Benzimidazole-derived ATP analogues as potential glutamine synthetase inhibitors

Article abstract of DOI:10.1080/00397910903289263

A series of mono-and dihydroxyalkyl-and-alkyloxybenzimidazoles and their phosphorylated derivatives have been prepared as adenosine triphoshate analogues for investigation as potential M. Tb. glutamine synthetase inhibitors. Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910903289263

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Benzimidazole-Derived ATP Analogues
as Potential Glutamine Synthetase
Inhibitors
Babalwa S. B. Gxoyiya a , Perry T. Kaye a & Colin Kenyon b
a Department of Chemistry and Centre for Chemico- and
Biomedicinal Research , Rhodes University , Grahamstown, South
Africa
b CSIR BIO/CHEMTEK , Modderfontein, South Africa
Published online: 05 Aug 2010.
To cite this article: Babalwa S. B. Gxoyiya , Perry T. Kaye & Colin Kenyon (2010) Benzimidazole-
Derived ATP Analogues as Potential Glutamine Synthetase Inhibitors, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 40:17, 2578-2587,
DOI: 10.1080/00397910903289263
To link to this article: http://dx.doi.org/10.1080/00397910903289263
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Synthetic Communications1, 40: 2578–2587, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903289263
BENZIMIDAZOLE-DERIVED ATP ANALOGUES AS
POTENTIAL GLUTAMINE SYNTHETASE INHIBITORS
Babalwa S. B. Gxoyiya,1 Perry T. Kaye,1 and Colin Kenyon2
1Department of Chemistry and Centre for Chemico- and Biomedicinal
Research, Rhodes University, Grahamstown, South Africa
2CSIR BIO=CHEMTEK, Modderfontein, South Africa
A series of mono- and dihydroxyalkyl- and -alkyloxybenzimidazoles and their phosphory-
lated derivatives have been prepared as adenosine triphoshate analogues for investigation
as potential M. Tb. glutamine synthetase inhibitors.
Keywords: ATP analogues; benzimidazole derivatives; glutamine synthetase inhibitors; phosphorylation
From being a well-controlled disease, tuberculosis (TB) has, once again, assumed
epidemic proportions, a situation exacerbated by the emergence of multiple
drug-resistant (MDR)[1] and, very recently, extreme drug-resistant (XDR) TB.[2]
Chemotherapeutic intervention began with the discovery by Waksman and
coworkers[3] that streptomycin effectively inhibited Mycobacterium tuberculosis
(M. Tb.). This was followed, in 1952, by the discovery of the two critically important
drugs, isoniazid (INH)[4–6] and pyrazinamide (PZA).[7] Other drugs that have proved
to be effective anti-TB agents include rifampicin,[8] pyrazinamide,[9] cycloserine,[10]
and the fluoroquinolone antibiotics.[11]
However, given the emergence of drug-resistant TB, there is clearly a need
to develop new drugs that inhibit different targets and shorten the duration of ther-
apy. Such targets include the M. Tb. type 1 glutamine synthetase (GSI), which is a
dodecamer, unlike the octameric, human GSII.[12] L-Methionine-(S,R)-sulfoximine
(MetSox)[13] has been found to inhibit both GSI and GSII, but the inhibitory effect
is greater with GSI.[14] Since GS enzymes are adenosine triphoshate (ATP) depen-
dent, research in our group has focused on the development of novel ATP analogues
as potential GSI inhibitors and, hence, as potential anti-TB agents. Attention has
been given to replacement of the three structural motifs present in ATP 1 (viz.,
the heterocyclic moiety, the linking group, and the triphosphate group), and in this
communication, we report the preparation of a series of benzimidazole derivatives,
such as 2, which incorporate the replacement motifs in parentheses in Fig. 1.
Received May 19, 2009.
Address correspondence to Perry T. Kaye, Department of Chemistry and Centre for Chemico- and
Biomedicinal Research, Rhodes University, Grahamstown 6140, South Africa. E-mail: P.Kaye@ru.ac.za
2578

BENZIMIDAZOLE-DERIVED ATP ANALOGUES
2579
Figure 1. General design features of ATP analogues.
Benzimidazole-based drugs, such as albendazole (albenza), mebendazole, and
thiabendazole, have enjoyed widespread application as microtubule inhibitors in
the treatment of parasitic-related diseases.[15] While benzimidazole 3 lacks the
4-amino substituent present in ATP and thus cannot undergo normal Watson–Crick
hydrogen bonding, this does not preclude the possibility that benzimidazole
derivatives may fit well into the GS receptor cavity and bind sufficiently strongly
to inhibit the normal functions of the enzyme.
N-Alkylation of benzimidazole 3 was first explored using the alkenyl bromides,
allyl bromide, 4-bromobutene, and 4-bromo-2-methylbut-2-ene. Prior deprotonation
was effected with sodium hydride, following the procedure described by Tan et al.[16]
(Scheme 1). Flash chromatography of the crude material, in each case, afforded
the corresponding N-alkenylbenzimidazoles, N-allylbenzimidazole 4, N-(but-3-enyl)
benzimidazole 5, and N-(3-methylbut-2-enyl)benzimidazole 6 in moderate to excel-
lent yields (43–96%). Two different methods were then investigated to achieve perhy-
[17]
droxylation of the N-alkenylbenzimidazoles 4–6, namely, oxidation with KMnO4
Scheme 1. Access to hydroxyl derivatives. Reagents and reaction conditions: (i) NaH, THF, 0 ꢀC, 15 min;
(ii) allyl bromide, 30 min reflux; (iii) 4-bromobutene, 4 h reflux; (iv) 4-bromo-2-methyl-2-butene, 40 min
reflux; (v) t-BuOH, KMnO4, H2O, 0 ꢀC then NaOH, rt; (vi) CTAP, t-BuOH, H2O, 20 ꢀC then CHCl3,
NaOH; (vii) 18 h reflux; (viii) 75% AcOH, 1 h reflux; (ix) NaH, THF, heat; and (x) LiAlH4, heat.

2580
B. S. B. GXOYIYA, P. T. KAYE, AND C. KENYON
and with cetyltrimethylammonium permanganate (CTAP), which was prepared from
KMnO4 and cetyltrimethylammonium bromide.[18] The reaction of compound 4
with KMnO4 was conducted in water at 0 ꢀC, and radial chromatography of the
crude product afforded the desired N-(2,3-dihydroxypropyl)benzimidazole 7 as a
colorless oil in only 15% yield. Attention was therefore turned to the use of CTAP.[18]
The N-alkenylbenzimidazoles 4–6 were thus treated with CTAP in t-BuOH for
several hours at 20 ꢀC, and, following workup and radial chromatography, the pure
dihydroxy derivatives 7–9 were isolated in yields that ranged from poor to good
(26–77%). In an attempt to improve the yield of diol 7, benzimidazole 3 was depro-
tonated as before and then treated with the bromoketal 10. Flash chromatography,
following workup, afforded the pure 1-[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl]-1H-
benzimidazole 11 in 38% yield. Subsequent hydrolysis with aqueous acetic acid gave
the diol 7 in 97% yield, resulting in a somewhat improved overall yield of 37% for the
two steps (3 þ 10 ! 11 ! 7).
Access to the hydroxyalkyloxy derivative 16 was provided by heating
benzimidazole 3 with 2-choloroethoxyethanol 15 in the presence of sodium hydride,
following Tan’s methodology.[16] Benzimidazole 3 was reacted similarly with (2-
bromomethoxy)ethyl acetate 12, but repeated chromatography was necessary to
separate the acetate 13 from the hydrolyzed product 14, concomitant formation of
which was attributed to the presence of excess sodium hydride and consequent
base-catalyzed hydrolysis of the acetyl group during work-up. The alkylation of
benzimidazole 3 with (2-bromomethoxy)ethyl acetate 12 was therefore repeated, but
the crude product was subjected, without further purification, to reduction with
lithium aluminum hydride (LAH) in diethyl ether to afford the alcohol 14 in 21% yield
after flash chromatography.
The monohydroxy derivatives 14 and 16 were phosphorylated following the
method reported by Kanayama et al.[19] Thus, compounds 14 and 16 were each
treated with molar equivalents of butyllithium and diethyl chlorophosphate at
0 ꢀC (Scheme 2) to afford, after flash chromatography, the monophosphates 17
and 18 as oils in 23% and 35% yield, respectively. It was hoped that similar treatment
of the diols 7 and 8 would afford the terminal monophosphates 19 and 20. However,
1
the diphosphates 21 and 22 were isolated instead, in very poor yield. The H NMR
Scheme 2. Access to phosphate esters. Reagents: (i) BuLi, THF, and (EtO)2POCl.

BENZIMIDAZOLE-DERIVED ATP ANALOGUES
2581
spectrum of the diphosphate 21 clearly shows the presence of multiplets at ca. 1.2
and 4.1 ppm, corresponding to the methyl and methylene groups of the two phos-
phate ester moieties. The 31P NMR spectrum reveals two distinct signals at ꢁ0.63
and ꢁ0.77ppm due to the chemically nonequivalent phosphorus nuclei, whereas the
13C and DEPT135 (distortionless enhancement by polarization transfer) spectra
exhibit splitting of the methyl and methylene carbons by the phosphorus nuclei.
While reaction conditions remain to be optimized in some cases, synthetic
routes to a range of benzimidazole derivatives have been established, thus providing
a series of novel ATP analogues for biochemical assay as possible glutamine synthetase
inhibitors. Depending on the results of such assays, attention could be given to the
preparation of the corresponding phosphate mono-ester phosphonic acid analogues.
EXPERIMENTAL
Low-resolution mass spectra were obtained on a Finnegan Mat GCQ spec-
trometer, whereas high-resolution mass spectra were recorded by the University of
Witwatersrand mass spectrometry unit. NMR spectra were recorded on a Bruker
400 MHz Avance spectrometer and were referenced using solvent signals (dH:
7.26 ppm for residual CHCl3; dC: 77.0 ppm for CDCl3). Melting points were determ-
ined using a Reichert hot-stage apparatus and are uncorrected. 1-Allylbenzimidazole
4,[16] 1-(but-3-enyl)benzimidazole 5,[16] 1-(3-methylbut-2-enyl)benzimidazole 6,[20]
the bromoketal 10,[21] 2-(bromomethoxy)ethyl acetate 12,[22] and CTAP[18] were pre-
pared following literature methods. The general procedures are illustrated by the
following examples.
1-(2,3-Dihydroxypropyl)benzimidazole 7[23]
Method A.[16] A solution of CTAP (2.8166 g, 6.98mmol) in t-BuOH (28 ml)
and H2O (7ml) was added dropwise to a stirred solution of N-allylbenzimidazole 4
(1.1016 g, 6.97mmol) in BuOH (5.6 ml), and the mixture was stirred for 9 h at 20ꢀC.
The mixture was diluted with CHCl3 (70 ml) and 5% NaOH (22 ml) and then stirred
for 30min. The layers were separated, and the aqueous phase was extracted with CHCl3
(3ꢂ 70ml). The organic layers were combined, dried over anhydrous MgSO4, and eva-
porated in vacuo. The residual oil was purified by flash chromatography [on silica gel;
elution with EtOAc-CH2Cl2 (3:2)] to afford, as a colorless oil, 1-(2,3-dihydroxypropyl)-
benzimidazole 7 (0.6089 g, 44.1%) (found: Mþ, 192.09095; C10H12N2O2 requires M,
192.08988); dH (300 MHz; DMSO-d6) 3.30 and 3.40 [(1H, td, J ¼ 5.7 and 11.4 Hz)
and (1H, td, J ¼ 5.2 and 10.7 Hz) HOCH2], 3.77–3.84 (1H, m, CHOH), 4.13 and 4.35
[(1H, dd, J ¼ 7.6 and 14.4) and (1H, dd, J ¼ 3.2 and 14.4 Hz) NCH2], 4.83 (1H, t,
J ¼ 5.6 Hz, CH2OH), 5.06 (1H, d, J ¼ 5.2 Hz, CHOH), 7.18 (1H, t, J ¼ 7.1 Hz, 6-H),
7.24 (1H, t, J ¼ 7.1 Hz, 5-H), 7.58 (1H, d, J ¼ 8.0 Hz, 4-H), 7.64 (1H, d, J ¼ 8.0 Hz,
7-H) and 8.13 (1H, s, 2-H); dC (100MHz, DMSO-d6) 47.4 (NCH2), 63.1 (CH2OH),
70.0 (CHOH), 110,5 (C-4), 119.1 (C-7), 121.1 (C-6), 121.9 (C-5), 134.3 (C-3a), 143.2
(C-7a) and 144.6 (C-2); m=z 192 (Mþ, 11.6%) and 131 (100%).
Method B.[17] To a vigorously stirred mixture of 1-allylbenzimidazole 4
(0.509 g, 3.22 mmol), in a solution of NaOH (0.0543 g, 1.36 mmol) in H2O (0.3 ml)
and t-BuOH (11 ml) cooled to ꢁ5 ꢀC by the addition of ice (5 g), a cooled solution

2582
B. S. B. GXOYIYA, P. T. KAYE, AND C. KENYON
of KMnO4 (0.340 g, 2.15 mmol) in H2O (11 ml) was added dropwise at a rate such
that the temperature did not exceed 15 ꢀC. Celite (0.1–0.2 g) was then added, and
the mixture was heated almost to boiling. The hot mixture was filtered by suction
and washed several times with H2O-t-BuOH [1:1 (5 ml)]. The filtrate was distilled
off until 6 ml of solution remained. The hot solution was weighed, and solid
K2CO3 (1 g=g of solution) was dissolved in small portions until an oil separated.
The oil was allowed to solidify, and the rest of the K2CO was added. The solid
was filtered off and redissolved in hot EtOAc, with the insoluble residue being
removed by gravity filtration. The EtOAc was evaporated in vacuo, and the residual
oil was purified by radial chromatography [on silica; elution with EtOH–CHCl3 (2:3)]
to afford, as a colorless oil, 1-(2,3-dihydroxypropyl)benzimidazole 7 (0.092 g, 15%).
Method C. A solution of 1-[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl]benzimi-
dazole 11 (0.205 g, 0.884 mmol) in 75% (v=v) acetic acid (20 ml) was boiled under
reflux for 1 h, and the solvent was removed in vacuo to afford, as a golden oil,
1-(2,3-dihydroxypropyl)benzimidazole 7 (0.165 g, 97.0%).
3-(Benzimidazol-1-yl)propane-1,2-diol bis(diethyl phosphate) 21
BuLi (1.6 M in hexane; 0.46 ml, 0.732 mmol) was added to a solution of
1-(2,3-dihydroxypropyl)benzimidazole 7 (0.140 g, 0.728 mmol) in dry tetrahydro-
furan (THF, 7 ml) cooled to 0 ꢀC under argon, and the reaction mixture was stirred
for 0.5 h at 0 ꢀC. Diethyl chlorophosphate (27 ml, 0.727 mmol) in dry THF (1 ml) was
added, and the reaction mixture was stirred for a further 3 h at 0 ꢀC. The reaction
was quenched with saturated aqueous NH4Cl (0.4 ml), and the solvent was
evaporated in vacuo. The residual solid was redissolved in EtOAc and washed with
brine (2 ml). The organic layer was dried with anhydrous MgSO4, and the solvent
was evaporated in vacuo. The residue was purified by radial chromatography [on
silica; elution with ethanol-CHCl3-hexane (1:1.5:2.5)] to afford, as a pale yellow
oil, 3-(benzimidazol-1-yl)propane-1,2-diol bis(diethyl phosphate) 21 (6.8 mg, 2.0%)
(found: Mþ, 464.14687; C18H30N2O8P2 requires M, 464.14774); dH (400 MHz;
CDCl3) 1.13 and 1.23 (6H, 2 ꢂ t, J ¼ 7.0 Hz, POCH2CH3), 1.30–1.36 (6H, m,
POCH2CH3), 3.84 (2H, q, J ¼ 6.9 Hz, OCH2CH3) 4.05–4.19 (8H, m, CH2OP and
3 ꢂ OCH2CH3), 4.44–4.58 (2H, m, CH2CHOP), 4.77–4.85 (1H, m, CH2CHOP),
7.29 (2H, m, 5- and 6-H), 7.47 (1H, d, J ¼ 7.5 Hz, 4-H), 7.79 (1H, d, J ¼ 7.7 Hz,
7-H) and 7.96 (1H, s, 2-H); dC (100 MHz; CDCl3) 15.8–16.2 (POCH2CH3), 45.4
(d, J ¼ 5.5 Hz, NCH2CHOP), 62.6 (d, J ¼ 5.4, CHCH2OP), 64.2–64.4 and 65.4 (C,
m, 4 ꢂ POCH2CH3), 73.5 (CHCH2OP), 109.6 (C-4), 120.5 (C-7), 122.5 (C-5), 123.3
(C-6), 133.9 (C-3a), 143.6 (C-2) and 143.7 (C-7a); dP (162 MHz; CDCl3) ꢁ0.63
and ꢁ1.27; m=z 464 (M, 12.7%) and 156 (100%).
Other new compounds prepared in this study are as follows:
1-(3,4-Dihydroxybutyl)benzimidazole 8
The experimental procedure (method A) employed for the synthesis of N-(2,3-
dihydroxypropyl)benzimidazole 7 was followed, using 1-(but-3-enyl)benzimidazole

BENZIMIDAZOLE-DERIVED ATP ANALOGUES
2583
5 (0.55 g, 3.2 mmol) in t-BuOH (2.6 ml), CTAP (1.3 g, 3.2 mmol) in H2O-t-BuOH [1:4
(16 ml)], CHCl3 (32 ml), and 5% aq. NaOH (10 ml). The reaction mixture was stirred
for 6.5 h, and the aqueous layer was then extracted with CHCl3 (3 ꢂ 32 ml). The
solvent was removed in vacuo, and the residual oil was purified by radial chromato-
graphy [on silica gel; elution with EtOH-CHCl3 (1:4)] to afford, as white crystals,
1-(3,4-dihydroxybutyl)benzimidazole 8 (0.172 g, 26%), mp 150–152 ꢀC (found: Mþ,
206.10361; C11H14N2O2 requires M, 206.10553); dH (400 MHz; DMSO-d6) 1.70
and 2.01 (2H, m, CH2CHOH), 3.25 (1H, dd, J ¼ 6.6 and 11.8 Hz, 40-CHaOH),
3.33 (2H, m, 40-CHbOH and 30-CHOH), 4.34 (2H, t, J ¼ 7.1 Hz, NCH2), 4.60 (1H,
t, J ¼ 5.4 Hz, CH2OH), 4.83 (1H, d, J ¼ 4.7 Hz, CHOH), 7.20 (1H, t, J ¼ 7.4 Hz,
6-H), 7.25 (1H, t, J ¼ 7.4 Hz, 5-H), 7.59 (1H, d, J ¼ 7.9 Hz, 4-H), 7.65 (1H, d,
J ¼ 7.9 Hz, 7-H), and 8.20 (1H, s, 2-H); dC (100 MHz; DMSO-d6) 33.6 (CH2CHOH),
41.0 (NCH2), 65.7 (CH2OH), 68.3 (CHOH), 110.3 (C-4), 119.3 (C-7), 121.3 (C-6),
122.1 (C-5), 133.7 (C-3a), 143.4 (C-7a) and 144.0 (C-2); m=z 206 (Mþ, 74.3%) and
132 (100%).
1-(3-Methyl-2,3-dihydroxybutyl)benzimidazole 9
The experimental procedure (method A) employed for the synthesis of N-
(2,3-dihydroxypropyl)benzimidazole 7 was followed, using 1-(3-methylbut-2-enyl)
benzimidazole 6 (0.239 g, 1.29 mmol) in t-BuOH (1 ml), CTAP (0.503 g, 1.29 mmol)
in H2O-t-BuOH (1:4; 6.5 ml), CHCl3 (13 ml), and 5% NaOH (3.9 ml). The reaction
mixture was stirred for 6.5 h, and the aqueous layer was then extracted with CHCl3
(3 ꢂ 13 ml). The residual oil was purified by flash chromatography [on silica; elution
with EtOH-CHCl3 (1:4)] to afford, as cream needles, 1-(3-methyl-2,3-dihydroxybu-
tyl)benzimidazole 9 (0.093 g, 33%), mp 144–146 ꢀC (found: Mþ, 220.12083;
C12H16N2O2 requires M, 220.12118); dH (400 MHz; DMSO-d6) 1.15 and 1.18 (6H,
s, 2 ꢂ CH3), 3.46 (1H, m, 20-H), 4.02 (1H, dd, J ¼ 10.0 and 14.2 Hz, 10-Ha), 4.52
(1H, d, J ¼ 1.4 and 14.2 Hz, 10-Hb), 4.65 (1H, s, 30-OH), 5.11 (1H, d, J ¼ 6.2 Hz,
20-OH), 7.19 (1H, t, J ¼ 7.4 Hz, 6-H), 7.25 (1H, t, J ¼ 7.4 Hz, 5-H), 7.54 (1H, d,
J ¼ 7.9 Hz, 4-H), 7.64 (1H, d, J ¼ 7.9 Hz, 7-H), and 8.13 (1H, s, 2-H); dC
(100 MHz; DMSO-d6) 23.6 and 27.5 (2 ꢂ CH3), 46.6 (C-10), 71.0 (C-20), 75.8
(C-30), 110.4 (C-4), 119.2 (C-7), 121.1 (C-6), 121.9 (C-5), 133.9 (C-3a), 143.4
(C-7a), and 144.8 (C-2); m=z 220 (Mþ, 75.5%) and 118 (100%).
1-[(2-Acetoxyethoxy)methyl]benzimidazole 13[23]
The experimental procedure employed for the synthesis of 1-allylbenzimidazole
4 was followed using benzimidazole 3 (1.025 g, 8.686 mmol), 60% NaH (0.6940 g,
28.92 mmol), 2-(bromomethoxy)ethyl acetate 12 (2.0614 g, 10.46 mmol), and THF
(15 mL). The mixture was boiled under reflux for 24 h, and the residue was purified
by radial chromatography [on silica; elution with EtOH-CHCl3 (1:9)] to afford, as a
yellow oil, 1-[(2-acetoxyethoxy)methyl]benzimidazole 13 (0.709 g, 34.9%) (found:
Mþ 234.09929; C12H14N2O3 requires M, 234.10044); dH (400 MHz; CDCl3) 1.95
(3H, s, CH3), 3.59 (2H, t, J ¼ 4.6 Hz, OCH2CH2OCO), 4.13 (2H, t, J ¼ 4.6 Hz,
OCH2CH2OCO), 7.31 (2H, m, 5- and 6-H), 7.52 (1H, d, J ¼ 6.2 Hz, 4-H), 7.79
(1H, d, J ¼ 6.2 Hz, 7-H) and 7.80 (1H, s, 2-H); dC (100 MHz; CDCl3) 20.6 (CH3),

2584
B. S. B. GXOYIYA, P. T. KAYE, AND C. KENYON
62.7 (OCH2CH2OCO), 66.5 (OCH2CH2OCO), 74.7 (NCH2O), 110.1 (C-4), 120.4
(C-7), 122.8 (C-6), 123.6 (C-5), 133.4 (C-3a), 142.8 (C-2), 144.0 (C-7a) and 170.7
=
(C O); m=z 235 (M þ 1, 100%).
1-[(2-Hydroxyethoxy)methyl]benzimidazole 14[23]
A solution of 1-[(2-acetoxyethoxy)methyl]benzimidazole 13 (0.4450 g, 1.90mmol)
in dry THF (2ml) was added dropwise to a suspension of LAH (0.0796 g, 2.1 mmol)
in dry THF (5ml) under nitrogen, and the mixture was heated at 60ꢀC for 9 h. The
reaction mixture was cooled to room temperature, and EtOAc was then added to
destroy excess LAH. Excess solvent was removed in vacuo, and the residual oil was pur-
ified by flash chromatography [on silica; elution with EtOH-CHCl3-hexane (1:1.5:2.5)]
to afford, as a golden oil, 1-[(2-hydroxyethoxy)methyl]benzimidazole 14 (77.8 mg,
21.3%) (found: Mþ, 192.09042; C10H12N2O2 requires M, 192.08988); dH (400MHz;
CDCl3) 3.52 and 3.71 (4H, 2 ꢂ t, J ¼ 4.6 Hz, OCH2CH2OH), 5.72 (2H, s, NCH2),
7.31 (2H, m, 5- and 6-H), 7.5 (1H, m, 4-H), 7.7 (1H, m, 7-H) and 7.92 (1H, s, 2-H);
dC (100 MHz; CDCl3) 61.1 (OCH2CH2OH), 70.1 (OCH2CH2OH), 74.8 (NCH2O),
110.2 (C-4), 120.1 (C-7), 122.8 (C-5), 123.6 (C-6), 133.3 (C-3a), 143.0 (C-2), and
143.5 (C-7a); m=z 193 (M þ 1, 100%).
1-[2-(2-Hydroxyethoxy)ethyl]benzimidazole 16[24]
The experimental procedure employed for the synthesis of N-allylbenzimidazole
4 was followed using benzimidazole 3 (1.007 g, 8.481 mmol), 60% NaH (0.6697 g,
27.9 mmol), 2-(chloroethoxy)ethanol 15 (1.2737 g, 10.22 mmol), and THF (20 ml).
The residual oil was purified by flash chromatography [on silica; elution with
EtOH-CHCl3-hexane (1:1.5:2.5)] to afford, as
a pale yellow oil, 1-[2-(2-
-hydroxyethoxy)ethyl]benzimidazole 16 (0.4089 g, 23.4%) (found: Mþ 206.10432;
C11H14N2O2 requires M, 206.10553); dH (400 MHz; CDCl3) 2.15 (1H, s, OH), 3.50
(2H, t, J ¼ 4.6 Hz, CH2), 3.66 (2H, t, J ¼ 4.6 Hz, CH2), 3.82 (2H, t, J ¼ 5.2 Hz,
CH2), 4.33 (2H, t, J ¼ 5.2 Hz, CH2), 7.25–7.29 (2H, m, 5- and 6-H), 7.40 (1H, d,
J ¼ 6.4 Hz, 4-H), 7.79 (1H, d, J ¼ 6.4 Hz, 7-H), and 7.96 (1H, s, 2-H); dC (100 MHz;
CDCl3) 45.0 (NCH2CH2O), 61.6 (OCH2CH2OH), 69.4 (NCH2CH2O), 72.6 (OCH2-
CH2OH), 109.4 (C-4), 120.3 (C-7), 122.2 (C-5), 122.9 (C-6), 133.8 (C-3a and C-7a),
and 143.5 (C-2); m=z 207 (M þ 1, 65.2%) and 132 (100%).
1-[(2-Hydroxyethoxy)methyl]benzimidazole diethyl phosphate 17
The experimental procedure employed for the synthesis of compound 21 was
followed, using 1-[(2-hydroxyethoxy)methyl]benzimidazole 14 (0.250 g, 1.30 mmol),
BuLi (1.6 M in hexane; 0.85 ml, 1.36 mmol), diethyl chlorophosphate (190 ml,
1.31 mmol), and THF (13 ml). The reaction mixture was stirred overnight at room
temperature, and the residual oil was purified by flash chromatography [on silica;
elution with EtOH=CHCl3=hexane (1:1.5:2.5)] to afford, as a yellow oil, 1-[(2-
hydroxyethoxy)methyl]benzimidazole diethyl phosphate 17 (0.0998 g, 23.3%); dH
(400 MHz; CDCl3) 1.25–1.28 (6H, m, POCH2CH3), 3.86–4.14 [6H, m, OCH2CH2OP
and P(OCH2CH3)2], 4.67 (2H, s, NCH2O), 7.24–7.31 (2H, m, 5- and 6-H), 7.39

BENZIMIDAZOLE-DERIVED ATP ANALOGUES
2585
(1H, d, J ¼ 8.2 Hz, 4-H), 7.78 (1H, d, J ¼ 8.2 Hz, 7-H), and 7.97 (1H, s, 2-H); dC
(100 MHz; CDCl3) 16.3 (d, J ¼ 7.3 Hz, POCH2CH3), 61.7 (d, J ¼ 5.6 Hz,
POCH2CH3), 64.1 (d, J ¼ 6.9 Hz, OCH2CH2OP), 66.2 (OCH2CH2OP), 94.7
(NCHO), 110.0 (C-40), 119.3 (C-7), 123.0 (C-5), 123.6 (C-6), 132.9 (C-3a), 140.8
(C-7a) and 143.2 (C-2); dP (162 MHz, CDCl3) ꢁ0.46.
1-[2-(2-Hydroxyethoxy)ethyl]benzimidazole diethyl phosphate 18
The experimental procedure employed for the synthesis of compound 21 was
followed, using N-[2-(2-hydroxyethoxy)ethyl]benzimidazole 16 (0.309 g, 1.50 mmol),
1.6 M BuLi in hexane (0.95 ml, 1.52 mmol), diethyl chlorophosphate (217 ml,
1.52 mmol), and THF (15 ml). The residual oil was purified by flash chromatography
[on silica; elution with EtOH=CHCl3=hexane (1:1.5:2.5)] to afford, as a yellow oil,
1-[2-(2-hydroxyethoxy)ethyl]benzimidazole diethyl phosphate 18 (0.129 g, 30%)
(found: Mþ, 342.13495; C15H23N2O5P requires M, 342.13446); dH (400 MHz;
CDCl3) 1.25 (6H, t, J ¼ 7.2 Hz, POCH2CH3), 3.48–3.51 (2H, m, OCH2CH2OP),
3.53–3.58 (2H, m, OCH2CH2OP), 3.78–3.80 (2H, m, NCH2CH2O), 3.97–4.09 (4H,
m, POCH2CH3), 4.30 (2H, t, J ¼Hz, NCH2CH2O), 7.21–7.25 (2H, m, 5- and
6-H), 7.35 (1H, d, J ¼ 6.8 Hz, 4-H), 7.73 (1H, d, J ¼ 6.8 Hz, 7-H) and 7.92 (1H, s,
2-H); dC (100 MHz; CDCl3) 16.0 (POCH2CH3), 44.9 (NCH2CH2O), 63.8
(POCH2CH3), 69.3 (NCH2CH2O), 70.0 (OCH2CH2OP), 70.5 (OCH2CH2OP),
109.5 (C-4), 120.1 (C-7), 122.0 (C-5), 122.8 (C-6), 133.7 (C-3a), 143.4 (C-7a), and
143.5 (C-2); dP (162 MHz, CDCl3) ꢁ0.48.
1-(3,4-Dihydroxybutyl)benzimidazole bis(diethyl phosphate) 22
The experimental procedure employed for the synthesis of compound 21 was
followed, using 1-(3,4-dihydroxybutyl)benzimidazole 8 (0.2140 g, 1.039 mmol), BuLi
(1.6 M in hexane; 0.65 ml, 1.1 mmol), diethyl chlorophoshate (39 ml, 1.1 mmol), and
THF (8ml). The residual oil was purified by radial chromatography [on silica;
elution with EtOH=CHCl3=hexane (1:1.5:2.5)] to afford, as a yellow oil, 1-(3,4-
dihydroxybutyl)benzimidazole bis(diethyl phosphate) 22 (24.2 mg, 4.87%) (found:
Mþ, 478.16403; C19H32N2O8P2 requires M, 478.16339); dH (400 MHz; CDCl3)
1.26–1.37 (12H, m, POCH2CH3), 1.90–2.05 and 2.23–2.67 (2H, m, 20-CH2), 4.04–4.16
{10H, m, [P(OCH2CH3)2]2 and 40-CH2}, 4.31–4.38 (2H, m, 10-CH2), 4.47–4.49 (1H,
m, 30-CH), 7.26–7.31 (1H, m, 5- and 6-H), 7.40 (1H, d, J ¼ 7.2Hz, 4-H), 7.79 (1H, d,
J ¼ 7.2 Hz, 7-H) and 8.05 (1H, s, 2-H); dC (100 MHz; CDCl3) 15.6–16.1 (POCH2CH3),
32.1 (d, J ¼ 8.1 Hz, C-20), 40.7 (C-1), 64.0 and 64.2 [P(OCH2CH3)2], 66.3 (d, J ¼ 10.2 Hz,
C-40), 71.3 (d, J ¼ 9.9 Hz, C-30), 109.5 (C-7). 120.0 (C-4), 122.0 (C-5), 122.9 (C-6), 133.4
(C-7a), 143.4 (C-2) and 143.6 (C-7a); dP (162MHz; CDCl3) ꢁ5.27 and ꢁ5.43.
ACKNOWLEDGMENTS
We are grateful to the South African Department of Science and Technology
(DST) Innovation Fund for a bursary (B.S.B.G.), the DST and Rhodes University
for generous financial support, and Ms. Y. C. Lee for running additional NMR
spectra.

2586
B. S. B. GXOYIYA, P. T. KAYE, AND C. KENYON
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