An efficient PyAOP-based C4-amination method for direct access of oxidized 5MedC derivatives

Article abstract of DOI:10.1016/j.tet.2018.10.046

In the past decade, synthetic oxidized ^5-MedC nucleosides and their derivatives have become essential tools for epigenetic research. The low efficacy of both conventional and newly reported BOP methods on C⁴-amination of these specific oxidized ^5-MedU substrates urged us to systematically investigate how the nature of onium salt-based coupling reagents affects the C⁴-amination of pyrimidine nucleobases and lead us to the findings that different onium coupling reagents result in the formation of distinctive activation intermediates and PyAOP is much more potent than BOP in both activation and aminolysis steps. Direct amination without the need of ribose protection, ultrafast activation, tolerance to aqueous N-nucleophiles, and excellent yields for diverse oxidized ^5MedC derivatives are the advantages of this PyAOP-based C⁴-amination method.

Full text of DOI:10.1016/j.tet.2018.10.046

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
An efficient PyAOP-based C4-amination method for direct access of
oxidized 5MedC derivatives
Xiu-An Zheng, Hua-Shan Huang, Rui Kong, Wei-Jie Chen, Shan-Shan Gong**, Qi Sun*
Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science & Technology Normal University, 605 Fenglin Avenue, Nanchang, 330013, China
a r t i c l e i n f o
a b s t r a c t
In the past decade, synthetic oxidized 5-MedC nucleosides and their derivatives have become essential
tools for epigenetic research. The low efficacy of both conventional and newly reported BOP methods on
C4-amination of these specific oxidized 5-MedU substrates urged us to systematically investigate how the
nature of onium salt-based coupling reagents affects the C4-amination of pyrimidine nucleobases and
lead us to the findings that different onium coupling reagents result in the formation of distinctive
activation intermediates and PyAOP is much more potent than BOP in both activation and aminolysis
steps. Direct amination without the need of ribose protection, ultrafast activation, tolerance to aqueous
N-nucleophiles, and excellent yields for diverse oxidized 5MedC derivatives are the advantages of this
PyAOP-based C4-amination method.
Article history:
Received 25 September 2018
Received in revised form
16 October 2018
Accepted 19 October 2018
Available online xxx
Keywords:
PyAOP
Amination
Activation
© 2018 Elsevier Ltd. All rights reserved.
Aminolysis
5-Methyl-2ʹ-deoxycytidine
1. Introduction
oligodeoxynucleotides (ODNs) have been developed [11e13]. Later,
Carell and co-workers achieved expeditious synthesis of long 5-
In mammalian DNA, cytosines are predominantly methylated
within CpG sites, and the methylation patterns could be passed on
to the next generation as stable epigenetic signals during cell di-
visions [1]. In the past 20 years, it has been revealed that DNA
methyltransferases-mediated cytosine methylation in eukaryotic
DNA is one of the most crucial epigenetic marks for transcriptional
gene silencing [2]. Meanwhile, DNA demethylation is also highly
important for the recovery of cytosine, thereby rendering flexible
regulation of gene expression during cellular development [3]. A
series of oxidized 5-methylcytosine (5-mC) derivatives, such as 5-
hydroxymethylcytosine (5-hmC), 5-formyl-cytosine (5-fC), and 5-
carboxycytosine (5-caC) have been isolated from mammalian
DNA [4e6]. The evidences reported by He [7] and Zhang [8] groups
strongly indicated that ten-eleven translocation proteins (TET)-
mediated oxidation of 5-mC leads to active DNA demethylation in
epigenetic reprogramming of cells [9,10].
hmC-, 5-fC-, and 5-caC-containing ODNs from 5HOMe-, 5-CHO-, and
5-COOH-dC triphosphates by polymerase chain reaction [14].
Apparently, the chemical synthesis of various oxidized 5MedC nu-
cleosides, phosphoramidite monomers, and nucleoside tri-
phosphates plays a crucial role in the progress of epigenetic
research.
Our ongoing research on the synthesis of oxidized 5MedC de-
rivatives showed that C4-amination of the corresponding oxidized
5MedU precursors is one of the most challenging steps. As we
described in previous reports [15,16], the conventional POCl3/1,2,4-
triazole/conc. NH4OH [17,18] or TsCl/1-methylpiperidine/conc.
NH4OH [19] methods could afforded the desired oxidized 30,50-O-
diTBS-protected 5MedC derivatives in 60e70% yields. However, due
to the reactivity of the activating reagents to OH groups, ribose
moiety must be fully protected before C4-amination. In addition,
hydrolysis of the triazole or quaternary ammonium intermediate
typically resulted in 15e25% recovery of the starting material.
When it comes to the synthesis of 30-phosphoramidite mono-
mer of 2-cyanoethyl-protected 5HOMedC, the above mentioned
methods can not be utilized due to the presence of unprotected 30-
OH. In our experiments, the application of the biphasic 2,4,6-
triisopropylbenzenesulfonyl chloride (TPSCl), Na2CO3, TBAB,
CH2Cl2/H2O/conc. NH4OH method [20,21] afforded the desired
product in only 53% (Fig. 1, Method A). In a recent report on the
To facilitate the investigation of mechanisms and enzymes
involved in 5-mC oxidation, solid phase approaches for the prep-
aration
of
5-hmC-,
5-fC-,
and
5-caC-containing
* Corresponding author.
** Corresponding author.
E-mail addresses: gongshanshan@jxstnu.edu.cn (S.-S. Gong), sunqi@jxstnu.edu.
cn (Q. Sun).
https://doi.org/10.1016/j.tet.2018.10.046
0040-4020/© 2018 Elsevier Ltd. All rights reserved.
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2
X.-A. Zheng et al. / Tetrahedron xxx (xxxx) xxx
preparation of the oxidized 2ʹ-O-methyl-5MeC derivatives, TPSCl-
based C4-amination gave the desired products in only 42e67%
yields [22].
Table 1
The activation of diTBS-dT (1) by onium salt-based coupling reagents.
Recently, Lakshman and coworkers reported a new approach to
conduct C4-amination on diTBS-protected thymidine by BOP/base/
N-nucleophile system [23], which has been previously utilized for
the preparation of N6-modified adenosine [24,25] and C6-modified
guanosine derivatives [26]. Unfortunately, the effects of unpro-
tected OH groups of ribose, oxidative thymine-modifications, and
aminolysis with aqueous ammonia on this method were still un-
known. In our initial trial, the employment of BOP/DBU/NH3 in
dioxane afforded the desired product. However, the 55% yield
indicated that the application of this BOP-based amination method
on oxidized 5MedU substrates was far from satisfactory (Fig. 1,
Method B). Since it is well known that changes in the structures of
phosphonium or benzotriazole moieties of onium salt-based
coupling reagents may significantly affect their reactivity in pep-
tide synthesis [27], we felt that it was quite important and neces-
sary to reveal how the nature of onium salt-based coupling
reagents, i.e. phosphonium vs aminium/uronium and OAt vs OBt,
would affect the C4-amination of pyrimidine nucleobases, espe-
cially more complicated 5-methyl-oxidized derivatives. Moreover,
the formation of carcinogenic HMPA is another big concern with
the current BOP-based method.
In this paper, a systematic and comparative study on the
commonly used phosphonium and aminium/uronium coupling
reagents lead us to the findings that different types of onium
coupling reagents have distinctive reaction mechanisms and PyAOP
is a much more potent reagent for the C4-amination of thymine and
5-methyl-oxidized derivatives in both activation and aminolysis
steps. Direct amination without the need of ribose protection, ul-
trafast activation, tolerance to aqueous N-nucleophiles, and excel-
lent yields for various oxidized 5MedC derivatives are the
advantages of the PyAOP-based method.
Entry
Coupling reagent
Equiv
Reaction time (min)
Conversion (%)a
1.1
1.2
2.1
2.2
3.1
3.2
4.1
4.2
5
PyAOP
PyAOP
PyBOP
PyBOP
AOP
AOP
BOP
BOP
2.0
1.6
2.0
1.6
2.0
1.6
2.0
1.6
2.0
2.0
2.0
1
1
1
3
10
15
10
15
1
quant. (79)b, 1a
quant., 1a
quant. (71)b, 1b
ca. 80, 1b
ca. 90, 1a
ca. 80, 1a
ca. 90, 1b
ca. 70, 1b
PyBrOP
HATU
HBTU
quant. (73)b, 1c
quant. (77)b, 1d
quant., 1d
6
7
1
1
a
As assessed by TLC.
Isolated yields.
b
OAt-based reagents was more efficient than that by OBt-based
ones. Previously, Lakshman et al. failed to isolated 1b from BOP-
activated reaction due to decomposition [23]. In our work, we
isolated both pure 1a and 1b in over 70% yields by flash column
chromatography from PyAOP- and PyBOP-activated reactions.
Interestingly, the reaction of PyBrOP with 1 quantitatively gener-
ated the phosphonium salt 1c, which was isolated in 73% yield. To
our surprise, the activation of 1 by both HATU and HBTU in the
presence of DBU ended up with the formation of uronium salt 1d
instead of 1a/1b, indicating that the stability of phosphonium and
uronium intermediates are of huge difference. Flash column chro-
matography yielded pure 1d in 77% yield.
2. Results and discussion
2.1. The activation of thymine by different onium salt-based
coupling reagents
In the preliminary experiment, we tested the activation capa-
bility of a series of commonly used onium salt-based coupling re-
agents. The results in Table 1 showed that in the presence of 2.0
equiv of PyAOP, PyBOP, AOP, and BOP and 2.0 equiv of DBU, the
conversion of 1 to the corresponding OAt/OBt derivatives (1a/1b)
was quite efficient (quant. to ca. 90%) in anhydrous THF
([1] ¼ 0.3 M). But it can be seen that the reaction rate of PyAOP/
PyBOP was significantly faster than that of AOP/BOP, indicating that
tris(pyrrolidino)phosphonium-based reagents are more reactive
than tris(dimethylamino)phosphonium-based ones. When the
amounts of coupling reagents and DBU were reduced to 1.6 equiv,
only PyAOP still could furnish quantitative activation of 1 in 1 min.
A significant amount of 1 was left (ca. 20e30%) in the cases of the
other three coupling reagents. It was obvious that the activation by
Fig. 1. C4-Amination for the synthesis of
a
30-phosphoramidite monomer of 2-
Fig. 2. 31P NMR tracing of the activation of 1 by 2 equiv of PyAOP (A), BOP (B), and
PyBrOP (C) and 2 equiv of DBU.
cyanoethyl-protected 5HOMedC.
Please cite this article as: X.-A. Zheng et al., An efficient PyAOP-based C4-amination method for direct access of oxidized 5MedC derivatives,
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X.-A. Zheng et al. / Tetrahedron xxx (xxxx) xxx
3
cyanoethyl-protected 50-DMT-5HOMedC (3′) was only obtained in
56% yield. ([3] was lowered from 0.3 M to 0.05 M to avoid depro-
tection of 2-cyanoethyl group.) In contrast, PyAOP well maintained
its high potency in the activation of 3 (ca. 90%, 1 min), and 3′ was
isolated in 84% yield. This result indicated that BOP is acceptable for
C4-amination of dT. However, in cases of structurally more
complicated oxidized 5MedU substrates, the efficacy of BOP drops
remarkably and more potent PyAOP is essential for efficient C4-
amination.
Table 2
The aminolysis of 1ae1d by conc. NH4OH.
2.4. The PyAOP-based C4-amination method for the preparation of a
diversity of oxidized 5MedU substrates
Entry
Substrates
Equiv of conc.
NH4OH
Reaction
time (h)
Isolated yields
of 10/1 (%)
To explore the generality of this PyAOP-based method, the C4-
amination was performed on a diversity of oxidized 5-MedU de-
rivatives including 2-cyanoethyl-protected 5-HOMedU (4), 5-HOMedU
(5), diTBS-5-AcOMedU (6), 5-CHOdU (7), and 5-COOBndU (8). As shown
in Table 4, other than compounds 3 and 4 (0.05 M, 4 h), the re-
actions of all other substrates with conc. NH4OH (4 equiv) were
performed at 0.3 M and finished in only 2 h. For non-aqueous
alkylamines (4 equiv), the aminolysis was much faster. While the
reactions with benzylamine, morpholine, and piperidine
completed in 5 min, those with diethylamine required 30 min to
1
2
3
4
1a
1b
1c
1d
10
10
10
20
4
9
5
12
93/0
88/3
81/10
0/21
31P NMR tracing of PyAOP-, BOP-, and PyBrOP-based reactions
(Fig. 2) confirmed that the activation by PyBrOP resulted in the
formation of phosphonium salt 1c (
and BOP directly lead to the formation of TPPO (
HMPA ( 25.4 ppm) [23,25]. In addition, PyAOP and PyBrOP almost
disappeared at 30 min, whereas ca. 40% of BOP remained unreacted,
suggesting that PyAOP and PyBrOP were more reactive and less
stable than BOP in the presence of DBU.
d
23.6 ppm), whereas PyAOP
d
15.4 ppm) and
d
5-
finish. PyAOP exhibited excellent reactivity to all these oxidized
MedU substrates and yielded the corresponding products in
75e88% yields.
3. Conclusions
2.2. The aminolysis of distinctive activated intermediates
In summary, the low efficacy of existing C4-amination methods
including the newly reported BOP-based method for the prepara-
tion of oxidized 5-MedC derivatives has urged us to systematically
investigate how the nature of onium salt-based coupling reagents
affects the C4-amination of pyrimidine nucleobases. The compara-
tive study on phosphonium and aminium/uronium coupling re-
agents revealed the advantages of tris(pyrrolidino)phosphonium
over tris(dimethylamino) phosphonium and OAt over OBt in the
activation step. In addition, different onium salt reagents resulted
in the formation of distinctive activation intermediates. The ami-
nolysis with conc. NH4OH showed that OAt-based intermediate is
not only resistant to hydrolysis but also more reactive than OBt-
based one. Further experiments showed that the efficacy of BOP
drops significantly in cases of structurally more complicated py-
rimidine substrates, and more potent PyAOP is essential for effi-
cient C4-amination of a diversity of oxidized 5MedU substrates.
The isolation of 1ae1d provided a valuable chance to compare
their reactivity in aminolysis step without the interference of
activation step. As listed in Table 2, the reactions of OAt-based 1a
with aqueous ammonia (10 equiv) afforded diTBS-5MedC (1′) in 93%
yield (4 h) without the recovery of 1, suggesting that 1a was quite
resistant to hydrolysis ([1a] ¼ 0.3 M). In contrast, the reaction of
OBt-based 1b was remarkably slower (9 h). Though yield of 1′ was
also very good (88%), however, a trace amount of 1 was obtained
due to hydrolysis of 1b. As expected, phosphonium salt 1c was also
reactive to aqueous ammonia (5 h), however, 1′ was obtained in
only 81% yield due to partial hydrolysis of 1c. To our surprise,
uronium salt 1d was completely unreactive to NH3. Treatment of 1d
with 20 equiv of conc. NH4OH only recovered 1 (21%) via hydrolysis
when the reaction was stopped at 12 h.
2.3. Comparison of PyAOP and BOP on the C4-amination of simple
dT and a more complicated oxidized 5MedU substrate
4. Experimental
Further application of PyAOP for direct C4-amination of OH-
unprotected and base-modified pyrimidine nucleosides was con-
ducted in a “one-pot, two-steps” manner along with BOP as a
reference and anhydrous DMF as solvent. The results in Table 3
showed that PyAOP afforded 5MedC (2ʹ) in excellent yield (92%).
The activation of dT (2) in DMF by PyAOP (1.6 equiv) only needed
1 min ([2] ¼ 0.3 M), and the subsequent aminolysis required less
conc. NH4OH (4 equiv) and reaction time (2 h) possibly due to the
presence of DBU. The role of DBU in the activation step was also
confirmed by replacing DBU with other bases. When DIPEA,
TMEDA, DABCO, or Cs2CO3 was used as base, no reaction was
observed, indicating that the deprotonation by strong base DBU
was essential for the initiation of activation. In comparison, BOP
also afforded 2′ in good yield (85%), but both steps were slower
than those of PyAOP. However, in case of 2-cyanoethyl-protected
50-O-DMT-5HOMedU (3), the activation by BOP was significantly
much less efficient (ca. 60%, 10 min). After aminolysis, 2-
4.1. General methods
General chemical reagents and solvents were obtained from
commercial suppliers. Compounds 3e8 were synthesized accord-
ing to reported methods [15,16,20]. All reactions were monitored by
thin layer chromatography on plates coated with 0.25 mm silica gel
60 F254. TLC plates were visualized by UV irradiation (254 nm) or by
staining with 20% H2SO4 in EtOH. THF and DMF were distilled from
CaH2 prior to use. Flash column chromatography employed silica
gel (particle size 32e63 mm). Melting points were determined with
a Thomas-Hoover melting point apparatus and uncorrected. NMR
spectra were obtained with a Bruker AV-400 instrument with
chemical shifts reported in parts per million (ppm, d) and refer-
enced to CDCl3, DMSO‑d6 or D2O. IR spectra were recorded on a
Bruker Vertex-70 spectrometer. Low- and high-resolution mass
spectra were reported as m/z and obtained with a Bruker amaZon
SL mass spectrometer and
a Bruker Dalton micrOTOF-Q II
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X.-A. Zheng et al. / Tetrahedron xxx (xxxx) xxx
eq). The reaction was stirred at 20 ꢀC for 1 min. Then the solution
was concentrated in vacuo. Flash column chromatography on silica
gel afforded 1aꢁ1d in pure form.
Table 3
The “one-pot, two-steps” C4-amination of dT (2) and an oxidized 50-O-DMT-5MedU
derivative (3) with PyAOP or BOP.
4.2.1. O4-(7-Aza-1H-benzotriazol-1-yl)-30,50-di-O-(t-
butyldimethylsilyl)thymidine (1a)
The reaction of 1 (94 mg, 0.2 mmol), PyAOP (208 mg, 0.4 mmol),
and DBU (61 mg, 0.4 mmol) in THF (0.67 mL) afforded (PE/EA ¼ 6:1)
1a (93 mg, 79%) as a white solid; mp 184e185 ꢀC. 1H NMR
(400 MHz, CDCl3):
d
8.70 (d, J ¼ 4.4 Hz, 1H), 8.43 (d, J ¼ 8.3 Hz, 1H),
8.16 (s, 1H), 7.47e7.41 (m, 1H), 6.15 (t, J ¼ 6.1 Hz, 1H), 4.38e4.32 (m,
1H), 3.99e3.97 (m, 1H), 3.96e3.92 (m, 1H), 3.78 (d, J ¼ 9.6 Hz, 1H),
2.50e2.42 (m, 1H), 2.30 (s, 3H), 2.04e1.96 (m, 1H), 0.95 (s, 9H), 0.87
(s, 9H), 0.14 (d, J ¼ 6.8 Hz, 6H), 0.05 (s, 6H) ppm; 13C NMR (100 MHz,
No
Compd
Coupling
reagent
Step 1 time (min)/
conv (%)a
Step 2
time (h)
Isolated
yield (%)
CDCl3):
d 169.0, 153.9, 151.8, 144.1, 140.8, 135.3, 129.8, 121.0, 100.8,
88.5, 87.4, 71.3, 62.6, 42.5, 26.1, 25.9, 18.6, 18.1,
1
2
3
4
2
2
3
3
PyAOP
BOP
PyAOP
BOP
1/quant.
5/90
1/ca. 90
10/ca. 60
2
3
4
5
92
85
84
56
12.0, ꢁ4.4, ꢁ4.7, ꢁ5.2 ppm; HRMS (ESIþ): m/z calcd for
C
27H45N6O5Si2 [MþH]þ 589.2984; found 589.2980.
4.2.2. O4-(1H-Benzotriazol-1-yl)-30,50-di-O-(t-butyldimethylsilyl)
thymidine (1b)
a
As assessed by TLC.
The reaction of 1 (94 mg, 0.2 mmol), PyBOP (208 mg, 0.4 mmol),
and DBU (61 mg, 0.4 mmol) in THF (0.67 mL) afforded (PE/EA ¼ 6:1)
1b (83 mg, 71%) as a white solid; mp 55e56 ꢀC. 1H NMR (400 MHz,
spectrometer, respectively.
CDCl3):
d
8.15 (s, 1H), 8.06 (d, J ¼ 8.3 Hz, 1H), 7.54e7.49 (m, 1H),
4.2. General procedure for the synthesis of activated di-TBS-dT
intermediates (1ae1d)
7.45e7.38 (m, 2H), 6.18 (t, J ¼ 6.2 Hz, 1H), 4.39e4.34 (m, 1H),
4.01e3.98 (m,1H), 3.98e3.93 (m,1H), 3.82e3.76 (m,1H), 2.54e2.46
(m, 1H), 2.28 (s, 3H), 2.05e1.97 (m, 1H), 0.95 (s, 9H), 0.87 (s, 9H),
0.14 (d, J ¼ 6.3 Hz, 6H), 0.06 (s, 6H) ppm; 13C NMR (100 MHz,
To a solution of diTBS-dT (1) in THF ([1] ¼ 0.3 M) were added
coupling reagent (PyAOP, PyBOP, PyBrOP, or HATU, 2 eq) and DBU (2
CDCl3): d 169.0, 153.9, 144.0, 143.7, 129.0, 128.8, 124.9, 120.7, 108.9,
Table 4
The PyAOP-based C4-amination method for oxidized 5MedC derivatives (3′e20′).
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X.-A. Zheng et al. / Tetrahedron xxx (xxxx) xxx
5
100.7, 88.6, 87.5, 71.6, 62.7, 42.6, 26.1, 25.9, 18.6, 18.1,
1.6 mmol) in DMF (1.33 mL) afforded (CH2Cl2/MeOH ¼ 8:1) 2′
(88 mg, 92%) as a white solid; mp 198e199 ꢀC. 1H NMR (400 MHz,
DMSO‑d6): d 7.79 (s, 1H), 7.62 (br, 1H), 7.08 (br, 1H), 6.31 (t,
12.0, ꢁ4.4, ꢁ4.7, ꢁ5.2 ppm; HRMS (ESIþ): m/z calcd for
C
28H46N5O5Si2 [MþH]þ 588.3032; found 588.3026.
J ¼ 6.8 Hz, 1H), 5.43 (br, 2H), 4.36e4.33 (m, 1H), 3.91e3.87 (m, 1H),
4.2.3. (1-(30,50-Di-O-(t-butyldimethylsilyl)-20-deoxy-
b-D-
ribofuranosyl)-2-oxo-5-methyl-(1H)pyrimidin-4-yl-oxy)
3.76e3.64 (m, 2H), 2.24e2.17 (m, 1H), 2.14e2.05 (m, 1H), 1.98 (s,
3H) ppm; 13C NMR (100 MHz, DMSO‑d6):
d 165.2, 155.1, 138.5, 101.5,
tripyrrolidinophosphonium hexafluorophosphate (1c)
87.3, 84.8, 70.5, 61.5, 40.4, 13.4 ppm; LRMS (ESIþ): m/z calcd for
The reaction of 1 (94 mg, 0.2 mmol), PyBrOP (186 mg, 0.4 mmol),
and DBU (61 mg, 0.4 mmol) in THF (0.67 mL) afforded (PE/EA ¼ 6:1)
1c (125 mg, 73%) as a white solid; mp 67e68 ꢀC. 1H NMR (400 MHz,
C
10H16N3O4 [MþH]þ 242.1; found 242.1.
4.3.3. 50-O-(4,40-Dimethoxytrityl)-5-(2-cyanoethoxy)methyl-20-
deoxycytidine (30)
CDCl3):
d
8.06 (s, 1H), 6.18 (t, J ¼ 6.5 Hz, 1H), 4.38e4.33 (m, 1H),
4.02e3.98 (m, 1H), 3.88e3.82 (m, 1H), 3.77e3.72 (m, 1H),
3.38e3.30 (m, 12H), 2.54e2.46 (m, 1H), 2.04 (s, 3H), 2.02e1.97 (m,
1H), 1.97e1.90 (m, 12H), 0.86 (s, 9H), 0.85 (s, 9H), 0.07 (s, 6H), 0.04
The reaction of
0.32 mmol), DBU (49 mg, 0.32 mmol), and conc. NH4OH (31
3
(123 mg, 0.2 mmol), PyAOP (167 mg,
L,
m
0.8 mmol) in DMF (4 mL) afforded (CH2Cl2/MeOH ¼ 20:1) 3′
(s, 6H) ppm; 13C NMR (100 MHz, CDCl3):
d 164.8, 164.7, 153.6, 145.2,
(103 mg, 84%) as a white solid; mp 143e145 ꢀC. 1H NMR (400 MHz,
103.6, 103.5, 88.8, 87.7, 72.2, 62.9, 48.1, 42.3, 26.2, 26.1, 26.0, 25.8,
CDCl3):
d
7.93 (s, 1H), 7.39 (d, J ¼ 7.4 Hz, 2H), 7.33e7.21 (m, 7H), 6.83
18.4, 18.0, 12.2, ꢁ4.6, ꢁ4.8, ꢁ5.4 ppm; 31P NMR (162 MHz, CDCl3):
(d, J ¼ 8.3 Hz, 4H), 6.51 (t, J ¼ 6.5 Hz, 1H), 6.01 (br, 1H), 4.70 (br, 1H),
4.56e4.49 (m, 1H), 4.13 (d, J ¼ 2.5 Hz, 1H), 3.78 (s, 6H), 3.73 (d,
J ¼ 12.4 Hz, 1H), 3.56e3.46 (m, 2H), 3.33e3.26 (m, 1H), 3.20e3.06
(m, 2H), 2.73e2.64 (m, 1H), 2.36e2.30 (m, 2H), 2.28e2.17 (m, 1H)
d
27.0 (s, 1P), ꢁ140.3 (m, 1P) ppm; HRMS (ESIþ): m/z calcd for
C
34H65N5O5PSi2 [M]þ 710.4256; found 710.4250.
4.2.4. (1-(30,50-Di-O-(t-butyldimethylsilyl)-20-deoxy-
b-D-
ribofuranosyl)-2-oxo-5-methyl-(1H)pyrimidin-4-yl-oxy)-N,N,N0,N0-
tetramethyluronium hexafluorophosphate (1d)
The reaction of 1 (94 mg, 0.2 mmol), HATU (152 mg, 0.4 mmol),
and DBU (61 mg, 0.4 mmol) in THF (0.67 mL) afforded (PE/EA ¼ 6:1)
1d (110 mg, 77%) as a white solid; mp 58e59 ꢀC. 1H NMR (400 MHz,
ppm; 13C NMR (100 MHz, CDCl3):
d 165.2, 158.8, 156.2, 144.5, 140.7,
135.6, 135.5, 130.3, 130.2, 128.5, 128.1, 127.3, 117.6, 113.4, 102.2, 86.8,
86.6, 86.3, 72.1, 67.6, 64.0, 63.6, 55.4, 42.2, 18.5 ppm; LRMS (ESIþ):
m/z calcd for C34H37N4O7 [MþH]þ 613.3; found 613.3.
4.3.4. 5-(2-Cyanoethoxy)methyl-20-deoxycytidine (40)
CDCl3):
d
7.62 (s, 1H), 6.25 (t, J ¼ 7.2 Hz, 1H), 4.41e4.37 (m, 1H),
The reaction of
0.48 mmol), DBU (73 mg, 0.48 mmol), and conc. NH4OH (46
4
(93 mg, 0.3 mmol), PyAOP (250 mg,
L,
3.96e3.93 (m, 1H), 3.86e3.81 (m, 1H), 3.77e3.71 (m, 1H), 3.39 (s,
6H), 3.10e2.99 (m, 6H), 2.34e2.26 (m, 1H), 2.19e2.10 (m, 1H), 1.94
(s, 3H), 0.91 (s, 9H), 0.87 (s, 9H) 0.10 (s, 6H), 0.07 (d, J ¼ 3.3 Hz, 1H)
m
1.2 mmol) in DMF (6 mL) afforded (CH2Cl2/MeOH ¼ 8:1) 4′ (74 mg,
80%) as a white solid; mp 176e177 ꢀC. 1H NMR (400 MHz, D2O):
ppm; 13C NMR (100 MHz, CDCl3):
d 160.4, 155.4, 147.4, 137.7, 110.4,
d
7.93 (s, 1H), 6.16 (t, J ¼ 6.4 Hz, 1H), 4.43e4.40 (m, 1H), 4.39e4.36
88.6, 86.3, 72.4, 63.2, 43.3, 40.9, 38.7, 26.1, 25.8, 18.5, 18.0,
(m, 2H), 4.04e3.96 (m, 1H), 3.85e3.77 (m, 1H), 3.76e3.72 (m, 1H),
3.71e3.66 (m, 2H), 2.75 (t, J ¼ 5.9 Hz, 2H), 2.45e2.36 (m, 1H),
12.7, ꢁ4.6, ꢁ4.8, ꢁ5.3 ppm; 31P NMR (162 MHz, CDCl3):
d
ꢁ140.2
(m, 1P) ppm; HRMS (ESIþ): m/z calcd for C27H53N4O5Si2 [M]þ
2.28e2.19 (m, 1H) ppm; 13C NMR (100 MHz, D2O):
d 164.6, 156.6,
569.3549; found 569.3545.
142.1, 120.0, 103.5, 86.9, 86.4, 70.4, 65.6, 64.3, 61.2, 39.7, 18.3 ppm;
IR (KBr): vmax 3470, 2900, 2267, 1666, 1489, 1304, 1093 cmꢁ1; HRMS
(ESIþ): m/z calcd for C13H19N4O5 [MþH]þ 311.1350; found 311.1347.
4.3. General procedure for the synthesis of 5MedC and oxidized
5MedC derivatives (10e200)
4.3.5. 30,50-Di-O-t-butyldimethylsilyl-5-acetoxymethyl-20-
To
a solution of the nucleosides (2e20) in DMF ([sub-
deoxycytidine (50)
strate] ¼ 0.3 M, except for 3 and 4, [3,4] ¼ 0.05 M) were added
PyAOP (1.6 eq) and DBU (1.6 eq). The reaction was stirred at 20 ꢀC
for 1 min. To the reaction solution was added N-nucleophiles (4 eq)
(or 1a in THF, conc. NH4OH (10 eq)). The reaction was stirred at
20 ꢀC for 5 minꢁ4 h and monitored by TLC. Upon completion, the
solution was concentrated in vacuo. Flash column chromatography
on silica gel afforded 5MedC and oxidized 5MedC derivatives (1′e20′)
in pure form.
The reaction of
0.32 mmol), DBU (49 mg, 0.32 mmol), and conc. NH4OH (31
0.8 mmol) in DMF (0.67 mL) afforded (PE/EA ¼ 2:1) 5′ (89 mg, 85%)
as a white solid; mp 87e88 ꢀC. 1H NMR (400 MHz, CDCl3):
7.86 (s,
5
(106 mg, 0.2 mmol), PyAOP (167 mg,
mL,
d
1H), 6.22 (t, J ¼ 6.0 Hz, 1H), 4.88e4.75 (m, 2H), 4.34e4.31 (m, 1H),
3.94e3.91 (m, 1H), 3.89e3.84 (m, 1H), 3.78e3.72 (m, 1H),
2.45e2.38 (m, 1H), 2.06 (s, 3H), 2.02e1.94 (m, 1H), 0.90 (s, 9H), 0.86
(s, 9H), 0.09 (s, 6H), 0.04 (s, 6H) ppm; 13C NMR (100 MHz, CDCl3):
4.3.1. 30,50-Di-O-(t-butyldimethylsilyl)-5-methyl-20-deoxycytidine
d
171.6,164.8,156.1,143.1,101.4, 87.9, 86.3, 71.4, 62.7, 60.5, 42.2, 26.1,
(10)
25.9, 20.9, 18.5, 18.1 ꢁ4.5, ꢁ4.8, ꢁ5.3 ppm; IR (KBr): vmax 3486,
2987, 1743, 1671, 1491, 1302, 1206, 845 cmꢁ1; HRMS (ESIþ): m/z
calcd for C24H46N3O6Si2 [MþH]þ 528.2920; found 528.2913.
The reaction of 1a (70 mg, 0.12 mmol) and conc. NH4OH (45
1.2 mmol) in THF (0.4 mL) afforded (PE/EA ¼ 2:1) 1′ (52 mg, 93%) as
a white solid; mp 91e92 ꢀC. 1H NMR (400 MHz, CDCl3):
7.49 (s,
mL,
d
1H), 6.28 (t, J ¼ 6.6 Hz, 1H), 4.35e4.28 (m, 1H), 3.90e3.86 (m, 1H),
3.85e3.80 (m, 1H), 3.74e3.69 (m, 1H), 2.36e2.30 (m, 1H), 1.95e1.88
(m, 1H),1.86 (s, 3H), 0.88 (s, 9H), 0.84 (s, 9H), 0.06 (d, J ¼ 2.6 Hz, 6H),
4.3.6. 5-Hydroxymethyl-20-deoxycytidine (60)
The reaction of
6 (103 mg, 0.4 mmol), PyAOP (333 mg,
0.64 mmol), DBU (97 mg, 0.64 mmol), and conc. NH4OH (62 mL,
0.02 (d, J ¼ 1.6 Hz, 6H) ppm; 13C NMR (100 MHz, CDCl3):
d
165.8,
1.6 mmol) in DMF (1.33 mL) afforded (CH2Cl2/MeOH ¼ 5:1) 60
156.1, 137.9, 101.6, 87.6, 85.8, 71.9, 62.8, 42.1, 26.0, 25.8, 18.4, 18.0,
(83 mg, 81%) as a white solid; mp 201e203 ꢀC. 1H NMR (400 MHz,
13.3, ꢁ4.5, ꢁ4.8, ꢁ5.3, ꢁ5.4 ppm; LRMS (ESIþ): m/z calcd for
D2O):
d
7.91 (s, 1H), 6.22 (t, J ¼ 6.4 Hz, 1H), 4.43 (s, 2H), 4.42e4.38
C
22H44N3O4Si2 [MþH]þ 470.3; found 470.3.
(m, 1H), 4.06e4.01 (m, 1H), 3.88e3.80 (m, 1H), 3.78e3.71 (m, 1H),
2.46e2.37 (m, 1H), 2.32e2.23 (m, 1H) ppm; 13C NMR (100 MHz,
4.3.2. 5-Methyl-20-deoxycytidine (20)
The reaction of (97 mg, 0.4 mmol), PyAOP (333 mg,
0.64 mmol), DBU (97 mg, 0.64 mmol), and conc. NH4OH (62 L,
D2O): d 164.2, 156.1, 140.8, 106.6, 86.8, 86.3, 70.4, 61.2, 57.7,
2
39.5 ppm; LRMS (ESIþ): m/z calcd for C10H16N3O5 [MþH]þ 258.1;
m
found 258.1.
Please cite this article as: X.-A. Zheng et al., An efficient PyAOP-based C4-amination method for direct access of oxidized 5MedC derivatives,
Tetrahedron, https://doi.org/10.1016/j.tet.2018.10.046

6
X.-A. Zheng et al. / Tetrahedron xxx (xxxx) xxx
4.3.7. 5-Formyl-20-deoxycytidine (70)
88%) as a white solid; mp 81e82 ꢀC. 1H NMR (400 MHz, CDCl3):
The reaction of
7
(102 mg, 0.4 mmol), PyAOP (333 mg,
d
7.75 (s, 1H), 6.29 (t, J ¼ 6.5 Hz, 1H), 4.79 (s, 2H), 4.36e4.33 (m, 1H),
0.64 mmol), DBU (97 mg, 0.64 mmol), and conc. NH4OH (62
mL,
3.94e3.88 (m, 1H), 3.84e3.72 (m, 2H), 3.65e3.48 (m, 4H),
2.46e2.38 (m, 1H), 2.06 (s, 3H), 2.02e1.94 (m, 1H), 1.21 (t, J ¼ 7.0 Hz,
6H), 0.88 (s, 9H), 0.87 (s, 9H), 0.07 (s, 6H), 0.05 (s, 6H) ppm; 13C
1.6 mmol) in DMF (1.33 mL) afforded (CH2Cl2/MeOH ¼ 7:1) 70
(76 mg, 75%) as a white solid; mp 193e195 ꢀC. 1H NMR (400 MHz,
D2O):
d
9.49 (s, 1H), 8.84 (s, 1H), 6.15 (t, J ¼ 6.0 Hz, 1H), 4.45e4.38
NMR (100 MHz, CDCl3): d 170.6, 162.6, 154.6, 146.1, 100.5, 87.9, 86.2,
(m, 1H), 4.14e4.10 (m, 1H), 3.93e3.87 (m, 1H), 3.80e3.73 (m, 1H),
72.1, 63.8, 63.1, 43.8, 42.1, 26.0, 25.9, 21.2, 18.5, 18.1,
13.8, ꢁ4.5, ꢁ4.8, ꢁ5.3 ppm; IR (KBr): vmax 2954, 2929, 2857, 1743,
1665, 1513, 1472, 1255, 837 cmꢁ1; HRMS (ESIþ): m/z calcd for
2.60e2.51 (m, 1H), 2.39e2.31 (m, 1H) ppm; 13C NMR (100 MHz,
D2O):
d 190.2, 161.7, 154.9, 153.8, 105.5, 87.7, 87.4, 69.9, 60.8, 57.7,
40.2 ppm; LRMS (ESIþ): m/z calcd for C10H14N3O5 [MþH]þ 256.1;
C
28H54N3O6Si2 [MþH]þ 584.3546; found 584.3545.
found 256.1.
4.3.12. N4-Benzyl-5-hydroxymethyl-20-deoxycytidine (120)
The reaction of (103 mg, 0.4 mmol), PyAOP (333 mg,
4.3.8. 5-Benzyloxycarbonyl-20-deoxycytidine (80)
6
The reaction of
0.48 mmol), DBU (73 mg, 0.48 mmol), and conc. NH4OH (46
8
(109 mg, 0.3 mmol), PyAOP (250 mg,
L,
0.64 mmol), DBU (97 mg, 0.64 mmol), and benzylamine (171 mg,
1.6 mmol) in DMF (1.33 mL) afforded (CH2Cl2/MeOH ¼ 5:1) 120
(118 mg, 85%) as a white solid; mp 183e184 ꢀC. 1H NMR (400 MHz,
m
1.2 mmol) in DMF (1 mL) afforded (CH2Cl2/MeOH ¼ 10:1) 8′ (85 mg,
79%) as a white solid; mp 165e167 ꢀC. 1H NMR (400 MHz,
DMSO‑d6):
d
7.76 (s, 1H), 7.55 (t, J ¼ 5.9 Hz, 1H), 7.34e7.28 (m, 4H),
DMSO‑d6):
d
8.95 (s, 1H), 7.98e7.96 (m, 1H), 7.64e7.62 (m, 1H),
7.25e7.21 (m,1H), 6.17 (t, J ¼ 6.5 Hz,1H), 5.20 (d, J ¼ 4.2 Hz,1H), 5.10
(t, J ¼ 5.3 Hz, 1H), 4.99 (t, J ¼ 5.2 Hz, 1H), 4.57 (d, J ¼ 6.0 Hz, 2H), 4.27
(d, J ¼ 5.2 Hz, 2H), 4.21e4.18 (m, 1H), 3.79e3.76 (m, 1H), 3.61e3.52
(m, 2H), 2.12e2.05 (m, 1H), 1.99e1.91 (m, 1H) ppm; 13C NMR
7.48e7.30 (m, 5H), 6.06 (t, J ¼ 6.2 Hz, 1H), 5.26 (s, 2H), 5.26 (s, 1H),
5.08e5.04 (m,1H), 4.26e4.19 (m,1H), 3.92e3.86 (m,1H), 3.64e3.53
(m, 2H), 2.33e2.25 (m, 1H), 2.08e2.01 (m, 1H) ppm; 13C NMR
(100 MHz, DMSO‑d6):
d
164.5, 163.0,153.2,148.6,136.2,128.5,128.0,
(100 MHz, DMSO‑d6): d 162.2, 154.9, 139.4, 138.4, 128.3, 127.1, 126.7,
127.7, 94.4, 88.1, 86.7, 70.2, 65.7, 61.0, 41.3 ppm; IR (KBr): vmax 3486,
106.3, 87.2, 84.8, 70.5, 61.5, 57.6, 43.2, 40.3 ppm; IR (KBr): vmax
2968,1705,1642,1512,1324,1204 cmꢁ1; HRMS (ESIþ): m/z calcd for
3443, 2883, 1565, 1508, 1056 cmꢁ1; HRMS (ESIþ): m/z calcd for
C
17H20N3O6 [MþH]þ 362.1347; found 362.1347.
C
17H22N3O5 [MþH]þ 348.1554; found 348.1549.
4.3.9. N4-Benzyl-50-O-(4,40-dimethoxytrityl)-5-(2-cyanoethoxy)
methyl-20-deoxycytidine (90)
4.3.13. N4,N4-Diethyl-5-formyl-20-deoxycytidine (130)
The reaction of (102 mg, 0.4 mmol), PyAOP (333 mg,
7
The reaction of
3
(123 mg, 0.2 mmol), PyAOP (167 mg,
0.64 mmol), DBU (97 mg, 0.64 mmol), and diethylamine (117 mg,
1.6 mmol) in DMF (1.33 mL) afforded (CH2Cl2/MeOH ¼ 8:1) 13′
(106 mg, 85%) as a white solid; mp 156e157 ꢀC. 1H NMR (400 MHz,
0.32 mmol), DBU (49 mg, 0.32 mmol), and benzylamine (86 mg,
0.8 mmol) in DMF (0.67 mL) afforded (CH2Cl2/MeOH ¼ 25:1) 9′
(119 mg, 85%) as a white solid; mp 89e91 ꢀC. 1H NMR (400 MHz,
D2O):
d
9.44 (s, 1H), 8.70 (s, 1H), 6.14 (t, J ¼ 6.1 Hz, 1H), 4.43e4.38
CDCl3):
d
7.93 (s, 1H), 7.40e7.36 (m, 2H), 7.34e7.30 (m, 4H),
(m, 1H), 4.11e4.06 (m, 1H), 3.89e3.83 (m, 1H), 3.78e3.72 (m, 1H),
3.57e3.49 (m, 4H), 2.56e2.47 (m, 1H), 2.36e2.27 (m, 1H), 1.20 (t,
7.29e7.24 (m, 8H), 6.83 (d, J ¼ 8.1 Hz, 4H), 6.48 (t, J ¼ 6.4 Hz, 1H),
6.15 (t, J ¼ 5.5 Hz, 1H), 4.70 (d, J ¼ 5.6 Hz, 2H), 4.62 (br, 1H), 4.16 (s,
1H), 4.14e4.12 (m, 1H), 3.78 (s, 6H), 3.76e3.71 (m, 1H), 3.59e3.53
(m, 1H), 3.44 (d, J ¼ 12.8 Hz, 1H), 3.35e3.30 (m, 1H), 3.15e3.13 (m,
2H), 2.68e2.60 (m, 1H), 2.32e2.26 (m, 1H), 2.25e2.21 (m, 2H) ppm;
J ¼ 7.0 Hz, 6H) ppm; 13C NMR (100 MHz, D2O):
d 187.9, 159.8, 154.4,
153.1, 108.8, 87.2, 70.1, 60.9, 45.0, 40.2, 12.0 ppm; IR (KBr): vmax
3465, 2975, 1564, 1508, 1250, 1088 cmꢁ1; HRMS (ESIþ): m/z calcd
for C14H22N3O5 [MþH]þ 312.1554; found 312.1551.
13C NMR (100 MHz, CDCl3):
d 162.8, 158.9, 156.2, 144.4, 139.9, 138.2,
135.7, 135.6,130.4, 130.3, 128.8, 128.5, 128.1, 127.6, 127.3, 117.4, 113.4,
101.9, 86.8, 88.2, 86.1, 71.8, 67.8, 63.7, 63.4, 55.4, 46.4, 42.3,
4.3.14. N4-Benzyl-5-benzyloxycarbonyl-20-deoxycytidine (140)
The reaction of
8 (109 mg, 0.3 mmol), PyAOP (250 mg,
18.5 ppm; IR (KBr): vmax 3465, 2968, 2242, 1680, 1564, 1250 cmꢁ1
;
0.48 mmol), DBU (73 mg, 0.48 mmol), and benzylamine (128 mg,
1.2 mmol) in DMF (1 mL) afforded (CH2Cl2/MeOH ¼ 8:1) 14′
(108 mg, 80%) as a white solid; mp 147e148 ꢀC. 1H NMR (400 MHz,
HRMS (ESIþ): m/z calcd for C41H43N4O7 [MþH]þ 703.3126; found
703.3125.
DMSO‑d6):
d
8.97 (s, 1H), 8.68 (t, J ¼ 5.8 Hz, 1H), 7.47e7.22 (m, 10H),
4.3.10. N4,N4-Diethyl-5-(2-cyanoethoxy)methyl-20-deoxycytidine
6.06 (t, J ¼ 6.1 Hz, 1H), 5.27 (s, 2H), 5.26 (s, 1H), 5.07 (t, J ¼ 4.8 Hz,
1H), 4.62 (d, J ¼ 5.9 Hz, 2H), 4.25e4.20 (m, 1H), 3.91e3.86 (m, 1H),
(100)
The reaction of
4
(93 mg, 0.3 mmol), PyAOP (250 mg,
3.64e3.54 (m, 2H), 2.33e2.25 (m, 1H), 2.09e2.01 (m, 1H) ppm; 13
C
0.48 mmol), DBU (73 mg, 0.48 mmol), and diethylamine (88 mg,
1.2 mmol) in DMF (1 mL) afforded (CH2Cl2/MeOH ¼ 8:1) 10′ (91 mg,
83%) as a white solid; mp 188e189 ꢀC. 1H NMR (400 MHz, D2O):
NMR (100 MHz, DMSO‑d6): d 164.7, 160.7, 153.1, 148.2, 138.6, 136.1,
128.5, 128.4, 128.0, 127.7, 127.4, 127.0, 94.6, 88.1, 86.7, 70.2, 65.8,
61.0, 43.4, 41.2 ppm; IR (KBr): vmax 3485, 2900, 1650, 1572, 1495,
1065 cmꢁ1; HRMS (ESIþ): m/z calcd for C24H26N3O6 [MþH]þ
452.1816; found 452.1816.
d
7.91 (s, 1H), 6.19 (t, J ¼ 6.7 Hz, 1H), 4.44e4.40 (m, 1H), 4.38 (s, 2H),
4.04e4.01 (m, 1H), 3.88e3.78 (m, 2H), 3.77e3.73 (m, 2H),
3.65e3.58 (m, 4H), 2.77 (t, J ¼ 5.8 Hz, 2H), 2.46e2.37 (m, 1H),
2.29e2.23 (m, 1H), 1.22e1.16 (m, 6H) ppm; 13C NMR (100 MHz,
4.3.15. 1-(50-O-(4,40-Dimethoxytrityl))-20-deoxy-
b-D-ribofuran-
D2O):
d
162.0, 156.2, 145.0, 119.8, 104.1, 86.7, 86.0, 70.4, 69.4, 64.1,
osyl)-5-(2-cyanoethoxy)methyl-4-(piperidin-1-yl)-2(1H)-
61.2, 44.2, 39.6, 18.3, 12.9 ppm; IR (KBr): vmax 3478, 2971, 2232,
pyrimidinone (150)
1650, 1519, 1293, 1095 cmꢁ1
;
HRMS (ESIþ): m/z calcd for
The reaction of 3 (123 mg, 0.2 mmol), PyAOP (167 mg,
C
17H27N4O5 [MþH]þ 367.1976; found 367.1972.
0.32 mmol), DBU (49 mg, 0.32 mmol), and piperidine (68 mg,
0.8 mmol) in DMF (0.67 mL) afforded (CH2Cl2/MeOH ¼ 20:1) 150
(112 mg, 82%) as a white solid; mp 95e96 ꢀC. 1H NMR (400 MHz,
4.3.11. N4,N4-Diethyl-30,50-di-O-t-butyldimethylsilyl-5-acetoxy-
methyl-20-deoxycytidine (110)
CDCl3): d 7.96 (s, 1H), 7.46e7.39 (m, 2H), 7.33e7.21 (m, 7H),
The reaction of
5
(106 mg, 0.2 mmol), PyAOP (167 mg,
6.86e6.81 (m, 4H), 6.45 (t, J ¼ 6.2 Hz, 1H), 4.60e4.55 (m, 1H), 4.52
(br, 1H), 4.17e4.12 (m, 1H), 3.82 (s, 1H), 3.79 (s, 6H), 3.71e3.66 (m,
4H), 3.55 (d, J ¼ 11.6 Hz, 2H), 3.27e3.22 (m, 1H), 2.95 (t, J ¼ 6.2 Hz,
0.32 mmol), DBU (49 mg, 0.32 mmol), and diethylamine (58 mg,
0.8 mmol) in DMF (0.67 mL) afforded (PE/EA ¼ 4:1) 110 (103 mg,
Please cite this article as: X.-A. Zheng et al., An efficient PyAOP-based C4-amination method for direct access of oxidized 5MedC derivatives,
Tetrahedron, https://doi.org/10.1016/j.tet.2018.10.046

X.-A. Zheng et al. / Tetrahedron xxx (xxxx) xxx
7
2H), 2.70e2.61 (m, 1H), 2.27e2.19 (m, 1H), 2.13 (t, J ¼ 6.1 Hz, 2H),
1.67e1.58 (m, 6H) ppm; 13C NMR (100 MHz, CDCl3):
164.1, 158.7,
108.4, 87.5, 87.4, 70.0, 66.4, 60.8, 48.8, 40.2 ppm; IR (KBr): vmax
3482, 2986, 1685, 1518, 1205, 1064 cmꢁ1; HRMS (ESIþ): m/z calcd
for C14H20N3O6 [MþH]þ 326.1347; found 326.1341.
d
155.3, 144.9, 144.7, 135.8, 135.6, 130.3, 130.2, 128.3, 128.0, 127.1,
117.6, 113.3, 103.5, 86.5, 86.3, 86.2, 71.9, 69.0, 64.1, 63.5, 55.3, 48.4,
42.3, 26.4, 24.6, 18.3 ppm; IR (KBr): vmax 3485, 2900, 2264, 1651,
1507, 1250, 1065 cmꢁ1; HRMS (ESIþ): m/z calcd for C39H45N4O7
[MþH]þ 681.3283; found 681.3279.
4.3.20. 1-(20-Deoxy-
(piperidin-1-yl)-2(1H)-pyrimidinone (200)
The reaction of (109 mg, 0.3 mmol), PyAOP (250 mg,
b-D-ribofuranosyl)-5-benzyloxycarbonyl-4-
8
0.48 mmol), DBU (73 mg, 0.48 mmol), and piperidine (102 mg,
1.2 mmol) in DMF (1.0 mL) afforded (CH2Cl2/MeOH ¼ 10:1) 20′
(98 mg, 76%) as a white solid; mp 153e154 ꢀC. 1H NMR (400 MHz,
4.3.16. 1-(20-Deoxy-
4-(morpholin-4-yl)-2(1H)-pyrimidinone (160)
The reaction of (93 mg, 0.3 mmol), PyAOP (250 mg,
0.48 mmol), DBU (73 mg, 0.48 mmol), and morpholine (104 mg,
1.2 mmol) in DMF (1 mL) afforded (CH2Cl2/MeOH ¼ 12:1) 16′
(89 mg, 78%) as a white solid; mp 191e193 ꢀC. 1H NMR (400 MHz,
b-D-ribofuranosyl)-5-(2-cyanoethoxy)methyl-
4
DMSO‑d6):
d
8.66 (s, 1H), 7.47e7.31 (m, 5H), 6.07 (t, J ¼ 6.3 Hz, 1H),
5.28e5.24 (m, 1H), 5.23 (s, 2H), 5.08e5.04 (m, 1H), 4.25e4.20 (m,
1H), 3.87e3.83 (m, 1H), 3.62e3.52 (m, 2H), 3.41e3.36 (m, 4H),
2.28e2.21 (m, 1H), 2.08e1.99 (m, 1H), 1.56 (s, 2H), 1.49 (s, 4H) ppm;
D2O):
d
8.02 (s, 1H), 6.20 (t, J ¼ 6.3 Hz, 1H), 4.46e4.40 (m, 3H),
13C NMR (100 MHz, DMSO‑d6):
d
164.1, 161.0, 152.8, 148.1, 136.0,
4.08e4.03 (m, 1H), 3.86e3.79 (m, 8H), 3.78e3.73 (m, 4H), 2.79 (t,
128.5, 128.2, 98.7, 87.9, 86.1, 70.4, 66.2, 61.2, 48.2, 41.0, 25.4,
J ¼ 5.7 Hz, 2H), 2.49e2.42 (m,1H), 2.34e2.26 (m,1H) ppm; 13C NMR
23.7 ppm; IR (KBr): vmax 3473, 2942, 1648, 1517, 1256, 1065 cmꢁ1
;
(100 MHz, D2O):
d 163.9, 156.4, 145.6, 119.9, 104.6, 86.9, 86.3, 70.3,
HRMS (ESIþ): m/z calcd for C22H28N3O6 [MþH]þ 430.1973; found
68.4, 66.6, 64.3, 61.1, 47.3, 39.7, 18.3 ppm; IR (KBr): vmax 3474, 2908,
430.1965.
2255, 1649, 1506, 1241 cmꢁ1
C
;
HRMS (ESIþ): m/z calcd for
17H25N4O6 [MþH]þ 381.1769; found 381.1769.
Acknowledgments
4.3.17. 1-(30,50-Di-O-t-butyldimethylsilyl-20-deoxy-
b-D-
We thank the National Natural Science Foundation of China
(21562021), Natural Science Foundation (20143ACB21014),
Fellowship for Young Scientists (2015BCB23009), and Sci & Tech
Project from Dept of Education (GJJ160763) of Jiangxi Province for
financial support.
ribofuranosyl)-5-acetoxymethyl-4-(morpholin-4-yl)-2(1H)-
pyrimidinone (170)
The reaction of
5 (106 mg, 0.2 mmol), PyAOP (167 mg,
0.32 mmol), DBU (49 mg, 0.32 mmol), and morpholine (70 mg,
0.8 mmol) in DMF (0.67 mL) afforded (PE/EA ¼ 4:1) 17′ (102 mg,
86%) as a white solid; mp 78e79 ꢀC. 1H NMR (400 MHz, CDCl3):
d
7.90 (s, 1H), 6.25 (t, J ¼ 6.4 Hz, 1H), 4.86e4.74 (m, 2H), 4.37e4.31
Appendix A. Supplementary data
(m, 1H), 3.92e3.98 (m, 1H), 3.81e3.76 (m, 2H), 3.75e3.68 (m, 8H),
2.50e2.43 (m, 1H), 2.06 (s, 3H), 2.01e1.93 (m, 1H), 0.88 (s, 9H), 0.87
(s, 9H), 0.07 (s, 6H), 0.05 (s, 6H) ppm; 13C NMR (100 MHz, CDCl3):
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2018.10.046.
d
170.5, 164.8, 154.7, 146.5, 101.7, 88.2, 86.7, 72.1, 66.9, 63.1, 62.4,
48.0, 42.1, 26.0, 25.9, 21.1, 18.5, 18.1, ꢁ4.5, ꢁ4.8, ꢁ5.3 ppm; IR (KBr):
vmax 2954, 2929, 1651, 1501, 1225, 1028, 838 cmꢁ1; HRMS (ESIþ): m/
z calcd for C17H25N4O6 [MþH]þ 598.3338; found 598.3330.
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4.3.18. 1-(20-Deoxy-
(piperidin-1-yl)-2(1H)-pyrimidinone (180)
The reaction of (103 mg, 0.4 mmol), PyAOP (333 mg,
b-D-ribofuranosyl)-5-hydroxymethyl-4-
6
0.64 mmol), DBU (97 mg, 0.64 mmol), and piperidine (136 mg,
1.6 mmol) in DMF (1.33 mL) afforded (CH2Cl2/MeOH ¼ 4:1) 18′
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D2O):
d
7.93 (s, 1H), 6.20 (t, J ¼ 6.4 Hz, 1H), 4.45 (s, 2H), 4.44e4.39
(m, 1H), 4.05e4.01 (m, 1H), 3.86e3.80 (m, 1H), 3.77e3.73 (m, 1H),
3.72e3.67 (m, 4H), 2.45e2.37 (m, 1H), 2.32e2.23 (m, 1H), 1.65 (s,
6H) ppm; 13C NMR (100 MHz, D2O):
d 161.7, 154.8, 143.9, 108.2, 86.9,
86.1, 70.5, 61.2, 59.7, 49.1, 39.5, 25.9, 23.6 ppm; IR (KBr): vmax 3462,
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2937, 1643, 1504, 1460, 1072 cmꢁ1; HRMS (ESIþ): m/z calcd for
C
15H24N3O5 [MþH]þ 326.1710; found 326.1708.
4.3.19. 1-(20-Deoxy-
yl)-2(1H)-pyrimidinone (190)
The reaction of (102 mg, 0.4 mmol), PyAOP (333 mg,
0.64 mmol), DBU (97 mg, 0.64 mmol), and morpholine (139 mg,
1.6 mmol) in DMF (1.33 mL) afforded (CH2Cl2/MeOH ¼ 8:1) 19′
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b-D-ribofuranosyl)-5-formyl-4-(morpholin-4-
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7
D2O):
d
9.38 (s, 1H), 8.84 (s, 1H), 6.16 (t, J ¼ 6.0 Hz, 1H), 4.46e4.41
(m, 1H), 4.15e4.10 (m, 1H), 3.92e3.86 (m, 1H), 3.83e3.79 (m, 4H),
3.78e3.74 (m,1H), 3.71e3.65 (m, 4H), 2.60e2.53 (m,1H), 2.40e2.32
(m, 1H) ppm; 13C NMR (100 MHz, D2O):
d 187.5, 160.6, 155.8, 154.5,
Please cite this article as: X.-A. Zheng et al., An efficient PyAOP-based C4-amination method for direct access of oxidized 5MedC derivatives,
Tetrahedron, https://doi.org/10.1016/j.tet.2018.10.046