Biomimetic cyclization of gallicin to form guaianolides

Gonzlez, Antonio G.; Galindo, Antonio; Mansilla, Horacio

doi:10.1016/0040-4020(80)80216-x

Cited by 19 publications

(12 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Compressanoltde {4<x-Hydroxy-/ , , ß,7 . 11 ß--guaian-10( 14i-en-6,12-olide} [4]. -Compound 4: C15H2203, mol wt 250, gum; eims mlz (% rel.…”

Section: Experimental General Experimentalmentioning

confidence: 99%

“…

A reinvestigation of BF,-mediated rearrangement products of 11,13-dihydroparthenolide [1] provided, besides the previously obtained dihydromichelliolide [5], the following new products: the xanthanolide 2-desoxy-11ß, 13-dihydro-epiparthemollin [2], a 4methylene-5a-hydroxy-«r-guaianolide [3], and the rZr-guaianolide compressanolide [4], Their mechanisms of formation were interpreted as rearrangements involving carbocation intermediates.

…”

mentioning

confidence: 99%

“…The structure determination of guaianolides 4 and 5 involved comparison of their spectroscopic data with those of known compounds previously reported in the literature (4,17). The trichloroacetylcarbamate derivative of 5 exhibited paramagnetic shift of 0.5 for H-5 and 0.35 ppm for the 4-Me.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Biomimetic Transformations of 11,13-Dihydroparthenolide and Oxidative Rearrangements ofa Guai- 1(10)-en-6,12-olide

Parodi¹,

Fronczek²,

Fischer³

1989

J. Nat. Prod.

View full text Add to dashboard Cite

“…Compressanoltde {4<x-Hydroxy-/ , , ß,7 . 11 ß--guaian-10( 14i-en-6,12-olide} [4]. -Compound 4: C15H2203, mol wt 250, gum; eims mlz (% rel.…”

Section: Experimental General Experimentalmentioning

confidence: 99%

“…

…”

mentioning

confidence: 99%

See 1 more Smart Citation

Biomimetic Transformations of 11,13-Dihydroparthenolide and Oxidative Rearrangements ofa Guai- 1(10)-en-6,12-olide

Parodi¹,

Fronczek²,

Fischer³

1989

J. Nat. Prod.

View full text Add to dashboard Cite

“… Therefore, these transformations can be considered as an alternative way to guaianolide biosynthesis. González et al described a similar transformation of the germacranolide gallicin to give guaianolides …”

Section: Resultsmentioning

confidence: 99%

15-Hydroxygermacranolides as Sources of Structural Diversity: Synthesis of Sesquiterpene Lactones by Cyclization and Rearrangement Reactions. Experimental and DFT Study

et al. 2018

View full text Add to dashboard Cite

A study on the electrophile-induced rearrangement of two 15-hydroxygermacranolides, salonitenolide and artemisiifolin, was carried out. These compounds underwent electrophilic intramolecular cyclizations or acid-mediated rearrangements to give sesquiterpene lactones with different skeletons such as eudesmanolides, guaianolides, amorphanolides, or other germacranolides. The cyclization that gives guaianolides can be considered a biomimetic route to this type of sesquiterpene lactones. The use of acetone as a solvent changes the reactivity of the two starting germacranolides to the acid catalysts, with a 4,15-diol acetonide being the main product obtained. The δ-amorphenolide obtained by intramolecular cyclization of this acetonide is a valuable intermediate for accessing the antimalarials artemisinin and its derivatives. Mechanistic proposals for the transformations are raised, and to provide support them, quantum chemical calculations [DFT B3LYP/6-31+G(d,p) level] were undertaken.

show abstract

“…This constant coincided with that for one of the gem-hydroxyl protons. Therefore, the vinylmethyl group was involved in the formation of a secondary-tertiary double bond, which is traditionally located at C 4 -C 5 in germacranolide dienes [7][8][9].…”

mentioning

confidence: 99%

Structure of iskenderolide

Serkerov

Aleskerova

2012

Chem Nat Compd

View full text Add to dashboard Cite

We continued research on the structure of a new sesquiterpene lactone isolated from the aerial part of Artemisia iskenderiana Rzazade, a new sage species described by Rzazade [1] but not recognized by Polyakov [2,3].The composition of iskenderolide was C 15 H 22 O 4 , mp 190-191°C. The IR spectrum showed absorption bands for hydroxyls (3300 cm -1 ), a J-lactone carbonyl (1755), and double bonds (1665, 1650). The appearance in the IR spectrum of a strong band at 910 cm -1 indicated that the molecule might contain a methylene double bond [4].The PMR spectrum of the compound exhibited a doublet for a secondary methyl on a lactone ring (1.42 ppm, J = 7 Hz, CH 3 -CH<) and a singlet characteristic of a vinylmethyl (1.60 ppm). Weakly split (by ~1.5 Hz) 1H doublets at 5.13 and 5.40 ppm belonged to a H 2 C=C< group.The appearance in the spectrum of resonances for exomethylene and vinylmethyl groups in addition to a doublet for an olefinic proton (5.28 ppm, J = 9.65 Hz) suggested that the molecule contained methylene and secondary-tertiary double bonds. A 2H resonance at 3.84 ppm was apparently the result of the overlap of lactone and gem-hydroxyl protons. The gemhydroxyl proton of a second OH group appeared in the spectrum as a triplet at 4.35 ppm (1H, J = 9.65 Hz).According to 13 C NMR, 13 C DEPT 135, 13 C DEPT 90, and 13 C DEPT 45 spectra, iskenderolide was based on a germacrane C skeleton and not guaiane, as proposed earlier [5]. The 13 C NMR spectrum taken with full suppression of proton spin-spin coupling showed 15 singlets (15.0, 17.0, 35.0, 36.0, 42.0, 43.0, 58.0, 72.0, 76.0, 83.0, 112.0, 129.0, 137.0, 152.0, and 180.0 ppm) that were consistent with the presence in the molecule of 15 C atoms. According to 13 C DEPT 45 and 13 C DEPT 135 spectra, 12 of these belonged to protonated C atoms. Of those, the ones at 15.0 and 17.0 were characteristic of two methyls; 35.0, 36.0, and 42.12, three cyclic methylenes; 112.0, an exocyclic methylene; 42.0, 58.0, 72.0, 76.0, and 83.0, five methines; 137.0, an olefinic C atom. Resonances at 138.0, 152.0, and 180.0 ppm in the 13 C NMR spectrum were due to three unprotonated C atoms, i.e., C-10, C-4, and C-12, respectively.Because the resonance of the gem-hydroxyl proton of one OH group overlapped the resonance of the lactone proton (3.84 ppm), the structure of the overlapping resonances could not be examined. Therefore, iskenderolide was acetylated. This produced a compound of formula C 19 H 26 O 6 , mp 142-143°C. Its IR spectrum showed absorption bands for a J-lactone C=O (1790 cm -1 ), ester C=O (1730, 1230), and double bonds (1675, 1650). The PMR spectrum exhibited two 3H singlets (2.01, 2.08 ppm) belonging to two acetyl groups. Now the gem-acetyl protons appeared in the spectrum as a doublet with weakly split (~1.5 Hz) components at 4.65 ppm (1H, J = 9.20 Hz) and a triplet at 5.40 ppm (1H, J = 9.65 Hz). The lactone proton appeared as a 1H multiplet at 3.9 ppm. A doublet at 1.35 ppm (3H, J = 7 Hz, CH 3 -CH<) and a singlet at 1.70 ppm (3H, CH 3 -C=) in the PMR spectrum of diacetyl...

show abstract

Biomimetic cyclization of gallicin to form guaianolides

Cited by 19 publications

References 12 publications

Biomimetic Transformations of 11,13-Dihydroparthenolide and Oxidative Rearrangements ofa Guai- 1(10)-en-6,12-olide

Biomimetic Transformations of 11,13-Dihydroparthenolide and Oxidative Rearrangements ofa Guai- 1(10)-en-6,12-olide

15-Hydroxygermacranolides as Sources of Structural Diversity: Synthesis of Sesquiterpene Lactones by Cyclization and Rearrangement Reactions. Experimental and DFT Study

Structure of iskenderolide

Contact Info

Product

Resources

About