Synthesis and screening of galactose-linked nitroimidazoles and triazoles against Mycobacterium tuberculosis

Article abstract of DOI:10.1016/j.ejmech.2011.05.045

A series of galactose-linked nitroimidazoles/triazoles were synthesised and screened against Mycobacterium tuberculosis H₃₇Rv. Preliminary results were promising with MIC values in the range 1.56-12.5 μg/mL. Most importantly they are active und

Full text of DOI:10.1016/j.ejmech.2011.05.045

European Journal of Medicinal Chemistry 46 (2011) 4725e4732
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Preliminary communication
Synthesis and screening of galactose-linked nitroimidazoles and triazoles against
Mycobacterium tuberculosis
G. Mugunthan a, Kuppala Ramakrishna a, Dharmarajan Sriram b, Perumal Yogeeswari b,
,
K.P. Ravindranathan Kartha a
*
a Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research, S.A.S Nagar, Punjab 160062, India
b Medicinal Chemistry Research Laboratory, Pharmacy Group, Birla Institute of Technology and Science, Hyderabad 500078, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of galactose-linked nitroimidazoles/triazoles were synthesised and screened against Mycobac-
terium tuberculosis H37Rv. Preliminary results were promising with MIC values in the range 1.56e12.5 mg/
mL. Most importantly they are active under aerobic condition under which metronidazole is inactive.
Received 3 December 2010
Received in revised form
14 May 2011
Accepted 19 May 2011
Available online 26 May 2011
Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords:
Mycobacterium tuberculosis
Diacetone galactose
Nitroimidazoles
Aerobic inhibition
Anti-tubercular activity
1. Introduction
Sugars are the privileged class of scaffolds in antibacterial drug
discovery [4], in particular D-galactose, that plays an important role
Starting from streptomycin many antimycobacterials are known
and are commercially available, but the biggest problem in the
antimicrobial drug therapy/discovery has come to be the drug
resistance. Mycobaterium tuberculosis (M.tb) has developed to
the stage of being extensively drug resistant (XDR-TB) and is often
so to at least rifampicin and isoniazid from among the first line
anti-TB drugs in addition to being resistant to any of the fluo-
roquinolones, and to one or the other of the three injectable
second-line anti-TB drugs such as capreomycin, kanamicin, and
amikacin used in the treatment of TB [1]. This along with the
alarming fact that an estimated 1.7 million people a year die from
TB (estimated for the year 2009) e equivalent to nearly 4700 deaths
a day [2] underlines the worsened global TB burden currently. Last
decade saw resurgence in the TB drug pipeline, with many prom-
ising candidates at various stages of clinical trials [3], but the
exceedingly high attrition rate associated with any drug develop-
ment effort makes research into new anti-TB drugs a continuing
urgent global health priority.
in the cell wall architecture of mycobacterium, existing in the rare
furanose form in the cell wall arabinogalatan [5,6]. The enzymes
involved in its biosynthesis are unique to pathogenic microbes and
hence potential targets for chemotherapy. In the past many galac-
tose derivatives were synthesized and screened against M.tb some
of which proving to be promising. Tripathi and coworkers have
reported a series sugar-derived aminoalcohols [7e9] active against
the mycobacterium.
Likewise, de Almedia and coworkers reported a series of gal-
actopyranosyl diamines and amino alcohols active against M.tb
[10,11]. The striking commonality among all of the potent mole-
cules in these reports is the presence of a diacetone galactose
moiety. Representative galactopyranosyl amino alcohols active
against mycobacteria are shown in Fig. 1.
Metronidazole (Fig. 2) a synthetic analog of the naturally
occurring azomycin was originally developed against parasitic
infection. In 1962, the antibacterial activity of metronidazole was
discovered by chance when it cured a patient with both tricho-
monad vaginitis and bacterial gingivitis [12]. Eventually metroni-
dazole was found to be effective against gram-positive and
gram-negative anaerobes. However while it was found to be
bactericidal against M.tb under anaerobic condition [13] it was
proven inactive under aerobic condition [13,14] during in vitro
* Corresponding author. Tel.: þ91 172 2214682 86; fax: þ91 172 2214692.
E-mail address: rkartha@niper.ac.in (K.P. Ravindranathan Kartha).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.05.045

4726
G. Mugunthan et al. / European Journal of Medicinal Chemistry 46 (2011) 4725e4732
H
N
H
N
O
10
7
15
HO
HO
HO
HO
N
NH
N
O
NH
10
7
O
O
O
O
O
O
O
O
O
O
O
HO
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
4
2
3
1
Fig. 1. Representative di-O-isopropylidene-D-galactopyranose-linked aminoalcohols active against mycobacterium.
studies. In vivo studies of metronidazole against mycobacterium in
mouse model was not promising [15]. However owing to the
difference in the pathophysiology of rodents and humans there are
hopes that metronidazole may have unique activity against an
anaerobic sub-population of the bacilli in humans. Dormant pop-
ulation under the anaerobic condition is the possible reason for
prolonged duration of TB treatment. With the aim of evaluating the
possible use of metronidazole as a second-line drug in combination
with other drugs, phase II clinical trial was initiated against
pulmonary tuberculosis in South Korea [16]. Apart from this other
bicyclic nitroimidazole derivatives PA-824 and OPC-67683 (Fig. 2)
are in different stages of clinical trials which are active against both
active and dormant mycobacteria [3].
shifts. The two possible ways of looking at this nucleophilic reaction
have been depicted in Scheme 1 (Path A and Path B). In Path A the
conjugate base (5a) of the alcohol 5 formed by the abstraction of
the alcoholic proton in 5 reacts at C-3 of the ECH moiety. The
ꢀ
epoxide ring-opening followed by the expulsion of the Cl anion
from C-1 leads to the formation of the epoxypropyl ether 6. Alter-
natively, as shown in Path B (Scheme 1), product 6 can also result
from a direct nucleophilic attack of the anion 5a at C-1 of the ECH
ꢀ
moiety and the subsequent displacement of the Cl anion present on
the carbon atom. In an attempt to obtain a possible clarification on
this, the alcohol 5 was treated with enantiomerically pure ECH [(R-)
and (S-)] in separate experiments and the resulting products were
analyzed. It was found that in both experiments the product 6
obtained was again in the form of mixture of diasteriomers.
This observation can be explained only if the reaction is
considered to occur in the following manner. Reaction of 5a at C1 of
the ECH moiety by an SN2 mechanism results in the direct
displacement of the chloride anion as depicted in Fig. 3, Path A
leaving the configuration of the epoxide 6a unaffected. On the other
hand, an attack of 5a at the C3 of the ECH moiety from the side
opposite to the oxirane bridge, again in an SN2 fashion, leads to the
opening of the epoxide ring. The ring-opening can concomitantly
give rise to the epoxypropyl ether 6b directly with the epoxide
bridge having migrated from C3-C2 to C2-C1 of the ECH residue, as
depicted in Path B, Fig. 3; and 6b formed now has a configuration
different from the ether formed by Path A (Fig. 3). Alternatively, the
oxirane ring-opening and the chloride displacement can also be
considered to take place in discrete steps in which case the oxy
anion 6c is formed as an intermediate resulting from the backside
attack of 5a on C3 of the ECH molecule (Path C, Fig. 3). The
subsequent epoxide ring-closure and the consequent chloride
displacement result in the formation of the product 6b (Path C,
Fig. 3) of the same configuration as obtained following Path B
(Fig. 3). Thus the product obtained in the form of a diastereomeric
mixture on reaction of 5a with both (R)- and (S)-ECH shows clearly
that it operates equally by Path A and Path B/C. Complete inversion
of stereochemistry has been demonstrated in the epoxide ring-
opening reaction of enatiomerically pure ECH with 1-naphthol
under milder condition [20].
Incorporation of cell wall constituent sugars to the bioactive
molecules was shown to increase the efficacy against the M.tb. For
example N-D
-arbinofuranosyl-N0-[p-(isoamyloxy)phenyl]-thiourea
was found to be more active than the parent molecule N, N0-bis[p-
(isoamyloxy)phenyl]-thiourea (THC), which is already known for the
antimycobacterial activity. Interestingly out of the different sugars
used, D-arabinofuranose, a cell wall constituent of the mycobacte-
rium, gave most promising results [17,18]. As a part of our ongoing
work on bioactive carbohydrate derivatives we planned to study the
synergistic effect of incorporating the nitroimidazole moiety into
derivatives of galactose, another important sugar constituent of the
cell wall of M.tb. Two different classes of galactose-linked nitro-
imidazoles were synthesized and were screened for activity against
M.tb; and the results are presented below.
2. Chemistry
The synthesis of the two different sets of molecules was carried
out starting from the known common starting material, namely,
1,2:3,4-di-O-isopropylidene-a-D-galactopyranose (5) [19]. When
compound 5 was treated with racemic epichlorohydrin (ECH) in the
presence of NaH in anhydrous DMF crystalline 6-O-(2,3-
epoxypropyl)-1,2:3,4-di-O-isopropylidene-a-D-galactopyranose (6)
was obtained as a diastereomeric mixture (Scheme 1) in 85% of
isolated yield. The 1H NMR spectrum of the epoxypropyl ether 6
had two doublets of equal integrals at
d 5.54 and 5.53 with
The diastereomeric mixture of 6 was subjected to epoxide ring
opening at the less substituted end with different nitroimidazoles
and triazoles in the presence of sodium hydride in anhydrous
dimethylformamide to get the alcohols 7aef in good yields
(Scheme 1). With a view to finding the effect of lipophilicity of the
molecules on their activity compounds 7aef were further deriva-
tised by protecting the secondary hydroxyl group on the exocyclic
propyl residue of the respective compound as the corresponding
palmitoyl esters 8aef on the one hand and as the corresponding
trifluoromethoxy benzyl ethers 9aed on the other (Scheme 2).
Another set of molecules 11aef in which the nitroimidazolyl
residue was attached directly to the C-6 of the galactopyranose
moiety was also prepared for evaluation of the antimycobacterial
J ¼ 5.0 Hz corresponding to the R-/S-isomers. Other proton signals
were also likewise observed in pairs at the expected chemical
O2N
O2N
N
N
N
O
N
N
O
O2N
N
OH
Metronidazole
OCF3
N
OCF3
PA-824
OPC-67683
O
Fig. 2. Nitroimidazole derivatives active against mycobacterium.

G. Mugunthan et al. / European Journal of Medicinal Chemistry 46 (2011) 4725e4732
4727
O
N
N
N
O
Ar =
O
O
Cl
h
Na
N
N
N
O
NO2
NO2
O
NO2
P
7a
a
7b
7c
t
5a
B
O
NaCl
Ar
H2
O
OH
O
O
O
O
O
O
O
O
O
O
O
HO
O
a
b
O
O
O
O
6
O
5
NaCl
A
H2
7a-f
NaH
Cl
h
t
a
P
N
N
N
NO2
O
O2N
N
O
Ar =
O
N
N
O
O
N
Na
NO2
O
7e
7d
7f
O
5a
Reagents and conditions: (a) NaH, ECH, DMF, 0 °C to 60 °C, 12 h, 85%; (b) nitroimidazole/triazole, NaH,
DMF, 0 °C to 80 °C, 12 h.
Scheme 1. Synthesis of galactose-linked nitroimidazoles and triazoles.
activity. The synthesis was accomplished in the following manner.
The diacetonide 5 was first converted to its known 6-deoxy-6-iodo-
derivative 10 [21] by refluxing it (5) with iodine and triphenyl-
phosphine in the presence of imidazole in anhydrous toluene. The
iodo- derivative 10 was then subjected to a displacement reaction
with different nitroimidazoles/triazoles as desired to get 11a-f in
very good yields (Scheme 3).
positive controls (along with rifampicin and isoniazid, entries 23 &
24 respectively, Table 1). Compounds 8b, 8c, 8f, 9a, 9b, 9d and 11c
also showed very good efficacy with an MIC value of 3.13 mg/mL
(Table 1). The hydroxyl group in compounds 7a, 7c and 7d was
found to be of importance for the activity as evident from the fact
that its protection either as the palmitoyl ester (8a, 8c and 8d
respectively) or the trifluoromethoxybenzyl ether (9a, 9d and 9e
respectively) led to a decrease in the activity despite the increased
lipophilicity of the molecule (Table 1). However, in the case of
compound 7b, its derivatization to the corresponding palmitoyl
ester 8b as well as as 4-(trifluoromethoxy)benzyl ether 9b led to an
enhancement in the activity with the MIC value having improved to
3. Biological screening
All the newly synthesized compounds were subjected to in vitro
antimycobacterial studies against M. tuberculosis H37Rv (ATCC
27294) using agar dilution method along with three standard first-
line drugs, namely, isoniazid, rifampicin and ethambutol as positive
control and the results have been summarised in Table 1.
3.13
mg/mL for 8b and 9b (entries 7 & 13, Table 1) from an initial
value in excess of 12.5
mg/mL (entry 2, Table 1). In general, the
nitroimidazole derivatives seemed to perform better than the tri-
azolyl derivatives (entries 5, 10, 15 & 20, Table 1). Likewise,
compounds in which the sugar moiety is attached to the hetero-
cycle via the three-carbon spacer group (compounds 7a, c and d)
performed more effectively than those formed (compounds 11a, c
and d) through direct linkage. This also possibly points towards the
role of a hydroxyl group-containing linker in imparting activity to
a molecule.
As the compounds evaluated in this study have been as mixtures
of their enantiomers, efforts are currently underway towards the
synthesis of optically pure R- and S- isomers along with their
detailed biological studies including cytotoxicity.
4. Results and discussion
Preliminary screening of the molecules against the drug resis-
tant strain H37RV gave promising results with MIC in the range
1.56e12.5
metronidazole as such under aerobic condition. Compounds 7a, 7c
and 7d were proved to be the best with an MIC value of 1.56 g/mL
mg/mL; all the compounds tested were more active than
m
(entries 1,3 & 4 respectively, Table 1) equal to that obtained for
ethambutol (entry 22, Table 1) which was used as one of the
Cl
Cl
1
1
H
5. Conclusion
2
3
1
1
2
RO
3
H
Path A
3
1
2
3
Path B
NaCl
B
2
H
O
(S)-
A
O
O
Synergy in the effectiveness of nitroimidazoles as antimyco-
bacterial agents was observed, as expected, when the heterocycles
were linked to the carbohydrate moiety, namely, D-galactose via
O
H
6b
[(R)-6]
OR
6a
[(S)-6]
O Na
5a
R
O Na
NaCl
R
5a
Cl
1
H
3
a n-propyl linker. Promising results show that simple sugar-derived
nitroimidazoles can serve as active antituberculosis agents under
aerobic condition unlike metronidazole that is active only under
anaerobic condition. The work is being extended to find structural
analogs of some of the molecules reported here with a view to
achieve improvements in their antitubercular activity.
2
Cl
H2C
O
O
O
O
1
C
2
3
Path C
O
R
=
H
3
O
O
2
H 6b
[(R)- ]
OR
OR
O
O Na
5a
R
6c
6
NaCl
Fig. 3. Possible modes of reaction of 5a with ECH.

4728
G. Mugunthan et al. / European Journal of Medicinal Chemistry 46 (2011) 4725e4732
O2N
O2N
O2N
OCF3
N
N
N
O
X
X
N
X
N
N
14
O
O
O
O
OH
O
a
b
O
O
O
O
O
O
O
O
O
O
O
O
O
O
9 a- d
8 a-f
7 a-f
O
Reagents and conditions: (a) Dry DCM, pyridine, palmitoyl chloride, 0 °C to RT, 8 h; (b) NaH,
4-(trifluoromethoxy)benzyl bromide, DMF, 0 °C to RT, 5 h.
Scheme 2. Derivatisation of galactose-linked nitroimidazoles and triazoles.
6. Experimental section
Yield 85%; mp 67.0e68.5 ꢀC; [
(400 MHz, CDCl3)
a
]
ꢁ77 (c 1, CHCl3); 1H NMR
D
d
5.54, 5.53 (2xd, J ¼ 5Hz, 1H, H-1, R-, S-), 4.61,
6.1. General
4.59 (2xdd, J1 ¼7.8 Hz, J2 ¼ 2.4 Hz 1H, H-3, R-, S-), 4.31 (dd, J1 ¼5 Hz,
J2 ¼ 2.4 Hz, 1H, H-2, R-, S-), 4.26, 4.24 (2xdd, J1 ¼ 7.8 Hz, J2 ¼ 1.9 Hz,
1H, H-4, R-, S-), 4.01e3.97 (m, 1H, H-5, R-, S-), 3.84e3.62 (m, 3H, H-
6a, b and H-10a, R-, S-), 3.50, 3.43 (2xdd, J1 ¼11.6, J2 ¼ 5.6, H-10b, R-,
S-), 3.20e3.15 (m, 1H, H-20 R-, S-), 2.79 (pt, J ¼ 4.7, J ¼ 4.4, 1H, H-30a,
R-, S-), 2.63, 2.60 (2xdd, J1 ¼ 5 Hz, J2 ¼ 2.6 Hz, 1H, H-30b R-, S-), 1.54,
1.44 (2s, 2x3H, eC(CH3)2, R-, S-), 1.33 (s, 6H, eC(CH3)2, R-, S-); 13C
All reagents and chemicals were purchased from SigmaeAldrich
and were used without further purification. TLC experiments were
performed on 0.2 mm Merck pre-coated silica gel 60 F254
aluminium sheets and the spots were visualized under a UV lamp
and (or) by dipping in an ethanolic solution of sulphuric acid (5%, v/
v) followed by heating. Final purifications were performed on
column of silica gel 200e400 mesh. Melting points were deter-
mined on a Büchi melting point (B-540) apparatus and are uncor-
rected. Specific rotations were recorded on a Rudolph Autopol IV
Polarimeter at 20e22 ꢀC. NMR spectra were recorded on Bruker
Avance DPX (400 MHz) spectrometer. 1H NMR and 13C NMR spectra
were referenced to the internal standard, tetramethylsilane, in the
respective deuterated solvents. Coupling constants (J) are reported
in Hertz. Abbreviations used in reporting the 1H NMR data are:
s-singlet, d-doublet, dd-double doublet, pt-pseudo triplet and
m-multiplet. Mass spectra were recorded on MALDI (Bruker
Daltonics, Ultraflex TOF/TOF) spectrometer.
NMR (100 MHz, CDCl3)
d 109.22, 108.53, 96.34, 72.25, 71.84,
2x71.15, 2x70.64, 2x70.58, 70.23, 70.06, 67.02, 66.69, 50.8, 50.7,
44.42, 44.3, 2x26.03, 2x25.94, 2x24.91, 2x24.42 (R-, S-); IR (Neat)
nmax 2988, 2930, 1382, 1255, 1211, 1169, 1105, 1069, 1004 cmꢁ1
;
MALDI-TOF MS: m/z calculated for C15H24O7: 316.347. Found:
339.407 [M þ Na]þ, 357.419 [M þ K]þ
.
6.3. General procedure for the synthesis of compounds 7aef
To a suspension of the nitromidazoles/nitrotriazole (2.5 mmol)
in anhydrous DMF (5 mL) maintained over an ice-bath, NaH (60%
suspension in mineral oil, 1 mol equiv) was added and the mixture
was stirred. After 15 min 6-O-(2,3-epoxypropyl)-1:2,3:4-di-O-iso-
6.2. Synthesis of 6-O-(2,3-epoxypropyl)-1,2:3,4-di-O-isopropylidene-
propylidene-a-D-galactopyranose (6, 1 mmol) was added and the
a
-
D
-galactopyranose (6)
stirring was continued. After the completion of the reaction, a few
drops of methanol were added. The solvent was evaporated off
under reduced pressure and the crude product was purified by
column chromatography (except in the case of compound 7f which
was directly converted to 8f, the corresponding palmitoyl ester.
To a solution of 5 (5 g, 20 mmol) in anhydrous DMF (50 mL)
maintained over an ice-bath was added NaH (1.5 g, 60% suspension
in mineral oil) with stirring. After 15 min, epichlorohydrin (15 mL,
50 mol equiv) was added and the mixture was stirred at 80 ꢀC
overnight (16 h). After the completion of the reaction a few drops of
methanol were added and the solvent was evaporated off under
reduced pressure. The crude product was taken up in CH2Cl2
(200 mL) and was washed successively with water and brine. The
organic layer was then dried over anhydrous sodium sulfate and
was concentrated under reduced pressure. The crude product was
purified by column chromatography to get pure 6 (5.15 g) as
a colorless solid.
6.3.1. 6-O-[2-Hydroxy-3-(4-nitroimidazolyl)propyl]-1,2:3,4-di-O-
isopropylidene-a-D-galactopyranose (7a)
To a suspension of 4-nitromidazole (0.28 g, 2.5 mmol) in
anhydrous DMF (5 mL) maintained over an ice-bath, NaH (60%
suspension in mineral oil, 1 mol equiv) was added and was stirred.
After 15 min 6-O-(2,3-epoxypropyl)-1:2,3:4-di-O-isopropylidene-
a-D-galactopyranose (6, 0.32 g, 1 mmol) was added and the stirring
was continued. After the completion of the reaction, a few drops of
O2N
N
X
I
N
O
O
O
O
O
O
a
b
O
O
O
O
O
HO
O
O
O
O
11 a-f
5
10
Reagents and conditions: (a) Iodine, PPh, imidazole, dry toluene, reflux, 4h; (b) NaH, nitroimidazole/ triazoles,
3
DMF, 0 °C to 80 °C, 12 h.
Scheme 3. Synthesis of C-6-linked nitroimidazoles and triazoles by direct displacement reaction.

G. Mugunthan et al. / European Journal of Medicinal Chemistry 46 (2011) 4725e4732
4729
Table 1
Results of in vitro assay of compounds synthesized against M.tb H37Rv.
6.3.3. 6-O-[2-Hydroxy-3-(5-methyl-4-nitroimidazolyl)propyl]-1,2:3,
4-di-O-isopropylidene- -galactopyranose (7c)
Yield 75%; Thick syrup; 1H NMR (400 MHz, CDCl3)
a-D
d
7.48, (s, 1H,
Entry
Molecule
MIC (
1.56
mg/mL)
ArH, R-, S-), 5.55 (pt, J ¼ 5 Hz, 1H, H-1, R-, S-), 4.64, 4.61 (2xpt,
J ¼ 2.36, 1H, H-3, R-, S-), 4.35e4.33 (m, 1H, H-2, R-, S-), 4.23e4.20
(2xdd, J ¼ 2 Hz, J ¼ 2.8 Hz, 1H, H-4, R-, S-), 4.08e4.00 (m, 3H, H-30a,
b, R-, S- and H-20, R-, S-), 3.99e3.97 (m, 1H, H-5, R-, S-), 3.80e3.66
(m, 3H, H-6a, b, R-, S- and eOH, R-, S-), 3.59e3.52 (m, 2H, H-10, R-, S-
) 2.61 (s, 3H, Ar-CH3, R-, S-), 1.53, 1.45 (2xs, 2x3H, eC(CH3)2, R-, S-),
1
7a
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
7b
7c
7d
7e
8a
8b
8c
8d
8e
8f
9a
9b
9d
9e
11a
11b
11c
11d
11e
11f
Ethambutol
Isoniazid
Rifampicin
>12.5
1.56
1.56
12.5
>12.5
3.13
3.13
6.25
6.25
3.13
3.13
3.13
3.13
6.25
>12.5
>12.5
3.13
6.25
12.5
12.5
1.56
0.05
0.10
1.33 (s, 6H, eC(CH3)2, R-, S-); 13C NMR (100 MHz, CDCl3)
d 144.3,
135.7, 131.0, 130.94 (Ar-C, R-, S-), 2x109.5, 2x108.8 (2x-C2-C-C2-, R-,
S-), 96.28 (C-1, R-, S-), 72.42, 72.03, 71.17, 71.11, 71.07, 70.64, 70.61,
70.51, 70.42, 70.35, 69.07, 68.59, 67.39, 66.86 (C-2,3,4,5,6,10 and 20,
R-, S-), 48.61, 48.55 (C-30, R-, S-) 26.02, 25.96, 24.86, 24.44, 24.41
(4x-CH3, R-, S-), 10.37 (Ar-CH3, R-, S-); IR (Neat) nmax 3363, 2986,
2931, 1573, 1499, 1378, 1350, 1268, 1255, 1169, 1108, 1070,
1004 cmꢁ1
; MALDI-TOF MS: m/z calculated for C19H29N3O9:
443.448. Found: 466.601 [M þ Na]þ, 482.610 [M þ K]þ
.
6.3.4. 6-O-[2-Hydroxy-3-(2-nitroimidazolyl)propyl]-1,2:3,4-di-O-
isopropylidene- -galactopyranose (7d)
Yield 60%; Thick syrup; 1H NMR (400 MHz, CDCl3)
a-D
d
7.29, 7.26
(2xd, J ¼ 1 Hz, 1H, ArH, R-, S-), 7.12 (pt, J1 ¼ 1.3 Hz, J2 ¼ 1.1 Hz, 1H,
ArH, R-, S-), 5.55, 5.54 (2xd, J ¼ 5 Hz, 1H, H-1, R-, S-), 4.68e4.60
(m, 2H, H-3R, S-and H-30a, R-, S-), 4.48e4.38 (m, 1H, H-30b, R-, S-),
4.35e4.33 (m, 1H, H-2, R-, S-), 4.24e4.20 (m, 1H, H-4, R-, S-),
4.16e4.08 (m, 1H, H-20, R-, S-), 4.00e4.39 (m, 1H, H-5, R-,
S-), 3.78e3.53 (m, 5H, H-6a, b, R-, S-, H-10a, bR, S-and eOH, R-, S-),
1.54, 1.44 (2xs, 2x3H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-);
MIC e Minimum concentration required for complete inhibition.
methanol were added. The solvent was evaporated off under
reduced pressure and the crude product was purified by column
chromatography.
Yield 74%; 1H NMR (400 MHz, CDCl3)
d
7.91 (d, J ¼ 1.5 Hz 1H, ArH,
13C NMR (100 MHz, CDCl3)
d 127.9, 127.5, 127.3 (Ar-C, R-,
R-, S-), 7.52 (pt, J1 ¼ 1.6, J2 ¼ 1.8, 1H, ArH, R-, S-), 5.57, 5.55 (2xd,
J ¼ 5 Hz, 1H, H-1, R-, S-), 4.63, 4.62 (2xpt, J1 ¼ 2.3 Hz, J2 ¼ 2.4 Hz, 1H,
H-3, R-, S-), 4.36e4.33 (m, 1H, H-2), 4.24e4.20 (m, J ¼ 1.9 Hz, 1H, H-
4, R-, S-), 4.18e4.05 (m, 3H, H-30a, b, R-, S- and H-20, R-, S-),
4.00e4.96 (m, J ¼ 1.9 Hz, 1H, H-5, R-, S-), 3.78e3.62 (m, 3H, H-6a, b,
R-, S- and eOH, R-, S-), 3.57e3.47 (m, 2H, H-10, R-, S-) 1.54, 1.46 (2xs,
2x3H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-); 13C NMR
S-), 2x109.5, 2x108.9 (2x-C(CH3)2, R-, S-), 96.26 (C-1, R-, S-), 72.70,
72.23, 71.14, 70.63, 70.48, 70.43, 70.38, 69.51, 69.15, 67.48, 66.70 (C-
2,3,4,5,6,10 and 20, R-, S-), 52.23, 52.11 (C-30, R-, S-) 26.02, 26.00,
25.94, 24.88, 24.46, 24.40 (4x-CH3, R-, S-); IR (Neat) nmax 3388,
2986, 2933, 1666, 1540, 1489, 1366, 1256, 1212, 1167, 1107, 1069,
1004 cmꢁ1
; MALDI-TOF MS: m/z calculated for C18H27N3O9:
429.422. Found: 452.392 [M þ Na]þ, 469.314 [M þ K]þ
(100 MHz, CDCl3)
d 147.9, 136.8 (Ar-C, R-, S-), 120.4 (ArC-2, R-, S-),
.
2x109.6, 2x108.9 (2x-C(CH3)2, R-, S-), 96.28 (C-1, R-, S-), 72.17, 71. 68
(C-10, R-, S-), 7.13 (C-4, R-, S- and C-6, -R/-S), 70.65 (C-3, R-, S-), 70.44
(C-2, -R/-S and C-6, -R/-S), 70.37 (C-2, -R/-S), 69.41, 68.83 (C-20, R-, S-
), 67.46, 66.87 (C-5, R-, S-) 50.68, 50.57 (C-30, R-, S-) 26.00, 25.93,
24.85, 24.46, 24.42 (4x-CH3, R-, S-); IR (Neat) nmax 3383, 2972, 2930,
1544, 1492, 1379, 1337, 1214, 1108, 1069, 1003 cm-1; MALDI-TOF
MS: m/z calculated for C18H27N3O9: 429.422. Found: 452.603
[M þ Na]þ, 468.600 [M þ K]þ.
6.3.5. 6-O-[2-Hydroxy-3-(3-nitro-1,2,4-triazolyl)propyl]-1,2:3,4-di-
O-isopropylidene- -galactopyranose (7e)
a-D
Yield 60%; Thick syrup; 1H NMR (400 MHz, CDCl3) 8.37, 8.36
(2xs, 1H, Ar-HR, S), 5.56, 5.53 (2xd, J ¼ 5 Hz, 1H, H-1, R-, S-),
4.63e4.61 (dd, J1 ¼ 2.4, J2 ¼ 7.8,1H, H-3, R-, S-), 4.46e4.31 (m, 3H, H-
30a, b, R-, S- and H-2, R-, S-), 4.26e4.15 (m, 2H, H-4, R-, S-and H-20, R-
, S-), 4.01e3.96 (m, 1H, H-5, R-, S-), 3.79e3.60 (m, 4H, H-6a, b, R-, S-,
eOH, R-, S- and H-10a, R-, S-), 3.57e3.49 (m, 1H, H-10b, R-, S-), 1.54,
6.3.2. 6-O-[2-Hydroxy-3-(2-methyl-4-nitroimidazolyl)propyl]-1,2:3,
1.44 (2xs, 2x3H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-); 13
NMR (100 MHz, CDCl3) 162.56, 146.3, 146.2 (Ar-C, R-, S-), 2x109.5,
C
4-di-O-isopropylidene-
a-D-galactopyranose (7b)
d
Yield 68%; Thick syrup; 1H NMR (400 MHz, CDCl3)
d
7.86, 7.85
2x108.9 (2x-C(CH3)2, R-, S-), 96.26 (C-1, R-, S-), 72.55, 71.95, 71.31,
71.16, 71.09, 70.65, 70.60, 70.45, 70.34, 68.80, 68.27, 67.61, 66.98 (C-
2,3,4,5,6,10 and 20, R-, S-), 53.78, 53.77 (C-30, R-, S-) 25.98, 25.92,
24.85, 24.82, 24.43, 24.38 (4x-CH3, R-, S-); IR (Neat) nmax 3422, 2987,
(2xs, 1H, ArH, R-, S-), 7.52 (pt, J1 ¼1.6 Hz, J2 ¼ 1.8 Hz, 1H, ArH, R-, S-),
5.57, 5.55 (2xd, J ¼ 4.8 Hz, 1H, H-1, R-, S-), 4.64, 4.62 (2xpt, J1 ¼ 2.2,
J2 ¼ 2.3, 1H, H-3, R-, S-), 4.36e4.33 (2xdd, J1 ¼ 2.4 Hz, J2 ¼ 5 Hz, 1H,
H-2, R-, S-), 4.23e4.20 (2xdd, J1 ¼ 2 Hz, J2 ¼ 2.8 Hz, 1H, H-4, R-, S-),
4.09e3.94 (m, 4H, H-30a, b, R-, S-, H-20, R-, S- and H-5, R-, S-),
3.80e3.65 (m, 3H, H-6a, b, R-, S- and eOH, R-, S-), 3.59e3.50 (m, 2H,
H-10, R-, S-) 2.44 (s, 3H, Ar-CH3, R-, S-), 1.53, 1.45 (2xs, 2x3H,
eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-); 13C NMR (100 MHz,
2932, 1635, 1555, 1414, 1380, 1256, 1212, 1170, 1070, 1004 cmꢁ1
;
MALDI-TOF MS: m/z calculated for C17H26N4O9: 430.410. Found:
453.580 [M þ Na]þ, 469.604 [M þ K]þ
.
CDCl3)
d
145.3, 120.8 (Ar-C, R-, S-), 2x109.6, 2x108.8 (2x-C(CH3)2, R-,
6.4. General procedure for the synthesis of compounds 8aee
S-), 96.29 (C-1, R-, S-), 72.32, 71.93, 71.18, 71.12, 70.68, 70.54, 70.44,
70.36, 69.63, 69.16, 67.46, 66.87 (C-2,3,4,5,6,10 and 20, R-, S-), 49.38,
49.28 (C-30, R-, S-) 26.00, 25.93, 24.85, 24.46, 24.42 (4x-CH3, R-, S-),
13.1 (Ar-CH3, R-, S-); IR (Neat) nmax 3316, 2986, 2932, 1542, 1505,
1458, 1380, 1294, 1255, 1169, 1109, 1070, 1004 cmꢁ1; MALDI-TOF
MS: m/z calculated for C19H29N3O9: 443.448. Found: 466.659
To a solution of alcohol 7aee, (1 mmol) in pyridine-CH2Cl2 (1:1,
10 mL) maintained over an ice-bath was added slowly palmitoyl
chloride, (2 mmol) and the mixture was stirred at room tempera-
ture for 8 h. After the completion of the reaction, the solvent was
evaporated off under reduced pressure. The crude product was
subjected to chromatographic purification to get pure compound.
[M þ Na]þ, 482.642 [M þ K]þ
.

4730
G. Mugunthan et al. / European Journal of Medicinal Chemistry 46 (2011) 4725e4732
6.4.1. Synthesis of 1,2:3,4-di-O-isopropylidene-6-O-[3-(4-nitroimid-
azolyl)-2-palmitoyloxypropyl]- -galactopyranose (8a)
Yield 82%; Syrup; 1H NMR (400 MHz, CDCl3)
7.95, 7.93 (2xd,
6.4.4. 1,2:3,4-Di-O-isopropylidene-6-O-[3-(2-nitroimidazolyl)-2-
palmitoyloxypropyl]- -galactopyranose (8d)
Yield 86%; Thick oil; 1H NMR (400 MHz, CDCl3)
d 7.26, 7.11 (2xs,
a
-D
a-D
d
J ¼ 1.5 Hz, 1H, ArH, R-, S-), 7.53, 7.51 (2xd, J ¼ 1.5 Hz, 1H, ArH, R-, S-),
5.61, 5.58 (2xd, J ¼ 5 Hz, 1H, H-1, R-, S-), 5.23e5.16 (m, 1H, H-20, R-,
S-), 4.64, 4.62 (pt, J1 ¼ 2.5 Hz, J2 ¼ 2.6 Hz, 1H, H-3, R-, S-), 4.37e4.31
(m, 3H, H-30a, b, R-, S- and H-2, R-, S-), 4.25e4.21 (2xdd, J1 ¼1.9 Hz,
J2 ¼ 4.8 Hz, 1H, H-4, R-, S-), 4.00e3.96 (m, 1H, H-5, R-, S-), 3.74e3.69
(m,1H, H-6a, R-, S-), 3.62e3.56 (m, 2H, H-6b, R-, S- and H-10a, R-, S-),
3.32e3.26 (m, 1H, H-10b, R-, S-), 2.32 (t, J ¼ 7.5 Hz, 2H, eCOCH2-, R-,
S-), 1.61, 1.25 (2xbr s, 26H, eCH2-, R-, S-), 1.54, 1.48 (2xs, 2x3H,
eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-), 0.87 (t, J ¼ 6.8 Hz, 3H,
2H, ArH, R-, S-), 5.56, 5.55 (2xd, J ¼ 5 Hz, 1H, H-1, R-, S-), 5.35e5.30
(m, 1H, H-20, R-, S-), 5.00e4.92 (m, 1H, H-30a, R-, S-), 4.65e4.51 (m,
2H, H-3, R-, S- and H-30b, R-, S-), 4.35 (dd, J1 ¼ 2.4 Hz, J2 ¼ 5 Hz, 1H,
H-2, R-, S-) 4.25e4.22 (m, 1H, H-4, R-, S-), 4.01e3.97 (m, 1H, H-5, R-,
S-), 3.73e3.59 (m, 3H, H-6a, R-, S- and H-10a, R-, S-), 3.50e3.44 (m,
1H, H-10b, R-, S-), 2.23 (t, J ¼ 7.5 Hz, 2H, eCOCH2-, R-, S-), 1.56, 1.26
(2x br s, 26H, eCH2-, R-, S-), 1.54, 1.48 (2xs, 2x3H, eC(CH3)2, R-, S-),
1.34 (s, 6H, eC(CH3)2, R-, S-), 0.88 (t, J ¼ 6.6 Hz, 3H, eCH3); 13C NMR
(100 MHz, CDCl3) d 172.55 (eCOe, R-, S-),128.04, 127.05, 126.93 (Ar-
eCH3); 13C NMR (100 MHz, CDCl3)
d
172.57 (eCOe, R-, S-), 137.13,
C, R-, S-), 109.46, 108.69, 96.34 (C-1, R-, S-), 71.15, 70.69, 70.54, 70.47,
70.43, 69.86, 69.77, 68.70, 66.87, 66.83, 49.35,49.18, 33.91, 31.91,
29.68, 29.64, 29.59, 29.43, 29.35, 29.20, 29.02, 26.05, 25.97, 24.90,
24.64, 24.44, 22.68, 14.11, (R-, S-); IR (Neat) nmax, 2925, 2849, 1743,
1556, 1504, 1378, 1307, 1285, 1210, 1171, 1071, 1005 cmꢁ1; MALDI-
TOF MS: m/z calculated for C33H57N4O10: 667.830. Found: 700.871
[M þ Na]þ 707.801 [M þ K]þ
120.56, 120.51 (Ar-C, R-, S-), 2x109.5, 2x108.9, 96.35 (C-1, R-, S-),
71.17, 71.06, 70.72, 70.70, 70.68, 70.42, 70.39, 70.39 (C-2,3 and 6, R-,
S-), 69.71, 69.37 (C-20, R-, S-), 67.61, 67. 44 (C-10, R-, S-), 67.04, 66.87
(C-5, R-, S-), 47.68 (C-30, R-, S-), 34.12, 31.91, 29.68, 29.65, 26.62,
29.58, 29.42, 29.35, 29.19, 29.05, 24.79, 22.68 (eCH2- palmitoyl),
26.02, 25.96, 25.94, 24.86, 24.49 (4x-CH3, R-, S-), 14.11 (eCH3, pal-
mitoyl); IR (Neat) nmax, 2925, 2849, 1742, 1545, 1378, 1289, 1212,
,
.
1170, 1070, 1004 cmꢁ1
;
MALDI-TOF MS: m/z calculated for
6.4.5. 1,2:3,4-Di-O-isopropylidene-6-O-[3-(3-nitro-1,2,4-triazolyl)-
2-palmitoyloxypropyl]- -galactopyranose (8e)
Yield 86%; Thick oil; 1H NMR (400 MHz, CDCl3)
C34H57N3O10: 667.830. Found: 690.910 [M þ Na] þ
a-D
.
d
8.42, 8.41 (2xs,
6.4.2. 1,2:3,4-di-O-isopropylidene-6-O-[3-(2-methyl-4-nitroimidazolyl)-
2-palmitoyloxypropyl]- -galactopyranose (8b)
Yield 78%; Thick oil; 1H NMR (400 MHz, CDCl3)
1H, ArH, R-, S-), 5.57 (d, J ¼ 5Hz, 1H, H-1, R-, S-), 5.35e5.30 (m, 1H,
H-20, R-, S-), 4.68e4.53 (m, 3H, H-3, R-, S- and H-30a, b R-, S-), 4.35
(dd, 1H, J1 ¼ 2.4 Hz, J2 ¼ 5 Hz, 1H, H-2, R-, S-) 4.23, 4.21 (2xpt,
J ¼ 1.9 Hz, J ¼ 2 Hz, 1H, H-4, R-, S-), 4.00e3.98 (m, 1H, H-5, R-, S-),
3.76e3.48 (m, 4H, H-6a, b, R-, S- and H-10a, b, R-, S-), 2.32 (t,
J ¼ 7.5 Hz, 2H, eCOCH2-, R-, S-), 1.59, 1.26 (2xbr s, 26H, eCH2-, R-, S-
), 1.54, 1.48 (2xs, 2x3H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-
a-D
d
7.91, 7.90 (2xs,
1H, ArH, R-, S-), 5.59, 5.58 (2xd, J ¼ 5 Hz, 1H, H-1, R-, S-), 5.21e5.11
(m, 1H, H-20, R-, S-), 4.65, 4.63 (2xpt, J ¼ 2.4 Hz, 1H, H-3, R-, S-),
4.36e4.35 (dd, J1 ¼ 2.4 Hz, J2 ¼ 5 Hz, 1H, H-2, R-, S-) 4.30e4.12 (m,
3H, H-30a, b, R-, S- and H-4, R-, S-), 4.02e3.97 (m, 1H, H-5, R-, S-),
3.81e3.57 (m, 3H, H-6a, R-, S- and H-10a, R-, S-), 3.50e3.46 (m, 1H,
H-10b, R-, S-), 2.48, 2.47 (2xs, 3H, Ar-CH3) 2.32 (t, J ¼ 7.5 Hz, 2H,
eCOCH2-, R-, S-), 1.58, 1.26 (2xbr s, 26H, eCH2-, R-, S-), 1.54, 1.48
(2xs, 2x3H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-), 0.88 (t,
), 0.88 (t, J ¼ 6.6 Hz, 3H, eCH3); 13C NMR (100 MHz, CDCl3)
d 172.62
(eCOe, R-, S-), 146.49, 146.44 (Ar-C, R-, S-), 109.57, 108.74, 96.34 (C-
1, R-, S-), 71.12, 70.70, 70.61, 70.38, 69.42, 69.23, 68.57, 68.37, 67.11,
66.96, 50.54, 34.08, 31.91, 29.68, 29.64, 29.59, 29.42, 29.35, 29.19,
29.05, 26.04, 25.98, 24.84, 24.72, 24.46, 22.68, 14.11 (R-, S-); IR
(Neat) nmax, 2923, 2848, 1743, 1540, 1360, 1289, 1214, 1171, 1070,
J ¼ 6.6 Hz, 3H, eCH3); 13C NMR (100 MHz, CDCl3)
d 172.69, 172.65
(eCOe, R-, S-), 146.75, 145.46, 145.40, 120.86, 120.81 (Ar-C, R-, S-),
109.60, 108.61, 96.35 (C-1, R-, S-), 71.17, 71.06, 70.72, 70.70, 70.68,
70.42, 70.39, 70.39 (C-2,3 and 6, R-, S-), 69.71, 69.37 (C-20, R-, S-),
67.61, 67. 44 (C-10, R-, S-), 67.04, 66.87 (C-5, R-, S-), 47.68 (C-30, R-, S-
), 34.12, 31.91, 29.68, 29.65, 26.62, 29.58, 29.42, 29.35, 29.19, 29.05,
24.79, 22.68 (eCH2- palmitoyl), 26.02, 25.96, 25.94, 24.86, 24.44,
24.49, 22.68 (4x-CH3 R, S), 14.11, 13.07 (eCH3, palmitoyl and Ar-CH3,
R-, S-); IR (Neat) nmax, 2925, 2854, 1742, 1541, 1378, 1293, 1212, 1171,
1004 cmꢁ1; MALDI-TOF MS: m/z calculated for C34H57N4O10
:
þ
667.84. Found: 690.77 [M þ Na]
.
6.4.6. 1,2:3,4-Di-O-isopropylidene-6-O-[3-(5-nitroimidazolyl)-2-
palmitoyloxypropyl]-
a-D-galactopyranose (8f)
Yield 86%; Thick oil; 1H NMR (400 MHz, CDCl3)
d
7.96, 7.94,
7.54, 7.52 (4xd, J ¼ 1.5 Hz, 2H, ArH, R-, S-), 5.61, 5.58 (2xd, J ¼ 5Hz,
1H, H-1, R-, S-), 5.23e5.16 (m, 1H, H-20, R-, S-), 4.65, 4.63 (2xpt,
J ¼ 2.5 Hz, 1H, H-3, R-, S-), 4.41e4.29 (m, 3H, H-2, R-, S- and H-30a,
b, R-, S-) 4.25e4.21 (m, 1H, H-4, R-, S-), 4.00e3.97(m, 1H, H-5, R-,
S-), 3.75e3.70 (m, 1H, H-6a, R-, S-), 3.50e3.46 (m, 2H, H-6b, R-, S-
and H-10a, R-, S-), 3.37e3.27 (m, 1H, H-10b, R-, S-), 2.33 (t,
J ¼ 7.5 Hz, 2H, eCOCH2-, R-, S-), 1.59, 1.26 (2xbr s, 26H, eCH2-, R-, S-
), 1.54, 1.48 (2xs, 2x3H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-,
S-), 0.88 (t, J ¼ 6.6 Hz, 3H, eCH3); 13C NMR (100 MHz, CDCl3)
1070, 1004 cmꢁ1; MALDI-TOF MS: m/z calculated for C35H59N3O10
:
þ
681.857. Found: 704.885 [M þ Na] 720.900 [M þ K]þ
,
.
6.4.3. 1,2:3,4-di-O-isopropylidene-6-O-[3-(5-methyl-4-nitroimid-
azolyl)-2-palmitoyloxypropyl]- -galactopyranose (8c)
Yield 75%; Thick oil; 1H NMR (400 MHz, CDCl3)
7.52 (s, 1H, ArH,
a-D
d
R-, S-), 5.56, 5.55 (2xd, J ¼ 5 Hz, 1H, H-1, R-, S-), 5.17e5.09 (m, 1H, H-
20, R-, S-), 4.64, 4.62 (2xpt, J1 ¼ 2.2 Hz, J2 ¼ 1.8 Hz, 1H, H-3, R-, S-),
4.35e4.34 (dd, J1 ¼ 2.4 Hz, J2 ¼ 5 Hz, 1H, H-2, R-, S-) 4.33e4.28 (m,
1H, H-4, R-, S-), 4.25e4.16 (m, 2H, H-30a, b, R-, S-), 4.00e3.97 (m, 1H,
H-5, R-, S-), 3.81e3.56 (m, 3H, H-6a, R-, S- and H-10a R-, S-),
3.50e3.46 (m, 1H, H-10b, R-, S-), 2.67, (s, 3H, Ar-CH3) 2.30 (t,
J ¼ 7.5 Hz, 2H, eCOCH2-, R-, S-), 1.56, 1.26 (2xbr s, 26H, eCH2-, R-, S-
), 1.54, 1.48 (2xs, 2x3H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-
d
172.58 (eCOe, R-, S-), 148.22, 137.12, 120.54, 120.49 (Ar-C, R-, S-),
109.7, 108.7 (2x -C(CH3)2, R-, S-), 96.36 (C-1, R-, S-), 71.17, 71.07,
70.73, 70.69, 70.41, 69.71, 69.38, 67.61, 67.44, 67.05, 66.87, 47.67,
34.12, 31.91, 29.68, 29.64, 29.62, 29.57, 29.42, 29.35, 29.19, 29.05,
26.02, 25.96, 24.86, 24.79, 24.48, 22.68, 14.11, (R-, S-); IR (Neat)
nmax 2923, 2848, 1743, 1540, 1360, 1289, 1214, 1171, 1070,
), 0.88 (t, J ¼ 6.6 Hz, 3H, eCH3); 13C NMR (100 MHz, CDCl3)
d
172.67
1004 cmꢁ1; MALDI-TOF MS: m/zþcalculated for C34H57N3O10
:
(eCOe, R-, S-), 135.59 (Ar-C, R-, S-), 109.57, 108.74, 96.33 (C-1, R-, S-),
70.70, 70.62, 70.38, 70.00, 69.70, 68.21, 67.16, 66.97, 45.02, 34.05,
31.91, 29.68, 29.64, 29.62, 29.58, 29.41, 29.35, 29.19, 29.13, 26.03,
667.830. Found: 690.775 [M þ Na]
.
6.5. General procedure for the synthesis of compounds 9a, b, d and e
25.99, 24.86, 24.71, 24.46, 22.68, 14.11, 10.35, (R-, S-); IR (Neat) nmax
,
2925, 2854, 1742, 1566, 1501, 1460, 1351, 1284, 1211, 1171, 1070,
To a solution of alcohol (7a, b, d or e, 1 mmol) in anhydrous DMF
(5 mL) maintained over an ice-bath was added NaH (60% suspen-
sion in mineral oil, 1.1 mol equiv) and was stirred. After 15 min,
1005 cmꢁ1; MALDI-TOF MS: m/z calculated for C35H59N3O10
:
þ
681.857. Found: 704.784 [M þ Na] 720.780 [M þ K]þ
,
.

G. Mugunthan et al. / European Journal of Medicinal Chemistry 46 (2011) 4725e4732
4731
4-(trifluoromethoxy)benzyl bromide (1 mol equiv) was added and
6.5.4. 1,2:3,4-Di-O-isopropylidene-6-O-[3-(3-nitro-1,2,4-triazolyl)-
2-(4-trifluoromethoxy)benzyloxypropyl]- -galactopyranose (9e)
Yield 70%; Thick syrup;1HNMR (400 MHz, CDCl3)
8.32, 8.31 (2xs,
stirred at room temperature for 5 h. After the completion of the
reaction, the excess sodium hydride was quenched by adding a few
drops of methanol. The solvent was evaporated off under reduced
pressure and the crude product was subjected to chromatographic
purification to get pure 9aee.
a-D
d
1H, triazole-H, R-, S-), 7.42e7.15 (m, 4H, ArH, R-, S-), 5.55 (d, J ¼ 5 Hz,
1H, H-1, R-, S-), 4.64e4.60(m, 2H, eCH2a-(benzylic), R-, S- and H-3, R-
, S-), 4.58e4.53 (m, 1H, H-30a, R-, S-), 4.49e4.45 (2xd, J ¼ 12 Hz, 1H,
eCH2b-(benzylic), R-, S-), 4.44e4.37 (m, 1H, H-30b, R-, S-), 4.35e4.33
(2xdd, J1 ¼ 2.4 Hz, J2 ¼ 5 Hz,1H, H-2, R-, S-), 4.23e4.19 (m,1H, H-4, R-,
S-), 4.02e3.96 (m, 2H, H-5, R-, S-and H-20, R-, S-), 3.76e3.56(m, 4H, H-
6a, b, R-, S- and H-10a, b, R-, S-),1.53,1.52, 2x1.45 (4xs, 6H, eC(CH3)2, R-
6.5.1. 1,2:3,4-Di-O-isopropylidene-6-O-[3-(4-nitroimidazolyl)-2-(4-
trifluoromethoxy)benzyloxypropyl]-
a
-
D
-galactopyranose (9a)
Yield 75%; Thick syrup; 1H NMR (400 MHz, CDCl3)
d
7.69, 7.88,
7.51, 7.50 (4xd, J ¼ 1.5 Hz, 2H, imidazole-H, R-, S-), 7.27e7.19 (m, 4H,
ArH, R-, S-), 5.59, 5.55 (2xd, J ¼ 5 Hz, 1H, H-1, R-, S-), 4.65e4.60 (m,
2H, eCH2a- (benzylic), R-, S- and H-3, R-, S-), 4.51e4.46 (2xd,
J ¼ 11.8 Hz, 1H, eCH2b- (benzylic), R-, S-), 4.34 (dd, J1 ¼ 2.4 Hz,
J2 ¼ 5 Hz, 1H, H-2, R-, S-), 4.27e4.13 (m, 3H, H-4, R-, S- and H-30a, b,
R-, S-), 3.98e3.94 (m, 1H, H-5, R-, S-), 3.86e3.79 (m, 1H, H-20, R-, S-),
3.72e3.68 (m, 1H, H-6a, R-, S-), 3.65e3.55 (m, 2H, H-6b, R-, S- and
H-10a, R-, S-), 3.35e3.29 (m, 1H, H-10b, R-, S-), 1.53, 1.51, 1.47, 1.45
(4xs, 6H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-); 13C NMR
, S-),1.33 (s, 6H, eC(CH3)2, R-, S-); 13C NMR (100 MHz, CDCl3)
d 148.97,
146.47, 135.71, 130.14, 129.32, 129.27, 121.67, 121.01, 119.11, 109.49,
108.68, 96.34, 75.36, 71.19, 71.14, 70.77, 70.67, 70.51, 70.37, 69.37,
67.32, 67.02, 52.14, 52.05, 26.03, 25.96, 24.84, 24.44, 24.41 (R-, S-); IR
(Neat) nmax 3131, 2989,1553,1504,1382,1307,1259,1070,1004 cmꢁ1
;
MALDI-TOF MS: m/z calculated for C25H31F3N4O10: 604.530. Found:
627.529 [M þ Na] þ, 643.795 [M þ K]þ
.
6.6. General procedure for the synthesis of compounds 11aef
(100 MHz, CDCl3)
d 137.18, 135.71, 129.14, 129.10, 121.12, 120.58,
109.59, 108.70, 108.65, 96.36, 71.31, 71.11, 70.70, 70.37, 68.78, 68.50,
67.21, 67.01, 49.12, 26.03, 25.94, 24.86, 24.44 (R-, S-); IR (Neat) nmax
3124, 2992, 2925, 1544, 1514, 1492, 1379, 1338, 1260, 1216, 1167,
To a suspension of nitroimidazole/nitrotriazole (2 mmol) in
anhydrous DMF (5 mL) maintained over an ice-bath, NaH (60%
suspension in mineral oil, 1 mol equiv) was added and stirred. After
15 min, compound 10 (1 mmol) was added and stirred at 100 ꢀC
overnight. After the completion of the reaction, the solvent was
evaporated off under reduced pressure. The crude product was
taken up in CH2Cl2 and was extracted with water. The organic layer
was dried over anhydrous sodium sulfate and was concentrated
under reduced pressure. The crude product was subjected to
column chromatography to get pure 11aef.
1071, 1004 cmꢁ1
;
MALDI-TOF MS: m/z calculated for
þ
C26H32F3N3O10: 603.542. Found: 626.791 [M þ Na]
642.807
,
[M þ K]þ
.
6.5.2. 1,2:3,4-Di-O-isopropylidene-6-O-[3-(2-methyl-4-nitroimi-
dazolyl)-2-(4-trifluoromethoxy)benzyloxypropyl]-
ranose (9b)
a
-
D
-galactopy-
Yield 68%; Thick syrup; 1H NMR (400 MHz, CDCl3)
d
7.81 (s, 1H,
Imidazole-H, R-, S-), 7.21e7.15 (m, 4H, ArH, R-, S-), 5.56 (pt, J ¼ 5 Hz,
1H, H-1, R-, S-), 4.64e4.59 (m, 2H, eCH2a- (benzylic), R-, S- and H-3,
R-, S-), 4.44e4.41 (m, 1H, eCH2b- (benzylic), R-, S-), 4.36e4.34 (dd,
J1 ¼ 2.4 Hz, J2 ¼ 5 Hz, 1H, H-2, R-, S-), 4.23e4.15 (m, 2H, H-4, R-, S-
and H-30a, R-, S-), 4.07e3.97 (m, 2H, H-5, R-, S- and H-30b, R-, S-),
3.78e3.62 (m, 3H, H-20, R-, S-, H-6a, b, R-, S- and H-10a, R-, S-),
3.54e3.46 (m, 1H, H-10b, R-, S-), 2.39 (s, 3H, Ar-CH3), 1.53, 1.46 (2xs,
6H, eC(CH3)2, R-, S-), 1.34 (s, 6H, eC(CH3)2, R-, S-); 13C NMR
6.6.1. 6-Deoxy-1,2:3,4-di-O-isopropylidene-6-(4-nitroimidazolo)-
a
-
D
-galactopyranose (11a)
Yield 74%; Thick syrup; [
a
]
ꢁ70.1 (c 1, CHCl3); 1H NMR
D
(400 MHz, CDCl3)
d
7.87, 7.52 (2xd, J ¼ 1.5 Hz, 2H, ArH), 5.54 (d,
J ¼ 5Hz,1H, H-1), 4.66 (dd, J1 ¼ 2.5 Hz, J2 ¼ 7.8 Hz,1H, H-3), 4.37 (dd,
J1 ¼ 2.5 Hz, J2 ¼ 5Hz, 1H, H-2), 4.28e4.15 (m, 3H, H-4 and H-6a, b),
4.03e4.00 (m, 1H, H-5), 1.47, 1.43, 1.36, 1.31 (4xs, 12H, 2x-C(CH3)2);
13C NMR (100 MHz, CDCl3)
d 148.05, 136.59, 120.01, 110.09, 109.04,
(100 MHz, CDCl3)
d 149.02, 146.51, 145.44, 135.69, 129.21, 121.08,
96.26, 70.93, 70.73, 70.14, 66.96, 48.36, 25.96, 25.88, 24.70, 24.38;
120.78, 109.57, 108.64, 96.36, 71.50, 71.43, 71.21, 70.86, 70.69, 70.64,
70.38, 69.27, 69.05, 67.25, 67.12, 48.37, 26.01, 25.94, 24.85, 24.45,
24.40, 13.14, 13.10, (R-, S-); IR (Neat) nmax 3124, 2985, 2925, 1540,
1506, 1380, 1293, 1260, 1216, 1167, 1071, 1003 cmꢁ1; MALDI-TOF
MS: m/z calculated for C27H34F3N3O10: 617.568. Found: 640.768
[M þ Na] þ 656.778 [M þ K]þ
IR (Neat) nmax 3136, 2989, 2934, 1674, 1546, 1493, 1337, 1290, 1169,
1004, 901, 859 cmꢁ1
; MALDI-TOF MS: m/z calculated for
C15H21N3O7: 355.343. Found: 378.403 [M þ Na]þ
.
6.6.2. 6-Deoxy-1,2:3,4-di-O-isopropylidene-6-(2-methyl-4-nitroimid-
azolo)- -galactopyranose (11b)
Yield 70%; Colorless solid; mp 117e118 ꢀC; [
CHCl3); 1H NMR (400 MHz, CDCl3)
7.85 (s, 1H, ArH), 5.53 (d,
a-D
,
.
a
]
ꢁ69.5 (c 1,
D
6.5.3. 1,2:3,4-Di-O-isopropylidene-6-O-[3-(2-nitroimidazolyl)-2-
(4-trifluoromethoxy)benzyloxypropyl]- -galactopyranose (9d)
Yield 65%; Thick syrup; 1H NMR (400 MHz, CDCl3)
7.29e7.10
d
a
-D
J ¼ 5 Hz,1H, H-1), 4.65 (dd, J1 ¼ 2.4 Hz, J2 ¼ 7.8 Hz,1H, H-3), 4.35 (dd,
J1 ¼ 2.4 Hz, J2 ¼ 5Hz, 1H, H-2), 4.15 (dd, J1 ¼1.8 Hz, J2 ¼ 7.8 Hz,1H, H-
4), 4.12e4.04 (m, 2H, H-6a, b), 4.02e3.99 (m, 1H, H-5), 2.44 (s, 3H,
Ar-CH3), 1.48, 1.45, 1.36, 1.32 (4xs, 12H, 2x-C(CH3)2); 13C NMR
d
(m, 6H, ArH, R-, S-), 5.55 (d, J ¼ 5 Hz, 1H, H-1, R-, S-), 4.80e4.76 (dd,
J1 ¼4 Hz, J2 ¼ 13.9 Hz,1H, H-30a, R-, S-), 4.63e4.57 (m, 2H, H-3, R-, S-
and eCH2a- (benzylic), R-, S-), 4.50e4.41 (m, 2H, H-30b, R-, S- and
eCH2b-(benzylic), R-, S-), 4.34e4.32 (dd, J1 ¼ 2.4 Hz, J2 ¼ 5 Hz, 1H,
H-2, R-, S-), 4.25e4.21 (m, 1H, H-4, R-, S-), 4.05e3.98 (m, 1H, H-5, R-,
S-), 3.86e3.89 (m, 1H, H-20, R-, S-), 3.74e3.55 (m, 4H, H-6a, b, R-, S-
and H-10a, b, R-, S-), 1.53, 1.45 (2xs, 6H, eC(CH3)2, R-, S-), 1.33 (s, 6H,
(100 MHz, CDCl3)
d 146.56, 145.17, 120.27, 110.10, 109.05, 96.32,
70.86, 70.76, 70.20, 66.58, 46.96, 26.01, 25. 94, 24.72, 24.44,13.17; IR
(Neat) nmax 3136, 2989, 2934, 1674, 1546, 1493, 1337, 1290, 1169,
1004, 901, 859 cmꢁ1
; MALDI-TOF MS: m/z calculated for
C16H23N3O7: 369.370. Found: 370.507 [M þ H] þ, 392.475 [M þ Na] þ
.
eC(CH3)2, R-, S-); 13C NMR (100 MHz, CDCl3)
d 148.86, 136.06,
129.19, 129.13, 127.94, 127.63, 127.55, 121.69, 120.98, 109.40, 108.66,
96.34, 71.20, 71.16, 70.73, 70.67, 70.43, 69.74, 69.69, 67.19, 66.87,
50.40, 50.22, 50.40, 50.22, 26.04, 25.98, 24.88, 24.46, 24.40 (R-, S-);
IR (Neat) nmax 3118, 2985, 2932, 2362, 1540, 1488, 1370, 1259, 1213,
6.6.3. 6-Deoxy-1,2:3,4-di-O-isopropylidene-6-(5-methyl-4-nitroimid-
azolo)-
Yield 78%; glassy solid; [
(400 MHz, CDCl3)
a-D-galactopyranose (11c)
a
]
D
ꢁ73.3 (c 1, CHCl3); 1H NMR
d
7.51 (s, 1H, ArH), 5.52 (d, J ¼ 5 Hz, 1H, H-1), 4.65
1165, 1070, 1004 cmꢁ1
;
MALDI-TOF MS: m/z calcþulated for
(J1 ¼ 2.5 Hz, J2 ¼ 7.8 Hz, 1H, H-3), 4.35 (dd, J1 ¼ 2.5 Hz, J2 ¼ 5Hz, 1H,
H-2), 4.14e4.10 (m, J ¼ 1.8 Hz, J ¼ 7.8 Hz, 3H, H-4, H-6a, b),
4.02e3.98 (m, 1H, H-5), 2.64 (s, 3H, Ar-CH3), 1.49, 1.43, 1.36, 1.31
C26H32F3N3O10: 603.542. Found: 626.791 [M þ Na]
642.807
,
[M þ K]þ
.

4732
G. Mugunthan et al. / European Journal of Medicinal Chemistry 46 (2011) 4725e4732
(4xs, 12H, 2x-C(CH3)2); 13C NMR (100 MHz, CDCl3)
d
143.22, 135.74,
Growth Supplement (Drug concentration from 12.5
mg/mL to
131.73,109.54,108.65, 96.34, 71.06, 70.85, 70.30, 67.08, 45.55, 24.92,
0.78 g/mL). Inoculum of M.tb H37Rv was prepared from fresh
m
24.75, 23.53, 23.16, 9.17; IR (Neat) nmax 3131, 2987, 2925, 1673, 1570,
Middlebrook 7H11 agar slants with OADC Growth Supplement
was adjusted to 1 mg/mL (wet weight) in Tween 80 (0.05%)
saline diluted to 10ꢁ2 to give a concentration of approximately
1498, 1349, 1255, 1212, 1169, 1005 cmꢁ1; MALDI-TOF MS: m/z
þ
calculated for C16H23N3O7: 369.370. Found: 392.470 [M þ Na]
.
107 cfu/mL. A 5
mL amount of the bacterial suspension was
6.6.4. 6-Deoxy-1,2:3,4-di-O-isopropylidene-6-(2-nitroimidazolo)-
spotted into 7H11 agar tubes containing 10-fold serial dilutions
of drugs per mL. The tubes were incubated at 37 ꢀC, and final
readings were recorded after 28 days. The minimum inhibitory
concentration (MIC) is defined as the minimum concentration of
the compound required to give the complete inhibition of
bacterial growth.
a
-
D
-galactopyranose (11d)
Yield 69%; Colorless solid; mp 94.5e96 ꢀC; [
a
]
ꢁ37.1 (c 1,
D
CHCl3); 1H NMR (400 MHz, CDCl3)
d
7.24, 7.13 (2xd, J ¼ 0.9 Hz, 2H,
ArH), 5.49 (d, J ¼ 5 Hz, 1H, H-1), 4.99 (dd, J1 ¼ 3.8 Hz, J2 ¼ 14 Hz, 1H,
H-6a), 4.64 (dd, J1 ¼ 2.5 Hz, J2 ¼ 7.8 Hz, 1H, H-3), 4.46 (dd,
J1 ¼ 8.2 Hz, J2 ¼ 14 Hz, 1H, H-6b), 4.32 (dd, J1 ¼ 2.5 Hz, J2 ¼ 5 Hz, 1H,
H-2), 4.24 (dd, J1 ¼ 1.8 Hz, J2 ¼ 7.8 Hz, 1H, H-4), 4.17e4.14 (m,
J ¼ 1.8 Hz, J ¼ 3.8 Hz, 1H, H-5), 1.46, 1.37, 1.35, 1.28 (4xs, 12H, 2x-
Acknowledgement
C(CH3)2); 13C NMR (100 MHz, CDCl3)
d 127.81, 126.67, 109.56,
Mugunthan G. sincerely acknowledges research fellowship from
NIPER.
108.64, 96.37, 71.16, 70.88, 70.38, 66.66, 49.67, 24.86, 24.62, 23.61,
23.16; IR (Neat) nmax 3151, 2985, 2925, 1539, 1488, 1365, 1255, 1212,
1166, 1069, 1005 cmꢁ1
; MALDI-TOF MS: m/z calculated for
References
C15H21N3O7: 355.343. Found: 377.545 [M þ Na] þ, 394.588 [M þ K]þ
.
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Antimicrob. Agents Chemother. 53 (2009) 849e862.
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2054e2058.
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W. Rittel, Antimicrob. Agents Chemother. 37 (1993) 183e186.
[15] J.V. Brooks, S.K. Furney, I.M. Orme, Antimicrob. Agents Chemother. 43 (1999)
1285e1288.
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Tuberculosis (South Korea) http://clinicaltrials.gov/ct2/show/NCT00425113.
(accessed 12.09.10).
6.6.5. 6-Deoxy-1,2:3,4-di-O-isopropylidene-6-(3-nitro-1,2,4-
triazolo)-
Yield 78%; syrup; [
CDCl3)
a-D-galactopyranose (11e)
a]
ꢁ14.9 (c 1, CHCl3); 1H NMR (400 MHz,
D
d
8.28 (s, 1H, ArH), 5.49 (d, J ¼ 4.8 Hz, 1H, H-1), 4.67 (dd,
J1 ¼ 2.4, J2 ¼ 7.8 Hz, 1H, H-3), 4.45e4.43 (m, 2H, H-6a, b), 4.35 (dd,
J1 ¼ 2.4 Hz, J2 ¼ 4.8 Hz, 1H, H-2), 4.26e4.23 (m, 1H, H-5), 4.20
(dd, J1 ¼ 1.8 Hz, J2 ¼ 7.8 Hz, 1H, H-4), 1.48, 1.42, 1.36, 1.29 (4xs, 12H,
eC(CH3)2); 13C NMR (100 MHz, CDCl3)
d 145.93, 110.12, 109.26,
96.14, 70.93, 70.77, 70.26, 66.22, 51.93, 25.92, 25.86, 24.81, 24.31; IR
(Neat) nmax 3131, 2988, 2932, 1555, 1504, 1380, 1308, 1255, 1212,
1168, 1068, 1006, 835 cmꢁ1; MALDI-TOF MS: m/z calculated for
C14H20N4O7: 356.331. Found: 379.661 [M þ Na] þ, 395.686 [M þ K]þ
.
6.6.6. 6-Deoxy-1,2:3,4-di-O-isopropylidene-6-(5-nitroimidazolo)-
a
-
D
-galactopyranose (11f)
Yield 72%; syrup; [
CDCl3)
a
]
ꢁ70.0 (c 1, CHCl3); 1H NMR (400 MHz,
D
d
7.87, 7.52 (2xd, J ¼ 1.4 Hz, 2H, ArH), 5.54 (d, J ¼ 5 Hz, 1H, H-
1), 4.65 (dd, J1 ¼ 2.4, J2 ¼ 7.8 Hz, 1H, H-3), 4.36 (dd, J1 ¼ 2.4 Hz,
J2 ¼ 5 Hz, 1H, H-2), 4.24e4.15 (m, J ¼ 1.8 Hz, 3H, H-4 and H-6a, b),
4.03e4.01 (m, J ¼ 1.8 Hz, 1H, H-5), 1.47, 1.43, 1.36, 1.31 (4xs, 12H, 2x-
C(CH3)2); 13C NMR (100 MHz, CDCl3)
d 136.57, 119.96, 110.10, 109.03,
96.27, 70. 92, 70. 73, 70.14, 66.96, 48.35, 25.97, 25.89, 24.71, 24.38;
IR (Neat) nmax 3140, 2986, 2935, 1544, 1492, 1383, 1289, 1212, 1068,
1005, 823 cmꢁ1; MALDI-TOF MS: m/z calculated for C15H21N3O7:
þ
355.343. Found: 378.461 [M þ Na] 394.435 [M þ K]þ
,
.
[17] A. Liav, S.K. Angala, P.J. Brennan, Synth. Commun. 38 (2008) 1176e1183.
[18] A. Liav, S.K. Angala, P.J. Brennan, M. Jackson, Bioorg. Med. Chem. Lett. 18
(2008) 2649e2651.
6.7. Agar dilution method
[19] K.P.R. Kartha, Tetrahedron Lett. 27 (1986) 3415e3416.
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Ten-fold serial dilutions of each test compound/drug were
incorporated into Middlebrook 7H11 agar medium with OADC