- "Instant methylide" modification of the Corey-Chaykovsky epoxide synthesis
-
We report that Me3S(O)+I- (1) and Me3S+I- (2) form stable, dry mixtures with KOt-Bu and NaH, respectively, which remain stable upon prolonged storage (> 1 year). The corresponding methylides (Me2SO=CH2 and Me2S=CH2) are generated upon addition of DMSO or DMSO/THF solutions of carbonyl compounds, cleanly affording epoxides via the Corey-Chaykovsky reaction in good yields and short reaction times (as short as 20 min when 1-2 mmol of various ketones and aldehydes were treated with a mixture of 1 and KOt-Bu at 50-60°C).
- Ciaccio, James A.,Drahus, Antoinette L.,Meis, Regina M.,Tingle, Carice T.,Smrtka, Michael,Geneste, Richard
-
-
Read Online
- In situ fabricated MOF-cellulose composite as an advanced ROS deactivator-convertor: Fluoroswitchable bi-phasic tweezers for free chlorine detoxification and size-exclusive catalytic insertion of aqueous H2O2
-
Combining the merits of structural diversity, and purposeful implantation of task-specific functionalities, metal-organic frameworks (MOFs) instigate targeted reactive oxygen species (ROS) scavenging and concurrent detoxification via self-calibrated emission modulation. Then again, grafting of catalytically active sites in MOFs can benefit developing a greener protocol to convert ROS generators to technologically important building blocks, wherein tailorable MOF-composite fabrication is highly sought for practical applications, yet unexplored. The chemo-robust and hydrogen-bonded framework encompassing free -NH2 moiety affixed pores serves as an ultra-fast and highly regenerable fluoro-probe for selective detection of toxic ROS producers hypochlorite ion (ClO-) and H2O2 with record-level nanomolar sensitivity. While the bio-relevant antioxidant l-ascorbic acid (AA) imparts notable quenching to the MOF, a significant 3.5 fold emission enhancement with bi-phasic colorimetric variation ensues when it selectively scavenges ClO- from uni-directional porous channels through an unprecedented molecular tweezer approach. Apart from a battery of experimental evidence, density functional theory (DFT) results validate "on-off-on"fluoroswitching from redistribution of MOF orbital energy levels, and show guest-mediated exclusive transition from "Tight state"to "Loose state". The coordination frustrated metal site engineered pore-wall benefits the dual-functionalized MOF in converting the potential ROS generator H2O2via selective alkene epoxidation under mild-conditions. Importantly, sterically encumbered substrates exhibit poor conversion and demonstrate first-ever pore-fitting-induced size selectivity for this benign oxidation. Judiciously planned control experiments in combination with DFT-optimized intermediates provide proof-of-concept to the ionic route of ROS conversion. Considering an effective way to broaden the advanced applications of this crystalline material, reconfigurable MOF@cotton fiber (CF) is fabricated via in situ growth, which scavenges free chlorine and concomitantly squeezes it upon exposure to AA with obvious colorimetric changes over multiple real-life platforms. Furthermore, multi-cyclic alkene epoxidation by MOF@CF paves the way to futuristic continuous flow reactors that truly serves this smart composite as a bimodal ROS deactivator-convertor and explicitly denotes it as an advanced promising analogue from contemporary state-of-the-art materials.
- Bankar, Balasaheb D.,Biradar, Ankush V.,Goswami, Ranadip,Neogi, Subhadip,Pillai, Renjith S.,Rajput, Sonal,Seal, Nilanjan
-
p. 4316 - 4332
(2022/03/07)
-
- Proton Switch in the Secondary Coordination Sphere to Control Catalytic Events at the Metal Center: Biomimetic Oxo Transfer Chemistry of Nickel Amidate Complex
-
High-valent metal-oxo species are key intermediates for the oxygen atom transfer step in the catalytic cycles of many metalloenzymes. While the redox-active metal centers of such enzymes are typically supported by anionic amino acid side chains or porphyrin rings, peptide backbones might function as strong electron-donating ligands to stabilize high oxidation states. To test the feasibility of this idea in synthetic settings, we have prepared a nickel(II) complex of new amido multidentate ligand. The mononuclear nickel complex of this N5 ligand catalyzes epoxidation reactions of a wide range of olefins by using mCPBA as a terminal oxidant. Notably, a remarkably high catalytic efficiency and selectivity were observed for terminal olefin substrates. We found that protonation of the secondary coordination sphere serves as the entry point to the catalytic cycle, in which high-valent nickel species is subsequently formed to carry out oxo-transfer reactions. A conceptually parallel process might allow metalloenzymes to control the catalytic cycle in the primary coordination sphere by using proton switch in the secondary coordination sphere.
- Kim, Soohyung,Jeong, Ha Young,Kim, Seonghan,Kim, Hongsik,Lee, Sojeong,Cho, Jaeheung,Kim, Cheal,Lee, Dongwhan
-
supporting information
p. 4700 - 4708
(2021/02/12)
-
- Total Synthesis of Tetrahydrolipstatin, Its Derivatives, and Evaluation of Their Ability to Potentiate Multiple Antibiotic Classes against Mycobacterium Species
-
Tetrahydrolipstatin (THL, 1a) has been shown to inhibit both mammalian and bacterial α/β hydrolases. In the case of bacterial systems, THL is a known inhibitor of several Mycobacterium tuberculosis hydrolases involved in mycomembrane biosynthesis. Herein we report a highly efficient eight-step asymmetric synthesis of THL using a route that allows modification of the THL α-chain substituent to afford compounds 1a through 1e. The key transformation in the synthesis was use of a (TPP)CrCl/Co2(CO)8-catalyzed regioselective and stereospecific carbonylation on an advanced epoxide intermediate to yield a trans-β-lactone. These compounds are modest inhibitors of Ag85A and Ag85C, two α/β hydrolases of M. tuberculosis involved in the biosynthesis of the mycomembrane. Among these compounds, 10d showed the highest inhibitory effect on Ag85A (34 ± 22 μM) and Ag85C (66 ± 8 μM), and its X-ray structure was solved in complex with Ag85C to 2.5 ? resolution. In contrast, compound 1e exhibited the best-in-class MICs of 50 μM (25 μg/mL) and 16 μM (8.4 μg/mL) against M. smegmatis and M. tuberculosis H37Ra, respectively, using a microtiter assay plate. Combination of 1e with 13 well-established antibiotics synergistically enhanced the potency of few of these antibiotics in M. smegmatis and M. tuberculosis H37Ra. Compound 1e applied at concentrations 4-fold lower than its MIC enhanced the MIC of the synergistic antibiotic by 2-256-fold. In addition to observing synergy with first-line drugs, rifamycin and isoniazid, the MIC of vancomycin against M. tuberculosis H37Ra was 65 μg/mL; however, the MIC was lowered to 0.25 μg/mL in the presence of 2.1 μg/mL 1e demonstrating the potential of targeting mycobacterial hydrolases involved in mycomembrane and peptidoglycan biosynthesis.
- Khan, Saniya S.,Sudasinghe, Thanuja D.,Landgraf, Alexander D.,Ronning, Donald R.,Sucheck, Steven J.
-
-
- Dinuclear Iron(III) and Nickel(II) Complexes Containing N-(2-Pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine: Catalytic Oxidation and Magnetic Properties
-
Dinuclear FeIII and NiII complexes, [(phenO)Fe(N3)]2(NO3)2 (1) and [(phenOH)Ni(N3)2]2 (2), were prepared by treating Fe(NO3)3?9 H2O and Ni(NO3)2?6 H2O in methanol, respectively, with phenOH (=N-(2-pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine) and NaN3; both 1 and 2 were characterized by elemental analysis, IR spectroscopy, X-ray diffraction, and magnetic susceptibility measurements. Two ethoxo-bridged FeIII and two azido-bridged NiII were observed in 1 and 2, respectively; corresponding antiferromagnetic interaction via the bridged ethoxo groups and strong ferromagnetic coupling via the bridged end-on azido ligands within the dimeric unit were observed. Complex 1 did not exhibit any catalytic activity, while 2 exhibited excellent catalytic activities for the epoxidation of aliphatic, aromatic, and terminal olefins.
- Jeong, Ah Rim,Shin, Jong Won,Jeong, Jong Hwa,Bok, Kwon Hee,Kim, Cheal,Jeong, Donghyun,Cho, Jaeheung,Hayami, Shinya,Min, Kil Sik
-
p. 3023 - 3033
(2017/03/13)
-
- Regiocontrolled syntheses of FAHFAs and LC-MS/MS differentiation of regioisomers
-
An efficient regiospecific total synthesis of several branched fatty acyl hydroxyl-fatty acids (FAHFA) has been achieved from available terminal alkenes and alkynes. The key steps feature a boron trifluoride mediated epoxide ring opening with acetylide carbanions, followed by hydrogenation of the alkyne function. The carboxylic acid of the hydroxylated chains is introduced at the last step of the synthesis to allow the esterification of the branched hydroxyl group by fatty acids beforehand. The chemical syntheses of a "linear" FAHFA and a branched FAHFA analog containing a Z-olefin in the hydroxyl-fatty acid chain are also reported. A LC-MS/MS method has been developed. Several reversed phase columns were compared. Regioisomers were separated.
- Balas, Laurence,Bertrand-Michel, Justine,Viars, Fanny,Faugere, Julien,Lefort, Corinne,Caspar-Bauguil, Sylvie,Langin, Dominique,Durand, Thierry
-
supporting information
p. 9012 - 9020
(2016/10/07)
-
- Trinuclear nickel and cobalt complexes containing unsymmetrical tripodal tetradentate ligands: Syntheses, structural, magnetic, and catalytic properties
-
The coordination chemistries of the tetradentate N2O2-type ligands N-(2-pyridylmethyl)iminodiethanol (H2pmide) and N-(2-pyridylmethyl)iminodiisopropanol (H2pmidip) have been investigated with nickel(ii) and cobalt(ii/iii) ions. Three novel complexes prepared and characterized are [(Hpmide)2Ni3(CH3COO)4] (1), [(Hpmide)2Co3(CH3COO)4] (2), and [(pmidip)2Co3(CH3COO)4] (3). In 1 and 2, two terminal nickel(ii)/cobalt(ii) units are coordinated to one Hpmide- and two CH3CO2-. The terminal units are each connected to a central nickel(ii)/cobalt(ii) cation through one oxygen atom of Hpmide- and two oxygen atoms of acetate ions, giving rise to nickel(ii) and cobalt(ii) trinuclear complexes, respectively. Trinuclear complexes 1 and 2 are isomorphous. In 3, two terminal cobalt(iii) units are coordinated to pmidip2- and two CH3CO2-. The terminal units are each linked to a central cobalt(ii) cation through two oxygen atoms of pmidip2- and one oxygen atom of a bidentate acetate ion, resulting in a linear trinuclear mixed-valence cobalt complex. 1 shows a weak ferromagnetic interaction with the ethoxo and acetato groups between the nickel(ii) ions (g = 2.24, J = 2.35 cm-1). However, 2 indicates a weak antiferromagnetic coupling with the ethoxo and acetato groups between the cobalt(ii) ions (g = 2.37, J = -0.5 cm-1). Additionally, 3 behaves as a paramagnetic cobalt(ii) monomer, due to the diamagnetic cobalt(iii) ions in the terminal units (g = 2.53, =D= = 36.0 cm-1). No catalytic activity was observed in 1. However, 2 and 3 showed significant catalytic activities toward various olefins with modest to good yields. 3 was slightly less efficient toward olefin epoxidation reaction than 2. Also 2 was used for terminal olefin oxidation reaction and was oxidised to the corresponding epoxides in moderate yields (34-75%) with conversions ranging from 47-100%. The cobalt complexes 2 and 3 promoted the O-O bond cleavage to ~75% heterolysis and ~25% homolysis.
- Shin, Jong Won,Jeong, Ah Rim,Lee, Sun Young,Kim, Cheal,Hayami, Shinya,Min, Kil Sik
-
p. 14089 - 14100
(2016/11/06)
-
- A discrete {Co4(μ3-OH)4}4+ cluster with an oxygen-rich coordination environment as a catalyst for the epoxidation of various olefins
-
Using the sterically hindered terphenyl-based carboxylate, the tetrameric Co(ii) complex [Co4(μ3-OH)4(μ-O2CAr4F-Ph)2(μ-OTf)2(Py)4] (1) with an asymmetric cubane-type core has been synthesized and fully characterized by X-ray diffraction, UV-vis spectroscopy, and electron paramagnetic resonance spectroscopy. Interestingly, the cubane-type cobalt cluster 1 with 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins, including terminal olefins which are more challenging targeting substrates. Moreover, this catalytic system showed a fast reaction rate and high epoxide yields under mild conditions. Based on product analysis and Hammett studies, the use of peroxyphenylacetic acid as a mechanistic probe, H218O-exchange experiments, and EPR studies, it has been proposed that multiple reactive cobalt-oxo species CoVO and CoIVO were involved in the olefin epoxidation.
- Lee, Sun Young,Kim, Namseok,Lee, Myoung Mi,Jo, Young Dan,Bae, Jeong Mi,Hyun, Min Young,Yoon, Sungho,Kim, Cheal
-
p. 1727 - 1736
(2016/01/30)
-
- Synthesis, characterization, crystal structure determination and catalytic activity in epoxidation reaction of two new oxidovanadium(IV) Schiff base complexes
-
The five coordinated vanadium(IV) Schiff base complexes of VOL1 (1) and VOL2 (2), HL1?=?2-{(E)-[2-bromoethyl)imino]methyl}-2- naphthol, HL2?=?2-{(E)-[2-chloroethyl)imino]methyl}-2- naphthol, have been synthesized and they were characterized by using single-crystal X-ray crystallography, elemental analysis (CHN) and FT-IR spectroscopy. Crystal structure determination of these complexes shows that the Schiff base ligands (L1 and L2) act as bidentate ligands with two phenolato oxygen atoms and two imine nitrogen atoms in the trans geometry. The coordination geometry around the vanadium(IV) is distorted square pyramidal in which vanadium(IV) is coordinated by two nitrogen and two oxygen atoms of two independent ligands in the basal plane and by one oxygen atom in the apical position. The catalytic activity of the Schiff base complexes of 1 and 2 in the epoxidation of alkenes were investigated using different reaction parameters such as solvent effect, oxidant, alkene/oxidant ratio and the catalyst amount. The results showed that in the presence of TBHP as oxidant in 1: 4 and 1:3 ratio of the cyclooctene/oxidant ratio, high epoxide yield was obtained for 1 (76%) and 2 (80%) with TON(= mole of substrate/mole of catalyst) of 27 and 28.5, respectively, in epoxidation of cyclooctene.
- Tahmasebi, Vida,Grivani, Gholamhossein,Bruno, Giuseppe
-
p. 367 - 374
(2016/07/07)
-
- Formal synthesis of tetrahydrolipstatin and tetrahydroesterastin
-
A versatile and efficient approach to (3S,5R)-methyl 3-(benzyloxy)-5- (methoxymethoxy)hexadecanoate, a key chiral building block and a common polyol fragment of the anti-tumor and anti-obesity agents tetrahydrolipstatin 3 and tetrahydroesterastin 4 using both hydrolytic kinetic resolution (HKR) and proline catalyzed sequential α-aminoxylation, followed by HWE-olefination reaction is described.
- Tripathi, Divya,Kumar, Pradeep
-
experimental part
p. 884 - 890
(2012/09/21)
-
- Terminal and internal olefin epoxidation with cobalt(II) as the catalyst: Evidence for an active oxidant CoII-acylperoxo species
-
A simple catalytic system that uses commercially available cobalt(II) perchlorate as the catalyst and 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins with high product selectivity under mild experimental conditions. More challenging targets such as terminal aliphatic olefins were also efficiently and selectively oxidized to the corresponding epoxides. This catalytic system features a nearly nonradical-type and highly stereospecific epoxidation of aliphatic olefin, fast conversion, and high yields. Olefin epoxidation by this catalytic system is proposed to involve a new reactive CoII-OOC(O)R species, based on evidence from H218O-exchange experiments, the use of peroxyphenylacetic acid as a mechanistic probe, reactivity and Hammett studies, EPR, and ESI-mass spectrometric investigation. However, the O-O bond of a CoII-acylperoxo intermediate (CoII-OOC(O)R) was found to be cleaved both heterolytically and homolytically if there is no substrate.
- Hyun, Min Young,Kim, Soo Hyun,Song, Young Joo,Lee, Hong Gyu,Jo, Young Dan,Kim, Jin Hoon,Hwang, In Hong,Noh, Jin Young,Kang, Juhye,Kim, Cheal
-
p. 7307 - 7312
(2012/11/07)
-
- Synthesis and biological investigation of the β-thiolactone and β-lactam analogs of tetrahydrolipstatin
-
The synthesis of β-thiolactone and β-lactam analogs of tetrahydrolipstatin is described from a common late-stage β-lactone derivative. These analogs, and a cis-disubstituted β-lactone analog of tetrahydrolipstatin, were screened for activity against porcine pancreatic lipase and for inhibition of cell growth of a panel of four human cancer lines. The Royal Society of Chemistry 2012.
- Aubry, Sylvain,Aubert, Genevieve,Cresteil, Thierry,Crich, David
-
p. 2629 - 2632
(2012/04/23)
-
- S-Methylidene agents: preparation of chiral non-racemic heterocycles
-
Reaction of sulfur ylide with aldehyde, imine, and ketone functionality affords the desired three-membered heterocycle in excellent yield. The sulfur ylide is generated in situ upon decarboxylation of carboxymethylsulfonium betaine functionality. Of the seven carboxymethylsulfonium betaine derivatives surveyed, the highest level of conversion of π-acceptor to heterocycle was obtained with the one having S-methyl and S-phenyl functionality bound to a thioacetate derivative. Methylene aziridinations and epoxidations involving the decarboxylation of carboxymethylsulfonium betaine functionality complements existing technologies with the advantages of the reaction protocol, levels of conversion, and scope. While moderate levels of diastereocontrol were observed in the aziridination of imine functionality, the four oxiranes resolved using Jacobsen's Co(II)-salen complex were obtained in both high yield and enantioselectivity. The isolated chiral non-racemic oxiranes constitute the formal synthesis of chelonin B and combretastatin starting from 3-bromo-4-methoxybenzaldehyde and 3,4,5-trimethoxybenzaldehyde, respectively.
- Forbes, David C.,Bettigeri, Sampada V.,Patrawala, Samit A.,Pischek, Susanna C.,Standen, Michael C.
-
supporting information; experimental part
p. 70 - 76
(2009/04/06)
-
- A simple and effective catalytic system for epoxidation of aliphatic terminal alkenes with manganese(II) as the catalyst
-
A simple catalytic system that uses commercially available manganese(II) Perchlorate as the catalyst and peracetic acid as the oxidant is found to be very effective in the epoxidation of aliphatic terminal alkenes with high product selectivity at ambient temperature. Many terminal alkenes are epoxidised efficiently on a gram scale in less than an hour to give excellent yields of isolated product (>90%) of epoxides in high purity. Kinetic studies with some C9-alkenes show that the catalytic system is more efficient in epoxidising terminal alkenes than internal alkenes, which is contrary to most commonly known epoxidation systems. The reaction rate for epoxidation decreases in the order: 1-nonene>cis-3-nonene> trans-3-nonene. ESI-MS and EPR spectroscopic studies suggest that the active form of the catalyst is a high-valent oligonuclear manganese species, which probably functions as the oxygen atomtransfer agent in the epoxidation reaction.
- Ho, Kam-Piu,Wong, Wing-Leung,Lam, Kin-Ming,Lai, Cheuk-Piu,Chan, Tak Hang,Wong, Kwok-Yin
-
experimental part
p. 7988 - 7996
(2009/11/30)
-
- Stereochemistry of Δ4 dehydrogenation catalyzed by an ivy (Hedera helix) Δ9 desaturase homolog
-
The stereochemistry of palmitoyl-ACP Δ4 desaturase-mediated dehydrogenation has been examined by tracking the fate of deuterium atoms located on stereospecifically monodeuterated substrates-(4S)- and (4R)-[4-2H1]-palmitoyl-ACP and (5S)- and (5R)-[5- 2H1]-palmitoyl-ACP. It was found that the introduction of the (Z)-double bond between C-4 and C-5 of a palmitoyl substrate occurs with pro-R enantioselectivity - a result which matches that obtained for a closely related homolog-castor stearoyl-ACP Δ9 desaturase. These data show that despite the difference in regioselectivity between the two enzymes, the stereochemistry of hydrogen removal is conserved. The Royal Society of Chemistry.
- Tremblay, Amy E.,Whittle, Edward,Buist, Peter H.,Shanklin, John
-
p. 1270 - 1275
(2008/02/02)
-
- (Z,Z)-4,7-tridecadien-(S)-2-YL acetate: Sex pheromone of Douglas-fir cone gall midge, Contarinia oregonensis
-
Our objectives were to identify and field test the sex pheromone of female Douglas-fir cone gall midge, Contarinia oregonensis (Diptera: Cecidomyiidae). Coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses of pheromone extract revealed a single compound (A) that elicited responses from male antennae. Hydrogenation of pheromone extract, followed by renewed GC-EAD analysis, revealed a new EAD-active compound with chromatographic characteristics identical to those of tridecan-2-yl acetate on five fused silica columns (DB-5, DB-210, DB-23, SP-1000, and Cyclodex-B). Syntheses, chromatography, and retention index calculations of all possible tridecen-2-yl acetates suggested that the candidate pheromone A was a tridecadien-2-yl acetate with nonconjugated double bonds. Synthetic candidate pheromone component (Z,Z)-4,7-tridecadien-2-yl acetate (Z4Z7) cochromatographed with A on all analytical columns and elicited comparable antennal activity. In GC-EAD analyses that separated the enantiomers (Z,Z)-4,7-tridecadien-(S)-2-yl acetate (2S-Z4Z7) and (Z,Z)-4,7-tridecadien-(R)-2-yl acetate (2R-Z4Z7) with baseline resolution, only 2S-Z4Z7 as a component in a racemic standard or in pheromone extract elicited antennal responses. In Douglas-fir seed orchards, sticky traps baited with 2S-Z4Z7 captured male C. oregonensis, whereas 2R-Z4Z7 was behaviorally benign. Comparable catches of males in traps baited with racemic Z4Z7 (50μg) or virgin female C. oregonensis suggested that synthetic pheromone baits could be developed for monitoring C. oregonensis populations in commercial Douglas-fir seed orchards.
- Gries, Regine,Khaskin, Grigori,Gries, Gerhard,Bennett, Robb G.,King, G.G. Skip,Morewood, Petra,Slessor, Keith N.,Morewood, W. Dean
-
p. 2283 - 2297
(2007/10/03)
-
- A practical enantioselective synthesis of (S)-3-hydroxytetradecanoic acid
-
(S)-3-Hydroxytetradecanoic acid 1 has been synthesized in an overall yield of 27% from (S)-epichlorohydrin 2 as follows: (1) regio and chemoselective epoxide opening of 2 with a Grignard reagent under the catalysis by Cu(I) followed by consecutive epoxide
- Matsuyama, Keisuke,Ikunaka, Masaya
-
p. 2945 - 2950
(2007/10/03)
-
- Polyaniline supported cobalt(II) catalyst: Oxidation of alkenes with molecular oxygen
-
Polyaniline supported Co(II) acetate catalyses the oxidation of different alkenes in the presence of 2-methylpropanol under the oxygen atmosphere at ambient temperature. This catalyst can be reused for epoxidations without any decline in its catalytic efficiency.
- Das, Bhaskar C,Iqbal, Javed
-
p. 1235 - 1238
(2007/10/03)
-
- Asymmetric synthesis of 5-hexadecanolide, pheromone of the queen of the Oriental hornet, Vespa orientalis
-
An efficient asymmetric synthesis of 5-hexadecanolide from a chiral epoxide is described. Both the enantiomeric forms of the chiral epoxide are easily available from mannitol and ascorbic acid. The key step in the synthesis is the formation of δ-lactone from δ-hydroxy acetal using m-CPBA and BF3-OEt2.
- Raina, Sushil,Singh, Vinod K.
-
p. 4479 - 4484
(2007/10/03)
-
- Reaction of diphenylsulfonium methylide with carbonyl compounds in non-basic media
-
Diphenylsulfonium methylide was formed by fluoride-induced desilylation of diphenyl[(trimethylsilyl)methyl]sulfonium triflate with cesium fluoride in dimethyl sulfoxide and allowed to react with carbonyl compounds in situ to give oxiranes.
- Hioki,Tani,Sato
-
p. 649 - 650
(2007/10/02)
-
- Chemoselective reduction of 2,3-epoxy tosylates with DIBAL-H as a general route to enantiomerically-enriched 1-tosyloxy-2-alkanols
-
2,3-Epoxy tosylates may be reduced with DIBAL-H in CH2Cl2 or ether at -40°C to 1-tosyloxy-2-alkanols in high (94-98%) yields.
- Michael Chong
-
p. 7197 - 7200
(2007/10/02)
-
- A simple synthesis of the queen substance of oriental hornet, Vespa orientalis from (R)-2,3-O-isopropylideneglycerol
-
(R)- and (S)-5-Hexadecanolides I have been synthesized in high optical purity using (R)-2,3-O-isopropylideneglycerol 1 as the chiral source.Stereoisomerization of 1,2-diol 3, Grignard coupling, regioselective Grignard reaction and oxidative cleavage of olefin are some of the key steps involved in it.
- Chattopadhyay, S.,Mamdapur, V. R.,Chadha, M. S.
-
p. 108 - 111
(2007/10/02)
-
- TWO POLYACETYLENIC PHYTOALEXINS FROM ARCTIUM LAPPA
-
Key Word Index-Arctium lappa; Compositae; burdock; stress metabolites; phytoalexins; polyacetylenes. Treatment of sliced burdock root tissue with copper (II) sulphate stimulated phytoalexin formation.Two were isolated and characterized as (S)-12,13-epoxy-2,4,6,8,10-tridecapentayne and 1-tridecen-3,5,7,9,11-pentayne by spectroscopic methods and some chemical transformations.
- Takasugi, Mitsuo,Kawashima, Shinji,Katsui, Nobukatsu,Shirata, Akira
-
p. 2957 - 2958
(2007/10/02)
-
- SYNTHESIS OF THE ENANTIOMERS OF 5-HEXADECANOLIDE, THE PHEROMONE OF THE QUEEN OF THE ORIENTAL HORNET, VESPA ORIENTALIS, EMPLOYING ENZYMIC RESOLUTION OF (+/-)-2-AMINOTRIDECANOIC ACID AS THE KEY-STEP
-
Optical resolution of (+/-)-2-chloroacetylaminotridecanoic acid with amino acylase gave (S)-2-aminotridecanoic acid, which was converted into highly optically pure (S)-5-hexadecanolide (the pheromone of Vespa orientalis).Similarly (R)-2-chloroacetylaminot
- Mori, Kenji,Otsuka, Tatsuya
-
p. 547 - 551
(2007/10/02)
-
- OPTICALLY PURE (S)-3-PHENYLTHIO-1,2-PROPANEDIOL: SYNTHESIS BY THE YEAST REDUCTION AND USE AS A PRECURSOR OF BOTH ENANTIOMERS OF SECONDARY ALCOHOLS
-
Optically pure (S)-3-phenylthio-1,2-propanediol was obtained by the enantioselective reduction of 1-hydroxy-3-phenylthio-2-propanone with the Baker's yeast, and was found to be a convenient precursor for both enantiomers of secondary alcohols, which was d
- Fujisawa, Tamotsu,Itoh, Toshiyuki,Nakai, Mikio,Sato, Toshio
-
p. 771 - 774
(2007/10/02)
-
- The Transition Metal Catalyzed Nucleophilic Epoxide Ring Opening Reaction
-
The catalytic influence of MoO2(acac)2, Mo(CO)6, MoCl5, WCl6 and TaCl5 on the reaction of 1,2-epoxy-octane with ethanol at 100 deg C in dioxan or chlorobenzene as solvents is proved.Water and hydroperoxides react with a higher rate than alcohols.When changing from primary to secondary and tertiary alcohols a decrease of the reaction rate is observed. 2,3- and 3,4-Epoxyheptane and cis- and trans-4,5-epoxy-octane react more slowly than the corresponding 1,2-epoxides.Epichlorhydrin and methylglycidether react with a lower, cyclohexene oxide, styrene oxide and norbornene oxide react with a higher rate than 1,2-epoxyoctane.The reactivities of the two dicyclopentadiene monoepoxides correspond with the reactivities of the norbornene and cyclopentene oxides.In the molybdenum catalyzed epoxide ring opening reaction an isomer distribution appears in favour of the 1-hydroxy-2-ethoxy-alkane 2.A mechanism in the coordination sphere of the transition metal complex is proposed.
- Lauterbach, G.,Posselt, G.,Schaefer, R.,Schnurpfeil, D.
-
p. 101 - 120
(2007/10/02)
-
- The Catalyzed Liquid-Phase Oxidation of Normal Alk-1-enes
-
The efficiencies of various homogeneous soluble transition metal compounds to increase epoxide yields in the autoxidation of alk-1-enes were studied.Combinations of typical autoxidation and typical epoxidation catalysts were also used.It was proved through balance experiments, that in no case yields of 50percent or more of the corresponding epoxides were obtained.The simple mechanism (epoxidation via allylic hydroperoxides) assumed only insufficiently reflects the reaction course.
- Barth, U.,Fiedler, H.,Gross, G.,Lauterbach, G.,Schnurpfeil, D.
-
p. 887 - 901
(2007/10/02)
-