Special Issue

Bernhard Witkop's Special Issues, Vol. 49, No. 1, 1998

69 data found. 31 - 60 listedFirst Previous Next Last
Paper | Special issue | Vol 49, No. 1, 1998, pp. 157 - 168
Published online:
DOI: 10.3987/COM-98-S11
The Structure of Aminoazoles and Its Relationship with Aromaticity. Crystal and Molecular Structure of Two Polymorphic Forms of 4-Aminopyrazole

Lourdes Infantes, Concepción Foces-Foces,* Pilar Cabildo,* Rosa María Claramunt, Otilia Mó, Manuel Yáñez, and José Elguero

*Departamento de Cristalografía, Instituto de Química-Física 'Rocasolano', C. S. I. C., Serrano, 119, E-28006 Madrid, Spain

Abstract

Quantum mechanic calculations have been done at MP2 and B3LYP/6-31G** levels on six C-aminoazoles (α-aminopyrrole, 3-aminopyrazole, 5-aminopyrazole, 4-aminopyrazole, 5-amino-1,2,4-triazole, and 5-amino-1,2,3,4-tetrazole). These calculations have been used to discuss the molecular structure of these compounds in relation to their aromaticity. The crystal and molecular structure of two polymorphic forms of 4-aminopyrazole has been determined by X-Ray analysis. The main differences, between the two polymorphs, at molecular level lie in the conformation of the amino group and at the packing level in the hydrogen interactions involving the amino group.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 169 - 180
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DOI: 10.3987/COM-98-S13
Stereoselective Synthesis of Antifungal Sulfoximines, Novel Triazoles I

Hiroyuki Kawanishi, Hiroshi Morimoto, Takao Nakano, Tadatoshi Miyajima, Kuniyuki Oda, Katsuo Takeda, Shigeru Yano, Naomitsu Hirano, and Kenji Tsujihara*

*Discovery Research Laboratory, Tanabe Seiyaku Co. Ltd., 2-2-50 Kawagishi, Toda, Saitama 335-8505, Japan

Abstract

Different types of sulfoximines, novel triazoles with three contiguous asymmetric centers on sulfur and two carbons, were stereoselectively synthesized and evaluated for antifungal activity. (R)-S-2-[(2R,3R)-3-(2,4-Difluorophenyl)-3-hydroxy-4-(1H-1,2,4-triazol-1-yl)]butyl-S-methylsulfoximine (2a) showed extremely potent antifungal activities.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 181 - 189
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DOI: 10.3987/COM-98-S14
Stereoselective Synthesis of Antifungal Sulfoximines, Novel Triazoles II

Hiroyuki Kawanishi, Hiroshi Morimoto, Takao Nakano, Tatsuya Watanabe, Kuniyuki Oda, and Kenji Tsujihara*

*Discovery Research Laboratory, Tanabe Seiyaku Co. Ltd., 2-2-50 Kawagishi, Toda, Saitama 335-8505, Japan

Abstract

Novel triazole derivatives with N-substituted sulfoximine moiety were synthesized and evaluated for antifungal activity. These compounds showed only significantly weak activity and N-H sulfoximine moiety was extremely important for the activity. A more practical and effective stereoselective synthesis of N-H sulfoximine, (R)-S-2-[(2R,3R)-3-(2,4-difluorophenyl)-3-hydroxy-4-(1H-1,2,4-triazol-1-yl)]butyl-S-methylsulfoximine (1), which was considered to be the most promising compounds, has been developed.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 191 - 195
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DOI: 10.3987/COM-98-S15
Concise Synthesis of Nitidine by Palladium-assisted Biaryl Coupling Reaction

Takashi Harayama* and Kentaro Shibaike

*Faculty of Pharmaceutical Sciences, Okayama University, Tsushima-naka 1-1-1, Okayama 700-8530, Japan

Abstract

Formal total synthesis of nitidine (1) was accomplished via oxynitidine (7) by the internal aryl-aryl coupling reaction of iodo-amide (6) using palladium-assisted cyclization reaction.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 197 - 204
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DOI: 10.3987/COM-98-S16
Synthesis of Acetylcholinesterase Inhibitors on the Basis of 9-Isothiocyanato-1,2,3,4-tetrahydroacridine: 2-[(1,2,3,4-Tetrahydroacridin-9-yl)imino]-3-substituted 1,3-Thiazolidin-4-ones

Pavol Kristian,* Slávka Hamul'aková, Juraj Bernát, Ján Imrich, Gundula Voss, and Tatiana Busová

*Department of Organic Chemistry, P. J. Safárik University, 041 67 Kosice, The Slovak Republic

Abstract

The synthesis of 2-[(1,2,3,4-tetrahydroacridin-9-yl)imino]-3-substituted 1,3-thiazolidin-4-ones (5a-e) via cyclization of N-(1,2,3,4-tetrahydroacridin-9-yl)-S-methoxycarbonylmethyl-N’-substituted isothiourea hydrobrodine, an analogue of tacrine, was used. The reaction represents a simple way for the preparation of new cholinergic compounds.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 205 - 214
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DOI: 10.3987/COM-98-S17
Organozinc Derivatives of Diazines, Metalation of Diazines XXIII

Alain Turck, Nelly Plé, Anne Leprêtre-Gaquere, and Guy Quéguiner*

*IRCOF , Laboratoire de Chimie Organique Fine et Hétérocyclique, UPRES-A 6014, INSA, B.P. 08, 76131 Mont St Aignan Cedex, France

Abstract

Some organozinc derivatives of diazines have been prepared from lithiated diazines and zinc chloride. They reacted in cross coupling reactions with iodobenzene, 2-bromopyridine and 5-bromopyrimidine. The use of sonication, for the first time in a Negishi reaction, lowered the reaction times significantly and improved the yields.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 215 - 232
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DOI: 10.3987/COM-98-S19
Ring Enlargement of Eight- and Nine-membered Cyclic Sulfonamide Derivatives in Reactions with 3-Amino-2H-azirines

Tonya R. Mihova, Anthony Linden, and Heinz Heimgartner*

*Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland

Abstract

The reactions of 3-dimethylamino-2H-azirines (1) with 3,4,5,6-tetrahydro-8,9-dimethoxy-2H-1,2-benzothiazocin-3-one 1,1-dioxide (6a) in acetonitrile gave the correspondingly substituted 3-dimethylamino-4,5,6,7,8,9-hexahydrobenzo-1-thia-2,5-diazacycloundecen-6-one 1,1-dioxides (8). In the case of the reaction of 1a with 6a, the 3-amino-5,6-dihydro-4H-benzothiazocine 1,1-dioxide derivative (9) was formed as a minor product. The structures of the starting material (6a), the unexpected 4,5-dimethoxy-2-(3-cyanopropyl)benzenesulfonyl chloride (7), the novel eleven-membered heterocycles (8a,8c) and that of 9 were established by X-Ray crystallography. With the nine-membered homologue 2,3,4,5,6,7-hexahydro-9,10-dimethoxy-1,2-benzothiazonin-3-one 1,1-dioxide (6b), only the most reactive aminoazirine yielded the ring enlarged twelve-membered heterocycle (10).

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 233 - 254
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DOI: 10.3987/COM-98-S20
New Silane Reduction of Aromatic Ketones Mediated by Titanium Tetrachloride: A Synthesis of γ- and δ-Aryl Substituted Amino Acids

Michihisa Yato, Koichi Homma, and Akihiko Ishida*

*Medicinal Chemistry Research Laboratory, Tanabe Seiyaku Co. Ltd., 2-2-50, Kawagishi, Toda, Saitama 335, Japan

Abstract

Several N-protected 4-aryl-2-aminobutanoic acids (γ-aryl substituted amino acids; 7a-f) and N-protected 5-aryl-2-aminopentanoic acids (δ-aryl substituted amio acids; 8a,b and d) were prepared in good yields by reduction of the corresponding aromatic or heteroaromatic ketones (3 and 4) with triethylsilane (Et3SiH) or dimethylphenylsilane (PhMe2SiH) in the presence of titanium tetrachloride (TiCl4), respectively. The reduction proceeded without racemization and was successfully applied to the synthesis of optically active γ- and δ-aryl substituted amino acids (14a and 15a).

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 255 - 260
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DOI: 10.3987/COM-98-S22
Synthesis of 6-Epoxygeranylgeraniol and Its Application to the Construction of A/B Acyclic Pimarane Type Diterpene

Yoshinobu Kashibuchi, Takashi Fukumoto, Minoru Oguchi, Toshifumi Hirukawa, and Tadahiro Kato*

*Department of Chemistry, Faculty of Science, Science University of Tokyo, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan

Abstract

Synthesis of A/B acyclic pimarane type diterpenes (1 and 2) was achieved through the TMS assisted cyclization of epoxy alcohol (5), which was prepared by Sharpless asymmetric epoxidation of allyl alcohol (6). The convenient preparation of the allyl alcohol (6) was explored starting from β-hydroxygeranylgeranioic acid (7) through bromo etherification to 8 followed by base treatment to give a mixture of conjugated epoxy esters (9a and b). The Z isomer (9b) was transformed to the E isomer (9a) by the action of tBuOK.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 261 - 267
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DOI: 10.3987/COM-98-S23
Studies on Novel and Chiral 1,4-Dihydropyridines. VI. Preparation of a Polymer-supported 1,4-Dihydropyridine Having a Chiral Sulfinyl Group and Its Application to Biomimetic Reduction

Satoshi Obika, Toshihiko Nishiyama, Satoshi Tatematsu, Masahiro Nishimoto, Kazuyuki Miyashita, and Takeshi Imanishi*

*Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan

Abstract

(SS)-3-(p-Tolylsulfinyl)-1,4-dihydropyridine was grafted on polymer matrix an N-1 position by the reaction between (SS)-1-lithio-3-(p-tolylsulfinyl)-1,4-dihydropyridine and Merrifield type resin. Asymmetric reduction with the polymer-supported 1,4-dihydropyridine was also studied.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 269 - 274
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DOI: 10.3987/COM-98-S26
Clavulazine, a New Marine Pyrazine Congener from the Okinawan Soft Coral Clavularia viridis

Kinzo Watanabe, Kazuo Iguchi,* and Ken Fujimori

*Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan

Abstract

A new marine pyrazine congener, clavulazine (2), was obtained from the polar portion of the MeOH extract of the Okinawan soft coral Clavularia viridis as its acetate (1). The structure of 2 was determined on the basis of spectral analysis and chemical conversion. The absolute configuration of 2 was unambigously determined by X-Ray crystallographic analysis on the p-bromobenzoate (3).

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 275 - 279
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DOI: 10.3987/COM-98-S28
Conformational Preference of Two Toad Poison Bufadienolides, Bufarenogin and ψ-Bufarenogin

Yoshiaki Kamano,* Ayano Kotake, Rui Takano, Hiroshi Morita, Koichi Takeya, and Hideji Itokawa

*Faculty of Science, Kanagawa University, 2946 Tsutiya, Hiratsuka, Kanagawa 259-1293, Japan

Abstract

The solution state conformations of two toad poison bufadienolides, bufarenogin and ψ-bufarenogin, which are the epimers at C-12, were analyzed by using NOE experiments and molecular dynamics simulation study. The C-ring of bufarenogin with 12β-hydroxy function was shown to take a chair form, whereas that of ψ-bufarenogin with 12α-hydroxy function, a boat form.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 281 - 296
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DOI: 10.3987/COM-98-S31
Synthesis of 2,2'-Bipyridines Bearing Amino or Carboxyl Group at the Side Chain and Physical Properties of Their Ruthenium(II) Complexes

Akira Katoh,* Yoshihiro Kitamura, Hideyuki Fujii, Yumi Horie, Tetsuji Satoh, Junko Ohkanda, and Yoshinobu Yokomori

*Department of Industrial Chemistry, Faculty of Engineering, Seikei University, Musashino, Tokyo 180-8633, Japan

Abstract

The synthesis of unsymmetrical 2,2’-bipyridines, in which one pyridine ring of bipyridine is linked to the amino or carboxyl group through the alkyl chain as the side chain became possible by the regioselective O-alkylation of pyridyl-2(1H)-pyridinones. Synthetic tris(bipyridine)ruthenium(II) showed characteristic metal-to-ligand charge transfer (MLCT) bands at around 480 nm. The standard redox potentials of new [Ru(bpy)3]2+ were about 200 mV lower than that of the parent [Ru(bpy)3]2+. The p-substituent effect of the benzene ring upon the redox potential was observed.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 297 - 303
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DOI: 10.3987/COM-98-S33
A Facile and Convenient Synthetic Method for Fluorine-containing Naphtho[1,2-e][1,4]diazepines, Naphtho[1,2-e][1,4]dithiepins and Naphtho[1,2-e][1,4]dioxepins

Etsuji Okada,* Norikado Tsukushi, Nobukazu Kunihiro, and Yoshitsugu Tomo

*Department of Chemical Science and Engineering, Faculty of Engineering, Kobe University, Kobe 657-8501, Japan

Abstract

N,N-Dimethyl-2,4-bis(trifluoroacetyl)-1-naphthylamine (1) reacted cleanly with 1,2-diamines, 1,2-ethanedithiol, and ethylene glycol to afford the corresponding naphtho[1,2-e][1,4]diazepines (2-4), naphtho[1,2-e][1,4]dithiepins (5), and naphtho[1,2-e][1,4]dioxepins (6), respectively, in excellent yields.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 305 - 314
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DOI: 10.3987/COM-98-S34
Intramolecular 1,5-Hydrogen Atom Transfer Radical Reaction of Pyrrolidine Derivatives

Miyuki Ishizaki, Hideaki Takano, and Osamu Hoshino*

*Faculty of Pharmaceutical Sciences, Science University of Tokyo, 12, Ichigaya Funagawara-machi, Shinjuku-ku, Tokyo 162-0826, Japan

Abstract

Intramolecular 1,5-hydrogen atom transfer radical cyclization reaction of pyrrolidine derivatives was examined. Radical reaction of 3,4-bis(α,β-unsaturated acyloxy)-(8,9) and 3,4-diacetoxy (13)-N-[(o-halobenzyl)pyrrolidines underwent elimination of two acyloxy groups to give mainly N-benzylpyrrole (11). On the other hand, the similar reaction of 3,4-diallyloxy-N-(o-bromobenzyl)pyrrolidine (16) gave desired hexahydrofuro[3,2-b]pyrroles (17,18) together with a dimeric hexahydrofuro[3,2-b]pyrrole (19).

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 315 - 325
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DOI: 10.3987/COM-98-S39
Chemical Conversion of Labdane-Type Diterpenoid Isolated from the Liverwort Porella perrottetiana into (-)-Ambrox

Toshihiro Hashimoto, Kousuke Shiki, Masami Tanaka, Shigeru Takaoka, and Yoshinori Asakawa*

*Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho Tokushima 770-8514, Japan

Abstract

As a part of our systematic investigation of biologically active substances of liverworts, the chemical conversion of labdabe-type diterpenoid, labda-12,14-dien-7α,8α-diol-(1) that the absolute configuration remained unidentified, isolated from the liverwort Porella perrottetiana into the animal perfume, (-)-ambrox (2) via 6 steps has been achieved. Consequently, the absolute configuration of 1 was determined.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 327 - 341
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DOI: 10.3987/COM-98-S40
Alkaloids of Some Mongolian Ranunculaceae Species: Detailed 1H- and 13C-NMR Studies of Denudatine and Lepenine

Dulamjav Batsuren, Jigjidsuren Tunsag, Nyamdari Batbaiar, Ali M. Mericli, Filiz Mericili, Quincy Teng, Haridutt K. Desai, Balawant S. Joshi, and S. William Pelletier*

*Institute for Natural Products Research, Department of Chemistry, The University of Georgia, Athens, Georgia 30602-2556, U.S.A.

Abstract

We have investigated the alkaloidal constituents of Aconitum barbatum, A. kusnezoffii, A. volubile, and Delphinium cheilanthum collected in Mongolia. Seven norditerpenoid and seven diterpenoid alkaloids were isolated and identified from these plants. 1H Decoupled 13C, 2D 1H phase sensitive COSY, ROESY, TOCSY, HMQC-TOCSY and HMBC NMR spectral studies were carried out on denudatine and lepenine to make definitive assignments for the carbon atoms of these alkaloids.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 343 - 354
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DOI: 10.3987/COM-98-S42
The Highly Stereocontrolled Radical-based Addition of a 2,2-Dichloroacyl Function to a 2-Oxazolone Heterocycle. A New Approach to MeBmt, the Key Component of Cyclosporin

Hirofumi Matsunaga, Hiroyoshi Ohta, Tadao Ishizuka, and Takehisa Kunieda*

*Faculty of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan

Abstract

The intramolecular Ru(II)-catalyzed addition of the 2,2-dichloro-4-hexenoyl pendant group to an 2-oxazolone moiety followed by treatment with (Me3Si)3SiH-Et3B provides a perfectly stereocontrolled approach to the unusual amino acid (2S,3R,4R,6E)-3-hydroxy-4-methyl-2-(methylamino)-6-octenoic acid (MeBmt), which contains three contiguous stereogenic centers and is a key component of cyclosporin.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 355 - 360
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DOI: 10.3987/COM-98-S43
Noelaquinone, a New Hexacyclic Triazine Quinone from an Indonesian Xestospongia Sp.

Ye Zhu, Wesely Y. Yoshida, Michelle Kelly-Borges, and Paul J. Scheuer*

*Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, U.S.A.

Abstract

Two derivatives of halenaquinone (1) have been isolated from a sponge, Xestospongia sp., from Derawan Island, Indonesia, In addition, a new quinone, which possesses an added triazine ring has been isolated. The regiochemistry of this compound was confirmed by spectroscopic methods.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 361 - 373
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DOI: 10.3987/COM-98-S45
Regioselective Metalation of γ-Carbolines

Cyril Papamicaël, Georges Dupas,* Guy Quéguiner, and Jean Bourguignon

*Laboratoire de Chimie Organique Fine et Hétérocyclique de l'IRCOF, UPRESA 6014 CNRS, Institut National des Sciences Appliquées de Rouen, BP08, 76131, Mont Saint Aignan Cédex , France

Abstract

The synthesis of new 3-substituted γ-carbolines is described and these products were subjected to ortho-lithiation experiments. Whereas 3-carboxamido derivatives (5a,b) were cleanly lithiated at 4-position, the 3-amino derivatives (6a,b) gave only small amounts of addition products. The results obtained are compared to those previously published in the α-carboline series and semi-empirical calculations were performed. Various 3,4-disubstituted γ-carbolines were obtained in acceptable yields.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 375 - 383
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DOI: 10.3987/COM-98-S49
The Structure and Antimalarial Activity of Some cis-Fused Bicyclic 1,2,4-Trioxane Derivatives

Charles W. Jefford,* Danielle Jaggi, Shigeo Kohmoto, Géza Timári, Gérald Bernardinelli, Craig J. Canfield, and Wilbur K. Milhous

*Department of Organic Chemistry and Laboratory of Crystallography, University of Geneva, 1211 Geneva 4, Switzerland

Abstract

(4aRS,7aRS)-4a,7a-Dihydro-3,3-dimethyl-6,7a-diphenyl-7H-cyclopenta[1,2-e][1,2,4]trioxine (1) was converted into its exo-5,6-epoxide (7) and dichloromethylene (8) derivatives. The reaction of (4’aRS,7’aRS)-6’,7’a-bis(4-fluorophenyl)-4’a,7’a-dihydrospiro[cyclopentane-1,3’-7’H-cyclopenta[1,2-e][[1,2,4]trioxine] (3) with Pb(OAc)4 and N-aminophthalimide gave the exo-5,6-N-phthalimidoimine (9). Acid catalysis of 9 afforded the cyclopentenylamino derivative (10). Treatment of 3 with Me3SiN3 and C6H5IO gave mainly the exo-5-azidobenzyl dimer (12) of C2 symmetry. A minor isomer was assigned as the meso-dimer (14). The structure of 12 was determined by X-Ray. The in vitro activity of 7,8,9,10 and 11 against Plasmodium falciparum was determined and found, with the exception of 8, to be similar to that of 1 and 3.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 385 - 392
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DOI: 10.3987/COM-98-S50
Mercurophilic Property of 23-Dicyanomethylene-5,8,11,14,17-pentaoxa-2,20-dithiabicyclo[19.4.1]hexacosa-1(26),21,24-triene

Kanji Kubo, Akira Mori,* Nobuo Kato, and Hitoshi Takeshita

*Institute of Advanced Material Study, 86, Kyushu University, Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan

Abstract

23-Dicyanomethylene-5,8,11,14,17-pentaoxa-2,10-dithiabicyclo[19.4.1]hexacosa-1(26),21,24-triene (1) showed selective transport of mercury(II) ion through a liquid membrane. The effective transport of mercury(II) ions was likely to correspond to association constants. Both the association constant and the transport rate of 1 were greater than the troponoid dithiocrown ether, 5,8,11,14-tetraoxa-2,17-dithiabicyclo[16.4.1]tricosa-18,20,22-trien-23-one (2). In the crystal structure of the mercury(II) chloride complex of 1, the mercury(II) atom was surrounded by only the five oxygen donor atoms in a pentagonal bipyramidal coordination. The sulfur atoms of 1 are far from the coordination to the mercury(II) ion.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 393 - 404
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DOI: 10.3987/COM-98-S51
Iron Chelators of the Pyridoxal-based Class. Part 7. The Synthesis and Single Crystal Structure of 1-(N-Ethoxy-carbonylmethylpyridoxyledenium)-2-(pyrimidyl)hydrazine Salts

Shalom Sarel,* Shelly Avramovici-Grisaru, and Shmuel Cohen

*Department of Medicinal Chemistry, Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 91120, Israel

Abstract

The syntheses of 1-pyridoxylidene-2-(2’-pyrimidyl)hydrazine (1), 1-(N-methylpyridoxylidenium)-2-(2’-pyrimidyl)hydrazine iodide (2), and 1-(N-ethoxycarbonylmethylpyridoxylidenium)-2-(pyrimidyl)hydrazine bromide (5a), and 1-(N-ethoxycarbonylmethylpyridoxylidenium)-2-(2’-pyrimidyl)hydrazine perchlorate (5b) are described. The single-crystal structure of 5b was determined from three-dimensional X-Ray data. Compound (5b), C16H22N5O8Cl, crystallizes in the space group P21/c with Z = 4 and the following cell dimensions: a = 12.363 (3)Å, b = 17.168(5)Å, c = 9.657(3)Å. The X-Ray data confirm that 5b crystallizes in the di-polar form, as a planar 20-membered ring dimer {preferred motif of R2(20)}. All the three proton-donors (O1-H, O2-H, and N3-H), and only three (N2,N5,O2) of the five available proton-acceptors 5b, are utilized in hydrogen-bonding.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 405 - 413
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DOI: 10.3987/COM-98-S54
Synthesis of 2-Aroylquinoxalines, 1-Aroylphthalazines, and 4-Aroylcinnolines; an Aroylation Method Using Arenecarbaldehydes Catalyzed by Azolium Salt

Akira Miyashita,* Yumiko Suzuki, Ken-ichi Iwamoto, Etsuo Oishi, and Takeo Higashino

*Schol of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan

Abstract

2-Aroylquinoxalines (5,6), 1-aroylphthalazines (10,11), and 4-aroylcinnolines (13) were synthesized by using arenecarbaldehydes (2) in the presence of an azolium salt (1) in moderate to good yields. 1,3-Dimethylimidazolium iodide (1a) and sodium sulfinate (7) were also effective catalysts in this aroylation.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 415 - 426
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DOI: 10.3987/COM-98-S58
Site Specificity in 1,3-Dipolar Cycloadditions to a Polycyclic Polyene Induced by Complexation with Tricarbonyliron

Mauro Freccero, Remo Gandolfi,* and Mirko Sarzi-Amade'

*Dipartimento di Chimica Organica, Universita' di Pavia, V. le Taramelli 10, 27100 Pavia, Italy

Abstract

Treatment of dimethyl tricyclo[4.2.2.02,5]deca-3,7,9-triene-7,8-dicarboxylate (1) with nonacarbonyldiiron led to dimethyl 7-10-tetrahaptotricyclo[4.2.2.02,5]deca-3,7,9-triene-7,8-dicarboxylate tricarbonyliron (12). This derivative reacted smoothly with several 1,3-dipoles (nitrones, nitrile oxides, nitrile imines and diazoalkanes) at the cyclobutene double bond to give adducts from which the tricarbonyliron group could be easily removed by oxidative decomplexation with trimethylamine N-oxide. Thus, a formal site specific attack of 1,3-dipoles to 1 was achieved.

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Paper | Special issue | Vol 49, No. 1, 1998, pp. 427 - 436
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DOI: 10.3987/COM-98-S61
The Isolation and Structure of the Novel cis-Fused Indolizidine 249H from Frog Skin: cis- vs. trans-Fused Indolizidines Distinguished by NMR

Takashi Tokuyama, Atsushi Shimada, H. Martin Garraffo, Thomas F. Spande, and John W. Daly*

*Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0820, U. S. A.

Abstract

A 5,6,8-trisubstituted indolizidine structure (1) is proposed for alkaloid 249H isolated from dendrobatid frogs based upon NMR and IR spectroscopy and MS spectrometry. It has an unusual (E)-3-hexen-3-yl side-chain, the first branched substituent reported among the simple indolizidines from frog skin, an unusual cis-fused indolizidine ring and finally an atypical E configuration of H-5 relative to H-9.

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Note | Special issue | Vol 49, No. 1, 1998, pp. 437 - 444
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DOI: 10.3987/COM-97-S1
Syntheses and Biological Evaluation of (±)-3a-Phenyl Congeners of Physostigmine and Phenserine

Xue-Feng Pei, Nigel H. Greig,* and Arnold Brossi

*Drug Design & Development, Laboratory of Cellular & Molecular Biology, National Institute on Aging, National Institutes of Health, 4940 Eastern Avenue, Baltimore, MD 21224, U.S.A.

Abstract

(±)-3a-Phenyl congeners of physostigmine and phenserine, synthesized for the first time by a modification of the Julian total synthesis of physostigmine, were evaluated for anticholinesterase action against human acetyl- and butyrylcholinesterase. These analogues were found to lack cholinesterase inhibitory activity, demonstrating that sterically bulky substitution at the 3a position is poorly tolerated.

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Note | Special issue | Vol 49, No. 1, 1998, pp. 445 - 450
Published online:
DOI: 10.3987/COM-98-S9
Preparation of (±)-Hirsutine and (±)-3-Isocorynantheidine

Mauri Lounasmaa,* Reija Jokela, Christiane Laine, and Pirjo Hanhinen

*Laboratory for Organic and Bioorganic Chemistry, Technical University of Helsinki, FIN-02150 Espoo, Finland

Abstract

Preparation of indole alkaloids (±)-hirsutine (1) and (±)-3-isocorynantheidine (2) is described.

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Note | Special issue | Vol 49, No. 1, 1998, pp. 451 - 457
Published online:
DOI: 10.3987/COM-98-S18
A Five-Step Synthesis of Psilocin from Indole-3-carbaldehyde

Fumio Yamada, Mayumi Tamura, and Masanori Somei*

*Faculty of Pharmaceutical Scicences, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-0934, Japan

Abstract

A novel preparative method of psilocin was established in only five steps from indole-3-carbaldehyde in 50% overall yield.

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Note | Special issue | Vol 49, No. 1, 1998, pp. 459 - 464
Published online:
DOI: 10.3987/COM-98-S24
A Convenient Preparation of α-Keto Esters by the Grignard Reaction on N-Acylpyrazoles

Choji Kashima,* Yoshie Shirahata, and Yoshihiro Tsukamoto

*Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki, 305-8571, Japan

Abstract

The α-keto esters were prepared by the formation of N-acylpyrazole followed by the appropriate Grignard reaction. These short step reaction conveniently afforded various α-keto esters in good yields.

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