Nucleosides XIII. Facile synthesis of 4-amino-1-(2-deoxy-β-D- ribofuranosyl)quinazolin-2-one as a 2′-deoxycytidine analog for oligonucleotide synthesis

Article abstract of DOI:10.1002/jccs.200500178

4-Amino-1-(2-deoxy-β-D-ribofuranosyl)quinazo1in-2-one (4) was prepared by Barton deoxygenation from 4-amino-1-(β-D-ribofuranosyl)quinazolin-2-one (3) as a 2′-deoxycytidine analog.

Full text of DOI:10.1002/jccs.200500178

Journal of the Chinese Chemical Society, 2005, 52, 1237-1244
1237
Nucleosides XIII.1 Facile Synthesis of
4-Amino-1-(2-deoxy-b-D-ribofuranosyl)quinazolin-2-one as a
2¢-Deoxycytidine Analog for Oligonucleotide Synthesis
Tun-Cheng Chien† (
School of Pharmacy, National Taiwan University, Taipei 100, Taiwan, R.O.C.
), Chien-Shu Chen (
) and Ji-Wang Chern* (
)
4-Amino-1-(2-deoxy-b-D-ribofuranosyl)quinazolin-2-one (4) was prepared by Barton deoxygenation
from 4-amino-1-(b-D-ribofuranosyl)quinazolin-2-one (3) as a 2¢-deoxycytidine analog.
Keywords: 2¢-Deoxycytidine; Cytidine; Quinazolinone; Barton deoxygenation; Markiewicz silylation.
INTRODUCTION
The development of automated solid-phase methods
dine bases have received some attention.3-8 While maintain-
ing Watson-Crick base pairing properties of pyrimidines,
these heterocycles, possessing an extended benzene or naph-
thalene ring fused to pyrimidines (Fig. 1), may provide addi-
tional stacking interactions and enhance the hydrogen bond-
ing. Such an approach could be readily applicable to anti-
sense or antigene research.
for the synthesis of nucleic acids in the last two decades has
prompted the use of synthetic oligonucleotides or modified
analogs to study DNA or RNA interactions. Since all nucleic
acid helices are formed predominantly by hydrogen bonding
and base stacking, strategies designed for improving nucleic
acid recognition/interactions have mainly relied on modifica-
tions of the nucleic acid structure by chemical synthesis. In
attempts of base modification, extending the aromatic do-
mains of aglycons has been considered to increase stacking
interactions between planar heterocyclic bases of nucleic ac-
ids, which would contribute to the stabilization of the nucleic
acid helices.2 Thus, oligonucleotides containing quinazolines
or their derivatives to substitute the corresponding pyrimi-
Quinazoline nucleosides were first synthesized by Stout
and Robins in 1968 as pyrimidine nucleoside analogs9 and
consequent synthetic studies were contributed by Dunkel and
Pfleiderer in the 1990s.10-12 Quinazoline nucleosides were
once used as a conformationally restricted model to study the
syn-anti conformational preference of pyrimidine nucleo-
sides in solution.3,13,14 More recently, several quinazoline-
2,4-dione nucleosides have been incorporated into oligo-
nucleotides as uridine or thymidine substitutes to study the
O
O
O
R5
HN
HN
HN
O
N
R
O
N
R
O
N
R
R5 = H, R2 = OH, uridine (RNA)
R5 = Me, R2 = H, thymidine (DNA)
NH2
NH2
N
O
R = HO
HN
N
O
O
N
R
O
N
R
O
N
R
HO
R2 = OH or H
R2
R
2 = OH, cytidine (1)
R2 = H, 2'-deoxycytidine (2)
Fig. 1. Quinazolines and benzoquinazolines as pyrimidine analogs.
* Corresponding author. Fax: +886-2-2393-4221; E-mail: chern@jwc.mc.ntu.edu.tw
†
Current address: Division of Medicinal Chemistry, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA

1238 J. Chin. Chem. Soc., Vol. 52, No. 6, 2005
Chien et al.
binding affinity and base-pairing selectivity.3-5
2¢-deoxy-b-ribonucleosides: (1) the direct glycosylation of
the base with a 2¢-deoxyribofuranose derivative; and (2) the
2¢-deoxygenation from an appropriately protected ribonu-
cleoside. The synthesis of 4-amino-1-(2-deoxy-b-D-ribo-
furanosyl)quinazolin-2-one (4) was previously reported by
Stout and Robins9 via a direct glycosylation of quinazoline-
2,4-dione with 2-deoxy-3,5-di-O-p-toluoyl-a-D-ribofurano-
syl chloride16-18 followed by a multi-step functional group
manipulation. The glycosylation was not very stereoselective
and the separation of the a/b anomeric mixture was difficult.
Therefore, this approach is not practical for large scale syn-
thesis.3,11 In our preliminary studies, a direct alkylation or
glycosylation at the N1-position of 4-amino-protected 4-ami-
noquinazolin-2-ones was unsuccessful, which prompted us
to investigate the 2¢-deoxygenation of 4-amino-1-(b-D-ribo-
furanosyl)quinazolin-2-one15 (3) as an alternative synthetic
route.
4-Aminoquinazolin-2-one nucleosides (3 and 4) are our
particular interest (Fig. 2). These quinazoline nucleosides
were previously synthesized via a multi-step procedure from
quinazoline-2,4-dione by Stout and Robins.9 But the use of
4-aminoquinazolin-2-one nucleosides (3 and 4) in oligo-
nucleotides has not yet been reported in the literature. Our
group has previously reported a convenient synthesis of the
4-amino-1-(b-D-ribofuranosyl)quinazolin-2-one (3).15 In an
effort to incorporate 4-aminoquinazolin-2-one into oligo-
deoxynucleotides, we hereby report a facile synthesis of 4-
amino-1-(2-deoxy-b-D-ribofuranosyl)quinazolin-2-one (4),
which could be used for automated DNA synthesis (Scheme
I).
RESULTS AND DISCUSSION
A convenient preparation of 2¢-deoxynucleosides from
the corresponding ribonucleosides using chemical 2¢-deoxy-
genation was reported by Robins and Wilson.19,20 This ap-
proach was achieved by the phenoxythiocarbonylation of
3¢,5¢-O-protected nucleosides followed by the Barton deoxy-
genation reaction.21 However, we have encountered some dif-
ficulties when we applied the same synthetic route to the
4-aminoquinazolin-2-one nucleoside (3). The 3¢,5¢-diol of
4-amino-1-(b-D-ribofuranosyl)quinazolin-2-one15 (3) was
selectively protected with the Markiewicz reagent22,23 to give
5 in an excellent yield. But our attempts to introduce the
phenoxythiocarbonyl group to the 2¢-O-position under sev-
eral conditions were unsuccessful and led to a mixture of un-
identified products. We speculated that the free amino group
There are two general approaches for the preparation of
NH2
N
NH2
N
N
N
O
O
HO
HO
O
O
HO
R
HO
R
1 R = OH (cytidine)
2 R = H (2'-deoxycytidine)
3 R = OH
4 R = H
Fig. 2. Cytosine nucleosides (1 and 2) and proposed
4-aminoquinazolin-2-one nucleosides (3 and
4).
Scheme I
O
O
P
O
Base
O
O
O
NH2
N
NHBz
N
NHBz
N
NH2
O
N
N
N
N
O
P
O
O
O
O
N
O
HO
HO
DMTrO
O
O
O
O
HO
OH
HO
O
O
O
P
CN
3
11
O P
O
O
N(i-Pr)2
Base
O

2¢-Deoxycytidine Analog
J. Chin. Chem. Soc., Vol. 52, No. 6, 2005 1239
at the 4-position of the quinazolinone might interfere with the
phenoxythiocarbonylation. We first tried to protect the 4-ami-
no group with N,N-dimethylformamide dimethyl acetal.1,15,24
This attempt only had moderate success because the overall
yield after the protecting steps was unsatisfactory. Therefore,
we decided to introduce a benzoyl group onto the 4-amino
group that could serve as a protecting group throughout the
oligonucleotide synthesis. Compound 5 was treated with 1.3
equivalents of benozyl chloride in pyridine to give 54% of the
monobenzoylated product 7a and 16% of the dibenzoylated
product 7b. The monobenzoylated product 7a was identified
as the desired 4-amino-benzoylated product. When the reac-
tion was carried out with 1.1 equivalents of benzoyl chloride,
the desired 4-amino-benzoylated product 7a was obtained in
53% yield, and about 24% of the unreacted starting material 5
was recovered. The recovered starting material was treated
under the same benzoylation condition. After two reaction
cycles, the 4-amino group of 5 was regioselectively protected
and the desired 4-amino-benzoylated product 7a was ob-
tained in 65-73% overall yield.
with a mixture of potassium fluoride and 18-crown-6 in tetra-
hydrofuran.26 The 4-amino-benzoyl group was removed by
treatment of 11 with methanolic ammonia to afford the de-
sired 4-amino-1-(2-deoxy-b-D-ribofuranosyl)quinazolin-2-
one (4) in 43% yield (Scheme II).
The split patterns of the anomeric protons (1¢-H) for 4
1
and 11 in the H NMR spectrums both exhibit as a pseudo-
triplet. Since the anomeric configuration has previously been
established as the b-configuration,15 this observation is con-
sistent with Townsend’s empirical rule that the anomeric pro-
tons of the 2¢-deoxyribofuranosyl nucleosides displaying a
pseudo-triplet split pattern mostly possess the b-configura-
tion.25
CONCLUSION
In summary, our investigation has provided a feasible
route for the synthesis of 4-amino-1-(2-deoxy-b-D-ribofu-
ranosyl)quinazolin-2-one (4). The 3¢,5¢-diol of 4-amino-1-
(b-D-ribofuranosyl)quinazolin-2-one15 (3) was selectively
protected with the Markiewicz reagent.22,23 Regioselective
protection of the 4-amino group on the base with benzoyl
chloride was accomplished. In an effort to introduce the phen-
oxythiocarbonyl group to the 2¢-O-position, we observed the
unexpected intramolecular nucleophilic ring-closure reac-
tion. But the undesired reaction can be avoided simply by the
solvent effect, i.e. by changing the solvent from acetonitrile
to dichloromethane.11 After phenoxythiocarbonylation at the
2¢-hydroxy group, the nucleoside 9 underwent Barton deoxy-
genation followed by the removal of the protecting groups to
give the desired 2¢-deoxynucleoside (4) as a 2¢-deoxycytidine
(2) analog. Incorporating the 2¢-deoxy quinazolinone nucleo-
side (4) into the oligodeoxynucleotide synthesis is in prog-
ress.
Phenoxythiocarbonylation of 7a under a commonly
used condition, phenyl chlorothionocarbonate and an excess
amount of 4-dimethylaminopyridine in acetonitrile,11,19,20
gave a single product 8. Mass spectrometry suggested that 8
is a dehydrated product of 7a. The 2¢-hydroxy group on the
sugar, the amide hydrogen on the base, and the desired phen-
1
oxythiocarbonyl group were all absent from the H NMR
spectrum. The structure was consequently assigned as 3¢,5¢-
O-protected O2,2¢-anhydronucleoside 8.11 It is noticeable that
the coupling constant between 1¢-H and 2¢-H (J1¢-2¢) in 8 is 8.3
Hz. This coupling constant is considerably greater than in
other compounds (5, 7a-b) with b-configuration in this series
(J1¢-2¢ ~ 0 Hz), which results from the cis-coupling between
the 1¢-H and 2¢-H.25 To avoid the intramolecular nucleophilic
ring-closure reaction, a modified condition using dichloro-
methane as the solvent was employed, and the reaction gave
exclusively the desired 2¢-O-phenoxythiocarbonylated prod-
uct 9 in 87% yield. An excess amount of 4-dimethylamino-
pyridine (2-3 equivalent) is essential in these reactions.
The deoxygenation was carried out with tri-n-butyltin
hydride by a homolytic cleavage of the C2¢-O2¢ bond followed
by a hydrogen transfer in a radical chain reaction to afford 10
in 49% yield. Deprotection of the Markiewicz’s disilyl group
with tetra-n-butylammonium fluoride in tetrahydrofuran
gave the 4-amino-benzoylated 2¢-deoxynucleoside 11 in 72%
yield. Alternatively, the disilyl group could also be deblocked
EXPERIMENTAL SECTION
General Chemical Procedures
Melting points were obtained on an Electrothermal ap-
paratus and are uncorrected. NMR spectra were obtained on
Varian Gemini-300, JEOL JNM-EX400 or Bruker DRX-500
spectrometers. Mass spectra were recorded on Finnigan
TSQ-46C (EI), JEOL JMS-D300 (EI), VG 70-250S (FAB) or
Micromass LCT (ESI) mass spectrometers. Elemental analy-

1240 J. Chin. Chem. Soc., Vol. 52, No. 6, 2005
Chien et al.
Scheme II
NH2
N
NH2
N
NH2
N
N
N
O
N
O
O
b or c
a
HO
O
O
iPr
iPr
iPr
iPr
O
O
O
Si
Si
O
O
HO
OH
O
OH
O
Si
O
OPh
Si
3
iPr
iPr
iPr
iPr
S
5
6
d
approximately
64-70% conversion
Bz
Bz
NHBz
HN
N
N
N
N
N
O
N
O
N
b
c
O
O
O
O
iPr
iPr
iPr
iPr
iPr
iPr
O
O
O
Si
Si
Si
O
O
O
O
O
O
O
OR2
O
Si
Si
Si
Ph
iPr
iPr
iPr
iPr
iPr
iPr
8 (53%)
S
9 (87%)
7a R2 = H (54%)
7b R2 = Bz (16%)
e
NHBz
N
NHR
N
N
O
O
N
f or g
O
HO
h
iPr
iPr
O
O
Si
O
O
HO
Si
11 R = Bz
4 R = H
iPr
iPr
10
Reagents and conditions: (a) TiPDS-Cl2, pyridine, rt, 5 hr, 89%; (b) PTC-Cl, 2-3 eq. DMAP, CH3CN, rt, overnight; (c) PTC-Cl,
2-3 eq. DMAP, CH2Cl2, 0 °C or rt, 3 hr; (d) BzCl, pyridine, 0 °C -rt, overnight; (e) AIBN, n-Bu3SnH, toluene, 80 °C, 3 hr, 49%;
(f) KF, 18-crown-6, H2O, THF, rt, 4 hr, 55%; (g) TBAF, THF, rt, 90 min, 72%; (h) NH3/MeOH, rt, 24 hr, 43% [TiPDS-Cl2 =
1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, the Markiewicz reagent; PTC-Cl = phenyl chlorothionocarbonate; AIBN =
2,2¢-azobisisobutyronitrile].
ses for C, H, and N were carried out either on a Heraeus ele-
mental analyzer or Perkin-Elmer 240 elemental analyzer and
were within ±0.4% of the theoretical values. Thin-layer chro-
matography (TLC) was performed on Merck plates precoated
with silica gel 60 containing fluorescent indicator. Com-
pounds on thin-layer chromatography were visualized by il-
lumination under UV light (254 nm), or dipped into 10%
methanolic sulfuric acid followed by charring on a hot plate.
Merck silica gel (230-400 mesh) was used for flash column
chromatography as described by Still, W. C. et al.27 Evapora-
tion was carried out with a rotary evaporator under reduced
pressure with the bath temperature below 50 °C unless speci-
fied otherwise. Materials obtained from commercial suppli-
ers were used without further purification unless otherwise

2¢-Deoxycytidine Analog
J. Chin. Chem. Soc., Vol. 52, No. 6, 2005 1241
stated. The solvents (THF, CH3CN, CH2Cl2, pyridine, tolu-
ene) and reagents (benzoyl chloride) were purified/dried by
distillation according to the standard procedures.28 The re-
ported yields have not been optimized.
H), 4.82 (d, 1H, J = 6.0 Hz), 5.10 (t, 1H, J = 6.7 Hz), 5.97 (s,
1H, 1¢-H), 7.27-7.74 (m, 6H, Ar), 8.39-8.41 (m, 2H, Ar),
8.66-8.68 (m, 1H, Ar), 13.02 (br s, 1H, NH); 13C NMR
(CDCl3, 75 MHz) d 13.2, 13.2, 13.6, 13.7, 13.8, 17.6, 17.8,
17.9, 18.1, 63.6, 72.6, 74.1, 83.1, 92.6, 115.1, 116.8, 124.5,
128.7, 128.8, 130.6, 133.4, 136.3, 137.4, 142.1, 147.6, 158.1,
180.3; MS (FAB) m/z 81 (20), 105 (100), 266 (60), 289 (25),
640 (12) (M + 1).
4-Amino-1-[3,5-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-
diyl)-b-D-ribofuranosyl]quinazolin-2-one (5)
To a suspension of 4-amino-1-(b-D-ribofuranosyl)-
quinazolin-2-one15 (3, 3.0 g, 10.2 mmol) in pyridine (50 mL)
at room temperature was added 1,3-dichloro-1,1,3,3-tetraiso-
propyldisiloxane (3.6 mL, 3.55 g, 11.25 mmol, 1.1 eq). The
mixture was stirred at room temperature for 5 hr. The solvent
was removed under reduced pressure and the residue was dis-
solved in CHCl3 (100 mL). The organic solution was washed
with H2O (2 ´ 30 mL), saturated NaCl solution (30 mL), dried
over anhydrous MgSO4, and the solvent was evaporated un-
der reduced pressure. The resulting residue was purified by
flash column chromatography (CHCl3/MeOH = 97.5:2.5) to
give 5 (foam, 4.90 g, 9.15 mmol, 89%, Rf = 0.31 (CHCl3/
MeOH = 95:5)). 1H NMR (CDCl3, 300 MHz) d 0.97-1.12 (m,
28H, iPr), 3.57 (br s, 1H, 2¢-OH), 3.92-4.06 (m, 3H, 4¢ &
5¢-H), 4.79 (d, 1H, J = 6.5 Hz), 5.04 (t, 1H, J = 6.9 Hz), 6.00
(s, 1H, 1¢-H), 7.07-7.13 (m, 1H, Ar), 7.41 (br s, 2H, NH2),
7.48-7.54 (m, 1H, Ar), 7.72-7.74 (m, 2H, Ar); 13C NMR
(CDCl3, 75 MHz) d 13.2, 13.7, 13.8, 17.7, 17.8, 17.8, 17.9,
18.0, 18.1, 64.2, 73.2, 73.6, 83.2, 92.8, 110.9, 115.1, 123.0,
125.0, 134.8, 143.2, 155.9, 163.9; MS (FAB) m/z 162 (100),
261 (12), 357 (10), 535 (7) (M).
When the reaction was carried out with 1.3 equivalents
of benzoyl chloride, the desired product (7a) was obtained in
54% yield and approximately 16% of 4-benzamido-1-[2-O-
benzoyl-3,5-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-
b-D-ribofuranosyl]quinazolin-2-one (7b) (Rf = 0.34 (Hex/
EtOAc = 8:2)) was obtained from the reaction mixture.
4-Benzamido-1-[2-O-benzoyl-3,5-O-(1,1,3,3-tetraisopropyl-
disiloxane-1,3-diyl)-b-D-ribofuranosyl]quinazolin-2-one
(7b)
1H NMR (CDCl3, 300 MHz) d 0.87-1.25 (m, 28H, iPr),
4.04-4.15 (m, 3H, 4¢ & 5¢-H), 5.23 (dd, 1H, J = 6.2, 8.4 Hz,
3¢-H), 6.16 (s, 1H, 1¢-H), 6.22 (d, 1H, J = 6.2 Hz, 2¢-H),
7.33-7.73 (m, 9H, Ar), 8.06-8.10 (m, 2H, Ar), 8.39-8.43 (m,
2H, Ar), 8.68-8.72 (m, 1H, Ar), 13.06 (br s, 1H, NH); MS
(FAB) m/z 77 (18), 105 (100), 261 (15), 479 (18), 744 (20) (M
+ 1).
O2,2¢-Anhydro-4-benzamido-1-[3,5-O-(1,1,3,3-tetraisopro-
pyldisiloxane-1,3-diyl)-b-D-ribofuranosyl]quinazolin-2-one
(8)
4-Benzamido-1-[3,5-O-(1,1,3,3-tetraisopropyldisiloxane-
1,3-diyl)-b-D-ribofuranosyl]quinazolin-2-one (7a)
To a mixture of 7a (0.65 g, 1.01 mmol) and 4-dimethyl-
aminopyridine (DMAP, 0.41 g, 3.33 mmol, 3.3 eq) in aceto-
nitrile (20 mL) at room temperature was added phenyl chlo-
rothionocarbonate (0.31 mL, 0.38 g, 2.22 mmol, 2.2 eq). The
mixture was stirred at room temperature overnight. The sol-
vent was removed under reduced pressure and the residue
was dissolved in CHCl3 (30 mL). The organic solution was
washed with H2O (15 mL) and saturated NaCl solution (15
mL), dried over anhydrous MgSO4, and the solvent was
evaporated under reduced pressure. The resulting residue
was purified by flash column chromatography (Hex/EtOAc
= 7:3) to give 8 (foam, 0.332 g, 0.53 mmol, 53%, Rf = 0.35
(Hex/EtOAc = 6:4)). 1H NMR (CDCl3, 300 MHz) d 1.00-1.26
(m, 28H, iPr), 3.83-4.04 (m, 3H, 4¢ & 5¢-H), 4.50 (dd, 1H, J =
4.5, 9.9 Hz, 3¢-H), 5.33 (dd, 1H, J = 4.5, 8.2 Hz, 2¢-H), 6.47
(d, 1H, J = 8.2 Hz, 1¢-H), 7.19-7.56 (m, 7H, Ar), 8.03-8.10
(m, 2H, Ar); 13C NMR (CDCl3, 75 MHz) d 13.0, 13.2, 13.7,
To a mixture of 5 (4.83 g, 9.01 mmol) in pyridine (100
mL) at 0 °C was added dropwise benzoyl chloride (1.14 mL,
1.39 g, 9.91 mmol, 1.1 eq). After the addition was completed,
the temperature was allowed to rise to room temperature and
the mixture was stirred overnight. The reaction was quenched
by adding H2O (1 mL). The solvent was removed under re-
duced pressure and the residue was dissolved in CHCl3 (100
mL). The organic solution was washed with H2O (2 ´ 30 mL)
and saturated NaCl solution (30 mL), dried over anhydrous
MgSO4, and the solvent was evaporated under reduced pres-
sure. The resulting residue was purified by flash column
chromatography (Hex/EtOAc = 85:15) to give 7a (foam, 3.06
g, 4.78 mmol, 53%, Rf = 0.27 (Hex/EtOAc = 8:2), also recov-
ered 24% of 5). 1H NMR (CDCl3, 300 MHz) d 1.00-1.26 (m,
28H, iPr), 3.36 (br s, 1H, 2¢-OH), 3.96-4.08 (m, 3H, 4¢ & 5¢-

1242 J. Chin. Chem. Soc., Vol. 52, No. 6, 2005
Chien et al.
13.9, 17.5, 17.5, 17.7, 17.8, 18.0, 62.7, 78.4, 83.8, 86.4, 89.7,
114.9, 117.3, 126.1, 128.1, 128.7, 130.2, 132.9, 133.7, 135.4,
135.8, 154.5, 157.6, 181.7; MS (FAB) m/z 105 (100), 622
(80) (M + 1).
9:1) to give 10 (oil, 1.13 g, 1.81 mmol, 49%, Rf = 0.25
(Hex/EtOAc = 9:1)). 1H NMR (CDCl3, 300 MHz) d 0.87-1.44
(m, 28H, iPr), 2.41 (ddd, 1H, J = 6.9, 9.0, 13.9 Hz, 2¢-H), 2.93
(ddd, 1H, J = 4.6, 9.0, 13.9 Hz, 2¢-H), 3.88 (dd, 1H, J = 5.1,
11.0 Hz, 5¢-H), 4.00-4.16 (m, 2H, 4¢ & 5¢-H), 5.00-5.08 (m,
1H, 3¢-H), 6.56 (dd, 1H, J = 4.6, 9.0 Hz, 1¢-H), 7.30-7.69 (m,
6H, Ar), 8.39-8.41 (m, 2H, Ar), 8.67-8.69 (m, 1H, Ar), 13.02
(br s, 1H, NH); 13C NMR (CDCl3, 75 MHz) d 13.1, 13.4, 13.8,
14.0, 14.7, 17.5, 17.6, 17.7, 17.8, 17.9, 18.0. 18.1, 38.0 (2¢-
CH2), 63.4 (5¢-CH2), 72.6, 84.5, 85.7, 115.8, 117.2, 124.3,
128.8 (2 ´ C), 130.6, 133.3, 135.8, 137.5, 141.3, 147.7,
158.0, 180.3; MS (ESI) m/z 543 (38), 646 (100) (M + Na);
HRMS (ESI) Calcd for C32H45N3O6Si2 · Na: 646.2745. Found
646.2732.
4-Benzamido-1-[2-O-phenoxythiocarbonyl-3,5-O-(1,1,3,3-
tetraisopropyldisiloxane-1,3-diyl)-b-D-ribofuranosyl]quin-
azolin-2-one (9)
To a mixture of 7a (0.968 g, 1.52 mmol) and 4-dimeth-
ylaminopyridine (DMAP, 0.407 g, 3.33 mmol, 2.2 eq) in di-
chloromethane (10 mL) at 0 °C was added phenyl chloro-
thionocarbonate (0.26 mL, 0.327 g, 1.89 mmol, 1.25 eq). The
mixture was stirred at room temperature for 3 hr. The reaction
was quenched by adding H2O (0.25 mL). The solvent was re-
moved under reduced pressure and the residue was dissolved
in EtOAc (100 mL). The organic solution was washed with
H2O (2 ´ 45 mL) and saturated NaCl solution (45 mL), dried
over anhydrous Na2SO4, and the solvent was evaporated un-
der reduced pressure. The resulting residue was purified by
flash column chromatography (Hex/EtOAc = 9:1) to give 9
(foam, 1.03 g, 1.33 mmol, 87%, Rf = 0.56 (Hex/EtOAc =
8:2)). 1H NMR (CDCl3, 400 MHz) d 1.09-1.43 (m, 28H, iPr),
4.01-4.17 (m, 3H, 4¢ & 5¢-H), 5.32 (dd, 1H, J = 5.8, 8.8 Hz,
3¢-H), 6.02 (s, 1H, 1¢-H), 6.68 (d, 1H, J = 5.8 Hz, 2¢-H), 7.09-
7.72 (m, 11H, Ar), 8.67-8.39 (m, 2H, Ar), 8.63-8.65 (m, 1H,
Ar), 11.20 (br s, 1H, NH); 13C NMR (CDCl3, 100 MHz) d
12.6, 12.8, 13.0, 13.2, 14.0, 16.8, 17.0, 17.1, 17.2, 17.4, 22.6,
31.5, 61.0, 70.1, 81.7, 83.4, 89.1, 114.3, 116.3, 121.7, 124.0,
126.5, 128.1, 128.2, 129.4, 130.0, 132.7, 135.7, 136.7, 141.2,
146.8, 153.3, 157.2, 179.7, 194.1; MS (ESI) m/z 644 (100)
(M + Na - HOC(=S)OPh), 798 (77) (M + Na); HRMS (ESI)
Calcd for C39H49N3O8Si2S · Na: 798.2677. Found 798.2672;
Anal. Calcd for C39H49N3O8Si2S: C, 60.36; H, 6.36; N, 5.41.
Found: C, 60.39; H, 6.49; N, 5.44.
4-Benzamido-1-(2-deoxy-b-D-ribofuranosyl)quinazolin-2-
one (11)
[Method A]
To a mixture of 10 (1.13 g, 1.81 mmol), potassium fluo-
ride (1.44 g, 24.8 mmol, 8 eq) and 18-crown-6 (0.66 g, 2.48
mmol, 0.8 eq) in THF (20 mL) was added one drop of H2O.
The mixture was stirred at room temperature for 5 hr. The sol-
vent was removed under reduced pressure and the residue
was dissolved in CHCl3 (50 mL). The solution was washed
with H2O (2 ´ 20 mL) and saturated NaCl solution (20 mL),
dried over anhydrous Na2SO4, and the solvent was evapo-
rated under reduced pressure. The resulting residue was pu-
rified by flash column chromatography (CHCl3/MeOH =
95:5, Rf = 0.21) to give 11 (378 mg, 0.99 mmol, 55%). An an-
alytical sample of 11 was obtained by recrystallization from
EtOAc.
[Method B]
To a solution of 10 (0.195 g, 0.31 mmol) in THF (5 mL)
was added 1 M TBAF solution in THF (1.55 mL, 5 eq). The
mixture was stirred at room temperature for 90 min. The
solvent was removed under reduced pressure and the result-
ing residue was purified by flash column chromatography
(CHCl3/MeOH = 95:5, Rf = 0.21) to give 11 (85.1 mg, 0.223
mmol, 72%). The compound was recrystallized from EtOAc
to give an analytical sample of 11 (57.2 mg, 0.15 mmol,
48%). mp 170-173 °C (decomp.) (EtOAc); 1H NMR (DMSO-
d6, 400 MHz) d 1.99 (ddd, 1H, J = 3.7, 7.5, 13.4 Hz, 2¢-H),
2.69 (dt, 1H, J = 7.9, 13.4 Hz, 2¢-H), 3.64-3.77 (m, 3H, 4¢ &
5¢-H), 4.42 (m, 1H, 3¢-H), 4.97 (br s, 1H, OH), 5.27 (br s, 1H,
OH), 6.69 (t, 1H, J = 7.5 Hz, 1¢-H), 7.36-7.40 (m, 1H, Ar),
7.51-7.55 (m, 2H, Ar), 7.60-7.64 (m, 1H, Ar), 7.72-7.76 (m,
4-Benzamido-1-[2-deoxy-3,5-O-(1,1,3,3-tetraisopropyl-
disiloxane-1,3-diyl)-b-D-ribofuranosyl]quinazolin-2-one
(10)
To a solution of 9 (2.8715 g, 3.70 mmol) and 2,2¢-azo-
bisisobutyronitrile (AIBN, 0.122 g, 0.74 mmol, 0.2 eq) in dis-
tilled toluene (80 mL) at room temperature under an argon at-
mosphere was added tri-n-butyltin hydride (3.0 mL, 3.23 g,
11.1 mmol, 3 eq). The mixture was then heated at 80 °C for 3
hr. After cooling to room temperature, the solution was con-
centrated under reduced pressure and the resulting oil was pu-
rified by flash column chromatography (Hex/EtOAc = 10:0-

2¢-Deoxycytidine Analog
J. Chin. Chem. Soc., Vol. 52, No. 6, 2005 1243
C.-S.; Chern, J.-W. J. Chin. Chem. Soc. (Taipei) 2004, 51,
1401-1406.
1H, Ar), 7.95-7.97 (m, 1H, Ar), 8.26-8.28 (m, 2H, Ar), 8.53-
8.55 (m, 1H, Ar), 12.68 (br s, 1H, NH); 13C NMR (DMSO-d6,
100 MHz) d 36.3 (2¢-CH2), 60.8 (5¢-CH2), 69.5, 84.0, 86.7,
115.8, 117.2, 123.7, 127.3, 128.4, 129.6, 132.9, 135.3, 136.2,
139.8, 147.5, 155.9, 178.4; MS (ESI) m/z 288 (50), 404 (100)
(M + Na); HRMS (ESI) Calcd for C20H19N3O5·Na: 404.1222.
Found 404.1223. Anal. Calcd for C20H19N3O5: C, 62.99; H,
5.02; N, 11.02. Found: C, 62.71; H, 5.04; N, 11.16.
2. Kool, E. T. Chem. Rev. 1997, 97, 1473-1487.
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G. R. Nucleosides Nucleotides 1995, 14, 45-63.
4. Michel, J.; Toulme, J.-J.; Vercauteren, J.; Moreau, S. Nu-
cleic Acids Res. 1996, 24, 1127-1135.
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hedron 1997, 53, 8457-8478.
6. Godde, F.; Toulme, J.-J.; Moreau, S. Biochemistry 1998, 37,
13765-13775.
4-Amino-1-(2-deoxy-b-D-ribofuranosyl)quinazolin-2-one9
(4)
7. Arzumanov, A.; Godde, F.; Moreau, S.; Toulme, J.-J.;
Weeds, A.; Gait, M. J. Helv. Chim. Acta 2000, 83, 1424-
1436.
Compound 11 (378 mg, 0.99 mmol) was dissolved in
methanolic ammonia (20 mL) and the solution was stirred at
room temperature for 24 hr. The solvent was removed under
reduced pressure and the resulting residue was recrystallized
from ethanol and H2O to give 4 (118 mg, 0.43 mmol, 43%).
mp 211-213 °C (decomp.) (EtOH/H2O) [lit.9 212.5-213 °C
(MeOH/H2O)]; 1H NMR (DMSO-d6, 500 MHz) d 1.86-1.89
(m, 1H, 2¢-H), 2.62 (dt, 1H, J = 8.2, 13.2 Hz, 2¢-H), 3.62-3.70
(m, 3H, 4¢-H & 5¢-H), 4.39-4.40 (m, 1H, 3¢-H), 4.96 (t, 1H, J
= 4.9 Hz, OH), 5.23 (d, 1H, J = 4.9 Hz, OH), 6.75 (t, 1H, J =
7.7 Hz, 1¢-H), 7.19-7.22 (m, 1H, Ar), 7.57-7.61 (m, 1H, Ar),
7.79-7.81 (m, 1H, Ar), 7.89 (br s, 1H, NH), 8.04-8.06 (m, 2H,
1 ´ Ar & 1 ´ NH); 13C NMR (DMSO-d6, 125 MHz) d 37.2
(2¢-CH2), 61.9 (5¢-CH2), 70.8 (CH), 84.7 (CH), 87.2 (1¢-CH),
111.3, 117.3 (CH), 122.4 (CH), 125.7 (CH), 134.1 (CH),
142.0, 156.0, 163.8; MS (ESI) m/z 184 (30) (4-aminoquin-
azolin-2-one + Na), 300 (100) (M + Na); HRMS (ESI) Calcd
for C13H15N3O4 · Na: 300.0960. Found 300.0962. Anal. Calcd
for C13H15N3O4 · ¼ H2O: C, 55.41; H, 5.54; N, 14.91. Found:
C, 55.56; H, 5.47; N, 14.87.
8. Godde, F.; Toulme, J.-J.; Moreau, S. Nucleic Acids Res.
2000, 28, 2977-2985.
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ACKNOWLEDGMENTS
20. Robins, M. J.; Wilson, J. S.; Hansske, F. J. Am. Chem. Soc.
1983, 105, 4059-4065.
This investigation was supported by a research grant
(NSC 84-2331-B-016-018) from the National Science Coun-
cil of the Republic of China, Taiwan.
21. Barton, D. H. R.; McCombie, S. W. J. Chem. Soc. Perkin
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Received January 18, 2005.
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