Synthesis and biological evaluation of phenolic Mannich bases of benzaldehyde and (thio)semicarbazone derivatives against the cysteine protease falcipain-2 and a chloroquine resistant strain of Plasmodium falciparum

Article abstract of DOI:10.1016/j.bmc.2006.09.055

A targeted series of phenolic Mannich bases of benzaldehyde and (thio)semicarbazone derivatives were synthesized and evaluated in vitro against the malarial cysteine protease falcipain-2 and a chloroquine resistant strain (W2) of Plasmodium falciparum. A

Full text of DOI:10.1016/j.bmc.2006.09.055

Bioorganic & Medicinal Chemistry 15 (2007) 273–282
Synthesis and biological evaluation of phenolic Mannich bases
of benzaldehyde and (thio)semicarbazone derivatives against the
cysteine protease falcipain-2 and a chloroquine resistant strain
of Plasmodium falciparum
Alex Chipeleme,a Jiri Gut,b Philip J. Rosenthalb and Kelly Chibalea,c,
*
aDepartment of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
bDepartment of Medicine, San Francisco General Hospital, University of California, San Francisco,
Box 0811, San Francisco, CA 94143, USA
cInstitute of Infectious Disease and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
Received 2 September 2006; revised 22 September 2006; accepted 26 September 2006
Available online 29 September 2006
Abstract—A targeted series of phenolic Mannich bases of benzaldehyde and (thio)semicarbazone derivatives were synthesized and
evaluated in vitro against the malarial cysteine protease falcipain-2 and a chloroquine resistant strain (W2) of Plasmodium falcipa-
rum. A novel series of 4-aminoquinoline semicarbazones were the most effective inhibitors of falcipain-2 (most potent inhibitor had
IC50 = 0.63 lM) while a bisquinoline semicarbazone compound 8f was the most potent antimalarial compound with an IC50 of
0.07 lM against W2. Compound 8f also weakly inhibited falcipain-2, with an IC50 of 3.16 lM, although its principal antiparasitic
activity did not appear to be due to inhibition of this enzyme.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
A number of compounds containing the phenolic Man-
nich base component have been synthesized and shown
to possess significant anticancer and antimalarial prop-
erties.4,5 The bioactivities have been attributed partially
to the a,b-unsaturated ketones liberated from the Man-
nich bases by deamination. These a,b-unsaturated
ketones have markedly greater affinity for thiols over
amino and hydroxy nucleophiles.6,7 This preferential
affinity may result in a lack of mutagenicity and carcin-
ogenicity, which are associated with certain alkylating
agents due to presumed interaction with nucleic acids.
On the other hand, compounds containing a thiosemi-
carbazone component have shown a broad spectrum
of chemotherapeutic properties, including antimalarial,8
antitumour,9 antibacterial,10 antitrypanosomal,11 and
antiviral12 activity. The compounds are also members
of a class of iron-chelators that are Schiff bases. Since
iron (Fe) is essential for the biological activity of a num-
ber of plasmodial proteins, including the rate-limiting
enzyme of DNA synthesis, ribonucleotide reductase,
withholding it inhibits the growth of the malaria para-
site.13,14 In vitro studies have shown that iron-chelating
agents inhibit parasite growth and proliferation.15
Recently, thiosemicarbazones have been synthesized
Malaria is one of the world’s most prevalent infectious
diseases and ranks among the major health and develop-
mental challenges facing large parts of the world, includ-
ing many of the poorest countries. Despite the fact that
effective antimalarial drugs exist, drug resistance, partic-
ularly to chloroquine, has become an enormous prob-
lem.1 This has necessitated the search for novel and
cost-effective drugs with high structural variation. A po-
tential strategy for the treatment of parasitic diseases is
to design compounds which selectively inhibit enzymes
that are pivotal for survival and are part of biochemical
pathways that are specific to the parasite.2 In this regard
the cysteine protease falcipain-2 is an attractive target
enzyme because of its key role in haemoglobin
hydrolysis.3
Keywords: Malaria; Antimalarial agents; Mannich bases; Thiosemic-
arbazones; Cysteine proteases; Falcipain-2.
*
Corresponding author. Fax: +27 21 689 7499; e-mail:
chibale@science.uct.ac.za
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.09.055

274
A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
and screened against the three parasitic cysteine proteas-
es cruzain, falcipain-2, and rhodesain and against their
respective parasite sources, Trypanosoma cruzi, Plasmo-
dium falciparium, and Trypanosoma brucei.16 The results
obtained suggested that thiosemicarbazones represent
validated leads that kill several species of protozoan par-
asites through the inhibition of cysteine proteases as well
as through action against other targets. Furthermore,
semicarbazones, which can also be regarded as urea
derivatives, have gained considerable importance17 in re-
cent years in the design of enzyme inhibitors,18 as
replacement for the amide (–CO–NH–) bond in pepti-
domimetics19 and as sources of self-complementary bi-
directional hydrogen bonding motif in supramolecular
chemistry.20 Since peptides have poor metabolic stability
and limited oral absorption, they are rarely useful drug
candidates. Unlike the peptide bond, the urea linkage
has remarkable resistance to proteolytic degradation
by enzymes in the gastrointestinal tract, which opens
perspectives for the oral delivery of these compounds.21
In addition, the hydrogen bond forming capacity of the
urea unit may assist in rendering the urea compounds
more water soluble.
associated with phenolic Mannich bases,4 the phenol
and/or bisphenol moiety was envisaged to markedly
improve antimalarial activity in combination with the
7-chloroquinoline moiety, which has been proposed
from earlier findings to bind to haematin in the para-
site’s acidic food vacuole, thus inhibiting haemazoin for-
mation. The details of synthesis and biological results
are presented herein.
2. Chemistry
The synthesis of phenolic Mannich bases of thiosemicar-
bazones and semicarbazones is operationally simple and
straightforward. Treatment of equimolar amounts of
2,4-dihydroxybenzaldehyde 1 with formaldehyde and
selected secondary amines in methanol at reflux afforded
phenolic Mannich bases 2a–f in high yields. Reaction of
the commercially available thiosemicarbazide with phe-
nolic Mannich bases in ethanol at reflux afforded 3a–f
(Scheme 1).
Compounds 8a–f were prepared in four steps as depicted
in Scheme 2. Treatment of 4,7-dichloroquinoline 4 with
ethylenediamine gave diamine 5, which was reacted with
phenylchloroformate to afford carbamate 6. Condensa-
tion of 6 with an excess of hydrazine monohydrate at
80–90 ꢁC gave hydrazide 7. Reaction of 2a–f with 7 in
methanol, catalyzed by p-toluenesulfonic acid, gave
compounds 8a–f in moderate to good yields. The new
compounds were fully characterized by spectroscopic
(1H NMR, IR) and their purity established by elemental
analyses.
In view of the prior discussion and our program on the
application of multicomponent reactions and hybridiza-
tion strategies to antimalarial drug discovery,22 we
decided to append the phenolic Mannich base group
to various (thio)semicarbazone entities (Fig. 1), and we
screened the resulting compounds against the malarial
cysteine protease falcipain-2, and against the chloro-
quine resistant P. falciparum W2 strain. As in our previ-
ous hybridization strategies,22c we reasoned that the
(thio)semicarbazone moiety could both be an electro-
philic warheard for the cysteine protease falcipain-2
and/or a metal binding template. On the other hand,
the basic protonatable hydrazinic and quinoline
nitrogens were envisaged to further increase accumula-
tion, and therefore antiplasmodial activity, of the mole-
cules. In view of the concept of sequential cytotoxicity
3. Biological results and discussion
It is apparent from the results in Table 1 that all the
aldehyde precursors except 2f were ineffective against
falcipain-2 and cultured parasites at the maximum con-
HO
R2R1N
N
Cl
X
N
HO
R2R1N
N
H
NH2
O
OH
N
NH
N
H
N
H
OH
X = O or S
(Thio)semicarbazone
Aminoquinoline semicarbazone
R2R1N = NEt2, pyrrolidino, piperidino, morpholino, methylpiperazino,4-(7-Cl-quinolinyl)-piperazino
Figure 1. Chemical structures of phenolic Mannich bases of aminoquinoline semicarbazone and (thio)semicarbazone derivatives.
HO
HO
R2R1N
HO
R2R1N
X
a
b
H
H
N
N
H
NH2
OH O
OH O
OH
1
2a-f
3a-g
X = O or S
Scheme 1. Reagents and conditions: (a) 1.0 equiv of R1R2NH, 1.0 equiv of CH2O, EtOH, 65 ꢁC, 1 h; (b) 1.0 equiv of thio/semicarbazide, MeOH,
reflux, 1 h.

A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
275
H
N
NH2
HN
O
Cl
N
HN
N
a
b
O
Cl
N
Cl
Cl
5
4
6
c
N
Cl
H
N
H
N
NH2
HN
HO
O
O
d
R2R1N
N
NH
N
H
N
H
Cl
N
OH
7
8a-f
Scheme 2. Reagents and conditions: (a) 5.0 equiv of NH2(CH2)2NH2, reflux, 6 h, 82%; (b) 1.0 equiv of chloroformate, 1.0 equiv of Et3N, DMF/
DCM (1:1), 0 ꢁC, 1 h; (c) 10 equiv of H2NNH2Æ.H2O, MeOH, reflux, 12 h; (d) 1.0 equiv of 45, 0.5 equiv of p-TsOH, MeOH, rt, 12 h.
Table 1. Effects of Mannich bases of aldehyde, (thio)semicarbazone and 4-aminoquinoline semicarbazone derivatives on the activity of falcipain-2
and development of Plasmodium falciparum W2 strain
HO
X = O
R2R1N
X
HN
X = NNHC(S)NH2
X = NNHC(O)NH2
X = NNHC(O)NHAQ
5
8
3
2
AQ =
OH
Cl
N
1
Compound
NR2R1
X
IC50 (lM)
Falcipain-2
W2
2a
2b
2c
2d
2e
2f
NEt2
O
O
O
O
O
O
>20
>20
>20
>20
>20
>20
11.07
5.85
3.80
>20
18.22
2.25
>20
>20
2.60
0.72
0.63
>20
>20
3.16
>10
>10
>10
>10
>10
1.07
>10
>10
>10
>10
>10
3.75
0.25
>10
0.44
1.07
0.27
0.11
0.38
0.077
0.24
Pyrrolidino
Piperidino
Morpholino
Methylpiperazino
4-(7-Cl-Quinolinyl)-piperazino
NEt2
Pyrrolidino
3a
3b
3c
3d
3e
3f
NNHC(S)NH2
NNHC(S)NH2
NNHC(S)NH2
NNHC(S)NH2
NNHC(S)NH2
NNHC(S)NH2
NNHC(O)NH2
NNHC(S)NH2
Piperidino
Morpholino
Methylpiperazino
4-(7-Cl-Quinolinyl)-piperazino
4-(7-Cl-Quinolinyl-)piperazino
NMBa
3g
3h
8a
8b
8c
8d
8e
8f
NEt2
Pyrrolidino
NNHC(O)NHAQ
NNHC(O)NHAQ
NNHC(O)NHAQ
NNHC(O)NHAQ
NNHC(O)NHAQ
NNHC(O)NHAQ
Piperidino
Morpholino
Methylpiperazino
4-(7-Cl-Quinolinyl)-piperazino
Chloroquine
a NMB, no Mannich base.
centration used. As expected for a 4-aminoquinoline,
compound 2f showed good activity (low-micromolar
IC50 value) against the W2 strain of P. falciparum but
exhibited poor inhibitory activity against falcipain-2.
Thiosemicarbazones 3b, 3c, and 3f were active against
falcipain-2 with IC50 values less than 10 lM. Since the
corresponding aldehyde precursors were ineffective
against falcipain-2, it is reasonable to suppose that the
thiosemicarbazone moiety plays a key role in the inhibi-
tion of falcipain-2.16 This statement is further supported
by the lack of activity displayed by semicarbazone 3g
which surprisingly showed superior antimalarial activity
against W2 compared to 3f, a thiosemicarbazone. How-
ever, of these thiosemicarbazones, only aminoquinoline

276
A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
3f showed antimalarial activity with an IC50 value less
than 10 lM. The antimalarial activity may be due to
the haem-binding aminoquinoline moiety. This is fur-
ther supported by 2f (aldehyde precursor) and 3g (semi-
carbazone), both aminoquinolines, which also showed
antimalarial activity despite exhibiting poor inhibitory
activity against falcipain-2.
inhibition of falcipain-2. In any case, it is evident from
the results that the aminoquinolinyl moiety plays a sig-
nificant role in determining the antimalarial activity of
the tested aminoquinoline semicarbazones, and this is
in agreement with results obtained with the phenolic
Mannich bases of benzaldehyde and (thio)semicarbaz-
one. The most potent compound against the W2 strain
is 8f, a bisquinoline, with an IC50 value of 0.077 lM.
Like chloroquine and other antimalarial bisquinolines,
compound 8f may exert its antimalarial properties by
inhibiting haemazoin formation.27–29 Although com-
pounds 8a, 8b and 8e were slightly less active compared
to chloroquine in the W2 strain, reliable comparative
studies may only be made upon screening against a wide
range of parasite strains of varying degrees of resistance
and/or sensitivity. This is because it is now well accepted
that drug resistance in malaria is often compound spe-
cific and strain-dependent. Compound 8c was almost
equipotent with chloroquine, whereas 8d and 8f were
more active, with 8f being 3 times more active than chlo-
roquine. In light of the results obtained, this series of
compounds particularly bisquinoline 8f, which is a novel
compound based on the semicarbazone scaffold, war-
rants further investigation
The only thiosemicarbazone from this limited series
which showed activity against both falcipain-2 and cul-
tured parasites with IC50 values of 2.25 and 3.75 lM,
respectively, is compound 3f.
Thiosemicarbazones 3b, 3c, and 3f and to a lesser extent
semicarbazone 3g, are potential metal chelators and may
be acting as iron chelators in P. falciparum. The antima-
larial action of chelators is dictated by three factors: ir-
on(III)-binding capacity, chelator ingress into
parasitized erythrocytes and chelator egress from para-
sites after treatment. Various iron chelators have been
shown to improve drug lipophilicity leading to increased
access of the drug to intracellular parasites and to faster
speed of action.23,24 For example, desferrioxamine 9
(Fig. 2) does penetrate the infected red blood cell, and
its antimalarial activity is dependent on this.25 It would
be predicted that an effective antimalarial iron chelator
would have the ability to cross lipid membranes well,
have a high affinity for iron, selectively bind iron as
compared with other trace metals and selectively bind ir-
on(III) rather than iron(II).26
In conclusion, we have synthesized, via simple and
straightforward routes, phenolic Mannich bases of ben-
zadehyde and, (thio)semicarbazone derivatives and
identified novel potential antimalarial agents. Future re-
search efforts should be directed towards aminoquino-
line semicarbazones since a vast improvement in the
activity of these antimalarial potential cysteine protease
inhibitors is possible by a rational modification of the
basic structure.
Since compound 3h was ineffective against both falci-
pain-2 and cultured parasites at the maximum tested
concentration, this suggests that the activity of com-
pounds 3a, 3b, 3c, and 3f is not due to the thiosemicar-
bazone side chain alone. Coupled with the data for
phenolic Mannich benzaldehyde derivatives, with an
exception of 2f, it may be concluded that the inhibitory
activity of phenolic Mannich bases of thiosemicabaz-
ones is due to the combined effects of both Mannich
base and thiosemicarbazone components.
4. Experimental data
4.1. General method A for the preparation of compounds
2a–f
Amine (10.86 mmol) was treated with paraformalde-
hyde (10.86 mmol) in methanol (7.5 ml) at 65 ꢁC for
1 h. To the reaction mixture, a solution of 2,4-dihydr-
oxybenzaldehyde (10.86 mmol) in methanol (5.0 ml)
was then added. After stirring for an additional 1 h,
the reaction mixture was cooled, concentrated and then
subjected to column chromatography on silica gel.
The results for aminoquinoline semicarbazones (Table
1) indicate that all compounds exhibited significant anti-
plasmodial activity. Compounds 8a, 8b, 8c, and 8f were
active against both falcipain-2 and cultured parasites.
There was generally no correlation between the ability
of these compounds to inhibit falcipain-2 and their anti-
plasmodial activity against W2 in vitro. As such, the
mechanism of action of these aminoquinoline semicar-
bazones is unclear. Most likely, their antimalarial effects
are due to a combination of mechanisms, which include
4.1.1. 3-Dimethylaminomethyl-2,4-dihydroxy-benzalde-
hyde 2a. The conditions employed for the preparation
of this compound were those described in General
Method E. Column chromatography (ethyl acetate)
afforded 2a as a dark brown solid (1.75 g, 72%); mp
74–76 ꢁC
(from
chloroform–hexane);
Rf = 0.40
O
O
(MeOH:DCM 1:9); IR mmax (Nujol)/cmꢀ1; 1050 (C–O),
1150 (C–N), 1640 (C@O), 3450 (OH); dH (400 MHz;
CDCl3) 1.16 (6H, t, J 7.2, H–N[CH2CH3]2), 2.71 (4H,
q, J 7.2, N[CH2CH3]2), 3.92 (2H, s, PhCH2N–), 6.40
(1H, d, J 8.4, H-5), 7.30 (1H, d, J 8.4, H-6), 9.58 (1H,
s, CHO); dc (100 MHz; CDCl3) 10.8 (2C), 46.6, 49.3
(2C), 106.7, 110.1, 113.2, 134.5, 161.5, 169.2, 190.7;
Anal. Found: C, 64.29; H, 7.79; N, 6.18% Calcd for
N
H
N
N
OH
OH
OH
O
N
NOH
N
OH
O
O
Figure 2. Chemical structure of desferrioxamine 9.

A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
277
C12H17NO3: C, 64.55; H, 7.67; N, 6.27%; HRMS (EI)
m/z Found: [M+H]+, 224.12861 Calcd for C12H18NO3:
M, 224.12866.
1060 (C–O), 1130 (C–N), 1665 (C@O), 3400 (OH); dH
(300 MHz; CDCl3) 1.67 (3H, m, HN[CH2CH2]2NCH3),
2.60 (8H, m, HN[CH2CH2]2NCH3), 3.82 (2H, s,
PhCH2N–), 6.40 (2H, d, J 8.7, H-5), 7.29 (1H, d, J
8.7, H-6), 9.60 (1H, s, CHO); dc (75 MHz; CDCl3)
45.8, 52.4 (2C), 53.1, 54.7 (2C), 106.7, 109.7, 113.8,
134.7, 161.7, 167.3, 194.1; Anal. Found: C, 61.41; H,
7.45; N, 10.82% Calcd for C13H18N2 O3: C, 62.38; H,
7.25; N, 11.19%; HRMS (EI) m/z Found: [M+H]+,
251.13958 Calcd for C13H19N2O3: M, 251.13956.
4.2. 2,4-Dihydroxy-3-pyrrolidin-1-ylmethyl-benzaldehyde
2b
The conditions employed for the preparation of this
compound were those described in General Method A.
Column chromatography (ethyl acetate) followed by
MeOH–DCM (1:9) afforded 2b as a brown oil (1.91 g,
79%); Rf = 0.28 (MeOH–DCM 1:9); IR mmax (Nujol)/
cmꢀ1; 1060 (C–O), 1210 (C–N), 1670 (C@O) 3450
(OH); dH (400 MHz; CDCl3) 1.91 (4H, m,
N[CH2CH2]2), 2.71 (4H, m, N[CH2CH2]2), 3.99 (2H, s,
PhCH2N), 6.40 (2H, d, J 8.4, H-5), 7.31 (1H, d, J 8.4,
H-6), 9.60 (1H, s, CHO); dc (100 MHz; CDCl3) 23.6
(2C), 50.9, 53.4 (2C), 107.4, 109.9, 113.4, 134.6, 161.2,
168.6, 193.8; HRMS (EI) m/z Found: [M+H]+,
222.11270 Calcd for C12H15NO3: M, 222.11301.
4.2.4. 3-[4-(7-Chloro-quinolin-4-yl)piperazin-1-ylmethyl]-
2,4-dihydroxy benzaldehyde 2f. The conditions employed
for the preparation of this compound were those de-
scribed in General Method A. Column chromatography
(ethyl acetate) afforded 2f as a cream white solid (4.06 g,
94%); mp 167–169 ꢁC (from chloroform–hexane);
Rf = 0.62 (MeOH–DCM 1:9); IR mmax (Nujol)/cmꢀ1
;
1040 (C–O), 1540 (C@N), 1600 (C@C), 1660 (C@O),
3350 (OH); dH (400 MHz; CDCl3) 2.94 (4H, br s,
N[CH2CH2]2NCH), 3.30 (4H, br s, N[CH2CH2]2NCH),
3.99 (2H, s, PhCH2N), 6.47 (1H, d, J 8.7, H-5), 6.85 (1H,
d, J 5.1, H-30), 7.36 (1H, d, J 8.7, H-6), 7.43 (1H, dd, J
2.1, 9.3, H-60), 7.91 (1H, d, J 9.3, H-50), 8.15 (1H, d, J
2.1, H-80), 8.74 (1H, d, J 5.1, H-20), 9.65 (1H, s,
CHO); dc (100 MHz; CDCl3) 51.8 (2C), 52.4 (2C),
53.0, 106.2, 109.2, 109.6, 114.0, 122.2, 124.7, 126.5,
129.0, 134.9, 150.5, 151.9, 156.2, 160.5, 166.6, 194.2;
Anal. Found: C, 63.30; H, 5.25; N, 10.31% Calcd for
C21H20ClN3O3: C, 63.40; H, 5.07; N, 10.56%; HRMS
(EI) m/z Found: [M+H]+, 398.12734 Calcd for
C21H21ClN3O3: M, 398.12714.
4.2.1.
2,4-Dihydroxy-3-piperidin-1-ylmethyl-benzalde-
hyde 2c. The conditions employed for the preparation
of this compound were those described in General Meth-
od A. Column chromatography (ethyl acetate) afforded
2c as a light brown solid (2.26 g, 88%); mp 107–109 ꢁC
(from chloroform–hexane); Rf = 0.40 (MeOH–DCM
1:9); IR mmax (Nujol)/cmꢀ1; 1050 (C–O), 1220 (C–N),
1660 (C@O), 3400 (OH); dH (400 MHz; CDCl3) 1.67
(10H, m, HN[CH2CH2]2CH2), 3.82 (2H, s, PhCH2N),
6.40 (2H, d, J 8.4, H-5), 7.29 (1H, d, J 8.4, H-6), 9.59
(1H, s, CHO); dc (100 MHz; CDCl3) 23.6, 25.5 (2C),
53.7, 60.0 (2C), 106.5, 109.9, 113.4, 134.6, 161.6, 168.5,
193.8; Anal. Found: C, 66.09; H, 7.36; N, 5.82% Calcd
for C13H17NO3: C, 66.36; H, 7.28; N, 5.96%; HRMS
(EI) m/z Found: [M+H]+, 236.12860 Calcd For
C13H18NO3: M, 236.12866.
4.3. General Method B for the preparation of compounds
3a–h
A mixture of aldehyde (1.65 mmol) and thiosemicarba-
zide/semicarbazide (1.65 mmol) was dissolved in dry
methanol (10 ml) under nitrogen. The resultant heated
at reflux for 3 h until the reaction was completed (mon-
itored by TLC). The solvent was removed under reduced
pressure, and resulting solid was recrystallised from
methanol to provide title compounds 3a–h.
4.2.2. 2,4-Dihydroxy-3-morpholin-1-ylmethyl-benzalde-
hyde 2d. The conditions employed for the preparation
of this compound were those described in General
Method A. Column chromatography (MeOH–DCM
1:9) afforded 2d as a cream white solid (2.48 g, 96%);
mp 150–152 ꢁC (from chloroform–hexane); Rf = 0.62
(MeOH–DCM 1:9); IR mmax (Nujol)/cmꢀ1; 1050 (C–
O), 1250 (C–N), 1660 (C@O) 3440 (OH); dH
(300 MHz; CDCl3) 2.63 (4H, m, N[CH2CH2]2O), 3.71
(4H, m, N[CH2CH2]2O), 3.84 (2H, s, PhCH2N–), 6.43
(1H, d, J 8.4, H-5), 7.32 (1H, d, J 8.4, H-6), 9.62 (1H,
s, CHO); dc (75 MHz; CDCl3) 52.8 (2C), 53.5, 66.6
(2C), 106.5, 109.6, 114.0, 134.8, 161.8, 166.8, 194.2;
Anal. Found: C, 64.29; H, 7.79; N, 6.18% Calcd for
C12H15NO4: C, 64.55; H, 7.67; N, 6.27%; HRMS (EI)
m/z Found: [M+H]+, 238.10793 Calcd for C12H16NO4:
M, 238.10799.
4.4. Compound 3h
The conditions employed for the preparation of this
compound were those described in General Method B,
which gave 3h as a cream white solid (2.90 g, 89%);
mp 237–239 ꢁC (from methanol); Rf = 0.50 (17%
NH4OH–MeOH–DCM 1:2:2); IR mmax (Nujol)/cmꢀ1
;
1150 (C@S), 1260 (C–N), 1540 (C@S), 1580 (C@C),
3150 (N–H), 3325 (N–H) 3450 (O–H/N–H); dH
(300 MHz; DMSO-d6) d 6.26 (1H, dd, J 2.4, 8.4, H-5),
6.30 (1H, d, J 2.4, H-3), 7.65 (1H, d, J 8.4, H-6), 7.72
(1H, br s, NHCSNH2), 7.92 (1H, s, NHCSNH2), 8.24
(1H, s, PhCH@NNH), 9.72 (2H, s, OH), 11.14 (1H, s,
PhCH@NNH); dc (75 MHz; DMSO-d6) 102.3, 107.7,
111.7, 128.4, 140.0, 158.0, 160.4, 177.1; Anal. Found:
C, 45.51; H, 4.34; N, 19.97; S, 15.59% Calcd for C8H9
N3O2S: C, 45.49; H, 4.29; N, 19.89; S, 15.18%; HRMS
(EI) m/z Found: [M+H]+, 212.04980 Calcd for
C8H10N3O2S: M, 212.14937.
4.2.3. 2,4-Dihydroxy-3-(4-methyl-piperazin-1-ylmethyl)-
benzaldehyde 2e. The conditions employed for the prep-
aration of this compound were those described in
General Method A. Column chromatography (ethyl
acetate) afforded 2e as a pale brown solid (2.35 g,
86%); mp 106–108 ꢁC (from chloroform–hexane);
Rf = 0.42 (MeOH–DCM 1:9); IR mmax (Nujol)/cmꢀ1
;

278
A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
4.5. Compound 3a
4.8. Compound 3d
The conditions employed for the preparation of this
compound were those described in General Method B,
which gave 3a as a yellow solid (0.46 g, 87%) (recrystal-
lised from methanol); decomposes above 180 ꢁC;
Rf = 0.60 (17% NH4OH–MeOH–DCM 1:2:2); IR mmax
(Nujol)/cmꢀ1 1050 (C–O), 1140 (C@S), 1580 (C@C),
3130 (N–H), 3245 (N–H) 3400 (O–H/N–H); dH
(300 MHz; CDCl3) 1.05 (6H, t, J 7.2, N[CH2CH3]2),
2.58 (4H, t, J 7.2, N[CH2CH3]2), 3.80 (2H, s, PhCH2N),
6.29 (1H, d, J 8.4, H-5), 7.55 (1H, d, J 8.4, H-6), 7.70
(1H, br s, NHCSNH2), 7.91 (1H, br s, NHCSNH2),
8.25 (1H, br s, PhCH@NNH), 12.34 (1H, s,
PhCH@NNH); dc (75 MHz; CDCl3) 10.8 (2C), 45.8
(2C), 49.2, 107.5, 111.7, 113.1, 126.1, 141.0, 158.9,
160.4, 177.0; LRMS (EI) m/z, M+ 332; Anal. Found:
C, 51.45; H, 6.76; N, 18.88; S, 11.24% Calcd for
C13H20N4SO2: C, 52.68; H, 6.80; N, 18.90; S, 10.82%;
HRMS (EI) m/z Found: [M+H]+, 297.13858 Calcd for
C13H21N4SO2: M, 297.13852.
The conditions employed for the preparation of this
compound were those described in General Method B,
gave 3d as a yellow solid (0.43 g, 84%) (recrystallised
from methanol); decomposes above 200 ꢁC; Rf = 0.48
(17% NH4OH–MeOH–DCM 1:2:2); IR mmax (Nujol)/
cmꢀ1 1060 (C–O), 1150 (C@S), 1590 (C@O), 3150 (N–
H), 3260 (N–H), 3400 (O–H/N–H); dH (400 MHz;
DMSO-d6) 2.48 (4H, br s, N[CH2CH3]2O), 3.60 (4H,
br s, N[CH2CH2]2O), 3.80 (2H, s, PhCH2N), 6.20 (1H,
d, J 8.4, H-5), 7.55 (1H, d, J 8.4, H-6), 7.69 (1H, br s,
NHCSNH), 7.89 (1H, br s, NHCSNH), 8.24 (1H, s,
PhCH = NNH), 11.16 (1H, s, PhCH@NNH); dc
(100 MHz; DMSO-d6) 53.1, 54.0 (2C), 66.7 (2C),
107.8, 108.1, 112.5, 127.6, 141.9, 158.7, 159.3, 177.;
Anal. Found: C, 50.88; H, 6.06; N, 17.96; S, 9.53%
Calcd for C13H18N4SO3: C, 50.31; H, 5.85; N, 18.05;
S, 10.33%; HRMS (EI) m/z Found: [M+H]+,
311.11802 Calcd for C13H19N4SO3: M, 311.11778.
4.9. Compound 3e
4.6. Compound 3b
The conditions employed for the preparation of this
compound were those described in General Method B,
which gave 3e as a yellow solid (0.52 g, 95%) (recrystal-
lised from methanol); decomposes above 200 ꢁC;
Rf = 0.52 (17% NH4OH–MeOH–DCM 1:2:2); IR mmax
(Nujol)/cmꢀ1; 1060 (C–O), 1140 (C@S), 1590 (C@C),
3150 (N–H), 3300 (N–H), 3400 (O–H/N–H); dH
(300 MHz; DMSO-d6) 2.19 (3H, s, N(CH2CH2)2NCH3),
2.38 (4H, br s, N[CH2CH2]2NCH3), 2.49 (4H, br s,
N[CH2CH2]2NCH3), 3.74 (2H, s, PhCH2N), 6.32 (1H,
d, J 8.4, H-5), 7.58 (1H, d, J 8.4, H-6), 7.71 (1H, br s,
NHCSNH), 7.91 (1H, br s, NHCSNH), 8.26 (1H, s,
PhCH@NNH), 11.17 (1H, s, PhCH@NNH); dc
(75 MHz; DMSO-d6) 45.4 (2C), 51.8, (2C), 53.1, 54.4,
107.1, 107.2, 111.7, 126.6, 140.9, 158.2, 158.4, 177.1;
Anal. Found: C, 50.86; H, 6.44; N, 17.99; S, 9.55%
Calcd for C14H21N5O2S: C, 51.99; H, 6.54; N, 21.65;
S, 9.91%; HRMS (EI) m/z Found: [M+H]+, 324.14950
Calcd for C14H22N5O2S: M, 324.14941.
The conditions employed for the preparation of this
compound were those described in General Method
B, which gave 3b as a yellow solid (0.39 g, 76%)
(recrystallised from methanol); decomposes above
180 ꢁC; Rf = 0.56 (17% NH4OH–MeOH–DCM 1:2:2);
IR mmax (Nujol)/cmꢀ1 1060 (C–O), 1150 (C@S), 1580
(C@C), 3400 (OH/N–H); dH (300 MHz; CDCl3) 1.77
(4H, m, N[CH2CH2]2), 2.58 (4H, m, N[CH2CH2]2),
3.84 (2H, s, PhCH2N), 6.29 (1H, d, J 8.4, H-5), 7.53
(1H, d, J 8.4, H-6), 7.69 (1H, br s, NHCSNH2), 7.89
(1H, br s, NHCSNH2), 8.24 (1H, br s, PhCHNNH),
11.54 (1H, s, PhCH@NNH); dc (75 MHz; CDCl3)
23.9 (2C), 51.6 (2C), 53.5, 107.8, 110.7, 112.3, 127.1,
159.3, 161.3, 177.7; Anal. Found: C, 53.02; H, 6.22;
N, 19.05; S, 10.82% Calcd for C13H18N4SO2: C,
53.04; H, 6.16; N, 19.03; S, 10.89%; HRMS (EI) m/z
Found: [M+H]+, 295.12291 Calcd for C13H19N4SO2:
M, 295.12287.
4.7. Compound 3c
4.10. Compound 3f
The conditions employed for the preparation of this
compound were those described in General Method
B, which gave 3c as a yellow solid (0.40 g, 78%)
(recrystallised from methanol); decomposes above
126 ꢁC; Rf = 0.48 (17% NH4OH–MeOH–DCM 1:2:2);
IR mmax (Nujol)/cmꢀ1; 1030 (C–O), 1130 (C–N), 1590
(C@C), 3150 (N–H), 3250 (N–H), 3400 (OH/N–H);
The conditions employed for the preparation of this
compound were those described in General Method B,
which gave 3f as a yellow solid (075 g, 96%) (recrystal-
lised from methanol); decomposes above 240 ꢁC;
Rf = 0.56 (17% NH4OH–MeOH–DCM 1:2:2); IR mmax
(Nujol)/cmꢀ1 (C–O), 1150 (C@S), 1560 (C@N), 1600
(C@C), 3140, 3275 (N–H), 3450 (O–H/N–H);
dH
(400 MHz;
DMSO-d6)
1.43
(2H,
m,
dH(400 MHz;
DMSO-d6)
2.81
(4H,
br
s,
N[CH2CH2]2CH2), 1.52 (4H, m, N[CH2CH2]2CH2),
2.48 (4H, m, N[CH2CH2]2CH2), 3.69 (2H, s,
PhCH2N), 6.28 (1H, d, J 8.8, H-5), 7.53 (1H, d, J
8.8, H-6), 7.70 (1H, br s, NHCSNH2), 7.90 (1H, br
s, NHCSNH2), 8.23 (1H, br s, PhCH@NNH), 11.52
(1H, s, PhCH@NNH); dc (100 MHz; DMSO-d6) 23.6
(2C), 25.5, 53.3, 54.2 (2C), 107.1, 111.1, 113.0, 125.3,
140.5, 158.7, 159.0, 177.2; HRMS (EI) m/z Found:
[M]+, 308.13071 Calcd For C14H20N4SO2: M,
308.13070.
N[CH2CH2]2NCH), 3.24 (4H, br s, N[CH2CH2]2NCH),
3.86 (2H, s, PhCH2N), 6.36 (1H, d, J 8.4, H-5), 7.03 (1H,
d, J 4.8, H-30), 7.54 (1H, dd, J 2.0, 9.2, H-60), 7.58 (1H,
d, J 8.4, H-6), 7.73 (1H, s, NHCSNH2), 7.93 (1H, s,
NHCSNH2), 7.97 (1H, d, J 2.0, H-80), 8.02 (1H, d, J
9.2, H-50), 8.27 (1H, s, PhCH@NNH), 8.70 (1H, d, J
4.8, H-20), 11.20 (1H, s, PhCH@NNH); dc (100 MHz;
DMSO-d6) 52.3 (2C), 52.6 (2C), 53.5, 108.2, 109.0,
110.4, 112.5, 122.1, 126.6, 126.7, 127.7, 128.8, 134.3,
141.9, 150.3, 152.9, 156.7, 158.7, 159.3, 177.8; Anal.

A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
279
Found: C, 55.96; H, 5.10; N, 17.71; S, 6.26% Calcd for
C22H23ClN6O2S: C, 56.10; H, 4.92; N, 17.84; S, 6.81%;
HRMS (EI) m/z Found: [M]+, 470.12910 Calcd for
C22H23ClN6SO2Cl: M, 470.129174.
134.4, 145.6, 148.8, 151.2, 152.0, 156.9, 157.5, 162.1.
Anal. Found: C, 57.90; H, 6.14; N, 15.09% Calcd for
C24H29ClN6O3: C, 57.30; H, 6.17; N, 16.72%; HRMS
(EI) m/z Found: [M]+, 484.19892 Calcd for
C24H29ClN6O3: M, 484.19897.
4.11. Compound 3g
4.14. Compound 8b
The conditions employed for the preparation of this
compound were those described in General Method B,
which gave 3g as a yellow solid (0.69 g, 92%) (recrystal-
lised from methanol); decomposes above 240 ꢁC;
Rf = 0.08 (17% NH4OH–MeOH–DCM 1:2:2); IR mmax
(Nujol)/cmꢀ1 1060 (C–O), 1560 (C@N), 1600 (C@C),
1650 (C@O), 3150 (N–H), 3300 (N–H), 3450 (O–H/N–
H); dH (400 MHz; DMSO-d6) 2.80 (4H, br s,
N[CH2CH2]2NCH), 3.22 (4H, br s, N[CH2CH2]2NCH),
3.85 (2H, s, PhCH2N), 6.24 (2H, s, CONH2), 6.35 (1H,
d, J 8.8, H-5), 7.02 (1H, d, J 4.8, H-30), 7.40 (1H, d, J
8.8, H-6), 7.53 (1H, dd, J 2.0, 9.2, H-60), 7.97 (1H, d,
J 2.0, H-80), 8.02 (1H, d, J 9.2, H-50), 8.03 (1H, s,
PhCH@NNH), 8.69 (1H, d, J 4.8, H-20), 9.97 (1H, s,
PhCH@NNH); dc (100 MHz; DMSO-d6) 52.3 (2C),
52.7 (2C), 53.3, 108.0, 108.3, 110.3, 112.6, 122.1, 126.5,
126.7, 127.9, 128.8, 134.3, 140.0, 150.3, 152.9, 156.7,
157.1, 157.8, 158.9; Anal. Found: C, 58.05; H, 4.68; N,
18.55% Calcd for C22H23ClN6 O3: C, 58.09; H, 5.10;
N, 18.47%. HRMS (EI) m/z Found: [M+H]+,
455.15970 Calcd for C22H24ClN6O3: M, 455.15984.
The conditions employed for the preparation of this
compound were those described in General Method C.
Column chromatography (MeOH–DCM 1:9 followed
by 17% NH4OH–MeOH–DCM 1:2:2) afforded 8b as a
brown solid (0.14 g, 52%) (recrystallised from metha-
nol); decomposes above 100 ꢁC; Rf = 0.30 (17%
NH4OH–MeOH–DCM 1:2:2); IR mmax (Nujol)/cmꢀ1
1060 (C–O), 1580 (C@N), 1650 (C@O), 3400 (N–H);
dH (300 MHz; CDCl3) 1.87 (4H, m, N[CH2CH2]2),
2.69 (4H, m, N[CH2CH2]2), 3.42 (2H, t, J 5.4, CON-
HCH2CH2N), 3.79 (2H, t, J 5.4, CONHCH2CH2N),
3.95 (2H, s, PhCH2N), 6.01 (1H, br s, NHNCONH),
6.30 (1H, d, J 5.4, H-30), 6.38 (1H, d, J 8.4, H-5), 6.83
(1H, br s, NHNCONH), 6.95 (1H, d, J 8.4, H-6), 7.28
(1H, dd, J 2.1, 9.0, H-60), 7.77 (1H, d, J 9.0, H-50),
7.85 (1H, s, PhCH@NNH), 7.88 (1H, d, J 2.1, H-80),
8.42 (1H, d, J 5.4, H-20); dc (75 MHz; CDCl3) 23.3
(2C), 48.5, 50.0 (2C), 52.0, 54.0, 98.3, 106.9, 107.8,
108.0, 114.8, 121.8, 125.2, 128.0, 130.9, 135.8, 145.8,
148.6, 150.2, 151.8, 156.7, 157.4, 163.; Anal. Found: C,
54.56; H, 5.85; N, 14.75% Calcd for C24H27ClN6O3: C,
54.54; H, 5.87; N, 15.90%; HRMS (EI) m/z Found:
[M+H]+, 483.18312 Calcd for C24H28ClN6O3: M,
483.18331.
4.12. General Method C for the preparation of compounds
8a–f
To a solution of semicarbazide (0.54 mmol) in methanol
(10 ml) was added a mixture of p-toluenesulfonic acid
and aldehyde. The resultant was stirred at room temper-
ature for 16 h. The reaction mixture was diluted with
chloroform (20 ml). The organic layer was separated,
washed with 5% aqueous sodium carbonate (3· 10 ml),
brine (2· 10 ml), dried (MgSO4) and concentrated under
reduced pressure to afford a solid residue, which was
column chromatographed on silica gel.
4.15. Compound 8c
The conditions employed for the preparation of this
compound were those described in General Method C.
Column chromatography (MeOH–DCM 1:9 followed
by 17% NH4OH–MeOH–DCM 1:2:2) afforded 8c as a
greenish yellow solid (0.14 g, 54%) (recrystallised from
methanol); decomposes above 200 ꢁC; Rf = 0.30 (17%
NH4OH–MeOH–CM 1:2:2); IR mmax(Nujol)/cmꢀ1 1050
(C–O), 1580 (C@N), 1650 (C@O), 3370 (N–H); dH
(400 MHz; CD3OD) 1.42 (2H, m, N[CH2CH2]2CH2),
1.58 (4H, m, N[CH2CH2]2CH2), 2.42 (2H, m,
4.13. Compound 8a
The conditions employed for the preparation of this
compound were those described in General Method C.
Column chromatography (MeOH–DCM 1:9 followed
by 17% NH4OH–MeOH–DCM 1:2:2) afforded 8a pale
green solid (0.16 g, 61%) (recrystallised from methanol);
decomposes above 150 ꢁC; Rf = 0.30 (17% NH4OH–
MeOH–DCM 1:2:2); IR mmax (Nujol)/cmꢀ1 1060 (C–
O), 1570 (C@N), 1650 (C@O), 3380 (N–H); dH
(300 MHz; DMSO-d6) 1.06 (6H, t, J 7.2, N[CH2CH3]2),
2.64 (4H, t, J 7.2, N[CH2CH3]2), 3.40 (2H, t, J 5.4,
N[CH2CH2]2CH2), 3.30 (2H, t,
J
5.2, CON-
HCH2CH2N), 3.68 (2H, t, J 5.2, CONHCH2CH2N),
3.98 (2H, s, PhCH2N), 6.13 (1H, d, J 5.2, H-30), 6.16
(1H, br s, NHNCONH), 6.23 (1H, d, J 8.4, H-5), 6.84
(1H, d, J 8.4, H-6), 6.85 (1H, br s, NHNCONH), 7.05
(1H, dd, J 2.0, 8.8, H-60), 7.60 (2H, d, J 8.8, H-50),
7.68 (1H, d, J 2.0, H-80), 7.80 (1H, s, PhCH@NNH),
8.25 (1H, d, J 5.2, H-20); dc (100 MHz; CDCl3) 23.8,
25.5 (2C), 26.3 (2C), 53.4, 54.3, 54.5, 99.6, 107.1,
108.8, 111.8, 116.2, 124.5, 126.8, 129.9, 132.2, 136.7,
146.5, 148.5, 151.5, 153.3, 158.7, 159.2, 162.2; HRMS
(EI) m/z Found: [M+H]+, 497.20614 Calcd for
C25H29ClN6O3: M, 497.20679.
CONHCH2CH2N), 3.45 (2H, t,
J
5.4, CON-
HCH2CH2N), 3.84 (2H, s, PhCH2N), 6.32 (1H, d, J
8.7, H-5), 6.60 (1H, d, J 5.4, H-30), 7.09 (1H, br s, NHN-
CONH), 7.37 (1H, d, J 8.7, H-6), 7.43 (1H, dd, J 2.1,
8.7, H-60), 7.66 (1H, br s, NHNCONH), 7.79 (1H, d, J
8.7, H-50), 8.04 (1H, s, PhCH@NNH), 8.24 (1H, d, J
2.1, H-80), 8.40 (1H, d, J 5.7, H-20); dc (100 MHz;
DMSO-d6) 11.3 (2C), 46.8, 49.4 (2C), 52.4, 54.6, 98.3,
106.9, 107.7, 108.0, 116.8, 121.8, 125.0, 127.6, 130.7,
4.16. Compound 8d
The conditions employed for the preparation of this
compound were those described in General Method C.

280
A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
Column chromatography (MeOH–DCM 1:9 followed
by 17% NH4OH–MeOH–DCM 1:2:2) afforded 8d a
cream white solid (0.18 g, 69%) (recrystallised from
methanol); decomposes above 220 ꢁC; Rf = 0.33 (17%
NH4OH–MeOH–DCM 1:2:2); IR mmax (Nujol)/cmꢀ1
1050 (C–O), 1570 (C@N) 1660 (C@O), 3350 (N–H);
dH (300 MHz; CDCl3) 2.62 (4H, br s, N[CH2CH2]2O),
3.50 (2H, t, J 5.1, CONHCH2CH2N), 3.58 (2H, t, J
5.1, CONHCH2CH2N), 3.65 (4H, br s, N[CH2CH2]2O),
3.81 (2H, s, PhCH2N), 6.11 (1H, br s, NHNCONH),
6.38 (1H, d, J 8.7, H-5), 6.89 (1H, d, J 6.9, H-30), 6.84
(1H, br s, NHNCONH), 7.11 (1H, d, J 9.0, H-50), 7.39
(1H, d, J 8.7, H-6), 7.68 (1H, dd, J 2.4, 9.0, H-60),
7.88 (1H, d, J 2.4, H-80), 8.05 (1H, s, PhCH@NNH),
8.51 (1H, d, J 6.9, H-20); dc (75 MHz; CDCl3) 38.4,
44.5, 53.1 (2C), 53.3, 66.3 (2C), 99.4, 107.4, 107.9,
112.5, 116.5, 121.8, 126.1, 128.7, 129.9, 137.7, 141.7,
145.8, 155.2, 156.8, 157.9, 159.0, 162.0; Anal. Found:
C, 54.82; H, 5.18; N, 12.57% Calcd for C24H27ClN6O4:
C, 54.75; H, 5.70; N, 15.97%; HRMS (EI) m/z Found:
[M+]+, 498.17798 Calcd for C24H27ClN6O4: M,
498.17823.
NHNCONH), 7.79(1H, d, J 2.1, H-80), 7.98 (1H, d,
J 2.1, H-8?), 8.02 (1H, d, J 9.0, H-50), 8.07 (1H, s,
PhCH@NNH), 8.21 (1H, d, J 9.0, H-500), 8.41 (1H, d,
J 5.1, H-20), 8.71 (1H, d, J 5.1, H-200); dc (75 MHz;
DMSO-d6) 37.7, 40.3, 51.5 (2C), 51.9, 52.2 (2C), 98.6,
107.2, 107.5, 109.5, 111.9, 117.2, 121.3, 123.8, 124.1,
125.7, 125.9, 127.1, 128.0, 133.4, 133.5, 139.8, 148.5,
149.6, 150.3, 151.4, 152.1, 155.9, 156.1, 156.2, 157.1,
158.1; Anal. Found C 54.76, H 4.71, N 14.70% Calc.
For C33H32Cl2N8O3: C 54.79, H 5.39, N 15.49%; HRMS
(EI) m/z Found: M+, 658.19784 Calc. For
C33H32Cl2N8O3: M, 658.19744.
4.19. N0-(7-Chloro-quinolin-4-yl)-ethane-1,2-diamine 5
A mixture of 1,3-diaminoethane (5.00 g, 25.0 mmol),
4,7-dichloroquinoline (2.25 g, 5.0 mmol), K2CO3
(0.52 g, 3.78 mmol), triethylamine (0.50 ml, 3.78 mmol)
and 1-methyl pyrrolidinone (9.0 ml) under nitrogen
was heated at 135 0 ꢁ C for 4 h. The reaction mixture
was cooled to room temperature and then aqueous sodi-
um hydroxide (1 M, 50 ml) was added. The resultant
mixture was extracted with hot ethyl acetate (3·
100 mm). The combined extracts were washed with
brine, dried (MgSO4) and concentrated to give a cream
white solid (2.06 g, 82%) which recrystallised from meth-
anol to give 5 as a white crystalline powder, mp 137–
139 ꢁC (from methanol) (Lit. mp 137–139 ꢁC);267
Rf = 0.35 (MeOH–DCM 1:4); dH (300 MHz; CDCl3)
3.46 (2H, t, J 5.6, NCH2CH2NH2), 3.71 (2H, t, J 5.6,
NCH2CH2NH2), 6.40 (1H, d, J 5.2, H-3), 7.36 (1H,
dd, J 2.4, 8.8, H-6), 7.77 (1H, d, J 2.4, H-8), 7.97 (1H,
d, J 8.8, H-5), 8.34 (1H, d, J 5.2, H-2).
4.17. Compound 8e
The conditions employed for the preparation of this
compound were those described in General Method C.
Column chromatography (MeOH–DCM 1:9 followed
by 17% NH4OH–MeOH–DCM 1:2:2) afforded 8e as a
cream white solid (0.22 g, 80%) (recrystallised from
methanol); decomposes above 140 ꢁC; Rf = 0.33 (17%
NH4OH–MeOH–DCM 1:2:2); IR mmax (Nujol)/cmꢀ1
1060 (C–O), 1130 (C–N), 1580 (C@N), 1650 (C@O)
3400 (N–H); dH (400 MHz; CDCl3) 2.30 (3H, s,
NCH3), 2.60 (8H, br s, N[CH2CH2]2N), 3.39 (2H, m,
CONHCH2CH2N), 3.80 (2H, m, CONHCH2CH2N),
3.83 (2H, s, PhCH2N), 6.11 (1H, br s, NHNCONH),
6.24 (1H, d, J 4.8, H-30), 6.37 (1H, d, J 8.4, H-5), 6.84
(1H, br s, NHNCONH), 6.96 (1H, d, J 8.4, H-6), 7.17
(1H, d, J 2.0, 8.8, H-60), 7.68 (1H, d, J 8.8, H-50), 7.79
(1H, s, PhCH@NNH), 7.86 (1H, d, J 2.0, H-80), 8.42
(1H, d, J 4.8, H-20); dc (100 MHz; CDCl3) 39.2, 45.8,
(2C), 46.0 (2C), 52.6, 53.6, 54.8, 98.2, 107.1, 109.0,
109.4, 117.2, 121.8, 125.2, 128.0, 131.1, 134.8, 147.2,
148.6.
4.20. 1-[2-(7-Chloro-quinolin-4-ylamino)-ethyl]-carbamic
acid phenyl ester 6
Phenyl chloroformate (1.41 g, 9.02 mmol) was added to a
stirred and cooled (0 ꢁC) solution of N0-(7-chloro-quino-
lin-4-yl)-ethane-1,2-diamine (2.00 g, 9.02 mmol) and tri-
ethylamine (1.26 ml, 9.02 mmol) in DMF (10 ml). The
mixture was stirred at room temperature for 45 min, dilut-
ed with water (50 ml) and extracted with chloroform (3·
50 ml). The combined organic layers were washed with
water (3· 50 ml), brine (50 ml), dried (MgSO4) and
concentrated to give a yellow residue. Column chroma-
tography on silica (MeOH–DCM 1:19) afforded 6 as a
white solid (2.22 g, 72%) which was recrystallised
from chloroform–hexane. mp 125–127 ꢁC; Rf = 0.43
(MeOH–DCM 1:9); IR mmax (Nujol)/cmꢀ1; 1060 (C–O),
4.18. Compound 8f
The conditions employed for the preparation of this com-
pound were those described in General Method C. Col-
umn chromatography (MeOH–DCM 1:9 followed by
17% NH4OH–MeOH–DCM 1:2:2) afforded 8f as a cream
white solid (0.26 g, 74%) (recrystallised from methanol);
decomposes above 140 ꢁC; Rf = 0.13 (17% NH4OH–
MeOH–DCM 1:2:2); IR mmax (Nujol)/cmꢀ1 1060 (C–O),
1580 (C@N) 1650 (C@O), 3400 (N–H); dH (300 MHz;
DMSO-d6) 2.82 (4H, br s, N[CH2CH2]2CH2Ph), 3.45
(4H, br s, N[CH2CH2]2CH2Ph), 3.41 (2H, t, J 5.4, CON-
HCH2CH2N), 3.47 (2H, t, J 5.4, CONHCH2CH2N), 3.87
(2H, s, PhCH2N), 6.38 (1H, d, J 8.4, H-5), 6.62 (1H, d,
J 5.1, H-30), 7.04 (1H, d, J 5.1, H-3?), 7.15 (1H, br s, NHN-
CONH), 7.43 (1H, d, J 8.4, H-6), 7.50 (1H, dd, J 2.1, 9.0,
H-60), 7.55 (1H, dd, J 2.1, 9.0, H-6?), 7.59 (1H, br s,
1
1580 (C@N), 1720 (C@O), 3225 (N–H); H NMR dH
(300 MHz; CDCl3) 3.47 (2H, q, J 6.0, NCH2CH2NHCO),
3.70 (2H, q, J 6.0, NCH2CH2NHCO), 6.02 (1H, br s,
HNCH2CH2NHCO), 6.21 (1H, br s, HNCH2CH2N
HCO), 6.40 (1H, d, J 5.1, H-3), 7.22 (5H, m, Ph), 7.26
(1H, dd, J 2.1, 9.0, H-6), 7.66 (1H, d, J 9.0, H-5), 7.93
(1H, d, J 2.1, H-8), 8.34 (1H, d, J 5.1, H-2); dc (75 MHz;
CDCl3) 40.0, 45.1, 98.5, 117.2, 121.5, 121.6 (2C), 125.5,
125.7, 128.3 (2C), 126.6, 135.2, 148.8, 150.0, 150.8,
151.7, 156.9; Anal. Found: C, 62.64; H, 4.74; N,
12.15%. Calcd for C18H16ClN3O2: C, 63.25; H, 4.72; N,
12.29%; HRMS (EI) m/z Found: [M+H]+, 342.100089
Calcd for C18H16ClN3O2: M, 342.10093.

A. Chipeleme et al. / Bioorg. Med. Chem. 15 (2007) 273–282
281
4.21. Compound 7
References and notes
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To a solution of [2-(7-chloro-quinolin-4-ylamino)-ethyl]-
carbamic acid phenyl ester (1.26 g, 3.70 mmol) in dry
methanol (10 ml) was added hydrazine monohydrate
(1.85, 37 mmol) and the resulting mixture was stirred at
90 ꢁC for 12 h. The reaction mixture was concentrated
to give a white residue, which was subjected to column
chromatography on silica gel (MeOH–DCM 1:9 followed
by 17% NH4OH–MeOH–DCM 1:2:2) to give 7 as white
crystals (0.87 g, 84%); mp 177–179 ꢁC (from methanol);
Rf = 0.12 (MeOH–DCM 1:9); IR mmax (Nujol)/cmꢀ1
;
1080 (C–O), 1140 (C–N), 1550 (C@N), 1600 (C@C),
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M, 280.09651.
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Acknowledgment
This work was supported by the South African National
Research Foundation under grant number 2053362
(KC) and by the National Institutes of Health
(AI35707, PJR). PJR is a Doris Duke Distinguished
Clinical Scientist.

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