2′-Linking of lipids and other functions to uridine through 1,2,3-triazoles and membrane anchoring of the amphiphilic products

Article abstract of DOI:10.1002/ejoc.200901073

A straightforward synthesis of 2'-functionalized uridines was developed based on a Cu-catalyzed cycloaddition of 2'azido-2'-deoxyuridine and functionalized alkynes. The functions comprise biochemically important groups such as lipids, a fluorescent marker (Cy5 analogue), pentaacetylglucose, lysine and biotin, and are linked to the 2'-position of uridine by a 1,2,3-triazole ring. A number of NMR spectroscopic investigations revealed that the lipidated 2'-triazolyl-2'-deoxyuridines anchor themselves in the phospholipid membranes without: affecting the molecular order in the double layers; the polar moieties - uracil, ribose and triazole - are located in the lipid/water interface of the membrane.

Full text of DOI:10.1002/ejoc.200901073

FULL PAPER
DOI: 10.1002/ejoc.200901073
2Ј-Linking of Lipids and Other Functions to Uridine through 1,2,3-Triazoles
and Membrane Anchoring of the Amphiphilic Products
Oliver Kaczmarek,[a][‡] Holger A. Scheidt,[b][‡] Andreas Bunge,[b] David Föse,[b]
Sebastian Karsten,[a] Anna Arbuzova,[c] Daniel Huster,[b] and Jürgen Liebscher*[a]
Dedicated to Rainer Mahrwald on the occasion of his 60th birthday
Keywords: Cycloaddition / Nucleosides / Lipids / Membranes / NMR spectroscopy / Azides
A straightforward synthesis of 2Ј-functionalized uridines was
developed based on a Cu-catalyzed cycloaddition of 2Ј-
azido-2Ј-deoxyuridine and functionalized alkynes. The func-
tions comprise biochemically important groups such as lipids,
a fluorescent marker (Cy5 analogue), pentaacetylglucose, ly-
sine and biotin, and are linked to the 2Ј-position of uridine
by a 1,2,3-triazole ring. A number of NMR spectroscopic in-
vestigations revealed that the lipidated 2Ј-triazolyl-2Ј-de-
oxyuridines anchor themselves in the phospholipid mem-
branes without affecting the molecular order in the double
layers; the polar moieties – uracil, ribose and triazole – are
located in the lipid/water interface of the membrane.
Introduction
with fatty acids, by carbamate formation, by alkylation, by
disulfide formation of 2Ј-thiohydroxy-2Ј-deoxyuridine, or
by acylation at 2Ј-amino-2Ј-deoxyuridine.[21–25] The latter
was obtained from 2Ј-azido-2Ј-deoxyuridine by Staudinger
reduction.[22] Position 2Ј of the nucleosides and oligonu-
cleotides has also been used for tethering other functions
such as nucleosides, spin labels, fluorescent labels, electro-
chemical probes, or terminally functionalized spacer
groups.[26–28] It was shown that such 2Ј-functionalized nu-
cleosides can be incorporated into oligonucleotides.[28–30]
Here, we report on the application of readily available 2Ј-
azido-2Ј-deoxyuridine to Cu-catalyzed 1,3-dipolar cycload-
ditions with alkynes.[31] Using this approach it was possible
to link lipids and other useful groups such as fluorescence
labels, monosaccharides, amino acids or biotin to the 2Ј-
position of uridine through a 1,2,3-triazole linker. Because
the 1,2,3-triazole system represents a bioisoster of phos-
phate or amide, the target molecules can be considered to
be 2Ј-phosphate or amide equivalents.[32] The potency of
2Ј-azido-2Ј-deoxyuridine in such cycloadditions has not yet
been explored. In this context, it has to be mentioned that
Cu-catalyzed azide–alkyne cycloaddition reactions have
been recently used for several post-synthetic DNA[26,33] and
nucleoside modifications.[34,35] Amongst them, 2Ј-azido-2-
deoxyadenosine derivatives have also been used.[35,36] How-
ever, lipid groups have not been tethered to the 2Ј-position
of nucleosides in this way. We will describe a method that
allows such an attachment and further disclose the results
of studies on anchoring of the lipid-containing 2Ј-triazolyl-
2Ј-deoxyuridines in phospholipid membranes.
Nucleolipids are conjugates of nucleic acids, oligonucleo-
tides, nucleosides or nucleobases with lipids.[1] They have
aroused the interest of researchers in the fields of supra-
molecular chemistry, functionalization of biocompatible
phospholipid membranes, triggered vesicle fusion, gene
silencing and biotechnology.[1–17] Several points, such as the
5Ј-, 2Ј-, and 3Ј-positions, and the heterocyclic ring of the
nucleobases, have been used for linking the lipid group to a
nucleic acid or its constituents. For example, lipid moieties
have been linked to the 5Ј-position of thymidines by Cu-
catalyzed cycloaddition of fatty alkynes to 5Ј-azido-5Ј-de-
hydrothymidine, leading to amphiphilic nucleolipids; such
compounds form hydrogels and have been considered for a
number of pharmacological and biochemical applica-
tions.[18–20] If the lipid group is to be situated in the interior
of oligonucleotides, positions 3Ј and 5Ј cannot be used as
tethering points, i.e. only the 2Ј-position and the nucleo-
bases can be used as connection points for the lipid group.
Linkage to the 2Ј-position has been achieved by acylation
[a] Institute of Chemistry, Humboldt University Berlin,
Brook-Taylor-Str. 2, 12489 Berlin, Germany
Fax: +49-30-2093-7552
E-mail: liebscher@chemie.hu-berlin.de
[b] Institute of Medical Physics and Biophysics, University of
Leipzig,
Härtelstr. 16–18, 04107 Leipzig, Germany
[c] Institute of Biology, Humboldt University Berlin,
Invalidenstr. 43, 10115 Berlin, Germany
[‡] Both authors contributed equally
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200901073.
Eur. J. Org. Chem. 2010, 1579–1586
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1579

J. Liebscher et al.
FULL PAPER
Scheme 1.
triazolyl-2Ј-deoxyuridines 3a and 3b, method B gave better
yields. However, there were examples (2d, 2f, and 2g)
wherein method B was unsatisfactory. Thus, method B was
modified by the addition of tris(1-benzyl-1,2,3-triazolyl-4-
methyl)amine (4; method C), which was recently reported
to improve the outcome of Cu-catalyzed Huisgen cycload-
dition.[37–39] This modification also helped to remarkably
improve the yields in our case. However, the overall per-
formance of the method was somewhat hampered by the
fact that traces of amine 4 were difficult to remove from the
products. Nevertheless, in most cases, high yields could be
obtained. Alkynes 2, which were used as starting materials,
are either commercially available or can be easily obtained
by introduction of the propargyl group as propargyl alcohol
or propargylamine. As shown with one example of each
respective case, fluorescence tags (Cy5-analogue, 3d), carbo-
hydrates (3e), amino acids (3f) or biological recognition
functions (biotin, 3g) could also be introduced instead of
lipid groups in this way. Thus, the Cu-catalyzed addition of
alkynes to 2Ј-azido-2Ј-deoxyuridine provides a versatile and
straightforward access to functionalized uridines, which are
interesting for various biochemical and biomedical applica-
tions. At present, we are exploring the possibility of incor-
porating the 2Ј-triazolyl-2Ј-deoxyuridines into oligonucleo-
tides and polymers.
Results and Discussion
Synthesis of 2Ј-Triazolyl-2Ј-deoxyuridines
Two major procedures for Cu-catalyzed variants of the
Huisgen 1,3-dipolar cycloadditions of alkynes to azides are
most frequently used: the application of an excess of cop-
per(I) iodide (method A) or of catalytic amounts of cop-
per(II) sulfate in the presence of sodium ascorbate (method
B). The former approach (method A) is more flexible in the
choice of solvent, whereas the latter is more economical.
We applied both methods A and B using acetonitrile and
tetrahydrofuran as solvents, respectively (Scheme 1,
Table 1). As can be seen in the synthesis of lipidated 2Ј-
Table 1. 2Ј-Triazolyl-2Ј-deoxyuridines 3.
Anchoring in Lipid Membranes
To study the membrane insertion of the two lipidated
nucleosides, we used a number of solid-state NMR tech-
niques. We investigated the membrane anchoring properties
of molecules 3b and 3c, which both carry a cholesterol moi-
ety as a potent membrane anchor, and uridine and triazole
as hydrophilic head groups. The two compounds differ only
in the length of the polar spacer between the hydrophilic
and lipophilic moieties. Such spacers are attractive for bio-
technological applications, because they increase the dis-
tance between the membrane surface and the DNA oligo-
nucleotide.
We performed standard biophysical NMR experiments
to investigate the incorporation of molecules of type 3 into
1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)
1580
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1579–1586

2Ј-Linking of Lipids and Other Functions to Uridine
membranes. To check for alterations in the membrane mor-
phology induced by the presence of the nucleosides, static
2
31P and H NMR experiments were carried out. Figure 1
shows the 31P NMR spectra in the presence of 20 mol-% of
each nucleoside.
Figure 2. Smoothed 2H NMR order parameter profiles of [D31]-
POPC in the presence of 20 mol-% 3c (᭡), 3b (᭢) and cholesterol
(᭺), as well as for pure [D31]POPC (ᮀ). The measurements were
conducted at 30 °C and with 40 wt.-% H2O in the samples.
Because both nucleosides exhibit order parameters that
are close to those of a pure [D31]POPC membrane – the
values are slightly increased for 3b and slightly decreased
for 3c – there are only minor effects on the lipid chain order
due to the addition of the nucleotides to a membrane. The
difference between the two nucleotides is most likely caused
by the longer spacer of 3c, which adds additional dynamics
and disorder to the membrane. In contrast to cholesterol,
neither nucleotide induced any ordering effect. The loss of
this condensation effect can be explained by differences in
the molecular structures of the nucleosides compared to
cholesterol. These modifications alter the very unique cho-
lesterol/phospholipid interactions. Such effects were also
observed for cholesterol analogues[41] and other sterols.[42,43]
These properties are also reflected in the average order pa-
rameter Sav and the average chain length ϽLc*Ͼ calculated
from the order parameters[44] and shown in Table 2.
Figure 1. 31P NMR spectra of [D31]POPC in the presence of
20 mol-% 3c (A) and 3b (B). The spectra were measured at 30 °C.
The samples contained 40 wt.-% H2O. The dashed lines represent
best-fit simulations.
Both spectra exhibit the typical line shape of a lamellar
liquid crystalline lipid membrane; there are no indications
for the presence of non-lamellar phases. The 31P chemical
shift anisotropy (CSA, ∆σ), given by the width of the 31P
NMR spectra, provides information about the dynamics
and orientation of the head group of the POPC molec-
ules.[40] The quantitative values for ∆σ (Table 2) are com-
parable to those of a pure POPC membrane. Only for 3b
was a slightly decreased value obtained. However, consider-
ing that the error in the measurement was about Ϯ1 ppm,
these small deviations indicate only a very slight variation
in the head group dynamics or orientation in the presence
of the nucleosides.
To provide information about the lipid chain dynamics,
square-law-plots are given in Figure 3.
Table 2. 31P NMR chemical shift anisotropies, average 2H NMR
order parameter, and average chain length of POPC in the presence
of 20 mol-% lipophilic nucleotide 3b, 3c or 20 mol-% cholesterol
for comparison.
[b]
Sample
∆σ[a] [ppm]
Sav
ϽLc*Ͼ[c] [Å]
POPC
POPC/3b
POPC/3c
45.2
44.2
45.5
44.8
0.153
0.155
0.143
0.223
11.46
11.59
11.20
13.33
Figure 3. Dependence of the segmental longitudinal relaxation rate
R1Z(i) on the corresponding squared order parameter of each meth-
ylene segment of [D31]POPC, in the presence of 20 mol-% 3c (᭡),
3b (᭢), and cholesterol (᭺), as well as for pure [D31]POPC (ᮀ).
The measurements were conducted at 30 °C. The samples con-
tained 40 wt.-% H2O.
POPC/cholesterol
[a] Chemical shift anisotropy (CSA). [b] Average order parameter.
[c] Chain extent according to ref.[44]
To investigate the influence of the nucleosides on the acyl
chains of the phospholipids and to study possible lipid con-
densation effects due to the cholesterol anchor of the nu-
To this end, the 2H NMR spin-lattice relaxation rates
2
cleotides, H NMR spectra of [D31]POPC in the presence were measured for each methylene/methyl group of [D31]-
of the nucleosides were acquired. The smoothed order pa- POPC, and these were correlated to the respective squared
rameter profiles obtained from these spectra are shown in order parameter. It is known that the elastic properties of
Figure 2.
the membrane are mirrored in these plots.[45] For purely sat-
Eur. J. Org. Chem. 2010, 1579–1586
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1581

J. Liebscher et al.
FULL PAPER
urated phospholipid membranes, these plots exhibit a linear
dependence with a specific positive slope.[46] Addition of
cholesterol increases the lipid chain order and decreases the
slope of the square-law plot, whereas softer membranes (for
instance due to the addition of a detergent) exhibit an in-
creased slope and a characteristically curved shape.[45,47,48]
The square-law plots of [D31]POPC membranes in the pres-
ence of either nucleoside 3b or 3c are similar to that of pure
[D31]POPC. Both exhibit similar slopes and a small degree
of curvature, which is typical for unsaturated phospho-
lipids.[19] None were comparable to the square-law plot of
[D31]POPC in the presence of the same molar amount of
cholesterol, which again shows that there is no lipid con-
densation effect induced by the nucleosides. Furthermore,
small differences between 3b and 3c due to the longer
spacer of 3c are visible, which is consistent with previous
observations made from the order parameter plots.
The localization of the lipophilic nucleoside in the mem-
brane was studied by two-dimensional 1H magic angle spin-
ning (MAS) NOESY NMR spectroscopy.[49] For the inves-
tigated molecules, this technique allows the distribution of
the sugar, the uridine, and the triazole moiety in the mem-
brane to be determined. The cross-relaxation rate, calcu-
lated according to the spin-pair model from intermolecular
crosspeaks between the moieties of the nucleotides and the
segments of POPC, reflect a contact probability between
the respective molecular groups. A plot of these values
along the membrane z-axis enables the distribution of these
molecular groups of the nucleosides in the membrane along
the normal to be assessed. The lipid coordinates could be
taken from a molecular dynamic simulation of POPC,[50]
because no significant changes in the membrane due to the
addition of the nucleotides were observed.
Because the absolute values of the cross-relaxation rates
are influenced by small differences in the correlation times,
a normalization of the data was required. The achieved dis-
tribution functions along the bilayer normal are shown in
Figure 4. The respective molecular groups are rather
broadly distributed within the lipid/water interface region
of the membrane. Such broad distribution functions are
caused by the generally high mobility and disorder in the
lipid membrane and have been observed for many different
membrane-bound molecules.[42] However, a clear maximum
for all molecular segments is visible. For both nucleotides,
the distribution functions are very similar for all three mo-
lecular groups. For both molecules, the sugar, uridine, and
triazole moieties have their highest probability of molecular
contacts in the glycerol region of the lipid membrane.
Moreover, the contact probabilities in the fatty acid region
are significantly lower than for the head group region.
Therefore, one has to conclude that the molecular groups
of both nucleosides occupy a position in the lipid/water
interface of the membrane, which is consistent with the
combination of polar character and the possible physical
membrane interactions of these molecular groups. Even the
long polar spacer in 3c does not lead to a significant differ-
Figure 4. Relative 1H NOESY cross-relaxation rates between the
nucleoside moieties of 3c (o,᭛) and 3b (᭢), and the segments of
POPC molecules within the membrane (molar ratio nucleoside/
POPC = 1:4) as a function of the coordinates of these lipid seg-
ments. The average localization of 6-H and 5-H of the uridine nu-
cleobase (top; for 3c 6-H o, for 5-H ᭛; for 3b the cross peaks of 6-
H and 5-H were not resolved so the data set ᭢ represents the cross
relaxation rates of both protons), of 4-H of the triazole (center)
and of the 1Ј-H of the ribose (bottom), can be estimated. The mea-
surements were conducted at 30 °C. The samples contained 40 wt.-
% D2O.
Furthermore, the small shift in the distribution function
of the triazole moiety compared to those of the sugar and
uridine moieties should also be noted. This shift reflects the
differences in the molecular structure of both nucleotides
with the membrane anchor bound to the triazole and the
uridine as the polar head group of the molecule.
Conclusions
A straightforward synthetic method has been developed
ence in the membrane localization compared to 3b, which that enables functionalization of the 2Ј-position of uridine.
does not carry the spacer. Starting from 2Ј-azido-2Ј-deoxyuridine, a Cu-catalyzed cy-
1582
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1579–1586

2Ј-Linking of Lipids and Other Functions to Uridine
MeOH, 9:1 Ǟ 5:1) to give the desired product (180 mg, 0.21 mmol,
69%) as a white foam.
cloaddition with alkynes was used to link lipid groups, a
fluorescent marker, a carbohydrate, an amino acid and bio-
tin as examples of recognition functions to the uridine
moiety through a 1,2,3-triazole unit. These products are
promising candidates that can be used to build up function-
alized oligonucleotides that are interesting for biochemical
and medical applications. A range of NMR spectroscopic
investigations revealed that the lipidated uridines anchor in
biocompatible phospholipid membranes without affecting
the order in the double layers, thus demonstrating that the
membranes can be equipped with nucleobases through this
approach. Furthermore, NMR spectroscopic measurements
provided evidence that the uridine moiety and the triazole
of the 2Ј-lipidated uridines are situated in the lipid/water
interface of the membrane.
Method B: To a mixture of a solution of 2Ј-azido-2Ј-deoxyuridine
in THF (0.5 , 1.00 mL, 0.50 mmol), a solution of CuSO4·H2O
(1 , 100µL, 0.10 mmol) and a solution of sodium ascorbate in
H2O (1 , 200 µL, 0.20 mmol) was added 2-propargylcholesterol
(210 mg, 0.50 mmol), and the mixture was stirred at room temp.
for 48 h. The solvent was evaporated, and the residue was purified
by column chromatography (EtOAc/MeOH, 9:1 Ǟ 5:1) to give the
product (290 mg, 0.41 mmol, 83%) as a white foam.
Method C: A mixture of a solution of 2Ј-azido-2Ј-deoxyuridine in
THF (0.5 , 2.00 mL, 1.00 mmol), 2-propargylcholesterol (210 mg,
0.50 mmol) and TBTA (110 mg, 0.20 mmol) was degassed under
argon in an ultrasonic bath. Afterwards, a solution of CuSO4·H2O
in H2O (1 , 200 µL, 0.20 mmol) and a solution of sodium ascorb-
ate in H2O (1 , 400 µL, 0.40 mmol) were added, and the reaction
mixture was stirred at room temp. for 1 h. The solvent was evapo-
rated under reduced pressure, and the residue was purified by col-
umn chromatography (EtOAc/MeOH, 9:1 Ǟ 5:1) to give the de-
sired product (610 mg, 0.88 mmol, 88%) as a white foam. Rf =
Experimental Section
1
General Remarks: H and 13C NMR spectra were recorded at 300
1
0.56 (CH2Cl2/MeOH, 5:1). M.p. 283–287 °C. H NMR (300 MHz,
and 75.5 MHz, respectively, with a Bruker AC 300 spectrometer in
CDCl3, with TMS as internal standard. Silica gel (0.04–0.063 mm,
Merck) was used for preparative column chromatography. Starting
materials 2b,[51] 2e,[52] and 2g[53] were synthesized by introduction
of the propargyl moiety according to literature procedures. For the
preparation of 2c, 2d, and 2f, see the Supporting Information. All
the other materials were purchased from commercial suppliers.
CDCl3): δ = 7.83 (d, J = 8.4 Hz, 1 H, 6-H), 7.79 (s, 1 H, CH), 6.35
(d, J = 7.5 Hz, 1 H, 1Ј-H), 5.48 (d, J = 8.4 Hz, 1 H, 5-H), 5.15 (t,
J = 9.6 Hz, 1 H, 2Ј-H), 5.09 (d, J = 4.2 Hz, 1 H, CH), 4.38 (s, 1
H, 3Ј-H), 4.02 (s, 1 H, 4Ј-H), 3.68 (dd, J1 = 11.7, J2 = 22.8 Hz, 2
H, 5Ј-H), 3.07 (s, 2 H, CH2), 2.00 (m, 1 H, CH), 1.72–0.90 (m, 27
H, CH + CH2), 0.89 (d, J = 6.6 Hz, 3 H, CH3), 0.85 (dd, J1 = 1.2,
J2 = 6.6 Hz, 6 H, CH3), 0.65 (s, 3 H, CH3) ppm. 13C NMR
(75 MHz, CDCl3): δ = 163.8, 150.5, 144.7, 140.3, 121.8, 102.8, 86.5,
85.8, 79.1, 70.7, 65.6, 61.1, 60.8, 42.3, 39.8, 39.5, 39.0, 37.2, 36.8,
36.2, 35.8, 31.9, 28.3, 28.2, 28.0, 24.3, 23.8, 22.6 ppm. HRMS
(ESI): calcd. for C39H60N5O6 [M + H]+ 694.4538; found 694.4470.
2Ј-Triazolyl-2Ј-deoxyuridine 3a
Method A: To a mixture of a solution of 2Ј-azido-2Ј-deoxyuridine
in MeCN (0.1 , 4.00 mL, 0.40 mmol) and H2O (0.40 mL) were
added CuI (380 mg, 2.00 mmol) and 1-dodecyne (0.05 mL,
0.40 mmol), and the mixture was stirred at 35 °C for 72 h (TLC
showed complete conversion). The solvent was removed, and the
residue was purified by column chromatography (CH2Cl2/MeOH,
10:1 Ǟ 5:1) to give the desired product (100 mg, 0.23 mmol, 57%)
as a white foam.
2Ј-Triazolyl-2Ј-deoxyuridine 3c: To a solution of 2Ј-azido-2Ј-deoxy-
uridine in THF (0.5 , 1.00 mL, 0.50 mmol) were added an aque-
ous solution of CuSO4·H2O (1 , 100µL, 0.1 mmol), a solution of
sodium ascorbate (1 , 200 µL, 0.20 mmol) in H2O (1.00 mL) and
11-(5-cholesten-3-yloxy)-1-O-(prop-2-ynyl)-3,6,9-trioxaundecane
(160 mg, 0.25 mmol), and the mixture was stirred at r.t. for 48 h.
The solvent was removed, and the residue was purified by column
chromatography (CH2Cl2/MeOH, 10:1 Ǟ 5:1) to give the desired
product (185 mg, 0.21 mmol, 85%) as a white powder. Rf = 0.61
(CH2Cl2/MeOH, 5:1). M.p. 183–187 °C. 1H NMR (300 MHz,
CDCl3): δ = 10.07 (s, 1 H, NH), 7.98 (s, 2 H, CH, 6-H), 6.45 (s, 1
H, 1Ј-H), 5.67 (d, J = 6.0 Hz, 1 H, 5-H), 5.39 (s, 1 H, 2Ј-H), 5.30
(d, J = 4.8 Hz, 1 H, CH), 5.06 (s, 1 H, 3Ј-H), 4.64 (m, 1 H, 4Ј-H),
4.55 (m, 2 H, CH2O), 3.85 (m, 2 H, 5Ј-H) 3.59 (m, 16 H, CH2),
3.14 (m, 1 H, OCH), 2.26 (m, 2 H, CH2), 2.08–0.90 (m, 29 H, CH,
Method B: To a solution of 2Ј-azido-2Ј-deoxyuridine in THF
(0.5 , 1.00 mL, 0.50 mmol) were added a solution of CuSO4·H2O
(1 , 100 µL, 0.10 mmol), a solution of sodium ascorbate in H2O
(1 , 200 µL, 0.20 mmol) and 1-dodecyne (58 µL, 0.50 mmol), and
the mixture was stirred at room temp. for 48 h. The solvent was
evaporated, and the residue was purified by column chromatog-
raphy (CH2Cl2/MeOH, 10:1 Ǟ 5:1) to give the product (216 mg,
0.49 mmol, quant.) as white foam. Rf = 0.40 (CH2Cl2/MeOH, 5:1).
1
M.p. 215–217 °C. H NMR (CDCl3): δ = 7.94 (d, J = 8 Hz, 1 H,
6-H), 7.62 (s, 1 H, CH), 6.47 (d, J = 9 Hz, 1 H, 1Ј-H), 5.66 (d, J
= 8 Hz, 1 H, 5-H), 5.25 (m, 1 H, 2Ј-H), 4.48 (s, 1 H, 3Ј-H), 4.20
(s, 1 H, 4Ј-H), 3.72 (m, 2 H, 5Ј-CH2), 2.58 (m, 2 H, NCHCH2),
1.55 (s, 2 H, CH2), 1.16 (s, 14 H, CH2), 0.78 (t, J = 6.6 Hz, 3 H,
CH3) ppm. 13C NMR (CDCl3): δ = 163.8, 150.6, 140.4, 102.8, 86.5,
86.1, 70.7, 65.6, 61.1, 31.7, 29.4, 29.3, 29.1, 29.0, 25.3, 22.5,
CH2), 0.89 (d, J = 6.6 Hz, 3 H, CH3), 0.85 (dd, J1 = 1.2, J2
=
6.6 Hz, 6 H, CH3), 0.63 (s, 3 H, CH3) ppm. 13C NMR (75 MHz,
CDCl3): δ = 164.2, 150.6, 144.2, 140.8, 121.7, 79.5, 77.3, 70.7, 70.4,
70.3, 69.6, 67.1, 56.7, 56.1, 50.5, 50.1, 42.3, 39.8, 39.5, 39.0, 37.2,
36.8, 36.2, 35.8, 31.9, 28.3, 28.2, 28.0, 24.3, 23.8, 22.6 ppm. HRMS
(ESI): calcd. for C47H74N5O10 [M – H]+ 868.5436; found 868.5413.
13.8 ppm. HRMS (ESI): calcd. for C21H34N5O5 [M
436.2549; found 436.2554.
+
H]+
2Ј-Triazolyl-2Ј-deoxyuridine 3d: To a solution of 2Ј-azido-2Ј-deoxy-
uridine in THF (0.5 , 0.50 mL, 0.25 mmol) were added an aque-
ous solution of CuSO4·H2O (1 , 50µL, 0.05 mmol), a solution of
sodium ascorbate (1 , 100 µL, 0.10 mmol) in H2O (1 mL) and 2-
(5-{3,3-dimethyl-1-[5-(propagylaminocarbonyl)pentyl]-1,3-dihydro-
indol-2-ylidene}penta-1,3-dien-1-yl)-1,3,3-trimethyl-3H-indolium
chloride (110 mg, 0.20 mmol), and the reaction mixture was stirred
at room temp. for 48 h. The solvent was removed, and the residue
was purified by column chromatography (CH2Cl2/MeOH, 10:1 Ǟ
2Ј-Triazolyl-2Ј-deoxyuridine 3b
Method A: To a mixture of a solution of 2Ј-azido-2Ј-deoxyuridine
in MeCN (0.05 , 8.00 mL, 0.40 mmol) and H2O (0.80 mL), were
added CuI (380 mg, 2.00 mmol) and 2-propargylcholesterol
(170 mg, 0.40 mmol), and the mixture was stirred at 35 °C for 72 h
(TLC showed complete conversion). The solvent was removed, and
the residue was purified by column chromatography (EtOAc/
Eur. J. Org. Chem. 2010, 1579–1586
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1583

J. Liebscher et al.
FULL PAPER
5:1) to give the desired product (120 mg, 0.21 mmol, 60%) as a
CH2), 1.20 (s, 9 H, CH3) ppm. 13C NMR (CDCl3/CD3OD): δ =
172.9, 163.8, 150.5, 140.1, 123.8, 102.7, 86.5, 85.8, 79.8, 70.6, 65.8,
violet foam. Rf = 0.53 (CH2Cl2/MeOH, 5:1). M.p. 85–88 °C. 1H
NMR (300 MHz, CD3OD): δ = 7.97 (d, J = 8.1 Hz, 1 H, 6-H), 61.0, 52.8, 51.9, 34.4, 31.6, 27.7, 27.2, 27.2 (CH2), 27.7 (CH3), 31.6
7.88 (s, 1 H, CH), 7.78 (t, J = 13.5 Hz, 2 H, CH), 7.32 (d, J =
7.5 Hz, 4 H, ArH), 7.18 (m, 2 H, ArH), 7.08 (d, J = 7.5 Hz, 2 H,
(CH2), 34.4 (CH2), 51.9 (OCH3), 52.8 (CH2), 61.0 [CH2(C5Ј)], 65.8
[CH(C2Ј)], 70.6 [CH(C3Ј)], 79.8 (Cq), 85.8 [CH(C1Ј)], 86.5
ArH), 6.49 (m, 2 H, 1Ј-H, CH), 6.15 (d, J = 13.5 Hz, 2 H, CH), [CH(C4Ј)], 102.7 (CH-5), 123.8 (CH), 140.1 (CH-6), 150.5 (C-2),
6.06 (d, J = 13.5 Hz, 2 H, CH), 5.65 (d, J = 8.1 Hz, 1 H, 5-H),
163.8 (C-4), 172.9 (CONH) ppm. HRMS (ESI): calcd. for
5.29 (t, J = 6.6 Hz, 1 H, 2Ј-H), 4.52 (m, 1 H, 3Ј-H), 4.36 (s, 2 H, C23H32N7O10 [M + H]+ 566.2211; found 566.2216.
CH2O), 4.19 (m, 1 H, 4Ј-H), 3.92 (m, 2 H, 5Ј-H), 3.49 (s, 3 H),
2.17 [t, J = 5.1 Hz, 2 H, CH2(CO)N], 1.80–1.59 (m, 18 H, CH2,
2Ј-Triazolyl-2Ј-deoxyuridine 3g
CH3) ppm. 13C NMR (75 MHz, CD3OD): δ = 174.2, 173.0, 172.9,
163.9, 162.1, 153.1, 152.7, 150.6, 142.4, 141.6, 140.8, 140.5, 128.9,
128.7, 128.5, 125.3, 125.2, 125.0, 122.0, 121.9, 111.4, 110.7, 110.3,
107.3, 103.3, 103.0, 102.7, 86.4, 86.3, 80.6, 77.2, 73.1, 70.4, 65.7,
61.0, 35.8, 34.5, 30.8, 29.4, 27.6, 26.8, 26.2, 25.1, 24.8 ppm. HRMS
(ESI): calcd. for C44H51N8O6 [M + H]+ 787.3932; found 787.3926.
Method B: To a mixture of a solution of 2Ј-azido-2Ј-deoxyuridine
in THF (0.5 , 2.75 mL, 1.37 mmol), a solution of CuSO4·H2O
(1 , 275µL, 0.14 mmol) and an aqueous solution of sodium as-
corbate in H2O (1 , 400 µL, 0.28 mmol) was added N-(prop-2-
ynyl)biotinamide (390 mg, 1.37 mmol), and the mixture was stirred
at room temp. for 48 h. The solvent was removed, and the residue
was crystallized from H2O to give the desired product (12 mg,
0.02 mmol, 2%) as a white foam.
2Ј-Triazolyl-2Ј-deoxyuridine 3e: To a solution of 2Ј-azido-2Ј-deoxy-
uridine in THF (0.5 , 1.00 mL, 0.50 mmol) were added an aque-
ous solution of CuSO4·H2O (1 , 100µL, 0.1 mmol), a solution of
sodium ascorbate in H2O (1 , 200 µL, 0.20 mmol) and propargyl-
β--peracetylglucose (190 mg, 0.50 mmol), and the reaction mix-
ture was stirred at room temp. for 48 h. The solvent was removed,
and the residue was purified by column chromatography (CH2Cl2/
Method C: A mixture of a solution of 2Ј-azido-2Ј-deoxyuridine in
THF (0.5 , 1.30 mL, 0.35 mmol), N-(prop-2-ynyl)biotinamide
(95 mg, 0.35 mmol) and TBTA (35 mg, 0.07 mmol) was degassed
under argon in an ultrasonic bath. Afterwards, a solution of
CuSO4·H2O in H2O (1 , 68 µL, 0.07 mmol) and a solution of so-
dium ascorbate in H2O (1 , 136 µL, 0.14 mmol) were added, and
the reaction mixture was stirred at room temp. for 1 h. The solvent
was evaporated under reduced pressure, and the residue was crys-
tallized from MeOH to give the desired product (110 mg,
0.20 mmol, 57%) as a white foam. Rf = 0.01 (EtOAc/MeOH. 5:1).
MeOH, 10:1
Ǟ 5:1) to give the desired product (255 mg,
0.39 mmol, 78%) as a white foam. Rf = 0.56 (CH2Cl2/MeOH, 5:1).
1
M.p. 118–121 °C. H NMR (300 MHz, CDCl3): δ = 9.83 (s, 1 H,
NH), 7.99 (s, 1 H, 6-H), 7.95 (s, 1 H, CH), 6.52 (d, J = 7.5 Hz, 1
H, 1Ј-H), 5.69 (d, J = 6.0 Hz, 1 H, 5-H), 5.35 (m, 1 H, 2Ј-H), 5.27
(t, J = 9.6 Hz, 1 H, CH), 5.05 (t, J = 9.6 Hz, 1 H, CH), 4.87 (t, J
= 9.6 Hz, 1 H, CH), 4.63 (m, 1 H, 3Ј-H), 4.55 (m, 2 H, CH2), 4.21
(m, 3 H, 4Ј-H, 5Ј-H), 3.75 (m, 2 H, CH2), 2.04 (s, 3 H, CH3), 1.97
(s, 6 H, CH3), 1.84 (s, 3 H, CH3) ppm. 13C NMR (75 MHz,
CDCl3): δ = 171.0, 170.7, 169.9, 169.5, 163.6, 150.4, 142.6, 140.3,
125.8, 103.0, 98.4, 86.9, 86.2, 77.3, 72.6, 71.6, 70.9, 70.8, 67.9, 66.0,
65.9, 61.6, 20.6, 20.5, 20.4 ppm. HRMS (ESI): calcd. for
C26H32O15N5 [M – H]+ 654.1895; found 654.1894.
1
M.p. 262–268 °C (decomp.). H NMR ([D6]DMSO): δ = 11.31 (s,
1 H, NH), 7.92 (d, J = 8.0 Hz, 1 H, 6-H), 7.83 (s, 1 H, NCH), 6.35
(d, J = 9.0 Hz, 1 H, 1Ј-H), 5.61 (d, J = 8.0 Hz, 1 H, 5-H), 5.25 (m,
1 H, 2Ј-H), 4.31 (m, 1 H, 3Ј-H), 4.24 (m, 2 H, CH2), 4.01 (m, 2 H,
4Ј-H, CH), 3.57 (m, 2 H, 5Ј-H), 3.01 (m, 1 H, CH), 2.65 (m, 2 H,
CH2), 2.00 [m, 2 H, CH2(CO)N], 1.21–1.50 (m, 8 H, CH2) ppm.
13C NMR ([D6]DMSO): δ = 172.1, 162.9, 150.4, 140.1, 123.8,
102.3, 85.7, 85.6, 69.1, 64.7, 61.0, 60.9, 59.2, 55.3, 38.2, 30.4, 28.2,
27.9, 25.1 ppm. HRMS (ESI): calcd. for C22H29N8O732S [M + H]
2Ј-Triazolyl-2Ј-deoxyuridine 3f
+
549.1880; found 549.1895.
Method B: To a solution of 2Ј-azido-2Ј-deoxyuridine in THF
(0.5 , 1.00 mL, 0.50 mmol) were added an aqueous solution of
CuSO4·H2O (1 , 100µL, 0.1 mmol), a solution of sodium ascorb-
ate in H2O (1 , 200 µL, 0.20 mmol) and (S)-Nα-Boc-Nδ-propar-
gylglutamine methyl ester (150 mg, 0.50 mmol), and the reaction
mixture was stirred at room temp. for 48 h. The solvent was re-
moved, and the residue was purified by column chromatography
(CH2Cl2/MeOH, 10:1 Ǟ 5:1). HPLC spectra showed some traces
of the desired product, but these could not be isolated.
Membrane Incorporation of Lipophilic Nucleosides: 1-Palmitoyl-2-
oleoyl-sn-glycero-3-phosphocholine (POPC), 1-[D31]palmitoyl-2-
oleoyl-sn-glycero-3-phosphocholine ([D31]POPC) and cholesterol
were purchased from Avanti Polar Lipids (Alabaster, AL) and used
without further purification. The samples for 2H, 31P and 1H
NOESY NMR measurements were prepared as described pre-
viously.[19] All samples had a water content of 40 wt.-%. 31P NMR
spectra were obtained with a Bruker DRX600 NMR spectrometer
(Bruker BioSpin, Rheinstetten, Germany) at a resonance frequency
of 242.8 MHz for 31P by using a Hahn-echo pulse sequence with a
Method C: A mixture of a solution of 2Ј-azido-2Ј-deoxyuridine in
THF (0.5 , 2.00 mL, 1.00 mmol), methyl (S)-2-(tert-butoxy- 90° pulse and a duration of 11 µs, a Hahn-echo delay of 50 µs, a
carbonylamino)-5-oxo-5-(prop-2-ynylamino)pentanoate (230 mg, spectral width of 100 kHz, and a recycle delay of 3 s. Continuous-
0.75 mmol) and TBTA (75 mg, 0.15 mmol) was degassed under ar-
gon in an ultrasonic bath. Afterwards, a solution of CuSO4·H2O
in H2O (1 , 150µL, 0.15 mmol) and a solution of sodium ascorb-
ate in H2O (1 , 300 µL, 0.30 mmol) were added, and the reaction
mixture was stirred at room temp. for 1 h. The solvent was evapo-
rated under reduced pressure, and the residue was purified by col-
umn chromatography (EtOAc/MeOH, 10:1 Ǟ 5:1) to give the de-
sired product (210 mg, 0.37 mmol, 49%) as a white foam. Rf = 0.31
(EtOAc/MeOH, 5:1). M.p. 118–121 °C. 1H NMR (CDCl3/
wave proton-decoupling was applied during signal acquisition.
Spectral simulations of the 31P NMR line shape were carried out
to obtain the chemical shift anisotropy (∆σ) by using a program
written in Mathcad 2001 (MathSoft Engineering & Education Inc.,
2
Cambridge, MA). H NMR spectra were recorded with a Bruker
Avance750 NMR spectrometer at
a resonance frequency of
115.1 MHz for 2H by using a solids probe with a 5 mm solenoid
coil. The 2H NMR spectra were obtained with a quadrupolar echo
sequence and a relaxation delay of 1 s. The two 3 µs π/2 pulses were
CD3OD): δ = 7.92 (d, J = 8.0 Hz, 1 H, 6-H), 7.79 (s, 1 H, NCH), separated by a 60 µs delay. 2H NMR spectra were depaked, and
6.40 (d, J = 9.0 Hz, 1 H, 1Ј-H), 5.59 (d, J = 8.0 Hz, 1 H, 5-H), 5.19 order parameters for each methylene group in the chain were deter-
2
(m, 1 H, 2Ј-H), 4.38 (s, 1 H, 3Ј-H), 4.24 (m, 2 H, CH2), 3.72 (m, 2
H, 5Ј-H), 3.54 (s, 1 H, CH), 2.11 (m, 2 H, CH2), 1.80 (m, 2 H,
mined as described previously.[54] For the H NMR T1Z relaxation
studies, a phase-sensitive inversion recovery quadrupolar echo-
1584
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1579–1586

2Ј-Linking of Lipids and Other Functions to Uridine
[15]
P. Barthelemy, C. A. H. Prata, S. F. Filocamo, C. E. Immoos,
B. W. Maynor, S. A. N. Hashmi, S. J. Lee, M. W. Grinstaff,
Chem. Commun. 2005, 1261–1263.
C. Lorenz, P. Hadwiger, M. John, H. P. Vornlocher, C. Unverz-
agt, Bioorg. Med. Chem. Lett. 2004, 14, 4975–4977.
F. Pincet, L. Lebeau, S. Cribier, Eur. Biophys. J. 2001, 30, 91–
97.
G. Godeau, P. Barthelemy, Langmuir 2009, 25, 8447–8450.
G. Godeau, J. Bernard, C. Staedel, P. Barthelemy, Chem. Com-
mun. 2009, 5127–5129.
pulse sequence with 11 delay times between 1 ms and 2.0 s was
used. For the analysis, the line shape of the 2H NMR powder spec-
tra with the longest delay time was simulated by a superposition of
the respective number of Pake doublets by using Mathcad 2001;
the program determines the relaxation time for each individual
Pake doublet by a fitting procedure that calculates the 2H NMR
spectrum for each inversion recovery delay and compares it with
[16]
[17]
[18]
[19]
1
the experimental spectrum. H MAS NMR spectra were acquired
at a spinning frequency of 600.1 MHz with a Bruker DRX 600
NMR spectrometer using a 4 mm HR MAS probe. Proton π/2
pulse lengths were 9.7 µs. A 2H lock was used for field stability.
[20]
[21]
G. Godeau, C. Staedel, P. Barthelemy, J. Med. Chem. 2008, 51,
4374–4376.
1
O. Kaczmarek, N. Brodersen, A. Bunge, L. Loser, D. Huster,
A. Herrmann, A. Arbuzova, J. Liebscher, Eur. J. Org. Chem.
2008, 1917–1928.
H. Chapuis, L. Bui, I. Bestel, P. Barthelemy, Tetrahedron Lett.
2008, 49, 6838–6840.
M. Manoharan, K. L. Tivel, T. P. Condon, L. K. Andrade, I.
BarberPeoch, G. Inamati, S. Shah, V. Mohan, M. J. Graham,
C. F. Bennett, S. T. Crooke, P. D. Cook, Nucleosides Nucleo-
tides 1997, 16, 1129–1138.
Two-dimensional H MAS NOESY spectra were acquired at vari-
ous mixing times (between 1 and 600 ms). The dwell time of the
indirect dimension was set equal to one rotor period to avoid fold-
ing of spinning sidebands into the central band region of the 2D
NOESY spectra. In the indirect dimension, 420 data points were
acquired with 32 scans per increment at a relaxation delay of 3.5 s.
The volumes of the diagonal and cross-peaks were integrated by
using the Bruker Topspin 2.1 software package. NOE build-up
curves were fitted to the spin-pair model to obtain cross-relaxation
rates.[8] All spectra were acquired at a temperature of 30 °C.
[22]
[23]
[24]
[25]
[26]
H. Saneyoshi, K. Seio, M. Sekine, J. Org. Chem. 2005, 70,
10453–10460.
M. Manoharan, L. A. Johnson, K. L. Tivel, R. H. Springer,
P. D. Cook, Bioorg. Med. Chem. Lett. 1993, 3, 2765–2770.
A. M. Jawalekar, N. Meeuwenoord, J. G. O. Cremers, H. S. Ov-
erkleeft, G. A. van der Marel, F. P. J. T. Rutjes, F. L. van Delft,
J. Org. Chem. 2008, 73, 287–290.
S. X. Jin, C. V. Miduturu, D. C. McKinney, S. K. Silverman, J.
Org. Chem. 2005, 70, 4284–4299.
S. Kumamoto, M. Watanabe, N. Kawakami, M. Nakamura, K.
Yamana, Bioconjugate Chem. 2008, 19, 65–69.
C. Hendrix, B. Devreese, J. Rozenski, A. Vanaerschot, A. De-
bruyn, J. Vanbeeumen, P. Herdewijn, Nucleic Acids Res. 1995,
23, 51–57.
M. Manoharan, G. Inamati, K. L. Tivel, B. Conklin, B. S.
Ross, P. D. Cook, Nucleosides Nucleotides 1997, 16, 1141–1143.
M. Meldal, C. W. Tornoe, Chem. Rev. 2008, 108, 2952–3015.
G. C. Tron, T. Pirali, R. A. Billington, P. L. Canonico, G.
Sorba, A. A. Genazzani, Med. Res. Rev. 2008, 28, 278–308.
P. M. E. Gramlich, C. T. Wirges, A. Manetto, T. Carell, Angew.
Chem. Int. Ed. 2008, 47, 8350–8358.
Supporting Information (see footnote on the first page of this arti-
cle): Synthetic procedures and analytical data of starting materials
2c, 2d, and 2f, and the procedure for the preparation of the lipid-
ated uridine/lipid samples for NMR measurements.
[27]
[28]
[29]
Acknowledgments
Financial support by the Bundesministerium für Bildung und For-
schung (BMBF) is gratefully acknowledged. We thank Bayer Ser-
vices GmbH & Co. OHG, BASF AG, and Sasol GmbH for do-
nations of chemicals.
[30]
[31]
[32]
[1] H. Rosemeyer, Chem. Biodiversity 2005, 2, 977–1062.
[2] J. Soutschek, A. Akinc, B. Bramlage, K. Charisse, R. Constien,
M. Donoghue, S. Elbashir, A. Geick, P. Hadwiger, J. Harborth,
M. John, V. Kesavan, G. Lavine, R. K. Pandey, T. Racie, K. G.
Rajeev, I. Rohl, I. Toudjarska, G. Wang, S. Wuschko, D.
Bumcrot, V. Koteliansky, S. Limmer, M. Manoharan, H. P.
Vornlocher, Nature 2004, 432, 173–178.
[3] I. Pfeiffer, F. Höök, J. Am. Chem. Soc. 2004, 126, 10224–10225.
[4] Y. H. M. Chan, P. Lenz, S. G. Boxer, Proc. Natl. Acad. Sci.
USA 2007, 104, 18913–18918.
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
[42]
[43]
[44]
[45]
F. Amblard, J. H. Cho, R. F. Schinazi, Chem. Rev. 2009, 109,
4207–4220.
G. O’Mahony, E. Ehrman, M. Grotli, Tetrahedron Lett. 2005,
46, 6745–6748.
G. O’Mahony, S. Svensson, A. Sundgreen, M. Grotli, Nucleo-
sides, Nucleotides Nucleic Acids 2008, 27, 449–459.
A. J. Link, D. A. Tirrell, J. Am. Chem. Soc. 2003, 125, 11164–
11165.
T. R. Chan, R. Hilgraf, K. B. Sharpless, V. V. Fokin, Org. Lett.
2004, 6, 2853–2855.
B. Y. Lee, S. R. Park, H. B. Jeon, K. S. Kim, Tetrahedron Lett.
2006, 47, 5105–5109.
J. Schiller, M. Müller, B. Fuchs, K. Arnold, D. Huster, Curr.
Anal. Chem. 2007, 3, 283–301.
H. A. Scheidt, P. Müller, A. Herrmann, D. Huster, J. Biol.
Chem. 2003, 278, 45563–45569.
D. Huster, H. A. Scheidt, K. Arnold, A. Herrmann, P. Müller,
Biophys. J. 2005, 88, 1838–1844.
G. Orädd, V. Shahedi, G. Lindblom, Biochim. Biophys. Acta
2009, 1788, 1762–1771.
H. I. Petrache, S. W. Dodd, M. F. Brown, Biophys. J. 2000, 79,
3172–3192.
M. F. Brown, R. L. Thurmond, S. W. Dodd, D. Otten, K. Be-
yer, J. Am. Chem. Soc. 2002, 124, 8471–8484.
M. F. Brown, J. Chem. Phys. 1982, 77, 1576–1599.
A. Vogel, C. P. Katzka, H. Waldmann, K. Arnold, M. F.
Brown, D. Huster, J. Am. Chem. Soc. 2005, 127, 12263–12272.
[5] C. Yoshina-Ishii, G. P. Miller, M. L. Kraft, E. T. Kool, S. G.
Boxer, J. Am. Chem. Soc. 2005, 127, 1356–1357.
[6] G. G. Borisenko, M. A. Zaitseva, A. N. Chuvilin, G. E. Pozmo-
gova, Nucleic Acids Res. 2009, 37, e28.
[7] G. Stengel, R. Zahn, F. Höök, J. Am. Chem. Soc. 2007, 129,
9584–9585.
[8] M. Banchelli, D. Berti, P. Baglioni, Angew. Chem. Int. Ed. 2007,
46, 3070–3073.
[9] M. Banchelli, F. Betti, D. Berti, G. Caminati, F. B. Bombelli,
T. Brown, L. M. Wilhelmsson, B. Norden, P. Baglioni, J. Phys.
Chem. B 2008, 112, 10942–10952.
[10] J. Wengel, Org. Biomol. Chem. 2004, 2, 277–280.
[11] M. Loew, L. Kang, L. Dahne, R. Hendus-Altenburger, O.
Kaczmarek, J. Liebscher, D. Huster, K. Ludwig, C. Bottcher,
A. Herrmann, A. Arbuzova, Small 2009, 5, 320–323.
[12] S. K. Choi, T. K. Vu, J. M. Jung, S. J. Kim, H. R. Jung, T. Y.
Chang, B. H. Kim, Chembiochem 2005, 6, 432–439.
[13] B. Moreau, P. Barthélemy, M. El Maataoui, M. W. Grinstaff,
J. Am. Chem. Soc. 2004, 126, 7533–7539.
[46]
[47]
[14] J. Arigon, C. A. H. Prata, M. W. Grinstaff, P. Barthélemy,
Bioconjugate Chem. 2005, 16, 864–872.
Eur. J. Org. Chem. 2010, 1579–1586
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1585

J. Liebscher et al.
[52] T. Maki, K. Ishida, J. Org. Chem. 2007, 72, 6427–6433.
[53] P. C. Lin, S. H. Ueng, S. C. Yu, M. D. Jan, A. K. Adak, C. C.
Yu, C. C. Lin, Org. Lett. 2007, 9, 2131–2134.
[54] D. Huster, K. Arnold, K. Gawrisch, Biochemistry 1998, 37,
17299–17308.
FULL PAPER
[48] M. F. Brown, R. L. Thurmond, S. W. Dodd, D. Otten, K. Be-
yer, Phys. Rev. E 2001, 64, 010901-1–010901-4.
[49] H. A. Scheidt, D. Huster, Acta Pharmacol. Sin. 2008, 29, 35–
49.
[50] S. E. Feller, personal communication.
[51] V. Pouzar, L. Schneiderova, P. Drasar, O. Strouf, M. Havel,
Collect. Czech. Chem. Commun. 1989, 54, 1888–1902.
Received: September 21, 2009
Published Online: January 27, 2010
1586
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1579–1586