- Synthesis of Terpineol from Alpha-Pinene Catalyzed by α-Hydroxy Acids
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We report the use of five alpha-hydroxy acids (citric, tartaric, mandelic, lactic and glycolic acids) as catalysts in the synthesis of terpineol from alpha-pinene. The study found that the hydration rate of pinene was slow when only catalyzed by alpha-hydroxyl acids. Ternary composite catalysts, composed of AHAs, phosphoric acid, and acetic acid, had a good catalytic performance. The reaction step was hydrolysis of the intermediate terpinyl acetate, which yielded terpineol. The optimal reaction conditions were as follows: alpha-pinene, acetic acid, water, citric acid, and phosphoric acid, at a mass ratio of 1:2.5:1:(0.1–0.05):0.05, a reaction temperature of 70? C, and a reaction time of 12–15 h. The conversion of alpha-pinene was 96%, the content of alpha-terpineol was 46.9%, and the selectivity of alpha-terpineol was 48.1%. In addition, the catalytic performance of monolayer graphene oxide and its composite catalyst with citric acid was studied, with acetic acid used as an additive.
- Hu, Yi-Ming,Huang, Xiao-Rui,Meng, Zhong-Lei,Qin, Rong-Xiu,Wen, Ru-Si,Zhou, Yong-Hong
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- Simple Plug-In Synthetic Step for the Synthesis of (?)-Camphor from Renewable Starting Materials
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Racemic camphor and isoborneol are readily available as industrial side products, whereas (1R)-camphor is available from natural sources. Optically pure (1S)-camphor, however, is much more difficult to obtain. The synthesis of racemic camphor from α-pinene proceeds via an intermediary racemic isobornyl ester, which is then hydrolyzed and oxidized to give camphor. We reasoned that enantioselective hydrolysis of isobornyl esters would give facile access to optically pure isoborneol and camphor isomers, respectively. While screening of a set of commercial lipases and esterases in the kinetic resolution of racemic monoterpenols did not lead to the identification of any enantioselective enzymes, the cephalosporin Esterase B from Burkholderia gladioli (EstB) and Esterase C (EstC) from Rhodococcus rhodochrous showed outstanding enantioselectivity (E>100) towards the butyryl esters of isoborneol, borneol and fenchol. The enantioselectivity was higher with increasing chain length of the acyl moiety of the substrate. The kinetic resolution of isobornyl butyrate can be easily integrated into the production of camphor from α-pinene and thus allows the facile synthesis of optically pure monoterpenols from a renewable side-product.
- Calderini, Elia,Drienovská, Ivana,Myrtollari, Kamela,Pressnig, Michaela,Sieber, Volker,Schwab, Helmut,Hofer, Michael,Kourist, Robert
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p. 2951 - 2956
(2021/06/18)
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- Synthesis and kinetic regularities of the thermal decomposition of new hydrotrioxides of cyclic alcohols
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Cyclic hydrotrioxides were synthesized by low-temperature (?78 °C) ozonolysis of a series of cyclic alcohols and identified using 1H NMR spectra. The kinetic regularities of the thermal decomposition of the synthesized hydrotrioxides were studied. The experimental proof of the induced decomposition of alcohol hydrotrioxides was obtained for the first time using cyclohexanol hydrotrioxide as an example. The influence of cyclic substituents on the thermal stability of the hydrotrioxides is shown.
- Grabovskiy,Khalitova,Fedorova,Lobov,Rol’nik,Kabal’nova
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p. 464 - 468
(2017/03/08)
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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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- Chiral β- and γ-aminoalcohols derived from (+)-camphor and (-)-fenchone as catalysts for the enantioselective addition of diethylzinc to benzaldehyde
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The addition of Me3SiCN and LiCH2CN to (+)-camphor and (-)-fenchone, respectively, followed by reduction leads to chiral β- and γ-aminoalcohols. The enantioselectivities realized using these aminoalcohols as ligands in the addition of Et2Zn to benzaldehyde were lower than those obtained using the corresponding δ-aminoalcohols.
- Dimitrov, Vladimir,Dobrikov, Georgi,Genov, Miroslav
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p. 1323 - 1329
(2007/10/03)
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- Synthesis and sweetness characteristics of L-aspartyl-D-alanine fenchyl esters
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Four isomers of the L-aspartyl-D-alanine fenchyl esters were prepared as potential peptide sweeteners. L-Aspartyl-D-alanine (+)-α-fenchyl ester and L-aspartyl-D-alanine (-)-β-fenchyl ester showed sweetness with potencies 250 and 160 times higher than that of sucrose, respectively. In contrast, L-aspartyl-D-alanine (+)-β-fenchyl ester and L-aspartyl-D-alanine (-)-α-fenchyl ester had the highest sweetness potencies at 5700 and 1100 times that of sucrose, respectively. In particular, L-aspartyl-D-alanine (-)-α-fenchyl ester had an excellent sweetness quality, but L-aspartyl-D-alanine (+)-β-fenchyl ester did not have an excellent quality of sweetness because it displayed an aftertaste caused by the strong sweetness.
- Yuasa,Nagakura,Tsuruta
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p. 5013 - 5018
(2007/10/03)
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- Preparation of chiral hydroxy carbonyl compounds and diols by ozonolysis of olefinic isoborneol and fenchol derivatives: Characterization of stable ozonides by 1H-, 13C-, and 17O-NMR and electrospray ionization mass spectrometry
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The allylic and homoallylic alcohols 1-8, prepared from (+)-camphor and (-)-fenchone, were ozonized in Et2O at -78°and treated with Et3N or LiAIH4 to give the chiral hydroxy carbonyl compounds 9-16 and the diols 17- 24, respectively (Scheme 1). In the case of the diols 19 and 24, the formation of new chiral centers proceeded with high diastercoselectivity. These diols were prepared highly diastereoselectively also by LiAIH4 reduction of the hydroxy carbonyl compounds 11 and 16a, respectively (Scheme 2). The absolute configuration of the new chiral centers in 19 and 24 was determined by X-ray and NMR methods. The ozonization of compounds 2, 3, 7, and 8 provided the relatively stable hydroxy-substituted 1,2,4-trioxolane derivatives (ozonides) 37-40 (Scheme 5) which were characterized by 1H- and 13C-NMR spectra, ESI-MS, and natural-abundance 17O-NMR spectra.
- Kostova, Kalina,Dimitrov, Vladimir,Simova, Svetlana,Hesse, Manfred
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p. 1385 - 1399
(2007/10/03)
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- Organic reactions in a solid matrix-VII sodium on alumina: A convenient reagent for reduction of ketones, esters and oximes
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Sodium dispersed on alumina is described and evaluated as a convenient off-the-shelf reagent (in a wax-coated form) for reduction of ketones, esters and oximes. While isopropanol is the preferred proton donor for the reduction of ketones and oximes, t-butanol is the alcohol of choice for the reduction of esters.
- Singh, Satendra,Dev, Sukh
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p. 10959 - 10964
(2007/10/02)
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- δ-Terpineol
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An improved and simple synthesis of crystalline δ-terpineol from β-pinene is reported.
- Bull, Steven D.,Carman, Raymond M.
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p. 2077 - 2081
(2007/10/02)
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- Synthesis of earthy-mouldy smelling compounds - II. Ethyl α and β-fenchols
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Several stereoselective routes to both ethyl α- and β- fenchols 1α and 1β are discussed. Direct addition of ethyllithium to fenchone was the best route to 1α whereas obtention of 1β was achieved through the highly stereoselective retroethylnylation of a mixture of ethynyl α- and β-fenchols 4α and 4β.
- Gosselin,Joulain,Laurin,Rouessac
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p. 3151 - 3154
(2007/10/02)
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- High potency dipeptide sweeteners. 1. L-aspartyl-D-phenylglycine esters
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Twenty esters of L-aspartyl-D-phenylglycine, as well as two substituted analogues, an o-fluoro and a p-hydroxyphenylglycine ester, were prepared. The L-aspartyl-D-phenylglycine (-)-α- and (+)-β-fenchyl esters had the highest sweetness potency at 1200 and 3700 times that of sucrose, respectively. The high potency of these sweeteners is surprising as the phenyl group occupies a position previously believed to accommodate only much smaller groups.
- Janusz,Gardklik,Young,Burkes,Stoll,Estelle,Riley
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p. 1052 - 1061
(2007/10/02)
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- Endo-Selectivity and Kinetic Control in Alkali Metal-NH3-NH4(1+) Reductions of Bicycloheptan-2-ones
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Reduction of five bicycloheptan-2-ones (6), (9), (12), (15), (18) and the parent bicyclohept-5-en-2-one (21) by alkali metals dissolving in NH3 and a cosolvent saturated with NH4Cl affords in every case predominantly (83 -> 99percent) the corresponding endo-alcohol (7), (10), (13), (16), (19), and (22), and since two of these endo-alcohols are the thermodynamically more stable and two the less stable isomers, these reductions are probably all kinetically controlled; a correlation is made between this endo-selectivity and exo-hydrogen-exchange in the ketones (6), (9), (12), (15), and (21).
- Rautenstrauch, Valentin
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p. 1558 - 1560
(2007/10/02)
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- MECHANISM OF THE γ-RADIOLYSIS OF 2-PROPANOL SOLUTIONS OF CYCLOHEXANONES
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The γ-radiolysis of 2-propanol solutions of cyclohexanone gives mainly hydrogen, acetone, pinacol, methane derived from 2-propanol, and cyclohexanol, 2-(2-cyclohexanonyl)-cyclohexanone, and 3-(2-hydroxy-2-propyl)cyclohexanone derived from cyclohexanone.The radiolytic yields of all these products were highly dependent on the initial cyclohexanone concentration.The formation of cyclic alcohols by radioreduction has been extended to various substituted cyclohexanones.Radiolytically generated solvated electrons are scavenged by cyclohexanone, leading to the corresponding radical anions.The protonation of these radical anions gives rise to cyclohexanol via the dismutation of the hydroxycyclohexyl radicals.Steady state radiolysis measurements were complemented by pulse radiolysis in dilute solution.It was established that radical-anions and hydroxylated radicals decayed according to a second order rate law.When ketone concentration was lower than 0.1M, radiolytic yields were in agreement with the mechanism mentioned above.However, in concentrated media the large increase in G(cyclohexanol) cannot be only accounted for by the involvement of radiolytically generated solvated electrons; probably it is due to an electron transfer from the cyclohexanone enolate to cyclohexanone itself, thus generating extra amounts of cyclohexanone radical anions.
- Alipour, E.,Vidril, D.,Micheau, J. C.,Paillous, N.,Lattes, A.,et al.
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p. 2807 - 2814
(2007/10/02)
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- TERPENE AMINES. IV. SYNTHESIS AND STUDY OF THE STRUCTURE OF AMINES FROM d-FENCHONE
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The reductive amination of d-fenchone by aliphatic nitriles has been studied.A probable reaction pathway is suggested, and the stereochemical composition of the products has been determined.It has been established with the aid of 13C NMR that reaction forms a mixture of isomeric optically active N-alkyl-1,2,3-trimethylbicyclohept-2-ylamines with a 3:1 ratio of endo and exo isomers.The absolute configurations of the amines synthesized have been determined.
- Kozlov, N. G.,Kalechits, G. V.,Vyalimyae, T. K.
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p. 451 - 454
(2007/10/02)
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- Natural and Magnetic Circular Dichroism Soectra of Selenofenchone. Evidence for a Singlet-Triplet Component of the n -> ?* Transition of Selenoketones
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Blue (-)-selenofenchone (1) is observed to give a negative long-wavelength Cotton effect (CE) Δε573max = -0.86, in addition to a series of CE's down to 190 nm, Δε270max = -5.21, Δε232max = +4.90, in its circular dichroism (CD) spectrum measured in n-heptane.The long-wavelength CD (573 nm) and UV (625 nm) λmax of 1 are found surprisingly well separated.Support for the singlet-triplet nature of this electronic transition may be found in a sharp positive magnetic CD band centered near 630 nm in (+/-)-selenofenchone.The CD and UV data are compared with those of thiofenchone (2) and fenchone (3).
- Wijekoon, W. M. Donald,Bunnenberg, Edward,Records, Ruth,Lightner, David A.
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p. 3034 - 3037
(2007/10/02)
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