21,22-Disubstituted 18α,19βH-Ursane Derivatives with Oxabicyclooctane System in Ring E

Autor:	Bohumil Máca, Jiří Klinot, Miloš Buděšínský, Václav Křeček, Eva Klinotová
Rok vydání:	1993
Předmět:	Diketone chemistry.chemical_classification chemistry.chemical_compound Polycyclic compound chemistry Stereochemistry Diazomethane Acetal Proton NMR General Chemistry Carbon-13 NMR Ring (chemistry) Lactone
Zdroj:	Collection of Czechoslovak Chemical Communications. 58:173-190
ISSN:	1212-6950 0010-0765
DOI:	10.1135/cccc19930173
Popis:	Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.
Databáze:	OpenAIRE
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