Monomers containing 2′-O-alkoxymethyl groups as synthons for the oligonucleotide synthesis by the phosphotriester method

Article abstract of DOI:10.1134/S1068162011050025

A general scheme for the synthesis of ribonucleotides containing an alkoxymethyl group at the 2′-O-position of ribose and an O-nucleophilic catalytic 4-methoxy-1-oxido-2-picolyl phosphate-protecting group has been developed for the introduction into oligonucleotides during their solid-phase synthesis by the phosphotriester method. The scheme has been tested in the synthesis of monomers with 2′-O-modifying groups as examples: 2-azidoethoxymethyl, propargyloxymethyl, and 3,4-cyclocarbonatebutoxymethyl groups.

Full text of DOI:10.1134/S1068162011050025

ISSN 1068ꢀ1620, Russian Journal of Bioorganic Chemistry, 2011, Vol. 37, No. 5, pp. 586–592. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.V. Aralov, V.N. Klykov, O.G. Chakhmakhcheva, V.A. Efimov, 2011, published in Bioorganicheskaya Khimiya, 2011, Vol. 37, No. 5, pp. 654–661.
Monomers Containing 2'ꢀOꢀAlkoxymethyl Groups as Synthons
for the Oligonucleotide Synthesis by the Phosphotriester Method
A. V. Aralov, V. N. Klykov, O. G. Chakhmakhcheva1, and V. A. Efimov†
Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences,
ul. MiklukhoꢀMaklaya 16/10, Moscow, 117997 Russia
Received November 27, 2010; in final form January 31, 2011
Abstract—A general scheme for the synthesis of ribonucleotides containing an alkoxymethyl group at the
2'ꢀOꢀposition of ribose and an Oꢀnucleophilic catalytic 4ꢀmethoxyꢀ1ꢀoxidoꢀ2ꢀpicolyl phosphateꢀprotecting
group has been developed for the introduction into oligonucleotides during their solidꢀphase synthesis by the
phosphotriester method. The scheme has been tested in the synthesis of monomers with 2'ꢀ ꢀmodifying
O
groups as examples: 2ꢀazidoethoxymethyl, propargyloxymethyl, and 3,4ꢀcyclocarbonatebutoxymethyl
groups.
Keywords: phosphotriester method, azides, alkynes, aldehydes, conjugation, crosslink
DOI: 10.1134/S1068162011050025
†1
INTRODUCTION
bases. Therefore, the use of 2'ꢀmodifying groups for
this purpose seems to be a more promising trend.
Oligoribonucleotides containing residues of 2'ꢀOꢀ
One of the first known examples of this approach
involved the formation of conjugates between peptides
and oligonucleotides containing a 2'ꢀamino group [9,
10]. However, this reaction proceeded ineffectively,
modified nucleotides are widely used at present in
molecular biology for the regulation of gene expresꢀ
sion. In particular, they are employed in the synthesis
of small interfering RNAs (siRNAs) [1, 2] and antiꢀ
sense oligonucleotides [3, 4], the preparation of conꢀ and the resulting amide bond led to a destabilization of
jugates stabilizing the structure of NA, and for the
covalent linking of reporter groups, e.g., fluorescent
and spin labels, as well as labels for the electrochemiꢀ
cal detection of NAs [5]. In addition, of great interest
are conjugates of NA with compounds facilitating
their entry into the cell, e.g., cholesterol or polycaꢀ
tionic molecules [6], and with biopolymers accomꢀ
plishing their targeted delivery, e.g., peptides and carꢀ
bohydrates [7].
the duplex of the oligonucleotide with the compleꢀ
mentary target [11]. Later, an approach was developed
in which a group containing the aldehyde function was
introduced into ribonucleotides, which enabled one to
perform a highly effective conjugation with various
organic molecules with the formation of the imino
group, thiazolidine, oxime or hydrazine bonds [12, 13].
Besides, the oxo group can be converted into a reactive
hydrazine group [14].
In the literature, conjugates of NAs with peptides
coupled to the terminal 3'ꢀ and 5'ꢀOH functions or the
heterocyclic bases of nucleotides have been described
[8]. In the first case, the number of peptides attached
to NA and their position are restricted; in the second
case, the thermal stability of duplexes formed by the
modified chain with a complementary target someꢀ
times decreases, due to the adverse effect of substituꢀ
ents on the hydrogen bonding between nitrogenous
The introduction of the acetylene function into the
2'ꢀ
Oꢀmodifying group made it possible to perform the
[3 + 2]ꢀdipolar cycloaddition reaction catalyzed by
Cu(I) [15]. In recent years, attention of many investiꢀ
gators has also been given to the development of
chemical methods of synthesis of cyclic [16–18] and
crossꢀlinked oligonucleotides [19–24], in particular,
for studying the mechanism of DNA repair [21, 25]
and the preparation of nanostructures [26].
Abbreviations: DBU, diazabicyclo[5.4.0]undecꢀ7ꢀene; DMTr,
The goal of this study was to develop methods for
4,4'ꢀdimethoxytrityl; NIS,
N
ꢀiodosuccinimide; TEA, triethylꢀ
the synthesis of monomers containing an
philic catalytic 4ꢀmethoxyꢀ1ꢀoxidoꢀ2ꢀpicolyl phosꢀ
phateꢀprotecting group and 2'ꢀ ꢀalkoxymethyl modiꢀ
Oꢀnucleoꢀ
amine; TBAF, tetraꢀnꢀbutylammonium fluoride; TfOH, trifluoꢀ
romethanesulfoacid; TPS, 2,4,6ꢀtriisopropylbenzenesulfonyl
chloride.
O
1
Corresponding author: phone: (495) 336ꢀ59ꢀ11; fax: (495) 330ꢀ
67ꢀ38; eꢀmail: eva@mx.ibch.ru.
Recently deceased.
fying groups for their introduction into the oligonucleꢀ
otide chain by the phosphotriester method.
†
586

MONOMERS CONTAINING 2'ꢀ
O
ꢀALKOXYMETHYL GROUPS
587
DMSO, Ac O
2
AcOH
ROH
ROCH2SCH3
IIа–c
(
Iа–c
)
(
)
NIS, TfOH
THF
B
O
O
Si
H
O
H
H
H
OH
O
Si
(III)
B
B
HO
O
O
O
Si
TBAF
THF
DMTrꢀCl
Py
H
H
O
H
O
H
H
Si
H
H
H
O
O
OH
OR
IVа–c
OR
(
)
(Vа–c)
H3CO
Oᮎ
P
O
O
N
O
1)
+ TPSꢀCl
B
O
B
DMTrO
DMTrO
R1
O
O
H
H
H
H
O
H3CO
R2
H
H
H
H
O
OH
O
O P O
Oᮎ
2) DBU/H O/CH CN for
а
and
b
2
3
or TEA/H O/CH CN for
OR
OR
VIIа–c)
c
2
3
1
2
а, b: R = Cl, R = H
: R = H, R = NO
N
O
(VIа–c
)
(
1
2
c
2
R =
a
b
c
: –CH2CH2N3
: –CH2C CH
: –CH2CH2CHO(CO)OCH2
B = Ura for
а and b
c
B = CytBz for
≡
Scheme 1.
RESULTS AND DISCUSSION
As an extension of studies devoted to the developꢀ
ment of the phosphotriester method for the synthesis
of modified RNA fragments, we obtained monomers
with 2'ꢀOꢀalkoxymethyl groups containing a catalytic
Unfortunately, attempts of targeted introduction
into the oligonucleotide chain of 3'ꢀOꢀphosphoroamiꢀ
dites of nucleosides [27] bearing azidoꢀcontaining
groups at the 2'ꢀposition failed [15] since the azide
group adversely affects the efficiency of internucleꢀ
otide condensation due to the formation of iminoꢀ
phosphorane by the reaction of Staudinger [28]. An
alternative approach, which enables the targeted
introduction of azidoꢀcontaining modifying and proꢀ
tective groups into oligonucleotides during the chain
elongation is the phosphotriester method, that is based
4ꢀmethoxyꢀ1ꢀoxidoꢀ2ꢀpicolyl phosphateꢀprotecting
group (Scheme 1). Methylthiomethyl derivatives
(
(
IIa)–(IIc) were obtained by treating the alcohols
Ia)–(Ic) with a mixture of DMSO, acetic anhydride,
and acetic acid, as described in [32]. 2'ꢀ
thyl modifying groups were introduced by treating the
3',5'ꢀ ꢀprotected derivative (III) with the appropriate
ꢀacetal (IIa)–(IIc) in the presence of TfOH and
OꢀAlkoxymeꢀ
O
O,S
NIS in dry THF. It should be noted that the synthesis
of compound (IVa) was earlier described by Bobkov et
al.; however, the method of its synthesis involved three
stages with a total yield of as little as 50–55% [33],
whereas our method made it possible to obtain this
on the Oꢀnucleophilic intramolecular catalysis at the
stage of the internucleotide link formation [29–31].
We have earlier demonstrated this in the synthesis of
2'ꢀOꢀazidomethylꢀ and 2'ꢀOꢀ(2ꢀazidomethyl)benꢀ
zoylꢀcontaining oligonucleotides [29, 30].
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 37
No. 5
2011

588
ARALOV et al.
compound in one stage with a yield of 78%. Subseꢀ
quent removal of the silyl protecting group from comꢀ nyl)phosphate (VIII) with 1ꢀoxidoꢀ4ꢀmethoxyꢀ2ꢀ
(X) obtained by the condensation of bis(4ꢀnitropheꢀ
pounds of the type (IV) by TBAF and the introduction
of the 5'ꢀ ꢀdimethoxytrityl group led to 5'ꢀ ꢀDMTrꢀ
2'ꢀ ꢀmodified derivatives (VIa)–(VIc).
In the case of compounds (VIa) and (VIb), the
introduction of a phosphate residue containing a
4ꢀmethoxyꢀ1ꢀoxidoꢀ2ꢀpicolyl group and the selective
splitting of 2ꢀchlorophenyl phosphoester was successꢀ
fully carried out as described previously (treatment
with DBU) [30]. However, the treatment of (VIc) in
pyridinemethanol in the presence of TPSꢀCl followed
by the selective removal of one 4ꢀnitrophenyl group
from the phosphotriester (IX) by TEA in an aqueous
organic medium (Scheme 2). The phosphorylation of
O
O
O
(
VIc) by phosphodiester (X) in the presence of a conꢀ
densation reagent followed by treatment with TEA in
an aqueous organic medium gave monomer (VIIc).
The introduction of the monomer (VIIc) into the oligoꢀ
nucleotide structure with the subsequent removal of the
cyclocarbonate protecting group after the termination
of chain elongation by the treatment with a base (in parꢀ
ticular, DBU) followed by the periodate oxidation of
this way led to a quantitative removal of its 2'ꢀOꢀcycloꢀ
carbonate group. We found that this group remains
resistant to TEA in aqueous organic medium at least
within 24 h. Therefore, phosphate group was introꢀ the resulting diol system makes it possible to obtain oliꢀ
duced into the compound (VIc) using phosphodiester gonucleotides containing 2'ꢀ
Oꢀaldehyde groups.
OCH3
OCH3
O2N
+ TPSꢀCl
O2N
HO
O
P
N
O
O
P
Oᮎ
O
O
O
O
O
N
Py
O
(IX)
(VIII
)
O2N
O2N
OCH3
O
O P O
Oᮎ
TEA
H O, CH CN
O2N
2
3
N
O
(X)
Scheme 2.
At present, we use synthons (VIIa)–(VIIc), which gates with organic molecules and crossꢀlinks with oliꢀ
gonucleotides containing the amino group.
contain a (2ꢀazidoethoxy)methyl, a propargyloxymeꢀ
thyl, or a (3,4ꢀcyclocarbonatebutoxy)methyl group at
the 2'ꢀOꢀposition, in the solidꢀphase synthesis of modꢀ
EXPERIMENTAL
ified oligonucleotides for the introduction of the corꢀ
responding modified units at different sites of the oligoꢀ
nucleotide chain. In addition, studies are carried out to
determine the conditions for the preparation of conjuꢀ
gates of these modified oligonucleotides with other
organic molecules and crossꢀlinked NA fragments.
Solvents and reagents were purchased from comꢀ
mercial sources and were used without additional
purification. 2ꢀAzidoethanol (Ia) was obtained from
2ꢀchloroethanol by the method described in [36].
NMR spectra (δ, ppm J, Hz) were recorded in CDCl3
Thus, by using 2'ꢀOꢀalkoxymethyl modifying groups:
or DMSOꢀd6 on a Bruker DPX300 device (Germany)
at a working frequency of 300 (1H) and 121.5 MHz
(31P). Chemical shifts are given relative to tetramethꢀ
ylsilane (1H) and H3PO4 (31P). Mass spectra were meaꢀ
sured in the linear mode with the registration of posiꢀ
tive and negative ions on an Ultraflex II MALDIꢀTOF
mass spectrometer (Bruker Daltonics). Column chroꢀ
matography was carried out on Silicagel 60 (Merck).
TLC was performed on Silicagel 60 F254 plates
the 2ꢀazidoethoxymethyl and the propargyloxymethyl
groups, after the introduction of the appropriate monoꢀ
mers into the oligonucleotide chain, it would be possiꢀ
ble to obtain conjugates with other organic molecules,
as well as cyclic singleꢀstrand and crossꢀlinked doubleꢀ
strand NA fragments by the [3 + 2]ꢀdipolar cycloaddiꢀ
tion reaction catalyzed by Cu(I) ions [15, 19, 34, 35]. In
turn, the (3,4ꢀcyclocarbonatebutoxy)methyl group
would enable one to generate a reactive aldehyde funcꢀ
(Merck) using the following systems: (A) CHCl3
–
tion [12–14], which can be useful in obtaining conjuꢀ hexane 1 : 1; (B) CHCl3–CH3OH–H2O, 65 : 25 : 4;
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 37
No. 5
2011

MONOMERS CONTAINING 2'ꢀ
O
ꢀALKOXYMETHYL GROUPS
589
(C) CHCl3–CH3OH, 9 : 1; and (D) CHCl3–CH3OH, (1 H, dd,
J
8.6, 8.0, CHO(CO)C
8.6, 7.4, CHO(CO)C
OС 2CH2), 2.13 (3 H, s, SCH3), 2.13–1.97 (2 H, m,
OСH2CH2).
H
αO), 4.18 (1 H, dd,
J
H
βO), 3.74–3.60 (2 H, m,
39 : 1. Derivatives (IIa)–(IIc) were detected on TLC
plates by iodine vapors.
H
1,2ꢀOꢀCyclocarbonatebutaneꢀ1,2,4ꢀtriol (Ic). A
mixture of 1,2,4ꢀbutanetriol (5.31 g, 50 mmol),
diphenylcarbonate (10.71 g, 50 mmol), and sodium
bicarbonate (1.01 g, 12.0 mmol) in anhydrous DMF
(75 ml) was refluxed for 5 min. After cooling to room
temperature, chloroform (150 ml) was added to the
reaction mixture, and the target product was
A General Method of Introducing
2'ꢀOꢀModifying Groups into Nucleosides
Molecular sieves (4 Å, 0.4 g) and 2.0 mmol of the
corresponding methylthiomethyl ester (IIa)–(IIc
)
were added to a solution of 5',3'ꢀ ꢀ(tetraisopropyldiꢀ
O
extracted with water (
extracts were evaporated to dryness, and the residue
was dried by evaporation with acetonitrile ( 50 ml).
3 × 100 ml). Combined water
siloxaneꢀ1,3ꢀdiyl)nucleoside (III) (1 mmol) in dry
THF (4 ml). Then TfOH (2.0 mmol) and a 1.0 M soluꢀ
tion of NIS (2.0 ml) in dry THF were added under stirꢀ
2
×
The product was purified by chromatography on a
silica gel column in a gradient of methanol (0–3%) in
ring and cooling to –40°С. The mixture was stirred at
–40 for 30 min, the reaction was terminated by the
°С
chloroform. Fractions containing compound (Ic
)
addition of TEA (5.0 mmol), and the reaction solution
was filtered, diluted with ethyl acetate (20 ml), and
washed with a saturated aqueous sodium thiosulfate
were evaporated to foam and dried in vacuo. Yield:
1
2.58 g (39%). Rf 0.55 (D); H NMR (DMSOꢀ
d
6):
solution (2 × 10 ml). The organic layer was evaporated
4
J
.93–4.83 (1 H, m,
5.0, ), 4.57 (1 H, dd,
CHO(CO)CH2O), 4.68 (1 H, t,
to oil, and the residue was purified by chromatography
on a silica gel column in a gradient of chloroform (50–
100%) in hexane. Fractions containing the target
compound (IV) were evaporated to foam, and the resꢀ
idue was dried in vacuo.
O
H
J
8.3, 7.9,
CHO(CO)C
CHO(CO)C
1
H
αO), 4.19 (1 H, dd, J 8.3, 7.4,
H
βO), 3.59–3.43 (2 H, m, OСH2CH2),
.95–1.76 (2 H, m, OСH2CH2).
5',3'ꢀOꢀ(Tetraisopropyldisiloxaneꢀ1,3ꢀdiyl)ꢀ2'ꢀOꢀ
A General Method for the Synthesis
of Methylthiomethyl Derivatives IIa)–(IIc
[(2ꢀazidoethoxy)methyl]uridine (IVa). Yield: 78%;
(
)
Rf 0.75 (D); 1H NMR (CDCl3): 9.11 (1 H, s,
N
H
'
Ura), 7.87 (1 H, d,
), 5.67 (1 H, d, 8.3,
7.2, OC 2O), 4.25 (1 H, d,
(2 H, m, 3'), 4.13 (1 H, dd,
(1 H, dd, 13.8, 2.2, ), 3.93–3.88 (1 H, m,
β5
OC
αCH2N3), 3.81–3.76 (1 H, m, OC βCH2N3),
.49–3.40 (2 H, m, OCH2C 2N3),1.12–0.94 (28 H, m,
+ Na]+, calculated
J
H
8.3,
Ura), 5.00 (2 H, dd,
13.8, ), 4.24–4.19
α5
9.3, 2.2, ), 3.98
H
6
Ura), 5.75 (1 H, s,
A solution of 1 mmol of the corresponding alcohol
Ia)–(Ic) in DMSO (2.8 ml) was treated for 48 h with
acetic anhydride (0.57 ml, 6 equivalents) and acetic
acid (0.95 ml, 16.6 equivalents) at room temperature.
Then a saturated aqueous NaHCO3 solution was
added at room temperature under stirring to the reaction
mixture until the gas liberation terminated, and the prodꢀ
H1
J
5
J
8.3,
(
H
H
J
H '
2
J
'
,
H
J
H4'
H '
H
H
3
H
H
uct was extracted with ethyl acetate (
The organic layer was separated, washed with a saturated
aqueous NaCl solution ( 30 ml), and dried over
2 × 15 ml).
Priꢀgroups); MS, m/z: 608.38 [
M
for C24H43N5NaO8Si2+
М
608.25; 624.34 [
+ K]+, calꢀ
M
3
×
Na2SO4. The solvent was distilled in vacuo, and the
product was purified by chromatography on a silica gel
column in a gradient of chloroform (0–15%) in hexꢀ
ane in the case of derivatives (IIa)–(IIb) and in a graꢀ
dient of chloroform (0–50%) in hexane in the case of
culated for C24H43KN5O8Si+2 624.23
5',3'ꢀ ꢀ(Tetraisopropyldisiloxaneꢀ1,3ꢀdiyl)ꢀ2'ꢀ
(propargyloxymethyl)uridine (IVb). Yield: 80%; Rf
0.70 (D); 1H NMR (CDCl3): 8.74 (1 H, s,
Ura),
7.88 (1 H, d, 8.3, Ura), 5.75 (1 H, s, ), 5.67
(1 H, dd, 8.3, 1.9, Ura), 5.10 (1 H, d, 7.0,
OC
αO), 5.03 (1 H, d, βO), 4.38 (2 H, d,
4J 2.3, OC
2C ), 4.26 (1 H, d,
(1 H, dd, 9.6, 4.4,
4.14 (1 H, dd, 9.6, 1.7,
1.7,
β5 ), 2.41 (1 H, t, 4J 2.3, C
m,
Priꢀgroups); MS, m/z: 577.38 [
lated for C25H42N2NaO8Si+2 577.24
4ꢀBenzoylꢀ5',3'ꢀ
ꢀ(tetraisopropyldisiloxaneꢀ1,3ꢀ
diyl)ꢀ2'ꢀ ꢀ[(3,4ꢀ ꢀcyclocarbonatebutoxy)methyl]cytiꢀ
dine (IVc). Yield: 82%; Rf 0.60 (D); 1H NMR
(CDCl3): 8.73 (1 H, br s, Cyt), 8.36 (1 H, d, 7.6,
Cyt), 7.92–7.48 (6 H, m, Bz, Cyt), 5.80
.
O
Oꢀ
N
H1'
H
(
IIc). Fractions containing product (II) were evapoꢀ
J
H
6
rated to oil and dried by an oil pump.
J
J
H
J
5
J
Methylthiomethyl ester of 2ꢀazidoethanol (IIa).
H
7.0, OC
H
J
1
Yield: 59%; Rf 0.50 (А). H NMR (CDCl3): 4.58
H
≡
J
13.7,
H
α5
4.4,
'
), 4.21
2'),
13.7,
), 1.13–0.93 (28 H,
+ Na]+, calcuꢀ
(2 H, s, OC
.86–3.82 (1 H, m, OC
OCH2C 2N3), 2.09 (3 H, s, SCH3).
Methylthiomethyl ester of 2ꢀpropinꢀ1ꢀol (IIb).
Yield: 61%; Rf 0.50 (А). 1H NMR (CDCl3): 4.52 (2 H,
s, OC 2C ), 2.43 (1 H,
2S), 4.41 (2 H, d, 4J 2.3, OC
t, 4J 2.3, C
), 2.08 (3 H, s, SCH3).
Methylthiomethyl ester of 1,2ꢀ
butaneꢀ1,2,4ꢀtriol (IIc). Yield: 64%; Rf 0.20 (А).
1H NMR (CDCl3):
.92–4.81 (1 H, m,
O(CO)CH2O), 4.61 (2 H, d, 0.9, OC 2S), 4.55
H
2S), 3.98–3.91 (1 H, m, OC
H
αCH2N3),
J
H
3'), 4.18 (1 H, d,
J
H
3
H
βCH2N3), 3.51–3.43 (2 H, m,
J
H4'), 3.98 (1 H, dd, J
H
H
H
'
H≡
M
.
H
H ≡
H≡
N
O
O
O
Oꢀcyclocarbonateꢀ
N
H
J
4
CH
J
H
H6
H
H5
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 37
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2011

590
ARALOV et al.
(1 H, d,
J
1.6,
H
1
'
), 5.05–4.80 (3 H, m, OC
.65–4.62 (1 H,
αO), 4.34–4.13 (5 H, m, 2', 3',
, CHO(CO)C
βO), 4.06–3.89 (1 H, m,
.76–3.65 (2 H, m, OС
H
2O, (3 H, m, OC
m,
H
2O, C
m, CHO(CO)C
αO), 4.21–4.09 (3 H, m,
CHO(CO)C
βO), 3.97–3.92 (1 H, m,
3.77 (1 H, m, ), 3.70–3.58 (3 H, m, OС
α5
β5
), 2.02–1.93 (2 H, m, OСH2CH2); MS, m/z:
492.20 [
HO(CO)CH2O), 4.62–4.54 (1 H,
C
H
O(CO)CH2O),
CHO(CO)C
α5
4
H
H2', H3',
H
H
H
H4',
H
H4
'
), 3.85–
2CH2,
H
'
H
H '),
β5
2CH2), 2.11–1.97 (2 H, m,
H
'
H
3
H
H
'
Priꢀgroups); MS,
M
+ H]+, calculated for C22H26N3O1+0 492.16;
M
+ Na]+, calculated for C22H25N3NaO+10
OСH2C
H
2), 1.14–0.94 (28 H, m,
H
m
/
z: 734.32 [
734.31; 756.30
C34H51N3NaO11Si+2 756.30; 772.28 [
lated for C34H51KN3O11Si+2 772.27
M
+ H]+, calculated for C34H52N3O11Si+2
Na]+
calculated for
+ K]+, calcuꢀ
514.19 [
514.14; 530.16
C22H25KN3O+10 530.12
[
M
+
,
[
M
+
K]+
,
calculated for
M
.
.
A General Method of the Tritylation of Nucleosides
A 2'ꢀ ꢀprotected derivative of type ( ) (1 mmol)
was dried by evaporation with pyridine after which dry
pyridine (5 ml) and DMTrꢀCl (0.41 g; 1.2 equivalent)
were added. The reaction mixture was allowed to stand
for 2 h at room temperature, the reaction was termiꢀ
nated by adding 1 M TEAB (5 ml), and the product
A General Method of Desilylation of Nucleosides
O
V
A 1 M TBAF solution (2.2 ml, 2.2 mmol) in dry THF
was added to a solution of 1 mmol 2'ꢀOꢀprotected
5',3'ꢀ ꢀ(tetraisopropyldisiloxaneꢀ1,3ꢀdiyl)nucleoside
O
derivative of type (IV) in dry THF (5 ml). After 2 h, the
solution was evaporated to oil, and the product was puriꢀ
fied by chromatography on a silica gel column in a graꢀ
dient of methanol (0–7%) in chloroform. Fractions
containing the target compound (V) were combined
and evaporated to dryness, and the residue was dried
in vacuo.
was extracted with chloroform (2 × 20 ml). Combined
organic fractions were evaporated to oil and evapoꢀ
rated again with toluene to remove pyridine traces.
The product was separated by chromatography on a
silica gel column in a gradient of methanol (0–2%) in
chloroform containing 0.1% TEA. Fractions containꢀ
ing the product (VI) were combined, evaporated to
dryness, and dried in vacuo.
2'ꢀ
O
ꢀ[(2ꢀAzidoethoxy)methyl]uridine (Va). Yield:
88%;
R
f 0.30 (C). 1H NMR (DMSOꢀ
d6): 11.28 (1 H,
s,
J
J
N
H
Ura), 7.92 (1 H, d,
5.2, H ), 5.64 (1 H, d,
5.5, O 3'), 5.10 (1 H, t,
2O), 4.17 (1 H, t, 5.0,
), 3.90–3.87 (1 H, m,
OC 2CH2N3), .46–3.35 (2 H, m,
2N3); MS, m/z: 366.26 [
+ Na]+, calcuꢀ
J
J
8.3,
8.3,
5.1, O
), 4.13 (1 H, dd,
), 3.69–3.55 (4 H,
H
6
Ura), 5.90 (1 H, d,
1
H
'
H5 Ura), 5.18 (1 H, d,
5'ꢀ
methyl]uridine (VIa). Yield: 84%; Rf 0.65 (D);
1H NMR (DMSOꢀ
6): 11.34 (1 H, s, Ura), 7.72
(1 H, d, 8.1, Ura), 7.41–7.23 (9 H, m, Ar DMTr),
6.92–6.89 (4 H, m, Ar DMTr), 5.87 (1 H, d, 3.2
), 5.33 (1 H, d, 8.1, Ura 5), 5.29 (1 H, d, 5.8,
3'), 4.82 (2 H, s, OC 2O), 4.28–4.24 (2 H, m,
), 4.01–3.98 (1 H, m, ), 3.75 (6 H, s, OCH3
DMTr), 3.73–3.65 (2 H, m, OC 2CH2N3), 3.46–3.37
(2 H, m, OCH2C 2N3), 3.31 (1 H, dd, 10.7, 4.4,
α5 β5'); MS, m/z: 668.27
), 3.26 (1 H, dd, 10.7, 2.6,
Oꢀ(4,4'ꢀDimethoxytrityl)ꢀ2'ꢀOꢀ[(2ꢀazidoethoxy)
J
H
5'), 4.76 (2 H, s,
OCH
J
H
2'
J
5.0,
d
NH
9.9,
H
H
3
'
5
H4'
J
H6
m,
',
H
3
J
,
OCH2C
H
M
H
O
H
1
H
'
J
H
J
lated for C12H17N5NaO+7 366.10; 382.23 [
+ K]+
calculated for C12H17KN5O+7 382.08
2'ꢀ ꢀ(Propargyloxymethyl)uridine (Vb). Yield:
74%; Rf 0.25 (C); 1H NMR (DMSOꢀ
6): 11.28 (1 H,
s, Ura), 7.92 (1 H, d, 8.3, Ura), 5.88 (1 H, d,
), 5.64 (1 H, dd, 8.3, 2.2, Ura), 5.20
5.5, O 3'), 5.11 (1 H, t, 5.0, O
6.9, OC 6.9, OC
αO), 4.77 (1 H, d,
2C ), 4.14 (1 H, t,
5.0, 9.9,
), 3.68–3.64 (1 H, m,
α5
), 3.35 (1 H, t, 4J 2.5, C
); MS, m/z: 335.24 [
Na]+, calculated for C13H16N2NaO+7 335.09; 351.21
+ K]+, calculated for C13H16KN2O+7 351.06
4ꢀBenzoylꢀ2'ꢀ
ꢀ[(3,4ꢀ ꢀcyclocarbonatebutoxy)
methyl]cytidine (Vc). Yield: 85%; Rf 0.20 (C); OCH3 DMTr), 3.42 (1 H, t, 4J 2.5, C
1H NMR (DMSOꢀ
6): 11.28 (1 H, br s, Cyt), 8.54 (2 H, m,
'); MS, m/z: 637.18 [
+ Na]+, calculated
(1 H, dd, 7.6, 3.0, Cyt), 8.03–7.48 (5 H, m,
M
,
H
H2',
3'
H4'
.
H
H
J
O
H
'
J
H
d
+ Na]+, calculated for C33H35N5NaO+9 668.23;
684.25 [
+ K]+, calculated for C33H35KN5O+9 684.21
5'ꢀ ꢀ(4,4'ꢀDimethoxytrityl)ꢀ2'ꢀ ꢀ(propargyloxyꢀ
N
5.0,
H
J
H6
[
M
J
H1
'
J
H5
M
.
(1 H, d,
J
J
H
H
J
H
5'), 4.80
H
J
(1 H, d,
J
βO),
5.0,
O
O
4.20 (2 H, d, 4J 2.5, OC
H ≡
methyl)uridine (VIb). Yield: 88%; Rf 0.60 (D);
1H NMR (DMSOꢀ
6): 11.38 (1 H, d, 2.0, N Ura),
7.72 (1 H, d, 8.1, Ura), 7.41–7.21 (9 H, m,
Ar DMTr), 6.94–6.87 (4 H, m, Ar DMTr), 5.83 (1 H,
d, 3.4, H ), 5.36 (1 H, d, 6.0, O 3'), 5.28 (1 H, dd,
8.1, 2.2, Ura), 4.86 (1 H, d, 7.0, OC
αO), 4.82
(1 H, d, 7.0, OC
βO), 4.30–4.19 (4 H, m,
OC 2C ), 4.02–3.96 (1 H, m, ), 3.74 (6 H, s,
), 3.34–3.16
H
m,
H
2
'
), 4.11 (1 H, dd,
J
H3'), 3.90–3.87 (1 H,
d
J
H
H
'
4'
H '), 3.59–3.55 (1 H, m,
J
H6
β5
H≡
M +
J
1'
J
H
J
H5
J
H
[M
.
J
≡
H
H2', H3',
H
H4'
N
O
O
H≡
d
NH
H5
M
for C34H34N2NaO+9 637.22; 653.16 [
+ K]+, calcuꢀ
M
J
H6
J
H
H
Bz), 7.34 (1 H, br d, 7.6, Cyt), 5.87 (1 H, br s,
H5
lated for C34H34KN2O+9 653.19
), 5.28–5.20 (2 H, m, 3', O 5'), 4.92–4.77
.
1'
OH
H
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 37
No. 5
2011

MONOMERS CONTAINING 2'ꢀ
O
ꢀALKOXYMETHYL GROUPS
591
with 20 equivalents of TEA in an acetonitrile–water
mixture 10 : 1. The product was purified by chromaꢀ
tography on a silica gel column in a gradient of methꢀ
anol (0–15%) in chloroform containing 0.1% TEA.
Fractions containing the target compound were comꢀ
bined, evaporated to dryness, and the residue was
dried in vacuo.
N
4ꢀBenzoylꢀ5'ꢀ
ꢀcyclocarbonatebutoxy)methyl]cytidine (VIc). Yield:
Oꢀ(4,4'ꢀdimethoxytrityl)ꢀ2'ꢀOꢀ[(3,4ꢀ
O
1
93%; Rf 0.50 (D); H NMR (DMSOꢀ
d6): 11.30 (1 H,
br s, Cyt), 8.39 (1 H, dd, 7.6, 1.5,
N
H
J
H6
Cyt), 8.03–
Bz), 7.45–7.24 (9 H, m, Ar DMTr),
7.6, Cyt), 6.96–6.89 (4 H, m,
), 5.34 (1 H, dd, 7.2, 3.2,
3'), 4.99–4.81 (3 H, m, OC 2O, C O(CO)CH2O),
.63–4.56 (1 H, m, CHO(CO)C
αO), 4.41–4.32 (1 H,
m, ), 4.22–4.15 (2 H, m, , CHO(CO)C
βO),
.11–4.05 (1 H, m, ), 3.76 (6 H, s, OCH3 DMTr),
3.73–3.64 (2 H, m, OС 2CH2), 3.43–3.33 (2 H, m,
), 2.05–1.96 (2 H, m, OСH2CH2); MS, m/z:
7.49 (5 H, m,
7.14 (1 H, d,
H
J
H5
Ar DMTr), 5.85 (1 H, br s,
H
1'
J
O
H
H
H
Triethylammonium salt of 5'ꢀ
tyl)ꢀ2'ꢀ ꢀ[(2ꢀazidoethoxy)methyl]uridine
oxidoꢀ4ꢀmethoxyꢀ2ꢀpicolyl)phosphate (VIIa). Yield:
79%;
f 0.45 (B); 1H NMR (CDCl3): 9.35 (1 H, br s,
Ura), 8.08 (1 H, d, 7.2, picolyl), 7.73 (1 H,
8.2, Ura), 7.37–7.19 (10 H, m, Ar DMTr,
picolyl), 6.84–6.77 (4 H, m, Ar DMTr), 6.71 (1 H,
7.2, 3.4, picolyl), 6.11 (1 H, d, 5.6, ),
.21–5.07 (3 H, m, PꢀOCH2 Ura), 5.05–4.94
(2 H, m, OC ), 4.77 (1 H, d, 7.0, OC
αO, βO),
.58–4.53 (1 H, m, ), 4.43–4.39 (1 H, m, ),
3.79 (3 H, s, OCH3 picolyl), 3.77 (6 H, d, 1.4, OCH3
DMTr), 3.72–3.67 (2 H, m, OC 2CH2N3), 3.57–
O
ꢀ(4,4'ꢀdimethoxytriꢀ
4
H
O
3'ꢀ ꢀ(1ꢀ
O
H
3'
H2'
H
R
4
H4'
NH
J
H6
H
d,
J
H6
H5'
H
dd,
3
816.27 [
+ Na]+, calculated for C43H43N3NaO+12
816.27; 832.22 calculated for
K]+
C43H43KN3O+12 832.25
M
J
H5
J
H1'
5
, H5
[
M
+
,
H
H3
'
J
H
.
4
H2
'
H4'
Triethylammonium salt of (4ꢀnitrophenyl)ꢀ(1ꢀ
oxidoꢀ4ꢀmethoxyꢀ2ꢀpicolyl)phosphate (X). A mixture
of 1ꢀoxidoꢀ4ꢀmethoxyꢀ2ꢀpyridinemethanol monohyꢀ
drate (0.52 g, 3.0 mmol) and pyridinium bis(4ꢀnitroꢀ
phenyl)phosphate (VIII) (1.12 g, 3.3 mmol) was evapꢀ
orated with pyridine to remove moisture traces, the
residue was dissolved in dry pyridine (15 ml), and
TPSꢀCl (1.51 g, 5 mmol) was added. The reaction
mixture was allowed to stand at room temperature for
15 min, diluted with CHCl3 (30 ml), and washed with
J
H
3.47 (2 H, m, OCH2CH2N3), 3.37–3.32 (2 H, m,
H
5
'
), 3.03 (6 H, q,
J
7.3, CH2 +HNEt3), 1.29 (9 H, t,
;
31P NMR (CDCl3): ꢀ0.14. MS,
J
7.3, CH3 +HNEt3)
m/z: 861.12 [M – TEAꢀH+]–, calculated for
C40H42N6O14P– 861.25
Triethylammonium salt of 5'ꢀ
tyl)ꢀ2'ꢀ ꢀ(propargyloxymethyl)uridine 3'ꢀ
4ꢀmethoxyꢀ2ꢀpicolyl)phosphate (VIIb). Yield: 80%;
.
O
ꢀ(4,4'ꢀdimethoxytriꢀ
O
Oꢀ(1ꢀoxidoꢀ
water (2 × 20 ml). The organic layer was evaporated to
1
R
f 0.45 (B); H NMR (CDCl3): 9.30 (1 H, br s,
Ura), 8.08 (1 H, d, 7.2, picolyl), 7.70 (1 H, d,
8.3, Ura), 7.36–7.17 (10 H, m, Ar DMTr, picꢀ
olyl), 6.84–6.77 (4 H, m, Ar DMTr), 6.71 (1 H, dd,
7.2, 3.4, picolyl), 6.13 (1 H, d, 6.1, ), 5.22–
5.07 (3 H, m, PꢀOCH2 Ura), 5.04–4.94 (2 H, m,
OC ), 4.85 (1 H, d, 7.2, OC
αO, βO), 4.63–4.55
(1 H, m, ), 4.45–4.39 (1 H, m, ), 4.20 (2 H,
ddd, 2C ), 3.79 (3 H, s,
24.8, 16.0, 4J 2.1, OC
OCH3 picolyl), 3.77 (6 H, br s, OCH3 DMTr), 3.57–
3.43 (2 H, m, ), 3.04 (6 H, q,
7.3, CH2 +HNEt3),
2.35 (1 H, t, 4J 2.1, C
), 1.30 (9 H, t, 7.3, CH3
+HNEt3); 31P NMR (CDCl3): ꢀ0.21. MS, m/z: 830.08
M – TEAꢀH+]–, calculated for C41H41N3O14P–
830.23
NH
oil, dissolved in 20 ml of an acetonitrile–water mixꢀ
ture (9 : 1, v/v), and TEA was added (2.8 ml,
20 mmol). The reaction mixture was held for 2 h at
room temperature and evaporated to oil. The target
product was purified by chromatography on a silica gel
column in a gradient of methanol (5–20%) in chloroꢀ
form. Fractions containing the substance were comꢀ
bined, evaporated to dryness, and dried in vacuo.
J
H6
J
H6
H3
J
H5
J
H1'
, H5
H
H
H
3
2
'
J
H
H4'
'
J
H ≡
1
Yield: 0.87 g (81%); Rf 0.30 (B); H NMR (CDCl3):
.14–8.08 (2 H, m,
8
H
Ar), 8.07 (1 H, d,
J
7.2,
Ar), 7.09 (1 H, d,
7.2, 3.4, picolyl), 5.22
H
6
picꢀ
H5
'
J
olyl), 7.43–7.37 (2 H, m,
picolyl), 6.71 (1 H, dd,
(2 H, d,
3.07 (6 H, q,
+HNEt3–C
354.92 [M – TEAꢀH+]–, calculated for C13H12N2O8P–
355.03
H
J
3.4, H3
H≡
J
J
H5
J
7.2, PꢀOC
7.3, +HNEt3ꢀC
3). 31P NMR (CDCl3): ꢀ5.32. MS, m/z:
H
2), 3.77 (3 H, s, OCH3 picolyl),
[
J
H
H
2), 1.32 (9 H, t, 7.3,
J
.
Triethylammonium salt of
dimethoxytrityl)ꢀ2'ꢀ ꢀ[(3,4ꢀ
methyl]cytidine 3'ꢀ ꢀ(1ꢀoxidoꢀ4ꢀmethoxyꢀ2ꢀpicolyl)
phosphate (VIIc). Yield: 83%; Rf 0.40 (B); H NMR
(CDCl3): 8.36 (1 H, d, 7.4, Cyt), 8.04 (1 H, d,
7.2, picolyl), 7.92–7.46 (5 H,m, Bz), 7.43–
Nucleosides (VIa)–(VIc) were phosphorylated as 7.19 (9 H, m, Ar DMTr), 7.16 (1 H, d, 3.2, picoꢀ
described previously [32], except that, in the case of lyl), 7.02 (1 H, br s, Cyt), 6.86–6.79 (4 H, m,
derivative (VIc), triethylammonium (4ꢀnitrophenyl)ꢀ Ar DMTr), 6.70 (1 H, dd, 7.2, 3.2, picolyl), 6.05
(1ꢀoxidoꢀ4ꢀmethoxyꢀ2ꢀpicolyl)phosphate was (1 H, d, 1.6, ), 5.18–4.84 (6 H, m, ', PꢀOCH2
used as a phosphorylation agent. The ꢀchlorophenyl OC 2O, C O(CO)CH2O), 4.63–4.47 (2 H, m,
group was removed from the phosphate group by treatꢀ CHO(CO)C αO), 4.44–4.36 (1 H, m, ), 4.23–
ment with DBU in an aqueous organic solvent, and in 4.11 (1 H, m, CHO(CO)C βO), 3.92–3.67 (2 H, m,
the case of the phosphotriester containing a 4ꢀnitroꢀ OС 2CH2), 3.79 (6 H, s, OCH3 DMTr), 3.76 (3 H, s,
phenyl phosphateꢀprotecting group, by treatment OCH3 picolyl), 3.77–3.50 (2 H, m, ), 3.03 (6 H, q,
N
4ꢀbenzoylꢀ5'ꢀ
Oꢀcyclocarbonatebutoxy)
Oꢀ(4,4'ꢀ
.
O
O
1
A General Method of the Synthesis
of Monomers VIIa)–(VIIc
J
H6
(
)
J
H6
H
J
H3
H5
J
H5
(X)
J
H1'
H
3
,
p
H
H
H
H2',
H4'
H
H
H5'
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 37
No. 5
2011

592
ARALOV et al.
17. ElꢀSagheer, A.H., Kumar, R., Findlow, S., Werner, J.M.,
Lane, A.N., and Brown, T., ChemBioChem, 2008,
vol. 9, pp. 50–52.
18. Meyer, A., Spinelli, N., Dumy, P., Vasseur, J.ꢀJ., Morꢀ
van, F., and Defrancq, E., J. Org. Chem., 2010, vol. 75,
pp. 3927–3930.
J
7.3, CH2 +HNEt3), 2.13–1.98 (2 H, m, OСH2C
1.28 (9 H, t,
7.3, CH3 +HNEt3); 31P NMR (CDCl3):
H2),
J
ꢀ0.14, ꢀ0.18. MS, m/z: 1009.47 [M – TEAꢀH+]–, calꢀ
culated for C50H50N4O17P– 1009.29
.
REFERENCES
19. Kocalka, P., ElꢀSagheer, A.H., and Brown, T., Chemꢀ
BioChem, 2008, vol. 9, pp. 1280–1285.
1. Soutschek, J., Akinc, A., Bramlage, B., Charisse, K.,
Constien, R., Donoghue, M., Elbashir, S., Geick, A.,
Hadwiger, P., Harborth, J., John, M., et al., Nature
2004, vol. 432, pp. 173–178.
20. Dooley, P.A., Tsarouhtsis, D., Korbel, G.A., Nechev, L.V.,
Shearer, J., Zegar, I.S., Harris, C.M., Stone, M.P., and
Harris, T.M., J. Am. Chem. Soc., 2001, vol. 123,
pp. 1730–1739.
21. Angelov, T., Guainazzi, A., and Schärer, O.D.,
Org. Lett., 2009, vol. 11, pp. 611–614.
22. Endo, M. and Majima, T., J. Am. Chem. Soc., 2003,
,
2. Bramsen, J.B., Laursen, M.B., Nielsen, A.F.,
Hansen, T.B., Bus, C., Langkjær, N., Ravindra,
BabuB., Højland, T., Abramov, M., van Aerschot, A.,
Odadzic, D., et al., Nucleic Acid Res., 2009, vol. 37,
pp. 2867–2881.
vol. 125, pp. 13654–13655.
23. Wilds, C.J., Noronha, A.M., Robidoux, S., and
Miller, P.S., J. Am. Chem. Soc., 2004, vol. 126,
pp. 9257–9265.
24. Wilds, C.J., Xu, F., and Noronha, A.M., Chem. Res.
Toxicol., 2008, vol. 21, pp. 686–695.
3. Prakash, T.P., Kawasaki, A.M., Wancewicz, E.V., Shen, L.,
Monia, B.P., Ross, B.S., Bhat, B., and Manoharan, M.,
J. Med. Chem., 2008, vol. 51, pp. 2766–2776.
4. Honcharenko, D., Barman, J., Varghese, O.P., and
Chattopadhyaya, J., Biochemistry, 2007, vol. 46,
pp. 5635–5646.
25. Guainazzi, A. and Schärer, O.D., Cell. Mol. Life Sci.
2010, vol. 67, pp. 3683–3697.
,
5. Zatsepin, T.S., Stetsenko, D.A., Gait, M.J., and
Oretskaya, T.S., Bioconjugate Chem., 2005, vol. 16,
pp. 471–489.
26. Tumpane, J., Sandin, P., Kumar, R., Powers, V.E.C.,
Lundberg, E.P., Gale, N., Baglioni, P., Lehn, J.ꢀM.,
Albinsson, B., Lincoln, P., Wilhelmsson, L.M., Brown, T.,
and Nordén, B., Chem. Phys. Lett., 2007, vol. 440,
pp. 125–129.
6. Shi, F. and Hoekstra, D., J. Controlled Release, 2004,
vol. 97, pp. 189–209.
7. Manoharan, M., Antisense Nucleic Acid Drug Dev.
,
27. Sproat, B., Methods in Molecular Biology, 2005,
2002, vol. 12, pp. 103–128.
vol. 288, pp. 17–31.
8. Lu, K., Duan, Q.ꢀP., Ma, L., and Zhao, D.ꢀX., Bioconꢀ 28. Wada, T., Mochizuki, A., Higashiya, S., Tsuruoka, H.,
jugate Chem., 2010, vol. 21, pp. 187–202.
Kawahar, S., Ishikawa, M., and Sekine, M., Tetraheꢀ
dron Lett., 2001, vol. 42, pp. 9215–9219.
29. Efimov, V.A., Aralov, A.V., Fedunin, S.V., Klykov, V.N.,
9. Hwang, J.ꢀT. and Greenberg, M.M., Org. Lett., 1999,
vol. 1, pp. 2021–2024.
and Chakhmakhcheva, O.G., Russ. J. Bioorg. Chem.
2009, vol. 35, pp. 250–253.
,
10. Hwang, J.ꢀT. and Greenberg, M.M., J. Org. Chem.
2001, vol. 66, pp. 363–369.
11. Hendrix, C., Devreese, B., Rozenski, J., De Bruyn, A.,
van Beeumen, J., and Herdewijn, P., Nucleic Acid Res.
1995, vol. 23, pp. 51–57.
,
30. Efimov, V.A., Aralov, A.V., Klykov, V.N., and Chakhꢀ
makhcheva, O.G., Nucleosides Nucleotides Nucleic
Acids, 2009, vol. 28, pp. 846–865.
31. Efimov, V.A., Aralov, A.V., Grachev, S.A., and Chakhꢀ
makhcheva, O.G., Russ. J. Bioorg. Chem., 2010, vol. 36,
pp. 628–633.
,
12. Zatsepin, T.S., Stetsenko, D.A., Arzumanov, A.A.,
Romanova, E.A., Gait, M.J., and Oretskaya, T.S., Bioꢀ
conjugate Chem., 2002, vol. 13, pp. 822–830.
32. Zhou, C., Honcharenko, D., and Chattapadhyaya, J.,
13. Zubin, E.M., Stetsenko, D.A., Zatsepin, T.S., Gait, M.J.,
and Oretskaya, T.S., Bioorg. Med. Chem., 2005, vol. 13,
pp. 4912–4920.
Org. Biomol. Chem., 2007, vol. 5, pp. 333–343.
33. Bobkov, G.V., Mikhailov, S.N., van Aerschot, A., and
Herdewijn, P., Tetrahedron, 2008, vol. 64, pp. 6238–
6251.
14. Zatsepin, T.S., Gait, M.J., Oretskaya, T.S., and Stetꢀ
senko, D.A., Tetrahedron Lett.
, 2006, vol. 47,
34. Brown, S.D. and Graham, D., Tetrahedron Lett., 2010,
pp. 5515–5518.
vol. 51, pp. 5032–5034.
15. Jawalekar, A.M., Meeuwenoord, N., Cremers, J.
(Sjef), G.O., Overkleeft, H.S., Van Der Marel, G.A.,
Rutjes, F.P.J.T., and van Delft, F.L., J. Org. Chem.
2008, vol. 73, pp. 287–290.
16. Kumar, R., ElꢀSagheer, A.H., Tumpane, J., Lincoln, P.,
Wilhelmsson, L.M., and Brown, T., J. Am. Chem. Soc.
2007, vol. 129, pp. 6859–6864.
35. Ustinov, A.V., Stepanova, I.A., Dubnyakova, V.V., Zaꢀ
tsepin, T.S., Nozhevnikova, E.V., and Korshun, V.A.,
Russ. J. Bioorg. Chem., 2010, vol. 36, pp. 401–445.
36. Chernyak, A.Ya., Sharma, G.V.M., Kononov, L.O.,
Radha Krishna, P., Levinsky, A.B., Kochetkov, N.K.,
and Rama Rao A.V., Carbohydr. Res., 1992, vol. 223,
pp. 303–309.
,
,
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 37
No. 5
2011