Convenient synthesis of 8-amino-2′-deoxyadenosine

Article abstract of DOI:10.1081/NCN-120019521

We studied the behaviour of 8-azido-2′-deoxyadenosine and 8-bromo-2′-deoxyadenosine in aqueous solutions of ammonia and primary and secondary amines. Unexpectedly, 8-Azido-2′-deoxyadenosine is converted to 8-amino-2′-deoxyadenosine in excellent yields. The use of this reaction for the preparation of 8-aminoadenine derivatives needed for the preparation of oligonucleotides carrying 8-aminoadenine is discussed.

Full text of DOI:10.1081/NCN-120019521

This article was downloaded by: [Moskow State Univ Bibliote]
On: 28 January 2014, At: 01:10
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Nucleosides, Nucleotides and Nucleic Acids
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lncn20
Convenient Synthesis of 8-Amino-2′-deoxyadenosine
a b
a
a c
Miriam Frieden
, Anna Aviñó & Ramon Eritja
a
Instituto de Biología Molecular de Barcelona , C.S.I.C. Jordi Girona, Barcelona, Spain
Cureon A/S, Copenhagen, Denmark
b
c
Instituto de Biología Molecular de Barcelona , C.S.I.C. Jordi Girona 18-26, E-08034
Barcelona, Spain
Published online: 24 Jun 2011.
To cite this article: Miriam Frieden , Anna Aviñó & Ramon Eritja (2003) Convenient Synthesis of 8-Amino-2′-deoxyadenosine,
Nucleosides, Nucleotides and Nucleic Acids, 22:2, 193-202, DOI: 10.1081/NCN-120019521
To link to this article: http://dx.doi.org/10.1081/NCN-120019521
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS
Vol. 22, No. 2, pp. 193–202, 2003
0
Convenient Synthesis of 8-Amino-2 -deoxyadenosine
1
Miriam Frieden, Anna Avi n˜ o´ , and Ramon Eritja
,2
1
1,*
1
Instituto de Biolog ´ı a Molecular de Barcelona,
C.S.I.C. Jordi Girona, Barcelona, Spain
2
Cureon A=S, Copenhagen, Denmark
ABSTRACT
0
0
We studied the behaviour of 8-azido-2 -deoxyadenosine and 8-bromo-2 -deoxy-
adenosine in aqueous solutions of ammonia and primary and secondary amines.
0
0
Unexpectedly, 8-Azido-2 -deoxyadenosine is converted to 8-amino-2 -deoxy-
adenosine in excellent yields. The use of this reaction for the preparation of
8-aminoadenine derivatives needed for the preparation of oligonucleotides
carrying 8-aminoadenine is discussed.
0
0
Key Words: 8-amino-2 -deoxyadenosine; Oligonucleotides; 8-azido-2 -deoxy-
adenosine; 8-aminopurine.
INTRODUCTION
Purine nucleosides carrying azido groups at the nucleobase are important inter-
mediates for the preparation of photoreactive nucleotides used in the study of
[
1]
protein-nucleic acid interactions. Moreover, they are useful intermediates in the
synthesis of modified nucleosides such as purine nucleosides carrying amino
[2,3]
groups.
For this purpose, a nucleoside carrying a halogen (Cl or Br) is treated with
*
Correspondence: Ramon Eritja, Instituto de Biolog ´ı a Molecular de Barcelona, C.S.I.C. Jordi
Girona 18-26, E-08034 Barcelona, Spain; Fax: 34-93-2045904; E-mail: recgma@cid.csic.es.
1
93
DOI: 10.1081/NCN-120019521
Copyright # 2003 by Marcel Dekker, Inc.
1525-7770 (Print); 1532-2335 (Online)
www.dekker.com

194
Frieden, Avi n˜ o´ , and Eritja
0
Scheme 1. Synthesis of the 8-substituted 2 -deoxyadenosine derivatives.
sodium or lithium azide yielding the azidopurine, which is reduced by catalytic
[2,4]
[3]
hydrogenation or reducing metals.
[5–8]
form very stable triple helices
Oligonucleotides carrying 8-aminoadenine
[8,9]
and parallel-stranded structures.
The introduc-
tion of the amino group at position 8 increases the stability of Hoogsteen structures
owing to the combined effect of the gain of one Hoogsteen purine-pyrimidine H-bond
and the tendency of the amino group to be integrated into the ‘spine of hydration’
[
6]
0
located in the minor-major groove of the triplex structure. 8-Amino-2 -deoxy-
adenosine (3) was prepared using the following three-step protocol: bromination of
dA, nucleophilic displacement to form the 8-azidonucleoside (2) and catalytic hydro-
0
[3]
genation of 8-azido-2 -deoxyadenosine (2) (Sch. 1).
0
Moreover, 8-azido-2 -deoxyadenosine (2) has been incorporated into oligo-
0
[10,11]
nucleotides.
8-Azido-2 -deoxyadenosine (2) is partially decomposed during the
ammonia treatment used for the removal of protecting groups of oligonucleotides
ꢀ
(
conc. NH , room temperature and 55 C). F a` brega et al. described the formation
[10]
of one single side product, 8-amino-2 -deoxyadenosine (3) and Liu et al. reported
two possible side compounds: 8-amino-2 -deoxyadenosine (3) and 8-oxo-2 -deoxy-
3
0
0
0
[11]
adenosine (4). These two products are also formed during the ammonia treatment
[12]
0
of oligonucleotides carrying 8-bromo-2 -deoxyadenosine.
0
We analysed the behaviour of 8-azido-2 deoxyadenosine (2) in ammonia solu-
tions and in solutions of primary and secondary amines. We confirmed that only
0
8
-amino-2 -deoxyadenosine (3) is formed and that the reaction of compound 2 with
0
volatile primary amines is useful for the preparation of 8-amino-2 -deoxyadenosine
without hydrogenation.
RESULTS AND DISCUSSION
0
-Bromo-2 -deoxyadenosine (1, Sch. 1) was prepared by bromination of dA
[13]
8
73% yield). Reaction of 1 with sodium azide
[
3,14]
0
(
gave 8-azido-2 -deoxyadenosine

0
8
-Amino-2 -deoxyadenosine
195
[
2) in 75% yield. Hydrogenation of compound 2 using Pd= activated charcoal as
3]
(
the catalyst gave 8-amino-2 -deoxyadenosine (3) in 90% yield. Finally, starting from
0
0
[13]
compound 1, 8-oxo-2 -deoxyadenosine (4) was prepared as described elsewhere.
Reverse-phase HPLC using a diode-array detector allowed the separation and rapid
identification of compounds 1–4. The elution order from more polar to less polar
was as follows: 8-amino-dA (3), 8-oxo-dA (4), 8-azido-dA (2) and 8-bromo-dA (1).
Aliquots of 8-azido-dA (2) and 8-bromo-dA (1) were treated with 3 mL of 30%
ꢀ
aqueous ammonia and 5M methanolic ammonia at 55 C. The reaction of 8-azido-
dA (2) with aqueous ammonia gave only 8-amino-dA (3). A 45% conversion was
observed after 20 h, 62% after 3 days and 90% after 6 days (Table 1). The product
1
13
was isolated and characterized by H and C-NMR. Compound 2 decomposed
slowly in methanolic ammonia (< 50% after 6 days, Table 1). On the other hand,
treatment of 8-bromo-dA (1) with 30% aqueous ammonia and 5M methanolic
ꢀ
ammonia at 55 C gave small amounts of a mixture of 8-amino-dA (3) and 8-oxo-
ꢀ
dA (4) (20% decomposition with aqueous ammonia after 16 h at 55 C, Table 1).
These results were in agreement with the behaviour of compounds 1 and 2 in
[10–12]
oligonucleotides,
except that 8-oxo-dA (4) was not formed in the treatment
of compound 2 with aqueous ammonia. Unexpectedly, the formation of 8-amino-
dA (3) from compound 2 was clean and faster than the formation of compound 3
from compound 1. To gain more information on this reaction, compound 2 was also
treated with an aqueous solution of several amines.
Aliquots of 8-azido-dA (2) were treated with solutions of amines (Sch. 2) at
5 C. The reaction of 8-azido-dA (2) with 40% aqueous methylamine gave complete
ꢀ
5
conversion to 8-amino-dA (3) in less than 5 h. Reaction with a 30% aqueous solution
of dimethylamine gave 70% conversion to 8-amino-dA (3) after 16 h. Treatment of
Table 1. Composition of the reaction mixtures obtained after the treatment of compounds 1
ꢀ
and 2 with amine solutions at 55 C.
Composition of the reaction mixture (%)
Compound
Treatment
30% aq.NH3
Time
16 h
2
3
1
4
5
2
55
45
62
90
4
–
–
–
–
–
–
–
–
–
3
6
days 38
days 10
2
5M NH
3
=MeOH
16 h
96
–
–
–
3
6
5 h
16 h
5 h
16 h
16 h
days 65
days 53
35
47
7
–
–
80
80
–
–
–
–
0
–
–
13
7
–
–
–
–
20
–
–
–
–
–
–
–
–
80
1
1
2
2
2
2
1
30% aqNH
5M NH =MeOH
3
–
–
0
30
0
0
#
#
#
9
3
40% aqCH NH
30% aq dimethylamine
1M aq piperidine
3
2
100
70
100
100
–
1M aq hexane-1,6-diamine 5 h
1M aq hexane-1,6-diamine 16 h
–
#
In addition 4% of a product eluting at 9.8 min (UV max 260 nm) was observed. Most prob-
0
ably the product was 8-methoxy-2 -deoxyadenosine.

196
Frieden, Avi n˜ o´ , and Eritja
0
Scheme 2. Treatment of 8-azido-2 -deoxyadenosine with amines.
compound 2 with 1M aqueous solutions of piperidine and hexane-1,6-diamine gave
ꢀ
8-amino-dA (3) after 16 and 5 h at 55 C , respectively. The identity of the product
was confirmed by HPLC analysis and by isolation of the products resulting from
1
the reactions and analysis of their H and C-NMR spectra.
13
On the other hand, treatment of 8-bromo-dA (1) with 1M aqueous hexane-1,6-
diamine gave the expected mixture of the products resulting from the attack of both
nucleophiles present in the mixture: 8-oxo-dA (4) and 8-(6-aminohexyl) amino-dA
(5) (Sch. 3), in agreement with the results obtained during the preparation of 8-N-
aminosubstituted dA derivatives.
[
3,15]
These data reveal a distinct behaviour of compounds 1 and 2 towards aqueous
amine solutions. The bromo derivative suffers a nucleophilic displacement by the
amine and water, while the azido derivative is converted to the amino derivative
(3) regardless of the amine present in the reaction and without interference with
water. The reaction in the presence of primary amines is faster than in the presence
of secondary amines, which is faster than in the presence of ammonia. This suggests
0
Scheme 3. Products obtained from the treatment of 8-bromo-2 -deoxyadenosine with
hexane-1,6-diamine.

0
8
-Amino-2 -deoxyadenosine
197
Scheme 4. Products obtained from the treatment of the ribonucleosides carrying azido
groups with methylamine.
the involvement of the amine in the thermal decomposition of the azido group to the
nitrene intermediate, which later abstracts hydrogen from the environment to give the
[
16]
8
-aminopurine.
nucleosides carrying azido groups. As expected the treatment of ribonucleoside-
-azidoadenosine (6) with 40% aqueous methylamine gave 8-aminoadenosine (7)
Sch. 4). However, treatment of 6-azido-2-aminopurine riboside (8) and 6-azidopur-
The scope of this reaction was assayed with several purine ribo-
8
(
ine riboside (10) resulted in the addition of methylamine at position 6 of the purine
with the subsequent displacement of the azido group (compounds 9 and 11) together
with some decomposition products. In these cases, the azido group is in the tetrazolo
ꢁ
1
tautomeric form (absence of an IR band in the region of 2000–2200 cm and pre-
ꢁ
1
sence of an intense band in the 1700–1500 cm region)
[17,18]
and a nitrene is not
formed. The reaction observed with compound 2 is only possible when the azido
group is at position 8.
Finally, we tested the reaction of compound 2 with amines for preparative
purposes. We selected the inexpensive 40% aqueous methylamine solution because
the formation of the desired compound 3 was very fast, and the amine was volatile.
Several reactions on a 1–5 gram scale gave the desired compound in quantitative
yields. The product resulting from the evaporation of methylamine was pure enough

198
Frieden, Avi n˜ o´ , and Eritja
[
19,20]
to perform the protection of the amino groups with the dimethylformamidine
0
groups needed for the preparation of oligonucleotides carrying 8-amino-2 -deoxy-
adenosine. The DMT-protected phosphoramidite derivative as well as oligonucleo-
tides carrying 8-amino-2 -deoxyadenosine were prepared as described elsewhere.
0
[5,6]
EXPERIMENTAL SECTION
General Methods
Solvents, including those of HPLC grade, were from SDS and E. Merck.
Reagents were from Aldrich and Fluka and were used without further purification.
Analytical TLC was run on aluminium sheets coated with silica gel 60 F254 from
Merck. Silica gel column chromatography was performed with Chromatogel 60 A
0
[13]
C.C. (40–60 microns, 230–400 mesh, SDS). 8-Bromo-2 -deoxyadenosine (1),
0
[3,14]
0
[3]
8
2
6
-azido-2 -deoxyadenosine (2),
-deoxyadenosine (4)
8-amino-2 -deoxyadenosine (3) and 8-oxo-
were prepared as described. 8-Bromoadenosine, 2-amino-
-chloro-9-b-D-ribofuranosylpurine, and 6-chloro-9-b-D-ribofuranosylpurine were
obtained from Pharma-Waldhof GmbH (D u¨ sseldorf, Germany). N -methyladeno-
sine (11) was purchased from Sigma.
0
[13]
6
Instrumental
1
13
H-NMR (250 MHz) and C-NMR (63 MHz) spectra were recorded on a
Br u¨ ker AM-250. HPLC chromatography was performed on an HPLC Shimadzu
equipped with a diode array detector.
0
0
Treatment of 8-Azido-2 -deoxyadenosine and 8-Bromo-2 -deoxyadenosine with
0
Ammonia and Amine Aqueous Solutions. To 50 mg aliquots of 8-azido-2 -deoxy-
0
adenosine or 8-bromo-2 -deoxyadenosine in screw-cap tubes was added 3 mL of the
ꢀ
appropriate ammonia or amine solutions. The mixtures were heated to 55 C for a
period of time between 5 h and 6 days, allowed to cool to room temperature and eva-
porated to dryness. The residues were analysed by HPLC. HPLC conditions were as
follows: Solution A, 0.1 M aqueous triethylammonium acetate pH 6.5=acetonitrile
(
(
2
7
1
8
95 : 5); solution B, 0.1 M aqueous triethylammonium acetate pH 6.5=acetonitrile
3 : 7); Column PRP-1 (Hamilton, 10 mm) 250 ꢂ 10 mm; flow rate, 3 mL=min;
0 min linear gradient from 0% B to 50% B. Retention time for 8-amino-dA:
.4 min; for 8-oxo-dA: 8.1 min; for 8-azido-dA: 11.3 min and for 8-bromo-dA:
1.4 min. UV maximum for 8-amino-dA: 276 nm; for 8-oxo-dA 272 nm; for
-azido-dA 284 nm and for 8-bromo-dA 267 nm. Reaction products were also iden-
1
3
tified by comparison of the chemical shift of C-8 in C-NMR spectra with published
spectra.
[10,13]
[
14]
8
-Azidoadenosine (6). Compound 6 was prepared as described in Ref.
minor modifications. 8-Bromoadenosine (250 mg, 0.72 mmol) was treated with
48 mg (2.17 mmol) of sodium azide in 5 mL of dimethylformamide (DMF) at
with
1

0
8
-Amino-2 -deoxyadenosine
199
ꢀ
60 C for 16 h. The solution was cooled and evaporated to dryness. The resulting
product was crystallized from water-methanol giving 130 mg (59% yield) of a white
ꢁ
1
solid. UV (max, pH 6.5) 284 nm. IR (KBr, cm ): intense bands at 2154 and 2043.
1
H-NMR (DMSO-d ): 8.05 (s, 1H, H-2), 7.31 (br s, 2H, amino), 5.60 (d, 1H,
6
0
0
OH), 5.38 (m, 2H, OH and H-1 ), 5.15 (d, 1H, OH), 4.84 (m, 1H, H-2 ), 4.18 (m,
1
0 0 0
H, H-3 ), 3.9 (m, 1H, H-4 ), 3.58 (m, 2H, H-5 ). C-NMR (DMSO-d ): 154.7
6
13
0
0
(
C-6), 156.8 (C-2), 149.6 (C-4), 144.6 (C-8), 117.5 (C-5), 87.8 (C-1 ), 86.5 (C-4 ),
0
0
0
7
3
1.5 (C-3 ), 71.0 (C-2 ), 62.3 (C-5 ). MS (electrospray) calculated for C H N O
12
1
0
8
4
þ
08.3. Found: 309.8 (M þ H ).
6-Azido-2-amino-9-b-D-ribofuranosylpurine (8). 6-Chloro-2-amino-9-b-D-ribo-
furanosylpurine (300 mg, 1 mmol) was treated with 211 mg (3 mmol) of sodium azide
ꢀ
in 7 mL of DMF at 60 C for 16 h. The solution was cooled and evaporated to dry-
ness. The resulting product was crystallized from water-methanol giving 200 mg
ꢁ
1
65% yield) of a white solid. UV (max, pH 6.5) 270, 300 nm. IR (KBr, cm ): absence
(
of bands in the region 2200–2000, intense band at 1694. H-NMR (DMSO-d ): 8.4
1
6
0
(
(
m, 3H, H-8 and amino), 5.91 (d, 1H, H-1 ), 5.45 (d, 1H, OH), 5.20 (d, 1H, OH), 5.02
0
0
0
t, 1H, OH), 4.5 (m, 1H, H-2 ), 4.18 (m, 1H, H-3 ), 3.9 (m, 1H, H-4 ), 3.6 (m, 2H,
13
H-5 ). C-NMR (DMSO-d ): 146.3 (C-6), 145.1 (C-2), 144.1 (C-4), 138.5 (C-8),
6
0
0
0
0
0
0
1
12.4 (C-5), 87.3 (C-1 ), 85.7 (C-4 ), 74.3 (C-3 ), 70.2 (C-2 ), 61.4 (C-5 ). MS (electro-
þ
spray) calculated for C H N O 308.3. Found: 309.0 (M þ H ).
1
0
12
8
4
6-Azido-9-b-D-ribofuranosylpurine (10). 6-Chloro-9-b-D-ribofuranosylpurine
(
500 mg, 1.75 mmol) was treated with 357 mg (5.2 mmol) of sodium azide in 10 mL
ꢀ
of DMF at 60 C for 16 h. The solution was cooled and concentrated to dryness.
The resulting product was crystallized from water-methanol giving 110 mg (21%
ꢁ
1
yield) of a white solid. UV (max, pH 6.5) 290 nm. IR (KBr, cm ): absence of bands
1
in the region 2200–2000, intense band at 1645. H-NMR (DMSO-d ): 10.1 (s 1H),
6
0
8.9 (s, 1H), 6.11 (d, 1H, H-1 ), 5.62 (d, 1H, OH), 5.29 (d, 1H, OH), 5.1 (t, 1H,
OH), 4.53 (m, 1H, H-2 ), 4.15 (m, 1H, H-3 ), 3.98 (m, 1H, H-4 ), 3.64 (m, 2H,
13
H-5 ). C-NMR (DMSO-d ): 145.6 (C-6), 142.8 (C-2), 142.1 (C-4), 136.3 (C-8),
0
0
0
0
6
0
0
0
0
0
1
21 (C-5), 88.5 (C-1 ), 85.9 (C-4 ), 74.8 (C-3 ), 70.2 (C-2 ), 61.1 (C-5 ). MS (electro-
þ
spray) calculated for C H N O 293.2. Found: 293.9 (M þ H ).
1
0
11
7
4
Treatment of Ribonucleosides Carrying Azido Groups with Methylamine. To
0 mg aliquots of azido-ribonucleosides (6, 8, 10) in screw-cap tubes was added
mL of 40% aqueous methylamine. The mixtures were heated to 60 C for a period
5
3
ꢀ
of time between 16 and 48 h, allowed to cool to room temperature and evaporated to
dryness. The residues were analysed by HPLC as described above. Retention time
(UV maxima) for compound 6: 9.6 min (284 nm); for compound 7: 6.4 min
(272 nm); for compound 8: 7.5 min (270, 300 nm); for compound 9: 2.7 min
(242 nm); for compound 10: 8.2 min (290 nm) and for compound 11: 3.8 min
(250 nm).
The reaction with compound 6 was completed after 16 h, giving one single pro-
1
duct that was characterized as 8-aminoadenosine (7) . H-NMR (DMSO-d ): 7.89
4 1
6
0
0
(
(
s, 1H, H-2), 6.54 (m, 2H, amino), 5.82 (d, 1H, H-1 ), 4.64 (m, 1H, H-2 ), 4.12
0
0
0
13
m, 1H, H-3 ), 3.9 (m, 1H, H-4 ), 3.58 (m, 2H, H-5 ). C-NMR (DMSO-d ): 152.6
6

200
Frieden, Avi n˜ o´ , and Eritja
0
0
(
(
C-6), 151.8 (C-2), 149.5 (C-4), 148.5 (C-8), 117.4 (C-5), 86.8 (C-1 ), 86.0 (C-4 ), 71.1
0
0
0
C-3 and C-2 ), 62.0 (C-5 ). MS (electrospray) calculated for C H N O 282.2.
1
0
14
6
4
þ
Found: 283.4 (M þ H ).
The reaction with compound 8 was completed after 48 h, giving one major pro-
[21]
6
duct that was characterized as 2-amino-N -methyladenosine (9)
together with
some minor products that were not characterized. H-NMR (DMSO-d ): 7.9
1
6
0
0
0
(
(
(
7
s, 1H, H-8), 5.49 (d, 1H, H-1 ), 4.32 (m, 1H, H-2 ), 4.12 (m, 1H, H-3 ), 3.86
0 0
m, 1H, H-4 ), 3.58 (m, 2H, H-5 ), 2.7 (s, 3H, CH ). C-NMR (DMSO-d ): 156.5
3 6
13
0
0
C-6), 155.6 (C-2), 150.7 (C-4), 133.7 (C-8), 112.7 (C-5), 87.6 (C-1 ), 84.4 (C-4 ),
0
0
0
4.6 (C-3 ), 69.6 (C-2 ), 60.6 (C-5 ), 27.9 (CH ). MS (electrospray) calculated for
3
þ
C H N O 296.3. Found: 297.5 (M þ H ).
1
1
16
6
4
The reaction with compound 10 was completed after 16 h, giving several pro-
6
ducts. One of the products was characterized as N -methyladenosine (11) by com-
parison with the commercially available product and mass spectrometry. MS
þ
(
electrospray) calculated for C H N O 281.2. Found 284.5 (M þ H ).
1
1
15
5
4
0
Synthesis of 8-Amino-N,N-bis(dimethylaminomethylidene)-2 -deoxyadenosine.
[3,14]
0
In a screw-cap tube, 4.62 g of 8-azido-2 -deoxyadenosine
2
was dissolved in
0 mL of 40% aqueous methylamine solution and 2 mL of dioxane. The solution
was heated overnight to 55 C. It was then cooled to room temperature and evapo-
rated to dryness, yielding an oil that was used in the following step without purifica-
tion. Purity assessed by HPLC (< 95%).
ꢀ
The product described above (approx. 17.5 mmol) was dissolved in 250 mL of
DMF and treated with 12.1 mL of DMF dimethyl acetal. The solution was stirred
overnight at room temperature and then evaporated to dryness. The resulting pro-
duct was purified by silica gel chromatography (0–20% methanol in dichloro-
methane), yielding 5.4 g of the desired compound (82% yield). Physical and
[
5,6]
spectral data were as described elsewhere.
ACKNOWLEDGMENTS
We thank the Direcci o´ n General de Investigaci o´ n Cient ´ı fica y T e´ cnica (grants
BQU2000-0649 and CAL01-058-C2-2), the Generalitat de Catalunya (2000-SGR-
0
018 and 2001-SGR-0049), and Cygene Inc. for financial support.
REFERENCES
1.
2.
3.
Sylvers, L.A.; Wower, J. Nucleic acid-incorporated azidonucleotides: probes
for studying the interaction of RNA or DNA with proteins and other nucleic
acids. Bioconjugate Chem. 1993, 4, 411–418.
Sproat, B.S.; Iribaren, A.M.; G u¨ imil Garc ´ı a, R.; Beijer, B. New synthetic
0
routes to synthons suitable for 2 -O-allyloligoribonucleotide assembly. Nucleic
Acids Res. 1991, 19, 733–738.
Long, R.A.; Robins, R.K.; Townsed, L.B. Purine nucleosides. XV. The synth-
esis of 8-amino- and 8-substituted aminopurine nucleosides. J. Org. Chem.
1967, 32, 2751–2756.

0
8
-Amino-2 -deoxyadenosine
201
4
.
.
Bartra, M.; Urp ´ı , F.; Vilarrasa, J. New synthetic tricks. Two useful reagents for
the reduction of azides to amines. Tetrahedron Lett. 1987, 28, 5941–5944.
Kawai, K.; Saito, I.; Sugiyama, H. Stabilization of Hoogsteen base pairing by
introduction of amino group at the C8 position of adenine. Tetrahedron Lett.
5
1998, 39, 5221–5224.
6
.
.
G u¨ imil Garc ´ı a, R.; Ferrer, E.; Macias, M.J.; Eritja, R.; Orozco, M. Theoretical
calculations, synthesis and base-pairing properties of oligonucleotides contain-
ing 8-amino-2 -deoxyadenosine. Nucleic Acids Res. 1999, 27, 1991–1998.
Avi n˜ o´ , A.; Frieden, M.; Morales, J.C.; de la Torre, B.G.; G u¨ imil Garc ´ı a, R.;
Azor ´ı n, F.; Gelp ´ı , J.L.; Orozco, M.; Gonz a´ lez, C.; Eritja, R. Properties of triple
helices formed by parallel-stranded hairpins containing 8-aminopurines.
Nucleic Acids Res. 2002, 30, 2609–2619.
0
7
8
.
.
Avi n˜ o´ , A.; Morales, J.C.; Frieden, M.; de la Torre, B.G.; G u¨ imil Garc ´ı a, R.;
Cubero, E.; Luque, F.J.; Orozco, M.; Azor ´ı n, F.; Eritja, R. Parallel-stranded
hairpins containing 8-aminopurines. Novel efficient probes for triple-helix for-
mation. Bioorg. Med. Chem. Lett. 2001, 11, 1761–1763.
Cubero, E.; Avi n˜ o´ , A.; de la Torre, B.G.; Frieden, M.; Eritja, R.; Luque, F.J.;
Gonzalez, C.; Orozco, M. Hoogsteen-based parallel-stranded duplexes of
DNA. The effect of 8-aminoderivatives. J. Am. Chem. Soc. 2002, 124, 3133–
9
3142.
1
1
1
1
0. F a` brega, C.; G u¨ imil Garc ´ı a, R.; D ´ı az, A.R.; Eritja, R. Studies on the synthesis
0
of oligonucleotides containing photoreactive nucleosides: 2-azido-2 -deoxyino-
0
sine and 8-azido-2 -deoxyadenosine. Biol. Chem. 1998, 379, 527–533.
1. Liu, J.; Fan, Q.R.; Sodeoka, M.; Lane, W.S.; Verdine, G.L. DNA bending by
an amino acid residue in the C-terminal half of the ReI homology region.
Chem. Biol. 1994, 1, 47–55.
2. Liu, J.; Verdine, G.L. Synthesis of photoactive DNA: incorporation of 8-
0
bromo-2 -deoxyadenosine into synthetic oligodeoxynucleotides. Tetrahedron
Lett. 1992, 33, 4265–4268.
3. Wood, M.L.; Esteve, A.; Morningstar, M.L.; Kuziemko, G.M.; Essigmann,
J.M. Genetic effects of oxidative DNA damage: comparative mutagenesis of
7,8-dihydro-8-oxoguanine and 7,8-dihydro-8-oxoadenine in Escherichia coli.
Nucleic Acids Res. 1992, 20, 6023–6032.
1
4. Holmes, R.E.; Robins, R.K. Purine nucleosides. IX. The synthesis of 9-b-D-
ribofuranosyl uric acid and other related 8-substituted purine ribonucleosides.
J. Am. Chem. Soc. 1965, 87, 1772–1776.
0
1
1
1
5. Sarfati, S.R.; Naname, A. Synthesis of fluoresceinylated 2 -deoxyadenosine.
Mono, di and triphosphate derivatives. Tetrahedron Lett. 1990, 31, 2581–2584.
6. Sheradsky, T. Azides as synthetic starting materials. In The Chemistry of the
Azido Group; Patai, S., Ed.; Interscience Publishers: London, 1971, 339–340.
7. Johnson, J.A.; Thomas, H.J.; Schaeffer, H.J. Synthesis of potential anticancer
agents. XIII. Ribosides of 6-substituted purines. J. Am. Chem. Soc. 1958, 80
699–702.
1
8. Math e´ , C.; Lioux, T.; Gosselin, G. Synthesis and biological evaluation of (b-D-
pentofuranonucleoside derivatives of 2-azidoadenine. Abstracts of papers. 15th
International Round Table on Nucleosides, Nucleotides and Nucleic Acids,
Leuven, Belgium, Sept. 10–14, 2002.

202
Frieden, Avi n˜ o´ , and Eritja
1
2
2
9. MacBride, L.J.; Kierzek, R.; Beaucage, S.L.; Caruthers, M.H. Amidine pro-
tecting groups for oligonucleotide synthesis. J. Am. Chem. Soc. 1986, 108,
040–2048.
0. Vu, H.; Mc Collum, A.; Jacobson, K.; Thiesen, P. Fast oligonucleotide depro-
tection phosphoramidite chemistry for DNA synthesis. Tetrahedron Lett. 1990,
2
31, 7269–7272.
1. Saladino, R.; Mincione, E.; Crestini, C.; Mezzetti, M. Transformations of thio-
pyrimidine and thiopurine nucleosides following oxidation with dimethyldi-
oxirane. Tetrahedron 1996, 52, 6759–6780.
Received October 8, 2002
Accepted December 23, 2002