- Detection, synthesis and absolute configuration of (+)-nortaylorione, a new terpene from Artemisia annua
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Nortaylorione a new nor-sesquiterpene, was identified among minor components of Artemisia annua (hybrid plants) essential oil. Its relative and absolute configurations were determined by GC and GC/MS equipped with a chiral column and coinjecting the essential oil with synthetic standards (racemic and homochiral), obtained in a few steps from commercial reagents. Pauson-Khand reaction was used as the key reaction in both synthetic pathways. The new natural product, named (+)-nortaylorione, is the (1'S)-cis-2-[2' ,2'-dimethyl-3'-(3''-butanon-1''-yl)-cyctopropyl]-2-cyclopenten-1-one.
- De Oliveira,Ferracini,Foglio,De Meijere,Marsaioli
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- 7-Step total synthesis of (+)-EBC-329: Photoisomerisation reveals new: Seco -casbane family member
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The first seco-casbane, EBC-329, isolated from the Australian rainforest, was synthesised from (+)-2-carene in seven steps. This endeavour not only established the absolute stereochemical assignment as (8R,9S)-EBC-329, but also identified, via photoisomer
- Vanden Berg, Timothy J.,Pinkerton, David M.,Williams, Craig M.
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p. 7102 - 7105
(2017/09/07)
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- Biomimetic synthesis of (+)-ledene, (+)-viridiflorol, (-)-palustrol, (+)-spathulenol, and psiguadial A, C, and D via the platform terpene (+)-bicyclogermacrene
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(+)-Bicyclogermacrene is a strained bicyclic and common sesquiterpene found in several essential oils. A short and good yielding synthesis of bicyclogermacrene proceeding in seven steps is reported. This terpene is used as key platform intermediate for a biomimetic access to several aromadendrene sesquiterpenoids, such as ledene, viridiflorol, palestrol, and spathulenol. Furthermore, bicyclogermacrene is shown to be the terpene component in the synthesis of the meroterpenoids psiguadial A, C, and D. Let nature be your guide! A concise synthesis of the terpene (+)-bicyclogermacrene enables its use as a platform for a fast access to a range of different terpenoids of the aromadendrene family and meroterpenoids of the psiguadial family (see scheme).
- Tran, Duc N.,Cramer, Nicolai
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p. 10654 - 10660
(2014/11/07)
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- Tandem ring opening/cyclization of vinylcyclopropanes: A facile synthesis of chiral bicyclic amidines
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An open and shut case: An interesting bromine-catalyzed tandem ring opening/cyclization reaction of bicyclic vinylcyclopropanes with chloramine-T ([TsNCl]Na) has been demonstrated to furnish chiral bicyclic amidine derivatives in good yield. A plausible m
- Ganesh, Venkataraman,Sureshkumar, Devarajulu,Chandrasekaran, Srinivasan
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p. 5878 - 5881
(2011/08/02)
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- Rhutenium-Catalyzed cis-Dihydroxylation of Alkenes: Scope and Limitations
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Oxidative ruthenium catalysis (0.07 molequiv RuCl3*(H2O)3, 1.5 molequiv NaIO4, EtOAc/CH3CN/H2O 3:3:1), beyond the usual C-C bond cleavage to give dicarbonyls, have been shown to syn-dihydroxylate a wide range of alkenes (except for strained bicyclic alkenes, sterically hindered trisubstituted alkenes, and most tetrasubstituted alkenes) to give vicinal diols rapidly (within minutes) and efficiently.The minor products are the usual oxidative fission products, namely, ketones and aldehydes or carboxylic acids, and sometimes ketols.Longer reaction times lower the yields of most diols, probably owing to oxidative glycol cleavage.Reactions with substrates containing one or more electron-withdrawing groups in conjugation with or adjacent to the alkene moiety are generally slower but give better yields.The diastereoselectivity of the present "flash" dihydroxylation, anti to the existing α-stereogenic center, with cycloalkenes is excellent whereas that with acyclic alkenes is moderate to poor.Sodium metaperiodate is still the best co-oxidant for the catalytic reaction.Aqueous acetonitrile (approximately 86percent) as an alternative solvent system was found to give better yields of 1,2-diols than the original solvent system in some cases. - Keywords: alkenes, catalysis, dihydroxylations, electrophilicity, ruthenium compounds.
- Shing, Tony K. M.,Tam, Eric K. W.,Tai, Vincent W.-F.,Chung, Ivan H. F.,Jiang, Qin
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- Synthesis of Macrocyclic Terpenoid Hydrocarbons by Intramolecular Carbonyl Coupling: Bicyclogermacrene, Lepidozene, and Casbene
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Total syntheses of two germacrane sesquiterpenes, bicyclogermacrene (1) and lepidozene (2), and of the cembrane sesquiterpene casbene (3) are discussed.Bicyclogermacrene and lepidozene were prepared in seven steps from geranylacetone by routes that involve titanium-induced cyclizations of cis- and trans-2,2-dimethyl-3-cyclopropanecarbaldehyde, respectively. (+)-Casbene was prepared from (+)-2-carene and 6-methyl-5-hepten-2-one by a route whose key steps were the palladium-catalysed cross-coupling of vinylic iodide 31 with homoallylic organozinc reagent 32 and titanium-induced cyclization of cis-2,2-dimethyl-3-cyclopropanecarbaldehyde (16).
- McMurry, John E.,Bosch, Gregory K.
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p. 4885 - 4893
(2007/10/02)
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