= h a l i r ~ l k y l :0.01 nitil) in 1)MF (50 m l j at 0" and the mixture was -1irrrti u n t i l i t hecame neutral itinie/temperature given,. Acidifi-
cation i.AcOHi and dilution with H20 afforded the crude product. which ~ v t i >recrystallized t'rom the appropriate solvent. 3-Substituted I-[~-(j-Nitro-2-furyl)-I ,3,4-thiadiazol-%yljhydantoins and -hydrouracils (IV, Table V). NaH (,io% in oil, 0,ii:i mol) was added in portions to a suspension of the hydanl o i n o r hytirouracil TI1 iO.O:3 mol) in DMF (6Uml, at 0'. ioiloweti t)> the appropriate alkylating agent. The mixture w a s then htirrcd until neutral (time temperature liitedl. acidified i . A c O H j . anti diluted w i t h H?O. The prnduct w a s filtered oif. aashed t\-ith HzO. d r i e d . m t l recrystallii.cd,
dhydroxyquinoxaline ( 1 ) with acetic anhydride a n d H2S04 as catalyst wab accomplished to give t h e corre sponding d i a c e t l l d e r n a t i r e 5 Scheme I
OH
0
A c k n o w l e d g m e n t s . T h e authors are indebted to Dr. K. E:. Bowman for encouragement a n d advice. t o Miss E. 11. .pectroscopic measurements. t o M r . F . I i . croanalyses. to M r . M. D. Closier for some technical assistance. a n d to Drs. 11. \V. Fisher and E'. K . '1'hompi;on anti their ociates of' t h e Departments of hlicrobiology a n d Experimental 'Therapeutics, respectively. I'cirke. I)a\,is a n t i Co.. Inc.. Detroit a n d Ann Arbor. \lic.h.. !iir t hr>biological results. Keferences
ii
0
4
3
T h e synthesis of ti,-cvclohexylpentyl-j,8-quinoxalinequinone ( 6 ) was effected by treating 5.8-quinoxalinequinone with diu.-cyclohexylhexanoyl peroxide in acetic acid ( S c h e m e 11). T h e yield of Gw-cvclohexylpen~yl-:i.8-quinosalinequinone (6) was very low Scheme I1
A n t i m e t a b o l i t e s of C o e n z y m e Q . 2O.t S y n t h e s i s of N e w Alkyl-5,8-quinoxalinequinonesas P o t e n t i a l I n h i b i t o r s of C o e n z y m e Q a n d as A n t i m a l a r i a l D r u g s 'l'honias H . Porter. Alexander 'ion Klaudy. and Karl Folkersr
6
C o m p o u n d s 2--4 were tested for antimalarial activity against blood-induced Plasmodium berghei in mice3 and I n j t i t L i i c for ijiiirnrdicai Hwearrh. 'The Cnicrr\lt\ of Tcxar. a t were inactive a t 640 mg/kg each. C o m p o u n d s 3 a n d 4 . \ u r t i n . .A[i\tin, 'I'csn.9 73/12. Kec!,ictd ,!4arch 19, 1973 were tested against Plasmodium gallinaceum in t h e sporozoite-induced chick test4 a n d were inactive a t 80 m g i k g . T h e synthesis is described of representative compounds C o m p o u n d 2 was also inactive against I? gallinaceum of a new category of alkyl-5,8-quinoxalinequinonesas po(blood-induced) in the chick3 a t 100 mg/kg. Additional tential antimetabolites of coenzyme Q for testing as a n t i compounds, particularly analogs of 3, merit synthesis a n d malarials a n d other biological activities. In view of t h e eftesting. f'ective antimalarial activity of' some of our recently synC o m p o u n d s 2 a n d 3 were tested in uitro for inhibitory it is of i n thesized alkylmercapto-5.8-quino1inequinones.l activity in mitochondrial DPNH-oxidase and succinoxiterest to synthesize a n d bioassay 5.8-quinoxalinequinones. dase enzyme systems ('Table I ) . Neither compound showed especially those with sulfur-containing side chains. T h e significant inhibition in DPNH-oxidase a t levels of 120 side chains were designed to i m p a r t t h e necessary lipoidal nmol of inhibitor/mg of mitochondrial protein: however. character to the molecule a n d toward simulation of t h e compounds 2 a n d 3 showed 25 a n d 29% inhibition, respechighly lipoidal coenzyme Q. tively, in succinoxidase a t t h i s s a m e concentration level. T h e initial s t e p in t h e two-step synthesis of 6-n-dodecylniercapto- a n d 6.7-di-n-dodecylmercapto-5,8-quinoxaline- T h e mitochondria were prepared by a method similar t o t h a t described by Blair.5 q u i n o r i ~ s ( 3 a n d 1, respectiveljr) ( S c h e m e I ) consisted of the 1.4 addition of n-dodecyl mercaptan to 5,8-quinoxalineExperimental Section quinone in a manner similar t o t h a t described by Snell All melting points were taken on a 'Thomas-Hoover melting a n d Weissberger2 for t h e syntheses of certain alkylmerpoint apparatus and are uncorrected. Where analyses are inclicatcaptobenzoquinones. Oxidation of t h e isolated mono- a n d ed only by symbols of the elements. analytical results obtained dialkylated dihydroxyquinoxalines (1 a n d 2, respectively) for those elements were within i.0.4'7~ of the theoretical values. with FeC13 gave t h e alkylated quinoxalinequinones 3 a n d Nmr spectra were taken on all new compounds and were consistent with the proposed structures. 4 , respectively. in high yield. A t t e m p t s t o oxidize t h e 6-n-Dodecylmercapto- and 6,7-Di-n-dodecylmercapt0-5.Xdihydroxyquinoxalines with AgzO resulted in extensive dihydroxyquinoxaline ( 1 and 2, respectively). 5.8-Quitioxalinedecomposition. Acetylation of 6-n-dodecylmercapto-5,8quinone6 (1.0 g. 6.24 mmol) in EtOH was treated "ith n-dodecyl 4('oenL>ine I$.l6:i mercaptan (1.5 g, 7.41 mmol). The reaction mixture !vas stirred
Journal ofMedicinal Chemistr),. 197.7. Voi. 16. .Vo 11
Not ES
Table I. In Vitro Assay of Certain Quinoxaline Derivatives in Coenzyme Q E n z y m e Systems, D P N H - O x i d a s e and Succinoxidase DPNH-oxidase % inhiConcn. bition
Succinoxidase ________
. ~ _ _ _ _ _ _ _
Compd
2 3
120 120
7 0
Concna
% inhibition
120 120
25 29
1311
(3) T. S. Osdene, P. B. Russell, and L. Rane. J . Med. Chem , 10, 431 (1967). (4) L. Rane and D. S. Rane, R o c . Heirninthol. Soc. Washington. 39,283 (1972). (5) P. V. Blair, Methods Enzymol., 10,78 (1967). (6) J. Adachi, Nippon Kagaku Zasshi, 76,311(1955). (7) Y. T.Pratt and N. L. Drake, J. Amer. Chem. S o c , 77, 4664 (1955). (8)Y. T . Pratt and N . L. Drake, ibid., 79,5024(1957). (9) L.S. Silbert and D. Swern, ibid., 81,2364(1959).
aNanomoles of inhibitor per m g of mitochondrial protein. for 1 week a t room temperature. and the resulting orange precipiDeaza A n a l o g s of S o m e 4-,6-, and 8 - A m i n o q u i n o l i n e s tate was collected by filtration. Fractional recrystallization from EtOH-EtzO-CHC13 and CHC13-EtOH gave -300 mg of 1, mp Daniel J . McCaustland, Ping-Lu Chien C C Cheng,= 144-145", as bright orange crystals (yield 13.2%); recrystallizaMidueit Rewarthlnrtitute, Kanta, C ' i h .Vli5\ouri h l l l f l tions from EtOH of solids from filtrates gave -600 mg of 2, mp 81-83" (yield 17.2%). Anal. (1, CZOH~ONZOZS) C, H, N, S. Anal. (2, C ~ Z H S ~ N Z O Z C,SH, Z )N, S. Jaroslav Novotny, Walter L . Schreiner, and Fred R .Starks 6-n-Dodecylmercapto-5,s-quinoxalinequinone (3).6-n-DodecStarks Associates, Inc., Buffalo, Neu York 14313. ylmercapto-5,8-dihydroxyquinoxaline( 1, 1.0 g, 2.76 mmol) disReceioed August 20, 1.973 solved in EtOH-CHC13 was treated with FeC13 (3 g, 18.5 mmol, in HzO). The CHC13 layer separated and was collected. Further CHC13 extractions were made, and the combined CHC13 extracts Among a n u m b e r of 8-aminoquinolines synthesized d u r were dried (anhydrous NazS04). Addition of hexane to the coning World W a r 11, pamaquine1.2 (1, R = C2H5) a n d pricentrated CHC13 extracts gave -860 mg of yellow crystals. Remaquine3 (1, R = H)were found t o exhibit good prophycrystallization from CHC13-EtOH-Et20 yielded -760 mg of 3, lactic antimalarial activity i n ani mal^^.^ and i n m a n . 6 mp 152-163" (yield 76.5%). Anal. (sample of 3, mp 152-153"from T h e major d r a w b a c k to t h e use of these compounds is another preparation) (CZOHZ~NZOZS) C, H, N , S. 6,7-Di-n-dodecylmercapto-5,8-quinoxalinequinone (4). 6,7their toxicity-the most severe being a c u t e hemolytic a n e Di-n-dodecylmercapto-5.8-dihgdroxgquinoxaline (2 g, 3.55 mmol) mia, particularly in persons whose r e d blood cells are suswas prepared in a manner similar to that described for the synceptible to drug-induced hemolysis d u e to glucose-6-phosthesis of 3. except the CHC13 extracts were allowed to evaporate p h a t e dehydrogenase d e f i ~ i e n c y Neurotoxicity .~ produced at room temperature to a solid residue. The residue was recrystalb y certain 8-aminoquinolines has also been noted.x lized from EtOH-EtzO-hexane (filtered) two times to yield -705 mg of orange crystals, mp 72-73" (yield 35.5%). Anal. (sample of 4, mp 72-73" from another preparation) (C3zH~zNzOzSz)C, H. N, S. 6-n-Dodecylmercapto-5,8-diacetoxyquinoxaline (5). 6-nDodecyimercapto-5.8-dihydroxyquinoxaline (1, 100 mg. 0.276 mmolj was treated with excess acetic anhydride and a catalytic amount of HzS04. After 1 day, addition of ice to the reaction CH OCH mixture caused the mixture to boil vigorously for a few seconds. A white solid precipitated upon addition of more ice. The reaction 1 2 mixture was filtered to yield a white solid which was recrystalProphylactic antimalarial activity h a s also been oblized from EtOH-Hz0 and EtOH-Et20 (charcoal, Celite, cornstarch) to give a white powder tinged with yellow, mp 107-108". served i n certain 6-aminoquinolines of t y p e 2.1.9-11 Again This material was recrystallized from EtOH-Et20 and then t h e high toxicity of these compounds in experimental aniEtOH-Et20 (charcoal, Celite, cornstarch) to yield crystals, mp m a l s h a m p e r e d realization of their clinical usefulness. 110-112".Anal. (5,C Z ~ H ~ ~ N ZC,O5~ ,SS;) H: calcd, 7.67;found, Previous structural modification s t u d y on compounds of 7.27. 6w-Cyclohexylpentyl-5,8-quinoxalinequinone (6). 5,8- t y p e 1 disclosed that reduction of t h e pyridine ring of these 8-aminoquinolines resulted i n compounds with inf'eQuinoxalinequinone6 (1.0 g, 6.24 mmol) in HOAc was treated rior antimalarial a c t i ~ i t y . Since ~ ~ . ~reduction ~ of t h e pyriwith crude diu.-cyclohexylhexanoyl peroxide in a manner similar to the syntheses of certain alkylated 5,8-quinolinequinones ded i n e ring system n o t only destroys t h e planarity of' t h e scribed by Pratt and Drake.7,8 The acid peroxide was prepared p a r e n t ring structure. but also increases t h e basicity of from w-cyclohexylhexanoic acid (5.0 g, 25.2 mmol) by a procedure t h e ring nitrogen, it suggests t h a t an increase in basicity similar to that described for other alkanoyl peroxides by Silber of t h e ring system m a y h a v e an adverse effect on a n t i m a 30% Hz02 was used. The reaction mixture and S ~ e r n except ,~ larial activity. T h i s information: together with t h e fact was stirred at -80-90" for 8 hr and then was stirred at room temthat compounds with more than one basic center i n t h e perature over the weekend. Acetic acid was removed in cacuo, and the oily residue after the addition of HzO was extracted requinoline ring (as exemplified by t h e synthesis of a n u m peatedly with Et20 and/or CHC13. Addition of hexane to the ber of 1,2-, 1,3-, 1,4-. 1 , 5 , a n d l,7-diaza analogs) d o not ether extracts yielded an orange powder. Repeated recrystallizashow t h e expected high antimalarial a ~ t i v i t y , ~ . ~ ~ - ~ 6 tions from EtzO-CHC13, and EtsO-EtOH-hexane gave bright orimplies that t h e nitrogen a t o m in t h e quinoline ring m a y ange crystals. mp 139-141"Anal. (6, C19H24N202) C, H, N. not be entirely necessary for t h e activity. T h i s postulation A c k n o w l e d g m e n t s . T h i s work was supported by U. S. has been supported by reports t h a t : (1) it is t h e aliphatic A r m y Research and Development C o m m a n d C o n t r a c t No. side chain (sometimes together with t h e methoxyl funcDADA 17-69-C-9067. Correspondingly, t h i s is Contribution) r a t h e r than t h e ring which contributes t o t h e bindtion No. 1156 from t h e A r m y Research P r o g r a m o n M a l a r ing of these compounds t o s o m e e n z y m e system a n d n u ia. cleic acids;li-19 (2) i n another series of antimalarial compounds whose mode of action m a y b e different. activity is References n o t only retained but increased by replacing t h e quinoline (1) T . H. Porter, C. M .Bowman, and K. Folkers, J. Med. Chem., unit of quinoline a m i n o alcohols with a n a p h t h a l e n e r i n g . t 16,115 (1973). (2) J . M . Snell and A. Weissberger. J . Amer. Chem. Soc., 63, tJ. S. Gillespie, personal communi'cation (WRAIK Antimalarial Confer2948 (1941). ence. July 14, 19i3).
-
