Copyright © 2004 by Institute of Pharmacology Polish Journal of Pharmacology Polish Academy of Sciences Pol. J. Pharmacol., 2004, 56, 755766 ISSN 1230-6002 SYNTHESIS AND CARDIOVASCULAR ACTIVITY OF NEW 8-ALKYLAMINO-1,3-DIMETHYL-7-(2-HYDROXY-3-PIPERAZI- NOPROPYL)-3,7-DIHYDRO-1H-PURINE-2,6-DIONES Gra¿yna Ch³oñ-Rzepa1, Maciej Paw³owski1,#, Ma³gorzata Zygmunt2, Barbara Filipek2, Dorota Maci¹g2 Department of Pharmaceutical Chemistry, Department of Pharmacodynamics, Laboratory of Pharmacological Screening, Collegium Medicum, Jagiellonian University, Medyczna 9, PL 30-688 Kraków, Poland Synthesis and cardiovascular activity of new 8-alkylamino-1,3-dimethyl- -7-(2-hydroxy-3-piperazinopropyl)-3,7-dihydro-1H-purine-2,6-diones. G. CH£OÑ- -RZEPA, M. PAW£OWSKI, M. ZYGMUNT, B. FILIPEK, D. MACI¥G. Pol. J. Pharmacol., 2004, 56, 755–766. 7-{2-Hydroxy-3-[4-(2-phenoxyethyl)-piperazinyl-1-yl]-propyl}-1,3-di- methyl-3,7-dihydro-1H-purine-2,6-dione dihydrochloride (2), and several of its 8-alkylamino substituted derivatives (11–17) were synthesized and tested for electrocardiographic, antiarrhythmic and hypotensive activity. Also their a- and a -adrenoreceptor affinities were determined. It was found that com- pound 2, and its analogue 15 with 8-(2-morpholin-4-yl-ethylamino) substitu- ent displayed a strong prophylactic antiarrhythmic activity in experimentally induced arrhythmia (LD#/ED# = 54.9 and 55.0, respectively). The hypoten- sive activity was observed for 8-benzylamino (11) or 8-(pyridin-2-yl- methylamino) (12) analogues. All the new derivatives (11–17) and 2 showed a weak affinity for a-(KE = 0.225–1.400 mM) and a -(KE = 0.152–4.299 mM) receptors. Key words: purine-2,6-diones, antiarrhythmics, hipotensive agents, a- and a -receptor ligands correspondence;e-mail: [email protected] G. Ch³oñ-Rzepa, M. Paw³owskI, M. Zygmunt, B. Filipek, D. Maci¹g INTRODUCTION arrhythmic and hypotensive activity as well as for a1- and a2-adrenoreceptor binding affinities. Theophylline (1,3-dimethyl-3,7-dihydro-1H-pu- rine-2,6-dione) and a number of its salts and 7-sub- MATERIAL and METHODS stituted derivatives exhibit multidirectional phar- macological properties. Their activities such as CNS stimulation, peripherial smooth muscle re- Chemical part laxation (broncho- and vasodilatation) heart rate in- crease result from the antagonism at adenosine re- Melting points (m.p.) were determined with ceptors and non-selective inhibition of the cyclic a Büchi SMP-20 apparatus and are uncorrected. nucleotide phosphodiesterases [23]. These com- UV spectra were recorded on a Perkin Elmer Lambda 12 UV-VIS spectrometer in5×105 mol/l pounds are commonly used in the treatment of sev- 1 eral diseases such as asthma (theophylline, amino- methanolic solutions. H-NMR spectra (Mercury Varian BB 300 MHz NMR spectrometer) were de- phylline, etophylline, proxyphylline, diprophyl- termined in CDCl solution, with TMS as an inter- line), cardiac failure, and peripheral circulation 3 nal standard. Chemical shifts (d) are reported in disorders (xanthinol nicotinate). It was also found ppm, coupling constants (J) are given in Hz. Mass that pyrimidine-8-on[2,1-f] theophylline-9-alkylcarb- spectra (MS) were taken with a AMD-604 mass oxylic acids derivatives possess hypnotic, sedative spectrometer (EI mode, 70 eV). Thin-layer chro- and tranquillizing properties [4]. matography (TLC) was performed on Merck pre- In the course of our search for new biologically coated silica gel 60 F aluminium plates, using: active compounds belonging to the group of 7,8- 254 S : benzene/acetone/methanol (1:1:1, v/v/v); S : disubstituted theophylline derivatives, we have 1 2 methanol/25% NH3 (100:5, v/v) as mobile phases. found that 7-(2-hydroxypropyl)-8-benzylaminotheo- The spots were visualized under UV light (l = 254 phyllines exhibited hypotensive effects and re- nm) or by iodine solution (0.05 M in 10% HCl). duced heart rate, as well as stimulated respiratory Elemental analyses (C, H, N) were carried out with activity [12]. Pharmacological investigation of Elementar Vario EL III apparatus and were within 7-(2-hydroxy-3-alkylamino)-propyl derivatives of ± 0.4% of the theoretical values. 8-benzylaminotheophylline and 7-(2-hydroxy-3-al- The 1,3-dimethyl-7-oxiranylmethyl-3,7-dihy- kylamino)-propyl derivatives of 8-(2-furfurylami- dro-1H-purine-2,6-dione (1) [24] and 8-bromo- no)-theophylline, revealed also hypotensive and 7-(3-chloro-2-hydroxypropyl)-1,3-dimethyl-3,7-di- bronchodilatatory effects [5, 14, 15]. It is known hydro-1H-purine-2,6-dione (3) [3] were used as that aryl and arylalkyl substituted piperazines show starting materials for the synthesis of new com- a -adrenolytic, hypotensive and vasodilatatory ac- pounds 2 and 11–17. tivity [6, 16, 18, 20]. The described pharmacologi- Compound 2 was synthesized by aminolysis cal effects prompted us to synthesize new theophyl- of 1 with 1-(2-phenoxyethyl)-piperazine [13]. The line derivatives with 1-(2-phenoxyethyl)-piper- 8-alkylamino derivatives of 7-{2-hydroxy-3-[4-(2- azine moiety attached to theophylline nucleus as phenoxyethyl)-piperazin-1-yl]-propyl}-3,7-dihyd- potential agents acting on the cardiovascular sys- ro-1H-purine-2,6-dione (11–16) were obtained by tem. two step procedure (Scheme 1). Compound 3 in the In this paper, we report the synthesis as well as reaction with the appropriate aryl-(heteroaryl-, the results of pharmacological evaluation (in vivo morpholino- or diethylamino)-alkylamine gave in- and in vitro tests) of 7-{2-hydroxy-3-[4-(2-phen- termediate products, previously described 4 and 7 oxyethyl)-piperazin-1-yl]-propyl}-1,3-dimethyl-3,7- [14], and the new ones 5, 6, 8 and 9. In the second dihydro-1H-purine-2,6-dione dihydrochloride (2) step, compounds 4–9 heated with 1-(2-phe- and its 8-alkylamino analogues (11–16). In order to noxyethyl)-piperazine in anhydrous ethanol (for establish the role of the arylalkyl substituent at compounds 11, 12, 14, 16, 17) or toluene (for com- 8 position, the unsubstituted 8-amino analogue (17) pounds 13, 15) in the presence of anhydrous was also obtained. Compound 2 and the newly syn- K2CO3 yielded final products 11–16 (Scheme 1). thesized 11–17 in a form of water soluble hydro- The reaction of 3 with 25% NH3 in dioxane yielded chlorides were tested for electrocardiographic, anti- the intermediate product 10, which treated with 756 Pol. J. Pharmacol., 2004, 56, 755–766 CARDIOVASCULAR ACTIVITY OF NEW 8-ALKYLAMINO-PURINE-2,6-DIONES Cl O OH H C N 3 N Br O N N 3 CH3 H2N-(CH2)n-R 25% NH3 methanol dioxane Cl Cl O O OH OH H C N H C N 3 N 3 N NH NH (CH2)n R 2 O N N O N N 4-9 10 CH CH3 3 O O HN N HN N K CO , ethanol K2CO3, ethanol or toluene 2 3 O O N N N N O O H C OH H C 3 N 3 N OH N 17 N 11-16 NH NH (CH )n R 2 2 N O N N O N CH CH 3 3 No 4, 11 5, 12 6, 13 7, 14 8, 15 9, 16 C H R N O N 2 5 O C H N N 2 5 n1 1 2 1 2 2 Scheme 1. Synthesis of compounds 4–17 1-(2-phenoxyethyl)-piperazine yielded the final General procedure for preparation of the 8-al- 8-aminoderivative 17 (Scheme 1). kylamino derivatives of 7-(3-chloro-2-hydroxy Compounds 11–17 were isolated and examined propyl)-1,3-dimethyl-3,7-dihydro-1H-purine-2,6- 1 as free bases for their H-NMR, MS and UV spec- dione (5-6, 8 and 9) tra as well as by elemental analyses. For pharma- cological studies the free bases 11–17 were con- verted into water soluble hydrochloride salts. The A solution of 3 (3.52 g, 0.01 mol) and appropri- salts were recrystallized and their composition was ate amine (0.02 mol) in methanol (40 ml) was established on the basis of an elemental analysis. heated under reflux for 5 h. Then the reaction mix- Yields and physicochemical properties of the ob- ture was cooled down. The precipitated solid prod- tained compounds (free bases and their salts) are uct was filtered off and purified by recrystallization presented in Table 1. from suitable solvent (Tab. 1). ISSN 1230-6002 757 G. Ch³oñ-Rzepa, M. Paw³owskI, M. Zygmunt, B. Filipek, D. Maci¹g Table 1. Physicochemical data of new compounds 5, 6 and 8–17 Comp. M.p. (°C) Yield (%) (base) Molecular formula (molecular RB (solvent system) Cryst. solvent weight)* Base Salt 5 171–172 52 C16H19N6O3Cl 0.88 (S1) methanol (378.8) 6 204–206 87 C17H21N6O3Cl 0.89 (S1) 2-methoxyethanol (392.8) 8 153–155 69 C16H25N6O4Cl 0.82 (S1) methanol (400.9) 9 147–149 71 C16H27N6O3Cl 0.43 (S2) methanol (386.9) 10 232–233 51 C10H14N5O3Cl 0.43 (S1) ethanol (287.7) 11 95–97 242–244 48 C29H37N7O4 ×2HCl×H2O 0.82 (S1) ethanol (638.6) 12 165–166 249–251 85 C28H36N8O4 × 3 HCl 0.58 (S1) ethanol (658.0) 13 140–142 180–185 75 C29H38N8O4 × 3 HCl 0.55 (S1) methanol (672.0) 14 118–120 231–233 55 C27H35N7O5 ×2HCl×H2O 0.80 (S1) methanol (628.5) 15 134–136 215–217 54 C28H42N8O5 × 3 HCl 0.15 (S1) acetone (680.0) 16 105–107 215–218 56 C28H44N8O4 ×3HCl×H2O 0.23 (S2) acetone (666.1) 17 154–156 262–264 56 C22H31N7O4 × 2 HCl × 1/2 H2O 0.33 (S1) ethanol (539.4) * calculated from elemental analysis 7-(3-Chloro-2-hydroxy-propyl)-1,3-dimethyl-8- CH3), 3.44 (s, 3H, N3-CH3), 3.51–3.70 (m, 2H, [(pyridin-2-yl-methyl)-amino]-3,7-dihydro-1H- NHCH2CH2), 3.77–3.90 (m, 2H, CH2Cl), 4.09–4.39 purine-2,6-dione (5) (m, 3H, N7-CH2,CHOH), 6.17 (t, 1H, NH), 7.14–7.18 (m, 1H, 5’pyridine), 7.23–7.25 (d, 1H, l e 1 UV: max (log ): 294 nm (4.26).