HETEROCYCLES
An International Journal for Reviews and Communications in Heterocyclic ChemistryWeb Edition ISSN: 1881-0942
Published online by The Japan Institute of Heterocyclic Chemistry
Special Issue
Volume 50's Special Issues, Vol. 50, No. 1, 1999
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■ Reactions of Alkyl Methyl Ketoximes with Tetrasulfur Tetranitride Antimony Pentachloride Complex (S4N4ÅESbCl5): A Regioselective Formation of 3-Alkyl-4-methyl-1,2,5-thiadiazoles and Their Mechanism of Formation
Kil Joong Kim and Kyongtae Kim*
*Department of Chemistry, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Gu, Seoul 151-742, Korea
Abstract
Treatment of alkyl methyl ketoximes with terasulfur tetranitride antimony pentachloride complex (S4N4.SbCl5) in aromatic solvents such as benzene and toluene at 60°C led to the regioselective formation of 3-alkyl-4-methyl-1,2,5-thiadiazoles in low yields, whereas the reactions of alkyl aryl ketoximes under the same conditions gave exclusively N-arylakanamides in good yields. A mechanism is proposed for the formation of 3-alkyl-4-methyl-1,2,5-thiadiazoles.
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■ Photochemical Transformation of Trithiobarbiturate into Thiohydantoin and Imidazolinothiophene Derivatives
Haruko Takechi,* Hajime Takahashi, and Minoru Machida
*Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
Abstract
Upon irradiation of trithiobarbiturate (1), ring contraction reaction occurred to give thiohydantoin (2 or 3) and imidazolinothiophene (4) derivatives. Further, on treating with iodine, the thiohydantoins (2 and 3) undergo ring closure, giving imidazolinothiophene derivatives (4).
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■ Synthesis of Vinca Alkaloids and Related Compounds. Part XCIII. Skeletal Rearrangement of Cyclovinblastine Derivatives: Formation of a Novel Bisindole System
Katalin Honty, Ádám Demeter, Csaba Szántay Jr., Miklós Hollósi, Pál Kolonits, and Csaba Szántay*
*Department of Organic Chemical Technology, Technical University Budapest, H-1521 Budapest, Gellért tér 4, Hungary
Abstract
Bisindole alkaloids of the vinblastine (VLB) type can be oxidized to give a ψ-aspidosperma-aspidosperma type skeleton via 3‘-7‘-transannular cyclization. Acid catalysis triggers an aspidospermane→eburnane skeletal rearrangement of these cyclic derivatives, thus giving a novel bisindole system with a ψ-eburnea-aspidosperma type skeleton. A previously unexplored aspect of this transformation is the obsereved retention or inversion at C(16’) depending on the starting C(16’) configuration. The present paper gives a detailed account of the synthetic aspect of this work together with preliminary NMR and CD results concerning the epimerization at C(16’).
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■ Synthesis and Reaction of S-Trimethylsilylmethyl Carbonimidodithioate Derivatives: Synthetic Equivalent of Thiocarbonyl Ylide
Makoto Oba, Masahiro Yoshihara, Chiharu Roppongi, and Kozaburo Nishiyama*
*Department of Material Science and Technology, Tokai University, 317, Nishino, Numazu, Shizuoka 410-0395, Japan
Abstract
S-Trimethylsilymethyl carbonimidodithioate derivatives (2-5) prepared by an addition of trimethylsilylmethanethiol (1) toward the isothiocyanate followed by S-alkylation were found to react with various carbonyl compounds in the presence of fluoride ion to give oxathiolane derivatives (6-9) in moderate yields, in which the silylated carbonimidodithioate derivatives formally served as thiocarbonyl ylide equivalents.
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■ Addition of 1-Boc-2-tert-butyldimethylsilyloxy-pyrrole to N-Methyleneamine Equivalents: Synthesis of1-Boc-5-aminomethyl-2,5-dihydropyrrol-2-ones and 1-Boc-2-oxo-1,7,9-triazaspiro[4,5]dec-3-enes
Hyun-Joon Ha,* Jang-Min Suh, Young-Gil Ahn, Yongkwan Dong, and Hoseop Yun
*Department of Chemistry, Hankuk University of Foreign Studies, Yongin, Kyunggi-Do, 449-791, Korea
Abstract
N-Methyleneamine equivalents generated from 1,3,5-triphenylhexahydro-1,3,5-triazines or N-methoxymethylanilines reacted with 1-Boc-2-tert-butyldimethylsilyloxypyrrole to give 1-Boc-5-anilinomethyl-2,5-dihydropyrrol-2-ones. However , the same reaction from 1,3,5-trialkylhexahydro-1,3,5-triazines yielded unexpected product of 1-Boc-7,9-dialkyl-2-oxo-1,7,9-triazaspiro[4,5]dec-3-enes.
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■ Synthesis of β-Substituted and α,β-Disubstituted δ-Carbolines Using a Halogen-Dance Reaction
Erwan Arzel, Patrick Rocca, Francis Marsais, Alain Godard, and G. Quéguiner*
*Institut de Recherche en Chimie Organique Fine, UPRESA 6014, INSA de Rouen, Place Emile Blondel, BP 08, 76131 Mont-Saint-Aignan Cedex, France
Abstract
The paper describes the first total syntheses of β-substituted δ-carbolines and α,β-disubstituted δ-carbolines strating from benzene and pyridine blocks using a halogen-dance reaction.
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■ Packing Modes in Eight 3-Ethoxycarbonylpyrazole Derivatives. Influence of the Substituents on the Crystal Structure and Annular Tautomerism
Lourdes Infantes, Concepción Foces-Foces,* Rosa M. Claramunt,* Concepción López, Nadine Jagerovic, and José Elguero*
*Centro de Química OrgÁnica 'Manuel Lora-Tamayo', Instituto de Química Médica, C. S. I. C., Calle Juan de Cierva, 3, E-28006 Madrid, Spain
Abstract
The crystal and molecular structures of eight N-unsubstituted ethoxycarbonylpyrazole derivatives have been determined by X-Ray analysis. The molecules are linked by bifurcated N-H···N/O bond giving rise to two hydrogen-bonding motifs: catemers and teramers that are further joined by weak interaction. Different packing modes are observed depending on the substituent at C5. The 3-ethoxycarbonyl-4-bromo-5-phenylpyrazole presents temperature dependent solid-solid phase transition. Having determined that all these compounds are 3-ethoxycarbonyl tautomers in the solid state, their annular tatuomerism was studied by 13CNMR spectroscopy.
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■ Substituent Effects on the Rate of Acid-catalysed Epimerization of Indolo[2,3-a]quinolizidines
Mauri Lounasmaa,* Mathias Berner, and Arto Tolvanen
*Laboratory for Organic and Bioorganic Chemistry, Technical University of Helsinki, P.O. Box 6100, FIN-02150 HUT Espoo, Finland
Abstract
10-Substituted indolo[2,3-a]quinolizidine derivatives were prepared to study the effect of substituents on the epimerization rate. Under the conditions employed, electron withdrawing substituents hindered epimerization and electron donating substituents accelerated it.
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■ Oxidation and Rearrangement of 5-Substituted 5-Ethoxycarbonyl[1,2,4]triazolidine-3-thiones
Joachim G. Schantl,* Sergius Lang, and Klaus Wurst
*Institut für Organische Chemie, Universität Innsbruck, Innrain 52, A-6020 Innsbruck, Austria
Abstract
The reaction of ethyl 2-(phenylhydrazono)alkanoates (1) with potassium thiocyanate in acetic acid affords 5-ethoxycarbonyl-substituted [1,2,4]triazolidine-3-thiones (3). Oxidation (KMnO4) converts 3 into 1-ethoxy-carbonyl-2,3-dihydro-1H-[1,2,4]triazole-3-thiones (9) as evidenced by the X-Ray structure analysis of 9a. Products (9) result from an oxidative conversion of 3 to the intermediates (5) and the cyclic valence isomers (7) followed by [1,5]sigmatropic rearrangement selectively involving the 5-ethoxycarbonyl group to migrate.
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■ An Efficient Preparative Route to Fused Imidazo[1,2-a]pyrazin-4-one Derivatives
Dominique Damour, Jean-Claude Aloup, Michel Barreau, Arielle Genevois-Borella, Patrick Jimonet, Jean-Pierre Leconte, Yves Ribeill, Marc Vuilhorgne, and Serge Mignani*
*Rhône-Poulenc Rorer S.A., Centre de Recherche de Vitry-Alfortville, 13 Quai Jules Guesde, 94400, Vitry-sur-Seine, France
Abstract
New fused imidazo[1,2-a]pyrazin-4-one derivatives (1a-f) are easily obtained from ring closure reactions of ethyl imidazole-2-carboxylate derivatives (4a,c,d) or imidazole-2-carboxamide derivatives (5b,e).
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■ A New Flavonol from Murraya paniculata var. omphalocarpa: 13C-NMR as a Useful Tool for Structure Elucidation of Polyoxyflavones
Takeshi Kinoshita
*Faculty of Pharmaceutical Sciences, Teikyo University, 1091-1 Suarashi, Sagamiko-machi, Tsukui-gun, Kanagawa 199-0195, Japan
Abstract
A highly oxgenated flavone was isolated from the leaves of Murraya paniculata var. omphalocarpa (Rutaceae). The spectroscopic analysis of this compound revealed the presence of an unusual para-diphenol moiety in the A ring and its structure was finally elucidated as 3’,4’,6,7-tetramethoxy-3,5,8-trihydroxyflavone (1). The assignment of 13C resonances of nineteen polyoxyflavones was also made by use of 2D correlation spectroscopy and the usefulness of 13CNMR for identifying polyoxyflavones was discussed.
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■ Photoreaction of Arenecarbothioamides with Furan. Facile Synthesis of Pentagonal Di- and Tri-heterocyclic Compounds
Kazuaki Oda,* Masayuki Sakai, Kosei Ohno, and Minoru Machida*
*Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
Abstract
Irradiation of arenecarbothioamides with furan in methanol gave 2-arylpyrrole derivatives in moderate yields. This reaction was applied to the synthesis of pentagonal di- and tri-heterocyclic compounds.
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■ A Study of Biflavanones from the Stems of Garcinia kola (Guttiferae)
Kenji Terashima, Yoshihito Kondo, Mohammad Aqil, Maimuna Waziri, and Masatake Niwa*
*Faculty of Pharmacy, Meijo University, 150 Yagoto, Tempaku-ku, Nagoya, Aichi 468-8503, Japan
Abstract
A new biflavanone (1) named (+)-GB-1b was isolated together with five known biflavonoids from the stem of Garcinia kola Heckel (Guttiferae) collected in Nigeria. The structure was characterized by analyses of the spectral data. The stereostructures of (-)-GB-1a, (+)-GB-1b and (-)-GB-2a are also discussed on the basis of chemical and spectroscopic evidence. Furthermore, 3,8”-biflavanones were successfully converted to 3,6”-biflavanone under thermal conditions.
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■ 1,3-Oxathiane Ring Formation through Intramolecular Pummerer Reaction of Alkyl ortho-Hydroxymethylphenyl Sulfoxides
Hitoshi Abe,* Kentaro Shibaike, Hiroyuki Fujii, Daisuke Tsuchida, Teruaki Akiyama, and Takashi Harayama*
*Faculty of Pharmaceutical Science, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8530, Japan
Abstract
The intramolecular Pummerer rearrangement of 2-(2-alkyl-sulfinylphenyl)-2-propanols (1a, 1c-1g) yielded 1,3-oxathianes (2a,2c-2g) in the presence of p-toluenesulfonic acid and molecular sieves 3A. Alkyl halides were converted into 1,3-oxathiane derivatives in three steps via this rearrangement.
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■ Synthesis of 6-(Bromoacetyl)amino-2,3-dimorpholinoquinoxaline and Application to a New Fluorescence Derivatization Reagent of Fatty Acids for the High-Performance Liquid Chromatographic Analysis
Akira Katoh,* Takeshi Fujimoto, Motoki Takahashi, and Junko Ohkanda
*Department of Industrial Chemistry, Faculty of Engineering, Seikei University, Musashino-shi, Tokyo 180-8633, Japan
Abstract
6-Amino-2,3-dimorpholinoquinoxaline (3) was allowed to react with bromoacetic acid in the presence of DCC to give 6-(bromoacetyl)amino-2,3-dimorpholinoquinoxaline (4). Five kinds of saturated fatty acids (C10,C12,C14,C16,and C18) were subjected to the derivatization with compound (4) within 50 min to afford the corresponding fluorescent products (5a-e). All the peaks of the derivatized products clearly separated within 15 min. The detection limit of decanoic acid (C10) was estimated to be 10 fmol/10μL injection volume (S/N=4).
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■ Synthesis of New Podand Possessing Three Tropolonoids Connected by Two Oligoethylene Glycol Chains
Tadahiro Kato,* Takehisa Kato, Takuro Kanbe, Yoshiko Tokuno, and Shigeyuki Kikumoto
*Department of Chemistry, Faculty of Science, Science University of Tokyo, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan
Abstract
For the purpose of exploitation of new podands possessing positive coopertivity in cation binding, three tropolonoid moieties are connected by two oligoethylene glycol chain. This note describes the preparation of diethylene to pentaethylene glycol derivatives possessing three tropolonoids(4n).
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■ 4-Dimethylaminomethylene-2-pyrazinyl-5(4H)-oxazolone as a Synthon for the Synthesis of Various Pyrazoles and Fused Pyrimidines
Vladimir Kepe, Viktor Kozjan, Slovenko Polanc, and Marijan Kočevar*
*Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, P.O. Box 537, SLO-1000 Ljubljana, Slovenia
Abstract
4-Dimethylaminomethylene-2-pyrazinyl-5(4H)-oxazolone(2) has been synthesized and transformed into various 1,4-disubstituted 1,2-dihydro-5H-pyrazol-5-ones (6) and fused pyrimidinones (8) by the reaction with selected hydrazines (5) and aminoheterocycles (7). Products (6) and (8) have also been prepared from methyl 3-dimethylamino-2-(pyrazinylcarbonylamino)propenoate (3) and nitrogen-containing nucleophiles (5) or (7).
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■ A New Route for Preparation of 5-Deoxy-5-hydroxyphosphinyl-D-gluco- and L-idopyranose Derivatives
Tadashi Hanaya,* Yasushi Fujii, Satoru Ikejiri, and Hiroshi Yamamoto*
*Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
Abstract
By strating with known 3,6-di-O-benzyl-1,2-O-isopropylidene-α-D-xylo-hexofuranos-5-ulose (5), the 3,6-di-O-benzyl derivatives (8 and 10) of the title phosph-sugar analogs were prepared in six steps through the key intermediates, 5-deoxy-5-dimethoxyphosphinyl-1,2-O-isopropylidene-α-D-gluco- and -L-idofuranoses (7a and 7b), respectively. These products ( 8 and 10 ) were respectively converted into the corresponding 1,2,4-tri-O-acetyl-5-methoxyphosphinyl derivatives ( 9 and 11), whose structures and conformations ( mostly in 4C1 ) were established by spectrospy.
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■ New Stereoselective Synthesis of (±)-trans-2-Butyl-5-heptyl-1-methylpyrrolidine, Ant Venom Alkaloid, by Aminyl Radical Cyclization
Hisanori Senboku,* Hikaru Hasegawa, Kazuhiko Orito, and Masao Tokuda*
*Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Abstract
New synthesis of (±)-trans-2-butyl-5-heptyl-1-methylpyrrolidine (1), ant venom alkaloid, was alkaloid, was achieved by the use of stereoselective cyclization of aminyl radicals. Thus, orthoester Claisen rearrangement of 1-hexen-3-ol (2) gave (E)-ethyl 4-octenoate (3). Reaction of ester (3) with 2-methylaminopyridine and AlCl3 afforded the corresponding N-methyl-N-(2-pyridyl)amide (4), which was treated with heptylmagnesium iodide at -78°C to give (E)-4-pentadecen-8-one (5). Reductive amination of ketone (5) with methylamine gave N-methyl-1-heptyl-4-octenylamine (6). Treatment of amine (6) with NCS in toluene gave the corresponding N-chloromine (12), and successive heating under reflux with Bu3SnH and AIBN resulted in stereoselective cyclization of the aminyl radical to give (±)-trans-2-butyl-5-heptyl-1-methylpyrrolidine (1) in a 59% yield. Similarly, give (±)-trans-2-butyl-5-heptyl-1-methylpyrrolidine (1) in a 59% yield. Similarly, 1-nonen-3-ol (7) was converted into N-methyl-1-butyl-4-undecenylamine (11), which was subjected to the aminyl radical cyclization to give 1 in a 49% yield.
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■ Coupling of Consecutive Pyridine Ring Units for Oligopyridine Synthesis
Jun'ichi Uenishi,* Tetsuya Ueno, Sin'ichiro Hata, Kenji Nishiwaki, Takakazu Tanaka, Shoji Wakabayashi, Osamu Yonemitsu, and Shigeru Oae
*Department of Chemistry, Faculty of Science, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005, Japan
Abstract
The reaction of 2-ethylsulfinyl-6-(ethylthio)pyridine (2), 6-ethylsulfinyl-6'-ethylthio-2,2'-bipyridine (6), and 6-ethylsufinyl-6''' -ethylthio-2,2'': 6',2'':,6'': ,2'''-quaterpyridine (10) with methylmagnesium bromide gave synmmetric oligopyridines 6,6'-bis(ethylthio)-2,2'-bipyridine (4), 6,6'''-bis(ethylthio)-2,2': 6',2'': 6'',2'''-quaterpyridine (8), and 6,6'''''''-bis(ethylthio)-2,2':6', 2'': 6'', 2''': 6''', 2'''': 6'''', 2''''': 6''''', 2'''''': 6'''''', 2'''''''-octipyridine (12) in respective yield of 70,56, and 3%. On the other hand, the reaction of 6 and 10 with 2-(6-bromopyridinyl)lithium and 6-(2,2'-bipyridinyl)lithium gave the corresponding unsymmetric oligopyridines (15,16,13,and 19). The reaction with chiral (S)-2-{6-[1-(tert-butyldimethylsiloxy)ethyl]pyridinyl}lithium gave optically active oligopyridines (17) and (18) in 78 and 58% yields, respectively.
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■ Isoquinolinium N-Arylimides and trans-Cyclooctenes
Rolf Huisgen,* Francisco Palacios-Gambra, Kurt Polborn, and Dieter Boeckh
*Institut für Organische Chemie, Universität München, Karlstrasse 23, D-80333 München, Germany
Abstract
The inertness of isoquinolinium N-arylimides (5a,b) versus common cycloalkenes is overcome by the highly reactive (E)-cyclooctene and (E, Z)-1,5-cyclooctadiene. NMR spectra and an X-Ray analysis established the retentio of dipolarophile configuration in the cycloadducts (7a,b) and (9a,b) which were obtained in > 90% yield. Acid-base catalysis effects the opening of the pyrazo-lidine ring by β-elimination ; the products are 1-[trans-2-arylaminocyclooctyl]isoquinolines (8,10).
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■ Expansion of Ring B in the Gibberellins: Entry to the Rabdosia Family of Kaurenoids
Lynda J. Benjamin, George Adamson, and Lewis N. Mander*
*Research School of Chemistry, Institute of Advanced Studies, Australian national University, Canberra, ACT 0200, Australia
Abstract
The Lewis acid or base-catalysed rearrangement of an α-hydroxyaldehyde derived from the gibberellin GA15 results in ring-expansion of the 5-membered B-ring of the gibberellin molecule and transformation into an ent-kaurene derivative. Further manipulation affords 19,7-acetals and access to the highly functionalised kaurenoid secondary metabolites that have been isolated from the genus Rabdosia.
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■ A Simple Synthetic Method for Fluorine-containing 4H-Pyrano[3,2-d]isoxazoles and 4-Cyanoethylisoxazoles from 5-Trifluoroacetyl-2-methoxy-3,4-dihydro-2H-pyran with Hydroxylamine Hydrochloride
Etsuji Okada,* Hiroshi Okumura, Yukihiro Nishida, and Takeshi Kitahora
*Department of Chemical Science andd Engineerring, Faculty of Engineering, Kobe University, Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
Abstract
5-Trifluoroacetyl-2-methoxy-3,4-dihydro-2H-pyran (1), prepared from 2-methoxy-3,4-dihydro-2H-pyran with trifluoroacetic anhydride, reacted clenly with hydroxylamine hydrochloride in alcohol to give fluorine-containing 4H-pyrano[3,2-d]isoxazoles (2a-g) or 4-cyanoethyldihydroisoxazoles (3) selectively in moderate to high yields. Further conversion of 3 into 4-cyanoethylisoxazoles (4) was also described.
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■ Diversity of Rearrangement of 3-Substituted 5-Carbamoyl-1-phenyluracil Derivatives
Hironao Sajiki, Yoshiaki Fujita, Itaru Niimoto, and Kosaku Hirota*
*Labolatory of Medicinal Chemistry, Gifu Pharmaceutical University, 6-1 Mitahora-higashi 5-chome, Gifu 502-8585, Japan
Abstract
Treatment of 3-substituted 5-carbamoyl-1-phenyluracil derivatives (1a-c) with NaH afforded 5-(N-substituted carbamoyl)-1-phenyluracil derivatives (2a-c) via rearrangement involving the rare C(2)-N(3) bond cleavage of a uracil ring system. Upon reaction of 5-N -methylcarbamonyl-1-phenyluracil derivatives (4a and 4b) and 3-methyl-1-phenyl-5-thiocarbamoyluracil (6) with NaH, 5-(anilinomethylene) barbituric acid derivatives (5a, b and 7) formed, respectively, via rearrangement involving the N(1)-C(2) bond cleavage.
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■ 1,4-Addition of Organolithium Compounds to 6-Ethoxy-3-phenyl-6H-1,2-oxazine
Reinhold Zimmer, Florian Hiller, and Hans-Ulrich Reissig*
*Institut für Organische Chemie, Technische Universität Dresden, Mommsenstr. 13, D-01062 Dresden, Germany
Abstract
Addition of organolothium compounds to 6-ethoxy-3-phenyl-6H-1,2-oxazine (1) proceeds in conjugate fashion generating 4-lithiated 1,2-oxazines. After trapping with various electrophiles 1,2-oxazines (2 - 9) were generally isolated in good yield and with predominant 4,5-trans / 5,6-trans-arrangement of the newly introduced substituents. Scope and limitations of this new route to tetrasubstituted 1,2-oxazines are discussed.
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■ First Synthesis of gem-Difluorothiiranes from Cycloaliphatic Thioketones and Difluorocarbene
Grzegorz Mloston,* Jaroslaw Romanski, and Heinz Heimgartner*
*Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
Abstract
The reaction of sterically crowded cycloaliphatic thioketones with phenyl(trifluoromethyl)mercury and sodium iodide in boiling benzene yielded gem-difluorothiiranes in fair yields whereas in the case of aromatic thioketones gem-difluoroalkenes were obtained. The formation of these products is rationalized by an addition of difluorocarbene onto the C,S-double bond, followed by the extrusion of sulfur.
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■ Absolute Stereostructures of 3S-Phyllodulcin, 3R- and 3S-Phyllodulcin Glycosides, and 3R- and 3S-Thunberginol H Glycosides from the Leaves of Hydrangea macrophylla SERINGE var. thunbergii MAKINO
Masayuki Yoshikawa,* Toshiyuki Murakami, Tomohiko Ueda, Hiroshi Shimoda, Johji Yamahara, and Hisashi Matsuda
*Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan
Abstract
A new dihydroisocoumarin, 3S-phyllodulcin, and nine new dihydroisocoumarin glycosides, 3R- and 3S-phyllodulcin 3’-O-glucosides, 3R- and 3S-thunberginol H 8-O-glucosides, 3R- and 3S -thunberginol I 4’-O-glucosides, 3R- and 3S-hydrangenol 4’-O-apiosylglucosides, and thunberginol I 8-O-glucoside, were isolated from the leaves of Hydrangea macrophylla SERINGE var. thunbergii MAKINO. The absolute stereostructures of 3S-phyllodulcin, 3R- and 3S-phyllodulcin 3’-O-glucosides, and 3R- and 3S-thunberginol H 8-O-glucosides were elucidated on the chemical and physicochemical evidence. Phyllodulcin from the unprocessed leaves was found to be ca.a 5:1 enantiomer mixure at the 3-position.
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■ Thiazole as Leaving Group. Thermal Elimination from Thiazolylketoses
Alessandro Dondoni* and Alberto Marra
*Dipartimento di Chimica, Laboratorio di Chimica Organica, Università degli Studi di Ferrara, Via Fossato di Mortara 17-19, I-44100 Ferrara, Italy
Abstract
Heating tiazolylketofuranoses and -ketopyranoses in refluxing toluene results in the elimination of thiazole and formation of the corresponding sugar lactones in nearly quantitative yield. The same reaction does not occur with 1-O-acetyl and 1-O-trimethylsilyl derivatives. Also model furyl- and thienyl-ketofuranoses and various thiazolyl alcohols proved to be stable under the above thermolysis conditions. A possible mechanism of the observed thermolysis of thiazolylketoses involves the thiazolium 2-ylide as the actual group.
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■ A Facile Construction of the Woodward Ketone by a Zinc(II) Chloride-catalyzed Stille Coupling Reaction
Kogyoku Shin and Kunio Ogasawara*
*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan
Abstract
The pentacyclic ketone, obtained by Woodward and co-workers during the first total synthesis of strychnine, has been prepared in a five-step sequence from 2-methyltryptamine by employing a zinc(II) chloride-catalyzed Still coupling reaction as the key step.
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■ Enantio- and Diastereoselective Synthesis of (+)-Asperlin by the Sharpless Asymmetric Kinetic Resolution of an Unsymmetrical Divinylcarbinol
Kazuo Kanai, Nobuko Sano, and Toshio Honda*
*Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
Abstract
An enantio- and diastereoselective synthesis of (+)-asperlin was achieved by employing the Sharpless asymmetric kinetic resolution of an unsymmetrical divinylcarbinol.