I. I. Okhunov, S. Aripova
Jul 1, 2013
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Chemistry of Natural Compounds
Abstract
The majority of plants of the genus Convolvulus (Convolvulaceae) are rich sources of tropane alkaloids. Individual species of this genus (C. subhirsutus, C. pseudocanthabrica, C. krauseanus) contained at certain vegetative periods from 0.6 to 4.0% total alkaloids [1]. The principal bases in these plant species with respect to total content were the two alkaloids convolvine and its N-methyl derivative convolamine. The content of the mixture of these two alkaloids in the total reached 70%. A series of compounds were synthesized and their biological activity was studied as a result of the good availability of convolvine, which is the ester of the amino alcohol nortropine and veratric acid [2]. The previous research found that the alkaloid convolvine and its derivatives exhibited anti-hypoxic, local anesthetic, anti-inflammatory, and immunomodulating activity [3, 4]. The alkaloids convolvine and convolamine showed antimicrobial and antifungal activity. This provided a basis for development of the antifungal preparation Consubin, which was proposed for application in dermatology [5]. In continuation of research in this direction, we synthesized 1 based on the alkaloid convolvine and adipic acid. The dichloride of the latter was prepared using SOCl2 and was esterified in toluene in the presence of NEt3. The synthesized product was purified by column chromatography over Al2O3. The IR spectrum of 1 was taken from pressed KBr pellets on a Model 2000 Fourier IR spectrometer (PerkinElmer) and exhibited absorption bands for CH– and CH2– bending vibrations at 2835 cm –1; –OCH3 and C–CH3 (1357, 1375); an ester carbonyl conjugated to an aromatic ring at 1702; an amide carbonyl (N–CO) at 1634; an aromatic ring (1602); an ether (1035), and a 3,4-disubstituted benzene ring (818, 873). The presence in the spectrum of a strong absorption band for an amide carbonyl indicated that the adipic acid was bonded through the N atom of convolvine. The PMR spectrum of 1 was recorded on a Unity 400+ spectrometer (Varian) at operating frequency 400 MHz for protons. Resonances for six aromatic protons were observed at 6.87 (2H, d, J = 9 Hz), 7.25 (2H, d, J = 2 Hz), and 7.36 and 7.38 ppm (1H each, dd, J1 = 2, J2 = 9 Hz). Diagnostic resonances for the 3 -H protons of the tropane core were found at 5.10 ppm. Two 2H multiplets for the C-1 and C-5 protons of the tropane ring occurred at 4.59 and 4.22 ppm. A singlet for the four OCH3 groups of the benzene ring appeared at 3.55 ppm. The region 2.48 ppm contained a multiplet (4H) for the CH2–C=O protons. The methylenes gave a broad resonance in the range 1.80–2.15 ppm (16H) for the eight methylene protons on C-2, C-4, C-6, and C-7 of the tropane core. The CH2–CH2–C=O protons formed a multiplet at 1.57 ppm. The spectral characteristics of 1 indicated that the product consisted of two symmetric convolvine molecules bonded to each other through their N atoms by adipic acid and had the structure bis-(convolvine)amide of 1,6-hexanedioic acid (1).