- Synthesis of the bicyclic core of pumiliotoxins
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The bicyclic core of the pumiliotoxins was synthesized in nine to eleven steps starting from L-(-)-proline. This chiral pool starting material was initially converted into an optically active 2-vinylpyrrolidine by standard operations. The first key step allowed the generation of a nine-membered ring lactam by means of a zwitterionic aza-Claisen rearrangement. The 1,4 chirality transfer was found to be low, but the double bond of the azoninone was generated with an exclusive trans configuration in a planar-S arrangement. The mixture of diastereomers thus obtained was immediately epoxidized; the planar chiral information could be completely used to build up new stereogenic centers. Subsequent ring closure under hydrogenolytic conditions resulted in the formation of the bicyclic core with a bridgehead of defined configuration. The hydroxyl group of that material could be protected as a TBS ether, or alternatively a sequence of a Swern oxidation and subsequent methyl Grignard addition gave the complete bicyclic framework with low C8 diastereoselectivity. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Sudau, Alexander,Muench, Winfried,Bats, Jan-W.,Nubbemeyer, Udo
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- Catalytic epoxidation of unfunctionalized alkenes by dinuclear nickel(II) complexes
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The synthesis, crystal and molecular structure and catalytic activity in epoxidation reactions of new dinuclear nickel(II)-complexes, octahedral μ-diacetato-μ-[2,6-bis[N-2-2'-pyridylethyl)formimidoyl]phenolato]bis nickel(II)·perchlorate·methanol (6) and square planar (μ-hydroxo-μ-[2,6-bis[N-((S)-1-benzyl-2-yl-pyrrolidine)formimidoyl]p henolato]bisnickel(II)·bisperchlorate (7), are described. For the preparation of 7 a new 5-step route for homochiral bisamine (S)-benzyl-2-aminomethyl-pyrrolidine (19) was developed starting from (S)-proline. Epoxidation of unfunctionalized alkenes with sodium hypochlorite and tert-butyl hydroperoxide as terminal oxidants was effectively catalyzed with bisnickel(II)-complexes 6 and 7, and a turnover of 165 was reached using trans-β-methylstyrene (34). The epoxidations probably proceed via a radical intermediate (such as OCl·) and no enantioselectivity is obtained under phase transfer conditions. In epoxidation reactions employing tert-butyl hydroperoxide as terminal oxidant a turnover of 43 was obtained with trans-stilbene (30) as substrate. Unexpectedly in the case of styrene (29) 1,2-bis-(tert-butylperoxy)ethylbenzene (59) was isolated as the major product.
- Rispens, Minze T.,Gelling, Onko Jan,De Vries, Andre H.M.,Meetsma, Auke,Van Bolhuis, Fre,Feringa, Ben L.
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- Lewis Acids as Activators in CBS-Catalysed Diels–Alder Reactions: Distortion Induced Lewis Acidity Enhancement of SnCl4
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The effect of several Lewis acids on the CBS catalyst (named after Corey, Bakshi and Shibata) was investigated in this study. While2H NMR spectroscopic measurements served as gauge for the activation capability of the Lewis acids, in situ FT-IR spectroscopy was employed to assess the catalytic activity of the Lewis acid oxazaborolidine complexes. A correlation was found between the Δδ(2H) values and rate constants kDA, which indicates a direct translation of Lewis acidity into reactivity of the Lewis acid–CBS complexes. Unexpectedly, a significant deviation was found for SnCl4as Lewis acid. The SnCl4–CBS adduct was much more reactive than the Δδ(2H) values predicted and gave similar reaction rates to those observed for the prominent AlBr3–CBS adduct. To rationalize these results, quantum mechanical calculations were performed. The frontier molecular orbital approach was applied and a good correlation between the LUMO energies of the Lewis acid–CBS–naphthoquinone adducts and kDAcould be found. For the SnCl4–CBS–naphthoquinone adduct an unusual distortion was observed leading to an enhanced Lewis acidity. Energy decomposition analysis with natural orbitals for chemical valence (EDA-NOCV) calculations revealed the relevant interactions and activation mode of SnCl4as Lewis acid in Diels–Alder reactions.
- N?dling, Alexander R.,M?ckel, Robert,Tonner, Ralf,Hilt, Gerhard
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- Azetidine based ligands in boron catalyzed asymmetric
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The preparation of a new class of azetidine-based auxiliaries and their selectivity in the BBr3 catalyzed Diels-Alder reaction is described. The results are compared with a similar proline-derived ligand and a known prolinol auxiliary. Results show that selectivities are highly dependent on the dienophile and the substituent of the chiral auxiliary.
- Starmans, Wim A. J.,Walgers, Richard W.A.,Thijs, Lambertus,De Gelder, Rene,Smits, Jan M.M.,Zwanenburg, Binne
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- Enantioselective Intermolecular [2+2] Photocycloaddition Reaction of Cyclic Enones and Its Application in a Synthesis of (-)-Grandisol
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The intermolecular [2+2] photocycloaddition of typical cyclic α,β-unsaturated enones, such as 2-cyclohexenone, with olefins was performed in moderate to good yields (42-82%) and with high enantioselectivity (82%-96% ee). An unusual substitution pattern at the chiral oxazaborolidine-AlBr3 Lewis acid complex that promotes the reaction was found to be crucial for the success of the reaction. The method was applied to the enantioselective synthesis of the monoterpene (-)-grandisol, which could be accomplished in six steps and with an overall yield of 13% starting from 3-methyl-2-cyclohexenone.
- Poplata, Saner,Bach, Thorsten
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- Synthesis of W-propionylated (S)-(-)-2-(pyrrolidin-2-yl)propan2-ol and its use as a chiral auxiliary and selectivity marker in asymmetric aldol reactions
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The N-propionylated pyrrolidine derivative and chiral auxiliary, (S)-(-)-2-(pyrrolidin-2-yl)propan-2-ol, was synthesised and used in stereoselective aldol reactions with benzaldehyde. Differences in stereoselectivity were investigated as a function of temperature, solvent, chelating agent and the amount of the chelating agent used by monitoring the 1H NMR spectra of the aldol adducts that were obtained. Among the additives that were investigated, Cp2ZrCl2 induced higher syn-selectivity, while SnCl2 induced higher syn-selectivity respectively. TMSCl was found to induce high selectivity for one syn- and one anti-diastereomer. Varying the ligand sets on titanium additives was found to induce differences in selectivity, with (i-PrO)3TiCl exhibiting syn-selectivity and Cp2TiCl2 exhibiting anti-selectivity. Differences in reactivity and stereoselectivity were also found to depend upon the amount of Lewis acid that was added. Methods for removal of the auxiliary were also investigated. Acidic hydrolysis was used successfully to obtain the desired 3-hydroxy-2-methyl-3-phenylpropionic acids, but was found to give low yields and resulted in a large amount of epimerisation. Furthermore, the ethyl esters of these hydroxy acids are easy to separate into pure syn- and anti-diastereomers by LC. The Royal Society of Chemistry 2000.
- Hedenstroem, Erik,Andersson, Fredrik,Hjalmarsson, Mats
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- Towards the Development of Frustrated Lewis Pair (FLP) Catalyzed Hydrogenations of Tertiary and Secondary Carboxylic Amides
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The development of the frustrated Lewis pair catalyzed hydrogenation of tertiary and secondary amides is reviewed. Detailed insight into our strategies in order to overcome challenges during the reaction development process is provided. Furthermore, the d
- K?ring, Laura,Paradies, Jan,Sitte, Nikolai A.
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supporting information
p. 1287 - 1300
(2022/01/20)
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- Continuous flow heterogeneous catalytic reductive aminations under aqueous micellar conditions enabled by an oscillatory plug flow reactor
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Despite the fact that continuous flow processing exhibits well-established technical advances, aqueous micellar chemistry, a field that has proven extremely useful in shifting organic synthesis to sustainable water-based media, has mostly been explored under conventional batch-based conditions. This is particularly because of the fact that the reliable handling of slurries and suspensions in flow has been considered as a significant technical challenge. Herein, we demonstrate that the strategic application of an oscillatory plug flow reactor enables heterogeneous catalytic reductive aminations in aqueous micellar media enhancing mass transport and facilitating process simplicity, stability and scalability. The micellar flow process enabled a broad range of substrates, including amino acid derivatives, to be successfully transformed under reasonably mild conditions utilizing only very low amounts of Pd/C as a readily available heterogeneous catalyst. The preparative capabilities of the process along with the recyclability of the heterogenous catalyst and the aqueous reaction media were also demonstrated. This journal is
- ?tv?s, Sándor B.,Buchholcz, Balázs,Darvas, Ferenc,Kappe, C. Oliver,Novák, Zoltán,Sipos, Gellért,Wernik, Michaela
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p. 5625 - 5632
(2021/08/16)
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- Synthesis of Optically Active N -(4-Hydroxynon-2-enyl)pyrrolidines: Key Building Blocks in the Total Synthesis of Streptomyces coelicolor Butanolide 5 (SCB-5) and Virginiae Butanolide A (VB-A)
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Starting from 5-methylhexanal and (S)-configured N -propargylprolinol ethers, coupling delivered N -(4-hydroxynon-2-ynyl)prolinol derivatives as mixtures of C4 diastereomers. Resolution of the epimers succeeded after introduction of an (R)-mandelic ester derivative and subsequent HPLC separation. Alternatively, suitable oxidation gave the corresponding alkynyl ketone. Midland reagent controlled diastereoselective reduction afforded a defined configured propargyl alcohol with high selectivity. LiAlH 4reduction and Mosher analyses of the allyl alcohols enabled structure elucidation. The suitably protected products are used as key intermediates in enantioselective Streptomyces γ-butyrolactone signaling molecule total syntheses.
- Donges, Jonas,Hofmann, Sandra,Walter, Johannes C.,Reichertz, Julia,Brüggemann, Moritz,Frank, Andrea,Nubbemeyer, Udo
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supporting information
p. 2632 - 2642
(2021/04/27)
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- London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction
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The well-known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions.
- Eschmann, Christian,Song, Lijuan,Schreiner, Peter R.
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p. 4823 - 4832
(2021/02/01)
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- Stereoselective Total Synthesis of (-)-(2 S,4 R)-3′-Methoxyl Citreochlorol: Preparation and Use of New Proline-Based Auxiliary for Asymmetric Acetate Aldol Reaction
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The first stereoselective total synthesis of (-)-(2S,4R)-3′-methoxy citreochlorol and (-)-(2S,4S)-3′-methoxy citreochlorol is demonstrated. A proline-based imidazolidinone was synthesized and used as chiral auxiliary for asymmetric acetate aldol reaction to generate initial chirality in the targeted molecule. Geminal dichloromethane functionality was introduced by the addition of in situ generated dichloromethyllithium to Weinreb's amide functional group.
- Sunnapu, Ranganayakulu,Banoth, Saikumar Naik,Reyno,Thomas, Aleena,Venugopal, Navyasree,Rajendar, Goreti
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p. 4103 - 4113
(2020/03/05)
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- Frustrated Lewis Pair Catalyzed Hydrogenation of Amides: Halides as Active Lewis Base in the Metal-Free Hydrogen Activation
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A method for the metal-free reduction of carboxylic amides using oxalyl chloride as an activating agent and hydrogen as the final reductant is introduced. The reaction proceeds via the hydrogen splitting by B(2,6-F2-C6H3)3 in combination with chloride as the Lewis base. Density functional theory calculations support the unprecedented role of halides as active Lewis base components in the frustrated Lewis pair mediated hydrogen activation. The reaction displays broad substrate scope for tertiary benzoic acid amides and α-branched carboxamides.
- Sitte, Nikolai A.,Bursch, Markus,Grimme, Stefan,Paradies, Jan
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supporting information
p. 159 - 162
(2019/01/04)
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- Asymmetric Synthesis of Cα-Substituted Prolines through Curtin–Hammett-Controlled Diastereoselective N-Alkylation
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Asymmetric synthesis of α-substituted proline derivatives has been accomplished by an efficient chirality-transfer method. High diastereoselectivity of the N-alkylation of the proline ester (C→N chirality transfer) was achieved when a 2,3-disubstituted be
- Cho, Hyunkyung,Jeon, Hongjun,Shin, Jae Eui,Lee, Seokwoo,Park, Soojun,Kim, Sanghee
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supporting information
p. 2447 - 2451
(2019/01/30)
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- Intramolecular [2+2] Photocycloaddition of Cyclic Enones: Selectivity Control by Lewis Acids and Mechanistic Implications
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The intramolecular [2+2] photocycloaddition of 3-alkenyl-2-cycloalkenones was performed in an enantioselective fashion (nine representative examples, 54–86 % yield, 76–96 % ee) upon irradiation at λ=366 nm in the presence of an AlBr3-activated oxazaborolidine as the Lewis acid. An extensive screening of proline-derived oxazaborolidines showed that the enantioface differentiation depends strongly on the nature of the aryl group at the 3-position of the heterocycle. DFT calculations of the Lewis acid–substrate complex indicate that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)-italicene.
- Poplata, Saner,Bauer, Andreas,Storch, Golo,Bach, Thorsten
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supporting information
p. 8135 - 8148
(2019/05/29)
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- Nickel-Catalyzed Amide Bond Formation from Methyl Esters
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Despite being one of the most important and frequently run chemical reactions, the synthesis of amide bonds is accomplished primarily by wasteful methods that proceed by stoichiometric activation of one of the starting materials. We report a nickel-catalyzed procedure that can enable diverse amides to be synthesized from abundant methyl ester starting materials, producing only volatile alcohol as a stoichiometric waste product. In contrast to acid- and base-mediated amidations, the reaction is proposed to proceed by a neutral cross coupling-type mechanism, opening up new opportunities for direct, efficient, chemoselective synthesis.
- Ben Halima, Taoufik,Masson-Makdissi, Jeanne,Newman, Stephen G.
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supporting information
p. 12925 - 12929
(2018/09/14)
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- SPIRO-LACTAM NMDA RECEPTOR MODULATORS AND USES THEREOF
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Disclosed are compounds having potency in the modulation of NMDA receptor activity. Such compounds can be used in the treatment of conditions such as depression and related disorders as well as other disorders.
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Page/Page column 38; 90-91
(2019/08/26)
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- Novel chiral amine oxide ligand and preparation method thereof
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The invention provides a novel chiral amine oxide ligand and a preparation method thereof. The method uses a simple amino acid or an amino acid derivative as a raw material, the raw material is modified, the modified material reacts with substances such as a coupling agent and an alkali, and therefore the pincher configuration chiral ligand compound is obtained, that is, the chiral amine oxide ligand. The chiral amine oxide ligand provided by the invention has a structure of a non-simple linear chain, has a soft skeleton in the molecular structure, contains a recognition gene containing heteroatoms such as oxygen or nitrogen, and can well coordinate with a series of metals and realize high enantioselectivity and high reactivity in a non-symmetric reaction; and the preparation method is simple, the steps are few, and the raw materials are cheap and easy to obtain.
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- Chiral urea-based ligand and preparation method thereof
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The invention discloses a chiral urea-based ligand and a preparation method thereof. The preparation method comprises the following steps: step 1, dissolving a chiral amine and isocyanate or isothiocyanate into an organic solvent according to a molar ratio of 1:(1-1.2), and performing full mixing; and step 2, performing a reaction at a temperature of -5 DEG C to 35 DEG C for 1-18 h, and performingcolumn chromatography purification to obtain the desired chiral urea-based ligand. The chiral urea-based ligand obtained by the method has a non-simple linear chain in the molecular structure and a soft skeleton in the molecular structure; the chiral urea-based ligand can utilizes multiple hydrogen-bond interaction of the urea structure to activate an electrophilic reagent or a nucleophilic reagent to improve the catalytic performance; and the chiral urea-based ligand has high enantioselectivity and high reactivity in an asymmetric reaction, the preparation method is simple, the steps are few, and the raw materials are cheap and easy to obtain.
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- Lewis Acid Catalyzed Enantioselective Photochemical Rearrangements on the Singlet Potential Energy Surface
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The oxadi-methane rearrangement of 2,4-cyclohexadienones to bicyclic ketones was found to proceed with high enantioselectivity (92-97% ee) in the presence of catalytic amounts of a chiral Lewis acid (15 examples, 52-80% yield). A notable feature of the transformation is the fact that it proceeds on the singlet hypersurface and that no triplet intermediates are involved. Rapid racemic background reactions were therefore avoided, and the catalyst loading could be kept low (10 mol %). Computational studies suggest that the enantioselectivity is determined within a Lewis acid bound singlet intermediate via a conical intersection. The utility of the method was demonstrated by a concise synthesis of the natural product trans-chrysanthemic acid.
- Leverenz, Malte,Merten, Christian,Dreuw, Andreas,Bach, Thorsten
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p. 20053 - 20057
(2019/12/30)
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- COMPOUNDS, COMPOSITIONS AND METHODS FOR SYNTHESIS
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The present disclosure, among other things, provides technologies for synthesis, including reagents and methods for stereoselective synthesis. In some embodiments, the present disclosure provides compounds useful as chiral auxiliaries. In some embodiments, the present disclosure provides reagents and methods for oligonucleotide synthesis. In some embodiments, the present disclosure provides reagents and methods for chirally controlled preparation of oligonucleotides. In some embodiments, technologies of the present disclosure are particularly useful for constructing challenging internucleotidic linkages, providing high yields and stereoselectivity.
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- Synthesis of diastereomeric pyrrolidine sulfamides via anchimerically assisted nucleophilic substitution reactions
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The Mitsunobu reaction was employed in a key step during the development of a convenient synthetic route for the enantioselective preparation of pyrrolidine-sulfamide ligands from (R)- or (S)- [(S)-1-benzylpyrrolidin-2-yl](phenyl)methanol, and employing tert-butyl pyrrolidin-1-yl-sulfonylcarbamate as a non-conventional nucleophilic source. Although it is well documented that the exposure of this type of diastereomeric amino alcohols to the above-mentioned nucleophile usually leads to the formation of piperidines via ring expansion, either through classical nucleophilic substitution or the Mitsunobu version, only the pyrrolidine derivatives were generated with retention of configuration on the exocyclic stereocenter, owing to the neighboring group participation (internal backside nucleophilic substitution, SNib). Final removal of the N-Boc protecting group from the sulfamide fragment afforded chiral compounds with significant potential as chiral ligands in asymmetric catalysis.
- Vargas-Caporali, Jorge,van der Lee, Arie,Dewynter, Georges,Juaristi, Eusebio
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supporting information
p. 352 - 358
(2018/05/22)
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- Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess
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The noncovalent combination of a supramolecular host with iminium organocatalysis is described. Due to cation–π interactions the reactive iminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented.
- Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
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supporting information
p. 7698 - 7701
(2016/07/07)
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- SPIRO-LACTAM NMDA RECEPTOR MODULATORS AND USES THEREOF
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Disclosed are compounds having enhanced potency in the modulation of NMD A receptor activity. Such compounds are contemplated for use in the treatment of conditions such as depression and related disorders. Orally available formulations and other pharmaceutically acceptable delivery forms of the compounds, including intravenous formulations, are also disclosed.
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Paragraph 00204
(2014/08/19)
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- Synthesis of chiral 2-(anilinophenylmethyl)pyrrolidines and 2-(anilinodiphenylmethyl)pyrrolidine and their application to enantioselective borane reduction of prochiral ketones as chiral catalysts
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Chiral diamines, 2-(anilinophenylmethyl)pyrrolidines and 2-(anilinodiphenylmethyl)pyrrolidine, were prepared from N-(tert-butoxycarbonyl) pyrrolidine or (S)-proline as a starting material, respectively. These chiral diamines were efficient for the catalytic enantioselective borane reduction of acetophenone. Using (S)-2-(anilinodiphenylmethyl)pyrrolidine, chiral secondary alcohols were obtained from prochiral ketones with good to excellent enantiomeric excesses (up to 98% ee).
- Hosoda, Naoya,Kamito, Hideaki,Takano, Miki,Takebe, Yoshitaka,Yamaguchi, Yoshitaka,Asami, Masatoshi
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p. 1739 - 1746
(2013/03/13)
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- Synthesis of acyclic ketones by catalytic, bidirectional homologation of formaldehyde with nonstabilized diazoalkanes. Application of a chiral diazomethyl(pyrrolidine) in total syntheses of erythroxylon alkaloids
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This work offers a catalytic approach to convergent ketone assembly based upon formal and tandem C-H insertion of diazoalkanes in the presence of limiting amounts of monomeric formaldehyde, which is easily generated as a gas by thermolysis of the inexpensive and abundant paraformaldehyde (～30 USD/kg). The method forms di-, tri-, and even tetrasubstituted acetones with high efficiency, and it has streamlined a synthesis of (-)-dihydrocuscohygrine in which the absolute stereochemistry of a proline-based starting material is preserved. Assisted by the advent of new protocols for hydrazone oxidation, we also provide full details on handling non-carbonyl-stabilized diazo compounds.
- Wommack, Andrew J.,Kingsbury, Jason S.
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p. 10573 - 10587
(2013/11/19)
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- Reactions of amines and hydrazides derived from L-proline with dialkyl dicyanofumarates
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The reaction of prolinamine derivatives (8a,b) and dialkyl dicyanofumarates (1) in dichloromethane at room temperature leads to the optically active enamines (10). Whereas products (10) in the case of 1-benzyl prolinamine (8a) are stable compounds, the corresponding enamines obtained from the non-protected prolinamine (8b) smoothly undergo a cyclocondensation at room temperature to give perhydropyrrolo[1,2-a]pyrazine derivatives (11). The molecular structure of 11a was established by X-Ray crystallography. In analogy to 8a, 1-benzyl prolinehydrazide (9a) and 1b in dichloromethane react to yield the enehydrazine (12b). On the other hand, the reaction of 9a and 1 in methanol at room temperature leads to the corresponding dialkyl 3-amino-1H-pyrazole- 4,5-dicarboxylates (13) and methyl 1-benzylprolinate (14b) Via a stepwise mechanism. The analogous reaction was observed between a 3-oxidoimidazole-4- carbohydrazide (15) and 1b.
- Mloston, Grzegorz,Pieczonka, Adam M.,Wroblewska, Aneta,Linden, Anthony,Heimgartner, Heinz
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p. 343 - 356
(2013/08/15)
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- Synthesis of versatile bifunctional derivatives of chiral diamines obtained through anchimerically assisted nucleophilic substitution reactions on diastereomeric phenylprolinols
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Diastereomeric [(S)-1-benzylpyrrolidin-2-yl]-(R)-[(phenyl)- methanamine] and [(S)-1-benzylpyrrolidin-2-yl]-(S)-[(phenyl)methanamine], were synthesized by selective internal backside nucleophilic substitution of the corresponding activated phenylprolinols. X-Ray diffraction structures of crystalline acetamide derivatives confirmed the anticipated stereochemistry for a SNib reaction mechanism. In order to apply this reaction to the synthesis of bifunctional analogs, a series of fragments such as a thiourea moiety and sulfonamide functions were introduced for the functionalization of the primary amino group in the substrate, obtaining more stable and potentially useful derivatives.
- Vargas-Caporali, Jorge,Cruz-Hernandez, Carlos,Juaristi, Eusebio
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p. 1275 - 1300
(2013/08/23)
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- Fluorinated organocatalysts for the enantioselective epoxidation of enals: Molecular preorganisation by the fluorine-iminium ion Gauche effect
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The fluorine-iminium ion gauche effect is triggered upon union of a secondary β-fluoroamine and an α,β-unsaturated aldehyde, providing a useful strategy for controlling the molecular topology of intermediates that are central to organocatalytic processes. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes. A process of structural editing has revealed that the efficiency of this catalyst is due to the (fluorodiphenyl)methyl group when it is embedded in a β-fluoroiminium motif. Epoxidations of challenging cyclic α,β-disubstituted, β,β-disubstituted and α,β,β-trisubstituted enals catalysed by 1 proceed with excellent levels of enantiocontrol (up to 98 % ee). Fluorine finesse. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes (see scheme). Application of this catalyst to challenging cyclic α,β-disubstituted enals, β,β-disubstituted enals, and an α,β,β-trisubstituted enal proceeds in a highly enantioselective fashion (up to 98 % ee). Copyright
- Tanzer, Eva-Maria,Zimmer, Lucie E.,Schweizer, W. Bernd,Gilmour, Ryan
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p. 11334 - 11342,9
(2020/08/31)
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- A systematic study of chiral homoprolinols and their derivatives in the catalysis of enantioselective addition of diethylzinc to aldehydes
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Homoprolinol analogs, a class of optically active γ-amino alcohols, were examined systematically in the enantioselective addition reactions of diethylzinc to aldehydes. By comparison of the results catalyzed by these γ-amino alcohols with those by the β-amino alcohols based on pyrrolidine architecture reported in the literature references, we have observed that the γ-amino alcohols are superior to the corresponding β-amino alcohols when the nitrogen and the oxygen are unsubstituted. Among the homoprolinols we tested, 2b gave the best results (45-88% yields, 44-81% ee) in the addition reactions. To the best of our knowledge, 2b has been noticed as one of the most efficient γ-amino alcohol catalysts based on pyrrolidine framework.
- Liu, Chang-Lu,Wei, Chang-Yong,Wang, Shi-Wen,Peng, Yun-Gui
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experimental part
p. 921 - 928
(2012/06/17)
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- The synthesis of piperidine nucleoside analogs - A comparison of several methods to access the introduction of nucleobases
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This work deals with the synthesis of piperidine and hydroxypiperidine analogs of nucleosides. Starting from commercially available 3-hydroxypiperidine, proline or 4-hydroxyproline, a series of piperidine derivatives of both purine and pyrimidine nucleobases was prepared. Various methods of nucleobase attachment were evaluated. The prepared compounds were tested for cytostatic, antibacterial, and antiviral properties but no significant activity was found.
- Kova?ková, Soňa,Dra?ínsky, Martin,Rejman, Dominik
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p. 1485 - 1500
(2011/04/15)
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- N-benzyl-protection of amino acid derivatives by reductive alkylation with α-picoline-borane
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A convenient method for N-protection of amino acid derivatives with a benzyl group by reductive alkylation of amino acid derivatives with α-picoline-borane is described. Amino acid esters or amino alcohols were treated with aryl aldehydes in methanol/acetic acid in the presence of -picoline-borane to give N-benzyl-protected amino acid derivatives in good yields. Georg Thieme Verlag Stuttgart - New York.
- Kawase, Yasushi,Yamagishi, Takehiro,Kutsuma, Teruo,Kataoka, Tadashi,Ueda, Kimio,Iwakuma, Takeo,Nakata, Tadashi,Yokomatsu, Tsutomu
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experimental part
p. 1673 - 1677
(2010/06/22)
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- A concise synthesis of (S)-2-(fluorodiphenylmethyl)pyrrolidine: A novel organocatalyst for the stereoselective epoxidation of α,β-unsaturated aldehydes
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A concise synthesis of (S)-2-(fluorodiphenylmethyl)pyrrolidine from cheap, commercially available starting materials is described. Pertinent features of this synthetic route include ease of synthesis, facile purification steps, and an operationally simple deoxy?fluorination step to install the C-F bond. Georg Thieme Verlag Stuttgart · New York.
- Sparr, Christof,Tanzer, Eva-Maria,Bachmann, Julia,Gilmour, Ryan
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experimental part
p. 1394 - 1397
(2010/07/02)
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- PYRAZINE COMPOUNDS AS PHOSPHODIESTERASE 10 INHIBITORS
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Pyrazine compounds, and compositions containing them, and processes for preparing such compounds. Provided herein also are methods of treating disorders or diseases treatable by inhibition of PDE10, such as obesity, non-insulin dependent diabetes, schizophrenia, bipolar disorder, obsessive-compulsive disorder, and the like.
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Page/Page column 91
(2010/06/15)
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- Allyltin tribromide: A versatile reagent involved in the ring-opening of epoxides
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This paper presents a versatile reagent for epoxide cleavage. The allyltin tribromide could act as a novel and easily prepared allylation reagent and halide atom donor to convert epoxides to the corresponding homoallyl alcohols and halohydrins in high yields with excellent regioselectivities under mild reaction conditions, respectively. It could also act as a Lewis acid to catalyze the ring opening reactions of epoxides with alcohols.
- Chen, Guohong,Wang, Xin,Jin, Xiaoqian,Liu, Lingyan,Chang, Weixing,Li, Jing
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experimental part
p. 1294 - 1301
(2010/11/05)
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- Enantioselective Michael addition of dicyanoolefins to α,β- unsaturated aldehydes in aqueous medium
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A pool of water-compatible catalysts, namely dialkyl-(S)-prolinols, has been developed for the enantioselective direct vinylogous Michael addition reaction of vinylmalononitriles to α,β-unsaturated aldehydes in aqueous medium. In many cases, the products can be obtained in almost optically pure form (>96% ee) after a single recrystallization.
- Lu, Jun,Liu, Feng,Loh, Teck-Peng
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supporting information; experimental part
p. 1781 - 1784
(2009/07/10)
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- A novel method for the synthesis of chiral epoxides from styrene derivatives using chiral acids in presence of Pseudomonas lipase G6 [PSL G6] and hydrogen peroxide
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Chiral epoxidation of styrene and its derivatives was carried out using series of chiral acids and urea hydrogen peroxide (UHP) or aqueous hydrogen peroxide (50%) in two phases under the catalytic influence of immobilized Pseudomonas lipase G6 [PSL G6] at 25-55 °C. A moderate to good yield and enantioselectivities of chiral epoxides were obtained.
- Sarma, Kuladip,Bhati, Nishi,Borthakur, Naleen,Goswami, Amrit
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p. 8735 - 8741
(2008/02/09)
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- Water-compatible iminium activation: Organocatalytic Michael reactions of carbon-centered nucleophiles with enals
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(Chemical Equation Presented) A pool of water-compatible catalysts, namely the chiral prolinol-based catalysts 1, has been developed for highly enantioselective C-C bond-forming Michael reactions in water (see scheme). The synthesis of (S)-Rolipram, a type IV phosphodiesterase inhibitor, was also demonstrated.
- Palomo, Claudio,Landa, Aitor,Mielgo, Antonia,Oiarbide, Mikel,Puente, Angel,Vera, Silvia
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p. 8431 - 8435
(2008/09/19)
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- Asymmetric Cyanosilylation of Ketones Catalyzed by Bifunctional Chiral N-Oxide Titanium Complex Catalysts
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A new bifunctional catalytic system based on chiral N-oxide titanium complexes has been used for the asymmetric cyanosilylation of ketones. Screening of a variety of chiral N-oxide metal complexes resulted in (1R,2S)-1-(2'-pyridylmethyl)-2-(diphenylhydroxymethyl)pyrrolidine N-oxide titanium complex, which gave O-TMS cyanohydrins in good yields with enantiometric excesses of up to 69 percent. A catalytic cycle based on experimental phenomena and studies was proposed to explain the origin of the asymmetric induction.
- Shen, Yongcun,Feng, Xiaoming,Li, Yan,Zhang, Guolin,Jiang, Yaozhong
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p. 129 - 137
(2007/10/03)
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- A new class of modular chiral ligands with fluxional groups
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In ligand design for asymmetric catalysis, the usual norm is to derive the face shielding elements from a chiral source. New ligands in which the face shielding is determined by fluxional groups are introduced. Their design, modular synthesis, and experim
- Sibi, Mukund P.,Zhang, Ruzhou,Manyem, Shankar
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p. 9306 - 9307
(2007/10/03)
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- Catalytic compositions and methods for asymmetric aldol reactions
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Methods and compositions are provided for the direct catalytic asymmetric aldol reaction of aldehydes with donor molecules selected from ketones and nitroalkyl compounds. The reactions employ as catalyst a Group 2A or Group 2B metal complex of a ligand of formula I, as defined further herein.
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- Optically active 3-amino-2H-azirines as synthons for enantiomerically pure α,α-disubstituted α-amino acids: Synthesis of the α-methylphenylalanine synthons and some model peptides
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The synthesis of a novel 2-benzyl-2-methyl-3-amino-2H-azirine derivative with a chiral amino group is described. Chromatographic separation of the diastereoisomer mixture yielded the pure diastereoisomers 9a and 9b which are the D- and L-2-methylphenylalanine ((α-Me)Phe) synthons, respectively. The reaction of 9a and 9b with thiobenzoic acid and with Z-leucine yielded the monothiodiamides 10a and 10b and the dipeptide derivatives 11a and 11b, respectively. Methanolysis of 11b yielded 12b. The absolute configuration of 10a was established by X-ray crystallography. The absolute configuration of (α-Me)Phe in 12b has been deduced from the known configuration of L-leucine.
- Bucher,Linden,Heimgartner
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p. 935 - 946
(2007/10/02)
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- TRANSITION METAL COMPLEXES - A NEW CLASS OF CATALYSTS OF INTERFACIAL ALKYLATION FOR THE ASYMMETRICAL SYNTHESIS OF α-AMINO ACIDS
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A new class of catalysts of interfacial asymmetrical alkylation is suggested for the synthesis of α-amino acids - positively charged complexes of the transition metals Cu(II), Ni(II), and Pd(II).These complexes consist of several fragments, by variation of which the structure of the catalysts can readily be modified.The complexes are chiral on account of (S)proline derivatives contained in them as one of the fragments.The catalyst complexes (C) were used in alkylation of amino acid fragments of Ni(II) complexes of the Schiff base of glycine with N-(2-pyridinecarbonyl)-o-aminobenzophenone (Ni-PBP-Gly) and the Schiff base of alanine with N-(2-pyridinecarbonyl)-o-aminobenzaldehyde (Ni-PBA-Ala) under interfacial conditions.After decomposition of alkylated complexes, phenylalanine and α-methyl-phenylalanine were isolated with yields of 33-87percent and optical purity (o. p.) from 3 to 21percent, depending on the C used.
- Belokon', Yu. N.,Maleev, V. I.,Videnskaya, S. O.,Saporovskaya, M. B.,Tsyryapkin, V. A.,Belikov, V. M.
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p. 110 - 118
(2007/10/02)
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