- Structure-activity relationships of untenone a and its derivatives for inhibition of DNA polymerases
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We found that untenone A and mannzamenone A inhibit mammalian DNA polymerases α and β, and human terminal deoxynucleotidyl transferase (TdT). The syntheses of both compounds and the structure-activity relationships of untenone A derivatives are described.
- Saito, Fumiyo,Takeuchi, Ryo,Kamino, Tomoyuki,Kuramochi, Kouji,Sugawara, Fumio,Sakaguchi, Kengo,Kobayashi, Susumu
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Read Online
- Synthesis of tetranor-PGE1: A urinary metabolite of prostaglandins E1 and E2
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Prostaglandin E2 is produced in response to inflammation, often associated with human disease. As prostaglandins are rapidly metabolized, quantification of end urinary metabolites depend on chemical synthesis of isotopically labeled standards to support metabolite quantification. A concise synthesis of tetranor-PGE1 is described including a late stage incorporation of an isotopically labeled side-chain.
- Kimbrough, Jennifer R.,Jana, Somnath,Kim, Kwangho,Allweil, Alexander,Oates, John A.,Milne, Ginger L.,Sulikowski, Gary A.
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Read Online
- Molecular Design of Crown Ethers. 6. Substitution Effect in 16-Crown-5
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A number of 14-, 15-, and/or 16-substituted 16-crown-5 derivatives were synthesized for systematic analysis of the effect of substitution in these crown ethers.The cation-binding ability of substituted 16-crown-5 rings was evaluated by the solvent extraction technique and found to be a critical function of the position, number, type, and stereochemistry of the substituent(s) introduced.Both 15- and 14/16-substituted 16-crown-5 exhibited gradually decreased extractabilities with increasing substitution, although the profiles of change in extractability were distinctly different between 15- and 14/16-substitution.The substitution-induced decrease of extractability is attributed to the limited access of counteranion and/or to the lack of conformational adjustments necessary to make a structure suitable for complex formation.The bridging substitutions at 14- and 16-positions dramatically enhanced the extractabilities for all cations without lowering the original relative cation selectivity.This may arise from the favorable entropic contribution of the conformational freezing by bridging substitution.
- Inoue, Yoshihisa,Wada, Kazuhito,Liu, Yu,Ouchi, Mikio,Tai, Akira,Hakushi, Tadao
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Read Online
- Enzyme immobilised novel core-shell superparamagnetic nanocomposites for enantioselective formation of 4-(R)-hydroxycyclopent-2-en-1-(S)-acetate
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Lipase immobilized novel high surface area core-shell superparamagnetic nanoparticles have been fabricated and used as efficient reusable catalysts for the selective production of pharmaceutically important chiral isomers from meso-cyclopent-2-en-1,4-diac
- Sharifabad, Maneea Eizadi,Hodgson, Ben,Jellite, Mourad,Mercer, Tim,Sen, Tapas
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Read Online
- Chemoselective formation of cyclo-aliphatic and cyclo-olefinic 1,3-diolsviapressure hydrogenation of potentially biobased platform molecules using Kn?lker-type catalysts
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The hydrogenative conversions of the biobased platform molecules 4-hydroxycyclopent-2-enone and cyclopentane-1,3-dione to their corresponding 1,3-diols are established using a pre-activated Kn?lker-type iron catalyst. The catalyst exhibits a high selectivity for ketone reduction, and does not induce dehydration. Moreover, by using different substituents of the ligand, thecis-transratio of the products can be affected substantially. A decent compatibility of this catalytic system with various structurally related substrates is demonstrated.
- Alsters, Paul L.,Chou, Khi Chhay,De Wildeman, Stefaan M. A.,Faber, Teresa,Hadavi, Darya,Han, Peiliang,Quaedflieg, Peter J. L. M.,Schwalb Freire, Alfonso J.,Verzijl, Gerard K. M.,van Slagmaat, Christian A. M. R.
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p. 10102 - 10112
(2021/08/03)
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- COLLECTIONS OF PEPTIDES, PEPTIDE AGENTS, AND METHODS OF USE THEREOF
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The present disclosure provides powerful technologies for the development, production, characterization, and/or use of stapled peptide compositions. Among other things, the present disclosure provides strategies for defining amino acid sequences particularly amenable or useful for stapling, as well as technologies, reagents, and systems for developing, producing, characterizing, and/or using stapled peptides having such amino acid sequences.
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Paragraph 0375-0376
(2020/03/15)
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- A Pd-catalyzed asymmetric allylic substitution cascade: Via an asymmetric desymmetrization for the synthesis of bicyclic dihydrofurans
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A Pd-catalyzed asymmetric allylic substitution cascade of allylic meso-dicarbonates with 3-oxo-nitriles has been developed for the synthesis of chiral bicyclic dihydrofurans bearing two vicinal carbon stereocenters. The reaction proceeds via an asymmetric desymmetrization process with the desired products being obtained in high yields and with up to 97% ee. The reaction was performed on a gram-scale and the corresponding bicyclic dihydrofurans could undergo several transformations. The methodology provides an efficient synthetic route to biologically active chiral bicyclic dihydrofurans derivatives.
- Xu, Kai,Liu, Hao,Hou, Yilin,Shen, Jiefeng,Liu, Delong,Zhang, Wanbin
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supporting information
p. 13295 - 13298
(2019/11/13)
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- Nickel-mediated reductive coupling of neopentyl bromides with activated alkenes at room temperature and its synthetic application
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Reductive coupling of sterically hindered neopentyl bromides with activated alkenes mediated by the in situ generated Ni(0) complexes along with some feedstock is achieved in good yield under the mild conditions. This practically useful method of C(sp3)?C(sp3) bond formation provides a complementary approach to the traditional conjugate addition of preformed organometallic reagents to electrophilic olefins, which often requires cryogenic temperature and rigorous exclusion of air and moisture. The robust application of this reductive coupling reaction was demonstrated in a formal synthesis of stereodivergent (?)-copacamphor and (?)-ylangocamphor, which are valuable intermediates for a class of tricyclo[5.3.0.03,8]decane sesquiterpenes. Moreover, this convenient protocol resulted in a facile access to the homolog of Corey aldehyde en route to prostaglandins, implying the possible involvement of radical-like species.
- Ouyang, Yan,Peng, Yu,Li, Wei-Dong Z.
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p. 4486 - 4496
(2019/07/05)
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- Combining engineering and chemistry for the selective continuous production of four different oxygenated compounds by photo-oxidation of cyclopentadiene using liquid and supercritical CO2 as solvents
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A range of products is reported from the photo-oxidation of cyclopentadiene from photochemically generated singlet oxygen (1O2) using carbon dioxide (CO2) as a solvent and 5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin (TPFPP) as a CO2-soluble photosensitizer. The endo-peroxide intermediate, generated from the reaction with singlet oxygen, is transformed into one of several different products in good yield depending on the conditions applied and by adding different reactors and reagents downstream of the photo-reactor, allowing the reaction products to be switched in one streamlined process. The addition of a thermal reactor facilitated the rearrangement of the endoperoxide to form Z-4,5-epoxy-2-pentanal. Quenching with thiourea yielded the syn-diol, (1R,3S)-cyclopent-4-ene-1,3-diol. Treatment with acid or base afforded furfuryl alcohol and 4-hydroxy-2-cyclopentenone respectively. High productivities for all products were obtained when compared to traditional batch reactions.
- Wu, Lingqiao,Abada, Zahra,Lee, Darren S.,Poliakoff, Martyn,George, Michael W.
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supporting information
p. 3107 - 3112
(2017/12/15)
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- Preparation of (1R,4S)-4-hydroxycyclopent-2-en-1-yl acetate via Novozym-435 catalyzed desymmetrization of cis-3,5-Diacetoxy-1-cyclopentene
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Photooxidation of cyclopentadiene has been carried out in methanol using white light of LED lamp, rose bengal as photo initiator, and compressed air at 0 °C. Under conditions of [thiourea] ? [cyclopentadiene], the consumption of thiourea follows a pseudo-first-order reaction kinetics with half life of 75 ± 10 min; corr. coeff. r = 0.989. Slow addition of the monomer and maintaining excess thiourea concentration in reaction mass improves the yield. cis-3,5-Dihydroxy-1-cyclopentene is acetylated without isolation to obtain cis-3,5-Diacetoxy-1-cyclopentene of high purity (>99%) with overall isolated yield of 30%. Desymmetrization of the diacetate to (1R,4S)-4-hydroxycyclopent-2-en-1-yl acetate has been carried out via enzymatic transesterification with methanol in methyl tert-butyl ether (MTBE) at 5 °C using Novozym-435. The enantiomerically pure monoacetate (e.e. >99%) was obtained in 95% isolated yield. The recovered enzyme was reused for more than 10 times without loss in yield and selectivity. The entire protocol does not require purification of final product by chromatography.
- Putta, Shekhar,Reddy, Annem Mallikarjun,Sheelu, Gurrala,Reddy, B.V. Subba,Kumaraguru, Thenkrishnan
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p. 6673 - 6679
(2018/10/15)
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- Synthesis of Guanine α-Carboxy Nucleoside Phosphonate (G-α-CNP), a Direct Inhibitor of Multiple Viral DNA Polymerases
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The synthesis of guanine α-carboxy nucleoside phosphonate (G-α-CNP) is described. Two routes provide access to racemic G-α-CNP 9, one via base construction and the other utilizing Tsuji-Trost allylic substitution. The latter methodology was also applied to the enantiopure synthesis of both antipodes of G-α-CNP, each of which showing interesting antiviral DNA polymerase activity. Additionally, we report an improved multigram scale preparation of the cyclopentene building block 10, starting material for the preferred Tsuji-Trost route to 9.
- Maguire, Nuala M.,Ford, Alan,Balzarini, Jan,Maguire, Anita R.
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p. 10510 - 10517
(2018/09/06)
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- Method of treating tumors
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The invention provides a method of treating tumors by adminstering to a human or animal patient an effective amount of a molecule of 2 to 4 amino acids or equivalent subunits in length, which incorporates a bulky and lipophilic group comprising at least 13 non-hydrogen atoms and containing no more than 2 polar functional groups, in which the bulky and lipophilic group incorporates one or more closed rings of 5 or more non-hydrogen atoms, and in which the molecule further has at least two more cationic than anionic moieties.
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Page/Page column 45; 46
(2015/09/23)
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- Chemoenzymatic routes to cyclopentenols: The role of protecting groups on stereo- and enantioselectivity
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Enantiopure (R)-4-triisopropylsilyloxycyclopent-2-en-1-one was obtained through short sequences including either the enzymatic resolution of racemic cis-4-triisopropylsilyloxycyclopent-2-en-1-ol or the enzymatic desymmetrization of cis-cyclopent-2-en-1,3-diol. Alternatively, the enantiopure (S)-4-triisopropylsilyloxycyclopent-2-en-1-one was very efficiently obtained from diacetate of cis-cyclopent-2-en-1,3-diol using enzymatic desymmetrization with CAL-B. In these sequences, TIPS proved to be the best protecting group.
- Specklin, Simon,Dikova, Anna,Blanc, Aurélien,Weibel, Jean-Marc,Pale, Patrick
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p. 6987 - 6991
(2015/02/02)
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- Reinvestigation of palladium-catalyzed allylation of the monoacetate of 4-cyclopentene-1,3-diol and synthesis of the coronafacic acid ethyl ester
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A larger quantity of a β-keto ester that is 1.5-1.7 equiv more than the base (t-BuOK, NaH) was found to be essential in securing sufficient yields of the products in the palladium-catalyzed allylic substitution of the monoacetate of 4-cyclopentene-1,3-diol with β-keto esters. This requirement also works well for substitutions with the TBS ether of the monoacetate and the monoacetate of 2-cyclohexene-1,4-diol. As an application, the coronafacic acid ethyl ester was synthesized as an optically active form.
- Kinouchi, Wataru,Kosaki, Yusuke,Kobayashi, Yuichi
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p. 7017 - 7020
(2013/12/04)
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- PREPARATION OF LUBIPROSTONE
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Aspects of the present application relate to process for the preparation of lubiprostone.
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Paragraph 0108
(2013/07/25)
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- IMPROVED PROCESSES FOR PREPARING PURE (3AR,4S,6R,6AS)-6-AMINO-2,2-DIMETHYLTETRAHDRO-3AH-CYCLOPENTA[D] [1,3]-DIOXOL-4-OL AND ITS KEY STARTING MATERIAL
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Provided herein is an improved, commercially viable and industrially advantageous process for the preparation of a ticagrelor intermediate, (3aR,4S,6R,6aS)-6-amino-2,2- dimethyltetrahydro-3aH-cyclopenta[d][l,3]-dioxol-4-ol, which is useful for preparing ticagrelor or a pharmaceutically acceptable salt thereof in high yield and purity. The present invention further relates to an improved process for the preparation of (lS,4R)-cis-4-acetoxy- 2-cyclopenten-l-ol, which is a key starting material in the preparation of the ticagrelor intermediate.
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Page/Page column 24-25
(2012/05/31)
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- Ligand-controlled selectivity in the desymmetrization of meso cyclopenten-1,4-diols via rhodium(I)-Catalyzed addition of arylboronic acids
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A highly enantioselective desymmetrization of meso cyclopent-2-ene-1,4- diethyl dicarbonates has been developed using a Rh-catalyzed asymmetric allylic substitution. Depending on the type of ligand used, each of two regioisomeric products can be obtained in good yield and excellent enantioselectivity. Under rhodium(I) catalysis, bisphosphine P-Phos ligands form trans-1,2- arylcyclopentenols as the major product, whereas Segphos ligands lead predominantly to trans-1,4-arylcyclopentenols.
- Menard, Frederic,Perez, David,Sustac Roman, Daniela,Chapman, Timothy M.,Lautens, Mark
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supporting information; experimental part
p. 4056 - 4068
(2010/08/07)
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- Unusual regioselectivity in Pd(0)-catalyzed coupling of allylic monoacetates and nitroalkanes: one-pot isomerization-alkylation
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A hitherto unknown palladium-catalyzed reaction of nitroalkanes with hydroxy allylic acetates is reported. The reaction led to the formation of γ-nitrocarbonyl compounds instead of the usual unsaturated nitroalcohol expected upon displacement of the allylic acetate group.
- Khan, Pasha M.,Bisht, Kirpal S.
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supporting information; experimental part
p. 1407 - 1410
(2010/04/25)
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- Studies toward the total synthesis of carba analogue of motif C of M. TB cell wall AG complex
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Herein we describe the synthesis of the carba analogue of motif C of arabinogalactan complex present in M. tuberculosis cell wall. Pd(0) catalyzed allylic alkylation and Fraser-Reid's glycosidation are the two key reactions that were employed for the synthesis of central glycosyl accepter unit and the glycosylation respectively.
- Gurjar, Mukund K.,Reddy, Challa Nageswar,Kalkote, Uttam R.,Chorghade, Mukund S.
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scheme or table
p. 909 - 925
(2010/10/20)
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- Silica- and polymer-supported platinum(II) polypyridyl complexes: Synthesis and application in photosensitized oxidation of alkenes
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Square-planar polypyridine platinum(II) complexes have been introduced into a silica/polymer matrix by covalent ligand modification. The photophysical properties of the supported matrices are well retained as their model complexes, and the quantum yields for singlet oxygen (1O2) generation are comparable with that of TPP (tetraphenylporphyrin) under similar conditions. A preliminary application in photosensitized oxidation indicates the silica/polymer-supported matrices are promising, which can be reused without loss of reactivity by a simple filtration. Moreover, the polymer-supported matrix exhibits excellent compatibility in various solvents. The Royal Society of Chemistry 2009.
- Feng, Ke,Peng, Ming-Li,Wang, Deng-Hui,Zhang, Li-Ping,Tung, Chen-Ho,Wu, Li-Zhu
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scheme or table
p. 9794 - 9799
(2010/03/04)
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- Triphenylphosphine reduction of saturated endoperoxides
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(Figure Presented) Triphenylphosphine reduction of saturated endoperoxides derived from 6,6-dimethylfulvene and spiro[2.4]hepta-4,6-diene in the presence of nucleophiles results in the formation of products that mainly stem from deoxygenation followed by carbocation formation. Nucleophilic attack by solvent proceeds by an SN1 like mechanism; allyl shifts and cyclopropylcarbinyl-cyclobutyl rearrangements also occur. With the systems lacking carbocation-stabilizing groups, the deoxygenation step is preceded by attack of H2O at the phosphorus.
- Erden, Ihsan,Gaertner, Christian,Saeed Azimi
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supporting information; experimental part
p. 3986 - 3989
(2009/12/05)
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- Synthesis of enantiomerically pure cyclopentene building blocks
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An efficient synthesis of the enantiomerically pure cis-annulated cyclopentenes 2 and ent-2 was established by the use of an enzymatic transesterification and hydrolysis, respectively, followed by an S N2-type substitution with a benzyloxymethyl cuprate and a sigmatropic rearrangement. The advantage of this approach is the short sequence combined with an excellent overall yield and an enantiomeric excess of 99%. Georg Thieme Verlag Stuttgart.
- Tietze, Lutz F.,Stadler, Christian,B?hnke, Niels,Brasche, Gordon,Grube, Alexander
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p. 485 - 487
(2007/12/27)
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- IRA-200 resin-supported platinum(II) complex for photooxidation of olefins
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Cyclometalated platinum(II) 4,6-diphenyl-2,2′-bipyridine complex is supported on a commercially available cationic ion-exchange resin (amberlite IRA-200). Photophysical and ESR determinations indicate that the combined photosensitized system is able to generate singlet oxygen with high quantum yield upon irradiation of light in the visible region. The platinum(II) complex loaded on IRA-200 resin is stable and the photooxidation occurs in an environmentally friendly way. Only a simple filtration is needed to recycle the expensive metal catalyst.
- Feng, Ke,Wu, Li-Zhu,Zhang, Li-Ping,Tung, Chen-Ho
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p. 4907 - 4911
(2008/02/01)
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- Photooxidation of olefins under oxygen in platinum(II) complex-loaded mesoporous molecular sieves
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Cyclometalated platinum(II) complex has been successfully incorporated into the (3-aminopropyl) triethoxysilane-modified channels of ordered mesoporous silica SBA-15 that has large pore hexagonal channels. Studies on the 1O2 generation conclusively demonstrates that the olefins in the nano-channels of SBA-15 can be enriched 8 times higher than those in the homogeneous solution as the diffusion quantum yield of singlet oxygen ( 1O2) is assumed to be unit. The platinum(II) complex loaded in the channel of SBA-15 is stable, and the photosensitized oxidation occurs efficiently. No obvious degradation and leaching of photosensitizers is observed even after 10 runs. Only a simple filtration is needed for the recycled use of the expensive noble metal catalysts. This versatile system is a good example of photochemical reactions occurring in the mesoporous silica molecular sieve. SBA-15 not only provides a support for the photosensitizer, but also acts as a nano-reactor to facilitate the photooxidation.
- Feng, Ke,Zhang, Ren-Yuan,Wu, Li-Zhu,Tu, Bo,Peng, Ming-Li,Zhang, Li-Ping,Zhao, Dongyuan,Tung, Chen-Ho
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p. 14685 - 14690
(2008/02/03)
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- A modular molecular tweezer designed using CAVEAT
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A pair of water-soluble molecular tweezers designed using the computer program CAVEAT were prepared and their binding to an N-ethylquinolinium cation was demonstrated by 1H NMR spectroscopy. The Royal Society of Chemistry 2006.
- Huang, Haidong,Drueckhammer, Dale G.
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p. 2995 - 2997
(2008/09/19)
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- Versatile photosensitization system for 1O2-mediated oxidation of alkenes based on nafion-supported platinum(II) terpyridyl acetylide complex
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(Matrix presented) Platinum(II) terpyridyl acetylide complex (1) was incorporated into Nafion membranes as a photosensitizer, and the Nafion was immersed in an aqueous or organic solution of 7-dehydrocholesterol, α-pinene, or cyclopentadiene. This photosensitizer system can generate singlet oxygen (1O2) in high quantum yield to oxidize the alkenes in the solution outside the Nafion and can be easily removed from the reaction vessel at the end of the photooxidation.
- Zhang, Dong,Wu, Li-Zhu,Yang, Qing-Zheng,Li, Xiao-Hong,Zhang, Li-Ping,Tung, Chen-Ho
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p. 3221 - 3224
(2007/10/03)
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- Chiral induction in cyclopentyl-derived 1,3-meso-diesters: enantioselective hydrolyses with electric eel acetylcholinesterase
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Eight 1,3-meso-diesters derived from a common cyclopentyl backbone were exposed to the hydrolase enzyme acetylcholinesterase from Electrophorus electricus. All eight compounds were hydrolyzed by the enzyme. The overall enantioselectivities were quite high, and the resulting e.e.s were generally >90%. The absolute configurations of the product monoesters were determined through stereochemical correlation. These data revealed that the preferred site for enzymatic hydrolysis in seven of the substrates was the pro-S ester function, with pro-R cleavage detected in the eighth.
- Deardorff, Donald R.,Amador, Roberto B.,Morton, James W.,Kim, Henry Y.,Taniguchi, Cullen M.,Balbuena, Arnel A.,Warren, Sam A.,Fanous, Vadim,Choe, S. W. Tina
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p. 2139 - 2152
(2007/10/03)
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- The preparation of optically active 2-cyclopenten-1,4-diol derivatives from furfuryl alcohol
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The preparation and enzymatic resolution of several cis-mono-4-O-protected-2-cyclopenten-1,4-diols are described. The process starts with inexpensive furfuryl alcohol and lends itself to the preparation of multigram quantities of various protected, optically active 2-cyclopenten-1,4-diol derivatives. Stereoselective reduction of 4-O-protected-2-cyclopentenone to the cis-mono-O-protected-2-cyclopenten-1,4-diol using LiAlH4/LiI or Red-Al/NaI is described. Subsequent pancreatin-promoted, stereoselective acylation was conducted on these cis-(+/-)-mono-O-protected-cyclopenten-1,4-diols to afford the corresponding alcohols and acetates in moderate to excellent enantioselectivities.
- Curran, Timothy T.,Hay, David A.,Koegel, Christopher P.,Evans, Jonathan C.
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p. 1983 - 2004
(2007/10/03)
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- Tandem ring opening-ring closing metathesis of cyclic olefins
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Ruthenium alkylidene 1 has been utilized in the tandem ring opening-ring closing metathesis of cyclic olefins. This reaction produces a bicyclic molecule from a cyclic olefin. Reactivity is dependent upon strain, and thus ring size, in the substrate molecules. Competing oligomerization is observed in substrates having low ring strain; this process is inhibited by increasing dilution of the reaction or by adding alkyl substitution to the acyclic olefins.
- Zuercher, William J.,Hashimoto, Masakazu,Grubbs, Robert H.
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p. 6634 - 6640
(2007/10/03)
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- A regioselective synthesis of 4-methyl-1-pyrindan-5-one
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The enamine 7 reacts with crotonic aldehyde in the presence of p-toluenesulphonic acid via the intermediate 8 to yield regioselectively the unknown title compound 9. In alkaline medium, 9 is also formed from 7 and acetylacetaldehyde dimethyl acetal as well as small amounts of 11 and 12; under acidic conditions, however, mixtures of the regioisomers 9/9a are obtained in poor yield. 9a can be separated by fractional crystallisation of the hydrochlorides. Corresponding to 7 the homologous enamine 13 and acetylacetaldehyde acetal by alkaline catalysis gives the 4-methyltetrahydroquinolinone 1, respectively. Improved experimental details for an efficient preparation of the starting compounds 3 and 4 are given.
- Reimann,Poschl
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p. 589 - 592
(2007/10/02)
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- 4-Hydroxycyclopent-2-en-1-one and derivatives as chiral synthetic equivalents of cyclopentadienone in asymmetric Diels-Alder reactions
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Endo-tricyclodecadienone 8a and related annelated-cyclopentenones (8b, 20, 21a-c and 22) are synthesized in good chemical yield by a Diels-Alder reaction of 4-hydroxycyclo-pent-2-en-1-one 12a and derivatives 12b-h with an appropriate diene. These additions are considerably accelerated by Lewis catalysts, high pressure and by using water as solvent. Due to opposing steric and electronic effects the diastereofacial selectivity of the asymmetric cycloadditions is moderate. By carefully choosing the substrate and reaction conditions an acceptable π-facial selectivity can be achieved.
- Dols,Klunder,Zwanenburg
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p. 8515 - 8538
(2007/10/02)
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- Chemoenzymatic Synthesis of 4-Substituted Riboses. S-(4'-Methyladenosyl)-L-homocysteine
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The synthesis of 4-C-methyl-D-ribose, 4-C-phenyl-D-ribose, D-ribose-4-d, and L-ribose derivatives as well as the title nucleoside by a chemoenzymatic strategy beginning from cyclopentadiene is described.
- Johnson, Carl R.,Esker, John L.,Zandt, Michael C. Van
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p. 5854 - 5855
(2007/10/02)
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- Facile synthesis of (+)-Brefeldin A
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(+)-Brefeldin A (1) was synthesized by using (+)-4-cyanomethylcyclopent-2-en-1-one (2) as a key compound. 4-Hydroxy-2-enoate functionality was built by the reaction of the aldehyde (7) with (S)-ethyl p-chlorophenylsulfinylacetate.
- Nokami,Ohkura,Dan-Oh,Sakamoto
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p. 2409 - 1412
(2007/10/02)
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- Vitamin B12, a Catalyst in the Synthesis of Prostaglandins
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A prostaglandin F2α precursor containing all structural features from C6 to C20 with 8R,9S, 11R and 12R chirality is obtained by the one step formation of two C-C bonds in the B12-catalyzed radical cyclization-addition sequence starting from a chiral cyclopentene bromoacetal and 1-octyne-3-one.The B12-catalyzed radical cyclization-elimination sequence of a chiral cyclopentene precursor leads to (-)-(3aR,6aS)-3,3a,6,6a-tetrahydro-2H-cyclopentafuran-2-one.Its (+)-(3aS,6aR)-enantiomer is obtained via B12-catalyzed, enantioselective isomerization of cyclopentene oxide to (R)-2-cyclopentene-1-ol followed by the B12-catalyzed cyclization-elimination sequence of its bromoacetal.
- Busato, Stephan,Tinembart, Olivier,Zhang, Zhong-da,Scheffold, Rolf
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p. 3155 - 3166
(2007/10/02)
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- Ruthenium(II)-Catalyzed Reactions of 1,4-Epiperoxides
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The behavior of 1,4-epiperoxides in the presence of transition-metal complexes is highly dependent on the structures of the substrates and the nature of the metal catalysts.Reaction of saturated epiperoxides such as 1,3-epiperoxycyclopentane, 1,4-epiperoxycyclohexane, or dihydroascaridole catalyzed by RuCl2(PPh3)3 in dichloromethane gives a mixture of products arising from fragmentation, rearrangement, reduction, disproportionation, etc.Prostaglandin H2 methyl ester undergoes clean and stereospecific fragmentation to afford methyl(5Z,8E,10E,12S)-12-hydroxy-5,8,10-heptadecatrienoate and malonaldehyde.Bicyclic 2,3-didehydro 1,4-epiperoxides give the syn-1,2:3,4-diepoxides by the same catalyst.The monocyclic analogues are transformed to a mixture of diepoxides and furan products.The stereochemical outcome of the epoxide formation reflects unique differences in the ground-state geometry of the starting epiperoxide substrates.FeCl2(PPh3)2 serves as a useful catalyst for the skeletal change of sterically hindered bicyclic 2,3-didehydro 1,4-epiperoxides to the syn-diepoxides.In addition, the Fe complex best effects the conversion of 1,4-unsubstituted 2,3-didehydro epiperoxides to furans.The Ru-catalyzed reactions are interpreted in terms of the intermediacy of inner-sphere radicals formed by atom transfer of the Ru(II) species to peroxy substrates, in contrast to the Fe-catalyzed reactions proceeding via free, outer-sphere radicals generated by an electron-transfer mechanism.
- Suzuki, Masaaki,Ohtake, Hiroaki,Kameya, Yoshimi,Hamanaka, Nobuyuki,Noyori, Ryoji
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p. 5292 - 5302
(2007/10/02)
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- Vinyl Epoxide Hydrolysis Reactions
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The rates of hydrolysis of cyclopentadiene oxide (3), cyclohexadiene oxide (4), cycloheptadiene oxide (5), cyclooctadiene oxide (6), butadiene oxide (7), and styrene oxide (8) have been determined as a function of pH.Each epoxide exhibited acid-catalyzed hydrolysis at low pH, and 3-5 showed significant rates for "spontaneous" reaction with solvent at intermediate pH values.The hydrolyses of several of the vinyl epoxides (4 and 5) showed kinetic terms in HO- at pH > ca. 13.Specific chloride effects attributed to nucleophilic addition of Cl- to neutral epoxide were observed for those compounds (3, 4, and 8) hydrolyzed in KCl solutions.From kinetic and product studies, mechanisms for hydrolyses of the vinyl epoxides are postulated.Acid-catalyzed hydrolyses of 3, 4, 5, and 6 were found to be A-1 in nature, proceeding via intermediate allyl cations.Product distributions depended on the structure of the cation.Mechanisms and product distributions for the spontaneous hydrolyses of vinyl epoxides were found to be variable, and dependent on the structure of the epoxide.
- Ross, Angela M.,Pohl, Terese M.,Piazza, Kathryn,Thomas, Michael,Fox, Bonnie,Whalen, Dale L.
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p. 1658 - 1665
(2007/10/02)
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- PALLADIUM(O) CATALYZED REACTION OF 1,3-DIENE 1,4-EPIPEROXIDES
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Reaction of 1,3-diene 1,4-epiperoxides with Pd(PPh3)4 catalyst forms the corresponding 4-hydroxy enones, syn diepoxides, and 1,4-diols as the major products.The results are interpreted as being due to competing Pd(O)/ Pd(II) and Pd(O)/ Pd(I) exchange mechanisms.
- Suzuki, M.,Oda, Y.,Noyori, R.
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p. 4413 - 4416
(2007/10/02)
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- STEREOCHEMICAL STUDIES - LVII. SYNTHESIS OF OPTICALLY ACTIVE COMPOUNDS BY THE NOVEL USE OF MESO-COMPOUNDS -1. EFFICIENT SYNTHESIS OF TWO STRUCTURAL TYPES OF OPTICALLY PURE PROSTAGLANDIN INTERMEDIATES.
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With an aim to overcome several inefficient aspects of ordinary methods of preparing optically active compounds, we have developed a new method which recommends utilization of symmetrically functionalized meso-compounds in place of racemic compounds.As shown in Scheme 1, when the meso-compound (I) is monofunctionalized by an optically active functional group (A) and each of the formed diastereomers (II and III) is subjected to further chemical elaborations including protective group transposition, it is theoretically possible to convert the total amount of the starting material (I) into the requisite optically pure product (VI or VII) by selecting synthetic schemes.By employing this novel concept, two structural types of the prostaglandin intermediates ((-)- and (+)-2a,b) have been prepared from the meso-diols (1a,b) by way of the two diastereomeric monoesters (13a,b and 14a,b) which are produced by the reactions 1a,b with N-mesyl- and N-phthaloyl-(S)-phenylalanyl chloride (3a,b).
- Nara, M,Terashima, S.,Yamada, S.
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p. 3161 - 3170
(2007/10/02)
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