Special Issue

Albert Eschenmoser's Special Issues, Vol. 82, No. 2, 2011

66 data found. 31 - 60 listedFirst Previous Next Last
Paper | Special issue | Vol 82, No. 2, 2011, pp. 1327 - 1336
Published online: 1st December, 2010
DOI: 10.3987/COM-10-S(E)79
Efficient Phenolic Oxidations to Construct ortho-Spirolactone Structures Using Oxo-Bridged Hypervalent Iodine(III) Compound

Naoko Takenaga, Teruyoshi Uchiyama, Daishi Kato, Hiromichi Fujioka, Toshifumi Dohi, and Yasuyuki Kita*

*College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan

Abstract

The intramoleular ortho-spirocyclization of naphthols 1 bearing carboxylic acid moieties as internal nucleophiles using hypervalent iodine reagents is described. The use of the μ-oxo-bridged hypervalent iodine(III) compound is remarkably effective for this transformation, and spirolactones 2 were obtained in good to excellent yields using the μ-oxo-bis[trifluoroacetato- (phenyl)iodine] 4 [PhI(OCOCF3)O(OCOCF3)IPh].The intramoleular ortho-spirocyclization of naphthols 1 bearing carboxylic acid moieties as internal nucleophiles using hypervalent iodine reagents is described. The use of the μ-oxo-bridged hypervalent iodine(III) compound is remarkably effective for this transformation, and spirolactones 2 were obtained in good to excellent yields using the μ-oxo-bis[trifluoroacetato- (phenyl)iodine] 4 [PhI(OCOCF3)O(OCOCF3)IPh].

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1337 - 1343
Published online: 2nd August, 2010
DOI: 10.3987/COM-10-S(E)82
A Molecular Orbital Calculation Study on the Interesting Reactivity of Fluorine-Containing 3,4-Dihydro-2H-pyrans with Aromatic Compounds in the Presence of Trifluoroacetic Acid

Norio Ota, Yasuhiro Kamitori,* Eisuke Nishiguchi, Makoto Ishii, and Etsuji Okada*

*Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan

Abstract

The reaction of 6-trifluoromethyl-3,4-dihydro-2H-pyrans (1) with aromatic compounds in trifluoroacetic acid gave 4-arylated dihydropyrans (3) selectively, whereas that of 5-trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2H-pyrans (2) with aromatic compounds in refluxing trifluoroacetic acid afforded the ring-opening products (4) via exclusive attack of aromatic compounds at the 2-position of 2. These two interesting reactions affording the quite different products from the similar substrates were elucidated on the basis of DFT calculations.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1345 - 1357
Published online: 13th August, 2010
DOI: 10.3987/COM-10-S(E)85
Design and Synthesis of Telomestatin Derivatives Containing Methyl Oxazole and Their G-Quadruplex Stabilizing Activities

Satoki Majima, Masayuki Tera, Keisuke Iida, Kazuo Shin-ya, and Kazuo Nagasawa*

*Division of Biotechnology and Life Science, Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei, Tokyo 184-8588, Japan

Abstract

Telomestatin derivatives of L2A2-6M(2)OTD (3b) and L2A2-6M(4)OTD (3c), which have a macrocyclic hexaoxazole skeleton (6OTD) containing bis- and tetra-methyl oxazoles, were synthesized as a novel G-quadruplex ligand. This new class of “methyl oxazole containing” ligands was revealed to stabilize various G-quadruplex forming oligonucleotides more potently than “no methyl oxazole containing” L2A2-6OTD (3a).

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1359 - 1369
Published online: 24th August, 2010
DOI: 10.3987/COM-10-S(E)86
Structural Reevaluations of Amphidinol 3, a Potent Antifungal Compound from Dinoflagellate

Respati T. Swasono, Mitsunori Kanemoto, Nobuaki Matsumori, Tohru Oishi, and Michio Murata*

*Department of Chemistry , Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan

Abstract

Among other homologues, amphidinol 3 (AM3) is the most potent antifungal compound isolated from the dinoflagellate Amphidinium klebsii. AM3 undergoes conformational changes in organic solvents while it takes relatively fixed configuration in a membrane model. By using NMR data of peracetyl AM3, we were able to confirm the configuration of C50-C51 of AM3 which remained uncertain in our previous study.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1371 - 1377
Published online: 16th August, 2010
DOI: 10.3987/COM-10-S(E)90
Reversible Dehydrogenation-Hydrogenation of Tetrahydroquinoline-Quinoline Using a Supported Cooper Nanoparticle Catalyst

Yusuke Mikami, Kaori Ebata, Takato Mitsudome, Tomoo Mizugaki, Koichiro Jitsukawa, and Kiyotomi Kaneda*

*Research Center for Solar Energy Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan

Abstract

Copper nanoparticles synthesized on a titania surface (Cu/TiO2) act as an efficient heterogeneous catalyst for the reversible dehydrogenation and hydrogenation of tetrahydroquinoline-quinoline under an atmospheric pressure of H2.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1379 - 1409
Published online: 13th August, 2010
DOI: 10.3987/COM-10-S(E)93
A Cyclic Acetal Tethered Intramolecular Diels-Alder Cycloaddition. Studies Directed toward a Total Synthesis of (±)-Fusidilactone C

Sunil K. Ghosh, Yonggang Wei, Aleksey I. Gerasyuto, John B. Feltenberger, Jiashi Wang,* and Richard P. Hsung*

*Department of Chemistry, Division of Pharmaceutical Sciences, University of Wisconsin, 777 Highland Aenue, Madison, WI 53705-2222, U.S.A.

Abstract

Efforts toward a synthesis of (±)-fusidilactone C is described here featuring a novel cyclic acetal tethered intramolecular Diels-Alder strategy. This unique and facile IMDA turned out to be highly endo-selective [endo-I and endo-II], as assessed from our mechanistic analyses. When using protic solvents or Lewis acids, the endo-I selectivity was greatly enhanced. Thus, it proved to be a real challenge to circumvent this excellent stereochemical outcome, which is undesired for the total synthesis, as an exo-II selectivity is desired. Progress was made to use the endo-II cycloadduct and to access the desired trans-2-oxadecalin motif in (±)-fusidilactone C.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1411 - 1421
Published online: 14th January, 2011
DOI: 10.3987/COM-10-S(E)94
Enantioselective Synthesis of α-Methylene-γ-butyrolactams Using N-tert-Butanesulfinamides

Haythem K. Dema, Francisco Foubelo,* and Miguel Yus*

*Department of Organic Chemistry, Faculty of Sciences and Institute of Organic Synthesis (ISO), University of Alicante, P.O. Box 99, 03080 Alicante, Spain

Abstract

Indium-mediated coupling of ethyl 2-(bromomethyl)acrylate (1) and chiral N-tert-butanelsulfinylimines 2 in a saturated sodium bromide aqueous solution leads to N-tert-butanesulfinyl aminoesters 3 in high yields and diastereoselectivities. After column chromatography purification, enantiomerically pure aminoesters 3 were converted into the expected α-methylene-γ-butyrolactams 4 in a one-pot process.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1423 - 1433
Published online: 8th September, 2010
DOI: 10.3987/COM-10-S(E)95
Preparation of β-Amino Esters and β-Lactams from Nitriles via Aldimine-Borane Complexes

P. Veeraraghavan Ramachandran,* Debanjan Biswas, and Guang-Ming Chen

*Herbert C. Brown Center for Borane Research, Department of Chemistry, Purdue University, 560 Oval Dr.; BRWN 5131
West Lafayette, IN 47907-2084, U.S.A.

Abstract

one-pot synthesis of β-amino esters has been achieved in 59-75% yield from aromatic and aliphatic nitriles via the condensation of the corresponding non-enolizable and enolizable aldimine-triethylborane complexes, respectively with methyl trimethylsilyl ketene acetals. Grignard-mediated lactamization of the intermediate β-amino esters provides the corresponding β-lactams in the same pot in 58-74% overall yield.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1435 - 1445
Published online: 15th September, 2010
DOI: 10.3987/COM-10-S(E)97
Transformations of Dimethyl (2E,3E)-2-[(Dimethylamino)methylene]-3-(1-methyl-2,5-dioxoimidazolidin-4-ylidene)succinate with C-Nucleophiles

Uroš Uršič, Jurij Svete, and Branko Stanovnik*

*Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, 1000 Ljubljana, Slovenia

Abstract

(2E,3E)-2-[(Dimethylamino)methylene]-3-(1-methyl-2,5-dioxoimidazolidin-4-ylidene)succinate (1) was transformed with 1,3-dicarbonyl compounds 2a,b via substituted dimethyl (2H-imidazol-4-yl)-2-butenedioates 3a,b and dimethyl (2,5-dioxo-4-imidazolidinylidene)succinates 4a,b into 2H-pyrano[2,3-d]pyrimidines 5a,b. Compound 1 was cyclized by heating sin glacial acetic acid into dimethyl 1H-pyrrolo[1,2-c]imidazole-6,7-dicarboxylate (8).

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1447 - 1476
Published online: 8th September, 2010
DOI: 10.3987/COM-10-S(E)98
Synthesis of Macrobi- and Macrotricyclic Compounds Comprising Pyrimidyl Substituted Cyclen and Cyclam

Sergei M. Kobelev, Alexei D. Averin, Alexei K. Buryak, Franck Denat, Roger Guilard,* and Irina P. Beletskaya*

*Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia

Abstract

The synthesis of novel N1,N7-bis(bromobenzyl) cyclens and N1,N8-bis(bromobenzyl) cyclams is described. Arylation of these compounds with excess 4,6-dichloropyrimidine and 2-chloropyrimidine gave corresponding tetrasubstituted cyclen and cyclam in good yields. Bis(bromobenzyl)bis(pyrimidyl) substituted cyclens and cyclams were used in the Pd-catalyzed reactions with polyamines to give macrobi- and macrotricycles. The yields of macropolycyclic compounds were shown to be dependent on the nature of starting tetraazamacrocycles and polyamines. In the case of cyclam monopyrimidyl derivatives were also obtained and macropolycyclic compounds were synthesized on their base.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1477 - 1488
Published online: 14th September, 2010
DOI: 10.3987/COM-10-S(E)99
Step-Growth Control in Template-Directed Polymerization

Xiaoyu Li, Andres F. Hernandez, Martha A. Grover, Nicholas V. Hud, and David G. Lynn*

*Department of Chemistry and Biology, Emory University, Emerson Hall, Atlanta, GA 30322, U.S.A.

Abstract

A self-organizing process is described that combines DNA template association thermodynamics and kinetic reductive amination to translate polymer sequence information into amine nucleoside polymers. The developed kinetic model analyses allowed this process to be extended to the translation of templates as long as catalytic ribozymes.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1489 - 1501
Published online: 30th September, 2010
DOI: 10.3987/COM-10-S(E)100
Synthesis of New Biheterocycles by a One-Pot Sonogashira Coupling Reaction

Mandar Deodhar, David StC Black,* and Naresh Kumar*

*School of Chemistry, The University of New South Wales, Sydney 2052, Australia

Abstract

Halogenated flavones, isoflavones and indoles were subjected to a one-pot Sonogashira coupling reaction to generate a series of new biheterocyclic compounds. The methodology can be readily adapted to the synthesis of a wide variety of substituted biheterocycles.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1503 - 1514
Published online: 5th October, 2010
DOI: 10.3987/COM-10-S(E)104
Unusual Oxidation in the Course of Synthesis of N-Confused Nickel Tetrahydrobilins

Jan-Erik Damke, Torben König, Gerold Haake, Lechosław Latos-Grażyński, and Franz-Peter Montforts*

*Institut für Organische Chemie des FB 2, Universität Bremen, Leobener Strasse,NW 2-C, D-28359 Bremen, Germany

Abstract

N-confused Tetrahydrobilins rac-16 and rac-17 were prepared to investigate their cyclization directed to the formation of N-confused chlorins. For achieving the desired cyclization the 5´-position of rac-16 respectively rac-17 was activated by an electron withdrawing cyano function and their 2´-positions were blocked by a methyl group. In addition, the insertion of Ni(II) was accomplished for exercising a template effect during the cyclization process, but the formed nickel complexes rac-18 and rac-19 underwent oxidation to yield oxo-tetrahydrobilins rac-20 and rac-21.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1515 - 1525
Published online: 2nd November, 2010
DOI: 10.3987/COM-10-S(E)106
α,α-Dichloroisoxazolidinones for the Synthesis and Chemoselective Peptide Ligation of α-Peptide α-Ketoacids

Tetsuo Narumi and Jeffrey W. Bode*

*Laboratory of Organic Chemistry, ETH Zürich, Wolfgang-Pauli-Strasse 10,
CH-8093 Zuerich, Switzerland

Abstract

In seeking to develop an iterative approach to the preparation of α-oligopeptides by the chemoselective amide-forming coupling of α-ketoacids and hydroxylamines, we have designed and synthesized novel enantiopure monomers. Key to our approach is the use of α,α-dichloroacids as masked α-ketoacids. The preparation of these monomers, their coupling with α-ketoacids, and the conversion of the α,α-dichloroacids to α-ketoacids is described. These studies provide a first step to a conceptually unique approach to peptide synthesis that does not require activating reagents or produce chemical byproducts.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1527 - 1540
Published online: 5th October, 2010
DOI: 10.3987/COM-10-S(E)108
Deconstructing Quinine. Part 1. Toward an Understanding of the Remarkable Performance of Cinchona Alkaloids in Asymmetric Phase Transfer Catalysis

Scott E. Denmark* and Robert C. Weintraub

*245 Roger Adams Laboratory Box 18-5 , Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, U.S.A.

Abstract

A study of catalyst structure-activity/selectivity relationships for Cinchona alkaloid-based asymmetric phase transfer catalysis (APTC) is described. An array of substituent modifications at C(9) and the quinuclidine nitrogen were introduced to examine the role of steric and electronic effects on rate and selectivity. The synthesis of the catalysts began with manipulation of the C(9) hydroxyl group followed by alkylation of the quinuclidine nitrogen to generate the quaternary ammonium salt. Catalysts that contained large substituents attached to the quinuclidinium nitrogen were found to be the most selective and those in which the hydroxyl group was protected generally afforded faster catalysts. The presence of a polar group at C(9) significantly impacted catalyst activity.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1541 - 1548
Published online: 6th September, 2010
DOI: 10.3987/COM-10-S(E)109
Convenient Synthesis of the Key Intermediate for Dihydrocorynantheol and Protoemetinol from the Monoacetate of 4-Cyclopentene-1,3-diol

Yuichi Kobayashi,* Kaori Yagi, and Yuki Kaneko

*Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan

Abstract

We invented an efficient method to obtain the key δ-lactone possessing the (CH2)2OTBDPS and Et groups at C3 and C4, respectively, starting with the acetate of 4-cyclopentene-1,3-diol, which was subjected to Pd-catalyzed allylation with malonate anion to attach the (CH2)2OTBDPS group. The Et group was then installed by 1,4-addition to the derived enone. Finally, the resulting enol TMS ether was oxidized to afford the lactone. Furthermore, the lactone was converted to dihydrocorynantheol and protoemetinol, both of which are typical examples of indoloquinolizidine and benzo[a]quinolizine alkaloids.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1549 - 1566
Published online: 13th October, 2010
DOI: 10.3987/COM-10-S(E)112
Non Covalent Inclusion of Nucleosides and Nucleotides in Water-Soluble Molecular Clips

Frank Bastkowski, Jolanta Polkowska, Thomas Schrader,* and Frank-Gerrit Klärner*

*Institute of Organic Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141 Essen, Germany

Abstract

The dimethylene-bridged molecular clips having naphthalene sidewalls and bearing either lithium phosphate or lithium methanephosphonate groups in the central benzene-spacer-unit bind various nucleosides and nucleotides in buffered aqueous solution at pH = 7.2. The binding constants (Ka) and the complexation-induced 1H NMR shifts of the guest signals (Δδmax) were determined by NMR titration experiments. The host-guest complexes of the phosphate-substituted clip with caffeine and theophylline (Ka = 31400 or 16800 M-1) are more stable than those with cytidine and uridine (Ka = 5240 or 5390 M-1) and with adenosine and guanosine (Ka = 1470 or 1120 M-1). In the case of the phosphonate-substituted clip 2 the selectivity in the complex formation toward one type of nucleoside is, however, less pronounced. The complexes of the nucleotides such as AMP, GMP, CMP, or UMP with both clips are less stable than the corresponding complexes of the nucleosides. To understand the observed selectivities in the complex formation we discuss attractive and repulsive electrostatic interactions on the basis of electrostatic potential surfaces (EPS) calculated for host and guest molecules by quantum chemical methods and hydrophobic effects which contribute to the complex stability to a large extent. The observed large complexation-induced 1H NMR shifts (Δδmax) of the guest signals provide good evidence that in each complex the nucleobase is encapsulated inside the clip cavity.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1567 - 1576
Published online: 16th November, 2010
DOI: 10.3987/COM-10-S(E)113
Differentiated Cyclization of the Ketoacid Derived from Tokinolide B.

Alejandra León, Rubén A. Toscano, J. Antonio Cogordán, and Guillermo Delgado*

*Institute of Chemistry, National Autonomous University of Mexico, University City, Coyoacan 04510, Mexico

Abstract

Treatment of the ketoacid derivative (5) of the bioactive natural dimeric phthalide tokinolide B under weakly basic conditions and pressure, produced the novel ketal compound 6 via addition of the carboxylate of 5 to the ketone, followed by Michael addition of the alcoholate (O-alkylation) and equilibration. On the other hand, treatment of 5 with strong base (NaOH, THF, MeOH) promoted C-alkylation, affording cyclotokinolide B (7). Relative theoretical energies indicated that derivatives 6 and 7 are energetically more stable than the starting material 5. The cytotoxicities of the natural product 3 and its analogues 57 against selected human cancer cells are reported.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1577 - 1584
Published online: 15th September, 2010
DOI: 10.3987/COM-10-S(E)114
De Novo Asymmetric Approach to the Disaccharide Portion of SCH-47554

Xiaomei Yu, Miaosheng Li,* and George A. O'Doherty*

*Department of Chemistry, West Virginia University, Morgantown, WV 26506-6045, U.S.A.

Abstract

A method for the asymmetric synthesis of the disaccharide portion of SCH-47554 has been developed in 6 steps. The route is shorter than the reported route to a related disaccharide. The route involves the use of the Noyori reduction to establish the asymmetry of the D- and L-sugar portion of the molecule. Diastereoselective Pd-glycosylation reaction and subsequent post-glycosylation transformation are used to establish the remaining stereocenter.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1585 - 1600
Published online: 28th October, 2010
DOI: 10.3987/COM-10-S(E)117
A Convenient Entry to New C-7-Modified Colchicinoids through Azide Alkyne [3+2] Cycloaddition: Application of Ring-Contractive Rearrangements

Norman Nicolaus, Jens Reball, Nikolay Sitnikov, Janna Velder, Andreas Termath, Alexey Yu. Fedorov, and Hans-Günther Schmalz*

*Department für Chemie, Universität zu Köln, Greinstrasse 4, D-50939 Köln 41, Germany

Abstract

Reliable procedures for the preparation of azides derived from colchicine (1), allocolchicine (3) and N-acetylcolchinol (4a) were developed. These azides were then employed in Cu-catalyzed Huisgen-Sharpless [3+2]-cycloaddition (“click”) reactions with alkynes under microwave irradiation. The method developed opens a convenient and efficient access to libraries of new C-7-modified colchicinoids (triazole derivatives). In addition, a plausible mechanistic rationale for the colchicine-allocolchicine rearrangement is suggested.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1601 - 1615
Published online: 11th November, 2010
DOI: 10.3987/COM-10-S(E)124
Design and Synthesis of Photocleavable Biotinylated-Dopamine with Polyethyleneoxy Photocleavable Linkers

Kengo Hanaya, Yoshiyuki Kageyama, Masanori Kitamura, and Shin Aoki*

*Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan

Abstract

Previously, we reported the synthesis of a biotin–dopamine conjugate (Btn–DA) with a photocleavable 8-quinolinyl benzenesulfonate (QB) linker for the isolation of an intact complex of DA and anti-DA antibody (IgG1) (DA–IgG1 complex). In this work, we synthesized a photocleavable Btn–DA conjugate with a polyethyleneoxy linker to improve the complexation efficiency and the recovery yields of DA–IgG1 complex. The results of QCM, ELISA, and Western blot analyses indicate that the introduction of polyethyleneoxy linkers improved the efficiency of DA–IgG1 complexation.

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1617 - 1631
Published online: 18th November, 2010
DOI: 10.3987/COM-10-S(E)125
Synthesis of 2- and 3-Indolylpyrroles via 1,3-Dipolar Cycloadditions of Münchnones and Nitroalkenes

Justin M. Lopchuk and Gordon W. Gribble*

*6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, U.S.A.

Abstract

A series of 2- and 3-indolylpyrroles were generated via 1,3-dipolar cycloadditions between (2-nitrovinyl)indoles and symmetrical and unsymmetrical 1,3-oxazolium-5-olates (münchnones).

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Paper | Special issue | Vol 82, No. 2, 2011, pp. 1633 - 1644
Published online: 11th November, 2010
DOI: 10.3987/COM-10-S(E)126
Regiospecific Rearrangement of Hydroxylamines to Secondary Amines Using Diisobutylaluminum Hydride

Hidetsura Cho,* Kenji Sugimoto, Yusuke Iwama, Nakako Mitsuhashi, Kentaro Okano, and Hidetoshi Tokuyama*

*Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan

Abstract

A systematic investigation of a reductive ring-expansion reaction of N-monosubstituted hydroxylamines with diisobutylaluminum hydride (DIBALH) was carried out. The reaction regiospecifically provided a variety of bicyclic or tricyclic heterocycles or linear secondary amines containing nitrogen attached to an aromatic ring.

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Note | Special issue | Vol 82, No. 2, 2011, pp. 1645 - 1656
Published online: 5th August, 2010
DOI: 10.3987/COM-10-S(E)58
Synthesis of a Chiral C3-Symmetric Bowl-Shaped Cyclohexapeptide Composed of Anthranilic Acid and Leucine

Motohiro Akazome,* Masashi Enzu, Yohei Goto, and Shoji Matsumoto

*Faculty of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

Abstract

A chiral C3-symmetric bowl-shaped cyclohexapeptide (1), composed of anthranilic acid (2-aminobenzoic acid) and α-amino acid in an alternating sequence, was synthesized from 2-nitrobenzoic acid and leucine. The 1H and 13C NMR spectra of 1 suggest a chiral C3-symmetric bowl-shaped structure. Molecular mechanic calculation revealed that the cyclohexapeptide becomes a bowl-shaped structure when all three α-amino acid components have homochiral side chains.

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Note | Special issue | Vol 82, No. 2, 2011, pp. 1657 - 1662
Published online: 17th August, 2010
DOI: 10.3987/COM-10-S(E)59
The Preparation of Ketene Dithioacetals and Thiophenes from Chloropyridines Containing an Active Methylene Group

Keith R. Sturrock,* David H. Bremner, and Grant Wishart

*School of Contemporary Sciences, University of Abertay Dundee, Bell Street, Dundee, DD1 1HG
Scotland, U.K.

Abstract

The base catalysed reaction of carbon disulphide with the active methylene groups of chloropyridines 4 and 7, followed by alkylation with reagents which also contain active methylene groups, lead to ketene dithioacetals. Further reaction with base afforded highly substituted thiophenes.

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Note | Special issue | Vol 82, No. 2, 2011, pp. 1663 - 1668
Published online: 10th September, 2010
DOI: 10.3987/COM-10-S(E)63
Synthesis of Polycyclic Aromatics from a Diiodosultine by Suzuki-Miyaura Cross-Coupling and Diels-Alder Reaction

Sambasivarao Kotha* and Milind Meshram

*Department of Chemistry, Indian Institute of Technology, Powai, Mumbai 400 076, India

Abstract

A convergent synthesis of polycyclic aromatic compounds by the application of Suzuki-Miyaura cross-coupling and Diels-Alder reaction as key steps is described.

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Note | Special issue | Vol 82, No. 2, 2011, pp. 1669 - 1674
Published online: 3rd September, 2010
DOI: 10.3987/COM-10-S(E)75
Synthesis of C3 and Cs Symmetric Cyclic Triglycerols

Masahiro Hamada, Ryou Fujiwara, Takao Kishimoto, and Noriyuki Nakajima*

*Biotechnology Research Center, Toyama Prefectural University, 5180 Kurokawa, Kosugi, Toyama 939-0398, Japan

Abstract

Authentic cyclic triglycerol standards have been efficiently synthesized. C3 and CS symmetric cyclic glycerols were effectively synthesized using intramolecular cyclization conditions and the stereochemistry of their isomers was confirmed.

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Note | Special issue | Vol 82, No. 2, 2011, pp. 1675 - 1683
Published online: 6th August, 2010
DOI: 10.3987/COM-10-S(E)80
An Efficient Synthesis of Antibiotic SF-2312 (3-Dihydroxyphosphoryl-1,5-dihydroxy-2-pyrrolidone)

Tadashi Hanaya* and Chika Itoh

*Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

N-Benzyloxy-2-(diethoxyphosphoryl)pent-4-enamide (6) was prepared from ethyl diethoxyphosphorylacetate in a 3-step sequence. Oxidative cleavage of the terminal olefin of 6 with osmium tetroxide and sodium periodate afforded 1-benzyloxy-3-diethoxyphosphoryl-5-hydroxy-2-pyrrolidone (7). The first synthesis of racemic SF-2312 was achieved by treatment of 7 with trimethylsilyl bromide, followed by hydrogenolysis.

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Note | Special issue | Vol 82, No. 2, 2011, pp. 1685 - 1692
Published online: 10th August, 2010
DOI: 10.3987/COM-10-S(E)81
New Oxidation Products from (-)-Epigallocatechin Gallate in Neutral Solution

Takayo Ohyabu, Shoko Taniguchi, Hideyuki Ito, and Tsutomu Hatano*

*Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

Two new products, EGCG-MOx-D5 (3) and EGCG-MOx-D6 (4), on the oxidation of (-)-epigallocatechin gallate (EGCG) (1) in its aqueous solution were isolated and their structures were elucidated. These structures and those of previously established ones suggested the pathways of the changes in the oxidation. Rapid decrease of 1 accompanied by the formations of the oxidative products suggested the participation of these products in the biological and pharmacological effects reported to be those of 1.

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Note | Special issue | Vol 82, No. 2, 2011, pp. 1693 - 1697
Published online: 28th September, 2010
DOI: 10.3987/COM-10-S(E)103
Polymyrifline A, a New Polymethoxyflavone from Citrus aurantium var. myrtifolia

Yusuke Hirasawa, Mari Hirata, Katsuya Haruna, Masahiro Takeda, Kazunori Ogawa, and Hiroshi Morita*

*Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan

Abstract

A new polymethoxyflavone, polymyrifline A (1) was isolated together with known polymethoxyflavones from the fruits of Citrus aurantium var. myrtifolia. Its structure was elucidated by spectroscopic methods and chemical means. Polymyrifline A (1) showed a moderate inhibition of the NO production in LPS-stimulated J774.1.

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