Journal of Medicinal Chemistry, 1974, Vol. 17, No. I
Notes (8) A. R. Battersby and T. P. Edwards, J. Chem. Soc., 1214 (1960). (9) D. Campbell and W. Richter, Acta Pharmacol. Toxicol., 25,
345 (1967). (10) W. Horst, W. Pool, and H. Spiegel, Eur. J. Pharmacol., 21, 337 (1973). (11) J. R. Cummings, A. N. Welter, J. L. Grace, Jr., and L. M. Lipchuk, J.Pharmacol. Exp. Ther., 161,fB (1968). (12) E. Spath and F. Dengel, Chem. Ber., 71,113 (1938).
Synthesis a n d Antibacterial Activity of Some Substituted 4-Quinolone-3-carboxylicAcids D. G. Markees,*,t Linda S. Schwab, and A. Vegotsky Departments of Chemistry and Biology, Wells College, Aurora, New York 13026. Received May 31, 1973
The activity of nalidixic1v2 (1) and 0xolinic~9~ (2) acids against gram-negative pathogens in refractory urinary tract infectionss suggested the synthesis and study of related compounds. Although a number of substituted N alkyl-4-quinolone-3-carboxylicacids have been prepared and claimed to have antibacterial activity,6 only few 8substituted representatives have been studied thus far. The present note deals with this type (3a-h) and with N ethylbenzo[h]-4-quinolone-3-carboxylic acid (4). In an attempt to improve upon the considerable antibacterial activity of the latter, we also synthesized 6- and 7-methoxybenzo[h]-4-quinolone-3-carboxylicacid ( 5 and 6), since it seemed possible that methoxy groups so placed might simulate the methylenedioxy ring of oxolinic acid. 0
0
Table I. Arylethylamines (ArNHEt) and Their Reaction with E M M E
Et
Et
0
.r
3a b c
d e
f g
h
R H Et Et H H Et Et Me
2
0
4
X Y MeOH Me0 H Et0 H C1 5-Me C1 H C1 H C1 6-C1 Me H n
5
6
The acids were obtained by modifications of the GouldJacobs synthesis. The required alkylanilines were prepared by reductive alkylation of the corresponding anilines with Raney nickel catalyst. The methoxynaphthylt This note is dedicated to Dr. Alfred Burger, with whom I had the pleasure to be associated some years ago and whose continued friendship I consider a privilege.
Condensation with E M M E Yield, Time, Temp, % hr "C
Bp or mp, "C
Ar ~~
2-Me0-C6H4
111-115
(9 mm). 114-117 2-EtO-CsH4 (10 mm)b 2-Cl-CsH4 98-100 (10 mmjC 2,4-(C1)2-C6H3d 96-97 (1mm) 5-MeO-ClnH7-a 70-72e 4-MeO-Cl~H7-w' 71-72.5
54
0.3
160
48
0.3
160
68
18
100
55
18 18
100
18
100
25 26
100
aLit. 117' (31 mm): M. Forster, J . Prukt. Chem., [21 21, 341 (1880). bLit. 234-236' (751 mm): E. Diepolder, Ber., 31, 495 (1898). CLit. 219' (726 mm): C. M. Suter and F. B. Dains, J . Amer. Chem. SOC.,50, 2733 (1928). dAnaZ. (CsHs74.5-75'. IAnal. ( C 1 3 H d O ) C, H, N. NC12) N. Table 11. Physical Properties and Preliminary Screening of 4-Quinolone-3-carboxylic Acids
Yield, %
No. 3a 3b 3c 3d 3e
(based on Method amine) A A A
f
62 51
58 76 83 16,43 12
4 5
A A,B B A A B
6 1 2
B 74 Nalidixic acid Oxolinic aci&
3f 3g
3h
1
137
85
76 19
MIC, pg/ml P. S. Mp,
O c a
282-283b 255-258c.d 199-202" 290-2920 239-242'~~ 161-163' 207-208.51 259-261' 242-243' 257.5258.S 249-251m
vulgaris >lo0
100 >lo0
>lo0 >lo0 50
25 >lo0
6.3 12.5
aureus
>loo >loo > 100 >loo >loo >loo >loo
>100 50
25
n 6.3 >loo 0.39 3.13-12.5
aRecrystallized from EtOH unless otherwise noted. bLit. 280' dec: W. M. Lauer, R. T. Arnold, B. Tiffany, and J. Tinker, J. Amer. Chem. SOC.,68, 1268 (1946). cRecrystallized from MeCN. dLit.8 261-262.5'. eLit.8 199-200". /Method of R. G. Gould and W. A. Jacobs, J . Amer. Chem. Soc., 61, 2890 (1939). QLit.285-286' dec: B. R. Baker and R. R . Bramhall, J . Med. Chem., 15, 230 (1972). hLit. 248250' dec: D. S. Tarbell, J. Amer. Chem. SOC.,68, 1277 (1946). %Anal.(C12HloNO3Cl) C, H, N. 1Anal. (C12HgN03C ~ ZC,) H, N, C1. kReference 7. ZAnal. (Cl7HI3NOd)C, H, N. mAnal. (Cl7Hl3NOP) C, H, N. .Too insoluble to test adequately by the method used. oData from ref 4a. ethylamines were obtained by reduction of the acetamido compounds with sodium bis(2-methoxyethoxy)aluminum hydride ("Red-Al," Aldrich). Condensations of the secondary amines with diethyl ethoxymethylenemalonate (EMME) require higher temperatures and longer times than those of primary amines728 (Table I). Cyclization to the acids was effected by Pz05 in nitrobenzene;? polyphosphoric acid8 was used to cyclize less reactive malonates (Table 11). The compounds were first screened against Proteus vulgaris and Staphylococcus aureus. The most promising acids were then tested against representatives of genera present in urinary tract infections. Determination of the minimal inhibitory concentration (MIC) was made by visual examination of a twofold dilution series. Results and Discussion The only compounds with significant antibacterial activity were acids 3f, 3g, 4, and 5 (Table 11). Their mini-
138 Journal of Medicinal Chemistry, 1974, Vol. 17, No. 1
Notes
Table 111. MIC (pg/ml) of Selected 4-Quinolone-3-carboxylic A c i d s
No.
A. aerogenes
3f 3g
>50 >50
4
50 >50 25
5
1 2
0.19
E.
E. coli
coli
R
50 >50 12.5 25 12.5 0.098-
1.56
50 25 6.3 6.3 6.3
A'.
catarrhalis >50 250 3.1 1.6
12.5 1.56
P. Ps. miru- fluoresbilis cens 50
12.5
>50 >50
3.1 1.6
>50 >50
6.3
>50
0.3% 0.78
"Data from ref 4a.
mal inhibitory c o n c e n t r a t i o n s a g a i n s t a wider r a n g e of org a n i s m s are c o n t a i n e d in Table I11 and c o m p a r e d w i t h t h e activity of nalidixic and oxolinic acids. Acids 3f and 3g are consistently less effective than nalidixic and oxolinic acids, whereas 4 and 5 are a p p r o x i m a t e l y as active as nalidixic but inferior t o oxolinic a c i d . Morphological examination of cultures of Escherichia coli and P. vulgaris w h i c h had been exposed to c o m p o u n d 4 revealed f i l a m e n t o u s forms similar t o t h o s e observed w h e n these o r g a n i s m s were treated w i t h nalidixiczb or oxolinic acid.*d This observation s u p p o r t s the view that all these c o m p o u n d s a c t b y a s i m i l a r m e c h a n i s m . The l i m i t e d data permit only few and mostly t e n t a t i v e conclusions regarding structure-activity correlations. O u r results are consistent w i t h the observation b y T u r n e r , et al.,*a that the N - e t h y l g r o u p on the quinoline r i n g is essential for significant activity ( a c i d s 3a, 3d, 3e, and 3h a r e i n a c t i v e ) . The n a t u r e of the 8 substituent i n the quinoline r i n g seems to b e i m p o r t a n t . Substituents a c t i v a t i n g the benzene r i n g (alkoxy 3b, 3c, and possibly m e t h y l 3h$) reduce a n t i b a c t e r i a l activity, b u t a d e a c t i v a t i n g chlorine atom (3f and 3g) favors it. T h u s , the C1-substituted acids m i g h t be considered nonclassical bioisosteresg of nalidixic a c i d , but t h i s view is o p e n to question, since the high activity of acids 4 and 5 could n o t be explained o n t h i s basis. The low solubility of the last t w o c o m p o u n d s in w a t e r suggests that a favorable lipid-water d i s t r i b u t i o n coefficient or a p e r m e a b i l i t y effect m a y account for the relative activities of all these compounds rather than electronic effects due t o a polar s u b s t i t u e n t i n position 8. Experimental Section Melting points were taken on a Mel-Temp apparatus and are uncorrected; ir spectra were obtained on a Beckman IR-8 spectrometer and transmittance measurements on a Bausch and Lomb Spectronic 20 colorimeter. An Orion Research Model 801 digital pH meter was used for pH measurements. Mr. J. F. Alicino (Metuchen, N . J . ) and Dr. Harry Agahigian (Orange, Conn.1 performed the analyses. Cultures were obtained from Carolina Biological Supply and were maintained on Trypticase Soy Agar (BBL); the assay broth was from Difco Laboratories. Nalidixic acid was a product of K&K Laboratories, Inc. Starting Materials. Diethyl ethoxymethylenemalonate. all primary amines. N-ethyl-I-naphthvlamine,and N-methyl-o-toluidine were commercial products. Other required N-ethylanilines were prepared by the method of' Emerson and Walters.Io In all cases 10-15 g of Raney nickel catalyst per 0.1-0.2 mol of amine was sufficient. Infrared spectra were consistent with the postulated structures: preparative details are in Table I. N-Ethyl-5-methoxy-l-naphthylamine.11 To a mechanically stirred solution of 23 ml of Red-AI (70% in benzene) was added 7.5 g of N-acetyl-5-methoxy-l-naphthylamine'2 suspended in 100 ml of dry benzene. When addition was complete, the mixture was refluxed for 3 hr. After decomposition with 10 ml of 20% H2SO4. benzene was removed by steam distillation; the residue was made $ T h e lack of activity of acid 3h may be owing to 8 suhstitution b\ methyl group or to the presence of methyl on the ring nitrogen, or both.
i-l
alkaline (l0Y0 NaOH) and extracted with several portions of Et20 (200 ml total). The ethereal solution was dried (Na2S04), the Et20 removed, and the residue distilled a t reduced pressure. The fraction boiling at 155-165" (0.8-0.9 mm) solidified and was recrystallized from cyclohexane (Table I). N-Ethyl-4-methoxy-1-naphthylamine. N-Acetyl-4-methoxy1-naphthylamine obtained by reduction of 4-nitro-1-methoxynaphthalene13 with iron in AcOH14 was reduced with Red-AI under the same conditions as the 5-methoxy analog. Distillation gave a fraction boiling over 150-160" (0.5 m m ) which solidified and was recrystallized from cyclohexane (Table I ) Condensations with Diethyl Ethoxymethylenemalonate (EMME). Equimolecular amounts of the primary amines and E M M E were mixed and heated at reduced pressure on the steam bath until EtOH evolution ceased. Reaction conditions for condensations of secondary amines are recorded in Table I: in these reactions also, residual EtOH was removed as above. The viscous oils and low-melting solids which resulted were used directly and not further purified. Cyclizations. Method A is described elsewhere.' Method B. Cyclization with polyphosphoric acid as reported by Xakagome, et ai..* was employed and the reaction mixture worked up as follows. After the reactants had been heated with PPA at 110-120" for 15 min, the resulting gum was mixed with ice-water and made strongly basic (2.5 iW NaOH). The alkaline mixture was boiled for 30 min, filtered with diatomaceous earth to remove oily material if necessary, acidified (3 M HCI), and cooled, and the product was collected (Table 11). Biological Tests. Before screening the acids were dried at 78" ( 1.5 mm) for several hours. The twofold dilution method used by Turner, et ~ / . , ~was a employed for determination of the MIC; the highest concentration tested in the preliminary screening was 100 pg/ml (Table 11) and 50 pg/ml in subsequent tests (Table 111). The low water solubility of these acids required that the tryptosephosphate broth be adjusted to pH 7.8 by addition of solid NaOH. The lowest concentration not showing visible growth (in 13 X 100 mm test tubes) was recorded as the MIC; in doubtful cases. the higher concentration was recorded. Values represent B minimum of four trials. For morphological examination, cultures of E. coli B and !' mirabiiis which had been exposed t u an inhibitory concentration of i for over 20 hr were compared with controls of the same species. The organisms were stained with Crystal Violet and examined under oil at l000X magnification.
Acknowledgment. The a u t h o r s wish to thank Dr. Norm a n G . B r i n k of M e r c k , Sharpe and D o h m e for kindly donating t h e sample olnalidixic acid. References G . Y. I,esher, E. ,J. Froelich. hl. I). Gruett. -1. H. Bailey. and K. 1'. Brundage, J. Med. Pharm. C'hem., 5 , 1063 (1962). ( a ) 'A', H. Deitz, ,J. H. Bailey. and E . J . Froelich. .4ntimi:rob. .IC. C h e m o t h e r , 583 (1964): ( b ) W. A. Goss. W.H. Deitz. and 'r. hl. Cook, J . Bacterid., 88, 1112 (1964); ( c ) ! b i d . . 89, 1068 (1965): ( d ) ibid..91, 768 (1966); (e) ibid., 91. 774 (1966): ( f ) ibid., 91,780 (1966):(g) ibid.,97,230 (1969). 1). Kaminaky and R. 1. Sleltzer, J . M e d . Chern.. 1 1 , 160 (19681. ( a ) F..I. 'Furrier, t't ai..Antimicrob. Chemothw.. 475 (1968); ( h r ibid.,480 (1968); (c) ibid.. 486 (1968); ( d ) R. S.Pianotti, K. I
