Synthesis of nucleoside aminooxy acids

Article abstract of DOI:10.1016/j.tet.2011.06.105

First nucleoside aminooxy acids were synthesized from furanoid sugar phthalimidooxy acids by N-glycosylation with uracil, thymine, N-benzoylcytosine, 6-N-benzoyladenine and 2-N-acetyl-6-O-diphenylcarbamoylguanine. Boc or Fmoc protected uridine aminooxy ac

Full text of DOI:10.1016/j.tet.2011.06.105

Tetrahedron 67 (2011) 7114e7120
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of nucleoside aminooxy acids
,
,
*
Yanchun Gong a b, Sandrine Peyrat a, Hongbin Sun b, Juan Xie a
a PPSM, ENS Cachan, Institut d’Alembert, CNRS, 61 av President Wilson, F-94230 Cachan, France
b Center for Drug Discovery, College of Pharmacy, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 May 2011
Received in revised form 28 June 2011
Accepted 30 June 2011
Available online 6 July 2011
First nucleoside aminooxy acids were synthesized from furanoid sugar phthalimidooxy acids by N-gly-
cosylation with uracil, thymine, N-benzoylcytosine, 6-N-benzoyladenine and 2-N-acetyl-6-O-diphe-
nylcarbamoylguanine. Boc or Fmoc protected uridine aminooxy acid derivatives have also been prepared.
As oxyamine protecting group, the phthalimido group was shown to be instable in MeOH, leading to the
imide ring-opening product in a reversible way. This reaction was accelerated under acid or basic con-
ditions. A uridine dimer linked by N-oxy amide has also been prepared by coupling of uridine aminooxy
ester with uridine phthalimidooxy acid. These nucleoside aminooxy acids might constitute useful
building blocks for the development of novel RNA mimics and conjugates with other biomolecules or
reporter compounds.
Keywords:
Nucleosides
Sugar aminooxy acids
Nucleoside aminooxy acids
N-Glycosylation
Dinucleosides
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
O
P
-O
Much recent efforts have been devoted to the development of
synthetic oligonucleotides for various therapeutic and diagnostic
applications because of their capability to cause selective inhibition
of gene expression by binding to the target DNA/RNA sequences
through mechanisms, such as antigen, antisense and RNA in-
terference.1 Nonionic analogues of nucleic acids are promising for
the treatment of viral diseases and cancer since nonionic phosphate
mimics could increase cellular permeability and resistance to extra-
and intracellular nucleases. A number of phosphodiester re-
placements have been reported, including amide,2 thioacetamide,3
triazole,4 sulfide,5 formacetal,6 thioformacetal,6b,7 dimethylene-
sulfone,8 methylene(methylimino),9 as well as silyl10 analogues.
Synthesis of modified RNA oligomers has attracted renewed
interest since the discovery of small interfering RNA (siRNA) for
gene regulation.1c,e,11 We are interested in the development of
novel nucleoside building blocks, especially ribonucleoside ami-
nooxy acid, which could be further used for the generation of N-oxy
amide-linked oligoribonucleosides as novel oligonucleotide mimics
(Fig. 1). Recent studies on aminooxy acids showed that amino-
oxypeptides can easily form intramolecular hydrogen bonds with
turns and helices structures, and a new family of foldamers has
O
O
B
B
O
O
OH
HO2C
B
O
OH
n
O
O
O
P
-O
HN
O
O
B
B
OH
O
O
O
H2N
Nucleoside
aminooxy acid
OH
OH
O
n
HN
O
n = 0, 1
DNA or RNA backbone
N-oxy amide backbone
Fig. 1. Structure of natural and modified oligonucleotide backbones and nucleoside
aminooxy acid.
hydrolysis. Very recently, we13 and others14 have developed gly-
coaminooxy acids as a new class of sugar building blocks, with
interesting secondary structure for their oligomers.14 Aminooxy
functionalized nucleoside9,15 and oligonucleotides16 have been
reported for the development of methylene(methylimino)-linked
oligonucleotide mimics, for prodrug design or for immobilization
in the fabrication of microarrays. An N-oxy amide-linked thymidine
dimer has been incorporated into DNA oligomer, which annealed to
complementary DNA with nearly the same affinity as the natural
sequence.17 To the best of our knowledge, N-oxy amide-linked ri-
bonucleosides have never been reported before. Like amide
been developed from a-, b- and g
-aminooxy acids.12 Furthermore,
N-oxy amide linkage is stable to chemical and enzymatic
* Corresponding author. Tel.: þ33 1 47405586; fax: þ33 1 47402454; e-mail
address: joanne.xie@ens-cachan.fr (J. Xie).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.06.105

Y. Gong et al. / Tetrahedron 67 (2011) 7114e7120
7115
oligonucleosides, N-oxy amide-linked ones should be resistant to
nucleases degradation. The stability towards peptidases, the easy
formation of hydrogen bond and the possibility of further func-
tionalization of N-oxy amide bond18 are among the particularity of
N-oxy amide derivatives compared to their amide counterparts.
Like amide-linked oligonucleotides, oligo N-oxy amide ana-
logues of nucleic acids could be prepared with straightforward
peptide coupling chemistry.12 The synthetic challenge for the de-
velopment of N-oxy amide-linked RNA is the synthesis of the nu-
cleoside aminooxy acid building blocks (Fig. 1). We reported herein
the synthesis of first nucleoside aminooxy acids. As a proof of
principle, a dimer resulting from the monomers is described. Apart
from oligomerization into oligonucleosides, several applications of
nucleoside aminoxy acids described herein can be envisaged.
Thanks to the presence of both aminooxyl and carboxyl functions,
these nucleosides can be readily used for oligonucleotide conju-
gation with peptides or carbohydrates,19 which might find appli-
cations for viral infections and/or cancer treatment.20 Nucleoside
aminooxy acids might also be suitable for conjugations with re-
porter compounds and markers.
in the presence of N,O-bis(trimethylsilyl)acetamide (BSA) and
TMSOTf under reflux led successfully to the corresponding nucleo-
side aminooxy acids 4e8 in 41e71% yields. 1,2-Dichloroethane was
used as solvent for the synthesis of 10 because of insolubility of 2-N-
acetyl-6-O-diphenylcarbamoylguanine in acetonitrile. The relative
low yields for the nucleoside formation is due to the loss of product
during purification, despite the fact that all the glycosylations were
clean on TLC.
In order to make nucleoside aminooxy acids suitable for further
transformations, we then tried to introduce different protecting
groups on the uridine derivative 4 (Scheme 2). Esterification of 4
with tert-butoxytrichloroacetimidate led not only to the desired
ester 10 but also the N-tert-butyl compound 9, which can be con-
verted into 10 by treatment with AcOH in CH2Cl2. Hydrazinolysis of
10 led to the oxyamine 12 and a small quantity of the trans-
acetylation product 11. Acidic deprotection of 12 led to the fully
deprotected aminooxy acid 13, which was somewhat instable9e and
difficult to be purified. Nevertheless, its structure has been
O
N
O
N
2. Results and discussion
NH
NtBu
O
Nucleoside aminooxy acids might be prepared either from nat-
ural nucleosides, by introducing aminooxy acid function on the
sugar ring, or from furanoid sugar aminooxy acids by N-glycosyla-
tion with nucleic bases. After unsuccessful ring opening of the 2,30-
anhydro uridine derivative with N-protected hydroxylamine, we
then decided to start the synthesis from our previously prepared
furanoid sugar aminooxy acid 1 (Scheme 1).13b Removal of the iso-
propylidene group under acidic condition followed by acetylation
with Ac2O led to 2, which can be readily transformed into ester 3. N-
Glycosylation of 2 with uracil, thymine, N-benzoylcytosine, 6-N-
benzoyladenine and 2-N-acetyl-6-O-diphenylcarbamoylguanine21
CO2tBu
O
CO2tBu
O
O
i
4
+
O
OAc
O
OAc
NPhth
NPhth
10 (42 %)
9 (51 %)
ii
CO2tBu
O
CO2H
CO2tBu
O
U
+
U
U
iii
O
iv
10
O
OH
O
O
OH
OH
NHAc
NH2
NH2
O
O
11 (8 %)
12 (77 %)
13
CO2H
CO2H
OH
Ref. 13b
O
O
O
i
CO2tBu
OAc
U
O
v
O
O
O
O
O
OAc
O
12
14
NPhth
NPhth
FmocHN
O
OH
2
1
CO2Me
O
U
ii
iii, vi, vii
4
CO2tBu
O
15
O
BocN
Me
OAc
OH
O
OAc
Base
CO2H
3
CO2tBu
O
NPhth
CO2tBu
O
U
U
O
iii
2
O
OAc
OH
OH
viii
O
O
NPhth
4 + 12
HN
HN
O
O
Base :
U
U
O
O
O
O
NHBz
N
OCONPh2
N
NHBz
N
N
N
N
HN
HN
N
OAc
O
OAc
PhthN
O
N
O
O
N
O
NHAc
17
N
N
N
16
CO-NH
CO2Me
4 (71 %)
5 (70 %)
7 (41 %)
8 (47 %)
6 (51 %)
Scheme 1. Reagents and conditions: (i) H2SO4, Ac2O, AcOH, 77%; (ii) t-BuOH, DCC,
DMAP, CH2Cl2, 60%; (iii) base: uracil for 4, thymine for 5, N-benzoylcytosine for 6, 6-N-
benzoyladenine for 7, 2-N-acetyl-6-O-diphenylcarbamoylguanine for 8; BSA, TMSOTf,
MeCN (for 4 to 7) or ClCH2CH2Cl (for 8).
Scheme 2. Reagents and conditions: (i) t-BuOC(]NH)CCl3 (2.6 equiv), cyclohexane,
CH2Cl2; (ii) 10% AcOH, CH2Cl2, 85%; (iii) NH2NH2, MeOH; (iv) TFA, CH2Cl2, 100%; (v)
FmocOSu, NaHCO3, 1,4-dioxane, H2O, 73%; (vi) Boc2O, NaHCO3, 1,4-dioxane, H2O; (vii)
MeI, NaHCO3, 25% for three steps; (viii) EDC, HOBt, DMF, 50% from 10.

7116
Y. Gong et al. / Tetrahedron 67 (2011) 7114e7120
confirmed by 1H and 13C NMR. Compound 13 could also be obtained
by hydrazinolysis of 4. The O-amine function of 13 can be readily
protected by the Fmoc group, offering the desired compound 14 in
73% yields. This function was also protected with Boc2O. To obtain
an analytical pure sample, the carboxylic acid was protected as
methyl ester. However, N-methylation occurred simultaneously,
leading to the compound 15. Finally, coupling of carboxylic acid 4
with oxyamine 12 led successfully to the dinucleoside 16 in 50%
overall yield from 10. Compound 16 has been fully characterized by
1H, 13C NMR and HRMS. Surprisingly, we have observed the for-
mation of phthalimido ring-opening product 17 during column
chromatography of 16 with CH2Cl2/MeOH (Scheme 2). The slowly
ring opening of the phthalimido group of 16 by CD3OD in the NMR
sample has also been observed. It is to be noticed that the instability
of phthalimidooxy group in MeOH has never been reported.22
We then decided to investigate the stability of uridine derivative
4 in the presence of MeOH (Scheme 3). Treatment of compound 4
with K2CO3 in MeOH at rt led to the ring-opening product 18 in 30%
isolated yield. Esterification of 4 with MeI and NaHCO3 in DMF led
quantitatively to the ester 19. Deacetylation of 19 with NaOMe led
firstly to the phthalimido ring-opening product 20 after 40 min
reaction. Compound 20 can be converted back to the phthalimi-
dooxy derivative 19 by heating at 130e140 ꢀC under reduced
pressure. Further treatment with NaOMe deprotected the 20-O-
acetyl group, providing a mixture of compounds 21 and 22. Similar
phenomena have been observed during the saponification of 19
with K2CO3 or NaOH (4 M) in MeOH. The ring closure reaction of the
phthalimido group has also been observed by heating 21 under
reduced pressure, along with some decomposition. Under acidic
condition in MeOH, we have observed successive transformations
of compound 4 to the methyl ester 22 through the intermediates 19,
20 and 21 on TLC.
3. Conclusion
In summary, nucleoside aminooxy acids have been successfully
synthesized for the first time by N-glycosylation of sugar aminooxy
acids with five common nucleic bases. Fmoc and Boc protected
uridine aminooxy esters have also been prepared. Coupling re-
action of uridine aminooxy acid derivatives led to the desired N-oxy
amide-linked dinucleoside. The instability of phthalimidooxy
group in methanol has been observed, leading reversibly to the
imide ring-opening product. This reaction was catalysed under
basic or acid conditions. These nucleoside aminooxy acid de-
rivatives might be useful building blocks for the synthesis of novel
oligoribonucleotides mimics as well as conjugates with peptides,
carbohydrates or reporter compounds.
4. Experimental
4.1. General
1H and 13C NMR spectra were recorded on a 400 spectrometer in
CDCl3, CD3OD or DMSO-d6 solutions. Column chromatography was
performed on Silica 60 (40e63 mM). Analytical thin-layer chroma-
tography was performed on aluminium percolated plates of Silica
Gel 60 F254 with detection by UV or by spraying with 6 N H2SO4 and
heating about 2 min at 300 ꢀC for sugar derivatives. Optical rota-
tions were measured using a Jasco P-2000 polarimeter. High res-
olution mass spectra (HRMS) were measured by the Service de
ꢀ
ꢀ
Spectrometrie de Masse de l’Universite Pierre et Marie Curie-Paris
6.
4.2. Preparation of 3-deoxy-1,2-O-diacetyl-3-
(phthalimidooxymethyl)-
D-ribofuranuronic acid 2
To a solution of 113b (600 mg, 1.65 mmol) in AcOH (21 mL) and
Ac2O (2.1 mL), was added concd H2SO4 (100 L, 1.98 mmol). After
m
CO2H
CO2H
U
stirring overnight, H2O was added and the mixture extracted with
EtOAc. The organic layer was washed with brine, dried (MgSO4),
filtered and evaporated to give a crude product (633 mg), pure
enough for the next steps. Purification by column chromatography
(CH2Cl2/MeOH/AcOH, 70/1/0.1) afforded 2 (521 mg, 77.3%) as
U
O
O
i
O
CO-NH
CO2Me
OAc
OH
O
NPhth
a syrup. Rf¼0.35 (CH2Cl2/MeOH/AcOH, 6/0.3/0.15); ½a D20
þ19.6 (c
ꢁ
18
4
0.55, CHCl3); 1H NMR (400 MHz, CDCl3):
d 2.11 (s, 3H, OAc), 2.22 (s,
3H, OAc), 3.30 (br s, 1H, H-3), 4.52e4.54 (m, 3H, H-4, CH2), 5.55 (d,
1H, J¼4.6 Hz, H-2), 6.21 (s, 1H, H-1), 7.70e7.85 (m, 4H, Phth). 13C
CO2Me
O
CO2Me
U
U
NMR (100 MHz, CDCl3):
d 20.8, 21.1 (CH3), 43.3 (CH), 73.4 (CH2),
O
ii
iii
iv
4
75.0, 78.1, 99.6 (CH); 123.8 (CH), 128.8 (C), 134.8 (CH), 163.3, 169.9
(C). IR (neat): nmax¼1726, 1460 cmꢂ1. HRMS (ESI) calcd for
C18H17NO10 [MþNa]þ: 430.0750; found: 430.0745.
CO-NH
CO2Me
O
OAc
O
OAc
NPhth
20
19
4.3. Preparation of tert-butyl 3-deoxy-1,2-O-diacetyl-3-
(phthalimidooxymethyl)-D-ribofuranuronate 3
v
To a solution of 2 (146 mg, 0.358 mmol) in CH2Cl2 (2.5 mL), were
added t-BuOH (69 L, 0.715 mmol), DMAP (18 mg, 0.143 mmol) and
m
CO2Me
O
CO2Me
O
U
U
DCC (96 mg, 0.468 mmol) in CH2Cl2 (0.5 mL) at 0 ꢀC. After stirring
overnight, the mixture was filtered and the filtrate diluted with
CH2Cl2, washed with H2O, dried (MgSO4), filtered, evaporated to
dryness and purified by chromatography (petroleum ether/EtOAc,
4/1) to give 3 (114 mg, 60%) as a colourless syrup. Rf¼0.59 (CH2Cl2/
+
CO-NH
CO2Me
O
OH
OH
O
NPhth
22
MeOH, 20/1); mp: 108 ꢀC; ½a D20
ꢁ
þ2.4 (c 1.61, CHCl3); 1H NMR
21
(51 %)
(15%)
iv
(400 MHz, CDCl3): d 1.48 (s, 9H, t-Bu), 2.07 (s, 3H, OAc), 2.20 (s, 3H,
OAc), 3.12e3.22 (m, 1H, H-3), 4.32 (d, 1H, J¼9.6 Hz, H-4), 4.40e4.50
vi
(m, 2H, CH2), 5.47 (d, 1H, J¼5.0 Hz, H-2), 6.15 (s, 1H, H-1), 7.70e7.85
19
22
4
20
21
(m, 4H, Phth). 13C NMR (100 MHz, CDCl3):
d 20.8, 21.1 (CH3), 43.4
Scheme 3. Reagents and conditions: (i) K2CO3, MeOH, 30%; (ii) MeI, NaHCO3, DMF,
100%; (iii) NaOMe, MeOH, rt, 40 min, 82%; (iv) 30e40 mmHg, 130e140 ꢀC, 2 h; (v)
(CH), 73.5 (CH2), 75.0, 78.8 (CH); 82.6 (C), 99.6, 123.8 (CH), 128.8 (C),
NaOMe, MeOH, rt, overnight; (vi) MeOH, HClconcd
.
134.8 (CH), 163.3, 169.2, 169.4, 169.9 (C). IR (neat): nmax¼3683, 1796,

Y. Gong et al. / Tetrahedron 67 (2011) 7114e7120
7117
1726, 1674 cmꢂ1. HRMS (ESI) calcd for C22H25NO10 [MþNa]þ:
1487 cmꢂ1. HRMS (ESI) calcd for C27H22N4O10 [MþNa]þ: 585.1234;
486.1376; found: 486.1371.
found: 585.1228.
4.4.4. 20-O-Acetyl-N-benzoyl-50-carboxylic acid-30-deoxy-30-(phtha-
limidooxymethyl)adenosine 7. Yield 41%. White solid: Rf¼0.44
4.4. General procedure for the coupling of 2 with nucleobases
(CH2Cl2/MeOH/AcOH, 20/3/0.2); mp: 146 ꢀC; ½a D20
þ15.4 (c 0.19,
ꢁ
CHCl3); 1H NMR (400 MHz, CDCl3):
d 2.35 (s, 3H, OAc), 3.35e3.45
To a mixture of crude 2 (1 mmol, 1 equiv) and nucleobase
(1.5 equiv) in anhyd MeCN or Cl(CH2)2Cl (15 mL), was added N,O-
bis(trimethylsilyl)acetamide (BSA, 4.5 equiv). The mixture was then
reflux for 30 min until the solution was clear. After cooling to rt,
TMSOTf (1.5 equiv) was added, and the mixture reflux again for
2e3 h until the reaction was complete, then cooled to rt. Different
treatments have been used for compounds 4e8. Compounds 4e6:
the solution was evaporated to dryness; the residue was dissolved
in EtOAc and washed with 1 N HCl, brine, dried (MgSO4), filtered,
evaporated and purified by column chromatography (CH2Cl2/
MeOH/AcOH, 40/1/0.1 to 20/1/0.05). Compound 7: saturated
NaHCO3 was added to the reaction mixture, then extracted with
CHCl3. The aqueous layer was acidified to pH 4e5 with AcOH, then
extracted with CHCl3. The combined organic layers were dried
(MgSO4), filtered, evaporated and purified by column chromatog-
raphy (CH2Cl2/MeOH/AcOH, 40/1/0.1 to 25/1/0.07). Compound 8:
saturated NaHCO3 was added to the reaction mixture, then
extracted with CHCl3. The organic layer was acidified to pH 4e5
with AcOH, then washed with H2O, dried (MgSO4), filtered, evap-
orated and purified by column chromatography (CH2Cl2/MeOH/
AcOH, 60/1/0.1 to 30/1/0.07).
(m, 1H, H-30), 4.45e4.52 (m, 1H, CHa-30), 4.57 (t, 1H, J¼9.2 Hz, CHb-
30), 4.75 (d, 1H, J¼9.6 Hz, H-40), 5.75 (m, 1H, J¼5.0 Hz, H-20), 6.3 (s,
1H, H-10), 7.52e7.60 (m, 3H, Bz), 7.70e7.85 (m, 4H, Phth), 8.02 (d,
2H, J¼6.7 Hz, Bz), 8.49 (s, 1H, H-8), 8.78 (s, 1H, 2-H). 13C NMR
(100 MHz, CDCl3):
d 20.8 (CH3), 43.6 (CH), 72.8 (CH2), 77.3, 80.3,
92.3, 123.9, 128.2 (CH), 128.8 (C), 129.0, 133.2, 134.9, 150.1, 152.3
(CH), 163.3 (C). IR (neat): nmax¼3678, 1735, 1604, 1582 cmꢂ1. HRMS
(ESI) calcd for C28H22N6O9 [MþNa]þ: 609.1346; found: 609.1352.
4.4.5. 50-Carboxylic acid-30-deoxy-2-N,20-O-diacetyl-6-O-dipenylcarba-
moyl-30-(phthalimidooxymethyl)guanosine 8. Yield 47%. White solid:
Rf¼0.65 (CH2Cl2/MeOH/AcOH, 20/3/0.2); mp: 179 ꢀC; ½a D20
þ46.3 (c
ꢁ
0.20, MeOH); 1H NMR (400 MHz, CD3OD):
d 1.99 (s, 3H, OAc), 2.22 (s,
3H, OAc), 4.15e4.25 (m, 1H, H-30), 4.55e4.70 (m, 3H, CH2-30, H-40),
6.08 (d, 1H, J¼5.5 Hz, H-20), 6.33 (s, 1H, H-10), 7.20e7.55 (m, 10H,
CONPh2), 7.78e7.79 (m, 4H, Phth), 8.58 (s, 1H, H-8). 13C NMR
(100 MHz, CD3OD): d 19.4, 23.2 (CH3), 43.0 (CH), 73.2 (CH2), 77.1, 79.7,
90.6, 123.0, 126.5, 126.9, 127.0, 127.4, 127.5 (CH), 128.9 (CH), 129.1 (C),
134.5 (CH), 144.4, 154.0, 163.7, 170.5 (C). IR (neat): nmax¼1726, 1626,
1600, 1496 cmꢂ1. HRMS (ESI) calcd for C36H29N7O11 [MþNa]þ:
758.1823; found: 758.1823.
4.4.1. 20-O-Acetyl-50-carboxylic
acid-30-deoxy-30-(phthalimidoox-
ymethyl)uridine 4. Yield 71%. White solid: Rf¼0.36 (CH2Cl2/MeOH/
4.5. Preparation of 20-O-acetyl-50-carboxylic acid tert-butyl
ester-30-deoxy-30-(phthalimidooxymethyl)-N-tert-
AcOH, 6/0.9/0.5); ½a D20
ꢁ
þ37.1 (c 0.24, CHCl3); mp: 154 ꢀC; 1H NMR
(400 MHz, CDCl3):
d
2.22 (s, 3H, OAc), 3.30e3.40 (m, 1H, H-30), 4.42
butyluridine 9 and 20-O-acetyl-50-carboxylic acid tert-butyl
ester-30-deoxy-30-(phthalimidooxymethyl)uridine 10
(dd, 1H, J¼5.0, 9.2 Hz, CHa-30), 4.48 (t, 1H, J¼9.2 Hz, CHb-30), 4.73 (d,
1H, J¼8.2 Hz, H-40), 5.78 (dd, 1H, J¼2.8, 6.9 Hz, H-20), 5.80 (d, 1H,
J¼2.3 Hz, H-10), 5.81 (d, 1H, J¼8.2 Hz, H-5), 7.70e7.85 (m, 5H, Phth,
To a solution of 4 (264 mg, 0.574 mmol) in anhyd CH2Cl2 (9 mL)
and cyclohexane(3 mL), was added t-BuOC(]NH)CCl3 (264 mL,
H-6), 9.47 (s, 1H, NH). 13C NMR (100 MHz, CDCl3):
d
20.8 (CH3), 43.5
(CH), 73.6 (CH2), 75.3, 79.3, 92.3, 102.6, 123.8 (CH), 128.8 (C); 134.8,
141.2 (CH), 150.2, 163.3, 164.0, 169.7, 173.2, 174.7 (C). IR (neat):
4.47 mmol). After overnight stirring at rt, EtOAc was added to the
reaction mixture. The solution was washed with saturated NaHCO3,
brine, dried (MgSO4), filtered and condensed under reduced pres-
sure to dryness, purified by chromatography (petroleum ether/
EtOAc, 4/1, 2/1 then 1/1) to get compounds 9 (51%) and 10 (42%).
Compound 9: white solid, Rf¼0.45 (CH2Cl2/MeOH, 20/1); mp:
nmax¼2978, 1726, 1687, 1465 cmꢂ1
. HRMS (ESI) calcd for
C20H17N3O10 [MþNa]þ: 482.0812; found: 482.0806.
4.4.2. 20-O-Acetyl-50-carboxylic
acid-30-deoxy-30-(phthalimidoox-
ymethyl)thymidine 5. Yield 70%. Colourless syrup: Rf¼0.41 (CH2Cl2/
76 ꢀC; ½a 2D0
ꢁ
þ85.6 (c 0.89, CHCl3); 1H NMR (400 MHz, CDCl3):
d 1.50
MeOH/AcOH, 20/3/0.2); mp: 173 ꢀC; ½a D20
ꢁ
þ47.1 (c 0.18, CHCl3); 1H
(s, 9H, t-Bu),1.64 (s, 9H, t-Bu) 2.20 (s, 3H, OAc), 2.90e2.96 (m,1H, H-
30), 4.28 (dd, 1H, J¼6.4, 8.7 Hz, CHa-30), 4.43 (dd, 1H, J¼6.8, 8.7 Hz,
CHb-30), 4.62 (d, 1H, J¼9.6 Hz, H-40), 5.74 (dd, 1H, J¼1.4, 5.5 Hz, H-
20), 5.82 (d, 1H, J¼7.8 Hz, H-5), 6.02 (d,1H, J¼1.8 Hz, H-10), 7.75e7.85
(m, 4H, Phth), 8.33 (d, 1H, J¼7.3 Hz, H-6). 13C NMR (100 MHz,
NMR (400 MHz, CDCl3):
d 1.88 (s, 3H, CH3), 2.21 (s, 3H, OAc),
3.30e3.40 (m, 1H, H-30), 4.40e4.50 (m, 2H, CH2-30), 4.70 (d, 1H,
J¼6.8 Hz, H-40), 5.71 (d, 1H, J¼6.0 Hz, H-20), 5.76 (s, 1H, H-10), 7.58 (s,
1H, H-6), 7.70e7.85 (m, 4H, Phth), 9.57 (s, 1H, NH). 13C NMR
(100 MHz, CDCl3):
d
12.5, 20.8 (CH3), 43.6 (CH), 73.7 (CH2), 75.6,
CDCl3): d 20.8, 28.0, 28.3 (CH3); 44.0 (CH), 73.4 (CH2), 76.0, 80.4
79.3, 93.7 (CH), 111.5 (C), 123.8 (CH), 128.8 (C), 134.8 (CH), 137.9
(CH), 150.7, 163.3, 164.4, 170.1, 173.1 (C). IR (neat): nmax¼1730, 1700,
1652 cmꢂ1. HRMS (ESI) calcd for C21H19N3O10 [MþNa]þ: 496.0968;
found: 496.0979.
(CH), 83.5, 83.6 (C), 92.1, 97.8,123.8 (CH),128.8 (C),134.8,141.9 (CH),
155.4, 163.0, 169.0, 169.6, 171.5 (C). IR (neat): nmax¼1734, 1656, 1630,
1526 cmꢂ1. HRMS (ESI) calcd for C28H33N3O10 [MþNa]þ: 594.2064;
found: 594.2041.
Compound 10: white solid, Rf¼0.33 (CH2Cl2/MeOH, 20/1); mp:
4.4.3. 20-O-Acetyl-N-benzoyl-50-carboxylic acid-30-deoxy-30-(phtha-
108 ꢀC; ½a 2D0
ꢁ
þ63.8 (c 0.51, CHCl3); 1H NMR (400 MHz, CDCl3):
d 1.50
limidooxymethyl)cytidine 6. Yield 51%. White solid: Rf¼0.53
(s, 9H, t-Bu), 2.22 (s, 3H, OAc), 2.98e3.07 (m, 1H, H-30), 4.34 (dd, 1H,
J¼6.0, 9.2 Hz, CHa-30), 4.45 (dd, 1H, J¼7.3, 9.2 Hz, CHb-30), 4.65 (d,
1H, J¼8.7 Hz, H-40), 5.67 (dd, 1H, J¼2.8, 6.4 Hz, H-20), 5.82 (d, 1H,
J¼2.3, 7.8 Hz, H-5), 6.02 (d, 1H, J¼2.3 Hz, H-10), 7.75e7.85 (m, 4H,
Phth), 8.15 (d, 1H, J¼8.3 Hz, H-6), 8.50 (s, 1H, NH). 13C NMR
(CH2Cl2/MeOH/AcOH, 20/3/0.2); ½a D20
ꢁ
þ145.6 (c 0.06, MeOH); mp:
d 2.26 (s, 3H, OAc), 3.30e3.40
143 ꢀC; 1H NMR (400 MHz, CDCl3):
(m, 1H, H-30), 4.44 (m, 1H, CHa-30), 4.50 (t, 1H, J¼9.2 Hz, CHb-30),
4.78 (d, 1H, J¼9.2 Hz, H-40), 5.88 (m, 2H, H-10,20), 7.52 (t, 2H,
J¼7.8 Hz, Ph), 7.58e7.60 (m, 1H, H-5), 7.65 (t, 1H, J¼7.3 Hz, Ph),
7.70e7.85 (m, 4H, Phth), 7.94 (d, 2H, J¼7.8 Hz, Ph), 8.33 (br s, 1H, H-
(100 MHz, CDCl3):
d 20.8, 28.1 (CH3); 43.9 (CH), 73.3 (CH2), 75.4,
79.8 (CH), 83.9 (C), 90.8, 102.9, 123.9 (CH), 128.8 (C), 134.9, 140.1
(CH),150.0, 162.9, 163.2, 169.4, 169.6 (C). IR (neat): nmax¼3683, 1735,
1696, 1457 cmꢂ1. HRMS (ESI) calcd for C24H25N3O10 [MþNa]þ:
538.1438; found: 538.1432.
6). 13C NMR (100 MHz, CDCl3):
d 20.8 (CH3), 43.9 (CH), 73.4 (CH2),
75.8, 80.2, 96.4, 97.6, 123.8, 128.1 (CH), 128.8 (C), 129.1, 133.6, 134.7
(CH), 163.2, 167.1, 169.8, 172.7 (C). IR (neat): nmax¼3696, 1735, 1713,

7118
Y. Gong et al. / Tetrahedron 67 (2011) 7114e7120
4.6. Conversion of compound 9 to 10
brine, dried, filtered and evaporated to dryness. The residue was
purified by column chromatography (CH2Cl2/MeOH, 60/1 to 40/1)
to afford 14 (12 mg, 73%) as a white solid, Rf¼0.39 (CH2Cl2/MeOH,
To a solution of 9 (7 mg, 0.0122 mmol) in CH2Cl2 (0.7 mL), was
added AcOH (0.3 mL). After stirring overnight at rt, the solvent was
evaporated, the residue dried by oil pump to give quantitatively the
compound 10.
20/1); mp: 106 ꢀC; ½a D20
ꢁ
þ39.8 (c 0.59, CHCl3); 1H NMR (400 MHz,
CDCl3): d
1.51 (s, 9H, t-Bu), 2,60e2.70 (br s, 1H, H-30), 4.14e4.21 (m,
2H, CHa-30, FmoceCH), 4.32 (t,1H, J¼10.1 Hz, CHb-30), 4.45e4.52 (m,
3H, H-40, FmoceCH2), 4.68 (m, 1H, H-20), 5.17 (s, 1H, OH), 5.69 (d,
1H, J¼8.2 Hz, H-5), 5.89 (d, 1H, J¼1.8 Hz, H-10), 7.25e7.28 (m, 2H,
HeAr), 7.34e7.39 (m, 2H, HeAr), 7.54 (d, 1H, J¼7.3 Hz, HeAr), 7.55
(d, 1H, J¼7.3 Hz, HeAr), 7.72 (d, 1H, J¼7.3 Hz, HeAr), 7.73 (d, 1H,
J¼7.3 Hz, HeAr), 8.43 (d, 1H, J¼8.2 Hz, H-6), 8.60 (s, 1H, NH), 10.5 (s,
4.7. Preparation of 30-aminooxymethyl-50-carboxylic acid
tert-butyl ester-30-deoxyuridine 12
To a solution of 10 (15 mg, 0.029 mmol) in MeOH (1 mL), was
added NH2NH2$H2O (8.3
mL, 0.17 mmol). After 3 h stirring, the
1H, NH). 13C NMR (100 MHz, CDCl3):
d 28.1 (CH3), 44.4, 47.0 (CH),
mixture was evaporated to dryness at rt, and to the residue was
added saturated NaHCO3, then extracted with EtOAc. The organic
layer was washed with brine, dried (MgSO4), filtered and con-
densed under reduced pressure to give the titled compound, which
was directly used for next steps. An analytical sample was purified
by column chromatography (CH2Cl2/MeOH, 40/1 to 20/1) to get two
products: compounds 12 and 30-acetamidooxymethyl-50-carbox-
ylic acid tert-butyl ester-30-deoxyuridine 11.
67.7, 71.7 (CH2), 75.5, 79.6 (CH), 83.5 (C), 93.2, 102.0 (CH), 120.1,
125.0, 127.2, 127.8, 141.0 (CH), 141.4, 143.5, 151.4, 157.8, 163.8,
170.7(C). IR (neat): nmax¼3670, 1926, 1691, 1448 cmꢂ1. HRMS (ESI)
calcd for C29H31N3O9 [MþNa]þ: 588.1958; found: 588.1971.
4.10. Preparation of 50-carboxylic acid methyl ester-30-(N-tert-
butoxycarbonyl-N-methyl)aminooxymethyl-30-deoxyuridine 15
Compound ꢀ12: yield 77%, white solid, Rf¼0.23 (CH2Cl2/MeOH,
To a solution of 4 (30 mg, 0.065 mmol) in MeOH (1 mL), was
added NH2NH2$H2O (19 mL, 0.196 mmol). After overnight stirring,
a 20
20/1); mp: 92 C; ½ ꢁD þ72.4 (c 0.20, MeOH); 1H NMR (400 MHz,
CDCl3):
d
1.56 (s, 9H, t-Bu), 2.50e2.60 (m, 1H, H-30), 3.93 (dd, 1H,
the mixture was evaporated to dryness. To this residue in 1,4-
dioxane/H2O (1/1, 3 mL), was added NaHCO3 (32 mg, 0.38 mmol).
After stirring for 30 min, Boc2O (50 mg, 0.23 mmol) was added to
the mixture and then stirred overnight. After addition of H2O, the
mixture was extracted with Et2O. The aqueous layer was acidified
to pH 3e4 with AcOH, then extracted with EtOAc. The combined
organic layers were washed with brine, dried, filtered and evapo-
rated to dryness. Purification by column chromatography (CH2Cl2/
MeOH/AcOH, 60/1/0.2 to 40/1/0.2) afforded a mixture. To get a pure
product, the mixture was dissolved in DMF (1.5 mL), NaHCO3
J¼5.5, 11.0 Hz, CHa-30), 4.09 (dd, 1H, J¼8.3, 11.0 Hz, CHb-30), 4.44 (d,
1H, J¼10.1 Hz, H-40), 4.55 (d, 1H, J¼6.4 Hz, H-20), 5.73 (d, 1H,
J¼8.2 Hz, H-5), 5.82 (s, 1H, J¼8.2 Hz, H-10), 8.44 (d, 1H, J¼8.2 Hz, H-
6). 13C NMR (100 MHz, CDCl3):
d 28.1 (CH3); 45.6 (CH), 70.5 (CH2),
75.9, 80.5 (CH), 83.3 (C), 93.8, 102.0, 140.7 (CH); 151.2, 163.9, 170.7
(C). IR (neat): nmax¼3674, 1735, 1691, 1452 cmꢂ1. HRMS (ESI) calcd
for C14H21N3O7 [MþNa]þ: 366.1277; found: 366.1272.
Compound 11: yield 8%, white syrup, Rf¼0.11 (CH2Cl2/MeOH, 20/
1); ½a 2D0
ꢁ
þ97.3 (c 0.44, MeOH); 1H NMR (400 MHz, CDCl3):
d 1.52 (s,
9H, t-Bu), 1.88 (s, 3H, OAc), 2.55e2.65 (m, 1H, H-30), 4.11e4.17 (m,
1H, CHa-30), 4.31 (t, 1H, J¼9.6 Hz, 1H, CHb-30), 4.51 (d, 1H, J¼8.7 Hz,
H-40), 4.69 (s, 1H, H-20), 5.57 (br s, 1H, OH), 5.70 (d, 1H, J¼7.8 Hz, H-
5), 5.87 (s,1H, H-10), 8.45 (d,1H, J¼7.8 Hz, H-6), 9.98 (s,1H, NH),10.7
(19 mg, 0.23 mmol) and MeI (10 mL, 0.15 mmol) were added. After
stirring overnight, the mixture was diluted with EtOAc, washed
with H2O, brine, dried, filtered, concentrated and purified by col-
umn chromatography (petroleum ether/EtOAc, 5/5) to give 7 mg
(23%) of 15 as a white solid, Rf¼0.5 (CH2Cl2/MeOH, 20/1); mp:
(s, 1H, ONHAc). 13C NMR (100 MHz, CDCl3):
d 19.8, 28.1 (CH3); 44.6
(CH), 71.2 (CH2), 75.3, 79.4 (CH), 83.5 (C), 93.2, 101.9, 141.2 (CH),
151.5, 164.1, 169.1, 170.7 (C). IR (neat): nmax¼3673, 1930, 1734, 1660,
1456 cmꢂ1. HRMS (ESI) C16H23N3O8 [MþNa]þ: 408.1383; found:
408.1392.
113 ꢀC; ½a 2D0
ꢁ
þ38.2 (c 0.06, CHCl3); 1H NMR (400 MHz, CDCl3):
d 1.47
(s, 9H, t-Bu), 2.45e2.55 (m, 1H, H-30), 3.33 (s, 3H, NeMe), 3.83 (s,
3H, CO2Me), 4.11 (dd, 1H, J¼8.7, 10.1 Hz, CHa-30), 4.19 (dd, 1H, J¼5.0,
8.7 Hz, 1H, CHb-30), 4.59 (m, 2H, H-20,40), 5.12 (d, 1H, OH), 5.80 (d,
1H, J¼8.2 Hz, H-5), 5.93 (d, 1H, J¼1.4 Hz, H-10), 7.35 (s, 1H, CONH),
4.8. Preparation of 30-aminooxymethyl-50-carboxylic acid-30-
deoxyuridine 13
8.09 (d, 1H, J¼7.8 Hz, H-6). 13C NMR (100 MHz, CDCl3):
d 27.7, 28.3
(CH3), 44.9 (CH), 52.9 (CH3), 72.2 (CH2), 76.4, 77.3, 79.1 (CH); 83.7
(C), 94.4, 101.5, 137.9 (CH), 163.2, 171.7 (C). IR (neat): nmax¼3196,
2996, 2848, 1748, 1704, 1652, 1626 cmꢂ1. HRMS (ESI) calcd for
C17H25N3O9 [MþNa]þ: 438.1488; found: 438.1483.
To a solution of 12 (30 mg, 0.065 mmol) in CH2Cl2 (0.5 mL) was
added TFA (0.1 mL). After stirring for 4e6 h at rt, the mixture was
diluted with EtOAc, evaporated to dryness to afford 19 mg (col-
ourless syrup, 100%) of 13, pure enough for NMR analysis. Rf¼0.34
4.11. Preparation of dinucleoside 16
(CH2Cl2/MeOH/AcOH, 6/1/0.1); ½a D20
ꢁ
þ68.8 (c 0.30, MeOH); 1H NMR
(400 MHz, CD3OD):
d
2.65e2.75 (m, 1H, H-30), 4.35 (dd, 1H, J¼5.0,
To a solution of 4 (30 mg, 0.065 mmol) in anhyd DMF (0.5 mL),
were added HOBt (16.5 mg, 0.118 mmol) and EDC (23 mg,
0.118 mmol) under N2 atmosphere at 0 ꢀC. After 20 min stirring,
compound 12 (22 mg, 0.065 mmol) in anhyd DMF (0.5 mL) was
added. The reaction mixture was stirred at rt overnight. The solu-
tion was diluted with EtOAc, washed with 1 N HCl, saturated
NaHCO3, brine, dried, filtered and concentrated to dryness. The
residue was dissolved in EtOAc (4 mL), and cyclohexane (6 mL) was
added to precipitate the product. Filtration afforded 16 as a white
9.2 Hz, CHa-30), 4.45 (t, 1H, J¼7.8 Hz, CHb-30), 4.50 (d, 1H, J¼5.5 Hz,
H-20), 4.63 (d,1H, J¼9.6 Hz, H-40), 5.80 (d,1H, J¼8.2 Hz, H-5), 5.83 (s,
1H, H-10), 8.25 (d, 1H, J¼7.8 Hz, H-6). 13C NMR (100 MHz, CDCl3):
d
44.4 (CH), 70.6 (CH2), 74.5, 79.1, 93.6, 100.8, 140.9 (CH), 150.9,
165.0, 172.7 (C). IR (neat): nmax¼3674, 1926, 1683, 1387 cmꢂ1
.
4.9. Preparation of 50-carboxylic acid tert-butyl ester-30-(9H-
fluoren-9-yl)methoxycarbonylaminooxymethyl-30-
deoxyuridine 14
solid (25 mg, 50%), Rf¼0.23 (CH2Cl2/MeOH, 15/1); mp: 197 ꢀC; ½a D20
ꢁ
þ60.7 (c 0.71, CHCl3); 1H NMR (400 MHz, DMSO-d6):
d 1.38 (s, 9H),
To a solution of 12 (10 mg, 0.029 mmol) in 1,4-dioxane/H2O (1/1,
1.3 mL) was added NaHCO3 (7 mg, 0.088 mmol). After stirring for
30 min, FmocOSu (15 mg, 0.044 mmol) was added and the mixture
stirred overnight. After addition of H2O, the mixture was extracted
with EtOAc. The organic layer was washed with 1 N HCl, NaHCO3,
2.10 (s, 3H), 2.40e2.50 (s, 1H), 3.20e3.25 (m, 1H), 3.93e3.97 (m,
1H), 4.11 (t, 1H, J¼10.1 Hz), 4.23e4.27 (m), 1.38 (s, 9H, t-Bu), 2.10 (s,
3H, OAc), 2.40e2.50 (s, 1H, H-30), 3.20e3.25 (m, 1H, H-30),
3.93e3.97 (m, 1H, CHON), 4.11 (t, 1H, J¼10.1 Hz, CHON), 4.23e4.27
(m, 1H, CHON), 4.31e4.38 (m, 4H, eCHONe, H-20, 2ꢃH-40), 5.59 (d,

Y. Gong et al. / Tetrahedron 67 (2011) 7114e7120
7119
1H, J¼6.4 Hz, H-20), 5.66e5.74 (m, 3H, H-10, 2ꢃH-50), 5.87 (s, 1H, H-
10), 6.07 (s, 1H, eOH), 7.82e7.89 (m, 4H, Phth), 7.94 (d, 1H, J¼7.8 Hz,
H-6), 8.08 (d, 1H, J¼8.3 Hz, H-6), 11.38 (s, 1H, NH), 11.41 (s, 1H, NH),
CDCl3): d 20.7 (CH3), 43.3 (CH), 52.7, 53.1 (CH3), 71.0 (CH2), 75.9,
79.7, 91.6, 102.4 (CH), 128.5 (C), 128.8, 130.3, 132.5 (CH), 135.2 (C),
140.5 (CH), 150.1, 163.1, 166.4, 169.7, 171.4 (C). IR (neat): nmax¼3683,
1717, 1682, 1460 cmꢂ1. HRMS (ESI) calcd for C22H23N3O11 [MþNa]þ:
528.1230; found: 528.1225.
11.75 (s, 1H, NH). 13C NMR (100 MHz, DMSO-d6):
d 21.0, 27.9 (CH3);
43.0, 44.7 (CH); 71.6, 73.8 (CH2); 74.6, 75.8, 78.6, 79.7 (CH), 82.9 (C),
91.4, 93.0, 101.7, 102.5, 123.9 (CH); 129.1(C), 135.4, 140.3, 141.9 (CH),
150.8, 150.9, 163.5, 163.7, 169.8, 170.8 (C). IR (neat): nmax¼3674,
1930, 1726, 1687, 1452 cmꢂ1. HRMS (ESI) calcd for C34H36N6O16
[MþNa]þ: 807.2085; found: 807.2080.
4.15. Preparation of 50-carboxylic acid methyl ester-30-deoxy-
30-[(methoxycarbonyl)benzamidooxy]methyluridine 21 and
50-carboxylic acid methyl ester-30-deoxy-30-
phthalimidooxymethyluridine 22
4.12. Preparation of 50-carboxylic acid-30-deoxy-30-
[(methoxycarbonyl)benzamidooxy]methyluridine 18
To a solution of 20 (32 mg, 0.068 mmol) in anhyd MeOH (1 mL)
was added 1.38 M NaOMe (10
mL, 0.068 mmol). After stirring
To a solution of 4 (131 mg, 0.285 mmol) in anhyd MeOH (2.8 mL)
was added Na2CO3 (13 mg, 0.124 mmol). After stirring overnight,
the solution was acidified to pH 1e2 with 4 M HCl, evaporated to
dryness at rt. The residue was purified by column chromatography
(CH2Cl2/MeOH, 50/1 to 40/1) to afford 18 (36 mg, 30%) as a white
overnight, the solution was acidified to pH 1e2 with 4 M HCl,
evaporated to dryness at rt, the residue was purified by column
chromatography (CH2Cl2/MeOH, 50/1 to 35/1) to afford two com-
pounds: 21 (15 mg, 51%) and 22 (4 mg, 15%).
Compound 21: white solid, Rf¼0.22 (CH2Cl2/MeOH, 20/1); mp:
solid. Rf¼0.39 (CH2Cl2/MeOH/AcOH, 20/1/0.07); mp: 156 ꢀC; ½a D20
ꢁ
103 ꢀC; ½a 2D0
ꢁ
þ92.2 (c 0.49, CHCl3); 1H NMR (400 MHz, CDCl3):
þ135.0 (c 0.08, MeOH); 1H NMR (400 MHz, CD3OD):
d 2.74 (s,1H, H-
d
2.78e2.83 (s, 3H, H-30), 3.86 (s, 6H, 2ꢃ CO2Me), 4.37 (t, 1H,
30), 3.87 (s, 3H, CO2Me), 4.29 (dd, 1H, J¼4.6, 9.6 Hz, CHa-30), 4.38 (t,
1H, J¼9.6 Hz, CHb-30), 5.58 (m, 2H, H-20,40), 5.66 (d, 1H, J¼7.8 Hz, H-
5), 5.84 (s, 1H, H-10), 7.44 (dd, 1H, J¼0.9, 7.8 Hz, Ph), 7.56e7.65 (m,
2H, Ph), 7.94e7.96 (m, 1H, Ph), 8.50 (d, 1H, J¼7.3 Hz, H-6). 13C NMR
J¼10.0 Hz, CHa-30), 4.42e4.50 (m, 1H, CHb-30), 4.60e4.70 (m, 2H, H-
20,40), 5.40 (s, 2H, H-5, OH), 5.85 (s, 1H, H-10), 7.43e7.55 (m, 3H, Ph),
7.89 (d, 1H, J¼7.8 Hz, Ph), 8.39 (d, 1H, J¼8.2 Hz, H-6), 9.92 (s, 1H,
OeNH), 10.9 (s, 1H, NH). 13C NMR (100 MHz, CDCl3):
d 44.0 (CH),
(100 MHz, CD3OD):
d 45.9 (CH), 53.1 (CH3), 72.4 (CH2), 76.6, 80.6,
52.7, 52.9 (CH3), 70.0 (CH2), 75.3, 78.7, 93.1, 101.4 (CH), 128.8 (C),
129.0, 130.0, 130.2, 132.5 (CH), 135.2 (C), 141.2 (CH), 151.6, 163.7,
95.0, 101.8, 129.5 (CH); 130.6 (C), 131.3, 131.6, 133.5 (CH), 136.0 (C),
142.5 (CH), 152.2, 166.5, 167.7, 169.7, 174.5 (C). IR (neat): nmax¼3670,
1735, 1678, 1452 cmꢂ1. HRMS (ESI) calcd for C19H19N3O10 [MþNa]þ:
472.0968; found: 472.0963.
166.3, 167.5, 172.3 (C). IR (neat): nmax¼3674, 1726, 1687, 1661 cmꢂ1
.
HRMS (ESI) calcd for C20H21N3O10 [MþNa]þ: 486.1125; found:
486.1119.
Compound 22: white solid, Rf¼0.42 (CH2Cl2/MeOH, 20/1); mp:
4.13. Preparation of 20-O-acetyl-50-carboxylic acid methyl
109 ꢀC; ½a 2D0
ꢁ
þ70.2 (c 0.08, CHCl3); 1H NMR (400 MHz, CDCl3):
ester-30-deoxy-30-(phthalimidooxymethyl)uridine 19
d
2.65e2.75 (m, 1H, H-30), 3.86 (s, 3H, CO2Me), 4.53 (m, 2H, CH2-30),
4.66 (d, 1H, J¼10.1 Hz, H-40), 4.77 (t, 1H, J¼4.6 Hz, H-20), 4.81 (d, 1H,
J¼4.6 Hz, OH), 5.78 (dd, 1H, J¼2.3, 8.2 Hz, H-5), 5.95 (s, 1H, H-10),
7.75e7.85 (m, 4H, Phth), 8.26 (d, 1H, J¼8.2 Hz, H-6), 9.03 (s, 1H, NH).
To a solution of 4 (30 mg, 0.065 mmol) in DMF (1 mL) were added
NaHCO3 (11 mg, 0.13 mmol) and CH3I (5.3 mL, 0.085 mmol). After
13C NMR (100 MHz, CDCl3):
d 44.9 (CH), 53.1 (CH3), 73.7 (CH2), 75.9,
stirring overnight, the mixture was diluted with EtOAc, washed with
H2O, brine, dried, filtered and concentrated to dryness to give
quantitatively 19, pure enough for next steps. An analytical sample
was purified by column chromatography (CH2Cl2/MeOH, 80/1 to 50/
1) to give a white solid, Rf¼0.51 (CH2Cl2/MeOH, 20/1); mp: 116 ꢀC;
79.1, 94.1, 102.2, 124.1 (CH); 128.7 (C), 135.0, 140.1 (CH), 150.6, 163.2,
163.7, 171.3 (C). IR (neat): nmax¼3670, 1739, 1674, 1456 cmꢂ1. HRMS
(ESI) calcd for C19H17N3O9 [MþNa]þ: 454.0862; found: 454.0857.
½
a 2D0
ꢁ
þ52.4 (c 0.78, CHCl3); 1H NMR (400 MHz, CDCl3):
d 2.20 (s, 3H,
Acknowledgements
OAc), 3.05e3.15 (m, 1H, H-30), 3.84 (s, 3H, CO2Me), 4.33 (dd, 1H,
J¼6.4, 9.2 Hz, CHa-30), 4.46 (dd,1H, J¼7.3, 9.2 Hz, CHb-30), 4.79 (d,1H,
J¼8.2 Hz, H-40), 5.65 (dd, 1H, J¼3.2, 6.4 Hz, H-20), 5.78 (dd, 1H, J¼1.8,
7.8 Hz, H-5), 6.00 (d,1H, J¼2.8 Hz, H-10), 7.75e7.85 (m, 4H, Phth), 7.98
(d, 1H, J¼8.2 Hz, H-6), 8.86 (s, 1H, NH). 13C NMR (100 MHz, CDCl3):
ꢀ
Y.G. thanks the Ecole Normale Superieure de Cachan for a Doc-
torate fellowship.
References and notes
d
20.7 (CH3); 43.7 (CH), 53.1 (OCH3), 73.4 (CH2), 75.2, 79.1, 90.9,103.0,
123.8 (CH), 128.8 (C), 134.9, 140.1 (CH), 150.0, 163.2, 169.5, 169.5,
170.9 (C). IR (neat): nmax¼3674, 1730, 1691, 1452 cmꢂ1. HRMS (ESI)
calcd for C21H19N3O10 [MþNa]þ: 496.0968; found: 496.0963.
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mL, 0.276 mmol). After stirring
30e40 min, the solution was acidified to pH 1e2 with 4 M HCl,
evaporated to dryness at rt. The residue was purified by column
chromatography (CH2Cl2/MeOH, 50/1 to 40/1) to afford 20 (28 mg,
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