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
Leo A. Paquette's Special Issues, Vol. 62, No. 1, 2004
Published online: 20th October, 2003
■ Synthesis of (+)-1-Deoxygalactonojirimycin
Sung-Jae Pyun, Kee-Young Lee, Chang-Young Oh, and Won-Hun Ham*
*College of Pharmacy, Sung Kyun Kwan University, Suwon 440-746, Korea
Abstract
A total synthesis of (+)-1-deoxygalactonojirimycin has been accomplished using stereoselective dihydroxylation and piperidine formation by catalytic hydrogenation.
Published online: 14th October, 2003
■ A Formal Synthesis of a Muscarinic M1 Receptor Antagonist, (-)-TAN1251A
Hirotake Mizutani, Jun Takayama, Yukio Soeda, and Toshio Honda*
*Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
Abstract
An aromatic oxidation reaction of a secondary amine, prepared from L-tyrosine and glycine, with hypervalent iodine reagent gave a spirocyclic product, which was further converted into the key intermediate for the synthesis of (-)-TAN1251A.
Published online: 14th October, 2003
■ A New and Convenient Route to Synthesis of Enynones and Dienones from TosMIC
Vishnu K. Tandon,* Vidisha Garg, Manoj Kumar, Kunwar A. Singh, Simon P. J. M. van Nispen, and Albert M. van Leusen
*Chemistry Department, Lucknow University, Lucknow 226007, India
Abstract
Dilithio- and disodiotosylmethylisocyanides react with pyridine N-oxide and pyridazine N-oxide leading to formation of ring opened unsaturated products which on reaction with aralkyl halides and further hydrolysis result in formation of dienones and enynones respectively.
Published online: 14th October, 2003
■ A New Synthesis of Mono- and Dibenzosapphyrins
Noboru Ono,* Kenji Kuroki, Eriko Watanabe, Naoyuki Ochi, and Hidemitsu Uno
*Departmnt of Chemistry, Faculty of Science, Ehime University, Matsuyama 790-8577, Japan
Abstract
Sapphyrins fused with mono-bicyclo[2.2.2]octadiene (BCOD) and di-BCOD units are prepared, which are converted into mono- and dibenzosappyrins by heating at 200 °C; soret bands are red shifted by 10-20 nm by introduction of fused benzene rings, but Q bands are not much affected in benzosapphyrins.
Published online: 16th September, 2003
■ Asymmetric Hydrogenation of Furan-containing Ketones over Tartaric Acid-modified Raney Nickel Catalyst
Noriko Haruna, Delicia E. Acosta, Satoshi Nakagawa, Kohei Yamaguchi, Akira Tai, Tadashi Okuyama, and Takashi Sugimura*
*Graduate School of Science, Himeji Institute of Technology, 3-2-1 Kohto, Kamigori, Ako-gun, Hyogo 678-1297, Japan
Abstract
The hydrogenation of β-keto esters containing a furan unit at the conjugated position to the β-carbonyl group was carried out over a chiral heterogeneous catalyst, tartaric acid-modified Raney nickel. The hydrogenation first proceeds at the carbonyl to give optically active alcohols, but a simple substrate undergoes further hydrogenation of the furan part to produce a diastereomeric mixture of alcohols having a tetrahydrofuran moiety. This over-reduction was efficiently suppressed by substitutions of a substituent at the furan part. The optical yield at the hydroxy group is in the range of 40–90%.
Published online: 7th November, 2003
■ 8-Oxabicyclo[3.2.1]octa-3,6-dien-2-one Synthesis Using a Pyrylium 3-Oxide Precursor Derived from a 4-Oxo-4H-pyrazole 1,2-Dioxide
John F. Hansen,* Andre L. Kilpatrick, and Anita Durairaj
*Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, U.S.A.
Abstract
Dimethyl acetylenedicarboxylate reacts with 3-methyl-5-phenyl-4-oxo-4H-pyrazole 1,2-dioxide in CH2Cl2 and water to give 3,4-bis(carbomethoxy)-8,8-dihydroxy-5-methyl-1-phenyl-2-oxa-6,7-diazabicyclo[3.2.1]octa-3,6-diene 7-oxide. This compound loses water and N2O when heated, producing a 3-oxidopyrylium derivative which reacts, in situ, with alkynes to give 8-oxabicyclo[3.2.1]octa-3,6-dien-2-one derivatives.
Published online: 14th October, 2003
■ A New Molecular Receptor Based on Thiophene Congener of Tröger’s Base: Selective Binding with Aliphatic and Aromatic Dicarboxylic Acids
Tomoshige Kobayashi* and Takashi Moriwaki
*Department of Chemistry, Faculty of Science, Shinshu University, Asahi, Matsumoto 390-8621, Japan
Abstract
A new molecular receptor bearing pyridylamino groups was prepared with a thiophene congener of Tröger’s base as a spacer, and was found to exhibit selective binding toward aliphatic and aromatic dicarboxylic acids, primarily depending on the length of the carbon chain.
Published online: 4th November, 2003
■ An Improved Synthesis of the Tricyclic Core of Sarains by a 3-Oxidopyridinium Betaine Cycloaddition
Hyoung Ik Lee, Moo Je Sung, Hee Bong Lee, and Jin Kun Cha*
*Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, U.S.A.
Abstract
An improved synthesis of a suitably functionalized tricyclic core of sarains has been developed by adaptation of Katritzky’s cycloaddition using a 3-oxidopyridinium betaine.
Published online: 14th October, 2003
■ Synthesis of Novel 1α,25-Dihydroxy-19-norvitamin D3 with an Amide Conjugate
Yoshitomo Suhara, Keiichiro Ono, Akihiro Yoshida, Toshie Fujishima, Nozomi Saito, Shinobu Honzawa, Seishi Kishimoto, Takayuki Sugiura, Keizo Waku, Hiroaki Takayama, and Atsushi Kittaka*
*Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, 1091-1 Suarashi, Sagamiko-machi, Tsukui-gun, Kanagawa 199-0195, Japan
Abstract
The diene system of 1α,25-dihydroxy-19-norvitamin D3 was replaced by a stable amide bond. A 3-hydroxypropoxy group, which was effective on enhancing binding affinity of 1α,25-dihydroxyvitamin D3 for vitamin D receptor (VDR), was introduced to the C2-position of the amide type analogue of 1α,25-dihydroxy-19-norvitamin D3. The amide analogue was found to be not suitable for binding to the ligand binding domain of the bovine thymus VDR, and additional modification at the C2-position did not improve the affinity. Potency in induction of HL-60 cell differentiation was evaluated for the novel amide analogues (3a-c).
Published online: 27th October, 2003
■ A Novel Preparation of 3-Hydroxy-3H-indole-3-ethanamines and -3H-indole-3-acetamides Having either a 4-Morpholinyl or 1-Pyrrolidinyl Group at the 2-Position
Toshikatsu Hayashi, Yu-ya Nakai, Fumio Yamada, and Masanori Somei*
*Faculty of Pharmaceutical Sciences, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-0934, Japan
Abstract
A novel synthetic method is discovered for 3-hydroxy-3H-indole-3-ethanamines and -3H-indole-3-acetamides having either a 4-morpholinyl or 1-pyrrolidinyl group at the 2-position by reacting the corresponding 1-hydroxyindoles with enamines in the presence of tosyl or mesyl chloride. A plausible mechanism is proposed.
Published online: 27th October, 2003
■ Total Synthesis of (±)-Xyloketal D and Model Studies towards the Total Synthesis of (-)-Xyloketal A
Jeremy D. Pettigrew, Jason A. Bexrud, Rebecca P. Freeman, and Peter D. Wilson*
*Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, B. C. V5A 1S6, Canada
Abstract
A stereoselective total synthesis of (±)-xyloketal D (±-2) has been achieved using a cycloaddition reaction of an ortho-quinone methide and a dihydrofuran as a key step. Preliminary model studies towards the total synthesis of xyloketal A (1) are also reported.
Published online: 4th November, 2003
■ Unexpected Reaction of 2,3-Epoxy Sulfonates: Novel Formation of Two Enones with Reversed Substituents at α- and β-Positions from the Single Isomer
Hiromichi Fujioka, Yusuke Ohba, Junko Futamura, and Yasuyuki Kita*
*Graduate School of Pharmaceutical Science, Osaka University, 1-6 Yamadaoka, Toyonaka, Osaka 560-0043, Japan
Abstract
The 2,3-epoxy sulfonates gave two types of enones with reversed substituents at the α- and β-positions under neat and weakly acidic conditions. The reaction mechanism is also discussed.
Published online: 27th October, 2003
■ Preparation and Structure of Di(2-azulenyl)ketene Adducts. γ-Lactone and β-Lactam Derivatives
Shingo Ito, Hideki Hamazaki, Yusuke Hirasawa, Akira Ohta, Kunihide Fujimori,* Noriyuku Tanaka, and Motoo Shiro
*Department of Chemistry, Faculty of Science, Shinshu University, Asahi, Matsumoto 390-8621, Japan
Abstract
Di(2-azulenyl)ketene (1) generated by thermal decomposition of diazodi(2-azulenyl)ethanone (2) via Wolff rearrangement of carbonyl carbene (8), and the reactive intermediate were confirmed by trapping reagents, such as azobenzene and cyclopentadienes. The reaction of 1 with tropone or imines afforded the corresponding γ-lactone (12) and β-lactams (15), respectively.
Published online: 4th November, 2003
■ Synthetic Studies of Proanthocyanidins. Part 5. Highly Stereoselective Synthesis and Inhibitory Activity of Maillard Reaction of 3,4-trans Catechin and Epicatechin Dimers, Procyanidin B1, B2, B3, B4 and Their Acetates
Akiko Saito, Noriyuki Nakajima,* Nobuyasu Matsuura, Akira Tanaka, and Makoto Ubukata
*Biotechnology Research Center, Toyama Prefectural University, 5180 Kurokawa, Kosugi, Toyama 939-0398
Abstract
TMSOTf-catalyzed condensation of a potential electrophile with a nucleophile was achieved with a high level of 3,4-trans condensation, and we succeeded in the stereoselective synthesis of procyanidin B2 and its peracetate. Studies on the inhibitory activity of the Maillard reaction of four 3,4-trans series of catechin and epicatechin dimers, procyanidin B1, B2, B3 and B4, and their peracetates were also carried out.
Published online: 27th October, 2003
■ Regioselective Aromatic Substitution of 6,8-Dihydroxy-4-ethoxycarbonyl-2H-isoquinolin-1-one Derivatives Using the Stille Coupling Reaction
Hidekazu Ouchi, Yoko Kawata, Mikako Ono, Yasuo Morita, Yutaka Yamamoto, and Hiroki Takahata*
*Faculty of Pharmaceutical Sciences, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan
Abstract
The novel synthesis of 6- or 7-aromatic substituted 2H-isoquinolin-1-ones, by two different routes is described. In the first route, 7-substituted derivatives were prepared by regioselective iodination at the 7-position of 6,8-dihydroxy-4-ethoxycarbonyl-2H-isoquinolin-1-one derivatives (1) followed by the Stille coupling reaction. In the second route, 6-subsutituted derivatives were prepared by the selective triflation of the 6-hydroxy group of 1 followed by the Stille coupling reaction.
Published online: 7th November, 2003
■ Developments of Enediyne Model Compounds Generating Biradicals with an Enhanced Radical Character – Regulation of Triggering Devices
Ichiro Suzuki, Akira Shigenaga, Hisao Nemoto, and Masayuki Shibuya*
*Faculty of Pharmaceutical Sciences, University of Tokushima, Sho-machi 1, Tokushima 770-8505, Japan
Abstract
Development of enediyne model compounds generating biradicals with an enhanced radical character is described. These model compounds generate enyne-allenes under mild acidic conditions and the resulting biradicals showed potent DNA cleaving abilities.
Published online: 7th November, 2003
■ Synthesis of 3-Acetyl-N-aryl-4-diethylaminoselenet-2(2H)-imines from 4-Diethylamino-3-butyn-2-one and Aryl Isoselenocyanates
Plamen K. Atanassov, Anthony Linden, and Heinz Heimgartner*
*Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
Abstract
The reaction of aryl isoselenocyanates (1a-d) with 4-diethyl-amino-3-butyn-2-one (6) in refluxing tetrahydrofuran afforded N-arylselenet-2(2H)-imines (7) in moderate yields. The structure of the stable 4-bromophenyl derivative (7b) has been established by X-Ray crystallography. A stepwise cycloaddition via an intermediate zwitterion (A/A′) is proposed as the reaction mechanism. In boiling tetrahydrofuran, the selenetimines (7) are in equilibrium with ketenimines (B), which were intercepted by amines to give 2-(diaminomethylene)-3-oxobutane selenamides of type (8).
Published online: 4th November, 2003
■ Novel Heterocyclic Troponoids: Synthesis of Pyridoimidazotropolones and Related Compounds by the Reaction of 5-Nitrosotropolone with Several Azines
Ohki Sato,* Kouichiro Tsurumaki, Syunnichi Tamaru, and Josuke Tsunetsugu*
*Department of Chemistry, Faculty of Science, Saitama University, Saitama, Saitama 338-8570, Japan
Abstract
Novel heterocyclic troponoids, such as pyridoimidazotropolones (3–4, 5–11, 12–13, 14–15 and 16) were synthesized by the reaction of 5-nitrosotropolone (1) with azines as pyridine, m- and p-substituted pyridines, pyridazine, isoquinoline and phthalazine. Similarly, thiazol afforded 17. The reaction mechanism involves multi-step reactions; acetylation of 1, Michael addition of azines to nitrosotropolone acetate (2), cyclization and deacetoxylation. The scope and limitation of this method are also discussed.
Published online: 7th November, 2003
■ A Concise Synthesis of an Indenopyrrolidine-based Dual αvβ3/αvβ5 Integrin Antagonist
Diane K. Luci, Rosemary J. Santulli, Diane A. Gauthier, Brett A. Tounge, Shyamali Ghosh, Jef C. Proost, William A. Kinney,* Bart De Corte, Robert A. Galemmo, Jr., Joan M. Lewis, Warren E. Dorsch, Michael W. Wagaman, Bruce P. Damiano, and Bruce E. Maryanoff
*Johnson & Johnson Pharmaceutical Research & Development, L. L. C., P. O. Box 776, Welsh and McKean Rds., Spring House, PA 19477-0776, U.S.A.
Abstract
A new class of dual αVβ3/αVβ5 integrin antagonists containing a central cis-fused cyclopentane ring was identified. Because of its increased structural rigidity, the indenopyrrolidine ring system provides insight into the active conformation of other αVβ3 ligands. A concise synthesis of the indenopyrrolidine ring system was accomplished by 1,3-dipolar cycloaddition. Individual isomers of the most active compound were separated by chiral HPLC and their biological activities were compared.
Published online: 17th November, 2003
■ A Highly Flexible Route to 1,2,3,4,5,6-Hexahydro-5-hydroxypyrimidin-2-ones as Potential HIV Protease Inhibitors
Dieter Enders,* Lars Wortmann, Gerhard Raabe, and Barbara Dücker
*Institut für Organische Chemie, Rheinisch-Westfälische, Technische Hochsch, Aachen University, Professor-Pirlet-Straße 1, D-52074 Aachen, Germany
Abstract
The first asymmetric synthesis of potential HIV protease inhibitors of type II, III and IV is described. Key step of the synthesis is an auxiliary based stereoselective alkylation by means of the (R)-1-amino-2-methoxymethyl-pyrrolidine (RAMP)- / (S)-1-amino-2-methoxymethylpyrrolidine (SAMP)-hydrazone method starting from a readily available key building block, pyrimidin-2,5-dione (6). The synthesis is short and highly versatile in the choice of the substitution pattern as well as the absolute configuration of the alkylated 1,2,3,4,5,6-Hexahydro-5-hydroxypyrimidin-2-ones.
Published online: 14th November, 2003
■ Intramolecular [4+3] Cycloadditions. Towards a Synthesis of Widdrol
Michael Harmata,* Mehmet Kahraman, Gilbert Adenu, and Charles L. Barnes
*Department of Chemistry, University of Missouri-Columbia, 601 South College Avenue, Columbia, Missouri 65211, U.S.A.
Abstract
Certain substituted alkoxyallylic sulfones were alkylated and treated with Lewis acids to produce vinylthionium ions that underwent intramolecular [4+3] cycloaddition reactions with a tethered furan. Manipulation of the cycloadduct led to the synthesis of widdrol. Other attempts to prepare the cycloadducts were made, but none were exceptionally better than the route using vinylthionium ions as intermediates. Interesting aspects of the alkylation chemistry of phenylthio-substituted alkoxyallylic sulfones are detailed as well.
Published online: 14th November, 2003
■ The Synthesis of (-)-Gloeosporone, a Potent Fungal Autoinhibitor of Spore Germination Using a π-Allyltricarbonyliron Lactone Complex and a New Reductive Decomplexation Procedure for the Installation of the Embedded 1,7-Diol Component of the Natural Product
Ed Cleator, Jürgen Harter, and Steven V. Ley*
*Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, U.K.
Abstract
The synthesis of (-)-gloeosporone has been achieved via a π-allyltricarbonyliron complex (7). The stereogenic centers observed in the natural product were constructed by a highly stereoselective Makaiyama aldol reaction to afford a new complex that upon reductive iron decomplexation gave a 1,7-diol motif found in the natural product.
Published online: 10th November, 2003
■ Facial Selectivity of the Sharpless Bromine Catalyzed Aziridination
Aaron C. Schmitt, Catherine M. Smith, Eric A. Voight, and George A. O’Doherty*
*Department of Chemistry, West Virginia University, Morgantown, WV 26506-6045, U.S.A.
Abstract
A bromine catalyzed aziridination reaction has been applied to 7,7-dibromo-3-norcarene, which resulted in a highly stereoselective route to cis-4,4-dibromo-8-(toluene-4-sulfonyl)-8-azatricyclo[5.1.0.0]octane in a 46% yield. In order to confirm the stereochemistry of the aziridination reaction trans-4,4-dibromo-8-(toluene-4-sulfonyl)-8-azatricyclo[5.1.0.0]octane and its diastereoisomer cis-4,4-dibromo-8-(toluene-4-sulfonyl)-8-aza-tricyclo[5.1.0.0]octane were prepared in a stereoselective manner from the corresponding cis- and trans-7,7-dibromo-3-norcarene epoxides (61 and 9.2% yields, respectively). These three routes offer stereochemical proof for the stereospecificity of the bromine-catalyzed aziridination of hindered alkenes.
Published online: 10th November, 2003
■ Ti-triol Catalysed Trimethylsilylcyanation of Acetophenones under High Pressure
Michael C. K. Choi,* Shu-Sun Chan, Man-Kong Chan, Jong Chul Kim, Hirokazu Iida, and Kiyoshi Matsumoto*
*Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan
Abstract
The first trimethylsilylcyanation of acetophenone to the corresponding (S)-cyanohydrin was accomplished with e.e. up to 60% in 93% yield at 0.8 GPa, using 0.01 eq. of a reusable catalyst prepared from (S)-3,3-dimethyl-1,2,4-butanetriol and titanium isopropoxide. Reactions of 4’-substituted acetophenones to the corresponding cyanohydrins gave lower e.e. and yields.
Published online: 14th November, 2003
■ Biotransformation of (-)-Maalioxide by Aspergillus niger and Aspergillus cellulosae
Toshihiro Hashimoto, Yoshiaki Noma, Yoshiaki Gotoh, Masami Tanaka, Shigeru Takaoka, and Yoshinori Asakawa*
*Faculty of Pharmaceutical Sciences, Tokushima Bunri University, 180 Nishihamabouji, Yamashiro-machi, Tokushima, 770-8514, Japan
Abstract
A sesquiterpene cyclic ether, (-)-maalioxide (1) from the liverwort Plagiochila sciophila was biotransformed by Aspergillus niger and A. cellulosae to afford the structurally interesting compounds. The stereostructures of the metabolites were established by a combination of high resolution NMR spectrum, X-Ray crystallographic analysis and the chemical reaction.
Published online: 10th November, 2003
■ Reactions of 4-Methoxy-2-(4-methoxyphenyl)-9-oxocyclohepta[b]pyrylium Perchlorate with Active Methylene Compounds
Dao-Lin Wang and Kimiaki Imafuku*
*Department of Chemistry, Faculty of Science, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555, Japan
Abstract
4-Methoxy-2-(4-methoxyphenyl)-9-oxocyclohepta[b]pyrylium perchlorate (1) reacted with active methylene compounds to give two types of products. The reactions with nitromethane and cyano-substituted active methylene compounds occurred at the 4-position to yield 4-methylene-substituted 4,9-di-hydrocyclohepta[b]pyran-9-ones (2, 3a-d). On the other hand, the reactions with active methylene compounds having an acetyl group took place at the 9a-position to give the ring-opened 6,7-dimethylenecyclohepta-2,4-dien-1-ones (4a-d). In the reactions with malonic acid diesters, 2H-cyclohepta[b]furan-2-ones (5a,b) were obtained by the attack at the 9a-position, ring-opening, and recyclization. Compound (5a) reacted with in situ-generated enamines to afford azulene derivatives (6a-e).
Published online: 18th November, 2003
■ Meisenheimer and Other Rearrangements of N-Oxides Derived from 2-Azabicyclo[2.2.1]hept-5-enes; the Influence of Reaction Conditions and Stereochemistry at Nitrogen
John R. Malpass,* Paul S. Skerry, and Stuart L. Rimmington
*Department of Chemistry, University of Leicester, Leicester LE1 7RH, U.K.
Abstract
N-Benzyl-2-azabicyclo[2.2.1]hept-5-ene reacts rapidly with m-CPBA and, on basification, a single N-oxide is released which rapidly forms N-benzyl-2-oxa-3- azabicyclo[3.2.1]oct-6-ene via a Meisenheimer rearrangement at room temperature. In addition, competition from a formal Cope elimination in a non-planar system leads to novel substituted cyclopentadienes; these show unusual VT NMR behavior and an unusually high Jgem value of 23.8 Hz is observed in one isomer at low temperature as a result of diastereotopicity induced by slow inversion at nitrogen in the side chain. N-Benzyl-2-azabicyclo[2.2.1]heptane forms two stable N-oxides with m-CPBA. Invertomer preferences are measured in the starting amines and the relationship between invertomer ratios, N-oxide stereochemistry, and rearrangement pathways is explored.
Published online: 18th November, 2003
■ Design and Synthesis of Pyrrolo[2,1-c][1,4]benzodiazepine (PBD)- Polyaminoalkyl Conjugates by the Use of SNAr Reaction of 2-Nitro-5-fluorobenzoate Precursor as Key Reaction
Hirokazu Iida, Naoto Hayashi, J. William Lown,* and Kiyoshi Matsumoto*
*Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan
Abstract
The design and synthesis of a series of pyrrolo[2,1-c][l,4]benzodiazepine (PBD)- polyaminoalkyl conjugates as DNA minor groove binders are described. To introduce polyaminoalkyl groups to the pyrrolo[2,1-c][1,4]benzodiazepine pharmacophore, SNAr reactions between 2-nitro-5-fluorophenyl ketone or 2-nitro-3-pehenyl ketone and polyaminoalkyl side chains were developed.
Published online: 17th November, 2003
■ Stereoselective Total Synthesis of the Nonenolide (+)-Microcarpalide
Martin G. Banwell* and David T. J. Loong
*Research School of Chemistry, Institute of Advanced Studies, The Australian National University, GPO Box 414, Canberra, ACT 0200, Australia
Abstract
The enantiomer [(+)-1] of the nonenolide natural product microcarpalide [(–)-1] has been prepared from (S)-malic acid (3) and 3-decyn-1-ol (11) via a sixteen step sequence involving, inter alia, two metathesis processes.
Published online: 17th November, 2003
■ Microwave Assisted Pericyclic Reactions in Cascade to Construct Decalin Frameworks Possessing Quaternary Centers. Scope and Limitations
Julie A. Farand, Irina Denissova, and Louis Barriault*
*Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada
Abstract
The synthesis of decalin skeletons possessing quaternary carbon centers at C9 using the tandem oxy-Cope/ene/Claisen is described. The degree of substitution at the terminal olefin plays an important role in determining the pathway of the reaction. In the case of 1,2-divinylcyclohexanol having a 1,2-disubstituted allyl ether, the corresponding decalin skeletons were obtained in good yields. In the case of trisubstituted allyl ethers, decalin products resulting from a radical 1,3-shift were isolated. The microwave irradiation of 1,2-divinylcyclohexanol propargyl ethers produced tetracyclic acetal sesquiterpenes via an oxy-Cope/ene/Claisen/5-exo dig cyclization reaction in high diastereoselectivity. The scope and limitation of the method is described.