HETEROCYCLES

■ Contents

■ Catalytic Dynamic Resolution Applied to the Synthesis of 2,6-Disubstituted Piperidines: Preparation of (+)-Lupetidine and (–)-Epidihydropinidine

Timothy K. Beng and Robert E. Gawley*

*Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, U.S.A.

Abstract

The diastereoselective synthesis of trans-2,6-disubstituted piperidines has been rendered enantioselective by incorporating a catalytic dynamic resolution into the first alkylation step. The method has been applied to the synthesis of (–)-epidihydropinidine and (+)-trans-lupetidine.

■ Computational Assessment of 1,3-Dipolar Cycloaddition of Nitrile Oxides with Ethene and [60]Fullerene

Lydia Rhyman, Sabina Jhaumeer-Laulloo, Luis R. Domingo, John A. Joule, and Ponnadurai Ramasami*

*Department of Chemistry, University of Mauritius, Réduit, Mauritius

Abstract

The 1,3-dipolar cycloaddition (1,3-DC) reactions of ethene and [60]fullerene with nitrile oxides, RCNO, have been studied in the gas phase, using DFT method at the B3LYP/6-31G(d) level. Energetics, thermodynamic and kinetic parameters have been determined at room temperature so as to investigate the effect of electron-withdrawing and electron-releasing substituents attached to the nitrile oxides on the 1,3-DCs. These parameters have been interpreted in terms of group electronegativity and reactivity indices. An atypical behavior has been observed for the 1,3-DC involving FCNO as it has some pseudodiradical character.

■ Enantioselective Cyclization Reactions of (Z)-N-Benzoyl-α-dehydro(1-naphthyl)alanine N’-Arylamides Initiated by Photoinduced Electron Transfer from Chiral Prolinol

Hiroyuki Yadai, Yuhki Sato, Tetsutaro Igarashi, and Tadamitsu Sakurai*

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

Abstract

An investigation was undertaken to explore substituent effects on the photoinduced electron transfer-initiated enantioselective cyclization of the title α-dehydronaphthylalanine N’-(2-hydroxyphenyl)amide [(Z)-1a], N’-(3-hydroxyphenyl)amide [(Z)-1b], N’-(4-hydroxyphenyl)amide [(Z)-1c], and N’-phenylamide [(Z)-1d] in 1,2-dichloroethane containing chiral N-methylprolinol or prolinol. 1H NMR spectral and HPLC chiral analyses of the target photoproducts, cis- and trans-4,5-dihydrooxazole isomers, confirmed that enantiomeric excess (ee) for these two isomers (estimated in the presence of the former prolinol) displayed a clear tendency to decrease in order of (Z)-1d > (Z)-1c > (Z)-1b > (Z)-1a. Hydrogen bonding and charge transfer interactions in radical ion pair and biradical intermediates were suggested to be key factors controlling ee, the value of which varied from 0 to 58%.

■ Molecular Recognition of 2-(Arylmethylthio)indolizine Derivatives through an Intramolecular Arene-π (Cation) Interaction

Akikazu Kakehi,* Kennosuke Itoh, Hiroyuki Suga, Nobuhiro Yamaguchi, Takashi Abe, Yohei Yuda, and Haruka Katsumata

*Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan

Abstract

Some 2-(arylmethylthio)indolizines bearing ethoxycarbonyl and/or cyano group(s) at the 1- and 3-positions were synthesized and their conformations were investigated by 1H-NMR spectra and X-ray analyses. Interestingly, it was indicated that the sulfide linkages in 2-(1-naphthylmethylthio)indolizine derivatives in CDCl3 solution are mainly present in gauche conformations and the intramolecular arene-π (cation) interactions reflect the electrophilic reactivity of the 1- and 3-substituents.

■ Microwave-Assisted Multicomponent Reaction in Water: Highly Stereoselective Synthesis of Pyrimidinespiroisoxazolo[5,4-b]pyridine Derivatives

Bo Jiang, Ning Ma, Xing-Han Wang, Shu-Jiang Tu,* and Guigen Li*

*Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, U.S.A.

Abstract

A multicomponent reaction has been established for the synthesis of pyrimidinespiroisoxazolo[5,4-b]pyridines that can serve as versatile building blocks for both organic and medicinal research. The reasonable reaction mechanism has proposed to explain the resulting stereochemistry of products. The present green synthesis shows several advantages including operational simplicity and fast reaction rate, which makes it a useful and attractive process for library generation for drug discovery.

■ Preparation of Furan Ring from 2-(Oxiran-2-yl)-1-alkylethanone Catalyzed by Nafion® SAC-13

Rihoko Tombe and Seijiro Matsubara*

*Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoudai-katsura, Nishikyo, Kyoto 615-8510, Japan

Abstract

Treatment of a 2-(oxiran-2-yl)-1-alkylethanone with Nafion® SAC-13 induced a cyclization reaction into furan ring. This method gave furans with a small amount of acid without aqueous work up.

■ Rearrangement Reaction of 1-Ethoxy- and 1-Hydroxy-2-phenylindole

Koji Yamada and Masanori Somei*

*Faculty of Pharmaceutical Scicences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192,

Abstract

Photoirradiation of 1-ethoxy-2-phenylindole in methanol and the reaction of 1-hydroxy-2-phenylindole with tosyl chloride produced 6-ethoxy- and 6-tosyloxy-2-phenylindoles, respectively, as minor products. The latter was derived to 6-ethoxy-2-phenylindole. The structure is determined by direct comparison of the spectral data with those of the authentic 4-, 5-, 6-, and 7-ethoxy-2-phenylindoles whose syntheses are reported in detail.

■ First Synthesis of a Natural Isoxanthopterin Glycoside, Asperopterin-A

Tadashi Hanaya,* Kazumasa Ejiri, and Hiroshi Yamamoto

*Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

The key precursor, N2-(N,N-dimethylaminomethylene)-6-hydroxymethyl-8-methyl-3-[2-(4-nitrophenyl)ethyl]-7-xanthopterin (9) was efficiently prepared from 2,5-diamino-6-methylamino-3H-pyrimidin-4-one (3) and ethyl 3-(tert-butyldimethylsilyloxy)-2-oxopropionate (11). The first synthesis of asperopterin-A (2b) was achieved by treatment of 9 with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (15) in the presence of tin(IV) chloride, followed by removal of the protecting groups.

■ Synthesis and Properties of Unsymmetrical N,N’-Dialkylterrylenebis(dicarboximide) Derivatives and Their Related Derivatives

Yukinori Nagao,* Tomohiro Iwano, Maki Hirano, Koji Arimitsu, and Kozo Kozawa

*Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan

Abstract

Terrylene derivatives have optical absorptions in the longer wavelength region than the perylene dyes and an unsymmetrical terrylene derivatives are expected to have an improved orientation and solubility. Unsymmetrical terrylenebis(dicarboximide) derivatives and their related dicarboximide derivatives were prepared, and the absorption or emission of light in a solution or solid film and their semiconductor-character for Schottky devices or dye sensitized solar cell devices were investigated. In solution, unsymmetrical and symmetrical terrylene derivatives showed the same absorption or emission spectra and have absorption or emission peaks in the longer wavelength region than that of the perylenedicarboximide derivatives. In a solid, the terrylene derivatives showed broad absorption peaks in the wavelength region shorter than that in solution. The terrylene derivatives behaved as an n-type semiconductor for a Schottky device and their conversion efficiencies were equivalent value to that of the typical semiconductor phthalocyanine (H2Pc). Perylenedicarboximide derivatives having a naphthalic anhydride moiety behave as a sensitizing dye for a dye sensitized solar cell.

■ Facile Synthesis of 4,9-Dihydro-2H-benz[f]- and 4,11-Dihydro-2H-naphth[2,3-f]isoindoles and Their Utility for Porphyrin Synthesis

Cai Chenxin, Hiroki Uoyama, Mitsunori Nakamura, and Hidemitsu Uno*

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

Abstract

Esters of 4,9-dihydro-2H-benz[2,3-f]isoindole-1-carboxylate and 4,11-dihydro-2H-naphth[2,3-f]isoindole-1-carboxylate were prepared by the modified Barton-Zard reaction of 2,3-bis(phenylsulfonyl)-1,2,3,4-tetrahydronaphthalene and anthracene with isocyanoacetate esters, respectively. The bis(phenylsulfonyl) derivatives were, in turn, prepared by the pericyclic reactions of the corresponding sultines with trans-1,2-bis(phenylsulfonyl)ethylene. The pyrrole esters were converted to the corresponding mono-naphthoporphyrin and mono-anthraporphyrin in good overall yields.

■ Development of an Intramolecular Gassman’s [2+2] Cycloaddition

John B. Feltenberger, Changhong Ko, Jun Deng, Sunil K. Ghosh, and Richard P. Hsung*

*Department of Chemistry, Division of Pharmaceutical Sciences, University of Wisconsin, 777 Highland Aenue, Madison, WI 53705-2222, U.S.A.

Abstract

The development of an intramolecular variant of Gassman’s cationic [2 + 2] cycloaddition is described herein. Mechanistic aspects of the stepwise nature of this cycloaddition process between vinyl acetals and unactivated olefins have been studied. We have also explored the scope of this reaction with regard to various oxygen-, nitrogen-, and carbon-tethered acetals to provide access to a diverse array of bicyclic scaffolds. Additionally, we have identified vinyl hemiaminals as having favorable reactivity for cationic [2 + 2] cycloaddition.

■ Catalytic Asymmetric Amination of Oxindoles under Dinuclear Nickel Schiff Base Catalysis

Shinsuke Mouri, Zhihua Chen, Shigeki Matsunaga,* and Masakatsu Shibasaki*

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

Abstract

Catalytic asymmetric synthesis of 3-aminooxindoles with a tetrasubstituted carbon stereocenter is described. 1 mol% of homobimetallic (R)-Ni2-Schiff base complex 1 catalyzed asymmetric amination of 3-alkyl-substituted oxindoles with azodicarboxylates to give products in 89-99% yield and 87-99% ee. For 3-aryl-substituted oxindoles, 10 mol% of (R)-Ni2-Schiff base complex was required to obtain products in 66-98% ee. Postulated catalytic cycle as well as transformation of the products are also described.

■ Expedient Synthesis of 3,4-Dihydroquinazolines via Tandem Addition — Conjugate Addition Cyclization of Carbodiimides Bearing a Michael Acceptor

Takao Saito,* Hayato Nakano, Hidenori Terada, Noriki Kutsumura, and Takashi Otani

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

Abstract

Michael acceptor-possessing N-phenylcarbodiimides, which were prepared by an aza-Wittig reaction of the corresponding functionalized iminophosphoranes with aromatic and aliphatic isocyanates, reacted with enolate carbon-nucleophiles of active methylene compounds via the tandem cumulene addition—hetero (NH) Michael addition cyclization, to provide 2,3,4-trisubstituted 3,4-dihydroquinazolines. It was also found that 2-aminoquinolines and 2-amino-3,4-dihydroquinolines were competitively formed in some cases. Based on these observations, possible mechanistic pathways leading to these heterocycles are proposed.

■ C-[o-(p-Tolyl)sulfinyl]phenylnitrones. Synthesis and Reactivity in [3+2] Dipolar Cycloadditions

José Luis García Ruano,* Alberto Fraile,* Alberto Núñez, M. Rosario Martín, and Inés Alonso

*Department of Organic Chemistry, Faculty of Sciences, Madrid Autonomous University, Madrid 28049, Spain

Abstract

The synthesis of the title compounds and the results obtained in their reactions with different dipolarophiles is presented. Alkylidene malonates afford the best conversions and stereoselectivities, providing enantiomerically pure isoxazolidines easily transformed into interesting tricyclic structures with t-BuLi.

■ Asymmetric Synthesis of 2-Propylisofagomine Using Allylic Hydroxy Group Accelerated Ring-Closing Enyne Metathesis

Tatsuya Taguchi, Tatsushi Imahori, Yuichi Yoshimura, Atsushi Kato, Isao Adachi, Masatoshi Kawahata, Kentaro Yamaguchi, and Hiroki Takahata*

*Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan

Abstract

An asymmetric synthesis of 2-propylisofagomine 5 using allylic hydroxy group accelerated ring-closing enyne metathesis (AHA-RCEM) was conducted with high diastereoselectivity in 13% overall yield starting from the commercially available (E)-hex-2-ol.

■ Reactivity of N-Alkylthiiranimines toward Simple Nucleophiles and Iso(thio)cyanates

Hildegard Nimmesgern, Ernst Schaumann,* and Gunadi Adiwidjaja

*Institute of Organic Chemistry, Clausthal University of Technology, Leibnizstrasse 6, D-38678 Clausthal-Zellerfeld, Germany

Abstract

Hydrolysis of N-(1-dimethylcarbamoyl-1-methylethyl)-thiiranimines occurs with S-C(sp2) ring cleavage while attack of hydrochloric acid results in S-C(sp3) ring opening. The latter mode of ring opening is also observed in [3+2] cycloaddition reactions with iso(thio)cyanates where the heterocumulene reacts via the C-chalcogen bond; only a sterically less hindered isopropyl substituted thiiranimine adds to the C=N bond in isocyanates to yield 4-thiohydantoins. The cycloadducts give a variety of hydrolysis products, in particular imidazo[2,1-b]oxazoles and –thiazoles, oxazolones, and stable thietes. Insertion of a thiocarbonyl into an isopropyl CH bond is observed yielding an annulated cyclopropane unit.

■ Synthesis of 6-Hydroxyisochromenes and 6-Hydroxyisocoumarins from 3-Ethoxycyclohex-2-en-1-one

George Majetich* and Jeremy L. Grove

*Department of Chemsitry, The University of Georgia, Athens, Georgia 30602, U.S.A.

Abstract

The synthesis of alkylated 6-hydroxyisochromenes and alkylated 6-hydroxyisocoumarins from 3-ethoxycyclohex-2-en-1-one was developed. The key reaction features a novel intramolecular hydroalkoxylation of a cyclohex-2-en-3-yn-1-one to assemble the dihydropyran moiety. Aromatization of the cyclohex-2-en-1-one ring used a selenylation/oxidative elimination sequence. The isochromenes were oxidized to their isocoumarin analogues using DDQ.

■ Synthesis of 8-Hydroxyisochromenes and 8-Hydroxyisocoumarins from 3-Ethoxycyclohex-2-en-1-one

George Majetich* and Jeremy L. Grove

*Department of Chemsitry, The University of Georgia, Athens, Georgia 30602, U.S.A.

Abstract

Two strategies were developed to prepare 8-hydroxyisocoumarins from substituted 3-ethoxycyclohex-2-en-1-ones. The key reactions in the first strategy were the cyclization of a 2-hydroxymethyl-3-ethynyl-cyclohex-2-en-1-one, followed by the aromatization of the resulting cyclohexenone-pyran intermediate. The second approach featured the reaction of 2-hydroxymethyl-3-vinyl-cyclohex-2-en-1-ones with DDQ to directly produce isocoumarins. This new two-step sequence was used to prepare oospolactone in 57% overall yield.

■ Alkyne-Acetal Cyclisation Reactions Mediated by Formic Acid; 3-Acylated-2,5-dihydrofurans and Related Oxygen and Nitrogen Heterocycles

James D. Cuthbertson, Andrew A. Godfrey, William P. Unsworth, and Richard J. K. Taylor*

*Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K.

Abstract

The utility of formic acid for the cyclisation of alkyne ω-acetals is described; the scope and limitations of this process are outlined and a range of acylated heterocyclic building blocks (2,5-dihydrofurans, 2,5-dihydro-1H-pyrroles, tetrahydropyridines, 2H-chromenes, 1,2-dihydroquinolines and benzoxepin-5(2H)-ones) are reported.

■ Dendronized Bi-2-quinoline Ligands and Their Metal Complexes: Dendron Synthesis and Metalloassembly

Anil Patri, Charles N. Moorefield, and George R. Newkome*

*Departments of Polymer Science and Chemistry, The University of Akron, Akron, OH 44325-4717, U.S.A.

Abstract

The synthesis of bis-biquinoline ligands possessing G1 and G2 Behera's amine-based dendrons with acid and ester termini was accomplished. Treatment with Cu(I) salts quantitatively generated the desired stable metallodendrimers with a Cu(I) core.

■ Multicomponent Click Synthesis of Potentially Biologically Active Triazoles Catalysed by Copper Nanoparticles on Activated Carbon in Water

Francisco Alonso,* Yanina Moglie, Gabriel Radivoy, and Miguel Yus*

*Department of Organic Chemistry, Faculty of Sciences and Institute of Organic Synthesis (ISO), University of Alicante, P.O. Box 99, 03080 Alicante, Spain

Abstract

A variety of potentially biologically active 1,2,3-triazoles, derived from (–)-menthol, lactic acid, D-glucose, oestrone, cholesterol, and phenacetin, have been synthesised through the multicomponent alkyne-azide 1,3-dipolar cycloaddition catalysed by copper nanoparticles on activated carbon in neat water.

■ Chiba-G-Catalyzed Intramolecular Oxo-Michael Addition: Synthetic Approaches to Vitamin E Skeleton

Sayaka Tokunou, Waka Nakanishi, Natsuko Kagawa, Takuya Kumamoto, and Tsutomu Ishikawa*

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

Abstract

A chroman skeleton with quaternary carbon chiral center, leadable to vitamin E after manipulation, was constructed through 6-exo-trig type intramolecular oxo-Michael addition in up to 44% yield with 81% ee when a phenol with (Z)-α,β-unsaturated ester at ortho position was reacted in the presence of a guanidine-type organocatalyst, Chiba-G [(-)-(4R,5R)-2-[(S)-1-hydroxymethyl-2-phenylethyl]imino-1,3-dimethyl-4,5-diphenylimidazolidine (or the enantiomer)].

■ Versatile Photorearrangement of Photocycloadducts from 5-Fluoro-1,3-dimethyluracil and Naphthalene

Kazue Ohkura,* Hiromichi Akizawa, Mikiko Kudo, Tetsuya Ishihara, Nobuhiro Oshima, and Koh-ichi Seki*

*Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan

Abstract

Direct UV-irradiation of 5-fluoro-1,3-dimethyluracil (5-FDMU) and naphthalene (1) with a 500 W high-pressure mercury lamp in a degassed Pyrex tube (λ > 300 nm) predominantly afforded benzopyrimidobarrelene derivative (2) through 1,4-addition, while irradiation in the presence of piperylene in singlet excited states preferentially afforded naphthocyclobuta- pyrimidine derivative (3) via 1,2-addition. Upon 254 nm light-irradiation of 2 gave rise to the formation of benzopyrimidosemibullvalene (4) in fair yields. The reaction pathway for the formation of 4 is reasonably explained in the terms of di-π-methane rearrangement. Adduct 3 was newly converted to the corresponding barrelene derivative (2) by long-wave-length irradiation in the presence of a triplet sensitizer.

■ Synthesis of Novel Oligosaccharides Based on 1,4-Dioxanyloxy 3-Oxasugars

Margaret Morozova, Sonali Wickremasinghe, and Mark A. Rizzacasa*

*School of Chemistry, The Bio21 Institute, The University of Melbourne, Building 102, 30 Flemington Road
Melbourne, Victoria 3010, Australia

Abstract

The synthesis of a new family of di and tri-3-oxaoligosaccharides based on the 1,4-dioxanyloxy or 3-oxapseudosugar moiety is described. The approach involved the glycosylation of trichloroacetamidate donors with acceptor alcohols to provide 3-oxadi- and trisaccharides. In all cases, the glycosylation was highly stereoselective providing the 1α anomers exclusively.

■ Structure and Mutagenicity of a Direct-Acting Mutagen Derived from the Reaction of N-Nitroso-N-methylbutylamine with Hydroxyl Radical

Keiko Inami, Motofumi Miura, Nozomi Tsutsumi, Eriko Okochi, Yoko Susaki, Satoko Ishikawa, Shigeyasu Motohashi, Junko Shiino, Kei Takeda, and Masataka Mochizuki*

*Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510,

Abstract

The mutagenicity of N-nitrosamines is usually detected in the presence of an S9 mix, which includes cytochrome P450. The mutagenicity of N-nitrosodialkylamines is induced by Fe2+-Cu2+-H2O2, which can be used as a chemical model for cytochrome P450. However, a direct-acting mutagen derived from N-nitroso-N-methylbutylamine (NMB) by the same oxidation system has not been reported. In this study, we determined the structure of a direct-acting mutagen obtained from the reaction of NMB with Fe2+-Cu2+-H2O2 by comparing its instrumental data (1H, 13C NMR and IR) with that from the synthesized compound. We confirmed that the direct-acting mutagen derived from NMB with Fe2+-Cu2+-H2O2 was 5-methyl-5-nitro-1-pyrazoline 1-oxide. Furthermore, we investigated the mechanism of the mutagenicity by 5-methyl-5-nitro-1-pyrazoline 1-oxide using Salmonella typhimurium strains. The mutagenicity of 5-methyl-5-nitro-1-pyrazoline 1-oxide in S. typhimurium YG7108, which is deficient O6-alkylguanine alkyltransferase, was higher than that in the parent strain S. typhimurium TA1535, indicating that the mutations are caused by DNA alkylation.

■ Applications of Multicomponent Assembly Processes to the Facile Syntheses of Diversely Functionalized Nitrogen Heterocycles

James R. Donald, Brett A. Granger, Simon Hardy, James J. Sahn, and Stephen F. Martin*

*Department of Chemistry and Biochemistry, The Texas Institute for Drug and Diagnostic Development, The University of Texas at Austin, Austin, Texas 78712-1074, U.S.A.

Abstract

Several multicomponent assembly processes have been developed for the synthesis of intermediates that may be elaborated by a variety of cyclizations to generate a diverse array of highly functionalized heterocycles from readily-available starting materials. The overall approach enables the efficient preparation of libraries of small molecules derived from fused, privileged scaffolds.

■ Synthesis of Norbornane-Fused 1,3-Dithiolanes and Evaluation of 1,3-Dithiolane-Containing Polymers as Absorbants for Mercury(II) Salts

R. Alan Aitken,* Kati M. Aitken, Stuart Lambert, Richard Playfair, and Neil J. Wilson

*School of Chemistry, University of St. Andrews, Fife KY 16 9ST, U.K.

Abstract

Hydrolysis of the zwitterionic adducts formed from Bu3P, CS2 and norbornene or norbornadiene gives Bu3PO and the corresponding norbornane-fused 1,3-dithiolanes. Oxidation of these gives endo-sulfoxides while attempted hydrolysis using HgCl2 and CdCO3 instead leads to formation of crystalline 1:1 HgCl2 adducts. Based on this observation, a range of robust and readily accessible polymers containing norbornane-fused dithiolane units are evaluated for absorption of HgCl2 from aqueous solution.

■ Regioselective Glycosylation of Unprotected Methyl Hexopyranoside by Transient Masking with Arylboronic Acid

Takashi Nishino, Yohei Ohya, Rie Murai, Tatsuya Shirahata, Daisuke Yamamoto, Kazuishi Makino, and Eisuke Kaji*

*School of Pharmacy, Kitasato University, Shirokane 5-9-1, Minato-ku, Tokyo 108-8641, Japan

Abstract

Unprotected methyl α/β-D-galactopyranoside, α/β-D-glucopyranoside, α-L-fucopyranoside, and α-L-rhamnopyranoside were regioselectively glycosylated by treatment with per-O-pivaloyl-α-D-glycopyranosyl bromide to give glycosyl-β(1→3)-galactopyranoside, glycosyl- β(1→2/3)-glucopyranoside, glycosyl-β(1→2)-fucopyranoside, and glycosyl- β(1→4)-rhamnopyranoside, respectively. The reaction mainly occurred at the secondary hydroxy group, even in the presence of a primary hydroxy group, which was masked with arylboronic acid.

■ Convergent Total Syntheses of the Pentacyclic Lamellarins K, T, U and W via the Addition of Azomethine Ylides to Tethered Tolans

Bernard L. Flynn and Martin G. Banwell*

*Research School of Chemistry, Institute of Advanced Studies, The Australian National University, Canberra, ACT 0200, Australia

Abstract

The title compounds, 1–4 respectively, have been prepared in a concise and fully regiocontrolled manner via the addition of an azomethine ylide to an ester-linked tolan. The resulting annulated dihydropyrrole was oxidized to the corresponding fully aromatic system and the associated isopropyl ethers then selectively cleaved with aluminium trichloride to reveal the free phenolic hydroxyl groups associated with the target compounds.