Photochemical Behavior of 2-Azidopurine Tri-O-Acetylribonucleoside in Aqueous Solution: Unprecedented Transformation into 1-(5′-O-Acetyl-β-D-Ribofuranosyl)-5-[(2-Oxo-1,3,5-Oxadiazocan-4-Ylidene)Amino]-1 H-Imidazole-4-Carbaldehyde

Article abstract of DOI:10.1080/15257770.2014.981342

The photochemical behavior of 2-azidopurine 2′,3′,5′-tri-O-acetylribonucleoside has been investigated in aqueous solution under aerobic and anaerobic conditions. The two major processes under anaerobic irradiation of 2-azidopurine 2′,3′,5′-tri-O-acetylribonucleoside involve unprecedented transformation into 1-(5′-O-acetyl-β-D-ribofuranosyl)-5-[(2-oxo-1,3,5-oxadiazocan-4-ylidene)amino]-1H-imidazole-4-carbaldehyde and photoreduction to respective 2-aminopurine derivative, whereas under aerobic conditions these two processes occur to a much lesser extent and photooxidation to respective 2-nitropurine derivative dominates. The structures of photoproducts formed were confirmed by NMR and high-resolution electrospray ionization mass spectral data.

Full text of DOI:10.1080/15257770.2014.981342

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Photochemical Behavior of 2-
Azidopurine Tri-O-Acetylribonucleoside
in Aqueous Solution: Unprecedented
Transformation into 1-(5′-O-Acetyl-β-
D-Ribofuranosyl)-5-[(2-Oxo-1,3,5-
Oxadiazocan-4-Ylidene)Amino]-1H-
Imidazole-4-Carbaldehyde
ab
a
b
Click for updates
Krzysztof Komodziński , Zofia Gdaniec & Bohdan Skalski
a
Institute of Bioorganic Chemistry, Polish Academy of Sciences,
Poznań, Poland
b
Faculty of Chemistry, Adam Mickiewicz University, Poznań, Poland
Published online: 16 Mar 2015.
To cite this article: Krzysztof Komodziński, Zofia Gdaniec & Bohdan Skalski (2015) Photochemical
Behavior of 2-Azidopurine Tri-O-Acetylribonucleoside in Aqueous Solution: Unprecedented
Transformation into 1-(5′-O-Acetyl-β-D-Ribofuranosyl)-5-[(2-Oxo-1,3,5-Oxadiazocan-4-
Ylidene)Amino]-1H-Imidazole-4-Carbaldehyde, Nucleosides, Nucleotides and Nucleic Acids, 34:4,
235-245, DOI: 10.1080/15257770.2014.981342
To link to this article: http://dx.doi.org/10.1080/15257770.2014.981342
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Nucleosides, Nucleotides and Nucleic Acids, 34:235–245, 2015
Copyright ꢀC Taylor and Francis Group, LLC
ISSN: 1525-7770 print / 1532-2335 online
DOI: 10.1080/15257770.2014.981342
PHOTOCHEMICAL BEHAVIOR OF 2-AZIDOPURINE
TRI-O-ACETYLRIBONUCLEOSIDE IN AQUEOUS SOLUTION:
ꢀ
UNPRECEDENTED TRANSFORMATION INTO 1-(5 -O-ACETYL-β-D-
RIBOFURANOSYL)-5-[(2-OXO-1,3,5-OXADIAZOCAN-4-
YLIDENE)AMINO]-1H-IMIDAZOLE-4-CARBALDEHYDE
Krzysztof Komodzi n´ ski,1 Zofia Gdaniec, and Bohdan Skalski
,2
1
2
1
Institute of Bioorganic Chemistry, Polish Academy of Sciences, Pozna n´ , Poland
Faculty of Chemistry, Adam Mickiewicz University, Pozna n´ , Poland
2
ꢁ
ꢁ
ꢁ
2
The photochemical behavior of 2-azidopurine 2 ,3 ,5 -tri-O-acetylribonucleoside has been in-
vestigated in aqueous solution under aerobic and anaerobic conditions. The two major pro-
ꢁ
ꢁ
ꢁ
cesses under anaerobic irradiation of 2-azidopurine 2 ,3 ,5 -tri-O-acetylribonucleoside involve
unprecedented transformation into 1-(5 -O-acetyl-β-D-ribofuranosyl)-5-[(2-oxo-1,3,5-oxadiazocan-
ꢁ
4
-ylidene)amino]-1H-imidazole-4-carbaldehyde and photoreduction to respective 2-aminopurine
derivative, whereas under aerobic conditions these two processes occur to a much lesser extent
and photooxidation to respective 2-nitropurine derivative dominates. The structures of photoprod-
ucts formed were confirmed by NMR and high-resolution electrospray ionization mass spectral
data.
Keywords 2-Azidopurine ribonucleoside; photochemistry; modified nucleoside; pho-
toreduction; photooxidation
INTRODUCTION
Azidopurine nucleosides, such as 2-azidoadenosine, 8-azidoadenosine,
-azidoguanosine, and 2,6-diazidonebularine, belong to a group of the most
8
popular photoaffinity labeling probes used for mapping nucleic acid – pro-
tein interactions.[ One of the major advantages of the azidonucleosides as
photoreactive agents is the generation of highly reactive nitrene intermedi-
ate capable of reacting in an indiscriminating manner with the surround-
ing functional groups and bonds present in the macromolecular system
studied. Despite their common use as photoaffinity probes, the knowledge
concerning photochemistry of these azidonucleosides alone is still rather
1]
Received 17 August 2014; accepted 22 October 2014.
Address correspondence to Dr. Bohdan Skalski, Faculty of Chemistry, Adam Mickiewicz University,
Umultowska 89b, 61-614 Pozna n´ , Poland. E-mail: bskalski@amu.edu.pl
2
35

2
36
K. Komodzi n´ ski et al.
limited. A better understanding of the detailed mechanisms of photochem-
istry of azidopurine nucleoside analogs and structures of photoproducts
formed is crucial for better understanding of the mechanism of the pho-
tocrosslinking reactions and further development of the photocrosslinking
technique using these type of compounds as photoprobes in molecular bi-
[
2]
[3]
[4]
ology. So far the photochemistry of 8-azidoadenine, 2-azidoadenine,
6
-azidopurine,[ and 2-amino-6-azidopurine ribonucleosides in aqueous
5]
[4]
solutions has been examined. It has been shown that the photochemical
behavior of these compounds is highly dependent on the position of the
azide group in the purine ring system, the presence of various substituents
(
H or NH ), and the presence or absence of oxygen. In the case of 8-
2
azidoadenosine, photoreduction of 8-aminoadenosine through the forma-
[
3]
tion of nitrene intermediate was observed. Our recent studies on the
photochemistry of a series of azidopurine nucleosides have shown that 6-
azidopurine nucleoside undergoes only partial photoreduction to adeno-
sine, and its dominant phototransformation involves purine ring expansion
to give a novel imidazole-fused 1,3,5-triazepinone nucleoside, independent
of the presence or absence of oxygen.[ The purine ring expansion was also
found to be a major photoreaction in the case of 6-azidopurine incorpo-
rated into an oligodeoxynucleotide chain. Completely different behavior
was observed in the case of near-UV irradiation of 2-azidoadenosine and 2-
amino-6-azidonebularine.[ Depending on the photoirradiation conditions,
aerobic or anaerobic, both azidopurine nucleosides were found to undergo
either photoreduction to respective amino derivatives or photooxidation to
respective 2- and 6-nitro analogs, and no purine ring expansion product
could be detected in both cases.[
5]
[6]
4]
4]
As a part of our ongoing studies of the photochemistry of azidop-
urine nucleosides, we report herein the results concerning the photo-
chemical transformations of novel azidopurine analog, 2-azidopurine tri-
O-acetylribonucleoside 1 in aqueous solution under aerobic and anaerobic
conditions.
RESULTS AND DISCUSSION
The synthesis of 2-azidopurine tri-O-acetylribonucleoside 1 was carried
[4,7]
out according to the reported procedure.
An aqueous solution of 1 was
irradiated at room temperature with a near-UV light (λ > 300 nm) us-
ing a high-pressure Hg lamp equipped with a 300-nm cut-off Pyrex glass
filter. The progress of photoreaction was monitored by UV absorption spec-
troscopy and high-performance liquid chromatography (HPLC) (Figure 1).
Complete disappearance of 1 was observed within 12 min of irradiation with
virtually identical rates under both aerobic and anaerobic conditions. As
shown in Figure 1A, irradiation of 1 under aerobic conditions resulted in

Photochemical Behavior of Azidopurine Analog in Aqueous Solution
237
FIGURE 1 Changes in the absorption spectrum of an aqueous solution of 1 measured with 1-min
increments during irradiation under (A) aerobic and (B) anaerobic conditions. The insets show HPLC
analyses of the solutions before (dotted lines) and after 12-min irradiation (solid lines).
the formation of one minor 2 (∼5%) and three major products, 3 (∼20%),
4
(∼25%), and 5 (∼40%), of which 5 was clearly dominant, whereas in the
absence of oxygen no formation of 5 was observed and 3 (∼45%) and 4
(
∼40%) were formed as two major photoproducts (Figure 1B). The photo-
products were isolated and purified by HPLC and were fully characterized
by means of spectroscopic methods (high-resolution electrospray ionization
time-of-flight mass spectrometry (HR ESI-TOF MS) and NMR). The struc-
tures of all photoproducts are shown in Scheme 1.
The structure of the minor photoproduct 2 formed under both con-
ꢁ
ꢁ
ꢁ
ditions was identified as 2 ,3 ,5 -tri-O-acetylguanosine in comparison (UV
spectrum and HPLC) with that of an authentic sample. Similarly, the struc-
ꢁ
ꢁ
ꢁ
ture of photoproduct 4 as 2-amino-9-(2 ,3 ,5 -tri-O-acetyl-β-D-ribofuranosyl)
purine was confirmed by comparison of its HR ESI-TOF MS, NMR, and UV
[9]
spectra with those reported in the literature.
The molecular formula of 5 (C H N O ), inferred from the high-
16
17
5
9
resolution ESI-TOF MS spectrum, indicated that the formation of this
photoproduct involves loss of a N molecule and addition of an oxygen
2
[4]
1
13
molecule. The H NMR and C NMR spectra of 5 showed the peak char-
acteristics of sugar and purine residues of the molecule. In the aromatic
1
part of H NMR spectrum of 5, two signals corresponding to C6-H and C8-
H protons appeared at δ = 9.20 and 8.48 ppm. In the aromatic region
H
13
of C NMR spectrum of 5, five signals appeared, two from the methine
carbon δ = 149.9 (C6) and 147.3 ppm (C8), and three from quaternary
C

2
38
K. Komodzi n´ ski et al.
SCHEME 1 Azide-tetrazole tautomeric equilibrium of 1[8] and structures of the photoproducts formed
during irradiation under aerobic and anaerobic conditions.
carbons at δ = 154.7 (C2), 151.9 (C4), and 137.2 ppm (C5). One bond
C
1
13
H- C correlation was detected between C6(δ = 149.9 ppm) and H6(δ
C
H
1
13
=
9.20 ppm); and C8(δ = 147.3 ppm) and H8(δ = 8.48 ppm). H- C
C
C
HMBC spectrum showed correlations of proton H6(δ = 9.20 ppm) with
H
carbon atoms C2(δ = 154.7 ppm) and C4(δ = 151.9 ppm). Furthermore,
C
C
1
13
typical for purine nucleosides, long-range H- C correlations were observed
for H8(δ = 8.48 ppm) with C4(δ = 151.9 ppm) and C5(δ = 137.2 ppm);
H
C
C
anomeric H1’(δ = 6.29 ppm) with C4(δ = 151.9 ppm) and C8(δ =
H
C
C
1
47.3 ppm). The UV spectrum of this photoproduct displays absorption
band centered at 272 nm and extending well above 300 nm. All the above
ꢁ
ꢁ
ꢁ
data clearly suggest that photoproduct 5 is 2-nitro-9-(2 ,3 ,5 -tri-O-acetyl-β-
D-ribofuranosyl)purine. This 2-nitropurine chromophore has not been de-
scribed previously in the literature.[ As in the case of 2-amino-6-azido
10]
[4]
and 6-amino-2-azido analogs of purine ribonucleosides, the most likely

Photochemical Behavior of Azidopurine Analog in Aqueous Solution
239
mechanism accounting for the formation of 2-nitropurine ribonucleoside
involves a triplet nitrene intermediate that reacts with the O molecule to
2
give 5 (Scheme 2).
SCHEME 2 The proposed mechanism of formation of photoproducts 4 and 5.
Based on careful analysis of NMR and MS spectral data, the structure
ꢁ
of photoproduct 3 was established as 1-(5 -O-acetyl-β-D-ribofuranosyl)-5-
[
(
(2-oxo-1,3,5-oxadiazocan-4-ylidene)amino] -1 H -imidazole-4-carbaldehyde
Scheme 3).
The molecular formula C H N O of photoproduct 3 was determined
1
6
21
5
8
1
13
by high-resolution ESI-TOF MS. The H and C NMR spectra showed that
the sugar moiety was deacetylated at 2 and 3 positions. Apart from the sugar
ꢁ
ꢁ
protons, three methylene resonances were observed at δ = 4.09 ppm (H8B),
H
2
.69 ppm (H6B), and 1.96 ppm (H7B), and were identified as belonging
1
1
to the one spin system as evidenced by H- H COSY and TOCSY spectra.
In addition, two singlets at δ = 7.66 ppm (H2A) and 9.47 ppm (aldehyde
H
1
group) appeared in H NMR spectrum. The latter, substantially deshilded
signal, was assigned to the proton of an H–C=O group based on the cor-
relation of this proton and the carbon atom resonating at δ = 183.4 ppm,
C
i.e., in the region typical for the aldehyde carbon. Two exchangeable pro-
tons were identified at 7.78 and 7.72 ppm and were assigned to NH protons
1
15
based on the one-bond H- N correlation observed in the Heteronuclear
Single Quantum Coherence (HSQC) spectrum. The aglycone structure was

2
40
K. Komodzi n´ ski et al.
SCHEME 3 The structures and numbering of ring systems of compound 3 and the product of its
∗
cyclization in methanolic solution (6/6 , see Scheme 4). The arrows show the connectivity of cross-peaks
1
13
due to couplings through 2 and 3 chemical bonds observed in the H- C HMBC experiment.
established mainly by analyzing long-range proton–carbon correlations in
1
13
the H- C HMBC spectrum shown on Scheme 3.
The presence of imidazole ring was confirmed from HMBC correlations
observed between proton H2A(δ = 7.66 ppm) with carbon atoms C5A(δ
H
C
=
146.6 ppm) and C4A(δ = 128.0 ppm) as well as between anomeric
C
proton H1’(δ = 5.47 ppm) with C5A(δ = 146.6 ppm) and C2A(δ =
H
C
C
1
32.8 ppm). The resonance at δ = 9.47 ppm revealed HMBC correlation
H
to C5A and C4A carbon atoms, placing the aldehyde group at C5 position
1
13
of imidazole ring. H and C chemical shifts of methylene groups of C6B
and C8B suggested that they were attached directly to the nitrogen and
oxygen atoms respectively. Further evidence of attachment of C6B group to
nitrogen atom could be obtained by the observation of NOE between H6 pro-
tons and NH signal at δ = 7.72 ppm. The H8 protons of methylene group
H
showed long-range correlation to quaternary carbon atom at δ = 168.9 ppm
C
(
δ
C2B), and H6 protons gave cross-peak to fully substituted carbon atom at
= 169.0 ppm (C4B). The UV spectrum of photoproduct 3 displays
C
an absorption band centered at 251 nm with shoulder at ca. 300 nm
extending up to 380 nm (Figure 2, solid line). All the above spec-
tral data are consistent with the proposed structure of photoproduct 3.
Considering the mechanism of the formation of this photoproduct, it can

Photochemical Behavior of Azidopurine Analog in Aqueous Solution
241
∗
FIGURE 2 Comparison of normalized UV absorption spectra of 3 (solid line) and 6/6 (dotted line).
be assumed that the key steps involve hydrolytic opening of pyrimidine ring
(
the presence of an aldehyde group) of the initially formed 2-nitrenopurine
intermediate, following by the formation of 4-imino-1,3,5-oxadiazocan-2-one
residue. The lack of two (2 , 3 ) acetyl groups observed only in the case of
this photoproduct indicate that they must participate in the formation of the
ꢁ
ꢁ
1
,3,5-oxadiazocan-2-one ring. However, the detailed knowledge of the pho-
tochemical pathway of this unexpected transformation of 1 requires further
study.
Photoproduct 3 is stable in aqueous solution, but in methanolic so-
lution it undergoes spontaneous cyclization to form two diastereomers
ꢁ
of a new ring-expanded nucleoside 3-(5 -O-acetyl-β-D-ribofuranosyl)-12-
hydroxy-3,5,6,7,8,12-hexahydro[1,3,5]oxadiazocino[3,4-a]purin-10-one, 6/
∗
6
, (stereogenic center at C12 carbon atom) in the ratio 1:1 (Scheme 4).
The transformation is quantitative and is accompanied by the appearance
of a new absorption band at ca. 305 nm in UV spectrum (Figure 2, dotted
line). The detailed proof of the structure is presented for diastereomer 6,

2
42
K. Komodzi n´ ski et al.
∗
1
which is completely analogous as isomer 6 . The main difference between H
NMR spectra of 3 and 6 is the disappearance of resonance at δ = 9.47 ppm
H
(
CHO) attributed to the aldehyde proton and appearance of a singlet at δ
6.39 ppm (H12). This new resonance gave one-bond H- C correlation
H
1
13
=
to carbon atom at δ = 88.9 ppm (C12) and two long-range correlations to
C
13
carbon atoms at δ = 115.8 (C12a) and 150.4 ppm (C10). The C signal at
C
1
15.8 ppm could be attributed to C12a carbon atom based on the observed
HMBC correlation with H2 signal at δ = 7.50 ppm (Scheme 3). In addi-
H
13
tion, C signal at δ = 150.4 ppm revealed long-range correlation with H8
C
methylene protons which supports the evidence for the cyclization process
leading to the formation of the tricyclic ring system in compound 6. The
1
13
connectivities through 2- and 3-chemical bond atoms observed in the H- C
HMBC experiment are shown in Scheme 3. This transformation provides
opportunities for the synthesis of potentially valuable novel ring-expanded
[
11]
nucleoside containing a 5:6:8-fused heterocyclic ring system.
∗
SCHEME 4 Transformation of 3 into diastereomers 6/6 in CH3OH.
CONCLUSIONS
In conclusion, the above results show that, depending on the irra-
ꢁ
ꢁ
ꢁ
diation conditions, the major photochemical transformations of 2 ,3 ,5 -
tri-O-acetylated derivative of 2-azidopurine ribonucleoside 1 in aque-
ous solution involve photooxidation and photoreduction to respec-
tive 2-nitro (5) and 2-amino (4) derivatives, and unprecedented for-
ꢁ
mation of 1-(5 -O-acetyl-β-D-ribofuranosyl)-5-[(2-oxo-1,3,5-oxadiazocan-4-
ylidene)amino]-1H-imidazole-4-carbaldehyde (3). Photooxidation is the ma-
jor process occurring under aerobic irradiation whereas in the absence of
oxygen, 3 is formed as the major photoproduct. Our results enlarge the
scope of the photoreactivity of azidopurine ribonucleosides used as pho-
toaffinity labeling probes in the photocrosslinking technique and tools in
synthetic organic chemistry.

Photochemical Behavior of Azidopurine Analog in Aqueous Solution
243
EXPERIMENTAL SECTION
Synthetic and Analytical Methods
High-performance liquid chromatography analysis was performed with
Agilent 1260 Infinity system equipped with diode-array UV-vis detectors.
Absorption spectra were measured using a Cary 300 Bio Varian spectropho-
tometer in CH CN. The high-resolution mass spectrometry (HRMS) analy-
3
ses were performed using ESI-TOF system (Bruker). The NMR spectra were
measured in CDCl on Bruker Avance III 700 spectrometer operating at
3
1
13
TM
7
00 MHz for H and 175 MHz for C. The QCI-P CryoProbe 5 mm was
used.
Spectral Data for Substrate
Characteristic Data for Compound 1
R 0.32 (CHCl :CH OH 95:5, v/v). UV (CH CN) λmax/nm: 230 and 286.
f
3
3
3
1
H NMR (CDCl ) δ: 8.91 (s, 1H, H6 ), 8.81 (s, 1H, H6 ), 8.09 (s, 1H, H8 ),
3
a
t
a
8
.02 (s, 1H, H8 ), 6.16 (d, J = 4.2 Hz, 1H, H1’ ), 6.13 (d, J = 4.2 Hz, 1H,
t
t
H1’ ), 5.79 (t, J = 5.2 Hz, 1H, H2’ ), 5.74 (t, J = 4.8 Hz, 1H, H2’ ), 5.56 (m,
a
a
t
1
2
1
1
8
H, H3’ ), 5.55 (m, 1H, H3’ ), 4.42 (m, 2H, H4’ ), 4.40 (m, 4H, H5’,H5” ),
t a a,t a,t
13
.11–1.97 (s, 18H, CH -Ac ). C NMR (CDCl ) δ: 169.6–168.4 (C=O-Ac ),
3
a,t
3
a
69.3–168.5 (C=O-Ac ), 160.3 (C2 ), 156.3 (C2 ), 151.6 (C4 ), 151.0 (C4 ),
t
a
t
a
t
49.6 (C6 ), 149.2 (C6 ), 142.1 (C8 ), 141.3 (C8 ), 130.9 (C5 ), 129.8 (C5 ),
a
t
a
t
a
t
8.8 (C1’ ), 85.1 (C1’ ), 81.9 (C4’ ), 79.2 (C4’ ), 73.9 (C2’ ), 72.1 (C2’ ), 70.3
t
a
a
t
a
t
(
(
C3’ ), 69.4 (C3’ ), 62.5 (C5’ ), 61.9 (C5’ ), 19.7–19.4 (CH -Ac ). HRMS
a t a t 3 a,t
+
ESI-TOF): calcd for C H N O Na [M + Na] 442.1082, found 442.1081.
16
17
7
7
UV Irradiation
An aqueous solution (200 mL) of 1 (75 mg) was irradiated in a photore-
actor with a 200 W, high-pressure immersion Hg lamp (TQ 150) equipped
with a cut-off Pyrex filter (λ > 300 nm) for 12 min (anaerobic conditions:
mixture was additionally degassed for 60 min under argon). The photo-
products formed were isolated and purified by preparative reversed-phase
HPLC using an HPLC instrument equipped with diode-array UV-vis detec-
tor. The column was Agilent Zorbax SB-C18 5.0 μm 9.1 × 150 mm, eluted
with H O/CH CN using a linear gradient of 10–45% of CH CN over 25 min
2
3
3
at a flow rate of 1.8 mL/min.
Spectral Data for Photoproducts
Characteristic Data for Compound 3
1
UV (CH CN) λ /nm: 251. H NMR (DMSO-d ) δ: 9.47 (s, 1H, CHO),
3
max
6
7.78 (s, 1H, N3-H), 7.72 (s, 1H, N5-H), 7.66 (s, 1H, H2A), 5.49 (d, J =

2
44
K. Komodzi n´ ski et al.
4
.8 Hz, 1H, H1’), 4.26 (m, 1H, H2’), 4.25–4.10 (m, 2H, H5’, H5”), 4.09
(
m, 2H, H8B), 4.07 (m, 1H, H3’), 3.98 (m, 1H, H4’), 2.69 (m, 2H, H6B),
.05 (s, 3H, CH -Ac), 1.96 (m, 2H, H7B). C NMR (DMSO-d ) δ: 183.4
13
2
3
6
(
(
(
CHO), 170.1 (C=O-Ac), 169.0 (C4B), 168.9 (C2B), 146.6 (C5A), 132.8
C2A), 128.0 (C4A), 87.3 (C1’), 81.5 (C4’), 73.9 (C2’), 70.6 (C3’), 65.7
C8B), 64.5 (C5’), 29.9 (C6B), 25.3 (C7B), 21.0 (CH -Ac). HRMS (ESI-
3
−
TOF): calcd for C H N O [M–H] 410.1347, found 410.1346.
16
20
5
8
Characteristic Data for Compound 4
UV (CH CN) λ /nm: 220, 246, and 308. H NMR (CDCl ) δ: 8.54 (s,
1
3
max
3
1
1
H, H6), 7.68 (s, 1H, H8), 5.87 (d, J = 5.1 Hz, 1H, H1’), 5.83 (t, J = 5.2 Hz,
H, H2’), 5.56 (t, J = 5.1 Hz, 1H, H3’), 4.94 (s, 2H, NH ), 4.30 (m, 1H,
2
13
H4’), 4.27 (m, 1H, H5’), 4.22 (m, 1H, H5”), 1.97–19.1 (s, 9H, CH -Ac). C
3
NMR (CDCl ) δ: 170.5–169.4 (C=O-Ac), 159.8 (C2), 152.6 (C4), 150.5 (C6),
3
1
40.8 (C8), 128.8 (C5), 86.3 (C1’), 79.8 (C4’), 72.7 (C2’), 70.5 (C3’), 62.9
(C5’), 20.7–20.5 (CH -Ac). HRMS (ESI-TOF): calcd for C H N O [M +
3
16 20
5
7
+
H] 394.1363, found 394.1378.
Characteristic Data for Compound 5
1
UV (CH CN) λ /nm: 218 and 272. H NMR (CDCl ) δ: 9.20 (s, 1H,
3
max
3
H6), 8.48 (s, 1H, H8), 6.29 (d, J = 5.5 Hz, 1H, H1’), 5.73 (t, J = 5.6 Hz, 1H,
H2’), 5.57 (t, J = 5.3 Hz, 1H, H3’), 4.50 (m, 1H, H4’), 4.42 (m, 2H, H5’,
1
3
H5”), 2.14–2.03 (s, 9H, CH -Ac). C NMR (CDCl ) δ: 170.2–169.6 (C=O-
3
3
Ac), 154.7 (C2), 151.9 (C4), 149.9 (C6), 147.3 (C8), 137.2 (C5), 86.8 (C1’),
8
1.2 (C4’), 73.7 (C2’), 70.8 (C3’), 63.1 (C5’), 20.8–20.4 (CH -Ac). HRMS
3
+
(ESI-TOF): calcd for C H N O Na [M + Na] 446.0924, found 446.0939.
16
17
5
9
∗
Characteristic Data for Compound 6/6
1
UV (CH CN) λ /nm: 253 and 305. H NMR (CDCl ) δ: 7.50 (s, 1H,
3
max
3
∗
∗
H2), 7.47 (s, 1H, H2 ), 6.39 (s, 1H, H12), 6.38 (s, 1H, H12 ), 5.71 (d, J =
∗
∗
5
.0 Hz, 1H, H1’), 5.67 (d, J = 4.7 Hz, 1H, H1’ ), 4.52 (m, 2H, H8 ), 4.32
∗
∗
∗
(
(
2
3
m, 1H, H2’ ), 4.31 (m, 2H, H4’, H4’ ), 4.30 (m, 3H, H3’ , H5’, H5”), 4.29
m, 3H, H8, H2’), 4.27 (m, 1H, H3’), 4.19 (m, 2H, H5’, H5”), 3.11 (m,
H, H6), 2.71 (m, 2H, H6 ), 2.13 (m, 2H, H7), 2.11 (m, 2H, H7 ), 1.99 (s,
∗
∗
∗
13
H, CH -Ac), 1.97 (s, 3H, CH -Ac ). C NMR (CDCl ) δ: 169.7 (C=O-Ac,
3
3
3
∗
∗
∗
∗
C=O=Ac ), 151.1 (C4a, C4a ), 150.4 (C10, C10 ), 133.8 (C2 ), 133.7 (C3a,
∗
∗
∗
C3a ), 133.4 (C2), 116.2 (C12a ), 115.8 (C12a), 90.1 (C1’ ), 89.9 (C1’), 88.9
∗
∗
∗
∗
(
(
C12, C12 ), 83.0 (C4’, C4’ ), 75.8 (C2’), 75.4 (C2’ ), 71.5 (C3’, C3’ ), 70.5
C8, C8 ), 63.5 (C5’ C5’ ), 24.7 (C6, C6 ), 23.3 (C7, C7 ), 20.7 (CH -Ac,
CH -Ac ). HRMS (ESI-TOF): calcd for C H N O [M + H] 412.1505,
∗
∗
∗
∗
3
∗
+
3
16 22
5
8
found 412.1508.

Photochemical Behavior of Azidopurine Analog in Aqueous Solution
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