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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Bioorg Med Chem. Author manuscript; available in PMC 2010 September 15.
Published in final edited form as:
PMCID: PMC2749251
NIHMSID: NIHMS137682

Synthesis and antimalarial activity of new chloroquine analogues carrying a multifunctional linear side chain

Abstract

We report the synthesis and in vitro antimalarial activity of several new 4-amino-and 4-alkoxy-7-chloroquinolines carrying a linear dibasic side chain. Many of these chloroquine analogues have submicromolar antimalarial activity versus HB3 (chloroquine sensitive) and Dd2 (chloroquine resistant strain of P. falciparum) and low resistance indices were obtained in most cases. Importantly, compounds 11–15 and 24 proved to be more potent against Dd2 than chloroquine. Branching of the side chain structure proved detrimental to the activity against the CQR strain.

Introduction

Malaria remains one of the world's most widespread and devastating infectious diseases and affects approximately 2.4 billion people living in malaria-endemic areas. Recent estimates calculate approximately 600 million annual clinical infections with Plasmodium falciparum, 80 million with Plasmodium vivax and more than 2 million casualties -malaria kills one child under the age of 5 years every 30 seconds.13 Among the protozoan parasites of the genus Plasmodium causing malaria in humans, Plasmodium falciparum is the most lethal species while vivax is less morbid but carries the problem of severe relapses. Inexpensive and stable antimalarial drugs such as the 7-chloro-4-aminoquinoline derivative chloroquine (CQ) have kept malaria in check in most regions for decades. However, the rising number of malarial deaths is due in part to increased resistance to CQ and other drugs in P. falciparum.

Since the discovery of the antimalarial potency of quinine and other cinchona alkaloids, a variety of agents exhibiting a 4-substituted quinoline pharmacophore has been introduced. In particular, chloroquine, quinine and amodiaquine have proved to be among the most effective antimalarial drugs.46 The exact molecular mechanism that describes how quinoline-based antimalarial drugs function is not yet precisely known. Aminoquinolines form a complex with ferriprotoporphyrin IX (FPIX), which is generated in the digestive vacuole (DV) of the intraerythrocytic malaria parasite as a result of proteolysis of host hemoglobin.7,8 Free FPIX is cytotoxic and it is sequestered in the form of hemozoin, a crystalline Fe-O41 dimer that is structurally identical to synthetic β-hematin.9,10 Hemozoin is also known as "malaria pigment" and appears as a dark spot in the DV of the parasite, the organelle in which hemoglobin digestion and hemozoin formation occur. Drug-FPIX interactions inhibit conversion of hematin to hemozoin and hence its detoxification via crystallization, and the accumulation of significant concentrations of toxic FPIX-aminoquinoline adducts is believed to be ultimately responsible for killing the parasite.1115 It is widely accepted that the 4-aminoquinoline pharmacophore plays a crucial role in the complexation to FPIX resulting in inhibition of hemozoin formation and parasite growth,16 while the presence of a basic amino group in the side chain is generally considered essential for trapping high concentrations of the drug in the acidic DV of the parasite.17

Previous studies relating the structure of aminoquinoline antimalarial drugs to their function have focused on modifications of the side chain and of the quinoline ring. Various studies have revealed that structural changes of the 7-chloroquinoline ring in CQ reduces the antimalarial activity,18,19 whereas variation of the CQ side chain appears to be more promising. In a study by Krogstad et al., 7-chloroquinolines with N,N-diethylaminoalkyl side chains exhibiting spacers consisting of two to twelve methylene units were found to be as effective as chloroquine against CQ sensitive (CQS) strains.20 Importantly, the homologues with either short or very long linkers between the two amino functions showed remarkable activity against CQ resistant (CQR) strains. Analogues of chloroquine with branched and linear side chains containing two and three methylenes between the amino groups were also found to have both in vitro and in vivo antiparasitic activity similar to that of chloroquine in CQS strains of P. falciparum, and were more effective than chloroquine against CQR strains.21,22

Results and discussion

Based on the above findings, we have begun to systematically modify the length and basicity of the CQ side chain.2325 In particular, 4-amino-7-chloroquinolines with a linear side chain bearing two aliphatic tertiary amino functions proved to be highly potent antimalarials and were found equally effective against both CQS and CQR strains. In a previous report, we altered the α-portion of the side chain in a series of 4-aminoquinolines and obtained superior antiplasmodial activities when the quinolyl nitrogen and the central amino group were kept in close proximity.23 We have therefore prepared analogues 1–15 exhibiting a varied β-segment while the α-portion was kept constant at optimized length (Figure 1).

Figure 1
Structures of 4-amino-7-chloroquinolines 115 carrying a linear side chain.

Our synthetic approach towards heme-targeted antimalarials generally involves inexpensive materials and high-yielding steps in most cases. Treatment of 4,7-dichloroquinoline with excess of 1,2-diaminoethane gave almost quantitative amounts of N-(7-chloro-4-quinolyl)diaminoethane, 16, as described previously.25 Primary amine 16 then served as the common starting material for the synthesis of β-segment varied amides 1–5, secondary amines 6–10 and tertiary amines 11–15 (Scheme 1). For example, one-pot amidation of 16 with bromoacetyl chloride followed by peripheral substitution with excess of diethylamine gave 1 in 60% yield. Reduction with borane and subsequent reaction with sodium borohydride in glacial acetic acid then furnished the corresponding amines 6 and 11 in 78% and 37% yield, respectively. The aminoquinolines 2, 7, and 12 were available from previous studies.23 For comparison, we prepared branched aminoquinoline 18 using our established nucleophilic substitution and reductive alkylation protocols.

Scheme 1
Synthesis of CQ-derived antimalarials carrying a linear side chain and of branched 4-aminoquinoline 18.

The antimalarial activity of compounds 1–15 and 18 was measured versus a CQS (HB3) and a CQR (Dd2) strain using a standardized assay based on SYBR Green I intercalation.2628 The IC50 values were calculated from experiments carried out in triplicate and compared to CQ (Table 1). Several compounds within this series showed promising antimalarial activity against both strains tested and a low resistance index (RI). The RI provides a quantitative measurement of the antiplasmodial activity against CQR strains relative to that against CQS strains and reveals promising drug discovery leads.

Table 1
Antiplasmodial activities of CQ analogues 115.

It is important to note that several of our aminoquinolines afford antimalarial activity versus HB3 similar to that of CQ and we were pleased to find that some compounds were significantly more potent against the resistant strain Dd2 than CQ. In general, the antiplasmodial activity of tertiary amines 11–15 proved superior over those obtained for the corresponding secondary amines 6–10 and the amides 1–5. Notably, the amines 11–15 have IC50′s between 19.9 and 53.0 nM for Dd2 (CQ IC50=122 nM). The resistance index for CQ is about 15 whereas the majority of the heme-targeted antiplasmodials prepared for this study have RI's below 10. Quinolines 12 to 15 combine high antimalarial activity against HB3 with low RI values ranging from 1.1 to 7.1. These new CQ analogues thus show activity versus a CQS strain similar to that of CQ and, more importantly, they retain their potency against a CQR strain. Our stepwise variation of one chain at a time reveals that small changes in the spacer length can have dramatic effects on the activity versus the two strains tested. For example, a shortening or lengthening of the β-segment in the side chain in compound 12 by only one methylene group increases the RI from 1.1 to 7.1 and 10.5, respectively. But excellent resistance indices are again obtained when the β-chain length is further increased (see compounds 14 and 15). The data also demonstrate that a linear side chain motif is superior over a branched structure. In analogy to linear amines 11–15, compound 18 has high potency against HB3 but significantly lower activity against Dd2.

Based on these observations and previous work,25 we then decided to prepare CQ analogues 19–24 in which the 4-quinolyl amino function is replaced by an ether linker (Figure 2). As shown in Scheme 2, the amide derivatives can be prepared in two steps from 4,7-dichloroquinoline and an amino alcohol in the presence of strong base followed by EDC-promoted coupling with 3-diethylaminopropionic acid. However, we found that 19 and 22 are not stable to typical amide reduction conditions and we therefore prepared the corresponding amines via mesylation of alcohols 25 and 26 and substitution with either N,N-diethyldiaminopropane or N,N,N′-triethyldiaminopropane.25

Figure 2
Structures of CQ 4O analogues 1924.
Scheme 2
Synthesis of 4-alkoxy-derived 7-chloroquinolines 1924.

The replacement of the 4-quinolyl amino moiety by an ether group is known to significantly reduce the basicity of the quinolyl nitrogen. Based on titration experiments previously performed in our laboratories,25 the pKa of the quinolyl N in 4-aminoquinolines is approximately 8.5 whereas 4-alkoxyquinolines have a pKa of 4.5. In contrast to the 4-aminoquinolines 1–15, ethers 19–24 can therefore be expected to have a free, nonprotonated quinoline ring in the acidic DV. Ethers 19 and 22 are essentially monoprotic bases under physiological conditions and thus less prone to effective bioaccumulation in the DV which explains their relatively low antiplasmodial activity (Table 2). The secondary and tertiary amines 20, 21, 23, and 24 possess two basic groups in the side chain which favors migration into the acidic DV. These compounds therefore show enhanced antimalarial activity versus HB3 and Dd2. Comparison with the screening results obtained for the 4-aminoquinolines 6–15, reveals that ethers 20, 21, 23, and 24 exhibit lower antimalarial potency but improved RI's. In particular, tertiary amine 24 is a promising new antimalarial lead and more effective against Dd2 than CQ.

Table 2
Antiplasmodial activities of CQ analogues 1924.

Conclusion

A series of new antiplasmodial 7-chloroquinolyl-derived amines and ethers have been synthesized and tested against CQR and CQS P. falciparum. Many of the CQ analogues prepared for this study showed submicromolar antimalarial activity versus HB3 and Dd2. The impressive activity against Dd2 combined with the low resistance indices values of 1115 and 24 demonstrate that systematic variations of both the CQ side chain structure and basicity provide new leads that can overcome antimalarial drug resistance.

Experimental

Cell Culture and Antimalarial Activity Measurements

Drug activities were assessed and IC50 were quantified essentially as described previously.2628 The aminoquinolines were diluted using complete media under sterile conditions and plated in a 96 well plate format. Sorbitol synchronized cultures were utilized with >95% of the parasites at the ring stage. Cultures were diluted to give a working stock of 0.5% parasitemia and 2% hematocrit (final hematocrit 1% & 0.5% Parasitemia). The plates were incubated for 72 h at 37 °C. After 72 h, 50 μL of 10x SYBR green I dye was added to each well, and the plate was incubated for 1 h at 37 °C. Fluorescence was measured at 530 nm (490 nm excitation) using a spectra geminiEM plate reader. Data analysis was performed using Sigma plot 9.0 software after downloading data in Excel format. For each assay, each drug dilution was analyzed in triplicate, and the results from at least two separate assays were averaged in each case (S.D. < 10% in each case). All drugs were tested against one chloroquine sensitive, and one chloroquine resistant strain of P. falciparum (HB3 and Dd2, respectively).

Synthesis

All reagents and solvents used were commercially available and used without further purification. Flash chromatography was performed on Kieselgel 60, particle size 0.032–0.063 mm. NMR spectra were obtained on a 400 MHz (1H-NMR) and 100 MHz (13C-NMR) Varian FT-NMR spectrometer using CDCl3 as solvent. Electrospray mass spectra (ESI-MS) were collected on a Thermo Finnigan LCQ instrument. Samples were dissolved in acetonitrile/water (1:1 v/v) containing 1% acetic acid (1 mg/mL) for MS analysis. Based on NMR spectroscopic and HPLC chromatographic analyses, all compounds were at least of 98% purity.

Representative procedure for the synthesis of compounds 1–5

A mixture of 16 (0.500 g, 2.26 mmol) and N,N-diisopropylethylamine (0.91 mL, 5.29 mmol) in anhydrous DMF was stirred vigorously at room temperature under nitrogen atmosphere. Bromoacetyl chloride (0.24 mL, 2.88 mmol) was added dropwise to the mixture and allowed to stir for 1 hour. Diethylamine (2.35 mL, 22.62 mmol) was then added and the reaction was stirred at room temperature for 72 hours. The mixture was concentrated in vacuo and purified by flash chromatography (1.1:1.0:0.1 hexanes:ethanol:triethylamine). Extraction of a solution in dichloromethane with aqueous NaHCO3 and NaOH solution, dried over MgSO4 and concentrated in vacuo to give 1 as a yellow solid (0.453 g, 1.36 mmol, 60%).

N-(7-Chloro-4-quinolyl)-N-(2-diethylaminoethanoyl)-1,2-diaminoethane, 1

1H-NMR (400 MHz, CDCl3) δ = 0.98 (t, J = 7.1 Hz, 6H), 2.54 (q, J = 7.1 Hz, 4H), 3.08 (s, 2H), 3.39 (m, 2H), 3.74 (m, 2H), 6.28 (d, J = 5.4 Hz, 1H), 6.92 (bs, 1H), 7.38 (dd, J = 2.1, 8.9 Hz, 1H), 7.81 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 2.1 Hz, 2H), 8.48 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 12.3, 38.5, 46.1, 48.2, 57.4, 98.0, 117.3, 122.1, 125.4, 128.4, 134.8, 149.1, 150.1, 151.9, 175.4; MS (ESI) m/z calcd for C17H23ClN4O 334.2. Found (M + H)+: 335.2.

N-(7-Chloro-4-quinolyl)-N-(4-diethylaminobutanoyl)-1,2-diaminoethane, 3

Employing 0.700 g (3.17 mmol) of 16 and 0.48 mL 4-bromobutyryl chloride (4.13 mmol) in the procedure described above gave 0.624 g (1.72 mmol, 54%) of 3 as a yellow solid. 1H-NMR (400 MHz, CDCl3) δ = 1.00 (t, J = 7.3 Hz, 6H), 1.76–1.82 (m, 2H), 2.41 (t, J = 6.6 Hz, 2H), 2.47–2.56 (m, 6H), 3.35 (m, 2H), 3.64 (m, 2H), 6.24 (d, J = 5.4 Hz, 1H), 7.11 (bs, 1H), 7.34 (dd, J = 2.1, 8.9 Hz, 1H), 7.88 (d, J = 8.9 Hz, 1H), 7.89 (s, 1H), 8.44 (d, J = 5.4 Hz, 1H), 8.86 (t, J = 5.8 Hz, 1H). 13C-NMR (100 MHz, CDCl3) δ= 10.9, 22.4, 35.4, 38.4, 46.5, 52.7, 97.8, 117.3, 122.6, 125.1, 125.5, 127.8, 134.8, 148.8, 150.3, 151.7, 176.2; MS (ESI) m/z calcd for C19H27ClN4o 362.2. Found (M + H)+ : 363.7.

N-(7-Chloro-4-quinolyl)-N-(5-diethylaminopentanoyl)-1,2-diaminoethane, 4

Employing 0.700 g (3.17 mmol) of 16 and 0.55 mL 5-bromovaleryl chloride (4.11 mmol) in the procedure described above gave 0.800 g (2.12 mmol, 67%) of 4 as a yellow solid. 1H-NMR (400 MHz, CDCl3) δ 0.92 = (t, J = 7.1 Hz, 6H), 1.38–1.46 (m, 2H), 1.61–1.69 (m, 2H), 2.29 (t, J = 7.3 Hz, 2H), 2.35 (t, J = 7.1 Hz, 2H), 2.41 (q, J = 7.1 Hz, 4H), 3.34 (m, 2H), 3.67 (m, 2H), 6.23 (d, J = 5.4 Hz, 1H), 7.09 (bs, 1H), 7.32 (dd, J = 2.1, 8.7 Hz, 1H), 7.83 (d, J = 5.3 Hz, 2H), 7.85 (s, 1H), 8.40 (d, J = 5.4 Hz, 1H). 13C-NMR (100 MHz, CDCl3) δ = 11.4, 23.8, 26.4, 36.2, 38.7, 46.2, 46.6, 52.4, 98.0, 117.2, 122.1, 125.4, 128.3, 134.8, 149.0, 150.1, 151.9, 176.3; MS (ESI) m/z calcd for C20H29ClN4O 376.2. Found (M + H)+: 377.3.

N-(7-Chloro-4-quinolyl)-N-(6-diethylaminohexanoyl)-1,2-diaminoethane, 5

Employing 0.700 g (3.17 mmol) of 16 and 0.62 mL 6-bromohexanoyl chloride (4.14 mmol) in the procedure described above gave 0.642 g (1.65 mmol, 52%) of 5 as a yellow solid. 1H-NMR (400 MHz, CDCl3) δ = 0.95 (t, J = 7.1 Hz, 6H), 1.21–1.29 (m, 2H), 1.35– 1.42 (m, 2H), 1.62–1.70 (m, 2H), 2.25–2.29 (m, 4H), 2.44 (q, J = 7.1 Hz, 4H), 3.34 (m, 2H), 3.68 (m, 2H), 6.23 (d, J = 5.4 Hz, 1H), 7.07 (bs, 1H), 7.32 (dd, J = 2.0, 9.0 Hz, 1H), 7.76 (t, J = 6.0 Hz, 1H), 7.82 (d, J = 2.0 Hz, 1H), 7.84 (s, 1H), 8.39 (d, J = 5.4 Hz, 1H). 13C-NMR (100 MHz, CDCl3) δ = 11.4, 25.5, 26.7, 27.0, 36.4, 38.7, 46.1, 46.7, 52.5, 98.0, 117.3, 122.1, 125.4, 128.3, 134.8, 149.0, 150.1, 151.8, 176.3; MS (ESI) m/z calcd for C21H31ClN4O 390.2. Found (M + H)+: 391.3.

Representative procedure for the synthesis of compounds 6–10

A solution of 1 (0.300 g, 0.90 mmol) in 10 mL of THF was heated to reflux and borane-dimethyl sulfide complex (0.45 mL, 5.4 mmol) was added. After 2.5 hours, 6 M HCl (1.45 mL, 9.0 mmol) and 2 mL of water were added and the mixture was heated to reflux for 1.5 hours. The clear solution was cooled to room temperature, basified with saturated NaOH and extracted with a 1:1 mixture of CH2Cl2 and CHCl3. The combined organic layers were dried over anhydrous MgSO4 and concentrated in vacuo. Purification by flash chromatography using EtOH:hexanes:Et3N (1:1:0.1 v/v) as the mobile phase gave 6 (0.224 g, 0.70 mmol, 78% yield) as a brown oil.

N-(7-Chloro-4-quinolyl)-N(2-diethylaminoethyl)-1,2-diaminoethane, 6

1H-NMR (400 MHz, CDCl3) δ = 1.01 (t, J = 7.1 Hz, 6H), 2.50–2.58 (m, 6H), 2.70 (t, J = 5.8 Hz, 2H), 3.02 (t, J = 5.8 Hz, 2H), 3.33 (m, 2H), 5.97 (bs, 1H), 6.38 (d, J = 5.4 Hz, 1H), 7.34 (dd, J = 2.1, 8.9 Hz, 1H), 7.73 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 2.1 Hz, 1H), 8.51 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.7, 42.0, 46.8, 47.0, 47.4, 52.5, 99.1, 117.4, 121.4, 125.1, 128.6, 134.7, 149.1, 149.9, 152.0; MS (ESI) m/z calcd for C17H25ClN4 320.2. Found (M + H)+ : 321.1.

N-(7-Chloro-4-quinolyl)-N-(4-diethylaminobutyl)-1,2-diaminoethane, 8

Employing 0.300 g (0.83 mmol) of 3 in the procedure described above gave 0.101 g (0.29 mmol, 35%) of 8 as yellow oil. 1H-NMR (400 MHz, CDCl3) δ = 1.01 (t, J = 7.2 Hz, 6H), 1.53– 1.56 (m, 4H), 2.45 (m, 2H), 2.53 (q, J = 7.2 Hz, 4H), 2.68 (m, 2H), 3.03 (m, 2H), 3.34 (m, 2H), 6.10 (bs, 1H), 6.36 (d, J = 5.4 Hz, 1H), 7.34 (dd, J = 2.1, 8.9 Hz, 1H), 7.79 (d, J = 8.9 Hz, 1H), 7.92 (d, J = 2.1 Hz, 1H), 8.50 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.4, 24.8, 28.1, 41.8, 46.7, 47.3, 49.2, 52.7, 99.0, 117.5, 121.6, 125.2, 128.6, 134.8, 149.2, 149.9, 152.0; MS (ESI) m/z calcd for C19H29ClN4 348.2. Found (M + H)+ : 349.2.

N-(7-Chloro-4-quinolyl)-N-(5-diethylaminopentyl)-1,2-diaminoethane, 9

Employing 0.300 g (0.80 mmol) of 4 in the procedure described above gave 0.170 g (0.47 mmol, 59%) of 9 as a yellow oil. 1H-NMR (400 MHz, CDCl3) δ = 1.07 (t, J = 7.2 Hz, 6H), 1.37 (m, 2H), 1.52–1.57 (m, 4H), 2.48 (m, 2H), 2.61 (q, J = 7.2 Hz, 4H), 2.68 (t, J = 7.0 Hz, 2H), 3.04 (m, 2H), 3.34 (m, 2H), 5.99 (bs, 1H), 6.38 (d, J = 5.4 Hz, 1H), 7.35 (dd, J = 2.1, 8.9 Hz, 1H), 7.76 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 2.1 Hz, 1H), 8.51 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.0, 25.2, 26.3, 29.8, 41.7, 46.8, 47.4, 48.9, 99.2, 121.5, 125.2, 128.7, 134.8, 149.2, 150.0, 152.1; MS (ESI) m/z calcd for C20H31ClN4 362.2. Found (M + H)+: 363.4.

N-(7-Chloro-4-quinolyl)-N-(6-diethylaminohexyl)-1,2-diaminoethane, 10

Employing 0.300 g (0.77 mmol) of 5 in the procedure described above gave 0.147 g (0.39 mmol, 51%) of 10 as a yellow oil. 1H-NMR (400 MHz, CDCl3) δ = 1.01 (t, J = 7.2 Hz, 6H), 1.25–1.55 (m, 9H), 2.38 (m, 2H), 2.51 (q, J = 7.2 Hz, 4H), 2.64 (m, 2H), 3.02 (m, 2H), 3.30–.34 (m, 2H), 5.94 (bs, 1H), 6.37 (d, J = 5.4 Hz, 1H), 7.34 (dd, J = 2.1, 8.9 Hz, 1H), 7.71 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 2.1 Hz, 1H), 8.50 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.6, 27.0, 27.3, 27.6, 30.2, 41.9, 46.9, 47.2, 49.2, 52.9, 99.2, 117.4, 121.3, 125.2, 128.8, 134.8, 149.2, 149.9, 152.1; MS (ESI) m/z calcd for C21H33ClN4 Found (M + H) +: 377.5.

Representative procedure for the synthesis of compounds 11–15

To a solution of 6 (0.070 g, 0.22 mmol) in 5 mL of glacial acetic acid, NaBH4 (0.293 g, 7.7 mmol) was added at 0 °C and the reaction temperature was increased to 60 °C. After 48 hours, the reaction mixture was cooled, basified with saturated NaOH, extracted with CH2Cl2 and washed with brine. The combined organic layers were dried over anhydrous MgSO4 and concentrated in vacuo. Purification by flash chromatography using CH2Cl2:hexanes (1:1 v/v) as the mobile phase gave 11 (0.029 g, 0.080 mmol, 37% yield) as a yellow oil.

N-(7-Chloro-4-quinolyl)-N′-ethyl-N′-(2-diethylaminoethyl)-1,2-diaminoethane, 11

1H-NMR (400 MHz, CDCl3) δ = 0.99 (t, J = 7.1 Hz, 6H), 1.06 (t, J = 7.1 Hz, 3H), 2.53–2.64 (m, 10H), 2.83 (t, J = 5.5 Hz, 2H), 3.24 (m, 2H), 6.34 (d, J = 5.4 Hz, 1H), 6.36 (bs, 1H), 7.32 (dd, J = 2.1, 8.9 Hz, 1H), 7.77 (d, J = 8.9 Hz, 1H), 7.92 (d, J = 2.1 Hz, 1H), 8.50 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.3, 11.9, 40.0, 47.3, 47.5, 50.6, 50.8, 99.1, 117.6, 121.8, 124.8, 134.6, 149.2, 150.0, 152.1; MS (ESI) m/z calcd for C19H29ClN4 348.2. Found (M + H)+: 349.1.

N-(7-Chloro-4-quinolyl)-N′-ethyl-N′-(4-diethylaminobutyl)-1,2-diaminoethane, 13

Employing 0.100 g (0.29 mmol) of 8 in the procedure described above gave 0.086 g (0.23 mmol, 80%) of 13 as a light yellow oil. 1H-NMR (400 MHz, CDCl3) δ = 0.99 (t, J = 7.1 Hz, 6H), 1.07 (t, J = 7.1 Hz, 3H), 1.46–1.48 (m, 4H), 2.39 (m, 2H), 2.43–2.48 (m, 4H), 2.52 (m, 2H), 2.59 (m, 2H), 2.81 (t, J = 5.6 Hz, 2H), 3.24 (m, 2H), 6.06 (bs, 1H), 6.35 (d, J = 5.3 Hz, 1H), 7.34 (dd, J = 2.0, 8.9 Hz, 1H), 7.64 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 2.0 Hz, 1H), 8.51 (d, J = 5.3 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.6, 11.9, 25.0, 25.4, 39.7, 46.8, 46.9, 51.1, 52.8, 52.9, 99.3, 117.4, 121.0, 125.2, 128.7, 134.7, 149.1, 149.8, 152.1; MS (ESI) m/z calcd for C21H33ClN4 376.2. Found (M + H)+ : 377.4.

N-(7-Chloro-4-quinolyl)-N′-ethyl-N′-(5-diethylaminopentyl)-1,2-diaminoethane, 14

Employing 0.100 g (0.28 mmol) of 9 in the procedure described above gave 0.075 g (0.19 mmol, 70%) of 14 as a light yellow oil. 1H-NMR (400 MHz, CDCl3) δ = 0.98 (t, J = 7.1 Hz, 6H), 1.07 (t, J = 7.1 Hz, 3H), 1.29 (m, 2H), 1.42–1.54 (m, 4H), 2.33 (m, 2H), 2.45–2.51 (m, 6H), 2.60 (q, J = 7.1 Hz, 4H), 2.81 (t, J = 5.6 Hz, 2H), 3.24 (m, 2H), 6.07 (bs, 1H), 6.36 (d, J = 5.2 Hz, 1H), 7.34 (dd, J = 2.1, 8.9 Hz, 1H), 7.63 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 2.1 Hz, 1H), 8.51 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.5, 12.0, 25.5, 27.0, 27.3, 39.7, 46.8, 46.9, 51.2, 52.8, 52.9, 99.3, 117.5, 121.1, 125.2, 128.8, 134.7, 149.2, 149.8, 152.2; MS (ESI) m/z calcd for C22H35ClN4 390.2. Found (M + H)+: 391.3.

N-(7-Chloro-4-quinolyl)-N′-ethyl-N′-(6-diethylaminohexyl)-1,2-diaminoethane, 15

Employing 0.100 g (0.27 mmol) of 10 in the procedure described above gave 0.085 g (0.21 mmol, 79%) of 15 as a light yellow oil. 1H-NMR (400 MHz, CDCl3) δ = 1.04 (t, J = 7.2 Hz, 6H), 1.07 (t, J = 7.1 Hz, 3H), 1.24–1.50 (m, 6H), 2.41 (m, 2H), 2.47–2.50 (m, 4H), 2.53–2.60 (m, 6H), 2.81 (t, J = 5.6 Hz, 2H), 3.24 (m, 2H), 6.12 (bs, 1H), 6.35 (d, J = 5.3 Hz, 1H), 7.34 (dd, J = 2.2, 8.9 Hz, 1H), 7.65 (d, J = 8.9 Hz, 1H), 7.93 (d, J = 2.2 Hz, 1H), 8.51 (d, J = 5.3 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.0, 12.0, 26.3, 27.2, 27.4, 27.5, 29.7, 39.7, 46.7, 46.8, 47.0, 51.2, 52.6, 52.7, 99.3, 117.5, 121.2, 125.2, 128.7, 134.7, 149.1, 152.2; MS (ESI) m/z calcd for C23H37ClN4 403.3. Found (M + H)+: 404.2.

N-(7-Chloro-4-quinolyl)-tris(2-aminoethyl)amine, 17

A mixture of 4,7-dichloroquinoline (1.0 g, 5.0 mmol) and tris(2-aminoethyl)amine (8.0 mL, 53.5 mmol) was heated to 90 °C for 30 hours under nitrogen atmosphere in a closed vessel with good stirring. The reaction was quenched with 20 mL of concentrated NaOH and extracted between CH2Cl2 and brine. The combined organic layers were dried over MgSO4 and concentrated in vacuo to give a yellow solid (1.47 g, 4.79 mmol, 95%). 1H-NMR (400 MHz, CDCl3) δ. (bs, 4H), 2.61 (t, J = 6.0 Hz, 4H), 2.80–2.83 (m, 4H), 2.85 (m, 2H), 3.28–3.32 (m, 2H), 6.33 (d, J = 5.4 Hz, 1H), 6.62 (bs, 1H), 7.28 (dd, J = 2.1, 8.9 Hz, 1H), 7.89 (dd, J = 2.1 Hz, 1H), 7.93 (d, J = 8.9 Hz, 1H), 8.48 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 39.8, 40.8, 52.0, 56.6, 99.1, 117.6, 122.0, 125.0, 128.5, 134.7, 149.2, 150.2, 152.0; MS (ESI) m/z calcd for C15H22ClN5 307.2. Found (M + H)+: 308.2.

N-(7-Chloro-4-quinolyl)-N',N”-tetraethyl-tris(2-aminoethyl)amine, 18

To a solution of 17 (0.462 g, 1.5 mmol) in 10 mL of glacial acetic acid, NaBH4 (4.26 g, 112.7 mmol) was added at 5 °C and the reaction was stirred at room temperature for 24 hours and then heated to 60 °C for 8 hours. The cooled reaction mixture was basified with saturated NaOH, extracted with CH2Cl2 and washed with brine. The combined organic layers were dried over anhydrous MgSO4 and concentrated in vacuo to give a yellow solid (0.315 g, 0.75 mmol, 50%). 1H-NMR (400 MHz, CDCl3) δ = 0.97 (t, J = 7.2 Hz, 12H), 2.50–2.56 (m, 12H), 2.64–2.68 (m, 4H), 2.86 (m, 2H), 3.25 (m, 2H), 6.33 (d, J = 5.4 Hz, 1H), 6.51 (bs, 1H), 7.31 (dd, J = 2.1, 8.9 Hz, 1H), 7.84 (d, J = 8.9 Hz, 1H), 7.91 (d, J = 2.1 Hz, 1H), 8.49 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.1, 40.2, 47.2, 50.7, 51.5, 52.1, 99.1, 117.6, 122.2, 124.6, 128.5, 134.6, 149.2, 150.1, 152.1; MS (ESI) m/z calcd for C23H38ClN5 419.2. Found (M + H)+ : 420.3.

1-(7-Chloro-4-O-quinolyl)-N-(3-diethylaminopropanoyl)-2-aminoethane, 19

A mixture of O-(7-chloro-4-quinolyl)-2-aminoethanol, (0.300 g, 1.35 mmol), 3-diethylaminopropionic acid (0.270 g, 1.49 mmol), EDC (0.311 g, 1.62 mmol) and Et3N(0.62 mL, 4.0 mmol) in 6 mL of anhydrous DMF and CHCl3 (1:1 v/v) was stirred at room temperature for 20 hours. The reaction was concentrated in vacuo. Flash chromatography using CH2Cl2:Et3N (1:0.2 v/v) as the mobile phase gave 0.045 g (0.13 mmol, 16% yield) of white crystals. 1H-NMR (400 MHz, CDCl3) δ = 0.97 (t, J = 7.1 Hz, 6H), 2.47–2.53 (m, 6H), 2.79 (t, J = 7.1 Hz, 2H), 3.57 (m, 2H), 4.49 (t, J = 5.1 Hz, 2H), 5.68 (bs, 1H), 6.39 (d, J = 5.3 Hz, 1H), 7.36 (dd, J = 2.1, 8.9 Hz, 1H), 7.69 (d, J = 8.9 Hz, 1H), 7.94 (d, J = 2.1 Hz, 1H), 8.53 (d, J = 5.3 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.7, 32.7, 43.1, 46.8, 48.2, 62.3, 98.9, 117.2, 125.5, 128.8, 135.0, 149.1, 149.5, 152.0, 173.8; MS (ESI) m/z calcd for C18H24ClN3O2 349.2. Found (M + H)+ : 350.1.

1-(7-Chloro-4-O-quinolyl)-N-(3-diethylaminopropyl)-2-aminoethane, 20

To a solution of 25 (0.200 g, 0.90 mmol) and Et3N (0.39 g, 2.7 mmol) in 4 mL of anhydrous THF at room temperature was added dropwise methanesulfonyl chloride (0.21 mL, 2.7 mmol). The reaction proceeded with good stirring for 15 minutes and was then quenched with saturated NaHCO3. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The residue was dissolved in anhydrous CH3CN (3.0 mL) under inert atmosphere and Et3N (0.62 g, 2.7 mmol) and N,N-diethyl diaminopropane (2.9 mL, 18.0 mmol) were added. The reaction mixture was stirred at 40 °C for 21 hours and saturated NaHCO3 solution was added. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The product was purified by flash column chromatography using CH2Cl2:Et3N (1:0.2 v/v) as the mobile phase to give a light yellow oil (0.265 g, 0.79 mmol, 88% yield) 1H-NMR (400 MHz, CDCl3) δ = 1.01 (t, J = 7.2 Hz, 6H), 1.76 (m, 2H), 2.37 (t, J = 6.0 Hz, 2H), 2.50 (q, J = 7.2 Hz, 4H), 3.30 (t, J = 5.1 Hz, 2H), 3.48 (t, J = 6.0 Hz, 2H), 3.95 (t, J = 5.1 Hz, 2H), 6.85 (d, J = 5.1 Hz, 1H), 7.36 (dd, J = 2.2, 9.0 Hz, 1H), 7.96 (d, J = 2.2 Hz, 1H), 8.33 (d, J = 9.0 Hz, 1H), 8.61 (d, J = 5.1 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 10.0, 22.7, 45.7, 49.5, 58.4, 60.0, 109.7, 123.0, 125.8, 125.9, 128.7, 134.8, 150.8, 151.1, 155.5; MS (ESI) m/z calcd for C18H26ClN3O 335.2. Found (M + H)+ 3 : 336.2.

1-(7-Chloro-4-O-quinolyl)-N′-ethyl-N′-(3-diethylaminopropyl)-2-aminoethane, 21

To a solution of 25 (0.200 g, 0.90 mmol) and Et3N (0.39 g, 2.7 mmol) in 4 mL of anhydrous THF at room temperature was added dropwise methanesulfonyl chloride (0.21 mL, 2.7 mmol). The reaction proceeded with good stirring for 15 minutes and was then quenched with saturated NaHCO3. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The residue was dissolved in anhydrous CH3CN (3.0 mL) under inert atmosphere and Et3N (0.62 g, 2.7 mmol) and N,N,N'-triethyl diaminopropane (0.340 g, 6.75 mmol) were added. The reaction mixture was stirred at 45 °C for 36 hours and saturated NaHCO3 solution was added. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The product was purified by flash column chromatography using EtOH:hexanes:Et3N (1:1.5:0.05 v/v) as the mobile phase to give a light yellow oil (0.035 g, 0.16 mmol, 18% yield) 1H-NMR (400 MHz, CDCl3) δ = 1.01 (t, J = 7.1 Hz, 6H), 1.10 (t, J = 7.1 Hz, 3H), 1.68 (m, 2H), 2.46 (t, J = 7.5 Hz, 2H), 2.52 (q, J = 7.1 Hz, 4H), 2.59 (t, J = 7.5 Hz, 2H), 2.68 (q, J = 7.1 Hz, 2H), 3.02 (t, J = 6.0 Hz, 2H), 4.25 (t, J = 6.0 Hz, 2H), 6.72 (d, J = 5.2 Hz, 1H), 7.42 (dd, J = 2.0, 8.9 Hz, 1H), 8.00 (d, J = 2.0 Hz, 1H), 8.12 (d, J = 8.9 Hz, 1H), 8.72 (d, J = 5.2 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.5, 12.0, 25.0, 46.8, 48.5, 50.9, 51.9, 52.6, 67.6, 101.0, 119.9, 123.5, 126.4, 127.9, 135.6, 149.7, 152.5, 161.5; MS (ESI) m/z calcd for C20H30ClN3O 363.2. Found (M + H)+: 364.0.

1-(7-Chloro-4-O-quinolyl)-N-(3-diethylaminopropanoyl)-3-aminopropane, 22

A mixture of O-(7-chloro-4-quinolyl)-3-aminopropanol (0.100 g, 0.45 mmol), 3-diethylaminopropionic acid (0.110 g, 0.6 mmol), EDC (0.110 g, 0.6 mmol) and Et3N (0.19 mL, 1.35 mmol) in 4 mL of anhydrous DMF and CHCl3 (1:1 v/v) was stirred at room temperature for 2 days. Saturated NaHCO3 solution was added to the cooled reaction mixture, which was then extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. Flash chromatography using EtOH:Et3N (1:0.05 v/v) as the mobile phase afforded 0.100 g (0.44 mmol, 55 %yield) of yellow crystals. 1H-NMR (400 MHz, CDCl3) δ = 0.99 (t, J = 7.5 Hz, 6H), 2.20 (m, 2H), 2.40 (t, J = 6.5 Hz, 2H), 2.56 (q, J = 7.1 Hz, 4H), 2.70 (t, J = 6.1 Hz, 2H), 3.58 (q, J = 6.5 Hz, 4H), 4.24 (t, J = 6.1 Hz, 2H), 6.74 (d, J = 5.4 Hz, 1H), 7.23 .40 (dd, J = 2.1, 9.0 Hz, 1H), 8.01 (bs, 1H), 8.20 (d, J = 9.0 Hz, 1H), 8.78 (d, J = 2.1 Hz, 1H), 8.90 (d, J = 5.4 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.7, 29.3, 32.7, 35.8, 46.3, 49.1, 66.4, 101.1, 120.03, 123.6, 126.8, 128.2, 136.0, 150.0, 152.7, 161.7, 173.5; MS (ESI) m/z calcd for C19H26ClN3O2 363.2. Found(M + H)+: 364.1.

1-(7-Chloro-4-O-quinolyl)-N-(3-diethylaminopropyl)-3-aminopropane, 23

To a solution of 26 (0.1 g, 0.4 mmol) and Et3N (0.25 g, 2.3 mmol) in 20 mL of anhydrous THF at room temperature was added dropwise methanesulfonyl chloride (0.11 g, 2.3 mmol). The reaction proceeded with good stirring for 10 minutes and was then quenched with saturated NaHCO3. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The residue was dissolved in anhydrous CH3CN (3.0 mL) under inert atmosphere and N,N-diisopropylethylamine (0.5 g, 4.1 mmol) and N,N-diethyl diaminopropane (1.2 g, 15.2 mmol) were added. The reaction mixture was stirred at 40 °C for 48 hours and saturated NaHCO3 solution was added. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The product was purified by flash column chromatography using CH2Cl2:EtOH:Et3N (5:1:0.005 v/v) as the mobile phase to give a light yellow oil (0.1g, 0.32 mmol, 55% yield). 1H-NMR (400 MHz, CDCl3) δ. (t, J = 6.6 Hz, 6H), 1.61–1.78 (m, 2H), 2.18 (m, 2H), 2.42–58 (m, 6H), 2.69 (t, J = 6.0 Hz, 2H), 2.90 (t, J = 6.0 Hz, 2H), 4.29 (t, J = 6.0 Hz, 2H), 6.72 (d, J = 5.1 Hz,1H), 7.40 (dd, J = 2.1, 9.0 Hz, 1H), 8.01 (bs, 1H), 8.13 (d, J = 9.0 Hz, 1H), 8.72 (d, J = 5.1 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ. 27.03, 29.3, 46.5, 46.8, 48.9, 51.3, 66.8, 100.9, 119.8, 123.4, 126.4, 127.9, 135.6, 149.7, 152.5, 161.5; MS (ESI) m/z calcd for C19H28ClN3O 349.2. Found (M + H)+: 350.2.

1-(7-Chloro-4-O-quinolyl)-N′-ethyl-N′-(3-diethylaminopropyl)-3-aminopropane, 24

To a solution of 26 (0.1 g, 0.4 mmol) and Et3N (0.25 g, 2.3 mmol) in 20 mL of anhydrous THF at room temperature was added dropwise methanesulfonyl chloride (0.11 g, 2.3 mmol). The reaction proceeded with good stirring for 10 minutes and was then quenched with saturated NaHCO3. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The residue was dissolved in anhydrous CH3CN (3.0 mL) under inert atmosphere and N,N-diisopropylethylamine (0.5 g, 4.1 mmol) and N,N,N'triiethyl diaminopropane (1.2 g, 14.3 mmol) were added. The reaction mixture was stirred at 40°C for 48 hours and was quenched with saturated NaHCO3. The mixture was extracted with CH2Cl2, dried over anhydrous MgSO4, and concentrated in vacuo. The product was purified by flash column chromatography using CH2Cl2:EtOH:Et3N (5:1:0.005 v/v) as the mobile phase to give a light yellow oil (0.03 g, 0.08 mmol, 40% yield). 1H-NMR (400 MHz, CDCl3) δ. (t, J = 6.6 Hz, 6H), 1.60 (m, 2H), 2.00–2.18 (m, 2H), 2.40–2.60 (m, 6H), 2.64 (t, J = 6.0 Hz, 2H), 4.23 (t, J = 6.0 Hz, 2H), 6.73 (d, J = 5.1 Hz,1H), 7.44 (dd, J = 2.1, 6.0 Hz, 1H), 8.01 (s, 1H), 8.13 (d, J = 6.0 Hz, 1H), 8.72 (d, J = 5.1 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ = 11.6, 12.4, 27.03, 28.5, 29.3, 46.5, 46.8, 48.9, 51.3, 66.8, 100.9, 119.8, 123.4, 126.4, 127.9, 135.6, 149.7, 152.5, 161.5; MS (ESI) m/z calcd for C21H32ClN3O 377.2. Found (M + H)+: 378.2.

Supplementary Material

01

Acknowledgment

We thank the National Institutes of Health (Grant RO1AI060792) for financial support. This work was in part supported by the National Science Foundation (REU CHE-0449829).

Footnotes

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