- NEW SESQUITERPENOIDS FROM THE OLEORESIN OF Abies alba
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The structures of four new sesquiterpenoids from the oleoresin of Abies alba have been studied, On the basis of various spectral characteristics, the structures of (10S, 11S)-himachala-2,4-diene, (10S, 11S)-himachala-3(12),4-diene, humula-4,9-dien-8-ol, and (4S, 5S, 10S)-selina-6-en-4-ol have been proposed for the compounds isolated.The stereochemistry of the assymetric centers was determined by the conversion of these compounds into known sesquiterpenes and also by analysis of PMR spectra with a shift reagent.
- Khan, V. A.,Tkachev, A. V.,Pentegova, V. A.
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p. 606 - 611
(2007/10/02)
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- Base-induced Thermal Decomposition of Terpenoid Tosylhydrazones: Part I - Chemistry of Diazolongibornanes
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The elusive progenitor neolongifolene (6) of Isolongifolene (2) has been synthesized (44percent yield) from longicamphor tosylhydrazone (8) by generating the crucial longibornyl-10-cation (5) under basic conditions in a protic (sodium-ethylene glycol) Bamford-Stevens reaction; Longicyclene (13, 15percent) and the ether-carbinol(14, 16percent) are the other products.Exposure of 6 to BF3.OEt2 in benzene transforms it to 2.Under aprotic conditions (sodium methoxide-diglyme) 8 gives longicyclene (13) as the major product (41percent) with a trace (5percent) of 6.When 8 is exposed to n-butyllithium in hexane, the novel longibornylene (21) (54percent) is formed.Generation of anelectron-deficient species at the C-4 position on the longibornane skeleton via 24->25->26 has been studied: a novel transannular carbene insertion product 30 is formed from 24 under aprotic conditions only .In this reaction olefins 27 and 28 are very minor (5percent); the major crystalline compound is the 4-oxolongibornane azine (31) (ca. 30percent).Refluxing 24 in ethylene glycol with the sodium salt of ethylene glycol yields 27 (15percent) and 28 (16percent), besides the oxygenated compound 29 (19percent).
- Satyanarayana, N.,Nayak, U. R.
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- A SYNTHESIS OF CULMORIN FROM LONGIFOLENE VIA 8,11-DIBROMO-LONGIBORNANE
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A 10-step synthesis of culmorin (XII) from longifolene (I), which involves the formation of 8,11-dibromo-longibornane (VII) as the key intermediate from longicyclene (III), is described.
- Reddy, R. Thimma,Nayak, U. R.
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p. 543 - 548
(2007/10/02)
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- STABLE CARBOCATIONS FROM TERPENOIDS. III. GENERATION OF STABLE IONS FROM LONGIFOLENE
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The salts of the stable carbocations previously postulated for the rearrangement of longifolene (I) into isolongifolene (II) were generated, and their spectral characteristics and some of their chemical properties were studied.A scheme is proposed for the rearrangement of the compounds (I) -> (II).It was shown that if the optically active olefin (I) is used the degree of racemization of the product (II) decreases with decrease in the acidity of the medium as a result, evidently, of a change in the ratio of the rates of the intramolecular rearrangements in the initially formed cation (IV), depending on the nature of the medium.
- Polovinka, M. P.,Osadchii, S. A.,Korchagina, D. V.,Dubovenko, Zh. V.,Barkhash, V. A.
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p. 1449 - 1457
(2007/10/02)
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- Methylcyclopropane - Soft Acid Reaction : Part I - Novel Lead Tetraacetate Oxidation of Longicyclene/Cyclene
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In a novel lead tetraacetate (LTA) oxidation of the methylcyclopropane moiety in longicyclene (2), the elusive "true" longicamphor (3) (10-ketolongibornane) has been generated for the first time.Furthermore, the homoenol --> homoketone mechanistic pathway has also been established for the LTA/base transformation of longicyclene (2)/cyclene (6) to longicamphor (3)/camphor (7) by actual isolation of the intermediate homoenolacetate in either case.That longicamphor (3) is truly the "longi" homologue of the monoterpenoid camphor has been convincingly proved by the positive response of 3 to two key raections of 7.
- Suryawanshi, S. N.,Nayak, U. R.
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