7715-91-5Relevant 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.
SYNTHESIS, BIOTRANSFORMATION AND STEREOCHEMISTRY OF 6β-SESQUITERPENE LACTONES: SYNTHESES OF 6β-ARTEPAULIN, 11,13-DIHYDRO-6β-TUBERIFERIN, 5,15-DIHYDRO-6β-OOPODIN, 4-EPI-6β-VULGARIN AND 6β-VULGARIN
Amate, Yolanda,Breton, Jose L.,Garcia-Granados, Andres,Martinez, Antonio,Onorato, Esther,Buruaga, Antonio Saenz de
, p. 6939 - 6950 (2007/10/02)
6β-Artepaulin, 11,13-dihydro-6β-tuberiferin, 4,15-dihydro-6β-oopodin, 4-epi-6β-vulgarin and 6β-vulgarin were obtained from α-santonin.Stereochemical studies showed that the configuration at C-6 is decisive in the chemical behaviour of the A ring.Biotransformation of 1-oxo-5,6α,4,11βH-eudesm-2-en-6,12-olide with Rhizopus nigricans cultures probed to be a very efficient alternative way to obtain 4-epi-6β-vulgarin, which was then converted to 6β-vulgarin, a convenient starting material for biogenetical studies of pseudoguaianolides.A new 8β-hydroxyl derivative obtained from this biotransformation constitutes a new approach to the synthesis of 8,12-eudesmanolides and other sesquiterpenolides.Molecular structures were determined mainly by mono- and bidimensional nmr experiments.
