- Alkylation of acylmetalates with alkyl halides to prepare Fischer carbene complexes: An improved protocol
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Alkoxy Fischer carbene complexes have been synthesized by alkylation of lithium acylmetalates with alkyl halides in the presence of catalytic amount (5-10 mol %) of n-tetrabutylammonium bromide (n-Bu4NBr) restricting the temperature below 55 °C to minimize decomposition of the product. The reaction occurs in a biphasic condition involving water and alkyl halide. The effect of cesium on this alkylation reaction has been studied. The presence of a radical quencher, di-tert-butyl phenol, neither affects the yield nor leads to the formation of dimer of di-tert-butyl phenol, which rules out the possibility of radical pathway mechanism. The kinetic study and the 1H NMR spectra of products suggest an SN2 pathway particularly involving alkyl halides.
- Nandi, Bappaditya,Sinha, Surajit
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- Biotransformation of (-)-menthone by human liver microsomes
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The aim of the current study was to investigate the metabolism of (-)-menthone by liver microsomes of humans. (-)-Menthone (1) was metabolized to (+)-neomenthol (2) (3-reduction) and 7-hydroxymenthone (3) by human liver microsomes. The metabolites formed were analyzed on GC and GC-MS. Kinetic analysis showed that Km and Vmax values for the metabolized (-)-menthone to respective (+)-neomenthol and 7-hydroxymenthone by liver microsomes of human sample HG70 were 0.37 mM and 4.91 nmol/min/mg protein and 0.07 mM and 0.71 nmol/min/mg protein.
- Miyazawa, Mitsuo,Nakanishi, Kyousuke
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- Revision of the stereochemistry of elisabethatriene, a putative biosynthetic intermediate of pseudopterosins
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In the past, we have questioned the accuracy of the stereochemistry of elisabethatriene, a putative biosynthetic intermediate of pseudopterosins, in light of the configuration of elisabethatrienol isolated from Pseudopterogorgia elisabethae, which was represented as 1S,4R,9S,11S. We have reinvestigated the stereochemistry of elisabethatriene. Elisabethatriene with the reported 1S,4R,9R,11S configuration was synthesized starting from (-)-isopulegol in its enantiomeric form. The 1H- and 13C-NMR data of the synthesized compound differed from those reported for elisabethatriene. In addition to the fact that elisabethatriene is converted into pseudopterosins, this finding has allowed us to propose that elisabethatriene should have the 1S,4R,9S,11S stereochemistry, which is identical to that of elisabethatrienol.
- Nasuda, Masayuki,Ohmori, Miho,Ohyama, Kiyoshi,Fujimoto, Yoshinori
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- Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
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One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
- Er?nen, Kari,M?ki-Arvela, P?ivi,Martinez-Klimov, Mark,Muller, Joseph,Murzin, Dmitry Yu.,Peurla, Markus,Simakova, Irina,Vajglova, Zuzana
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- Heterogeneous Hydroxyl-Directed Hydrogenation: Control of Diastereoselectivity through Bimetallic Surface Composition
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Directed hydrogenation, in which product selectivity is dictated by the binding of an ancillary directing group on the substrate to the catalyst, is typically catalyzed by homogeneous Rh and Ir complexes. No heterogeneous catalyst has been able to achieve equivalently high directivity due to a lack of control over substrate binding orientation at the catalyst surface. In this work, we demonstrate that Pd-Cu bimetallic nanoparticles with both Pd and Cu atoms distributed across the surface are capable of high conversion and diastereoselectivity in the hydroxyl-directed hydrogenation reaction of terpinen-4-ol. We postulate that the OH directing group adsorbs to the more oxophilic Cu atom while the olefin and hydrogen bind to adjacent Pd atoms, thus enabling selective delivery of hydrogen to the olefin from the same face as the directing group with a 16:1 diastereomeric ratio.
- Shumski, Alexander J.,Swann, William A.,Escorcia, Nicole J.,Li, Christina W.
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p. 6128 - 6134
(2021/05/29)
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- Preparation of Neutral trans - Cis [Ru(O2CR)2P2(NN)], Cationic [Ru(O2CR)P2(NN)](O2CR) and Pincer [Ru(O2CR)(CNN)P2] (P = PPh3, P2= diphosphine) Carboxylate Complexes and their Application in the Catalytic Carbonyl Compounds Reduction
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The diacetate complexes trans-[Ru(κ1-OAc)2(PPh3)2(NN)] (NN = ethylenediamine (en) (1), 2-(aminomethyl)pyridine (ampy) (2), 2-(aminomethyl)pyrimidine (ampyrim) (3)) have been isolated in 76-88% yield by reaction of [Ru(κ2-OAc)2(PPh3)2] with the corresponding nitrogen ligands. The ampy-type derivatives 2 and 3 undergo isomerization to the thermodynamically most stable cationic complexes [Ru(κ1-OAc)(PPh3)2(NN)]OAc (2a and 3a) and cis-[Ru(κ1-OAc)2(PPh3)2(NN)] (2b and 3b) in methanol at RT. The trans-[Ru(κ1-OAc)2(P2)2] (P2 = dppm (4), dppe (5)) compounds have been synthesized from [Ru(κ2-OAc)2(PPh3)2] by reaction with the suitable diphosphine in toluene at 95 °C. The complex cis-[Ru(κ1-OAc)2(dppm)(ampy)](6) has been obtained from [Ru(κ2-OAc)2(PPh3)2] and dppm in toluene at reflux and reaction with ampy. The derivatives trans-[Ru(κ1-OAc)2P2(NN)] (7-16; NN = en, ampy, ampyrim, 8-aminoquinoline; P2 = dppp, dppb, dppf, (R)-BINAP) can be easily synthesized from [Ru(κ2-OAc)2(PPh3)2] with a diphosphine and treatment with the NN ligands at RT. Alternatively these compounds have been prepared from trans-[Ru(OAc)2(PPh3)2(NN)] by reaction with the diphosphine in MEK at 50 °C. The use of (R)-BINAP affords trans-[Ru(κ1-OAc)2((R)-BINAP)(NN)] (NN = ampy (11), ampyrim (15)) isolated as single stereoisomers. Treatment of the ampy-type complexes 8-15 with methanol at RT leads to isomerization to the cationic derivatives [Ru(κ2-OAc)P2(NN)]OAc (8a-15a; NN = ampy, ampyrim; P2 = dppp, dppb, dppf, (R)-BINAP). Similarly to 2, the dipivalate trans-[Ru(κ1-OPiv)2(PPh3)2(ampy)] (18) is prepared from [Ru(κ2-OPiv)2(PPh3)2] (17) and ampy in CHCl3. The pincer acetate [Ru(κ1-OAc)(CNNOMe)(PPh3)2] (19) has been synthesized from [Ru(κ2-OAc)2(PPh3)2] and HCNNOMe ligand in 2-propanol with NEt3 at reflux. In addition, the dppb pincer complexes [Ru(κ1-OAc)(CNN)(dppb)] (CNN = AMTP (20), AMBQPh (21)) have been obtained from [Ru(κ2-OAc)2(PPh3)2], dppb, and HAMTP or HAMBQPh with NEt3, respectively. The acetate NN and pincer complexes are active in transfer hydrogenation with 2-propanol and hydrogenation with H2 of carbonyl compounds at S/C values of up to 10000 and with TOF values of up to 160000 h-1.
- Baldino, Salvatore,Giboulot, Steven,Lovison, Denise,Nedden, Hans Günter,P?thig, Alexander,Zanotti-Gerosa, Antonio,Zuccaccia, Daniele,Ballico, Maurizio,Baratta, Walter
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p. 1086 - 1103
(2021/05/06)
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- Synthesis of new mixed (-)-menthylalkyltin dihydrides. stereoselective reduction of chiral and prochiral ketones
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This paper reports de synthesis of a series of (-)-menthylalkyltin dihydrides, (-)-MenRSnH2 (R = Me, n-Bu, i-Pr, t-Bu, Neophyl), starting from (-)-menthyltrimethyltin. The new (-)-menthylalkyltin dihydrides 12–16 were used in a study on the stereoselective reduction of chiral (-)-menthone under different reaction conditions. Also the results obtained in the reductions of prochiral acetophenone (27) and 2-acetylnaphthalene (28), with (-)-menthylmethyl- (12) and (-)-menthyli-propyltin (14) dihydrides are informed. Some physical properties as well as full 1H-, 13C-, and 119Sn NMR data of the new organotin compounds are informed.
- Terraza, V. Fabricio,Gerbino, Darío C.,Podestá, Julio C.
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- Continuous flow synthesis of menthol: Via tandem cyclisation-hydrogenation of citronellal catalysed by scrap catalytic converters
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A continuous flow synthesis of menthol starting from citronellal catalysed by scrap catalytic converters is reported. The reaction was conducted in a tandem system connecting in series two catalytic systems, with the first having Lewis acid properties (favouring the cyclisation of citronellal to isopulegols) and the second having hydrogenation catalytic activity (catalysing the hydrogenation of isopulegols to menthols). A Lewis acid catalyst was prepared by supporting iron oxide nanoparticles over a waste material, i.e. the ceramic core of scrap catalytic converters (SCATs) via a microwave assisted method. Most importantly, SCATs, containing a low residual noble metal content, could be directly employed in the second step as hydrogenation catalysts. The reaction was performed studying the influence on the yield and selectivity to (-)-menthol of various reaction parameters (T, p and flow rate). Under the best reaction conditions (at a flow rate of 0.1 mL min-1 and at 373 K and 413 K for cyclisation and hydrogenation steps respectively) a conversion of >99% of (+)-citronellal to (-)-menthol with 77% final yield was achieved.
- Zuliani, Alessio,Cova, Camilla Maria,Manno, Roberta,Sebastian, Victor,Romero, Antonio A.,Luque, Rafael
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p. 379 - 387
(2020/02/13)
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- Chemoselective Oxidation of Equatorial Alcohols with N-Ligated λ3-Iodanes
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The site-selective and chemoselective functionalization of alcohols in complex polyols remains a formidable synthetic challenge. Whereas significant advancements have been made in selective derivatization at the oxygen center, chemoselective oxidation to the corresponding carbonyls is less developed. In cyclic systems, whereas the selective oxidation of axial alcohols is well known, a complementary equatorial selective process has not yet been reported. Herein we report the utility of nitrogen-ligated (bis)cationic λ3-iodanes (N-HVIs) for alcohol oxidation and their unprecedented levels of selectivity for the oxidation of equatorial over axial alcohols. The conditions are mild, and the simple pyridine-ligated reagent (Py-HVI) is readily synthesized from commercial PhI(OAc)2 and can be either isolated or generated in situ. Conformational selectivity is demonstrated in both flexible 1,2-substituted cyclohexanols and rigid polyol scaffolds, providing chemists with a novel tool for chemoselective oxidation.
- Mikhael, Myriam,Adler, Sophia A.,Wengryniuk, Sarah E.
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supporting information
p. 5889 - 5893
(2019/08/26)
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- Flat and Efficient H CNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction
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The bidentate HCNN dicarbonyl ruthenium complexes trans,cis-[RuCl2(HCNN)(CO)2] (1-3) and trans,cis-[RuCl2(ampy)(CO)2] (1a) were prepared by reaction of [RuCl2(CO)2]n with 1-[6-(4′-methylphenyl)pyridin-2-yl]methanamine, benzo[h]quinoline (HCNN), and 2-(aminomethyl)pyridine (ampy) ligands. Alternatively, the derivatives 1-3 were obtained from the reaction of RuCl3 hydrate with HCO2H and HCNN. The pincer CNN cis-[RuCl(CNN)(CO)2] (4) was isolated from 1 by reaction with NEt3. The monocarbonyl complexes trans-[RuCl2(HCNN)(PPh3)(CO)] (5-7) were synthesized from [RuCl2(dmf)(PPh3)2(CO)] and HCNN ligands, while the diacetate trans-[Ru(OAc)2(HCNN)(PPh3)(CO)] (8) was obtained from [Ru(OAc)2(PPh3)2(CO)]. Carbonylation of cis-[RuCl(CNN)(PPh3)2] with CO afforded the pincer derivatives [RuCl(CNN)(PPh3)(CO)] (9-11). Treatment of 9 with Na[BArf]4 and PPh3 gave the cationic complex trans-[Ru(CNN)(PPh3)2(CO)][BArf4] (12). The dicarbonyl derivatives 1-4, in the presence of PPh3 or PCy3, and the monocarbonyl complexes 5-12 catalyzed the transfer hydrogenation (TH) of acetophenone (a) in 2-propanol at reflux (S/C = 1000-100000 and TOF up to 100000 h-1). Compounds 1-3, with PCy3, and 6 and 8-10 were proven to catalyze the TH of carbonyl compounds, including α,β-unsaturated aldehydes and bulky ketones (S/C and TOF up to 10000 and 100000 h-1, respectively). The derivatives 1-3 with PCy3 and 5 and 6 catalyzed the hydrogenation (HY) of a (H2, 30 bar) at 70 °C (S/C = 2000-10000). Complex 5 was active in the HY of diaryl ketones and aryl methyl ketones, leading to complete conversion at S/C = 10000.
- Giboulot, Steven,Baldino, Salvatore,Ballico, Maurizio,Figliolia, Rosario,P?thig, Alexander,Zhang, Shuanming,Zuccaccia, Daniele,Baratta, Walter
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p. 1127 - 1142
(2019/03/14)
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- Hydrogen Sulfide: A Reagent for pH-Driven Bioinspired 1,2-Diol Mono-deoxygenation and Carbonyl Reduction in Water
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Hydrogen sulfide (H2S) was evaluated for its peculiar sulfur radical species generated at different pHs and was used under photolytical conditions in aqueous medium for the reduction of 1,2-diols to alcohols. The conversion steps of 1,2-cyclopentanediol to cyclopentanol via cyclopentanone were analyzed, and it was proven that the reaction proceeds via a dual catalytic/radical chain mechanism. This approach was successfully adapted to the reduction of a variety of carbonyl compounds using H2S at pH 9 in water. This work opens up the field of environmental friendly synthetic processes using the pH-driven modulation of reactivity of this simple reagent in water.
- Barata-Vallejo, Sebastián,Ferreri, Carla,Golding, Bernard T.,Chatgilialoglu, Chryssostomos
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supporting information
p. 4290 - 4294
(2018/07/29)
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- 1-Hydrosilatrane: A Locomotive for Efficient Ketone Reductions
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An efficient method for the reduction of ketones with 1-hydrosilatrane is described. In the presence of a Lewis base activator, the resulting secondary alcohols are rapidly formed in good to excellent yields (20 examples, 71–99 % yields). The relative bulkiness of 1-hydrosilatrane also enables the diastereoselective reduction of (–)-menthone to (+)-neomenthol, and the use of a chiral alkoxide activator can lead to the enantioselective reduction of prochiral ketones.
- Varjosaari, Sami E.,Skrypai, Vladislav,Suating, Paolo,Hurley, Joseph J. M.,Gilbert, Thomas M.,Adler, Marc J.
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supporting information
p. 229 - 232
(2017/01/24)
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- COMPOSITIONS AND METHODS FOR REDUCTION OF KETONES, ALDEHYDES AND IMINIUMS, AND PRODUCTS PRODUCED THEREBY
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A method of producing an alcohol, comprises reducing an aldehyde or a ketone with a hydridosilatrane. The reducing is carried out with an activator.
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Paragraph 0091-0092
(2018/01/20)
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- BENZO[H]QUINOLINE LIGANDS AND COMPLEXES THEREOF
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The present invention provides substituted tridentate benzo[h]quinoline ligands and complexes thereof. The invention also provides the preparation of the ligands and the respective complexes, as well as to processes for using the complexes in catalytic reactions.
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Page/Page column 73-75
(2016/12/22)
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- A synthetic process of L-menthol
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The invention relates to the field of spice synthesis and particularly relates to a synthetic process of L-menthol. The process includes steps of d,l-menthol synthesizing, d,l-menthol rectification, d,l-menthol esterification, d,l-menthyl benzoate rectification, d,l-menthyl benzoate resolution, D-menthol synthesizing, menthol isomerization and L-menthol synthesizing. The process adopts thymol that is a simple, easily available and cheap chemical product as a raw material. Esterification conditions are optimized and the esterification and rectification are performed at the same time so as to allow the esterification to be converted into a way beneficial to d,l-menthyl benzoate production, thus increasing the esterification yield. Crystallization and resolution are optimized by utilization of the d,l-menthyl benzoate. Preparation of the L-menthol by the process is characterized by being high in yield, low in cost, simple and convenient in operation, suitable for continuous and large-scale production, and the like. According to the process, operation of the process is cyclic with a whole system being sealed, and the process is free of waste water, energy-saving and environmental friendly.
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Paragraph 0076; 0077; 0078
(2017/02/24)
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- Pinpointing a Mechanistic Switch Between Ketoreduction and “Ene” Reduction in Short-Chain Dehydrogenases/Reductases
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Three enzymes of the Mentha essential oil biosynthetic pathway are highly homologous, namely the ketoreductases (?)-menthone:(?)-menthol reductase and (?)-menthone:(+)-neomenthol reductase, and the “ene” reductase isopiperitenone reductase. We identified a rare catalytic residue substitution in the last two, and performed comparative crystal structure analyses and residue-swapping mutagenesis to investigate whether this determines the reaction outcome. The result was a complete loss of native activity and a switch between ene reduction and ketoreduction. This suggests the importance of a catalytic glutamate vs. tyrosine residue in determining the outcome of the reduction of α,β-unsaturated alkenes, due to the substrate occupying different binding conformations, and possibly also to the relative acidities of the two residues. This simple switch in mechanism by a single amino acid substitution could potentially generate a large number of de novo ene reductases.
- Lygidakis, Antonios,Karuppiah, Vijaykumar,Hoeven, Robin,Ní Cheallaigh, Aisling,Leys, David,Gardiner, John M.,Toogood, Helen S.,Scrutton, Nigel S.
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supporting information
p. 9596 - 9600
(2016/08/10)
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- Facile Protocol for Catalytic Frustrated Lewis Pair Hydrogenation and Reductive Deoxygenation of Ketones and Aldehydes
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A series of ketones and aldehydes are reduced in toluene under H2 in the presence of 5 mol % B(C6F5)3 and either cyclodextrin or molecular sieves affording a facile metal-free protocol for reduction to alcohols. Similar treatment of aryl ketones resulted in metal-free deoxygenation yielding aromatic hydrocarbons.
- Mahdi, Tayseer,Stephan, Douglas W.
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supporting information
p. 8511 - 8514
(2015/11/27)
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- P450-catalyzed regio- and stereoselective oxidative hydroxylation of disubstituted cyclohexanes: Creation of three centers of chirality in a single CH-activation event This paper is dedicated to the memory of Harry H. Wasserman
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Wild-type P450-BM3 is able to catalyze in a highly regio- and diastereoselective manner the oxidative hydroxylation of non-activated disubstituted cyclohexane derivatives lacking any functional groups, including cis- and trans-1,2-dimethylcyclohexane, cis- and trans-1,4-dimethylcyclohexane, and trans-1,4-methylisopropylcyclohexane. In all cases except chiral trans-1,2-dimethylcyclohexane as substrate, the single hydroxylation event at a methylene group induces desymmetrization with simultaneous creation of three centers of chirality. Certain mutants increase selectivity, setting the stage for future directed evolution work.
- Ilie, Adriana,Agudo, Rubén,Roiban, Gheorghe-Doru,Reetz, Manfred T.
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p. 470 - 475
(2015/02/02)
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- Selective ruthenium-catalyzed epimerization of chiral sec-alcohols
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Extension of secondary alcohol racemization catalyzed by homogeneous half-sandwich ruthenium complexes to the epimerization of natural products containing additional non-functionalized stereo-centers has been investigated. Ruthenium-catalysed epimerization of the sec-alcohols (-)-menthol, (-)-isopulegol, (+)-borneol, (+)-fenchol and cholesterol under mild reaction conditions and low catalyst loadings (2mol%) provides rapid access to their less abundant diastereoisomers (+)-neomenthol, (+)-neoisopulegol, isoborneol, beta-fenchol and epicholesterol in admixture with the parent diastereomers in ratios ranging from 1:4.9 to 1:2.4 (epimer:parent).
- L?ngvik, Otto,Mavrynsky, Denys,Leino, Reko
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p. 255 - 259
(2015/03/14)
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- Selective ruthenium-catalyzed epimerization of chiral sec-alcohols
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Extension of secondary alcohol racemization catalyzed by homogeneous half-sandwich ruthenium complexes to the epimerization of natural products containing additional non-functionalized stereo-centers has been investigated. Ruthenium-catalysed epimerization of the sec-alcohols (-)-menthol, (-)-isopulegol, (+)-borneol, (+)-fenchol and cholesterol under mild reaction conditions and low catalyst loadings (2 mol%) provides rapid access to their less abundant diastereoisomers (+)-neomenthol, (+)-neoisopulegol, isoborneol, beta-fenchol and epicholesterol in admixture with the parent diastereomers in ratios ranging from 1:4.9 to 1:2.4 (epimer:parent).
- L?ngvik, Otto,Mavrynsky, Denys,Leino, Reko
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p. 255 - 259
(2015/02/19)
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- Substrate flexibility and reaction specificity of tropinone reductase-like short-chain dehydrogenases
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Annotations of protein or gene sequences from large scale sequencing projects are based on protein size, characteristic binding motifs, and conserved catalytic amino acids, but biochemical functions are often uncertain. In the large family of short-chain dehydrogenases/reductases (SDRs), functional predictions often fail. Putative tropinone reductases, named tropinone reductase-like (TRL), are SDRs annotated in many genomes of organisms that do not contain tropane alkaloids. SDRs in vitro often accept several substrates complicating functional assignments. Cochlearia officinalis, a Brassicaceae, contains tropane alkaloids, in contrast to the closely related Arabidopsis thaliana. TRLs from Arabidopsis and the tropinone reductase isolated from Cochlearia (CoTR) were investigated for their catalytic capacity. In contrast to CoTR, none of the Arabidopsis TRLs reduced tropinone in vitro. NAD(H) and NADP(H) preferences were relaxed in two TRLs, and protein homology models revealed flexibility of amino acid residues in the active site allowing binding of both cofactors. TRLs reduced various carbonyl compounds, among them terpene ketones. The reduction was stereospecific for most of TRLs investigated, and the corresponding terpene alcohol oxidation was stereoselective. Carbonyl compounds that were identified to serve as substrates were applied for modeling pharmacophores of each TRL. A database of commercially available compounds was screened using the pharmacophores. Compounds identified as potential substrates were confirmed by turnover in vitro. Thus pharmacophores may contribute to better predictability of biochemical functions of SDR enzymes.
- Reinhardt, Nicole,Fischer, Juliane,Coppi, Ralph,Blum, Elke,Brandt, Wolfgang,Draeger, Birgit
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- PROCESS FOR THE PREPARATION OF MENTHOL
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The invention relates to a process for the preparation of 2-isopropyl-5-methylcyclohexanol (D,L-menthol) via the hydrogenation of thymol to menthone and subsequent further hydrogenation to give D,L-menthol.
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Paragraph 0085-0086
(2014/03/25)
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- PROCESS FOR THE PREPARATION OF MENTHOL
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The invention relates to a process for the preparation of 2-isopropyl-5-methylcyclohexanol (menthol) via the hydrogenation of thymol to neomenthol and the subsequent isomerization to give D/L (+/?)-menthol.
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Paragraph 0049-0053
(2014/03/25)
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- Highly practical iron-catalyzed C-O cleavage reactions
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Facile iron-catalyzed cleavage of various allyl, cinnamyl and benzyl C-O linkages has been effected in the presence of ethylmagnesium chloride. The protocol is operationally simple (xylene-THF, r.t., 1 h), requires low catalyst loading (1 mol% FeCl2) and tolerates halides, esters, amines, ethers and olefins. The allyl moiety is converted to volatile hydrocarbons which renders laborious product separation unnecessary.
- Gaertner, Dominik,Konnerth, Hannelore,Von Wangelin, Axel Jacobi
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p. 2541 - 2545
(2013/09/24)
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- Mitsunobu reaction with 4-(diphenylphosphino)benzoic acid: A separation-friendly bifunctional reagent that serves as both a reductant and a pronucleophile
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4-(Diphenylphosphino)benzoic acid was used for the Mitsunobu reaction as a bifunctional reagent that served as both a reductant and a pronucleophile. When combined with di-2-meth-oxyethyl azodicarboxylate, inversion of a secondary alcohol stereospecifically occurred to give an ester carrying a phosphine oxide group. The reaction mixture was directly hydrolyzed to give an inverted secondary alcohol in sufficient stereo and chemical purities by the presently developed chromatography-free process in conjunction with basic extraction, drying, and concentration. Georg Thieme Verlag Stuttgart - New York.
- Muramoto, Natsuko,Yoshino, Kazuki,Misaki, Tomonori,Sugimura, Takashi
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p. 931 - 935
(2013/05/21)
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- MCl2(ampy)(dppf) (M = Ru, Os): Multitasking catalysts for carbonyl compound/alcohol interconversion reactions
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The easily accessible complexes [MCl2(dppf)(ampy)] (M = Ru (cis-1), Os (trans-2); dppf = 1,1′-bis(diphenylphosphino)ferrocene; ampy = 2-aminomethylpyridine) in the presence of base (NaOiPr, KOtBu) are efficient catalysts for several reactions involving carbonyl compounds and alcohols. The derivatives 1 and 2 catalyze the selective transfer hydrogenation of aldehydes and ketones to alcohols with 2-propanol using 0.1-0.005 mol % of catalyst at 82 °C with TOF values up to 3.0 × 105 h-1. These compounds (0.1-0.02 mol %) promote the hydrogenation of aldehydes and ketones in EtOH or a MeOH/EtOH mixture at 30-90 °C (5 atm of H2) and the acceptorless dehydrogenation of alcohols to ketones in tBuOH at 130-145 °C (0.4 mol %). Complexes 1 and 2 (0.5 mol %) catalyze the racemization of chiral alcohols at 70 °C in 2-propanol and the isomerization of allylic alcohols to ketones in tBuOH at 70-120 °C (1 mol %). In addition, 1 and 2 (0.5 mol %) promote the α alkylation of α-tetralone with primary alcohols (EtOH, nPrOH, and nBuOH) at 120 °C in a tBuOH/toluene mixture (1/2 v/v). Complex 2 is easily obtained in 93% yield from [OsCl2(PPh3) 3], dppf, and ampy in toluene.
- Putignano, Elisabetta,Bossi, Gianluca,Rigo, Pierluigi,Baratta, Walter
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experimental part
p. 1133 - 1142
(2012/04/04)
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- MOFs as multifunctional catalysts: One-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst
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A bifunctional MOF catalyst containing coordinatively unsaturated Cr 3+ sites and palladium nanoparticles (Pd@MIL-101) has been used for the cyclization of citronellal to isopulegol and for the one-pot tandem isomerization/hydrogenation of citronellal to menthol. The MOF was found to be stable under the reaction conditions used, and the results obtained indicate that the performance of this bifunctional solid catalyst is comparable with other state-of-the-art materials for the tandem reaction: Full citronellal conversion was attained over Pd@MIL-101 in 18 h, with 86% selectivity to menthols and a diastereoselectivity of 81% to the desired (-)-menthol, while up to 30 h were necessary for attaining similar values over Ir/H-beta under analogous reaction conditions. The Royal Society of Chemistry 2012.
- Cirujano,Llabres I Xamena,Corma
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scheme or table
p. 4249 - 4254
(2012/05/07)
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- Bu4N[Fe(CO)3(NO)]-catalyzed hydrosilylation of aldehydes and ketones
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The nucleophilic Fe complex Bu4N[Fe(CO)3(NO)] (TBAFe) has been used as a highly active catalyst for the mild hydrosilylation of a variety of functionalized aldehydes and ketones using inexpensive PMHS as stoichiometric reductant. The corresponding alcohols were obtained in good-to-excellent yields at low catalyst loadings of only 1 mol-% and reaction temperatures of 30-50 °C.
- Dieskau, Andre P.,Begouin, Jeanne-Marie,Plietker, Bernd
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experimental part
p. 5291 - 5296
(2011/11/13)
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- One-step microwave-assisted asymmetric cyclisation/hydrogenation of citronellal to menthols using supported nanoparticles on mesoporous materials
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The selective conversion of citronellal to menthols, with good diastereoselectivities to (-)-menthol for the case of (+)-citronellal as starting material, can effectively be carried out in a one-step reaction under microwave irradiation catalysed by supported nanoparticles on mesoporous materials. 2% Pt/Ga-MCM-41 was found to be the optimum catalyst for the reaction, with a quantitative conversion of starting material and selectivities above 85% to menthols obtained in short reaction times (typically 15 min). These results constitute the first report of a simple microwave-assisted one-step cyclisation/hydrogenation process for the production of menthols.
- Balu, Alina Mariana,Campelo, Juan Manuel,Luque, Rafael,Romero, Antonio Angel
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experimental part
p. 2845 - 2849
(2010/08/21)
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- One-pot synthesis of menthol catalyzed by a highly diastereoselective Au/MgF2 catalyst
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No toxic compounds such as KCN and no thermal activation is required for the preparation of Au/MgF2 complexes by a simple and facile incipient wetness impregnation method in which hydrogen tetrachloroaurate (HAuCl 4) is the gold precursor. One of the complexes prepared exhibits unique catalytic properties and serves as a heterogeneous catalyst for the highly diastereoselective one-pot synthesis of (±)-menthol from citronellal (see picture).
- Negoi, Alina,Wuttke, Stefan,Kemnitz, Erhard,MacOvei, Dan,Parvulescu, Vasile I.,Teodorescu,Coman, Simona M.
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supporting information; experimental part
p. 8134 - 8138
(2011/02/24)
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- Hydrogen-transfer reduction of carbonyl compounds promoted by nickel nanoparticles
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Nickel(0) nanoparticles, generated from nickel(II) chloride, lithium powder and a catalytic amount of 4,4-di-tert-butylbiphenyl (DTBB) in THF at room temperature, have been found to promote the reduction of a variety of ketones and aldehydes by transfer hydrogenation using isopropanol as the hydrogen donor. The nickel nanoparticles were characterised and could be re-utilised with a good performance in the absence of a base. A mechanistic study demonstrates that the reaction proceeds through a dihydride-type mechanism.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
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p. 1847 - 1852
(2008/09/18)
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- Highly enantio- and s-trans C=C bond selective catalytic hydrogenation of cyclic enones: Alternative synthesis of (-)-menthol
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A highly enantioselective catalytic hydrogenation of cyclic enones was achieved by using the combination of a cationic Rh1 complex, (S)-5,5′-bis{di(3,5-di-tert-butyl-4-methoxyphenylphosphino)}-4, 4′-bi-1,3-benzodioxole (DTBM-SEGPHOS), and (CH2CH 2PPh3Br)2. The presence of an s-cis C=C bond isopropylidene moiety on the cyclic enone influenced the enantioselectivity of the hydrogenation. Thus, the hydrogenation of 3-alkyl-6-isopropylidene-2- cyclohexen-1-one, which contains both s-cis and s-trans enones, proceeded in excellent enantioselectivity (up to 98% ee). To obtain high enantio- and s-trans selectivities, the addition of a halogen source to the cationic Rh complex was the essential step. With the key step of the s-trans selective asymmetric hydrogenation of piperitenone, we demonstrated a new synthetic method for optically pure (-)-menthol via three atom-economical hydrogenations. Moreover, we found that the complete s-trans and s-cis C=C bond selective reactions were also realized by the proper choice of both the chiral ligands and halides.
- Ohshima, Takashi,Tadaoka, Hiroshi,Hori, Kiyoto,Sayo, Noboru,Mashima, Kazushi
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experimental part
p. 2060 - 2066
(2009/04/07)
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- Daucus carota and baker's yeast mediated bio-reduction of prochiral ketones
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Stereoselective reduction of prochiral ketones to the corresponding alcohols using biocatalysts has attracted much attention, from the viewpoint of green chemistry. Asymmetric reduction of indanone, tetralone and hydroxyl trimonoterpene ketones to the corresponding enantiomerically pure (S)-alcohols, using Daucus carota plant homogenate and fermented baker's yeast cells, is described. The present study illustrates the broad substrate selectivity of the dehydrogenase enzymes present in the D. carota in the synthesis of a wide range of chiral secondary alcohols of biological importance.
- Yadav, Jhillu S.,Reddy, Garudammagari S.K.K.,Sabitha, Gowravaram,Krishna, Avvaru D.,Prasad, Attaluri R.,Hafeez-U-R-Rahaman,Vishwaswar Rao, Katta,Bhaskar Rao, Adari
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p. 717 - 723
(2008/02/02)
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- Design of catalyst systems for the one-pot synthesis of menthols from citral
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Stable, active, and highly selective bifunctional Ni/Al-MCM-41 catalysts were developed for the one-pot synthesis of menthols from citral. The liquid-phase hydrogenation of citral to citronellal was studied on silica-supported noble (Pt, Pd, Ir) and nonnoble (Ni, Co, Cu) metals. It was found that citronellal is selectively formed at the beginning of the reaction only on Pd and Ni catalysts. The consecutive ene-cyclization of citronellal to isopulegols was investigated on solid acids containing exclusively Lewis (ZnO/SiO2) or strong Broensted (CsHPA) acid sites, and also on catalysts containing both Lewis and Broensted acid sites of either strong (zeolites, SiO2-Al2O3) or moderate (Al-MCM-41) strength. The isopulegol formation rate was higher on samples exhibiting dual Lewis/Broensted acidity, such as SiO2-Al2O3, Al-MCM-41, and zeolite HBEA. Based on these previous results, bifunctional catalysts containing Pd or Ni supported on SiO2-Al2O3, Al-MCM-41, or zeolite HBEA were prepared and tested for citral conversion to menthols. The catalyst stability and the effect of hydrogen pressure and metal loading on menthol productivity were also investigated. The best catalyst was Ni(8%)/Al-MCM-41, which yielded more than 90% menthols at 2026.0 kPa and showed no significant deactivation after two consecutive catalytic tests.
- Trasarti,Marchi,Apesteguia
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p. 155 - 165
(2008/02/03)
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- Carbonyl reduction with CaH2 and R3SiCl catalyzed by ZnCl2
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Ketones and aldehydes were effectively reduced to the corresponding alcohols (or their silyl ethers) by the reaction with CaH2 and R3SiCl in the presence of a catalytic amount of ZnCl2. In the absence of the carbonyl substrate, the reagent reduced R3SiCl to the corresponding hydrosilane under mild reaction conditions.
- Tsuhako, Akiko,He, Jing-Qian,Mihara, Mariko,Saino, Naoko,Okamoto, Sentaro
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p. 9120 - 9123
(2008/09/17)
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- 2-(Prenyloxymethyl)benzoyl (POMB) group: a new temporary protecting group removable by intramolecular cyclization
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2-(Prenyloxymethyl)benzoates can be prepared from alcohols and readily available 2-(prenyloxymethyl)benzoic acid by standard acylation techniques or by Mitsunobu reaction with inversion of configuration. The POMB group can be cleaved first by oxidative removal of the prenyl group with DDQ followed by lactonization with expulsion of the alcohol catalyzed by Yb(OTf)3. These reaction conditions are compatible with the presence of a large number of common protecting groups.
- Vatèle, Jean-Michel
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p. 10921 - 10929
(2008/02/12)
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- Domino-cyclisation and hydrogenation of citronellal to menthol over bifunctional Ni/Zr-Beta and Zr-beta/Ni-MCM-41 catalysts
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The one-pot conversion of (±)-citronellal to menthol can be selectively catalysed by either a bifunctional Ni/Zr-zeolite beta catalyst or a dual catalyst system of Zr-beta and Ni/MCM-41, giving a high diastereoselectivity to (±)-menthol of 90-94%. The Royal Society of Chemistry 2006.
- Nie, Yuntong,Chuah, Gaik-Khuan,Jaenicke, Stephan
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p. 790 - 792
(2008/02/03)
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- Pt/H-beta zeolites as productive bifunctional catalysts for the one-step citronellal-to-menthol conversion
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Pt-loaded H-beta zeolite was identified as a highly active catalyst for the bifunctional transformation of citronellal to menthol, with isopulegol as the intermediate. With a 2 wt% Pt-loaded catalyst, citronellal is fully converted within 12 h, with only 2.5 wt% catalyst with respect to citronellal, and with a citronellal to Pt molar ratio of 2500. 1, 4-Dioxane is the best reaction solvent, because it minimizes the unwanted direct hydrogenation of citronellal and promotes its stereoselective cyclization to isopulegol, leading to high menthol yields. The stereoselectivity can be improved moderately by using a Zr-impregnated support and more substantially by performing high-temperature (750 °C) treatment of the calcined and reduced catalyst. This treatment presumably creates extra Lewis acidity on the catalyst and results in 88% stereoselectivity for the desired menthol. Overall, an 85% yield of (-)-menthol was obtained.
- Mertens, Pascal,Verpoort, Francis,Parvulescu, Andrei-Nicolae,De Vos, Dirk
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- RUTHENIUM COMPLEXES, THEIR PREPARATION AND USE AS CATALYSTS
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The patent describes a novel class of ruthenium(II) complexes, containing a cyclometallated phosphine, which have been shown to be effective catalysts of the reduction reaction of ketones to alcohols through transfer hydrogenation. With such ruthenium complexes, using 2-propanol as a source of hydrogen, it is possible to obtain the corresponding alcohol starting from linear and cyclic diaryl, alkylaryl and dialkyl ketones, rapidly and with high yield. Using such complexes and starting from ketone compounds, the process for the production of various types of alcohols, which are important intermediates for the pharmaceutical, agrochemical and the fine chemical industries in general, is particularly convenient.
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Page/Page column 12-14
(2010/02/11)
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- Method of using a compound of menthol and L-arginine as a preparation for the topical delivery of alprostadil for the treatment of female sexual dysfunction
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A manual application of a topical clitoral sensitizing compound combination consisting og L-arginine and a cooling agent comprised of Menthol and aplrostadil, wherein the combination is applicable manually to the clitoris
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- Topical menthol, or a related cooling compound, to induce lubrication
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Vaginal Lubrication is an important component of a woman's sexual arousal. The other components are vaginal vasocongestion and the establishment of a clitoral erection. The use of menthol or any related cooling compound, topically applied to the clitoris, evokes a reflex vaginal lubrication, via the clitoral nociceptors, the spinal autonomic nerves, and inducing the reflex release of vasoactivepolypeptides adjacent to the vaginal arterioles. The vaginal lubrication can be an effective therapy for atrophic vaginitis, the most common cause of dyspareunia (pain with intercourse).
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- Methods to treat one or all of the defined etiologies of female sexual dysfunction
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The U.S. Food and Drug Administration defines the four separate components of Female Sexual Dysfunction (FSD) to be decreased sexual desire, decreased sexual arousal, dyspareunia (pain with intercourse), and persistent difficulty in achieving or inability to achieve orgasm (anorgasmia). To establish a diagnosis of FSD, these components must be associated with personal distress, as determined by the affected woman. A topical combination of menthol/L-arginine and the specific 5-PDE inhibitor vardenafil can be used to treat any of the defined components, or a combination of two or more of the defined components of FSD, as a safe, first-line therapy for FSD.
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- Stereoselective reduction of menthone by molecularly imprinted polymers
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Polymeric chiral reductants selective for the reduction of (-)-menthone 1 to the diastereomeric products (-)-menthol 2 and (+)-neomenthol 3 were prepared by a covalentmolecular imprinting using 2 as the template. The LiAlH4 derivatized imprinted polymers altered the natural outcome of the reduction reaction (LiAlH4) from 2:1 [(-)-menthol:(+)-neomenthol] to 1:1. The reaction mechanism is discussed in terms of reaction site structure. The molecularly imprinted polymers demonstrated enantioselective recognition for 2 (0.15μmol enantioselective sites/g polymer) in batch binding experiments.
- Hedin-Dahlstroem, Jimmy,Shoravi, Siamak,Wikman, Susanne,Nicholls, Ian A.
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p. 2431 - 2436
(2007/10/03)
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- METHOD FOR PRODUCING MENTHOL
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To the invention relates to a method for producing menthol by catalytically hydrogenating compounds, which comprise the carbon skeleton of methane having at least one double bond and which are substituted at the 3-position by oxygen, and/or by catalytically rearranging stereoisomers of methanol in the presence of hydrogen and doped nickel catalysts.
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Page/Page column 8-10
(2008/06/13)
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- Rate enhancement with a bowl-shaped phosphane in the rhodium-catalyzed hydrosilylation of ketones
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Up to 154-fold rate enhancement (see picture) and higher yields are achieved with the bowl-shaped triarylphosphane ligand P(tm-tp)3 compared with common phosphane ligands in Rh-catalyzed hydrosilylation of ketones. The superior performance of P(tm-tp)3 over the similar P(tp)3 is apparently related to the deeper bowl formed by the methyl-bearing terphenyl substituents in the former.
- Niyomura, Osamu,Tokunaga, Makoto,Obora, Yasushi,Iwasawa, Tetsuo,Tsuji, Yasushi
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p. 1287 - 1289
(2007/10/03)
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- Method for producing 1-menthol
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Provided is a method for the production of 1-menthol, which comprises hydrogenation of piperitenone with a transition metal complex of a specified optically active phosphine to produce pulegone, hydrogenation of the obtained pulegone with a ruthenium-phosphine-amine complex in the presence of base to obtain pulegol, and further hydrogenation of the pulegol with a transition metal catalyst.
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- Chiral aminoalcohols with a menthane skeleton as catalysts for the enantioselective addition of diethylzinc to benzaldehyde
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Novel chiral aminoalcohols were synthesized by highly diastereoselective addition of Me3SiCN and LiCH2CN to (-)-menthone followed by LiAlH4 reduction. The addition of CH2=CH-MgBr and PhCH=CH-MgBr to menthone and the following epoxidation, provided useful hydroxy epoxides, one of which could be aminolyzed to afford an aminodiol. In one case, the configuration of the newly formed epoxidic stereogenic center was determined by X-ray crystallography. When applied as catalysts in the enantioselective addition of Et2Zn to benzaldehyde, the aminoalcohols induced enantiomeric excesses (e.e.s) of up to 77%.
- Panev, Stefan,Linden, Anthony,Dimitrov, Vladimir
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p. 1313 - 1321
(2007/10/03)
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- Mapping the substrate selectivity of new hydrolases using colorimetric screening: Lipases from Bacillus thermocatenulatus and Ophiostoma piliferum, esterases from Pseudomonas fluorescens and Streptomyces diastatochromogenes
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Recent advances in biochemistry and molecular biology have simplified the discovery and preparation of new hydrolases. Although these hydrolases might solve problems in organic synthesis, measuring their selectivity, especially enantioselectivity, remains tedious and time consuming. Recently, we developed a colorimetric screening method to measure the enantioselectivity of hydrolases. Here we apply this rapid screening method to map the substrate selectivity of four new hydrolases: lipases from the thermophilic Bacillus thermocatenulatus (DSM 730, BTL2) and a filamentous fungus Ophiostoma piliferum (NRRL 18917, OPL) and esterases from two bacteria, Pseudomonas fluorescens (SIK-W1, esterase I, PFE) and Streptomyces diastatochromogenes (Tue 20, SDE). We screened a general library of 29 substrates and a chiral library of 23 pairs of enantiomers. All four hydrolases catalysed the hydrolysis of unnatural substrates, but the two lipases accepted a broader range of substrates than the two esterases. As expected, the two lipases favoured more hydrophobic substrates, while the two esterases showed a preference for smaller substrates. Several moderately enantioselective reactions were identified for the solketal esters: BTL2, butyrate, E = 7.9 (R); octanoate, E = 4.9 (R) and 3-bromo-2-methyl propionate methyl esters, PFE, E = 12 (S); SDE, E = 5.6 (S). OPL showed low enantioselectivity toward all substrates tested. The current colorimetric screen could not measure the selectivity for several slow-reacting substrates. Traditional screening identified high enantioselectivity of BTL2 and PFE toward one of these slow substrates, 1-phenylethyl acetate (E>50).
- Liu, Andrew Man Fai,Somers, Neil A.,Kazlauskas, Romas J.,Brush, Terry S.,Zocher, Frank,Enzelberger, Markus M.,Bornscheuer, Uwe T.,Horsman, Geoff P.,Mezzetti, Alessandra,Schmidt-Dannert, Claudia,Schmid, Rolf D.
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p. 545 - 556
(2007/10/03)
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- Preparation and use of sterically hindered organobis(2,4,6-triisopropylphenyl)hydroborates and their polystyrene derivatives for the diastereoselective reduction of ketones
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Preparations of benzyl and phenylbis(2,4,6-triisopropylphenyl)hydroborates [organoditripylhydroborates] are outlined. The lithium and potassium benzylditripylhydroborates reduce substituted cyclohexanones with diastereoselectivities comparable to those obtained with the most selective reagents known (eg. 99% cis-4-methylcyclohexanol from 4-methylcyclohexanone). Lithium phenylditripylhydroborate also reduces ketones with significant selectivity. For example, 4-methylcyclohexanone is reduced to cis-4-methylcyclohexanol in 88% isomeric purity. Unlike with most other highly selective reagents the reactions take place at room temperature and have the additional advantage that the boron reagent can be recovered quantitatively. Coupling of Merrifield's resin with ditripylfluoroborane in the presence of lithium naphthalenide affords (ditripylborylmethyl)polystyrene. Similarly, coupling of bromopolystyrene with ditripylfluoroborane in the presence of n-BuLi affords (ditripylboryl)polystyrene. Reactions of these polymeric organoboranes with t-BuLi give the corresponding polymer-supported lithium hydroborates. Lithium ditripylhydroboratylmethylpolystyrene reduces cyclic ketones in identical fashion to its non-polymeric counterpart, giving the corresponding thermodynamically less stable alcohols in 99% or better isomeric purity. Similarly, lithium ditripylhydroboratylpolystyrene behaves like its non-polymeric counterpart and reduces 4-methylcyclohexanone to cis-4-methylcyclohexanol in 89% isomeric purity. Recovery and reuse of the organoboranes are even easier for the polymeric reagents. The Royal Society of Chemistry 1999.
- Smith, Keith,El-Hiti, Gamal A.,Hou, Duanjie,DeBoos, Gareth A.
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p. 2807 - 2812
(2007/10/03)
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- Picolinic acid as a partner in the Mitsunobu reaction: Subsequent hydrolysis of picolinate esters under essentially neutral conditions with copper acetate in methanol
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The use of picolinic acid and 6-methyl picolinic acid in the Mitsunobu reaction has been studied. These substrates are excellent partners in the Mitsunobu reaction, and offer the added advantage that the resulting esters can be cleaved under essentially neutral conditions using Cu(OAc)2 and methanol.
- Sammakia, Tarek,Jacobs, Jon S.
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p. 2685 - 2688
(2007/10/03)
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