Stereochemistry of tropane alkaloid of convolvine and their derivatives European Journal of Chemistry 10 (4) (2019) 376-380 European Journal of Chemistry View Journal Online View Article Online Stereochemistry of tropane alkaloid of convolvine and their derivatives Kambarali Kuchkarovich Turgunov 1,2,*, Dilfuza Kadirova 1, Rasul Okmanov 1, Salima Fazilovna Aripova 1 and Bakhodir Tashkhodjaev 1 1 Institute of Chemistry of Plant Substances, Tashkent, 100170, Uzbekistan kk_turgunov@rambler.ru (K.K.T.), kadirova_dilfuza@inbox.ru (D.K.), raxul@mail.ru (R.Y.O.), salima_aripova@mail.ru (S.F.A.), tashkhodjaev@rambler.ru (B.T. 2 Natural and Mathematical Sciences, Turin Polytechnic University in Tashkent, Tashkent, 1000095, Uzbekistan * Corresponding author at: Institute of Chemistry of Plant Substances, Tashkent, 100170, Uzbekistan. Tel: +998.71.1206475 Fax: +998.71.1206475 e-mail: kk_turgunov@rambler.ru (K.K. Turgunov). 10.5155/eurjchem.10.4.376-380.1909 Received: 27 June 2019 Received in revised form: 13 October 2019 Accepted: 17 October 2019 Published online: 31 December 2019 Printed: 31 December 2019 Structures of alkaloid convolvine (1) isolated from Convolvulus subhirsutus and its derivatives-convolamine(N-methylconvolvine) (2) and hydrochloride of N-benzylconvolvine (3) have been determined by single crystal X-ray diffraction technique. Compounds were crystallized in monoclinic space groups having four molecules in unit cell. All compounds contain a bicyclic ring system of tropane, where piperidine rings in all case adopt chair conformation. Hydrogen atom and methyl- and benzyl-substituents located in nitrogen atom of studied compounds occupy equatorial positions. The substituent of tropane core- the veratroyloxy group containing in all compound molecules is an α-axial oriented relative to the tropane core. In crystal structures of compound 1 and 2, the molecules are located in the distance of van der Waals interactions. The H-bond between the anion Cl and the proton of the N atom is observed in the crystal of N-benzylconvolvine hydrochloride (Cl···N 3.337 Å, Cl···H 2.42 Å and Cl-H-N 175°). Convolvine Convolamine Tropane alkaloids N-Benzylconvolvine X-ray crystallography Convolvulus subhirsutus Cite this: Eur. J. Chem. 2019, 10(4), 376-380 Journal website: www.eurjchem.com 1. Introduction It is known that some tropane alkaloids (atropine, scopolamine) have a quinolytic effect and are used in medicine as drugs [1]. In order to search for physiologically active substances among alkaloids of this class, modification is carried out on the basis of available substances. So plants of the Convolvulus genus are a source of convolvine alkaloids, which can be produced on an industrial scale. Based on this alkaloid, we previously synthesized a number of derivatives [2]. Convolamine (2) was obtained by methylation of convolvine (1) and N-benzylconvolvine (3) was obtained by reaction of convolvine with benzyl chloride (Scheme 1). Biological studies on some cultures of cancer cells have established a high anticancer activity of benzylconvolvine, superior to the activity of anticancer drugs used in medicine [3]. The issue of obtaining convolvine derivatives is based on natural compound and it is dependent on the structure of the starting natural product and the reactant. These factors govern not only the derivation of new products, but also chemical property of product molecule, manifestation of biological activity by the formation of intra- and inter-molecular H- bonds, as well as the stereochemistry of the veratroyloxy group. In this connection, the stereochemical behavior of the nitrogen atom and substituent in derivatives is of interest. To this end, for the consideration of structural issues, a X-ray analysis on single crystals of the obtained derivatives was performed. NR O O OCH3 OCH3 1' 2' 3' 4' 5'6' 3 2 4 1 5 6 7 R=H (1), R=CH3 (2), CH2C6H5 (3) Scheme 1 ABSTRACT RESEARCH ARTICLE KEYWORDS European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2019 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. http://dx.doi.org/10.5155/eurjchem.10.4.376-380.1909 http://dx.doi.org/10.5155/eurjchem.10.4.376-380.1909 https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.10.4.376-380.1909&domain=pdf&date_stamp=2019-12-31 http://www.eurjchem.com/ http://dx.doi.org/10.5155/eurjchem.10.4.376-380.1909 mailto:kk_turgunov@rambler.ru mailto:kadirova_dilfuza@inbox.ru mailto:raxul@mail.ru mailto:salima_aripova@mail.ru mailto:tashkhodjaev@rambler.ru mailto:kk_turgunov@rambler.ru http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.10.4.376-380.1909&domain=pdf&date_stamp=2019-12-31� Turgunov et al. / European Journal of Chemistry 10 (4) (2019) 376-380 377 Table 1. Crystal data and details of the structure refinement for compounds 1-3. Parameters Compound 1 Compound 2 Compound 3 Empirical formula С16Н21NО4 С17Н23NО4 С23Н28NО4·Cl Formula weight 291.34 305.36 417.91 Temperature (K) 293 293 293 Crystal system Monoclinic Monoclinic Monoclinic Space group Cc P21/n P21/c a, (Å) 10.2405(7) 8.8351(5) 15.4528(4) b, (Å) 20.429 (2) 19.6231(11) 9.0258(2) c, (Å) 7.1993(7) 9.2514(5) 16.5962(5) β (°) 94.587(7) 91.977(5) 111.121(3) Volume (Å3) 1501.3(2) 1603.0(2) 2159.2(1) Z 4 4 4 ρcalc (g/cm3) 1.289 1.265 1.286 μ (mm-1) 0.76 0.73 1.80 F(000) 624 656 888 Crystal size (mm3) 0.60 × 0.45 × 0.40 0.55 × 0.45 × 0.25 0.25 × 0.30 × 0.40 Radiation CuKα (λ = 1.54184) CuKα (λ = 1.54184) CuKα (λ = 1.54184) 2Θ range for data collection (°) 9.6 to 152.6 9.0 to 152.6 10.8 to 176.4 Index ranges -9 ≤ h ≤ 12 -22 ≤ k ≤ 25 -9≤ l ≤ 8 -10 ≤ h ≤ 10 -17 ≤ k ≤ 24 -11≤ l ≤ 11 -17 ≤ h ≤ 20 -11 ≤ k ≤ 8 -19 ≤ l ≤ 18 Reflections collected 4762 6255 8728 Independent reflections 2197 [Rint = 0.045] 3228 [Rint = 0.033] 4317 [Rint = 0.033] Data/restraints/parameters 2197/2/193 3228/0/199 4317/0/269 Goodness-of-fit on F2 1.067 0.996 1.022 Final R indexes [I≥2σ (I)] R1 = 0.061, wR2 = 0.135 R1 = 0.051, wR2 = 0.119 R1 = 0.050, wR2 = 0.133 Final R indexes [all data] R1 = 0.105, wR2 = 0.167 R1 = 0.078, wR2 = 0.141 R1 = 0.070, wR2 = 0.146 Largest diff. peak/hole (e.Å-3) 0.19/-0.15 0.16/-0.20 0.31/-0.22 2. Experimental 2.1. Materials and apparatuses Convolvine (1) was isolated from Convolvulus subhirsutus. Reagents and solvents were purchased from commercial suppliers and used without further purifications. Single crystal X‐ray diffraction (XRD) data was collected by using CuKα radiation (λ = 1.54184 Å) on a CCD Xcalibur Ruby diffracto- meter (Oxford Diffraction) at a room temperature. Data reduction including multi-scan absorption correction was done using CrysAlisPRO [4]. 2.2. X-ray crystal structure determination of compounds 1-3 Structures were solved by direct methods within the SHELXS-97 program [5] and refined with SHELXL-2014/7 refinement program [6]. All non-hydrogen atoms were refined by the least squares method (F2) in the full-matrix anisotropic approximation. Hydrogen atoms at carbon atoms were positioned geometrically and refined according to a riding model with fixed isotropic displacement parameters Uiso = nUeq, where n = 1.5 for methyl groups and 1.2 for the others, (Ueq is the equivalent isotropic parameter of displacement of the corresponding carbon atoms). The hydrogen atoms of the NH group are found from difference syntheses of electron density and refined isotropically. 2.3. Preparation of convolvine and its derivatives Isolation of convolvine (1) was performed according to the method [7]. The air-dried aerial part of C. subhirsutus (3 kg) was moistened with ammonia solution (10%), placed in a percolator, and after 2 h treated with CHCl3 (six times). The combined CHCl3 extracts were condensed to a volume of 2 L and worked up with H2SO4 solution (10%) to extract exhaustively the alkaloids. The combined acidic solutions were washed twice with a small quantity of CHCl3 and made basic with ammonia solution (25%). The alkaloids were extracted with CHCl3 to afford total bases (10.7 g). Total bases (10.7 g) were dissolved in CHCl3 (2 L) and worked up with KOH solution (4%, 4 × 100 mL). The alkaline extracts were acidified with H2SO4 solution (20%), cooled, and made basic with ammonia solution (25%). Alkaloids were extracted exhaustively with CHCl3. The CHCl3 solution was dried over anhydrous Na2SO4. Solvent was distilled off to produce phenolic alkaloids (2.5 g). After work up with base, the CHCl3 solution was washed with distilled water and worked up successively with citrate-phosphate buffer at pH = 6.8 and 5.6 to extract completely the alkaloids. The buffer extracts were made basic with cooling using conc. NH4OH solution. Alkaloids were extracted with CHCl3 to afford bases from the fractions with pH = 6.8 (5.5 g, convolvine) and 5.6 (2.2 g, convolamine with an impurity of convolvine). A mixture of 0.1 g of convolvine alkaloid, 1 mL of methyl iodide and 0.4 g of potassium iodide in 30 mL of dry acetone was heated in a water bath for 1 hour. When the cooled filtrate was concentrated, a crystalline precipitate (2) was formed with M.p.: 114-115 ° (acetone) in the amount of 0.11 g and not giving melting point depression with a convolamine sample. Synthesis of N-benzylconvolvine (3) was carried out according to the method [2]. A mixture of convolvine (0.15 g) and benzylchloride (0.1 mL) was left at room temperature for 2 d. After this time the product was separated by treatment with acetone and purified over a column of Al2O3 to afford crystals (0.15 g, 78.9%) with M.p.: 88-89 °C. 3. Results and discussion The molecular structures of convolvine 1 and its derivatives 2 and 3 are shown in Figure 1. Crystallographic data are presented in Table 1. The tropane alkaloid and derivatives are crystallized in the Cc space groups (containing glade plane) and P21/n, P21/c (with elements of the center of symmetry and glade plane), respectively. Consequently, the crystals contain both enantiomers of the molecules of the alkaloid 1 and its derivatives 2 and 3. XRD analysis result allows to set the relative configuration of the center C3. The substituent the veratroyloxy group in position C3 has an α-axial orientation relative to the tropane core. The orientation and location of the substituents of the N and C3 atoms in compounds 1, 2 and 3 coincides with those observed in convolinine [8] and o-benzoyltropine hydro- chloride [9]. In molecules 1-3, the veratroyloxy group is planar with an accuracy of ±0.040, ±0.039 and ±0.036 Å, respectively, and the benzyl group at N1 in 3 is ±0.008 Å. 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.4.376-380.1909 378 Turgunov et al. / European Journal of Chemistry 10 (4) (2019) 376-380 Table 2. Selected bond lengths and bond angles of molecule 1. Atom-Atom Bond length (Å) Atom-Atom Bond length (Å) Atom-Atom Bond length (Å) O1-C16 1.348 (8) N1-C5 1.468 (10) C6-C7 1.539 (11) O1-C3 1.465 (7) N1-H1A 0.85 (8) C1'-C6' 1.379 (9) O2-C16 1.205 (7) C1-C2 1.517 (10) C1'-C2' 1.398 (8) O3-C4' 1.364 (7) C1-C7 1.539 (9) C1'-C16 1.486 (8) O3-C17 1.427 (8) C2-C3 1.513 (9) C2'-C3' 1.378 (8) O4-C3' 1.361 (7) C3-C4 1.521 (10) C3'-C4' 1.413 (8) O4-C18 1.424 (8) C4-C5 1.534 (10) C4'-C5' 1.383 (8) N1-C1 1.466 (10) C5-C6 1.545 (10) C5'-C6' 1.379 (9) Atom-Atom-Atom Bond angles (°) Atom-Atom-Atom Bond angles (°) Atom-Atom-Atom Bond angles (°) C16-O1-C3 117.4 (5) N1-C5-C4 106.6 (6) O4-C3'-C4' 114.6 (5) C4'-O3-C17 117.7 (5) N1-C5-C6 106.3 (6) C2'-C3'-C4' 120.1 (5) C3'-O4-C18 116.8 (5) C4-C5-C6 112.4 (6) O3-C4'-C5' 126.0 (5) C1-N1-C5 100.9 (5) C7-C6-C5 102.7 (6) O3-C4'-C3' 115.5 (5) N1-C1-C2 106.8 (6) C6-C7-C1 104.5 (6) C5'-C4'-C3' 118.5 (5) N1-C1-C7 105.7 (6) C6'-C1'-C2' 120.5 (6) C6'-C5'-C4' 121.8 (6) C2-C1-C7 112.7 (6) C6'-C1'-C16 117.8 (5) C5'-C6'-C1' 119.3 (6) C3-C2-C1 113.4 (6) C2'-C1'-C16 121.7 (5) O2-C16-O1 122.9 (6) O1-C3-C2 109.2 (5) C3'-C2'-C1' 119.8 (6) O2-C16-C1' 124.5 (6) O1-C3-C4 106.9 (5) O4-C3'-C2' 125.3 (6) O1-C16-C1' 112.6 (5) (1) (2) (3) Figure 1. The molecular structures of compounds 1-3. The veratroyloxy group is distorted from the plane of symmetry of the tropane core, which is characterized by the torsion angle H3-C3-O1-C1’, whose values for compound 1-3 are 33, 29 and 33°, respectively. It should be noted that the carbonyl group in these compounds and analogues known in the literature [8-12] is always syn-directed relative to the β- axially located hydrogen atom at C3. But the methoxyl group in the ortho position of the C3’ veratroyloxy fragment in these compounds is located differently relative to the tropine core (Figure 1), which indicates a free rotation around the C16-C1’ bond forming different rotamers. 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.4.376-380.1909 Turgunov et al. / European Journal of Chemistry 10 (4) (2019) 376-380 379 Table 3. Selected bond lengths and bond angles of molecule 2. Atom-Atom Bond length (Å) Atom-Atom Bond length (Å) Atom-Atom Bond length (Å) O1-C16 1.340 (3) N1-C5 1.469 (3) C6-C7 1.536 (3) O1-C3 1.468 (3) N1-C1 1.474 (3) C1'-C6' 1.381 (3) O2-C16 1.208 (3) C1-C2 1.530 (3) C1'-C2' 1.403 (3) O3-C4' 1.357 (2) C1-C7 1.547 (3) C1'-C16 1.478 (3) O3-C17 1.426 (3) C2-C3 1.516 (3) C2'-C3' 1.370 (3) O4-C3' 1.366 (2) C3-C4 1.517 (3) C3'-C4' 1.412 (3) O4-C18 1.419 (3) C4-C5 1.524 (3) C4'-C5' 1.384 (3) N1-C19 1.466 (3) C5-C6 1.545 (3) C5'-C6' 1.386 (3) Atom-Atom-Atom Bond angles (°) Atom-Atom-Atom Bond angles (°) Atom-Atom-Atom Bond angles (°) C16-O1-C3 117.03 (17) O1-C3-C4 107.46 (19) O4-C3'-C2' 124.95 (18) C4'-O3-C17 117.67 (18) C3-C4-C5 113.36 (19) O4-C3'-C4' 115.34 (17) C3'-O4-C18 116.52 (17) N1-C5-C4 107.22 (19) C2'-C3'-C4' 119.71 (18) C19-N1-C5 112.2 (2) N1-C5-C6 105.72 (18) O3-C4'-C5' 125.61 (18) C19-N1-C1 111.92 (18) C4-C5-C6 112.61 (19) O3-C4'-C3' 114.90 (18) C5-N1-C1 100.67 (17) C7-C6-C5 103.54 (19) C5'-C4'-C3' 119.49 (18) N1-C1-C2 107.47 (18) C6-C7-C1 103.76 (18) C4'-C5'-C6' 120.33 (19) N1-C1-C7 105.22 (19) C6'-C1'-C2' 119.40 (19) C1'-C6'-C5' 120.4 (2) C2-C1-C7 112.9 (2) C6'-C1'-C16 123.69 (19) O2-C16-O1 123.1 (2) C3-C2-C1 113.02 (19) C2'-C1'-C16 116.87 (18) O2-C16-C1' 124.3 (2) O1-C3-C2 109.29 (19) C3'-C2'-C1' 120.62 (19) O1-C16-C1' 112.59 (18) Table 4. Selected bond lengths and bond angles of molecule 3. Atom-Atom Bond length (Å) Atom-Atom Bond length (Å) Atom-Atom Bond length (Å) O1-C16 1.306 (2) N1-H1 0.92 (3) C3'-C4' 1.478 (3) O1-C3 1.426 (2) C1-C2 1.606 (3) C4'-C5' 1.320 (3) O2-C16 1.270 (3) C2-C3 1.526 (3) C5'-C6' 1.358 (3) O3-C4' 1.322 (3) C3-C4 1.467 (3) C19-C20 1.396 (3) O3-C17 1.511 (3) C1-C7 1.584 (3) C20-C25 1.391 (3) O4-C3' 1.295 (2) C6-C7 1.522 (3) C20-C21 1.422 (4) O4-C18 1.490 (3) C1'-C2' 1.341 (3) C21-C22 1.300 (4) N1-C1 1.422 (2) C1'-C6' 1.443 (3) C22-C23 1.375 (5) N1-C5 1.507 (3) C1'-C16 1.460 (3) C23-C24 1.428 (5) N1-C19 1.550 (2) C2'-C3' 1.344 (3) C24-C25 1.277 (4) Atom-Atom-Atom Bond angles (°) Atom-Atom-Atom Bond angles (°) Atom-Atom-Atom Bond angles (°) C16-O1-C3 110.32 (17) C4-C3-C2 112.88 (17) O3-C4'-C3' 119.99 (19) C4'-O3-C17 121.10 (19) C3-C4-C5 113.89 (18) C4'-C5'-C6' 115.0 (2) C3'-O4-C18 118.22 (18) N1-C5-C6 102.29 (17) C5'-C6'-C1' 124.22 (19) C1-N1-C5 103.74 (15) N1-C5-C4 104.55 (16) O2-C16-O1 126.0 (2) C1-N1-C19 108.16 (16) C6-C5-C4 121.10 (16) O2-C16-C1' 128.48 (18) C5-N1-C19 112.08 (15) C7-C6-C5 102.05 (17) O1-C16-C1' 105.46 (18) C1-N1-H1 107.2 (15) C6-C7-C1 106.92 (17) C20-C19-N1 109.10 (18) C5-N1-H1 109.4 (16) C2'-C1'-C16 111.9 (2) C25-C20-C19 116.3 (2) C19-N1-H1 115.4 (15) C6'-C1'-C16 126.77 (18) C25-C20-C21 124.2 (2) N1-C1-C7 99.06 (16) C1'-C2'-C3' 114.6 (2) C19-C20-C21 119.4 (2) N1-C1-C2 105.04 (17) O4-C3'-C2' 119.9 (2) C22-C21-C20 118.6 (3) C7-C1-C2 119.44 (17) O4-C3'-C4' 116.3 (2) C21-C22-C23 116.1 (3) C3-C2-C1 114.75 (17) C2'-C3'-C4' 123.85 (18) C22-C23-C24 125.7 (3) O1-C3-C2 111.96 (18) C5'-C4'-O3 119.1 (2) C25-C24-C23 117.8 (3) O1-C3-C4 99.66 (18) C5'-C4'-C3' 120.9 (2) C24-C25-C20 117.6 (3) Table 5. Intra- and inter-molecular interactions in the crystals 1-3. D-H…A d(D-H), Å d(H…A), Å d(D…A), Å ∠(DHA), ° Symmetry Compound 1 C17-H17a…O2 0.96 2.47 3.405(9) 164 1+x, y, z Compound 2 C18-H18c...O2 0.96 2.53 3.268(3) 134 1-x, 1-y, 2-z Compound 3 N1-H…Cl1 0.93(3) 2.42(3) 3.337(2) 174(2) - C2-H2a…Cl1 0.97 2.76 3.499(2) 133 - C4-H4b…Cl1 0.97 2.82 3.552(3) 133 - C7-H7a…O4 0.97 2.20 3.106(3) 155 -x, -y, -z C19-H19b...Cl1 0.97 2.64 3.577(2) 162 1-x, -1-y, -z Bond length in the molecules 1-3 closely comparable with only small variations around the N1 nitrogen atom. N1-C1 (1.466(10) Å), N1-C5 (1.468(10) Å) bonds in molecule 1 and N1-C1 (1.466(10) Å), N1-C5 (1.468(10) Å) and N1-C19 1.466(3) Å bonds in molecule 2 are almost the same. In case molecule 3 with protonation of N1 atom those bond lengths equals to 1.422(2), 1.507(3), 1.550(2) Å, respectively (Tables 2-4). In crystal structures 1 and 2, the molecules are located in the distance of van der Waals interactions. However, the crystal structure indicates that the molecules in the crystals are associated by intermolecular weak C-H…O interactions (Table 5). Crystal 3 is the hydrochloride salt. The H-bond between the anion Cl and the proton of the N atom is observed in the crystal, the H-bond parameters are the following: Cl1···N1 3.337(2) Å, Cl1···H 2.42(3) Å, Cl1···HN1 174(2)°. A weak H-bond of C7-H···O4 type is observed, and also π-π interactions between the aromatic sites of the veratroyloxy group of molecules transformed by the center of symmetry. 4. Conclusion Crystal structures of convolvine alkaloid and its two derivatives were deduced by single crystal XRD analysis. Piperidine rings in compounds adopt chair conformation. Hydrogen atom and methyl- and benzyl-substituents located 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.4.376-380.1909 380 Turgunov et al. / European Journal of Chemistry 10 (4) (2019) 376-380 in nitrogen atom of 1-3 occupy equatorial positions. The veratroyloxy group containing in all compound molecules is an α-axial oriented relative to the tropane core. Free rotation of dimethoxyphenyl- group around the C16-C1’ bond leads different rotamers in crystals of compound 1-3. Acknowledgements The project is supported by the Academy of Sciences of the Republic of Uzbekistan, (Grant no: VA-FA-F-6-010). Supporting information CCDC 1935317 (1), CCDC 1935318 (2) and CCDC 1935324 (3) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/, or by e-mailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033. Disclosure statement Conflict of interests: The authors declare that they have no conflict of interest. Author contributions: All authors contributed equally to this work. Ethical approval: All ethical guidelines have been adhered. Sample availability: Samples of the compounds are available from the author. ORCID Kambarali Kuchkarovich Turgunov http://orcid.org/0000-0001-5741-6347 Dilfuza Kadirova http://orcid.org/0000-0001-6488-0738 Rasul Yangiberdiyevich Okmanov http://orcid.org/0000-0003-2154-0746 Salima Fazilovna Aripova http://orcid.org/0000-0001-6416-7756 Bakhodir Tashkhodjaev http://orcid.org/0000-0003-3027-9893 References [1]. Mashkovskiy, M. D. Lekarstvennie sredstva, Medicine, Tashkent, 1984. Part 1, pp. 239, [in Russian]. [2]. Gapparov, A. M.; Okhunov, I. I.; Aripova, S. F.; Nabiev, A.; Khuzhaev, V. U. Chem. Nat. Compd. 2011, 47, 608-611. [3]. Xashimova, Z. S.; Aripova, S. F.; Seomashko, N. E.; Terenteva, E. O.; Ohunov, I. I.; Kadirova, D. B.; Azimova, Sh. S. Patent RUz, No IAP 04965; «Sredstvo, proyavlyayushee izbiratelnuyu sitotoksicheskuyu aktivnost po otnosheniyu k kletkam raka gortani» (in Russian). [4]. Oxford Diffraction, CrysAlis PRO. Version 1.171.37.34. Oxford Diffraction Ltd., Yarnton, Oxfordshire, England. [5]. Sheldrick, G. M. Acta Cryst. A 2008, 64, 112-122. [6]. Sheldrick, G. M. Acta Cryst. C 2015, 71, 3-8. [7]. Gapparov, A. M.; Razzakov, N. A.; Aripova, S. F. Chem. Nat. Compd. 2007, 43, 291-292. [8]. Gapparov, A. M.; Aripova, S. F.; Tashkhodzhaev, B.; Levkovich, M. G.; Aripov, O. Chem. Nat. Compd. 2010, 46, 590-592. [9]. Chananont, P.; Hamor, T.A. J. Chem. Res. 1978, 10, 414-415. [10]. Hamor, T.A. J. Chem. Soc., Perkin Trans. 2 1976, 1359-1363. [11]. Dalpiaz, A.; Ferretti, V.; Gilli, P.; Bertolasi, V. Acta Cryst. B 1996, 52, 509-518. [12]. Zhu, N.; Reynolds, M.; Klein, C. L.; Trudell, M. Acta Cryst. C 1994, 50, 2067-2069. Copyright © 2019 by Authors. This work is published and licensed by Atlanta Publishing House LLC, Atlanta, GA, USA. The full terms of this license are available at http://www.eurjchem.com/index.php/eurjchem/pages/view/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (http://www.eurjchem.com/index.php/eurjchem/pages/view/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). 2019 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.10.4.376-380.1909 https://www.ccdc.cam.ac.uk/structures/ mailto:data_request@ccdc.cam.ac.uk http://orcid.org/0000-0001-5741-6347 http://orcid.org/0000-0001-6488-0738 http://orcid.org/0000-0003-2154-0746 http://orcid.org/0000-0001-6416-7756 http://orcid.org/0000-0003-3027-9893 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms http://creativecommons.org/licenses/by-nc/4.0 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms 1. Introduction 2. Experimental 2.1. Materials and apparatuses 2.2. X-ray crystal structure determination of compounds 1-3 2.3. Preparation of convolvine and its derivatives 3. Results and discussion 4. Conclusion Acknowledgements Supporting information Disclosure statement ORCID References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: