7715-89-1Relevant academic research and scientific papers
Unified synthesis of eudesmanolides, combining biomimetic strategies with homogeneous catalysis and free-radical chemistry
Barrero, Alejandro F.,Rosales, Antonio,Cuerva, Juan M.,Oltra, J. Enrique
, p. 1935 - 1938 (2007/10/03)
(Matrix presented) A general procedure for the synthesis of both 12,6- and 12,8-eudesmanolides has been developed. The key step is the titanocene-catalyzed radical cyclization of accessible epoxygermacrolides. The novel reagent 2,4,6-trimethyl-1-trimethylsilylpyridinium chloride, both compatible with oxiranes and capable of regenerating Cp2TiCl 2 from Cp2Ti(Cl)H and Cp2Ti(Cl)OAc, played an important role in the catalytic cycle leading to exocyclic alkenes.
Effects of solvents and water in Ti(III)-mediated radical cyclizations of epoxygermacrolides. Straightforward synthesis and absolute stereochemistry of (+)-3α-hydroxyreynosin and related eudesmanolides
Barrero, Alejandro F.,Enrique Oltra,Cuerva, Juan M.,Rosales, Antonio
, p. 2566 - 2571 (2007/10/03)
The Cp2TiCl-mediated rearrangement of 1,10-epoxy-11β,13-dihydrocostunolide (4) was carried out using different solvents and additives to develop an expeditious procedure for the synthesis of natural eudesmanolides via free-radical chemistry. In the nonhalogenated solvents THF, benzene, and toluene the transannular cyclization, initiated by the homolytic opening of the oxirane ring, selectively led to the desired exocyclic alkene 5. When water was added to THF, however, the main product was reduced eudesmanolide 8. Experiments with D2O confirmed that the H-4 of 8 comes from water. To rationalize these results, a mechanistic hypothesis based on a water-solvated Cp2TiCl complex is proposed. Finally, the usefulness of Cp2TiCl for the synthesis of natural eudesmanolides has been proved using this reagent in the key step for the chemical preparation of (+)-3α-hydroxyreynosin (1) and (+)-reynosin (17). These syntheses confirmed the chemical structure of 1 and established the absolute stereochemistry of the natural products 1 and 17. The results obtained suggest that the combination of the biomimetic strategy employed, with Ti(III)-mediated free-radical chemistry, may come to represent a general method for the enantiospecific synthesis of more than 170 natural eudesmanolides containing an exocyclic double bond between C-4 and C-15.
Syntheses of Four Possible Diastereoisomers of Bohlmann's Structure of Isoepoxyestafiatin. The Stereochemical Assignment of Isoepoxyestafiatin
Ando, Masayoshi,Yoshimura, Hideki
, p. 4127 - 4131 (2007/10/02)
The stereochemistry of isoepoxyestafiatin was determined to be 1β,10β:3α,4α-diepoxyguaia-11(13)-eno-12,6α-lactone by the syntheses of the four possible diastereoisomers 23-26.
Microbial Transformations of Sesquiterpenoids: Conversion of Deoxyvulgarin by Rhizopus nigricans and Aspargillus ochraceous
Arias, Jose M.,Breton, Jose L.,Gavin, Jose A.,Garcia-Granados, Andres,Martinez, Antonio,Onorato, M. Esther
, p. 471 - 474 (2007/10/02)
Microbial transformation of the sesquiterpene lactone deoxyvulgarin (2) has been carried out with Aspergillus ochraceous and Rhizopus nigricans cultures.A. ochraceous converted deoxyvulgarin (2) into vulgarin (3) and 11,13-dihydrodouglanin (4).R. nigricans transformed deoxyvulgarin (2) into vulgarin (3), erivanin (6), and 1β-hydroxy-2-oxoeudesm-3-en-6,13-olide (7).Vulgarin (3) was obtained chemically by epoxidation of deoxyvulgarin (2) in one-step process in virtually quantitative yield.A pathway proposed for the conversion of deoxyvulgarin (2) into more functionalized metabolites is discussed.
BIOMIMETIC SYNTHESIS OF 5α-HYDROXY-GUAIANOLIDES
Gonzalez, Antonio,Galindo, Antonio,Palenzuela, Jose A.,Mansilla, Horacio
, p. 2771 - 2774 (2007/10/02)
A 5α-hydroxy-guaianolide was synthesized biomimetically from a 5-oxo-E-1(10)-germacrenolide, the stereoselectivity of the cyclization being attributed to preferred conformation.
THE TOTAL SYNTHESIS OF 1-OXYGENATED EUDESMANOLIDES
Hijfte, Luc Van,Vandewalle, Maurits
, p. 4371 - 4382 (2007/10/02)
A route towards 1-oxygenated eudesmanolides, via a (2+2) photocycloaddition reaction for constructing the decalin framework is described.The following natural substances have been synthesized. (+/-)-dihydroreynosin (1), (+/-)-1-oxo-dihydromagnolialide (2)
Studies on the Syntheses of Sesquiterpene Lactones. 8. Syntheses of Saussurea Lactone, 8-Deoxymelitensin, and 11,12-Dehydro-8-deoxymelitensin via a Novel Fragmentation Reaction
Ando, Masayoshi,Tajima, Kiyoshi,Takase, Kahei
, p. 1210 - 1216 (2007/10/02)
Saussurea lactone (4), 8-deoxymelitensin (18), and 11,12-dehydro-8-deoxymelitensin (23) have been synthesized from (11S)-1,1-(ethylenedioxy)eudesm-3-eno-13,6α-lactone (6) in ten steps, seven steps, and nine steps, respectively.The key step involves a nove
Biogenetic-type Synthesis of Santonin, Chrysanolide, Dihydrochrysanolide, Tulirinol, Arbusculin-C, Tanacetin, and Artemin
El-Feraly, Farouk S.,Benigni, Daniel A.,McPhail, Andrew T.
, p. 355 - 364 (2007/10/02)
The title compounds were synthsised from their possible biogenetic precursors through hydroperoxide intermediates generated by photo-oxygenation.This route for biological oxygenation may serve as a substitute to epoxidation.The 13C n.m.r. special assignments for all intermediates were made.Single-crystal X-ray analyses unequivocally established the 1S configuration in dihydrochrysanolide (14) and its hydroperoxy-analogue (12).Isomorphous crystals of (12) and (14) belong to the monoclinic system, space group P21, with a = 14.350(6), b = 5.882(3), c = 10.343(3) Angstroem, β = 107.64(2) deg, Z = 2, for (12), and a = 14.461(6), b = 5.887(3), c = 9.698(4) Angstroem, β = 107.44(2) deg, Z = 2, for (14).Least-squares refinement of atomic parameters converged to R 0.040 for (12) and 0.033 for (14) over 1484 and 1300 reflections, respectively, measured by diffractometer.
