Special Issue

Derek H. R. Barton's Special Issues, Vol. 28, No. 1, 1989

75 data found. 61 - 75 listedFirst Previous
Paper | Special issue | Vol 28, No. 1, 1989, pp. 383 - 387
Published online:
DOI: 10.3987/COM-88-S59
Phytochemical Studies on Meliaceous Plants. V. Structure of a New Apotirucallane-Type Triterpene, 21-O-Methyltoosendanpentol from Fruits of Melia toosendan Sieb. et Zucc

Akira Inada, Mari Konishi, anmd Tsutomu Nakanishi*

*Faculty of Pharmaceutical Sciences, Setsunan University, 45-1, Nagaotoge-cho, Hirakata-shi, Osaka 573-0101, Japan


21-O-Methyltoosendanpentol (1), a new apotirucallane-N type triterpene, has been isolated from fruits of Melia toosendan Sieb. et Zucc. (Meliaceae). The structure of 1 has been established by lines of chemical and spectral evidence.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 389 - 403
Published online:
DOI: 10.3987/COM-88-S60
The Third Row Anomeric Effect. Conformational Analysis of 2-Phenylthio- and 2-Phenylseleno-1,3-diselenanes

B. Mario Pinto,* Blair D. Johnston, and Ruby Nagelkerke

*Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, B. C. V5A 1S6, Canada


conformational behavior of cis- and trans-5-methyl-2-phenylthio- and-2-phenylseleno-1,3-diselenanes has been examined by means of 13C nmr and 77Se nmr spectroscopy. Whereas the cis isomers exhibit highly biased equilibria, the trans isomers display readily measurable equilibria at the slow-exchange limit. Direct integration of the individual conformer resonances in the low temperature spectra of the latter isomers yields δG’147k values of -0.33 ± 0.01 (SPh) and -0.08 ± 0.01 (SePh) kcal mol-1 in favor of the diaxial confomr. The conformational free energy of the methyl group in 5-methyl-1,3-diselenane (δG°147k = +0.87 ± 0.03 kcal mol-1) is then used to derive δG°147k values of -1.20 ± 0.04 and -0.96 ± 0.04 kcal mol-1 for the equilibrium in 2-phenylthio- and 2-phenylseleno-1,3-diselenane, respectively. Since the conformational free energy, δG°147k, of the 2-methyl group in 2-methyl-1,3-diselenane is +1.04 ± 0.01 kcal mol-1, it is argued that there exists a significant Se-C-S and Se-C-Se anomeric effect.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 405 - 410
Published online:
DOI: 10.3987/COM-88-S63
Benz-fused Lactones. I. Synthesis of 3-Methyl-1(3H)-isobenzofuranones [Phthalides]

Camille André Boulet and Gerald Arthur Poulton*

*Department of Chemistry, University of Victoria, Victoria, BC V8W 3V6, Canada


Unsubstituted and 3-alkyl substituted l(3H)-isobenzofuranones [phthalides] are readily prepared in good yields via ortho-metallation of appropriate aromatics.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 411 - 419
Published online:
DOI: 10.3987/COM-88-S78
Structural Modifications of Dalbergin Using Benzeneseleninic Anhydride

Dervilla M. X. Donnelly,* Roslynn Busteed, Peter M. Kenny, Judith Polonsky, Jean-Pierre Finet, and Thierry Prangé

*Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland


Reaction of dalbergin (6-hydroxy-7-methoxy-4-phenylcoumarin) (1) with benzeneseleninic anhydride afforded two quinones, the major being an o-quinone (2) arising from oxidation of ring A of the chromanone moiety and the minor (3) resulting from a rearrangement of (2). The p-quinone ( 3 ) was isolated independently from benzeneseleninic acid oxidation of 8-hydroxy-7-methoxy-4-phenylcoumarin (7). The benzopyran-2-ones (8) and (9) when reacted with benzeneseleninic anhydride yielded the o-quinones (10, 11) only. Confirmation of the o- quinone structure (2) was obtained by single crystal X-ray analysis. The structures and chemistry of the compounds are discussed. The o-quinones displayed significant fungicidal properties.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 421 - 424
Published online:
DOI: 10.3987/COM-88-S81
Chemical Transformations of Qinghaosu, a Peroxidic Antimalarial, II

Xiao Shang, Cun-Heng He, Qi-Tai Zheng, Jing-Jing Yang, and Xiao-Tian Liang*

*Institute of Materia Medica, Chinese Academy of Medica lSceince, Nan-wei Road, Beijing 100050, China


Qinghaosu (1) is known to give a plethora of products in alkaline media. This paper is concerned with the amended stereochemistry of products 3 ,4 and 5, with attendant mechanistic implications. Lactonization of 5 is also discussed.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 425 - 432
Published online:
DOI: 10.3987/COM-88-S85
Synthesis of (R)-(—)- and (2R,3R)-(—)-[2-2H]Mevalonolactones

Tomihisa Ohta, Nobuaki Tabei, and Shigeo Nozoe*

*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan


Facile synthesis of (R) - (-) - and (2R,3R) - (-) -[2-2H] mevalonolactones (1) from geraniol (2) is described.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 433 - 444
Published online:
DOI: 10.3987/COM-88-S87
The Facile Conversion of Pyranoid Glycals into 2-Deoxy-glycosidic Orthoesters

Cedric W. Holzapfel,* Gerhardus J. Engelbrecht, and Gerhard H. Verdoorn

*Department o f Chemistry and Biochemistry, Rand Afrikaans University, P.O. Box 524, Auckland Park, 2006, Johannesburg, South Africa


The formation of 2-deoxy-glycosidic orthoesters involving the palladium(II) catalysed reaction of pyranoid glycals with alcohols in the presence of sodium hydrogen carbonate is described.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 445 - 451
Published online:
DOI: 10.3987/COM-88-S89
Reaction os Singlet Oxygen with α,β-Unsaturated Aldimines: Novel Formation of 3-Amino-4-methylene-1,2-dioxolanes

Takeshi Akasaka, Kikuko Takeuchi, Yoshihisa Misawa, and Wataru Ando*

*Department of Chemistry, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba-shi, Ibaraki, 305-8571, Japan


The reaction of singlet oxygen with several α,β -unsaturated aldimines (N-1-(2-alky1idene)-t-butylamines, 1a-c) gave the novel unsaturated hemiperacetal derivatives (3-amino-4-methylene-1,2-dioxolanes, 2a-c) of the hydroperoxy aldimines (3). α,β-Unsaturated aldimine (1e) which was held in the s-trans conformation failed to react vith singlet oxygen. The mechanistic implications are also discussed.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 453 - 465
Published online:
DOI: 10.3987/COM-88-S96
Biosynthetic Studies on the Chaetoglobosins K and L. Origin of the Extra Methyl Groups at C(10) and C(11)

Christph Spöndlin and Christoph Tamm*

*Institut für Organische Chemie, Universitat Basel, St. Johanns-Ring 19, CH-4056 Basel, Switzerland


Incorporation experiments on chaetoglobosin K (1) established that the 10’- as well as the 11’-methyl group are derived as C1-units from methionine. The methylation was shown to occur with retention of all three H-atoms in the cases of the 11’-, 12- and 18’-methyl groups, agreeing with the “CD3”-mechanism. The two diastereoisomeric racemates of 3-methyltryptophan with a 14C-label at the 2’-position were synthesized and administered to chaetoglobosin K (1) producing cultures, both leading to high incorporation rates. The deuterium atom of (2S,3R)-3-methyl-[2-2H]tryptophan, obtained by selective hydrolysis of the methyl ester with α-chymotrypsin was partially incorporated into the metabolite, establishing the (2S,3R)-enantiomer of the amino acid as a direct precursor.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 467 - 475
Published online:
DOI: 10.3987/COM-88-S98
New Furo[3,2-b]furans Derived from L-Ascorbic Acid

Kawporn Sussangkarn, Gabor Fodor,* Douglas Strope, and Clifford George

*Department of Chemistry, West Virginia University, Morgantown, WV 26506-6045, U.S.A.


The role of ascorbic aeid (1) as a Michael carbanion donor has been extended to a cyclic enedione, 2,3-dihydrobenzoquinone (6). Although 6 is a desmotropic form of hydroquinone it reacted with 1 as an α,β-unsaturated monoketone giving rise to 2-(1’,4’-diketo-2’-cyelohexyl)-3-keto-L-gulonolactone-3,6-cyclohemiketal which, in turn, was stabilized as the 3,1’-cyclohemiketal (8). The latter structure was proven by X-ray crystallography.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 477 - 480
Published online:
DOI: 10.3987/COM-88-S99
Enzymatic Aldol Condensation as a Route to Heterocycles: Synthesis of 1,4-Dideoxy-1,4-imino-D-arabinitol, Fagomine, 1-Deoxynojirimycin and 1-Deoxymannojirimycin

Richars L. Pederson and Chi-Huey Wong*

*Department of Chemistry, Texas A & M University, College Station, Texas 77843-3255, U.S.A.


1,4-Dideoxy-l,4-imino-D-arabinitol, fagomine (1, 2, 5-trideoxy-1, 5-imino-D-arabinohexitol), 1-deoxynojirimycin (1,5-dideoxy-1,5-imino-D-glucitol) and 1-deoxymannojirimycin (1,5-dideoxy-1,5-imino-D-mannitol) have been prepared via fructose-1,6-diphosphate aldolase catalyzed condensation followed by catalytic intramolecular reductive amination.

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Paper | Special issue | Vol 28, No. 1, 1989, pp. 481 - 487
Published online:
DOI: 10.3987/COM-88-S115
1-Methylpyrrolidine-2-acetic Acid, a Plausible Intermediate in the Biosynthesis of Cocaine

Edward Leete*

*Natural Products Labratory, Department of Chemistry, University of Minnesota, Misseapolis, Minnesota 55455, U.S.A.


Radioactive 1-methylpyrrolidine-2-acetic acid (0.5% absolute incorporation) was isolated from Erythroxylum coca plants which had been fed [2-14C]-1-methyl-δ1-pyrrolinium chloride. A systematic degradation of the 1-methylpyrrolidine-2-acetic acid established that all the radioactivity was located at its C-2 position. Since the cocaine isolated from this feeding experiment was labeled at C-5, this result is consistent with the hypothesis that 1-methylpyrrolidine-2-acetic acid, or a suitably activated ester, is an intermediate in the biosynthesis of cocaine.

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Review | Special issue | Vol 28, No. 1, 1989, pp. 489 - 519
Published online:
DOI: 10.3987/REV-88-SR1
Recent Developments of Free-Radical Substitutions of Heteroaromatic Bases

Francesco Minisci,* Elena Vismara, and Francesca Fontana

*Dipartimento di Chimica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy


The most recent mechanistic and synthetic aspects of the substitution of protonated heteroaromatic bases by nucleophilic carbon-centered radicals are reviewed. From mechanistic point of view the following aspects are discussed; i ) Structurereactivity relationship; i i ) Rearomatization of the radical adducts; iii) Solvent and isotope effects; iv) Overlap area with ionic reactions. The synthetic developments concern the following topics: i) Selectivity with carbonyl radicals; ii) Alkyl iodides as sources of alkyl radicals; iii) Alkylation by carboxylic acids; iv) Vinylation by olefins; v) Oxyalkylation by ethers; vi) Catalytic processes; vii) Substitution with strongly nucleophilic radicals.

Review | Special issue | Vol 28, No. 1, 1989, pp. 521 - 527
Published online:
DOI: 10.3987/REV-88-SR2
The Chemistry of 1,4-Dioxene(2,3-Dihydro-1,4-dioxin). Part VIII

Marcel Fétizon,* Pierre Goulaouic, and Issam Hanna

*Laboratoire de Syntèse, Ecole Polytechnique, 91128 Palaiseau, France


The chemistry of 1,4-dioxene has been reviewed, with a special emphasis on reactions potentially useful in synthesis .

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Review | Special issue | Vol 28, No. 1, 1989, pp. 529 - 545
Published online:
DOI: 10.3987/REV-88-SR4
Biomimetic Transformations of Sesquiterpene Lactones

Antonio G. Gonzárez,* A. Galindo, and H. Mansilla

*Instituto de QUímica Orgánica, Instituto de Productos Naturales Orgánicos, C. S. I. C./ Unversidad de La Laguna, La Laguna, Tenerife, Canary Islands, Spain


Some of the biomimetic transformations of sesquiterpene lactones practised in our laboratory are presented here and the biogenetic implications of the work are discussed.

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