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VERA, W.; MORA, H.; LAYA, M. S.; BEDOYA, L.; CABRERA, E. V.; J. Sci. Ind. Res. 65 (2006) 4, 299-308; Cent. Quim., Inst. Venez. Invest. Cient., Caracas 1020-A, Venez.; Eng.) -Lindner 33-282

The data on the use of silica gel in organic synthesis are The data on the use of silica gel in organic synthesis are presented. Some specific features of cyclisation (both intra-and presented. Some specific features of cyclisation (both intra-and intermolecular) reactions, rearrangements, reduction, oxidation, intermolecular) reactions, rearrangements, reduction, oxidation, condensation, formylation, hydration and dehydration, protec-condensation, formylation, hydration and dehydration, protection of functional groups, tion of functional groups, etc etc., in the presence of silica gel, are ., in the presence of silica gel, are discussed. The bibliography includes 96 references discussed. The bibliography includes 96 references. .

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This article reviews the isolation, biological activity and syntheses of several diterpenes. The chemistry and biological activities of norditerpene dilactones have been described. The aim of the present article is to provide an overview on the important role of diterpenoid compounds in medicine and agriculture. The synthetic discussions of these diterpenes are very briefly described. Dedicated to Professor Kenji Mori for his valuable contributions to Terpene Chemistry.COOH Me Me OH Me Me H The Chemistry of Bioactive Diterpenes

Diallylphenyl, allylbenzylphenyl and allylmethylphenyl phosphines were pyrolized in a stirred-flow reactor at 380-429"C/7-20 A six-center cyclic transition state unimolecular reaction mechanism, consistent with the aboue Arrhenius parameters, is proposed for the propene elimination reaction.

Po. S. Poon, who received her Doctorate degree in 2007 from Venezuelan Institute of Scientific Research (IVIC), is working at IVIC as an Investigator in the Department of Chemistry. Her research encompases the synthesis of terpenoid and bioactive compounds. She was received the Paula Prize from IVIC for her high academic achievement.Manuel S. Laya obtained his MSc degree in 1997 from IVIC and is now working as Research Associate in the Department of Organic Chemistry, IVIC. He has published more than 30 papers, most of which are related to synthetic studies on terpenoid compounds.Ajoy K. Banerjee, who received his PhD in 1965 from the University of Kolkata (India), joined IVIC in 1968. Since 1982 he has been working as Senior Research Scientist. Most of his work is related to synthetic studies on terpenoid compounds (diterpenes and sesquitepenes). He teaches organic chemistry and supervises students who join IVIC for MSc or PhD degrees. Dr Banerjee is the author of two books on organic chemistry, written in Spanish, and several papers. Modifications 4. Synthetic applications 2. General features 5. Conclusion 3. Mechanism 6. ReferencesThis review provides a brief description of the Krapcho dealkoxycarbonylation and its recent applications in the synthesis of organic compounds and natural products. The general features of the Krapcho reaction, its mechanism and several modifications of the Krapcho reaction are discussed.