Synthesis of symmetrically 1,4-disubstituted piperazine-2,5-diones: A new class of antileishmanial agents

Article abstract of DOI:10.3184/030823407X228254

A series of 1,4-diphenyl-2,5-dioxopiperazine derivatives were synthesised in one pot sequence. The compounds demonstrated appreciable cytotoxic activity against Leishmania donovani on both forms of the parasite, and the results suggested that some derivat

Full text of DOI:10.3184/030823407X228254

JOURNAL OF CHEMICAL RESEARCH 2007
JULY, 381–383
RESEARCH PAPER 381
Synthesis of symmetrically 1,4-disubstituted piperazine-2,5-diones: a
new class of antileishmanial agents
Abhijit Hazraa, Priyankar Pairaa, Partha Palitb, Sukdeb Banerjeea, Nirup B. Mondala and
Niranjan P. Sahua*
aSteroid and Terpenoid Chemistry Division, and bDivision of Infectious Diseases, Indian Institute of Chemical Biology,
4 Raja S.C. Mullick Road, Jadavpur, Kolkata 700 032, India
A series of 1,4-diphenyl-2,5-dioxopiperazine derivatives were synthesised in one pot sequence. The compounds
demonstrated appreciable cytotoxic activity against Leishmania donovani on both forms of the parasite, and the
results suggested that some derivatives (4, 11 and 12) could be exploited as antileishmanial agents.
Keywords: piperazine-2,5-diones, diketopiperazines, Leishmania donovani, antiprotozoals, chloroacetanilides
In recent years, piperazine scaffolds have been prevalent
in scientific literature due to the high number of positive
hits encountered in the biological evaluation of this hetero-
cycle and its congeners.1,2 Prominent among these are the
diketopiperazine (DKP) derivatives, a family of secondary
metabolites, many of which are produced by microorganisms.3
Being relatively simple compounds, 2,5-diketopiperazines are
amongst the most widespread of the small cyclo-dipeptide
derivatives found in nature.4 Their existence was first reported
around the year 1900 and many of the simpler members of
this family were later synthesised by Emil Fischer.5 The parent
compound, piperazine-2,5-dione, was first synthesised in
1888.6 Later, innumerable molecules bearing the piperazine-
2,5-dione ring have been isolated from cultures and received
much attention due to their diverse and interesting biological
activities.7-9 Some of the potent molecules are albonoursin,10-12
bicyclomycin13 and glyotoxin.14 The biosynthetic pathways to
the formation of piperazine-2,5-diones in microorganisms,
though not properly explored, are believed to be the result
of the operation of enzymes like cyclic dipeptide oxidase
(CDO) and non-ribosomal peptide synthetase (NRPS).15
However, the chemical synthesis of piperazine-2,5-diones
include the cyclisation of peptide derivatives, intramolecular
attack of amines on activated carbonyl groups, cyclisation of
N-pyruvoyl amino acid amides, intramolecular Diels–Alder
reactions, and synthesis of a-haloacyl derivatives of aminoacid
esters.16 Most of the methods employ aminoacid building
blocks and involve multistep operations.17,18 Recently several
groups, including ours, have reported the formation of diketo-
piperazines not from amino acid precursors.19-24 However,
no reports have appeared as yet with regard to their antileish-
manial activity. In continuation of our search for antileish-
manial agents25-27 the diverse biological activity of piperazine-
2,5-dione derivatives led us to explore the possibility of there
being privileged motifs for their antileishmanial activity.
In the present investigation, we disclose the synthesis of
symmetrically disubstituted 1,4-piperazine-2,5-diones from
a-chlorophenyl acetamides and their differently substituted
analogues as model substrates, emphasising the yield of
formation, ease of isolation and homogeneity of the product
formed, besides an evaluation of their antileishmanial activity
against Leishmania donovani promastigotes and amastigotes
in vitro. To the best of our knowledge this is the first report of
diketopiperazine derivatives as antileishmanial agents.
material was prepared from the acylation of aniline with a-
chloroacetyl chloride in dry CH2Cl2/benzene. Varying the time
and temperature of the reaction, it was observed that exclusive
formation of 1 in >90% yield resulted at a temperature of 60
± 5°C (Table 1) in 1 h when carried out in dry DMSO under
dry nitrogen in the presence of NaH. The spectral data of
compound 1 fully support the assigned structure. Formation
of 1 must have taken place by self-condensation between two
molecules of the substrate, the base causing the generation of
the anion on the nitrogen atom stabilised by both phenyl and
keto groups attached to the nitrogen atom, and subsequently
the reaction proceeds via a SN2 pathway (Scheme 1).
To establish the generality of the reaction, differently
substituted a-chloroacetanilides were used as substrates. Thus,
carrying out the reaction with other substrates under the same
conditions as for the 1,4-diphenylpiperazine-2,5-dione (1)
afforded a variety of substituted phenyl analogues (Table 1).
Following the same protocol, 2-chloro-N-cyclohexylacetamide
furnished 1,4-dicyclohexylpiperazine-2,5-dione (12) in 85%
yield (Scheme 1). Optimisation of the reaction conditions
with respect to time and percentage of yield of the derivatives
provided the results summarised in Table 1.
Experimental
Melting points were determined with a capillary melting point
apparatus. IR spectra were recorded on a JASCO FTIR (model 410)
in KBr pellets; major/significant peaks only are recorded. MALDI-
TOF MS (positive) was conducted using Perspective Bio System
Voyager DE-STR Mass spectrometer with 2,5-dihydroxybenzoic acid
as matrix. 1H and 13C NMR spectra were taken on a Bruker 300 MHz
DPX spectrometer at 300 and 74.99 MHz, respectively, with tetra-
methylsilane as internal standard, in DMSO-d6 unless otherwise
stated. Sodium hydride, anilines and chloroacetyl chloride were
purchased from Aldrich Chemical Ltd (USA). Organic solvents used
for the chemical synthesis and for chromatography, acquired from
E. Merck (India), were of analytical grade. All chromatographic
purification was performed with silica gel (60–120 mesh) and was
obtained from SRL (India). TLC was performed on pre-coated
silica gel 60 F254 aluminum sheets (E. Merck, Germany) using the
solvent system 1-6% MeOH in CHCl3; spots were developed using
Liebermann-Burchard solution. Medium 199 was purchased from
GIBCO BRL, USA.
Table
1
Optimisation of the reaction conditions of the
diketopiperazine analogues (1–12)
Compd
Time/h
Yield/%
Compd
Time/h
Yield/%
Results and discussion
1
2
3
4
5
6
1
1
1
2
2
2
90
95
94
85
88
80
7
8
2
89
93
90
88
90
85
In our synthetic approach, we tried to optimise the reaction
conditions for the formation of 1,4-diphenylpiperazine-2,5-
dione (1) from N-phenyl a-chloroacetamide. The starting
1.5
2
9
10
11
12
2
2
1
* Correspondent. E-mail: npsahu@iicb.res.in
PAPER: 07/4641

382 JOURNAL OF CHEMICAL RESEARCH 2007
R2
Cl
Cl
R2
R2
O
O
Cl
O
NaH, DMSO
60oC,N2 atm
N
N
N
H
R1
R1
R1
Cl
R2
2'
O
O
R1
3
R2
2
2''
R1
1'
1
N
1''
N
4'
4''
N
N
R2
5
R1
R1
O
R2
O
Cl
1-11
1 R1 = R2 = H
7 R1 = Cl, R2 = 5-Cl
2 R1 = OMe, R2 = 5-Cl
3 R1 = H, R2 = 4-Me
4 R1 = Cl, R2 = H
5 R1 = Cl, R2 = 3-Cl
6 R1 = Cl, R2 = 4-Cl
8 R1 = H, R2 = 4-OMe
9 R1 = H, R2 = 3-COCH3
10 R1 = Cl, R2 =4,6-Cl2
11 R1 = H, R2 =3-Cl
O
O
Cl
NaH,DMSO
60oC, N2 atm
N
N
NH
O
12
Scheme 1
2,5-Diketopiperazines 1-12: general procedure
(s, C-1', 1"), 166.4 (s, C-2, 5); MS:(MALDI-TOF, positive ion):
m/z 373 [M + K]+. Anal. Calcd for C16H12Cl2N2O2: C, 57.33; H, 3.61;
N, 8.36. Found: C, 57.61; H, 3.43; N, 8.08%.
A three-necked reaction flask was fitted with a condenser, a dropping
funnel and a stopcock connected to a nitrogen source. Sodium hydride
(0.5 mol) was taken in the reaction flask and washed free from
mineral oils by dry petroleum ether. Dry dimethylsulfoxide (DMSO)
was then added to the flask. Heating and stirring was continued until
the temperature reached 40–42°C. The chloroacetanilide substrate
(0.5 mol) was then added and stirring was continued for 1 h at
60±5°C. The reaction mixture was cooled, poured into ice-cold water
and extracted with CHCl3. The extract was washed free from alkali,
dried over anhydrous sodium sulfate, concentrated under reduced
pressure and crystallised from CH3OH.
1,4-Bis-(2,3-dichlorophenyl)piperazine-2,5-dione (5): M.p. 163–
165ºC. IR: 1697, 1590, 1531, 1407cm-1. NMR (CDCl3): dH 4.36
(s, 4H, H-3 and 6), 7.25–7.27 (m, 4H, H-6', 6" and H-4', 4"), 8.35–
8.38 (m, 2H, H-5', 5"); dC 71.9 (t, C-3, 6), 119.8 (d, C-6', 6"), 122.2
(s, C-2', 2"), 126.4 (d, C-4', 4"), 128.4 (d, C-5', 5"), 133.4 (s, C-3',
3"), 135.5 (s, C-1', 1"), 166.3 (s, C-2, 5); MS (MALDI-TOF, positive
ion): m/z 443 [M+K]+. Anal. Calcd. for C16H10Cl4N2O2: C, 47.56; H,
2.49; N. 6.93. Found: C, 47.42; H, 2.53; N, 6.78 %.
1,4-Bis-(2,4-dichlorophenyl)piperazine-2,5-dione (6): M.p. 228–
230°C. IR: 1682, 1481, 1447 cm-1. NMR dH 4.38 (s, 4H, H-3 and
6), 7.10–7.12 (m, 4H, H-5', 5", and 6', 6"), 7.34 (s, 2H, H-3', 3");
dC 53.8 (t, C-3, 6), 123.6 (d, C-6', 6"), 127.1 (s, C-2', 2"), 127.3 (d,
C-5', 5"), 129.7 (d, C-3', 3"), 130.6 (s, C-4', 4"), 139.3 (s, C-1' and
1"), 166.8 (s, C-2 & 5). MS (MALDI-TOF, positive ion): m/z 443
[M + K]+. Anal. Calcd. for C16H10Cl4N2O2: C, 47.56; H, 2.49; N,
6.93. Found: C, 47.39; H, 2.28; N, 7.18%.
1,4-Bis-(2,5-dichlorophenyl)piperazine-2,5-dione (7): M.p. 162–
164°C. IR: 1691, 1591, 1530, 1453, 1411 cm-1. NMR: dH 4.38 (s,
4H, H-3 and 6), d 7.08 (s, 2H, H-6', 6"), 7.21–7.24 (m, 4H, H-3',
3", and 4', 4"); dC 53.1 (t, C-3, 6), 122.6 (d, C-6', 6"), 123.8 (s,
C-2', 2"), 125.7 (d, C-4', 4"), 130.6 (d, C-3', 3"), 132.2 (s, C-5', 5"),
142.6 (s, C-1', 1"), 166.6 (s, C-2, 5). MS (MALDI-TOF, positive ion):
m/z 443 [M + K]+. Anal. Calcd. for C16H10Cl4N2O2: C, 47.56;
H, 2.49; N, 6.93. Found: C, 47.75; H, 2.61; N, 6.64%.
1,4-Bis-(4-methoxyphenyl)piperazine-2,5-dione(8):M.p.248–250°C.
IR: 1651, 1587, 1513, 1466 cm-1. NMR dH 3.72 (s, 6H, OCH3), 4.39
(s, 4H, H-3 and 6), 6.87 (d, J = 8 Hz, 4H, H-3', 3", and 5', 5"), 7.10 (d,
J = 7.8 Hz, 4H, H-2', 2" and H-6', 6"); dC 53.1 (t, C-3, 6), 55.9 (q, OCH3),
114.3 (d, C-3', 3" and 5', 5"), 121.6 (d, C-2', 2" and C-6', 6"), 133.2 (s,
C-1' and 1"), 157.5 (s, C-4', 4"), 166.8 (s, C-2 & 5). MS (MALDI-TOF,
positive ion): m/z 349 [M + Na]+. Anal. Calcd. for C18H18N2O4: C,
66.25; H, 5.56; N, 8.58. Found: C, 65.97; H, 5.83; N, 8.24%.
1,4-Diphenylpiperazine-2,5-dione (1): M.p. 267°C (lit.24 266–
267°C). IR: 1658, 1476, 1459 cm-1. NMR: dH 4.52 (s, 4H, H-3 and
6), 7.31 (m, 4H, H-2', 2" and H-6', 6"), 7.45 (m, 6H, H-3', 3", 4',
4" and 5', 5"); dC 53.6 (t, C-3, 6), 126.1 (d, C-2', 2" and C-6', 6"),
127.6 (d, C-4', 4"), 129.8 (d, C-3', 3" and 5', 5"), 140.9 (s, C-1' and
1"), 164.9 (s, C-2 and 5). MS (MALDI-TOF, positive ion): m/z 267
[M + H]+. Anal. Calcd for C16H14N2O2: C, 72.16; H, 5.30; N, 10.52.
Found: C, 72.37; H, 5.24; N, 10.36%.
1,4-Bis-(5-chloro-2-methoxyphenyl)piperazine-2,5-dione
(2):
M.p. 300–301°C. IR: 1671, 1497, 1464 cm-1. NMR: dH 3.74 (s, 6H,
2"-OMe), 4.32 (s, 4H, H-3 and 6), 6.78 (d, J = 8 Hz, 2H, H-3', 3"),
7.08–7.12 (m, 4H, H-4', 4", and 6', 6"); dC 53.5 (t, C-3, 6), 56.0 (q,
2', 2"-OCH3), 115.6 (d, C-3', 3"), 121.7 (d, C-6', 6"), 125.6 (d, C-4',
4"), 126.4 (s, C-5', 5"), 127.8 (s, C-1', 1"), 152.3 (s, C-2', 2"), 166.9
(s, C-2, 5). MS (MALDI-TOF, positive ion): m/z 418 [M + Na]+.
Anal. Calcd for C18H16Cl2N2O4: C, 54.70; H, 4.08; N, 7.09. Found:
C, 54.46; H, 4.21; N, 7.28%.
1,4-Di-p-tolylpiperazine-2,5-dione (3): M.p. 233–235°C. IR: 1656,
1514, 1467 cm-1. NMR dH 2.3 (s, 6H, 4', 4"-Me), 4.34 (s, 4H, H-3 and
6), 7.10 (d, J = 7.8 Hz, 4H, H-2', 2" and H-6', 6"), 7.38 (d, J = 7.8
Hz, 4H, H-3', 3", and 5', 5"); dC 21.2 (q, p-Me) 53.7 (t, C-3, 6), 126.6
(d, C-2', 2" and C-6', 6"), 128.1 (s, C-4', 4"), 129.8 (d, C-3', 3" and
5', 5"), 140.7 (s, C-1' and 1"), 164.8 (s, C-2 and 5). MS (MALDI-
TOF, positive ion): m/z 295.14 [M + H]+and 317.13 [M + Na]+. Anal.
Calcd for C18H16N2O2: C, 73.45; H, 6.16; N, 9.52. Found: C, 73.74;
H, 6.31; N, 9.23%.
1,4-Bis-(2-chlorophenyl)piperazine-2,5-dione (4): M.p. 134–
136°C. IR: 1694, 1594, 1536, 1445 cm-1. NMR (CDCl3): dH 4.34 (s,
4H, H-3 and 6), 7.09 (t, J = 8 Hz, 2H, H-4', 4"), 7.30 (t, J = 8 Hz,
2H, H-5', 5"), 7.38 (d, J = 7.8 Hz, 2H, H-6', 6"), 8.39 (d, J = 7.8 Hz,
2H, H-3', 3"); dC 71.9 (t, C-3, 6), 122.0 (d, C-6', 6"), 123.6 (s, C-2',
2"), 125.7 (d, C-4', 4"), 128.2 (d, C-3', 3"), 129.5 (d, C-5', 5"), 133.9
1,4-Bis-(3-acetylphenyl)piperazine-2,5-dione (9): M.p. 180–
181°C. IR: 1687, 1657, 1580, 1464 cm-1. NMR (CDCl3): dH 2.63 (s,
3H, –Me), 4.58 (s, 4H, H-3 and 6), 7.54–7.62 (m, 4H, H-5', 5"and 6',
6"), 7.90–7.94 (m, 4H, H-2', 2" and 4', 4"); dC 27.1 (Me), 53.52 (t,
C-3, 6), 124.7 (d, C-2', 2"), 127.8 (d, C-4', 4"), 129.9 (d, C-6', 6"),
130.1 (d, C 5', 5"), 138.7 (s, C-3', 3"), 140.3 (s, C-1', 1"), 164.3 (s, C-
2, 5), 197.3 (s, –C=O). MS (MALDI-TOF, positive ion): m/z 351 [M
+ H]+and 373 [M + Na]+. Anal. Calcd. for C20H18N2O4: C, 68.56; H,
5.18; N, 8.00. Found: C, 68.28; H, 5.39; N, 7.83%.
PAPER: 07/4641

JOURNAL OF CHEMICAL RESEARCH 2007 383
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H, 1.70; N, 5.92. Found: C, 40.19; H, 1.64; N, 6.04%.
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236°C. IR: 1671, 1576, 1523 cm-1. NMR: dH 4.33 (s, 4H, H-3 and 6),
6.99 (d, J = 7.8 Hz, 2H, H-6', 6"), 7.13 (s, J = 7.8 Hz, 2H, H-2', 2"),
7.26 (m, 4H, H-4', 4", and 5', 5"); dC 53.2 (t, C-3, 6), 118.7 (d, C-6',
6"), 120.8 (d, C-2', 2"), 124.6 (d, C-4', 4"), 130.2 (d, C-5', 5"), 134.1
(s, C-3', 3"), 142.0 (s, C-1', 1"), 166.3 (s, C-2, 5). MS (MALDI-TOF,
positive ion): m/z 373 [M + K]+. Anal. Calcd. for C16H12Cl2N2O2: C,
57.33; H, 3.61; N, 8.36. Found: C, 57.14; H, 3.86; N, 8.62%.
1,4-Dicyclohexylpiperazine-2,5-dione (12): M.p. 224–226°C. IR:
1636, 1472, 1450, 1324 cm-1. NMR: dH 1.10–1.75 (m, 20H), 3.79-
3.83 (m, 2H), 4.99 (s, 4H, H-3 and 6); dC 21.9 (t, C-3', 3" and 5', 5"),
27.4 (t, C-4', 4"), 30.2 (t, C-2', 2"and 6', 6"), 46.2 (d, C-1' and 1"),
50.1 (t, C-3, 6), 169.3 (s, C-2, 5); MS (MALDI-TOF, positive ion):
m/z 317 [M + K]+. Anal. Calcd. for C16H26N2O2: C, 69.03; H, 9.41;
N, 11.49. Found: C, 69.29; H, 9.17; N, 11.58%.
4
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We gratefully acknowledge funding from the Department
of Biotechnology, Government of India and Council
of Science & Industrial Research for the award of
ES to N.P. Sahu and fellowships to A. Hazra and P.
Paira. P Palit is thankful to ICMR for his fellowship.
We are also thankful to Dr B. Achari, Emeritus Scientist,
CSIR, for his helpful suggestions and encouragement.
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Received 10 May 2007; accepted 9 July 2007
Paper 07/4641 doi: 10.3184/030823407X228254
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PAPER: 07/4641