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
Edward C. Taylor's Special Issues, Vol. 35, No. 2, 1993
Published online:
■ Efficient Olefinaton with α-Alkyl Cyclic Phosphonamides
Stephen Hanessian,* Youssef L. Bennani, and Yves Leblanc
*Department of Chemistry, University of Montreal, Montréal, Que’bec H3C 3J7, Canada
Abstract
A variety of acyclic and cyclic aldehydes and ketones can be converted into the corresponding alkylidene, benzylidene and methoxycarbonyl alkylidene derivatives by treatment with 1,3,2-diazaphospholidine-2-alkyl-1,3-dimethyl 2-oxides (α-alkyl cyclic phosphonamides) under mild conditions. This olefination method is particularly useful in the case of enolizable carbonyl compounds.
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■ Simple and Effective Approaches to Coumestans and Azacoumestans
Wolfgang Stadlbauer and Thomas Kappe*
*Institute for Organic Chemistry, Karl-Franzens-University Graz, Heinrichstrasse. 28, A-8010 Graz, Austria
Abstract
Coumestans and its mono- and diaza-analogs (1-4), which possess potential estrogenic or antiestrogenic activities, can be synthesized easily in excellent yields (60-95%) by the following four methods, starting either from 4-hydroxy-3-arylcoumarins and -quinolones (16) (or from 4-amino derivatives (19)) by catalytic dehydrogenation or reacting 3-hydroxy-3-arylquinoline-2,4-diones (21) by acid-catalyzed dehydration. Phenyl ethers (25) cyclize by catalytic or photochemical dehydrohalogenation to give 1 or 2. Another way is the thermal or photochemical decomposition of 4-azido-3-aryl derivatives (28) to the azacoumestans (3-4).
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■ New Chemistry of Oxazoles
Alfred Hassner* and Bilha Fischer
*Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
Abstract
Oxazoles are versatile compounds that can undergo reaction with electrophiles (e.g. bromine) leading either to aromatic substitution or to addition products. The latter reactions are shown to proceed via N-bromooxazolium salts and can also be used for introduction of 4-substituents. Intramolecular formation of oxazolium salts also can take place and subsequent reaction with nucleophiles leads via azomethine ylides to interesting products. Diels-Alder reactions of oxazoles with olefins or acetylenes continue to be useful for synthesis of natural products containing pyridine or furan rings respectively. Heterodienophiles (N=N, C=O, C=N, C=S, N=O) are shown to react with electron rich oxazoles either inter or intramolecularly and give rise to triazolines, oxazolines, imidazolines, thiazolines or oxadiazolines. Lithiated oxazoles are useful intermediates either for isocyanides or for alkylated oxazoles.
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■ Antitumor Substtances from Higher Plants
Hideji Itokawa* and Koichi Takeya
*Department of Pharmacognosy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
Abstract
In this review, we summarize the isolation, structural determination and bioactivity of antitumor and cytotoxic substances from higher plants which were collected in Japan, China, Korea, Southeast Asia and South America by us.
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■ The Beirut Reaction
Makhluf J. Haddadin* and Costas H. Issidorides
*American University of Beirut, Beirut, Lebanon
Abstract
Progress since 1976 in the chemistry of quinoxaline 1,4-dioxides, phenazine 9,10-dioxides and benzimidazole 1,3-dioxides is reviewed with special emphasis on the synthesis, via the Beirut reaction, of these products and their thermal and photochemical reactions.
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■ The Chemistry of DDATHF (5,10-Dideaza-5,6,7,8-tetrahydrofolic Acid) as Antitumor Agent
Inci Durucasu*
*Atatürk Üniversitesi, Fen-Edebiyet Fakültesi, Kimya Bölümü 25240 Erzurum, Turkey
Abstract
Over the past 40 years, big efforts have been devoted to the development of novel folate antimetabolites. All of the potent antifolates have reportedly been inhibitors of dihydrofolate reductase (DHFR). In 1985, Taylor and et al. reported the synthesis of 5,10-dideaza-5,6,7,8-tetrahydrofolic acid, DDATHF, which exhibits broad and selective antitumor activity as an inhibitor of glycinamide ribonucelotide formyltransferase (GARFT). DDATHF is a close analog of tetrahydrofolic acid, differs only by replacement of the 5- and 10-position nitrogen atoms by carbon. It may exist in two diastereomeric forms, differing in configuration at carbon 6. Both diastereomers of DDATHF are potent inhibitors of cell growth in culture. DDATHF is currently in Phase II clinical trials.
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■ Molybdenum Cofactor: Its Biological Significance, Structural, and Synthetic Aspects
Shyamaprosad Goswami*
*B. V. Patel Pharmaceutical Education, Reserach Development Centre, Sarkhej-Gadginagar Highway, Thaltej, Ahmedabad 380054, India
Abstract
A brief review of the biological importance, structural and synthetic aspects of the extremely labile molybdenum cofactor (Moco) and its different stable oxidative degradation forms has been presented.