Microwave-assisted click chemistry for nucleoside functionalization: Useful derivatives for analytical and biological applications

Article abstract of DOI:10.1055/s-0032-1317964

A series of novel 5-(1,2,3-triazolyl)-2′-deoxyuridines were synthesized using a simple and convenient one-step synthetic procedure via the Huisgen reaction. The key step in these syntheses is a click reaction at the C-5 position under solvent free microwave irradiation and CuI as a catalyst. 5-Azidomethyl-2′-deoxyuridine was synthesized from thymidine and its click reactions with several alkynes provided triazole derivatives in good yields. The synthesized compounds showed only marginal antiviral activities [against human rhinovirus (HRV), hepatitis C virus (HCV) and HIV] and antibacterial activities against a series of Gram positive and Gram negative bacteria. Evaluation of fluorescence properties of pyrene-modified and EPR studies of nitroxyl spin-labeled deoxyuridines demonstrate the applicability of these compounds as valuable analytical tools. Georg Thieme Verlag Stuttgart - New York.

Full text of DOI:10.1055/s-0032-1317964

396▌
PAPER
paper
Microwave-Assisted Click Chemistry for Nucleoside Functionalization:
Useful Derivatives for Analytical and Biological Applications
Synthesis of Novel 5-(1,2,3-Triazolyl)-2′-deoxyuridines
Jamal Krim,a,b Moha Taourirte,a Christian Grünewald,b Ivan Krstic,c Joachim W. Engels*b
a
Laboratoire de Chimie Bioorganique et Macromoléculaire, Faculté des Sciences et Techniques-Guéliz, BP 549, 40 000 Marrakech, Maroc
b
c
Institute of Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Frankfurt am Main 60438, Germany
Fax +49(69)79829148; E-mail: joachim.engels@chemie.uni-frankfurt.de
Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt,
Frankfurt am Main 60438, Germany
Received: 22.10.2012; Accepted after revision: 11.12.2012
acids,8 or arylstannanes.9 A large number of the C-5-het-
eroaromatic derivatives of 2′-deoxyuridine have been syn-
thesized by Herdewijn and co-workers from 5-iodo-2′-
deoxyuridine.10 The [3+2] cycloaddition is a very power-
Abstract: A series of novel 5-(1,2,3-triazolyl)-2′-deoxyuridines
were synthesized using a simple and convenient one-step synthetic
procedure via the Huisgen reaction. The key step in these syntheses
is a click reaction at the C-5 position under solvent free microwave
irradiation and CuI as a catalyst. 5-Azidomethyl-2′-deoxyuridine ful reaction for synthesizing a diverse range of heteroaro-
matic five-membered rings.11 A number of 5-substituted
pyrimidine nucleosides, including those with substantial
was synthesized from thymidine and its click reactions with several
alkynes provided triazole derivatives in good yields. The synthe-
sized compounds showed only marginal antiviral activities [against
steric size and bearing polar substituents, are known to be
human rhinovirus (HRV), hepatitis C virus (HCV) and HIV] and
antibacterial activities against a series of Gram positive and Gram
a rich source for further exploration as antiviral and anti-
tumor agents.12
negative bacteria. Evaluation of fluorescence properties of pyrene-
modified and EPR studies of nitroxyl spin-labeled deoxyuridines
demonstrate the applicability of these compounds as valuable ana-
lytical tools.
Efforts aimed at synthesizing and isolating new active nu-
cleosides now require the development and elaboration of
new strategies yielding facile and rapid access to a large
variety of compounds. Click reactions were widely used
Key words: 5-azidomethyl-2′-deoxyuridine, microwave irradia-
tion, click chemistry, EPR, antibacterial
for the synthesis of modified nucleosides and oligonucle-
otides.13,14 Triazole heterocycles are found to be potent
antimicrobial,15 antiviral,16 and antiproliferative agents.16
Synthetic nucleoside analogues have high potential in me-
dicinal chemistry due to their important role as chemo-
therapeutic agents against viruses and cancer.1 These
agents behave as antimetabolites, compete with physio-
logic nucleosides, and consequently, interact with a large
number of intracellular targets to induce cytotoxicity.2
Due to the need for the base moiety to preserve the base
pairing functionalities, only minor modifications of the
base are usually found in biologically active nucleosides
analogues. The C-5 position is usually the position of
choice for introducing substituents in pyrimidine nucleo-
sides since it is not involved in Watson–Crick base pair-
ing.3 Among them, nucleosides with some heterocyclic
function at C-5 have emerged as an important class of nu-
cleoside analogues.4
The pharmaceutical importance of triazoles has prompted
us to design and synthesize various triazolo nucleosides.
In view of the biological importance of 1,2,3-triazoles, it
was of considerable interest to develop a rapid, facile, and
practical protocol for the formation of nucleosides incor-
porating this ring system (Figure 1).
O
N
HN
N
N
O
N
R1
R2O
O
OR2
A common approach is based upon the attachment of ac-
tive units at the C-5 position of the uracil base via an ethy-
nyl linker. Many procedures for modification of
pyrimidine nucleosides at C-5 involve palladium-cata-
lyzed cross-coupling reactions.5 More recently, proce-
dures have been developed employing the palladium-
catalyzed coupling of 5-iodo-2′-deoxyuridine and termi-
nal alkynes,6 electron-deficient alkenes,7 arylboronic
Figure 1 General structure of investigated compounds
Synthesis
The most widely used method now for the synthesis of tri-
azoles is the Huisgen–Meldal–Sharpless 1,3-dipolar cy-
cloaddition of alkynes with organic azides. In order to
obtain these triazolo nucleosides in higher yields with
shorter reaction times under mild reaction conditions, our
attention was turned to microwave irradiation reactions.
The use of microwave-assisted organic synthesis has at-
SYNTHESIS 2013, 45, 0396–0405
Advanced online publication: 09.01.2013
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DOI: 10.1055/s-0032-1317964; Art ID: SS-2012-T0817-OP
© Georg Thieme Verlag Stuttgart · New York

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Synthesis of Novel 5-(1,2,3-Triazolyl)-2′-deoxyuridines
397
O
O
N
O
HN
HN
HN
Br
O
N
O
O
N
TBDMSO
HO
TBDMSO
a
b
O
O
O
OTBDMS
OH
OTBDMS
O
N
1
O
N
O
N
HN
N3
N
N
HN
N
N
HN
N
N
O
O
O
TBDMSO
R
R
c
d
e
O
TBDMSO
HO
O
O
OTBDMS
OTBDMS
OH
2
3
4
Scheme 1 Reagents and conditions: (a) TBDMSCl, imidazole, DMF, r.t., 7 h; (b) NBS, CCl4, AIBN, 2 h, reflux; (c) NaN3, DMF, 4 h, reflux;
(d) CuI, RC≡CH, MW, 250 Hz, 120 °C, 2 min; (e) MeCN, TBAF, THF–H2O, r.t., 8 h.
tracted considerable interest over the last two decades, ditions, various acetylene derivatives were reacted with
leading often to remarkable decrease in reaction times, azidonucleoside 2 using microwave-assisted synthesis
significant enhancement of yields, easier workup and with copper iodide as a catalyst to afford the desired 1,4-
higher regioselectivity.17,18 Copper-catalyzed click chem- disubstituted 1,2,3-triazole nucleosides in good yields
istry involving azides and terminal acetylenes furnished (Scheme 1, Table 1). It should be noted that all these nu-
practical and efficient preparation of 1,4-disubstituted cleosides were obtained in moderate to good yields (from
1,2,3-triazoles from a wide range of substrates with excel- 56 to 91%) and high chromatographic purity (TLC) re-
lent selectivity.19–22
gardless of chemical nature of the starting alkyne. No
traces of 1,5-regioisomer were observed. Different al-
kynes were chosen in order to increase the molecular di-
versity around the triazole ring (long chain, polar,
aromatic, and heteroaromatic alkynes). The TBDMS
groups of the protected nucleosides 3a–g were then
cleaved using tetrabutylammonium fluoride (TBAF) in
THF solution to afford the corresponding free analogues
4a–g in high yields (Scheme 1). The structures of all com-
pounds were confirmed on the basis of 1H and 13C NMR
spectra and mass spectra. The formation of 1,4-disubsti-
tuted triazoles was unequivocally established by the char-
acteristic chemical shift value of the triazolyl proton (5-
CH) at δ = 8.05–8.52. The triazole ring formation can also
be identified from the 13C NMR spectra with the new sig-
nals of the olefinic C-atoms of the 1,2,3-triazole moiety at
δ (C-5) = 119.34–123.57 and δ (C-4) = 142.28–146.98.
Based on these ideas and in continuation of our project,18
we envisaged using this kind of reaction to functionalize
nucleosides at C-5 of the pyrimidine nucleobase. With
this aim in view, we wanted to synthesize new nucleosides
modified at C-5 by coupling with heterocyclic fragments
leading to either potentially biologically active deriva-
tives or tools for molecular biological studies. In the pres-
ent work, a strategy is developed for the synthesis of
desired compounds, a general structure of which is shown
in Figure 1.
The suggested approach by us to the synthesis of the
desired compounds involves first the preparation of pro-
tected 5-azidomethyl-2′-deoxyuridine from 2′-deoxythy-
midine. This method comprises three steps and two of
them (bromination and azidation) were performed in one
pot (Scheme 1). The protection of the 3′- and 5′-hydroxyl
groups of 2′-deoxythymidine was achieved using tert-bu-
tyldimethylsilyl chloride (TBDMSCl) in DMF for seven
hours to provide compound 1 in good yield (Scheme 1).
The bromination was achieved using N-bromosuccin-
imide (NBS) and a catalytic amount of 2,2′-azobis(isobu-
tyronitrile) (AIBN) under reflux condition in anhydrous
CCl4. Residual N-bromosuccinimide and succinimide
formed were removed from the reaction mixture by filtra-
tion.23 The resulting bromide was then azidated by using
sodium azide in DMF at 90–95 °C for four hours. This
three-step procedure afforded azide 2 in a good overall
yield of 46% (Scheme 1). Under optimized reaction con-
Biological Results
Antibacterial Activity
The deprotected compounds 4a–g were screened against
a panel of bacteria. These compounds were tested against
both Gram negative [Haemophilus influenzae (Hi3 Q1),
Escherichia coli (ATCC25922), Pseudomonas aerugino-
sa (Pa1)] and Gram positive strains [Staphylococcus aure-
us (Sa26 ATCC25923, Sa1 ATCC13709, Sa4, and Sa2
MultiR), Enterococcus faecalis (Ecalis ATCC29212), En-
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 396–405

398
J. Krim et al.
PAPER
was observed, which means that they did not inhibit the
replication (induction of viral cytopathogenicity).
Table 1 Triazolyl Compounds 3 and 4 Synthesized from 2
Entry
1
R
Producta Yield
(%)b
Producta Yield
(%)b
Fluorescence Properties of 1,2,3-Triazolpyrene and
Biphenyl Conjugates Bearing Deoxyuridine Tethers
3a
91
4a
74
Recently, much attention has been paid to modified nucle-
osides based on fluorescent nucleobases that are sensitive
to the close environment as easily detectable probes for
DNA hybridization.26 Therefore, development of conve-
nient labeling protocols and acquirement of suitably la-
beled bioactive molecules are important and becoming an
attractive research area in organic chemistry. Sharpless
click chemistry dramatically improved the regioselectivi-
ty and reaction rate of Huisgen 1,3-dipolar cycloaddition
and thus eliminates the need for elevated temperatures and
affords the 1,2,3-triazole product with easy purification.
These improvements make the Huisgen reaction to be an
ideal research tool in many applications, including the
fluorescent labeling of biomolecules. On the other hand,
pyrene and its derivatives have been widely used as fluo-
rescence probes in many applications, for example, fluo-
rescent labeling of oligonucleotides for DNA assays.26,27
For this, many modified nucleosides including pyrene at
C-5 position were synthesized using palladium-catalyzed
cross-coupling reaction.5 In continuation of our research
on fluorescent compounds,28 we report here the synthesis
and photophysical properties of two types of 1,2,3 triazole
nucleoside modified with pyrene and biphenyl.
2
3
3b
3c
78
91
4b
4c
85
90
N
OMe
F
4
5
3d
3e
88
74
4d
4e
88
80
O
N
NH
6
7
3f
56
61
4f
84
80
O
O
N
NH
3g
4g
O
a All products were characterized by 1H and 13C NMR spectroscopy
and mass spectrometry.
b Yields of the isolated products.
The 1,2,3-triazole ring formed from the terminal alkyne
(1-ethynylpyrene and 1-ethynylbiphenyl) and azidonucle-
oside was found to yield fluorescence. Compounds 3i and
3j were prepared employing a similar procedure as de-
scribed in the previous protocol of Scheme 1. The 1,4-di-
substituted [1,2,3]-triazole moiety was obtained in good
yield, 86% for 3i and 91% for 3j, respectively (Table 2).
terococcus faecium (Ecium1), Streptococcus pneumoniae
(Pn1 ATCC49619 and Pn9)] where linezolid and cipro-
floxacin were used as standard drugs. Antibacterial activ-
ities of the 5-(1,2,3-triazolyl)-2′-deoxyuridine derivatives
were determined by using agar dilution procedure. The
minimum inhibitory concentration (MIC)24 of synthesized
compounds against Gram positive and Gram negative
bacteria are summarized in Table S1 in the Supporting In-
formation. As shown in Table S1, none of the compounds
were found to be active against all the tested bacteria
strains at a range of the MICs below 64 μg/mL.
Table 2 1,2,3-Triazole Nucleoside 3i and 3j Synthesized from 2
Entry
1
R
Producta Yield (%)b
3i
86
Antiviral Activity and Cytotoxicity
The compounds 4a–g were then evaluated for their cyto-
toxicity and antiviral activity in human epithelial (HeLa)
cells for HRV and Human hepatocarcinoma (Huh) cells
for HCV. The EC50 and EC90 (represent concentrations, at
which respective 50% and 90% inhibition of viral replica-
tion is observed) and the CC50 (represent the concentra-
tion at which the metabolic activity of the cells would be
reduced to 50% of the metabolic activity of untreated
cells) were obtained. As can be seen in Table S2 (see the
Supporting Information), none of the compounds exhibit-
ed specific antiviral activity. 5-(1,2,3-Triazolyl)-2′-de-
oxyuridine was also tested against HIV25 but no activity
2
3j
91
a All products were characterized by 1H and 13C NMR spectroscopy
and mass spectrometry.
b Yields of the isolated products.
The structures of the ‘click’ functionalized compounds
3i–j were proved by 1H and 13C NMR spectroscopy. The
1H NMR spectra showed the disappearance of two termi-
nal hydrogens, two new singlets appeared at 8.0–8.2 ppm
attributed to the hydrogen from newly formed triazole
Synthesis 2013, 45, 396–405
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Synthesis of Novel 5-(1,2,3-Triazolyl)-2′-deoxyuridines
399
rings. The characteristic signals of the olefinic carbon methodology produced only one regioisomer in excellent
atoms of the 1,2,3-triazole moiety were identified in the yields of >90% (Table 4).
range of δ (C-5) = 120.86–124.13 and δ (C-4) = 147.60–
Table 4 Spin-Labeled 1,2,3-Triazoles
147.65.
Producta
Yield (%)b
In order to study the spectroscopic properties of deriva-
tives of 5-(1,2,3-triazolyl)deoxyuridines 3i,j, a prelimi-
nary investigation of their UV/Vis and fluorescence
emission spectra in dimethyl sulfoxide at room tempera-
ture was performed. Compound 3i exhibits a strong ab-
sorption around 280 and 350 nm, however, the absorption
band of 3i is centered around 280 nm (see Figure S1 in the
Supporting Information). Next, fluorescence measure-
ments were performed for the two compounds (see Figure
S2 in the Supporting Information) using identical concen-
trations as used for the measurement of the UV/Vis spec-
tra. Nucleoside click product 3i with pyrene ring shows
typical fluorescence around 394 nm (Table 3, entry 1)
with quantum yield (Φ = 0.04) and 3j shows fluorescence
at 344 nm (Φ = 0.01).
Entry
R
O
N
1
3k
>90
N
O
2
3l
>90
a All products were characterized by 1H and 13C NMR spectroscopy
(after reduction with phenylhydrazine) and mass spectrometry.
b Yields of the isolated products.
EPR Spectroscopy
Excitation and emission maxima and fluorescence quan-
tum yields are reported in Table 3. The fluorescence quan-
tum yields were determined according to the correlation
of Crosby29 using quinine sulfate (Φ = 0.55) in aqueous
0.1 N H2SO4 as standard.
Nitroxide radical contains one unpaired electron shared
between the nitrogen and the oxygen atoms. EPR spec-
trum of a nitroxide is determined by Zeeman interactions
of electron and nuclear spins with the external magnetic
field and hyperfine interaction of the electron spin
(S = 1/2) with the nuclear spin of nitrogen 14N (I = 1) and
carbon 13C (1.11% natural abundance, I = 1/2). At X-band
frequency (9.5 GHz) the spectra are dominated by the hy-
perfine interaction resulting in three intense lines coming
from 14N hyperfine interaction accompanied by weak sat-
ellite lines arising from 13C hyperfine splitting (Figure 2).
Table 3 Spectroscopic Properties of 3i–j in DMSO at Room Tem-
perature
Entry
Compd
λ
abs (nm) λem (nm)
Quantum yield (%)
1
2
3i
3j
352
282
394
344
0.04
0.01
However, the shape of an EPR spectrum depends not only
on static interactions within the paramagnetic molecule,
but also on dynamic processes (e.g., molecular tumbling)
on the time scale of the EPR experiment. Thus, at X-band
EPR spectra are sensitive to ps-ns tumbling time scales.
Molecular tumbling is a random process with a timescale
determined by the rotational correlation time τc, which is
the characteristic time after which initially aligned mole-
cules lose their alignment. When the radical motion slows
down the lines become broader and spectral shape chang-
es. For degassed or argon saturated samples, as in our
case, the line width depends on nonresolved hyperfine
coupling of the protons.
The reason for the low quantum yield might be other de-
activation processes like charge transfer between nucleo-
base and the modified triazole moiety and needs further
investigation.
Spin Labeling by Click Chemistry
Structures and dynamic of macromolecules including oli-
gonucleotides and proteins have been extensively studied
using EPR spectroscopy.30 These studies require the in-
corporation of a spin label (a stable free radical, e.g., a ni-
troxide) into the oligonucleotides31 or protein.32 In order
to expand the repertoire of 1,2,3-triazoles nucleoside
analogues33 we investigated the synthesis of novel spin-
labeled 5-(1,2,3-triazolyl)deoxyuridines containing ni-
troxides TPA (2,2,5,5-tetramethylpyrrolin-1-oxyl-3-acet-
ylene) and TEMPA (2,2,6,6-tetramethyl-1,2,3,6-
tetrahydropyridine-1-oxyl-4-acetylene).
By simulating the line width and the shape of nitroxide
spectra the rotational correlation time can be accessed.
For isotropic rotational diffusion of the molecule in solu-
tion, the size of the molecule can be related to correlation
time according to Stokes–Einstein equation (Equation 1).
4pha3
tc
=
3kT
Construction of the desired spin label at the 1,2,3-triazole
moiety was again achieved using Cu(I)-catalyzed Huis-
gen’s 1,3-dipolar cycloaddition under solvent-free and
microwave irradiation (Scheme 1). As expected, this
Equation 1 Stokes–Einstein where α is the hydrodynamic radius of
the probe, η is the viscosity, and k and T represent the Boltzmann con-
stant and the temperature, respectively.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 396–405

400
J. Krim et al.
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Figure 2 EPR spectra of spin label TPA (black) and product 3k (red) in toluene–mineral oil mixture at room temperature (A) and at 230 K (B)
normalized to the number of spins
Our intention was to use EPR spectroscopy to follow the solid-phase synthesis of spin-labeled nucleic acids for
synthesis of 3k and 3l from 2. As can be seen directly from structural studies by pulsed electron–electron double res-
the spectra, already at room temperature (Figure 2, A), at- onance (PELDOR) spectroscopy.30
tachment of protected nucleoside to small radical TPA
In conclusion, we have developed efficient methods for
leads to broadening of all the lines and loss in the peak
the introduction of 1,2,3-triazole heterocycles in the 5-po-
height. According to simulations performed using EasyS-
sition of pyrimidine nucleosides. These reactions were
pin,34 the rotational correlation time changes from 10 ps to
carried out under microwave irradiation and solvent-free
160 ps corresponding to a 2.5-fold increase in the diame-
conditions. This new strategy gives facile and rapid access
ter of the investigated molecule upon reaction. In more
to a large variety of compounds. The antibacterial and an-
viscous solution of the solvent mixture at 230 K, tumbling
tiviral activities of these 1,2,3-triazole compounds were
tested. None of the compounds was found to be really ac-
tive against all the tested bacterial strains. Some com-
gets slower and since the 3k enters intermediate dynamic
regime the differences in spectra are more pronounced
(Figure 2, B). The rotational correlation time changes now
pounds showed antibacterial activity only in a range of the
from 90 ps for TPA to 1600 ps for the product 3k. Simu-
MICs higher than 64 μg/mL. The compounds 4a–g were
lations depicted in Figure 3 clearly show that reaction was
evaluated for their cytotoxicity and antiviral activity in
quantitative and that there is no residual, unreacted adduct
human epithelial (HeLa) cells for HRV and Human hepa-
TPA left, because this small species gives a very sharp
tocarcinoma (Huh) cells for HCV. None of the com-
spectrum (Figure 3, A) and would be easily detected on
pounds exhibited specific antiviral activity. Moreover for
analytical use, alkynylpyrene and biphenyl were conju-
gated with azido 2′-deoxyuridine yielding weakly fluores-
top of broad lines coming from 3k (Figure 3, B) when
more than 10% is present.
Based on EPR experimental results and spectral simula- cent 1,2,3-triazole conjugates. Evaluation of spin label
tions, we inferred that coupling of spin labels TPA and properties and EPR studies of five- and six-membered ni-
TEMPA to protected nucleoside 2 by click chemistry pro- troxide compounds (TPA, TEMPO) were carried out and
ceeded in yields higher than 90%. This procedure, there- their spectra measured, proving very high labeling effi-
fore, sets the ground for application of these precursors for ciency.
Figure 3 EPR spectra recorded at 230 K (green) and simulation (blue) for spin label TPA (A) and product 3k (B)
Synthesis 2013, 45, 396–405
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PAPER
Synthesis of Novel 5-(1,2,3-Triazolyl)-2′-deoxyuridines
401
25.7 (CCH3a), 25.6 (CCH3b), 17.9 (CCH3a), 17.6 (CCH3b), 12.1
(CH3), –5.6 (SiCH3a), –5.0 (SiCH3b), –4.9 (SiCH3c).
All chemicals were purchased from Alfa Aesar, Acros, Aldrich,
Sigma, or Fluka. Solvents were of laboratory grade. TLC: alumi-
num sheets, silica gel 60 F254, column flash chromatography (FC).
1H and 13C NMR spectra were recorded in CDCl3 and DMSO-d6 on
a Bruker AC 250 MHz and AC 400 MHz with TMS as an internal
standard. Chemical shifts are given in ppm and spin-spin coupling
constants, J, are given in Hz (standard abbreviations are used to de-
scribe the signal multiplicity). DIEA: N,N-diisopropylethylamine;
T: 1,2,3-triazole; B: heterocyclic base; TPA: 2,2,5,5-tetramethyl-
pyrrolin-1-yloxyl); TEMPO: 2,2,6,6-tetramethylpiperidin-1-ylox-
yl). Mass spectra were obtained by using ESI/MS.
ESI-MS: m/z calcd for C22H42N2O5Si2 [M + H]: 471.26; found:
471.6.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-(azidomethyl)-2′-deoxy-
uridine (2)
NBS (0.75 g, 4.25 mmol) and a catalytic amount of AIBN were add-
ed to a solution of 1 (1 g, 2.12 mmol) in anhyd CCl4 (300 mL) under
an inert atmosphere. The reaction mixture was refluxed for 2 or 5 h,
during which time the solution changed from colorless to orange
and then dry N2 was bubbled through the solution for 30 min to re-
move the HBr formed. Residual NBS and succinimide were re-
moved by filtration. Finally, solvents were evaporated under
reduced pressure and the crude syrup was dissolved in anhyd DMF
(100 mL). To the solution was added NaN3 (0.34 g, 5.3 mmol), and
the resulting mixture was stirred at 90 °C for 4 h. After cooling, the
solution was extracted with Et2O (2 × 80 mL), and the combined
Et2O layers were washed with brine (2 × 40 mL), and dried (MgSO4).
After removal of solvent under reduced pressure, the crude product
was chromatographed on silica gel using CH2Cl2–MeOH (99:1) to
afford a pale yellow viscous residue; yield: 0.49 g (46%).
Microwave Irradiation Experiments: All microwave irradiation ex-
periments were carried out in a dedicated CEM-Discover mono-
mode microwave apparatus, operating at a frequency of 2455 MHz
with continuous irradiation power from 0 to 300 W ± 10%.
UV/VIS and fluorescence spectroscopy: The electronic absorption
spectra were obtained on Jasco V-650 spectrometer and fluores-
cence emission spectra were recorded on Hitachi F-4500 fluores-
cence spectrometer, in both cases using quartz cuvettes (1 cm). The
fluorescence quantum yields were calculated by the comparative
method relative to quinine sulfate (Φ = 0.55) in aq 0.1 N H2SO4.
1H NMR (CDCl3): δ = 9.41 (s, 1 H, NH), 7.60 (s, 1 H, H-6), 6.19
(dd, J = 5.94, 7.54 Hz, 1 H, H-1′), 4.32–4.25 (m, 1 H, H-3′), 4.00 (q,
J = 13.91 Hz, CH2N, 2 H), 3.85 (m, 1 H, H-4′), 3.75 (dd, J = 2.70,
11.3 Hz, 1 H, H-5′a), 3.65 (dd, J = 2.5, 11.4 Hz, 1 H, H-5′b), 2.21
(ddd, J = 2.6, 5.7, 13.1 Hz, 1 H, H-2′a), 1.95–1.79 (m, 1 H, H-2′b),
0.81 [s, 9 H, C(CH3)3], 0.78 [s, 9 H, C(CH3)3], 0.00 [s, 6 H,
Si(CH3)2], –0.03 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 162.79 (C-4), 150.04 (C-2), 138.53 (C-6),
109.53 (C-5), 88.13 (C-4′), 85.45 (C-1′), 72.23 (C-3′), 63.02 (C-5′),
47.19 (CH2), 41.66 (C-2′), 25.98 (CCH3a), 25.79 (CCH3b), 18.47
(CCH3a), 18.04 (CCH3b), –4.59 (SiCH3a), –4.79 (SiCH3b), –5.38
(SiCH3c).
Biological Test: MICs were determined based on CLSI
methodology24 by a 2-fold broth dilution technique in Mueller Hin-
ton (MH, pH 7.4 Biorad). For S. pneumoniae the medium was brain
heart infusion broth +4% red blood cell extract. For H. influenzae
the medium was HTM (Haemophilus Test Medium consisting of
MH + 5 g/L yeast extract + hemin 15 mg/L + NAD 20 mg/L). Over-
night cultures were diluted to obtain the final inoculum of
105 cfu/well. Incubation was at 37 °C overnight in ambient air.
EPR measurements: X-band (9.54 GHz) cw-EPR measurements
were performed at r.t. and at 230 K using Bruker E500 spectrometer
equipped with a TE102 cavity and BVT 3000 variable temperature
unit. Experimental parameters were set at 100 kHz modulation fre-
quency, 0.05 mT modulation amplitude, 1 mW microwave power,
40.96 ms time constant, 40.96 ms conversion time, 1024 points, 7
mT sweep width, 4 scans.
ESI-MS: m/z calcd for C22H41N5O5Si2 [M + H]: 512.26; found:
512.8.
5-(1,2,3-Triazolyl)-2′-deoxyuridines 3; General Procedure
A mixture of azide 2 (100 mg, 0.19 mmol), DIEA (24.5 mg, 0.19
mmol), CuI (3.6 mg, 0.019 mmol), and the corresponding alkyne
(0.38 mmol) was subjected to microwave irradiation for 2 min (250
W, 120 °C) without solvent under stirring. The obtained residue
was purified on silica gel with CH2Cl2–MeOH (98:2) as eluent to
give 3 as a white powder (Table 1).
Aliquots of 100 μL of 0.5 mM radical solution in toluene–mineral
oil mixture (1:1) were placed into quartz EPR tubes with 4 mm outer
diameter and prior the EPR measurements purged 15 min with ar-
gon to remove traces of O2, which cause line broadening.
Simulation of the spectra was conducted with EasySpin software
package using the following parameters: g = [2.00809 2.00585
2.00202], A(14N) = [11.2 11.2 96] MHz, A(13C) = [16.8 16.8 16.8]
MHz, Sys.lwpp = 0.13 mT and the only variable was the isotropic
rotational correlation time.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-[(4-phenyl-1H-1,2,3-tri-
azol-1-yl)methyl]-2′-deoxyuridine (3a)
Yield: 0.106 g (91%); amorphous solid.
Sugar Protection Procedure; 3′,5′-Bis-O-(tert-butyldimethylsi-
lyl)thymidine (1)
1H NMR (CDCl3): δ = 9.44 (s, 1 H, NH), 8.00 (s, 1 H, H-5, triazole),
7.90 (s, 1 H, H-6), 7.74 (d, J = 7.1 Hz, H-2–6, phenyl, 2 H), 7.47–
7.20 (m, 3 H, H-4 and H-3–5, phenyl), 6.19 (dd, J = 5.82, 7.78 Hz,
1 H, H-1′), 5.17 (s, 2 H, T-CH2-B), 4.35–4.28 (m, 1 H, H-3′), 3.90
(m, 1 H, H-4′), 3.77 (dd, J = 3.1, 11.3 Hz, 1 H, H-5′a), 3.69 (dd,
J = 2.8, 11.3 Hz, 1 H, H-5′b), 2.23 (ddd, J = 2.0, 5.6, 13.0 Hz, 1 H,
H-2′a), 2.00–1.89 (m, 1 H, H-2′b), 0.86 [s, 9 H, C(CH3)3], 0.81 [s, 9
H, C(CH3)3], 0.07 [s, 6 H, Si(CH3)2], 0.00 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 163.01 (C-4), 149.81 (C-2), 147.94 (C-4, tri-
azole), 140.73 (C-6), 130.67 (C-1, phenyl), 128.77 (C-3 and C-5,
phenyl), 128.07 (C-4, phenyl), 125.82 (2 × C, C-2 and C-6, phenyl),
120.88 (C-5, triazole), 108.78 (C-5), 88.39 (C-4′), 85.84 (C-1′),
72.55 (C-3′), 63.22 (C-5′), 46.46 (CH2), 41.65 (C-2′), 26.02
(CCH3a), 25.80 (CCH3b), 18.53 (CCH3a), 18.04 (CCH3b), –4.60
(SiCH3a), –4.77 (SiCH3b), –5.19 (SiCH3c), –5.27 (SiCH3d).
Thymidine (2.42 g, 10.0 mmol) was added to imidazole (4.08 g,
60.0 mmol) and TBDMSCl (4.52 g, 30.0 mmol) in DMF (75 mL) at
r.t. under argon atmosphere, and the mixture was stirred for 7 h. The
reaction was quenched with MeOH (5 mL) and diluted with EtOAc
(400 mL). The organic layer was washed with H2O (2 × 200 mL),
sat. aq NaHCO3 (200 mL) and brine (200 mL), dried (Na2SO4), and
concentrated to afford a solid mass, which was then purified by col-
umn chromatography on silica gel, elution with 15% EtOAc in hex-
ane yielded 4.51g (96%) of a white amorphous solid.
1H NMR (CDCl3): δ = 8.69 (br s, 1 H, NH), 7.47 (s, 1 H, H-6), 6.33
(t, J = 6.6 Hz, 1 H, H-1′), 4.40 (m, 1 H, H-3′), 3.93 (m, 1 H, H-4′),
3.89–3.85 (m, 1 H, H-5′a), 3.77–3.74 (m, 1 H, H-5′b), 2.26–2.22 (m,
1 H, H-2′a), 2.02–1.97 (m, 1 H, H-2′b), 1.91 (s, 3 H, CH3), 0.92 [s,
9 H, C(CH3)3], 0.89 [s, 9 H, C(CH3)3], 0.10 [s, 6 H, Si(CH3)2], 0.08
[s, 6 H, Si(CH3)2].
ESI-MS: m/z calcd for C30H47N5O5Si2 [M + H]: 614.31; found:
13C NMR (CDCl3): δ = 163.5 (C-4), 150.3 (C-2), 135.5 (C-6), 109.4
(C-5), 86.6 (C-4′), 83.6 (C-1′), 71.9 (C-3′), 62.6 (C-5′), 39.0 (C-2′),
614.6.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 396–405

402
J. Krim et al.
PAPER
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-{[4-(pyridin-2-yl)-1H-
1,2,3-triazol-1-yl]methyl}-2′-deoxyuridine (3b)
Yield: 0.091 g (78%); amorphous solid.
1H NMR (CDCl3): δ = 8.41 (s, 1 H, NH), 7.78 (s, 1 H, H-5, triazole),
7.40 (s, 1 H, H-6), 6.10 (dd, J = 5.7, 7.8 Hz, 1 H, H-1′), 5.02 (s, 2 H,
T-CH2-B), 4.30–4.21 (m, 1 H, H-3′), 3.83 (m, 1 H, H-4′), 3.67 (m,
1 H, H-5′a), 3.62 (dd, J = 3.0, 11.4 Hz, 1 H, H-5′b), 2.58–2.49 (m,
2 H, T-CH2), 2.14 (m, 1 H, H-2′a), 1.94–1.80 (m, 1 H, H-2′b), 1.34
[m, 8 H, (CH2)4], 0.79 [s, 9 H, C(CH3)3], 0.75 [s, 12 H, C(CH3)3,
CH3], 0.00 [s, 6 H, Si(CH3)2], –0.06 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 162.40 (C-4), 149.55 (C-2), 148.67 (C-4, tri-
azole), 140.58 (C-6), 121.73 (C-5, triazole), 108.87 (C-5), 88.40 (C-
4′), 85.85 (C-1′), 72.60 (C-3′), 63.26 (C-5′), 46.20 (CH2), 41.56 (C-
2′), 31.60 (C-1′′), 29.44 (C-2′′), 28.99 (C-3′′), 26.04 (CCH3a), 25.78
(CCH3b, C-4′′), 22.58 (C-6′′), 18.81 (CCH3a), 18.03 (CCH3b), 14.09
(C-6′′), –4.62 (SiCH3a), –4.78 (SiCH3b), –5.20 (SiCH3c), –5.30
(SiCH3d).
1H NMR (CDCl3): δ = 9.37 (br s, 1 H, NH), 8.51 (s, 1 H, H-2, pyr-
idine), 8.38 (s, 1 H, H-5, triazole), 8.06 (d, J = 7.52 Hz, 1 H, H-4,
pyridine), 7.87 (s, 1 H, H-6), 7.67 (t, J = 7.03 Hz, 1 H, H-5, pyri-
dine), 7.13 (s, 1 H, H-3, pyridine), 6.23–6.15 (m, 1 H, H-1′), 5.21 (s,
2 H, T-CH2-B), 4.35–4.27 (m, 1 H, H-3′), 3.90 (m, 1 H, H-4′), 3.77
(dd, J = 3.0, 11.3 Hz, 1 H, H-5′a), 3.68 (dd, J = 2.7, 11.3 Hz, 1 H,
H-5′b), 2.24 (ddd, J = 1.7, 5.40, 12.8 Hz, 1 H, H-2′a), 1.87–2.00 (m,
1 H, H-2′b), 0.85 [s, 9 H, C(CH3)3], 0.81 [s, 9 H, C(CH3)3], 0.06 [s,
6 H, Si(CH3)2], 0.00 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 162.56 (C-4), 149.85 (2 × C, C-2 and C-6,
pyridine), 149.41 (C-2, pyridine), 140.55 (C-4, triazole, C-6),
136.87 (C-4, pyridine), 123.13 (C-5, pyridine), 122.78 (C-3, pyri-
dine), 120.29 (C-5, triazole), 108.54 (C-5), 88.29 (C-4′), 85.75 (C-
1′), 72.49 (C-3′), 63.18 (C-5′), 46.53 (CH2), 41.61 (C-2′), 26.03
(CCH3a), 25.79 (CCH3b), 18.50 (CCH3a), 18.03 (CCH3b), –4.61
(SiCH3a), –4.78 (SiCH3b), –5.21 (SiCH3c), –5.31 (SiCH3d).
ESI-MS: m/z calcd for C30H55N5O5Si2: 621.37; found: 621.8.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-[(4-methylthyminyl-1H-
1,2,3-triazol-1-yl)methyl]-2′-deoxyuridine (3f)
Yield: 0.071 (56%); viscous residue.
1H NMR (CDCl3): δ = 10.42 (s, 1 H, NH), 9.99 (s, 1 H, NH), 7.96
(s, 1 H, H-5, triazole), 7.91 (s, 1 H, H-6), 7.26 (s, 1 H, H-6, thy-
mine), 6.23–6.14 (m, 1 H, H-1′), 5.13 (s, 2 H, T-CH2-B), 4.88 (s, 2
H, B-CH2-T), 4.34–4.29 (m, 1 H, H-3′), 3.90 (m, 1 H, H-4′), 3.79
(dd, J = 11.33, 2.56 Hz, 1 H, H-5′a), 3.69 (dd, J = 11.3, 2.3 Hz, 1 H,
H-5′b), 2.30–2.19 (m, 1 H, H-2′a), 2.07–1.86 (m, 1 H, H-2′b), 1.81
(s, 3 H, CH3), 0.85 [s, 9 H, C(CH3)3], 0.81 [s, 9 H, C(CH3)3], 0.06
[s, 6 H, Si(CH3)2], 0.00 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 164.64 (C-4), 163.34 (C-4), 151.17 (C-2),
150.08 (C-2), 140.84 (C-4, triazole), 140.19 (2 × C, C-6, C-6),
124.72 (C-5, triazole), 111.29 (C-5), 108.31 (C-5), 88.35 (C-4′),
85.84 (C-1′), 72.46 (C-3′), 63.15 (C-5′), 46.63 (CH2), 42.66 (CH2),
41.76 (C-2′), 26.03 (CCH3a), 25.79 (CCH3b), 18.50 (CCH3a), 18.04
(CCH3b), 12.35 (CH3), –4.59 (SiCH3a), –4.78 (SiCH3b), –5.22
(SiCH3c), –5.31 (SiCH3d).
ESI-MS: m/z calcd for C29H46N6O5Si2 [M + H]: 615.3; found: 615.8.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-{[4-(4-methoxyphenyl)-
1H-1,2,3-triazol-1-yl]methyl}-2′-deoxyuridine (3c)
Yield: 0.111 g (91%); amorphous solid.
1H NMR (CDCl3): δ = 9.21 (s, 1 H, NH), 7.89 (2 s, 2 H, H-6 and H-
5, triazole), 7.66 (d, J = 8.59 Hz, 2 H, H-3 and H-5, phenyl), 6.85
(d, J = 8.6 Hz, 2 H, H-2 and H-6, phenyl), 6.19 (dd, J = 5.9, 7.61 Hz,
1 H, H-1′), 5.16 (s, 2 H, T-CH2-B), 4.35–4.28 (m, 1 H, H-3′), 3.90
(m, 1 H, H-4′), 3.81–3.65 (m, 5 H, H-5′a, H-5′b, OCH3), 2.29–2.18
(1 H, H-2′a), 2.00–1.87 (m, 1 H, H-2′b), 0.86 [s, 9 H, C(CH3)3], 0.81
[s, 9 H, C(CH3)3], 0.07 [s, 6 H, Si(CH3)2], 0.00 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 162.85 (C-4), 159.58 (C-1, phenyl), 149.76
(C-2), 147.81 (C-4, triazole), 140.69 (C-6), 127.10 (2 × C, C-3 and
C-5, phenyl), 123.40 (C-4, phenyl), 120.03 (C-5, triazole), 114.22
(2 × C, C-2 and C-6, phenyl), 108.83 (C-5), 88.38 (C-4′), 85.83 (C-
1′), 72.55 (C-3′), 63.22 (C-5′), 55.33 (CH3), 46.40 (CH2), 41.62 (C-
2′), 26.05 (CCH3a), 25.79 (CCH3b), 18.52 (CCH3a), 18.04 (CCH3b),
–4.61 (SiCH3a), –4.77 (SiCH3b), –5.19 (SiCH3c), –5.28 (SiCH3d).
ESI-MS: m/z calcd for C30H49N7O7Si2 [M + H]: 676.32; found:
676.9.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-[(4-methyluracilyl-1H-
1,2,3-triazol-1-yl)methyl]-2′-deoxyuridine (3g)
Yield: 0.076 g (61%); viscous residue.
ESI-MS: m/z calcd for C31H49N5O6Si2: 643.32; found: 643.54.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-{[4-(4-fluorophenyl)-1H-
1,2,3-triazol-1-yl]methyl}-2′-deoxyuridine (3d)
Yield: 0.105 g (88%); amorphous solid.
1H NMR (CDCl3): δ = 10.59 (s, 1 H, NH), 10.25 (s, 1 H, NH), 8.00
(s, 1 H, H-5, triazole), 7.91 (s, 1 H, H-6), 7.45 (d, J = 7.8 Hz, 1 H,
H-6, uracil), 6.19 (dd, J = 5.96, 7.5 Hz, 1 H, H-1′), 5.63 (d, J = 7.6
Hz, 1 H, H-5, uracil), 5.13 (s, 2 H, T-CH2-B), 4.92 (s, 2 H, B-CH2-
T), 4.35–4.28 (m, 1 H, H-3′), 3.90 (m, 1 H, H-4′), 3.79 (dd, J = 2.8,
11.3 Hz, 1 H, H-5′a), 3.69 (dd, J = 2.6, 11.3 Hz, 1 H, H-5′b), 2.30–
2.18 (m, 1 H, H-2′a), 2.00–1.88 (m, 1 H, H-2′b), 0.85 [s, 9 H,
C(CH3)3], 0.81 [s, 9 H, C(CH3)3], 0.06 [s, 6 H, Si(CH3)2], 0.00 [s, 6
H, Si(CH3)2].
13C NMR (CDCl3): δ = 164.27 (C-4), 163.52 (C-4), 151.17 (C-2),
150.12 (C-2), 144.43 (C-4, triazole), 140.89 (2 × C, C-6, C-6),
108.29 (C-5, triazole), 102.71 (2 × C, C-5, C-5), 88.32 (C-4′), 85.81
(C-1′), 72.45 (C-3′), 63.15 (C-5′), 46.69 (CH2), 42.87 (CH2), 41.70
(C-2′), 26.03 (CCH3a), 25.79 (CCH3b), 18.50 (CCH3a), 18.03
(CCH3b), –4.59 (SiCH3a), –4.78 (SiCH3b), –5.22 (SiCH3c), –5.30
(SiCH3d).
1H NMR (CDCl3): δ = 9.64 (s, 1 H, NH), 7.97 (s, 1 H, H-5, triazole),
7.92 (s, 1 H, H-6), 7.71 (dd, J = 5.4, 8.5 Hz, 2 H, H-3 and H-5, phe-
nyl), 6.99 (t, J = 8.67 Hz, 2 H, H-2 and H-6, phenyl), 6.19 (dd,
J = 5.8, 7.7 Hz, 1 H, H-1′), 5.17 (s, 2 H, T-CH2-B), 4.35–4.28 (m, 1
H, H-3′), 3.90 (m, 1 H, H-4′), 3.78 (dd, J = 2.9, 11.3 Hz, 1 H, H-5′a),
3.69 (dd, J = 2.7, 11.37 Hz, 1 H, H-5′b), 2.23 (ddd, J = 1.9, 5.5, 12.9
Hz, 1 H, H-2′a), 1.99–1.87 (m, 1 H, H-2′b), 0.85 [s, 9 H, C(CH3)3],
0.80 [s, 9 H, C(CH3)3], 0.07 [s, 6 H, Si(CH3)2)], 0.00 [s, 6 H,
Si(CH3)2].
13C NMR (CDCl3): δ = 164.62–160.68 (C-4, penhyl), 163.19 (C-4),
149.85 (C-2), 147.05 (C-4, triazole), 140.81 (C-6), 127.59 and
127.46 (2 × C, C-2 and C-6, phenyl), 126.88 (C-1, phenyl), 120.70
(C-5, triazole), 115.91 and 115.56 (C-3 and C-5, phenyl), 108.69
(C-5), 88.41 (C-4′), 85.84 (C-1′), 72.55 (C-3′), 63.22 (C-5′), 46.52
(CH2), 41.70 (C-2′), 26.05 (CCH3a), 25.79 (CCH3b), 18.52 (CCH3a),
18.04 (CCH3b), –4.61 (SiCH3a), –4.78 (SiCH3b), –5.19 (SiCH3c),
–5.28 (SiCH3d).
ESI-MS: m/z calcd for C29H47N7O7Si2 [M + H]: 662.31; found:
663.0.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-{[4-(pyren-2-yl)-1H-
1,2,3-triazol-1-yl]methyl}-2′-deoxyuridine (3i)
Yield: 0.120 g (86%); viscous residue.
1H NMR (CDCl3): δ = 9.31 (s, 1 H, NH), 8.61 (d, J = 9.31 Hz, 1 H,
pyrene), 8.20 (s, 1 H, H-5, triazole), 8.16–7.85 (m, 9 H, H-6 and H-
pyrene), 6.20 (dd, J = 7.8, 5.7 Hz, 1 H, H-1′), 5.28 (s, 2 H, T-CH2-
B), 4.37–4.29 (m, 1 H, H-3′), 3.91 (m, 1 H, H-4′), 3.75 (ddd,
J = 23.1, 11.38, 3.0 Hz, 2 H, H-5′), 2.24 (ddd, J = 13.0, 5.61, 2.1
ESI-MS: m/z calcd for C30H46FN5O5Si2 [M + H]: 632.3; found:
632.4.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-[(4-hexyl-1H-1,2,3-tri-
azol-1-yl)methyl]-2′-deoxyuridine (3e)
Yield: 0.087 g (74%); amorphous solid.
Synthesis 2013, 45, 396–405
© Georg Thieme Verlag Stuttgart · New York

PAPER
Synthesis of Novel 5-(1,2,3-Triazolyl)-2′-deoxyuridines
403
Hz, 1 H, H-2′a), 2.03–1.89 (m, 1 H, H-2′b), 0.88 [s, 9 H, C(CH3)3],
0.81 [s, 9 H, C(CH3)3], 0.09 [s, 6 H, Si(CH3)2], 0.00 [s, 6 H,
Si(CH3)2].
1.91 (m, 1 H, H-2′b), 1.14 (m, 6 H, CH3 TEMPO), 1.22 (s, 6 H, CH3
TEMPO), 0.82 [s, 9 H, C(CH3)3], 0.85 [s, 9 H, C(CH3)3], 0.05 [s, 6
H, Si(CH3)2], 0.00 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 162.96 (C-4), 149.85 (C-2), 147.60 (C-4, tri-
azole), 140.81 (C-6), 130.96 (C, pyrene), 131.29 (C, pyrene),
131.41 (C, pyrene), 128.59 (C, pyrene), 128.11 (C, pyrene), 127.75
(C, pyrene), 127.37 (C, pyrene), 127.24 (C, pyrene), 126.02 (C, py-
rene), 125.32 (2 C, pyrene), 125.09 (2 C, pyrene), 124.96 (C, py-
rene), 124.82 (2 C, pyrene), 124.13 (C-5, triazole), 108.77 (C-5),
88.43 (C-4′), 85.93 (C-1′), 72.56 (C-3′), 63.24 (C-5′), 46.65 (CH2),
41.71 (C-2′), 26.08 (CCH3a), 25.81 (CCH3b), 18.55 (CCH3a), 18.05
(CCH3b), –4.58 (SiCH3a), –4.75 (SiCH3b), –5.15 (SiCH3c), –5.25
(SiCH3d).
13C NMR (CDCl3 with phenylhydrazine): δ = 163.69 (C-4), 151.40
(C-2), 150.61 (C-4, triazole), 148.05 (C=CH TEMPO), 140.60 (C-
6), 131.27 (CH=C TEMPO), 121.42 (C-5, triazole), 108.79 (C-5),
88.28 (C-4′), 85.75 (C-1′), 72.58 (C-3′), 63.27 (C-5′), 60.37
[C(CH3)2 TEMPO], 58.08 [C(CH3)2 TEMPO], 46.41 (CH2), 41.45
(C-2′), 40.72 (CH2 TEMPO), 26.12 (CCH3b and CCH3 TEMPO),
25.89 (CCH3a), 25.01 (CCH3 TEMPO), 18.56 (CCH3a), 18.11
(CCH3b), 14.29 (CCH3b), –4.51 (SiCH3a), –4.68 (SiCH3b), –5.12
(SiCH3c), –5.20 (SiCH3d).
ESI-MS: m/z calcd for C33H57N6O6Si2· [M + H]: 690.38; found:
ESI-MS: m/z calcd for C40H51N5O5Si2 [M + H]: 738.34; found:
691.3.
739.1
Deprotection of 3′,5′-Hydroxy Groups in 3a–h;
General Procedure
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-{[4-biphenyl-1H-1,2,3-
triazol-1-yl]methyl}-2′-deoxyuridine (3j)
Yield: 0.119 g (91%); viscous residue.
Compound 3 (0.1 mmol) was dissolved in MeCN (ca. 20 mL) and
treated with TBAF (65 mg, 0.25 mmol) in THF–H2O (0.25 mL).
The reaction mixture was stirred at r.t. for 5–8 h. The solvent was
removed under reduced pressure and the residue obtained was puri-
fied on silica gel column using CH2Cl2 and MeOH (95:5) as eluent
(Table 1).
1H NMR (CDCl3): δ = 8.99 (br s, 1 H, NH), 8.02 (s, 1 H, H-5, tri-
azole), 7.91 (s, 1 H, H-6), 7.84–7.78 (m, 2 H, phenyl), 7.59–7.49 (m,
4 H, phenyl), 7.40–7.24 (m, 3 H, phenyl), 6.19 (dd, J = 7.9, 5.7 Hz,
1 H, H-1′), 5.19 (s, 2 H, T-CH2-B), 4.32 (m, 1 H, H-3′), 3.90 (dd,
J = 5.2, 2.7 Hz, 1 H, H-4′), 3.74 (dq, J = 11.3, 3.0 Hz, 2 H, H-5′),
2.24 (ddd, J = 13.1, 5.6, 2.2 Hz, 1 H, H-2′a), 2.01–1.86 (m, 1 H, H-
2′b), 0.86 [s, 9 H, C(CH3)3], 0.82 [s, 9 H, C(CH3)3], 0.08 [s, 6 H,
Si(CH3)2], 0.00 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3): δ = 162.82 (C-4), 149.73 (C-2), 147.65 (C-4, tri-
azole), 140.84 (C-6), 140.73 (C, phenyl), 140.69 (C, phenyl),
129.66 (C, phenyl), 128.81 (2 C, phenyl), 127.44 (3 C, phenyl),
127.01 (2 C, phenyl), 126.18 (2 C, phenyl), 120.86 (C-5, triazole),
108.77 (C-5), 88.41 (C-4′), 85.86 (C-1′), 72.55 (C-3′), 63.23 (C-5′),
46.49 (CH2), 41.67 (C-2′), 26.06 (CCH3a), 25.79 (CCH3b), 18.53
(CCH3a), 18.04 (CCH3b), –4.60 (SiCH3a), –4.77 (SiCH3b), –5.18
(SiCH3c), –5.27 (SiCH3d).
5-[(4-Phenyl-1H-1,2,3-triazol-1-yl)methyl]-2′-deoxyuridine (4a)
Yield: 0.028 g (74%); white solid.
1H NMR (DMSO-d6): δ = 11.50 (s, 1 H, NH), 8.40 (s, 1 H, H-5, tri-
azole), 8.14 (s, 1 H, H-6), 7.76 (d, J = 7.5 Hz, 2 H, H-2–6, phenyl),
7.36 (t, J = 7.3 Hz, 1 H, H-4, phenyl), 7.26 (d, J = 6.9 Hz, 2 H, H-
3–5, phenyl), 6.08 (m, 1 H, H-1′), 5.20 (d, J = 3.8 Hz, 1 H, O3′-H),
5.16 (s, 2 H, T-CH2-B), 4.97 (br, 1 H, O5′-H), 4.18 (m, 1 H, H-3′),
3.73 (d, J = 2.7 Hz, 1 H, H-4′), 3.51 (d, J = 4.3 Hz, 2 H, H-5′), 2.12–
2.05 (m, 2 H, H-2′).
13C NMR (DMSO-d6): δ = 162.57 (C-4), 150.24 (C-2), 146.04 (C-
4, triazole), 141.22 (C-6), 130.79 (C-1, phenyl), 128.82 (C-3 and C-
5, phenyl), 127.76 (C-4, phenyl), 125.13 (2 × C, C-2 and C-6, phe-
nyl), 121.21 (C-5, triazole), 107.32 (C-5), 87.56 (C-4′), 84.55 (C-
1′), 70.16 (C-3′), 61.20 (C-5′), 46.33 (CH2), 40.17 (C-2′).
ESI-MS: m/z calcd for C36H51N5O5Si2 [M + H]: 690.34; found:
691.4.
ESI-MS: m/z calcd for C18H19N5O5 [M – H]: 384.14; found: 384.2.
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-{[4-(2,2,5,5-tetramethyl-
pyrrolin-1-yloxyl)-1H-1,2,3-triazol-1-yl]methyl}-2′-deoxyuri-
dine (3k)
5-{[4-(Pyridin-2-yl)-1H-1,2,3-triazol-1-yl]methyl}-2′-deoxyuri-
dine (4b)
Yield: 0.032 g (85%); white solid.
Yield: 0.122 g (>95%); viscous residue.
1H NMR (CDCl3 with phenylhydrazine): δ = 7.80 (s, 1 H, H-5, tri-
azole), 7.70 (s, 1 H, H-6), 6.11 (d, J = 2.0 Hz, 1 H, H-1′), 5.93 (s, 1
H, C=CH), 5.02 (s, 2 H, T-CH2-B), 4.28–4.20 (m, 1 H, H-3′), 3.83
(d, J = 2.3 Hz, 1 H, H-4′), 3.74–3.58 (m, 1 H, H-5′), 2.15 (m, 1 H,
H-2′a), 1.88 (m, 1 H, H-2′b), 1.29 (m, 6 H, CH3 TPA), 1.19 (s, 6 H,
CH3 TPA), 0.79 [s, 9 H, C(CH3)3], 0.74 [s, 9 H, C(CH3)3], 0.00 [s,
6 H, Si(CH3)2], –0.07 [s, 6 H, Si(CH3)2].
13C NMR (CDCl3 with phenylhydrazine): δ = 162.97 (C-4), 151.26
(C-2), 150.47 (C-4, triazole), 141.97 (C=CH TPA), 140.47 (C-6),
129.39 (CH=C TPA), 122.04 (C-5, triazole), 108.81 (C-5), 88.37
(C-4′), 85.82 (C-1′), 72.55 (C-3′), 63.22 (C-5′), 46.59 (CH2), 41.68
(C-2′), 26.04 (CCH3a), 25.78 (CCH3b), 25.07 (CCH3 TPA), 24.50
(CCH3 TPA), 18.51 (CCH3a), 18.03 (CCH3b), –4.60 (SiCH3a), –4.78
(SiCH3b), –5.19 (SiCH3c), –5.28 (SiCH3d).
1H NMR (DMSO-d6): δ = 11.57 (br s, 1 H, NH), 8.62–8.57 (m, 1 H,
H-2, pyridine), 8.52 (s, 1 H, H-5, triazole), 8.22 (s, 1 H, H-6), 8.06–
8.00 (m, 1 H, H-4, pyridine), 7.94–7.84 (m, 1 H, H-5, pyridine),
7.39–7.31 (m, 1 H, H-3, pyridine), 6.19–6.12 (m, 1 H, H-1′), 5.28
(d, J = 4.17 Hz, 3 H, O3′-H and T- CH2-B), 5.09–5.02 (m, 1 H, O5′-
H), 4.30–4.22 (m, 1 H, H-3′), 3.84–3.77 (m, 1 H, H-4′), 3.64–3.55
(m, 2 H, H-5′), 2.17 (d, J = 0.8 Hz, 2 H, H-2′).
13C NMR (DMSO-d6): δ = 162.63 (C-4), 150.19 and 149.95 (C-2
and C-6, pyridine), 149.50 (C-2 pyridine), 146.98 (C-4, triazole),
141.26 (C-6), 137.12 (C-4, pyridine), 123.11 (C-5, pyridine),
122.87 (C-3, pyridine), 119.34 (C-5, triazole), 107.30 (C-5), 87.50
(C-4′), 84.52 (C-1′), 70.12 (C-3′), 61.17 (C-5′), 46.49 (CH2), 40.17
(C-2′).
ESI-MS: m/z calcd for C17H18N6O5 [M – H]: 385.13; found: 385.2.
ESI-MS: m/z calcd for C32H55N6O6Si2· [M + H]: 676.37; found:
676.9.
5-{[4-(4-Methoxyphenyl)-1H-1,2,3-triazol-1-yl]methyl}-2′-de-
oxyuridine (4c)
3′,5′-Bis-O-(tert-butyldimethylsilyl)-5-{[4-(2,2,6,6-tetramethyl-
piperidin-1-yloxyl)-1H-1,2,3-triazol-1-yl]methyl}-2′-deoxyuri-
dine (3l)
Yield: 0.037 g (90%); white solid.
1H NMR (DMSO-d6): δ = 11.55 (s, 1 H, NH), 8.34 (s, 1 H, H-5, tri-
azole), 8.18 (s, 1 H, H-6), 7.74 (d, J = 8.7 Hz, 2 H, H-3 and H-5,
phenyl), 6.98 (d, J = 8.7 Hz, 2 H, H-2 and H-6, phenyl), 6.14 (t,
J = 6.5 Hz, 1 H, H-1′), 5.26 (d, J = 4.2 Hz, 1 H, O3′-H), 5.19 (d,
J = 2.4 Hz, 2 H, T-CH2-B), 5.03 (t, J = 5.3 Hz, 1 H, O5′-H), 4.28–
Yield: 0.125 g (>95%); viscous residue.
1H NMR (CDCl3 with phenylhydrazine): δ = 7.77 (s, 1 H, H-5, tri-
azole), 7.59 (s, 1 H, H-6), 6.14 (m, 2 H, H-1′ and C=CH), 5.00 (s, 2
H, T-CH2-B), 4.32–4.25 (m, 1 H, H-3′), 3.89–3.82 (m, 1 H, H-4′),
3.69 (m, 1 H, H-5′), 2.42 (s, 2 H, CH2), 2.23–2.10 (m, 1 H, H-2′a),
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 396–405

404
J. Krim et al.
PAPER
4.20 (m, 1 H, H-3′), 3.79 (m, 1 H, H-4′), 3.77 (s, 3 H, OCH3), 3.57
(dd, J = 9.7, 5.2 Hz, 2 H, H-5′), 2.18–2.10 (m, 2 H, H-2′).
J = 4.1 Hz, 1 H, O3′-H,), 5.13 (s, 2 H, T-CH2-B), 4.98 (m, 1 H, O5′-
H), 4.87 (s, 2 H, B-CH2-T), 4.19 (m, 1 H, H-3′), 3.74 (d, J = 3.2 Hz,
1 H, H-4′), 3.52 (d, J = 4.5 Hz, 2 H, H-5′), 2.08 (t, J = 6.2 Hz, 2 H,
H-2′).
13C NMR (DMSO-d6): δ = 163.63 (C-4), 162.57 (C-4), 150.72 (C-
2), 150.16 (C-2), 145.44 (C-4, triazole), 142.12 (C-6), 141.01 (C-6),
123.57 (C-5, triazole), 107.57 (C-5), 101.20 (C-5), 87.53 (C-4′),
84.47 (C-1′), 70.18 (C-3′), 61.18 (C-5′), 46.21 (2 × CH2), 42.22 (C-
2′).
13C NMR (DMSO-d6): δ = 162.57 (C-4), 158.94 (C-1, phenyl),
150.24 (C-2), 145.99 (C-4, triazole), 141.16 (C-6), 126.48 (2 × C,
C-3 and C-5, phenyl), 123.40 (C-4, phenyl), 120.25 (C-5, triazole),
114.24 (2 × C, C-2 and C-6, phenyl), 107.42 (C-5), 87.56 (C-4′),
84.55 (C-1′), 70.17 (C-3′), 61.20 (C-5′), 55.14 (OCH3), 46.25
(CH2), 40.16 (C-2′).
ESI-MS: m/z calcd for C19H21N5O6 [M – H]: 414.15; found: 414.5.
ESI-MS: m/z calcd for C17H19N7O7 [M – H]: 432.13; found: 432.5.
5-{[4-(4-Fluorophenyl)-1H-1,2,3-triazol-1-yl]methyl}-2′-deoxy-
uridine (4d)
Yield: 0.035 g (88%); yellow solid.
Acknowledgment
1H NMR (DMSO-d6): δ = 11.62 (s, 1 H, NH), 8.51 (s, 1 H, H-5, tri-
azole), 8.25 (s, 1 H, H-6), 7.92 (dd, J = 8.74, 5.5 Hz, 2 H, H-2 and
H-6, phenyl), 7.31 (t, J = 8.9 Hz, 2 H, H-3 and H-5, phenyl), 6.20 (t,
J = 6.5 Hz, 1 H, H-1′), 5.31 (d, J = 4.2 Hz, 1 H, O3′-H), 5.27 (d,
J = 2.34 Hz, 2 H, T-CH2-B), 5.08 (t, J = 5.29 Hz, 1 H, O5′-H,),
4.34–4.25 (m, 1 H, H-3′), 3.84 (q, J = 3.6 Hz, 1 H, H-4′), 3.62 (dd,
J = 9.7, 5.2 Hz, 2 H, H-5′), 2.24–2.15 (m, 2 H, H-2′).
We gratefully acknowledge the experimental help in testing the
compounds by Phil Dudfield VP, Alliances and Informatics Galap-
agos NV 102, avenue Gaston Roussel 93230 Romainville.
Supporting Information for this article is available online at
http://www.thieme-connect.com/eJournals/toc/synthesis.SnuIomopifrtgaoringSnIuoopifmntrrat
13C NMR (DMSO-d6): δ = 163.65–159.78 (C-4, phenyl), 162.56 (C-
4), 150.24 (C-2), 145.19 (C-4, triazole), 141.23 (C-6), 127.36 (C-1,
phenyl), 127.21 (2 × C, C-2 and C-6, phenyl), 121.13 (C-5, tri- References
azole), 115.91 and 115.56 (C-3 and C-5, phenyl), 107.30 (C-5),
87.56 (C-4′), 84.55 (C-1′), 70.16 (C-3′), 61.20 (C-5′), 46.36 (CH2),
40.18 (C-2′).
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5-[(4-Hexyl-1H-1,2,3-triazol-1-yl)methyl]-2′-deoxyuridine (4e)
Yield: 0.031 g (80%); white solid.
1H NMR (DMSO-d6): δ = 11.50 (s, 1 H, NH), 8.05 (s, 1 H, H-5, tri-
azole), 7.71 (s, 1 H, H-6), 6.10 (m, 1 H, H-1′), 5.22 (d, J = 4.2 Hz,
1 H, O3′-H), 5.09 (s, 2 H, T-CH2-B), 4.99 (m, 1 H, O5′-H), 4.20 (m,
1 H, H-3′), 3.75 (d, J = 3.2 Hz, 1 H, H-4′), 3.52 (d, J = 4.5 Hz, 2 H,
H-5′), 2.57–2.49 (m, 2 H, T-CH2), 2.08 (t, J = 6.3 Hz, 2 H, H-2′),
1.59–1.44 (m, 2 H, CH2), 1.30–1.17 [m, 6 H, (CH2)3], 0.82 (t,
J = 6.4 Hz, 3 H, CH3).
13C NMR (DMSO-d6): δ = 162.53 (C-4), 150.16 (C-2), 146.77 (C-
4, triazole), 140.73 (C-6), 121.64 (C-5, triazole), 107.90 (C-5),
87.52 (C-4′), 84.46 (C-1′), 70.21 (C-3′), 61.23 (C-5′), 45.86 (CH2),
40.17 (C-2′), 30.97 (C-1′′), 28.93 (C-2′′), 28.27 (C-3′′), 25.00 (C-
4′′), 22.00 (C-5′′), 13.90 (C-6′′).
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ESI-MS: m/z calcd for C18H27N5O5 [M – H]: 393.2; found: 393.5.
5-[(4-Methylthymine-1H-1,2,3-triazol-1-yl)methyl]-2′-deoxy-
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Yield: 0.037 g (84%); white solid.
1H NMR (DMSO-d6): δ = 11.54 (s, 1 H, NH), 11.27 (s, 1 H, NH),
8.11 (s, 1 H, H-5, triazole), 7.98 (s, 1 H, H-6), 7.59 (s, 1 H, H-6, thy-
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4.22 (m, 1 H, H-3′), 3.77 (d, J = 3.2 Hz, 1 H, H-4′), 3.55 (d, J = 4.5
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2), 150.14 (C-2), 142.28 (C-4, triazole), 141.05 (2 × C, C-6, C-6),
123.54 (C-5, triazole), 108.81 (C-5), 107.60 (C-5), 87.54 (C-4′),
84.49 (C-1′), 70.19 (C-3′), 61.20 (C-5′), 48.58 (CH2), 46.19 (CH2),
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Synthesis 2013, 45, 396–405
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Synthesis of Novel 5-(1,2,3-Triazolyl)-2′-deoxyuridines
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