- A synthesis of cephalostatin 1
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A synthesis of cephalostatin 1 from hecogenin is described in detail. The gram-scale synthesis of south part features a Baeyer–Villiger oxidation of hecogenin to 16,20-diol, a selective oxidation of C16–OH with Dess–Martin periodinane, a Rh(I)-catalyzed C15–C16 double bond shift to C14–C15 position, and a Hg(OAc)2-mediated spiroketal formation from cyclic enol ethers with alkenyl side chain at 2-position. Key transformations in the synthesis of north part, also on gram scale, include an abnormal Baeyer–Villiger oxidation of hecogenin to the corresponding dinorcholanic lactone, where a catalytic amount of iodine acts as a traceless and catalytic switch, an umpolung of steroidal 22-aldehyde to forge C22–C23 bond with good stereochemical control, a cascade spiroketal-forming process to establish DEF rings in one operation, and a selective oxidation of C3–OH. There are also other noteworthy transformations that, although not used in our final route, are valuable and could be applied to other syntheses, including: intra- or intermolecular SN2′ processes of C14-heteroatom-substituted C15–C16 alkenes, an unprecedented rearrangement of β-adduct of D-ring dienes and singlet oxygen, a chelation-controlled methylallylation of C23 aldehyde, and so on.
- Shi, Yong,Xiao, Qing,Lan, Quan,Wang, Da-Hai,Jia, Lan-Qi,Tang, Xiao-Hu,Zhou, Tao,Li, Min,Tian, Wei-Sheng
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Read Online
- A CONTRATHERMODYNAMIC EPIMERIZATION OF A 2,3-TRANS-DISUBSTITUTED BUTYROLACTONE: INTERMEDIATES FOR CHIRAL POLYPROPIONATE UNITS.
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A method is described which produces the less thermodynamically stable cis-2,3-disubstituted lactone 8 from its more stable epimer 6.These substances are complementary to aldol and crotyl organometallics in the constrution of chiral polypropionate residues.
- Ziegler, Frederick E.,Kneisley, Alyssa
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Read Online
- Synthesis and olfactory evaluation of optically active β-alkyl substituted γ-lactones and whiskey lactone analogues
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Optically active β-alkyl substituted γ-lactones and whiskey lactone analogues were synthesized, and the odor properties were evaluated. During the preparation of the chiral intermediates, we found good reaction conditions for the highly enantioselective esterification of 3-arylmethyl-2-methyl-1-propanols to kinetically resolve them. The results of the olfactory evaluations of the synthesized lactones revealed that the alkyl groups on the γ-lactone rings played an important role for the odor profiles.
- Kato, Daiki,Kawasaki, Masashi,Morita, Yuko,Okada, Takuya,Tanaka, Yasuo,Toyooka, Naoki
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- Regioselective Hydrogenation of Itaconic Acid to Γ-Isovalerolactone by Transition-Metal Nanoparticle Catalysts
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Current methods for hydrogenation of bio-derived itaconic acid (IA) lead to a mixture of isomeric lactone products. Transition-metal nanoparticles (TM-NPs), in situ-generated through thermolysis of TM(0) (Ru, Fe, W, Cr) carbonyls, in particular Ru-NPs, were found to catalyze regioselective hydrogenation of IA by syngas (2 H2/CO) into γ-isovalerolactone (GiVL) in approximately 70 % isolated yield. Key sustainability features of this new route include: a one-pot direct transformation of bio-renewable IA into value-added GiVL selectively, use of inexpensive and renewable syngas in aqueous solution, and development of a supported recyclable NP catalyst system, Al2O3-Ru-NPs.
- Gowda, Ravikumar R.,Chen, Eugene Y.-X.
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p. 973 - 977
(2019/02/06)
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- METHOD FOR REDUCTION OF ORGANIC MOLECULES
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A method for the reduction organic molecules comprising a Ruthenium-Triphosphine complex with aromatic ligands at the phosphors which are ortho or meta substituted.
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Paragraph 0050; 0052; 0053; 0054; 0055
(2018/02/06)
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- First chemo-enzymatic synthesis of the (R)-Taniguchi lactone and substrate profiles of CAMO and OTEMO, two new Baeyer–Villiger monooxygenases
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Abstract: This study investigates the substrate profile of cycloalkanone monooxygenase and 2-oxo-Δ3-4,5,5-trimethylcyclopentenylacetyl-coenzyme A monooxygenase, two recently discovered enzymes of the Baeyer–Villiger monooxygenase family, used as whole-cell biocatalysts. Biooxidations of a diverse set of ketones were performed on analytical scale: desymmetrization of substituted prochiral cyclobutanones and cyclohexanones, regiodivergent oxidation of terpenones and bicyclic ketones, as well as kinetic resolution of racemic cycloketones. We demonstrated the applicability of the title enzymes in the enantioselective synthesis of (R)-(?)-Taniguchi lactone, a building block for the preparation of various natural product analogs such as ent-quinine. Graphical abstract: [Figure not available: see fulltext.]
- Rudroff, Florian,Fink, Michael J.,Pydi, Ramana,Bornscheuer, Uwe T.,Mihovilovic, Marko D.
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p. 157 - 165
(2017/01/17)
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- METHODS OF FORMING DIOL COMPOUNDS
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Methods of forming a C4 to C7 diol compound, the methods including a first step of reacting a C4 to C7 dicarboxylic acid with hydrogen (H2) gas on a first heterogeneous catalyst at a first temperature and a first pressure to form a C4 to C7 lactone; and a subsequent step of reacting the lactone with hydrogen (H2) gas on a second heterogeneous catalyst at a second temperature and a second pressure, wherein the second temperature is lower than the first temperature. Also disclosed are methods of forming a solvent, the methods including reacting a C4 to C7 dicarboxylic acid with hydrogen (H2) gas on a first heterogeneous catalyst at a first temperature and a first pressure to form a solvent. Further disclosed herein are methods that include reacting mevalonolactone with hydrogen (H2) gas on a second heterogeneous catalyst at a second temperature and a second pressure to form a diol compound.
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Paragraph 0115
(2017/11/06)
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- Branched Diol Monomers from the Sequential Hydrogenation of Renewable Carboxylic Acids
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A prominent challenge in replacing petrochemical polymers with bioderived alternatives is the efficient transformation of biomass into useful monomers. In this work, we demonstrate a practical process for the synthesis of multifunctional alcohols from five- and six-carbon acids using heterogeneous catalysts in aqueous media. Design of this process was guided by thermodynamic calculations, which indicate the need for two sequential high-pressure hydrogenations: one, reduction of the acid to a lactone at high temperature; two, further reduction of the lactone to the corresponding diol or triol at low temperature. For example, the conversion of mesaconic acid into (α or β)-methyl-γ-butyrolactone was achieved with 95 % selectivity at a turnover frequency of 1.2 min?1 over Pd/C at 240 °C. Subsequent conversion of (α or β)-methyl-γ-butyrolactone into 2-methyl-1,4-butanediol was achieved with a yield of 80 % with Ru/C at 100 °C. This process is an efficient method for the production of lactones, diols, and triols, all valuable monomers for the synthesis of bioderived branched polyesters.
- Spanjers, Charles S.,Schneiderman, Deborah K.,Wang, Jay Z.,Wang, Jingyu,Hillmyer, Marc A.,Zhang, Kechun,Dauenhauer, Paul J.
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p. 3031 - 3035
(2016/10/11)
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- A sustainable process for the production of 2-methyl-1,4-butanediol by hydrogenation of biomass-derived itaconic acid
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Pd-ReOx/C catalysts with different Re contents were prepared and employed to catalyze the aqueous hydrogenation of itaconic acid in this study. The Pd-ReOx/C catalysts were characterized by XRD, TEM, BET, NH3-TPD and H2-TPR. Results showed that the addition of ReOx species in supported Pd catalysts promoted the direct conversion of itaconic acid to 2-methyl-1,4-butanediol. The promoting effect was ascribed to the interaction between Pd and ReOx species, as has been proved by the characterizations. A 2-methyl-1,4-butanediol yield of above 80% could be obtained over Pd-3ReOx/C under the reaction condition of 180 °C, 4 MPa H2.
- Liu, Xiaoran,Wang, Xicheng,Liu, Qiang,Xu, Guoqiang,Li, Xuemin,Mu, Xindong
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- Direct hydrogenation of biobased carboxylic acids mediated by a nitrogen-centered tridentate phosphine ligand
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A novel nitrogen-centered tridentate ligand was identified from a series of multidentate ligands and applied for the direct hydrogenation of 9 biogenic acids into alcohols, lactones and esters with high yields. Comparison of substrates and ruthenium precursors suggested that the RuII hydride cationic species was more active to transform acids than the corresponding lactone or esters.
- Deng, Li,Kang, Bin,Englert, Ulli,Klankermayer, Jürgen,Palkovits, Regina
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p. 177 - 180
(2016/02/05)
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- Efficient and Selective Cu/Nitroxyl-Catalyzed Methods for Aerobic Oxidative Lactonization of Diols
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Cu/nitroxyl catalysts have been identified that promote highly efficient and selective aerobic oxidative lactonization of diols under mild reaction conditions using ambient air as the oxidant. The chemo- and regioselectivity of the reaction may be tuned by changing the identity of the nitroxyl cocatalyst. A Cu/ABNO catalyst system (ABNO = 9-azabicyclo[3.3.1]nonan-N-oxyl) shows excellent reactivity with symmetrical diols and hindered unsymmetrical diols, whereas a Cu/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl) displays excellent chemo- and regioselectivity for the oxidation of less hindered unsymmetrical diols. These catalyst systems are compatible with all classes of alcohols (benzylic, allylic, aliphatic), mediate efficient lactonization of 1,4-, 1,5-, and some 1,6-diols, and tolerate diverse functional groups, including alkenes, heterocycles, and other heteroatom-containing groups.
- Xie, Xiaomin,Stahl, Shannon S.
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supporting information
p. 3767 - 3770
(2015/04/14)
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- Aqueous-phase hydrogenation of biomass-derived itaconic acid to methyl-γ-butyrolactone over Pd/C catalysts: Effect of pretreatments of active carbon
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The effect of active carbon pretreatment on the catalytic performance of Pd/C catalysts in the hydrogenation of itaconic acid was studied. The catalysts were prepared by deposition-precipitation and characterized by XRD, BET, NH3-TPD, TEM and F
- Li, Sha,Wang, Xicheng,Liu, Xiaoran,Xu, Guoqiang,Han, Sheng,Mu, Xindong
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- Dehydrogenative lactonization of diols in aqueous media catalyzed by a water-soluble iridium complex bearing a functional bipyridine ligand
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A new catalytic system for the dehydrogenative lactonization of a variety of benzylic and aliphatic diols in aqueous media was developed. By using a water-soluble, dicationic iridium catalyst bearing 6,6′-dihydroxy-2, 2′-bipyridine as a functional ligand, highly atom economical and environmentally benign synthesis of various lactones was achieved in good to excellent yields. Recovery and reuse of the catalyst were also accomplished by a simple phase separation and the recovered catalyst maintained its high activity at least until the fifth run. Copyright
- Fujita, Ken-Ichi,Ito, Wataru,Yamaguchi, Ryohei
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p. 109 - 112
(2014/01/23)
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- TRICYCLIC COMPOUNDS
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The present invention provides a compound of formula I or a pharmaceutically acceptable salt thereof; and its therapeutic uses. The present invention further provides a combination of pharmacologically active agents and a pharmaceutical composition.
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Paragraph 1921; 1922
(2014/06/25)
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- Application of the palladium-catalysed norbornene-assisted catellani reaction towards the total synthesis of (+)-linoxepin and isolinoxepin
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Our ongoing effort towards the development of highly selective transition-metal-catalysed C-H activation processes has led to the expansion of the Catellani reaction. In a Pd0/PdII/Pd IV-catalysed domino reaction, an aryl iodide, alkyl iodide and tert-butyl acrylate were combined to synthesize the carbon framework of the novel lignan (+)-linoxepin. The enantioselective synthesis highlights the work accomplished in our group and provides an excellent procedure for the reliable and scalable synthesis of architecturally complex scaffolds. This report outlines the synthetic approaches towards this interesting class of biologically active molecules. After the key Catellani/Heck reaction, our synthesis features a Leimeux-Johnson oxidation and a titanium tetrachloride mediated aldol condensation. Finally, a tuneable Mizoroki-Heck reaction was performed to furnish not only the natural product (+)-linoxepin but also its isoform, which we have named isolinoxepin. The enantioselective total synthesis of the natural product (+)-linoxepin has been accomplished in eight steps starting from commercial materials. The key Pd-catalysed Catellani step served to combine aryl iodide, alkyl iodide and tert-butyl acrylate in a domino sequence. By tuning the final Heck reaction, both the natural product and its structural isomer were synthesized. Copyright
- Qureshi, Zafar,Weinstabl, Harald,Suhartono, Marcel,Liu, Hongqiang,Thesmar, Pierre,Lautens, Mark
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p. 4053 - 4069
(2014/07/08)
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- ANTIBACTERIAL COMPOUNDS AND METHODS FOR USE
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The present description relates to compounds and forms and pharmaceutical compositions thereof and methods for use thereof to treat or ameliorate bacterial infections caused by wild-type and multi-drug resistant Gram-negative and Gram-positive pathogens. The present description further relates to a compound having activity toward wild-type and MDR bacteria. The present description also relates to a compound having activity against quinolone-resistant Gram-negative strains (including MDR strains) as well as antibacterial activity to MDR resistant Gram-positive pathogens (including MRSA strains).
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Page/Page column 107-108
(2013/03/28)
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- A versatile aqueous reduction of bio-based carboxylic acids using syngas as a hydrogen source
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Syngas as a versatile hydrogen source: Using readily available and economically favorable syngas as a convenient hydrogen source, an efficient and sustainable aqueous reduction of bio-based carboxylic acids has been achieved over a highly robust catalyst system consisting of gold nanoparticles supported on acid-tolerant single-phase monoclinic zirconia (Au/m-ZrO2). A range of bio-based multifunctional carboxylic acids have been selectively converted into their corresponding lactones or diols in high to excellent yields. Copyright
- Yu, Lei,Du, Xian-Long,Yuan, Jing,Liu, Yong-Mei,Cao, Yong,He, He-Yong,Fan, Kang-Nian
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- Chiral hetero- and carbocyclic compounds from the asymmetric hydrogenation of cyclic alkenes
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Several types of chiral hetero- and carbocyclic compounds have been synthesized by using the asymmetric hydrogenation of cyclic alkenes. N,P-Ligated iridium catalysts reduced six-membered cyclic alkenes with various substituents and heterofunctionality in good to excellent enantioselectivity, whereas the reduction of five-membered cyclic alkenes was generally less selective, giving modest enantiomeric excesses. The stereoselectivity of the hydrogenation depended more strongly on the substrate structure for the five- rather than the six-membered cyclic alkenes. The major enantiomer formed in the reduction of six-membered alkenes could be predicted from a selectivity model and isomeric alkenes had complementary enantioselectivity, giving opposite optical isomers upon hydrogenation. The utility of the reaction was demonstrated by using it as a key step in the preparation of chiral 1,3-cis-cyclohexane carboxylates. Copyright
- Verendel, J. Johan,Li, Jia-Qi,Quan, Xu,Peters, Byron,Zhou, Taigang,Gautun, Odd R.,Govender, Thavendran,Andersson, Pher G.
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supporting information; experimental part
p. 6507 - 6513
(2012/06/29)
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- Synergy between the metal nanoparticles and the support for the hydrogenation of functionalized carboxylic acids to diols on Ru/TiO2
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Ruthenium nanoparticles supported on titania are over three times more active than conventional ruthenium on carbon for the hydrogenation of lactic acid. This superior catalytic activity can be due to a combined action of small ruthenium nanoparticles and the titania support.
- Primo, Ana,Concepcion, Patricia,Corma, Avelino
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scheme or table
p. 3613 - 3615
(2011/04/25)
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- Synthesis of quaternary carbon centers via hydroformylation
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The application of hydroformylation to the synthesis of quaternary carbon centers is reported. The synthesis of the highly substituted carbon is achieved by applying a catalytic amount of 1. Ligand 1 serves as a catalytic directing group by covalently and reversibly binding to both the substrate and catalyst. The intramolecular nature of the directing group strategy accelerates the hydroformylation reaction such that the reaction is performed at mild temperatures (35-55 °C) and with excellent regioselectivity (b:l > 94:6).
- Sun,Frimpong,Tan
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supporting information; experimental part
p. 11841 - 11843
(2010/11/04)
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- Oxidant-free lactonization of diols using a hydrotalcite-supported copper catalyst
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We newly synthesized well-crystallized hydrotalcite-supported copper nanoparticles, denoted as Cu/HT(c), which acted as a highly efficient heterogeneous catalyst for oxidant-free lactonization of various diols under liquid-phase conditions. The Cu/HT(c) catalyst could be recovered by simple filtration and reused without the significant loss of its activity and selectivity.
- Mikami, Yusuke,Ebata, Kaori,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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experimental part
p. 855 - 861
(2010/09/16)
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- Selective and flexible transformation of biomass-derived platform chemicals by a multifunctional catalytic system
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(Figure Presented) A sustainable supply chain: The controlled transformation of the biomassderived platform compounds levulinic acid (LA) and itaconic acid (IA) into the corresponding lactones, diols, or cyclic ethers (see picture) by using a multifunctional molecular catalyst is described.
- Geilen, Frank M. A.,Engendahl, Barhel,Harwardt, Andreas,Marquardt, Wolfgang,Klankermayer, Juergen,Leitner, Walter
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body text
p. 5510 - 5514
(2010/09/16)
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- Supported gold nanoparticles as a reusable catalyst for synthesis of lactones from diols using molecular oxygen as an oxidant under mild conditions
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The oxidative lactonization of various diols using molecular oxygen as a primary oxidant can be efficiently catalyzed by hydrotalcite-supported Au nanoparticles (Au/HT). For instance, lactonization of 1,4-butanediol gave γ-butyrolactone with an excellent turnover number of 1400. After lactonization, the Au/HT can be recovered by simple filtration and reused without any loss of its activity and selectivity.
- Mitsudome, Takato,Noujima, Akifumi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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experimental part
p. 793 - 797
(2010/04/23)
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- Exploration of the molecular origin of the azinomycin epoxide: Timing of the biosynthesis revealed
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(Equation Presented) Streptomyces sahachiroi whole cell feeding experiments, utilizing putative precursors labeled with stable isotopes, established that the epoxide unit of the DNA cross-linked agents, azinomycin A and B, proceeds via a valine-dependent pathway and that hydroxylation and dehydration precedes formation of the terminal epoxide. Sodium 3-methyl-2-oxobutenoate, formed through a transimination reaction, was shown to be the penultimate precursor incorporated into the azinomycin epoxide.
- Sharma, Vasudha,Kelly, Gilbert T.,Watanabe, Coran M. H.
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supporting information; experimental part
p. 4815 - 4818
(2009/05/31)
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- Stereoselective reduction of 2-butenolides to chiral butanolides by reductases from cultured cells of Glycine max
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The stereoselective reduction of 2-butenolides by two reductases, p51 and p83, from cultured plant cells of Glycine max was investigated. The reduction of 2-methyl-2-butenolide by p51 reductase produced (R)-2-methylbutanolide, whereas the reduction by p83 reductase gave (S)-2-methylbutanolide. Both reductases reduced 3-methyl-2-butenolide to (R)-3-methylbutanolide. The reduction of 2,3-dimethyl-2-butenolide by p51 reductase gave (2R,3R)-2,3-dimethylbutanolide, whereas the reduction by p83 reductase produced (2S,3R)-2,3-dimethylbutanolide. The reduction of 4-alkyl-2-butenolides with these reductases was accompanied by resolution of chiral centers affording (R)-4-alkylbutanolides.
- Shimoda, Kei,Kubota, Naoji,Hirata, Toshifumi,Kondo, Yoko,Hamada, Hiroki
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p. 1345 - 1347
(2007/10/03)
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- Catalytic asymmetric synthesis of mycocerosic acid
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The first catalytic asymmetric total synthesis of mycocerosic acid was achieved via the application of iterative enantioselective 1,4-addition reactions and allows for the efficient construction of 1,3-polymethyl arrays with full stereocontrol; further exemplified by the synthesis of tetramethyl-decanoic acid, a component of the preen-gland wax of the graylag goose, Anser anser. The Royal Society of Chemistry.
- Ter Horst, Bjorn,Feringa, Ben L.,Minnaard, Adriaan J.
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p. 489 - 491
(2007/10/03)
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- Catalytic asymmetric synthesis of phthioceranic acid, a heptamethyl-branched acid from Mycobacterium tuberculosis
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The first total synthesis of phthioceranic acid (1) has been achieved by an iterative catalytic asymmetric 1,4-addition protocol. This method provides a robust and high-yielding route for the preparation of 1,3-oligomethyl (deoxypropionate) arrays. After the desired number of methyl groups has been introduced, these arrays can be further functionalized at both ends to polymethyl-substituted lipids such as phthioceranic acid, a heptamethyl-branched fatty acid from the virulence factor Sulfolipid-I (2), found in Mycobacterium tuberculosis.
- Ter Horst, Bjorn,Feringa, Ben L.,Minnaard, Adriaan J.
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p. 3013 - 3015
(2008/02/10)
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- Catalytic asymmetric synthesis of acyclic arrays by tandem 1,4-addition-aldol reactions
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Herein, we report efficient acyclic stereocontrol in tandem 1,4-addition-aldol reactions triggered by catalytic asymmetric organometallic addition. Grignard reagents add to α,β-unsaturated thioesters in a 1,4-fashion and the resulting magnesium enolates are trapped with aromatic or aliphatic aldehydes. The process provides a range of tandem products bearing three contiguous stereocenters with excellent control of relative and absolute stereochemistry. The various diastereomeric products have been fully characterized using single-crystal X-ray analysis and the origins of stereocontrol in this tandem protocol are discussed. The versatility and efficiency of this methodology are demonstrated in the first catalytic asymmetric synthesis of (-)-phaseolinic acid with 54% overall yield via a short and concise route.
- Howell, Gareth P.,Fletcher, Stephen P.,Geurts, Koen,Ter Horst, Bjorn,Feringa, Ben L.
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p. 14977 - 14985
(2008/02/04)
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- Cobalt(II)-azabis(oxazoline)-catalyzed conjugate reduction of α,β-unsaturated carbonyl compounds
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Azabis(oxazolines) prove to be superior ligands for the enantioselective, cobalt(II)-catalyzed conjugate reduction of α,β-unsaturated carbonyl compounds with sodium borohydride. β-Trisubstituted α,β- unsaturated esters and amides as well as γ-butenolides are readily converted to their corresponding saturated counterparts with enantioselectivities up to 97% ee.
- Geiger, Christian,Kreitmeier, Peter,Reiser, Oliver
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p. 249 - 254
(2007/10/03)
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- New approach to the synthesis of(R)-3-methyl-γ-butyrolactone
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Optically active pure (R)-3-methyl-γ-butyrolactone was synthesized from (R)-4-menthenone.
- Kharisov,Latypova,Talipov,Ishmuratov,Tolstikov
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p. 482 - 483
(2007/10/03)
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- Process for preparing alpha- and beta-methyl-gamma-butyrolactone and 3-methyltetrahydrofuran
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The present invention pertains to a novel process for preparing alpha- and beta-methyl-gamma-butyrolactones (MeGBL) and/or 3-Methyltetrahydrofuran (MeTHF) from 3-(hydroxymethyl)tetrahydrofuran (HOMeTHF), 3-formyltetrahydrofuran (FTHF) or a mixture thereof
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- Synthesis of xyloketals, natural products from the mangrove fungus Xylaria sp.
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The xyloketal family of compounds was synthesized by condensation of phloroglucinol (7) or 2,4-dihydroxyacetophenone (15) with the enone 8a or 14 in multistep, one-pot, domino reactions, leading to the xyloketals and 5-demethyl-xyloketals, respectively. I
- Krohn, Karsten,Riaz, Muhammad,Floerke, Ulrich
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p. 1261 - 1270
(2007/10/03)
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- Total synthesis of (+)-xyloketal D, a secondary metabolite from the mangrove fungus Xylaria sp.
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(+)-Xyloketal D was prepared in a one-pot multistep domino reaction by heating optically active 5-hydroxy-4-methyl-3-methylenepentan-2-one (R) in toluene with 2,4-dihydroxyacetophenone. The absolute configuration of the natural product was confirmed by preparation of the starting enone from a lactone of established absolute configuration.
- Krohn, Karsten,Riaz, Muhammad
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p. 293 - 294
(2007/10/03)
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- A convenient route to 1,4-monoprotected dialdehydes, 1,4-ketoaldehydes, γ-lactols and γ-lactones through radical alkylation of α,β-unsaturated aldehydes in organic and organic-aqueous media
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α,β-Unsaturated aldehydes were smoothly alkylated by radicals generated through photosensitised hydrogen abstraction of benzophenone. In this way, and by using 1,3-dioxolane as radical precursor, monoprotected 1,4-dialdehydes were obtained from crotonaldehyde, 2-hexenal, 4-methyl-2-pentenal and cyclohexencarboxyaldehyde in a moderate yield, and in a low yield from β-aryl-α,β-unsaturated aldehydes. With 2-alkyl-1,3-dioxolanes, monoprotected 1,4-ketoaldehydes were analogously prepared. By using methanol, ethanol and isopropanol as radical precursors γ-lactols were likewise obtained from the above aliphatic aldehydes. These single-step syntheses compared favorably with multi-step approaches previously proposed for some of these compounds. The lactols were conveniently oxidized to the corresponding γ-lactones. An alternative to the photosensitisation in organic medium was the use of mixed aqueous-organic solvent and a hydrosoluble photosensitiser (benzophenone disodium disulfonate was prepared for this purpose and successfully used), which allowed a more convenient work up.
- Dondi, Daniele,Caprioli, Ilaria,Fagnoni, Maurizio,Mella, Mariella,Albini, Angelo
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p. 947 - 957
(2007/10/03)
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- Process for the preparation of 3-methyltetrahydrofuran
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Disclosed is a process for the preparation of 3-methyltetrahydrofuran (MeTHF) from 3-(hydroxymethyl)tetrahydrofuran (HOMeTHF) by contacting HOMeTHF with hydrogen in the presence of an acidic, supported catalyst comprising a Group VIII metal.
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Page/Page column 6-7
(2008/06/13)
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- Synthesis of chiral β-methyl tryptamine-derived GnRH antagonists
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The stereospecific formation of 2-aryl-β-methyl tryptamine derivatives 15 and 16 from chiral 4-chloro-1-(3,5-dimethylphenyl)-3-methylbutanones is described. These intermediates were further manipulated into the GnRH antagonists 1b and 1c in five steps.
- Simeone, Joseph P.,Bugianesi, Robert L.,Ponpipom, Mitree M.,Goulet, Mark T.,Levorse, Mark S.,Desai, Ranjit C.
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p. 6459 - 6461
(2007/10/03)
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- Radical reaction by a combination of phosphinic acid and a base in aqueous media
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Treatment of various organic halides with phosphinic acid (hypophosphorous acid) in aqueous ethanol in the presence of a radical initiator and a base gave the corresponding reduced products in high yields. Addition of a base is indispensable for the reduction of halides by phosphinic acid. Allylic ether of o-iodophenol or 2-haloalkanal allylic acetal underwent radical cyclization under the same conditions to afford the corresponding cyclic product in excellent yield. Deuterated phosphinic acid was found to be an efficient chain carrier for the radical deuteration of organic halides. For example, a deuterium oxide solution of deuterated phosphinic acid, potassium carbonate, 2,2′-azobis(isobutyramidine) dihydrochloride as an initiator, and p-iodobenzoic acid was heated at reflux to give p-deuteriobenzoic acid in 94% yield. A mixed dioxane/D2O solvent system combined with DBU and potassium peroxodisulfate was crucial to deuterate hydrophobic substrates in high yields and with high deuterium incorporation. Complete deuterium incorporation was accomplished only by the reaction in D2O without an organic cosolvent and an organic base.
- Yorimitsu,Shinokubo,Oshima
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p. 225 - 235
(2007/10/03)
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- Reduction of organic halides with tri-2-furylgermane: Stoichiometric and catalytic reduction
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Tri-2-furylgermane proved to be an effective reagent for the radical reduction of organic halides. Treatment of 1-bromododecane with tri-2-furylgermane in THF at 25 °C in the presence of a catalytic amount of triethylborane afforded dodecane almost quantitatively. Radical cyclization of 2-iodoethanal allyl acetal afforded five-membered products under the same reaction conditions. These reactions proceeded with NaBH4 in the presence of a catalytic amount of germanium hydride. The reaction took place in water as well as in THF to give the corresponding reduced compounds in good yields.
- Nakamura,Yorimitsu,Shinokubo,Oshima
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p. 747 - 752
(2007/10/03)
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- Raney Nickel: An effective reagent for reductive dehalogenation of organic halides
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Raney Nickel is an effective reagent to achieve the chemoselective reductive dehalogenation of organic halides. Fluorides and vinyl halides are unreactive under the used experimental conditions.
- Barrero,Alvarez-Manzaneda,Chahboun,Meneses,Romera
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p. 485 - 488
(2007/10/03)
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- New and Convenient Synthesis of (R)-(+)-4,5-Dihydro-4-methyl-2(3H)-furanone and (R)-(-)-4-Bromo-3-methyl-1-O-tert-butyldimethylsilylbutan-1-ol
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A convenient partial synthesis of the lactone (+)-10 is reported starting from the readily available methyl (S)-(+)-3-hydroxy-2-methylpropanoate (+)-1. Furthermore, an efficient three step route to the optically active saturated isoprene unit (-)-13 in high yield starting from the lactone (+)-10 is reported for the first time.
- Pemp, Alexander,Seifert, Karlheinz
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- Highly regioselective intramolecular hydroxymethylation of α,β-unsaturated carboxylic acids
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A convenient synthesis of hydroxy esters 7 and lactones 8 by starting from easily available α,β-unsaturated carbocylic acids 4 is described. The key step of this transformation is a hitherto unknown radical cyclization of silyl esters, which exhibits a high degree of regioselectivity through steric and orbital control.
- Linker, Torsten,Maurer, Michael,Rebien, Frank
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p. 8363 - 8366
(2007/10/03)
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- Lipase-Catalyzed Sequential Esterification of (+/-)-2-Methylbutanedioic Anhydride - A Biocatalytical Access to an Enantiomerically Pure 1-Monoester of (S)-2-Methylbutanedioic Acid
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The preparation of enantiomerically pure 1-(2-methylpropyl) 4-hydrogen (S)-2-methylbutanedioate (ent-3) by an enzyme-catalyzed sequential esterification of (+/-)-2-methylbutanedioic anhydride (rac-1) demands two different enzymes.Lipozyme, a lipase from Mucor miehei, was used for the alcoholysis of rac-1 to a mixture of the isomeric monoesters 2/ent-2 and 3/ent-3, whereas Novozym 435, a lipase from Candida antarctica, was required for the enantioselective conversion of a mixture of 3 and ent-3 into the easily separable neutral diester 4 and the acidic monoester ent-3, which thus was obtained in a yield of 26percent with an enantiomeric excess of 99percent ent-3 was reduced by LIBH4 to (S)-3-methylbutan-4-olide (ent-10), a versatile chiral intermediate. - Keywords: Enzymes / Butanedioic anhydride, 2-methyl / Alcoholysis, enantio- and regioselective / Esterification, enantioselective / (S)-3-Methylbutan-4-olide
- Ozegowski, Ruediger,Kunath, Annamarie,Schick, Hans
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p. 1699 - 1702
(2007/10/02)
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- and Annulation Reactions of α-(Phenylthio) Dicarbonyl Electrophiles with Bis(trimethylsilyl) Enol Ethers: Synthesis of Highly Functionalized Medium Ring Cycles
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The and annulations of bis(trimethylsilyl) enol ethers with 1,4- and 1,5-dicarbonyl electrophiles bearing α-phenylthio substituents leads to the formation of bicyclic and ethers with good regiochemical and stereochemical control.Subsequent oxidation of the phenylthio moiety followed by reduction with SmI2 constitutes a high-yielding and regioselective process for cleavage of the bridging ether linkage.The overal strategy provides a synthetic pathway for the synthesis of highly functionalized medium ring carbocycles.
- Molander, Gary A.,Eastwood, Paul R.
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p. 8382 - 8393
(2007/10/02)
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- Asymmetric Synthesis of a Key Synthetic Precursor for (+)-Strigol and Sorgolactone
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En-route to non-racemic iodomethyl butyrolactone 23g a number of stereoselective 1,4-additions and reductions have been studied.The only satisfactory approach involved baker's yeast reduction (21c->23c) as key step.
- Schroeer, Josef,Welzel, Peter
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p. 6839 - 6858
(2007/10/02)
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- The synthesis and biochemical pharmacology of enantiomerically pure methylated oxotremorine derivatives
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Previous pharmacological studies of methylated oxotremorine derivatives bearing substituents at the 3-, 4-, and 5-positions of the pyrrolidinone ring have been conducted using racemic mixtures, and not with optically active compounds. The synthesis and radioligand binding data of optically active, methylated oxotremorine derivatives at the 3- and 4-positions are described. There are significant pharmacological differences between the 3- and 4- position derivatives. The 4-position enantiomers have weak, approximately equal affinity and antagonist-like profiles, whereas the 3-position enantiomers have significantly different affinities and partial agonist-like profiles.
- Trybulski,Zhang,Kramss,Mangano
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p. 3533 - 3541
(2007/10/02)
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- NEW METHODS FOR REDUCTIVE FREE-RADICAL CYCLIZATIONS OF α-BROMOACETALS TO 2-ALKOXYTETRAHYDROFURANS WITH ACTIVATED CHROMIUM(II)-ACETATE
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A method for the synthesis of γ-butyrolactones 6 is described in which the key step is a free-radical cyclization of α-bromoacetals 4 to 2-alkoxytetrahydrofurans 5 in 54-93percent yield induced by activated chromium(II)-acetate.Four new methods have been developed in order to activate the transition metal.Two of them require only catalytic amounts of chromium(II)-acetate, because it can be regenerated in situ chemically or electrochemically.The diastereoselectivity of the cyclization depends on the substitution pattern of 4 and ranges between 30.4:1 and 1:54.8.
- Hackmann, Claus,Schaefer, Hans J.
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p. 4559 - 4574
(2007/10/02)
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- Synthesis of the Enantiomers of Lasiol, the Major Volatile Component of the Mandibular Gland Secretion of Lasius meridionalis
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Both enantiomers of lasiol, erythro-2,3,6-trimethyl-5-hepten-1-ol (1), were synthesized in 6 steps from the enantiomers of 3-methyl-4-butanolide (2).Key Words: Lasiol / Lavandulyl skeleton / Lasius meridionalis / Terpenes
- Kuwahara, Shigefumi,Shibata, Yasuo,Hiramatsu, Akira
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p. 993 - 996
(2007/10/02)
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- A convenient lactonization of diols to γ- and δ-lactones catalyzed by transition metals polyhydrides
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Transition metal polyhydrides-catalyzed oxidative condensation of diols to 5 and 6-ring lactones was studied.The regioselective dehydrogenation of unsymmetrically substituted 1,4-diols gave β- or γ-substituted γ-lactones in high yields.The mechanism of dehydrogenation under neutral and mild conditions was discussed.
- Lin, Yingrui,Zhu, Xianchao,Zhou, Yuefen
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p. 269 - 274
(2007/10/02)
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- Absolute Configuration and Synthesis of 2-Hydroxy-2-(1-hydroxyethyl)-3-methyl-γ-butyrolactone, a Presumed Pheromone of Ithomiine Butterflies
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2-Hydroxy-2-(1-hydroxyethyl)-3-methyl-γ-butyrolactone (1) is a constituent of scent glands of male ithomiine butterflies.All diastereomers and the respective (3R)-enantiomers were synthesized by starting from rac- or (3S)-3-methyl-γ-butyrolactone 3.Their relative configurations were determined by difference NOE-NMR spectroscopy or by X-ray diffraction analysis.The absolute configuration of the natural product was determined by gas chromatography on a chiral stationary phase of the respective dioxolane derivatives.The natural lactone could be shown to be the .In addition, the corresponding ketone, (2S,3R)-2-acetyl-2-hydroxy-3-methyl-γ-butyrolactone , could be identified as a new natural product from Prittwitzia hymaenea. Key Words: Pheromones / Ithomiinae / Ithomiolide / Keto lactone / Butterflies
- Schulz, Stefan
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p. 829 - 834
(2007/10/02)
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