Synthesis of nucleosides with 2′-fixed lipid anchors and their behavior in phospholipid membranes

Article abstract of DOI:10.1002/ejoc.200701064

Various new nucleosides bearing one or two lipophilic groups at the 2′-position have been synthesized. The lipophilic substituents were attached to a 2′-hydroxy, 2′-amino, or 2′-thio function. These lipophilic nucleosides anchor in large unilamellar POPC vesicles serving as phospholipid membrane models. The insertion of these molecules into the membranes was investigated by NMR techniques. For comparison, nucleosides with two or three lipophilic groups at the 2′-, 3′-, or 5′-positions have also been studied. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200701064

FULL PAPER
DOI: 10.1002/ejoc.200701064
Synthesis of Nucleosides with 2Ј-Fixed Lipid Anchors and Their Behavior in
Phospholipid Membranes
Oliver Kaczmarek,[a] Nicolai Brodersen,[a] Andreas Bunge,[b,c] Ludwig Löser,[b,c]
Daniel Huster,[b,c] Andreas Herrmann,[d] Anna Arbuzova,[d] and Jürgen Liebscher*[a]
Keywords: Nucleosides / Amphiphiles / Lipophiles / Membrane anchoring / Membranes
Various new nucleosides bearing one or two lipophilic
groups at the 2Ј-position have been synthesized. The lipo-
philic substituents were attached to a 2Ј-hydroxy, 2Ј-amino,
or 2Ј-thio function. These lipophilic nucleosides anchor in
large unilamellar POPC vesicles serving as phospholipid
membrane models. The insertion of these molecules into the
membranes was investigated by NMR techniques. For com-
parison, nucleosides with two or three lipophilic groups at
the 2Ј-, 3Ј-, or 5Ј-positions have also been studied.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
tions are free. Such nucleosides can then be transformed
into the corresponding 5Ј-DMT-protected 3Ј-phosphorami-
dites and used in automated synthesis to be introduced at
any given position within the growing oligonucleotide
chain. So far, only a very few examples of such compounds
with free 3Ј- and 5Ј-positions have been reported.[7–10] As
an alternative, nucleosides in which the lipophilic group is
attached to the nucleobase could also be incorporated into
any position of an oligonucleotide.[11]
Recently we showed that nucleosides with lipid moieties
connected either to the nucleobase[12] or to the 5Ј-posi-
tion[13] anchor in the phospholipid double layers of giant
and large unilamellar vesicles (GUV and LUV). The corre-
sponding oligonucleotides with two lipophilic nucleotides
along the chain could be anchored in such liposomes and
were shown to form double-strand DNA with complemen-
tary oligonucleotides in solution.[11,14] Membrane incorpo-
ration could be achieved in a lipid-domain specific manner
being enriched in liquid-disordered domains but not in li-
quid-ordered domains.
As a continuation of our efforts to find suitable lipophilic
nucleosides that can be introduced into any position of an
oligonucleotide strand, we aimed to introduce the lipid scaf-
fold into the 2Ј-position of uridine to obtain products of
the general structure 1 in which X represents O, N, or S.
Herein, we report the synthesis and membrane incorpora-
tion of lipophilic uridines of the type 1. As it has previously
been reported that nucleobases have a tendency to be lo-
cated at the lipid/water interface of the membrane,[12,15]
which renders the recognition of these membrane-associ-
ated molecules by single-stranded DNA difficult, we also
studied the influence of the number of acyl chain anchors
on the average localization of the nucleobases. Based on
Nucleic acids equipped with lipophilic groups (long-
chain alkyl, fatty acyl, fatty alkyloxy, steroidyl, terpenyl)
have gained interest because of their ability to anchor in
lipid membranes and to form double strands with comple-
mentary single-stranded nucleotides. Further, the lipophilic
group may enable nucleic acids to traffic through cell mem-
branes. The former property is useful in the field of chip
technology and diagnostics.[1] Membrane passage of lipo-
philic nucleic acids was recently applied in siRNA-mediated
in vivo gene therapy.[2,3] The ability of oligonucleotides to
permeate cell membranes by the introduction of lipidic
structures into the oligonucleotides has been used in the
development of antiviral compounds.[4–6] In all these cases
the lipophilic moiety was attached either to the 5Ј- or 3Ј-
OH group of the oligonucleotide by using the correspond-
ing 3Ј- or 5Ј-lipidated nucleosides, respectively, as building
blocks in the phosphoramidite method. In order to study
the effect of the position of the lipidated nucleotide in an
oligonucleotide strand and also the position within the lipo-
philic nucleotide itself (positional screening) it is necessary
to develop nucleosides in which both the 3Ј- and 5Ј-posi-
[a] Institute of Chemistry, Humboldt University Berlin,
Brook-Taylor-Str. 2, 12489 Berlin, Germany
E-mail: Liebscher@chemie.hu-berlin.de
[b] Junior Research Group “Structural Biology of Membrane Pro-
teins”, Institute of Biochemistry/Biotechnology, Martin Luther
University Halle-Wittenberg,
06120 Halle, Germany
[c] Institute of Medical Physics and Biophysics, University Leipzig
Härtelstr. 16–18, 04107 Leipzig, Germany
[d] Institute of Biology, Molecular Biophysics, Humboldt Univer-
sity Berlin,
Invalidenstr. 42, 10115 Berlin, Germany
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
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J. Liebscher et al.
FULL PAPER
these results we conclude that the most optimal structure
for nanotechnological applications is a lipophilic nucleoside
with two acyl chains and a spacer between the ribose and
the nucleobase moieties.
Results and Discussion
Synthesis of Lipophilic Uridines
In order to attach the lipophilic moiety to the 2Ј-hydroxy
group of uridine two strategies were applied. First, the
3Ј,5Ј-disilylated uridine 2[16] was used as the starting mate-
rial and transformed into the imidazole-1-carboxylate 3
with carbonyldiimidazole (Scheme 1).[17] Reaction with oc-
tadecylamine and final deprotection of the resulting 4 af-
forded the N-octadecylcarbamate 5. Use of Et3N·3HF in-
stead of TBAF is recommended in order to prevent mi-
gration of the carbamate group from the 2Ј- to the 3Ј-posi-
tion.[17]
Scheme 2.
In an extreme case the 2Ј-[(1,3-di-O-oleoylglycer-2-O-yl)-
succinyl] substituent of the acylation product 10, obtained
from the 3Ј,5Ј-protected uridine 2, migrated completely to
the 3Ј-position when the protective groups were removed by
fluoride. Thus, product 11 was obtained as the sole product
with two lipophilic groups attached to the 3Ј-position rather
than the 2Ј-position (Scheme 3).
This migration is prevented when acyl groups are at-
tached to the 2Ј-position of the corresponding arabinose
nucleoside. Thus, Mitsunobu reaction of the 3Ј,5Ј-protected
uridine 6 with succinoyl dioleoyl glycerol 9[22] yielded the
stable 2Ј-acyl arabinose derivative 13 in high yield after de-
protection of the resulting acylation product 12 (Scheme 4).
In this product two lipid anchors are tethered to the 2Ј-
position.
In order to investigate the effect of the number and posi-
tion of lipid anchors in uridines on the membrane-anchor-
ing behavior we also synthesized the diesters 15 and 17 by
two-fold acylation of 5Ј-dimethoxytrityl-protected uridine
14[23] (Scheme 5). In the latter case the succinate linkers
were first introduced to yield 16, which was then esterified
with pentadecanol[24] to afford 17.
With the same motivation the trispalmityl ester 19 was
synthesized by three-fold acylation of uridine 18 with palm-
itoyl chloride following a literature method.[25]
Nucleosides in which lipophilic groups are attached to a
2Ј-amino or 2Ј-thio group were synthesized starting from
5Ј-DMT-uridine.[23] N- or S-unsubstituted 5Ј-DMT-pro-
tected 2Ј-amino-2Ј-deoxyuridine 21 and 2Ј-thio-2Ј-deoxyur-
Scheme 1.
However, when fatty acyl groups are attached to the 2Ј- idine 22 were obtained following a known route via the so-
position of 3Ј,5Ј-diprotected uridines[18] the 2Ј-acyl group called 2Ј,2-O-anhydrouridine 20 which was treated with tri-
migrates after deprotection.[19–21] In this way, a mixture of chloroacetonitrile and subsequently with NaOH solution[8]
the 2Ј- and 3Ј-palmitoyluridines 7 and 8 was obtained in a or with (4-methoxyphenyl)methanethiol and then with
4:9 ratio starting from 6 (Scheme 2).
TFA,[26] respectively (Scheme 6).
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Nucleosides Bearing Lipid Anchors
Scheme 3.
Scheme 4.
Lipidation of the 2-amino group of 21 was achieved in
three different ways: N-Acylation, N-alkylation, and re-
ductive amination (Scheme 7).[27]
Acylation of the 2Ј-aminouridine 21 with the known
glycerol triester 23[28–30] afforded 50% of the expected 2Ј-
acylaminouridine 24 in which two lipophilic oleoyl groups
are tethered to the amino group. Alternatively, two lipo-
philic groups could be introduced into 21 (formation of 26)
by alkylation with glycerol ether tosylate 25[31,32] obtained
from the known 1,3-dioctadecylglycerol. Reductive amin-
ation of 2Ј,3Ј-dioctadecylglyceraldehyde using 21 in the Scheme 5.
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J. Liebscher et al.
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(Figure 1). Interestingly, lipophilic and polar layers are
formed in the crystal by hydrophobic interaction of the lipid
chains and hydrogen bonding of the uracil moieties, respec-
tively. The lipid layers are twisted with respect to each other
by about 120°. Products 29 and 30 contain pyrene and dan-
syl, respectively, as the fluorescence labels. In the case of 31
two lipid groups were introduced by alkylation. Diisopropyl
azodicarboxylate-mediated formation of unsymmetrical di-
sulfides from thiols is an established way to link ligands to
biological SH-containing molecules.[35] This methodology
was used here (Method A) to introduce the lipophilic octa-
Scheme 6.
Figure 1. X-ray crystal structure of 2Ј-hexadecylthio-2Ј-deoxyurid-
ine (27). The upper structure shows the single molecule and the
lower panel depicts the molecular assembly in the crystal.
Scheme 7.
presence of sodium cyanoborohydride gave 26.[27] The low
yield of the dioctadecyloxyethyl product 26 can be attrib-
uted to problems in its isolation and purification.
Tethering lipophilic substituents at the sulfur atom of 2Ј-
thio-2Ј-deoxyuridine 22 was possible without protection of
the hydroxy groups. It is known from the literature that S-
alkyl groups can be introduced into the 2Ј-position of 22
by S-alkylation with the corresponding alkyl bromides or
iodides.[33,34] Here, the lipophilic thioethers 27–30 could be
obtained in the former way. The structure of the S-hexade-
cyl thioether 27 was confirmed by X-ray crystal analysis Scheme 8.
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Nucleosides Bearing Lipid Anchors
decylthio group to the 2Ј-thio-2Ј-deoxyuridine 22 to afford
the disulfide 33, albeit in low yield (Scheme 8). An alterna-
tive access to 33 (Method B) was achieved by treatment of
the uridine 4-methoxybenyl thioether 32 with octadecylsul-
fenyl chloride following a literature procedure.[36]
Anchoring in Lipid Membranes
To characterize membrane insertion of selected lipophilic
nucleosides we used solid-state NMR spectroscopy.
Molecules 7/8, 15, and 19 feature a uridine moiety in the
“head group”. The membrane affinity of these nucleosides
is provided by one, two, or three lipophilic groups con-
nected to the 2Ј-, 3Ј-, or 5Ј-positions of ribose. These struc-
tures are ideal targets to investigate the effect of the number
and position of the lipophilic anchors on the membrane-
binding properties of these molecules. In addition, we
studied the membrane anchorage of thionucleoside 27 and
the corresponding chain-deuteriated molecule 28 with one
lipophilic anchor at the 2Ј-position as well as the membrane
anchorage of 11 carrying two unsaturated anchors con-
nected to the 3Ј-position via a polar spacer.
Alterations in the structural and dynamic characteristics
of the phospholipid membranes after incorporation of the
lipophilic nucleosides were investigated by 31P and 2H
NMR spectroscopy.[37,38] The 31P NMR spectra of POPC
membranes in the presence of 20 mol-% of the five selected
compounds are presented in Figure 2.
Figure 2. 31P NMR spectra of POPC membranes in the presence
of 20 mol-% 7/8 (A), 15 (B), 19 (C), 11 (D), 27 (E), and of pure
POPC membranes as the reference (F). The measurements were
conducted at a water content of 40 wt.-% and a temperature of
30 °C. The dashed lines represent best-fit simulations of the 31P
NMR spectra.
All lipophilic nucleoside/lipid dispersions exhibit a 31P
axially symmetric powder pattern with an intense high-field
peak and a shallow low-field shoulder typical of liquid crys-
talline bilayers. There are no indications of nonlamellar or
isotropic phases indicating that even high concentrations of
lipophilic nucleosides do not alter the structure and dynam-
ics of the membrane head group. The width of the 31P spec-
tra is called the chemical shift anisotropy (CSA, ∆σ). Alter-
ations in the CSA can be attributed to changes in the dy-
namics or orientation of the lipid head group. Quantitative
values for ∆σ obtained from best-fit simulations are listed
in Table 1. All lipophilic nucleosides except for 15 slightly
reduce the CSA compared with pure POPC membranes.
The largest but still fairly modest alterations can be ob-
served for 7/8, 19, and 11.
Table 1. Chemical shift anisotropies, average order parameters, and
average chain lengths of POPC in membranes containing 20 mol-
2
% of lipophilic nucleosides, as determined from 31P and H NMR
spectra.
Sample
∆σ [ppm]
Sav
ϽLC*Ͼ [Å]
POPC
45.2
43.4
44.1
45.5
44.0
44.7
–
0.153
0.162
0.167
0.165
0.183
0.154
0.152
11.46
11.74
11.88
11.84
12.35
11.51
11.36
POPC/7/8
POPC/11
POPC/15
POPC/19
POPC/27
POPC/28
To investigate the effect of the incorporation of lipophilic branes in the presence of 7/8, 11, and 15, whereas 27 has
nucleosides on the packing properties in the membrane acyl a negligible effect on the phospholipid chain order in the
chain region, 2H NMR spectra of chain-perdeuteriated membrane. This can also be seen from the average order
[D31]POPC were acquired. From these spectra, smoothed parameters reported in Table 1. As order parameters are
order parameter profiles were extracted (Figure 3).[39] The directly related to the average length of the lipid chains,
carbon atoms are numbered starting from the carbonyl these effects can also be seen from the average order param-
group of the perdeuteriated palmitoyl chain of [D31]POPC. eter and the hydrocarbon chain length reported in Table 1.
2
All the lipophilic nucleosides increase the chain order of
To provide information about lipid-chain dynamics, H
pure [D31]POPC membranes. The lipophilic nucleoside 19 NMR spin-lattice relaxation measurements were con-
2
drastically increases the order of the lipids within the mem- ducted. For each peak doublet in the H NMR spectra the
brane. This can be explained by the cone-shaped molecule Zeeman order longitudinal relaxation time (T1Z) was deter-
with a relative small head group size relative to the large mined in an inversion recovery experiment. By correlating
acyl chain area of the three hydrocarbon chains. Moderate the longitudinal relaxation rate R1Z (inverse relaxation
order parameter changes are observed for [D31]POPC mem- time) with the squared order parameters for the individual
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J. Liebscher et al.
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(i)
Figure 4. Dependence of the longitudinal relaxation rate R on
1Z
Figure 3. Smoothed order parameter profiles obtained from 2H
NMR spectra of [D31]POPC of the samples [D31]POPC (᭺), (7/8)/
[D31]POPC (✧), 11/[D31]POPC (), 15/[D31]POPC (ᮀ), 19/[D31]-
POPC (ٌ), and 27/[D31]POPC (*) all at a molar ratio of 1:4 and a
temperature of 30 °C.
the corresponding order parameter squared for 27/[D31]POPC (*)
and 28/POPC () at a molar ratio of 1:4, and for pure [D31]POPC
(᭺) at 40 wt.-% H2O and a temperature of 30 °C. The elastic prop-
erties of the [D31]POPC membranes are unchanged in the presence
of the lipophilic nucleoside 27 indicating that this molecule is well
incorporated into the bilayer without interfering with the elastic
properties of the membrane. This is also seen from the square-law
plot of deuteriated 28 which is essentially identical to POPC in the
presence and in the absence of 27.
methylene and methyl groups, a linear dependence for satu-
rated acyl chains is typically found for phospholipid mem-
branes.[40,41] The slope of such a square-law plot directly
relates to the elastic properties of the membrane and is in-
versely related to the softness of the membrane.[42] For this collected. The lipid coordinates were obtained from a mo-
more time-consuming measurement, we chose the lipophilic lecular dynamics simulation of POPC.[45] Because the abso-
nucleoside that showed the least membrane perturbation lute values of the cross-relaxation rates belonging to 7/8,
(27). To obtain information about the molecular dynamics 11, 15, and 19 vary as a result of small correlation time
of the host membrane in the presence of the lipophilic nu- differences normalization is needed. The nucleoside moie-
cleoside as well as for the lipophilic nucleoside itself, we ties of the molecules are broadly distributed along the bi-
also studied the deuteriated analogue (28) of molecule 27. layer normal illustrated in Figure 5.
The square-law plots for the samples 27/[D31]POPC, 28/
POPC, and pure [D31]POPC membranes at 30 °C are shown sugar moiety, that is, the highest probability of molecular
in Figure 4. contacts, is found in the lipid/water interface of the mem-
The maximum of the distribution of the nucleobase/
The square-law plots of the [D31]POPC membranes are brane for all lipophilic nucleosides. Significantly lower
identical in the presence and in the absence of 28 indicating probabilities of contacts are found in the fatty acid chain
unchanged elastic properties of the lipid matrix despite in- region. The cross-relaxation rates in the lipid head group
corporation of the lipophilic nucleoside into the membrane. are significantly increased for 15 compared with 19. Yet a
The chain-deuteriated 27, that is, 28, shows identical behav- higher probability of contacts in this region can be observed
ior suggesting that it is homogeneously distributed and well for 7/8. The highest relative cross-relaxation rates in the li-
incorporated into the membrane.
pid head group are measured for 11. The shift of the prob-
The preferential localization of the lipophilic nucleosides ability distribution to the head-group region can be ex-
within the lipid matrix was determined by 1H NOESY plained by the different number of lipophilic anchors in the
NMR spectroscopy under magic-angle spinning condi- three nucleosides. Nucleoside 19 carries three lipophilic
tions.[43,44] The intermolecular NOESY cross-peaks be- groups and exhibits the highest hydrophobic energy with
tween the nucleobase/ribose moiety of the lipophilic nucleo- the most stable incorporation into the membrane and local-
sides and the segments of the lipid molecules were inte- ization of the nucleobase in the upper-chain region. The
grated and cross-relaxation rates σij were determined by nucleosides 7/8 contain one lipophilic anchor. The prob-
using the spin-pair model. The cross-relaxation rates reflect ability distribution of the uracil of these molecules is signifi-
the probability of the contacts of protons and can be used cantly shifted to the head-group region. The lipophilic nu-
to characterize the preferential localization of the lipophilic cleoside 15 shows a distribution with respect to the mem-
nucleosides within the membrane.[43,44] By plotting the val- brane that is intermediate between 7/8 and 19. In contrast,
ues of σij between hydrogen atoms of the nucleobase/ribose the most probable localization of the nucleobase close to
and the lipid segments as a function of the membrane coor- the head group is found for substance 11. This is achieved
dinates of such segments information about the distribution as a result of the polar spacer between the ribose and the
of the nucleosides parallel to the membrane normal can be lipophilic anchors pushing the uracil moiety outwards.
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Nucleosides Bearing Lipid Anchors
such nucleosides should not interfere with the integrity of
the membranes causing enhanced permeability or even lysis.
However, the influence of individual molecules on lipid or-
der varies. The best-suited lipophilic nucleoside is 27 which
does not seem to alter membrane structure or dynamics.
The sugar/nucleobase moiety of the all molecules is located
in the lipid/water interface of the membrane. An increased
number of hydrocarbon chains attached to the lipophilic
nucleoside drag the nucleobase deeper into the membrane.
Therefore, to expose it to the aqueous environment for pos-
sible base-pairing, a molecular spacer may provide the de-
sired property.
Experimental Section
1
General Remarks: H and 13C NMR spectra were recorded at 300
and 75.5 MHz, respectively, with a Bruker AC 300 in CDCl3 with
TMS as the internal standard. Silica gel (0.04–0.063 mm, Merck)
was used for preparative column chromatography. Starting materi-
als 3,[17] 20,[8] 21,[8] and 22[26,34] were synthesized according to lit-
erature procedures. All other materials were purchased from com-
mercial suppliers.
Membrane Incorporation of Lipophilic Nucleosides: POPC (1-palmi-
toyl-2-oleoyl-sn-glycero-3-phosphocholine) and [D31]POPC (1-
[D31]palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) were pur-
chased from Avanti Polar Lipids (Alabaster, AL) and used without
2
1
further purification. For H, 31P, and H NOESY NMR measure-
ments, mixtures of phospholipids and lipophilic nucleosides were
prepared in a chloroform/methanol mixture (1:1 v/v). The solvent
was removed by rotary evaporation and the resulting lipid film was
redissolved in cyclohexane and lyophilized overnight to obtain a
fluffy powder. Samples were hydrated with 40 wt.-% water and
equilibrated by 10 freeze–thaw cycles and gentle centrifugation.
The liposome dispersions were transferred into 4 mm high-resolu-
tion MAS rotors fitted with spherical Kel-F inserts for liquid sam-
2
ples or into 5 mm glass vials for static H NMR experiments. 31P
NMR spectra were accumulated with a Bruker DRX 600 NMR
spectrometer (Bruker BioSpin, Rheinstetten, Germany) at a reso-
nance frequency of 242.8 MHz for 31P NMR by using a Hahn echo
pulse sequence with a 90° pulse length of 7 µs, a Hahn echo delay
of 50 µs, a spectral width of 100 kHz, and a recycle delay of 4 s.
Continuous-wave proton-decoupling was applied during signal ac-
quisition. Spectral simulations of the 31P NMR line-shape were car-
ried out to obtain the chemical shift anisotropy (∆σ) using a pro-
gram written in Mathcad 2001.[46] 2H NMR spectra were recorded
with a Bruker Avance 400 NMR spectrometer at a resonance fre-
quency of 61.5 MHz for 2H by using a solid probe with a 5 mm
solenoid coil. The 2H NMR spectra were accumulated by using the
quadrupolar echo sequence and a relaxation delay of 1 s. The two
3.1 µs π/2 pulses were separated by a 60 µs delay. 2H NMR spectra
were depeaked and order parameters for each methylene group in
the chain were determined as described previously.[39]
Figure 5. Relative 1H NOESY cross-relaxation rates between the
nucleoside moiety of (7/8) (ꢀ), 11 (᭤), 15 (᭿), and 19 (᭢) and
segments of the POPC molecules within the membrane as a func-
tion of the coordinates of such lipid segments. Localization of 6-H
(top) and 5-H (middle) of the uracil nucleobase and of 1Ј-H of
the ribose with respect to the membrane normal is shown. The
approximate localization of these hydrogen atoms with respect to
various segments of the lipid molecules in the host membrane can
be estimated from the phospholipid molecule drawn below. The
measurements were carried out at a 1:4 molar ratio of lipophilic
nucleoside/POPC and at a temperature of 30 °C.
Conclusions
A series of new uridines have been synthesized bearing
one or two lipophilic groups in the 2Ј-position. The lipo-
philic moieties can be fixed with or without spacers at O,
N, or S atoms at the 2Ј-position. The syntheses are straight
forward and provide flexibility as far as the lipophilic
groups are concerned. The lipophilic uridine products have
the potential to be incorporated into any position of the
oligonucleotide chain. All the lipophilic nucleosides can be
incorporated into lipid membranes without inducing non-
2
For the H NMR relaxation studies a phase-sensitive inversion re-
covery quadrupolar echo pulse sequence was used to obtain the
spin-lattice relaxation time T1Z. Spectral simulations of the 2H
NMR spectra were carried out to obtain the cross-relaxation rates
by using a program written in Mathcad 2001.
1H MAS NMR spectra were acquired at a spinning frequency of
6009 Hz with a Bruker DRX 600 NMR spectrometer by using a 4
lamellar or isotropic phases. Hence, the incorporation of mm HR-MAS probe. Typical π/2 pulse lengths were 9 µs. A 2H
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J. Liebscher et al.
FULL PAPER
lock was used for field stability. Two-dimensional 1H MAS NOESY
spectra were acquired at various mixing times (between 1 and
600 ms). The dwell time of the indirect dimension was set equal to
one rotor period to avoid folding of spinning sidebands into the
center band region of the 2D NOESY spectra. Typically, between
400 and 500 data points were acquired in the indirect dimension
with 32 scans per increment at a relaxation delay of 3.5 s. The vol-
umes of the diagonal and the cross-peaks were integrated by using
the Bruker TopSpin software package.[47] NOE build-up curves
were fitted to the spin-pair model to obtain cross-relaxation rates.
All spectra were acquired at a temperature of 30 °C.
3Ј,5Ј-diprotected product was obtained as a light-brown foam
(1.06 g, ca. 1.30 mmol) and was deprotected without any further
purification. It was dissolved in MeOH (20 mL) and NH4F (1.00 g,
27 mmol) was added. The mixture was stirred at ambient tempera-
ture overnight. The volatiles were evaporated and partitioned
(CH2Cl2/brine). The organic layer was dried (MgSO4), evaporated,
and the residue was purified by column chromatography (cyclohex-
ane/EtOAc, 2:1) to give the crystalline product (300 mg, 0.64 mmol,
48% over two steps) as a mixture of 7/8 in a 4:9 ratio.
7: 1H NMR (300 MHz, CDCl3): δ = 7.7 (d, J = 6.0 Hz, 1 H, 6-H),
5.88 (d, J = 2.3 Hz, 1 H, 1Ј-H), 5.62 (d, J = 6.0 Hz, 1 H, 6-H), 5.08
(d, J = 2.1 Hz, 1 H, CH), 4.32 (m, 1 H, CH), 3.98 (m, 1 H, CH),
3.66 (m, 2 H, 5Ј-H), 2.32 (m, 2 H, CH2), 1.52 (m, 2 H, CH2), 1.2
(m, 26 H, CH2), 0.78 (t, J = 6.8 Hz, 3 H, CH3) ppm.
CCDC-679143 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
8: 1H NMR (300 MHz, CDCl3): δ = 7.8 (d, J = 6.0 Hz, 1 H, 6-H),
5.78 (d, J = 2.3 Hz, 1 H, 1Ј-H), 5.64 (d, J = 6.0 Hz, 1 H, 6-H), 5.06
(d, J = 2.1 Hz, 1 H, CH), 4.35 (m, 1 H, CH), 3.98 (m, 1 H, CH),
3.66 (m, 2 H, 5Ј-H), 2.32 (m, 2 H, CH2), 1.52 (m, 2 H, CH2), 1.2
(m, 26 H, CH2), 0.78 (t, J = 6.8 Hz, 3 H, CH3) ppm. 7/8: 13C NMR
3Ј,5Ј-O-[Oxybis(diisopropylsilyl)]-2Ј-O-(stearoylaminocarbonyl)urid-
ine (4): n-Octadecylamine (550 mg, 2.2 mmol) was added to a solu-
tion of 3 (1.16 g, 4.0 mmol) in CH2Cl2 (30 mL) and the completion
of reaction (from 1 h to several days) was monitored by TLC
(EtOAc). After 48 h the reaction mixture was diluted with CH2Cl2 (75 MHz, CDCl3): δ = 176.7 (C=O), 176.4 (C=O), 173.8 (C=O),
(5 mL), washed with water (10 mL), 5% citric acid (10 mL), and
water (10 mL), then dried (MgSO4), evaporated, and the residue
purified by chromatography (EtOAc) to give 4 (1.17 g, 1.6 mmol,
78%) as a white solid. H NMR (300 MHz, CDCl3): δ = 8.60 (s, 1
H, NH), 7.64 (d, J = 8.1 Hz, 1 H, 6-H), 5.87 (s, 1 H, 1Ј-H), 5.21
171.7 (C=O), 164.1 (C-4), 151.1 (C-6), 147.0 (C-6), 141.1 (C-2),
139.1 (C-2), 113.5 (C-5), 102.5 (C-5), 89.8 (CH), 88.1 (CH), 84.9
(CH), 83.4 (CH), 72.9 (CH), 72.6 (CH), 68.5 (CH), 61.3 (CH2),
60.5 (CH2), 53.9 (CH2), 37.5 (CH2), 35.7 (CH2), 34.0 (CH2), 33.9
(CH2), 33.7 (CH2), 31.8 (CH2), 29.6–28.9 (CH2), 27.2 (CH2), 25.5
1
(d, J = 8.1 Hz, 1 H, 5-H), 5.26 (d, J = 5.1 Hz, 1 H, CH), 4.82 (d, (CH2), 24.8 (CH2), 22.5 (CH2), 20.9 (CH2), 13.9 (CH3) ppm.
J = 6.1 Hz, 1 H, CH), 4.41 (d, J = 5.1 Hz, 1 H, CH), 4.19 (m, 1
2Ј-O-[1,3-Bis(oleoyloxy)isopropyloxysuccinyl]-3Ј,5Ј-O-[oxybis(diiso-
H, CH), 4.00 (m, 2 H, CH2), 3.21 (m, 2 H, 5Ј-H), 1.50 (s, 2 H,
propylsilyl)]uridine (10): A solution of 2 (0.75 g, 1.5 mmol) in dry
CH2), 1.26 (s, 26 H, CH2), 1.01 (s, 24 H, –CH–CH3), 0.89 (t, J =
THF (20 mL), 1,3-bis(oleyloxy)isopropyl succinate (1.25 g,
6.6 Hz, 3 H, –CH2–CH3) ppm. 13C NMR (75 MHz, CDCl3): δ =
1.7 mmol), DCC (0.35 g, 1.7 mmol), and DMAP (0.5 g, 0.40 mmol)
161.5 (C-4), 154.6 (C=O), 149.5 (C-6), 139.6 (C-2), 102.2 (C-5),
were stirred under argon at ambient temperature for 3 days. The
88.8 (CH), 82.2 (CH), 75.6 (CH), 68.1 (CH), 59.8 (CH2), 41.2
volatiles were evaporated and the residue was purified by column
(CH2), 31.9 (CH2), 29.8–29.3 (CH2), 26.7 (CH2), 22.7 (CH2), 17.5
chromatography (cyclohexane/EtOAc, 3:1) to give the product 10
(–CH–CH3), 16.9 (–CH–CH3), 14.1 (–CH2–CH3), 13.4 (–CH–
as colorless oil (0.76 g, 0.68 mmol, 45 %). 1H NMR (300 MHz,
CH3), 12.9 (–CH–CH3) ppm.
CDCl3): δ = 9.2 (s, 1 H, NH), 7.7 (d, J = 7.9 Hz, 1 H, 6-H), 5.79
2Ј-O-(Stearoylaminocarbonyl)uridine (5): Triethylamine trihydro-
fluoride (10 mL, 2.00 mmol) was added to a solution of 4 (1.1 g,
1.5 mmol) in THF (5 mL) in a screw-top Teflon can (Nalgene) and
the mixture was left for 6 h at room temperature [the completion
of deprotection was checked by TLC (15% MeOH in CH2Cl2,
v/v)] and then diluted with hexane (5 mL). The upper layer was
discarded, the residue was washed with a 1:1 (v/v) toluene/hexane
mixture (3ϫ5 mL) by decantation and trituration in absolute
EtOH (1 mL) gave the crystalline product 5 (0.48 g, 0.9 mmol,
(s, 1 H, 1Ј-H), 5.39 (m, 1 H, 5-H), 5.33 (m, 4 H, –CH=CH–), 5.24
(m, 1 H, CH), 4.26 (s, 1 H, CH), 4.20 (m, 4 H, CH2), 3.98 (m, 2
H, CH2), 3.65 (m, 2 H, CH2), 2.71 (m, 4 H, CH2), 2.66 (m, 2 H,
CH2), 2.29 (t, J = 11.9 Hz, 8 H, CH2), 1.97 (d, J = 8.9 Hz, 2 H,
CH2), 1.58 (m, 34 H, CH2), 1.04 (m, 24 H, –CH–CH3), 0.85 (t, J
= 6.4 Hz, 6 H, –CH2–CH3) ppm. 13C NMR (75 MHz, CDCl3): δ
= 173.23 (C=O), 171.07 (C=O), 170.07 (C=O), 163.26 (C-4), 149.68
(C-6), 139.31 (C-2), 129.97 (–CH=CH–), 129.69 (–CH=CH–),
102.15 (C-5), 88.53 (CH), 82.11 (CH), 77.49 (CH), 77.07 (CH),
76.64 (CH), 75.63 (CH), 69.55 (CH), 67.63 (CH), 61.85 (CH2),
1
60%). H NMR (300 MHz, CDCl3): δ = 7.66 (d, J = 8.1 Hz, 1 H,
6-H), 5.91 (s, 1 H, 1Ј-H), 5.77 (d, J = 8.1 Hz, 1 H, 5-H), 5.26 (t, J 59.50 (CH2), 33.96 (CH2), 31.89 (CH2), 29.75 (CH2), 29.69 (CH2),
= 5.3 Hz, 1 H, CH), 4.58 (t, J = 5.0 Hz, 1 H, CH), 4.22 (s, 1 H, 29.51 (CH2), 29.30 (CH2), 29.16 (CH2), 29.10 (CH2), 27.20 (CH2),
CH), 3.90 (m, 2 H, CH2), 3.17 (m, 2 H, 5Ј-H), 1.64 (s, 2 H, CH2), 27.15 (CH2), 24.80 (CH2), 22.67 (CH2), 17.41 (–CH–CH3), 17.32
1.26 (s, 26 H, CH2), 0.89 (t, J = 6.6 Hz, 3 H, CH3) ppm. 13C NMR
(–CH–CH3), 17.25 (–CH–CH3), 17.19 (–CH–CH3), 16.91 (–CH–
(75 MHz, CDCl3): δ = 161.5 (C-4), 150.5 (C-6), 141.2 (C-2), 103.6 CH3), 16.80 (–CH–CH3), 16.75 (–CH–CH3), 16.70 (–CH–CH3),
(C-5), 91.2 (CH), 84.4 (CH), 80.2 (CH), 63.8 (CH), 60.2 (CH2), 44.2 14.10 (–CH2–CH3), 13.38 (–CH–CH3), 12.87 (–CH–CH3) ppm.
(CH2), 33.7 (CH2), 30.9–29.7 (CH2), 19.9 (CH2), 14.1 (CH3) ppm.
3Ј-O-[1,3-Bis(oleoyloxy)isopropyloxysuccinyl]uridine (11): Triethyl-
2Ј-O-(Palmitoyl)uridine (7) and 3Ј-O-(Palmitoyl)uridine (8): Uridine amine trihydrofluoride (0.2 mL, 1.22 mmol) was added to a solu-
6 (500 mg, 1.30 mmol), palmitoyl chloride (540 mg, 1.95 mmol),
and DMAP (40 mg, 0.40 mmol) were dissolved in anhydrous pyr-
idine (10 mL). The reaction was stirred overnight at ambient tem-
perature. TLC analysis (CH2Cl2/MeOH, 20:1) showed the complete
disappearance of the starting material. The pyridine was removed
in vacuo and the residue was then coevaporated with toluene
(3ϫ50 mL). The dark-brown residue was taken up in CH2CI2
(100 mL) and washed with saturated brine. After drying the organic
phase with MgSO4 the solvent was removed in vacuo. The crude
tion of 10 (0.68 g, 0.61 mmol) in THF (5 mL) in a screw-top Teflon
can (Nalgene) and the mixture was left at room temperature for
2 h [completion of deprotection was checked by TLC (cyclohexane/
EtOAc, 1:1, v/v)] and then diluted with water (5 mL). The organic
layer was washed with water (3ϫ2 mL), dried with Na2SO4, and
evaporated to give the crystalline product 11 (0.47 g, 0.49 mmol,
81%). H NMR (300 MHz, CDCl3): δ = 7.83 (d, J = 8.1 Hz, 1 H,
6-H), 5.83 (d, J = 8.1 Hz, 1H. 5-H), 5.73 (s, 1 H, 1Ј-H), 5.36 (m, 1
H, CH), 5.33 (m, 4 H, –CH=CH–), 5.24 (m, 1 H, CH), 4.64 (s, 1
1
1924
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1917–1928

Nucleosides Bearing Lipid Anchors
H, CH), 4.28 (s, 1 H, CH), 4.20 (m, 4 H, CH2), 3.91 (m, 2 H, CH2), layer was dried (MgSO4) and concentrated in vacuo to give a yellow
2.73 (m, 4 H, CH2), 2.69 (m, 2 H, CH2), 2.32 (t, J = 11.9 Hz, 8 H,
CH2), 2.00 (d, J = 8.9 Hz, 4 H, CH2), 1.58 (m, 2 H, CH2), 1.27 (m,
32H, –CH2–), 0.88 (t, J = 6.4 Hz, 3 H, CH3) ppm. 13C NMR
(75 MHz, CDCl3): δ = 173.37 (C=O), 171.98 (C=O), 171.70 (C=O),
171.57 (C=O), 163.57 (C-4), 150.92 (C-6), 141.61 (C-2), 129.95
oil. Purification by column chromatography (SiO2) eluting with cy-
clohexane/EtOAc (1:3 with 1% Et3N) gave 2Ј,3Ј-O-dipalmitoyl-5Ј-
O-(4,4Ј-dimethoxytrityl)uridine (1.66 g, 1.66 mmol, 82 %) as a
white solid. H NMR (300 MHz, CDCl3): δ = 9.02 (s, 1 H, NH),
7.76 (d, J = 6 Hz, 1 H, 6-H), 7.16–7.25 (m, 9 H, CHar), 6.82–6.88
1
(–CH=CH–), 129.65 –CH=CH–), 102.59 (C-5), 90.61 (CH), 83.47 (m, 4 H, CHar), 6.25 (d, J = 6 Hz, 1 H, 1Ј-H), 5.61 (d, J = 3.9 Hz,
(CH), 73.54 (CH), 72.90 (CH), 69.68 (CH), 61.72 (CH2), 33.94 1 H, 5-H), 5.41 (m, 2 H, CH),4.22 (s, 1 H, CH), 3.80 (s, 6 H,
(CH2), 31.84 (CH2), 29.70 (CH2), 29.65 (CH2), 29.46 (CH2), 29.26 OCH3), 3.50 (s, 2 H, CH2), 2.36 (m, 4 H, CH2), 2.04 (m, 8 H, CH2),
(CH2), 29.13 (CH2), 29.07 (CH2), 29.03 (CH2), 27.16 (CH2), 27.12 1.63 (t, J = 6.99 Hz, 4 H, CH2), 1.13 (s, 40 H, CH2), 0.90 (t, J =
(CH2), 24.76 (CH2), 22.62 (CH2), 14.07 (CH3) ppm.
6.42 Hz, 6 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 172.9
(C=O), 164.2 (C-4), 159.5 (C-6), 150.4 (C-2), 143.8 (Cq), 139.9 (Cq),
134.9 (Cq), 130.2–127.0 (CHar), 125.3 (CHar), 113.7 (CHar), 113.1
(CHar), 102.9 (C-5), 87.6 (CH), 85.6 (CH), 82.2 (CH), 72.8 (CH),
71.0 (CH), 60.4 (CH2), 55.2 (OCH3), 33.9 (CH2), 31.9 (CH2), 29.7–
27.1 (CH2), 24.8 (CH2), 22.7 (CH2), 14.2 (–CH2–CH3) ppm.
1-{2Ј-O-[1,3-Bis(oleoyloxy)isopropylsuccinyl]-3Ј,5Ј-O-(di-tert-butyl-
silanediyl)-(β-D-arabinofuranos-1-yl)}uracil (12): DIAD (0.14 mL)
was added slowly to a solution of 6 (290 mg, 0.75 mmol), 9
(650 mg, 0.90 mmol), and PPh3 (230 mg, 0.90 mmol) in dry THF
(1.5 mL) until the red color had vanished. After 16 h at ambient
temperature the volatiles were evaporated and the residue was puri-
fied by column chromatography (cyclohexane/EtOAc, 1:1) to give
A solution of 5Ј-O-(4,4Ј-dimethoxytrityl)-protected 15 (1.66 g,
1.66 mmol) in 80% CF3COOH (15 mL) was stirred at ambient
12 (510 mg, 0.46 mmol, 61%). 1H NMR (300 MHz, CDCl3): δ = temperature for 15 h. The reaction was diluted with CH2Cl2
7.21 (d, J = 7.9 Hz, 1 H, 6-H), 6.45 (s, 1 H, 1Ј-H), 5.65 (d, J = (20 mL), carefully washed with saturated aq. NaHCO3, and dried
8.0 Hz, 1 H, 5-H), 5.60 (m. 1 H, CH), 5.27 (m, 4 H, –CH=CH–), with MgSO4. Silica gel flash chromatography with a short column
4.70 (m, 1 H, CH), 4.59 (m, 1 H, CH), 4.41 (m, 1 H, CH), 4.21 using cyclohexane/EtOAc (2:1) gave the product 15 as a white solid
(m, 2 H, CH2), 4.05 (m, 4 H, CH2), 2.59 (s, 2 H, CH2), 2.24 (t, J (310 mg, 0.43 mmol, 29%). 1H NMR (300 MHz, CDCl3): δ = 9.11
= 6 Hz, 4 H, CH2), 1.95 (m, 8 H, CH2), 1.52 (m, 4 H, CH2), 1.26 (s, 1 H, NH), 7.68 (d, J = 8 Hz, 1 H, 6-H), 5.99 (d, J = 5.7 Hz, 1
(s, 40 H, CH2), 1.00 (s, 18 H, C–CH3), 0.80 (t, J = 6.8 Hz, 3 H, H, 1Ј-H), 5.79 (d, J = 7.82 Hz, 1 H, 5-H), 5.41 (m, 2 H, CH), 4.12
CH2–CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 173.3 (C=O),
171.7 (C=O), 171.4 (C=O), 163.0 (C-4), 156.4 (C-6), 149.8 (C-2),
130.0 (–CH=CH–), 129.7 (–CH=CH–), 102.8 (C-5), 84.7 (CH),
(s, 1 H, CH), 3.85 (q, J = 1.9, 11.5 Hz, 2 H, CH2), 2.32 (m, 4 H,
CH2), 1.54 (t, J = 6.99 Hz, 4 H, CH2), 1.18 (s, 40 H, CH2), 0.80 (t,
J = 6.42 Hz, 6 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ =
81.6 (CH), 70.0 (CH), 69.6 (CH), 67.2 (CH2), 65.8 (CH2), 64.2 172.9 (C=O), 172.5 (C=O), 163.2 (C-4), 150.4 (C-2), 103.2 (C-5),
(CH2), 61.8 (CH2), 60.4 (CH2), 51.8 (CH2), 33.9 (CH2), 31.8 (CH2), 87.7 (CH), 83.6 (CH), 72.9 (CH), 70.9 (CH), 61.8 (CH2), 34.0
29.7–26.6 (CH2), 25.8 (CH2), 22.7 (CH2), 21.9 (CH2), 21.8 (CH2), (CH2), 33.8 (CH2), 31.9 (CH2), 29.7–29.1 (CH2), 24.8 (CH2), 22.7
21.0 (CH2), 20.1 (CH2), 19.7 (C–CH3), 15.2 (C–CH3) 14.1 (CH2– (CH2), 14.2 (CH3) ppm.
CH3) ppm.
5Ј-O-(4,4Ј-Dimethoxytrityl)-2Ј,3Ј-O,O-disuccinyluridine (16): 5Ј-O-
1-{2Ј-O-[1,3-Bis(oleoyloxy)isopropyloxysuccinyl]-(β-
D
-arabino-
(4,4Ј-Dimethoxytrityl)uridine (1.10 g, 2.00 mmol), succinic anhy-
dride (0.60 g, 6.00 mmol), and DMAP (120 mg, 1.00 mmol) were
dissolved in anhydrous pyridine (10 mL). The reaction was stirred
for 3 days at ambient temperature. TLC analysis (EtOAc/MeOH,
9:1) showed the complete disappearance of the starting material.
Pyridine was removed in vacuo and the residue was then co-evapo-
rated with toluene (3ϫ50 mL). The dark-brown residue was taken
furanos-1-yl)}uracil (13): NH4F (1.00 g, 27 mmol) was added to a
solution of 12 (510 mg, 0.46 mmol) in MeOH (20 mL). The reac-
tion mixture was stirred overnight at ambient temperature, the vol-
atiles were evaporated, and the remainder was partitioned (CH2Cl2/
brine). The organic layer was dried (MgSO4), evaporated, and the
residue was purified by column chromatography (cyclohexane/
EtOAc, 1:1) to give 13 (330 mg, 0.35 mmol, 77 %). 1H NMR up in CH2CI2 (100 mL) and washed with saturated brine. The or-
(300 MHz, CDCl3): δ = 10.0 (s, 1 H, NH), 7.54 (d, J = 7.5 Hz, 1 ganic phase was dried with MgSO4 and concentrated in vacuo to
H, 6-H), 6.53 (s, 1 H, 1Ј-H), 5.76 (d, J = 3.0 Hz, 1 H, 5-H), 5.71
provide the crude product 14 as light-brown foam (1.56 g,
(d, J = 7.9 Hz, 1 H, CH), 5.27 (m, 4 H, –CH=CH–), 4.70 (m, 1 H, 2.00 mmol, quant. yield). 1H NMR (300 MHz, CDCl3): δ = 10.0
CH), 4.59 (m, 1 H, CH), 4.32 (m, 1 H, CH), 4.12 (m, 2 H, CH2), (s, 1 H, COOH), 8.6 (s, 1 H, NH), 7.6 (d, J = 8.1 Hz, 1 H, 6-H),
4.10 (m, 4 H, CH2), 2.25 (t, J = 7.2 Hz, 2 H, CH2), 1.92 (m, 8 H,
7.29–7.08 (m, 9 H, CHar), 6.76 (m, 4 H, CHar), 6.15 (d, J = 6.8 Hz,
CH2), 1.54 (m, 4 H, CH2), 1.19 (s, 40 H, CH2), 0.81 (t, J = 6.8 Hz, 1 H, 1Ј-H), 5.56 (m, 2 H, 5-H, CH), 5.41 (m, 1 H, CH), 4.18 (s, 1
3 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 173.4 (C=O), H, CH), 3.72 (s, 6 H, OCH3), 3.40 (m, 2 H, CH2), 2.58 (s, 8 H,
171.8 (C=O), 171.6 (C=O), 163.7 (C-4), 151.0 (C-6), 140.1 (C-2),
130.0 (–CH=CH–), 129.7 (–CH=CH–), 102.6 (C-5), 90.7 (CH),
81.9 (CH), 74.7 (CH), 70.1 (CH), 69.9 (CH), 68.1 (CH2), 63.7
CH2) ppm. 13C NMR (75 MHz, CDCl3): δ = 171.4 (C=O), 171.3
(C=O), 163.7 (C-4), 158.8 (C-2), 143.9 (Cq), 140.0 (C-6), 139.7 (Cq),
139.4 (CHar), 134.9 (CHar), 134.7 (CHar), 130.2 (CHar), 130.0
(CH2), 61.8 (CH2), 33.9 (CH2), 31.8 (CH2), 29.7–29.1 (CH2), 27.2 (CHar), 129.1–127.1 (CHar), 125.3 (CHar), 113.4 (CHar), 113.2
(CH2), 24.8 (CH2), 22.7 (CH2), 21.9 (CH2), 14.1 (CH3) ppm.
(CHar), 103.1 (C-5), 87.6 (CH), 85.7 (CH), 82.1 (CH), 72.9 (CH),
71.7 (CH), 62.8 (CH2), 55.3 (OCH3), 29.1–28.3 (CH2) ppm.
2Ј,3Ј-O,O-Dipalmitoyl-5Ј-O-(4,4Ј-dimethoxytrityl)uridine and 2Ј,3Ј-
O,O-Dipalmitoyluridine (15): Palmitoyl chloride (1.65 g,
6.00 mmol) and DMAP (30 mg, 0.25 mmol) were added in one
batch to a solution of 5Ј-O-(4,4Ј-dimethoxytrityl)uridine (14)
(1.10 g, 2.00 mmol) in dry pyridine (25 mL) at 0 °C. The reaction
mixture was warmed to room temp. and the completion of the reac-
tion was monitored by TLC (cyclohexane/EtOAc, 1:3). After 2 h
the reaction mixture was concentrated in vacuo and partitioned
between diethyl ether (200 mL) and brine (100 mL). The organic
5Ј-O-(4,4Ј-Dimethoxytrityl)-2Ј,3Ј-O,O-bis(pentadecyloxysuccinyl)-
uridine and 2Ј,3Ј-O,O–Bis(pentadecyloxysuccinyl)uridine (17): The
disuccinate 16 (1.20 g, 1.60 mmol), pentadecanol (0.23 g,
0.80 mmol), DCC (0.19 g, 0.90 mmol), and DMAP (0.02 g,
0.20 mmol) were dissolved in anhydrous toluene (10 mL). The reac-
tion was stirred for 3 days under argon at ambient temperature.
The volatiles were evaporated and the residue was purified by col-
umn chromatography (CHCl3/MeOH, 9:1, with 1% Et3N) to give
Eur. J. Org. Chem. 2008, 1917–1928
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1925

J. Liebscher et al.
FULL PAPER
the 5Ј-DMT-protected 17 (0.44 g, 0.38 mmol, 95 %). 1H NMR
(300 MHz, CDCl3): δ = 8.9 (s, 1 H, NH), 7.7 (d, J = 8.1 Hz, 1 H,
(MeOH/DCM, 1:30, 1% Et3N, Rf = 0.5). Compound 24 (0.48 g,
0.38 mmol, 50 %) was obtained as a colorless oil. 1H NMR
6-H), 7.31–7.18 (m, 9 H, CHar), 6.85 (m, 4 H, CHar), 6.3 (d, J = (300 MHz, CDCl3): δ = 7.65 (d, J = 8.9 Hz, 1 H, 6-H), 7.29 (m, 10
5.7 Hz, 1 H, 1Ј-H), 5.62 (m, 2 H, 5-H, CH), 5.31 (m, 1 H, CH), H, CHar), 6.90 (m, 4 H, CHar), 6.18 (d, J = 8.1 Hz, 1 H, 1Ј-H),
4.26 (s, 1 H, CH), 4.09 (m, 4 H, CH2), 3.81 (s, 6 H, OCH3), 3.65 5.44 (d, J = 8.9 Hz, 1 H, 5-H), 5.36 (m, 4 H, –CH=CH–), 4.66 (d,
(m, 2 H, CH2), 2.71 (s, 8 H, CH2), 1.62 (m, 4 H, CH2), 1.28 (s, 48 J = 5.3 Hz, 1 H, CH), 4.54 (s, 1 H, CH), 4.24 (m, 5 H, CH2, CH),
H, CH2), 0.90 (t, J = 6.4 Hz, 3 H, CH3) ppm. 13C NMR (75 MHz, 3.81 (s, 3 H, OCH3), 3.80 (s, 3 H, OCH3), 3.42 (m, 2 H, 5Ј-H), 2.33
CDCl3): δ = 172.1 (C=O), 171.5 (C=O), 171.3 (C=O), 162.9 (C-4),
158.8 (C-2), 143.9 (Cq), 140.7 (C-6), 139.9 (Cq), 139.5 (CHar), 137.9
(t, J = 7.6 Hz, 4 H, CH2), 2.02 (m, J = 6.2 Hz, 8 H, CH2), 1.61
(m, 4 H, CH2), 1.29 (m, 40 H, CH2), 0.90 (t, J = 6.9 Hz, 6 H,
(CHar), 134.9 (CHar), 134.7 (CHar), 130.2 (CHar), 130.0 (CHar), –CH2–CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 173.6 (–O–
129.5 (CHar), 129.0 (CHar), 128.2–127.0 (CHar), 125.3 (CHar), C=O), 173.5 (–NH–C=O), 172.8 (–NH–C=O), 172.6 (C-4), 158.7
113.4 (CHar), 113.2 (CHar), 113.0 (CHar), 102.9 (C-5), 87.6 (CH), (Cq,ar), 158.6 (Cq,ar), 151.4 (C-2), 144.1 (Cq,ar), 139.5 (C-6), 135.3
85.7 (CH), 82.1 (CH), 81.4 (CH), 73.1 (CH), 71.3 (CH), 65.9 (CH2), (Cq,ar), 135.0 (Cq,ar), 130.2 (–CH=CH–), 130.1 (–CH=CH–), 130.0
65.1 (CH2), 63.1 (CH2), 62.7 (CH2), 55.2 (OCH3), 33.8 (CH2), 32.8
(–CHar–), 129.7 (–CH=CH–), 129.2 (–CH=CH–), 128.2 (CHar),
(CH2), 32.0 (CH2), 29.7–28.6 (CH2), 25.9 (CH2), 25.8 (CH2), 24.8 128.1 (CHar), 127.9 (CHar), 127.8 (CHar), 127.1 (CHar), 127.0
(CH2), 22.7 (CH2), 21.5 (CH2) 14.1 (–CH2–CH3) ppm.
(CHar), 113.4 (CHar), 113.3 (CHar), 113.1 (CHar), 103.1 (C-5), 87.1
(–Cq–), 85.4 (CH), 81.5 (CH), 71.6 (CH), 69.9 (CH), 63.8 (CH2),
61.6 (CH2), 55.2 (OCH3), 34.0 (CH2), 31.9 (CH2), 29.8 (CH2), 29.7
(CH2), 29.5 (CH2), 29.3 (CH2), 29.2 (CH2), 29.1 (CH2), 29.1 (CH2),
27.2 (CH2), 24.8 (CH2), 22.7 (CH2), 14.1 (–CH2–CH3) ppm.
HRMS: calcd. for C73H10539KN3O14+ 1286.7228; found 1286.7233.
A solution of 5Ј-DMT-protected 17 (0.44 g, 0.38 mmol) in dry
CH2Cl2 (80 mL) was stirred for 5 min. After adding trifluoroacetic
acid (2.4 mL) the reaction mixture was stirred for 30 min and
quenched with MeOH (3.0 mL). The reaction was diluted with
CH2Cl2 (20 mL). The solution was washed carefully with saturated
NaHCO3 and dried with MgSO4. Flash chromatography with a
short column using CHCl3/MeOH (9:1) with 1% Et3N gave the
2Ј-N-[2,3-Bis(octadecyloxy)propylamino]-2Ј-deoxy-5Ј-O-(4,4Ј-di-
methoxytrityl)uridine (26). Method A: The tosylate 25 was prepared
according to the literature.[31,32] Nucleoside 21 (0.42 g, 0.37 mmol)
was dissolved in THF (4.5 mL) and 25 (1.46 g, 1.94 mmol) was
1
product 17 as a white solid (150 mg, 0.17 mmol, 40%). H NMR
(300 MHz, CDCl3): δ = 9.1 (s, 1 H, NH), 7.7 (d, J = 8.1 Hz, 1 H,
6-H), 6.00 (d, J = 5.3 Hz, 1 H, 1Ј-H), 5.78 (d, J = 8.1 Hz, 1 H, 5- added whilst stirring. DIPEA (0.3 mL) was added to the solution
H), 5.52 (m, 1 H, CH), 4.23 (s, 1 H, CH), 4.09 (m, 4 H, CH2), 3.92 and the solvent slowly evaporated at 80 °C to give a melt. The
(m, 2 H, CH2), 2.71 (s, 8 H, CH2), 1.62 (m, 4 H, CH2), 1.26 (s, 48 temperature was raised to 150 °C and the melt was stirred for 4 h.
H, CH2), 0.88 (t, J = 6.4 Hz, 3 H, CH3) ppm. 13C NMR (75 MHz, The mixture was cooled to room temperature and the crude mate-
CDCl3): δ = 172.2 (C=O), 171.6 (C=O), 171.4 (C=O), 163.1 (C-4),
rial was purified by silica-gel chromatography (EtOAc/cyclohexane,
150.4 (C-2), 141.1 (C-6), 103.1 (C-5), 88.5 (CH), 83.5 (CH), 73.1
1:12 and then MeOH/CHCl3, 1:30, 1% Et3N, Rf = 0.7). Product
(CH), 71.2 (CH), 65.1 (CH2), 61.7 (CH2), 31.9 (CH2), 29.7–28.6 26 (0.091 g, 0.08 mmol, 25%) was obtained as a colorless oil which
(CH2), 25.9 (CH2), 22.7 (CH2), 14.1 (–CH2–CH3) ppm.
solidifies after standing in a refrigerator. 1H NMR (300 MHz,
CDCl3): δ = 7.78 (s, 1 H, 6-H), 7.27 (m, 8 H, CHar), 6.85 (m, 5 H,
CHar), 5.96 (m, 1 H, 1Ј-H), 5.39 (s, 1 H, 5-H), 4.29 (m, 2 H, CH),
3.81 (s, 6 H, OCH3), 3.57 (s, 1 H, CH), 3.46 (m, 9 H, CH, CH2),
2.84 (m, 2 H, CH2), 1.57 (m, 4 H, CH2), 1.27 (s, 60 H, CH2), 0.89
(s, 6 H, –CH2–CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 162.7
(C-4), 158.7 (Cq,ar), 150.7 (C-2), 144.2 (Cq,ar), 144.1 (Cq,ar), 140.1
(C-6), 135.2 (Cq,ar), 135.0 (Cq,ar), 130.1 (CHar), 128.0 (CHar), 113.3
(CHar), 102.3 (C-5), 88.1 (CH), 88.0 (C-1Ј, CH), 87.1 (Cq), 86.1
(CH), 85.8 (CH), 71.9 (CH2), 71.8 (CH2), 70.9 (CH2), 70.6 (CH2),
70.5 (CH2), 70.4 (CH, C-3Ј), 66.4 (CH, C-2Ј), 63.6 (CH2), 55.2
(OCH3), 49.4 (CH2, C-5Ј), 31.9 (CH2), 30.0 (CH2), 29.7 (CH2), 29.5
(CH2), 29.4 (CH2), 26.1 (CH2), 22.7 (CH2), 14.1 (–CH2–CH3) ppm.
2Ј,3Ј,5Ј-O,O,O-Tripalmitoyluridine (19): Palmitoyl chloride
(10.00 mL, 45.00 mmol) was added dropwise to a solution of urid-
ine (2.44 g, 10.00 mmol) in dry pyridine (130 mL). After 4 h pyr-
idine was removed in vacuo and the residue was crystallized
1
(EtOH) to give 19 (3.55 g, 3.70 mmol, 37%). H NMR (300 MHz,
CDCl3): δ = 8.93 (s, 1 H, NH), 7.82 (d, J = 8 Hz, 1 H, 6-H), 6.05
(d, J = 5.7 Hz, 1 H, 1Ј-H), 5.77 (m, 3 H, 5-H, CH), 4.59 (s, 1 H,
CH), 4.40 (m, 2 H, CH2), 4.19 (s, 1 H, CH), 2.32 (m, 6 H, CH2),
1.61 (t, J = 6.99 Hz, 6 H, CH2), 1.24 (s, 60 H, CH2), 0.86 (t, J =
6.3 Hz, 9 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 173.8
(C=O), 163.7 (C-4), 151.1 (C-2), 141.6 (C-6), 102.8 (C-5), 90.7 (CH)
83.5 (CH), 80.2 (CH), 73.2 (CH), 61.8 (CH2), 34.0 (CH2), 31.9
(CH2), 29.7–29.1 (CH2), 24.7 (CH2), 22.7 (CH2), 14.1 (CH3) ppm.
+
HRMS: calcd. for C69H110N3O9 1124.8242; found 1124.8235.
Method B: A solution of NaCN·BH3 (20 mg, 0.32 mmol) in MeOH
(5 mL) was added o a solution of 21 (500 mg, 0.92 mmol) and 2,3-
bis(octadecyloxy)propanal (590 mg, 1.00 mmol) in a mixture of
MeOH (15 mL) and cyclohexane (10 mL) at 0 °C over 30 min. The
volatiles were evaporated and the residue was partitioned (Et2O/
brine). The organic layer was dried (MgSO4) and concentrated in
vacuo to give a yellow oil. Purification by column chromatography
(CHCl3/MeOH, 60:1 Ǟ 30:1) gave the product 26 (120 mg,
0.11 mmol, 12%) as a white solid (identical NMR spectra).
2Ј-Amino-2Ј-N-[1,3-bis(oleoyloxy)isopropyloxysuccinyl]-2Ј-deoxy-
5Ј-O-(4,4Ј-dimethoxytrityl)uridine (24): Acyl chloride 23 was pre-
pared from 1,3-bis(oleoyloxy)isopropyl succinate which was synthe-
sized according to the literature[28–30] as follows. The acid (6.9 g,
9.5 mmol) was dissolved in dry DCM (10 mL) and DMF (0.1 mL)
whilst stirring. The solution was cooled to 0 °C and oxalyl chloride
(1 mL, 10.0 mmol) was added. The solution was stirred for 3 h and
then the solvent was evaporated. The residue was dried in vacuo.
NaOAc (0.64 g, 7.7 mmol) and water (3 mL) were added to a solu-
tion of 21 (0.42 g, 0.77 mmol) in THF (5 mL). Compound 23 2Ј-(Hexadecylthio)-2Ј-deoxyuridine
(27):
DIEA
(0.87 mL,
(0.57 g, 0.77 mmol) was dissolved in dry THF (3 mL) and slowly
added to the stirred emulsion of 21. After 1 h and 30 min the reac-
tion mixture was quenched with a saturated NaHCO3 solution
(15 mL). The aqueous phase was extracted with diethyl ether
1.50 mmol) and hexadecyl bromide (0.45 mL, 1.5 mmol) were
added to a solution of 22 (260 mg, 1.00 mmol) in MeCN (5 mL).
After 16 h the reaction mixture was partitioned (CH2Cl2/
NaHCO3). The organic layer was dried (MgSO4), evaporated, and
(30 mL) three times. The combined organic phases were concen- the residue was purified by column chromatography (CH2Cl2/
trated in vacuo and the residue purified by column chromatography MeOH, 9:1) to give 27 (300 mg, 0.62 mmol, 62%). Crystallization
1926
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1917–1928

Nucleosides Bearing Lipid Anchors
(CH2Cl2) gave an analytically pure compound. 1H NMR
(500 mg, 2.00 mmol) in MeCN (10 mL)/CH2Cl2 (10 mL). After
(300 MHz, CDCl3): δ = 10.2 (s, 1 H, NH), 7.76 (d, J = 8.0 Hz, 1 16 h the reaction mixture was partitioned (CH2Cl2/NaHCO3). The
H, 6-H), 5.81 (d, J = 8.1 Hz, 1 H, 1Ј-H), 5.73 (d, J = 8.1 Hz, 1 H, organic layer was dried (MgSO4), evaporated, and the residue was
5-H), 4.30 (d, J = 4.2 Hz, 1 H, CH), 4.11 (s, 1 H, CH), 3.88 (q, J
= 11.9, 20.1 Hz, 1 H, CH), 3.40 (m, 2 H, 5Ј-H), 2.50 (t, J = 7.35 Hz,
2 H, CH2), 1.53 (t, J = 7.17 Hz, 2 H, CH2), 1.28 (s, 26 H, CH2),
0.84 (t, J = 6.06 Hz, 3 H, CH3) ppm. 13C NMR (75 MHz, CDCl3):
purified by column chromatography (CH2Cl2/MeOH, 9:1) to give
31 (220 mg, 0.28 mmol, 14%). 1H NMR (300 MHz, CDCl3): δ =
9.56 (s, 1 H, NH), 7.66 (d, J = 8.0 Hz, 1 H, 6-H), 5.76 (d, J =
8.1 Hz, 1 H, 1Ј-H), 5.67 (d, J = 8.1 Hz, 1 H, 5-H), 4.30 (d, J =
δ = 163.8 (C-4), 150.8 (C-2), 141.7 (C-6), 102.8 (C-5), 90.2 (CH), 4.2 Hz, 1 H, CH), 4.17 (s, 1 H, CH), 3.98 (q, J = 11.9, 20.1 Hz, 1
86.3(CH), 71.4 (CH), 62.2 (CH2), 53.9 (CH), 34.1 (CH2), 32.7 H, CH), 3.76 (m, 7 H, CH, CH2), 3.42 (m, 2 H, 5Ј-H), 2.55 (t, J =
(CH2), 32.1 (CH2), 31.8 (CH2), 29.9–28.1 (CH2), 22.6 (CH2), 14.3 7.35 Hz, 1 H, CH), 1.52 (m, 4 H, CH2), 1.19 (s, 60 H, CH2), 0.84
(–CH2–CH3) ppm.
(t, J = 6.06 Hz, 3 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ =
163.4 (C-4), 150.6 (C-2), 142.3 (C-6), 102.8 (C-5), 91.4 (CH), 86.3
(CH), 71.4 (CH), 62.2 (CH2), 53.9 (CH), 34.1 (CH2), 32.4 (CH2),
31.9 (CH2), 31.8 (CH2), 29.9–28.1 (CH2), 22.7 (CH2), 14.1 (–CH2–
CH3) ppm.
2Ј-([D33]Hexadecylthio)-2Ј-deoxyuridine (28): DIEA (1.25 mL,
2.13 mmol) and [D33]hexadecyl bromide (730 mg, 2.13 mmol) were
added to a solution of 22 (370 mg, 1.42 mmol) in MeCN (10 mL).
After 16 h the reaction mixture was partitioned (CH2Cl2/
NaHCO3). The organic layer was dried (MgSO4), evaporated, and 2Ј-(Octadecyldisulfanyl)-2Ј-deoxyuridine (33). Method A: DIAD
the residue was purified by column chromatography (CH2Cl2/
(0.40 mL, 3.00 mmol) was added to a solution of 22 (780 mg,
3.00 mmol) in dry THF (80 mL). TLC analysis (CHCl3/MeOH,
MeOH, 9:1) to give 28 (500 mg, 0.97 mmol, 68%). 1H NMR
(300 MHz, CDCl3): δ = 10.4 (s, 1 H, NH), 7.76 (d, J = 8.0 Hz, 1 9:1) showed the complete disappearance of the starting material
H, 6-H), 5.80 (d, J = 8.1 Hz, 1 H, 1Ј-H), 5.68 (d, J = 8.1 Hz, 1 H, after 16 h. Octadecylthiol (17.2 g, 60 mmol) was added and the re-
5-H), 4.25 (d, J = 4.2 Hz, 1 H, CH), 4.20 (s, 1 H, CH), 3.82 (q, J
= 11.9, 20.1 Hz, 1 H, CH), 3.30 (m, 2 H, 5Ј-H) ppm. 13C NMR and the residue was purified by column chromatography (CHCl3/
(75 MHz, CDCl3): δ = 163.8 (C-4), 150.8 (C-2), 141.7 (C-6), 102.8
EtOH, 9:1) to give 33 (0.40 g, 0.74 mmol, 25%). 1H NMR
(C-5), 90.2 (CH), 86.3 (CH), 71.4 (CH), 62.2 (CH2), 53.9 (300 MHz, [D6]DMSO/CDCl3): δ = 7.70 (d, J = 8.1 Hz, 1 H, 6-H),
action mixture was refluxed for 72 h. The volatiles were evaporated
(CH) ppm.
6.02 (d, J = 8.3 Hz, 1 H, 1Ј-H), 5.6 (d, J = 8.1 Hz, 1 H, 5-H), 4.34
(d, J = 2.1 Hz, 1 H, CH), 3.68 (m, 3 H, CH, 5Ј-H), 2.50 (m, 2 H,
CH2), 1.55 (t, J = 6.2 Hz, 2 H, CH2), 1.12 (s, 28 H, CH2), 0.75 (t,
J = 6.2 Hz, 3 H, CH3) ppm. 13C NMR (75 MHz, [D6]DMSO/
CDCl3): δ = 164.1 (C-4), 150.8 (C-2), 141.6 (C-6), 102.5 (C-5), 90.1
(CH), 86.4 (CH), 72.2 (CH), 61.7 (CH2), 58.6 (CH), 38.9 (CH2),
31.6 (CH2), 29.3–28.2 (CH2), 22.4 (CH2), 13.7. (CH3) ppm.
2Ј-[4-(Pyren-2-yl)butylthio]-2Ј-deoxyuridine (29): DIEA (0.87 mL,
1.5 mmol) and 2-(4-bromobutyl)pyrene (500 mg, 1.5 mmol) were
added to a solution of 22 (260 mg, 1.00 mmol) in MeCN (15 mL).
After 16 h the reaction mixture was partitioned (CH2Cl2/
NaHCO3). The organic layer was dried (MgSO4), concentrated,
and the residue was purified by column chromatography
(CH2Cl2 ǞCH2Cl2/MeOH, 10:1) to give 29 (430 mg, 0.83 mmol,
Method B: A solution of 2Ј-(4-methoxybenzylthio)-2Ј-deoxyuridine
83%). 1H NMR (300 MHz, CDCl3): δ = 10.6 (s, 1 H, NH), 8.12 (32) (0.57 g, 1.50 mmol) in CH2Cl2 (20 mL) and a solution of hexa-
(m, 8 H, CHar), 7.77 (d, J = 8.3 Hz, 1 H, 6-H), 5.88 (d, J = 7.8 Hz, decylsulfenyl chloride (2.41 g, 7.5 mmol) in CH2Cl2 (20 mL) were
1 H, 1Ј-H), 5.72 (d, J = 8.1 Hz, 1 H, 5-H), 4.25 (s, 1 H, CH), 3.97
added carefully to a flask containing CH2Cl2 (65 mL) and AcOH
(m. 3 H, CH, 5Ј-H), 2.77 (m, 2 H, CH, 5Ј-H), 2.52 (m, 2 H, CH2), (65 mL) at 0 °C. TLC analysis (CH2Cl2/MeOH, 9:1) showed the
1.63 (m, 4 H, CH2) ppm. 13C NMR (75 MHz, CDCl3): δ = 164.1
(C-4), 159.8 (Car), 150.9 (C-2), 141.8 (C-6), 136.1 (Car), 132.3–123.2
(Car), 102.8 (C-5), 90.4 (CH), 86.1 (CH), 71.2 (CH), 62.1 (CH2),
complete disappearance of the starting material after 62 h. The vol-
atiles were evaporated and the residue was purified by column
chromatography (CH2Cl2 ǞCH2Cl2/MeOH, 9:1) to give 33 (0.30 g,
53.9 (CH), 35.0 (CH2), 32.1 (CH2), 30.7 (CH2), 29.7 (CH2), 29.0 0.55 mmol, 37%).
(CH2) ppm.
Supporting Information (see also the footnote on the first page of
2Ј-(6-Dansyloxyhexylthio)-2Ј-deoxyuridine (30): DIEA (0.43 mL,
0.75 mmol) and 6-bromohexyl 5-(dimethylamino)naphthalene-1-
sulfonate (420 mg, 1.0 mmol) were added to a solution of 22
(130 mg, 0.50 mmol) in MeCN (10 mL). After 16 h the reaction
mixture was partitioned (CH2Cl2/NaHCO3). The organic layer was
dried (MgSO4), evaporated, and the residue was purified by column
chromatography (CH2Cl2 ǞCH2Cl2/MeOH, 20:1) to give 30
(200 mg, 0.33 mmol, 67%). 1H NMR (300 MHz, CDCl3): δ = 10.6
(s, 1 H, NH), 7.87 (d, J = 8.3 Hz, 1 H, 6-H), 7.4 (m, 6 H, CHar),
5.88 (d, J = 7.8 Hz, 1 H, 1Ј-H), 5.70 (d, J = 8.1 Hz, 1 H, 5-H), 4.1
(s, 1 H, CH), 3.97 (m, 2 H, CH), 3.80 (m, 1 H, CH), 3.66 (m, 3 H,
CH, 5Ј-H), 2.57 (m, 6 H, CH3), 2.52 (m, 2 H, CH2), 1.53 (m, 8 H,
CH2) ppm. 13C NMR (75 MHz, CDCl3): δ = 164.3 (C-4), 150.9 (C-
2), 141.6 (C-6), 132.4 (Car), 131.9 (Car), 130.7 (Car), 128.7 (Car),
102.7 (C-5), 89.6 (CH), 86.2 (CH), 72.3 (CH), 71.2 (CH), 71.0
(CH), 70.8 (CH), 62.1 (CH2), 53.9 (CH), 45.5 (CH3), 42.5 (CH3),
35.2 (CH2), 33.8 (CH2), 32.4 (CH2), 31.7 (CH2), 31.6 (CH2), 30.3
(CH2), 29.5–27.5 (CH2), 26.1 (CH2) ppm.
this article): Synthesis of the starting materials, NMR spectra of
new products.
Acknowledgments
Financial support by the Bundesministerium für Bildung und For-
schung (BMBF) is gratefully acknowledged. We thank Dr. Burk-
hard Ziemer, Institute of Chemistry, Humboldt-University Berlin,
for X-ray crystal structure analyses and Bayer Services GmbH &
Co. OHG, BASF AG, and Sasol GmbH for the donation of chemi-
cals.
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1927

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Received: November 9, 2007
Published Online: March 3, 2008
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