Reduced 8-Aminoquinoline Analogues
Journal of Medicinal Chemistry, 1976, Vol. 19, No. 9 1111
Reduced 8-Aminoquinoline Analogues as Potential Antimalarial Agents F. I. Carroll,* J. T. Blackwell, Abraham Philip, and Charles E. Twine Chemistry and Life Sciences Division, Research Triangle Institute, Research Triangle Park, North Carolina 27709. Received December 16, 1975
The synthesis of l-alkyl-8-(aminoalkylamino)-6-methyl-1,2,3,4-tetrahydroquinolines, 8-(4‘-amino-l’-methylbutylamino)-6-methoxy-l-methyl-1,2-dihydroquinoline, 5-substituted 8-(4’-amino-l’-methylbutylamino)-l-methyl1,2-dihydroquinolines, 8-alkylamino-L-(2-N,~-diethylaminoethyl)-6-methoxy-l,2,3,4-tetrahydroquinolines, 1-(2N,N-diethylaminoethyl)-6-methoxy-l,2,3,4-tetrahydroquinoline, 1-(2-N,N-diethylaminoethyl)-8-(2-N,N-diethylaminoethylamino)-6-methoxy-1,2,3,4-tetrahydroquinoline, and 2-substituted 8-methoxy-5,6-dihydro-4-imidazo[ijlquinolines is described. These compounds as-wellas most of the intermediates used in their preparation were tested against Plasmodium berghei in mice, and a few compounds were tested for prophylactic activity against Plasmodium cynomolgi in rhesus monkeys.
The 8-aminoquinolines such as pamaquine (la) and primaquine (lb) are highly active against the primary exoerythrocytic forms of Plasmodium uiuax and PlasI I modium falciparum and against the gametocytes of all four YH R NHR C H z C H z N ( C 2 H 5 ) 2 species of plasmodia that infect man.1-3 In fact, the main R’CH(CH2)3N, clinical value of these drugs derives from their ability to 4 R”’ destroy the exoerythrocytic forms of both P. uiuax and 3 Plasmodium malariae, a property not common to any x other group of compounds so far tested. I The effect of variation of the nuclear substituent as well as the position-8 side chain in the 8-aminoquinolines has been extensively investigated and s u m m a r i ~ e d . ~In~ ~ addition, 8-(5-diethylamino-2-pentylamino)-6-methoxy1,2,3,4-tetrahydroquinoline (2a, tetrahydropamaquine), a reduced analogue of pamaquine, was shown to possess an 6 activity of 30 Q4in Plasmodium lophurae in duck (sup5 pressive test) and an activity of 15 Q in Plasmodium Chemistry. In order to achieve the synthesis of the gallinaceum in chick (suppressive test).5a In latter studies desired l-alkyl-8-(aminoalkylamino)-6-methoxy-l,2,3,4Gray and Hill reported that tetrahydropamaquine (2a)was tetrahydroquinolines (3 and 4) and the l-alkyl-8-(amiapproximately one-fourth as active as the parent comnoalkylamino)-6-methoxy-l,2-dihydroquinolines (5), it was pound against P. gallinaceum in chicks and Plasmodium necessary to devise synthetic schemes for the preparation relictum in canaries.6 In clinical trials tetrahydroof l-alkyl-8-amino-6-methoxy-1,2,3,4-tetrahydroquinolines pamaquine was found to be both less active and less toxic (7) and l-alkyl-8-amino-6-methoxy-1,2-dihydroquinolines than pamaquine against P. falciparum gametocyte^.^^^ (a), followed by the incorporation of an appropriate side The 1-substituted analogue, 1-(9-diethylaminonony1)-6chain at position 8. methoxy-1,2,3,4-tet,rahydroquinoline (2b), was active A synthetic procedure for the preparation of 8against P. lophurae in turkeys (prophylactic test).5b To amino-6-methoxy-1-methyl-1,2,3,4-tetrahydroquinoline C H30 (7a) and 8-amino-6-methoxy-l-methyl-1,2-dihydroquinoline (8) was developed and is shown in Scheme I. Conversion of the appropriate 6-methoxy-8-nitroquinoline (9)to the methiodides followed by reduction of 10 NHR with sodium borohydride yielded the corresponding 6l a , R = -CH(CH,)(CH,),N(C,H,), methoxy-l-methyl-8-nitro-l,2-dihydroquinoline (11). The b, R = CH(CH,)(CH,),NH, 8-nitro compounds lla-c gave 8a-c on reduction with stannous chloride or hydrazine in the presence of Raney nickel and lla afforded 8-amino-6-methoxy-1-methyl1,2,3,4-tetrahydroquinoline (7a)on catalytic reduction with Raney nickel catalyst. Since the alkylation of 9a to give k l-butyl-6-methoxy-8-nitroquinolinium salts occurred in only very low yield, we developed a different procedure 2a, R = NHCH(CH,)(CH,),N(C,H,); for the preparation of 7b and 7c which is shown in Scheme R‘= H b, R = H; R’= (CH,),N(C,H,), 11. Reduction of 9 with sodium borohydride in acetic acid gave the dihydro derivative 128which on butyrylation gave our knowledge no other reduced analogues have been 13. Treatment of 13 with diborane followed by treatment tested. In the present paper we describe the preparation with acetic acid effected both reduction of the 3,4double and test results obtained on some l-alkyl-8-(aminobond and the amide group to give 14. Reduction of 14a alkylamino)-6-methoxy-1,2,3,4-tetrahydroquinolines (3), and 14b with h e y nickel and hydrazine gave the desired S-(alkylamino)-l-(2-diethylaminoethyl)-6-methoxy-1,2,- amine 7b and 7c,respectively. 3,4-tetrahydroquinolines (41, l-alkyl-8-(aminoalkylThe second phase of these syntheses involved the atamino)-6-methoxy-1,2-dihydroquinolines (51, and 2-subtachment of side chains to the amines 7 and 8. The 4stituted 8-methoxy-5,6-dihydro-4-imidazo[ i,j]quinolines NJV-diethylaminobutyl side chain was attached to 7a and (6). 7b as shown in Scheme 111. Condensation of 7a and 7b , R il
qo
cH30w A t
1112 Journal of Medicinal Chemistry, 1976, Vol. 19, No. 9
Scheme I
C
H
3
0
7
J
p
;
;;;ol2So2+
cH30*
'N NO2
NO2
9
I-
CH3
10
X
NO;,
CH3
11
7a
/
NH2
CH3
8
a,X= H b, X = CH,O C, X = p-ClC,H,S Scheme I1 X
X
NO2
NO,
H
12
9a,X=H b, X = OCH,
I
C 3 H ,COCl
X
C6H6
I
COHSN
X
NO2
COC3H7
13
14
k'"', N2H4
X
cH30+3 NH,
C4H9
7b, X = H c, X = OCH,
with N,N-diethylsuccinamic acid (prepared from succinic anhydride and diethylamine) using DCI as the coupling agent gave the corresponding amides 15a and 15b. Reduction of 15a and 15b with diborane or sodium bis(2-
Carroll, H l a c k w d l , Phzlzp, TwznP
methoxyethoxy)aluminum hydride yielded 8-(4-diethylaminobutylamino)-6-methoxy-l-methyl-1,2,3,4-tetrahydroquinoline (3a) and l-butyl-8-(4-diethylaminobutylamino)-6-methoxy-1,2,3,4-tetrahydroquinoline (3b). respectively. We devised two methods for adding the 4-aminobutyl side chain to 7a which are also outlined in Scheme 111. In one scheme 7a was condensed with N-benzylsuccinamic acid (prepared from succinic anhydride and benzyl amine) in the presence of DCI to give 15c. Reduction of 15c with diborane afforded 8-(4'-benzylaminobutylamino)-6methoxy-1-methyl-1,2,3,4-tetrahydroquinoline (3c) which also served as an intermediate for the preparation of the 8-(4-aminobutylamino)-6-methoxy-l-methyl1,2,3,4tetrahydroquinoline (3d). This conversion was effected by catalytic debenzylation of 15c using palladium-oncarbon catalyst in ethanol containing hydrochloric acid. An alternate synthesis of 3d involved the alkylation of 7a with N-(4-bromobutyl)phthalimideto give 16a followed by removal of the phthaloyl-protecting group with hyd r a ~ i n e .If~ 7a and 8a-c were alkylated with 4-bromo1-phthalimidopentane in the presence of a base, the protected derivatives 16a- were obtained. Treatment of 16 with hydrazine in ethanol gave the primaquine analogue 3e, 5a, and 5b. The synthesis of the 8-alkylamino-l-(2-diethylaminoethyl)-6-methoxy-l,2,3,4-tetrahydroquinolines (4)is shown in Scheme IV. Acylation of 17 with butyryl chloride or ethyl chloroformate yields 18a and 18b which on reduction gave 19a and 19b, respectively. Treatment of 19a and 19b with sodium and alcohol afforded 20a and 20b which yielded 8-butylamino-l-(2-diethylaminoethyl)-6-methoxy-1,2,3,4-tetrahydroquinoline(4a) and 1-(2-diethylaminoethyl)-6-methoxy-8-methylamino-1,2,3,4-tetrahydroquinoline (4b), respectively, on alkylation with diethylaminoethyl chloride. 8-(2-N,N-Diethylaminoethylamino)-l-( a-N,N-diethylaminoethyl)-6-methoxy-1,2,3,4-tetrahydroquinoline (4c) was obtained by the route shown in Scheme V. Alkylation of 17 with N,N-diethylaminoethyl chloride followed by reduction with sodium and alcohol afforded 22 which yielded 4c on treatment with N,N-diethylaminoethyl chloride. Scheme VI outlines the reaction schemes used to prepare 2-(n-propyl)-&methoxy-5,6-dihydro-4-imidazo[ i jlquinoline (6a), 2- [2'-(N,N-diethylcarbimido)ethyl]-8-methoxy5,6-dihydro-4-imidazo[i,j]quinoline(6b), and 2-(3-diethylaminopropyl)-8-methoxy-5,6-dihydro-4-imidazo[ijlquinoline (6c). Catalytic reduction of 18a or 18c, prepared by coupling 17 with N,N-diethylsuccinamic acid, with Adams catalyst in acetic acid or ethanol gives 6a and 6b, respectively. Similar compounds have been prepared by Elderfield and KreysalO using a different route. Keduction of 6b with diborane gave 6c. Biological Activity. Compounds 3a-e, 4a- c, 6a-c, 7a,b, lla, 15c, 18a,and 22 were tested for antimalarial activity against mice infected with P. berghei."%l2 None of the compounds tested caused any significant increase in mean survival time. Compound 4a which showed an increase in life span of 5.5 days was the most active compound. The compounds tested were nonlethal to mice at dose levels as high as 640 mg/kg. Compounds 3e, 5a, and 5b were tested for prophylactic antimalarial activity against P. cynomolgi in rhesus monkeys. The results obtained are listed in Table I. Test results were carried out by Dr. L. H. Schmidt, Southern Research Institute, Birmingham, Ala.I3 In this test animals are given an iv injection of 100 000--500000 sporozoites
Journal of Medicinal Chemistry, 1976, Vol. 19, No. 9
Reduced 8-Aminoquinoline Analogues
1113
Scheme 111
NH2
k
7a, R = CH, ; X = H b, R = C,H,; X = H 8a, R = CH,; X = H; 3,4 double bond b, R = CH,; X = CH,O; 8,4double bond C , R = CH,; X = p-ClC,H,S; 3,4 double bond
15a, R = CH,; k = R" = C,H, b, R = C,H,; R = R" = C,H, C, R = CH,; R' = H; R" = C,H,CH,
cH30y
X I
-
\ \
cH30*
cH30*
NH CH3 I RCH(CH2) 3 NPht
NH
I / (cH2 N,
I RCH(CH2)3NH2
16a, R = X = H b, R = C H , ; X = H c, R = CH,; X = H; 3,4 double bond d, R = CH,; X = CH,O; 3,4double bond e, R = CH,; X = p-ClC,H,S: 3,4 double bond
k
NH
CH3
14
R' R,,
3a,R=CH,;R'=R"=C,H, b, R = C,H, ; R' = R" = C, H, c, R = CH,; R' = H; R " = C,H,CH,
3d, R = X = H e, R = C H , ; X = H 5a, R = CH,; X = H; 3,4 double bond b, R = CH,; X = CH,O; 3,4 double bond
cH3093 -"';93 cH3013p'"73p
Scheme IV
Scheme V
RCOCl
IC&)2NCH2CH2CI NaOAc, C &OH
NHCR
"2
"2
II
17
c
0
17
18a, R = C,H, b, R = OC,H, NaAlH2(0CH2CH20CH3
l2
kH
I
6H2CH2N(C2H,)2
CH2CH2N(C2H5)2 NHR
H
NHR
20a, R = C,H, b, R = CH,
19a, R = C,H, b, R = CH,
4c
NH
I
k
CHZCH~N(C~H&
22
Table I. Antimalarial Test Results against P. cynomolgia Dose, No. of Compdb mg/kg animals CuresC Relapsesd
cH30m
3e
I
NHR
I
CH~CH~N(C~HS)Z
4a, R = C,H, b, R = CH,
prepared from a homogenate of A . freeborni mosquito salivary glands infected with the Bastianelli strain of P. cynomolgi. The test compound is adminibtered for nine consecutive days beginning on the day before sporozoite
10 1 0 1U3) 1 1 0 1UO) 0 5a 10 1 1 1 1 0 1 (11) 5b 10 1 1 0 1 1 0 1(12) Data supplied through courtesy of Dr.E. A. Steck. MonCompounds were tested as their fumarate salts. keys that do not relapse in 90 days are considered cured. The number in parentheses is the relapse day.
inoculation. Blood examinations are made on the last day of drug administration and are repeated until parasitemia
1114 Journal o f Medicinal Chemistry, 1976, Vol. 19, No. 9 Scheme VI
17
18a, R = CH, c, R = CON(C,H,),
i + / c
H
3
j
0
A
O2
6a, R = CH, b, R = CON(C,H,),
m
N IJ H2C H2 C H #(C 2 H 5 )2
C- -N
6c
is found. If patency is not observed within 60 days after challenge, the compound used is scored as having prophylactic activity. Untreated control monkeys are consistently patent on the eighth day after inoculation. Primaquine serves as a baseline in this test; at 1.0 mg/kg relapse occurs about 12 days post-medication. The two dihydro derivatives, 5a and 5b, were curative at a dose level of 10 mg/kg but were inactive at 1.0 mg/kg. The above data indicate that reduction or partial reduction of the heterocyclic ring of 8-aminoquinidine antimalarials combined with the addition of an alkyl group to the heterocyclic nitrogen either eliminates or lessens their antimalarial activity against P. berghei in mice and P. cynomolgi in rhesus monkeys. Experimental Section15 Melting points were determined on a Kofler hot-stage microscope using a calibrated thermometer. Ir spectra were measured with a Perkin-Elmer Model 267 or 467 grating infrared spectrophotometer. NMR spectra were recorded on a Varian Model HA-100 spectrometer using tetramethylsilane as an internal standard. MS were determined on an AEI-MS 902 spectrometer. Microanalyses were carried out by Micro-Tech Laboratories, Skokie, Ill. 6-Methoxy- 1-methyl-8-nitroquinoline Methiodide (loa). The title compound was prepared by the procedure reported by Mislow and K ~ e p f l i .The ~ yield of 10a was 90-95% of theory, mp 155-157' (lit.: mp 149'). 6-Methoxy-l-methyl-8-nitro-1,2-dihydroquinoline (1 la). T o a solution of 32 g (0.092 mol) of 10a in 960 ml of water was added 32 g of h sodium borohydride portionwise. Immediate evolution of hydrogen occurred, and a dark red color developed. After 0.5 h the solution was extracted with ether. The extracts were dried (Na2S04) and concentrated to give 19.7 g (97%) of 1la as dark red crystals. The analytical sample was prepared by recrystallization from an ether and hexane mixture: mp 56-61' (resolidified and melted at 174-180'); ir (CHZC12) 1565 (C=C), 1518 and 1336 cm (N02); NMR (CDC13) 6 2.68 (s, >NCH3), 3.73 (s, CH30-), 4.13 (q. NCHzC=C-), 5.89 (m, ArCH=CH-), 6.38 (m, ArCH=CH-), 6.67 (d, 5 H, J = 2.8 Hz), and 7.08 ppm (d, 7 H); MS (70 eV) m / e 220. Anal. (C11H12N203)C, H, N. 8-Amino-6-methoxy-1-methyl-1,2,3,4-tetrahydroquinoline (7a). A solution of 0.5 g (2.27 mmol) of lla in 35 ml of ethanol containing Raney nickel was hydrogenated in a Parr hydrogenator until hydrogen ceased to be absorbed. The catalyst was removed by filtration. The solid obtained on concentration of the filtrate was recrystallized from a methylene chloride and hexane mixture to give 0.30 g (69%) of 7a: mp 74-75' (with sublimation); ir
Carroll, Blackwell, Philip, Twine (CHzClz) 3322 and 3418 cm ("2); NMR (CDC13) 6 1.88 (m, 3CH2), 2.60 (s, CH3N
