- Volatiles from the hypoxylaceous fungi Hypoxylon griseobrunneum and Hypoxylon macrocarpum
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The volatiles emitted by the ascomycetes Hypoxylon griseobrunneum and Hypoxylon macrocarpum (Hypoxylaceae, Xylariales) were collected by use of a closed-loop stripping apparatus (CLSA) and analysed by GC-MS. The main compound class of both species were polysubstituted benzene derivatives. Their structures could only be unambiguously determined by comparison to all isomers with different substitution patterns. The substitution pattern of the main compound from H. griseobrunneum, the new natural product 2,4,5-trimethylanisole, was explainable by a polyketide biosynthesis mechanism that was supported by a feeding experiment with (methyl-2H3)methionine.
- Rinkel, Jan,Babczyk, Alexander,Wang, Tao,Stadler, Marc,Dickschat, Jeroen S.
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p. 2974 - 2990
(2019/01/05)
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- A ligand-free, powerful, and practical method for methoxylation of unactivated aryl bromides by use of the CuCl/HCOOMe/MeONa/MeOH system
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A ligand-free, powerful, and practical method for mono and polymethoxylation of unactivated aryl bromides has been developed; CuCl was used as catalyst, HCOOMe as cocatalyst, and methanolic MeONa as both nucleophile and solvent. This eco-friendly procedure is characterized by operational simplicity, inexpensive substrates (unactivated mono to polybromoarenes), full conversion, and direct recovery of pure MeOH.
- Guo, Ying,Ji, Si-Zhe,Chen, Cheng,Liu, Hong-Wei,Zhao, Jian-Hong,Zheng, Yu-Lin,Ji, Ya-Fei
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p. 8651 - 8664
(2015/03/05)
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- Molecular Dynamics Simulations of the Initial-State Predict Product Distributions of Dediazoniation of Aryldiazonium in Binary Solvents
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The dediazoniation of aryldiazonium salts in mixed solvents proceeds by a borderline SN1 and SN2 pathway, and product distribution should be proportional to the composition of the solvation shell of the carbon attached to the -N2 group (ipso carbon). The rates of dediazoniation of 2,4,6-trimethylbenzenediazonium in water, methanol, ethanol, propanol, and acetonitrile were similar, but measured product distributions were noticeably dependent on the nature of the water/cosolvent mixture. Here we demonstrated that solvent distribution in the first solvation shell of the ipso carbon, calculated from classical molecular dynamics simulations, is equal to the measured product distribution. Furthermore, we showed that regardless of the charge distribution of the initial state, i.e., whether the positive charge is smeared over the molecule or localized on phenyl moiety, the solvent distribution around the reaction center is nearly the same.
- Cruz, Gustavo N.,Lima, Filipe S.,Dias, Luís G.,El Seoud, Omar A.,Horinek, Dominik,Chaimovich, Hernan,Cuccovia, Iolanda M.
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p. 8637 - 8642
(2015/09/15)
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- Complexation of dichlorocarbene by methylanisoles
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Dichlorocarbene generated by laser flash photolysis of dichlorodiazirine readily forms UV-vis active π- and O-ylidic complexes with methylanisole derivatives.
- Moss, Robert A.,Wang, Lei,Odorisio, Christina M.,Krogh-Jespersen, Karsten
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body text
p. 1467 - 1470
(2010/05/18)
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- Mimicking the reaction of phenylalanine ammonia lyase by a synthetic model
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Phenylalanine and histidine ammonia lyases (PAL and HAL) catalyze the reversible conversion of α-amino acids to the corresponding acrylic acids by elimination of ammonia. The prosthetic group 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO) at the active site of both enzymes supposedly undergoes an electrophilic attack at the aromatic nucleus in the first step of the mechanism of action. Since no chemical analogy existed for such an electrophile-assisted elimination, we synthesized model compounds, some portion of which mimicked the essentials of the substrate phenylalanine and another portion the electrophilic Michael acceptor in a sterically appropriate distance. The first model, (±)-rel-(1R,2S,3S)-3-[1-methylidene-2-oxo-2-(pyrrolidin-1-yl)ethyl]-2-phenyl cyclohexanamine (7) did not react under Friedel-Crafts conditions in the expected way (Scheme 2). The second model compound (±)-2-rel-(1R,2S,3S)-3-(dimethylamino)-2-(3-methoxyphenyl)cyclohexyl]prop-2- enal (12) with a more nucleophilic methoxyphenyl and a more electrophilic α,β-unsaturated carbonyl moiety, underwent an intramolecular Friedel-Crafts-type substitution, but no elimination of the dimethylamino group (Scheme 4). The third model compound, (±)-γ-[(dimethylamino)methyl]-3-methoxy-2,4,6-trimethyl-α-methylidenebenze nebutanal (25) eliminated dimethylamine upon treatment with Lewis acids and subsequent hydrolysis of the intermediate (Scheme 6). When the 3-methoxy-2,4,6-trimethylphenyl moiety of 25 was replaced by the 2,4,6-trimethyl-3-nitrophenyl group, no elimination product could be observed (Scheme 7).
- Rettig, Martin,Sigrist, Andreas,Retey, Janos
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p. 2246 - 2265
(2007/10/03)
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- Arene complexes of transition metals in reactions with nucleophilic reagents. XXIX. Poly[(p-cyclopentadienylmethylstyrene)rhodium]2+ as catalyst of alkoxydefluorination of fluoroarenes
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The poly[(p-cyclopentadienylmethylstyrene)rhodium]2+ produced in situ by treating the respective dichloride complex with silver triflate in the presence of primary alcohols (methanol, propanol, hexanol) was used as catalyst grafted on polymeric sublayer for alkoxydefluorination of fluoroarenes. The activity of the catalyst in alcoholysis of fluorobenzene and p-fluorotolyene is similar to that of the corresponding homogeneous catalysts. The catalyst conserves its activity for repeated application.
- Goryunov,Steingarts
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p. 246 - 251
(2007/10/03)
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- Endothelin antagonists: Substituted mesitylcarboxamides with high potency and selectivity for ET(A) receptors
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We have previously disclosed the discovery of 2,4-disubstituted anilinothiophenesulfonamides with potent ET(A)-selective endothelin receptor antagonism and the subsequent identification of sitaxsentan (TBC11251, 1) as a clinical development compound (Wu et al. J. Med. Chem. 1997, 40, 1682 and 1690). The orally active 1 has demonstrated efficacy in a phase II clinical trial of congestive heart failure (Givertz et al. Circulation 1998, 98, Abstr. 3044) and was active in rat models of myocardial infarction (Podesser et al. Circulation 1998, 98, Abstr. 2896) and acute hypoxia-induced pulmonary hypertension (Chen et al. FASEB J. 1996, 10 (3), A104). We now report that an additional substituent at the 6-position of the anilino ring further increases the potency of this series of compounds. It was also found that a wide range of functionalities at the 3-position of the 2,4,6-trisubstituted ring increased ETA selectivity by ~10-fold while maintaining in vitro potency, therefore rendering the compounds amenable to fine-tuning of pharmacological and toxicological profiles with enhanced selectivity. The optimal compound in this series was found to be TBC2576 (7u), which has ~10- fold higher ETA binding affinity than 1, high ET(A)/ET(B) selectivity, and a serum half-life of 7.3 h in rats, as well as in vivo activity.
- Wu, Chengde,Decker, E. Radford,Blok, Natalie,Bui, Huong,Chen, Qi,Raju,Bourgoyne, Andree R.,Knowles, Vippra,Biediger, Ronald J.,Market, Robert V.,Lin, Shuqun,Dupré, Brian,Kogan, Timothy P.,Holland, George W.,Brock, Tommy A.,Dixon, Richard A. F.
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p. 4485 - 4499
(2007/10/03)
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- Preparation and properties of unsymmetrical benzoins and related compounds
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Synthesis of unsymmetrical benzoins and their esters can be compromised by isomerisation via the enediol (or its anion). This could be avoided by suitable reaction conditions for the benzoins and their esters 2a/b and 3a/b but not for the 3-furyl compound 4a. A convenient synthesis of 3,5-dimethoxy- 2,4,6-trimetbylbenzaldehyde 10 is described and the compound was converted to the hindered benzoin 5a.
- Corrie, John E.T.
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p. 5407 - 5416
(2007/10/03)
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- Mapping the Enantiomerization Routes of Triarylvinyl Propellers. Barriers for the Three-Ring Flip and the Three Different Two-Ring Flips of m-Methoxy-Substituted Trimesitylvinyl Isopropyl Ethers
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E- and Z-(m-methoxymesityl)-1,2-dimesitylethenols (3a and 4a), their isopropyl ethers 3c and 4c, and 1-(m-methoxymesityl)-2,2-dimesitylvinyl isopropyl ether (2c) were prepared.X-ray structures of 3a and 3c were determinated.The rotational barriers for the
- Rochlin, Elimelech,Rappoport, Zvi
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p. 3857 - 3870
(2007/10/02)
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- Anodic Oxidation of Methylbenzenes. Synthetic Routes to Certain Cyclohexa-1,4-dienes
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The anodic methoxylation of a series of methylbenzenes (mesitylene, pseudocumene, hemimellitene, pentamethylbenzene, and hexamethylbenzene) afforded chain methoxylated products as well as nuclear-addition products.For nuclear-addition products both cis/trans isomers are possible.In the cyclohexa-1,4-dienes obtained from these substrates the cis/trans ratio found is different.A probable mechanism is provided.
- Barba, Isidoro,Chinchilla, Rafael,Gomez, Cecilia
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p. 3673 - 3676
(2007/10/02)
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- Enhancement of the Resonance Interaction of Out-of-Plane Methoxy Groups By Ortho Substituents in Crowded Anisoles
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The 17O and 13C NMR chemical shifts of substituted anisoles provide evidence that the resonance interaction of methoxy groups which are perpendicular to the aromatic ring in crowded anisoles is influenced, to varying degrees, by ortho substituents.Enhance
- Schuster, Ingeborg I.,Parvez, Masood,Freyer, Alan J.
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p. 5819 - 5825
(2007/10/02)
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- Substituent and Ring Size Dependence of the 4J(Me-C-C-H) Coupling Constant
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The magnitude of the 4J proton-proton coupling constant across the fragment CH3-C-C-H (a probe of the bond order between the central sp2-sp2 hybridized carbon atoms) has been found to be essentially independent of substitution on a toluene fragment and the size of the ring containing the ortho-allylic fragment.The coupling constant is sensitive to direct substitution on the ortho-allilyc fragment, especially where the substituent is placed α to methyl group.KEY WORDS - 4J proton-proton coupling constant ortho-benzylic coupling constant ring size dependence substituent dependence
- Collins, M. J.,Hatton, P. M.,Sternbell, S.,Tansey, C. W.
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p. 824 - 828
(2007/10/02)
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- EVOLUTION THERMIQUE DE VINYLPHOSPHORANES
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The thermal evolution of aryloxy or enoxyvinylphosphoranes 1 is reported.It leads to spirophosphoranes 2.The yield as well as the reaction time decrease when the ?-deficient character of the aryloxy or enoxy system increases.With very electron withdrawing systems, the main reaction is analogous to the second step of the Arbuzov reaction and gives rise to the vinylphosphonate 6 and to the corresponding aromatic ether 7.When the carboxylate group the nearest to the phosphorus atom is replaced by a phenyl group or an hydrogen atom, no spirophosphorane 2 is obtained.The hydrolysis of compounds 2, under mild condition, leads to a new class of phosphonates 3 and 16.
- Labaudiniere, L.,Burgada, R.
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p. 3521 - 3536
(2007/10/02)
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- ACTIVATION NUCLEOPHILE PAR LES POLYOXYDES D'ETHYLENE
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Acyclic polyethylene oxides exhibit useful catalytic effects in various organic reactions, and can be used in lieu of cryptands and crown ethers as nucleophile activators.
- Slaoui, S.,Goaller, R. Le,Pierre, J. L.,Luche, J. L.
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p. 1681 - 1684
(2007/10/02)
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