Amine oxides МП.* Preparation, infrared spectra, and antimicrobial activity of some iv-oxides of N,N-dialkylaminoalkylesters and iv^n'-dimethylaminoalkylamides of dodecanoic acid F. DEVÍNSKY, -L LACKO, b D. MLYNARČÍK, and T. KRASNEC "Department of Inorganic and Organic Chemistry, Faculty of Pharmacy, Komenský University, CS-8 Bratislava ь Department of Biochemistry and Microbiology, Faculty of Pharmacy, Komenský University, CS-8 Bratislava Received 1 February 198 Paper published on the occasion of the th anniversary of the foundation of the Faculty of Pharmacy, Komenský University, Bratislava Preparation, infrared spectra, and antimicrobial activity of some N-oxides of N,N -dialkylaminoalkylesters and iv,n'-dimethylaminoaikyiamides of dodecanoic acid are described. An influence of the structure on antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans has been found. Описано получение, ИК-спектры и антимикробиальная активность некоторых N-окисей, производных ^^диалюшаминоалкиловых эфиров и N^'-диметиламиноалкиламидов додекановой кислоты. Обнаружено влияние структуры на антимикробиальную активность по отношению к Staphylococcus aureus, Escherichia coli и Candida albicans. Amine oxides represent a large group of compounds derived from tertiary amines containing a strongly polarized NО bond [1]. Great number of amine oxides occurring in nature or prepared synthetically are known as biologically active compounds (antimetabolites and chemotherapeutics, psychotropic and cancerostatic compounds, etc.). Though some nonaromatic amine oxides have found wide industrial utilization due to their good surface-active properties [4, 5], relatively little attention has been paid to their biological activity, contrary to aromatic amine oxides [68]. * For Part V see Collect. Czech. Chem. Commun. 47, 11 (198). Chem. zvesti 7 () 671 (198) 6
F. DEVÍNSKY, I. LACKO, D. MLYNARČÍK, Ľ. KRASNEC Nonaromatic surface-active amine oxides represent biodegradable nonionic amphiphiles well soluble both in water and polar organic solvents [9, 1]. Besides these properties they show significant antimicrobial activity [1114] and also lower acute toxicity when compared with the appropriate amines and structurally similar organic ammonium salts [15, 16]. In the present paper attention has been paid to such types of amine oxides which would be antimicrobially active, biodegradable, possess good surface-active properties, but simultaneously, their unwanted side effects would be suppressed. The compounds of this type belong to the so-called "soft" antimicrobially active compounds [17]. Experimental Infrared spectra were measured in the form of film (IШ) or in nujol mull (IVXXVII) on an IR 75 (Zeiss, Jena) spectrophotometer calibrated by polystyrene foil; the reading accuracy was ± 1 cm -1. The results are presented in Tables and 4. The purity of all compounds was followed by t.l.c. (the R f was the average value from 5 measurements) on a Silufol plates in the system acetone1 M-C1 (1:1); the compounds were detected with Dragendorf reagent as modified by Munier [18, 19]. Antimicrobial activity was determined by dilution test as minimum inhibitory concentration (MIC) []. The results are presented in Table 5. Amino esters To the solution of N,N-dialkyIaminoalkyl alcohol (.1 mol) in dry toluene (1 cm ) dodecanoyl chloride (.11 mol) was added at room temperature under stirring within 45 min [1]. The reaction mixture was allowed to react under reflux for min. After cooling the formed ammonium chloride was dissolved in water and the product was freed with 1 % aqueous solution of NaO under cooling. Ester was extracted with chloroform and after drying the extracts and removing the solvent by distillation, the products were redistilled. The prepared compounds are characterized in Table 1. Amino amides Methyl dodecanoate (1 mol) and a,ö)-alkanediamine (4 mol) were refluxed for 57 h and the excess diamine and methanol, formed during the reaction, were distilled off under reduced pressure. Diamides as by-products were separated either by crystallization from 1-butanol [] (in the preparation of IVVI) or with the derivatives containing longer alkyl chains, where the diamide was solubilized by the monoamide, the reaction mixture was dissolved in formic acid which formed water-soluble formate with the monoamide. The insoluble diamide was filtered of and monoamides were released from the salt with 1 % 64 Chem. zvesti 7 () 671 (198)
AMINE OXIDES. VIII aqueous solution of NaO. The resulting products were crystallized from the mixture of ethanolether (1:5) and are characterized in Table 1. The prepared co-aminoalkyldodecanamide (.1 mol) was added to 981 % formic acid (.7 mol) under stirring so that the temperature did not rise above 5 C. Then 6 % solution of formaldehyde (.5 mol) was added and the mixture was allowed to react at 4 C under stirring until evolution of C [, 4]. After the evolution stopped, the mixture was heated under reflux for min. The excess methylation mixture was distilled off in vacuo and N',N'-dimethylalkylamide of dodecanoic acid was released with 1 % aqueous solution of sodium hydroxide under stirring. The product was extracted with ether or chloroform, dried and after removal of the solvent by distillation, it was redistilled under reduced pressure in the atmosphere of inert gas. The resulting products are characterized in Table 1. Amine oxides All amine oxides characterized in Table were prepared by the reaction of the appropriate tertiary amine (.1 mol) dissolved in -propanol ( ml) with % aqueous solution of hydrogen peroxide (.1 mol) [11, 57] and were recrystallized from dry acetone. Discussion The most important step in the whole synthesis was the preparation of co-aminoalkyldodecanamides (Table 1). Ref. [8] described a possibility of preparing such compounds in very good yields (~8%) by reaction of equimolar amounts of a,co-alkanediamine and acyl chlorides. Repeated syntheses showed that it was impossible to obtain monoamides by this method, as proved also by [], because the main products of this reaction were diamides. Therefore, we applied the method after [] and found that the ratio of ester: a,a>-diamine could be reduced from 1:6 to 1:4 maintaining good yields. Moreover, in the case of the compounds MIX we used a different method for separation of monoamides from diamides than described in []. The prepared amine oxides (Table ) are slightly hygroscopic and soluble both in water and polar organic solvents. Amine oxides derived from esters are less soluble in water than the amide derivatives. In the i.r. spectra of amine oxides (Tables and 4), contrary to the spectra of the corresponding tertiary amines, a doublet of new bands belonging to v(no) occurred at 969 cm -1. Both bands were sharp and approximately of the same medium intensity. The more intensive band was denoted as I. The position as well as the shape of these bands were in accordance with the literature data for amine oxides [9]. The positions of other bands practically did not differ from those in the spectra of the corresponding tertiary amines. owever, the band belonging to v(nc ) vanished from the Chcm. zvesti 7 () 671 (198) 65
Table 1 Characterization of N,N-diaIkylaminoalkylesters and of N',N'-dimethyIaminoalkyIamides of dodecanoic acid сн - (сн ) ю -с--x(c >n < R n R x Formula Calculated/found %C % %N Yield % В.р., C/kPa Л D M.p. c R f I / II Ш IV V VI MI vni IX X 4 6 8 1 1 CÄ o o o C 16 N 71.45 C 18 7 N 99.5 C 17 5 N 85.47 C 14 O 4.41 C I5 56.4 C I6 4 7.47 Cig 8 98.57 Qo^N.O 6.6 Q.ajsr.o 54.7 C 4 5 O 8.77 7.79 7.65 7.19 7.4 71.5 71.76 69.7 69.56 7.6 69.98 71.5 7.89 7.41 7. 7.55 7.5 74.49 74.5 75.1 75.4 1.6 11.9 1.45 1.1 1.6 1.16 1.47 1.51 1.58 1.4 1.67 1.81 1.8 1.91 1.96 1. 1.7 1.91 1.17 1. 5.16 4.9 4.68 4.71 4.91 5.4 11.57 11.8 1.9 11.11 1.6 1.6 9.8 9.44 8.58 8.7 7.9 8.6 7. 7.6 6 77 7 5 74 7 8 79 94 9 15/.7 1.4418 146/.1 1.445 148/.1 1.444 87-^89 9811 1517 996 8587 9596 9911.68.76.67.68.67.64.6.6.6.58 ľ 1! a í r 5 p a r í 1
Table 1 (Continued) n R Formula М г Calculated/found % С % % N Yield B.p., C/kPa % «о" XT XII ХП1 4 XTV 6 XV 8 XVI 1 СН XVU 1 C 16 4 7.47 C 17 6 84.5 C 18 98.57 C 4 6.6 С Н4^ 54.7 C 4 5 O 8.77 C 6 54 41.87 71.5 7.88 71.77 71.75 7.41 7.8 7.55 7.78 74.49 74.6 75.1 75.7 76.1 76.15 1.67 1.5 1.75 1.55 1.8 1.6 1.96 1.1 1.7 1.15 1.17 1.9 1.5 1. 1.6 1.48 9.85 1.7 9.8 9.9 8.58 8. 7.9 8.7 7. 7.44 6.8 6.75 74 1/.1 71 16167/.4 7 19194/.6 71 4/.5 89 4/.15 98 9 1.65 68.6.61 68.44 515.1 551.18 554.
Os Table Characterization of N-oxides of N,N-dialkylaminoalkylesters and of N'.N'-dimethylaminoalkylamides of dodecanoic acid R C (C ) 1 СX(СН ) Л NR lole R Formula Calculated/found %C % %N Yield % M.p. c R< XVIII XIX XX XXI ХХП ХХШ XXIV XXV XXVI XXVII 4 6 8 1 1 C CÄ C C, о о о CÄNO 87.44 C, 7N 15.49 C 17 5 N 1.47 C I6 4 86.46 C I7 6.49 C 8 14.5 C 4 4.57 С Н4^ 7.6 C 4 5o 98.68 C 6 54 46.7 66.86 66.74 68.5 68.78 67.7 68. 67.6 66.9 67.95 68.1 68.74 68.56 7.1 7.1 71.8 71.4 7. 7.11 7.18 7. 11.57 11.71 11.8 1.1 11.7 1.81 11.96 1. 1.7 11.8 1.18 11.84 1.6 1.9 1.51 1.5 1.64 1.75 1.77 1.81 4.87 4.57 4.44 4.5 4.65 4. 9.79 9.9 9. 9.47 8.91 8.7 8.19 8. 7.56 7.8 7. 6.98 6.56 6.69 91 78 8 7 75 87 7 9 86 95 68 8 4-^5 1714 1191 111 1171 115 19111 1517.4.55..54.55.5.4.9.15.5 ö m r > n > z
AMINE OXIDES. VIII Table Infrared spectral data (cm -1 ) of N,N-diaIkyIaminoalkyIesters and of N\N'-dimethylaminoaIkylamides of dodecanoic acid v() v(nc ) v(c=) v(cn) + Ô(C--) vuc-oc) / II III XI XII XIII XIV XV XVI XVII 9 15 7 16 18 764 761 е 76 767 75 765 761 75 748 75 17 176 17 164" 164" 164" 16" 168"' 166" 164" 155" 155" 155 b 154" 158 6 15 b 157" Uli Uli 1166 a) Amide I; b) amide И; с) NСН. Table 4 Infrared spectral data (cm - ') of N-oxides of N,N-diaIkyIaminoaIkylesters and of N\N'-dimethyIaminoaIkyIamides of dodecanoic acid v(c=) v(cоc) v() v(no) I v(no) II XVIII XIX XX XXI XXII XXIII XXIV XXV XXVI XXVII 1747 17 174 1657 1644 165 16 16 16 168 1174 1175 1164 1 18 1 9 95 966 96 954 96 959 956 959 96 967 9 99 99 9 94 98" 94" 944 95 9 a) More intensive band of the doublet. spectra of N-oxides. This is the consequence of the change in spatial arrangement of the dimethylalkylamineoxide group in comparison with the dimethylalkylamine group []. The dilution test was applied to examine the antimicrobial activity of the compounds in dependence on their structures. Strains of gram-positive bacteria Chem. zvesti 7 () 671 (198) 69
F. DEVÍNSKY, I. LACKO, D. MLYNARČÍK, Ľ. KRASNEC (Staphylococcus aureus), gram-negative bacteria (Escherichia coli), and yeasts (Candida albicans) from the Czechoslovak State Collection of Typical Cultures were used for tests. The effect of the length of the joining alkyl chain in N-oxides of N,N-dialkylaminoalkyIesters and N\N'-dimethyIaminoaIkylamides of dodecanoic acid and the presence of ester and amide groups in the molecule on antimicrobial activity was investigated. As illustrated in Table 5, only three compounds of the amide group were active against gram-negative Escherichia coli. Lengthening of the joining chain in N-oxides derived both from esters and amides positively affected their antimicrobial activity. In the amides maximum activity was achieved with the compound XXV (length of the joining chain C 8 ), further lengthening led to decrease in activity. The compound XXV was most active of all derivatives of dodecanoic acid. Lengthening of the alkyl chains linked directly to nitrogen (methylethyl) in esters caused a significant improvement of the effect on S. aureus, but a slight decrease in activity against С albicans was observed (XVIII, XIX). It can be stated that N-oxides of esters (XVIII, XXI) are more active than N-oxides of amides Table 5 Bacteriostatic and fungistatic properties of N-oxides of N,N-dialkyIaminoaIkyIesters and of N',N'-dimethyIaminoaIkylamides of dodecanoic acid (MIC in ug cm" /mmol dm - ) 5. aureus E. coli С albicans XVIII XIX XX XXI XXII XXIII XXIV XXV XXVI xxvn Septonex 9.1 1. 5.166 1.49.666.954 1.9 5.15 1.51 > 1..5 >.48 >.17 >. >.49 >. >.18 6 1.75.54 5 1.5 > 1..5 8.7c 1.17 5.166.698.998.66 8..81 9.6 > 1..8. 7 diem, zvesti 7 () 671 (198)
AMINE OXIDES. VIII (XX, XXII), however, their disadvantage is that the higher homologies are little or not soluble at all in water. The structurally similar organic ammonium salt Septonex, -(ethoxycarbonyl)pentadecyltrimethylammonium bromide, belonging to the so-called "hard" antimicrobially active compounds was used as standard, because at present, amine oxides are not used for disinfections in Czechoslovakia. This standard was in all cases more active than the compounds investigated. References 1. French,. S. and Gens, C. M., J. Amer. Chem. Soc. 59, 6 (197).. Culvenor, C. C. J., Rev. Pure Appl. Chem. (Australia), 8 (195).. Linton, E. P., J. Amer. Chem. Soc. 6, 1945 (194). 4. Lindner, K., Tenside 1, 11 (1964). 5. Nowak, G. A., Kosmetik 4, 951 (197). 6. Ochiai, E., Aromatic Amine Oxides. Elsevier, Amsterdam, 1967. 7. Katritzky, A. R. and Lagowski, J. M., Chemistry of the eterocyclic N-Oxides. Academic Press, London, 1971. 8. Bickel, M.., Pharmacol. Rev. 1, 5 (1969). 9. Liras, P. and Lampen, О., Biochim. Biophys. Acta 7, 141 (1974). 1. Swisher, R., /. Amer. Oil Chem. Soc. 4, 648 (196). ll.šubík, J., Takácsová, G., Pšenák, M., and Devínsky, F., Antimicrob. Ag. Chemother. 1, 19 (1977). 1. Mlynarčík, D., Čupková, V., Devínsky, F., and Lacko, L, Folia Microbiol. (Prague),49 (1978). 1. Mlynarčík, D., Devínsky, F., and Lacko, L, Folia Microbiol. (Prague) 4, 188 (1979). 14. Takácsová, G. and Šubík, J., Folia Microbiol. (Prague) 4, 15 (1979). 15. Dechezlepretre, S., Porter, R., and Cheymol, J., Med. Pharmacol. Exp. 16, 59 (1967). 16. Vrbovský, L., Excerpta Med. Int. Cong. Ser. No. 11, 15, 1 (197). 17. Bodor, N., J. Med. Chem., 469 (198). 18. Šaršúnová, M., Schwarz, V., and Michalec, C, Chromatografía na tenkých vrstvách vo farmácii a klinickej biochémii. (Thin-Layer Chromatography in Pharmacy and Clinical Biochemistry.) P. 458. Osveta, Martin, 1977. 19. WoIIman, Ch., Nagej, S., and Scheibe, E., Pharmazie 1, 665 (1966).. Lacko, L, Devínsky, F., Mlynarčík, D., and Krasnec, Ľ., Acta Fac. Pharm. Univ. Comenianae, 19 (1977). 1. Vogel, A. J., Textbook of Practical Organic Chemistry, 4thEd.,p. 498. Longmans, London, 1978.. Domariska, A. and Ropuszynski, S., Tenside Detergents 17, (198).. Pecher, M. and Martin, Т., Bull. Soc. Chim. Belg. 66, 545 (1957). 4. Baldy, J., Maurice, N., and Desnuelle, P., Bull. Soc. Chim. FT. 1951, 1174. 5. Devínsky, F., Lacko, I., and Krasnec, Ľ., Collect. Czech. Chem. Commun. 44, 11 (1979). 6. Devínsky, F., Lacko, L, and Krasnec, Ľ., Czech. 1715 (198). 7. Devínsky, F., Lacko, L, and Krasnec, Ľ., Czech. 1716 (198). 8. Baldy, J. and Naudet, M., Bull Soc. Chim. FT. 1954, 117. 9. Devínsky, F., Thesis. Faculty of Pharmacy, Komenský University, Bratislava, 198 and literature cited therein.. Giinzler,. and Bock,., IR-Spektroskopie. Verlag Chemie, Weinheim, 1975. Translated by A. Kardošová Chem. zvesti 7 () 671 (198) 71