Phytochemical investigations of Cotinus coggygria Scop. wood, a medicinal and tinctorial plant used since antiquity, resulted in the isolation and structure elucidation of the novel C-3/C-3'' dimer of butin (3',4',7-trihydroxyflavanone) and other known compounds: gallic acid and its methyl ester; catechin; profisetinidins: fisetinidol-(4α→8)-(+)-catechin and epifisetinidol-(4β→8)-(+)-catechin; flavanonols: fustin and dihydroquercetagetin; flavanones: butin and eriodictyol; flavonols: fisetin and quercetin; the chalcone butein and the aurone sulfuretin. The isolated compounds were used for the development and validation of a HPLC-method which enables the determination of these bioactive substances in C. coggygria extracts. Separation was possible on an ether-linked phenyl column material, using as mobile phase mixtures of water, methanol, and acetonitrile with 0.02% trifluoroacetic acid. Sensitivity, selectivity, linearity, precision, accuracy, and repeatability of the method were verified and assured suitability for its intended use. LC-MS experiments performed in positive and negative electrospray ionization mode confirmed the identity of analytes and allowed unambiguous assignment of all peaks of interest. The analysis of different C. coggygria samples revealed that sulfuretin (0.38-0.69%) and fustin (0.33-0.59%) dominated, followed by dihydroquercetagetin (0.12-0.35%), a rare flavanonol derivative with a 5,6,7-trihydroxysubstituted A-ring. The new natural compound C-3/C-3'' flavanone dimer occurred in concentrations of 0.03-0.06%; the two latter compounds could represent valuable markers for the identification and quality control of C. coggygria wood.
Tetraferrocenylallene is synthesized in 49% yield from
triferrocenylallenylium tetrafluoroborate by nucleophilic addition of 1-cuprioferrocene. Other, more
conventional approaches
failed, due to steric hindrance or the known reluctance of a
diferrocenyl-substituted sp2 carbon
to undergo condensation reactions. Side products include
triferrocenyl(2-tetrahydrofuranyl)allene, 1,1,3,4,6,6-hexaferrocenylhexane-1,2,4,5-tetraene, and
1,1‘-bis(triferrocenylallenyl)ferrocene, indicating the involvement of allenyl radicals in the course
of this reaction. X-ray
crystal structure analyses show these allenes to be sterically
congested cumulenes with
interesting helical propeller conformations. Tetraferrocenylallene
can be reversibly oxidized
in three consecutive steps to the tetracation, as shown by
low-temperature cyclic voltammetry.
The expected nucleophilic reactivity of the central carbon of the
allenic unit is hampered by
the steric bulk of the metallocenyl substituents and only observed for
the smallest electrophile
possible, H+, which yields a rather labile
tetraferrocenylallylium cation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.