Meridianin G and its analogs as antimalarial agents

Article abstract of DOI:10.1039/c3md00097d

The marine-derived indole alkaloids meridianin C and G and their N1-substituted and C-ring modified analogs were synthesized and screened for antiprotozoal and antimicrobial activities. Meridianin C and G showed antimalarial activity against both chloroquine-resistant (D6) as well as sensitive (W2) clones of Plasmodium falciparum with IC₅₀ values in the range of 4.4 to 14.4 μM. Meridianin G showed better activity against the W2 clone, showing a higher selectivity index >24.1. Among the analogs, N1-morpholinoyl meridianin C analog displayed antimalarial activity against both clones, showing selectivity indices up to 25.1. Meridianin C along with a few other analogs showed weak to moderate antileishmanial activity against Leishmania donovani promastigotes, the best analog being a C-ring modified 5-iodo meridianin showing an IC₅₀ of 9.17 μM. A few compounds also showed mild antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus, and antifungal activity against Cryptococcus neoformans.

Full text of DOI:10.1039/c3md00097d

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Meridianin G and its analogs as antimalarial agents†‡
ac
Rammohan R. Yadav,ac Shabana I. Khan,b Babu L. Tekwani,b
*
Sandip B. Bharate,
Cite this: DOI: 10.1039/c3md00097d
b
b
ac
*
Melissa R. Jacob, Ikhlas A. Khan and Ram A. Vishwakarma
The marine-derived indole alkaloids meridianin C and G and their N1-substituted and C-ring modified
analogs were synthesized and screened for antiprotozoal and antimicrobial activities. Meridianin C and
G showed antimalarial activity against both chloroquine-resistant (D6) as well as sensitive (W2) clones of
Plasmodium falciparum with IC50 values in the range of 4.4 to 14.4 mM. Meridianin G showed better
activity against the W2 clone, showing
a higher selectivity index >24.1. Among the analogs,
N1-morpholinoyl meridianin C analog displayed antimalarial activity against both clones, showing
selectivity indices up to 25.1. Meridianin C along with a few other analogs showed weak to moderate
antileishmanial activity against Leishmania donovani promastigotes, the best analog being a C-ring
modified 5-iodo meridianin showing an IC50 of 9.17 mM. A few compounds also showed mild
antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus, and antifungal
activity against Cryptococcus neoformans.
Received 29th March 2013
Accepted 9th April 2013
DOI: 10.1039/c3md00097d
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meridianin analogs substituted with both 20-piperidinyl and
60-aryl moieties have been reported to display an MIC of 3–
Introduction
Parasitic diseases such as malaria and leishmaniasis1 are major
health concerns, particularly in the regions of South East Asia
and South America. Malaria is a serious and life-threatening
parasitic disease that is particularly devastating in sub-Saharan
Africa where more than 90% of malaria-related deaths occur.
Malaria is caused by four species of Plasmodium, viz. P. falci-
parum, P. vivax, P. ovale and P. malariae, amongst which most
cases of malaria and deaths are caused by P. falciparum.
Development of resistance to mainstay conventional drugs has
created an urgent need to discover new antimalarial as well as
antileishmanial agents.1
Indole alkaloids are known to possess promising antima-
larial activities;2 for example ellipticine,3 cryptolepine,4 canthin-
6-one,5 cryptoheptine,6 nostocarboline7 and meridianin A8
showed antimalarial activity against Plasmodium falciparum.
Meridianins A–G (1–7) are indole alkaloids substituted at the
C-3 position by a 2-aminopyrimidine ring, isolated from the
tunicate Aplidium meridianum (family: Ascidiae, Polyclinidae).9
Meridianins showed the ability to inhibit various protein
kinases10 and also displayed antitumor activity.11 The
30 mM (analog 8, MIC 3 mM) against the malaria parasite Plas-
modium falciparum NF-54.12 Baker and coworkers8 reported that
meridianin A (1), its OMe analog 9 and a meridianin–chloro-
quine hybrid structure 10 showed antimalarial activity against
P. falciparum with IC50 values of 12, 40, 200 mM, respectively.
Furthermore, the amino-pyrimidine compound pyrimethamine
(Daraprimꢀ) has been used for treatment of malaria. The
structures of meridianins A–G (1–7) and antimalarial mer-
idianin analogs 8–10 are shown in Fig. 1.
Based on the literature precedence for the antimalarial2–8,12
and antileishmanial13 activity of indole alkaloids, and as a part
of our medicinal chemistry program on marine natural product
scaffolds,14 herein we have investigated the antimalarial and
aMedicinal Chemistry Division, Indian Institute of Integrative Medicine (CSIR), Canal
Road, Jammu-180001, India. E-mail: ram@iiim.ac.in; sbharate@iiim.ac.in; Fax: +91-
191-2569333; Tel: +91-191-2569111
bNational Center for Natural Products Research (NCNPR), School of Pharmacy,
University of Mississippi, MS 38677, USA
cAcademy of Scientic and Innovative Research (AcSIR), Anusandhan Bhawan, 2 Ra
Marg, New Delhi-110001, India
† IIIM Communication number. IIIM/1544/2013
‡ Electronic supplementary information (ESI) available: Experimental details and
NMR spectra of all new compounds. See DOI: 10.1039/c3md00097d
Fig. 1 Chemical structures of meridianin A–G and its antimalarial analogs.
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antileishmanial activity of natural meridianins and their N1- by deprotection of the tosyl group was carried out by treatment
substituted and C-ring modied analogs. The antimicrobial of enaminones 14a,b with guanidine hydrochloride in
potential of these analogs has also been investigated. The 2-methoxyethanol in the presence of potassium carbonate,
previous efforts on meridianin-based scaffolds for antimalarial which led to the formation of meridianins G (7) and C (3) in 66
drug discovery were primarily focused on modications at the and 55% yields, respectively.20 While synthesizing meridianin C
pyrimidine ring. Chauhan and coworkers12 have identied the (3), the N-alkylated side product 15 was also formed along with
antimalarial analog 8 in which the –NH2 group of the amino- the desired product 3, as depicted in Scheme 1. The source of
pyrimidine ring was replaced with an N-methylpiperazine unit. the alkyl moiety in the N-alkylated side product 15 was identi-
Further, the meridianin–chloroquine hybrid structure 10 ed to be the solvent 2-methoxyethanol used in the reaction.
synthesized by Baker's group8 was weakly active. Although the The synthesized meridianins C and G were characterized by
modications on the pyrimidine ring provided 8 with low comparison of their spectral data with literature values.9,21
micromolar antiplasmodial activity, the substitution at the
Aer the synthesis of meridianins C (3) and G (7), their N1-
indolic-NH was never explored. In the present study, we have substituted analogs were synthesized as depicted in Scheme 2.
synthesized indolic N1-substituted analogs to investigate their The treatment of 3 or 7 with different aryl/heteroaryl acid chlo-
antimalarial potential. For N1-substitution, we have selected rides 16a–e or aryl/heteroaryl alkyl halides 18a–d in acetonitrile in
moieties such as N-methylpiperazine (which is present in 8)12 the presence of potassium carbonate led to the formation of the
and its structural variants (e.g. morpholine). Furthermore, corresponding N1-substituted analogs 17a–h and 19a–g in 32–
several antimalarial and antileishmanial scaffolds consist of 86% yields. The position of acylation or alkylation, either on the
1
benzoyl15 or benzyl16 functionalities, thus various CO- and NH2 or the indolic NH was established based on H NMR data
CH2-linked aryl and heteroaryl moieties were incorporated to and extensive 2-D NMR data for selected analogs.
understand the structural requirements for antimalarial/anti-
leishmanial activities.
Further, indolyl quinazolinone type C-ring modied analogs
22a–c were synthesized by treatment of indole-3-carbox-
aldehydes 20a–c with anthranilamide (21) in acetonitrile in the
presence of Amberlyst-15 in 43–57% yield as depicted in
Results and discussion
Chemistry
Scheme 3. All synthesized analogs were characterized by 1H, 13
NMR, IR, MS, HRMS and melting point analysis.
C
Meridianin C (3) and G (7) were synthesized17 in 4 steps starting
from commercially available indoles 11a,b using the synthetic
strategy shown in Scheme 1. The treatment of indoles 11a,b
with acetyl chloride in the presence of SnCl4 led to the forma-
tion of 3-acetylindoles 12a,b.18 The next step was the protection
of the indolic NH by tosyl chloride in the presence of DIPEA and
DMAP to yield products 13a,b in 72–85% yield.18 N-Tosyl indoles
13a,b on treatment with dimethyl formamide dimethylacetal
(DMF–DMA) led to the formation of enaminones 14a,b.19 The
enaminones 14a,b were found to exist only in the Z-congura-
tion.11 The construction of the aminopyrimidine ring followed
Biological activity
All compounds were evaluated for antimalarial, antileishmanial,
antibacterial and antifungal activities. The in vitro antimalarial
activity was evaluated against chloroquine-sensitive (D6) and
resistant (W2) clones of P. falciparum via determination of plas-
modial LDH activity (Table 1).22 Natural meridianins along with
Scheme 1 Synthesis of meridianins C (3) and G (7). Reagents and conditions: (a)
AcCl (2 equiv.), SnCl4 (2 equiv.), toluene, 0 ꢀC, 2 h, 84–95%; (b) TsCl (1.1 equiv.),
DIPEA (1.5 equiv.), DMAP (0.05 equiv.), DCM, rt, 20 h, 72–85%; (c) DMF–DMA
(1.5 equiv.), DMF, 110 ꢀC, 4 h; 50–55%; (d) guanidine HCl (1.5 equiv.), 2-
methoxyethanol, K2CO3 (2 equiv.), 120 ꢀC, 24 h, 55–66%.
Scheme
2
Synthesis of N1-substituted meridianin analogs. Reagents and
conditions: (a) K2CO3 (2 equiv.), alkyl halide or acyl halide (1 equiv.) ACN, 12 h, rt,
32–86%.
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against the W2 clone with IC50 values of 4.58 and 3.98 mM. Like
compound 8, the N-methylpiperazine substituted meridianin G
analog 17c showed moderate antimalarial activity against both
clones of P. falciparum with IC50 values of 9.63 and 14.5 mM,
respectively; however the N-methylpiperazine substituted mer-
idianin C analog was devoid of antimalarial activity. The C-ring
modied meridianin analogs 22a–c were found to be inactive.
These results indicates that the presence of the aminopyrimidine
ring is essential for antimalarial activity; replacement of this ring
with other heterocycles results in loss of activity; however
substitutions on the aminopyridine ring are tolerated.12 Mer-
idianins are known to possess cyclin-dependent kinase inhibitory
activity.23 Thus, the mechanism of antimalarial activity could be
the ability of these compounds to inhibit malarial CDK(s).
Since this class of compounds is known to possess anti-
proliferative activities9,10,24 against a variety of cell lines, deter-
mining the selectivity towards parasite was also desirable. Baker
and coworkers8 observed that meridianin A (1) possesses anti-
plasmodial activity with an IC50 value of 12 mM and was
not cytotoxic towards Hep2, HT29, LMM3 and SH-SH5Y cells
Scheme 3 Synthesis of C-ring modified meridianin analogs. Reagents and
conditions: (a) indole aldehyde (20, 1 equiv.). anthranilamide (21, 1 equiv.),
Amberlyst-15 (50% w/w), ACN, 12 h, rt, 43–57%.
several synthetic analogs showed signicant antimalarial activity
against both clones of P. falciparum. Meridianins C (3) and G (7)
inhibited P. falciparum D6 and W2 clones with IC50 values in the
range of 4.4 to 14.4 mM. Amongst the synthesized analogs,
N1-morpholinoyl substituted meridianin G analog 17a was the
best analog showing antimalarial activity against both D6 and W2
clones with IC50 values of 4.01 and 3.08 mM respectively. The N1-
benzoyl substituted analogs 17e,f also showed good antimalarial
activity against both clones; however they were more active
Table 1 The in vitro antimalarial activity, antileishmanial activity and cytotoxicity of meridianin analogsa
Antimalarial activity against D6 and W2
clones of P. falciparum
cytotoxicityj
Antileishmanial
activity against L. donovani
IC50 in mM
IC50d in mM (mg mLꢁ1
)
IC50 in mM
D6
W2
Entryh
IC50
S.I.c
IC50
S.I.c
HEPG2i
VEROi
LLC-PK1i
IC50b/IC90
b
b
b
3
7
17a
17c
17d
17e
17f
17h
19a
19b
19c
19d
19f
19g
15
22b
14.43
9.69
4.01
9.63
na
11.42
7.45
na
12.40
9.62
na
13.59
7.06
11.05
na
>6.0
11.67
4.44
3.08
14.49
na
4.58
3.98
na
na
14.55
na
10.06
10.95
11.60
na
>7.4
>87 (>25)
>119 (>25)
>77 (>25)
>74 (>25)
>60 (>25)
>80 (>25)
>64 (>25)
>70 (>25)
>78 (>25)
>63 (>25)
>74 (>25)
>60 (>25)
>63 (>25)
>52 (>25)
>72 (>25)
73 (25)
>87 (>25)
119 (25)
>77 (>25)
>74 (>25)
>60 (>25)
>80 (>25)
>64 (>25)
>70 (>25)
>78 (>25)
>63 (>25)
>74 (>25)
>60 (>25)
>63 (>25)
>52 (>25)
>72 (>25)
>73 (>25)
>65 (>25)
nd
>87 (>25)
107 (22.5)
>77 (>25)
>74 (>25)
>60 (>25)
>80 (>25)
>64 (>25)
>70 (>25)
>78 (>25)
>63 (>25)
>74 (>25)
>60 (>25)
>63 (>25)
>52 (>25)
43 (15)
64.86/—g
na/na
na/na
>11.1e
>19.3
>7.7
—
>24.1f
>25.1
>5.1
—
na/na
40.5/108.5
na/na
>7.0
>8.5
—
>6.3
>6.5
—
>4.4
>8.9
>4.7
—
—
—
—
—
nd
nd
nd
>17.4
>16.0
—
—
>4.3
—
>5.9
>5.7
>4.5
—
—
—
105.3/—g
47.40/—g
na/na
107.3/na
41.3/na
29.12/41.2
79.98/—g
na/na
23.63/52.2
79.94/—g
9.17/14.2
nd/nd
na
na
<0.09
<0.08
nd
na
na
<0.09
0.72
nd
53 (18)
>65 (>25)
nd
nd
nd
22c
>65 (>25)
nd
nd
nd
nd
Artemisinin
Chloroquine
Pentamidine
Amphotericin B
Doxorubicin
—
—
nd
nd
nd
nd
nd
7 (4)
nd/nd
3.29/6.21
0.17/0.35
nd/nd
nd
nd
nd
nd
nd
<1 (<0.55)
nd
2 (0.85)
a
b
c
na, not active. IC50 and IC90 are sample concentrations that inhibit 50% and 90% growth of parasites compared to solvent controls. S.I.,
d
selectivity index ¼ IC50 HEPG2/Vero/LLC-PK1 cells/IC50 P. falciparum. IC50 values for cytotoxicity are in mM. These values are also mentioned
as mg mLꢁ1 in parentheses. The selectivity (S.I.) of compound 7 for the P. aciparum D6 clone with respect to HEPG2/Vero/LLC-PK1 cells was
e
f
>12.3, >12.3 and >11.1, respectively. The selectivity (S.I.) of compound 7 for the P. aciparum W2 clone with respect to HEPG2/Vero/LLC-PK1
cells was >26.8, >26.8 and >24.1, respectively. IC90 > highest tested concentration. Analogs 17b, 17g, 19e and 22a were not active in
g
h
i
antimalarial as well as antileishmanial activity, therefore are not listed in this Table. HEPG2, human hepatoma cells; LLC-PK1, pig kidney
epithelial cells; Vero, monkey kidney broblasts. The compounds for which cytotoxicity values are mentioned as >25 mg mLꢁ1, no cytotoxicity
j
was observed up to this concentration. Thus, these compounds can be referred as ‘not cytotoxic' up to 25 mg mLꢁ1
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(IC50 > 100 mM), although it displayed cytotoxicity against A549 Clinical Laboratory Standards (NCCLS). The susceptibility of M.
cells (IC50 15 mM). Thus, in order to investigate the selectivity of intracellulare was tested using the modied Alamar Blue
the synthesized compounds for malarial parasites, the in vitro procedure.26 Ciprooxacin was used as a positive control for
cytotoxicity25 was determined up to a high concentration of comparison. The results of antibacterial activity screening are
25 mg mLꢁ1 against three mammalian cell lines including: Vero shown in Table 2. Amongst the tested analogs, only 5-chlor-
(monkey kidney broblasts), HEPG2 (human hepatoma cells) othiophen-2-methylene substituted analog 19d and C-ring
and LLC-PK1 (pig kidney epithelial cells). Most of the modied analog 22b showed mild antibacterial activity against
compounds were not toxic up to a concentration of 25 mg mLꢁ1
.
S. aureus with IC50 values of 40.5 and 25.2 mM respectively.
The analog 22a was found to display cytotoxicity below 25 mg Analog 22b also showed inhibition of methicillin-resistant
mLꢁ1, showing IC50 values of 17.5, >25 and 14.5 mg mLꢁ1, for S. aureus with an IC50 of 20.9 mM (Table 2).
HEPG2, Vero and LLC-PK1, respectively. Meridianin G (7) and
All compounds were screened for antifungal activities
analog 15 also displayed cytotoxicity below 25 mg mLꢁ1 against against a panel of pathogenic fungi (Candida albicans, Crypto-
LLC-PK1 cells (IC50 15 and 22.5 mg mLꢁ1, respectively). In coccus neoformans and Aspergillus fumigatus) associated with
general, the synthesized compounds were not toxic to these opportunistic infections. Amphotericin B was used as a positive
cells and thus the selectivity index for antimalarial activity was control for comparison. Meridianin C (3) along with several
found to be good (in the range of >4 to >25). Meridianin G (7) analogs showed antifungal activity against C. neoformans. The
showed better antiplasmodial activity against the W2 clone with thiophenyl-2-methylene substituted analog 19c was the best
a selectivity index of >24.1. The N1-morpholinoyl substituted among tested analogs, which showed IC50, MIC and MFC values
meridianin G analog 17a displayed the best selectivity indices of 13, 14.7 and 14.7 mM respectively. None of the compounds
against both D6 and W2 clones (S.I. ¼ >19.3 and >25.1) amongst showed activity against fungi other than C. neoformans. The
all synthesized compounds. Furthermore, the N1-benzoyl antifungal activity of meridianin analogs against C. neoformans
substituted analogs 17e and 17f displayed better selectivity is shown in Table 2.
indices for the W2 clone (S.I. ¼ >17.4 and >16.0) compared to
the D6 clone (S.I. ¼ >7.0 and >8.5).
Conclusion
The in vitro antileishmanial activity of meridianins (3 and 7)
and analogs 17a–h, 19a–g and 22a–c was evaluated against a
culture of Leishmania donovani promastigotes. Several
compounds showed mild to moderate antileishmanial activities
as depicted in Table 1. Meridianin C (3) showed mild anti-
leishmanial activity with an IC50 of 64.9 mM; and the N1-
substituted meridianin analogs displayed activity in the range
of 23–107 mM. The iodo-substituted C-ring modied analog 22c
showed better activity against L. donovani promastigotes
exhibiting IC50 and IC90 values of 9.17 and 14.24 mM.
The antibacterial activity was tested against Staphylococcus
aureus, methicillin-resistant Staphylococcus aureus and Myco-
bacterium intracellulare, Escherichia coli and Pseudomonas aeru-
ginosa. The susceptibility of S. aureus and methicillin-resistant
S. aureus (MRSA) to test compounds was determined according
to the procedure as described by the National Committee for
In summary, herein we have identied N1-substituted and
C-ring modied meridianin analogs as antimalarial and anti-
leishmanial agents. Through this study, the N1-morpholinoyl
substituted meridianin C analog 17a was identied as a lead
antimalarial structure (S.I. ¼ >25.1 for the W2 clone and >19.3
for the D6 clone) which can be taken forward for lead optimi-
zation studies to discover potent antimalarial agents.
Experimental section
Procedure for synthesis of meridianins C (3) and G (7)
A mixture of enaminone 14a or 14b, guanidine hydrochloride
(1.5 equiv.), anhydrous K2CO3 (2 equiv.) and 2-methoxyethanol
was heated at reux temperature for 24 h under N2 atmosphere.
Aer cooling, the solution was poured into water and then
Table 2 In vitro antibacterial and antifungal activity of meridianin analogsa
Antibacterial IC50/MIC/MBC
Antifungal IC50/MIC/MFC
Entry
S. aureus
MRSA
C. neoformans
3
17f
17h
19c
19d
19e
15
22b
na/na/na
na/na/na
na/na/na
na/na/na
40.5/na/na
na/na/na
na/na/na
25.2/na/na
0.39/1.51/1.51
nd/nd/nd
na/na/na
na/na/na
na/na/na
na/na/na
na/na/na
na/na/na
na/na/na
20.9/na/na
0.39/1.51/1.51
nd/nd/nd
56.5/na/na
24.3/na/na
45.6/na/na
13.0/14.7/14.7
19.9/47.7/47.7
26.9/na/na
27.4/57.6/57.6
14.81/na/na
nd/nd/nd
Ciprooxacin
Amphotericin B
0.85/1.35/1.35
a
Values in mM. na, not active; nd, not determined.
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extracted with EtOAc. The combined organic layers were dried 6.8 Hz), 7.77–7.73 (m, 1H), 7.68–7.64 (t, 2H, J ¼ 7.6 Hz), 7.48–
(Na2SO4) and concentrated to dryness under reduced pressure. 7.39 (m, 2H), 7.09 (d, 1H, J ¼ 5.2 Hz), 6.11 (s, 2H, NH2); 13C NMR
The residue was chromatographed on a silica gel column using (CDCl3, 100 MHz): 168.62, 162.98, 161.67, 157.67, 137.08,
DCM/methanol as eluent to obtain the title products 3 or 7 as 133.98, 132.45, 129.90, 129.37, 128.86, 128.73, 128.35, 128.01,
pale yellow solids. The side product 15 was formed during 125.68, 124.70, 121.67, 120.08, 116.47, 108.38; IR (CHCl3): nmax
synthesis of meridianin C (3). Products 3 and 7 were charac- 3307, 2955, 2924, 2857, 1695, 1571, 1450, 1400, 1360, 1330,
terized by comparison of their spectral data with literature 1275, 1235, 1201, 1082, 1015 cmꢁ1; HRMS: m/z 315.1236 calcd
values.9,21 The spectral data for the side product 15 are provided for C19H14N4O + H+ (315.1240).
in the ESI.‡
(3-(2-Aminopyrimidin-4-yl)-5-bromo-1H-indol-1-yl)(phenyl)
General procedure for synthesis of N1-substituted meridianin
analogs 17a–h and 19a–g
methanone (17f)
Yield: 62%; pale yellow solid; m. p. 205–207 ꢀC; 1H NMR
To a solution of meridianin G (7) or meridianin C (3) in aceto- (Acetone-d6, 400 MHz): d 8.92 (d, 1H, J ¼ 2.0 Hz), 8.31 (d, 1H, J ¼
nitrile, anhydrous potassium carbonate (2 equiv.) and aryl acid 8.8 Hz), 8.22–8.21 (t, 2H, J ¼ 2.0 Hz), 7.92–7.89 (m, 2H), 7.78–
chloride/aryl alkyl halide (1 equiv.) were added. The resultant 7.74 (m, 1H), 7.68–7.67 (m, 2H), 7.61–7.59 (m, 1H), 7.08 (d, 1H,
mixture was allowed to stir for 12 h. Aer completion of the J ¼ 5.2 Hz), 6.23 (s, 2H–NH2); 13C NMR (125 MHz, DMSO) d
reaction, solvent was evaporated, the mixture was extracted with 168.14, 163.49, 159.93, 158.09, 135.14, 133.04, 132.62, 130.40,
ethyl acetate, dried over Na2SO4, and puried by column chro- 129.66, 129.49, 128.79, 127.85, 125.04, 118.17, 117.40, 116.98,
matography (#100–200) using dichloromethane and methanol 105.91; IR (CHCl3): nmax 3391, 2955, 2924, 2857, 1693, 1579,
(99 : 1 to 97 : 3) to get the title products 17a–h or 19a–g. The 1445, 1362, 1345, 1263, 1193, 1020 cmꢁ1; HRMS: m/z 393.0325
spectral data for selected compounds are provided below; and calcd for C19H13BrN4O + H+ (393.0346).
the spectral data for remaining compounds are provided in
the ESI.‡
4-(1-((3,5-Dimethylisoxazol-4-yl)methyl)-1H-indol-3-yl)
pyrimidin-2-amine (19a)
(3-(2-Aminopyrimidin-4-yl)-1H-indol-1-yl)(morpholino)
methanone (17a)
Yield: 64%; pale yellow solid; m. p. 183–185 ꢀC; 1H NMR
(CD3OD, 400 MHz): d 8.47–8.45 (t, 1H, J ¼ 7.6 Hz), 8.11 (d, 1H,
Yield: 83%; pale yellow solid; m. p. 188–190 ꢀC; 1H NMR J ¼ 5.6 Hz), 7.97 (s, 1H), 7.44 (d, 1H, J ¼ 7.6 Hz), 7.29–7.21 (m,
(CD3OD, 400 MHz): d 8.43 (d, 1H, J ¼ 7.6 Hz), 8.09 (t, 2H, J ¼ 2H), 7.05 (d, 1H, J ¼ 5.2 Hz), 5.27 (s, 2H), 2.37–2.33 (t, 3H, J ¼ 7.6
3.6 Hz), 7.58 (d, 1H, J ¼ 8.4 Hz), 7.29–7.19 (m, 2H), 7.03 (d, 1H, Hz), 2.01 (d, 3H, J ¼ 9.2 Hz); 13C NMR (CD3OD, 100 MHz):
J ¼ 5.2 Hz), 3.61 (d, 4H, J ¼ 5.2 Hz), 3.55–3.53 (t, 4H, J ¼ 4.8 Hz); 168.78, 164.83, 164.64, 160.79, 157.78, 138.79, 131.65, 127.58,
13C NMR (CD3OD, 100 MHz): 164.78, 163.95, 158.40, 154.83, 123.96, 123.44, 122.55, 115.38, 111.33, 111.12, 107.60, 40.03,
137.70, 129.53, 128.10, 125.52, 124.02, 123.73, 118.96, 114.10, 10.86, 10.11; IR (CHCl3): nmax 3307, 2956, 2925, 2855, 1739,
108.21, 67.65, 48.12; IR (neat): nmax 3351, 2920, 2355, 2347, 2325, 1575, 1537, 1455, 1393, 1343, 1248, 1193, 1082, 1015 cmꢁ1
1685, 1575, 1452, 1420, 1306, 1273, 1236, 1203, 1114, 1018 HRMS: m/z 320.1508 calcd for C18H17N5O + H+ (320.1506).
cmꢁ1; HRMS: m/z 324.1461 calcd for C12H17N5O2 + H+
;
(324.1455).
4-(5-Bromo-1H-indol-3-yl)-N-((3,5-dimethylisoxazol-4-yl)
methyl)pyrimidin-2-amine (19b)
Yield: 85%; yellow solid; m. p. 172–174 ꢀC; 1H NMR (CDCl3,
400 MHz): d 8.59 (d, 1H, J ¼ 2.0 Hz), 8.24 (d, 1H, J ¼ 5.2 Hz), 7.58
(3-(2-Aminopyrimidin-4-yl)-1H-indol-1-yl)(4-methylpiperazin-
1-yl)methanone (17c)
Yield: 89%; yellow solid; m. p. 195–197 ꢀC; 1H NMR (CDCl3, 400 (s, 1H), 7.42–7.39 (m, 1H), 7.23 (d, 1H, J ¼ 8.8 Hz), 6.88 (d, 1H,
MHz): d 8.38 (t, 1H, J ¼ 7.6 Hz), 8.30 (d, 1H, J ¼ 5.6 Hz), 7.97 (s, J ¼ 5.2 Hz), 5.05 (s, 4H, CH2 and NH2), 2.35 (s, 3H), 2.08 (s, 3H);
1H), 7.66 (d, 1H, J ¼ 7.6 Hz), 7.39 (m, 2H), 7.02 (t, 1H, J ¼ 5.6 Hz), 13C NMR (125 MHz, CDCl3) d 167.24, 162.56, 161.23, 159.07,
5.06 (s, 2H, NH2), 3.65 (t, 4H, J ¼ 4.8 Hz), 2.52 (t, 4H, J ¼ 4.8 Hz), 157.59, 135.80, 129.12, 127.65, 125.92, 124.77, 115.06, 114.39,
2.35 (s, 3H); 13C NMR (CDCl3, 125 MHz): 162.08, 160.81, 157.09, 110.81, 108.66, 107.14, 39.39, 11.17, 10.21; IR (CHCl3): nmax
153.24, 135.14, 126.74, 125.72, 123.23, 121.77, 121.33, 116.91, 3326, 2955, 2924, 2854, 1727, 1576, 1537, 1458, 1392, 1191,
112.18, 107.13, 53.75, 46.21, 45.06; IR (CHCl3): nmax 3341, 3210, 1020 cmꢁ1; HRMS: m/z 398.0588 calcd for C18H16BrN5O + H+
2955, 2924, 2854, 2802, 1684, 1623, 1574, 1545, 1454, 1421, (398.0611).
1330, 1294, 1263, 1248, 1153, 1082, 1050, 1018, 1001 cmꢁ1
;
HRMS: m/z 337.1773 calcd for C18H20N6O + H+ (337.1771).
4-(5-Bromo-1H-indol-3-yl)-N-((5-chlorothiophen-2-yl)methyl)
pyrimidin-2-amine (19d)
Yield: 73%; yellow solid; m. p. 175–177 ꢀC; 1H NMR (CDCl3, 400
MHz): d 8.59 (s, 1H), 8.25 (d, 1H, J ¼ 5.2 Hz), 7.78 (s, 1H), 7.40–
(3-(2-Aminopyrimidin-4-yl)-1H-indol-1-yl)(phenyl)methanone
(17e)
Yield: 67%; pale yellow solid; m. p. 242–244 ꢀC; 1H NMR 7.37 (m, 1H), 7.24 (s, 1H), 6.91 (d, 1H, J ¼ 5.2 Hz), 6.91 (d, 1H, J ¼
(Acetone-d6, 400 MHz): d 8.66 (d, 1H, J ¼ 7.6 Hz), 8.39 (d, 1H, J ¼ 5.2 Hz), 6.78–6.75 (m, 2H), 5.38 (s, 2H), 5.02 (s, 2H–NH2); 13C
8.4 Hz), 8.23 (d, 1H, J ¼ 5.2 Hz), 8.14 (s, 1H), 7.90–7.88 (t, 2H, J ¼ NMR (CDCl3, 100 MHz): d 163.11, 161.99, 157.84, 136.92,
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135.65, 130.62, 130.18, 127.92, 126.11, 125.98, 125.92, 124.94, 114.49, 107.82, 85.29; IR (CHCl3): nmax 3306, 2955, 2924, 2857,
115.23, 114.68, 111.26, 107.37, 45.84; IR (CHCl3): nmax 1739, 1650, 1491, 1464, 1400, 1343, 1191, 1168, 1082,
3400, 2955, 2924, 2854, 1738, 1577, 1537, 1457, 1389, 1015 cmꢁ1; HRMS: m/z 387.9950 calcd for C16H10IN3O + H+
1189, 1156, 1019 cmꢁ1
17H12BrClN4S + H+ (418.9727).
; HRMS: m/z 418.9723 calcd for (387.9941).
C
Biological evaluation
4-(1-(Anthracen-10-ylmethyl)-1H-indol-3-yl)pyrimidin-2-amine
The antimalarial, antileishmanial, antimicrobial and cytotox-
icity evaluation was done as reported earlier.25,27
(19f)
Yield: 86%; pale yellow solid; m. p. 246–248 ꢀC; 1H NMR (DMSO-
d6, 500 MHz): d 8.87 (s, 1H), 8.41 (d, 1H, J ¼ 3.4 Hz), 8.39 (s, 2H),
8.29–8.27 (m, 2H), 8.04–8.02 (m, 2H), 7.65–7.63 (m, 3H), 7.37
(s, 3H), 6.77 (d, 1H, J ¼ 5.3 Hz), 6.48 (s, 2H–NH2), 6.36 (s, 2H);
13C NMR (DMSO-d6, 125 MHz): d 163.26, 161.24, 157.38, 137.37,
131.02, 130.75, 129.22, 128.96, 128.52, 127.19, 125.75, 125.59,
125.56, 125.40, 123.62, 122.34, 121.86, 121.01, 113.36, 113.33,
110.77, 105.32, 105.29, 42.03; IR (CHCl3): nmax 3307, 2954, 2924,
2855, 1738, 1572, 1561, 1452, 1399, 1309, 1219, 1203, 1156,
1082, 1019 cmꢁ1; HRMS: m/z 401.1760 calcd for C27H20N4 + H+
(401.1761).
Acknowledgements
RRY thanks CSIR for a Senior Research Fellowship. The authors
are thankful to the analytical department, IIIM for analytical
support. Surendra Jain, Marsha Wright and John Trott are
acknowledged for technical support in biological activity testing
at NCNPR. The United States Department of Agriculture (USDA),
Agricultural Research Service Specic Cooperative Agreement
no. 58-6408-2-0009 and the US Department of Defense CDMRP
grant # W81XWH-09 (BLT) are acknowledged for partial support
of this work. Antifungal testing was supported by NIH, NIAID,
Division of AIDS grant # AI27094.
4-(1-(Anthracen-10-ylmethyl)-5-bromo-1H-indol-3-yl)
pyrimidin-2-amine (19g)
Yield: 84%; pale yellow solid; m. p. 247–249 ꢀC; 1H NMR (DMSO-
d6, 400 MHz): d 8.80 (s, 1H), 8.67 (d, 1H, J ¼ 2.0 Hz), 8.33–8.31
(m, 2H), 8.23–8.21 (m, 2H), 7.96–7.91 (m, 2H), 7.60–7.57
(m, 4H), 7.49–7.46 (dd, 1H, J ¼ 2.0 Hz), 7.34 (s, 1H), 6.64 (d, 1H,
J ¼ 5.2 Hz), 6.42 (s, 2H), 6.40 (s, 2H–NH2); 13C NMR (DMSO-d6,
100 MHz): d 163.34, 160.98, 157.51, 136.17, 131.10, 130.81,
129.90, 129.33, 129.18, 127.34, 127.28, 125.48, 125.06, 124.27,
123.59, 114.06, 112.97, 112.87, 105.29, 42.38; IR (CHCl3): nmax
3400, 2955, 2924, 2854, 1735, 1575, 1535, 1453, 1385, 1196,
1158, 1020 cmꢁ1; HRMS: m/z 479.0806 calcd for C27H19BrN4 +
H+ (479.0866).
Notes and references
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