- Determination of the Absolute Configurations and Sensory Properties of the Enantiomers of a Homologous Series (C6-C10) of 2-Mercapto-4-alkanones
-
The enantiomers of a homologous series (C6-C10) of 2-mercapto-4-alkanones were obtained by lipase-catalyzed kinetic resolution of the corresponding racemic 2-acetylthio-4-alkanones. Their configurations were assigned via vibrational circular dichroism and 1H NMR anisotropy based methods. Odor thresholds and odor qualities were determined by capillary gas chromatography-olfactometry using chiral stationary phases. There were minima of the odor thresholds for the chain lengths C7 and C8. Except for chain length C8, the enantiomers of the other homologues showed similar odor thresholds. The odor qualities ranged from pungent (C5) to mushroom (C9 and C10) and were similar to those known for the corresponding 1-alken-3-ones with one less C atom. In contrast to their positional isomers (4-mercapto-2-alkanones), the investigated 2-mercapto-4-alkanones do not meet the requirements of a "tropical olfactophore" (i.e., compounds possessing a 1,3-oxygen-sulfur functionality and specific arrangements of the substituents).
- Kiske, Christiane,Riegel, Anja Devenie,Hopf, Ronja,Kvindt, Anna,Poplacean, Iulia,Engel, Karl-Heinz,Taniguchi, Tohru,Swamy, Mahadeva M. M.,Monde, Kenji,Eisenreich, Wolfgang
-
-
Read Online
- Ruthenium catalyzes the synthesis of γ-butenolides fused with cyclohexanones
-
Ruthenium(II)-catalyzed reactions of cyclic diazodicarbonyl compounds with β-ketoamides for chemo- and stereoselective construction of cyclohexanone-fused γ-butenolides are described. This study represents the first example of the addition of an enol substrate which is formed by the tautomerization of the β-ketoamides to the electrophilic carbene center for unusual cyclization through amide cleavage. The combined experimental and computational studies shed light on the mechanistic pathway favouring the unusual ring formation reaction instead of the involvement of the general carbonyl ylide intermediates for the product generation.
- Thombal, Raju S.,Kim, Seoung-Tae,Baik, Mu-Hyun,Lee, Yong Rok
-
-
Read Online
- Synthesis of enantiopure (R)-(-)-massoialactone through ruthenium-SYNPHOS asymmetric hydrogenation
-
Total synthesis of enantiopure (R)-(-)-massoialactone was achieved. The key step includes the asymmetric hydrogenation of an achiral β-keto ester using a ruthenium-SYNPHOS catalyst to set the hydroxyl function in a stereocontrolled manner with excellent enantioselectivity (>99% ee). Ring closing metathesis (RCM) in the presence of Grubbs' catalyst allows the final construction of the six-membered lactone.
- Touati, Ridha,Ratovelomanana-Vidal, Virginie,Hassine, Bechir Ben,Genet, Jean-Pierre
-
-
Read Online
- A scaffold replacement approach towards new sirtuin 2 inhibitors
-
Sirtuins (SIRT1–SIRT7) are an evolutionary conserved family of NAD+-dependent protein deacylases regulating the acylation state of ε-N-lysine residues of proteins thereby controlling key biological processes. Numerous studies have found association of the aberrant enzymatic activity of SIRTs with various diseases like diabetes, cancer and neurodegenerative disorders. Previously, we have shown that substituted 2-alkyl-chroman-4-one/chromone derivatives can serve as selective inhibitors of SIRT2 possessing an antiproliferative effect in two human cancer cell lines. In this study, we have explored the bioisosteric replacement of the chroman-4-one/chromone core structure with different less lipophilic bicyclic scaffolds to overcome problems associated to poor physiochemical properties due to a highly lipophilic substitution pattern required for achieve a good inhibitory effect. Various new derivatives based on the quinolin-4(1H)-one scaffold, bicyclic secondary sulfonamides or saccharins were synthesized and evaluated for their SIRT inhibitory effect. Among the evaluated scaffolds, the benzothiadiazine-1,1-dioxide-based compounds showed the highest SIRT2 inhibitory activity. Molecular modeling studies gave insight into the binding mode of the new scaffold-replacement analogues.
- Seifert, Tina,Malo, Marcus,Kokkola, Tarja,Stéen, E. Johanna L.,Meinander, Kristian,Wallén, Erik A.A.,Jarho, Elina M.,Luthman, Kristina
-
-
- Control Mechanism for cis Double-Bond Formation by Polyunsaturated Fatty-Acid Synthases
-
Polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) are essential fatty acids for humans. Some microorganisms biosynthesize these PUFAs through PUFA synthases composed of four subunits with multiple catalytic domains. These PUFA synthases each create a specific PUFA without undesirable byproducts, even though the multiple catalytic domains in each large subunit are very similar. However, the detailed biosynthetic pathways and mechanisms for controlling final-product profiles are still obscure. In this study, the FabA-type dehydratase domain (DHFabA) in the C-subunit and the polyketide synthase-type dehydratase domain (DHPKS) in the B-subunit of ARA synthase were revealed to be essential for ARA biosynthesis by in vivo gene exchange assays. Furthermore, in vitro analysis with truncated recombinant enzymes and C4- to C8-acyl ACP substrates showed that ARA and EPA synthases utilized two types of DH domains, DHPKS and DHFabA, depending on the carbon-chain length, to introduce either saturation or cis double bonds to growing acyl chains.
- Hayashi, Shohei,Satoh, Yasuharu,Ogasawara, Yasushi,Maruyama, Chitose,Hamano, Yoshimitsu,Ujihara, Tetsuro,Dairi, Tohru
-
supporting information
p. 2326 - 2330
(2019/02/01)
-
- Isolation of the antibiotic pseudopyronine B and SAR evaluation of C3/C6 alkyl analogs
-
Natural products are an abundant source of structurally diverse compounds with antibacterial activity that can be used to develop new and potent antibiotics. One such class of natural products is the pseudopyronines. Here we present the isolation of pseudopyronine B (2) from a Pseudomonas species found in garden soil in Western North Carolina, and SAR evaluation of C3 and C6 alkyl analogs of the natural product for antibacterial activity against Gram-positive and Gram-negative bacteria. We found a direct relationship between antibacterial activity and C3/C6 alkyl chain length. For inhibition of Gram-positive bacteria, alkyl chain lengths between 6 and 7 carbons were found to be the most active (IC50?=?0.04–3.8?μg/mL) whereas short alkyl chain analogs showed modest activity against Gram-negative bacteria (IC50?=?223–304?μg/mL). This demonstrates the potential for this class of natural products to be optimized for selective activity against either Gram-positive or Gram-negative bacteria.
- Bouthillette, Leah M.,Darcey, Catherine A.,Handy, Tess E.,Seaton, Sarah C.,Wolfe, Amanda L.
-
supporting information
p. 2762 - 2765
(2017/05/29)
-
- Inversion of cpADH5 Enantiopreference and Altered Chain Length Specificity for Methyl 3-Hydroxyalkanoates
-
Expanding the substrate scope of enzymes opens up new routes for synthesis of valuable chemicals. Ketone-functionalized fatty acid derivatives and corresponding chiral alcohols are valuable building blocks for the synthesis of a variety of chemicals including pharmaceuticals. The alcohol dehydrogenase from Candida parapsilosis (cpADH5) catalyzes the reversible oxidations of chiral alcohols and has a broad substrate range; a challenge for cpADH5 is to convert alcohols with small substituents (methyl or ethyl) next to the oxidized alcohol moiety. Molecular docking studies revealed that W286 is located in the small binding pocket and limits the access to substrates that contain aliphatic chains longer than ethyl substituent. In the current manuscript, we report that positions L119 and W286 are key residues to boost oxidation of medium chain methyl 3-hydroxy fatty acids; interestingly the enantiopreference toward methyl 3-hydroxybutyrate was inverted. Kinetic characterization of W286A showed a 5.5 fold increase of Vmax and a 9.6 fold decrease of Km values toward methyl 3-hydroxyhexanoate (Vmax: 2.48 U mg? and Km: 4.76 mm). Simultaneous saturation at positions 119 and 286 library yielded a double mutant (L119M/W286S) with more than 30-fold improved activity toward methyl 3-hydroxyoctanoate (WT: no conversion; L119M/W286S: 30 %) and inverted enantiopreference (S-enantiomer ≥99 % activity decrease and R-enantiomer >20-fold activity improvement) toward methyl 3-hydroxybutyrate.
- Ensari, Yunus,Dhoke, Gaurao V.,Davari, Mehdi D.,Bocola, Marco,Ruff, Anna Jo?lle,Schwaneberg, Ulrich
-
p. 12636 - 12645
(2017/09/18)
-
- An Unsaturated Quinolone N-Oxide of Pseudomonas aeruginosa Modulates Growth and Virulence of Staphylococcus aureus
-
The pathogen Pseudomonas aeruginosa produces over 50 different quinolones, 16 of which belong to the class of 2-alkyl-4-quinolone N-oxides (AQNOs) with various chain lengths and degrees of saturation. We present the first synthesis of a previously proposed unsaturated compound that is confirmed to be present in culture extracts of P. aeruginosa, and its structure is shown to be trans-Δ1-2-(non-1-enyl)-4-quinolone N-oxide. This compound is the most active agent against S. aureus, including MRSA strains, by more than one order of magnitude whereas its cis isomer is inactive. At lower concentrations, the compound induces small-colony variants of S. aureus, reduces the virulence by inhibiting hemolysis, and inhibits nitrate reductase activity under anaerobic conditions. These studies suggest that this unsaturated AQNO is one of the major agents that are used by P. aeruginosa to modulate competing bacterial species.
- Szamosvári, Dávid,B?ttcher, Thomas
-
supporting information
p. 7271 - 7275
(2017/06/13)
-
- A Formal Synthesis of (-)-Perhydrohistrionicotoxin Using a Cross Metathesis-Hydrogenation Approach
-
The development of an efficient, high yielding six-step convergent synthesis of the semisynthetic alkaloid (-)-perhydrohistrionicotoxin is described. The key transformations include the cross metathesis of a Br?nsted-acid masked primary homoallylic amine with a vinyl cyclohexenone and a regioselective palladium catalyzed hydrogenation. This sequence generated the advanced Winterfeldt spirocyclic precursor in 47% overall yield, with a longest linear sequence of five steps.
- Spiccia, Nicolas D.,Burnley, James,Subasinghe, Kamani,Perry, Christopher,Lefort, Laurent,Jackson, W. Roy,Robinson, Andrea J.
-
p. 8725 - 8732
(2017/08/23)
-
- Polyhydroxyalkanoate-based 3-hydroxyoctanoic acid and its derivatives as a platform of bioactive compounds
-
A library of 18 different compounds was synthesized starting from (R)-3-hydroxyoctanoic acid which is derived from the bacterial polymer polyhydroxyalkanoate (PHA). Ten derivatives, including halo and unsaturated methyl and benzyl esters, were synthesized and characterized for the first time. Given that (R)-3-hydroxyalkanoic acids are known to have biological activity, the new compounds were evaluated for antimicrobial activity and in vitro antiproliferative effect with mammalian cell lines. The presence of the carboxylic group was essential for the antimicrobial activity, with minimal inhibitory concentrations against a panel of bacteria (Gram-positive and Gram-negative) and fungi (Candida albicans and Microsporum gypseum) in the range 2.87.0 mM and 0.16.3 mM, respectively. 3-Halogenated octanoic acids exhibited the ability to inhibit C. albicans hyphae formation. In addition, (R)-3-hydroxyoctanoic and (E)-oct-2-enoic acids inhibited quorum sensing-regulated pyocyanin production in the opportunistic pathogen Pseudomonas aeruginosa PAO1. Generally, derivatives did not inhibit mammalian cell proliferation even at 3-mM concentrations, while only (E)-oct-2-enoic and 3-oxooctanoic acid had IC50 values of 1.7 and 1.6 mM with the human lung fibroblast cell line.
- Radivojevic, Jelena,Skaro, Sanja,Senerovic, Lidija,Vasiljevic, Branka,Guzik, Maciej,Kenny, Shane T.,Maslak, Veselin,Nikodinovic-Runic, Jasmina,OConnor, Kevin E.
-
p. 161 - 172
(2016/01/09)
-
- A General and Robust Method for the Preparation of (E)- and (Z)-Stereodefined Fully Substituted Enol Tosylates: Promising Cross-Coupling Partners
-
A robust method for preparing (E)- and (Z)-stereodefined fully substituted enol tosylates is described. α-Substituted β-keto esters undergo (E)-selective enol tosylations using TsCl-Me2N(CH2)6NMe2 as the reagent (method A, 13 examples; 63-96%) and (Z)-selective enol tosylations using TsCl-TMEDA-LiCl as the reagent (method B, 13 examples; 62-99%). A plausible mechanism for the (E)- and (Z)-enol tosylation selectivity is proposed. A 1H NMR monitoring experiment revealed that TsCl coupled with TMEDA formed a simple N-sulfonylammonium intermediate.
- Ashida, Yuichiro,Sato, Yuka,Honda, Atsushi,Nakatsuji, Hidefumi,Tanabe, Yoo
-
supporting information
p. 4072 - 4080
(2016/11/26)
-
- Preparation of the even-numbered 3-oxo fatty acid nicotinyl esters from C6:0 to C18:0
-
Here, we report a systematic comparison of different methods for the transesterification of 3-oxo fatty acid alkyl esters to the corresponding nicotinyl esters. A simple method producing the target esters in high yields and purity has been developed. Nicotinyl esters are of interest for mass spectrometry analysis of fatty acids. Also, the hydrophilic head group of nicotinyl esters can be used as the basis for the preparation of liposome-building molecules.
- Sieben, Daniela,Santana, Alexander,Nowka, Paul,Weber, Sven,Funke, Kai,Hüttenhain, Stefan H.
-
supporting information
p. 808 - 810
(2016/02/03)
-
- Characterization of FabG and FabI of the Streptomyces coelicolor dissociated fatty acid synthase
-
Streptomyces coelicolor produces fatty acids for both primary metabolism and for biosynthesis of the secondary metabolite undecylprodiginine. The first and last reductive steps during the chain elongation cycle of fatty acid biosynthesis are catalyzed by FabG and FabI. The S. coelicolor genome sequence has one fabI gene (SCO1814) and three likely fabG genes (SCO1815, SCO1345, and SCO1846). We report the expression, purification, and characterization of the corresponding gene products. Kinetic analyses revealed that all three FabGs and FabI are capable of utilizing both straight and branched-chain β-ketoacyl-NAC and enoyl-NAC substrates, respectively. Furthermore, only SCO1345 differentiates between ACPs from both biosynthetic pathways. The data presented provide the first experimental evidence that SCO1815, SCO1346, and SCO1814 have the catalytic capability to process intermediates in both fatty acid and undecylprodiginine biosynthesis.
- Singh, Renu,Reynolds, Kevin A.
-
p. 631 - 640
(2015/03/31)
-
- Fatty acyl incorporation in the biosynthesis of WAP-8294A, a group of potent anti-MRSA cyclic lipodepsipeptides
-
WAP-8294A is a family of at least 20 cyclic lipodepsipeptides exhibiting potent anti-MRSA activity. These compounds differ mainly in the hydroxylated fatty acyl chain; WAP-8294A2, the most potent member of the family that reached clinical trials, is based on (R)-3-hydroxy-7-methyloctanoic acid. It is unclear how the acyl group is incorporated because no acyl-CoA ligase (ACL) gene is present in the WAP-8294A gene cluster in Lysobacter enzymogenes OH11. Here, we identified seven putative ACL genes in the OH11 genome and showed that the yield of WAP-8294A2 was impacted by multiple ACL genes with the ACL6 gene having the most significant effect. We then investigated several (R)-3-hydroxy fatty acids and their acyl SNAC (N-acetylcysteamine) thioesters as substrates for the ACLs. Feeding (R)-3-hydroxy-7-methyloctanoate-SNAC to the ACL6 gene deletion mutant restored the production of WAP-8294A2. Finally, we heterologously expressed the seven ACL genes in E. coli and purified six of the proteins. While these enzymes exhibit a varied level of activity in vitro, ACL6 showed the highest catalytic efficiency in converting (R)-3-hydroxy-7-methyloctanoic acid to its CoA thioester when incubated with coenzyme A and ATP. These results provided both in vivo and in vitro evidence to support the fact that ACL6 is the main player for fatty acyl activation and incorporation in WAP-8294A2 biosynthesis. The results also suggest that the molecular basis for the acyl chain diversity in the WAP-8294A family is the presence of functionally overlapping ACLs.
- Chen, Haotong,Olson, Andrew S.,Su, Wei,Dussault, Patrick H.,Du, Liangcheng
-
p. 105753 - 105759
(2015/12/26)
-
- Synthesis of β-ketoesters from renewable resources and Meldrum's acid
-
β-Ketoesters are valuable building blocks for the synthesis of compounds with different biological activities. In this study, a series of fatty β-ketoesters were obtained from fatty acids and Meldrum's acid using N,N-dicyclohexylcarbodiimide and dimethylaminopyridine. In addition, we demonstrate for the first time the synthesis of new fatty β-ketoesters from oleic (cis-C18:1), elaidic (trans-C18:1), ricinoleic (cis-C18:1, 12-OH), linoleic (cis,cis-C18:2), and linolenic (cis,cis,cis-C18:3) acids in good yields.
- Brinkerhoff, Rafael C.,Tarazona, Hernan F.,De Oliveira, Patrick M.,Flores, Darlene C.,Montes D'Oca, Caroline Da R.,Russowsky, Dennis,Montes D'Oca, Marcelo G.
-
p. 49556 - 49559
(2014/12/10)
-
- Highly atom-efficient oxidation of electron-deficient internal olefins to ketones using a palladium catalyst
-
A 100 % atom-efficient synthesis of ketones from electron-deficient internal olefins was achieved using O2 as a "green" oxidant (see scheme, DMA=N,N-dimethylacetamide, EWG=electron-withdrawing group). Various electron-deficient olefins were oxidized to the corresponding ketones with over 99 % selectivity and without the formation of olefin isomers or their oxidized products. Copyright
- Mitsudome, Takato,Yoshida, Syuhei,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
-
p. 5961 - 5964
(2013/06/27)
-
- Robust routes for the synthesis of N-acylated-l-homoserine lactone (AHL) quorum sensing molecules with high levels of enantiomeric purity
-
The ready availability of native quorum sensing molecules and related structural analogues is of significant biological interest in the development of methods to manipulate bacterial quorum sensing systems in a useful fashion. In this Letter we report robust routes for the synthesis of a range of N-acylated-l-homoserine lactone (AHL) quorum sensing molecules. Crucially, we have analysed the enantiopurity of the final AHLs and in all cases, excellent levels were observed.
- Hodgkinson, James T.,Galloway, Warren R.J.D.,Casoli, Mariangela,Keane, Harriet,Su, Xianbin,Salmond, George P.C.,Welch, Martin,Spring, David R.
-
supporting information; experimental part
p. 3291 - 3294
(2011/06/28)
-
- Discovery of a potent nicotinic acid receptor agonist for the treatment of dyslipidemia
-
Nicotinic acid has been used clinically for decades to control serum lipoproteins. Nicotinic acid lowers very low-density lipoprotein (VLDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, and lipoprotein-a (LPa), and it is also effective in raising high-density lipoprotein (HDL)-cholesterol. However, nicotinic acid has several side effects in clinical use. The most notable is intense cutaneous vasodilation "flushing"+ on the upper body and face. We discovered a pyranopyrimidinedione series to be nicotinic acid receptor agonists. A potent nicotinic acid receptor agonist from this series {5-(3-cyclopropylpropyl)-2-(difluoromethyl)-3H-pyrano[2,3-d] pyrimidine-4,7-dione}with reduced flushing side effect in dogs was identified.
- Qin, Jun,Rao, Ashwin,Chen, Xiao,Zhu, Xiaohong,Liu, Zhidan,Huang, Xianhai,Degrado, Sylvia,Huang, Ying,Xiao, Dong,Aslanian, Robert,Cheewatrakoolpong, Boonlert,Zhang, Hongtao,Greenfeder, Scott,Farley, Constance,Cook, John,Kurowski, Stan,Li, Qiu,Van Heek, Margaret,Chintala, Madhu,Wang, Ganfeng,Hsieh, Yunsheng,Li, Fangbiao,Palani, Anandan
-
scheme or table
p. 171 - 176
(2011/03/23)
-
- Biomimetic synthesis of a new class of bacterial signaling molecules
-
The first synthesis of a newly discovered class of bacterial signaling molecules from Streptomyces coelicolor has been developed. These molecules, known as the methylenomycin furans (MMFs), trigger production of the antibiotic methylenomycin. The synthesis features a scandium triflatecatalyzed domino reaction of β-ketoesters and dihydroxyacetone yielding 2,3,4-substituted furans. The proposed reaction sequence (aldol reaction, cyclization, and dehydrative aromatization) may be reminiscent of the biosynthetic reaction in which dihydroxyacetone phosphate and a β-ketothioester are condensed by an enzyme.
- Davis, Jesse B.,Bailey, J. Daniel,Sello, Jason K.
-
supporting information; experimental part
p. 2984 - 2987
(2009/12/05)
-
- Efficient synthesis of γ-Keto esters through neighboring carbonyl group-assisted regioselective hydration of 3-Alkynoates
-
The Au(III)-catalyzed hydration of 3-alkynoates led to a practical one-step synthesis of γ-keto esters in high yields, through a carbonyl group participation enabled by a favored 5-endodig cyclization. This mild-aqueous ethanol, room temperature, and atom
- Wang, Weibo,Xu, Bo,Hammond, Gerald B.
-
supporting information; experimental part
p. 1640 - 1643
(2009/07/01)
-
- Asymmetric synthesis of tetrahydrolipstatin and valilactone
-
The highly diastereoselective aldol reaction between acyl complexes of the iron chiral auxiliary [(η5-C5H5)Fe(CO)(PPh3)] and β-hydroxy aldehydes (obtained via a Noyori asymmetric hydrogenation), followed by a tandem oxidative decomplexation-cyclisation process gives access to β-substituted and α,β-disubstituted β-lactones in high ee. This methodology has been employed in the asymmetric syntheses of tetrahydrolipstatin and valilactone.
- Case-Green, Stephen C.,Davies, Stephen G.,Roberts, Paul M.,Russell, Angela J.,Thomson, James E.
-
experimental part
p. 2620 - 2631
(2009/04/06)
-
- General enantioselective synthesis of butyrolactone natural products via ruthenium-SYNPHOS-catalyzed hydrogenation reactions
-
Enantioselective syntheses of several paraconic acids have been achieved using catalyzed asymmetric hydrogenation of β-keto esters with SYNPHOS as a ligand. This strategy allowed the short synthesis of biologically active (-)-methylenolactocin 1, (-)-protolichesterinic acid 2, (-)-phaseolinic acid 3 and (+)-roccellaric acid 4.
- Blanc, Delphine,Madec, Jonathan,Popowyck, Florence,Ayad, Tahar,Phansavath, Phannarath,Ratovelomanana-Vidal, Virginie,Genet, Jean-Pierre
-
p. 943 - 950
(2008/03/27)
-
- COMPOUNDS AND METHODS FOR MODULATING COMMUNICATION AND VIRULENCE IN QUORUM SENSING BACTERIA
-
The present invention provides compositions and methods for modulating the communication and virulence of quorum sensing bacteria. In various exemplary embodiments, the invention provides a combinatorial library of quorum sensing compounds including synthetic analogs of naturally occurring and non-naturally occurring acyl-homoserine lactone (AHL) analogs, and methods of synthesizing and using these compounds.
- -
-
Page/Page column 17
(2008/06/13)
-
- Small molecule inhibitors of bacterial quorum sensing and biofilm formation
-
Bacteria monitor their local population densities using small molecules (or autoinducers) in a process known as quorum sensing. Here, we report a new and efficient synthetic route to naturally occurring bacterial autoinducers [N-acyl L-homoserine lactones (AHLs)] that is readily amenable to the synthesis of analogues. This route has been applied in the first synthesis of a library of non-native AHLs. Evaluation of these compounds in bacterial reporter gene and biofilm assays has revealed a potent set of quorum sensing antagonists. These ligands will serve as valuable new tools to explore the role of quorum sensing in bacterial pathogenesis. Copyright
- Geske, Grant D.,Wezeman, Rachel J.,Siegel, Adam P.,Blackwell, Helen E.
-
p. 12762 - 12763
(2007/10/03)
-
- Dynamic kinetic resolution: An efficient route to anti α-amino- β-hydroxy esters via Ru-SYNPHOS catalyzed hydrogenation
-
The Ru(II)-catalyzed hydrogenation of α-amino-β-keto esters as their hydrochloride salts affords preparation of the corresponding anti α-amino-β-hydroxy esters under mild conditions with high diastereoselectivities and enantioselectivities via dynamic kinetic resolution.
- Mordant, Celine,Duenkelmann, Pascal,Ratovelomanana-Vidal, Virginie,Genet, Jean-Pierre
-
p. 1296 - 1297
(2007/10/03)
-
- Synthesis of (-)-Syringolides 1 and 2
-
The enatioselective synthesis of (-)-syringolides 1 and 2 which were isolated as specific elicitors produced by Pseudomonas syringae pv. tomato was accomplished in 11 steps from diethyl D-tartrate.The specific rotations of synthetic samples were in good accord with those of the natural syringolides, and synthetic syringolide 2 showed almost the same biological activity as that of natural syringolide 2.
- Kuwahara, Shigefumi,Moriguchi, Masahiko,Miyagawa, Kazuhiro,Konno, Masako,Kodama, Osamu
-
p. 8809 - 8814
(2007/10/02)
-
- Hydration of Alkynes in Anhydrous Medium with Formic Acis as Water Donor
-
Formic acid has been found to hydrate alkynes in the absence of water to give oxo products and carbon monoxide.The scope of the reaction of alkynes and formic acid has been delineated.Hydrocarbon alkynes were found to be reactive in the absence of catalyst.Functionalized alkynes, in particular oxygenated alkynes, are inert toward formic acid but can be activated catalytically with Ru3(CO)12.Consequently, all the tested types of alkynes were found to give oxo products and CO with formic acid.The mechanism of the reaction was examined.With some alkynes, the primary oxo products underwent secondary reactions that gave rise to unexpected products.
- Menashe, Naim,Shvo, Youval
-
p. 7434 - 7439
(2007/10/02)
-
- Process for the preparation of β-ketocarboxylic acid esters
-
The invention relates to a process for the preparation of β-ketocarboxylic acid esters of the general formula STR1 in which R1 is an alkyl radical having 1 to 4 C atoms, R2 is an alkyl radical or alkenyl radical having 2 to 15 C atoms or a phenyl radical and R3 is hydrogen or an alkyl or alkenyl radical having 1 to 6 C atoms, characterized in that acetocarboxylic acid esters of the general formula STR2 in which R1 and R3 are as defined, are reacted with calcium hydroxide or calcium oxide in the presence of an organic solvent and in the absence of water, the calcium chelate complexes formed are acylated with carboxylic acid chloride and the products are then cleaved with aqueous ammonium salt solution to form the β-ketocarboxylic acid esters of formula (I). The β-ketocarboxylic acid esters readily accessible by the process according to the invention can be used as important intermediates in the synthesis of pharmaceutically active ingredients or plant protection agents.
- -
-
-
- Metalation of Alkynes. Part 2. Behaviour of Alkynes with Mercury(II)Acetate in Methanol: a Systematic Reinvestigation
-
The reaction of a series of alkynes with mercury(II)acetate, both in equimolar and catalytic amounts, were investigated in methanol.Hex-1-yne, oct-1-yne, oct-4-yne, 1,4-diacetoxybut-2-yne, methyl oct-2-ynoate, methyl 3-phenylpropynoate, oct-2-ynoic acid, phenylpropynoic acid, oct-1-yn-3-ol, 1-ethynylcyclohexanol, 1-ethynylcyclohexamine, phenylethyne, diphenylethyne, and ethynylferrocene were the examined substrates.The non-mercuriated products from the reaction were the corresponding vinyl ether, dialkoxyalkane, and ketone, isolated under preparative conditions.The presence of 0.1percent toluene-p-sulphonic acid increased the reactivity.The reactions of oct-1-yne and oct-4-yne were studied in detail by following with time the formation of the products under a variety of conditions, and a mechanistic scheme was drawn.For comparison, styrene, trans-oct-4-ene, and trans-β-methylstyrene were treated with 5 molpercent mercury(II) acetate.The reaction of alkenes was found to be non-catalytic.
- Bassetti, Mauro,Floris, Barbara
-
p. 227 - 234
(2007/10/02)
-
- CYCLISATION PHOTOCHIMIQUE D'ALKYL-2 ARYL-3 CYCLOHEXENE-2 ONES
-
In methanol, 2-alkyl-3-aryl-2-cyclohexenones undergo an oxidative photocyclization at 254 nm to provide polycyclic compounds with a phenanthrenic skeleton.
- Fort, Yves,Pete, Jean-Pierre
-
p. 215 - 218
(2007/10/02)
-
- Meerwein Saponification of Alkyl 3-Oxoalkanoates in the Gas Chromatograph
-
Alkyl 3-oxoalkanoates decompose by unevitable traces of water in the gas chromatograph to yield the corresponding methyl ketones and alcohols (Meerwein saponification).Decomposition occurs in the hot injector (T= 270 deg C) of the gas chromatograph and also on glass capillary columns (T> 160 deg C).Decomposition in routine work can be avoided by preparing the corresponding 3-trimethylsilyl enol ethers.
- Thoma, Heinz,Spiteller, Gerhard
-
p. 1237 - 1248
(2007/10/02)
-