Chemoenzymatic synthesis of 3′-O-acetal-protected 2′-deoxynucleosides as building blocks for nucleic acid chemistry

Article abstract of DOI:10.1002/ejoc.200901428

We have developed a simple and convenient synthetic strategy for the preparation of tetrahydropyranyl, 4-methoxy-tetrahydropyranyl, and tetrahydrofuranyl ethers of 2′-deoxynucleosides, which are useful building blocks for nucleic acid chemistry. Enzymatic benzoylation provides an efficient alternative for protecting the 5′-hydroxy group of the parent nucleosides in a regioselective manner. Subsequently, tetrahydropyranylation and tetrahydrofuranylation of the 2′-deoxynucleosides at the 3′-hydroxy group were accomplished with p-toluensulfonic acid, MgBr₂, or camphorsulfonic acid as catalysts. Deprotection of the 5′-O-benzoyl group furnished 3′-O-acetal-protected 2′-deoxynucleosides. The three-step process is expected to enable the large-scale synthesis of protected nucleosides.

Full text of DOI:10.1002/ejoc.200901428

FULL PAPER
DOI: 10.1002/ejoc.200901428
Chemoenzymatic Synthesis of 3Ј-O-Acetal-Protected 2Ј-Deoxynucleosides as
Building Blocks for Nucleic Acid Chemistry
Tatiana Rodríguez-Pérez,[a] Susana Fernández,[a] Saúl Martínez-Montero,[a]
Tania González-García,[a] Yogesh S. Sanghvi,[b] Vicente Gotor,*[a] and Miguel Ferrero*[a]
Dedicated to Professor Benito Alcaide on the occasion of his 60th birthday
Keywords: Nucleosides / Enzymes / Acylation / Protecting groups / Green chemistry
We have developed a simple and convenient synthetic strat-
egy for the preparation of tetrahydropyranyl, 4-methoxy-
tetrahydropyranyl, and tetrahydrofuranyl ethers of 2Ј-deoxy-
nucleosides, which are useful building blocks for nucleic acid
chemistry. Enzymatic benzoylation provides an efficient al-
ternative for protecting the 5Ј-hydroxy group of the parent
nucleosides in a regioselective manner. Subsequently, tetra-
hydropyranylation and tetrahydrofuranylation of the 2Ј-de-
oxynucleosides at the 3Ј-hydroxy group were accomplished
with p-toluensulfonic acid, MgBr2, or camphorsulfonic acid
as catalysts. Deprotection of the 5Ј-O-benzoyl group fur-
nished 3Ј-O-acetal-protected 2Ј-deoxynucleosides. The
three-step process is expected to enable the large-scale syn-
thesis of protected nucleosides.
tecting groups that can be removed under milder acid con-
ditions or even under neutral conditions are of considerable
value. A recent report on the thermolabile deprotection of
tetrahydropyranyl (THP) and tetrahydrofuranyl (THF)
ethers during the polymerase chain reaction (PCR) has at-
tracted our attention.[5] The merits of acetal groups like
THP and THF lie in their stability in the presence of vari-
ous reagents such as basic media, alkyllithiums, metal hy-
drides, Grignard reagents, oxidative reagents, and alkylating
or acylating reagents and under mild acidic conditions or
heating, which promote cleavage.[6]
Numerous methods have been reported for the tetra-
hydropyranylation of alcohols.[2] Generally, protic and
Lewis acids are used as catalysts for this reaction.[7] The
reaction proceeds by the protonation of the enol ether car-
bon atom to generate a highly electrophilic oxonium ion,
which is then attacked by the hydroxy group of the alcohol.
Some reagents recently used for acetal protection are SO3H-
functionalized silica,[8] polystyrene-supported AlCl3,[9] bro-
modimethylsulfonium bromide,[10] magnesium halides,[11]
bismuth triflate,[12] or ruthenium trichloride.[13]
Introduction
The demand for DNA sequencing has never been greater
than it is today due to its wide-spread application in geno-
mics research, forensics, medical diagnostics, and thera-
peutic discovery. 2Ј-Deoxyribonucleoside-5Ј-triphosphates
(dNTPs) modified at the 3Ј-hydroxy position have been ex-
tensively utilized in DNA sequencing as chain termin-
ators.[1] The synthesis of 3Ј-modified nucleotides requires
the selective introduction and removal of protecting groups
in multifunctional molecules, which is an essential part of
organic synthesis.[2] The presence of various hydroxy,
amino, and phosphate linkages in nucleic acids demands
the use of appropriate blocking functions to simplify the
synthetic sequences. For example, orthogonal protecting
groups are core to the success of therapeutic oligonucleo-
tides assembled by solid-phase synthesis.[3]
The protection of hydroxy groups as esters is one of the
oldest and most frequently used strategies in the synthesis
of nucleosides. Acetyl and benzoyl protecting groups are
prized because they can be removed by alkaline hydrolysis
without cleaving the glycosidic bond in nucleosides.[4] Pro-
The use of the THF group is less prolific due to the lim-
ited protocols available in the literature. The reaction of
tetrahydrofuran with an alcohol in the presence of ceric tri-
ethylammonium nitrate also provides a general procedure
for protecting the hydroxy group.[14] Recently, an efficient
method that involves the use of Mn0 powder and CCl4 in
tetrahydrofuran has also been reported.[15]
[a] Departamento de Química Orgánica e Inorgánica and Instituto
Universitario de Biotecnología de Asturias, Universidad de
Oviedo,
33006 Oviedo, Asturias, Spain
Fax: +34-98-510-3448
E-mail: MFerrero@uniovi.es
vgs@uniovi.es
[b] Rasayan Inc.,
The THP group has found considerable use in oligonu-
2802 Crystal Ridge Road, Encinitas, CA 92024-6615, USA
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200901428.
cleotide synthesis.[16] The synthesis of 2Ј-O-THP and 2Ј,5Ј-
1736
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Chemoenzymatic Synthesis of Acetal-Protected Deoxynucleosides
di-O-THP derivatives of nucleosides starting from appro- guanosine (1d) hampered the reaction rate. In this case, the
priately protected precursors has been described. One of the use of 10 equiv. of vinyl benzoate, a substrate/enzyme ratio
practical problems of THP or THF protection is the com- of 1:2 (w/w), and a 0.1  concentration furnished the best
plexity of the NMR spectroscopic data, which is a result of results. Note that exclusive selectivity towards the 5Ј-posi-
the introduction of a new chiral center into the molecule. tion was maintained, resulting in the easy isolation of the
As an alternative, the 4-methoxytetrahydropyran-4-yl group products in high yields by simple precipitation from the
(MTHP) has been used for oligonucleotide synthesis as a crude reaction mixtures. No further purification of 3a–d
symmetrical protecting group devoid of chirality.[17,18] The was needed. Moreover, the excess acylating agent was reco-
use of THF is preferred over THP as a protecting group vered by solvent evaporation from the filtrate and success-
because the hydrolysis of THF ethers is much faster than fully recycled.
that of THP ethers. The synthesis of 2Ј-O-THF nucleosides
has been reported from 2,3-dihydrofuran via 3Ј,5Ј-di-O-tert-
butyldimethylsilyl nucleosides.[19]
However, protocols for the synthesis of 3Ј-O-THP and
3Ј-O-THF ethers of 2Ј-deoxynucleosides are not efficient.
Often, dimethoxytrityl and silyl protecting groups are em-
ployed as blocking groups for the 5Ј-hydroxy group during
the synthesis of the 3Ј-O-acetal. The use of these reagents
has limitations for scale-up due to the higher cost and cor-
rosive nature of the silyl chloride. Furthermore, tert-butyldi-
Scheme 1. Enzymatic benzoylation of 2Ј-deoxynucleosides.
methylsilyl-protected nucleosides require chromatographic
purification.[20] Similarly, 5Ј-O-acyl protection by a chemi-
Table 1. Reaction conditions for the benzoylation of 1a–d.
cal route is nonselective, resulting in a mixture of products.
We have already addressed the selectivity problems arising
during the acylation of nucleosides by enzymatic pro-
cesses.[21] For example, 5Ј-O-benzoyl-2Ј-deoxynucleoside
derivatives have been synthesized by selective acylation of
the parent nucleosides with vinyl benzoate catalyzed by
Candida antarctica lipase B (CAL-B).[21a] This procedure is
very attractive for a variety of reasons. First, the reagents
are available at a reasonable cost. Secondly, enzyme-cata-
lyzed reactions are nonhazardous, avoid pollution, and use
less energy than conventional chemistry-based methods
using trityl or silyl reagents.
Entry
1
2
1/CAL-B[a] Conc.
[]
t [h] Yield of
3 [%][b]
[equiv.]
1
2
3
4
1a
1b
1c
1d
5
10
3
1:1
1:1
1:1
1:2
0.2
0.1
0.2
0.1
116
68
23
93
92
95
89
10
95
[a] Ratio substrate/enzyme, w/w. [b] Isolated yield.
The tetrahydropyranylation of pyrimidine nucleoside de-
rivatives 3a,b was accomplished by conventional treatment
with 3,4-dihydro-2H-pyran (DHP, 4) in the presence of
catalytic p-toluenesulfonic acid (Scheme 2). The reactions
were carried out at room temperature in 1,4-dioxane, which
proved to be the solvent of choice among the other organic
solvents tested. After 3 h, the starting nucleosides had been
completely transformed into the tetrahydropyranyl ethers
5a,b, which were isolated in 95 and 80% yields, respectively.
Herein, we report a practical and efficient synthetic pro-
tocol for the large-scale synthesis of 3Ј-O-THP-, 3Ј-O-
MTHP-, and 3Ј-O-THF-2Ј-deoxynucleosides starting from
readily available 5Ј-O-benzoyl-protected derivatives.
1
The H NMR spectra show the presence of two diastereo-
Results and Discussion
isomers (1:1).
The regioselective synthesis of 5Ј-O-benzoyl-2Ј-deoxynu-
cleosides was accomplished by the reaction of 2Ј-deoxynu-
cleosides 1 with vinyl benzoate in the presence of Candida
antarctica lipase B (Scheme 1). Different ratios of acylating
agent and conditions were tested.[21a] The results are sum-
marized in Table 1. The enzymatic benzoylation of thymid-
ine (1a) with 5 equiv. of vinyl benzoate afforded exclusively
5Ј-O-benzoylthymidine in 93% yield (entry 1, Table 1). For
the acylation of N4-benzoyl-2Ј-deoxycytidine (1b), 10 equiv.
of the vinyl ester was required for optimum conversion. The
lower solubility of the starting material required the use of
a dilute solution (0.1  instead 0.2 ) for completion of the
Scheme 2. Reaction of 5Ј-O-Bz-T and 5Ј-O-Bz-dCBz with DHP.
This procedure was also shown to be effective for the
reaction (entry 2, Table 1). N6-Benzoyl-2Ј-deoxyadenosine tetrahydropyranylation of 3a,b with 4-methoxy-5,6-dihydro-
(1c) was more reactive and only 3 equiv. of vinyl benzoate 2H-pyran (MDHP, 6) with high yields of MTHP ethers 7a,b
were necessary to drive the reaction to completion (entry 3, being obtained (Scheme 3). 4-Methoxytetrahydropyran-4-yl
Table 1). The poor solubility of N2-isobutyryl-2Ј-deoxy- ethers have the advantage that they generate no new
Eur. J. Org. Chem. 2010, 1736–1744
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1737

V. Gotor, M. Ferrero et al.
FULL PAPER
stereogenic centers. Recently, an efficient preparation of
MDHP was reported which allows the wider use of MTHP
protection.[17]
Scheme 5. Reaction of 5Ј-O-Bz-dABz with DHP, MDHP, and DHF.
In the search for a suitable procedure for the installation
of a 3Ј-O-acetal into guanosine derivative 3d, we used DHF
instead of DHP and p-toluenesulfonic acid as the catalyst.
MeCN proved to be a more convenient solvent than 1,4-
dioxane. These conditions provided the THF ether 9d in
40% yield.
The use of camphorsulfonic acid (CSA) as the catalyst
led to improved yields (Scheme 6). When 3d was treated
with MDHP or DHF in the presence of a catalytic amount
of CSA at room temperature for 2 h, ethers 7d and 9d were
isolated in 50–52% yields. However, treatment of 3d with
DHP led to the formation of several byproducts.
Scheme 3. Reaction of 5Ј-O-Bz-T and 5Ј-O-Bz-dCBz with MDHP.
To develop a general and convenient procedure for the
protection of the 3Ј-hydroxy group in nucleosides with an
acetal, the reaction was explored with 2,3-dihydrofuran
(DHF, 8). Tetrahydrofuranylation proceeded well and THF
ethers 9a,b were isolated in excellent yields (Scheme 4).
Scheme 4. Reaction of 5Ј-O-Bz-T and 5Ј-O-Bz-dCBz with DHF.
Scheme 6. Reaction of 5Ј-O-Bz-dGIbu with DHF and MDHP.
Next we attempted the THP and THF protection of the
purine nucleosides 3c,d. The reaction of N-protected 5Ј-O-
benzoyl-2Ј-deoxyadenosine and 5Ј-O-benzoyl-2Ј-deoxygu-
anosine derivatives with DHP in 1,4-dioxane with p-tolu-
enesulfonic acid as catalyst did not yield the desired THP
ethers. In the case of the adenosine derivative 3c, cleavage
of the glycosidic bond was observed, probably due to the
acidic reaction media. For the guanosine derivative 3d, a
mixture of complex products was observed.
The 5Ј-O-benzoyl group was deprotected with ammonia
in MeOH to afford the corresponding THP and THF ethers
10 as the exclusive products in high yields (Scheme 7). In
addition to the 5Ј-O-benzoyl group, concomitant cleavage
It has been shown that the tetrahydropyranylation of
alcohols can be accomplished under neutral conditions
using a catalytic amount of MgBr2 with CH2Cl2 as sol-
vent.[11] The reaction with 3c in CH2Cl2 failed to proceed
due to its poor solubility. Thus, the reaction was carried out
with DHP in the presence of MgBr2 and MeCN as solvent
(Scheme 5). After 20 h at room temperature, 3Ј-O-THP de-
rivative 5c was isolated in 92% yield. Similarly, we success-
fully converted 3c into the corresponding 3Ј-O-MTHP and
3Ј-O-THF ethers 7c and 9c under identical reaction condi-
tions using the same catalyst. However, the reaction of a
solution of 5Ј-O-benzoyl-N2-isobutyryl-2Ј-deoxyguanosine
(3d) in MeCN with 5 equiv. of DHP and MgBr2 afforded
undesired products.
Scheme 7. Synthesis of 3Ј-O-THP-, MTHP-, and THF-2Ј-deoxynu-
cleosides.
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Chemoenzymatic Synthesis of Acetal-Protected Deoxynucleosides
of the base protecting group in cytidine, adenosine, and
guanosine derivatives occurred. In the case of guanosine
derivatives 7d and 9d, the reaction temperature was in-
creased to 60 °C to drive the hydrolysis reaction to comple-
tion.
In view of the potential industrial applications, it should
be noted that purification by flash chromatography of the
3Ј,5Ј-protected intermediates was not necessary, with the
exception of the guanosine derivatives 7d and 9d, for which
Experimental Section
General: Candida antarctica lipase B (CAL-B, Novozym 435,
7300 PLU/mg solid) was a gift from Novo Nordisk Co. All the
enzymatic reactions were carried out in a temperature-controlled
incubator shaker (Heidolph Unimax 2010) at 250 rpm and 60 °C.
Melting points were taken on samples in open capillary tubes and
are uncorrected. IR spectra were recorded with an Infrared FT
spectrophotometer by using NaCl pellets. TLC was performed on
silica gel 60 F254 plates (Merck), and column chromatography was
chromatographic purification was required. Compounds carried out by using silica gel Merck 60 (230–240 mesh). NMR
spectra were recorded with Bruker DPX-300 or NAV300 spectrom-
eters in CDCl3, [D6]DMSO or [D4]MeOH. APCI+ and ESI+ were
used to record mass spectra (MS).
5a–c, 7a–c, and 9a–c were sufficiently pure to carry forward
to the deprotection step without purification.
General Procedure for the Synthesis of 3a–d: A suspension of 1
(0.4 mmol), vinyl benzoate, and CAL-B in anhydrous THF under
nitrogen was stirred at 60 °C and 250 rpm (orbital shaker) under
the conditions and reaction times indicated in Table 1. The enzyme
was filtered off and washed with CH2Cl2 and THF, and the solvents
were then evaporated under vacuum. The residue was precipitated
in hexane to afford, after filtration and washing with hexane, the
5Ј-O-benzoyl nucleosides 3 as solids. Excess vinyl benzoate was re-
covered by solvent evaporation under vacuum from the hexane
mother liquors.
Large-Scale Studies
The industrial utility of this protocol was proven by the
synthesis of 3Ј-O-tetrahydropyranylthymidine on a large
scale. Thus, treatment of thymidine (10 g) with 5 equiv. of
vinyl benzoate in the presence of CAL-B at 60 °C provided
5Ј-O-benzoylthymidine (3a) in the pure form and in 96%
yield by precipitation from hexane. Nucleoside 3a was sub-
jected to tetrahydropyranylation with 3,4-dihydro-2H-pyran
and p-toluenesulfonic acid as the catalyst, which cleanly al- 5Ј-O-Benzoylthymidine (3a): White solid, yield 128.8 mg, 93%. Rf
(10% MeOH/CH2Cl2) = 0.7; m.p. 167–169 °C. [α]2D0 = –9.6 (c = 1.1,
lowed the conversion to the 5Ј-O-benzoyl-3Ј-O-THP deriva-
MeOH). IR (NaCl): ν = 3371, 3188, 1723, 1657 cm–1. 1H NMR
˜
tive 5a. Treatment of crude 5a with NH4OH/MeOH fur-
nished 3Ј-O-(tetrahydropyranyl)thymidine (10a) in high pu-
rity and 80% overall yield.
([D6]DMSO, 300 MHz): δ = 1.57 (s, 3 H, Me), 2.20 (m, 2 H, 2Ј-
H), 4.03 (m, 1 H, 4Ј-H), 4.37–4.55 (m, 3 H, 5Ј-H, 3Ј-H), 5.47 (d,
3
3JHH = 3.7 Hz, 1 H, OH), 6.19 (apparent t, JHH = 6.8 Hz, 1 H,
1Ј-H), 7.37 (s, 1 H, 6-H), 7.53 (m, 2 H, m-H), 7.67 (m, 1 H, p-H),
7.97 (apparent d, 3JHH = 8.3 Hz, 2 H, o-H), 11.3 (s, 1 H, NH) ppm.
13C NMR ([D6]DMSO, 75.5 MHz): δ = 11.8 (Me), 38.7 (C-2Ј), 64.3
(C-5Ј), 70.2 (C-3Ј), 83.6, 83.7 (C-1Ј, C-4Ј), 109.7 (C-5), 128.8, 129.1
(Co, Cm), 129.3 (Ci), 133.5 (Cp), 135.6 (C-6), 150.3 (C-2), 163.6 (C-
4), 165.5 (Ph-C=O) ppm. MS (ES+): m/z (%) = 347 (10) [M +
H]+, 369 (45) [M + Na]+.
Conclusions
An efficient and high yielding preparation of 3Ј-O-(tetra-
hydropyranyl)-, 3Ј-O-(4-methoxytetrahydropyranyl)-, and
3Ј-O-(tetrahydrofuranyl)-2Ј-deoxynucleosides has been de-
scribed. The easy access to 3Ј-O-acetal-protected nucleo-
sides will lead to the expeditious synthesis of 5Ј-triphos-
phates (dNTPs) required for PCR related applications.[5,22]
The chemoenzymatic methodology detailed herein is a sig-
nificant improvement over reported methods. A key step in
the synthesis is the regioselective 5Ј-hydroxy protection of
the 2Ј-deoxynucleosides catalyzed by Candida antarctica li-
pase B. Enzyme-catalyzed reactions are environmentally at-
tractive due to their safe and cost-effective features relative
to conventional chemistry-based methods using silyl or di-
methoxytrityl reagents. The immobilized CAL-B used
herein offers considerable advantages due to its high selec-
tivity, stability, reusability, and ease of handling during
large-scale operations.[21] Also, we found that tetrahydro-
pyranylation and tetrahydrofuranylation can be achieved ef-
ficiently under mild reaction conditions and shorter reac-
tion times. In addition, this strategy does not require sol-
vents traditionally used in nucleoside chemistry such as pyr-
idine or DMF thereby avoiding tedious reaction work-up.
We believe this strategy will find use in the large-scale syn-
thesis of 3Ј-protected nucleosides, which are needed for di-
agnostic[23] and therapeutic applications.
N4,5Ј-O-Dibenzoyl-2Ј-deoxycytidine (3b): White solid; yield
160.1 mg, 92%. Rf (10% MeOH/CH2Cl2) = 0.45; m.p. 190–192 °C.
[α]2D0 = +68.1 (c = 1.1, DMSO). IR (NaCl): ν = 3393, 2936, 1705,
˜
1698 cm–1. 1H NMR ([D6]DMSO, 300 MHz): δ = 2.23 (m, 1 H, 2Ј-
H), 2.40 (m, 1 H, 2Ј-H), 4.20 (m, 1 H, 4Ј-H), 4.37 (m, 1 H, 3Ј-H),
4.54 (m, 2 H, 5Ј-H), 5.52 (d, 3JHH = 4.3 Hz, 1 H, OH), 6.18 (appar-
3
3
ent t, JHH = 6.1 Hz, 1 H, 1Ј-H), 7.29 (d, JHH = 6.8 Hz, 1 H, 5-
H), 7.28–7.64 (m, 6 H, m-H, p-H), 7.97 (m, 4 H, o-H), 8.18 (d,
3JHH = 7.4 Hz, 1 H, 6-H), 11.24 (br. s, 1 H, NH) ppm. 13C NMR
([D6]DMSO, 75.5 MHz): δ = 40.1 (C-2Ј), 64.3 (C-5Ј), 69.9 (C-3Ј),
84.4, 86.4 (C-1Ј, C-4Ј), 96.2 (C-5), 128.4, 128.7, 129.1 (Co, Cm),
129.3 (Ci), 132.7 (Cp), 133.1 (Ci), 133.5 (Cp), 144.7 (C-6), 154.2 (C-
2), 162.9 (C-4), 165.5 (Ph-C=O), 167.3 (Ph-C=O) ppm. MS (ES+):
m/z (%) = 436 (35) [M + H]+, 458 (15) [M + Na]+.
N6,5Ј-O-Dibenzoyl-2Ј-deoxyadenosine (3c): White solid; yield
174.5 mg, 95%. Rf (10% MeOH/CH2Cl2) = 0.5; m.p. 165–167 °C.
[α]2D0 = –7.7 (c = 1.1, DMSO). IR (NaCl): ν = 3279, 3092, 1705,
˜
1674 cm–1. 1H NMR ([D6]DMSO, 300 MHz): δ = 2.47 (m, 1 H, 2Ј-
H), 3.00 (m, 1 H, 2Ј-H), 4.18 (m, 1 H, 4Ј-H), 4.45–4.54 (m, 2 H,
5Ј-H), 4.68 (m, 1 H, 3Ј-H), 5.60 (d, 3JHH = 4.4 Hz, 1 H, OH), 6.50
3
(apparent t, JHH = 6.7 Hz, 1 H, 1Ј-H), 7.49 (m, 4 H, m-H), 7.63
3
(m, 2 H, p-H), 7.90 (apparent, JHH = 7.4 Hz, 2 H, o-H), 8.63 (s,
1 H, 8-H), 8.69 (s, 1 H, 2-H), 11.19 (s, 1 H, NH) ppm. 13C NMR
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1739

V. Gotor, M. Ferrero et al.
([D6]DMSO, 75.5 MHz): δ = 38.2 (C-2Ј), 64.3 (C-5Ј), 70.4 (C-3Ј), 63.6, 63.8 (C-5Ј, C-6ЈЈ), 74.6 (C-3Ј), 75.3 (C-3Ј), 82.6 (C-4Ј), 83.5
FULL PAPER
83.6, 83.1 (C-1Ј, C-4Ј), 125.9 (C-5), 128.4, 128.7, 129.1 (Co, Cm),
129.3 (Ci), 132.4 (Cp), 133.2 (Ci), 133.4 (Cp), 143.3 (C-8), 150.3 (C-
6), 151.5 (C-2), 151.8 (C-4), 165.5 (Ph-C=O), 165.6 (Ph-C=O) ppm.
MS (ES+): m/z (%) = 460 (95) [M + H]+, 482 (60) [M + Na]+.
(C-4Ј), 87.3 (C-1Ј), 96.9, 97.5, 98.5 (C-5, C-2ЈЈ), 127.4, 128.4, 128.5,
128.7, 129.0, 129.1, 129.2, 129.3 (Co, Cm, Ci), 132.8 (Ci), 132.4 (Cp),
143.5 (C-6), 154.5 (C-2), 162.1 (C-4), 165.9 (Ph-C=O) ppm. MS
(ES+): m/z (%) = 520 (10) [M + H]+, 542 (75) [M + Na]+.
5Ј-O-Benzoyl-N2-isobutyryl-2Ј-deoxyguanosine (3d): White solid; 5Ј-O-Benzoyl-3Ј-O-(4-methoxytetrahydropyranyl)thymidine
yield 157.1 mg, 89%. Rf (15% MeOH/CH2Cl2) = 0.6; m.p. 117– White solid; yield 79.2 mg, 86%. Rf (5% MeOH/CH2Cl2) = 0.47;
(7a):
119 °C. [α]2D0 = –18.3 (c = 1.0, DMSO). IR (NaCl): ν = 3351, 1721,
m.p. 84–86 °C. IR (NaCl): ν = 3413, 3059, 2954, 1698, 1606, 1461,
˜
˜
1
3
1684 cm–1. H NMR ([D6]DMSO, 300 MHz): δ = 1.07 (d, JHH
=
1265 cm–1. 1H NMR (CDCl3, 300 MHz): δ = 1.63 (s, 3 H, Me),
6.9 Hz, 6 H, Me-Ibu), 2.36 (m, 1 H, 2Ј-H), 2.67 (m, 2 H, CH-Ibu 1.77 (m, 4 H, 3ЈЈ-H), 2.19 (m, 1 H, 2Ј-H), 2.43 (m, 1 H, 2Ј-H), 3.20
3
+ 2Ј-H), 4.12 (m, 1 H, 4Ј-H), 4.35–4.55 (m, 3 H, 2Ј-H, 5Ј-H), 6.25 (s, 3 H, OMe), 3.55–3.81 (m, 4 H, 2ЈЈ-H), 4.29 (apparent q, JHH
3
(apparent t, JHH = 6.6 Hz, 1 H, 1Ј-H), 7.50 (m, 2 H, m-H), 7.66
= 3.5 Hz, 1 H, 4Ј-H), 4.43–4.7 (m, 3 H, 3Ј-H, 5Ј-H), 6.28 (apparent
3
3
(m, 1 H, p-H), 7.92 (d, JHH = 7.2 Hz, 2 H, o-H), 8.03 (s, 1 H, 8-
t, JHH = 6.5 Hz, 1 H, 1Ј-H), 7.21 (d, |4JHH| = 1.1 Hz, 1 H, 6-H),
H) ppm. 13C NMR ([D6]DMSO, 75.5 MHz): δ = 18.9 (Me), 34.8 7.39–7.47 (m, 2 H, m-H), 7.55–7.61 (m, 1 H, p-H), 8.01 (apparent
(CH-Ibu), 38.8 (C-2Ј), 64.5 (C-5Ј), 70.4 (C-3Ј), 82.9 (C-1Ј), 84.1 (C- d, JHH = 7.2 Hz, 2 H, o-H), 9.6 (s, 1 H, NH) ppm. 13C NMR
3
4Ј), 120.4 (C-5), 128.4, 129.2 (Co, Cm), 129.4 (Ci), 133.5 (Cp), 137.5
(CDCl3, 75.5 MHz): δ = 12.1 (Me), 34.2 (C-3ЈЈ), 34.7 (C-3ЈЈ), 39.6
(C-8), 148.1 (C-2), 148.4 (C-4), 154.8 (C-6), 165.6 (Ph-C=O), 180.1 (C-2Ј), 48.1 (OMe), 63.7, 64.6 (C-2ЈЈ, C-5Ј), 69.1 (C-3Ј), 83.0 (C-
(Ibu-C=O) ppm. MS (ES+): m/z (%) = 442 (20) [M + H]+, 464 (100)
4Ј), 84.9 (C-1Ј), 99.1 (C-4ЈЈ), 111.1 (C-5), 128.5, 129.2 (Co, Cm),
129.3 (Ci), 133.4, 134.6 (Cp, C-6), 150.3 (C-2), 163.7 (C-4), 165.9
(Ph-C=O) ppm. MS (ES+): m/z (%) = 483 (90) [M + Na]+.
[M + Na]+.
General Procedure for the Synthesis of 5a,b, 7a,b, and 9a,b: p-Tolu-
enesulfonic acid monohydrate (0.1 mmol) was added to a solution
of 5Ј-O-benzoyl-protected thymidine or N4-benzoyl-2Ј-deoxycytid-
ine (0.2 mmol) in anhydrous 1,4-dioxane (1.3 mL) followed by 3,4-
dihydro-2H-pyran, 4-methoxy-5,6-dihydro-2H-pyran or 2,3-dihy-
drofuran (1 mmol). After 3 h, the reaction mixture was poured into
a saturated NaHCO3 solution and extracted with CH2Cl2. The
combined organic fractions were dried (Na2SO4) and concentrated
under vacuum. The resulting crude was purified by flash
chromatography using 50% hexane/EtOAc for 5a, 7a, and 9a and
33% hexane/EtOAc for 5b, 7b, and 9b.
N4,5Ј-O-Dibenzoyl-3Ј-O-(4-methoxytetrahydropyranyl)-2Ј-deoxycy-
tidine (7b): White solid; yield 104.4 mg, 95%. Rf (5% MeOH/
CH Cl ) = 0.39; m.p. 79–81 °C. IR (NaCl): ν = 3415, 3060, 2948,
˜
2
2
1723, 1697, 1621, 1484, 1271 cm–1. 1H NMR (CDCl3, 300 MHz):
δ = 1.74–1.89 (m, 4 H, 3ЈЈ-H), 2.22 (m, 1 H, 2Ј-H), 2.72 (m, 1 H,
2Ј-H), 3.17 (s, 3 H, OMe), 3.58–3.75 (m, 4 H, 2ЈЈ-H), 4.40 (apparent
3
q, JHH = 3.7 Hz, 1 H, 4Ј-H), 4.51–4.67 (m, 3 H, 3Ј-H, 5Ј-H), 6.22
3
(apparent t, JHH = 5.9 Hz, 1 H, 1Ј-H), 7.39–7.61 (m, 7 H, m-H,
p-H, 5-H), 7.87 (apparent d, 3JHH = 7.2 Hz, 2 H, o-H), 7.96 (appar-
3
3
ent d, JHH = 7.0 Hz, 2 H, o-H), 8.12 (d, JHH = 7.4 Hz, 1 H, 6-
H), 8.97 (br. s, 1 H, NH) ppm. 13C NMR (CDCl3, 75.5 MHz): δ =
34.2 (C-3ЈЈ), 34.7 (C-3ЈЈ), 40.7 (C-2Ј), 48.1 (OMe), 63.3 (C-5Ј), 64.6
(C-2ЈЈ), 68.3 (C-3Ј), 83.6 (C-4Ј), 87.3 (C-1Ј), 96.4 (C-5), 99.6 (C-
4ЈЈ), 127.5, 128.6, 128.7, 129.1, 129.3 (Co, Cm, Ci), 132.8 (Ci), 132.9
(Cp), 133.5 (Cp), 143.1 (C-6), 154.5 (C-2), 162.1 (C-4), 165.6 (Ph-
C=O) ppm. MS (ES+): m/z (%) = 550 (50) [M + H]+, 572 (100) [M
+ Na]+.
5Ј-O-Benzoyl-3Ј-O-(tetrahydropyranyl)thymidine (5a): White hygro-
scopic solid (two diastereoisomers); yield 81.8 mg, 95%. Rf (5%
MeOH/CH Cl ) = 0.50. IR (NaCl): ν = 3431, 3055, 2944, 1703,
˜
2
2
1
1623, 1260 cm–1. H NMR (CDCl3, 300 MHz): δ = 1.43–1.59 (m,
4 H, 4ЈЈ-H), 1.63 (d, |4JHH| = 1.3 Hz, 3 H, Me), 1.65 (d, |4JHH| =
1.1 Hz, 3 H, Me), 1.66–1.86 (m, 8 H, 3ЈЈ-H, 5ЈЈ-H), 2.08 (m, 1 H,
2Ј-H), 2.20 (m, 1 H, 2Ј-H), 2.45 (m, 1 H, 2Ј-H), 2.59 (m, 1 H, 2Ј-
H), 3.52 (m, 2 H, 6ЈЈ-H), 3.82 (m, 2 H, 6ЈЈ-H), 4.30–4.74 (m, 10 H,
5Ј-O-Benzoyl-3Ј-O-(tetrahydrofuranyl)thymidine (9a): White hygro-
2ЈЈ-H, 3Ј-H, 4Ј-H, 5Ј-H), 6.30 (apparent q, 3JHH = 6.8 Hz, 2 H, 1Ј- scopic solid (two diastereoisomers); yield 79.9 mg, 96%. Rf (5%
H), 7.21 (d, |4JHH| = 1.1 Hz, 1 H, 6-H), 7.24 (d, |4JHH| = 1.3 Hz, 1 MeOH/CH Cl ) = 0.46. IR (NaCl): ν = 3316, 2938, 1718, 1664,
˜
2
2
H, 6-H), 7.45 (t, 3JHH = 7.2 Hz, 4 H, m-H), 7.59 (t, 3JHH = 7.2 Hz,
1509, 1263 cm–1. H NMR (CDCl3, 300 MHz): δ = 1.60 (d, |4JHH
|
1
3
2 H, p-H), 8.02 (dd, JHH = 7.2, 1.2 Hz, 4 H, o-H), 9.37 (s, 2 H,
= 1.1 Hz, 3 H, Me), 1.62 (d, |4JHH | = 1.1 Hz, 3 H, Me), 1.78–2.23
NH) ppm. 13C NMR (CDCl3, 75.5 MHz): δ = 12.1 (Me), 19.1, (m, 10 H, 2Ј-H, 3ЈЈ-H, 4ЈЈ-H), 2.45 (m, 2 H, 2Ј-H), 3.83 (m, 4 H,
19.2, 25.1, 30.5 (C-3ЈЈ, C-4ЈЈ, C-5ЈЈ), 37.9 (C-2Ј), 39.0 (C-2Ј), 62.6 5ЈЈ-H), 4.21–4.67 (m, 8 H, 3Ј-H, 4Ј-H, 5Ј-H), 5.20 (m, 2 H, 2ЈЈ-H),
(C-6ЈЈ), 64.2 (C-5Ј), 75.4 (C-3Ј), 76.2 (C-3Ј), 82.1 (C-4Ј), 82.9 (C- 6.26 (m, 2 H, 1Ј-H), 7.17 (d, |4JHH| = 1.1 Hz, 1 H, 6-H), 7.20 (d,
4Ј), 84.8 (C-1Ј), 85.1 (C-1Ј), 97.8 (C-2ЈЈ), 98.5 (C-2ЈЈ), 111.2 (C-5),
128.6, 129.4 (Co, Cm), 129.4 (Ci), 133.4 (Cp), 134.6 (C-6), 134.8 (C-
6), 150.3 (C-2), 163.7 (C-4), 166.0 (Ph-C=O) ppm. MS (ES+): m/z
(%) = 431 (20) [M + H]+, 453 (90) [M + Na]+.
|4JHH| = 1.1 Hz, 1 H, 6-H), 7.42 (m, 4 H, m-H), 7.56 (m, 2 H, p-
3
3
H), 7.98 (d, JHH = 7.3 Hz, 2 H, o-H), 7.99 (d, JHH = 7.3 Hz, 2
H, o-H), 9.45 (s, 2 H, NH) ppm. 13C NMR (CDCl3, 75.5 MHz): δ
= 12.0 (Me), 23.2, 23.3, 32.2, 32.3 (C-3ЈЈ, C-4ЈЈ), 37.9 (C-2Ј), 39.3
(C-2Ј), 63.9, 64.0, 67.1 (C-5Ј, C-5ЈЈ), 75.5 (C-3Ј), 76.1 (C-3Ј), 81.9,
83.1, 84.6, 84.7 (C-1Ј, C-4Ј), 103.2 (C-2ЈЈ), 103.9 (C-2ЈЈ), 111.0 (C-
5), 111.1 (C-5), 128.5, 129.3 (Co, Cm), 129.4 (Ci), 133.3, 133.4,
134.6, 134.7 (Cp, C-6), 150.3 (C-2), 163.6 (C-4), 165.9 (Ph-
C=O) ppm. MS (ES+): m/z (%) = 417 (10) [M + H]+, 439 (85) [M
+ Na]+.
N4,5Ј-O-Dibenzoyl-3Ј-O-(tetrahydropyranyl)-2Ј-deoxycytidine (5b):
White hygroscopic solid. (two diastereoisomers); yield 83.1 mg,
80%. R (5% MeOH/CH Cl ) = 0.48. IR (NaCl): ν = 3411, 3072,
˜
f
2
2
2956, 1718, 1698, 1623, 1481, 1264 cm–1. 1H NMR (CDCl3,
300 MHz): δ = 1.47–1.80 (m, 12 H, 3ЈЈ-H, 4ЈЈ-H, 5ЈЈ-H), 2.13 (m,
1 H, 2Ј-H), 2.30 (m, 1 H, 2Ј-H), 2.79 (m, 2 H, 2Ј-H), 3.49 (m, 2 H,
6ЈЈ-H), 3.73 (m, 2 H, 6ЈЈ-H), 4.33–4.69 (m, 10 H, 3Ј-H, 4Ј-H, 5Ј-H,
N4,5Ј-O-Dibenzoyl-3Ј-O-(tetrahydrofuranyl)-2Ј-deoxycytidine (9b):
White hygroscopic solid (two diastereoisomers); yield 89.9 mg,
3
2ЈЈ-H), 6.22 (apparent q, JHH = 6.2 Hz, 2 H, 1Ј-H), 7.39–7.68 (m,
3
14 H, 5-H, m-H, p-H), 7.83–7.89 (m, 8 H, o-H), 8.11 (d, JHH
=
89%. R (5% MeOH/CH Cl ) = 0.38. IR (NaCl): ν = 3413, 3065,
˜
f 2 2
3
7.5 Hz, 1 H, 6-H), 8.12 (d, JHH = 7.4 Hz, 1 H, 6-H), 9.01 (br. s, 2
2955, 1720, 1698, 1661, 1487, 1268 cm–1. 1H NMR (CDCl3,
H, NH) ppm. 13C NMR (CDCl3, 75.5 MHz): δ = 18.8, 19.2, 25.0,
300 MHz): δ = 1.81–2.17 (m, 9 H, 2Ј-H, 3ЈЈ-H, 4ЈЈ-H), 2.33 (m, 1
30.2, 30.3 (C-3ЈЈ, C-4ЈЈ, C-5ЈЈ), 38.8 (C-2Ј), 40.1 (C-2Ј), 62.2, 62.5, H, 2Ј-H), 2.77 (m, 2 H, 2Ј-H), 3.89 (m, 4 H, 5ЈЈ-H), 4.28–4.46 (m,
1740
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1736–1744

Chemoenzymatic Synthesis of Acetal-Protected Deoxynucleosides
4 H, 3Ј-H, 4Ј-H), 4.66 (m, 4 H, 5Ј-H), 5.19 (m, 2 H, 2ЈЈ-H), 6.24 H, 2ЈЈ-H), 6.42 (m, 2 H, 1Ј-H), 7.36–7.58 (m, 12 H, m-H, p-H),
3
(apparent t, JHH = 5.5 Hz, 2 H, 1Ј-H), 7.45–7.62 (m, 14 H, m-H,
7.96 (m, 8 H, o-H), 8.15 (s, 1 H, 2-H or 8-H), 8.16 (s, 1 H, 2-H or
8-H), 8.70 (s, 1 H, 2-H or 8-H), 8.71 (s, 1 H, 2-H or 8-H) ppm. 13
NMR (CDCl3, 75.5 MHz): δ = 23.2, 23.3, 32.5 (C-3ЈЈ, C-4ЈЈ), 37.9
3
p-H, 5-H), 7.92–8.04 (m, 8 H, o-H), 8.15 (d, JHH = 7.5 Hz, 2 H,
C
6-H), 9.02 (br. s, 2 H, NH) ppm. 13C NMR (CDCl3, 75.5 MHz): δ
= 23.2, 23.3, 32.2 (C-3ЈЈ, C-4ЈЈ), 39.1 (C-2Ј), 40.6 (C-2Ј), 63.5 (C- (C-2Ј), 39.0 (C-2Ј), 64.0, 64.1. 67.3 (C-5ЈЈ, C-5Ј), 76.1 (C-3Ј), 76.4
5Ј), 63.8 (C-5Ј), 67.3 (C-5ЈЈ), 74.8 (C-3Ј), 75.1 (C-3Ј), 82.7 (C-4Ј),
83.9 (C-4Ј), 87.3 (C-1Ј), 87.4 (C-1Ј), 96.4 (C-5), 103.1 (C-2ЈЈ), 104.2
(C-2ЈЈ), 127.6, 128.6, 128.7, 128.9 (Co, Cm), 129.4 (Ci), 129.5 (Ci),
132.8, 133.6 (Cp), 144.1 (C-6), 154.5 (C-2), 161.9 (C-4), 166.1 (Ph-
C=O) ppm. MS (ES+): m/z (%) = 506 (10) [M + H]+, 528 (100) [M
+ Na]+.
(C-3Ј), 82.6, 83.8, 84.8, 84.9 (C-1Ј, C-4Ј), 103.5 (C-2ЈЈ), 104.1 (C-
2ЈЈ), 123.4 (C-5), 123.5 (C-5), 127.8, 128.8, 128.7, 129.1, 129.3 (Co,
Cm), 129.5 (Ci), 133.1 (Cp), 133.2 (Cp), 133.4 (Ci), 141.3 (C-8), 141.4
(C-8), 149.5 (C-6), 151.3 (C-2), 151.4 (C-4), 165.1 (Ph-C=O), 166.0
(Ph-C=O) ppm. MS (ES+): m/z (%) = 530 (100) [M + H]+. HRMS
(EI): calcd. for C28H28N5O6 [M]+ 530.2041; found 530.2034.
General Procedure for the Synthesis of 5c, 7c, and 9c: 3,4-Dihydro-
2H-pyran, 4-methoxy-5,6-dihydro-2H-pyran, or 2,3-dihydrofuran
(1.1 mmol) and catalytic amounts (8–10 mol-%) of MgBr2 were
added to a solution of N6,5Ј-O-dibenzoyl-2Ј-deoxyadenosine (3c;
0.22 mmol) in anhydrous acetonitrile (4.4 mL). The solution was
stirred for 20 h at room temperature. After completion of the reac-
tion, the solvent was evaporated and the crude was purified by
flash chromatography using 2% MeOH/CH2Cl2.
General Procedure for the Synthesis of 7d and 9d: 5,6-Dihydro-4-
methoxy-2H-pyran or 2,3-dihydrofuran (1.15 mmol) and cam-
phorsulfonic acid (0.12 mmol) were added to a solution of 5Ј-O-
benzoyl-N2-isobutyryl-2Ј-deoxyguanosine (3d; 0.23 mmol) in anhy-
drous 1,4-dioxane (2.3 mL). After 2 h, the solvent was evaporated
and the crude was purified by flash chromatography using 2%
MeOH/CH2Cl2.
5Ј-O-Benzoyl-N2-isobutyryl-3Ј-O-(4-methoxytetrahydropyranyl)-2Ј-
N6,5Ј-O-Dibenzoyl-3Ј-O-(tetrahydropyranyl)-2Ј-deoxyadenosine deoxyguanosine (7d): White solid; yield 63.9 mg, 50 %. Rf (2 %
(5c): White hygroscopic solid (two diastereoisomers); yield
MeOH/CH Cl ) = 0.35; m.p. 111–112 °C. IR (NaCl): ν = 3427,
˜
2 2
1
110.1 mg, 92%. R (2% MeOH/CH Cl ) = 0.41. IR (NaCl): ν = 2930, 1721, 1683 cm–1. H NMR ([D4]MeOH, 300 MHz): δ = 1.39
˜
f
2
2
3409, 3058, 2947, 1717, 1611 cm–1
.
1H NMR ([D4]MeOH,
(dd, JHH = 6.8, 1.8 Hz, 6 H, Me-Ibu), 1.99 (m, 4 H, 3ЈЈ-H), 2.72
3
300 MHz): δ = 1.62–2.11 (m, 12 H, 3ЈЈ-H, 4ЈЈ-H, 5ЈЈ-H), 2.84 (m, (m, 1 H, CH-Ibu), 2.90 (m, 1 H, 2Ј-H), 3.06 (m, 1 H, 2Ј-H), 3.41
2 H, 2Ј-H), 3.25 (m, 2 H, 2Ј-H), 3.66 (m, 2 H, 6ЈЈ-H), 4.09 (m, 2
H, 6ЈЈ-H), 4.55–4.86 (m, 6 H, 4Ј-H, 5Ј-H), 4.95 (m, 4 H, 2ЈЈ-H, 3Ј-
(s, 3 H, OMe), 3.74–3.93 (m, 4 H, 2ЈЈ-H), 4.55 (m, 1 H, 4Ј-H), 4.74
3
(m, 2 H, 5Ј-H), 4.94 (m, 1 H, 3Ј-H), 6.49 (apparent t, JHH
=
3
3
H), 6.45 (apparent q, JHH = 6.6 Hz, 2 H, 1Ј-H), 7.56 (t, JHH
=
6.4 Hz, 1 H, 1Ј-H), 7.61 (t, 3JHH = 7.8 Hz, 2 H, m-H), 7.75 (t, 3JHH
7.9 Hz, 4 H, m-H), 7.73 (m, 8 H, m-H, p-H), 8.07 (d, 3JHH = 8.6 Hz, = 7.4 Hz, 1 H, p-H), 8.09 (d, JHH = 7.2 Hz, 2 H, o-H), 8.25 (s, 1
3
4 H, o-H), 8.22 (d, 3JHH = 8.6 Hz, 4 H, o-H), 8.63 (s, 2-H or 8-H),
8.77 (s, 2-H or 8-H) ppm. 13C NMR ([D4]MeOH, 75.5 MHz): δ =
20.7, 22.1, 26.7, 32.1, 33.7 (C-3ЈЈ, C-4ЈЈ, C-5ЈЈ), 38.0 (C-2Ј), 39.3
H, 8-H) ppm. 13C NMR ([D4]MeOH, 75.5 MHz): δ = 19.6 (Me),
35.8 (C-3ЈЈ), 36.3 (C-3ЈЈ), 37.2 (CH-Ibu), 40.1 (C-2Ј), 48.8 (OMe),
65.5 (C-5Ј), 66.1 (C-2ЈЈ), 66.2 (C-2ЈЈ), 71.8 (C-3Ј), 85.3, 86.4 (C-4Ј,
(C-2Ј), 64.2, 65.4, 65.6 (C-5Ј, C-6ЈЈ), 78.0 (C-3Ј), 78.6 (C-3Ј), 84.3 C-1Ј), 122.1 (C-5), 129.9, 130.8 (Co, Cm), 131.1 (Ci), 134.8 (Cp),
(C-4Ј), 85.0 (C-4Ј), 86.7 (C-1Ј), 86.9 (C-1Ј), 100.0 (C-2ЈЈ), 100.3 (C- 139.5 (C-8), 148.5 (C-2), 149.8 (C-4), 157.6 (C-6), 167.8 (Ph-C=O),
2ЈЈ), 125.4 (C-5), 129.6, 129.8, 129.9, 130.7 (Co, Cm), 131.1 (Ci),
131.2 (Ci), 134.1 (Ci), 134.6 (Cp), 135.2 (Cp), 144.6 (C-8), 151.3 (C-
6), 153.1 (C-2), 153.3 (C-4), 167.7 (Ph-C=O), 168.0 (Ph-C=O) ppm.
MS (ES+): m/z (%) = 544 (90) [M + H]+. HRMS (EI): calcd. for
C29H30N5O6 [M]+ 544.2188; found 544.2191.
181.9 (Ibu-C=O) ppm. MS (ES+): m/z (%) = 556 (100) [M + H]+.
HRMS (EI): calcd. for C27H34N5O8 [M]+ 556.2386; found
556.2402.
5Ј-O-Benzoyl-N2-isobutyryl-3Ј-O-(tetrahydrofuranyl)-2Ј-deoxyguanos-
ine (9d): White hygroscopic solid (two diastereoisomers); yield
N6,5Ј-O-Dibenzoyl-3Ј-O-(4-methoxytetrahydropyranyl)-2Ј-deoxyad- 61.2 mg, 52%. R (2% MeOH/CH Cl ) = 0.33. IR (NaCl): ν =
enosine (7c): White solid; yield 102.2 mg, 81 %. Rf (2 % MeOH/
˜
f
2
2
3429, 1715, 1683 cm–1. H NMR ([D4]MeOH, 300 MHz): δ = 1.40
(d, 3JHH = 6.8 Hz, 6 H, Me-Ibu), 1.42 (d, 3JHH = 6.8 Hz, 6 H, Me-
Ibu), 2.16 (m, 8 H, 3ЈЈ-H, 4ЈЈ-H), 2.79 (m, 2 H, CH-Ibu), 2.91 (m,
1
CH Cl ) = 0.37; m.p. 107–110 °C. IR (NaCl): ν = 3439, 3056, 2963,
˜
2
2
1708, 1634 cm–1. H NMR (CDCl3, 300 MHz): δ = 1.85 (m, 4 H,
1
3ЈЈ-H), 2.61 (m, 1 H, 2Ј-H), 3.02 (m, 1 H, 2Ј-H), 3.23 (s, 3 H, OMe), 2 H, 2Ј-H), 3.11 (m, 2 H, 2Ј-H), 4.08 (m, 4 H, 5ЈЈ-H), 4.54 (m, 2
3.59 (m, 2 H, 2ЈЈ-H), 3.72 (m, 2 H, 2ЈЈ-H), 4.44 (m, 2 H, 4Ј-H, 5Ј- H, 4Ј-H), 4.79 (m, 6 H, 3Ј-H, 5Ј-H), 5.53 (m, 2 H, 2ЈЈ-H), 6.49
3
3
H), 4.66 (dd, |2JHH| = 11.8, JHH = 3.7 Hz, 1 H, 5Ј-H), 4.87 (m, 1 (apparent t, JHH = 7.5 Hz, 2 H, 1Ј-H), 7.63 (m, 4 H, m-H), 7.78
3
H, 3Ј-H), 6.44 (apparent t, JHH = 6.4 Hz, 1 H, 1Ј-H), 7.36–7.58
(m, 6 H, m-H, p-H), 7.94 (m, 4 H, o-H), 8.17 (s, 1 H, 2-H or 8-H),
8.71 (s, 1 H, 2-H or 8-H) ppm. 13C NMR ([D4]MeOH, 75.5 MHz):
δ = 35.8 (C-3ЈЈ), 36.4 (C-3ЈЈ), 39.5 (C-2Ј), 48.9 (OMe), 65.0 (C-5Ј),
66.2 (C-2ЈЈ), 71.4 (C-3Ј), 85.1 (C-4Ј), 86.9 (C-1Ј), 99.6 (C-4ЈЈ), 125.5
(C-5), 129.6, 129.8, 130.7 (Co, Cm), 131.1 (Ci), 134.1 (Cp), 134.7
(m, 2 H, p-H), 8.11 (m, 4 H, o-H), 8.25 (s, 2 H, 8-H) ppm. 13C
NMR (CDCl3, 75.5 MHz): δ = 18.8 (Me), 18.9 (Me), 23.2, 23.3,
32.2, 33.3 (C-3ЈЈ, C-4ЈЈ), 35.9 (CH-Ibu), 36.8 (C-2Ј), 38.3 (C-2Ј),
63.8, 67.1 (C-5ЈЈ, C-5Ј), 75.6 (C-3Ј), 76.7 (C-3Ј), 82.1, 83.2, 85.0,
85.1 (C-1Ј, C-4Ј), 103.1 (C-2ЈЈ), 103.7 (C-2ЈЈ), 121.7 (C-5), 128.3,
128.4, 129.2 (Co, Cm), 129.3 (Ci), 133.2 (Cp), 133.3 (Cp), 137.9 (C-
(Cp), 135.2 (Ci), 145.1 (C-8), 151.3 (C-6), 153.3 (C-2), 153.4 (C-4), 8), 147.5 (C-2), 147.7 (C-4), 155.8 (C-6), 166.5 (Ph-C=O), 166.6
167.7 (Ph-C=O), 168.1 (Ph-C=O) ppm. MS (ES+): m/z (%) = 574
(100) [M + H]+. HRMS (EI): calcd. for C30H32N5O7 [M]+
574.2305; found 574.2296.
(Ph-C=O), 179.1 (Ibu-C=O) ppm. MS (ES+): m/z (%) = 512 (50)
[M + H]+. HRMS (EI): calcd. for C25H30N5O7 [M]+ 512.2155;
found 512.2140.
N6,5Ј-O-Dibenzoyl-3Ј-O-(tetrahydrofuranyl)-2Ј-deoxyadenosine (9c):
White hygroscopic solid (two diastereoisomers); yield 93.1 mg,
General Procedure for the Synthesis of 10: Compounds 5a–c, 7a–
d, and 9a–d (0.27 mmol) were each treated with NH4OH/MeOH
(5.4 mL, 1:1, v/v) and the solutions were stirred overnight at room
temperature (at 60 °C for 7d and 9d). The solvents were evaporated
80%. R (2% MeOH/CH Cl ) = 0.34. IR (NaCl): ν = 3299, 3056,
˜
f
2
2
1710, 1674 cm–1. H NMR (CDCl3, 300 MHz): δ = 1.81–2.06 (m,
1
8 H, 3ЈЈ-H, 4ЈЈ-H), 2.65 (m, 2 H, 2Ј-H), 2.93 (m, 2 H, 2Ј-H), 3.88 and the crude products were purified by flash chromatography
(m, 4 H, 5ЈЈ-H), 4.36–4.70 (m, 8 H, 3Ј-H, 4Ј-H, 5Ј-H), 5.26 (m, 2 using 4% MeOH/CH2Cl2 (10% MeOH/CH2Cl2 for 10d–f).
Eur. J. Org. Chem. 2010, 1736–1744
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1741

V. Gotor, M. Ferrero et al.
FULL PAPER
Large-Scale Preparation of 3Ј-O-(Tetrahydropyranyl)thymidine
(10a): A suspension of thymidine (10 g, 0.04 mol), vinyl benzoate
(29 mL, 0.21 mol), and CAL-B (10 g) in anhydrous THF (200 mL)
was stirred under nitrogen at 250 rpm and 60 °C for 116 h. The
enzyme was filtered off and washed with CH2Cl2 and THF. The
solvents were then evaporated under vacuum. The residue was pre-
cipitated in hexane to afford after filtration 5Ј-O-benzoylthymidine
(3a) as a white solid. 3,4-Dihydro-2H-pyran (18 mL, 0.19 mol) and
pTsOH (3.8 g, 0.02 mol) were added to a solution of 3a in anhy-
drous 1,4-dioxane (266 mL) and the reaction was stirred at room
temperature for 3 h. Next the mixture was poured into a saturated
aqueous NaHCO3 solution and extracted with CH2Cl2. The com-
bined organic fractions were dried (Na2SO4) and concentrated un-
der vacuum. The crude material was dissolved in NH4OH/MeOH
(800 mL, 1:1, v/v) and the mixture was stirred overnight at room
temperature. The solvents were evaporated and the residue purified
by flash chromatography using 2% MeOH/CH2Cl2 to afford 10.5 g
of 10a as a white hygroscopic solid (80% yield).
HRMS (EI): calcd. for C14H20N2NaO6 [M + Na]+ 335.1216; found
335.1214.
3Ј-O-(Tetrahydropyranyl)-2Ј-deoxycytidine (10d): White hygroscopic
solid (two diastereoisomers); yield 73.1 mg, 87%. Rf (5% MeOH/
CH Cl ) = 0.22. IR (NaCl): ν = 3362, 3060, 2947, 1653, 1612, 1493,
˜
2
2
1268 cm–1. 1H NMR ([D4]MeOH, 300 MHz): δ = 1.72–2.03 (m, 12
H, 3ЈЈ-H, 4ЈЈ-H, 5ЈЈ-H), 2.32 (m, 2 H, 2Ј-H), 2.66 (m, 2 H, 2Ј-H),
3.67 (m, 2 H, 6ЈЈ-H), 3.86–4.10 (m, 6 H, 5Ј-H, 6ЈЈ-H), 4.22 (appar-
ent q, 3JHH = 3.4 Hz, 1 H, 4Ј-H), 4.31 (apparent q, 3JHH = 3.1 Hz,
1 H, 4Ј-H), 4.62 (m, 2 H, 3Ј-H), 4.91–4.98 (m, 2 H, 2ЈЈ-H), 6.11 (d,
3
3JHH = 7.2 Hz, 2 H, 5-H), 6.42 (apparent q, JHH 6.6 Hz, 2 H, 1Ј-
3
H), 8.17 (d, JHH 7.2 Hz, 2 H, 6-H) ppm. 13C NMR ([D4]MeOH,
75.5 MHz): δ = 20.5 (C-3ЈЈ), 20.6 (C-3ЈЈ), 26.4, 31.9 (C-4ЈЈ, C-5ЈЈ),
39.1 (C-2Ј), 40.4 (C-2Ј), 62.7 (C-5Ј), 62.8 (C-5Ј), 63.7 (C-5ЈЈ), 63.8
(C-5ЈЈ), 77.3 (C-3Ј), 77.9 (C-3Ј), 86.8, 87.4, 87.5, 87.6 (C-1Ј, C-4Ј),
96.1 (C-5), 99.1 (C-2ЈЈ), 99.9 (C-2ЈЈ), 142.7 (C-6), 158.1 (C-2), 167.4
(C-4) ppm. MS (ES+): m/z (%) = 312 (20) [M + H]+, 334 (95) [M
+ Na]+. HRMS (EI): calcd. for C14H22N3O5 [M]+ 312.1553; found
312.1554.
3Ј-O-(Tetrahydropyranyl)thymidine (10a): White hygroscopic solid
(two diastereoisomers); yield 74.1 mg, 84%. Rf (5% MeOH/
3Ј-O-(4-Methoxytetrahydropyranyl)-2Ј-deoxycytidine (10e): White
solid; yield 82.9 mg, 90%. Rf (5% MeOH/CH2Cl2) = 0.2; m.p. 145–
CH Cl ) = 0.37. IR (NaCl): ν = 3433, 3057, 2948, 1691, 1260 cm–1.
˜
2
2
1H NMR ([D4]MeOH, 300 MHz): δ = 1.71–1.85 (m, 8 H, 4ЈЈ-H,
5ЈЈ-H), 1.89–2.04 (m, 4 H, 3ЈЈ-H), 2.06 (s, 6 H, Me), 2.31–2.67 (m,
4 H, 2Ј-H), 3.73 (m, 2 H, 6ЈЈ-H), 3.87–4.09 (m, 6 H, 5ЈЈ-H, 6ЈЈ-H),
4.02 (apparent q, 3JHH = 3.4 Hz, 1 H, 4Ј-H), 4.28 (apparent q, 3JHH
= 3.2 Hz, 1 H, 4Ј-H), 4.61 (m, 1 H, 3Ј-H), 4.67 (m, 1 H, 3Ј-H),
147 °C. [α]2D0 = +67 (c = 0.7, MeOH). IR (NaCl): ν = 3357, 3061,
˜
2966, 2873, 1651, 1612, 1492 cm–1. 1H NMR ([D4]MeOH,
300 MHz): δ = 1.91–2.07 (m, 4 H, 3ЈЈ-H), 2.35 (m, 1 H, 2Ј-H), 2.57
(m, 1 H, 2Ј-H), 3.42 (s, 3 H, OMe), 3.75–4.01 (m, 6 H, 5Ј-H, 2ЈЈ-
3
H), 4.24 (apparent q, JHH = 3.4 Hz, 1 H, 4Ј-H), 4.74 (m, 1 H, 3Ј-
3
4.94 (m, 2 H, 2ЈЈ-H), 6.42 (apparent q, JHH = 7.4 Hz, 2 H, 1Ј-H),
3
3
H), 6.10 (d, JHH = 7.5 Hz, 1 H, 5-H), 6.42 (apparent t, JHH
=
7.97 (d, |4JHH| = 1.2 Hz, 1 H, 6-H), 7.98 (d, |4JHH| = 1.1 Hz, 1 H,
6-H) ppm. 13C NMR ([D4]MeOH, 75.5 MHz): δ = 12.9 (Me), 21.0,
21.1, 26.9, 32.4 (C-4ЈЈ, C-5ЈЈ, C-3ЈЈ), 38.9 (C-2Ј), 40.1 (C-2Ј), 63.3
(C-5Ј), 63.5 (C-5Ј), 64.2 (C-6ЈЈ), 77.8 (C-3Ј), 78.6 (C-3Ј), 86.6, 86.8,
87.1, 87.7 (C-1Ј, C-4Ј), 99.6 (C-2Ј), 100.3 (C-2Ј), 112.0 (C-5), 112.1
(C-5), 138. 5 (C-6), 152.8 (C-2), 166.8 (C-4) ppm. MS (ES+): m/z
(%) = 349 (100) [M + Na]+. HRMS (EI): calcd. for C15H22N2NaO6
[M + Na]+ 349.1368; found 349.1370.
6.9 Hz, 1 H, 1Ј-H), 8.17 (d, JHH = 7.5 Hz, 1 H, 6-H) ppm. 13C
NMR ([D4]MeOH, 75.5 MHz): δ = 35.6 (C-3ЈЈ), 36.0 (C-3ЈЈ), 41.1
(C-2Ј), 47.2 (OMe), 62.5 (C-5Ј), 65.9 (C-2ЈЈ), 70.8 (C-3Ј), 87.6, 87.7
(C-1Ј, C-4Ј), 96.1 (C-5), 100.1 (C-4ЈЈ), 142.6 (C-6), 158.1 (C-2),
167.4 (C-4) ppm. MS (ES+): m/z (%) = 342 (18) [M + H]+, 364
(100) [M + Na]+. HRMS (EI): calcd. for C15H24N3O6 [M]+
342.1657; found 342.1660.
3
3Ј-O-(Tetrahydrofuranyl)-2Ј-deoxycytidine (10f): White hygroscopic
solid (two diastereoisomers); yield 71.4 mg, 89%. Rf (5% MeOH/
3Ј-O-(4-Methoxytetrahydropyranyl)thymidine (10b): White solid;
yield 82.7 mg, 86%. Rf (5% MeOH/CH2Cl2) = 0.35; m.p. 128–
CH Cl ) = 0.17. IR (NaCl): ν = 3346, 3085, 2985, 2948, 1651, 1610,
˜
2
2
130 °C. IR (NaCl): ν = 3434, 3057, 2967, 1691, 1471, 1260 cm–1.
1268 cm–1. 1H NMR ([D4]MeOH, 300 MHz): δ = 1.98–2.39 (m, 10
H, 2Ј-H, 3ЈЈ-H, 4ЈЈ-H), 2.62 (m, 2 H, 2Ј-H), 3.88–4.11 (m, 8 H, 5Ј-
H, 5ЈЈ-H), 4.17 (apparent q, 3JHH = 3.8 Hz, 1 H, 4Ј-H), 4.22 (appar-
˜
1H NMR ([D4]MeOH, 300 MHz): δ = 1.91–2.06 (m, 4 H, 3ЈЈ-H),
2.07 (d, |4JHH| = 1.1 Hz, 3 H, Me), 2.36–2.55 (m, 2 H, 2Ј-H), 3.43
(s, 3 H, OMe), 3.76–4.02 (m, 6 H, 5Ј-H, 2ЈЈ-H), 4.21 (apparent q,
3JHH = 3.4 Hz, 1 H, 4Ј-H), 4.77 (m, 1 H, 3Ј-H), 6.43 (apparent t,
3JHH = 6.2 Hz, 1 H, 1Ј-H), 7.97 (d, |4JHH| = 1.1 Hz, 1 H, 6-H) ppm.
13C NMR ([D4]MeOH, 75.5 MHz): δ = 12.4 (Me), 35.6 (C-3ЈЈ),
36.1 (C-3ЈЈ), 40.3 (C-2Ј), 48.4 (OMe), 62.6, 65.9 (C-2ЈЈ, C-5Ј), 70.8
(C-3Ј), 86.3, 87.6 (C-1Ј, C-4Ј), 100.1 (C-4ЈЈ), 111.6 (C-5), 138.1 (C-
6), 152.3 (C-2), 166.3 (C-4) ppm. MS (ES+): m/z (%) = 379 (100)
[M + Na]+. HRMS (EI): calcd. for C16H24N2NaO7 [M + Na]+
379.1488; found 379.1476.
3
ent q, JHH = 3.4 Hz, 1 H, 4Ј-H), 4.50 (m, 1 H, 3Ј-H), 4.55 (m, 1
3
H, 3Ј-H), 5.45 (m, 2 H, 2ЈЈ-H), 6.11 (d, JHH = 7.4 Hz, 2 H, 5-H),
3
6.38 (m, 2 H, 1Ј-H), 8.18 (d, JHH = 7.5 Hz, 1 H, 6-H), 8.19 (d,
3JHH = 7.5 Hz, 1 H, 6-H) ppm. 13C NMR ([D4]MeOH, 75.5 MHz):
δ = 24.8 (C-3ЈЈ), 24.8 (C-3ЈЈ), 33.9 (C-4ЈЈ), 39.9 (C-2Ј), 41.3 (C-2Ј),
63.2 (C-5Ј), 68.5 (C-5ЈЈ), 77.9 (C-3Ј), 78.1 (C-3Ј), 87.2, 88.1, 88.2
(C-1Ј, C-4Ј), 96.6 (C-5), 105.1 (C-2ЈЈ), 105.6 (C-2ЈЈ), 143.2 (C-6),
158.6 (C-2), 167.9 (C-4) ppm. MS (ES+): m/z (%) = 298 (50) [M +
H]+, 320 (35) [M + Na]+. HRMS (EI): calcd. for C13H19N3NaO5
[M + Na]+ 320.1211; found 320.1217.
3Ј-O-(Tetrahydrofuranyl)thymidine (10c): White hygroscopic solid
(two diastereoisomers); yield 90.2 mg, 81%. Rf (5% MeOH/
3Ј-O-(Tetrahydropyranyl)-2Ј-deoxyadenosine (10g): White hygro-
scopic solid (two diastereoisomers); yield 72.4 mg, 80%. Rf (5%
CH Cl ) = 0.32. IR (NaCl): ν = 3369, 3059, 2949, 1711, 1664,
˜
2
2
1270 cm–1. H NMR ([D4]MeOH, 300 MHz): δ = 2.05 (d, |4JHH| =
MeOH/CH Cl ) = 0.23. IR (NaCl): ν = 3402, 3056, 2948, 1642,
1
˜
2
2
1.0 Hz, 6 H, Me) 2.06–2.94 (m, 8 H, 3ЈЈ-H, 4ЈЈ-H), 2.31–2.55 (m, 1266 cm–1. 1H NMR ([D6]DMSO, 300 MHz): δ = 1.49–1.78 (m, 12
4 H, 2Ј-H), 3.87–4.21 (m, 10 H, 4Ј-H, 5Ј-H, 5ЈЈ-H), 4.55 (m, 2 H,
H, 3ЈЈ-H, 4ЈЈ-H, 5ЈЈ-H), 2.53 (m, 2 H, 2Ј-H), 2.81 (m, 2 H, 2Ј-H),
3
3Ј-H), 5.45 (m, 2 H, 2ЈЈ-H), 6.39 (apparent t, JHH = 6.6 Hz, 2 H, 3.55–3.82 (m, 8 H, 5Ј-H, 6ЈЈ-H), 4.11 (m, 2 H, 4Ј-H), 4.51 (m, 2 H,
1Ј-H), 7.98 (d, |4JHH| = 1.0 Hz, 1 H, 6-H), 8.01 (d, |4JHH| = 1.0 Hz,
1 H, 6-H) ppm. 13C NMR ([D4]MeOH, 75.5 MHz): δ = 12.4 (Me),
24.3, 33.5 (C-3ЈЈ, C-4ЈЈ), 38.7 (C-2Ј), 39.9 (C-2Ј), 62.6, 62.8, 68.0
3Ј-H), 4.77 (s, 2 H, OH), 5.43 (m, 2 H, 2ЈЈ-H), 6.35 (m, 2 H, 1Ј-
H), 7.36 (s, 4 H, NH), 8.18 (s, 2 H, 2-H or 8-H), 8.38 (s, 1 H, 2-H
or 8-H), 8.39 (s, 1 H, 2-H or 8-H) ppm. 13C NMR ([D6]DMSO,
(C-5Ј, C-5ЈЈ), 77.4 (C-3Ј), 77.8 (C-3Ј), 86.1, 86.3, 86.6, 87.6 (C-1Ј, 75.5 MHz): δ = 23.2, 23.3, 29.0, 34.5, 34.6 (C-3ЈЈ, C-4ЈЈ, C-5ЈЈ),
C-4Ј), 104.5 (C-2ЈЈ), 105.1 (C-2ЈЈ), 111.6 (C-5), 138.1 (C-6), 152.4 40.3 (C-2Ј), 41.3 (C-2Ј), 65.7, 66.1 (C-6ЈЈ, C-5Ј), 80.1 (C-3Ј), 81.1
(C-2), 166.4 (C-4) ppm. MS (ES+): m/z (%) = 335 (70) [M + Na]+.
(C-3Ј), 81.2, 81.3, 89.7, 90.2 (C-1Ј, C-4Ј), 100.6 (C-2ЈЈ), 101.6 (C-
1742
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1736–1744

Chemoenzymatic Synthesis of Acetal-Protected Deoxynucleosides
2ЈЈ), 123.4 (C-5), 143.7 (C-8), 152.9 (C-6), 156.5 (C-2), 160.2 (C-
4) ppm. MS (ES+): m/z (%) = 336 (100) [M + H]+. HRMS (EI):
calcd. for C15H22N5O4 [M]+ 336.1657; found 336.1666.
Acknowledgments
Financial support of this work by the Spanish Ministerio de Educa-
ción y Ciencia (MEC) (Project MEC-07-CTQ-61126) is gratefully
acknowledged. S.M.-M. thanks MEC for a predoctoral FPU fel-
lowship.
3Ј-O-(4-Methoxytetrahydropyranyl)-2Ј-deoxyadenosine (10h): White
solid; yield 87.7 mg, 89%. Rf (5% MeOH/CH2Cl2) = 0.21; m.p.
161–163 °C. IR (NaCl): ν = 3405, 3056, 2983, 1638, 1288 cm–1. 1H
˜
NMR ([D4]MeOH, 300 MHz): δ = 1.96–2.11 (m, 4 H, 3ЈЈ-H), 2.68
(m, 1 H, 2Ј-H), 3.01 (m, 1 H, 2Ј-H), 3.46 (s, 3 H, OMe), 3.83 (m,
2 H, 2ЈЈ-H), 3.94 (m, 3 H, 2ЈЈ-H, 5Ј-H),4.03 (dd, |2JHH| = 12.2,
3JHH = 3.2 Hz, 1 H, 5Ј-H), 4.37 (m, 1 H, 4Ј-H), 4.96 (m, 1 H, 3Ј-
[1] a) H. Mitsuya, K. J. Weinhold, P. A. Furman, M. H. St. Clair,
S. Nusinoff-Lehrman, R. C. Gallo, D. Bolognesi, D. W. Barry,
S. Broder, Proc. Natl. Acad. Sci. USA 1985, 82, 7096–7100; b)
H. Mitsuya, R. Yarchoan, S. Broder, Science 1990, 249, 1533–
1544; c) T. V. Kutateladze, A. M. Kritzyn, V. L. Florentjev,
V. M. Kavsan, Z. G. Chidgeavadze, R. Sh. Beabealashvilli,
FEBS 1986, 207, 205–212; d) D. Z. Chinchaladze, D. A. Prang-
ishvili, A. V. Scamrov, R. Sh. Beabealashvilli, N. B. Dyatkina,
A. A. Krayevsky, Biochim. Biophys. Acta 1989, 1008, 113–115;
e) A. A. Yuzhakov, Z. G. Chidgeavadze, R. Sh. Beabealashvilli,
FEBS 1992, 306, 185–188; f) D. G. Semizaroz, L. S. Victorova,
A. A. Krayevsky, M. K. Kukhanova, FEBS 1993, 327, 45–48.
[2] For a review, see: G. Sartori, R. Ballini, F. Bigi, G. Bosica, R.
Maggi, P. Righi, Chem. Rev. 2004, 104, 199–250.
[3] S. L. Beaucage, M. H. Caruthers, in: Current Protocols in Nu-
cleic Acid Chemistry, (Eds.: S. L. Beaucage, D. E. Bergstrom,
G. D. Glick, R. A. Jones), Wiley, New York, 2000, chapter 3,
pp. 3.3.1–3.3.20.
[4] P. G. M. Wuts, T. W. Greene, in: Greene’s Protective Groups in
Organic Synthesis, 4th ed., Wiley, New Jersey, 2006, pp. 223
and 255.
[5] I. Koukhareva, A. Lebedev, Anal. Chem. 2009, 81, 4955–4962.
[6] W. E. Parham, E. L. Anderson, J. Am. Chem. Soc. 1948, 70,
4187–4189.
[7] a) V. V. Namboodiri, R. S. Varma, Tetrahedron Lett. 2002, 43,
1143–1146; b) R. Nouquier, Tetrahedron Lett. 1982, 23, 2951–
2952; c) J. H. van Boom, J. D. M. Herschied, C. B. Reese, Syn-
thesis 1973, 169–170; d) H. Alper, L. Dinkes, Synthesis 1972,
81–82.
[8] K.-I. Shimizu, E. Hayashi, T. Hatamachi, T. Kodama, Y. Ki-
tayama, Tetrahedron Lett. 2004, 45, 5135–5138.
3
H), 6.60 (dd, JHH = 7.8, 6.1 Hz, 1 H, 1Ј-H), 8.37 (s, 1 H, 8-H),
8.51 (s, 1 H, 2-H) ppm. 13C NMR ([D6]DMSO, 75.5 MHz): δ =
38.4 (C-3ЈЈ), 38.6 (C-3ЈЈ), 42.4 (C-2Ј), 51.7 (OMe), 65.8, 68.4 (C-
2ЈЈ, C-5Ј), 74.3 (C-3Ј), 88.4, 90.7 (C-1Ј, C-4Ј), 102.9 (C-4ЈЈ), 123.4
(C-5), 143.8 (C-8), 153.0 (C-6), 156.6 (C-2), 160.2 (C-4) ppm. MS
(ES+): m/z (%) = 366 (100) [M + H]+. HRMS (EI): calcd. for
C16H24N5O5 [M]+ 366.1778; found 366.1772.
3Ј-O-(Tetrahydrofuranyl)-2Ј-deoxyadenosine (10i): White hygro-
scopic solid (two diastereoisomers); yield 70.3 mg, 81%. Rf (5%
MeOH/CH Cl ) = 0.19. IR (NaCl): ν = 3337, 3058, 1642,
˜
2
2
1266 cm–1. 1H NMR ([D4]MeOH, 300 MHz): δ = 2.16 (m, 8 H,
3ЈЈ-H, 4ЈЈ-H), 2.74 (m, 2 H, 2Ј-H), 2.99 (m, 2 H, 2Ј-H), 3.89–4.17
(m, 8 H, 5Ј-H, 5ЈЈ-H), 4.35 (m, 2 H, 4Ј-H), 4.74 (m, 2 H, 3Ј-H),
3
5.50 (m, 2 H, 2ЈЈ-H), 6.55 (apparent t, JHH = 6.0 Hz, 2 H, 1Ј-H),
8.37 (s, 2 H, 8-H), 8.49 (s, 1 H, 2-H), 8.51 (s, 1 H, H2) ppm. 13C
NMR ([D4]MeOH, 75.5 MHz): δ = 24.6, 33.7, 33.8 (C-3ЈЈ, C-4ЈЈ),
39.4 (C-2Ј), 40.6 (C-2Ј), 63.8, 63.9, 68.3 (C-5ЈЈ, C-5Ј), 78.6 (C-3Ј),
78.9 (C-3Ј), 87.3, 87.4, 87.8, 88.9 (C-1Ј, C-4Ј), 104.9 (C-2ЈЈ), 105.4
(C-2ЈЈ), 121.1 (C-5), 141.7 (C-8), 150.2 (C-6), 153.8 (C-2), 157.8 (C-
4) ppm. MS (ES+): m/z (%) = 322 (100) [M + H]+. HRMS (EI):
calcd. for C14H20N5O4 [M]+ 322.1509; found 322.1510.
3Ј-O-(4-Methoxytetrahydropyranyl)-2Ј-deoxyguanosine (10j): White
solid; yield 101.8 mg, 99%. Rf (5% MeOH/CH2Cl2) = 0.26; m.p.
106–109 °C. IR (NaCl): ν = 3422, 3056, 2962, 1694, 1266 cm–1. 1H
˜
NMR ([D4]MeOH, 300 MHz): δ = 2.06 (m, 4 H, 3ЈЈ-H), 2.66 (m,
1 H, 2Ј-H), 2.88 (m, 1 H, 2Ј-H), 3.45 (s, 3 H, OMe), 3.89 (m, 6 H,
2ЈЈ-H, 5Ј-H), 4.32 (m, 1 H, 4Ј-H), 4.91 (m, 1 H, 3Ј-H), 6.45 (appar-
ent t, 3JHH = 6.2 Hz, 1 H, 1Ј-H), 8.16 (s, 1 H, 8-H) ppm. 13C NMR
([D6]DMSO, 75.5 MHz): δ = 38.5, 38.7 (C-3ЈЈ), 42.1 (C-2Ј), 65.7,
68.5 (C-2ЈЈ, C-5Ј), 74.2 (C-3Ј), 87.1, 90.4 (C-4Ј, C-1Ј), 102.9 (C-4ЈЈ),
120.8 (C-5), 139.7 (C-8), 151.1 (C-2), 153.9 (C-4), 157.2 (C-6) ppm.
MS (ES+): m/z (%) = 382 (50) [M + H]+. HRMS (EI): calcd. for
C16H24N5O6 [M]+ 382.1708; found 382.1721.
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3Ј-O-(Tetrahydrofuranyl)-2Ј-deoxyguanosine (10k): White hygro-
scopic solid (two diastereoisomers); yield 78.3 mg, 86%. Rf (5%
MeOH/CH Cl ) = 0.24. IR (NaCl): ν = 3427, 2930, 1694,
˜
2
1
2
1266 cm–1. H NMR ([D4]MeOH, 300 MHz): δ = 2.02–2.25 (m, 8
H, 3ЈЈ-H, 4ЈЈ-H), 2.67 (m, 2 H, 2Ј-H), 2.89 (m, 2 H, 2Ј-H), 3.87–
4.15 (m, 8 H, 5ЈЈ-H, 5Ј-H), 4.29 (m, 2 H, 4Ј-H), 4.69 (m, 2 H, 3Ј-
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3
H), 5.48 (m, 2 H, 2Ј-H), 6.38 (apparent t, JHH = 6.4 Hz, 2 H, 1Ј-
H), 8.14 (s, 2 H, 8-H) ppm. 13C NMR ([D6]DMSO, 75.5 MHz): δ
= 27.1, 36.2 (C-3ЈЈ, C-4ЈЈ), 40.7 (C-2Ј), 41.9 (C-2Ј), 65.6, 70.4 (C-
5ЈЈ, C-5Ј), 80.2 (C-3Ј), 80.7 (C-3Ј), 86.7, 86.8, 89.2, 90.0 (C-4Ј, C-
1Ј), 106.3 (C-2ЈЈ), 106.9 (C-2ЈЈ), 120.7 (C-5), 139.4 (C-8), 154.9 (C-
2), 157.7 (C-4), 160.8 (C-6) ppm. MS (ES+): m/z (%) = 338 (90) [M
+ H]+. HRMS (EI): calcd. for C14H20N5O5 [M]+ 338.1458; found
338.1459.
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Supporting Information (see also the footnote on the first page of
this article): 1H, 13C, and DEPT NMR spectra in addition to some
2D NMR experiments (HSQC, HMBC, COSY, NOESY), which
were used for peak assignment.
Eur. J. Org. Chem. 2010, 1736–1744
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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Received: December 7, 2009
Published Online: February 3, 2010
1744
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1736–1744