Chemistry of Natural Compounds, Vol. 49, No. 1, March, 2013 [Russian original No. 1, January–February, 2013]
ELECTROCHEMICAL SYNTHESIS OF BIFLAVONOIDS
1*
2
2
R. K. Nadirov, K. S. Nadirov, A. M. Esimova,
UDC 541.138.2
2
and Zh. K. Nadirova
Biologically active biflavonoids have consistently attracted the attention of researchers [1]. However, only a few of
these compounds have a broad spectrum of biological activity. This has prompted scientists to prepare their semi-synthetic
and synthetic analogs [2]. Thus, several approaches including metal-catalyzed cross coupling, oxidative coupling, Ulmann
condensation with nucleophiles, etc. have been used to synthesize biflavonoids [2]. We hypothesized that it would be possible
to use an electrochemical method to prepare novel compounds based on flavonoids [3–5].
The flavonols isorhamnetin and kaempferide that were isolated earlier by us from Alhagi pseudalhagi (M. Bieb.)
Fisch. were used for the synthesis. The flavonol (1 mmol) was dissolved in CH CN (100 mL). The electrolysis was carried
3
2
out in the presence of LiClO (0.1 M) in a cell with a diaphragm and a Pt anode of working surface 2 cm and current density
5 mA/cm for 3 h. When the electrolysis was finished, about 90% of the solvent was distilled off. The remainder was used to
4
2
separate the products by column chromatography over silica gel. In both instances, the principal products were recrystallized
from acetone to afford light-brown powders in 0.22 0.05 g yields. Their physicochemical and spectral characteristics were
determined by known methods.
20
Compound 1. C H O , mp 285 3°C, [ꢀ] +39.7° (c 0.57, MeOH). UV spectrum (MeOH, ꢁ , nm): 251, 325,
32 22 14
–1
D
max
356. IR spectrum (KBr, ꢂ , cm ): 3430, 3370 (OH), 1681, 1600 (C=O), 1607, 1570 (aromatic C=C). Mass spectrum (EI,
70 eV), m/z (I , %): 630 (M , 100), 615 (13), 315 (17). PMR spectrum (400 MHz, CDCl , ꢃ, ppm): 3.96 (6H, d, 3ꢄ, 3ꢅ-OCH ),
max
+
rel
3
3
6.83 (2H, s, H-6, 6ꢅ), 7.23 (2H, s, H-5ꢄ, 5ꢅꢄ), 7.52 (4H, s, H-2ꢄ, 6ꢄ, 2ꢅꢄ, 6ꢅꢄ), 9.35 (2H, s, OH-4ꢄ, 4ꢅꢄ), 10.12 (2H, s, OH-7, 7ꢅ),
10.82 (2H, s, OH-3, 3ꢅ), 12.10 (2H, s, OH-5, 5ꢅ).
20
Compound 2. C H O , mp 291 3°C, [ꢀ] +38.4° (c 0.52, MeOH). UV spectrum (MeOH, ꢁ , nm): 210, 271,
32 20 12
D
max
–1
368. IR spectrum (KBr, ꢂ , cm ): 3423 (OH), 1590 (C=O), 1520, 1460 (aromatic C=C). Mass spectrum (EI, 70 eV),
max
+
m/z (I , %): 596 (M , 100), 581 (12), 298 (22). PMR spectrum (400 MHz, CDCl , ꢃ, ppm): 3.83 (6H, d, OCH -4ꢄ, 4ꢅꢄ), 6.83
rel
3
3
(2H, s, H-6, 6ꢅ), 7.36 (4H, s, H-3ꢄ, 3ꢅꢄ, 5ꢄ, 5ꢅꢄ), 7.50 (4H, s, H-2ꢄ, 6ꢄ, 2ꢅꢄ, 6ꢅꢄ), 10.16 (2H, s, OH-7, 7ꢅ), 10.76 (2H, s, OH-3, 3ꢅ),
12.17 (2H, s, OH-5, 5ꢅ).
O
OH
HO
R
R
2
R
R
1
O
OH
O
HO
1
2
OH
OH
O
1, 2
1: R = OH, R = OCH
3
1
2
2: R = OCH , R = H
1
3
2
UV absorption maxima of the prepared compounds were characteristic of flavonoids. IR spectra of the synthesized
compounds retained absorption bands corresponding to functional groups of the starting compounds. The molecular ions
were the base peaks in mass spectra of 1 and 2, which is typical of flavonoids. The m/z values for the molecular ions corresponded
to dimers of the starting flavonoids. Fragments with m/z 315 and 298 were identified as radicals of isorhamnetin and kaempferide,
1) Al-Farabi Kazakh National University, 050012, Kazakhstan, Almaty, Prosp. Al-Farabi, 71,
e-mail: nadirov.rashid@gmail.com; 2) M. Auezov South-Kazakhstan State University, 486000, Kazakhstan, Shymkent, Prosp.
Tauke-Khana, 5, e-mail: kazim57@rambler.ru. Translated from Khimiya Prirodnykh Soedinenii, No. 1, January–February,
2013, p. 96. Original article submitted June 19, 2012.
©
108
0009-3130/13/4901-0108 2013 Springer Science+Business Media New York
Nadirov
