The constituents of cacalia decomposita A. Gray—IV: Structure of decompostin

doi:10.1016/0040-4020(68)89046-5

Tetrahedron

Volume 24, Issue 1, 1968, Pages 477-483

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Abstract

Decompostin, a constituent of Cacalia decomposita A. Gray has been shown to be a sesquiterpene of eremophylane series with structure Ia.

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Cited by (28)

Vibrational circular dichroism behavior of quinol cacalolides from Psacalium aff. sinuatum
2021, Journal of Molecular Structure
Citation Excerpt :
Cacalolides take their name after the isolation of cacalol (1a) and cacalone (2a) from the roots of Cacalia decomposita [1] which is currently a synonym for Psacalium decompositum [2]. The structure of cacalol suffered a couple of revisions to ascertain the location of the secondary methyl group [3–6] on the scaffold of this non-sesquiterpenoid which is biogenetically generated by a Wagner-Meerwein migration of the angular methyl group of the eremophilane decompostin isolated from the same roots [7] as evidenced by chemical correlation [8]. The structure of 1a (Fig. 1) was independently confirmed by total synthesis [8–11] and by single-crystal X-ray diffraction of its derived methyl ether [12].
In search to find levels of density functional theory (DFT) for the accurate prediction of vibrational circular dichroism (VCD) spectra of cacalolides, we undertook the evaluation of isomeric quinols. To gain compounds that provide experimental VCD spectra for comparative purposes to the calculated spectra, we prepared the hexanes extracts of the roots of Psacalium aff. sinuatum (Cerv.) H. Rob. & Brettell. They afforded the known furotetralin cacalol (1a), the isomeric quinols cacalone (2a) and epi‑cacalone (3a), and the furodehydrotetralin cacalohastine (4). In an earlier work we found that the absolute configuration (AC) determination of 1a by VCD required the study of its acetyl derivative 1b when comparing the experimental data with DFT spectra calculated at the commonly used B3LYP/DGDZVP level of theory. Herein the AC of acetylcacalone (2b) and of non-acetylated 3a were addressed using the same VCD methodology for which it is difficult to predict which DFT level of theory would provide satisfactory results for the uncommon quinol chromophores. It turned out that epi‑cacalone (3a) required the B3PW91/DGDZVP2 level of theory, while in the case of natural occurring 2a it was necessary, as in the case of 1a, to study the acetyl derivative 2b since in 2a the tertiary hydroxy group is prone to intermolecular associations in solution. In addition, the dihydronaphthofuran 4 required the PBEPBE/DGDZVP level of theory, mainly used for aromatic compounds, to be modeled satisfactorily.
Furanoeremophilanes from Euryops arabicus alleviate metabolic syndrome-associated exaggerated vasoconstriction via direct vasodilatation
2019, Phytochemistry Letters
Citation Excerpt :
Moreover, a secondary methyl group was found to be responsible for a doublet at δH 0.88 (J = 6.8 Hz) and a singlet at δH 0.93 for an angular methyl group in addition to a singlet proton at δH 6.41. The previous data suggested the presence of acyloxy substituted furanoeremophilane nucleus (Rodriguez-Hahn et al., 1968). HMBC spectrum indicated a correlation between the proton at δH 6.41 and carbonyl groups at δC 170.8 assigned for the acyloxy carbonyl at C1.
Eremophilane, bakkane, secoeremophilane, and secobakkane sesquiterpenoids from Ligularia virgaurea collected in China
2019, Tetrahedron
Secobakkane B (C-6/C-7 cleaved secobakkane type aldehyde), secovirgaurenols B and C (C-8/C-9 cleaved secoeremophilane type), a 1β,10β-epoxyfuranoeremophilane, two 1β,10β-epoxyeremophilanolides, and fukinospirolide C (bakkane-type lactone), as well as 33 known compounds were isolated from three samples of Ligularia virgaurea collected in China. Two of the three analyzed samples were grouped in the neoadenostylone (N) type, and the rest, a mixture of the 6-hydroxyeuryopsyn (H) and cacalol (C) types, out of five chemotypes found in this species.
Chemical and genetic diversity of Ligularia virgaurea collected in northern Sichuan and adjacent areas of China. Isolation of 13 new compounds
2012, Tetrahedron
Citation Excerpt :
The isolated compounds were grouped into five, i.e., (1) cacalol (5) and its derivatives, (2) furanoeremophilanes, (3) non-furanoeremophilanes, (4) other terpenoids, and (5) sesquiterpene dimers, as listed in Chart 1 and Table 2. Among the isolated compounds, virgaurenones A (1),3 B (2),3 cacalol (5),13,14 6,15,16 cacalolide (7),17 epicacalolide (8),17 hydroxycacalolide (9),18 hydroxyepicacalolide (10),18 cacalone (11),19 epicacalone (12),19 13,20,21 14,20,21 16,22 adenostylone (17),23 18,24 neoadenostylone (19),25 decompostin (20),26 21,16,27 6-hydroxyeuryopsin (22),28 6-acetoxyeuryopsin (24),28 6-angeloyloxyeuryopsin (25),29 26,28 27,30 28,30 29,30 30,31,32 31,32 32,33 33,16,27,30 34,34 35,30 36,29 6-hydroxyligularenolide (39),31 toluccanolide A (40),35 41,33 eremoligenol (42),36 43,37 9-hydroxyfarfugin B (46),6 48,38 51,39 52 (commercially available), and adenostin A (57)40 were known. The structures of new compounds (15, 23, 37, 38, 44, 45, 47, 49, 50, 53, 54, 55, and 56) were determined mainly by 2D NMR spectroscopy and the details are described below.
Root chemicals and DNA sequences were analyzed for Ligularia virgaurea collected in the northern Sichuan Province and adjacent areas of China. Thirty-eight samples were found to contain five chemotypes, two known and three new ones. From samples of the new chemotypes, 13 new compounds were isolated, including 3 sesquiterpene dimers and some rearranged eremophilanes. The DNA sequences suggested that the chemotype differentiation had a genetic origin.
Five new subspicatins and noreremophilane from Parasenecio petasitoides collected in China
2011, Tetrahedron Letters
Five new 1β-angeloyloxyeremophilanolides (subspicatins H–L) and 1β-angeloyloxytetranoreremophilanone (norsubspicatin A), were isolated from the EtOAc extracts of Parasenecio petasitoides and their structures established on the basis of spectroscopic analyses. They are biogenetically mutually related to each other and represent a new category in the Parasenecio group. These findings suggest that there is diversity in this species, too.
Recent Advances in Furan Chemistry. Part II
1982, Advances in Heterocyclic Chemistry
Furan resembles thiophene rather than pyrrole that is photochemically converted to a derivative of 5-azabicyclo pentane. The reactivity of furan is most often associated with triplet states. Calculations (INDO) of charge distribution agree with reactivities actually found, and triplet σ-complexes are suggested as key intermediates. Low-lying triplet states have been detected in furan by variable-angle electron-impact spectroscopy. The excited state may be quenched by the furan without any indication of exciplex formation. The well-known 1,4-cycloadditions to furan are accorded much attention for both theoretical and synthetic reasons. Furans are used to trap transient alkenes. The chapter discusses the chemistry of furanols, furanamines and furanthiols. These two aspects—rearrangements and eliminations—of furan chemistry are placed together as neither is particularly extensive and as they often have points in common, especially in reactions leading to methylene dihydrofurans. These are regarded as tautomers of alkylfurans that often rearrange themselves to true furans. The chapter discusses macrocycles containing furan units where the chemistry of the furan is more than a passing interest. Furans have played a considerable part in the development of annulene chemistry, largely because they provide suitable building blocks for generating macrocyclic rings. The structure, physicochemical properties, and reactivity of furan chemistry are also described.

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^☆: Contribution No. 245 from the Instituto de Química de la Universidad Nacional Autónoma de México.

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The constituents of cacalia decomposita A. Gray—IV: Structure of decompostin☆

Abstract

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