13C-NMR spectroscopy of biflavanoids

13 C NMR Spectra of Chromeno-and Prenylated Flavones Structure Revision of Mulberrin, Mulberrochromene, Cyclomulberrin and Cyclomulberrochromene

“…4.5 ppm) in flavones and flavonols. Substitution of C-6 or C-8 in 5,7-dihydroxy flavonoids, as expected on the basis of well established results, does not result in a marked shift (i 0.8 ppm) of the signal of the other carbon atom [7]. The potential of this information is immediately obvious.…”

“…In the course of our work [2,6,7] on the i 3 C NMR spectra of 5,7-dihydroxy flavonoids, the C-6 and C-8 resonances were always found in the interval 90.0 ppm to 100.0 ppm. The signal for C-6 is always found to be at lower fields than C-8.…”

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Flavones, Mulberrin, Mulberrochromene, 13 C NMR Reappraisal of the 13 C NMR data for mulberrin and mulberrochromene indicate a revision of structure for these two compounds as well as for cyclomulberrin and cyclomulberrochromene .The 13 C-NMR spectroscopy of various flavonoids and their derivatives has been extensively studied in the past few years [1][2][3][4][5][6][7]. In the course of our work [2,6,7] on the i 3 C NMR spectra of 5,7-dihydroxy flavonoids, the C-6 and C-8 resonances were always found in the interval 90.0 ppm to 100.0 ppm.

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Biodiversidade flavonoídica e aspectos farmacológicos em espécies dos gêneros Ouratea e Luxemburgia (Ochnaceae)

“…A ligação tipo C-O-C é característica das ochnaflavonas (C-3'→O-C-4''') e das lanaraflavonas (C-4'-O→C-8''), sendo o grupo das ochnaflavonas (20) Uma característica do gênero Ouratea é a ligação entre seus monômeros, sendo as mais abundantes C-3→C-8'' e C-6→C-8'', acrescentando uma variação no padrão de metilação. No caso dos derivados da agatisflavona (C-6→C-8'') a metilação é mais freqüente na posição 7 (10). Com ligações (C-O-C), foram isolados os dímeros (C-4'-O→C-8'') e (C-3'→O-C-4'''), incluindo a ligação entre os monômeros das bichalconas, que são característicos do gênero Luxemburgia ,12,24 , enquanto que de Ouratea se isolaram os derivados de lanaraflavona (C-4'-O-C-8'') com diferentes padrões de metilação (16, 17, 34).…”

Phytochemical Study on American Plants I. Two New Phenol Glucosides, together with Known Biflavones and Diterpene, from Leaves of Juniperus occidentalis HOOK.

“…Identities of cupressuflavone 2,3) and amentoflavone 3,4) were established by comparison of 1 H-and 13 C-NMR data with those reported for the respective authentic specimens. The physicochemical and spectral data {mp, [a] D , 1 H-and 13 C-NMR (600, 150 MHz, respectively), EI-MS} of the isolated diterpene were in agreement with the reported values for authentic 3b-hydroxy sandaracopimaric acid.…”