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Ring fission of chiral cyclic acetals plus intramolecular [4 + 2] cycloaddition: a sequential access to medium-size lactones. Application to the synthesis of carbasugars
- Source :
- Organic and Biomolecular Chemistry, Organic and Biomolecular Chemistry, Royal Society of Chemistry, 2005, 3 (7), pp.1308-1318. ⟨10.1039/B419381D⟩
- Publication Year :
- 2005
-
Abstract
- A set of alpha,beta-unsaturated cyclic acetals were reacted with t-butyllithium in THF. A conjugate elimination took place, triggering a ketal ring cleavage when two eq. of TMEDA were added to the medium. The lithium alcoholate thus obtained could be trapped in situ by 2,2,2-trifluoroethyl acrylate. The resulting acryloyl (1Z,3E)-dienyl ether was then submitted to an intramolecular Diels-Alder cycloaddition under high pressure (12 kbar, 50 degrees C). Depending on the structure of the linkage between the diene and the acrylate, the expected ("fused") lactones were obtained with total endo- or exo-selectivities and high to complete diastereoselectivities. A remarkable inversion of selectivity, from endo to exo, with respect to the stereochemical elements of the tether could be observed in these cases. A five step diastereoselective transformation of two of the resulting nine-membered ring lactones into modified carbasugars was finally achieved in 23% overall yield.
- Subjects :
- Models, Molecular
Diene
Stereochemistry
Carbohydrates
Ether
010402 general chemistry
Ring (chemistry)
Biochemistry
01 natural sciences
Medicinal chemistry
chemistry.chemical_compound
Lactones
Acetals
[CHIM.CRIS]Chemical Sciences/Cristallography
[CHIM]Chemical Sciences
Physical and Theoretical Chemistry
ComputingMilieux_MISCELLANEOUS
Acrylate
[CHIM.ORGA]Chemical Sciences/Organic chemistry
010405 organic chemistry
Chemistry
Organic Chemistry
Carbasugars
Stereoisomerism
[CHIM.MATE]Chemical Sciences/Material chemistry
General Medicine
Cycloaddition
0104 chemical sciences
Cyclization
Intramolecular force
Selectivity
Subjects
Details
- ISSN :
- 14770520 and 14770539
- Volume :
- 3
- Issue :
- 7
- Database :
- OpenAIRE
- Journal :
- Organicbiomolecular chemistry
- Accession number :
- edsair.doi.dedup.....d0ab4d44118e3d36cb72e98307fc2ce2