- On the electron withdrawing nature of ethers in glycosylation chemistry
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The present paper is a commentary on the electronic effects that protecting groups exert on glycosylation chemistry. Specifically, its purpose is to rectify the misguided use of the term electron donating benzyl groups, which hardly makes sense in the context of protecting groups on alcohols in saturated systems such as carbohydrates. It is argued that benzyl ethers (OBn) should rightfully be referred to as being inductively electron withdrawing, even if they are less so than benzoyl esters (OBz).
- Marqvorsen, Mikkel H.S.,Brink?, Anne,Jensen, Henrik H.
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Read Online
- Toward the stereoselective synthesis of zaragozic acid framework: A desilylation-aldol reaction approach
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A convergent synthesis of the C3-C8 fragment of zaragozic acids is described. The key reactions include desilylation-aldol reaction, rearrangement induced by regioselective reductive cleavage, BAIB/TEMPO-Pinnick oxidation, esterification, silylation, and hydrogenolysis.
- Kurniawan, Yudhi D.,Tuck, Kellie L.,Castillón, Sergio,Robinson, Andrea J.
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supporting information
(2021/11/08)
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- Oxidation of Primary Alcohols and Aldehydes to Carboxylic Acids via Hydrogen Atom Transfer
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The oxidation of primary alcohols and aldehydes to the corresponding carboxylic acids is a fundamental reaction in organic synthesis. In this paper, we report a new chemoselective process for the oxidation of primary alcohols and aldehydes. This metal-free reaction features a new oxidant, an easy to handle procedure, high isolated yields, and good to excellent functional group tolerance even in the presence of vulnerable secondary alcohols and tert-butanesulfinamides.
- Tan, Wen-Yun,Lu, Yi,Zhao, Jing-Feng,Chen, Wen,Zhang, Hongbin
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supporting information
p. 6648 - 6653
(2021/09/08)
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- Nickel-Catalyzed Cyanation of Aryl Thioethers
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A nickel-catalyzed cyanation of aryl thioethers using Zn(CN)2 as a cyanide source has been developed to access functionalized aryl nitriles. The ligand dcype (1,2-bis(dicyclohexylphosphino)ethane) in combination with the base KOAc (potassium acetate) is essential for achieving this transformation efficiently. This reaction involves both a C-S bond activation and a C-C bond formation. The scalability, low catalyst and reagents loadings, and high functional group tolerance have enabled both late-stage derivatization and polymer recycling, demonstrating the reaction's utility across organic chemistry.
- Delcaillau, Tristan,Woenckhaus-Alvarez, Adrian,Morandi, Bill
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supporting information
p. 7018 - 7022
(2021/09/13)
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- Oxidative carbon-carbon bond cleavage of 1,2-diols to carboxylic acids/ketones by an inorganic-ligand supported iron catalyst
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The carbon-carbon bond cleavage of 1,2-diols is an important chemical transformation. Although traditional stoichiometric and catalytic oxidation methods have been widely used for this transformation, an efficient and valuable method should be further explored from the views of reusable catalysts, less waste, and convenient procedures. Herein an inorganic-ligand supported iron catalyst (NH4)3[FeMo6O18(OH)6]·7H2O was described as a heterogeneous molecular catalyst in acetic acid for this transformation in which hydrogen peroxide was used as the terminal oxidant. Under the optimized reaction conditions, carbon-carbon bond cleavage of 1,2-diols could be achieved in almost all cases and carboxylic acids or ketones could be afforded with a high conversion rate and high selectivity. Furthermore, the catalytic system was used efficiently to degrade renewable biomass oleic acid. Mechanistic insights based on the observation of the possible intermediates and control experiments are presented.
- Chen, Weiming,Xie, Xin,Zhang, Jian,Qu, Jian,Luo, Can,Lai, Yaozhu,Jiang, Feng,Yu, Han,Wei, Yongge
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supporting information
p. 9140 - 9146
(2021/11/23)
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- A Triazolotriazine-Based Dual GSK-3β/CK-1δ Ligand as a Potential Neuroprotective Agent Presenting Two Different Mechanisms of Enzymatic Inhibition
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Glycogen synthase kinase 3β (GSK-3β) and casein kinase 1δ (CK-1δ) are emerging targets for the treatment of neuroinflammatory disorders, including Parkinson's disease. An inhibitor able to target these two kinases was developed by docking-based design. Compound 12, 3-(7-amino-5-(cyclohexylamino)-[1,2,4]triazolo[1,5-a][1,3,5]triazin-2-yl)-2-cyanoacrylamide, showed combined inhibitory activity against GSK-3β and CK-1δ [IC50(GSK-3β)=0.17 μm; IC50(CK-1δ)=0.68 μm]. In particular, classical ATP competition was observed against CK-1δ, and a co-crystal of compound 12 inside GSK-3β confirmed a covalent interaction between the cyanoacrylamide warhead and Cys199, which could help in the development of more potent covalent inhibitors of GSK-3β. Preliminary studies on in vitro models of Parkinson's disease revealed that compound 12 is not cytotoxic and shows neuroprotective activity. These results encourage further investigations to validate GSK-3β/CK-1δ inhibition as a possible new strategy to treat neuroinflammatory/degenerative diseases.
- Redenti, Sara,Marcovich, Irene,De Vita, Teresa,Pérez, Concepción,De Zorzi, Rita,Demitri, Nicola,Perez, Daniel I.,Bottegoni, Giovanni,Bisignano, Paola,Bissaro, Maicol,Moro, Stefano,Martinez, Ana,Storici, Paola,Spalluto, Giampiero,Cavalli, Andrea,Federico, Stephanie
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supporting information
p. 310 - 314
(2019/01/24)
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- Glycerol conversion to high-value chemicals: The implication of unnatural α-amino acid syntheses using natural resources
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Glycerol derivatives are an important class of compounds, which have great applications as basic structural building blocks in organic synthesis. O-Benzylglycerol was oxidised to produce a high-value compound in high yield using a NaOtBu-O2 system. Furthermore, the synthetic utility of the resulting product was demonstrated by its transformation into unnatural α-amino acids, thus showing the valorisation of glycerol biomass.
- Park, Yun Ji,Yang, Jung Woon
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supporting information
p. 2615 - 2620
(2019/06/03)
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- A colourful azulene-based protecting group for carboxylic acids
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An intensely blue-coloured protecting group for carboxylic acids has been developed. The protecting group is introduced through a Steglich esterification that couples 6-(2-hydroxyethyl)azulene (AzulE) and the carboxylic acid substrate. Deprotection is effected under basic conditions by the addition of the amidine base DBU, whereupon cleavage occurs, accompanied by a colour change. A two-step deprotection methodology comprising activation with oxalyl chloride and deprotection with a very mild base was developed for use with base-sensitive substrates. The AzulE esters were found to be compatible with other commonly employed protecting groups – silyl ethers, MOM acetals – by studying their orthogonal and concomitant deprotections. The stability of the new protecting group towards various synthetic processes – oxidation, reduction, cross-coupling, olefination and treatment with base – provided the basis of a versatility profile. This indicated that AzulE esters are sensitive to strongly oxidising and basic agents while being compatible with reducing conditions and selected other reactions. The convenience of a highly coloured protecting group for tracking material (and avoiding loss of compound) through laboratory processes warrants further investigation of this and/or related species.
- Bevan, Thomas W.,Francis-Taylor, James,Wong, Helena,Northcote, Peter T.,Harvey, Joanne E.
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supporting information
p. 2942 - 2955
(2018/05/16)
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- 4,5-Disubstituted N-Methylimidazoles as Versatile Building Blocks for Defined Side-Chain Introduction
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Fungerin is a 1,4,5-trisubstituted imidazole natural product characterised by a broad spectrum of antifungal activities. We planned to develop flexible strategies to access to such compounds. Imidazoles bearing suitable anchor groups at C-4 and C-5 allow the introduction of various substituted side-chains, generating libraries of fungerin derivatives for biological tests. Starting from commercially available reactants, two N-methyl 4,5-substituted imidazole core units were synthesised. Derivatives of type 1 contained two orthogonally protected C-1 anchors. Selective side-chain introduction was achieved through a sequence of Grignard coupling at C-5 to replace a tosylate and a Horner olefination through an aldehyde attached to C-4. Two target fungerin derivatives were synthesised. Since the organometallic substitution of the C-5-CH2-positioned leaving group proved to suffer from limitations concerning potential competing side-reactions, a type 2 imidazole core was built up. These structures had a halogen centre at C-4 and a hydroxyethyl anchor at C-5. Now, selective side-chain introduction allowed us to use Julia olefination to form the allyl side-chain at C-5 and Heck reactions to introduce the C-4 acryl substituents. Eight derivatives, including fungerin, were synthesised by this latter strategy, without producing any regioisomers. The second approach had the advantage that various side-chains could be coupled at C-4 and C-5 in two final steps. Thus, this strategy represents a versatile way to build up libraries of fungerin derivatives for biological testing.
- Przybyla, Daniel,Nubbemeyer, Udo
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supporting information
p. 695 - 703
(2017/02/05)
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- PREPARATION METHOD FOR CHIRAL INTERMEDIATE FOR USE IN STATINS
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The present invention relates to a preparation method for a chiral intermediate for use in statins, acquired with chloroacetic acid and benzyl alcohol as starting materials via a series of reactions, namely etherification, condensation, substitution, and asymmetric reduction. The preparation method provided in the present invention has a novel route of synthesis, allows an intermediate compound to be introduced conveniently into the chiral center of a glycol via enzyme reduction, and not only is low in costs, but also is reliable in quality. The route of synthesis provided in the present invention uses raw materials of low costs, has an easy to operate process, and provides a final product of great purity and high yield.
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Paragraph 0065; 0066; 0081
(2017/08/01)
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- Discovery of 1,4-Benzodiazepine-2,5-dione (BZD) Derivatives as Dual Nucleotide Binding Oligomerization Domain Containing 1/2 (NOD1/NOD2) Antagonists Sensitizing Paclitaxel (PTX) to Suppress Lewis Lung Carcinoma (LLC) Growth in Vivo
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Nucleotide-binding oligomerization domain-like receptors (NLRs) are intracellular sensors of pathogen-Associated molecular patterns (PAMPs) and damage-Associated molecular patterns (DAMPs). Previously, we reported nucleotide-binding oligomerization domain-containing protein 1 (NOD1) antagonists (11, 12) and a NOD2 antagonist (9) that sensitized docetaxel (DTX) or paclitaxel (PTX) treatment for breast or lung cancer. In this article, we describe for the first time a 1,4-benzodiazepine-2,5-dione (BZD) derivative (26bh) that acts as a dual NOD1/NOD2 antagonist and inhibits both nuclear factor B (NF-B) and mitogen-Activated protein kinase (MAPK) inflammatory signaling, thereby sensitizing PTX to suppress Lewis lung carcinoma (LLC) growth. After investigation of the compound's cytotoxicity, a systematic structure-Activity relationship (SAR) was completed and revealed several key factors that were necessary to maintain antagonistic ability. This study establishes the possibility for using adjuvant treatment to combat cancer by antagonizing both NOD1 and NOD2 signaling.
- Wang, Suhua,Yang, Jingshu,Li, Xueyuan,Liu, Zijie,Wu, Youzhen,Si, Guangxu,Tao, Yiran,Zhao, Nan,Hu, Xiao,Ma, Yao,Liu, Gang
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supporting information
p. 5162 - 5192
(2017/06/28)
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- Reactions of peroxide products of ozonolysis of allyl ethers/esters in the AcOH-CH2Cl2 system on treatment with semicarbazide hydrochloride
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Background: A one-pot method for the preparation of the corresponding alkoxy acetic acids by low-temperature ozonolysis of allyl ethers/esters followed by treatment with semicarbazide hydrochloride has been suggested. The reaction occurs via formation of acetoxyhydroperoxide, subsequent reduction of which depends on the process temperature and the nature of the starting substrate. Objective: The article is aimed at the development of one-pot method for obtaining practically important alkoxy acetic acids, because the ozonolytic cleavage of a ?=? double bond is the key step in full syntheses of many biologically active compounds. Methods: We used a low temperature ozonolysis of functionally substituted olefins in the system acetic acid-methylene dichloride followed by reduction of semicarbazide hydrochloride. To create a method we have used available allyl ethers/esters as starting materials. Results: We investigated reaction of the peroxide products of ozonolysis of monoallyl ethers, ester and diallyl ethers in an AcOH/CH2Cl2 mixture on treatment with semicarbazide hydrochloride at various temperatures. We have discovered that the selectivity of reduction of acetoxyhydroperoxide formed at the first stage depends both on the process temperature and on the nature of the starting substrate. A decrease in temperature favors acid hydrolysis and formation of a carboxylic acid. Conclusion: We have proposed a simple and highly efficient one-pot method for the preparation alkoxy acetic acids without isolation of intermediate peroxides.
- Raskil'dina, Gulnara Z.,Legostaeva, Yuliya V.,Garifullina, Liliya R.,Sultanova, Rimma M.,Ishmuratov, Gumer Y.,Zlotskii, Simon S.
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p. 652 - 656
(2017/01/13)
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- Design and synthesis of new vancomycin derivatives
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A set of vancomycin derivatives with lipid chain attached via a glyceric acid linker was designed and synthesized. A concise synthesis towards these derivatives was developed and the IC50s of these new lipoglycopeptides were tested. Some of them showed very potent activity against both vancomycin sensitive and resistant strains.
- Gu, Wen,Chen, Bei,Ge, Min
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p. 2305 - 2308
(2014/05/20)
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- An examination of the scope and stereochemistry of the Ireland-Claisen rearrangement of boron ketene acetals
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The Ireland-Claisen rearrangement of boron ketene acetals is described. The boron ketene acetal intermediates are formed through a soft enolization that obviates the use of strong bases and the intermediacy of alkali metal enolates. Yields and diastereoselectivities of these rearrangements are very sensitive to the choice of boron reagent, even among those that have been shown to effect quantitative formation of boron ketene acetals from esters. The rearrangement occurs at room temperature for all substrates with generally high levels of stereoselectivity. In contrast to previous reports using boron triflates, the use of a commercially available boron iodide reagent allows for a wider substrate scope that extends to propionates and arylacetates, as well as the previously described α-oxygenated esters. This work also provides insight into the dynamic nature of boron ketene acetals and the ramifications of this behavior for reactions in which they are intermediates. Borane down: Boron enolates of allylic esters are efficiently generated at -78 °C using cHx2BI (dicyclohexyliodoborane)·Et3N. These rearrange smoothly on being warmed to room temperature to give generally high diastereoselectivity in forming γ,δ-unsaturated acids (see scheme). The rearrangements provide a key insight into the dynamic nature of boron ketene acetals.
- Seizert, Curtis A.,Ferreira, Eric M.
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supporting information
p. 4460 - 4468
(2014/05/06)
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- SYNTHESIS OF TELAPREVIR AND BOCEPREVIR, OR PHARMACEUTICALLY ACCEPTABLE SALTS OR SOLVATES AS WELL AS INTERMEDIATE PRODUCTS THEREOF INCLUDING ?-AMINO ACIDS PREPARED VIA MUKAIYAMA ALDOL ADDITION
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The invention relates to synthetic routes for preparing telaprevir and boceprevir, and its intermediates as well as peptides other than telaprevir. The synthetic routes are based on a Mukaiyama aldol addition reaction of a silyl enol ether or an enolate with an imine. The invention also refers to novel intermediates for preparing telaprevir/boceprevir or other peptides.
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Page/Page column 31
(2014/01/09)
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- Asymmetric hydrogenation of α- Or β-acyloxy α,β- unsaturated phosphonates catalyzed by a Rh(i) complex of monodentate phosphoramidite
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The Rh(i) complex of a monodentate phosphoramidite bearing a primary amine moiety (DpenPhos) has been disclosed to be highly efficient for the asymmetric hydrogenation of a variety of α- or β-acyloxy α,β- unsaturated phosphonates, providing the corresponding biologically important chiral α- or β-hydroxy phosphonic acid derivatives with excellent enantioselectivities (90->99% ee).
- Zhang, Jinzhu,Dong, Kaiwu,Wang, Zheng,Ding, Kuiling
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supporting information; scheme or table
p. 1598 - 1601
(2012/03/22)
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- Nitroxyl radical/PhI(OAc)2: One-pot oxidative cleavage of vicinal diols to (di)carboxylic acids
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A mild and user-friendly one-pot oxidative cleavage of vicinal diols to their corresponding (di)carboxylic acids using AZADOs and PhI(OAc)2 is described. 1,2-Diols and 2,3-diols as well as 1,2,3-triol gave one- or two-carbon-unit-shorter carboxylic acids. Internal vicinal diols also smoothly underwent one-pot oxidative cleavage to afford the corresponding dicarboxylic acids. Cyclic vicinal diols are converted to their corresponding open-form dicarboxylic acids.
- Shibuya, Masatoshi,Shibuta, Takuro,Fukuda, Hayato,Iwabuchi, Yoshiharu
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supporting information
p. 5010 - 5013
(2013/01/15)
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- Synthesis of α-CF3-substituted carbonyl compounds with relative and absolute stereocontrol using electrophilic CF3-transfer reagents
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Evans-type chiral lithium imide enolates undergo diastereoselective α-trifluoromethylation with a hypervalent iodine-CF3 reagent with up to 91% combined isolated yield and 97:3 dr. The resulting isolated diastereopure products can be further transformed into valuable products without racemization.
- Matousek, Vaclav,Togni, Antonio,Bizet, Vincent,Cahard, Dominique
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supporting information; experimental part
p. 5762 - 5765
(2012/01/06)
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- [3,3]-sigmatropic rearrangement/5-exo-dig cyclization reactions of benzyl alkynyl ethers: Synthesis of substituted 2-indanones and indenes
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Substituted benzyl alkynyl ethers, prepared from the corresponding α-alkoxy ketones in a two-step sequence involving enol triflate formation and KOtBu-induced E2 elimination, undergo [3,3]-sigmatropic rearrangement/ intramolecular 5-exo-dig cyclization at 60 °C to form substituted 2-indanones in good overall yields. 1,3-cis-Disubstituted-2-indanones are formed preferentially when the benzylic substituent R1 is bulky. Substituted indenes may be prepared from 2-indanones in high yields by Horner-Wadsworth-Emmons reaction.
- Tudjarian, Armen A.,Minehan, Thomas G.
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supporting information; experimental part
p. 3576 - 3581
(2011/06/25)
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- Stereoselective synthesis of a monocyclic peloruside A analogue
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Chemical Equation Presentation The stereoselective synthesis of the monocyclic peloruside A analogue 4 has been achieved, following a new efficient approach for the introduction of the side chain, involving a late-stage addition of vinyl lithium species 7a to aldehyde 8. Further key steps are a highly diastereoselective allyltitanation reaction and a RCM-based macrocyclization.
- Wulischleger, Christoph W.,Gertsch, Juerg,Altmann, Karl-Heinz
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supporting information; experimental part
p. 1120 - 1123
(2010/06/13)
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- Synthesis of kurasoin B using phase-transfer-catalyzed acylimidazole alkylation
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The hydroxy ketone natural product kurasoin B is synthesized using a phase-transfer-catalyzed alkylation reaction with benzyloxyacetyl imidazole. A biscinchonidinium dimethylnaphthalene catalyst allowed for high yield and near complete selectivity (99% ee
- Christiansen, Michael A.,Butler, Aaron W.,Hill, Amanda R.,Andrus, Merritt B.
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body text
p. 653 - 657
(2009/08/07)
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- Practical preparation of benzyloxyacetic acids
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An efficient and practical method for the preparation of benzyloxyacetic acids is described. The procedure involves the reaction of readily available chloroacetic acid with benzyl alcohol in the presence of powdered KOH providing a safer alternative to the known literature procedures, which completely eliminates the use of pyrophoric bases such as sodium hydride and sodium metal.
- Linn, Kathleen,Kuethe, Jeffrey T.,Peng, Zhihui,Yasuda, Nobuyoshi
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p. 3762 - 3765
(2008/09/21)
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- Oxazole cyclopeptides for chirality transfer in C3-symmetric octahedral metal complexes
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A straightforward synthesis of C3-symmetric oxazole-containing macrocyclic peptide scaffolds is presented. This type of macrocycles bears three functional groups on the oxazole rings, which allows fixing of various receptor arms on them in an easy manner. The chiral backbone of the macrocycle proved to be a powerful tool for chirality induction, thus predetermining the configuration of helically coordinated metal centres. The diastereoselective formation of CoII, NiII, CuII and Zn II complexes with tripodal bipyridyl ligand 4 was proved by UV- and CD-absorption spectrophotometric titration experiments. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Pinter, Aron,Haberhauer, Gebhard
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experimental part
p. 2375 - 2387
(2009/04/05)
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- Phase-transfer-catalyzed asymmetric acylimidazole alkylation
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(Chemical Equation Presented) 2-Acylimidazoles are alkylated under phase-transfer conditions with cinchonidinium catalysts at -40°C with allyl and benzyl electrophiles in high yield with excellent enantioselectivity (79 to >99% ee). The acylimidazole substrates are made in three steps from bromoacetic acid via the N-acylmorpholine adduct. The catalyst is made in high purity allowing for S-product formation (6-20 h) under mild conditions, consistent with an ion-pair mechanism. The products are readily converted to useful ester products using methyltriflate and sodium methoxide, via a dimethylacylimidazolium intermediate without racemization. The process is efficient, direct, and amenable to other electrophiles and transformations that proceed through an enolate intermediate.
- Andrus, Merritt B.,Christiansen, Michael A.,Hicken, Erik J.,Gainer, Morgan J.,Bedke, D. Karl,Harper, Kaid C.,Mikkelson, Shawn R.,Dodson, Daniel S.,Harris, David T.
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p. 4865 - 4868
(2008/03/14)
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- First total synthesis of the bioactive anthraquinone kwanzoquinone C and related natural products by a Diels-Alder approach
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The first total synthesis of the novel anticancer agent kwanzoquinone C (1), an anthraquinone glycoside which has been isolated from extracts of the roots of orange daylilies (Kaempfer) (Hemerocallis fulva) is reported. The strategy involves the preparati
- Tietze, Lutz F.,Gericke, Kersten M.,Guentner, Carlos
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p. 4910 - 4915
(2007/10/03)
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- SILICON COMPOUNDS AND THEIR USE
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A compound of formula (1): wherein A is -CH2CH2-, -CH=CH- or -C=-C-; B is aryl or heteroaryl; D is optionally present and is -C(O)-, -C(O)NH-, -C(O)CH2- or -C(O)CH2- O-; E is optionally present and is alkylene or heteroarylene; R1 is hydrogen or alkyl; R2 is hydrogen, alkyl, aryl, cycloalkyl, heteroaryl or heterocycloalkyl; R3 and R4 are the same or different and are each hydrogen, alkyl or cycloalkyl; and each R5 is the same or different and is alkyl, -alkyl-aryl or -alkyl-cycloalkyl, or R5-Si-R5 taken together form heterocycloalkyl; or a pharmaceutically acceptable salt thereof.
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Page/Page column 15
(2008/06/13)
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- Radiohalogenated benzamide derivatives and their use in tumor diagnosis and tumor therapy
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This invention relates to new radiohalogenated benzamide derivatives and their use in tumor diagnosis and tumor therapy. The radiohalogenated benzamide derivatives according to the invention exhibit novel and especially advantageous properties, in particular with respect to tumor concentration and retardation, liver concentration and blood accumulation. The radiation-therapy doses to be achieved in the tumor, compared to healthy body tissue, are advantageous for the compounds according to the invention.
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Page/Page column 13
(2008/06/13)
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- A facile synthesis of 2-benzyloxy/2-(4-isopropylbenzyloxy)-2-methyl-3-(4- substituted phenyl)propanoic acid based insulin sensitizing agents: RSR 13-15 and PKR13-15
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The title compounds (RSR13-15) and (PKR13-15) were prepared by the etherification of benzyl alcohol and 4-isopropylbenzyl alcohol respectively with ethyl-2-bromo-2-methyl-3-(4-substituted phenyl)propanoates in the presence of sodium hydride in THF followed by alkaline hydrolysis of the ethyl esters. The substituted propanoic acids used in this synthetic sequence were prepared by magnesium-methanol reduction of correspondingly substituted propenoic acids, which in turn were prepared via 'Perkin Reaction' of 4-substituted benzaldehydes with propanoic anhydride. The details of the synthetic sequence followed for the preparation of all these compounds having almost all the structural features required for a compound to act as a potent insulin sensitizing agent are reported. Birkhaeuser Boston 2004.
- Verma, Raman K.,Singla, Rubina,Punniyakoti
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p. 660 - 676
(2007/10/03)
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- Chiral hetero Diels-Alder products by enantioselective and diastereoselective zirconium catalysis. Scope, limitation, mechanism, and application to the concise synthesis of (+)-prelactone C and (+)-9-deoxygoniopypyrone
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Catalytic asymmetric hetero Diels-Alder (HDA) reactions using a chiral zirconium complex have been developed. The reactions of aldehydes with Danishefsky's dienes proceeded smoothly to afford the corresponding pyranone derivatives in high yields with high diastereo- and enantioselectivities in the presence of a chiral zirconium complex, which was prepared from zirconium tert-butoxide, (R)-3,3′-diiodobinaphthol or its derivative, a primary alcohol, and a small amount of water. It is noted that 2,3-trans-pyranone derivatives were obtained with remarkably high diastereo- and enantioselectivities in the reaction with 4-methyl Danishefsky's diene. This is the first example of catalytic asymmetric trans-selective hetero Diels-Alder reactions of aldehydes. Furthermore, asymmetric HDA reactions with 4-benzyloxy Danishefsky's dienes were conducted to afford 2,3-cis-pyranone derivatives in high selectivities. Isolation of an intermediate of this asymmetric hetero Diels-Alder reaction indicated that the reaction proceeded in a stepwise cycloaddition pathway. Finally, these catalytic, asymmetric hetero Diels-Alder reactions were successfully applied to concise syntheses of biologically important natural pyranone derivatives, (+)-Prelactone C and (+)-9- deoxygoniopypyrone.
- Yamashita, Yasuhiro,Saito, Susumu,Ishitani, Haruro,Kobayashi, Shu
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p. 3793 - 3798
(2007/10/03)
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- Stereoselective synthesis of the α-glucosidase inhibitor nectrisine
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The α-glucosidase inhibitor nectrisine was synthesised in 12 steps (31% overall yield) starting from D-serine. The three contiguous stereocentres of this iminosugar were introduced via a highly diastereoselective boron mediated glycolate aldol reaction.
- Hulme, Alison N.,Montgomery, Charles H.
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p. 7649 - 7653
(2007/10/03)
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- An inexpensive carbohydrate derivative used as a chiral auxiliary in the synthesis of α-hydroxy carboxylic acids
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Protected α-hydroxy carboxylic acids were synthesized in moderate yield and high diastereoselectivity by alkylation of glycolate (α-hydroxy acetate) enolates using a D-fructose-derived chiral auxiliary. The new chiral center was assigned the R configuration based on comparisons of optical rotations and on one crystal structure analysis. This alkylation methodology is compatible with several hydroxyl protecting groups. The free hydroxy acids were obtained upon removal of the protecting group from the hydroxyl functionality followed by saponification.
- Yu, Hongwu,Ballard, C.Eric,Boyle, Paul D,Wang, Binghe
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p. 7663 - 7679
(2007/10/03)
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- Non-carbonyl-stabilized metallocarbenoids in synthesis: The development of a tandem rhodium-catalyzed bamford-stevens/thermal aliphatic claisen rearrangement sequence
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A tandem rhodium-catalyzed Bamford-Stevens/Claisen rearrangement is presented. The tandem reaction uses Eschenmoser hydrazones for the in situ generation of non-carbonyl-stabilized diazo alkanes, which are presumably intercepted by Rh(II) catalysts to induce a 1,2-hydride migration. This sequence provides high levels of stereocontrol for the generation of simple acyclic (Z)-enol ethers. These enol ethers undergo either thermal or Lewis acid accelerated Claisen rearrangements to provide products of high diastereopurity. Also presented are cascade reactions, wherein a third chemical step occurs after the initial tandem sequence (i.e., Bamford-Stevens/Claisen/ene and Bamford-Stevens/Claisen/Cope). Copyright
- May, Jeremy A.,Stoltz, Brian M.
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p. 12426 - 12427
(2007/10/03)
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- Asymmetric total synthesis of Taxol
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The asymmetric total synthesis of Taxol was achieved by way of B to BC to ABC to ABCD ring construction. Optically active 8-membered ring enones 1 and 2 corresponding to the B ring of Taxol have been synthesized in high yields from the linear precursors 28 and 32, respectively, by intramolecular aldol cyclization using SmI2. The optically active linear polyoxy compounds 28 and 32 were obtained by way of diastereoselective aldol reaction between aldehyde 4 and ketene silyl acetal 8 catalyzed by MgBr2 · OEt2. The chiral pentanal 4 was synthesized either by asymmetric aldol reaction of achiral aldehyde 7 and ketene silyl acetal 8 by means of a chiral Lewis acid or by diastereoselective aldol reaction between the chiral aldehyde 16, derived from L-serine, and the lithium enolate derived from methyl isobutyrate. Optically active bicyclo[6.4.0]dodecanone 38β, corresponding to the BC ring system of Taxol, was prepared from 8-membered ring enone 2 in high yield by stereoselective Michael addition and successive intramolecular aldol cyclization. Furthermore, baccatin III, the ABCD ring system of Taxol, was efficiently synthesized from the BC ring system 38β by successive construction of the A and D rings by intramolecular pinacol coupling cyclization, introduction of the C-13 hydroxyl group and an oxetane-forming reaction. Finally, the total synthesis of Taxol was accomplished by dehydration condensation between a protected N-benzoylphenylisoserine 70 or 75 and 7-TES baccatin III, prepared from baccatin III. Taxol side chains 70, 73, 75, and 77, optically active protected N-benzoylphenylisoserines, were synthesized by enantioselective aldol reaction from two achiral starting materials, benzaldehyde and an enol silyl ether 65 derived from S-ethyl benzyloxyethanethioate.
- Mukaiyama, Teruaki,Shiina, Isamu,Iwadare, Hayato,Saitoh, Masahiro,Nishimura, Toshihiro,Ohkawa, Naoto,Sakoh, Hiroki,Nishimura, Koji,Tani, Yu-Ichirou,Hasegawa, Masatoshi,Yamada, Koji,Saitoh, Katsuyuki
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p. 121 - 161
(2007/10/03)
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- Synthetic study of pinnatoxin A: Intramolecular Diels-Alder approach to the AG-ring
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A chiral quaternary carbon (C5) with the G-ring of pinnatoxin A has been diastereoselectively constructed via an intramolecular Diels-Alder reaction.
- Ishiwata, Akihiro,Sakamoto, Satoshi,Noda, Takeshi,Hirama, Masahiro
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p. 692 - 694
(2007/10/03)
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- Highly enantiopure (tert-butyldiphenylsilyloxymethyl)oxiranes from barium carbonate
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The synthesis of (2R)-(tert-butyldiphenylsilyloxymethyl)oxirane and the (2S)-enantiomer from barium carbonate was developed. Methyl glycolate or the hydroxamate analog was prepared and in turn reacted with (S)-(-)-methyl p- tolylsulfoxide or the (R)-enantiomer to make β-keto sulfoxides. From the sulfoxides, we made the diastereoisomeric alcohols in a highly selective sulfoxide group directed hydride reduction, and a Pummerer rearrangement reaction followed by deprotection yielded the enantiomeric diols. (2R)- (tert-Butyldiphenylsilyloxymethyl)oxirane and its (2S)-enantiomer were derived from these diols in an overall yield of 56 % from barium carbonate. This method was developed to provide a convenient access to isotope-labeled analogs of these compounds.
- Ekhato, I. Victor,Palazzolo, Mark
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p. 3727 - 3741
(2007/10/03)
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- Ferrocene compounds XXIII. Synthesis and reactions of the new type of methyl ferrocyloxyalkanoates
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The new types of ferrocenyloxaaliphatic acid ester, FcCHROCHR′COOMe (R = H, Me, Ph; R′ = H, Me) (7) have been prepared by the action of alkoxides derived from methyl glycolate or methyl lactate on the corresponding ferrocenylcarbinyl acetates (2) or N,N,N-trimethylferrocylammonium iodides (4). The esters obtained were accompanied by a small quantity of oligomeric esters, FcCHR(OCHR′CO)nOMe (9), and with more or less ferrocyl methyl ethers (8). As opposed to the alkaline hydrolysis of the analogous methyl benzoxyacetate (6) into benzoxyacetic acid (5) the acidification of sodium alkanoates 10 obtained by saponification of esters 7 gave unexpectedly the corresponding ferrocenylcarbinols 1. In a similar way the esters 7 were converted into mixtures of the mentioned carbinols and diferrocyl ethers 11 under action of aqueous hydrochloric acid. The mechanisms of the reactions 10 → 1 and 7 → 1, 11 are discussed.
- Kovac,Rapic,Susnik,Suprina
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p. 149 - 158
(2007/10/03)
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- BENZOXAZINONE DERIVATIVE
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A benzoxazinone derivative represented by general formula (I) or a pharmaceutically acceptable acid addition salt thereof, and an anti-inflammatory, a neutrophil infiltration inhibitor and a serine protease inhibitor each containing the derivative as an active ingredient, wherein R, R1, R2 and R3 may be the same or different from one another and each represents hydrogen or lower alkyl; A represents optionally halogenated phenyl, heterocycle or adamantyl; B represents hydrogen or optionally halogenated phenyl or heterocycle; U represents =CH-, =C= or =N-; V represents -O-, -CH2-, =N-, -NH-, -CH= or a single bond; X represents -O-, =CH-, -CH2- or a single bond; Y represents -CH2-, -NH-, -O- or a single bond; Z represents -CO- or -CH2-; and l represents an integer of 0 to 3. This compound has excellent activities of inhibiting serine protease, neutrotaxis, and infiltration of neutrophils into carragheenin-induced pneumocephalus.ψ
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- Facile syntheses of amino-6-deoxyaldohexoses from simple achiral starting materials
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Three kinds of amino-6-deoxyaldohexoses are synthesized from simple achiral starting materials, trans-crotonaldehyde and chloroacetic acid, via the three key steps of the chiral tin(II) triflate-mediated asymmetric aldol reaction, the dihydroxylation using osmium tetroxide, and the SN2 displacement of the corresponding triflates with azide anions. Keywords: Amino sugars / asymmetric aldol reaction / osmium tetroxide / SN2 displacement / amino-6-deoxyaldohexose
- Mukaiyama, Teruaki,Anan, Hideki,Shiina, Isamu,Kobayashi, Shu
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p. 388 - 394
(2007/10/02)
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- Preparation of protected 2-hydroxymethyl isocyanates: An application to agricultural synthesis
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The preparation of N-benzyloxymethyl isocyanate (4) and t-butyldiphenylsiloxymethyl isocyanate (9) via the diphenylphosphoryl azide modified Curtius rearrangement is described. These isocyanates have been amployed in the synthesis of a herbicide metabolit
- Roth,McClymont
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p. 411 - 420
(2007/10/02)
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- Chemoselective deprotection of benzyl esters in the presence of benzyl ethers, benzyloxymethyl ethers and N-benzyl groups by catalytic transfer hydrogenation
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-COOBn, -PO(OH)OBn, -O-CBz and N-CBz groups are efficiently and chemoselectively deprotected in the presence of Bn and BOM ethers and N-Bn groups by hydrogenolysis under catalytic transfer hydrogenation using 10% palladium on carbon as the catalyst and cyclohexadiene as the hydrogen donor.
- Bajwa
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p. 2299 - 2302
(2007/10/02)
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- A HIGHLY EFFECTIVE ASYMMETRIC SYNTHESIS OF α-HYDROXY ACIDS BY ALKYLATION OF CHIRAL N-(BENZYLOXYACETYL)-TRANS-2,5-BIS(METHOXYMETHOXYMETHYL)PYRROLIDINE
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Alkylation of lithiated N-(benzyloxyacetyl)-trans-2,5-bis(methoxymethoxymethyl)-pyrrolidine proceeded with high stereoselectivity (>96percent de) and subsequent transformations of the alkylated products gave synthetically useful α-benzyloxy acids or α-hydroxy acids of high enantiomeric purity.
- Enomoto, Masayuki,Ito, Yoshio,Katsuki, Tsutomu,Yamaguchi, Masaru
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p. 1343 - 1344
(2007/10/02)
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- Photolysis of Alkoxyacetic Acids in the presence of Mercury(II) Oxide and Iodine
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Homolytic decarboxylation of a series of alkoxyacetic acids has furnished alkoxyalkyl alkoxyacetates when no substituents were present at the 2-position.Electron donating and withdrawing 2-substituents, with the exception of trichloromethyl, afforded products due to fragmentation of the alkoxyacetic acids.The reaction pathway is rationalised on the basis of the reactivity of the alkoxyalkyl iodide intermediates.
- Glover, Stephen A.,Golding, Stephen L.,Goosen, Andre,McCleland, Cedric W.
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p. 2479 - 2483
(2007/10/02)
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- The Synthesis of N(τ)-(2-hydroxypropyl)histidine, N(τ)-2-hydroxyethyl)histidine, and Their Deuteriated Analogues
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The synthesis of N(τ)-(2-hydroxypropyl)histidine (1), N(τ)-(2-hydroxypropyl)histidine (2), N(τ)-(2-hydroxyethyl)histidine (3), and N(τ)-(2-hydroxyethyl)histidine (4) by reaction of protected histidine derivatives with bromoacetone, bromoacetone, 2-benzyloxyethyl toluene-p-sulphonate (17), and 2-benzyloxyethyl toluene-p-sulphonate (18), respectively, is described.
- Campbell, John B.
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p. 1213 - 1218
(2007/10/02)
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- Antibacterial agents, and 4-thio azetidinone intermediates
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This invention relates to 2-substituted and 2,6-disubstituted penem compounds of the formula STR1 wherein Y is hydrogen, halo or certain organic substituents and X represents certain organic substituents. Also included in the invention are pharmaceutically acceptable salts of the above compounds and derivatives of the above compounds in which the carboxyl group at the 3-position is protected as by an easily removable ester protecting group. The compounds of the present invention are potent antibacterial agents or are of use as intermediates in the preparation of such agents.
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