- The Stoichiometry and Promoter Role of Chlorosulfuric and Fuming Sulfuric Acids for α-Halogenation of Aliphatic Acid
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The stoichiometry for the chlorosulfuric acid promoted α-halogenation and the role of fuming sulfuric acid instead of chlorosulfuric acid have been studied.In the α-bromination with molecular bromine, 1 mol of halogen afforded 2 mol of aliphatic α-bromo acid just as the α-iodination, but it is different from α-chlorination which affords only 1 mol of α-chloro acid.Fuming sulfuric acid instead of chlorosulfuric acid was found to be effective for α-bromination, but the yield was lower, while no α-iodination was observed with fuming sulfuric acid.
- Ogata, Yoshiro,Watanabe, Shinya
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- Synthesis and biological evaluation of novel N-α-haloacylated homoserine lactones as quorum sensing modulators
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Novel N-α-haloacylated homoserine lactones, in which a halogen atom was introduced at the α-position of the carbonyl function of the N - acyl chain, have been studied as quorum sensing (QS) modulators and compared with a library of natural N - acylated homoserine lactones (AHLs). The series of novel analogues consists of α-chloro, α-bromo and α-iodo AHL analogues. Furthermore, the biological QS activity of the synthetic AHL analogues compared to the natural AHLs was evaluated. Halogenated analogues demonstrated a reduced activity in the Escherichia coli JB523 bioassay, with the α-iodo lactones being the less active ones and the α-chloro AHLs the most potent QS agonists. Most of the α-haloacylated analogues did not exhibit a significant reduction when tested in the QS inhibition test. Therefore, these novel analogues could be utilized as chemical probes for QS structure-activity studies.
- Syrpas, Michail,Ruysbergh, Ewout,Stevens, Christian V.,De Kimpe, Norbert,Mangelinckx, Sven
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p. 2539 - 2549
(2015/02/19)
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- Enantioselective construction of tetrasubstituted stereogenic carbons through bronsted base catalyzed michael reactions: α′-hydroxy enones as key enoate equivalent
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Catalytic and asymmetric Michael reactions constitute very powerful tools for the construction of new C-C bonds in synthesis, but most of the reports claiming high selectivity are limited to some specific combinations of nucleophile/electrophile compound types, and only few successful methods deal with the generation of all-carbon quaternary stereocenters. A contribution to solve this gap is presented here based on chiral bifunctional Bronsted base (BB) catalysis and the use of α′-oxy enones as enabling Michael acceptors with ambivalent H-bond acceptor/donor character, a yet unreported design element for bidentate enoate equivalents. It is found that the Michael addition of a range of enolizable carbonyl compounds that have previously demonstrated challenging (i.e., α-substituted 2-oxindoles, cyanoesters, oxazolones, thiazolones, and azlactones) to α′-oxy enones can afford the corresponding tetrasubstituted carbon stereocenters in high diastereo- and enantioselectivity in the presence of standard BB catalysts. Experiments show that the α′-oxy ketone moiety plays a key role in the above realizations, as parallel reactions under identical conditions but using the parent α,β-unsaturated ketones or esters instead proceed sluggish and/or with poor stereoselectivity. A series of trivial chemical manipulations of the ketol moiety in adducts can produce the corresponding carboxy, aldehyde, and ketone compounds under very mild conditions, giving access to a variety of enantioenriched densely functionalized building blocks containing a fully substituted carbon stereocenter. A computational investigation to rationalize the mode of substrate activation and the reaction stereochemistry is also provided, and the proposed models are compared with related systems in the literature.
- Badiola, Eider,Fiser, Bla,Gmez-Bengoa, Enrique,Mielgo, Antonia,Olaizola, Iurre,Urruzuno, Iaki,Garca, Jess M.,Odriozola, Jos M.,Razkin, Jess,Oiarbide, Mikel,Palomo, Claudio
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supporting information
p. 17869 - 17881
(2015/02/19)
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- Mesoionic 5-alkyl-1,3-dithiolium-4-thiolates: Synthesis and brine shrimp toxicity
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A series of twelve 1,3-dithiolium-4-thiolate mesoionic compounds were synthesized and characterized. The synthetical approach starting from α-bromoalkanoic acids to obtain the corresponding 2-N-morpholino-dithiocarbamoyl-carboxylic acids that by on-pot reaction with carbon disulfide and acetic anhydride in triethylamine formed not isolate intermediates, 1,3-dithiolium-4-olates. After, the 2-N-morpholino-5-alkyl-1,3-dithiolium-4-thiolates were obtained by retro 1,3-dipolar addition reactions. The alkyl moiety linked to C-5 of heterocyclic ring permitted the increase of the hydrophobic character and this effect was evaluated on Artemia salina lethality. The results indicated a bell-shaped relationship between the number of carbon of side chain in mesoionic derivatives and LD50 in brine shrimp toxicity assays.
- De Almeida, Paulo Afonso,Da Silva, Tania Maria Sarmento,Echevarria, Aurea
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p. 593 - 600
(2007/10/03)
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- N-hdroxy-2-(alkyl, aryl, or heteroaryl, sulfanyl, sulfinyl or sulfonyl)-3-substituted alkyl, aryl or heteroarylamides as matrix metalloproteinase inhibitors
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Matrix metalloproteinases (MMPs) are a group of enzymes that have been implicated in the pathological destruction of connective tissue and basement membranes. These zinc containing endopeptidases consist of several subsets of enzymes including collagenases, stromelysins and gelatinases. TNF-α converting enzyme (TACE), a pro-inflammatory cytokine, catalyzes the formation of TNF-α from membrane bound TNF-α precursor protein. It is expected that small molecule inhibitors of MMPs and TACE therefore have the potential for treating a variety of disease states. The present invention provides low molecular weight, non-peptide inhibitors of matrix metalloproteinases (MMPs) and TNF-α converting enzyme (TACE) for the treatment of arthritis, tumor metastasis, tissue ulceration, abnormal wound healing, periodontal disease, bone disease, diabetes (insulin resistance) and HIV infection having the formula wherein R2and R3form a heterocyclic ring and A is S, S(O), or S(O)2, and R1and R4are defined herein.
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- Enzymatic lactonization stategy for enantioselective synthesis of a tetrahydrolipstatin synthon
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A novel lipase-catalyzed protocol has been formulated for the simultaneous enantiocontrol of three stereogenic centers in a flexible acyclic system. This involved a porcine pancreatic lipase (PPL)-catalyzed δ- lactonization of a racemic 3,5-dihydroxy-2-alkyl ester to produce the lactone with high enantioselectivity (92.8%). The product lactone and its analogues are useful synthons for the asymmetric synthesis of various bioactive compounds, which include the potential anti-obesity compound, tetrahydrolipstatin.
- Sharma,Chattopadhyay
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p. 8059 - 8062
(2007/10/03)
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- Adsorption of Metal Ions to Surface-Template Resins Prepared with Amphiphilic Styrene Monomers Bearing Amino Carboxylic Acid
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Monomer-type functional surfactants, 2-(p-vinylbenzylamino)alkanoic acid (RnAc) and N,N-dialkyl derivatives (RRnNAc), have been used as both a ligand and an emulsifier for the preparation of surface-template resins. The surfactants adsorbed at the toluene-water interface and emulsified divinylbenzene-styrene in a Cu2+ or Zn2+ solution. Emulsion polymerization using a K2S2O8 initiator (80 °C) or by irradiation with γ-rays gave fine particles of 200-800 nm in diameter. Metal-imprinted resins prepared with RnNAc and RRnNAc showed a high adsorptive capacity for the metal ion (surface-template effect). Cu-imprinted resins prepared with R8NAc were 2.69-times as effective for Cu2+ in competitive sorption from a Cu2+-Zn2+ mixture and Zn-imprinted resins were 1.84-times as effective for Zn2+, compared with unimprinted resins. Because of the great emulsifying power, metal-imprinted resins prepared with R8NAc showed the most metal-selective adsorption and the largest capacity among resins prepared with RnNAc and RRnNAc.
- Koide, Yoshifumi,Tsujimoto, Keigo,Shosenji, Hideto,Maeda, Mizuo,Takagi, Makoto
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p. 789 - 796
(2007/10/03)
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- Semisynthetic Myxovirescins: Exchange of the &α-Hydroxycarboxylic Acid Segment and Modification of the Ring Size
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Partial degradation reactions of the macrocyclic lactam-lacton antibiotic myxovirescin A1 (1) yield the key building blocks 2 and 26.From these myxovirescin analoga are reconstituted with various alkyl groups at position C-2 with R and S configuration.Furthermore a ring-contracted (24) and a ring-enlarged (29) macrocycle are synthesized.The growth of E. coli is best inhibited by the natural myxovirescin A1 with a (2S) propyl substitution whilst 24 and 29 do not inhibit the growth of E. coli at all.
- Borgschulte, Katrin,Trowitzsch-Kienast, Wolfram,Hoefle, Gerhard
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- ONE POT SYNTHESIS OF α-BROMO AND α-IODO KETONES FROM EPOXIDES
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α-bromo and α-iodo ketones are obtained in good yield and in one pot by reaction of terminal and disubstituted epoxides with trimthylsilyl halides and further oxidation (CrO3/H2SO4).
- Denis, J. N.,Krief, A.
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p. 1429 - 1430
(2007/10/02)
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