastereoisomers phosphonylate the enzyme by P-N bond fission with the elimination of proline. Conversely, gas chromatographic detection of ethanol release by the less reactive proline diastereoisomer suggests phosphonylation occurs by P-O bond fission. The enzyme enhances the rate of phosphonylation with P-N fission by at least 106 compared with that effected by hydroxide-ion. The pH dependence of the rate of inhibition of the β-lactamase by the more reactive diasteroisomer is consistent with the reaction of the diprotonated form of the enzyme, EH2, with the inhibitor, I (or its kinetic equivalents EH with IH). This pH dependence and the rate enhancement indicate that the enzyme appears to use the same catalytic apparatus for phosphonylation as that used for hydrolysis of β-lactams. The stereochemical consequences of nucleophilic displacement at the phosphonyl centre are discussed.
- Slater, Martin J.,Laws, Andrew P.,Page, Michael I.
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- Solution-phase automated synthesis of tripeptide derivatives
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An improved general method for automated synthesis of tripeptides was developed, in which methanesulfonic acid (MSA) was used in place of trifluoroacetic acid (TFA), thus making it possible to avoid, 1) corrosion of the apparatus by strong acid vapor, 2) formation of emulsions, and 3) use of the restricted solvent, dichloromethane. As an application of the automated synthesis apparatus, 216 fragment tripeptide derivatives were synthesized systematically using the MSA method, in excellent yield and with increased efficiency.
- Kuroda,Hattori,Kitada,Sugawara
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p. 1138 - 1146
(2007/10/03)
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- Convenient synthesis of L-proline benzyl ester
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Mesylates or tosylates of δ-hydroxy-L-norvaline esters spontaneously afford L-proline esters upon exposure to aqueous buffer in near quantitative yield. This novel reaction has led to the development of a simple route to optically active proline esters.
- Cordova, Armando,Reed, Neal N.,Ashley, Jon A.,Janda, Kim D.
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p. 3119 - 3122
(2007/10/03)
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- Rational design and synthesis of unsaturated 2,5-dioxopiperazine derivatives as potential protein tyrosine kinase inhibitors
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The first general method for the synthesis of a library of trifunctionalized (Z)-3-alkylidene-2,5-piperazinediones as potential protein tyrosine kinase inhibitors from commercially available amino compounds, α- keto acids and aldehydes using a novel cyclization/cleavage strategy on solid support is described.
- Li, Wen-Ren,Peng, Shao-Zheng
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p. 7373 - 7376
(2007/10/03)
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- Secondary effects in flexible hydrogen bonding networks
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Extension of Jorgensen's secondary interaction hypothesis to conformationally flexible systems has been examined. The results indicate that secondary interactions between covalently adjacent hydrogen bonding groups are as important as secondary interactions between hydrogen bonding groups brought together by the primary interactions.
- Gardner, Robb R.,Gellman, Samuel H.
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p. 9881 - 9890
(2007/10/03)
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- The Pent-4-enoyl Group: A Novel Amine-Protecting Group That Is Readily Cleaved under Mild Conditions
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Primary and secondary amines are readily protected as N-pent-4-enoyl derivatives, the resulting N-pent-4-enamides being usually highly crystalline.Deprotection is rapidly and efficiently effected under mild conditions by treatment with 3 equiv of iodine in aqueous THF solution.Although an oxidizing medium, these deprotection conditions do not affect oxidizable functionalities including p-methoxybenzyl ethers and alkyl sulfides.
- Madsen, Robert,Roberts, Carmichael,Fraser-Reid, Bert
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p. 7920 - 7926
(2007/10/03)
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- Substituted lactones of amino acids
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Novel substituted lactones of amino acids in all their possible stereoisomeric forms or mixtures thereof of the formula STR1 wherein A is a hydrocarbon chain of 1 to 10 chain members containing one or more heteroatoms and one or more unsaturations and the chain members being a mono- or polycyclic system or comprises a system of spiro or endo type and may contain one or more chiral atoms or the lactone copula can present a supplementary chirality due to the asymetric spatial configuration of the molecule make up and R is selected from the group consisting of: STR2 wherein Z is the organic remainder of an amino acid of the formula: STR3 Y is derived from a primary, secondary or tertiary alcohol of the formula Y-OH and B is the remainder of a heterocycle amino acid of 3 to 6 carbon atoms of the formula: STR4 and their preparation and their use for the resolution of amino acids.
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