Special Issue

Albert Eschenmoser's Special Issues, Vol. 82, No. 1, 2010

69 data found. 31 - 60 listedFirst Previous Next Last
Paper | Special issue | Vol 82, No. 1, 2010, pp. 449 - 460
Published online: 17th May, 2010
DOI: 10.3987/COM-10-S(E)16
Synthesis of 3,4-Ethylenedioxythiophene (EDOT) from (Z)-But-2-ene-1,4-diol or But-2-yne-1,4-diol

Iwao Hachiya, Tomohiro Matsumoto, Tatsuhiko Inagaki, Atsushi Takahashi, and Makoto Shimizu*

*Department of Chemistry for Materials, Graduate School of Engineering, Mie University, 1577 Tsu, Mie 514-8507, Japan

Abstract

3,4-Ethylenedioxythiophene (EDOT) was synthesized from commercially available (Z)-but-2-ene-1,4-diol or but-2-yne-1,4-diol using epoxidation, etherification, and thiophene formation.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 461 - 472
Published online: 17th May, 2010
DOI: 10.3987/COM-10-S(E)19
Studies on the Biosynthesis of the Stephacidins and Notoamides. Total Synthesis of Notoamides

Timothy J. McAfoos, Shengying Li, Sachiko Tsukamoto, Daivd H. Sherman, and Robert M. Williams*

*Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, U.S.A.

Abstract

Notoamide S has been suggested to be the final common precursor between two different Aspergillus sp. fungal strains before diverging to form enantiomerically opposite natural products (+)- and (–)-stephacidin A and (+)- and (-)-notoamide B. The synthesis of notoamide S comes from the coupling of N-Fmoc proline with a 6-hydroxy-7-prenyl-2-reverse prenyl tryptophan derivative that was synthesized via a late stage Claisen rearrangement from a 6-propargyl-2-reverse prenylated indole.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 473 - 478
Published online: 2nd June, 2010
DOI: 10.3987/COM-10-S(E)20
Unexpected Fluorescent Behavior of a New pH Chemosensor Based upon Bis-4-piperidine-1,8-naphthalimide Linked by the Diethylenetriamine

Hui Xu,* Huiling Dai, and Junqiang Ran

*Laboratory of Pharmaceutical Design & Synthesis, College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, China

Abstract

A new fluorescent chemosensor 3 based upon bis-4-piperidine-1,8-naphthalimide linked by the diethylenetriamine was synthesized, and its fluorescent properties were also investigated. Different from other bis-1,8-naphthalimides, no changes in the fluorescence spectra of 3 in the presence of metal cations was observed, and it displayed an unexpectedly strong fluorescence quench in weakly acidic aqueous solutions. Its pKa value (7.25) indicated that it would be suited as a new pH fluorescent chemosensor to monitor changes at the physiological pH range.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 479 - 489
Published online: 22nd June, 2010
DOI: 10.3987/COM-10-S(E)21
Relative Stabilities of 1- and 2-Substituted 1,2,3-Triazoles

Alan R. Katritzky,* Ana-Maria Buciumas, Ekaterina Todadze, Munawar Ali Munawar, and Levan Khelashvili

*Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, U.S.A.

Abstract

N-(α-Aminoalkyl)-1,2,3-triazoles are potentially tautomeric between the 1- and 2-substituted forms. They exist in solution predominantly as 2-isomers as shown by 1H and 13C NMR; electron attracting substituents on the amino nitrogen increase the proportion of the 1-isomer in the equilibrium mixture.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 491 - 504
Published online: 2nd June, 2010
DOI: 10.3987/COM-10-S(E)22
Asymmetric Syntheses of Highly Functionalized Bicyclo[2.2.2]octene Derivatives

Masafumi Iwatsu, Daisuke Urabe, and Masayuki Inoue*

*Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

Abstract

Highly functionalized bicyclo[2.2.2]octene derivatives bearing two quaternary carbon centers were synthesized in an asymmetric fashion. The key transformations were the regioselective Diels-Alder reaction between 3,6-dimethyl-o-quinone monoacetal and 1,1-diethoxyethylene and the subsequent enzymatic resolution. The optically active bicyclo[2.2.2]octene derivatives obtained should serve as versatile chiral building blocks for highly functionalized natural products such as ryanodine.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 505 - 529
Published online: 2nd June, 2010
DOI: 10.3987/COM-10-S(E)23
Iterative Extension of Thiophene Ring Leading to Head-to-Tail-Type Oligothiophenes via Stepwise CH Arylation and Halogen Exchange Sequence

Shunsuke Tanba, Atsushi Sugie, Naoyuki Masuda, Daiki Monguchi, Nagatoshi Koumura, Kohjiro Hara, and Atsunori Mori*

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

Abstract

Iterative extension of the thiophene ring unit leads to oligothiophenes. The coupling reaction at the CH bond of thiophene with halo-thiophene occurs at the 5-position of 2-bromothiophene with 2-iodothiophene in the presence of a palladium catalyst and AgNO3/KF as an activator to give the corresponding bithiophene, whose carbon-bromine bond remains. Halogen exchange converts the bromine atom to iodide, which also allows further reaction to form thiophene-thiophene bond. Oligothiophenes are obtained by repeating such sequense.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 531 - 542
Published online: 8th June, 2010
DOI: 10.3987/COM-10-S(E)24
A Synthetic Approach to Anhydroketopyranoses Having a 6,8-Dioxabicyclo[3.2.1]octane Structure from Ketopyranoses

Takashi Yamanoi,* Kazuhide Matsumura, Sho Matsuda, and Yoshiki Oda

*The Noguchi Institute, 1-8-1, Kaga, Itabashi-ku, Tokyo 173-0003, Japan

Abstract

We investigated a synthetic approach to the anhydroketopyranoses having a 6,8-dioxabicyclo[3.2.1]octane structure from D-glucopyranose derivatives. The paper describes the nucleophilic addition of the organometallic reagents RLi or RMgX to the glucono-1,5-lactone derivatives to produce the ketopyranose derivatives having a glucose backbone and their intramolecular cyclization into the desired structural anhydroketopyranoses.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 543 - 554
Published online: 8th June, 2010
DOI: 10.3987/COM-10-S(E)25
An Efficient Synthesis of Methyl Esters of Heterocyclic α,β-Didehydro-α-amino Acid Derivatives

Franc Požgan, Klavdija Lukman, and Marijan Kočevar*

*Department of Organic Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, P.O. Box 537, SI-1000 Ljubljana, Slovenia

Abstract

N-Benzoyl-protected α,β-didehydro-α-amino acid (DDAA) derivatives containing a pyrazole or an isoxazole ring at the β-position were transformed with diazomethane into the corresponding methyl esters. Applying this method, the double C=C bond of the DDAA derivatives was not affected, thus selectively giving the corresponding esters in good-to-excellent yields.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 555 - 562
Published online: 3rd June, 2010
DOI: 10.3987/COM-10-S(E)26
Silver-Catalyzed Oxidative Coupling of Terminal Aromatic Alkynes and Benzylic Ethers

Camille A. Correia and Chao-Jun Li*

*Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, Quebec H3A 2K6, Canada

Abstract

The Cross-Dehydrogenative-Coupling (CDC) of terminal aromatic alkynes and benzylic ethers was achieved through the use of a catalytic amount of silver triflate and employing 2,3-dichloro-5,6-dicyanoquinone (DDQ) as the oxidant.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 563 - 579
Published online: 11th June, 2010
DOI: 10.3987/COM-10-S(E)27
Total Synthesis of (+)- and (-)-Galanthamine

Tomoaki Kato, Hiroki Tanimoto, Hisako Yamada, and Noritaka Chida*

*Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi, Kohoku-ku Yokohama 223-8522, Japan

Abstract

The stereoselective total synthesis of (+)-galanthamine [(+)-1], an antipode of the natural product, and (–)-galanthamine [(–)-1] starting from D-glucose is described. The cyclohexene unit in (+)-1 was prepared in an optically active form from D-glucose using Ferrier’s carbocyclization reaction, and the benzylic quaternary carbon was stereoselectively generated via chirality transfer by Johnson- or Eschenmoser-Claisen rearrangement. The dibenzofuran skeleton was effectively constructed by the bromonium ion-mediated intramolecular dealkylating etherification. After the introduction of a carbon-carbon double bond, the Pictet-Spengler type cyclization, followed by reduction of an amide function afforded (+)-1. Starting from D-glucose, (–)-galanthamine [(–)-1] was also totally synthesized.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 581 - 591
Published online: 16th June, 2010
DOI: 10.3987/COM-10-S(E)28
Dehydrogenation of 5,6-Dihydropyrido[3,2-d]pyrimidin-7(8H)-ones: A Convenient Last Step for a Synthesis of Pyrido[2,3-d]pyrimidin-7(8H)-ones

Irene Pérez-Pi, Xavier Berzosa, Iñaki Galve, Jordi Teixidó , and José I. Borrell*

*Molecular Engineering Group, IQS, Ramon Llull University, Via Augusta 390, E-08017 Barcelona, Spain

Abstract

Two new protocols for the dehydrogenation of 5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones to pyrido[2,3-d]pyrimidin-7(8H)- -ones are described. The first one uses NaH in DMSO an affords the corresponding pyridopyrimidines when an aryl substituent is present at C6. The second one is of a more general use, allowing dehydrogenation of aryl and alkyl substituted 5,6-dihydropyridopyrimdines upon treatment with Na2SeO3 in DMSO.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 593 - 601
Published online: 16th June, 2010
DOI: 10.3987/COM-10-S(E)29
Direct Oxidative Conversion of Aldehydes into 2-Substituted 1,4,5,6-Tetrahydropyrimidines Using Molecular Iodine or 1,3-Diiodo-5,5-dimethylhydantoin

Shogo Takahashi and Hideo Togo*

*Graduate School of Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

Abstract

Various aromatic and aliphatic aldehydes were efficiently converted into the corresponding 1,4,5,6-tetrahydro-2-arylpyrimidines and 1,4,5,6-tetrahydro-2-alkylpyrimidines in good yields by the reaction with 1,3-propanediamine in the presence of molecular iodine•K2CO3 or 1,3-diiodo-5,5-dimethylhydantoin. Those 1,4,5,6-tetrahydropyrimidines were oxidized to the corresponding 2-aryl- and 2-alkylpyrimidines in moderate yields using MnO2.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 603 - 617
Published online: 21st July, 2010
DOI: 10.3987/COM-10-S(E)33
Diastereoselective Cyclization Reactions of Chiral Proline Auxiliary-Substituted N-Benzoyl-α-dehydro(1-naphthyl)alaninamide Derivatives via Photoinduced Electron Transfer

Yuhki Sato, Yuhta Haruyama, Tetsutaro Igarashi, and Tadamitsu Sakurai*

*Material and Life Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan

Abstract

Irradiation of the title 1-naphthylalaninamide derivatives [(Z)-1] bearing N’-substituted (S)-prolinamide auxiliaries in 1,2-dichloroethane and methanol containing triethylamine mainly afforded the corresponding (4S,5S)-4,5-dihydrooxazoles [(4S,5S)-2, diastereomeric excess (de) = 21–84%] and (4R,5R)-2 (de = 18–43%), respectively. Analysis of substituent and solvent effects on the diastereoselective photocyclization of (Z)-1 substantiated that steric bulkiness of the chiral auxiliary, solvent polarity, and intramolecular hydrogen bond are major factors controlling de, while intermolecular hydrogen-bonding and charge-transfer interactions invert the configuration of the dihydrooxazole diastereomer preferentially formed.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 619 - 629
Published online: 7th July, 2010
DOI: 10.3987/COM-10-S(E)34
Reactions of Heterocyclic Ketene Aminals with Acrylonitrile: An Efficient Synthesis of Dihydropyridine-Fused 1,3-Diazaheterocycles

Hui Zhao, Ai-Qun Zeng, Wei-Lin Liao, Yue-Mei Jia, Li-Ben Wang, Zhi-Tang Huang,* and Chu-Yi Yu*

*Institute of Chemistry, Chinese Academy of Sciences, No. 2, 1st North Street, Zhongguancun, Beijing 100190, China

Abstract

A simple and efficient method for the synthesis of dihydropyridine-fused 1,3-diazaheterocycles has been developed via reactions of heterocyclic ketene aminals (HKAs) with acrylonitrile in good to excellent yields.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 631 - 639
Published online: 18th June, 2010
DOI: 10.3987/COM-10-S(E)35
Reductive Cyclization of 3-Cyanomethyloxindoles to Hexahydro-2-oxopyrrolo[2,3-b]indoles with Lithium Aluminum Hydride

Masashi Shinada, Yoshiyuki Aihara, Satoshi Takiguchi, Naoko Ban, Kazuhiro Higuchi, and Tomomi Kawasaki*

*Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan

Abstract

Reduction of 3-cyanomethyloxindoles with lithium aluminum hydride at low temperature proceeded smoothly with cyclization to afford hexahydro-2-oxopyrrolo[2,3-b]indoles.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 641 - 647
Published online: 18th June, 2010
DOI: 10.3987/COM-10-S(E)37
A Concise Total Synthesis of (±)-Centrolobine

Haruhiko Fuwa,* Kenkichi Noto, and Makoto Sasaki

*Tohoku University, 1-1, Tsutsumidori, Amamiya, Aoba-ku, Sendai, 981-8555, Japan

Abstract

A concise total synthesis of (±)-centrolobine has been achieved in four linear steps from commercially available p-benzyloxybenzaldehyde via our developed domino olefin cross-metathesis/intramolecular oxa-conjugate cyclization.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 649 - 661
Published online: 1st July, 2010
DOI: 10.3987/COM-10-S(E)40
Studies on the Synthesis and Metabolism of 14-epi-2α-(3-Hydroxypropyl)-19-norvitamin D3 and Its 2β-Isomer

Atsushi Kittaka,* Hideki Hara, Kaori Yasuda, Masashi Takano, Midori A. Arai, Daisuke Sawada, Hiroshi Saito, Kazuya Takenouchi, Tai C. Chen, and Toshiyuki Sakaki*

*Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, 1091-1 Suarashi, Midori-ku, Sagamihara-shi, Kanagawa 252-5195, Japan

Abstract

Two derivatives of 14-epi-1α,25-Dihydroxy-19-norvitamin D3, 14-epi-2α-(3-hydroxypropyl)-1α,25-dihydroxy-19-norvitamin D3 (14-epi-MART-10) and its 2-epimeric analog (14-epi-MART-11), were synthesized using Julia coupling reaction to connect between the C5 position (steroidal numbering) of an A-ring precursor ketone derived from (–)-quinic acid and the C6 position of a protected 14-epi-CD-ring benzothiazole sulfone. The coupling and deprotection reactions generated a mixture of 14-epi-MART-10 and 14-epi-MART-11 in a moderate yield. The C2-isomers were then separated as their pivalate forms. The C2-stereochemistry of 2α- and 2β-isomers was determined by 1H NMR studies including NOE experiments. The pivaloyl group was removed under basic conditions to obtain the target molecules of 14-epi-MART-10 and 14-epi-MART-11. The metabolism of these two new analogs was further studied in a reconstituted cell-free human CYP24A1 system to elucidate the potential mechanism of their super agonistic action on vitamin D receptor. Our results indicate that epimerization at C14 makes the analogs less susceptible to CYP24A1 degradation and therefore more bio-available, leading to enhanced biological activities.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 663 - 687
Published online: 8th July, 2010
DOI: 10.3987/COM-10-S(E)42
Synthesis and Anti-HIV Activity of New 3’-O-Phosphonomethyl Nucleosides

Michal Cesnek and Piet Herdewijn*

*K.U. Leuven, Rega Institute for Medical Research, Minderbroedersstraat 10, B-3000 Leuven, Belgium

Abstract

The synthesis of 4’(S)-ethynyl-2’-deoxythreosyl and β-D-galactofuranose nucleosides starting from D-galactose is described. The nucleobase is introduced using Vorbruggen glycosylation. The 4’(S)-ethynyl derivatives are obtained by selective oxidation of vicinal diol to the aldehyde and subsequent Bestmann modification of Seyferth-Gilbert homologation. All compounds were evaluated for activity against HIV (MT4 cells), RSV (Hep2 cells) and HCV (HCV replicon cells), however, none of these compounds demonstrate biological activity.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 689 - 697
Published online: 5th July, 2010
DOI: 10.3987/COM-10-S(E)44
Synthesis of Bis(benzo[b]thiophenyl)methanes by Gold-Catalyzed Double Carbothiolation

Itaru Nakamura,* Masashi Okamoto, Takuma Sato, and Masahiro Terada

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

Abstract

Gold-catalyzed double cyclization of bis(2-alkynylphenylthio)acetals (1) produced bis(benzo[b]thiophen-3-yl)methanes (2) in good to excellent yields with high catalyst turnover number. For example, the reaction of (phenylmethylene)bis((2-(phenylethynyl)phenyl)sulfane) (1b) in the presence of 1 mol% of AuCl in toluene at 25 °C for 1 hour gave 3,3'-(phenylmethylene)bis(2-phenylbenzo[b]thiophene) (2b) in 97% isolated yield. The present reaction proceeded through two successive intramolecular carbon-sulfur bond addition reactions, or the so-called carbothiolation.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 699 - 711
Published online: 5th August, 2010
DOI: 10.3987/COM-10-S(E)49
Immobilisation of the Vitamin B12 Derivative B12-Tyramide on Electrode Surfaces

Luisa M. Abrantes, Jorge P. Correia, Ana M. Tenreiro, and Reinhart Keese*

*Institut für Organische Chemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

Abstract

The hexamethyl cob(III)yrinic acid c-tyramide was prepared for its immobilisation on electrodes. The electropolymerisation of this compound onto Pt and glassy carbon electrodes was successful and details of these reactions were explored. The grafting procedure, in which tyramine was first electropolymerized on the electrode followed by the electro-oxidative attachment of the B12-tyramide provided a further method for this immobilisation. Exploratory experiments for the electrocatalytic activity of these coated electrodes are reported.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 713 - 728
Published online: 16th July, 2010
DOI: 10.3987/COM-10-S(E)51
Synthesis of 8,1’-etheno and 8,2’-ethano Bridged Guanosine Derivatives Using Radical Cyclization

Julian Strohmeier, André Nadler, Daniel Heinrich, Ansgar Fitzner, and Ulf Diederichsen*

*Institute of Organic Chemistry, Georg-August-University, Tammannstrasse 2, D-37077 Göttingen, Germany

Abstract

Conformationally constrained nucleosides can be readily generated by radical cyclization reactions. The radical cyclization of two guanosine derivatives containing a 2,2’-dibromovinyl group or a iodovinyl group tethered at the C8 position is described, respectively. The cyclization of the guanosine derivative with the 2,2’-dibromovinyl group initiated by tributyltin hydride formed an anomeric spiro nucleoside with an 8,1’-etheno bridge as the major cyclization product. In contrast, the conversion of guanosine and 2’-deoxyguanosine derivatives carrying the iodovinyl group provided 8,2’-ethano bridged nucleosides as the major products.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 729 - 737
Published online: 22nd July, 2010
DOI: 10.3987/COM-10-S(E)52
Crystal-State Structure Analysis of β-Hydroxy-γ-lactam Constrained Ser/Thr Peptidomimetics

Daniel J. St-Cyr, Thierry Maris, and William D. Lubell*

*Department of Chemistry, University of Montreal, CP 6128, Succursale-Centre-Ville
Montreal, Quebec, H3C 3J7, Canada

Abstract

Crystallographic evidence has been obtained in support of the ability of β-hydroxy-α-amino-γ-lactams to induce β-turn conformations within peptides. Two dipeptide model systems of these β-hydroxylated variants of the so-called Freidinger-Veber lactams were prepared from the reaction of N-(Fmoc)oxiranylglycine 2 with methyl m-amino benzoate and methyl lysinate, respectively, and crystallized from benzene or ether. In the solid-state, the lactam moiety was found to adopt dihedral angle geometry similar to extended as well as type II β-turn conformations contingent on the C-terminal amino ester moiety. The β-hydroxyl group of the trans-isomer was shown to point away from the turn suggesting its potential for interaction with receptors in conformationally rigid mimics of serine and threonine-containing peptides.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 739 - 760
Published online: 13th July, 2010
DOI: 10.3987/COM-10-S(E)54
Nucleotides Part: LXXVII. New Types of Fluorescence Labeling of 2’-Deoxyguanosine

Thomas Maier and Wolfgang Pfleiderer*

*Department of Chemistry, University of Konstanz, Posttach 55 60, D-78457 Konstantz, Germany

Abstract

Protected 3',5'-diacetyl-(5) and 3',5'-O-(tetraisopropyldisiloxan-1,3-diyl)-2'-deoxy-guanosine (6) have been labeled with 5-aminofluorescein (9) to form 10 and 11 which reacted under Mitsunobu conditions with 2-(4-nitrophenyl)ethanol to 13 and 14, respectively. 14 could also been synthesized directly from 6 with 15 in one step. Selective desililation with fluoride ion led from 1 to 12 and from 14 to 16. Dimethoxytritylation of 16 gave 18 which was further converted into the building blocks 19-21. The synthesis of the 2'-deoxyguanosylyl[3'5']-2'-deoxy-N2-{[(fluorescein-5-yl)amino]carbonyl}guano- sysyl[3'5']-2'-deoxyguanosine trimer (28) was achieved by step-wise built-up from 20 with 22 to 23 and followed by coupling of 24 with 26 yielding 27. Due to the unified blocking group pattern in 27 fully deprotection afforded afforded only one step by treatment with DBU to give 28. Several oligo-2'-deoxynucleotides containing fluorescein labeled 2'-deoxyguanosines at various positions of the chain were formed in a DNA-synthesizer and their fluorescence properties and the Tm s of the corresponding duplexes measured.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 761 - 774
Published online: 27th July, 2010
DOI: 10.3987/COM-10-S(E)61
Stereoselective Synthesis of Caribbean Ciguatoxin M-Ring Using [2+2] Photocyclization

Shuji Yamashita,* Naoya Iijima, Takahiro Shida, and Masahiro Hirama*

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

Abstract

Ciguatoxins, the principal causative toxins of ciguatera seafood poisoning, are potent toxic polycyclic ethers. We report herein a stereoselective synthesis of the seven-membered M-ring moiety of Caribbean ciguatoxin C-CTX-1. The key features of the synthesis are the photo-induced [2+2] electrocyclization and enzymatic asymmetric hydrolysis to construct the congested oxepane ring.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 775 - 790
Published online: 16th July, 2010
DOI: 10.3987/COM-10-S(E)65
Screening the Structural Space of Bicyclo-DNA: Synthesis and Properties of Bicyclo-DNA Functionalized at C(6’)

Samuel Luisier and Christian J. Leumann*

*Department of Chemistry and Biochemistry, University of Bern, Freiestrasse, CH-3012 Bern, Switzerland

Abstract

The synthesis of a novel bicyclo-thymidine nucleoside bearing an ester functionality at C(6’) (bcα-alk-nucleosides) is reported. This nucleoside was incorporated into oligodeoxynucleotides via solid phase phosphoramidite chemistry, and the ester moiety was post-synthetically converted to an amide or a carboxy group, or was left unchanged. Thermal melting data (Tm) with complementary DNA and RNA were collected and compared to natural DNA and to bc- and bcox-DNA. It was found that single incorporations of bcα-alk-nucleosides in DNA duplexes were destabilizing by 0.5 to 2.5 °C/mod, whereas two consecutive bcα-alk-residues were less destabilizing, and in some cases even stabilizing by 0.5 °C/mod. In duplexes with complementary RNA, isolated bcα-alk-residues destabilized the duplex by -1.0 to -4.0 °C/mod, depending on the chemical nature of the substituent, whereas two consecutive modifications were only destabilizing by 0.3-1.0 °C/mod. The pairing selectivity was similar to that of unmodified or bc-DNA.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 791 - 802
Published online: 29th July, 2010
DOI: 10.3987/COM-10-S(E)69
Preparation of Highly Conjugated Oligoaza-PAHs Based on the Oxidative Intramolecular Coupling of Bicyclo[2.2.2]octadiene-Fused Pyrrole

Hidemitsu Uno,* Takahiro Takiue, Hiroki Uoyama, Tetsuo Okujima, Hiroko Yamada, and Go Masuda

*Department of Chemistry and Biology, Graduate School or Science and Engineering, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan

Abstract

The substitution reactions of tetrafluoro-p-phthalonitrile and hexafluorobenzene with 4,7-dihydro-4,7-ethano-2H-isoindole under basic conditions afforded tetra(4,7-dihydro-4,7-ethano-2H-isoindol-2-yl)-substituted p-phthalonitrile and 1,4-difluorobenzene in good yields, respectively. Oxidative coupling reactions of these compounds gave tetra(bicycle[2.2.2]octadiene)-fused tetrapyrrolo[1,2-a;1’,2’-c;1”,2”-h;1’”,2’”-j][1,4,5,8]tetraazaanthracenes, which were then converted to tetraisoindolo[1,2-a;1’,2’-c;1”,2”-h;1’”,2’”-j]- [1,4,5,8]tetraazaanthracenes by the retro-Diels-Alder reaction.

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Paper | Special issue | Vol 82, No. 1, 2010, pp. 803 - 812
Published online: 29th July, 2010
DOI: 10.3987/COM-10-S(E)71
A Facile Synthesis of Fluorine-Containing 1,7-Phenanthrolines by the Cyclization of N-Propargyl-6,8-bis(trifluoroacetyl)quinolin-5-amine with Various Active Methylene Compounds

Dai Shibata, Ayaka Sakai, Mizuki Hatakenaka, Shohei Saikawa, Yasuhiro Kamitori, Maurice Médebielle, 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 N-propargyl-6,8-bis(trifluoroacetyl)quinolin-5-amine (1) with various active methylene compounds gave the novel fluorine-containing 1,7-phenanthroline derivatives (3). Furthermore, changing the electron-withdrawing groups on active methylene compounds induced interesting alternation of the reaction site wherein the enolate anions attack first and led to construction of the different nitrogen-containing heterocyclic systems, 1,7-phenanthrolinone (4) and 1,4-dihydro-1,7-phenanthroline (5).

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Note | Special issue | Vol 82, No. 1, 2010, pp. 813 - 824
Published online: 13th April, 2010
DOI: 10.3987/COM-10-S(E)6
New and Known Constituents from Iris unguicularis and Their Antioxidant Activity

_ Atta-ur-Rahman,* Sumaira Hareem, M. Iqbal Choudhary, Bilge Sener, Ahmed Abbaskhan, Hina Siddiqui, Shazia Anjum, Ilkay Orhan, Ilhan Gurbuz, and Filiz Ayanoglu

*International Centre for Chemical Sciences, H. E. J. Research Institute of Chemistry, University of Karachi, Karachi-75270, Pakistan

Abstract

A new compound, 1,3-O-diferuloylsucrose (1), and a synthetically known compound, 5,7-dihydroxy-6-methoxychromone (2), along with several known natural products, irilone (3), 4′,5,7-trihydroxy-6-methoxyflavanone (4), tectorigenin (5), kaempferol (6), 4′,5,7-trihydroxy-3′,8-dimethoxyflavanone (7), 8-methoxyeriodictyol (8), hispidulin (9), and mangiferin (10) were isolated from the rhizomes of Iris unguicularis. Compounds 1, 6, 8 and 10 showed a considerable DPPH radicals scavenging activity. Their structures have been deduced through different spectroscopic techniques. The structure of compound 2 was also confirmed by single-crystal X-ray diffraction techniques as well.

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Note | Special issue | Vol 82, No. 1, 2010, pp. 825 - 832
Published online: 16th April, 2010
DOI: 10.3987/COM-10-S(E)10
An Efficiently Sonochemical Synthesis of 2-(N-Arylsulfonylindol-3-yl)-3-N-acyl-5-phenyl-1,3,4-oxadiazolines

Hui Xu,* Zhi-ping Che, and Qin Wang

*Laboratory of Pharmaceutical Design & Synthesis, College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, 712100, China

Abstract

An efficient and rapid synthesis of 2-(N-arylsulfonylindol-3-yl)-3-N-acyl-5-phenyl-1,3,4-oxadiazolines from N-arylsulfonyl-3-formylindole benzoyl hydrazones and anhydrides under ultrasonic irradiation in good yields is described.

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Note | Special issue | Vol 82, No. 1, 2010, pp. 833 - 838
Published online: 10th May, 2010
DOI: 10.3987/COM-10-S(E)17
Synthesis and Complexation Behavior of 4,10-bis(1-Pyrenylmethyl)-1,7-dioxa-4,10-diazacyclododecane

Kanji Kubo,* Hanae Komatsuzaki, Tadamitsu Sakurai, Tetsutaro Igarashi, Taisuke Matsumoto, Hajime Takahashi, and Haruko Takechi

*School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan

Abstract

Fluorescent photoinduced electron transfer (PET) fluoroionophore (2c) that consists of diaza-12-crown-4 and two 1-pyrenylmethyl pendants shows fluorescent enhancement with various metal cations. The sensor (2c) exhibited Zn2+ selectivity and in the presence of this cation the host fluorescence was increased by a factor of 38.

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