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
Koji Nakanishi's Special Issues, Vol. 47, No. 1, 1998
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■ Total Synthesis of NPTX-643, a Neurotoxin of the Madagascar Spider (Nephilengys borbonica ) Having a Novel Acylpolyamine Structure
Masaaki Miyashita,* Takanori Kanemura, Masayuki Matsushita, Susumi Hatakeyama, Yasuhiro Itagaki, Terumi Nakajima, Masahiro Miyazawa, and Hiroshi Irie
*Division of Chemistry, Graduate Sachool of Sceince, Hokkaido University, Sapporo 060-0810, Japan
Abstract
The first total synthesis of NPTX-643, a neurotoxin of the Madagascar spider (Nephilengys borbonica) having a unique cadaverine - nor-putreanine - putreanine acylpolyamine chain, has been achieved by using three key azide intermediates.
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■ Mitsunobu Type C-N Bond Formation with 4,7-Dimethyl-3,5,7-hexahydro-1,2,4,7-tetrazocin-3,8-dione(DHTD), a New Cyclic Azodicarboxamide
Tetsuto Tsunoda,* Yumi Kawamura, Kaori Uemoto, and Shô Itô*
*Faculty of Pharmaceutical Sciences, Tokushima Bunri University, 180 Nishihamabouji, Yamashiro-machi, Tokushima, 770-8514, Japan
Abstract
The combination of 4,7-dimethyl-3,5,7-hexahydro-1,2,4,7-tetrazocin-3,8-dione (DHTD) and tributylphosphine (TBP) was found to mediate successfully C-N bond formation between N-methyltosylamide, a typical N-nucleophile, and several alcohols of different structural types. The unique feature of this combination is that it activates the reaction of sec-alcohols at room temperature.
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■ 5-endo-trig Radical Cyclization of 2-Chloro- and 2,2-Bis(phenylthio)-N-methyl- N-(6-phenylcyclohex-1-en-1-yl)-acetamides
Masazumi Ikeda,* Shinji Ohtani, Michiyo Okada, Emi Minakuchi, Tatsunori Sato, and Hiroyuki Ishibashi
*Kyoto Pharmaceutical University, Misasagi-Shichonocho, Yamashina, Kyorto 607-8414, Japan
Abstract
Treatment of 2-chloro-N-methyl-N-(6-phenylcyclohex-1-en-1-yl)acetamide (4a) with Bu3SnH in the presence of AIBN gave a 2.5: 1 mixture of cis- and trans-fused N-methyl-7-phenyloctahydroindol-2-ones (5a and 5b) (13% combined yield), N-methyl-N-(2-phenylcyclohex-1-en-1-yl)acetamide (6) (19%), N-methyl-N-(6-phenylcyclohex-1-en-1-yl)acetamide (7) (13%), and N-(cyclohex-1-en-1-yl)-N-methyl-2-phenylacetamide (8) (4%). Similar treatment of the 2,2- bis(phenylthio)acetamide (4b) gave a 1:1 mixture of 5a and 5b (61% combined yield) along with 6 (24%) and 7 (trace). Possible mechanisms for the formation of the products (6)-(8) are also discussed.
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■ Base-catalyzed Rearrangement of α-Benzotriazolyl Alkoxide Anions: Synthesis of One-Carbon Homologatedα-Substituted Alkyl Ketones
Alan R. Katritzky,* Zhongxing Zhang, Hengyuan Lang, and Linghong Xie
*Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, U.S.A.
Abstract
Deprotonated benzotriazole derivatives (1a-c) reacted with aldehydes to give the α-oxyanion substituted intermediates (2), which upon further treatment with butyllithium, without separation, resulted in the formation of one-carbon homologated α-substituted alkyl ketones (6a-f). Similar treatment of benzotriazole derivatives (1d-f) generated the benzotriazole ring-opening and rearranged products (7a-f). Plausible mechanisms for these reactions have been proposed.
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■ Isomerization of Dimeric 2,9-Disubstituted1-Oxaquinolizidine Alkaloids and Structural Revision of Araguspongines B and E, Isolated from a Marine Sponge of Xestospongia Sp.
Motomasa Kobayashi,* Yasuhisa Miyamoto, Shunji Aoki, Nobutoshi Murakami, Isao Kitagawa, Yasuko In, and Toshimasa Ishida
*Faculty of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Toyonaka, Osaka 565, Japan
Abstract
Isomerization reaction of araguspongines B (1), D (2), and E (3) having dimeric 2,9-disubstituted 1-oxaquinolizidine moiety was studied in detail. Conformational aspects of 1, 2, and 3 were also analyzed on the basis of NMR and X-ray crystallographic analysis. The C-9 stereochemistry of 1 and 3 was revised.
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■ Synthesis of Vinca Alkaloids and Related Compounds, Part LXXXIX. Some Unexpected Reactions of Compounds Containing the D-Seco-aspidospermane Ring System
György Kalaus, Imre Juhász, Kinga Steinhauser, István Greiner, Mária Kajtár-Peredy, János Brlik, Lajos Szabó, and Csaba Szántay*
*Department of Organic Chemistry, Technical University of Budapset, Gellért tér 4, P.O. Box 91, H-1521 Budapset, Hungary
Abstract
Interaction of the tryptamine derivative (3) with the formyl ester (4) gave (±)-20-deethyl-2,16-didehydro-14,16-bis(methoxycarbonyl)-3-phenyl-3,14-seco-20-epiaspidospermidine (7) instead of the expected acetal (6). The product of the reaction of 3 with the acetoacetic aldehyde derivative (5) was ethylene acetal of (±)-2,16-didehydro-16-methoxycarbonyl-3-phenyl-14,15-dinoraspidospermidin-19-one (8), it was readily convertible into the reactive intermediate (10). Further build-up starting from secondary amine (11) gave the N(4)-substituted derivatives, while 10 afforded products with unexpected structures. The reaction of 10 with acetic anhydride yielded different products depending on the reaction conditions.
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■ Synthesis and Chemical Reactions of New Phosphono-phosphino Substituted γ-Thiapyrones
Richard Neidlein,* Dirk Uwe Hahn, Walter Kramer, and Claus Krieger
*Pharmazeutisch Chemishes Institut, Im Neuenheimer Feld 364, 6900 Heidelberg, Germany
Abstract
1,3-Dithietane-2,4-diylidenebis(cyanomethylphosphonates) and -phenylphosphinates (1/2) react with various substituted acetonitriles (3) to give phosphono-phosphino substituted γ-thiapyrones (4/5). The constitution of one reaction product is confirmed by an X-ray crystal structure analysis (4.2c). The γ-thiapyrones are converted to boc-protected γ-thiapyrones (6/7) and to γ-pyrones (8/9) via oxidation.
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■ An Applied Stereocontrolled Synthesis of Piperidine Derivative Utilizing Diastereo- selective Reaction of Chiral 1,3-Oxazolidine with Grignard Reagent; Asymmetric Synthesis of an Alkaloid, (-)-Sedamine
Hadi Poerwono, Kimio Higashiyama,* and Hiroshi Takahashi
*Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
Abstract
A facile total synthesis of enantiomerically pure (-)-sedamine, known as a naturally occurring alkaloid, was accomplished by use of the diastereoselective addition of Grignard reagent to a chiral 1,3-oxazolidine, and utilizing of 1-aza-4-oxabicyclo[4.3.0]nonane derivative as a key intermediate. A diastereomeric pair, (-)-allosedamine, was also recovered as a minor product.
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■ Synthesis of Isomeric Cage-functionalized Diacylfuroxans and Their Subsequent Thermolytic Fission to an Acyl Nitrile Oxide
Alan P. Marchand,* G. V. M. Sharma, Rajesh Shukla, and Simon G. Bott
*Department of Chemistry, University of North Texas, NT Station, P.O. Box 305070, Denton, TX 76203-5070, U.S.A.
Abstract
A three step synthesis of a mixture of isomeric cage-functionalized furoxans (4) is described. When heated in the presence of ethyl propiolate, furoxans (4) undergo cycloreversion to afford two equivalents of the corresponding acyl nitrile oxide (5) which is trapped in situ by ethyl propiolate. The trapping reaction proceeds via a highly regioselective [3 + 2] cycloaddition to produce 6 (61% yyrld), whose structure was established unequivocally via application of X-Ray crystallographic methods. The observed regioselectivity of the [3 + 2] cycloaddition process is rationalized via frontier molecular orbital analysis by using semiempirical MO calculations (AM1 Hamiltonian) and at the HF/3-21G* level of theory.
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■ A Short Synthesis of (±)-Ricciocarpin A Using Intramolecular Reductive Michael Reaction
Kei Takeda,* Naoki Ohkawa, Kozo Hori, Toru Koizumi, and Eiichi Yoshii
*Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama, Toyama 930-0194, Japan
Abstract
A synthesis of furanosesquiterpene ricciocpin A (3), featuring the efficient construction of the cyclohexane framework by intramolecular reductive annulation using L-Selectride‚, is described.
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■ Synthesis of Polycyclic 1,2-Dioxanes from Endoperoxides
Charles W. Jefford,* Harald Eschenhof, and Gérald Bernardinelli
*Department of Organic Chemistry, Laboratory fo Crystallography, University of Geneva, 30, quai Ernest Ansermet, 1211 Geneva 4, Switzerland
Abstract
1,4-Diphenylcyclohex-2-ene 1,4-endoperoxide (7) on catalysis with trimethylsilyl trifluoromethanesulfonate (TMSOTf) in CH2Cl2 at -78°C reacted partially with 1,4-diphenylcyclopenta-1,3-diene (5) to give 3a,5a,6,7,9a,9b-hexahydro-2,5a,8,9b-tetraphenyl-1H-4,5-dioxacyclopenta[a]naphthalene (8) in 7.5% yield. Similar reaction of 1-phenylcyclohex-2-ene 1,4-endoperoxide (9) with1-phenylcyclohexa-1,3-diene (10) afforded three 1,2-dioxanes in a combined yield of 45%, one of which was identified as 1,2,4a,6a,7,8,10a,10b-octahydro-3,9-diphenyl-5,6-dioxaphenanthrene (11). The TMSOTf-catalysed reaction of 1,4-dihydro-1,4-dimethylnaphthalene 1,4-endoperoxide (12) with 1,4-diphenyl-cyclopenta-1,3-diene (5), benzofuran (14) and 1,1-diphenylethylene (16) gave the endo cis-fused tricyclic 1,2-dioxanes, (13), (15), and the cis-fused bicyclic 1,2- dioxane (17) as single products in yields of 46, 81, and 72% respectively. The structures of 8, 11, 13, 15 and 17 were elucidated by X-Ray analysis.
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■ Synthesis of the 3-O-Retinoyl-L-ascorbic Acid and Related Compounds: Characterization and Reducing Activity against DPPH
Yumiko Yamano and Masayoshi Ito*
*Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan
Abstract
Novel hybrid vitamin, 3-O-retinoyl-L-ascorbic acid (3a) was conveniently prepared by reaction of sodium L-ascorbate with retinoyl fluoride. The 3-O-acylated structure was confirmed by the comparison of spectral data of its methylated compound with those of 3-O-methyl-2-O-retinoyl-L-ascorbic acid (20) prepared from 5,6-O-isopropylidene-3-O-methyl-L-ascorbic acid. 3-O-Retinoyl-L-ascorbic acid (3a) showed a reducing activity against the stable radical, α,α-diphenyl-β-picrylhydrazyl (DPPH).
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■ A Multinuclear NMR Study (1H, 13C, 15N) of 1-Monosubstituted Pyrazoles
Rosa María Claramunt,* Dionisia Sanz, María Dolores Santa María, José Antonio Jiménez, María Luisa Jimeno, and José Elguero*
*Instituto de Química Médica, C. S. I. C., Calle Juan de Cierva, 3, 28006 Madrid, Spain
Abstract
The chemical shifts and coupling constants of twenty-three pyrazoles bearing different substituents at position 1 have been studied by 1H, 13C and 15N NMR spectroscopy in solution. Three new pyrazoles (N-pyrazolyl-P,P,P-triphenylphospha-λ5-azene, sodium 1-hydroxypyrazolate and 1-trifluoromethanesulfonylpyrazole) have been prepared; moreover, to assign the signals of some compounds, two other pyrazoles have been synthesized labelled in both nitrogen atoms with 15N (1-benzyl and 1-hydroxypyrazole). The tautomerism of 1-hydroxypyrazole has been reexamined.
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■ A New Approach to Fused 1,2-Diazepines by Cyclization of Enhydrazines with α- and β-Keto Esters
Tetsuo Yamasaki,* Kaoru Nishida, Yoshinari Okamoto, Tadashi Okawara, and Mitsuru Furukawa
*Faculty of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-hon-machi, Kumamoto 862-0973, Japan
Abstract
The cyclization of 6-(1,2-diethoxycarbonylethylidene)hydrazino-1,3-dimethyluracil (3) and 6-(1,2-diethoxycarbonylethylidene)hydrazino-3-methyl-2-methylthiopyrimidin-4(3H)-one (8) in the presence of polyphosphoric acid (PPA) provided 2,5-dihydropyrimido[4,5-c]-1,2-diazepine-5,6,8(1H,7H,9H)-trione (4) and 4,5-dihydropyrimido[4,5-c]-1,2-diazepine-5,6(1H,7H)-dione (9), respectively. 4-Hydrazino-5-methyl-2-pyrone (27) and 5,5-dimethyl-3-hydrazinocyclohexen-1-one (31) readily reacted with ethyl benzoylacetate (28) to give 4,5-dihydropyrano[4,3-c]-1,2-diazepine-5,6(1H,7H)-dione (30) and 3-phenyl-1,8,8-trimethyl-4,5,6,7,8,9-hexahydro-1,2-benzodiazepine-5,6(1H)-dione (33), respectively.
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■ Consolarine, a Novel Norditerpenoid Alkaloid from Consolida armeniaca
Ali H. Meriçli, Filiz Meriçli, Ayhan Ulubelen, Haridutt K. Desai, Balawant S. Joshi, S. William Pelletier,* Seçkin Özden, and Mustafa Küçükislamoglu
*Institute for Natural Products Research and Department of Chemistry, Chemistry Building, The University of Georgia, Chemistry Building, Athens Georgia 30602-2556, U.S.A.
Abstract
From the aerial parts of Consolida armeniaca, (Stapf. Ex Huth.) Schröd. a new norditerpenoid alkaloid named consolarine has been isolated along with the known alkaloids ajadelphinine, gigactonine, and lycoctonine. The structure of consolarine (2) was established on the basis of 1H, 13C, DEPT, homonuclear 1H COSY, HETCOR, NOESY, and COLOC NMR spectral studies.
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■ Stereoselective Synthesis of 2-epi-Pena-residin A and Its (15R,16R)-Stereoisomer
Guo-qiang Lin* and Ding-guo Liu
*Shanghai Institute of Organic Chemistry, Chinese Academy of Science, 354 Finglin Lu, Shanghai 200032, China
Abstract
Stereoselective synthesis of 2-epi-penaresidin A and its (15R, 16R)- stereoisomer was described.
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■ Efficient Synthesis of Specifically Deuterated Nucleosides: Preparation of 4'-Deuteriothymidine
Michael E. Jung* and Yue Xu
*Department of Chemistry and Biochemistry, University of California, 405 Hilgard Avenue Los Angels, CA 90095-1569, U.S.A.
Abstract
A very straightforward synthesis of 4’-deuteriothymidine (1) from inexpensive thymidine (2) is described. The key step involves triple deprotonation of the ester prepared by selective oxidation of unprotected thymidine (and esterification) and deuteration from the α-face to produce the desired 4’-deuterio derivative (5) which is then taken on to 1. Thus one can prepare the 4’-deuteriothymidine (1) in only five steps from thymidine (2) in an overall yield of 16%.
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■ Stereocontrolled Aldol Reaction of N-Acylpyrazoles with Aldehydes Using LDA or MgBr2-DIEA
Choji Kashima,* Iwao Fukuchi, Katsumi Takahashi, Kiyoshi Fukusaka, and Akira Hosomi
*Department of Chemistry, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba-shi, Ibaraki, 305-8571, Japan
Abstract
The aldol reaction of 1-acyl-3,5-dimethylpyrazoles (1) was kinetically controlled with syn stereoselectivity through lithium enolate intermediate using LDA. On the contrary, the anti stereoselective aldol reaction of 1 was caused by the action of DIEA in the presence of MgBr2 under the thermodynamic control. In the formation of syn-aldol products using 3-phenyl-l-menthopyrazole as a chiral auxiliary, the diastereoselectivity was observed up to 81% de with the predominant configuration of 2’S form.
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■ Synthesis of 4-(2-Aminoethyl)indoles through Claisen ortho-Amide Rearrangement of3-Hydroxy-2-methoxyindolines
Tomomi Kawasaki, Hiroaki Ohtsuka, Ado Mihira, and Masanori Sakamoto*
*Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan
Abstract
Reaction of 3-hydroxy-2-methoxyindolines (5) with amide acetal (6) and ketene aminal (13) gives 4carbamoylmethylindole (9) and -indoline (11), which are converted into 4-(2-aminoethyl)indole (7) by treatment of the indoline (11) with hydrochloride followed by sodium hydroxide to form the indole (9), and then by reduction of 9 with lithium aluminum hydride.
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■ Chemoselectivity in the Intramolecular Aza-Wittig Reaction of N-[2-(Trisubstituted Phosphoranylidene)aminobenzoyl]-2-pyrrolidone-5-carboxylic Acid Derivatives
Tomohiro Okawa, Toshiyuki Sugimori, Shoji Eguchi,* and Akikazu Kakehi
*Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya, Aichi 464-8601, Japan
Abstract
The intramolecular aza-Wittig reaction of (5S)-N-[2-(trisubstituted phosphoranylidene)aminobenzoyl]-2-pyrrolidone-5-carboxylic acid derivatives gave chemoselectively pyrrolo[2,1-c][1,4]benzodiazepin derivatives or pyrrolo[2,1-b]quinazoline derivatives depending on their substituents and phosphorus reagent.
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■ Methylation of 5-Isonitroso-1,3-dioxine- 4,6-diones with Diazomethane and Some Reactions of Its Products
Nobuya Katagiri,* Yoshihiro Morishita, and Chikara Kaneko
*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan
Abstract
Methylation of 5-isonitroso-1,3-dioxine-4,6-diones (1) with diazomethane afforded 5-methoxyimino-1,3-dioxine- 4,6-diones (4) and 5-methylimino-1,3-dioxine-4,6-dione N-oxides (5) together with a cyclic nitrone (7) as a minor product. Compound (5) reacted with two molar equivalents of triphenylphosphine to give phosphonium betaines (8) whereas photoreaction of 5 formed novel spiro compounds (9) via oxaziridine intermediates (G).
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■ Conformational Analysis of Thiosegetalins by Distance Geometry Calculation
Hiroshi Morita, Young Sook Yun, Koichi Takeya, and Hideji Itokawa*
*Department of Pharmacognosy, School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
Abstract
Three-dimensional structures in DMSO-d6 of cyclic thiopeptides, thiosegetalins A2, B1 and B2, prepared from segetalins A and B, were determined by distance geometry calculation and restrained energy minimization from NMR data. The backbone structure of thiosegetalin A2, consisting of two β-turns, a β II turn at Trp5-Ala6 and a β VI turn at Val2-Pro3, retains the backbone conformation of segetalin A, both of which showed estrogen-like activity. Whereas, the backbone conformations of cyclic pentapeptides, thiosegetalins B1 and B2 were different from that of the parent compound, segetalin B. The backbone conformations are important for segetalins to show estrogenic activity. Though thionation is a minimal variation of isosteric replacement, it is a useful conformational modification of cyclic peptides.
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■ Medicinal Foodstuffs. VIII. Fenugreek Seed.(2) : Structures of Six New Furostanol Saponins, Trigoneosides IVa, Va, Vb, VI, VIIb, and VIIIb, from the Seeds of Indian Trigonella foenum-graecum L.
Masayuki Yoshikawa,* Toshiyuki Murakami, Hajime Komatsu, Johji Yamahara, and Hisashi Matsuda
*Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan
Abstract
Following the characterization of trigoneosides la, Ib, Ila, IIb, IIIa, and IIIb, seven new steroidal saponins called trigoneosides IVa, Va, Vb, VI, VIIb, VIIIb, and IX were isolated from a medicinal foodstuff fenugreek seed, the seeds of Trigonella foenum-graecum L. (Leguminosae) originating from India. The structures of trigoneosides IVa, Va, Vb, VI, VIIb, and VlIlb were elucidated on the basis of chemical and physicochemical evidence.
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■ Several Approaches to Cyanide Ion-catalyzed Synthesis of 4-Aroyl-1-phenyl-1H-pyrazolo-[3,4-d]pyrimidines
Akira Miyashita,* Yumiko Suzuki, Kiyono Ohta, Ken-ichi Iwamoto, and Takeo Higashino
*Schol of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan
Abstract
4-Aroyl-1-phenyl-1H-pyrazolo[3,4-d]pyrimidines (5) were formed in low yields by reaction of 4-chloro-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine (4) with arenecarbaldehydes (3) in the presence of potassium cyanide. Similar reaction of 4-tosyl-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine (9) with 3 gave the ketones (5) in higher yields (60-74%). In the presence of catalytic amounts of both sodium p-toluenesulfinate (10) and potassium cyanide, the reaction of 4 with 3 gave the ketones (5) in good yields.
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■ Total Synthesis of Constanolactone E, a Marine Eicosanoid from the Alga Constantinea simplex; Absolute Structure of Constanolactone E
Hiroaki Miyaoka, Tatsuya Shigemoto, and Yasuji Yamada*
*School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
Abstract
Synthesis of marine eicosanoid constanolactone E was achieved through the one-pot formation of chiral cyclopropane derivative (6) using the anion of allyl phenyl sulfone and chiral epoxy mesylate (5). The absolute structure of constanolactone E was determined as 1 by the present synthesis.
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■ Acid-catalyzed Photoreaction of 6-Chloro-1,3-dimethyluracil in Frozen Benzene: Formation of Photocycloadducts and Their Isomerization through Photo-Diels-Alder Reaction
Kazue Ohkura, Yukari Noguchi, and Koh-ichi Seki*
*Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
Abstract
Photolysis of 6-chloro-1,3-dimethyluracil (6-CIDMU) in frozen benzene in the presence of TFA gave novel photocycloadducts, pentalenopyrimidine derivatives and a diazapentacyclo[6.4.0.01,3.02,6.04,8]dodecane derivative as the major cycloadducts. Their formation is well explained by the mechanism involving the initial ortho-cycloaddition of 6-CIDMU to benzene, but not meta-cycloaddition.
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■ Asymmetric Synthesis of Thietanose
Jun'ichi Uenishi,* Mitsuhiro Motoyama, Yumi Kimura, and Osamu Yonemitsu
*Department of Chemistry, Faculty of Science, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005, Japan
Abstract
Syntheses of optically active thietanose, (2R,3R,4R)-4-acetoxymethyl-3-(tert-butyldimethylsilyl)oxy-2-ethoxythietane (6) and (2R,3R,4R)-3-(tert-butyldimethylsilyl)oxy-4-[(tert-butyldimethylsilyl)oxy]methyl-2-ethoxythietane (23) are described. The key intermediate, (2S,3S)-4,4-bis(ethoxy)-3-(tert-butyldimethylsilyl)oxy-1,2-epithiobutane (7) has been derived from (Z)-2-butene-1,4-diol in 13 steps. Although direct transformation of 7 to thietanose (6) failed, regio and stereospecific ring opening of the episulfide ring in 7 and acid catalyzed cyclization of the resulting 3-mercaptobutanal diethyl acetal (20) was successful in forming of a thietane ring to give 6. The structure of 6 and 23 was confirmed by spectroscopic analyses including NOE experiments.
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■ Reactions of O,O'-Disubstituted Benzonitrile Oxides with 8-Azaheptafulvenes
Mauro Freccero, Remo Gandolfi,* and Mirko Sarzi Amade'
*Dipartamento di Chimica Organica, Universita de Pavia, V. le Taramelli 10, 27100 Pavia, Italy
Abstract
In the reaction of O,O’-disubstituted benzonitrile oxides (1f-h) with 8-p-tolyl-8-azaheptafulvene (2) in cyclohexane there is a competition between attack by the nitrile oxides on the C=N moiety [to give a mixture of equilibrating “fused” and “spiro” adducts (3/4)] and on the C2-C3 double bond (to give 12 which isomerizes to 13) of 2. Site selectivity was highly enhanced by carrying out the reaction in polar solvents. Only the attack on the C=N moiety was observed in the polar and protic methanol. A synthesis of 13 by a mild new procedure of decomplexation of the tricarbonyliron complex of 12 (i.e., 15) is described.
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■ A Novel Method for Michael Addition and Epoxidation of Chalcones in a Water Suspension Medium: A Completely Organic Solvent-Free Synthetic Procedure
Fumio Toda,* Hideaki Takumi, Masuhiro Nagami, and Kenya Tanaka
*Department of Applied Chemistry, Faculty of Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, 790-8577 Ehime, Japan
Abstract
Very efficient Michael addition reactions of amines, thiophenol and methyl acetylacetate to chalcone, and epoxidation of chalcone derivatives with NaOCI, in a water suspension medium have been developed as completely organic solvent-free reactions.
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■ Alternative Access to 20-Hydroxyecdysteroid Side Chain by Means of Samarium Iodide-promoted Radical Addition of Tetrahydrofuran to a 20-Keto Steroid
Toshio Honda* and Miho Katoh
*Institute of Medicinal Chemistry, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
Abstract
Samarium iodide-promoted radical addition of tetrahydrofuran to the 20-keto steroid afforded the adducts as a mixture of diastereomers at the 22-position in high yield. Both adducts were further converted into (20R,22R)-5α-cholestane-3β,20,22,25-tetraol.