The stereochemistry of the 1,3-dipolar cycloadditions of diazomethane to pseudoguaianolides
| Autor: | Pedro Joseph-Nathan, J. Jesús Manríquez-Torres, Adriana Ortiz-León, José G. Alvarado-Rodríguez, J. Martín Torres-Valencia, Carlos M. Cerda-García-Rojas |
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| Rok vydání: | 2017 |
| Předmět: |
010405 organic chemistry
Stereochemistry Diazomethane Organic Chemistry Absolute configuration 010402 general chemistry Sesquiterpene 01 natural sciences Catalysis Cycloaddition 0104 chemical sciences Inorganic Chemistry chemistry.chemical_compound chemistry Organic chemistry Physical and Theoretical Chemistry Coronopilin Chemoselectivity Helenalin |
| Zdroj: | Tetrahedron: Asymmetry. 28:367-373 |
| ISSN: | 0957-4166 |
| Popis: | The 1,3-dipolar cycloaddition of diazomethane to the sesquiterpene lactones, parthenin, coronopilin, and psilostachyin, gave their respective spiropyrazolines with complete chemoselectivity, while the diastereoselectivity in favour of the (11S)-stereoisomer was 86–98%. Similarly, mexicanin I acetate, helenalin, and helenalin acetate provided the (11R)-diastereoisomer. When helenalin and its acetate were treated with a large excess of diazomethane, they afforded their respective dipyrazolines with 98% diastereoselectivity in favour of the (2R,3S,11R)-diastereoisomer. All compounds were characterized by their physical and spectroscopic properties and their absolute configuration was established by X-ray diffraction analysis calculating the Flack and Hooft parameters. |
| Databáze: | OpenAIRE |
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