A new protocol for selective cleavage of acyl protecting groups in 2′-O-modified 3′,5′-O -(Tetraisopropyldisiloxane-1,3-diyl) ribonucleosides

Article abstract of DOI:10.1055/s-0030-1258270

The stability of tetraisopropyldisiloxane-1,3-diyl (TIPDS) protection in nucleosides in ammonia/amine solutions in methanol and ethanol was studied. In ammonia-methanol at ambient temperature significant partial cleavage of TIPDS was observed. When ethano

Full text of DOI:10.1055/s-0030-1258270

PAPER
3827
A New Protocol for Selective Cleavage of Acyl Protecting Groups in
2¢-O-Modified 3¢,5¢-O-(Tetraisopropyldisiloxane-1,3-diyl)ribonucleosides
Selective Cleavage of
.
A
cyl
P
rotecti
S
ng Groups . Drenichev, I. V. Kulikova, G. V. Bobkov, V. I. Tararov, S. N. Mikhailov*
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov str. 32, Moscow 119991, Russian Federation
Fax +7(499)1351405; E-mail: smikh@eimb.ru
Received 9 August 2010; revised 16 August 2010
have found that in several cases the TIPDS group is not
stable. As a result, the yields of the corresponding deacy-
lated derivatives were moderate.
Abstract: The stability of tetraisopropyldisiloxane-1,3-diyl (TIPDS)
protection in nucleosides in ammonia/amine solutions in methanol
and ethanol was studied. In ammonia–methanol at ambient temper-
ature significant partial cleavage of TIPDS was observed. When
ethanol was used instead of methanol this undesired side reaction
was completely inhibited. It was found that commercially available
8 M methylamine–ethanol solution is the reagent of choice for se-
lective deacylation of N- or/and O-acyl protected nucleosides with-
out notable cleavage of 3′,5′-TIPDS group. Several examples of the
developed protocol for the preparation 2′-O-modified nucleosides
with overall high yields are presented.
It is known that TIPDS protection has limited stability
both in acidic and basic media. The reactions that take
place under these conditions are shown in Scheme 1.
B
HO
O
B
O
O
Si
O
i
Key words: nucleosides, blocking group stability, tetraisopropyl-
disiloxane-1,3-diyl, protecting group, N-deacylation, O-deacylation
O
O
Si
O
OH
Si
Si
1
O
ii
The 1,1,3,3-tetraisopropyldisiloxane-1,3-diyl (TIPDS)
group developed by Markiewicz1 is widely used for the si-
multaneous protection of the 3′,5′-dihydroxy groups in ri-
bonucleosides and subsequent manipulation of the 2′-OH
group, such as deoxygenation,2 oxidation,3 alkylation,4–6
glycosylation,7–12 protection,13–18 preparation of 2′-amino-
2′-deoxynucleosides,19,20 and many others. This group is
one of the most popular and useful protecting group in nu-
cleoside chemistry. Moreover simultaneous protection of
3′- and 5′-hydroxy groups can be carried out with both N-
unprotected and N-acyl-protected ribonucleosides. It is
assumed that the reaction of 1,3-dichloro-1,1,3,3-tetraiso-
propyldisiloxane with the ribonucleoside starts with sily-
lation of the primary 5′-hydroxy group followed by the
formation of an eight-membered ring. As a result, the 2′-
hydroxy group remains free for further chemical modifi-
cation. The TIPDS group is usually removed with tetrabu-
tylammonium fluoride trihydrate in tetrahydrofuran.21
iii
B
HO
O
Si
Si
B
O
O
HO
O
O ;H
O
OH
HO
Si
Si
HO
O
Scheme
1
Transformations of TIPDS-protected nucleosides.
Reagents and conditions: (i) mesitylenesulfonic acid or Py·HCl,
DMF, 20 °C; (ii) 0.2 M HCl in dioxane–H2O (4:1), 20 °C, 2.5 h; (iii)
0.2 M NaOH in dioxane–H2O (4:1), 20 °C, 1 h.
Previously it has been shown that under anhydrous acidic
conditions (mesitylenesulfonic acid or Py·HCl, DMF, 20
°C, 30–50% yield), 3′,5′-O-TIPDS-nucleosides undergo
transformation
into
2′,3′-O-TIPDS-nucleosides
(Scheme 1).27 Thus, the seven-membered ring is thermo-
dynamically more favorable than the eight-membered. It
was shown that the isomerization occurred in boiling
chloroform in the presence of 4-toluenesulfonic acid.28
Trimethylsilyl triflate is an efficient promoter of such an
isomerization in 1,2-dichloroethane at 0 °C, and 2′,3′-O-
TIPDS-ribonucleosides can be obtained in 55–90%
yields.29
Another valuable feature of this group is the conforma-
tional rigidity of the 3′,5′-O-TIPDS-ribonucleosides; they
have a small J1′,2′ < 1.5 Hz coupling which is widely used
for configurational assignments in sugar moieties.22
We have used 3′,5′-O-(tetraisopopyldisiloxane-1,3-
diyl)ribonucleosides extensively for the preparation of 2′-
O-pentafuranosylnucleosides and 2′-O-(alkoxymeth-
yl)nucleosides.23–26 Additional hydroxy groups within the
residue were usually protected with acyl blocking groups.
When using common deacylation procedures, such as am-
monia in methanol or sodium methoxide in methanol, we
It has been shown that mild acidic hydrolysis [0.2 M HCl
in dioxane–H2O (4:1), 20 °C, 2.5 h] of 1a (B = Ura) re-
sulted in the formation of a mixture of 5′-, 3′-, and 2′-de-
rivatives in the ratio 2:5:3 (Scheme 1), thus showing that
the hydrolysis is accompanied by 3′ → 2′ isomerization.1
Under alkaline conditions [0.2 M NaOH in dioxane–H2O
(4:1), 20 °C, 1 h] the other Si–O bond in 1a is cleaved se-
lectively forming the 5′-O-isomer.1 In order to overcome
SYNTHESIS 2010, No. 22, pp 3827–3834
x
x.
x
x
.
2
0
1
0
Advanced online publication: 28.09.2010
DOI: 10.1055/s-0030-1258270; Art ID: P10510SS
© Georg Thieme Verlag Stuttgart · New York

3828
M. S. Drenichev et al.
PAPER
this instability, bis(tetraisopropylsilyl)methylene30 groups oms of OH groups at the 2′- and 3′-positions of the ribose
have been proposed, but they have limited application due moiety, since on the addition of deuterium oxide they un-
to the higher cost.
dergo exchange. Unfortunately protons attached to the 2′-,
3′-, 4′-, and 5′-positions of the ribose moiety form an un-
resolved multiplet in the d = 3.8–4.05 region and it is im-
possible to identify the corresponding spin-spin coupling
constants thus to make an unequivocal structural assign-
ment. For an unambiguous structural assignment, 2 was
transformed into its 2′,3′-O-diacetyl derivative 3. In the
1H NMR spectrum (CDCl3) of 3, a significant downfield
shift of H2′ (dd, d = 5.33) and H3′ (dd, d = 5.42) is ob-
served. A spin-spin coupling constant 3J = 5.5 Hz can be
found in both multiplets, thus confirming the structure of
3 and, hence, the site of ring opening in compound 1a.
The instability of TIPDS protection under a variety of
conditions makes the problem of finding orthogonal con-
ditions for deacylation very challenging. In spite of the
long history of practical applications of TIPDS protection
in nucleoside chemistry, a well-documented, selective
procedure for deacylation is not yet available.
Herein we disclose our results on the study of the stability
of 3′,5′-O-TIPDS-protected nucleosides under aminolysis
conditions.
It was originally found by Markiewicz that the TIPDS
group could be completely removed in dioxane–1 M sodi-
um hydroxide at ambient temperature after seven days.
Shorter reaction times (1–3 h) resulted in partial cleavage
of the 3′-O-Si bond and the corresponding products were
isolated in 95% yield.1 To the best of our knowledge, there
is no information available on the behavior of the TIPDS
group in methanolic ammonia solution, which is also
commonly employed for the removal of acyl groups.
The high regioselectivity of partial TIPDS cleavage in ri-
bonucleoside 1a is in striking contrast to the 2′-deoxy
analogue 3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)thy-
midine 4. Treatment of 4 with DBU–methanol results in
formation of two regioisomers 5 and 6 in a 2:1 ratio
(Scheme 3) which can be easily separated by column
chromatography (silica gel) in 70% total yield.
In order to improve yields and optimize the protection–
deprotection strategy, we examined the stability of this
group under ammonolysis/aminolysis conditions in detail.
A set of TIPDS-protected nucleosides of general structure
1 were chosen as model compounds for our study. The re-
sults and structure of nucleobases (B) are summarized in
Table 1.
MeO Si
O
Si
O
Thy
O
O
Thy
O
Si
O
(i)
5
HO
Thy
O
Si
HO
O
4
First we studied the stability of protected uridine deriva-
tive 1a in ammonia solution in methanol. To our surprise
it undergoes partial cleavage (ring opening) of the TIPDS
group with the formation of compound 2 (Scheme 2)
(Table 1, entry 1). After treatment of 1a with 7 M ammo-
nia in methanol for 24 hours at room temperature, the
ring-opened product 2 was isolated in 40% yield. The
same product 2 was isolated in considerably higher (75%)
yield after treatment of 1a with an excess of a stronger
base such as DBU in methanol at the same temperature.
Interestingly, treatment of 1a with concentrated ammonia/
water solution resulted in complete removal of the TIPDS
group and near quantitative formation of uridine after 20
hours at room temperature.
MeO Si
O
Si
O
6
Scheme 3 Reagents and conditions: (i) DBU, MeOH, 20 °C, 24 h,
70% (5 + 6).
The ratio was estimated on the basis of 1H NMR spectra
of the mixture in dimethyl sulfoxide-d6. The signal of the
OH group in isomer 5 appears as doublet at d = 5.38, while
in isomer 6 it appears as a triplet at d = 5.12. Both reso-
nances show H–D exchange with the addition of deuteri-
um oxide. Singlets in the region of d = 3.5 are assigned to
OMe groups.
In the case of 4 the reaction is much slower and the ob-
served difference in regioselectivity of partial TIPDS
cleavage in compounds 1a and 4 is clearly associated with
the participation of the free neighboring hydroxy group in
1a. Such participation can be explained by hydrogen
bonding of 2′-OH with the oxygen atom in the 3′-position.
This may result in increasing d+ on the adjacent silicon
atom and, thus, making more preferable the attack of a nu-
cleophile on this site.
(i)
MeO Si
O Si O
Ura
O
1a
RO OR
2 R = H
(ii)
3 R = Ac
Scheme 2 Reagents and conditions: (i) Method A: 7 M NH3–
MeOH, 20 °C, 24 h, 40%, or Method B: DBU–MeOH, 20 °C, 8 h,
75%; (ii) Ac2O, Py, 20 °C, 1.5 h, 88%.
To the best of our knowledge the instability of the TIPDS
protection group in methanol in the presence of base has
not been previously reported.
1
The 400 MHz H NMR spectrum (DMSO-d6) of com-
pound 2 reveals a singlet for the methyl group at d = 3.48.
Doublets at d = 5.45 and 5.10 are assigned to hydrogen at-
Synthesis 2010, No. 22, 3827–3834 © Thieme Stuttgart · New York

PAPER
Stability of Tetraisopropyldisiloxane-1,3-diyl Group
3829
For the stability studies 4 M amine in alcohol solutions comparable (entry 14). Replacement of methanol with
were used. The experiments were carried out at ambient ethanol strongly reduced the side reaction (entries 5, 10,
temperature and the reactions were followed by TLC. 15). On the other hand, the rate of N-deacylation is also
NMR spectrometry was used in some cases to confirm the strongly suppressed. In order to overcome this problem
conversions. The results are collected in Table 1.
we investigated the action of lower amines in ethanol so-
lution. It appeared that methylamine–ethanol was even
more active in deacylation than ammonia–methanol (cf.
entries 6, 11, 16 with entries 4, 9, 14). The formation of
open-ring products was ca. 2%. The use of ethylamine or
propylamine in ethanol (entries 7, 8, 12, 13, 17, 18) result-
ed in a decrease in the rate of deacylation and negligible
decrease in the yield of a open-ring product. Under similar
conditions the rate of deacylation follows the order 1c >
1b > 1d.
Table 1 Relative Stability of TIPDS and N-Acyl Protecting Groups
in 4 M Amine–Alcohol Solutions at 20 °C
Entry Ba,
compd
Reagent
Time for
complete
deacylation
of 1
Extent of
TIPDS ring
opening after
24 h
1
2
NH3–MeOH
NH3–EtOH
25%
<2%
Ura
It is noteworthy to mention that treatment of the benzoyl
derivative of cytosine 1b with alkylamine solutions gave
an additional side product, 4-N-alkyl-3′,5′-O-(1,1,3,3,-tet-
raisopropyldisiloxane-1,3-diyl)cytidine, which is formed
in 5–6% yield.31 In the case of the parent acetyl derivative
1c, no products of this type were detected.
1a
3
4
5
6
MeNH2–EtOH
NH3–MeOH
NH3–EtOH
2%
3.5 h
40 h
50%
<2%
2%
CytBz
MeNH2–EtOH 30 min
Thus, simple substitution of ammonia–methanol for am-
monia–ethanol results in a substantial increase in stability
of the TIPDS protecting group. The disadvantage of am-
monia–ethanol is a significant fall in the deacylation rate.
Replacement of ammonia with methylamine in ethanol
solution results in the highest deacylation capacities. The
commercial availability of 8 M methylamine in ethanol
solution is an important advantage for this reagent over
others studied.
1b
7
8
EtNH2–EtOH
PrNH2–EtOH
NH3–MeOH
NH3–EtOH
3.5 h
3.5 h
10 min
10 h
<2%
<2%
50%
<2%
2%
9
10
11
CytAc
MeNH2–EtOH 5 min
We have used the TIPDS group intensively for the prepa-
ration of disaccharide nucleosides and their acyclic deriv-
atives. It was shown that in several cases the yields of
deacylation were moderate because of partial cleavage of
the TIPDS group. Here we present some applications of
the conditions developed herein in multistep synthesis for
deprotection of earlier reported intermediate compounds
bearing different types of acyl groups (Schemes 4– 6).
1c
12
13
14
15
16
EtNH2–EtOH
PrNH2–EtOH
NH3–MeOH
NH3–EtOH
10 min
10 min
15 h
<2%
<2%
50%
<2%
2%
4 d
GuaiBu MeNH2–EtOH 2.5 h
1d
It was shown that the use of the traditional 7 M ammonia
in methanol solution for the deacetylation of 7 resulted in
compound 8 in only 50% yield (Scheme 4). Under another
traditional condition (NaOMe–MeOH), compound 810
was isolated in 70% yield. The yield of 8 was substantially
improved up to 85% when using 8 M methylamine in eth-
anol solution at ambient temperature.
17
18
EtNH2–EtOH
PrNH2–EtOH
35 h
35 h
<2%
<2%
a iBu = isobutyroyl (adopted abbreviation in nucleoside chemistry).
We found that TIPDS-protected compounds 1a had sur-
prisingly better resistance to ammonia–ethanol (entry 2)
in comparison with ammonia–methanol solution (entry
1). This finding enabled us to study the possibility of us-
ing ammonia and amine solutions in ethanol for the selec-
tive removal of commonly used N-acyl blocking groups in
nucleosides 1b–d.
O
B
O
Si
O
7 R = Ac
8 R = H
(i)
OR
O
O
O
Si
Scheme 4 B = Ura. Reagents and conditions: (i) 1. 7 M NH3–
MeOH, 20 °C, 24 h, 50%; 2. 0.1 M NaOMe–MeOH, 20 °C, 20–30
min, 70%; or 3. 8 M MeNH2–EtOH, 20 °C, 24 h, 85%.
Prolonged (24 h) reaction of 1b–d with ammonia in meth-
anol gave reasonable amounts of open-ring products (en-
tries 4, 9, 14). Deacylation of 1b and 1c was much faster
than the ring-opening reaction (entries 4, 9), and, in the
case of compound 1d, the rates of both reactions were
One of the key steps in the preparation of 2′-O-a-D-ribo-
furanosyladenosine,11 monomeric unit of poly(ADP-ri-
Synthesis 2010, No. 22, 3827–3834 © Thieme Stuttgart · New York

3830
M. S. Drenichev et al.
PAPER
bose), was debenzoylation of disaccharide nucleoside 9 made it possible to prolong the synthetic scheme and pre-
(Scheme 5). Using sodium methoxide in methanol it was pare compounds 15a–c which mimic known poly(ADP-
possible to achieve only O-debenzoylation, and the N6- ribose)polymerase inhibitors. The biological activity of
benzoyl derivative of 11 was isolated in 47% yield.11 An these compounds is under study.
attempt to cleave simultaneously the N- and O-benzoyl
groups using 7 M ammonia in methanol solution gave 11
in only 40% yield. The yield of valuable intermediate 11
In conclusion, we have evaluated alkylamine solutions in
ethanol as selective deacylation reagents for TIPDS-pro-
tected nucleosides. We have shown that the TIPDS pro-
increased to 77% when using 8 M methylamine in ethanol
tecting group is very stable under these conditions as
solution. The same results were obtained when using
compared with other usually employed deacylation meth-
ods. Commercially available solutions of 8 M methyl-
compound 10 in this reaction.
amine in ethanol are convenient reagents for the selective
B
O
deacylation of TIPDS-protected nucleosides. To run pre-
parative experiments we can also recommend solution of
propylamine in ethanol. Successful application of the de-
veloped protocol in the multistep synthesis of complex
biomolecules is also reported. The overall yields of the
target compounds were significantly increased. We have
shown also that N-acetyl protection is advantageous over
N-benzoyl. It is much more labile in alkylamine–ethanol
solutions and in the case of cytosine derivatives, no com-
peting formation of the corresponding N-alkylcytosines is
observed. The simple substitution of widely used ammo-
nia–methanol for commercially available alkylamine–
ethanol results in a substantial increase in the stability of
the TIPDS protection group with retention of deacylation
capacities.
O
Si
O
Si
O
9 B = AdeBz, R = Bz
10 B = Ade, R = Bz
11 B = Ade, R = H
O
(i)
(i)
RO
RO
O
RO
Scheme 5 Reagents and conditions: (i) 8 M MeNH2–EtOH, 20 °C,
24 h, 77%.
The best conditions were used in the synthesis of several
conjugates of adenosine and acids as potential poly(ADP-
ribose)polymerase inhibitors.32,33 The side chain N-trifluo-
roacetyl group was removed quantitatively in compound
12,12 using 8 M methylamine in ethanol at 35 °C
(Scheme 6). Slightly elevated temperature was required to
reduce the reaction time. For comparison, by using of 7 M
ammonia in methanol the desired compound 13 was ob-
tained in only 10% yield. The enhanced outcome of 13
The solvents and materials of reagent grade were used without ad-
ditional purification. Column chromatography was performed on
silica gel (Kieselgel 60 Merck, 0.063–0.200 mm) using EtOH–
CH2Cl2 gradient increasing in polarity from CH2Cl2 to CH2Cl2–
EtOH (9:1). TLC was performed on Alugram SIL G/UV254
(Macherey-Nagel) with UV visualization. Melting points were de-
termined on a Electrothermal apparatus and are uncorrected. 1H and
Ade
O
Ade
O
O
O
Si
O
Si
(i)
O
O
O
O
O
O
O
Si
Si
NHCOCF3
NH2
12
13
(ii)
Ade
O
Ade
O
HO
O
O
Si
O
(iii)
O
O
O
Si
HO
O
NHR
NHR
15a–c
14a–c
O
O
O
b R =
NH
a R =
c R =
N
O
N
O
Scheme 6 Reagents and conditions: (i) 8 M MeNH2–EtOH, 35 °C, 100%; (ii) Bz2O, Et3N, DCE, 20 °C, 4 h (for 14a); corresponding RCO2H,
N-hydroxysuccinimide, DCC, DCE, 20 °C, 16 h then 13, Et3N, DCE, 20 °C, 4 h (for 14b,c); (iii) TBAF, THF, 20 °C, 10–15 min.
Synthesis 2010, No. 22, 3827–3834 © Thieme Stuttgart · New York

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Stability of Tetraisopropyldisiloxane-1,3-diyl Group
3831
13C (with complete proton decoupling) NMR spectra were recorded
on Bruker AMX 400 NMR instrument relative to the residual sol-
73.59 (C2′), 84.09 (C4′), 88.22 (C1′), 101.64 (C5), 140.37 (C6),
150.66 (C2), 163.19 (C4).
1
vent signals as internal standards (CDCl3, H: d = 7.26, 13C: d =
1
77.1; DMSO-d6, H: d = 2.50, 13C: d = 39.534). Double resonance
1-[2,3-O-Diacetyl-5-O-(1,1,3,3-tetraisopropyl-3-methoxydisil-
oxan-1-yl)-b-D-ribofuranosyl]uracil (3)
technique was applied to assign the resonances. UV spectra were re-
corded on a Cary300UV/VIS spectrophotometer (Varian). LC-MS
analysis was performed on Surveyor MSQ instrument (Thermo
Finnigan, USA), operating in APCI mode with detection of positive
and negative ions, and equipped with an Onyx Monollithic C18
25 × 4.6 mm Part No CHO-7645 column; eluent: 0.1% HCO2H–
H2O gradient in MeCN. Chromatographic peaks were detected si-
multaneously with ELSD, PAD, and TIC detectors. In all cases only
one peak was revealed and the chromatographic purity of com-
pounds was more than 99%.
Ac2O (0.076 mL, 0.81 mmol) was added dropwise to a soln of 2 (70
mg, 0.135 mmol) in pyridine (0.4 mL) with stirring. After 1.5 h the
mixture was diluted with CH2Cl2 (10 mL) and washed with 10% aq
NaHCO3 (10 mL) and H2O (20 mL). The organic layer was dried
(Na2SO4) and evaporated in vacuo. The residue was subjected to
column chromatography to yield 3 (72 mg, 88%) as foam; Rf = 0.61
(CH2Cl2–EtOH, 95:5).
1H NMR (400 MHz, CDCl3): d = 0.98–1.13 (m, 28 H, i-Pr), 2.07 (s,
3 H, MeCO), 2.12 (s, 3 H, MeCO), 3.55 (s, 3 H, MeO), 4.02 (dd,
TIPDS-protected nucleosides 1a,b,d were prepared according to
literature1,2 and had similar NMR spectra. The synthesis of com-
pound 7,10 9,11 10,11 and 1312 are given in the literature.
J5¢b,5¢a = –11.3 Hz, J5¢b,4¢ = 2.0 Hz, 1 H, H5′b), 4.05 (dd, J5¢a,5¢b
=
–11.3 Hz, J5¢a,4¢ = 2.0 Hz, 1 H, H5′a), 4.23 (ddd, J4¢,3¢ = 2.5 Hz,
J4¢,5¢b = 2.0 Hz, J4¢,5¢a = 2.0 Hz, 1 H, H4′), 5.33 (dd, J2¢,1¢ = 6.7 Hz,
J
2¢,3¢ = 5.5 Hz, 1 H, H2′), 5.42 (dd, J3¢,2¢ = 5.5 Hz, J3¢,4¢ = 2.5 Hz, 1 H,
N4-Acetyl-1-[3,5-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-
b-D-ribofuranosyl]cytosine (1c)
H3′), 5.72 (dd, J5,6 = 8.3 Hz, J5,NH = 1.8 Hz, 1 H, H5), 6.26 (d,
J
1¢,2¢ = 6.7 Hz, 1 H, H1′), 7.78 (d, J6,5 = 8.3 Hz, 1 H, H6), 8.84 (br s,
1-[3,5-O-(1,1,3,3-Tetraisopropyldisiloxane-1,3-diyl)-b-D-ribofura-
nosyl]cytosine1 (300 mg, 0.62 mmol) was dissolved in anhyd DMF
(3 mL) and Ac2O (0.174 mL, 1.86 mmol) was added to the soln. Af-
ter 3 h, the mixture was diluted with EtOAc (20 mL) and washed
successively with 10% aq NaHCO3 (10 mL) and H2O (2 × 10 mL).
The organic layer was dried (Na2SO4) and evaporated in vacuo. The
residue was purified by column chromatography affording 1c (245
mg, 75%) as a white powder; Rf = 0.34 (CH2Cl2–EtOH, 98:2).
unresolved d, JNH,5 = 1.8 Hz, 1 H, NH).
13C NMR (100 MHz, CDCl3): d = 12.79, 12.85, 13.09, 17.30 17.36
(i-Pr), 20.43 (MeC=O), 20.68 (MeC=O), 50.75 (OMe), 62.40 (C5′),
71.31 (C3′), 73.31 (C2′), 83.60 (C4′), 85.46 (C1′), 103.26 (C5),
139.45 (C6), 150.60 (C2), 162.88 (C4), 169.57 (MeC=O), 169.82
(MeC=O).
MS (APCI): m/z [M + H+] calcd for C26H47N2O10Si2: 603.28; found:
603.42; m/z [M – H–] calcd for C26H45N2O10Si2: 601.26; found:
603.27; m/z [M – H– + HCOOH] calcd for C27H47N2O12Si2: 647.27;
found: 647.18.
1H NMR (400 MHz, CDCl3): d = 0.91–1.2 (m, 28 H, i-Pr), 2.30 (s,
3 H, MeCO), 3.95 (dd, J5¢b,5¢a = –13.4 Hz, J5¢b,4¢ = 2.5 Hz, 1 H, H5′b),
4.19 (ddd, J4¢,5¢b = 13.4 Hz, J4¢,3¢ = 9.2 Hz, J4¢,5¢a = 1.8 Hz, 1 H, H4′),
4.22 (d, J2¢,3¢ = 4.4 Hz, 1 H, H2′), 4.26 (dd, J5¢a,5¢b = –13.4 Hz,
1-[2-Deoxy-3,5-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-b-
D-ribofuranosyl]thymine (4)
The 2′-deoxythymidine (500 mg, 2.065 mmol) was protected ac-
cording to ref.1,2 to give 4 as a foam; yield: 960 mg (96%); Rf = 0.50
(CH2Cl2–EtOH, 95:5).
J
5¢a,4¢ = 1.8 Hz, 1 H, H5′a), 4.30 (dd, J3¢,4¢ = 9.2 Hz, J3¢,2¢ = 4.4 Hz, 1
H, H3′), 5.81 (s, 1 H, H1′), 7.42 (d, J5,6 = 7.5 Hz, 1 H, H5), 8.22 (d,
J6,5 = 7.5 Hz, 1 H, H6), 9.61 (br s, 1 H, NH).
13C NMR (100 MHz, CDCl3): d = 12.58, 13.00, 13.44, 16.88, 16.95,
17.04, 17.34, 17.45, 17.51 (i-Pr), 25.00 (MeC=O), 60.15 (C5′),
68.70 (C3′), 75.28 (C2′), 82.12 (C4′), 91.69 (C1′), 99.65 (C5),
144.48 (C6), 154.94 (C2), 163.19 (C4), 171.21 (MeC=O).
1H-NMR (400 MHz, CDCl3): d = 0.95–1.15 (m, 28 H, i-Pr), 1.91 (d,
JMe,6 = 1 Hz, 3 H, Me-Thy), 2.25 (ddd, J2¢b,2¢a = 13.4 Hz, J2¢b,3¢ = 7.4
Hz, J2¢b,1¢ = 2.2 Hz, 1 H, H2′b), 2.48 (ddd, J2¢a,2¢b = 13.4 Hz,
J
2¢a,3¢ = 9.5 Hz, J2¢a,1¢ = 7.4 Hz, 1 H, H2′a), 3.74 (ddd, J4¢,3¢ = 8.1 Hz,
1-[5-O-(1,1,3,3-Tetraisopropyl-3-methoxydisiloxan-1-yl)-b-D-
ribofuranosyl]uracil (2)
Method A: Compound 1d (100 mg, 0.205 mmol) was dissolved in 7
M NH3 in MeOH (5 mL) and left at 20 °C for 24 h. The mixture was
evaporated in vacuo and the residue was applied to column chroma-
tography to give 2 (42 mg, 40%) as a foam.
J4¢,5¢b = 3.1 Hz, J4¢,5¢a = 2.5 Hz, 1 H, H4′), 4.02 (dd, J5¢b,5¢a = –13.4
Hz, J5¢b,4¢ = 3.1 Hz, 1 H, H5′b), 4.10 (dd, J5¢a,5¢b = –13.4 Hz,
J
5¢a,4¢ = 3.1 Hz, 1 H, H5′a), 4.49 (ddd, J3¢,2¢a = 9.5 Hz, J3¢,4¢ = 8.1 Hz,
J3¢,2¢b = 7.4 Hz, 1 H, H3′), 6.08 (dd, J1¢,2¢a = 7.4 Hz, J1¢,2¢b = 2.2 Hz, 1
H, H1′), 7.40 (q, J6,Me = 1 Hz, 1 H, H6), 9.04 (br s, 1 H, NH).
13C NMR (100 MHz, CDCl3): d = 12.58, 12.68, 12.88, 13.11 (i-Pr),
13.57 (Me-Thy), 16.93, 17.05, 17.08, 17.19, 17.35, 17.40, 17.48,
17.53 (i-Pr), 39.91 (C2′), 60.39 (C5′), 67.81 (C3′), 83.90 (C4′),
85.07 (C1′), 110.64 (C5), 110.64 (C5), 135.26 (C6), 150.25 (C2),
163.95 (C4).
Method B: Compound 1d (100 mg, 0.205 mmol) was dissolved in
MeOH (3 mL) and DBU (0.445 mL, 3 mmol) was added and the
soln was kept at r.t. After 8 h mixture was cooled to 0 °C and AcOH
(0.343 mL, 6 mmol) was added to neutralize DBU. The resulted
mixture was diluted with EtOAc (20 mL), washed successively with
H2O (10 mL), 10% aq NaHCO3 (20 mL), and H2O (20 mL), dried
(Na2SO4), and evaporated in vacuo. Column chromatography of the
residue yielded 2 (80 mg, 75%); Rf = 0.58 (CH2Cl2–EtOH, 9:1).
1H NMR (400 MHz, DMSO-d6): d = 0.98–1.15 (m, 28 H, i-Pr), 3.48
(s, 3 H, Me), 3.8–3.88 (m, 1 H, H5′b), 3.89–4.05 (m, 4 H, H5′a, H2′,
H3′, H4′), 5.10 (d, J = 5.3 Hz, 1 H, OH)*, 5.45 (d, J = 5.3 Hz, 1 H,
OH)*, 5.55 (d, J5,6 = 7.8 Hz, 1 H, H5), 5.76 (d, J1¢,2¢ = 5.0 Hz, 1 H,
H1′), 7.68 (d, J6,5 = 7.8 Hz, 1 H, H6), 11.32 (br s, 1 H, NH); * ex-
changeable with D2O.
1-[2-Deoxy-5-O-(1,1,3,3-tetraisopropyl-3-methoxydisiloxan-1-
yl)-b-D-ribofuranosyl]thymine (5) and 1-[2-Deoxy-3-O-(1,1,3,3-
tetraisopropyl-3-methoxydisiloxan-1-yl)-b-D-ribofurano-
syl]thymine (6)
Compound 4 (100 mg, 0.206 mmol) was dissolved in MeOH (3 mL)
and DBU (0.445 mL, 3 mmol) was added to the soln. After 24 h the
mixture was cooled to 0 °C and AcOH (0.343 mL, 6 mmol) was
added to neutralize DBU. The resulted mixture was diluted with
EtOAc (20 mL) and washed successively with H2O (10 mL), 10%
aq NaHCO3 (20 mL), and H2O (20 mL). The organic layer was dried
(Na2SO4) and evaporated in vacuo. The residue applied to column
chromatography. Two products 5 and 6 were isolated; compound 6
was eluted first.
13C NMR (100 MHz, DMSO-d6): d = 12.26, 12.31, 12.46, 17.10,
17.15, 17.19, 17.24 (i-Pr), 50.29 (OMe), 62.28 (C5′), 69.62 (C3′),
Synthesis 2010, No. 22, 3827–3834 © Thieme Stuttgart · New York

3832
M. S. Drenichev et al.
PAPER
5-O-(1,1,3,3-Tetraisopropyl-3-methoxydisiloxan-1-yl) Deriva-
tive 5
6.50 (s, 1 H, H1′Ado), 6.50 (br s, 2 H, NH2), 8.19 (s, 1 H, H2), 8.49
s (1 H, H8).
White amorphous powder; yield: 49 mg (46%); Rf = 0.21 (CH2Cl2–
EtOH, 95:5).
13C NMR (100 MHz, CDCl3): d = 12.82, 13.01, 13.08, 13.66, 16.90,
17.08, 17.13, 17.20, 17.43, 17.49, 17.61 (i-Pr), 59.65 (C5′Ado),
61.42 (C5′′Ara), 67.61 (C3′Ado), 76.28 (C3′′Ara), 77.18 (C2′Ado),
78.61 (C2′′Ara), 78.76 (C4′Ado), 82.17 (C4′′Ara), 87.39 (C1′Ado),
89.19 (C1′′Ara), 105.71 (C5), 138.53 (C8), 148.70 (C4), 153.27
(C6), 155.52 (C2).
MS (APCI): m/z [M + H+] calcd for C27H48N5O9Si2: 642.30; found:
642.42; m/z [M – H+ + HCOOH] calcd for C28H48N5O11Si2: 686.29;
found: 686.27.
1H NMR (400 MHz, DMSO-d6): d = 0.95–1.17 (m, 28 H, i-Pr), 1.75
(d, JMe,6 = 1 Hz, 3 H, Me-Thy), 2.06–2.13 (m, 2 H, overlapping
H2′b and H2′a), 3.48 (s, 3 H, MeO), 3.81–3.91 (m, 3 H, overlapping
H4′, H5′b and H5′a), 4.21–4.27 (m, 1 H, H3′), 5.38 (d, J3¢-OH,3¢ = 4.4
Hz, 1 H, 3′-OH, exchangeable with D2O), 6.26 (dd, J1¢,2¢b = 7.2 Hz,
J1¢,2¢a = 6.8 Hz, 1 H, H1′), 7.38 (q, J6,Me = 1 Hz, 1 H, H6), 11.28 (br
s, 1 H, NH).
13C NMR (100 MHz, DMSO-d6): d = 12.03, 12.16, 12.28 (i-Pr),
12.40 (Me-Thy), 17.02, 17.05, 17.08, 17.13 (i-Pr), 39.24 (C2′),
50.17 (MeO), 62.73 (C5′), 70.29 (C3′), 83.76 (C4′), 86.55 (C1′),
109.45 (C5), 135.43 (C6), 150.35 (C2), 163.63 (C4).
UV (MeOH): lmax (log e) = 259 nm (4.155), pH 7–13; 259 nm
(4.146), pH 1.
9-{2-O-[(2-Aminoethoxy)methyl]-3,5-O-(1,1,3,3-tetraisopropyl-
disiloxane-1,3-diyl)-b-D-ribofuranosyl}adenine (13)
MS (APCI): m/z [M + H+] calcd for C23H45N2O7Si2: 517.27; found:
517.43; m/z [M – H– + HCOOH] calcd for C24H45N2O9Si2: 561.27;
found: 561.27.
Compound 12 (1.56 g, 2.3 mmol) was dissolved in 8 M MeNH2 in
EtOH soln (70 mL). The soln was kept at 35 °C. The reaction was
monitored by TLC (CH2Cl2–EtOH, 9:1); after 6 h complete conver-
sion of 12 was observed. The soln was evaporated to dryness (bath
temp <35 °C) and co-evaporated with CH2Cl2 (2 × 20 mL) to afford
13 (1.33 g, 100%) as a foam of sufficient purity to use in further re-
actions; Rf = 0.33 (CH2Cl2–EtOH, 9:1).
1H NMR (400 MHz, CDCl3): d = 0.9–1.2 (m, 28 H, i-Pr), 1.93 (br s,
2 H, aliphatic NH2), 2.88 (t, J2¢¢,1¢¢b = J2¢¢,1¢¢a = 5.1 Hz, 2 H,
OCHbHaCH2NH2), 3.63 (dt, J1¢¢b,1¢¢a = –10, J1¢¢b,2¢¢ = 5.1 Hz, 1 H,
OCHbHaCH2NH2), 3.79 (dt, J1¢¢a,1¢¢b = –10, J1¢¢a,2¢¢ = 5.1 Hz, 1 H,
OCHbHaCH2NH2), 4.02 (dd, J5¢b,5¢a = –13.4 Hz, J5¢b,4¢ = 2.5 Hz, 1 H,
H5′b), 4.14 (ddd, J4¢,3¢ = 9.1 Hz, J4¢,5¢b = 2.5 Hz, J4¢,5¢a = 1.8 Hz, 1 H,
H4′), 4.23 (dd, J5¢a,5¢b = –13.4 Hz, J5¢a,4¢ = 1.8 Hz, 1 H, H5′a), 4.50
(d, J2¢3¢ = 4.4 Hz, 1 H, H2′), 4.70 (dd, J3¢,4¢ = 9.1 Hz, J3¢,2¢ = 4.4 Hz,
1 H, H3′), 4.99 (d, J = –6.9 Hz, 1 H, OCHbHaO), 5.01 (d, J = –6.9
Hz, 1 H, OCHbHaO), 6.01 (br s, 2 H, 6-NH2), 6.06 (s, 1 H, H1′), 8.12
(s, 1 H, H2), 8.28 (s, 1 H, H8).
3-O-(1,1,3,3-Tetraisopropyl-3-methoxydisiloxan-1-yl) Deriva-
tive 6
Syrup; yield: 26 mg (24%); Rf = 0.28 (CH2Cl2–EtOH, 95:5).
1H NMR (400 MHz, DMSO-d6): d = 0.90–1.18 (m, 28 H, i-Pr), 1.77
(d, JMe,6 = 1.0 Hz, 3 H, Me-Thy), 2.11 (ddd, J2¢b,2¢a = –13.1 Hz,
J2¢b,1¢ = 5.7 Hz, J2¢b,3¢ = 2.7 Hz, 1 H, H2′b), 2.20 (ddd, J2¢a,2¢b = –13.1
Hz, J2¢a,1¢ = 7.9 Hz, J2¢a,3¢ = 5.3 Hz, 1 H, H2′a), 3.48 (s, 3 H, MeO),
3.56 (ddd, J5¢b,5¢a = –12.1 Hz, J5¢b,OH = 5.0 Hz, J5¢b,4¢ = 3.5 Hz, 1 H,
H5′b), 3.62 (ddd, J5¢a,5¢b = –12.1 Hz, J5¢a,OH = 5.0 Hz, J5¢a,4¢ = 4.1 Hz,
1 H, H5′a), 3.86 (ddd, J4¢,5¢b = 3.5 Hz, J4¢,5¢a = 4.1 Hz, J4¢,3¢ = 2.6 Hz,
1 H, H4′), 4.59 (ddd, J3¢,2¢a = 5.3 Hz, J3¢,2¢b = 2.7 Hz, J3¢,4¢ = 2.6 Hz, 1
H, H4′), 5.12 (dd, JOH,5¢b = JOH,5¢a = 5.0 Hz, 5′-OH, exchangeable
with D2O), 6.18 (dd, J1¢,2¢a = 7.9 Hz, J1¢,2¢b = 5.7 Hz, 1 H, H1′), 7.70
(q, J6,Me = 1.0 Hz, 1 H, H6), 11.24 (br s, 1 H, NH).
13C NMR (100 MHz, DMSO-d6): d = 12.17, 12.17, 12.19, 12.40 (i-
Pr), 12.44 (Me-Thy), 16.98, 17.02, 17.11, 17.15 (i-Pr), 39.81 (C2′),
50.21 (MeO), 61.02 (C5′), 71.99 (C3′), 83.85 (C4′), 87.42 (C1′),
109.39 (C5), 135.91 (C6), 150.42 (C2), 163.71 (C4).
MS (APCI): m/z [M + H+] calcd for C23H45N2O7Si2: 517.27; found:
517.43; m/z [M – H+ + HCOOH] calcd for C24H45N2O9Si2: 561.27;
found: 561.29.
13C NMR (100 MHz, CDCl3): d = 12.77, 12.96, 13.03, 13.48, 16.97,
17.10, 17.24, 17.36, 17.42, 17.52 (i-Pr), 41.83 (OCH2CH2NH2),
60.03 (C5′), 69.19 (OCH2CH2NH2), 70.75 (C3′), 77.42 (C2′), 81.60
(C4′), 88.86 (C1′), 95.32 (OCH2O), 120.35 (C5), 138.67 (C2),
149.11 (C4), 153.10 (C8), 155.62 (C6).
9-{2-O-[(2-Benzamidoethoxy)methyl]-3,5-O-(1,1,3,3-tetraiso-
propyldisiloxane-1,3-diyl)-b-D-ribofuranosyl}adenine (14a)
Bz2O (190 mg, 0.8 mmol) and Et3N (0.25 mL, 1.5 mmol) were add-
ed to a soln of 13 (400 mg, 0.7 mmol) in DCE (50 mL) at r.t. with
TLC monitoring (CH2Cl2–EtOH, 95:5); after 4 h the conversion was
completed. The mixture was quenched by addition of sat. aq
NaHCO3 soln (20 mL). The resulting mixture was stirred vigorous-
ly at r.t. for additional 1 h. The organic layer was separated, washed
with H2O (20 mL), dried (Na2SO4), and evaporated in vacuo. The
residue was purified by column chromatography to yield 14a (410
mg, 85%) as a foam; Rf = 0.25 (CH2Cl2–EtOH, 95:5).
1-{2-O-[(2-Hydroxyethoxy)methyl]-3,5-O-(1,1,3,3-tetraisopro-
pyldisiloxane-1,3-diyl)-b-D-ribofuranosyl}uracil (8)
Compound 7 (275 mg, 0.46 mmol) was dissolved in 8 M MeNH2 in
EtOH soln (3 mL). After 20 h (20 °C) the resulted soln was evapo-
rated. The residue was purified by column chromatography afford-
ing 8 (219 mg, 85%) as a powder.
1H NMR and 13C NMR spectra were identical to those reported ear-
lier.12
9-[2-O-(a-D-Arabinofuranosyl)-3,5-(1,1,3,3-tetraisopropyl-
disiloxane-1,3-diyl)-b-D-ribofuranosyl]adenine (11)
Disaccharide 9 (1.00 g, 0.94 mmol) was dissolved in 8 M MeNH2
in EtOH soln (8mL) and left at r.t. After 24 h the solvent was evap-
orated. The residue was purified by column chromatography to
yield 11 (465 mg, 77%) as a foam; Rf = 0.17 (CH2Cl2–EtOH, 9:1).
1H-NMR (400 MHz, CDCl3): d = 0.9–1.2 (m, 28 H, i-Pr), 3.63–3.76
(m, 2 H, OCH2CH2NH), 3.83 (dt, J1¢¢b,1¢¢a = –10.4 Hz, J1¢¢b,2¢¢ = 5.0
Hz, 1 H, OCHbHaCH2NH), 3.96 (dt, J1¢¢a,1¢¢b = –10.4 Hz, J1¢¢a,2¢¢ = 5.0
Hz, 1 H, OCHbHaCH2NH), 4.00 (dd, J5¢b,5¢a = –13.1 Hz, J5¢b,4¢ = 2.6
Hz, 1 H, H5′b), 4.15 (ddd, J4¢,3¢ = 9.3 Hz, J4¢,5¢b = 2.6 Hz, J4¢,5¢a = 2.0
Hz, 1 H, H4′), 4.24 (dd, J5¢a,5¢b = –13.1 Hz, J5¢a,4¢ = 2.0 Hz, 1 H,
H5′a), 4.47 (d, J2¢3¢ = 4.7 Hz, 1 H, H2′), 4.63 (dd, J3¢,4¢ = 9.3 Hz,
1H NMR (400 MHz, CDCl3): d = 0.80–1.10 (m, 28 H, i-Pr), 3.71
(dd, J5¢¢a,5¢¢b = –12.5 Hz, J5¢¢b,4¢¢ = 1.2 Hz, 1 H, H5′′bAra), 3.80 (dd,
J5¢¢a,5¢¢b = –12.5 Hz, J5¢¢a,4¢¢ = 2.3 Hz, 1 H, H5′′aAra), 3.95 (dd,
J5¢b,5¢a = –13.5 Hz, J5¢b,4¢ = 2.3 Hz, 1 H, H5′bAdo), 4.01 (m, 1 H,
H4′bAdo), 4.10 (dd, J3¢¢,4¢¢ = 8.9 Hz, J3¢¢,2¢¢ = 1.7 Hz, 1 H, H3′′Ara), 4.14
(m 2 H, overlapping H2′′Ara and H4′′Ara), 4.23 (d, J5¢a,5¢b = –13.4 Hz,
1 H, H5′aAdo), 4.52 (d, J2¢,3¢ = 5.0 Hz, 1 H, H2′Ado), 4.58 (dd,
J
3¢,2¢ = 4.7 Hz, 1 H, H3′), 5.01 (d, J = –6.9 Hz, 1 H, OCHbHaO), 5.07
(d, J = –6.9 Hz, 1 H, OCHbHaO), 7.09 (br t, J = 5.3 Hz, 1 H, NH),
7.31 (t, J = 7.5 Hz, 2 H, m-HBz), 7.41 (t, J = 7.5 Hz, 1 H, p-HBz),
7.68 (t, J = 7.5 Hz, 2 H, o-HBz), 8.14 (s, 1 H, H2), 8.23 (s, 1 H, H8).
13C NMR (100 MHz, CDCl3): d = 12.71, 12.96, 13.00, 13.47, 16.91,
17.04, 17.08, 17.22, 17.36, 17.42, 17.52 (i-Pr), 40.10
(OCH2CH2NH), 59.80 (C5′), 68.40 (OCH2CH2NH), 68.82 (C3′),
J3¢,4¢ = 9.0 Hz, J3¢,2¢ = 5.0 Hz, 1 H, H3′Ado), 5.66 (s, 1 H, H1′′Ara),
Synthesis 2010, No. 22, 3827–3834 © Thieme Stuttgart · New York

PAPER
Stability of Tetraisopropyldisiloxane-1,3-diyl Group
3833
79.26 (C2′), 81.65 (C4′), 88.77 (C1′), 95.65 (OCH2O), 120.31 (C5),
126.99 (m-CBz), 128.42 (o-CBz), 131.35 (p-CBz), 134.75 (C1Bz),
138.66 (C2), 148.88 (C4), 152.68 (C8), 155.37 (C6), 167.93 (C=O).
(OCH2CH2NH2), 69.20 (C3′), 80.16 (C2′), 81.83 (C4′), 88.96
(C1′), 96.17 (OCH2O), 110.92 (C5Thy), 119.79 (C5), 139.32 (C2),
141.14 (C6Thy), 148.54 (C4), 152.07 (C8), 155.50 (C6), 165.43
(C=O-Thy), 167.41 (C=O).
9-{2-O-[(2-Nicotinamidoethoxy)methyl]-3,5-O-(1,1,3,3-tetraiso-
propyldisiloxane-1,3-diyl)-b-D-ribofuranosyl}adenine (14b);
Typical Procedure
DCC (5.15 g, 25 mmol) was added with stirring to a mixture of nic-
otinic acid (2.46 g, 20 mmol) and N-hydroxysuccinimide (2.53 g, 22
mmol) in DCE (20 mL) and the mixture was stirred for 16 h. The
precipitated dicyclohexylurea was filtered off. The filtrate was
evaporated in vacuo to provide crude N-(nicotinoyloxy)succinimide
(3.56 g, 81%); Rf = 0.8 (CH2Cl2–EtOH, 95:5).
Removal of TIPDS Protecting Group; General Procedure
Protected compound (0.6 mmol) was dissolved in 0.5 M TBAF·3
H2O (5 mL). After 10–15 min the mixture was evaporated in vacuo
and the residue was purified by column chromatography.
9-{2-O-[(2-Benzamidoethoxy)methyl]-b-D-ribofuranosyl}ade-
nine (15a)
Yield: 94%; mp 164 °C; Rf = 0.18 (CH2Cl2–MeOH, 95:5).
To a soln of 13 (400 mg, 0.7 mmol) in DCE (50 mL) was added N-
(nicotinoyloxy)succinimide (260 mg, 1.2 mmol) and Et3N (0.25
mL, 1.5 mmol); after 4 h at r.t. the reaction was quenched by the ad-
dition of sat. aq NaHCO3 (20 mL). The organic layer was separated,
washed with H2O (20 mL), dried (Na2SO4), and evaporated in vac-
uo. Purification of the residue by column chromatography afforded
14b (410 mg, 85%) as a foam; Rf = 0.45 (CH2Cl2–EtOH, 9:1).
1H NMR (400 MHz, CDCl3–CD3OD, 9:1): d = 3.23–3.33 (m, 1 H,
OCHbHaCHbHaNH), 3.36–3.49 (m, 2 H, overlapping OCHbHaCHb-
HaNH), 3.54 (dd, J5¢b,5¢a = –12.8 Hz, J5¢b,4¢ = 1.6 Hz, 1 H, H5′b),
3.59–3.67 (m, 1 H, OCHbHaCHbHaNH), 3.82 (dd, J5¢a,5¢b = –12.8 Hz,
J
5¢a,4¢ = 1.7 Hz, 1 H, H5′a), 4.15 (ddd, J4¢,5¢a = 1.7 Hz, J4¢,5¢b = 1.6 Hz,
J4¢,3¢ = 1.2 Hz, 1 H, H4′), 4.34 (dd, J3¢,2¢ = 4.7 Hz, J3¢,4¢ = 1.2 Hz, 1 H,
H3′), 4.52 (d, J = –6.5 Hz, 1 H, OCHbCHa), 4.62 (d, J = –6.5 Hz, 1
H, OCHbCHa), 4.77 (dd, J2¢,1¢ = 7.2 Hz, J2¢,3¢ = 4.7 Hz, 1 H, H2′),
5.91 (d, J1¢,2¢ = 7.2 Hz, 1 H, H1′), 7.33 (t, J = 7.8 Hz, 2 H, m-HBz),
7.41 (t, J = 7.8 Hz, 1 H, p-HBz), 7.44 (br t, J = 5 Hz, NH), 7.69 (t,
J = 7.8 Hz, 2 H, o-HBz), 7.92 (s, 1 H, H2), 8.14 (s, 1 H, H8).
1H NMR (400 MHz, CDCl3): d = 0.89–1.10 (m, 28 H, i-Pr), 3.71 (q,
J2¢¢,1¢¢b = J2¢¢,1¢¢a = J2¢¢,NH = 5.0 Hz, 2 H, OCHbHaCH2NH), 3.83 (dt,
J1¢¢b,1¢¢a = –10 Hz, J1¢¢b,2¢¢ = 5.0 Hz, 1 H, OCHbHaCH2NH), 3.98 (dt,
3.79 (dd, J1¢¢a,1¢¢b = –10 Hz, J1¢¢a,2¢¢ = 5.1 Hz, 1 H, OCHbHaCH2NH),
4.00 (dd, J5¢b,5¢a = –13.3 Hz, J5¢b,4¢ = 2.5 Hz, 1 H, H5′b), 4.16 (ddd,
13C NMR (100 MHz, CDCl3–CD3OD, 9:1):
d = 39.67
J4¢,3¢ = 9.3 Hz, J4¢,5¢b = 2.5 Hz, J4¢,5¢a = 1.0 Hz, 1 H, H4′), 4.24 (dd,
(OCH2CH2NH), 62.58 (C5′), 67.13 (OCH2CH2NH), 71.11 (C3′),
80.04 (C2′), 87.68 (C4′), 88.96 (C1′), 95.81 (OCH2O), 120.28 (C5),
126.98 (m-CBz), 128.40 (o-CBz), 131.56 (p-CBz), 133.95 (C1Bz),
140.81 (C2), 148.31 (C4), 151.96 (C8), 155.69 (C6), 168.51 (C=O).
J5¢a,5¢b = –13.3 Hz, J5¢a,4¢ = 1.0 Hz, 1 H, H5′a), 4.45 (d, J2¢3¢ = 4.5 Hz,
1 H, H2′), 4.62 (dd, J3¢,4¢ = 9.3 Hz, J3¢,2¢ = 4.5 Hz, 1 H, H3′), 5.00 (d,
J = –6.9 Hz, 1 H, OCHbHaO), 5.08 (d, J = –6.9 Hz, 1 H, OCHbHaO),
6.03 (s, 1 H, H1′), 6.10 (br s, 2 H, 6-NH2), 7.26 (dd, J5,4 = 7.9 Hz,
J5,6 = 4.8 Hz, 1 H H5Nic), 7.40 (br t, JNH,2¢¢ = 5.0 Hz, 1 H, NH), 8.02
(ddd, J4,5 = 7.9 Hz, J4,2 = J4,6 = 1.9 Hz, 1 H H4Nic), 8.15 (s, 1 H, H2),
8.22 (s, 1 H, H8), 8.63 (dd, J6,5 = 4.8 Hz, J6,4 = 1.9 Hz, 1 H H6Nic),
8.92 (d, J2,4 = 1.9 Hz, 1 H H2Nic).
MS (APCI): m/z [M + H+] calcd for C20H25N6O6: 445.18; found:
445.37; m/z [M – H+ + HCOOH] calcd for C21H25N6O8: 489.17;
found: 488.57.
UV (MeOH): lmax (log e) = 259 nm (4.079), pH 7–13; 257 nm
(4.053), pH 1.
13C NMR (100 MHz, CDCl3): d = 12.71, 12.97, 12.99, 13.48, 16.88,
17.00, 17.08, 17.22, 17.35, 17.41, 17.51 (i-Pr), 40.28
(OCH2CH2NH), 59.79 (C5′), 68.50 (OCH2CH2NH), 68.81 (C3′),
79.42 (C2′), 81.67 (C4′), 88.72 (C1′), 95.79 (OCH2O), 120.33 (C5),
123.33 (C5Nic), 130.40 (C3Nic), 135.06 (C4Nic), 138.60 (C2), 148.16
(C6Nic), 148.83 (C4), 152.12 (C2Nic), 152.58 (C8), 155.39 (C6),
165.96 (C=O).
9-{2-O-[(2-Nicotinamidoethoxy)methyl]-b-d-ribofuranosyl}ad-
enine (15b)
Yield: 92%; mp 209 °C (dec); Rf = 0.35 (CH2Cl2–MeOH, 9:1).
1H NMR (400 MHz, CDCl3–CD3OD 9:1): d = 3.25–3.36 (m, 1 H,
OCHbHaCHbHaNH), 3.40–3.49 (m, 2 H, overlapping OCHbHaCHb-
HaNH), 3.58 (dd, J5¢b,5¢a = –12.9 Hz, J5¢b,4¢ = 1.7 Hz, 1 H, H5′b),
3.59–3.67 (m, 1 H, OCHbHaCHbHaNH), 3.83 (dd, J5¢a,5¢b = –12.9 Hz,
9-{2-O-[({2-[(1-Thyminyl)methyl]carboxamido}ethoxy)meth-
yl]-3,5-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-b-D-ribo-
furanosyl}adenine (14c)
Activation of 1-(carboxymethyl)thymine (1.84 g, 10 mmol) follow-
ing the typical procedure for 14b gave crude 1-(carboxymeth-
yl)thymine N-hydroxysuccinimide ester (2.09 g, 79%); Rf = 0.7
(CH2Cl2–EtOH, 95:5).
J
5¢a,4¢ = 1.7 Hz, 1 H, H5′a), 4.17 (ddd, J4¢,5¢a = 1.7 Hz, J4¢,5¢b = 1.7 Hz,
J4¢,3¢ = 1.2 Hz, 1 H, H4′), 4.36 (dd, J3¢,2¢ = 4.9 Hz, J3¢,4¢ = 1.2 Hz, 1 H,
H3′), 4.54 (d, J = –6.9 Hz, 1 H, OCHbCHa), 4.62 (d, J = –6.9 Hz, 1
H, OCHbCHa), 4.77 (dd, J2¢,1¢ = 7.2 Hz, J2¢,3¢ = 4.9 Hz, 1 H, H2′),
5.92 (d, J1¢,2¢ = 7.2 Hz, 1 H, H1′), 7.33 (dd, J5,4 = 7.9 Hz, J5,6 = 4.7
Hz, 1 H H5Nic), 7.95 (s, 1 H, H2), 8.10 (ddd, J4,5 = 7.9 Hz,
J4,2 = J4,6 = 1.6 Hz, 1 H, H4Nic), 8.13 (s, 1 H, H8), 8.56 (dd, J6,5 = 4.7
Hz, J6,4 = 1.6 Hz, 1 H H6Nic), 8.89 (d, J2,4 = 1.6 Hz, 1 H, H2Nic).
The compound 14c was prepared as it was described for 14b. Thus
13 (400 mg, 0.7 mmol) provided 14c (450 mg, 85%) as a foam;
Rf = 0.35 (CH2Cl2–EtOH, 9:1).
13C NMR (100 MHz, CDCl3–CD3OD, 9:1):
d = 39.72
(OCH2CH2NH), 62.56 (C5′), 67.19 (OCH2CH2NH), 71.10 (C3′),
80.27 (C2′), 87.66 (C4′), 88.91 (C1′), 95.99 (OCH2O), 120.26 (C5),
123.63 (C5Nic), 130.26 (C3Nic), 135.82 (C4Nic), 140.74 (C2), 147.78
(C6Nic), 148.33 (C4), 151.46 (C2Nic), 152.10 (C8), 155.77 (C6),
166.06 (C=O).
MS (APCI): m/z [M – H+ + HCOOH] calcd for C20H24N7O8: 490.17;
found: 490.36.
1H NMR (400 MHz, CDCl3): d = 0.91–1.12 (m, 28 H, i-Pr), 1.83 (s,
3 H, Me-Thy), 3.25–3.40 (m, 1 H, OCHbHaCHbHaNH), 3.70–3.88
(m, 3 H, overlapping OCHbHaCHbHaNH), 4.02 (dd, J5¢b,5¢a = –13.2
Hz, J5¢b,4¢ = 2.3 Hz, 1 H, H5′b), 4.14 (dt, J4¢,3¢ = 9.2 Hz, J4¢,5¢b = 2.3
Hz, 1 H, H4′), 4.21 (d, J = –15.9 Hz, 1 H, CHbHa-Thy), 4.25 (d,
J5¢a,5¢b = –13.2 Hz, 1 H, H5′a), 4.43 (d, J = –15.9 Hz, 1 H, CHbHa-
Thy), 4.44 (d, J2¢3¢ = 4.5 Hz, 1 H, H2′), 4.67 (dd, J3¢,4¢ = 9.2 Hz,
J
3¢,2¢ = 4.5 Hz, 1 H, H3′), 4.93 (s, 2 H, OCH2O), 6.16 (s, 1 H, H1′),
UV (MeOH): lmax (log e) = 259 nm (4.193), pH 13; 259 nm (4.107),
pH 7; 264 nm (4.079), pH 1.
7.022 (br s, 2 H, 6-NH2), 7.08 (s, 1 H, H6Thy), 8.26 (s, 1 H, H8), 8.32
(br s, NHCO), 8.33 (s, 1 H, H2), 12.27 (br s, NHThy).
13C NMR (100 MHz, CDCl3): d = 12.30, 12.79, 13.02 (i-Pr), 13.52
(Me-Thy), 17.03, 17.16, 17.39, 17.44, 17.60 (i-Pr), 40.06
(OCH2CH2NH2), 50.64 (CH2-Thy), 60.16 (C5′), 68.64
9-{2-O-[(2-{[(1-Thyminyl)methyl]carboxamido}ethoxy)meth-
yl]-b-D-ribofuranosyl}adenine (15c)
Yield: 91%; mp 239 °C (dec); Rf = 0.10 (CH2Cl2–MeOH, 9:1).
Synthesis 2010, No. 22, 3827–3834 © Thieme Stuttgart · New York

3834
M. S. Drenichev et al.
PAPER
(9) Efimtseva, E. V.; Bobkov, G. V.; Mikhailov, S. N.;
Van Aerschot, A.; Schepers, G.; Busson, R.; Rozenski, J.;
Herdewijn, P. Helv. Chim. Acta 2001, 84, 2387.
(10) Bobkov, G. V.; Brilliantov, K. V.; Mikhailov, S. N.;
Rozenski, J.; Van Aerschot, A.; Herdewijn, P. Collect.
Czech. Chem. Commun. 2006, 71, 804.
1H NMR (400 MHz, DMSO-d6): d = 1.74 (s, 3 H, Me-Thy), 2.89–
3.01 (m, 1 H, OCHbHaCHbHaNH), 3.03–3.15 (m, 1 H, OCHbHa-
CHbHaNH), 3.18–3.28 (m, 1 H, OCHbHaCHbHaNH), 3.30–3.45 (m,
1 H, OCHbHaCHbHaNH), 3.58 (dd, J5¢b,5¢a = –12.1 Hz, J5¢b,4¢ = 2.5
Hz, 1 H, H5′b), 3.69 (dd, J5¢a,5¢b = –12.1 Hz, J5¢a,4¢ = 3.1 Hz, 1 H,
H5′a), 4.01 (ddd, J4¢,3¢ = 3.3 Hz, J4¢,5¢a = 3.1 Hz, J4¢,5¢b = 2.5 Hz, 1 H,
H4′), 4.23 (s, 1 H, CH2-Thy), 4.31 (dd, J3¢,2¢ = 5.0 Hz, J3¢,4¢ = 3.3 Hz,
1 H, H3′), 4.63 (d, J = –6.9 Hz, 1 H, OCHbCHaO), 4.69 (d, J = –6.9
Hz, 1 H, OCHbCHaO), 4.72 (dd, J2¢,1¢ = 6.2 Hz, J2¢,3¢ = 5.0 Hz, 1 H,
H2′), 5.31 (br s, 1 H, OH)*, 5.44 (br s, 1 H, OH)*, 6.05 (d, J1¢,2¢ = 6.2
Hz, 1 H, H1′), 7.31 (s, 2 H, 6-NH2)*, 7.37 (s, 1 H, H6-Thy), 8.11 (br
t, J = 5.3 Hz, 1 H, NHCO,)*, 8.15 (s, 1 H, H8), 8.38 (s, 1 H, H2),
11.22 (br s, 1 H, NHThy); * exchangeable with D2O.
(11) Mikhailov, S. N.; Kulikova, I. V.; Nauwelaerts, K.;
Herdewijn, P. Tetrahedron 2008, 64, 2871.
(12) Bobkov, G. V.; Mikhailov, S. N.; Van Aerschot, A.;
Herdewijn, P. Tetrahedron 2008, 64, 6238.
(13) Scaringe, S. A. Methods Enzymol. 2000, 317, 3.
(14) Saneyoshi, H.; Seio, K.; Sekine, M. J. Org. Chem. 2005, 70,
10453.
(15) Semenyuk, A.; Foldesi, A.; Johansson, T.; Estmer-Nilsson,
C.; Blomgren, P.; Brannvall, M.; Kirsebom, L. A.;
Kwiatkowski, M. J. Am. Chem. Soc. 2006, 128, 12356.
(16) Cieslak, J.; Kauffman, J. S.; Kolodziejski, M. J.; Lloyd, J. R.;
Beaucage, S. L. Org. Lett. 2007, 9, 671.
(17) Parey, N.; Baraguey, C.; Vasseur, J.-J.; Debart, F. Org. Lett.
2006, 8, 3869.
(18) Shiba, Y.; Masuda, H.; Watanabe, N.; Ego, T.; Takagaki, K.;
Ishiyama, K.; Ohgi, T.; Yano, J. Nucleic Acids Res. 2007, 35,
3287.
13C NMR (100 MHz, DMSO-d6): 11.87 (Me-Thy), 38.51
(OCH2CH2NH2), 49.26 (CH2-Thy), 61.47 (C5′), 66.06
(OCH2CH2NH2), 69.36 (C3′), 78.37 (C2′), 86.27 (C4′), 86.36
(C1′), 94.20 (OCH2O), 108.01 (C5Thy), 119.30 (C5), 139.82 (C2),
142.41 (C6Thy), 149.03 (C4), 151.04 (C8), 152.56 (C6), 164.51
(C=O-Thy), 166.99 (C=O).
MS (APCI): m/z [M – H+] calcd for C20H25N8O8: 505.18; found:
505.11; m/z [M – H+ + HCOOH] calcd for C21H27N8O10: 551.19;
found: 551.13.
(19) Robins, M. J.; Hawrelak, S. D.; Hernandez, A. E.; Wnuk, S.
F. Nucleosides Nucleotides 1992, 11, 821.
UV (MeOH): lmax (log e) = 261 nm (3.982), pH 13; 262 nm (4.114),
pH 7; 261 nm (3.996), pH 1.
(20) Karpeisky, A.; Sweedler, D.; Haeberli, P.; Read, J.; Jarvis,
K.; Beigelman, L. Bioorg. Med. Chem. Lett. 2002, 12, 3345.
(21) (a) Kocieński, P. J. Protecting Groups; Georg Thieme
Verlag: Stuttgart, 2005, 171–173. (b) Wuts, P. G. M.;
Greene, T. W. Greene’s Protective Groups in Organic
Synthesis; J. Wiley & Sons: Hoboken, 2007, 356–360.
(22) Robins, M. J.; Wilson, J. S.; Sawyer, L.; James, M. N. G.
Can. J. Chem. 1983, 61, 1911.
Acknowledgment
This work was supported by the Russian Foundation for Basic Re-
search and Russian Academy of Sciences (Program ‘Molecular and
Cell Biology’).
(23) Efimtseva, E. V.; Mikhailov, S. N. Biochemistry (Moscow)
2002, 67, 1136.
References
(24) Efimtseva, E. V.; Mikhailov, S. N. Russ. Chem. Rev. (Engl.
Transl.) 2004, 73, 401.
(25) Efimtseva, E. V.; Kulikova, I. V.; Mikhailov, S. N. Curr.
Org. Chem. 2007, 11, 337.
(1) Markiewicz, W. T. J. Chem. Res., Synop. 1979, 24.
(2) Robins, M. J.; Wilson, J. S.; Hansske, F. J. Am. Chem. Soc.
1983, 105, 4059.
(3) Hansske, F.; Madej, D.; Robins, M. J. Tetrahedron 1984, 40,
(26) Efimtseva, E. V.; Kulikova, I. V.; Mikhailov, S. N.
125.
Molecular Biology (Moscow) 2009, 43, 301.
(4) Sproat, B. S.; Beijer, B.; Iribarren, A. Nucleic Acids Res.
1990, 18, 41.
(5) Cuenoud, B.; Casset, F.; Husken, D.; Natt, F.; Wolf, R. M.;
Altman, K.-H.; Martin, P.; Moser, H. E. Angew. Chem. Int.
Ed. 1998, 37, 1288.
(27) Verdegaal, C. H. M.; Jansse, P. L.; de Rooij, J. F. M.;
van Boom, J. H. Tetrahedron Lett. 1980, 21, 1571.
(28) Markiewicz, W. T.; Bartoszuk, A. Bull. Pol. Acad. Sci. 1984,
32, 453.
(29) Kulikova, I. V.; Muradova, D. A.; Mikhailov, S. N.
ARKIVOC 2009, (iii), 158.
(30) Chow, S.; Wen, K.; Sanghvi, Y. S.; Theodorakis, E. A.
Nucleosides, Nucleotides Nucleic Acids 2003, 22, 583.
(31) McBride, L. J.; Kierzek, R.; Beaucage, S. L.; Caruthers, M.
H. J. Am. Chem. Soc. 1986, 108, 2040.
(6) Kawasaki, A. M.; Casper, M. D.; Prakash, T. P.; Manalili, S.;
Sasmor, H.; Manoharan, M.; Cool, D. P. Tetrahedron Lett.
1999, 40, 661.
(7) Mikhailov, S. N.; Efimtseva, E. V.; Gurskaya, G. V.;
Zavodnik, V. E.; De Bruyn, A.; Rozenski, J.; Herdewijn, P.
J. Carbohydr. Chem. 1997, 16, 75.
(32) Jagtap, P.; Szabó, C. Nat. Rev. Drug Discovery 2005, 4, 421.
(33) Curtin, N. J. Expert Rev. Mol. Med. 2005, 7, 1.
(34) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem.
1997, 62, 7512.
(8) Markiewicz, W. T.; Niewczyk, A.; Gdaniec, Z.; Adamiak,
D. A.; Dauter, Z.; Rypniewski, W.; Chmielewski, M.
Nucleosides Nucleotides 1998, 17, 411.
Synthesis 2010, No. 22, 3827–3834 © Thieme Stuttgart · New York