- Supramolecular gels from sugar-linked triazole amphiphiles for drug entrapment and release for topical application
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A simple molecular framework obtained by cross-linking a hydrophobic chain with S,S- and R,R-tetritol by the copper-catalysed azide-alkyne cycloaddition reaction is found to serve as an excellent bioisostere for self-assembly. The hexadecyl-linked triazolyl tetritol composite spontaneously self-assembles in n-hepane and methanol to form hierarchical organogels. Microscopic analyses and X-ray diffraction studies demonstrate eventual formation of nanotubes through lamellar assembly of the amphiphiles. A rheological investigation shows solvent-dictated mechanical properties that obey power law behavior similar to other low molecular weight gelators (LMOGs). The gel network was then utilized for the entrapment of drugs e.g. ibuprofen and 5-fluorouracil, with tunable mechanical behaviour under applied stress. The differential release profiles of the drugs over a period of a few hours as a result of the relative spatio-temporal location in the supramolecular network can be utilized for topical formulations.
- Sharma, Komal,Joseph, Jojo P.,Sahu, Adarsh,Yadav, Narender,Tyagi, Mohit,Singh, Ashmeet,Pal, Asish,Kartha, K.P. Ravindranathan
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- Left-Handed Helix of Three-Membered Ring Amino Acid Homopeptide Interrupted by an N-H···Ethereal O-Type Hydrogen Bond
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A chiral three-membered ring Cα,α-disubstituted α-amino acid (R,R)-Ac3cdMOM, in which the α-carbon is not a chiral center, but two side chain β-carbons are chiral centers, was synthesized from dimethyl l-(+)-tartrate, and its homopeptides were prepared. X-ray crystallographic analysis of (R,R)-Ac3cdMOM pentapeptide showed bent left-handed (M) 310-helical structures with an unusual intramolecular hydrogen bond of the N-H···O (ethereal) type. The left-handedness of the bent helices was exclusively controlled by the side-chain β-carbon chiral centers.
- Koba, Yurie,Ueda, Atsushi,Oba, Makoto,Doi, Mitsunobu,Kato, Takuma,Demizu, Yosuke,Tanaka, Masakazu
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- Concise approach to the "higher sugar" core of the nucleoside antibiotic hikizimycin
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A highly productive synthesis of phenylthio glycoside 33 is described which constitutes a fully functional surrogate for the hikosamine core of hikizimycin 1, a complex nucleoside antibiotic endowed with promising anthelmintic properties. The chosen approach to this undecose derivative starts from mannofuranose 7 which was one-carbon homologated to alkyne 8 in one step on treatment with lithio (trimethylsilyl)diazomethane. Alkynyl iodide 12 derived from 8 was combined with the tartrate-derived aldehyde 17 by a Nozaki-Hiyama-Kishi reaction that can either be performed using overstoichiometric amounts of CrCl2 or by means of a catalytic manifold based on the turnover of a cat. CrCl2/chlorosilane/manganese redox couple. Semi-hydrogenation of the resulting alkyne 18 to (Z)-olefin 19 required the use of Pd/ C as the catalyst, whereas conventional Lindlar reduction was unsatisfactory. Attempted cis-dihydroxylation of alkene 22 (formed from 19 by a Mitsunobu reaction with phthalimide) by using catalytic amounts of OsO4 and NMO as the stoichiometric oxidant essentially failed, whereas a stoichiometric osmylation afforded the stable osmate ester 26 a as a single diastereomer. Since the use of OsO4 in stoichiometric amounts deemed inappropriate for a total synthesis project, recourse was taken to catalytic "Blitz dihydroxylation" with RuO4 in the presence of FeCl2·4 H2O as co-catalyst. Application of these conditions to alkene 30 bearing a free aldehyde function at the terminus of the "higher sugar" chain furnished pyranose 32 in good yield and excellent diastereoselectivity, which was converted into the targeted thioglycoside 33 on treatment with PhSSPh/Et3P. It is particularly noteworthy that the conformational constraints of the acyclic substrate 30 enforce the dihydroxylation to violate Kishi's empirical rule for transformations of this type.
- Fuerstner, Alois,Wuchrer, Margarita
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- Synthesis of diacylglycerol analogs bearing photoaffinity tags for labelling mammalian diacylglycerol kinase
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Signaling lipids such as diacylglycerol (DAG), phosphatidic acid, and the phosphatidylinositol polyphosphates are site-specific ligands for protein binding partners. Herein, we report the apotheoses of our initial approach to the development of diverse probes which are vital for understanding lipid-protein interactions. When incorporated into liposomes, these probes reduce mammalian diacylglycerol kinase's (DGK) enzymatic activity in a concentration, time, and light dependent manner. This journal is
- Eni, Sammy Eni,Rowland, Meng,Best, Michael D.
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- The Detosylation of Chiral 1,2-Bis(tosylamides)
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The deprotection of chiral 1,2-bis(tosylamides) to their corresponding 1,2-diamines is mostly unsuccessful under standard conditions. In a new methodology, the use of Mg/MeOH with sufficient steric additions allows the facile synthesis of 1,2-diamines in 78-98% yields. These results are rationalized using density functional theory and the examination of inner and outer-sphere reduction mechanisms.
- Butler, Nicholas M.,Clark, Timothy,Gaston, Jayden J.,Keller, Paul A.,Smyth, Jamie E.,Tague, Andrew J.,Van Eikema Hommes, Nico,Willis, Anthony C.,Yu, Haibo
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p. 9163 - 9180
(2021/07/19)
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- Concise synthesis of: N -phosphorylated amides through three-component reactions
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N-Phosphorylated amides continue to be an unparalleled asset for the development of pharmaceutical molecules, and the importance of this framework has inspired researchers to look for concise and efficient methods for the synthesis of this unit. In this work, a new strategy was developed in which a one-pot synthesis of N-phosphorylated amides was achieved by a three-component reaction with carboxylic acids, phosphorus chlorides and azides under mild reaction conditions. To our knowledge, this is the first study in which this framework was constructed through a multicomponent reaction, which is innovative, efficient and economical. This journal is
- Yang, Shang-Dong,Zhang, Tao,Zhou, Linlin,Zhu, Yuan-Yuan
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supporting information
p. 9417 - 9421
(2021/12/09)
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- Domino Hydroalkoxylation-[4+2]-Cycloaddition for Stereoselective Synthesis of 1,4-Heterocycle-Fused Chromenes: Rapid Access to the [6-6-7-6] Tetracyclic Core of Cytorhizhins B–D
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A substrate dependent regio- and stereoselective domino hydroalkoxylation-formal-[4+2] cycloaddition is described for the facile synthesis of linear as well as spirocyclic 1,4-heterocycle-fused chromene ketals. Enantiospecific synthesis of oxazepino chromene derivatives was successfully carried out using chiral pool amino alkynols. The developed hydroalkoxylation cascade offered rapid access to the spirocyclic [6-6-7-6] tetracyclic core of cytorhizhins B–D with correct relative configuration.
- Fartade, Dipak J.,Gharpure, Santosh J.,Nanda, Santosh K.,Vishwakarma, Dharmendra S.
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supporting information
p. 6892 - 6897
(2020/01/25)
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- A Synthesis Strategy for the Production of a Macrolactone of Gulmirecin A via a Ni(0)-Mediated Reductive Cyclization Reaction
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A synthesis strategy for the production of a key synthetic intermediate of gulmirecin A was described. The key reaction in the preparation of the 12-membered macrolactone is the Ni(0)-mediated reductive cyclization reaction of ynal using an N-heterocyclic carbene ligand and silane reductant. In addition, the α-selective glycosylation reaction of the macrolactone was performed to demonstrate the synthesis of gulmirecin and disciformycin precursors.
- Ichikawa, Satoshi,Katsuyama, Akira,Kitahata, Shun
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supporting information
(2020/03/30)
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- Total Synthesis of the Echinodermatous Ganglioside LLG-3 Possessing the Biological Function of Promoting the Neurite Outgrowth
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A total synthesis of echinodermatous ganglioside LLG-3 with neuritogenic activity was accomplished by a convergent strategy. The synthesis of 2-hydroxyethyl 8-O-Me-α-sialoside 2 was started from the phenyl 7,8-di-O-Pico-thiosialoside 5, which can be chemoselectively removed the picoloyl group, and then the methyl group in 8-O-MeNeu5Ac moiety was chemoselectively prepared using TMSCHN2/FeCl3. For preparation of the terminal disialic unit, oxidative amidation was initially utilized by our group to efficiently construct the α(2,11) linkage of 8-O-Me-Neu5Acα(2,11)Neu5Gc. Herein, we also demonstrate that the synthesized ganglioside LLG-3 exhibited the neuritogenic activity toward the primary cortical neurons and that biological activity is superior to that of ganglioside DSG-A.
- Huang, Yuahn-Sieh,Shih, Jing-Feng,Tsai, Yow-Fu,Wu, Yu-Fa
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supporting information
p. 7491 - 7495
(2020/10/09)
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- Combination of chemotherapy and oxidative stress to enhance cancer cell apoptosis
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Cancer cells are vulnerable to reactive oxygen species (ROS) due to their abnormal redox environment. Accordingly, combination of chemotherapy and oxidative stress has gained increasing interest for the treatment of cancer. We report a novel seleno-prodrug of gemcitabine (Gem), Se-Gem, and evaluated its activation and biological effects in cancer cells. Se-Gem was prepared by introducing a 1,2-diselenolane (a five-membered cyclic diselenide) moiety into the parent drug Gemvia a carbamate linker. Se-Gem is preferably activated by glutathione (GSH) and displays a remarkably higher potency than Gem (up to a 6-fold increase) to a panel of cancer cell lines. The activation of Se-Gem by GSH releases Gem and a seleno-intermediate nearly quantitatively. Unlike the most ignored side products in prodrug activation, the seleno-intermediate further catalyzes a conversion of GSH and oxygen to GSSG (oxidized GSH) and ROS via redox cycling reactions. Thus Se-Gem may be considered as a suicide agent to deplete GSH and works by a combination of chemotherapy and oxidative stress. This is the first case that employs a cyclic diselenide in prodrug design, and the success of Se-Gem as well as its well-defined action mechanism demonstrates that the 1,2-diselenolane moiety may serve as a general scaffold to advance constructing novel therapeutic molecules with improved potency via a combination of chemotherapy and oxidative stress.
- Fang, Jianguo,Hou, Yanan,Li, Jin,Li, Xinming,Wang, Song,Zhao, Jintao
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p. 3215 - 3222
(2020/04/08)
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- Phosphite-thioether/selenoether Ligands from Carbohydrates: An Easily Accessible Ligand Library for the Asymmetric Hydrogenation of Functionalized and Unfunctionalized Olefins
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A large family of phosphite-thioether/selenoether ligands has been easily prepared from accessible L-(+)-tartaric acid and D-(+)-mannitol and applied in the M-catalyzed (M=Ir, Rh) asymmetric hydrogenation of a broad number of substrates (46 in total). Its highly modular architecture has been crucial to maximize the catalytic performance. Improving most of the reported approaches, this ligand family presents a broad substrate scope. By selecting the ligand parameters high enantioselectivities (ee's up to 99 %) have therefore been achieved in a broad range of both, functionalized and unfunctionalized substrates. Interestingly, both enantiomers of the hydrogenation products can be usually achieved by changing the ligand parameters.
- Margalef, Jèssica,Borràs, Carlota,Alegre, Sabina,Alberico, Elisabetta,Pàmies, Oscar,Diéguez, Montserrat
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p. 2142 - 2168
(2019/04/13)
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- Induction of chirality in 4,4′-azopyridine by halogen-bonding interaction with optically active ditopic donors
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Optically active ditopic halogen bond donors bearing two 4-iodotetrafluorophenyl groups were obtained by reaction of chiral diols with iodopentafluorobenzene. Co-crystallization of these donors with anti-4,4′-azopyridine afforded binary complexes containing infinite chains of the alternating component molecules connected by halogen bonds. The solid state CD measurements confirmed that complexation induces optical activity of the azo chromophore due to the twisting of the aryl-N═N system or external chiral perturbation exerted by host molecules.
- Alfuth, Jan,Chojnacki, Jaros?aw,Po?oński, Tadeusz,Olszewska, Teresa
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supporting information
p. 5512 - 5517
(2019/04/04)
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- Synthesis of [7]Helicene Enantiomers and Exploratory Study of Their Conversion into Helically Chiral Iodoarenes and Iodanes
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The facile and convenient preparation of both enantiomers of a [7]helicene scaffold from inexpensive (l)-(+)-tartaric acid and 4-methylstyrene is described. These helical structures were transformed into bis-iodinated ether derivatives in order to explore their potential as precursors of novel chiral organoiodane reagents or as iodoarene pre-catalysts. Promising results were obtained in hydroxylative phenol dearomatization/[4+2] cycloaddition cascade and dearomative spirolactonization reactions with encouraging enantiomeric excesses.
- Antien, Kevin,Pouységu, Laurent,Deffieux, Denis,Massip, Stéphane,Peixoto, Philippe A.,Quideau, Stéphane
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supporting information
p. 2852 - 2858
(2019/02/05)
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- Palladium- and Rhodium-Catalyzed Dynamic Kinetic Resolution of Racemic Internal Allenes Towards Chiral Pyrazoles
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A complementing Pd- and Rh-catalyzed dynamic kinetic resolution (DKR) of racemic allenes leading to N-allylated pyrazoles is described. Such compounds are of enormous interest in medicinal chemistry as certified drugs and potential drug candidates. The new methods feature high chemo-, regio- and enantioselectivities aside from displaying a broad substrate scope and functional group compatibility. A mechanistic rational accounting for allene racemization and trans-alkene selectivity is discussed.
- Hilpert, Lukas J.,Sieger, Simon V.,Haydl, Alexander M.,Breit, Bernhard
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supporting information
p. 3378 - 3381
(2019/02/06)
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- Stereoselective synthesis of the lichen metabolite, (+) montagnetol and its congeners as antimicrobial agents
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In view of structural diversity, (+) montagnetol, the major metabolite of the fruticose lichen, Roccella montagnei was synthesized along with three of its congeners by employing highly efficient protocols. (+) Montagnetol (2 R, 3S; 11) and (-) montagnetol (2S, 3R; 5) were synthesized in 7 and 9 steps, respectively, from L-ascorbic acid. The two new congeners 3 (2 R, 3R) and 6 (2S, 3S), which differ in configuration at C-2 and C-3 positions of the (+) montagnetol, were synthesized from (?) diethyl D-tartrate and (+) diethyl L-tartrate, respectively. The synthesized compounds were evaluated in vitro for antimicrobial activity against two Gram-positive (S. aureus and E. coli) and two Gram-negative (S. typhi and P. aeruginosa) bacteria and one fungal strain Candida albicans. Interestingly, the congener 3 showed promising anti-bacterial activity (MIC: 0.062 μg/ml) against P. aeruginosa, whereas the congener 6 displayed potent anti-fungal activity (MIC: 0.062 μg/ml) against C. Albicans.
- Mallavadhani, Uppuluri Venkata,Boddu, Ramakrishna,Rathod, Balaji B.,Reddy Setty, Prakasam
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supporting information
p. 2992 - 2999
(2018/10/15)
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- Chiroptical properties of 2,2’-bioxirane
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The two enantiomers of 2,2′-bioxirane were synthesized, and their chiroptical properties were thoroughly investigated in various solvents by polarimetry, vibrational circular dichroism (VCD), and Raman optical activity (ROA). Density functional theory (DFT) calculations at the B3LYP/aug-cc-pVTZ level revealed the presence of three conformers (G+, G?, and cis) with Gibbs populations of 51, 44, and 5% for the isolated molecule, respectively. The population ratios of the two main conformers were modified for solvents exhibiting higher dielectric constants (G? form decreases whereas G+ form increases). The behavior of the specific optical rotation values with the different solvents was correctly reproduced by time-dependent DFT calculations using the polarizable continuum model (PCM), except for the benzene for which explicit solvent model should be necessary. Finally, VCD and ROA spectra were perfectly reproduced by the DFT/PCM calculations for the Boltzmann-averaged G+ and G? conformers.
- Daugey,De Rycke,Brotin,Buffeteau
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p. 342 - 350
(2018/01/15)
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- Turning the Nitrogen Atoms of an Ar2P?CH2?N?N?CH2?PAr2 Motif into Uniquely Configured Stereocenters: A Novel Diphosphane Design for Asymmetric Catalysis
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Hexahydropyridazines with CH2PAr2 groups at both N atoms are newly designed 1,4-diphosphanes and were synthesized for the first time. Their N atoms assume a single configuration under the influence of stereocenters at C-5 and C-6. In the solid state, these N-atoms bind the CH2PAr2 substituents axially. Combined with Pd0, N,N′-chiral diphosphanes of this kind catalyzed Tsuji–Trost type allylations of dialkyl malonates with racemic 1,3-diphenylallyl acetate efficiently and with up to 91 % ee.
- Diehl (née Knobloch), Eva,Brückner, Reinhard
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supporting information
p. 3429 - 3433
(2018/02/16)
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- Total Enantioselective Synthesis of the Endophytic Fungal Polyketide Phomolide H and Its Structural Revision
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A total synthesis of the proposed structure of the natural polyketide-macrolactone phomolide H 2 has been achieved following a bidirectional strategy from l-tartaric acid. The originally assigned structure of phomolide H displayed discordant NMR spectroscopic data in comparison with synthetic 2. The synthetic strategy was extended to prepare diastereomers and epimeric methyl-ethers of the natural product, structural analysis of which revealed a match of the natural product with diastereomer 27. The structural revision of phomolide H from 2 to the methanol solvate of compound 27 is presented.
- McNulty, James,McLeod, David
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supporting information
p. 29 - 33
(2017/01/14)
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- MANUFACTURING METHOD OF COMPOUND HAVING 3-OXABICYCLO[3.3.0]OCTANE SKELETON, COMPOUND, INTERMEDIATE PRODUCT OF COMPOUND, SEXUAL STIMULANT OF ANOPLOPHORA MALASIACA AND PREVENTION AGENT OF ANOPLOPHORA MALASIACA
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PROBLEM TO BE SOLVED: To provide a manufacturing method of a compound having 3-oxabicyclo[3.3.0]octane skeleton which can be chemosynthesized more easily from a lead compound having 3-oxabicyclo[3.3.0]octane skeleton. SOLUTION: A manufacturing method of a compound shown in the formula 1, a sexual stimulant of Anoplophora malasiaca containing the compound as an active component and a prevention agent of the Anoplophora malasiaca containing pesticide further are provided. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0031; 0033; 0078
(2017/07/18)
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- Hydrogen Bonding-Assisted Enhancement of the Reaction Rate and Selectivity in the Kinetic Resolution of d,l-1,2-Diols with Chiral Nucleophilic Catalysts
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An extremely efficient acylative kinetic resolution of d,l-1,2-diols in the presence of only 0.5 mol% of binaphthyl-based chiral N,N-4-dimethylaminopyridine was developed (selectivity factor of up to 180). Several key experiments revealed that hydrogen bonding between the tert-alcohol unit(s) of the catalyst and the 1,2-diol unit of the substrate is critical for accelerating the rate of monoacylation and achieving high enantioselectivity. This catalytic system can be applied to a wide range of substrates involving racemic acyclic and cyclic 1,2-diols with high selectivity factors. The kinetic resolution of d,l-hydrobenzoin and trans-1,2-cyclohexanediol on a multigram scale (10 g) also proceeded with high selectivity and under moderate reaction conditions: (i) very low catalyst loading (0.1 mol%); (ii) an easily achievable low reaction temperature (0 °C); (iii) high substrate concentration (1.0 M); and (iv) short reaction time (30 min). (Figure presented.).
- Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
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supporting information
p. 2778 - 2788
(2017/08/23)
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- A facile approach for the synthesis of C13-C24 fragments of maltepolides A, C and D
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A linear, chiron approach for the synthesis of C13-C24 fragments of cytostatic maltepolides A, C and D consisting of a tetrahydrofuran subunit and a chiral alkenyl/alkyl substituent is achieved from (+)-diethyl l-tartrate. The other chiral stereocenters were generated by employing key reactions such as Crimmins aldol, alkynylation and CeCl3·7H2O mediated Luche reduction reactions.
- Rao, P. Sankara,Srihari
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p. 9629 - 9638
(2016/10/22)
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- Enantioselective Total Synthesis of the Proposed Structure of the Endophytic Fungal Metabolite Phomolide G: Structural Revision and Unambiguous Stereochemical Assignment
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A total synthesis of the proposed structure of the natural macrolactone phomolide G (1) by a bidirectional strategy from L-tartaric acid is reported. The ω-terminus of the molecule was elaborated by nitrile extension, C3-alkylation and a substrate-controlled 1,3-ketone reduction. The α-terminus was extended by a C2aldehyde-to-alkenal homologation followed by an auxiliary controlled aldol reaction. Macrolactonization and deprotection yielded compound 1 (confirmed by X-ray analysis). This putative structure of phomolide G displayed discordant NMR spectroscopic data in comparison with those of the natural product. Detailed inspection of all NMR spectroscopic data available indicated phomolide G to be likely a diastereomer of 1. The synthetic strategy developed allows control of the absolute stereochemistry at all four chiral secondary alcohol groups. Further manipulation allowed for the preparation of diastereomer 33, the1H and13C NMR spectroscopic data of which are in full accord with that reported for the natural product.
- McNulty, James,McLeod, David,Jenkins, Hilary A.
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supporting information
p. 688 - 692
(2017/01/18)
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- Total synthesis of ivorenolide a following a base-induced elimination protocol
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A concise and stereocontrolled first total synthesis of Ivorenolide A (1) is reported in 16 longest linear steps with a 13.4% overall yield starting from (+)-diethyl tartrate (DET). Key features are base-induced elimination protocol for the construction of chiral propargyl alcohols in both fragments, Pd-catalyzed cross-coupling of terminal acetylenes, and Shiina's 2-methyl-6-nitrobezoic anhydride (MNBA) mediated macrolactonization.
- Mohapatra, Debendra K.,Umamaheshwar, Gonela,Rao, R. Nageshwar,Rao, T. Srinivasa,R, Sudheer Kumar,Yadav, Jhillu S.
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supporting information
p. 979 - 981
(2015/03/30)
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- Synthesis of the revised structure of acortatarin A
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A novel Maillard-type condensation between a primary amine derived from D-mannitol and a dihydropyranone, was used as a key step to access the unusual morpholine-spiroketal acortatarin A. The synthetic approach also enabled access to a C-2 analogue of acortatarin A, and can be used for the synthesis of related 2-formylpyrrole natural products.
- Geng, Hui Min,Stubbing, Louise A.,Li-Yang Chen, Jack,Furkert, Daniel P.,Brimble, Margaret A.
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p. 6227 - 6241
(2015/03/30)
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- Synthesis and protein kinase C (PKC)-C1 domain binding properties of diacyltetrol based anionic lipids
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The protein kinase C (PKC) family of lipid-activated kinases plays a significant role in the regulation of diverse cellular functions including tumor promotion, apoptosis, differentiation, and others. The lipophilic second messenger diacylglycerols (DAGs) act as endogenous ligands for the PKCs in the presence of anionic phospholipids. To develop effective PKC regulators and understand the importance of anionic phospholipids in DAG binding of PKC isoforms, we conveniently synthesized octanoic acid containing diacyltetrol (DAT) based hybrid lipids with both DAG and anionic phospholipid headgroups within the same molecule. We also used palmitic and oleic acid containing hybrid lipids for additional understanding of the PKC-C1 domain binding mechanism. Biophysical studies showed that hydrophobic side chains, DAG and anionic phospholipids headgroups are necessary for their interaction with the C1-domain of PKC isoforms. The hybrid lipids DAT-PS and DAT-PA specifically interact with the PKCδ-C1b and PKCθ-C1b subdomains and showed 5- and 2.5-fold stronger binding affinity compared with DAG, respectively. Whereas, the PKCα-C1a subdomain interacts with the hybrid lipids, without any significant specificity. The present results show that hybrid lipids bind to the PKC C1b/a subdomains and can be further studied to decipher their binding mechanism and biological activities. This study proposes a new concept of developing PKC activators by using tetrol-based anionic hybrid lipids having both phospholipids and diacylglycerol headgroups within the same molecule. This study also supplies useful information for the binding potencies of hybrid lipids with PKC-C1 domains. This journal is
- Mamidi, Narsimha,Panda, Subhankar,Borah, Rituparna,Manna, Debasis
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p. 3002 - 3013
(2015/01/08)
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- A facile chiral pool synthesis of 9-epi-decarestrictine-D, decarestrictine-D and O
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A facile chiral pool total synthesis of 9-epi-decarestrictine-D, decarestrictine-D and O has been achieved from l-(+)-diethyl tartrate. The strategy utilized is conventional and flexible. Wittig homologation and Grubbs ring closing metathesis are the key reactions employed for the synthesis of the title molecules.
- Vamshikrishna, Kuchena,Srinu, Garlapati,Srihari, Pabbaraja
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p. 203 - 211
(2014/03/21)
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- Synthesis and electrochemical properties of a chiral silyl-substituted tetrathiafulvalene derivative
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A new chiral tetrathiafulvalene (TTF) derivative and related silyl-substituted 1,3-dithiole-2-(thi)one compounds were synthesized and characterized by 1H NMR, 13C NMR, MS and IR spectra. Single crystal structure of the silyl-substituted 1,3-dithiole-2-one revealed the high degree of conjugation of the five-membered ring moiety in the compound. The electrochemical properties of the new TTF derivative were studied by cyclic voltammetry and the results indicated that the electron-donating ability of the chiral TTF derivative was similar to that of BEDT-TTF. The ΔE value for the new TTF derivative was smaller than those for TTF and BEDT-TTF, indicative of decreased Coulombic repulsion in the dicationic redox state. Formation of charge-transfer (CT) complex between the new donor and electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was demonstrated.
- Liang, Guo-Qi,Zhang, Zhong-Bao,Li, Hong-Qi,Wang, Ya-Ping,Xian, Chun-Ying
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p. 579 - 582
(2014/05/06)
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- Synthesis of C2-symmetric bisphosphine ligands from tartaric acid, and their performance in the Pd-Catalyzed asymmetric o-allylation of a phenol
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Starting from tartaric acid derived chiral diols or dicarboxylic acid dichlorides with either a 2,2-dimethyl-1,3-dioxolane (Taddol) or a 2,3-dimethoxy-2,3-dimethyl-1,4-dioxane (Tatrol) core structure, and BH 3-protected ortho-phosphanyl phenols, a set of fourteen new C 2-symmetric diphosphine ligands was synthesized. In addition, three related ligands were obtained from ortho-diphenylphosphino-anilines. The fully characterized ligands were then tested in the Pd-catalyzed enantioselective O-allylation of 4-methoxyphenol using crotyl methyl carbonate as a reagent. In addition, a pseudo-intramolecular variant of the reaction, using crotyl 4-methoxyphenyl carbonate as a substrate, was studied. The so-called Trost ligand was used as a reference. Although the Trost ligand (3 mol-%) gave up to 84% ee, one of the new ligands showed higher activity (50% ee with 0.075 mol-%). Copyright
- Dindaroglu, Mehmet,Akyol Dincer, Sema,Schmalz, Hans-Guenther
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supporting information
p. 4315 - 4326
(2014/07/21)
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- A convergent approach for the total synthesis of the α-glucosidase inhibitor (-)-panaxjapyne-C
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The stereoselective total synthesis of (-)-panaxjapyne-C was accomplished in a convergent fashion. The synthesis utilizes the readily available enantiomers l-(+)-diethyltartrate and d-(-)-diethyltartrate and involves a Cadiot-Chodkiewicz coupling reaction, and an Ohira-Bestmann reaction as the key steps.
- Sathish Reddy,Gangadhar,Srihari
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p. 1524 - 1530
(2013/12/04)
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- Stereoselective synthesis of the C13-C28 subunit of (-)-laulimalide utilizing an α-chlorosulfide intermediate
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A stereoselective route to the C13-C28 subunit of (-)-laulimalide is described. l-Tartaric acid is the source of the hydroxy groups at C19 and C20. An α-chlorosulfide is employed as the key intermediate for the creation of the C17-C18 bond and the C16-C17 double bond was introduced using the Mislow-Braverman rearrangement and Hutchin's dexoxygenation with concomitant double bond transposition reaction. The C15 and C23 stereogenic centers were created using catalytic asymmetric reactions. The trisubstituted and trans-disubstituted alkenes were created stereoselectively by taking advantage of ring-closing metathesis and the Julia-Kocienski olefination reaction, respectively. Georg Thieme Verlag Stuttgart, New York.
- Raghavan, Sadagopan,Samanta, Pradip Kumar
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supporting information
p. 1983 - 1987
(2013/09/24)
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- Polyhydroxylated pyrrolizidine alkaloids from transannular iodoaminations: Application to the asymmetric syntheses of (-)-hyacinthacine A1, (-)-7a-epi-hyacinthacine A1, (-)-hyacinthacine A2, and (-)-1-epi-alexine
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The transannular iodoamination of substituted 1,2,3,4,7,8-hexahydroazocine scaffolds has been developed into a versatile, diastereodivergent route to enable the synthesis of a range of pyrrolizidine alkaloids, as demonstrated by the syntheses of (-)-hyacinthacine A1, (-)-7a-epi-hyacinthacine A1, (-)-hyacinthacine A2, and (-)-1-epi-alexine. The requisite 1,2,3,4,7,8- hexahydroazocines (bearing either an N-α-methyl-p-methoxybenzyl group or no N-substituent) were readily prepared via conjugate addition of lithium (R)-N-but-3-enyl-N-(α-methyl-p-methoxybenzyl)amide to either tert-butyl (4S,5R,E)-4,5-dihydroxy-4,5-O-isopropylidene-2,7-dienoate (derived from d-ribose) or tert-butyl (S,S,E)-4,5-dihydroxy-4,5-O-isopropylidene-2,7-dienoate (derived from l-tartaric acid) coupled with in situ enolate oxidation with (-)-camphorsulfonyloxaziridine, followed by ring-closing metathesis with Grubbs I catalyst. Subsequent reaction with I2 resulted in transannular iodoamination (accompanied by concomitant loss of the N-α-methyl-p- methoxybenzyl group for tertiary amine substrates) to give the corresponding pyrrolizidine scaffolds. The Royal Society of Chemistry 2013.
- Brock, E. Anne,Davies, Stephen G.,Lee, James A.,Roberts, Paul M.,Thomson, James E.
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p. 3187 - 3202
(2013/06/04)
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- Versicolactones A and B: Total synthesis and structure revision
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To further determine absolute configurations of versicolactones A and B, total synthesis of versicolactones A and B and their six stereoisomers were reported in this Letter. The 1H and 13C NMR spectra of the synthetic erythro-stereoisomers matched perfectly with those of the natural products. Combined with the comparison of the specific rotations, the absolute configuration of versicolactones A and B were revised as (4Z,6R,7S)- and (4E,6R,7S)- from the corresponding (4Z,6R,7R)- and (4E,6R,7R)-6,7-dihydroxyocta- 2,4-dien-4-lactone, respectively.
- Wang, Liping,Zhu, Weiming
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supporting information
p. 6729 - 6731
(2013/11/19)
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- Stereoselective total synthesis of seimatopolide a
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Stereoselective total synthesis of the naturally occurring bioactive macrolide, seimatopolide A has been achieved starting from commercially available (+)-diethyl tartrate. Chelation-controlled Grignard reaction, Yamaguchi esterification, ring closing cross metathesis and CBS reduction reactions are involved as key steps.
- Bhunia, Nisith,Das, Biswanath
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p. 1633 - 1642
(2014/01/17)
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- Stereoselective total synthesis of paecilomycin e
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First total synthesis of recently isolated resorcylic acid lactone paecilomycin E has been accomplished. The key reactions include olefin metathesis, Mitsunobu reaction, Stille coupling and regioselective allylation.
- Srihari,Mahankali,Rajendraprasad
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supporting information; experimental part
p. 56 - 58
(2012/01/06)
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- An efficient chiral-pool synthesis of botryolide-E
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An efficient stereoselective total synthesis of botryolide-E by a chiral-pool approach is described. 2012 Elsevier Ltd. All rights reserved.
- Madabhushi, Sridhar,Godala, Kondal Reddy,Beeram, China Ramanaiah,Chinthala, Narsaiah
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supporting information
p. 5539 - 5540
(2012/11/07)
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- AMPHIPHILIC COMPOUNDS AND SELF-ASSEMBLING COMPOSITIONS MADE THEREFROM
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The present disclosure relates to amphiphilic compounds, self assembling compositions formed from the amphiphilic compounds and methods of making such compositions.
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Page/Page column 9
(2012/03/12)
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- On the origins of diastereoselectivity in the conjugate additions of the antipodes of lithium N-benzyl-(N-α-methylbenzyl)amide to enantiopure cis- and trans-dioxolane containing α,β-unsaturated esters
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"Matching" and "mismatching" effects in the doubly diastereoselective conjugate additions of the antipodes of lithium N-benzyl-(N-α-methylbenzyl)amide to enantiopure cis- and trans-dioxolane containing α,β-unsaturated esters have been investigated. High levels of substrate control were established first upon conjugate addition of achiral lithium N-benzyl-N-isopropylamide to both tert-butyl (S,S,E)-4,5-O- isopropylidene-4,5-dihydroxyhex-2-enoate and tert-butyl (4R,5S,E)-4,5-O- isopropylidene-4,5-dihydroxyhex-2-enoate. However, upon conjugate addition of lithium (R)-N-benzyl-(N-α-methylbenzyl)amide and lithium (S)-N-benzyl-(N-α-methylbenzyl)amide to these substrates, neither reaction pairing reinforced the apparent sense of substrate control. These reactions do not, therefore, conform to the classical doubly diastereoselective "matching" or "mismatching" pattern usually exhibited by this class of reaction. A comparison of these reactions with the previously reported doubly diastereoselective conjugate addition reactions of lithium amide reagents to analogous substrates is also discussed.
- Davies, Stephen G.,Foster, Emma M.,Frost, Aileen B.,Lee, James A.,Roberts, Paul M.,Thomson, James E.
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supporting information; experimental part
p. 6186 - 6200
(2012/09/05)
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- Total synthesis of ent-calystegine B4 via nitro-Michael/aldol reaction
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Optically active ent-calystegine B4 was prepared in 13 steps from commercially available chiral l-dimethyl tartrate. The synthesis was achieved by the Michael addition and the aldol reaction of nitromethane to form cycloheptanone in a stereoselective manner. Reduction of the nitro group in the presence of Boc2O accomplished an efficient conversion to amino cycloheptanone, which readily afforded the desired ent-calystegine B4.
- Kamimura, Akio,Miyazaki, Koichiro,Suzuki, Shuzo,Ishikawa, Shingo,Uno, Hidemitsu
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experimental part
p. 4362 - 4366
(2012/06/18)
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- A convergent synthesis of the 2-formylpyrrole spiroketal natural product acortatarin A
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A concise and flexible synthesis of the morpholine-spiroketal natural product acortatarin A, isolated from the traditional Chinese medicine Acorus tatarinowii, is reported. The key step involves a Maillard-type condensation of an amine derived from d-mannitol with a dihydropyranone. The approach also enables access to analogues of acortatarin A for biological evaluation and can be applied to the synthesis of related 2-formylpyrrole natural products. Georg Thieme Verlag Stuttgart . New York.
- Geng, Huimin,Chen, Jack L.Y.,Furkert, Danielp.,Jiang, Shende,Brimble, Margaret A.
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p. 855 - 858
(2012/05/20)
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- An efficient stereoselective approach for the synthesis of (+)-(4S,5S)-muricatacin
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An efficient stereoselective total synthesis of (+)-(4S,5S)-muricatacin was accomplished in good yields from inexpensive, commercially available chemicals ((+)-diethyl tartrate (DET) and undecan-1-ol) by utilizing Mitsunobu and Julia-Kocienski reactions, Wittig homologation, Swern oxidation, and lactonization. Copyright
- Srinivas, Chiguru,Naga Sesha Sai Pavan Kumar, Chebolu,China Raju, Bhimapaka,Jayathirtha Rao, Vaidya
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experimental part
p. 669 - 674
(2011/06/18)
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- A stereoselective total synthesis of 7,8-O-isopropylidene iriomoteolide-3a
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A stereoselective total synthesis of 7,8-O-isopropylidene iriomoteolide-3a has been achieved by using Yamaguchi esterification, Julia-Kocienski olefination, organocatalytic α-oxidation, and ring-closing metathesis reaction as key bond-forming steps.
- Zhang, Yao,Deng, Lisheng,Zhao, Gang
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scheme or table
p. 4518 - 4526
(2011/07/29)
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- Synthesis of chiral alkenyl epoxides: The sex pheromone of the elm spanworm Ennomus subsignaria (Hübner) (Lepidoptera: Geometridae)
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The identification of the sex pheromone of the elm spanworm Ennomos subsignaria (Hübner), as the chiral alkenyl epoxide (6Z)-cis-9,10-epoxy- nonadecene has been accomplished. Both enantiomers of (6Z)-cis-9,10-epoxy- nonadecene have been synthesized via two routes. The key steps in the first route were to prepare both threo-epoxy tosylates and then to perform an alkylative rearrangement of these intermediates to obtain the target molecules. An alternative enantioenriched synthesis that took advantage of the Sharpless dihydroxylation reaction was developed so that a common starting material could be used to access both enantiomers. A field study and GC/EAD testing indicated that Z6-cis-9S,10R-epoxy-nonadecene was the sex pheromone of the elm spanworm E. subsignaria (Hübner).
- Magee, David I.,Silk, Peter J.,Wu, Junping,Mayo, Peter D.,Ryall, Krista
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experimental part
p. 5329 - 5338
(2011/08/04)
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- DIBAL-mediated reductive transformation of trans-dimethyl tartrate acetonide into ε-hydroxy α,β-unsaturated ester and its derivatives
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Stepwise, selective DIBAL reduction of the acetonide diester derived from tartaric acid followed by the Horner- Emmons reaction effectively provided desymmetrized hydroxy mono-olefination products in a one-pot operation.
- Tomioka, Takashi,Yabe, Yuki,Takahashi, Tohru,Simmons, Tracy K.
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experimental part
p. 4669 - 4674
(2011/07/30)
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- Total synthesis of (+)-varitriol
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The total synthesis of natural (+)-varitriol (1) was accomplished by starting from dimethyl L-tartrate. The key features were a substrate selective and diastereoselective PdII-catalysed bicyclisation of unsaturated protected triol 9 followed by regioselective ring-opening of bicyclic skeleton 10. The absolute configuration of the target was confirmed by single-crystal X-ray analysis for the first time.
- Palik, Miroslav,Karlubikova, OL'Ga,Lasikova, Angelika,Kozisek, Jozef,Gracza, Tibor
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scheme or table
p. 709 - 715
(2009/07/19)
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- Doubly diastereoselective conjugate addition of homochiral lithium amides to homochiral α,β-unsaturated esters containing cis- and trans-dioxolane units
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As part of a long-term goal directed towards the ab initio asymmetric synthesis of unnatural amino sugars, the doubly diastereoselective conjugate addition reactions of the antipodes of lithium N-benzyl-N-(α-methylbenzyl) amide to a range of homochiral α,β-unsaturated esters containing cis- and trans-dioxolane units was investigated. These reactions resulted in "matching" and "mismatching" effects. In the "matched" cases a single diastereoisomer of the corresponding β-amino ester (containing three contiguous stereocentres) is produced. Upon conjugate addition to a homochiral α,β-unsaturated ester containing a cis-dioxolane unit, in the "mismatched" case it is the stereocontrol of the substrate which is dominant over that of the lithium amide, whilst upon addition to homochiral α,β-unsaturated esters containing a trans-dioxolane unit the stereocontrol of the homochiral lithium amide is dominant. Hydrogenolytic N-deprotection of the β-amino ester products of conjugate addition gives access to polyoxygenated β-amino acid derivatives.
- Davies, Stephen G.,Durbin, Matthew J.,Goddard, Euan C.,Kelly, Peter M.,Kurosawa, Wataru,Lee, James A.,Nicholson, Rebecca L.,Price, Paul D.,Roberts, Paul M.,Russell, Angela J.,Scott, Philip M.,Smith, Andrew D.
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supporting information; experimental part
p. 761 - 776
(2009/06/19)
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- Hydrogen-bonding sheets in crystals for chirality recognition: synthesis and application of (2S,3S)-2,3-dihydroxy- and (2S,3S)-2,3-dibenzyloxy-1,4-bis(hydroxyamino)butanes
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Two enantiopure bis(hydroxyamino) compounds were successfully prepared from dialkyl tartrate by a chiral-pool method and applied as basic resolving agents in the enantioseparation of 2-arylpropanoic acids and arylglycolic acids. (2S,3S)-2,3-Dihydroxy-1,4-bis(hydroxyamino)butane (2S,3S)-1a could moderately recognize the chirality of the 2-arylpropanoic acids, while (2S,3S)-2,3-dibenzyloxy-1,4-bis(hydroxyamino)butane (2S,3S)-1b could not due to the low crystallinity of both the corresponding diastereomeric salts. On the other hand, (2S,3S)-1b showed a similar chirality-recognition ability for the arylglycolic acids. The ability of (2S,3S)-1b was different from those generally observed for widely used primary amine-type resolving agents with regard to the relationship between the resolution efficiency and the similarity in the relative molecular length of a resolving agent and a target racemate. The X-ray crystallographic analyses of the less-soluble diastereomeric salts revealed that in the salts (2S,3S)-1a formed a supramolecular sheet, of which the distance was variable to make the resultant dissymmetric space fit to the shape of the target acids, and that (2S,3S)-1b was constructed from a robust supramolecular sheet, consisting of hydrogen-bonding 21 columns, with the participation of the hydroxy group of the arylglycolic acids. These X-ray crystallographic analyses also suggested that for the formation of a supramolecular sheet, the coexistence of two hydroxyamino groups is essential.
- Kobayashi, Yuka,Kokubo, Yasushi,Aisaka, Takamitsu,Saigo, Kazuhiko
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experimental part
p. 2536 - 2541
(2009/04/11)
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- Facile and highly selective deprotection of tert-butyldimethyl silyl ethers using sulfated SnO2 as a solid catalyst
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Highly selective deprotection of tert-butyldimethylsilyl ethers at room temperature has been described using sulfated SnO2 as an efficient solid catalyst. Copyright Taylor & Francis Group, LLC.
- Bhure, Mahesh H.,Kumar, Indresh,Natu, Arun D.,Rode, Chandrashekhar V.
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p. 346 - 353
(2008/09/16)
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- First total synthesis and absolute configuration of the styryl lactone gonioheptolide A
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Efficient asymmetric syntheses of both naturally occurring and non-naturally occurring enantiomers of gonioheptolide A are reported. The absolute configuration of (+)-gonioheptolide A was established by NOESY, Mosher ester analysis, and comparison with the specific rotation of the isolated (+)-gonioheptolide A. Georg Thieme Verlag Stuttgart.
- Gupta, Shuchi,Rajagopalan, Murali,Alhamadsheh, Mamoun M.,Tillekeratne, L. M. Viranga,Hudson, Richard A.
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p. 3512 - 3518
(2008/09/20)
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- Bifunctional acyclic nucleoside phosphonates: synthesis of chiral 9-{3-hydroxy[1,4-bis(phosphonomethoxy)]butan-2-yl} derivatives of purines
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We report herein a general method for the synthesis of new types of chiral acyclic nucleoside four-carbon bisphosphonates. The alkylation of 2-amino-6-chloropurine and adenine was performed with (2S,3S)- or (2R,3R)-1,4-[bis(diisopropoxyphosphoryl)methoxy]]-3-[(methylsulfonyl)oxy]butan-2-yl benzoate. Alkylations provided (2R,3R) or (2S,3S) N9-substituted nucleobases, which were further converted to other derivatives. These conversions included either a modification of the nucleobase or transformation of the bisphosphonate chain. Subsequent deprotection of the diisopropyl esters with bromotrimethylsilane provided the resulting (2R,3R)- or (2S,3S)-bisphosphonic acids.
- Vrbkova, Silvie,Dracinsky, Martin,Holy, Antonin
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p. 2233 - 2247
(2008/02/11)
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