期刊
PURE AND APPLIED CHEMISTRY
卷 84, 期 7, 页码 1621-1631出版社
WALTER DE GRUYTER GMBH
DOI: 10.1351/PAC-CON-11-10-34
关键词
aromatic; aryl spiroketals; chroman; [4+2] cycloaddition; Diels-Alder; natural products; ortho-quinone methide; oxidative [3+2] cycloaddition; spiroketals; total synthesis
资金
- Direct For Mathematical & Physical Scien [0840521] Funding Source: National Science Foundation
- Division Of Chemistry [0840521] Funding Source: National Science Foundation
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [0806356] Funding Source: National Science Foundation
- NIGMS NIH HHS [R01 GM064831] Funding Source: Medline
Two cycloaddition strategies are described that lead to various chroman spiroketals from assorted exocyclic enol ethers. Unlike conventional thermodynamic ketalization strategies, the stereochemical outcome for this approach is determined by a kinetic cycloaddition reaction. Thus, the stereochemical outcome reflects the olefin geometry of the starting materials along with the orientation of the associated transition state. However, the initial kinetic product can also be equilibrated by acid catalysis and reconstituted into a thermodynamic stereochemical arrangement. Thus, these strategies uniquely enable synthetic access to either the thermodynamic or kinetic conformation of the spiroketal stereocenter itself. Applications of these strategies in the syntheses of berkelic acid, beta-rubromycin, and paecilospirone are presented along with the use of a chroman spiroketal for the construction of heliespirones A and C.
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