- Compound with mutton smell fragrance as well as preparation method and application thereof
-
The invention relates to the field of spices, and in particularrelates to a compound with mutton smell fragrance as well as a preparation method and application thereof. The invention discloses the compound with mutton smell fragrance. The compound has a structure shown as a formula (I). Research finds that the prepared compound with the mutton smell fragrance has the remarkable mutton smell fragrance, the fragrance intensity is high, and the fragrance lasting time is long. Compared with a traditional acidic mutton smell aroma substance, the compound with the mutton smell fragrance prepared by the invention belongs to ester compounds, so that the compound can stably exist when being applied to essence containing alkaline substances. The invention further provides a preparation method and application of the compound with the mutton smell fragrance. The raw materials for preparing the compound with the mutton smell fragrance are wide and easy to obtain, the technological operation is simple and convenient, and the compound is suitable for batch production.
- -
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Paragraph 0074-0086; 0088-0091; 0093-0096
(2021/04/14)
-
- Radical dehydroxylative alkylation of tertiary alcohols by Ti catalysis
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Deoxygenative radical C?C bond-forming reactions of alcohols are a long-standing challenge in synthetic chemistry, and the current methods rely on multistep procedures. Herein, we report a direct dehydroxylative radical alkylation reaction of tertiary alcohols. This new protocol shows the feasibility of generating tertiary carbon radicals from alcohols and offers an approach for the facile and precise construction of all-carbon quaternary centers. The reaction proceeds with a broad substrate scope of alcohols and activated alkenes. It can tolerate a wide range of electrophilic coupling partners, including allylic carboxylates, aryl and vinyl electrophiles, and primary alkyl chlorides/bromides, making the method complementary to the cross-coupling procedures. The method is highly selective for the alkylation of tertiary alcohols, leaving secondary/primary alcohols (benzyl alcohols included) and phenols intact. The synthetic utility of the method is highlighted by its 10-g-scale reaction and the late-stage modification of complex molecules. A combination of experiments and density functional theory calculations establishes a plausible mechanism implicating a tertiary carbon radical generated via Ti-catalyzed homolysis of the C?OH bond.
- Xie, Hao,Guo, Jiandong,Wang, Yu-Quan,Wang, Ke,Guo, Peng,Su, Pei-Feng,Wang, Xiaotai,Shu, Xing-Zhong
-
supporting information
p. 16787 - 16794
(2020/11/09)
-
- Electrochemical anion pool synthesis of amides with concurrent benzyl ester synthesis
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An electrosynthesis method for amide bond formation has been developed in an attempt to increase the atom economy for this class of reactions. This "anion pool" method electrochemically generates strong nucleophiles from amine substrates. The amine nucleophiles then react with acid anhydrides to generate amides, and the by-product from this reaction undergoes further chemical transformations to generate pharmaceutically relevant benzoic esters. These one-pot reactions are operationally simple, are performed at room temperature, and avoid rare transition metals and added bases. The amide synthesis is amenable to primary and secondary amines and a variety of anhydrides with yields up to 90% obtained. Atom economy and process mass index (PMI) values calculated for this procedure indicate that this process can be considered greener compared to traditional amide synthesis routes used by industry. Furthermore, this electrochemical approach showed unique selectivity when substrates that contained two inequivalent amine moieties were examined.
- Mevan Dissanayake,Melville, Alex D.,Vannucci, Aaron K.
-
supporting information
p. 3165 - 3171
(2019/06/18)
-
- Dienolates of Cycloalkenones and α,β-Unsaturated Esters Form Diels–Alder Adducts by a Michael/Michael-Tandem Reaction Rather Than in One Step
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α,β-Unsaturated esters and lithium 1,3-dien-2-olates are known to furnish bicyclic lithium enolates by anionic Diels–Alder reactions. However, in principle, the respective products might form not only in a single step but also in two consecutive – or “tandem” – Michael additions, the first of which occurs intermolecularly, the second intramolecularly. Three cyclic lithium dienolates and four esters with a stereogenic Cα=Cβ bond reacted to give Diels–Alder adducts (10 times) or failed to react (2 times). Seven of the reactive combinations furnished adducts wherein the configuration of the former ester moiety had in part inverted. This precludes concerted pathways as their origins. This was a surprise since donors at C-2 of the 1,3-diene accelerate normal electron-demand Diels–Alder reactions in the order alkyl ⊕O? being a far better donor still, it is not obvious why the mechanism is non-concerted rather than concerted (and still more asynchronous).
- Loesche, Ann-Christine,Brückner, Reinhard
-
supporting information
p. 562 - 573
(2018/12/11)
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- SUBSTITUTED PYRROLIDINES AND THEIR USE
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The invention discloses compounds of Formula (I) wherein R1, R2, R3, R3A, R4, and R5 are as defined herein. The present invention relates to compounds and their use in the treatment of cystic fibrosis, methods for their production, pharmaceutical compositions comprising the same, and methods of treating cystic fibrosis by administering a compound of the invention.
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-
Paragraph 0340; 0374
(2019/10/30)
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- Carboxylative Suzuki coupling reactions of benzyl chlorides with allyl pinacolborate catalyzed by palladium nanoparticles
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Palladium-catalyzed carboxylative Suzuki coupling reactions of benzyl chlorides with allyl pinacolborate were successfully conducted in the absence of any extra ligand to produce β,γ-unsaturated esters in satisfactory to good yields. The carboxylative Suzuki coupling reaction proceeded smoothly under mild conditions in the presence of palladium nanoparticles generated in situ through the formation of a π-benzylpalladium chloride intermediate.
- Sun, Jian,Wang, Jiasheng,Feng, Xiujuan,Yamamoto, Yoshinori,Almansour, Abdulrahman I.,Arumugam, Natarajan,Kumar, Raju Suresh,Bao, Ming
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p. 1258 - 1262
(2018/06/21)
-
- A Tunable Route to Prepare α,β-Unsaturated Esters and α,β-Unsaturated-γ-Keto Esters through Copper-Catalyzed Coupling of Alkenyl Boronic Acids with Phosphorus Ylides
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A tunable strategy to prepare α,β-unsaturated esters and α,β-unsaturated-γ-keto esters in good to excellent yields was developed through copper-catalyzed oxidative coupling of phosphorus ylides with alkenyl boronic acids under mild conditions. The reaction without water afforded α,β-unsaturated esters, ketones, and amides while α,β-unsaturated-γ-keto esters, 1,4-α,β-unsaturated diketones and α,β-unsaturated-γ-keto amides were obtained when using 5.0 equiv. of water. H2O18 labeling experiments showed that water played an important role in the formation of α,β-unsaturated-γ-keto esters. A plausible formation mechanism for α,β-unsaturated esters and α,β-unsaturated-γ-keto esters was proposed based on mechanistic studies. Phosphonium salts could also be used directly as coupling partners instead of phosphorus ylides. The reaction exhibited a broad substrate scope, good functional group tolerance, good regioselectivity, and diverse coupling products. (Figure presented.).
- Bi, Hong-Yan,Liu, Feng-Ping,Liang, Cui,Su, Gui-Fa,Mo, Dong-Liang
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p. 1510 - 1516
(2018/03/05)
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- A New Approach to Models of the 4,5-Dihydroxycyclopentenone Core of the Kodaistatins A–D: Elucidation of the Diol Configuration in Kodaistatin A
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The kodaistatins A–D are strongly anti-diabetic natural products from Aspergillus terreus that hold some promise of a novel diabetes cure. However, considerations of that kind face two drawbacks: 1) The kodaistatins A–D contain a heavily substituted pulvinone/cyclopentenone combination; 2) they are 1,2-diols, the 3D structures of which have not been assigned yet. However, we can exclude two of the four possible stereostructures. We conclude that kodaistatin A is a trans-, not a cis-diol from NMR comparisons with a pair of cis, trans-isomeric kodaistatin models, which we synthesized in 11 and 12 steps, respectively. The stereocenters of the diol moiety arose from stereocomplementary, highly diastereoselective aldol additions of a lithium enolate or the corresponding silyl ketene acetal. The cyclopentenone moieties stemmed from intramolecular aldol additions and ensuing dehydrations. The requisite enolates were obtained by the reduction of α-bromoketones with samarium diiodide.
- Peter, David,Brückner, Reinhard
-
supporting information
p. 12104 - 12109
(2017/09/14)
-
- Reductive Coupling of Acrylates with Ketones and Ketimines by a Nickel-Catalyzed Transfer-Hydrogenative Strategy
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Nickel-catalyzed coupling of benzyl acrylates with activated ketones and imines provides γ-butyrolactones and lactams, respectively. The benzyl alcohol byproduct released during the lactonization/lactamization event is relayed to the next cycle where it serves as the reductant for C?C bond formation. This strategy represents a conceptually unique approach to transfer-hydrogenative C?C bond formation, thus providing examples of reductive heterocyclizations where hydrogen embedded within an alcohol leaving group facilitates turnover.
- Buxton, Craig S.,Blakemore, David C.,Bower, John F.
-
supporting information
p. 13824 - 13828
(2017/10/24)
-
- NOVEL SINGLE STEP ESTERIFICATION PROCESS OF ALDEHYDES USING A HETEROGENEOUS CATALYST
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The present invention relates to a novel simple, efficient and single-step process for esterification of aldehydes using a heterogeneous catalyst with high yields. More particularly, the present invention relates to a novel simple, efficient and single-step process for esterification of aldehydes using Titanium superoxide with greater than 80% yields.
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Page/Page column 9; 15
(2016/06/20)
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- Chemoselective Transesterification of Acrylate Derivatives for Functionalized Monomer Synthesis Using a Hard Zinc Alkoxide Generation Strategy
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A new practical method for the synthesis of functionalized acrylate derivatives with the view to prepare functional polymers was explored. Hard zinc alkoxide generation enabled the highly chemoselective transesterification of acrylate derivatives over the undesired conjugate addition, which caused polymerization. The combined use of the catalytic zinc cluster Zn4(OCOCF3)6O and 4-(dimethylamino)pyridine delivered various functionalized acrylate derivatives through the transesterification of commercially available methyl acrylate derivatives with functionalized alcohols under mild conditions.
- Nakatake, Daiki,Yazaki, Ryo,Ohshima, Takashi
-
supporting information
p. 3696 - 3699
(2016/08/20)
-
- Preparation method of alpha, beta-unsaturated carboxylate compound
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The invention relates to the technical field of CO2 activation and conversion and related chemistry, relates to a method for synthesizing alpha, beta-unsaturated carboxylate by using CO2 as a C1 source, and especially relates to a method for synthesizing alpha, beta-unsaturated carboxylate based on (hetero)arylmethyl halide and trisubstituted allylsilane. The method is characterized in that a carboxylation reaction of (hetero)arylmethyl halide and trisubstituted allylsilane is realized under the catalysis of a Pd catalyst by using carbon dioxide as the C1 source. The invention mainly provides new simple external ligand-free nanometer catalysis system. CO2 is used as the C1 source to synthesize alpha, beta-unsaturated carboxylate. The catalysis system has the advantages of green and easily available reaction raw materials, mild reaction conditions, simple experiment operation, and good compatibility of function groups. CO2 is the plentiful, cheap, easily-available and renewable C1 source, so the method has large application values and large social and economic benefits.
- -
-
Paragraph 0032; 0033; 0034
(2016/11/02)
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- SALT OF PYRROLIDIN-3-YL ACETIC ACID DERIVATIVE AND CRYSTALS THEREOF
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An organic carboxylic acid salt of 2-[(3S,4R)-1-{[2-chloro-6-(trifluoromethyl)phenyl]methyl}-3-{[1-(cyclohex-1-en-1-ylmethyl) piperidin-4-yl]carbamoyl}-4-methylpyrrolidin-3-yl]acetic acid and a crystal thereof.
- -
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Paragraph 0090; 0091
(2016/03/05)
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- Titanium superoxide-a stable recyclable heterogeneous catalyst for oxidative esterification of aldehydes with alkylarenes or alcohols using TBHP as an oxidant
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Titanium superoxide efficiently catalysed the oxidative esterification of aldehydes with alkylarenes or alcohols, under truly heterogeneous conditions, to afford the corresponding benzyl and alkyl esters in excellent yields. Mechanistic studies have established that this "one pot" direct oxidative esterification process proceeds through a radical pathway, proven by a FTIR spectral study of a titanium superoxide-aldehyde complex as well as spin trapping experiments with TEMPO. The intramolecular version of this protocol has been successfully demonstrated in the concise synthesis of 3-butylphthalide, an anti-convulsant drug.
- Dey, Soumen,Gadakh, Sunita K.,Sudalai
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p. 10631 - 10640
(2015/11/17)
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- PYRROLIDINE-3-YLACETIC ACID DERIVATIVE
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A compound represented by formula (1) or a pharmaceutically acceptable salt thereof has an inhibitory effect in the fractalkine-CX3CR1 pathway: wherein R represents a C1-6 alkyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group A, a C3-8 cycloalkyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group A, or a C3-8 cycloalkenyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group A, X represents a C1-6 alkyl group, Y and Z are the same or different from each other and each represents a halogen atom or a C1-6 alkyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group B, n represents 0 or 1, Substituent Group A consists of halogen atoms, and Substituent Group B consists of halogen atoms.
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-
Paragraph 0154
(2014/08/06)
-
- Palladium-catalyzed carboxylative coupling of benzyl chlorides with allyltributylstannane: Remarkable effect of palladium nanoparticles
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Palladium-catalyzed carboxylative coupling of benzyl chlorides with allyltributylstannane was successfully conducted to produce benzyl but-3-enoates in satisfactory to good yields. The carboxylative coupling reaction occurred smoothly under mild conditions in the presence of palladium nanoparticles in tetrahydrofuran.
- Feng, Xiujuan,Sun, Anle,Zhang, Sheng,Yu, Xiaoqiang,Bao, Ming
-
supporting information
p. 108 - 111
(2013/04/10)
-
- PYRROLIDIN-3-YLACETIC ACID DERIVATIVE
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A compound represented by formula (1) or a pharmaceutically acceptable salt thereof has an inhibitory effect in the fractalkine-CX3CR1 pathway: wherein R represents a C1-6 alkyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group A, a C3-8 cycloalkyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group A, or a C3-8 cycloalkenyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group A, X represents a C1-6 alkyl group, Y and Z are the same or different from each other and each represents a halogen atom or a C1-6 alkyl group unsubstituted or having 1 to 3 substituents selected from Substituent Group B, n represents 0 or 1, Substituent Group A consists of halogen atoms, and Substituent Group B consists of halogen atoms.
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Paragraph 0206; 0207
(2013/03/28)
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- Use of diethoxymethane as a solvent for phase-transfer esterification of carboxylic acids
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The esterification of carboxylic acids with selected primary alkyl halides in diethoxymethane (DEM) utilizing solid-liquid phase-transfer catalysis has been studied. The use of DEM as the solvent simplifies the process in that a single solvent can be used for both reaction and workup.
- Coleman, M. Todd
-
scheme or table
p. 1911 - 1913
(2012/06/04)
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- Well-defined binuclear chiral spiro copper catalysts for enantioselective N-H insertion
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An asymmetric N-H insertion of α-diazoesters with anilines catalyzed by well-defined copper complexes of chiral spiro bisoxazoline ligands was studied in detail. The copper-catalyzed asymmetric N-H insertion of a wide range of α-alkyl-α-diazoacetates with anilines was accomplished with excellent enantioselectivity (up to 98% ee) and provided an efficient method for the preparation of optically active α-amino acid derivatives. A correlation study of the electronic properties of the substrates with the enantioselectivity of the N-H insertion reaction supports a stepwise insertion mechanism, and the significant first-order kinetic isotope effect proves that the proton transfer is most likely the rate-limiting step. A binuclear chiral spiro copper catalyst having 14-electron copper centers, a trans coordination model, a perfect C2-symmetric chiral pocket, and significant Cu-Cu interaction was isolated and extensively studied. The novel structure of the binuclear chiral spiro copper catalyst leads to unique reactivity as well as enantioselectivity in the N-H insertion reaction.
- Zhu, Shou-Fei,Xu, Bin,Wang, Guo-Peng,Zhou, Qi-Lin
-
supporting information; experimental part
p. 436 - 442
(2012/03/07)
-
- Scalable synthesis of enantiomerically pure syn -2,3-dihydroxybutyrate by sharpless asymmetric dihydroxylation of p -phenylbenzyl crotonate
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An efficient four-step synthetic route to the useful chiral building block (2R,3S)-dihydroxybutyric acid acetonide in >95% ee is detailed. The sequence is readily scaled, requires no chromatography, and allows for efficient recycling of p-phenylbenzyl alcohol, an expedient for enantio- and diastereoenrichment by recrystallization.
- Smaltz, Daniel J.,Myers, Andrew G.
-
body text
p. 8554 - 8559
(2011/12/03)
-
- PREPARATION OF ALKENES BY MILD THERMOLYSIS OF SULFOXIDES
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Embodiments of this disclosure, among others, encompass methods for generating alkenes under mild thermolytic conditions that can provide almost total conversion of a precursor compound to an alkene without isomerization or the need to chromatographically purify the final product By selectively blocking the amino and carboxy groups of the depvatized amino acid, the methods of the disclosure provide for the synthesis of a peptide having the vinylglycine moiety at either the carboxy or the amino terminus of the peptide The mild conditions for the thermolytic removal of an o-NO2-phenyl substituted aryl group ensure that there is minimal if any damage to thermally sensitive conjugates such as a peptide bearing the vinylglycine The methods of the present disclosure have practical applications for the preparation of unsaturated compounds under mild, thermolytic conditions.
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Page/Page column 5
(2010/07/02)
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- O-Nitrophenyl sulfoxides: Efficient precursors for the mild preparation of alkenes
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(Chemical Equation Presented) o-Nitrophenyl sulfoxides were found to be efficient synthetic precursors of various alkene types. The elimination occurs in toluene and NaOAc to generate substituted and terminal alkenes. Alkene products were easily obtained in high purity due to the simultaneous precipitation of the o-nitrophenyl sulfenic acid byproduct. The methods described have practical applications for the preparation of unsaturated compounds under mild, thermolytic conditions. 2009 American Chemical Society.
- Lu, Xiao,Long, Timothy E.
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scheme or table
p. 249 - 252
(2010/04/06)
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- 5,5′-Dimethyl-3,3′-azoisoxazole as a new heterogeneous azo reagent for esterification of phenols and selective esterification of benzylic alcohols under Mitsunobu conditions
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5,5′-Dimethyl-3,3′-azoisoxazole is used as a new efficient heterogeneous azo reagent for the highly selective esterification of primary and secondary benzylic alcohols and phenols with aliphatic and aromatic carboxylic acids via Mitsunobu protocols. The reaction is highly selective for primary benzylic alcohols versus secondary ones, aliphatic alcohols and also phenols. The isoxazole hydrazine byproduct can be simply isolated by filtration and recycled to its azoisoxazole by oxidation.
- Iranpoor, Nasser,Firouzabadi, Habib,Khalili, Dariush
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supporting information; experimental part
p. 4436 - 4443
(2010/11/05)
-
- Copper-catalyzed enantioselective carbenoid insertion into S-H bonds
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An asymmetric carbenoid insertion into S-H bonds catalyzed by copper-chiral spiro bisoxazoline complexes has been developed, in which a series of α-mercaptoesters were produced in high yields with moderate to good enantioselectivities (up to 85% ee); this
- Zhang, Yong-Zhen,Zhu, Shou-Fei,Cai, Yan,Mao, Hong-Xiang,Zhou, Qi-Lin
-
body text
p. 5362 - 5364
(2009/12/08)
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- The effect of fluoromethyl groups on the diastereoselectivity in the electrophilic alkylation
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The effect of fluoromethyl groups on the diastereoselectivity in the electrophilic alkylation is described. In particular, the electrophilic alkylation of enolates with a trifluoromethyl group was proceeded with highly diastereofacial selectivity based on the steric and/or electrostatic effect of substituent with strong electron withdrawing.
- Tamura, Kenji,Yamazaki, Takashi,Kitazume, Tomoya,Kubota, Toshio
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p. 918 - 930
(2007/10/03)
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- CCR5 antagonists: 3-(pyrrolidin-1-yl)propionic acid analogues with potent anti-HIV activity
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(Matrix presented) A novel approach to α,α-disubstituted-β -amino acids (β2,2-amino acids) was employed in the synthesis of a series of 3-(pyrrolidin-1-yl)-propionic acids possessing high affinity for the CCR5 receptor and potent anti-HIV activity. The rat pharmacokinetics for these new analogues featured higher bioavailabilities and lower rates of clearance as compared to cyclopentane 1.
- Lynch, Christopher L.,Hale, Jeffrey J.,Budhu, Richard J.,Gentry, Amy L.,Finke, Paul E.,Caldwell, Charles G.,Mills, Sander G.,MacCoss, Malcolm,Shen, Dong-Ming,Chapman, Kevin T.,Malkowitz, Lorraine,Springer, Martin S.,Gould, Sandra L.,DeMartino, Julie A.,Siciliano, Salvatore J.,Cascierl, Margaret A.,Carella, Anthony,Carver, Gwen,Holmes, Karen,Schleif, William A.,Danzeisen, Renee,Hazuda, Daria,Kessler, Joseph,Lineberger, Janet,Miller, Michael,Emini, Emilio
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p. 2473 - 2475
(2007/10/03)
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- Direct ester condensation from a 1:1 mixture of carboxylic acids and alcohols catalyzed by hafnium(IV) or zirconium(IV) salts
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To promote atom efficiency in synthesis and to avoid the generation of environmental waste, the use of stoichiometric amounts of condensing reagents or excess substrates should be avoided. In esterification, excess amounts of either carboxylic acids or alcohols are normally needed. We found that the direct condensation of equimolar amounts of carboxylic acids and alcohols could be achieved using hafnium(IV) or zirconium(IV) salts. These metal salts are highly effective as catalysts for the selective esterification of primary alcohols with carboxylic acids in the presence of secondary alcohols or aromatic alcohols. The present methods can be applied to direct polyesterification and may be suitable for large-scale operations.
- Ishihara, Kazuaki,Nakayama, Masaya,Ohara, Suguru,Yamamoto, Hisashi
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p. 8179 - 8188
(2007/10/03)
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- Zinc promoted mild and efficient method for the esterification of acid chlorides with alcohols
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The esterification of variety of acid chlorides with alcohols in the presence of zinc is described. The easy formation of t-butyl and pivaloyl esters are the additional importance of this procedure.
- Yadav,Reddy, Gondi Sudershan,Srinivas, Dale,Himabindu, Konuru
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p. 2337 - 2342
(2007/10/03)
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- Glycoluril as an efficient molecular template for intramolecular Claisen-type condensations
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The readily prepared 3,4,7,8-tetramethylglycoluril 1 acts as a template to promote efficient intramolecular Claisen-like condensations between two acyl groups which are attached to the N-1 and N-6 positions. Thus, two sequential acylations of 1 give symmetric or unsymmetric diacylglycolurils 9-18 in good yield. Treatment of 9-18 with lithium tert-alkoxides furnishes N-(β-ketoacyl)glycolurils 19-27 under mild conditions and in high yields; rate-limiting deprotonation, predominantly on the least substituted of the two acyl groups, precedes a fast intramolecular Claisen-type condensation. Reduction of the keto group in 19 and 26, followed by elimination of water gives alk-2-enoylglycolurils 6 and 7; conjugate hydride addition (L-Selectride) then gives alkanoylglycoluril 5. Compounds 5-7 undergo further rounds of N-acylation then intramolecular condensation. Linear chains can thus be constructed on 1 by repetitive sequences of acylation-condensation-functional group transformation. N1-Alk-2-enoyl-N6-alkanoylglycolurils 14-17 also afford condensation products with high selectivity upon treatment with L-Selectride, effecting a method for net reversal of the regioselectivity observed in the base-promoted rearrangement. The synthesized chains can be readily removed from the template, regenerating 1. The efficiency of the condensation reaction, the sequence of transformations and the ability to grow linear carbon chains in a repetitive manner mimic these aspects of the catalytic cycle of fatty acid synthases and polyketide synthases.
- Sun, Sengen,Edwards, Louise,Harrison, Paul
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p. 437 - 448
(2007/10/03)
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- Highly reactive, water soluble carbodiimides, intermediates and derivatives thereof
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Novel water soluble carbodiimides, and intermediates or derivatives thereof, such as isoureas or isothioureas, are described. A particularly preferred embodiment is bis[4-(2,2-dimethyl-1,3-dioxolyl)methyl] carbodiimide (BDDC), which can be synthesized efficiently from 1,2-isopropylideneglycerol (solketal). The isoureas are effective esterifying agents. The corresponding N-protected amino acid tert-butyl, benzyl, isopropyl, ethyl, and methyl esters can be synthesized in high yield under neutral conditions, with no urea residue after simply washing with aqueous acid. Amino acid couplings utilizing carbodiimide embodiments give peptides in good yield, free of carbodiimide by-products, after washing with dilute acid, while racemization-free peptides are also obtained.
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- Transesterification of carboxylic acids
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Carboxylic acids may be esterified by reaction with esters in the presence of a catalytic amount of a tin halide catalyst, the reaction being effected at temperatures ranging from about 0° to about 150° C.
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