- Palladium(II)-catalysed Oxidative Ring Cleavage of Cyclic Acetals with t-Butyl Hydroperoxide: Preparation of Monoesters of Diols
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Reaction of five- and six-membered cyclic acetals with tBuOOH in the presence of palladium(II) catalyst gives monoesters of diols in good yields.
- Hosokawa, Takahiro,Imada, Yasushi,Murahashi, Shun-Ichi
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Read Online
- Chemoselective Cleavage of Si-C(sp3) Bonds in Unactivated Tetraalkylsilanes Using Iodine Tris(trifluoroacetate)
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Organosilanes are synthetically useful reagents and precursors in organic chemistry. However, the typical inertness of unactivated Si-C(sp3) bonds under conventional reaction conditions has hampered the application of simple tetraalkylsilanes in organic synthesis. Herein we report the chemoselective cleavage of Si-C(sp3) bonds of unactivated tetraalkylsilanes using iodine tris(trifluoroacetate). The reaction proceeds smoothly under mild conditions (-50 °C to room temperature) and tolerates various polar functional groups, thus enabling subsequent Tamao-Fleming oxidation to provide the corresponding alcohols. NMR experiments and density functional theory calculations on the reaction indicate that the transfer of alkyl groups from Si to the I(III) center and the formation of the Si-O bond proceed concertedly to afford an alkyl-λ3-iodane and silyl trifluoroacetate. The developed method enables the use of unactivated tetraalkylsilanes as highly stable synthetic precursors.
- Matsuoka, Keitaro,Komami, Narumi,Kojima, Masahiro,Mita, Tsuyoshi,Suzuki, Kimichi,Maeda, Satoshi,Yoshino, Tatsuhiko,Matsunaga, Shigeki
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p. 103 - 108
(2021/01/13)
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- Copper-catalyzed enantioselective synthesis of bridged bicyclic ketals from 1,1-disubstituted-4-methylene-1,6-hexanediols and related alkenols
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Bridged bicyclic ketals display a range of bioactivities. Their catalytic enantioselective synthesis from acyclic 1,1-disubstituted alkene diols is disclosed. This reaction combines asymmetric catalysis with a distal radical migration. Alkynes and arenes
- Burde, Ameya S.,Karyakarte, Shuklendu D.,Sylvester, Eric D.,Chemler, Sherry R.
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supporting information
p. 105 - 108
(2021/01/14)
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- Design, synthesis, and in vitro evaluation of 4-aminoalkyl-1(2H)-phthalazinones as potential multifunctional anti-Alzheimer's disease agents
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A series of 4-aminoalkyl-1(2H)-phthalazinone derivatives was designed and synthesized as potential multifunctional agents for Alzheimer's disease (AD) treatment. In vitro biological assay results demonstrated that most synthesized compounds exhibited sign
- Ye, Chanyuan,Xu, Rui,Cao, Zhongcheng,Song, Qing,Yu, Guangjun,Shi, Yichun,Liu, Zhuoling,Liu, Xiuxiu,Deng, Yong
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- Electrochemical esterification reaction of alkynes with diols: Via cleavage of carbon-carbon triple bonds without catalyst and oxidant
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A novel electrochemical esterification of alkynes for the synthesis of esters was developed in which diols and their derivatives were used as the partners. This method is green as it is catalyst-free, oxidant-free, and additive-free and shows atom-economy. This is the first example of an electrochemical reaction via cleavage of carbon-carbon triple bonds. Meanwhile, this is also the first example of a carbon-carbon triple bond cleavage reaction of alkynes with diols. This journal is
- Cheng, Hui-Hui,Gao, Hui,Li, Pin-Hua,Shen, Hui-Zhi,Wang, Pei-Long
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supporting information
p. 6783 - 6791
(2020/11/09)
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- Protecting-group-free synthesis of hydroxyesters from amino alcohols
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The synthesis of hydroxyesters from carboxylic acids and unprotected amino alcohols in both continuous flow and batch processes is reported. The formation of a transient diazonium species with a dinitrite reagent is key in this transformation. The reaction conditions are compatible with a variety of functional groups.
- Joseph-Valcin, Eve-Marline,Lebel, Hélène,Reynard, Guillaume
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supporting information
p. 10938 - 10941
(2020/10/02)
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- Synthesis and mesomorphic properties of H-bonded side-chain liquid crystal polymers of two modifications of poly(4-vinylphenol) and poly(4-vinylpyridine)
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Poly(4-vinylphenol) was modified to poly(4-(4-vinylphenoxy)butan-1-ol) and poly(4-(6-(4-vinylphenoxy)hexyloxy)benzoic acid). Methyl 4-((E)-2-pyridin-4-yl)vinyl)benzoate ligand was synthesized and hydrogen bonded with two modified polymers. Complexes of po
- Muhammad, Khushi,Siddiqi, Humaira M.,Hameed, Shahid
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- Axial-to-Central Chirality Transfer for Construction of Quaternary Stereocenters via Dearomatization of BINOLs
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All-carbon quaternary stereocenters are versatile building blocks, and their asymmetric construction has attracted much attention. Herein, we disclose an axial-to-central chirality transfer strategy for the synthesis of chiral quaternary stereocenters via dearomatization of (S)-BINOLs. The reaction proceeded smoothly with a wide range of propargyl carbonates to afford chiral spiro-compounds in high yields with excellent enantioselectivities. In addition, the strategy was extended to kinetic resolution of rac-BINOLs albeit with moderate s value.
- Min, Xiao-Long,Xu, Xu-Ran,He, Ying
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supporting information
p. 9188 - 9193
(2019/11/14)
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- ANTIBACTERIAL COMPOSITION INCLUDING BENZOIC ACID ESTER AND METHODS OF INHIBITING BACTERIAL GROWTH UTILIZING THE SAME
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Antibacterial compositions and methods for inhibiting bacterial growth are disclosed. The antibacterial compositions can include a carrier and an antibacterial agent including a benzoic acid ester. The benzoic acid ester can have a carbon chain having a length of two to ten. The benzoic acid ester can have a hydroxyl group on the carbon chain.
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Page/Page column 23-24
(2018/08/26)
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- Catalytic Oxygenative Allylic Transposition of Alkenes into Enones with an Azaadamantane-Type Oxoammonium Salt Catalyst
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The first catalytic oxygenative allylic transposition of unactivated alkenes into enones has been developed using an oxoammonium salt as the catalyst. This reaction converts various tri- and trans-disubstituted alkenes into their corresponding enones with transposition of their double bonds at ambient temperature in good yields. The use of a less-hindered azaadamantane-type oxoammonium salt as the catalyst and a combination of two distinct stoichiometric oxidants, namely, iodobenzene diacetate and magnesium monoperoxyphthalate hexahydrate (MMPP?6 H2O) are essential to facilitate the enone formation efficiently.
- Nagasawa, Shota,Sasano, Yusuke,Iwabuchi, Yoshiharu
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supporting information
p. 10276 - 10279
(2017/08/07)
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- Effect of Partially Fluorinated N-Alkyl-Substituted Piperidine-2-carboxamides on Pharmacologically Relevant Properties
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The modulation of pharmacologically relevant properties of N-alkyl-piperidine-2-carboxamides was studied by selective introduction of 1–3 fluorine atoms into the n-propyl and n-butyl side chains of the local anesthetics ropivacaine and levobupivacaine. The basicity modulation by nearby fluorine substituents is essentially additive and exhibits an exponential attenuation as a function of topological distance between fluorine and the basic center. The intrinsic lipophilicity of the neutral piperidine derivatives displays the characteristic response noted for partially fluorinated alkyl groups attached to neutral heteroaryl systems. However, basicity decrease by nearby fluorine substituents affects lipophilicities at neutral pH, so that all partially fluorinated derivatives are of similar or higher lipophilicity than their non-fluorinated parents. Aqueous solubilities were found to correlate inversely with lipophilicity with a significant contribution from crystal packing energies, as indicated by variations in melting point temperatures. All fluorinated derivatives were found to be somewhat more readily oxidized in human liver microsomes, the rates of degradation correlating with increasing lipophilicity. Because the piperidine-2-carboxamide core is chiral, pairs with enantiomeric N-alkyl groups are diastereomeric. While little response to such stereoisomerism was observed for basicity or lipophilicity, more pronounced variations were observed for melting point temperatures and oxidative degradation.
- Vorberg, Raffael,Trapp, Nils,Zimmerli, Daniel,Wagner, Bj?rn,Fischer, Holger,Kratochwil, Nicole A.,Kansy, Manfred,Carreira, Erick M.,Müller, Klaus
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p. 2216 - 2239
(2016/10/19)
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- 1-mercapto methyl propyl process for the preparation of acetic acid
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The invention provides a preparation method of 1-mercaptomethylcyclopropyl acetic acid. The preparation method is used for solving the problems of high cost, high toxicity, low yield and heavy environmental pollution of the existing preparation method. The preparation method comprises the step of preparing the 1-mercaptomethylcyclopropyl acetic acid with 1,4-butanediol as a starting raw material which is cheap, low in toxicity and easy to obtain as a starting raw material through reactions such as etherification or esterification, oxidization, corey-chaykovsky or simmons-smith, reduction, substitution, deprotection and the like. The preparation method provided by the invention has the technical characteristics of simple and convenient operation, easy purification of product, high yield, and suitability for industrial large production.
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Paragraph 0067; 0071-0073
(2019/01/28)
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- Facile and selective deprotection of PMB ethers and esters using oxalyl chloride
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Oxalyl chloride, (0.5 equiv) was found to cleave the PMB group from alkyl, aryl PMB ethers, and esters to give corresponding alcohol and acid in good yields. This method offers simple and efficient protocol for the selective deprotection of PMB ether and ester in DCE at ambient temperature.
- Ilangovan, Andivelu,Anandhan, Karnambaram,Kaushik, Mahabir Prasad
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p. 1081 - 1084
(2015/02/19)
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- A mild and efficient method for the selective cleavage of primary p-methoxybenzyl protecting group of saccharides by Co2(CO)8-Me2PhSiH-CO system
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A mild and efficient method to selectively cleave p-methoxybenzyl (PMB) ether with a catalytic amount of Co2(CO)8, hydrosilane and CO (1 atm) is presented. The cleavage reaction shows regioselectivity to primary O-PMB of a variety of
- Qian, Peng-Zhan,Yao, Wang,Huang, Lu-Bai,Meng, Xiang-Bao,Li, Zhong-Jun
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supporting information
p. 5238 - 5241
(2015/08/19)
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- Compositions and methods for treating viral infections
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The present invention provides compositions methods for treating susceptible viral infections, especially hepatitis C viral (HCV) infections as well as co infections of HCV with other viruses such as HBV and/or HIV. In one embodiment, the present inventio
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Page/Page column 38; 39
(2015/10/28)
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- Reactivity of hydroxy- and aquo(hydroxy)-λ3-iodane-crown ether complexes
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We have designed a series of hydroxy(aryl)-λ3-iodane-[18] crown-6 complexes, prepared from the corresponding iodosylbenzene derivatives and superacids in the presence of [18]crown-6, and have investigated their reactivities in aqueous media. These activated iodosylbenzene monomers are all non-hygroscopic shelf-storable reagents, but they maintain high oxidizing ability in water. The complexes are effective for the oxidation of phenols, sulfides, olefins, silyl enol ethers, and alkyl(trifluoro)borates under mild conditions. Furthermore, hydroxy-λ3-iodane-[18]crown-6 complexes serve as efficient progenitors for the synthesis of diaryl-, vinyl-, and alkynyl-λ3-iodanes in water. Other less polar organic solvents, such as methanol, acetonitrile, and dichloromethane, are also usable in some cases. Aqua-friendly iodosylbenzene equivalents: Hydroxy- and aquo(hydroxy)-λ3-iodane-[18]crown-6 complexes (see graphic), readily prepared from commercial PhI(OAc)2 or PhIO, serve as excellent oxygen atom donors toward olefins, phenols, sulfides, and alkyl(trifluoro)borates. They also serve as progenitors for diaryl-, vinyl-, and alkynyl-λ3-iodane-[18]crown-6 complexes. These reactions can be carried out in aqueous media under mild reaction conditions.
- Miyamoto, Kazunori,Yokota, Yukie,Suefuji, Takashi,Yamaguchi, Kentaro,Ozawa, Tomoyuki,Ochiai, Masahito
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supporting information
p. 5447 - 5453
(2014/05/20)
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- A convenient approach for the deprotection and scavenging of the PMB group using POCl3
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A convenient and high yielding approach for the deprotection and scavenging of the p-methoxybenzyl (PMB) group in PMB ethers and PMB esters was developed using POCl3 as the reagent. 4-Methoxybenzyl chloride, a starting material used for the preparation of PMB ethers and esters was regenerated in the deprotection step. This mild and selective procedure tolerates several acid sensitive functional groups. The Royal Society of Chemistry 2013.
- Ilangovan, Andivelu,Saravanakumar, Shanmugasundar,Malayappasamy, Subramani,Manickam, Govindaswamy
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p. 14814 - 14828
(2013/09/02)
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- Formal enantioselective synthesis of aplykurodinone-1
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Step economy and simplicity were combined in the asymmetric formal synthesis of aplykurodinone-1 (see scheme; TBS=tert-butyldimethylsilyl). The key features of the strategy involve a one-pot aerobic and directed oxidation/deoxygenation and a late-stage co
- Peixoto, Philippe A.,Jean, Alexandre,Maddaluno, Jacques,De Paolis, Michael
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supporting information
p. 6971 - 6973
(2013/07/26)
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- Imidazol(in)ium-2-carboxylates as latent, thermally activated organocatalysts for transesterification reactions
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1,3-Disubstituted imidazol(in)ium-2-carboxylates (ImCO2) were used as precatalysts for transesterification reactions of unactivated ethyl benzoate with monohydric alcohols, dihydric alcohols, and amino alcohols. Highly active N-heterocyclic carbenes (NHCs) are usually not used directly as catalysts because of their air and moisture sensitivity. Here they were liberated in situ by thermal decarboxylation of ImCO2 at designated temperatures. The results showed that the yield of the reactions reached up to 95 within 3 h using only 0.5 mol catalyst. No active enol esters, molecular sieves, or a 20-fold excess of alcohol were used to drive the reaction to completion. It was proved that unsaturated imidazolium-2-carboxylates have a better activity than saturated species in this type of reaction. Different types of substituting groups of ImCO2 exhibited varied transesterification activity.
- Wang, Yanqin,Li, Zhenjiang
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experimental part
p. 502 - 507
(2012/07/17)
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- Imidazol(in)ium-2-carboxylates as Latent, Thermally Activated Organocatalysts for Transesterification Reactions
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1,3-Disubstituted imidazol(in)ium-2-carboxylates (ImCO2) were used as precatalysts for transesterification reactions of unactivated ethyl benzoate with monohydric alcohols, dihydric alcohols, and amino alcohols. Highly active N-heterocyclic carbenes (NHCs) are usually not used directly as catalysts because of their air and moisture sensitivity. Here they were liberated in situ by thermal decarboxylation of ImCO2 at designated temperatures. The results showed that the yield of the reactions reached up to 95% within 3 h using only 0.5 mol% catalyst. No active enol esters, molecular sieves, or a 20-fold excess of alcohol were used to drive the reaction to completion. It was proved that unsaturated imidazolium-2-carboxylates have a better activity than saturated species in this type of reaction. Different types of substituting groups of ImCO2 exhibited varied transesterification activity.
- Wang, Yanqin,Li, Zhenjiang
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p. 502 - 507
(2016/04/10)
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- A mild ligand-free iron-catalyzed liberation of alcohols from allylcarbonates
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Different from most carbonates the allyloxy carbonyl protecting group can be cleaved under neutral conditions using metal catalysis. However, most of the catalysts employed to date are based upon precious metals. Herein we present two protocols for the mild Fe-catalyzed liberation of alcohols from allylcarbonates that are characterized by broad functional group tolerance and exclusive chemoselectivity.
- Dieskau, Andre P.,Plietker, Bernd
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supporting information; experimental part
p. 5544 - 5547
(2011/12/05)
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- Rate-acceleration in gold-nanocluster-catalyzed aerobic oxidative esterification using 1,2- and 1,3-diols and their derivatives
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Aerobic oxidation of aldehydes to 1,2- and 1,3-diol monoesters was catalyzed by polymer-incarcerated gold nanoclusters under ambient conditions. The esterification proceeded much faster with 1,2- and 1,3-diols and their derivatives rather than with methanol. Magnum PI: Gold-nanocluster catalysts, PI-Au, that were immobilized on polystyrene-based polymers with cross-linking moieties, were used to catalyze the syntheses of 1,2 and 1,3-diol monoesters and their derivatives from aldehydes. The effect of neighboring-group participation in the esterification reaction is also described. Copyright
- Yasukawa, Tomohiro,Miyamura, Hiroyuki,Kobayashi, Shu
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experimental part
p. 621 - 627
(2011/10/12)
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- Oxidation of organotrifluoroborates via oxone
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A method for the oxidation of organotrifluoroborates using Oxone was developed. A variety of aryl-, heteroaryl-, alkenyl-, and alkyltrifluoroborates were converted into the corresponding oxidized products in excellent yields. This method proved to be tolerant of a broad range of functional groups, and in secondary alkyl substrates it was demonstrated to be completely stereospecific.
- Molander, Gary A.,Cavalcanti, Livia N.
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experimental part
p. 623 - 630
(2011/03/20)
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- Design, synthesis, and biological evaluation of coumarin derivatives tethered to an edrophonium-like fragment as highly potent and selective dual binding site acetylcholinesterase inhibitors
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A large series of substituted coumarins linked through an appropriate spacer to 3-hydroxy-N,N-dimethylanilino or 3-hydroxy-N,N,N-trialkylbenzaminium moieties were synthesized and evaluated as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. The highest AChE inhibitory potency in the 3-hydroxy-N,N-dimethylanilino series was observed with a 6,7-dimethoxy-3-substituted coumarin derivative, which, along with an outstanding affinity (IC50=0.236 nm) exhibits excellent AChE/BChE selectivity (SI>300 000). Most of the synthesized 3-hydroxy-N,N,N- trialkylbenzaminium salts display an AChE affinity in the sub-nanomolar to picomolar range along with excellent AChE/BChE selectivities (SI values up to 138 333). The combined use of docking and molecular dynamics simulations permitted us to shed light on the observed structure-affinity and structure-selectivity relationships, to detect two possible alternative binding modes, and to assess the critical role of π-π stacking interactions in the AChE peripheral binding site.
- Pisani, Leonardo,Catto, Marco,Giangreco, Ilenia,Leonetti, Francesco,Nicolotti, Orazio,Stefanachi, Angela,Cellamare, Saverio,Carotti, Angelo
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experimental part
p. 1616 - 1630
(2011/11/29)
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- Rational design, synthesis, and evaluation of new selective inhibitors of microbial class II (zinc dependent) fructose bis-phosphate aldolases
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We report the synthesis and biochemical evaluation of several selective inhibitors of class II (zinc dependent) fructose bis-phosphate aldolases (Fba). The products were designed as transition-state analogues of the catalyzed reaction, structurally relate
- Daher, Racha,Coin?on, Mathieu,Fonvielle, Matthieu,Gest, Petra M.,Guerin, Marcelo E.,Jackson, Mary,Sygusch, Jurgen,Therisod, Michel
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supporting information; experimental part
p. 7836 - 7842
(2011/02/24)
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- Nucleotide and oligonucleotide prodrugs
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The present invention discloses compounds of formula (I): which exhibit antiviral properties. The present invention further relates to pharmaceutical compositions comprising the aforementioned compounds for administration to a subject in need of anti-HBV
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Page/Page column 23
(2008/06/13)
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- Chromatography-free Pd-catalyzed deprotection of allyl ethers using PS-DEAM as a scavenger of boronic acids and Pd catalyst
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Polystyrene-bound diethanolamine (PS-DEAM) work-up for a newly developed Pd(PPh3)4-catalyzed cleavage of allylic alkyl ethers using phenylboronic acid can effectively release Pd-free parent alcohols. Furthermore, chromatography-free deallylation can be conducted by using vinylboronic anhydride pyridine complex as an allyl scavenger with a catalytic amount of Pd(OAc)2 and 4-(diphenylphosphino)benzoic acid instead of Pd(PPh3)4 to yield the desired products in high purities and yields after removal of volatile byproducts and the phosphine-derived contaminants by evaporation and sequestration through acid-base interaction with PS-DEAM, respectively.
- Tsukamoto, Hirokazu,Suzuki, Takamichi,Sato, Masanori,Kondo, Yoshinori
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p. 8438 - 8441
(2008/03/13)
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- Remarkable solvent effect on Pd(0)-catalyzed deprotection of allyl ethers using barbituric acid derivatives: Application to selective and successive removal of allyl, methallyl, and prenyl ethers
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Pd(0)-catalyzed deprotection of allyl ethers using barbituric acid derivatives in protic polar solvent such as MeOH and aqueous 1,4-dioxane proceeds at room temperature without affecting a wide variety of functional groups. Control of the reaction temperature allows selective and successive cleavage of allyl, methallyl, and prenyl ethers. A study of ligand effects on the deprotection reveals that the improved reactivity in MeOH results from the accelerated oxidative addition to Pd(O). Georg Thieme Verlag Stuttgart.
- Tsukamoto, Hirokazu,Suzuki, Takamichi,Kondo, Yoshinori
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p. 3131 - 3136
(2008/09/19)
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- Pyrimidine acyclonucleoside derivatives, preparation method and use thereof
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The invention relates to a compound having general formula (I): wherein n is equal to 3; R1 is an ethyl or isopropyl group; each of the R2 groups is independently of each other a hydrogen atom, a C1-C3 alkyl group or a halogen atom; one of the R3 and R4 groups represents a hydrogen atom while the other of the R3 and R4 groups represents an OH or OR5 group, where R5 can be a C2-C7 acyl group, an alkyl(C1-C6)animo-carbonyl group, an aralkyl(C1-C6)aminocarbonyl optionally substituted on the aryl, an arylcarbonyl group optionally substituted or a heteroarylaminocarbonyl group. Said compound is particularly suitable as an antiviral agent and especially as an anti-HIV-1 agent.
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Page/Page column 24
(2010/02/12)
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- A mild and efficient selective tetrahydropyranylation of primary alcohols and deprotection of THP ethers of phenols and alcohols using PdCl 2(CH3CN)2 as catalyst
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Primary alcohols were selectively tetrahydropyranylated in good to excellent yields at room temperature using PdCl2(CH 3CN)2 as catalyst in tetrahydrofuran (THF) in the presence of phenols, secondary, and tertiary alcohols. The tetrahydropyranyl (THP) group could be efficiently removed using PdCl2(CH 3CN)2 as catalyst in CH3CN, while other protection groups such as p-toluenesulfonyl (Ts), tert-butyldiphenylsilyl (TBDPS), benzyloxycarbonyl (Cbz), allyl, benzyl (Bn), and benzoyl (Bz) remained intact under these conditions.
- Wang, Yan-Guang,Wu, Xiao-Xing,Jiang, Zhi-Yong
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p. 2973 - 2976
(2007/10/03)
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- Al2O3/MeSO3H (AMA) as a new reagent with high selective ability for monoesterification of diols
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A new facile method for monoesterification of diols has been developed. A variety of diols, in particular oligoethylene glycols, were selectively monoesterified in excellent yields by reaction with aromatic and aliphatic acids in the presence of Al2O3/MeSO3H as a new reagent without use of any solvents.
- Sharghi, Hashem,Sarvari, Mona Hosseini
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p. 3627 - 3633
(2007/10/03)
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- Lipase-catalyzed monoprotection of 1,4-diols in an organic solvent using vinyl benzoate as acyl transfer agent
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Lipase from Mucor miehei (MML) has been selected as the most suitable enzyme to catalyze the efficient monobenzoylation of 1,4-diols using vinyl benzoate as acyl transfer reagent in tert-butyl methyl ether. The regioselectivity of the monobenzoylation of
- Ciuffreda, Pierangela,Casati, Silvana,Santaniello, Enzo
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p. 3663 - 3665
(2007/10/03)
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- A facile zirconium(IV) chloride catalysed selective deprotection of t-butyldimethylsilyl (TBDMS) ethers
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A simple and efficient protocol for the selective deprotection of t-butyldimethylsilyl (TBDMS) ethers using 20 mol% ZrCl4 in 20-45 min and in high yields, is reported, wherein it is demonstrated that acid and base sensitive groups and allylic and benzylic groups are unaffected.
- Sharma,Srinivas,Radha Krishna, Palakodety
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p. 4689 - 4691
(2007/10/03)
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- Facile and selective cleavage of allyl ethers based on palladium(0)-catalyzed allylic alkylation of N,N′-dimethylbarbituric acid
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The classical palladium(0)-catalyzed allylic alkylation of N,N′-dimethylbarbituric acid can be applied to the facile and selective cleavage of allylic alkyl ethers to release the corresponding alcohols in excellent yield. This reaction proceeds under neutral conditions without any additive to activate the allyl ethers and tolerates various functional groups, such as ester, ether, ketone, alkyl and aryl chloride, nitrile and nitro groups.
- Tsukamoto, Hirokazu,Kondo, Yoshinori
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p. 1061 - 1063
(2007/10/03)
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- Stereoselective synthesis of fully protected (S)-1,7-dioxaspiro[5,5]undec-4-ene derivatives of sugars
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Perbenzylated 1,7-dioxaspiro[5,5]undec-4-ene derivatives of sugars are obtained in three steps, starting from fully protected glycono-1,5-lactones. The procedure is based on the attack of a lithiated dithiinyl reagent (6) on the starting δ-glyconolactone.
- Caputo, Romualdo,Ciriello, Umberto,Festa, Pasquale,Guaragna, Annalisa,Palumbo, Giovanni,Pedatella, Silvana
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p. 2617 - 2621
(2007/10/03)
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- Facile cleavage of triethylsilyl (TES) ethers using o-lodoxybenzoic acid (IBX) without affecting tert-butyldimethylsilyl (TBS) ethers
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(matrix presented) In DMSO cleavage of triethylsilyl (TES) ethers by o-iodoxybenzoic acid (IBX) was significantly faster than cleavage of tert-butyldimethylsilyl (TBS) ethers or further oxidation into carbonyl compounds. In most cases, TES protecting groups be removed in good to excellent yields within 1 h, whereas similar TBS protecting groups remained intact under the same conditions. The procedure also could be adapted for direct one-pot conversion of TES ethers into carbonyl compounds.
- Wu, Yikang,Huang, Jia-Hui,Shen, Xin,Hu, Qi,Tang, Chao-Jun,Li, Liang
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p. 2141 - 2144
(2007/10/03)
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- A facile and chemoselective cleavage of trityl ethers by indium tribromide
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Trityl ethers are chemoselectively, deprotected to the corresponding alcohols in high yields by a catalytic amount of indium tribromide in aqueous acetonitrile. The method is compatible with various functional groups such as acetonides, acetates, benzoates, olefins, carbamates, esters and ethers present in the substrate.
- Yadav,Reddy, B.V. Subba,Srinivas,Maiti
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p. 528 - 529
(2007/10/03)
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- A mild and feasible deprotection of alcohol tetrahydropyranyl or methoxymethyl ethers catalyzed by Sc(OTf)3
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Tetrahydropyranyl or methoxymethyl ethers can be easily deprotected by treatment of a catalytic amount of scandium trifluoromethanesulfonate along with methanol or 1,3-propanediol, respectively, to afford the corresponding parent alcohols in high to excellent yields.
- Oriyama,Watahiki,Kobayashi,Hirano,Suzuki
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p. 2305 - 2311
(2007/10/03)
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- Chemo- and stereoselective monobenzoylation of 1,2-diols catalyzed by organotin compounds
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A new facile method for monoacylation of diols has been developed. A variety of cyclic and acyclic diols, in particular 1,2-diols, were selectively monobenzoylated in good yields by the reaction with benzoyl chloride in the presence of a catalytic amount of dimethyltin dichloride and inorganic bases such as potassium carbonate. Furthermore, the method was successfully applied to a kinetic resolution of racemic 1-phenyl-1,2- ethanediol using a chiral organotin catalyst. The ee was dependent on the kind of base, water as an additive, and the reaction temperature.
- Iwasaki, Fumiaki,Maki, Toshihide,Onomura, Osamu,Nakashima, Waka,Matsumura, Yoshihiro
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p. 996 - 1002
(2007/10/03)
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- Deprotection of tetrahydropyranyl ethers with montmorillonite K-10 clay in methanol
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A variety of tetrahydropyranyl (THP) ethers are removed by Montmorillonite K-10 clay in methanol at room temperature to give alcohols. It has been shown that the THP ethers carrying epoxy, methoxymethoxy (MOMO), tertbutyldiphenylsiloxy (TBDP-SO-), acetoxy (AcO-) and benzoyloxy (BzO-) functionalities are stable under the conditions, while the ethers carrying ketal, tertbutyldimethylsioxy (TBSO-) and β,β,β-trichloroethylimidoxy [CCl3C(=NH)O-] functionalities are unstable.
- Taniguchi, Takahiko,Kadota, Kohei,Elazab, Adel S.,Ogasawara, Kunio
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p. 1247 - 1248
(2007/10/03)
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- Extremely facile and selective nickel-catalyzed allyl ether cleavage
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Child's play! Allyl ethers as protecting groups for hydroxyl functions can be removed readily with a combination of DIBAL and catalytic amounts of [NiCl2(dppp)]. Propene is expelled in this remarkably selective reaction, and a nickel-catalyzed hydroalumination-elimination pathway is proposed. dppp = propane-1,3-diylbis(diphenylphosphane).
- Taniguchi, Takahiko,Ogasawara, Kunio
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p. 1136 - 1137
(2007/10/03)
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- A new convenient method for selective monobenzoylation of diols
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A new facile method for monoacylation of diols has been developed. A variety of cyclic and acyclic diols, in particular 1,2-diols, was selectively monobenzoylated in good yields by their reaction with benzoyl chloride in the presence of a catalytic amount of dimethyltin dichloride and inorganic bases.
- Maki, Toshihide,Iwasaki, Fumiaki,Matsumura, Yoshihiro
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p. 5601 - 5604
(2007/10/03)
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- A mild and selective deprotection of p-methoxybenzyl (PMB) ether by magnesium bromide diethyl etherate-methyl sulfide
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The magnesium bromide diethyl etherate (MgBr2 · OEt2)-methyl sulfide (Me2S) system is useful for the mild and chemo-selective deprotection of p-methoxybenzyl (PMB) ether in the presence of 1,3-diene, t-butyldimethylsilyl (TBDMS) ether, benzoate, benzyl ether and acetonide.
- Onoda, Toshihiko,Shirai, Ryuichi,Iwasaki, Shigeo
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p. 1443 - 1446
(2007/10/03)
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- Rhutenium-Catalyzed Oxidation of Cyclic Acetals with tert-Butyl Hydroperoxide. A Facile Synthesis of Glycol Monoesters
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The ruthenium-catalyzed oxidation of cyclic acetals with tert-butyl hydroperoxide under mild conditions gives the corresponding glycol monoesters efficiently.The present oxidation reaction provides a useful method for the synthesis of glycol monoesters from 1-alkenes by combination with palladium-catalyzed acetalization of 1-alkenes.
- Murahashi, Shun-Ichi,Oda, Yoshiaki,Naota, Takeshi
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p. 2237 - 2240
(2007/10/02)
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- Photoinduced Molecular Transformations. Part 113. One-step Transformations of Cyclic Ethers into ω-Iodoalkyl Formates and of Aldehyde Cyclic Acetals into Monoesters of α,ω-Alkanediols by Iodoxyl Radical
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The reaction of cyclic ethers with iodoxyl radical and iodine oxide gives the corresponding ω-iodoalkyl formates in one step; tetrahydrofuran can be transformed into ω-iodoalkyl formate in 31percent yield.Aldehyde cyclic acetals under conditions similar to the reaction of cyclic ethers lead to monoesters of α,ω-alkanediols in one step; cyclohexanecarboxaldehyde ethylene acetal gives 2-hydroxy cyclohexanecarboxylate in 60percent yield.The pathways leading to ω-iodoalkyl formatesand monoesters of α,ω-alkanediols are discussed based on the results of 18O-labelling studies with (18)OI and I2(18)O.
- Suginome, Hiroshi,Wang, Jian Bo
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p. 2825 - 2829
(2007/10/02)
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- Oxidation of ω-(Benzoyloxy)alkanols with an Oxoaminium Salt
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Oxoaminium chloride (2), the oxidized derivative of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, 1), was found to display a novel selectivity in the oxidation of ester group containing alcohols.The oxidation of (2 to 6)-(benzoyloxy)alkanols and related alcohols were carried out at room temperature with 1.0 equiv. of the oxoaminium chloride in dichloromethane (method A) or with 0.1 equiv. of TEMPO, 1.5 equiv. of cupric chloride, and 1.5 equiv. of cupric hydroxide (method B).Whereas the oxoaminium chloride did not significantly oxidize 2-(benzoyloxy)ethanol and 3-(benzoyloxy)propanol, it did oxidize 4-(benzoyloxy)butanol, 5-(benzoyloxy)pentanol and 6-(benzoxyloxy)hexanol to the corresponding (benzoyloxy)alkanals.The origin of this selectivity was investigated, and NMR and other studies suggest that the selectivity might be attributed to the inductive effect of the ester group.
- Yamaguchi, Masao,Takata, Toshikazu,Takeshi, Endo
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p. 1490 - 1492
(2007/10/02)
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- Conversion of 4-Oxy-Substituted Crotonaldehyde into 1-Protected (2R)-1,2,4-Butanetriol: A New Synthetic Capacity of Bakers' Yeast
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The bakers' yeast mediated conversion of 4-oxy-substituted crotonaldehydes 3 and 4 into 1-protected (2R)-1,2,4-butadienetriols 7a and 8a, in ca. 25percent yields, is reported.
- Fronza, Giovanni,Fuganti, Claudio,Grasselli, Piero,Poli, Gianluigi,Servi, Stefano
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p. 6153 - 6154
(2007/10/02)
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- Syntheses of Tetrahydrofurobenzofurans: A Synthesis of (+/-)-Aflatoxin B2
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Aldehyde O-aryl oximes, on treatment with hydrogen chloride in tetrahydrofuran, are converted to 2-hydroxy-2,3-dihydrobenzofurans and their corresponding 4-chlorobutanol ketals.The major reaction pathway, a 3,4-oxaza Cope rearrangement, is accompanied by Beckmann fragmentation, the relative amount of which is sensitive to the stereochemistry of the oxime and the specific acid conditions.With appropriately substituted oximes, the 2,3,3a,8a-tetrahydrofurobenzofuran ring system is efficiently prepared, as is demonstrated for the 4-hydroxy-6-methoxy derivative and its regioisomer.The former compound provides a total synthesis of alfatoxin B2.
- Castellino, Angelo J.,Rapoport, Henry
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p. 1006 - 1011
(2007/10/02)
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- DABCO-Catalyzed Coupling of Aldehydes with Activated Double Bonds. 4. Stereoselective Synthesis of Trisubstituted Olefins and Terpenoid Building Blocks via 2-(Hydroksyalkyl)-2-propenoic Esters.
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A variety of 2-(hydroksyalkyl)-2-propenoic esters 16a-g has been prepared in high yield by DABCO-catalyzed coupling of aldehydes 14a-g with methyl acrylate.The product esters 16a-g are useful building blocks in syntheses which undergo regioselective and Z-selective SN2 reactions with N-bromosuccinimide/dimethyl sulfide and N-chlorosuccinimide/dimethyl sulfide to furnish (Z)-2-(bromomethyl)-2-alkenoic esters 17a-g and (Z)-2-(chloromethyl)-2-alkenoic esters 18b,c,d, respectively.Similarly, the derived allylic acetates 21g,h, and also allylic bromide 17g react with lithium triethylhydridoborate via mechanism SN2' to give (E)-2-methyl-2-alkenoic esters 22g,h and respectively, 2-methylenealkanoic esters 20g.Methyl (Z)-6,6-(ethylenedioxy)-2-methyl-2-heptenoate (22h) has been prepared as an intermediate en route to the norsesquiterpenoid ketone 23.The allylic bromides 17d,e,f also furnish (Z)-6-methyl-5--4-heptene-1,6-diol (19a), (Z)-2-methyl-3--3-octene-2,7-diol (19e), and (Z)-7-methyl-6--5-octene-1,2,7-triol (19f), which are terpenoid building blocks.
- Hoffmann, H. Martin R.,Rabe, Juergen
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p. 3849 - 3859
(2007/10/02)
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