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Thioderivatives of Resorcin[4]arene and Pyrogallol[4]arene: Are Thiols Tolerated in the Self-Assembly Process?
Three novel thiol bearing resorcin[4]arene and pyrogallol[4]arene derivatives were synthesized. Their properties were studied with regards to self-assembly, disulfide chemistry, and Br?nsted acid catalysis. This work demonstrates that (1) one aromatic thiol on the resorcin[4]arene framework is tolerated in the self-assembly process to a hexameric hydrogen bond-based capsule, (2) thio-derivatized resorcin[4]arene analogs can be covalently linked through disulfides, and (3) the increased acidity of aromatic thio-substituent is not sufficient to replace HCl as cocatalyst for capsule catalyzed terpene cyclizations.
Nemat, Suren J.,Tiefenbacher, Konrad
supporting information
p. 6861 - 6865
(2021/09/14)

Preparation of α-terpineol and perillyl alcohol using zeolites beta
The preparation of α-terpineol by direct hydration of limonene catalyzed by zeolites beta was studied. The same catalyst was used to prepare perillyl alcohol by isomerization of β-pinene oxide in the presence of water. The aim was to optimize the reaction conditions to achieve high conversions of starting material and high selectivity to the desired products. In the case of limonene, it was found that the highest selectivity to α-terpineol was 88% with conversion of 36% under the conditions: 50?wt% of catalyst beta 25, 10% aqueous acetic acid (10?mL) (volume ratio limonene:H2O = 1:4.5), temperature 50?°C, after 24?h. In the case of β-pinene oxide, it was found that the highest selectivity to perillyl alcohol, which was 36% at total conversion, was obtained in the reaction under the following conditions: dimethyl?sulfoxide as solvent (volume ratio β-pinene oxide:DMSO = 1:5), catalyst beta 25 without calcination (15?wt%), demineralized water (molar ratio β-pinene oxide:H2O = 1:8), temperature 70?°C, 3?h. The present study shows that the studied reactions are suitable for the selective preparation of chosen compounds.
?erveny, Libor,Vysko?ilová, Eli?ka,Zítová, Kate?ina
p. 4297 - 4310
(2021/07/26)

Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization
This report discloses the deallylation of O - and N -allyl functional groups by using a combination of a Ni-H precatalyst and excess Bronsted acid. Key steps are the isomerization of the O - or N -allyl group through Ni-catalyzed double-bond migration followed by Bronsted acid induced O/N-C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.
Kathe, Prasad M.,Berkefeld, Andreas,Fleischer, Ivana
supporting information
p. 1629 - 1632
(2021/02/09)

Hydration of alpha-Pinene to obtain alpha-terpineol, using an ionic liquid as solvent, which is synthesized from a tertiary amine and an inorganic acid
An ionic liquid as a solvent in the hydration reaction of α-pinene to α-terpineol. The ionic liquid is obtained from the reaction of an amine and an inorganic acid. The use of the ionic liquid as solvent favors the selectivity towards the formation of α-terpineol and once the reaction product has been brought to room temperature, the organic phase can be physically separated from the inorganic one by decantation. The inorganic phase contains the ionic liquid, water and reaction catalyst and can be directly reused for a new reaction batch.
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(2021/06/11)

Preparation of α-Terpineol from Biomass Resource Catalysed by Acid Treated Montmorillonite K10
Abstract: A new type of heterogeneous catalyst for hydration of α-pinene was prepared. Montmorillonite K10 was treated by various acids (H2SO4, HCl, HNO3, and ClCH2COOH) and successfully used for the mentioned reaction. The used characterization techniques showed that the acid treatment improved the properties of K10 important for the catalytic activity (SBET and acidity). On the other hand, the morphology and particle size distribution remained the same. Regarding the selectivity (side and consecutive reactions can proceed), the optimal reaction conditions were found (temperature, type of the catalyst, amount of the catalyst, molar ratio α-pinene:?water, type of water, solvent). Using the optimal reaction conditions, 60% conversion of α-pinene was achieved with 45% selectivity to α-terpineol (80?°C, 25 wt% of K10/HCl, or K10/H2SO4, nα-pinene:nwater 1:7.5, 1,4-dioxane as a solvent, 24?h). Higher conversions of α-pinene, as well as higher selectivity to α-terpineol, were achieved using all acid treated K10 in comparison to raw K10. Considering the heterogeneous form of prepared catalysts, its availability, low price and easy method of preparation, these catalysts dispose of a large potential for application as catalysts for hydration reactions. Graphic Abstract: [Figure not available: see fulltext.].
Sekerová, Lada,?erná, Hana,Vysko?ilová, Eli?ka,Vrbková, Eva,?erveny, Libor
p. 2673 - 2683
(2021/01/15)

Coupling Reaction between Aldehydes and Non-Activated Hydrocarbons via the Reductive Radical-Polar Crossover Pathway
Herein, we describe the generation of an organochromium-type carbanion species from a non-activated C-H bond and its nucleophilic addition to aldehydes. The catalytic carbanion generation occurred through formal deprotonation of a non-activated C-H bond under mild conditions and did not need the prefunctionalization or anion stabilizing group. Carbon radical intermediates generated by decatungstate photocatalyst-mediated hydrogen abstraction were captured by a chromium salt with the reductive radical-polar crossover reaction to produce organochromium carbanions.
Yahata, Kenzo,Sakurai, Shu,Hori, Shuhei,Yoshioka, Shin,Kaneko, Yuki,Hasegawa, Kai,Akai, Shuji
supporting information
p. 1199 - 1203
(2020/02/04)

Requirements for Terpene Cyclizations inside the Supramolecular Resorcinarene Capsule: Bound Water and Its Protonation Determine the Catalytic Activity
The elucidation of the requirements for efficient catalysis within supramolecular host systems is an important prerequisite for developing novel supramolecular catalysts. The resorcinarene hexamer has recently been shown to be the first supramolecular catalyst to promote the tail-to-head terpene cyclization in a biomimetic fashion. We herein present the synthesis of a number of resorcinarene-based macrocycles composed of different ratios of resorcinol and pyrogallol units capable of self-assembly and compare the corresponding assemblies regarding their catalytic activity in the cyclization of monoterpenes. The assemblies were investigated in detail with respect to a number of properties including the encapsulation of substrate and ion pairs, the structural incorporation of water, and the response to externally added acid (HCl). The results obtained strongly indicate that water incorporated into the hydrogen-bond network of the self-assembled structure plays an integral role for catalysis, effectively acting as a proton shuttle to activate the encapsulated substrate. These findings are also supported by molecular dynamics simulations, providing further insight into the protonation pathway and the relative energies of the intermediates involved.
Merget, Severin,Catti, Lorenzo,Piccini, Giovannimaria,Tiefenbacher, Konrad
supporting information
p. 4400 - 4410
(2020/03/04)

Terpene Cyclizations inside a Supramolecular Catalyst: Leaving-Group-Controlled Product Selectivity and Mechanistic Studies
The tail-to-head terpene cyclization is arguably one of the most complex reactions found in nature. The hydrogen-bond-based resorcinarene capsule represents the first man-made enzyme-like catalyst that is capable of catalyzing this reaction. Based on noncovalent interactions between the capsule and the substrate, the product selectivity can be tuned by using different leaving groups. A detailed mechanistic investigation was performed to elucidate the reaction mechanism. For the cyclization of geranyl acetate, it was found that the cleavage of the leaving group is the rate-determining step. Furthermore, the studies revealed that trace amounts of acid are required as cocatalyst. A series of control experiments demonstrate that a synergistic interplay between the supramolecular capsule and the acid traces is required for catalytic activity.
Zhang, Qi,Catti, Lorenzo,Pleiss, Jürgen,Tiefenbacher, Konrad
supporting information
p. 11482 - 11492
(2017/08/30)

Sulfoxide-Chelated Ruthenium Benzylidene Catalyst: a Synthetic Study on the Utility of Olefin Metathesis
We provide an experimental summary of selected advances in olefin metathesis methodology that were reported over the past decades. A stable and universal sulfoxide-chelated ruthenium olefin metathesis catalyst [RuCl2(SIMes)(=CH?C6H4?S(O)Ph)], SIMes=1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene, was introduced and its application profile was studied in detail. A range of model substrates of natural origin was developed and successfully metathesized with variants of the reaction, such as ene–yne, cross, or ring-closing metathesis. All reported reactions were performed in non-pretreated solvents and in air to demonstrate the user-friendliness of the system. Besides the great functional group tolerance exhibited by the reported complex, its compatibility with multiple solvents was determined along with its air and moisture stability. Additionally, an interesting effect increasing the reaction efficiency was observed, if reactions were performed at temperatures around the solvent boiling point.
?ukowska, Karolina,P?czek, ?ukasz,Grela, Karol
p. 2817 - 2823
(2016/09/13)

Unravelling transition metal-catalyzed terpenic alcohol esterification: A straightforward process for the synthesis of fragrances
Iron nitrate is a simple and commercially available Lewis acid and is demonstrated to be able to catalyze β-citronellol esterification with acetic acid, achieving high conversion and ester selectivity (ca. 80 and 70%, respectively), within shorter reaction times than those reported in the literature. To the best of our knowledge, this is the first report of a terpenic alcohol esterification reaction catalyzed by Fe(NO3)3. This process is an attractive alternative to the slow and expensive enzymatic processes commonly used in terpenic alcohol esterification. Moreover, it avoids the undesirable steps of neutralizing the products, which are always required in mineral acid-catalyzed reactions. We have performed a study of the activity of different metal Lewis acid catalysts, and found that their efficiency is directly linked to the ability of the metal cation to generate H+ ions from acetic acid ionization. The measurement of pH as well as the conversions achieved in the reactions allowed us to obtain the following trend: Fe(NO3)3 > Al(NO3)3 > Cu(NO3)2 > Ni(NO3)2 > Zn(NO3)2 > Mn(NO3)2 > Co(NO3)2 > LiNO3. The first three are recognized as stronger Lewis acids and they generate more acidic solutions. When we carried out reactions with different iron salts, it was possible to conclude that the type of anion affects the solubility of the catalyst, as well as the conversion and selectivity of the process. Fe2(SO4)3 and FeSO4 were insoluble and less active. Conversely, though they were equally soluble, Fe(NO3)3 was more selective for the formation of β-citronellyl acetate than FeCl3. We assessed the effects of the main reaction variables such as reactant stoichiometry, temperature, and catalyst concentration. In addition to citronellol, we investigated the efficiency of the iron(iii) catalyst in the solvent free esterification of several terpenic alcohols (geraniol, nerol, linalool, α-terpineol) as well as other carboxylic acids.
Da Silva,Ayala
p. 3197 - 3207
(2016/05/24)

Terpene cyclization catalysed inside a self-assembled cavity
In nature, complex terpene natural products are formed by the so-called tail-to-head terpene (THT) cyclization. The cationic reaction cascade is promoted efficiently in complex enzyme pockets, in which cationic intermediates and transition states are stabilized. In solution, the reaction is hard to control and man-made catalysts able to perform selective THT cyclizations are lacking. We herein report the first example of a successful THT cyclization inside a supramolecular structure. The basic mode of operation in cyclase enzymes was mimicked successfully and a catalytic non-stop THT was achieved with geranyl acetate as the substrate. The results presented have implications for the postulated reaction mechanism in cyclase enzymes. Evidence indicates that the direct isomerization of a geranyl cation to the cisoid isomer, which so far was considered unlikely, is feasible.
Zhang, Q.,Tiefenbacher, K.
p. 197 - 202
(2015/04/21)

Isotope sensitive branching and kinetic isotope effects to analyse multiproduct terpenoid synthases from Zea mays
Multiproduct terpene synthases TPS4-B73 and TPS5-Delprim from Zea mays exhibit isotopically sensitive branching in the formation of mono- and sesquiterpene volatiles. The impact of the kinetic isotope effects and the stabilization of the reactive intermediates by hyperconjugation along with the shift of products from alkenes to alcohols are discussed.
Gatto, Nathalie,Vattekkatte, Abith,K?llner, Tobias,Degenhardt, J?rg,Gershenzon, Jonathan,Boland, Wilhelm
supporting information
p. 3797 - 3800
(2015/03/30)

Fe(III)-catalyzed α-terpinyl derivatives synthesis from β-pinene via reactions with hydrogen peroxide in alcoholic solutions
In this study, a novel and environmentally benign Fe(iii)-catalyzed terpinyl derivatives synthesis using hydrogen peroxide in alcohol solutions (i.e. methyl, ethyl, propyl, isopropyl and butyl alcohols) was investigated. The use of Bronsted acid catalysts was avoided and β-pinene was used as the starting reactant. High conversions (ca. 90%) and combined selectivities for the α-terpineol and terpinyl alkyl ethers (ca. 70-73%) were obtained when Fe(NO3)3 was used as the catalyst. The role of each component catalyst system was studied with special focus on the solvent. The use of a biodegradable and renewable origin solvent (ethyl alcohol), which was added to an inexpensive and mildly toxic catalyst and a green oxidant are the main positive features of this process.
Da Silva,Carari,Manoel Da Silva, Adalberto
p. 10529 - 10536
(2015/01/30)

Fe(NO3)3-catalyzed monoterpene oxidation by hydrogen peroxide: An inexpensive and environmentally benign oxidative process
Simple Fe(NO3)2·9H2O was demonstrated to be able to catalyze the oxidation of monoterpenes by hydrogen peroxide in methyl alcohol solution. Compared with the previous iron-catalyzed methods, the present procedure avoids the use of stabilizing ligands, additives, and corrosive peroxide organic oxidants. A novel, simple and highly efficient catalyst system was developed for oxidizing monoterpenes into a valuable derivates using hydrogen peroxide, an environmentally friendly oxidant. Graphical Abstract: Possible steps involved in the Fe(III)-catalyzed oxidation of β-pinene by hydrogen peroxide into myrtenol methyl ether in methyl alcohol[Figure not available: see fulltext.]
Carari, Danieli Marcolan,Da Silva, Marcio Jose
p. 615 - 622
(2014/04/03)

A novel Fe(III) salt-catalyzed monoterpene aerobic oxidation in methyl alcohol
The Fe(III)-catalyzed aerobic oxidation of monoterpenes in CH3OH has been developed, in which simple Fe(III) salts are used as catalysts in the absence of stabilizing ligands. Remarkably, Fe(NO3)3 catalyst efficiently promotes the oxidation of monoterpenes under air or dioxygen. The highest TON and TOF reached 476 and 162 h- 1, respectively. In general, reactions with 1.0-9.0 mol% of catalyst reached high conversions (ca. 90-99%) and high oxidation products selectivity (ca. 80%). Notably, α-pinene and β-pinene were selectively oxidized into only allylic product, myrtenol methyl ether. The significant breakthroughs of this simple oxidative process are the use of inexpensive Fe(III) salts as catalysts and environmentally-friendly oxidants (air or dioxygen).
Ferreira De Paula, Fabiano Gomes,Berllini, Lilian,Da Silva, Márcio José
p. 129 - 133
(2013/10/01)

Amberlyst-15: A reusable heterogeneous catalyst for the dehydration of tertiary alcohols
Tertiary alcohols react under mild conditions in the presence of Amberlyst-15 (dry) (solid-supported sulfonic acid) to give predominantly the most stable alkene in very good yield. The dehydration of tertiary alcohol functionality occurs without observation of rearrangement and polymerization products, and with outstanding substrate tolerance, which include the NHCBz, NHBoc, OSEM, OTBDMS, OBOM and ethylene ketal functional groups. Amberlyst-15 (dry) can be easily recovered from the reaction medium and reused for five cycles, maintaining the catalytic efficiency. In addition, the dehydration can occur under continuous operation.
Frija, Luís M.T.,Afonso, Carlos A.M.
scheme or table
p. 7414 - 7421
(2012/09/22)

A mild method for the deprotection of tetrahydropyranyl (THP) ethers catalyzed by iron(III) tosylate
A mild method for the deprotection of THP ethers catalyzed by iron(III) tosylate (2.0 mol %) in CH3OH has been developed. Iron(III) tosylate, Fe(OTs)3·6H2O, is a commercially available solid that is inexpensive, noncorrosive, and easy to handle. The room temperature reaction conditions make this method attractive for deprotection of a range of THP ethers.
Bockman, Matthew R.,Angeles, Veronica V.,Martino, Julia M.,Vagadia, Purav P.,Mohan, Ram S.
experimental part
p. 6939 - 6941
(2012/02/05)

Study of solid acid catalysis for the hydration of α-pinene
The hydration of α-pinene using solid acid catalysts was studied. The catalysts were prepared by impregnating trichloroacetic acid (TCA) on different supports such as silica, titania and zirconia (TCA/SiO2, TCA/TiO2 and TCA/ZrO2·nH2O, respectively). The TCA/TiO2 catalyst converted α-pinene into hydrocarbons, while the TCA/ZrO2·nH2O catalyst was active and selective for producing alcohols, with a conversion of 57% and a selectivity of 75% of total alcohols, and showed 57% selectivity for α-terpineol. The TCA/SiO2 sample did not show catalytic activity due to the elimination of the trichloroacetic acid during the preparation step of the catalyst. An additional stability study was performed with the TCA/ZrO2·nH2O sample. The presence of TCA in the different impregnated samples was studied using FT-IR, and the TCA content was determined by thermogravimetric analysis. The surface content of TCA in fresh and used catalysts was studied with XPS, and the textural properties and crystalline structures were analysed by BET and XRD, respectively. Additionally, the nature of the acid centres was characterised by pyridine adsorption coupled with FT-IR, and the acidity was determined by potentiometric titration.
ávila, Maria C.,Comelli, Nora A.,Rodríguez-Castellón,Jiménez-López,Carrizo Flores,Ponzi,Ponzi
experimental part
p. 106 - 112
(2010/07/08)

A facile method for the rapid and selective deprotection of methoxymethyl (MOM) ethers
We describe a rapid and efficient method for selective deprotection of methoxymethyl (MOM) ethers using ZnBr2 and n-PrSH, which completely removed MOM from diverse MOM ethers of primary, secondary, and tertiary alcohols or phenol derivatives. The deprotection takes less than ten minutes with both high yield and selectivity in the presence of other protecting groups. In addition, the rapid deprotection of MOM ethers of tertiary hydroxyls in high yield with no epimerization allows MOM to be a suitable protecting group for tertiary alcohols.
Han, Jae Hyun,Kwon, Young Eun,Sohn, Jeong-Hun,Ryu, Do Hyun
experimental part
p. 1673 - 1677
(2010/04/04)

Titanocene-promoted intermolecular couplings of epoxides with nitriles. An easy access to β-hydroxyketones
(Chemical Equation Presented) Radical couplings of epoxides and nitriles mediated by Cp2TiCl provide a diastereoselective route to the synthesis of β-hydroxyketones. The conditions of this "aldol- like" reaction are mild enough to avoid the dehydration of the β-hydroxyketone. The scope of the coupling reaction with functionalized and tetrasubstituted epoxides has been studied. The radical character of the coupling reactions is demonstrated.
Fernandez-Mateos,Encinas Madrazo,Herrero Teijon,Rubio Gonzalez
supporting information; experimental part
p. 3913 - 3918
(2009/10/20)

Hydration of α-pinene in a triphasic system consisting of α-pinene, water, and Cs2.5H0.5PW12O 40-SiO2 composite
Cs2.5H0.5PW12O40-SiO 2 composite combined with (3-aminopropyl)triethoxysilane exhibited greater activity and selectivity for hydration of α-pinene at 333 K in a triphasic system (α-pinene/water/solid acid) compared to previously reported water-tolerant catalysts such as zeolites, polymer-resins (Amberlyst 15 and Nafion-H), oxides, and liquid acids such as H3PW 12O40 and H2SO4. The selectivity toward alcohols, including mono- and dialcohols, was approximately 80% over Cs2.5H0.5PW12O40-SiO2 composite. Copyright
Horita, Naoto,Kamiya, Yuichi,Okuhara, Toshio
p. 1346 - 1347
(2007/10/03)

Facile cleavage of silyl protecting groups with catalytic amounts of FeCl3
A very mild and environmentally benign method for removal of silyl protecting groups using catalytic amounts of iron ion in MeOH is presented. The method is particularly effective for cleaving triethylsilyl (TES) protecting groups. Georg Thieme Verlag Stuttgart.
Yang, Yong-Qing,Cui, Jia-Rong,Zhu, Lin-Gui,Sun, Ya-Ping,Wu, Yikang
p. 1260 - 1262
(2007/10/03)

Y-zeolite-catalyzed cyclizations of terpenols
Depending on the metal doped and the activation temperature, Y-zeolites can catalyze a diversity of reactions of geraniol (1), linalool (2) and nerol (3). Compound 1 can be transformed to α- and/or γ-cyclogeraniol (4 and 5) highly efficiently.
Yu, Wei,Bian, Fengling,Gao, Yuan,Yang, Li,Liu, Zhong-Li
p. 59 - 62
(2007/10/03)

A high loading sulfonic acid-functionalized ordered nanoporous silica as an efficient and recyclable catalyst for chemoselective deprotection of tert-butyldimethylsilyl ethers
A high loading sulfonic acid-functionalized ordered nanoporous silica efficiently catalyzes the deprotection of a variety of alcoholic TBDMS (tert-butyldimethylsilyl)ethers in methanol. The catalyst shows high thermal stability (up to 240°C) and can be recovered and reused for at least seven reaction cycles without loss of reactivity. This method can be used to deprotect TBDMS ethers of alcohols in the presence of TBDMS ethers of phenols.
Karimi, Babak,Zareyee, Daryoush
p. 4661 - 4665
(2007/10/03)

N-Iodosuccinimide (NIS) as a mild and highly chemoselective catalyst for deprotection of tert-butyldimethylsilyl ethers
A variety of alcoholic TBDMS (t-butyldimethylsilyl) ethers are easily removed in excellent yields by treatment with a catalytic amount of N-iodosuccinimide (NIS, 5 mol %) in methanol. This method is able to deprotect TBDMS ethers of alcohols in the presence of TBDMS ethers of phenols.
Karimi, Babak,Zamani, Asghar,Zareyee, Daryoush
p. 9139 - 9141
(2007/10/03)

A Convenient Method for Protection and Deprotection of Alcohols and Phenols as Alkylsilyl Ethers Catalyzed by Iodine under Microwave Irradiation
Irradiation of alcohols or phenols with tert-butyldimethylsilyl chloride (TBDMSCl) or trimethylsilyl chloride (TMSCl) in presence of catalytic amount (20 mol%) of iodine in a microwave oven for 2 min gives the corresponding silyl ethers in excellent yield. Iodine in methanol deprotects the silyl ether into its parent alcohol or phenol under similar reaction conditions.
Saxena, Ira,Deka, Nabajyoti,Sarma, Jadab C.,Tsuboi, Sadao
p. 4185 - 4191
(2007/10/03)

Lithium-potassium superbases as key reagents for the base-catalysed isomerisation of some terpenoids
Some representative monoterpenes have been isomerised under the influence of Schlosser's lithium-potassium mixed superbases, promoting β-elimination reactions. The results are compared with those obtained with butyllithium and LDA. Different selectivities and different reaction yields are achieved as a function of the base employed. These results confirm the particular reactivity of bimetallic reagents. In this paper it is proposed that the observed selectivities might depend on the conformational features of the substrate, on the strength of the organometallic reagent, as well as on steric requirements of the elimination reaction.
Deagostino,Tivola,Prandi,Venturello
p. 2856 - 2860
(2007/10/03)

Acid-catalyzed hydrolysis of alcohols and their β-D-glucopyranosides
The hydrolysis, in model wine at pH 3, of the allylic, homoallylic, and propargylic glycosides, geranylβ-D-glucopyranoside, [3'-(1'-cyclohexenyl)- 1'-methyl-2'-propynyl]-β-D-glucopyranoside, (3'RS,9'SR)(3'-hydroxy-5'- megastigmen-7-yn-9-yl)-β-D-glucopyranoside, (3',5',5'-trimethyl-3'- cyclohexenyl)-β-D-glucopyranoside, E-(7'-oxo-5',8'-megastigmadien-3'-yl)-β- D-glucopyranoside (3-hydroxy-β-damascone-β-D-glucopyranoside), and their corresponding aglycons has been studied. In general, aglycons were more rapidly converted to transformation products than were the corresponding glucosides. Glycoconjugation of geraniol in grapes is a process that reduces the flavor impact of this compound in wine, not only because geraniol is an important flavor component of some wines but also because the rate of formation of other flavor compounds from geraniol during bottle-aging is reduced. However, when flavor compounds such as β-damascenone are formed in competition with flavorless byproducts, such as 3-hydroxy-β-damascone, by acid-catalyzed hydrolytic reactions of polyols, then glycoconjugation is a process that could enhance as well as suppress the formation of flavor, depending on the position of glycosylation. (3'RS,9'SR)-(3'-Hydroxy-5'- megastigmen-7'-yn-9'-yl)-β-D-glucopyranoside hydrolyzed more slowly but gave a higher proportion of β-damascenone in the products than did the aglycon at 50 °C. Reaction temperature also effected the relative proportion of the hydrolysis products. Accelerated studies do not parallel natural processes precisely but only approximate them.
Skouroumounis, George K.,Sefton, Mark A.
p. 2033 - 2039
(2007/10/03)

Purification and characterization of an α-L-rhamnosidase from Pichia angusta X349
An intracellular α-L-rhamnosidase from Pichia angusta X349 was purified to homogeneity through four chromatographic steps. The α-L-rhamnosidase appeared to be a monomeric protein with a molecular mass of 90 kDa. The enzyme had an isoelectric point at 4.9, and was optimally active at pH 6.0 and at around 40°C. The Ki for L-rhamnose inhibition was 25 mM. The enzyme was inhibited by Cu2+, Hg2+, and p-chloromercuribenzoate. The α-L-rhamnosidase was highly specific for α-L-rhamnopyranoside and liberated rhamnose from naringin, rutin, hesperidin, and 3-quercitrin. The α-L-rhamnosidase was active at the ethanol concentrations of wine. It efficiently released monoterpenols, such as linalool and geraniol, from an aroma precursor extracted from Muscat grape juice.
Yanai, Takaaki,Sato, Michikatsu
p. 2179 - 2185
(2007/10/03)

Superacidic cyclization of ω-hydroxygeraniol diacetate and ω-hydroxygeraniol benzyl ether acetate
Low-temperature superacidic cyclization of (E,E)-3,7-dimethylocta-2,6-diene-1,8-diol (ω-hydroxygeraniol) diacetate and (E,E)-8-acetoxy-1-benzyloxy-3,7-dimethylocta-2,6-diene leads to the same mixtures of two diastereomeric 9-acetoxy-8-hydroxy-p-menth-1-enes epimeric at the C(8) atom.
Kulcitki,Ungur,Deleanu,Vlad
p. 136 - 138
(2007/10/03)

An efficient method for the reductive transposition of allylic alcohols
The Mitsunobu reaction of allylic alcohols with o- nitrobenzenesulfonylhydrazine (NBSH) as nucleophile proceeds at -30 °C with invertive displacement; warming the resultant N-allylic sulfonylhydrazine derivative to 23 °C then leads to allylic diazene formation followed by sigmatropic elimination of dinitrogen. This one-step method for reductive 1,3-transposition is shown to be efficient and highly regio- and stereocontrolled within a wide range of allylic alcohol substrates.
Myers, Andrew G.,Zheng, Bin
p. 4841 - 4844
(2007/10/03)

Selective cleavage of ethers using silica-alumina gel catalysts prepared by the sol-gel method
The selective cleavage of tetrahydropyranyl (THP), methoxymethyl (MOM), 1-ethoxyethyl (EE), 1-methyl-1-methoxyethyl (MME) and trimethylsilyl (TMS) ether groups with silica-alumina gels prepared by the sol-gel method has been investigated. The deprotection rate follows the order: TMS > MME >>, EE > THP >> MOM. The selective deprotection of diol derivatives with mixed protecting groups was achieved efficiently. Bis-THP and bis-MOM ether derivatives of a substrate which contained a primary and a tertiary hydroxyl groups were mono- deprotected with moderate selectivity. The selective deprotection of glycerol ethers was also examined. The silica-alumina gels prepared by the sol-gel method are thus shown to be a good catalyst for selective cleavage of ether protecting groups giving the product in a simple manner under mild conditions.
Matsumoto, Yoshihiko,Mita, Keisuke,Hashimoto, Keiji,Iio, Hideo,Tokoroyama, Takashi
p. 9387 - 9398
(2007/10/03)

Large Pore Bifunctional Titanium-Aluminosilicates: the Inorganic Non-enzymatic Version of the Epoxidase Conversion of Linalool to Cyclic Ethers
Bifunctional aluminosilicate catalysts containing framework Ti are prepared, with two different topologies and pore sizes; these samples contain both acid and oxidizing catalytic sites and are highly selective for carrying out multistep reactions with selectivities close to those obtained with epoxidases, this is shown to occur for the oxidation of linalool to cyclic hydroxy ethers.
Corma, A.,Iglesias, M.,Sanchez, F.
p. 1635 - 1636
(2007/10/02)

Process for separating ketones from alcohols
The invention relates to a process for separating ketones from alcohols by chemical interaction. More specifically, a difference in chemical reactivity between ketones and alcohols with a third compound is used as a basis for the separation. The third compound in this case is an organo-metallic compound of the general formula M(X)n. Herein is M a polyvalent metal atom, n equals the valence of the metal and X is an organic or inorganic group or atom, with the proviso that at least one organic group is present in the organo-metallic compounds according to the invention. If the ketone-alcohol mixture is subjected to the organo-metallic compounds according to the invention under suitable conditions, an exchange reaction between the alcohols and the groups X takes place, and the ketones can be isolated from the reaction mixture in a conventional way.
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(2008/06/13)

PRODUCTS OF THE CATALYTIC LIQUID-PHASE OXIDATION OF 3-CARENE
The liquid-phase oxidation of 3-carene in the presence of various catalytic systems has been studied.The possibility has been shown of the directed preparation of 3-carene oxide, of ketones with a carane skeleton and a 7-membered ring, or of aromatic tertiary alcohols.
Vyglazov, O. G.,Manukov, E. N.,Fedorishcheva, M. N.,Ariko, N. G.,Chuiko, V. A.,Bazhina, G. N.
p. 283 - 287
(2007/10/02)

Reduction of tri- and tetra-substituted oxiranes with lithium in ethylenediamine
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Gurudutt,Rao,Shaw
p. 345 - 346
(2007/10/02)

CYCLIZATION OF SOME LINEAR TERPENOLS INITIATED BY "ACTIVATED" DMSO
It was shown that the acylhydroxysulfonium salt generated in situ from DMSO and trifluoroacetic anhydride causes low-temperature cyclization of geraniol, linalool, and nerol in an aprotic medium to a mixture of p-menthane monoterpenoids, and the maximum yield is obtained in the case of the last two terpenols.A similar result was obtained for E-nerolidol.
Surkova, A. A.,Lozanova, A. V.,Dragan, V. A.,Gur'yan, V. A.,Moiseenkov, A. M.
p. 760 - 762
(2007/10/02)

BIOTRANSFORMATION OF LINALYL ACETATE BY SUSPENSION CULTURES OF PAPAVER BRACTEATUM
Suspension cultures of Papaver bracteatum biotransform the acyclic monoterpene, linalyl acetate, into linalool, geraniol and the monocyclic alcohol, α-terpineol.Total metabolism of linalyl acetate occurs within eight days of substrate addition, with 40percent of the substrate being transformed within the first 36hr.No regiospecific hydroxylation of the 3-methyl-2-butenyl group is observed.
Hook, Ingrid,Lecky, Rhonda,McKenna, Brian,Sheridan, Helen
p. 2143 - 2144
(2007/10/02)

Micellar-Induced Selectivity and Rate Enhancement in the Acid-Catalyzed Cyclization and Rearrangement of Monoterpenes. The Solvolysis of Linalyl and Geranyl Acetates
The monoterpene linalyl acetate (1) undergoes acid-catalyzed solvolysis/cyclization at pH 3 in HCl/citrate buffer to yield three major acyclic alcohols, geranol (2), linalool (3), and nerol (4), and one cyclic alcohol, α-terpineol (5).The acyclic/cyclic alcohol ratio is 2.7 in no sodium dodecyl sulfate (SDS) controls after ca. 3 half-lives, compared to 8.5 when the reaction is carried out in a SDS micelle.No micellar rate effect was observed.The SDS-induced selectivity is explained in terms of the micelle-favoring acyclic conformers of linalyl acetate.In contrast to linalyl acetate, solvolysis of geranyl acetate (6) in the SDS micelle at pH 2 gives little product selectivity but yields a 7-fold rate effect relative to no SDS controls.This rate effect results in very different product distributions after 90percent completion of the reaction.The observed SDS rate effect for geranyl acetate is compatible with a difference in solvolysis mechanism for linalyl and geranyl acetate.
Clark, Benjamin C.,Chamblee, Theresa S.,Iacobucci, Guillermo A.
p. 1032 - 1036
(2007/10/02)

Isomerizations of Citronellal to Isopulegol and Geraniol to Linalool Catalyzed by Solid Acids and Bases
Citronellal was isomerized to isopulegol over SiO2-Al2O3, TiO2,-ZrO2, FeSO4, NiSO4, Ti(SO4)2, Zr(SO4)2 and Al2O3, with the selectivity higher than 91percent.Geraniol was also isomerized mainly to linalool over SiO2-Al2O3 and those four metal sulfates, and the selectivity on SiO2-Al2O3 and FeSO4 was higher than 81percent.
Arata, Kazushi,Matsuura, Chiharu
p. 1797 - 1798
(2007/10/02)

DEPROTECTION OF 'SEM' ETHERS: A CONVENIENT, GENERAL PROCEDURE
A new set of standard conditions for removal of SEM ethers is described.
Lipshutz, Bruce H.,Miller, Todd A.
p. 7149 - 7152
(2007/10/02)

Ultrasound in Organic Synthesis. 18. Selective Oxymercuration via Sonochemically in Situ Generated Mercury Salts
Selective mercuration of diolefins is favored by a proper choice of the mercuric salt, which can be generated in situ from mercuric oxide and the corresponding acid under sonochemical activation.
Einhorn, J.,Einhorn, C.,Luche, J. L.
p. 4479 - 4481
(2007/10/02)

REGIOSPECIFIC HYDROXYLATION OF ACYCLIC MONOTERPENE ALCOHOLS BY ASPERGILLUS NIGER
Aspergillus niger was shown to carry out the regiospecific hydroxylation of acyclic monoterpene alcohols.
Madyastha, Madhava K.,Krishna Murthy, N. S. R.
p. 579 - 580
(2007/10/02)

EFFECTIVE DEPROTECTION OF 2-(TRIMETHYLSILYLETHOXY)METHYLATED ALCOHOLS (SEM ETHERS). SYNTHESIS OF THYRSIFERYL-23 ACETATE
New conditions for effective cleavage of SEM ethers were developed (TBAF/HMPA in the presence of MS 4A) and usefulness of this reaction was demonstrated by the synthesis of thyrsiferyl-23 acetate.
Kan, Toshiyuki,Hashimoto, Masaru,Yanagiya, Mitsutoshi,Shirahama, Haruhisa
p. 5417 - 5418
(2007/10/02)

Studies on the Decomposition of Alkyl Hydroperoxides by Different Catalysts
The catalytic decomposition of cumene, 1-methylcyclohexyl and cyclohexyl hydroperoxides was studied in cyclohexane, cis- and trans-1,4-dimethylcyclohexane and cis-pinane as the solvents.The stearates and the acetylacetonates of manganese, cobalt and chromium, the acetylacetonates of molybdenum and vanadium, n-butyl orthoborate and n-butyl metaborate were used as the catalysts.The chromium-, vanadium-, molybdenum- and boron-containing catalysts brought about some Hock-type decomposition of cumene hydroperoxide and thus proved to be acidic.Of these more of less acidic catalysts only molybdenyl acetylacetonate effected a partially stereospecific hydroxylation of the tertiary C-H-bonds in cis- and trans-1,4-dimethylcyclohexane.The well-known selectivity of chromium catalysts for the ketone formation during the decomposition of secondary hydroperoxides is caused by the catalytic oxidation of secondary alcohols by hydroperoxides in the presence of chromium compounds.In the presence of all the catalysts used the free-radical pathways of the hydroperoxide decomposition predominated, and the attack of the intermediate radicals on the starting hydroperoxide was more important than the attack on the solvent molecules.
Lauterbach, Gerlinde,Pritzkow, W.,Tien, Tieu Dung,Voerckel, V.
p. 933 - 946
(2007/10/02)

SYNTHESIS OF BISABOL-10-ENE-3,7-OXIDE
The synthesis of bisabol-10-ene-3,7-oxide was accomplished using as the key intermediate a radical obtained in the reduction of an organomercuric compound, and starting either from limonene or β-terpineol.
Pascual-T., J. de,Hernandez, M. L.,Moran, J. R.,Caballero, C.,Anaya, J.,Alcazar, V.
p. 5109 - 5112
(2007/10/02)

Hydrolysis od Bismetallic Complexes of Linalyldiphosphate and their Participation in the Biosynthesis of Cyclic Monoterpenes
The allylic diphosphate ester linalyldiphosphate forms mono- and bis-metallic complexes with Mg(2+) and Mn(2+).Complexes of the trianion of the ligand are 50 to 100 times more stable than those of the dianion.Mg(2+) and Mn(2+) are bound in the monometallic complex 1E3 and 1E4 times more strongly than in the bismetallic species.The rate constant of the uncatalysed hydrolysis of linalyldiphosphate at pH 7.0 is 1.2 x E4 s-1, which is higher than reported values for the primary diphosphates.Mg(2+) and Mn(2+) affect its rate of hydrolysis and it is shown that the rate enhancement observed is a function of the concentration of the bismetallic complexes.The rate of cyclic terpene hydrocarbon biosynthesis catalysed by carbocyclase from Citrus limonum also correlates with the concentration of the bismetallic complexes.Linalyl monophosphate, which is not a substrate for carbocyclase hydrolyses at a rate proportional to the concentration of the monometallic complex of Mn(2+).The neutral charge of this complex, as opposed to the positively charged bismetallic complex of linalyl diphosphate may be an explanation of the absence of utilization of this complex as a substrate.It appears from the data presented and from previous evidence that bismetallic complexes of allylic diphosphates are the most reactive species in their hydrolysis and the only reactive species in the enzymic cyclizaton of these precursors of monoterpenes.
Portilla, Gloria,Rojas, M. Cecilia,Chiong, Evaristo,Cori, Osvaldo
p. 1479 - 1484
(2007/10/02)

Methane- and Difluoromethanediphosphonate Analogues of Geranyl Diphosphate: Hydrolysis-Inert Alternate Substrates
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Stremler, Kay E.,Poulter, C. Dale
p. 5542 - 5544
(2007/10/02)

Rearrangement of Linalool, Geraniol, and Nerol and Their Derivatives
Acid-catalyzed conversion of linalool into geraniol, nerol, and α-terpineol is slower than the corresponding reactions of geraniol and nerol, because the tertriary linalyl carbocation reverts to linalool rather than going forward to rearranged products.The linalyl carbocation does not lose its stereochemical identity, and oxygen exchange of linalool is faster than rearrangement or cyclization.Solvolyses of linalyl esters and chloride are faster than those of the geranyl and neryl derivatives.These solvolyses are different from acid heterolysis of linalool in that there is extensive racemization of linalool, but cyclization to α-terpineol goes with considerable retention of configuration.Participation by the 6,7-double bond controls the stereochemistry of linalool heterolysis and solvolysis of linalyl esters, but it does not markedly affect the reaction rates.
Cori, Osvaldo,Chayet, Liliana,Perez, Luz Maria,Bunton, Clifford A.,Hachey, David
p. 1310 - 1316
(2007/10/02)

PRENYLATION OF OLEFINS IN NITROMETHANE
The prenylation of isopentenyl and 3,3-dimethylallyl derivatives could be achieved efficiently with dimethyl vinyl carbinol and a variety of acids in nitromethane.Geraniol and isopentenylacetate led to farnesyl derivatives.
Julia, M.,Schmitz, C.
p. 2485 - 2490
(2007/10/02)