A new short and efficient synthetic route to C8-N-acetylarylamine 2′-deoxyguanosine phosphoramidites

Article abstract of DOI:10.1055/s-2007-990913

In addition to their C8-NH-arylamine-dG counterparts, C8-N-acetylarylamine adducts of 2′-deoxyguanosine (2′-dG) play an important role in the possible induction of chemical carcinogenesis. A new synthetic pathway of this adduct type using different aromatic amines has been developed following most probably an electrophilic amination reaction. These adducts can be converted into the corresponding phosphoramidites for incorporation into oligonucleotides. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-990913

FEATURE ARTICLE
3907
A New Short and Efficient Synthetic Route to C8-N-Acetylarylamine
2¢-Deoxyguanosine Phosphoramidites
S
ynthesis of dG–A
i
rylami
c
ne
A
dductsolas Böge, Sarah Krüger, Marcus Schröder, Chris Meier*
Institute of Organic Chemistry, Department of Chemistry, Faculty of Science, University of Hamburg,
Martin-Luther-King Platz 6, 20146 Hamburg, Germany
Fax +49(40)428382495; E-mail: chris.meier@chemie.uni-hamburg.de
Received 22 October 2007; revised 5 November 2007
sponding derivatives of 4-aminobiphenyl 1b and 2b
(Figure 1). Although 9H-fluoren-2-amine (2-AF) 2a and
N-acetyl-9H-fluoren-2-amine (2-AAF) 1a differ only by
one acetyl group, they have very different physicochemi-
Abstract: In addition to their C8-NH-arylamine-dG counterparts,
C8-N-acetylarylamine adducts of 2¢-deoxyguanosine (2¢-dG) play
an important role in the possible induction of chemical carcinogen-
esis. A new synthetic pathway of this adduct type using different ar-
omatic amines has been developed following most probably an cal properties and biological effects. The acetylated form
electrophilic amination reaction. These adducts can be converted
into the corresponding phosphoramidites for incorporation into oli-
gonucleotides.
1a causes a much more severe local distortion within the
DNA double helix than the nonacetylated form 2a.9,10
Also the 2-AAF adduct 1a is a more potent blocker of rep-
Key words: arylamines, DNA damage, electrophilic addition, C8-
N-Ac-dG adducts
lication and transcription; however, it is also a better sub-
strate for DNA-repair enzymes.11,12
Due to the importance of these two C8-dG adducts, an
easy and straightforward synthesis of the corresponding
phosphoramidites would be of great interest as these ad-
ducts could be incorporated site-specifically into DNA us-
ing standard automated solid-phase synthesis.
Introduction
Exposure to chemical carcinogens can occur from envi-
ronmental or work conditions, diet, smoking, and endog-
enous processes. Poly- and monocyclic aromatic amines
belong to the class of chemical carcinogens that form co-
valently bonded adducts with DNA. Covalent alteration of
DNA (by electrophiles) may be the reason for the induc-
tion of chemical carcinogenesis.1 If these covalently
bonded modifications are not repaired,2 they may compro-
mise the fidelity of DNA replication, leading to mutations
and possibly cancer.3,4 Prior to adduct formation, the aro-
matic amines undergo a metabolic activation that runs in
parallel to the detoxification process. Ring oxidation and
N-acetylation normally leads to detoxification. However,
N-oxidation catalyzed by the monooxygenase cytochrome
P450 leads to the formation of N-arylhydroxylamines. If
these are esterified e.g. by acetyl-CoA to yield N-acet-
oxyarylamines, highly electrophilic reagents are formed
that react with bionucleophiles, e.g. with the DNA base
guanine.5 Thus, the latter metabolite can act as a so-called
O
O
N
N
N
N
Ar
H
Ar
NH
NH
N
N
O
N
NH2
N
NH2
HO
HO
O
O
OH
OH
1
2
a: Ar =
b: Ar =
Figure 1 C8-Arylamine adducts of 2¢-deoxyguanosine formed by
metabolites of the strong carcinogens 9H-fluoren-2-amine [C8-(2-
AAF)dG, 1a; C8-(2-AF)dG, 2a] and 4-aminobiphenyl [C8-(4-
ultimate carcinogen.6 Additionally, N-arylamides follow AAB)dG, 1b; C8-(4-AB)dG, 2b]
this pathway and initially N-arylhydroxamic acids are
formed that are transformed into N-acetoxy-N-acetylaryl-
Results and Discussion
amines, which then react with guanine in an electrophilic
amination reaction. Several covalent adducts have been
identified in vivo.7
Our interest is related to DNA lesions caused by mono-
cyclic aromatic amines that act as so-called borderline
carcinogens like toluidine and anisidine.13,14 In contrast to
polycyclic N-arylamines, these are often used, for exam-
ple, in pharmacophores or in dyes. In contrast, for exam-
ple, to the strong liver carcinogens 2-AF and 2-AAF, their
biological effects are only sparsely understood. Most im-
portantly, it is not understood why these lesions of mono-
cyclic aromatics do not lead to the same biological
So far, the most extensively studied arylamine adducts are
derived from N-acetyl-9H-fluoren-2-amine (2-AAF) 1a
and 9H-fluoren-2-amine (2-AF) 2a,8 as well as the corre-
SYNTHESIS 2007, No. 24, pp 3907–3914
x
x.
x
x
.
2
0
0
7
Advanced online publication: 28.11.2007
DOI: 10.1055/s-2007-990913; Art ID: E19807SS
© Georg Thieme Verlag Stuttgart · New York

3908
N. Böge et al.
FEATURE ARTICLE
consequences as the strong carcinogens, although they 2¢-deoxyadenosine. In 2002 we published the first synthe-
form the same type of adducts in the same amounts in bio- sis of C8-arylamine–dG adducts 5 using a palladium
mimetic studies.15
cross-coupling reaction of the protected 8-bromo-dG de-
rivative 4, its conversion into the corresponding phos-
phoramidites 7 via intermediates 6, and the site-specific
In our earlier work we focussed on the synthesis of the C8-
NH-arylamine adducts of 2¢-deoxyguanosine (2¢-dG) and
Biographical Sketches
Nicolas Böge was born in group as a Ph.D. student in participation at the Round-
Hamburg, Germany in 2005. In the same year he table on Nucleosides, Nu-
1981. He studied chemistry was invited to the Criegee- cleotides, & Nucleic Acids
at the University of Ham- Gedenkveranstaltung
in in Bern, Switzerland. At
burg, Germany and received Karlsruhe, Germany. In present he is working on
his diploma under the guid- 2006 he received a fellow- arylamine-modified oligo-
ance of Prof. Chris Meier ship from the Gesellschaft nucleotides.
and joined the research Deutscher Chemiker for the
Sarah Krüger was born in University of Hamburg, search group of Prof. Chris
Zeven, Germany in 1983. Germany and joined the re- Meier in 2007.
She studied chemistry at the
Marcus Schröder was born University of Hamburg, ported by the Erasmus
in Hamburg, Germany in Germany. In 2006 he spent programme.
1982. Since 2003, he has three months at the Univer-
studied chemistry at the sity of Oslo, Norway, sup-
Chris Meier was born in 1991 he returned to the Uni- for Antiviral Research. In
1962 in Berlin, Germany. versity of Frankfurt/Main 2005 he became Head of
He studied Chemistry at the and finished his habilitation Department of the Chemis-
University of Marburg/ in 1996. In 1994 he received try Department of the Uni-
Lahn, where he received his the Adolf Messer Award for versity of Hamburg. His
diploma in 1987 and his interdisciplinary research. research interests: DNA
Ph.D. in 1989 with Profes- In 1997 he became Associ- damage induced by aryl-
sor G. Boche. During that ate Professor of Organic amine carcinogens, pronu-
time he became interested in Chemistry at the University cleotide design for antiviral
bioorganic chemistry. Dur- of Würzburg and 1999 he nucleoside analogues, ste-
ing his postdoctoral studies moved to the University of reoselective synthesis of
at the Pasteur Institute in Hamburg as a Full Professor carbocyclic nucleoside ana-
Paris, France he became in- of Organic Chemistry. In logues, and the develop-
volved in the chemistry of 2007 he received the Will- ment of new synthesis
nucleosides, oligonucleo- iam Prusoff Young Investi- pathways for important
tides, and prodrugs. In gator Award of the Society phosphorylated biomole-
cules.
Synthesis 2007, No. 24, 3907–3914 © Thieme Stuttgart · New York

FEATURE ARTICLE
Synthesis of dG–Arylamine Adducts
3909
incorporation into oligonucleotides.16,17 Recently, we ex- Recently, we performed initial experiments concerning
tended the studies to rarely investigated C8-arylamine-dA the action of such lesions on DNA polymerases. We ob-
adducts that were site-specifically incorporated into oli- served that the interaction with DNA polymerases de-
gonucleotides via automated phosphoramidite chemis- pends very much on the DNA polymerase that is used and
try.18
the chemical structure of the adduct. In contrast to the ex-
pectation, the highest mutation incident was found when
a high-fidelity DNA polymerase promoted nucleotide in-
sertion opposite the lesion of the borderline carcinogen 4-
anisidine instead of a 4-aminobiphenyl lesion.
Since then we have improved the synthesis by introducing
the N2-formamidine, instead of the isobutyryl, group
(Scheme 1).19 Using this mild deprotection strategy the
cleavage was achieved in four hours at 40 °C instead of
eight hours at 55 °C. Thus, the yield of adducted oligonu- In addition to these C8-NH-arylamine adducts 2, their N-
cleotides was four- to fivefold higher than using the isobu- acetylated counterparts 1 were found in in vivo studies
tyryl strategy.
and thus, obviously, may also play an important role in
arylamine-induced carcinogenesis. The acetyl group is
most probably introduced in a very early step of the
biotransformation catalyzed by two N-acetyl transferases
NAT1 or NAT2.20 This acetylation of the arylamine into
an arylamide should promote the detoxification because
the amide is less susceptible to N-oxidation.
With the synthesized modified oligonucleotides (30mer)
we investigated the effect of the modification concerning
the thermal stability (Tm value) and the conformation of
the DNA strand (CD spectra). For oligonucleotides mod-
ified with a strong carcinogen, such as 2-AF, a decrease of
the Tm value was observed, whereas the modification
with borderline carcinogens like aniline had no influence Former synthesis of the C8-N-acetylarylamine adducts of
on the stability as compared to the unmodified strand.18 dG were based on ‘damaging’ nucleosides or oligonucle-
To study the overall conformation of the damaged DNA otides post-synthetically with N-acetoxy-N-acetylaryl-
hybrids, the CD spectra were recorded. The reference oli- amines or N-acetoxyarylamines and subsequent
gonucleotide as well as oligonucleotides bearing the le- acetylation.21 However, this strategy resulted in poor
sions showed the typical spectra of a B-type DNA chemical yields and only damaged oligonucleotides con-
conformation; thus no strong conformational change of taining one guanine base were accessible.22
the C8-NH-arylamine ‘damage’ was induced.
A major aspect for the development of an efficient synthe-
sis is the base lability of the N8-acetyl function. To ensure
OBn
O
N
N
N
N
1) NBS, H2O
2) TBDMSCl, imidazole
pyridine
NH
Br
N
N
NH2
TBDMSO
N
NH2
O
HO
O
3) BnOH, PPh3
DIAD, 1,4-dioxane
4
OTBDMS
3
OH
OBn
1) Pd/C, MeOH
2) Et3N⋅3HF,
N
N
ArNH2, K3PO4,
rac-BINAP, Pd2(dba)3,
DME
Ar
HN
N
Et3N, THF, CH2Cl2
N
NH2
TBDMSO
O
3) (EtO)2CHNMe2, pyridine
62–64%
70–72 h, 80 °C
62–65%
OTBDMS
5a,b
a: Ar = 4-methoxyphenyl
b: Ar = 4-biphenyl
O
O
N
N
Ar
NH
N
N
Ar
HN
N
NH
H
1) DMTrCl, pyridine
N
N
NMe2
DMTrO
O
N
N
NMe2
HO
O
7a,b
2) [NC(CH2)2O]P[N(i-Pr)2]2
DCI, CH2Cl2, MeCN
O
OH
P
CN
58–61%
6a,b
(i-Pr)2N
O
Scheme 1 Improved synthesis of the C8-arylamine adducts of dG and conversion into their phosphoramidites
Synthesis 2007, No. 24, 3907–3914 © Thieme Stuttgart · New York

3910
N. Böge et al.
FEATURE ARTICLE
that the acetyl group of dG-AAF is stable under the con- Buchwald–Hartwig cross-coupling and a complex tran-
ditions for the deprotection step after oligonucleotide syn- sient protecting-group strategy.
thesis, very labile protecting groups are required. The first
The key step of this unprecedented reaction is the reaction
attempts to solve this problem were made by Zhou and
between O6-(1H-benzotriazol-1-yl)-dG 8 and N-arylace-
Romano.22,23 They used the 9-fluorenylmethoxycarbonyl
tohydroxamic acids that led to the C8-N-acetylated ad-
ducts. Due to the mild reaction conditions it is possible to
(Fmoc) protecting-group strategy and mild deprotection
conditions that ensured the stability of AAF-dG. Howev-
introduce a very labile protecting group suitable for auto-
er, a limiting factor of this strategy is that Fmoc-protected
mated DNA synthesis at the N2-position after the adduct
nucleotide phosphoramidites are not commercially avail-
formation.
able.
Thus, after protection of the 5¢- and 3¢-hydroxy groups of
In a further strategy, Schärer and Gillet24 used a transient
dG 3 using tert-butyldimethylsilyl chloride, the benzotri-
4,4¢-dimethoxytrityl (DMTr) protecting group for the N2-
position of an 8-Br-dG derivative. After a palladium-cata-
lyzed cross-coupling reaction of 8-Br-dG with the aryl-
amine, the products were subsequently acetylated at the
N8-position. Finally, in two further steps the N2-DMTr
group was replaced by the N2-isopropylphenoxyacetyl
(i-PrPac) group, which yielded monomers suitable for
DNA synthesis. In 2005 they reported the successful con-
version of these adducts into the corresponding phosphor-
amidite (12 steps overall) and site-specific incorporation
into oligonucleotides. It was proven that the N8-acetyl
group was not cleaved during the final deprotection.25
azole moiety was introduced into the O6-position using
(1H-benzotriazol-1-yloxy)tris(dimethylamino)phospho-
nium hexafluorophosphate (BOP) (Scheme 2).26
The dG derivative 8 was reacted with an N-arylacetohy-
droxyamic acid 10a–c, prepared by reduction of nitroaryl-
amine compounds 9a–c to the corresponding N-aryl-
hydroxylamines and subsequent reaction with acetyl
chloride to give N-arylacetohydroxamic acids 10a–c in
44–65% yield (Scheme 2).27,28
The coupling reaction was performed in 1,2-dimethoxy-
ethane using cesium carbonate as base and the C8-N-
acetylaryl adducts 11a–c were isolated in 67–89% yield;
the formation of 11 in this way is previously unknown.
The reaction mechanism for the formation of the C8 ad-
duct remains unclear, but it is assumed that the N-aryl-
acetohydroxamic acid reacts with 8 in a nucleophilic
Despite these advances, an efficient method and short
synthetic route for the synthesis of N8-acetylarylamine ad-
ducts of dG is still needed. Here, we disclose our approach
for a new synthesis of this adduct type without using the
dG
ArNO2
3
9a–c
1) Raney nickel,
1) TBDMSCl,
imidazole,
65% (2 steps)
pyridine
N2H4⋅H2O, DCE–EtOH
2) AcCl, NaHCO3, Et2O
2) BOP, DIPEA,
DMF
44–65% (2 steps)
N
O
N
O
N
O
OH
N
N
N
Ar
NH
10a–c Ar
Cs2CO3, DME
N
N
N
N
O
N
NH2
TBDMSO
N
NH2
TBDMSO
O
O
67–89%
OTBDMS
11a–c
OTBDMS
8
a: Ar = Ph
b: Ar = 3,5-Me2C6H3
c: Ar = fluorenyl
O
N
N
N
NH
1) Et3N⋅3HF, Et3N,
CH2Cl2, THF
2) (EtO)2CHNMe2, pyridine
N
O
O
N
NMe2
DMTrO
3) DMTrCl, pyridine
4) [NC(CH2)2O]P[N(i-Pr)2]2,
DCI, CH2Cl2, MeCN
O
P
12a
NC
O
N(i-Pr)2
overall yield = 45%
Scheme 2 Preparation of N-acetylated adducts 11a–c and the C8-[acetyl(phenyl)amino]-2¢-dG phosphoramidite 12a
Synthesis 2007, No. 24, 3907–3914 © Thieme Stuttgart · New York

FEATURE ARTICLE
Synthesis of dG–Arylamine Adducts
3911
displacement at the nitrogen atom with formation of the Due to the facile access to many nitroaryl compounds, this
protected dG and the benzotriazolylated hydroxamic acid. newly developed route for the preparation of 2¢-dG–aryl-
The latter could form an arylnitrenium ion, which under- amine adducts should be useful for the synthesis of vari-
goes electrophilic amination at C8 (presumably at N7 and ous C8-(acetylamino) adducts of mono- and polycyclic
subsequent rearrangement to C8). The prior formation of aromatic amines. Work along these lines is currently on-
the O6-benzotriazolyl derivative 8 is essential; in a sepa- going.
rate experiment the pre-incubation of the N-arylacetohy-
droxamic acids 10a–c with the BOP reagent and
subsequent addition of TBDMS-protected dG did not give
11a–c.
All reactions (except the synthesis of the hydroxylamines and hy-
droxamic acids) were performed in flame-dried glassware under an
N2 atmosphere. Commercial solvents and reagents were used with-
out further purification with the following exceptions: pyridine,
CH2Cl2, MeCN were distilled from CaH2, DME and Et2O were
dried with potassium and distilled under N2. H2O was purified on a
Milli-Q Water System. 1H NMR and 13C NMR spectra were record-
ed on AMX 400 MHz or DMX 500 MHZ Bruker spectrometer.
For the conversion of 11a into the corresponding phos-
phoramidite 12a, the hydroxy groups were first deprotect-
ed (Et3N·3HF, Et3N) to yield the N-acetylated dG adduct;
the sensitive N8-acetyl group was found to be stable under
these conditions. For oligonucleotide synthesis, the N2- NMR spectra were reported relative to the NMR solvent peaks [1H
NMR: d = 2.50 (DMSO-d6) and 7.16 (C6D6); 13C NMR: d = 39.52
(DMSO-d6) and 128.06 (C6D6)]. HRMS analysis were performed
on an analytical VG/70-250 F using FAB or Finnigan MAT 95 XL
Thermo Quest spectrometer using ESI. IR spectra were recorded on
an Avatar 370 FT-IR spectrophotometer using KBr plates. Melting
points were measured on an apotec capillary melting point appara-
position was selectively blocked using the formamidine
group (mild deprotection strategy). The formamidine
group has been used previously29 and we have recently
used this group successfully for C8-NH-arylamine-dG-
oligonucleotides.17 We have shown that this protecting
group can be cleaved from 11a and from oligonucleotides
at 45 °C within only four hours using ammonia solution.
Recently, Schärer et al. reported that the i-PrPac group
can be cleaved from an oligonucleotide using the same
cleavage conditions without losing the N-acetyl group.25
After N2-protection, the 5¢-hydroxy function was blocked
with DMTr and the corresponding phosphoramidite was
synthesized using previously described conditions.16,18
We have shown that these phosphoramidites can be suc-
cessfully incorporated into a 12mer-oligonucleotide by
automated DNA synthesis.
tus. TLC was performed on aluminum sheets coated with silica gel
60 F254 from Merck.
The synthesis of 3¢,5¢-bis-O-(tert-butyldimethylsilyl)-2¢-dG was
performed as previously described.31
O6-(1H-Benzotriazolyl)-3¢,5¢-bis-O-(tert-butyldimethylsilyl)-2¢-
deoxyguanosine (8)
In a dried flask, 3¢,5¢-bis-O-(tert-butyldimethylsilyl)-2¢-deoxygua-
nosine (6.60 g, 13.3 mmol) and BOP (12.12 g, 27.54 mmol) were
diluted in anhyd DMF (120 mL) and DIPEA (4.80 mL, 27.6 mmol)
was added. The mixture was stirred at r.t. for 72 h and then the sol-
vent was removed in vacuo. The residue was diluted with EtOAc,
extracted with H2O, and dried (Na2SO4). The solvent was removed
under reduced pressure. Column chromatography (33% EtOAc–
hexanes) gave the product as a yellow solid; yield: 5.45 g (67%); mp
88–90 °C.
For all N-acetylated compounds, a line-broadening in the
1H NMR at room temperature was observed; similar be-
havior was previously described by Beland et al.30 They
suggested that the line-broadening was most likely due to
a hindered rotation of the N-acetyl group in 2-AAF be-
cause of partial double-bond character in analogy to pep-
tide bonds. Therefore, we performed high-temperature
NMR studies with C8-acetylaniline adduct 11a to confirm
this assumption. As expected, in these experiments the
resolution of the signals increased while heating the sam-
ple, and the determination of individual coupling con-
stants from the NMR spectra was possible at 333 K (55
°C).
[a]54620 +27 (c 0.22, CHCl3).
IR (KBr): 3204, 2954, 2928, 2884, 1514, 1445, 1280, 1227, 1190,
946, 882, 780, 742 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 8.30 (s, 1 H, H8), 8.11 (d,
J = 8.4 Hz, 1 H, H14), 7.75 (d, J = 8.3 Hz, 1 H, H11), 7.64 (t,
J = 7.2, 7.2 Hz, 1 H, H12), 7.51–7.55 (m, 1 H, H13), 6.74 (br s, 2 H,
NH2), 6.25 (dd, J = 6.7, 6.7 Hz, 1 H, H1¢), 4.54 (ddd, J = 3.4, 3.4,
8.6 Hz, 1 H, H3¢), 3.83–3.86 (m, 1 H, H4¢), 3.70 (dddd, J = 5.2,
11.1, 15.6 Hz, 2 H, H5¢a, H5¢b), 2.75–2.82 (m, 1 H, H2¢a), 2.31
(ddd, J = 3.6, 6.1, 13.2 Hz, 1 H, H2¢b), 0.89 [s, 9 H, SiC(CH3)3],
0.86 [s, 9 H, SiC(CH3)3], 0.11 [s, 6 H, Si(CH3)2], 0.04, 0.03 [2 × s,
In conclusion, we have developed a new synthesis for C8- 2 × 3 H, Si(CH3)2].
13C NMR (101 MHz, DMSO-d6): d = 159.1, 158.9, 156.7, 142.6,
139.7, 129.2, 128.9, 124.9, 119.3, 111.8, 109.0, 86.9, 82.6, 71.8,
62.4, 38.8, 26.1, 24.6, 17.9, 17.5, –5.1, –6.5.
[acetyl(aryl)amine]-2¢-dG adducts. With this much short-
er route it is possible to introduce variable protecting
groups for the exocyclic N2-amino function of dG. More-
over, the expensive and time-consuming cross-coupling
reaction for the formation of the C8-NH-arylamine ad-
duct, which has to be acetylated in a separate step, can be
circumvented. According to our new approach, this type
of DNA damage was synthesized using N-arylacetohy-
droxamic acids within seven steps starting from dG to
yield the corresponding phosphoramidite.
HRMS-FAB: m/z [M]+ calcd for C28H44N8O4Si2: 612.3024; found:
613.3102 [M + H]+.
Arylhydroxylamines; General Procedure 1
In a flask, the nitroaryl compound (1 equiv) was dissolved in EtOH–
DCE (1:1), Raney nickel was added and the mixture was cooled to
0 °C. After the addition of hydrazine hydrate (10 equiv), the soln
was stirred for 1 h and filtered. The solvent was removed in vacuo
and the product was recrystallized (toluene).
Synthesis 2007, No. 24, 3907–3914 © Thieme Stuttgart · New York

3912
N. Böge et al.
FEATURE ARTICLE
N-Phenylhydroxylamine
IR (KBr): 2901, 1641, 1593, 1545, 1308, 1177, 1101, 1034, 907,
691 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.62 (s, 1 H, OH), 7.61 (d,
J = 7.9 Hz, 2 H, H2), 7.34–7.38 (m, 2 H, H3), 7.14 (t, J = 7.3, 7.3
Hz, 1 H, H4), 2.20 (s, 3 H, H6).
13C NMR (101 MHz, DMSO-d6): d = 170.1, 142.0, 128.7, 123.3,
119.3, 22.8.
Following general procedure 1, 9a (12.32 g, 100.07 mmol) and hy-
drazine hydrate (31.25 mL, 1 mol) gave the product as a white solid;
yield: 7.62 g (70%); mp 92.3 °C.
IR (KBr): 3246, 2847, 2019, 1957, 1935, 1875, 1854, 1784, 1725,
1602, 1521, 1494, 1470, 1421, 1321, 1305, 1236, 1221, 1156, 1106,
1088, 1058, 1024, 925, 897, 833, 795, 749, 692, 595, 501, 433 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 8.32 (d, J = 2.2 Hz, 1 H, NH),
8.25 (br s, 1 H, OH), 7.19 (dd, J = 7.4, 8.4 Hz, 2 H, H3), 6.87 (d,
J = 7.9 Hz, 1 H, H2), 6.78 (t, J = 7.3, 7.3 Hz, 1 H, H4).
HRMS-FAB: m/z [M]+ calcd for C8H9NO2: 151.0633; found:
152.0659 [M + H]+.
13C NMR (101 MHz, DMSO-d6): d = 152.0, 128.7, 119.2, 120.9,
N-(3,5-Dimethylphenyl)acetohydroxamic Acid (10b)
Following general procedure 2, N-(3,5-dimethylphenyl)hydroxyl-
amine (450 mg, 3.29 mmol), AcCl (0.23 mL, 3.51 mmol), and sat.
NaHCO3 soln (4.05 mL) gave the product as a slightly yellow solid;
yield: 547.8 mg (93%); mp 49.0 °C.
113.0.
HRMS-FAB: m/z [M]+ calcd for C6H7NO: 109.0528; found:
109.0753.
N-(3,5-Dimethylphenyl)hydroxylamine
IR (KBr): 3851, 3646, 3141, 2915, 1627, 1478, 1381, 1297, 1270,
1181, 1115, 1037, 999, 943, 890, 843, 811, 688, 584 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.49 (s, 1 H, OH), 7.23 (s, 2
H, H2, H6), 6.79 (s, 1 H, H4), 2.26 (s, 6 H, 2 Me), 2.17 (s, 3 H, Ac-
Me).
13C NMR (101 MHz, DMSO-d6): d = 141.5, 137.3, 126.1, 22.4,
21.0.
Following general procedure 1, 9b (5 g, 33 mmol) and hydrazine
hydrate (17.0 mL, 350.5 mmol) gave the product as a white solid;
yield: 3.86 g (85%); mp 105.2 °C.
IR (KBr): 3238, 3136, 3014, 2913, 2848, 1617, 1602, 1520, 1469,
1414, 1373, 1305, 1090, 1062, 1037, 949, 893, 868, 859, 839, 812,
695, 643 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 8.17 (d, J = 2.2 Hz, 1 H, NH),
8.07–8.09 (m, 1 H, OH), 6.44 (s, 2 H, H2, H6), 6.37 (s, 1 H, H4),
2.17 (s, 6 H, 2 Me).
HRMS-FAB: m/z [M]+ calcd for C10H13NO2: 179.0946; found:
180.1045 [M + H]+.
13C NMR (101 MHz, DMSO-d6): d = 152.0, 137.1, 120.9, 110.7,
N-(9H-Fluoren-2-yl)acetohydroxamic Acid (10c)
Following general procedure 2, N-(9H-fluoren-2-yl)hydroxylamine
(100 mg, 0.51 mmol), AcCl (0.04 mL, 0.56 mmol), and sat.
NaHCO3 soln (0.9 mL) gave the product as a yellow solid; yield:
94.6 mg (78%); mp 153.6 °C.
21.1.
HRMS-FAB: m/z [M]+ calcd for C8H11NO: 137.0919; found:
137.0828 [M]+.
N-(9H-Fluoren-2-yl)hydroxylamine
IR (KBr): 3149, 2848, 1620, 1484, 1453, 1428, 1395, 1304, 1286,
1252, 1215, 1179, 1138, 1090, 1029, 1002, 945, 870, 832, 764, 727,
622 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.68 (s, 1 H, OH), 7.87–7.88
(m, 3 H, H2, H9, H12), 7.62–7.64 (m, 1 H, H13), 7.56–7.58 (m, 1
H, H6), 7.36–7.39 (m, 1 H, H8), 7.27–7.31 (m, 1 H, H7), 3.93 (s, 2
H, CH2), 2.22 (s, 3 H, Ac-Me).
13C NMR (101 MHz, DMSO-d6): d = 143.2, 143.0, 140.6, 140.5,
126.7, 126.4, 126.3, 125.0, 119.7, 119.6, 36.5, 36.4, 22.4.
HRMS-FAB: m/z [M + H]+ calcd for C15H14NO2: 240.1025; found:
240.1030.
Following general procedure 1, 9c (6.36 g, 30.00 mmol) and hydra-
zine hydrate (15 mL, 309 mmol) gave the product as a yellow solid;
yield: 3.90 g (66%); mp 211.3 °C.
IR (KBr): 3446, 3360, 3254, 2920, 2349, 2284, 1950, 1615, 1585,
1480, 1454, 1418, 1401, 1349, 1316, 1304, 1278, 1264, 1211, 1194,
1177, 1156, 1136, 1122, 1099, 1050, 1025, 1000, 951, 903, 870,
859, 827, 814, 764, 731, 711, 691, 573, 418 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 8.38–8.39 (m, 2 H, NH, OH),
7.65–7.71 (m, 2 H, H9, H12), 7.48 (d, J = 7.4 Hz, 1 H, H6), 7.29 (t,
J = 7.4, 7.4 Hz, 1 H, H8), 7.18 (t, J = 7.4, 7.4 Hz, 1 H, H7), 7.07 (s,
1 H, H2), 6.85 (dd, J = 1.5, 8.2 Hz, 1 H, H13), 3.82 (s, 2 H, CH2).
13C NMR (101 MHz, DMSO-d6): d = 151.6, 143.8, 141.9, 141.6,
C8-N-Acetylarylamine Adducts 11a–c; General Procedure 3
In a dried flask, 8 (1 equiv), Cs2CO3 (10 equiv), and N-arylacetohy-
droxamic acid 10a–c (10 equiv) were suspended in anhyd DME and
stirred under a N2 atmosphere at r.t.. When the reaction was com-
plete H2O and CH2Cl2 were added and the aqueous layer was ex-
tracted with CH2Cl2 (3 ×). The combined organic layers were dried
(Na2SO4) and the solvent was removed in vacuo. The product was
isolated by column chromatography (10% MeOH–CH2Cl2).
132.8, 126.4, 124.9, 124.7, 119.9, 118.5, 111.8, 109.5, 36.2.
HRMS-FAB: m/z [M]+ calcd for C13H11NO: 197.0919; found:
197.0841 [M]+.
N-Arylacetohydroxamic Acids 10a–c; General Procedure 2
In a flask, arylhydroxylamine (1 equiv) and sat. NaHCO3 soln were
suspended in Et2O and stirred at 0 °C. After the addition of AcCl
(1.1 equiv), the mixture was stirred at r.t. for 1 h. The layers were
separated and the organic layer was extracted with 1 M NaOH (3 ×).
Then the aqueous layer was extracted with Et2O (3 ×). 3 M HCl was
added until the aqueous layer was acidic and it was then extracted
with Et2O (3 ×). The combined organic layers were dried (Na2SO4)
and the solvent was removed in vacuo.
8-[Acetyl(phenyl)amino]-3¢,5¢-bis-O-(tert-butyldimethylsilyl)-
2¢-deoxyguanosine (11a)
Following general procedure 3, 8 (321 mg, 520 mmol) and 10a (157
mg, 1.04 mmol) gave the product as a slightly brown solid; yield:
246 mg (73%); mp 227–229 °C (dec.).
[a]54620 +90 (c 0.17, CHCl3).
N-Phenylacetohydroxamic Acid (10a)
IR (KBr): 2954, 2886, 1704, 1602, 1542, 1431, 1330, 1112, 1031,
812, 779, 691 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.65 (s, 1 H, H1), 7.60–7.62
(m, 2 H, H11), 7.33–7.36 (m, 2 H, H12), 7.12–7.15 (m, 1 H, H13),
6.40 (br s, 2 H, NH2), 5.90–6.09 (m, 1 H, H1¢), 4.49–4.58 (m, 1 H,
Following general procedure 2, N-phenylhydroxylamine (3 g, 27.49
mmol), AcCl (2.3 mL, 32.35 mmol), and sat. NaHCO3 soln (40.5
mL) gave the product as a brown solid; yield: 3.51 g (84%); mp 120
°C.
Synthesis 2007, No. 24, 3907–3914 © Thieme Stuttgart · New York

FEATURE ARTICLE
Synthesis of dG–Arylamine Adducts
3913
H3¢), 3.66–3.75 (m, 4 H, H2¢a, H4¢, H5¢a, H5¢b), 3.06–3.17 (m, 1 H,
H2¢b), 2.19 (s, 3 H, H15), 0.86 [s, 9 H, SiC(CH3)3], 0.80 [s, 9 H,
SiC(CH3)3], 0.07 [m, 6 H, Si(CH3)2], –0.04 [s, 6 H, Si(CH3)2].
13C NMR (101 MHz, DMSO-d6): d = 170.2, 156.2, 153.5, 141.6,
129.1, 128.6, 128.3, 122.9, 118.9, 118.7, 115.1, 87.3, 83.2, 72.2,
63.8, 25.6, 25.5, 22.4, 17.8, 17.5, –5.4, –5.5.
H3¢), 3.80–3.83 (m, 1 H, H4¢), 3.53–3.67 (m, 2 H, H5¢a, H5¢b),
3.06–3.12 (m, 2 H, H2¢a, H2¢b), 2.02 (s, 3 H, H15).
13C NMR (101 MHz, DMSO-d6): d = 128.9, 126.1, 125.0, 87.9,
83.6, 71.3, 62.3, 45.5, 22.3.
HRMS-FAB: m/z [M]+ calcd for C18H20N6O5: 400.1589; found:
401.1621 [M + H]+.
HRMS-FAB: m/z [M]+ calcd for C30H48N6O5Si2: 628.3225; found:
629.3303 [M + H]+.
8-[Acetyl(phenyl)amino]-2¢-deoxy-N2-[(dimethylamino)methyl-
ene]guanosine
8-[Acetyl(3,5-dimethylphenyl)amino]-3¢,5¢-bis-O-(tert-butyl-
dimethylsilyl)-2¢-deoxyguanosine (11b)
Following general procedure 3, 8 (4.00 g, 6.53 mmol) and 10b
(2.33 g, 13.1 mmol) gave the product as a slightly brown solid;
yield: 2.89 g (67%); mp >200 °C (dec.).
In a dried flask, 8-[acetyl(phenyl)amino]-2¢-deoxyguanosine (75
mg, 0.18 mmol) was diluted in anhyd pyridine (4 mL) and N,N-di-
methylformamide diethyl acetal (0.40 mL, 2.30 mmol) were added.
After stirring the mixture at r.t. for 17 h, the solvent was removed in
vacuo and the product was isolated by column chromatography
(CH2Cl2–MeOH, 0–20%) as a yellow solid; yield: 65 mg (80%); mp
153–155 °C.
[a]54620 –3.3 (c 0.5, CHCl3).
IR (KBr): 3337, 3162, 2954, 2929, 2857, 1699, 1628, 1596, 1542,
1472, 1434, 1368, 1314, 1257, 1110, 1082, 1032, 1006, 941, 837,
779, 714, 675 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.83 (s, 1 H, NH), 6.94 (s, 3
H, H2, H4, H6), 6.37 (s, 2 H, NH2), 5.99 (s, 1 H, H1¢), 4.54 (s, 1 H,
H3¢), 3.60–3.76 (m, 5 H, H4¢, H5¢a, H5¢b, H2¢a, H2¢b), 2.25 (s, 6 H,
2 Me), 2.00 (s, 3 H, Ac-Me), 0.87 [s, 9 H, SiC(CH3)3], 0.81 [s, 9 H,
SiC(CH3)3], 0.09 [s, 6 H, Si(CH3)2], –0.03 [s, 6 H, Si(CH3)2].
[a]54620 +59 (c 0.29, CH2Cl2–MeOH, 1:1).
IR (KBr): 2931, 1734, 1653, 1594, 1569, 1491, 1436, 1357, 1286,
1055, 844 cm–1.
1H NMR (500 MHz, DMSO-d6): d = 11.48 (s, 1 H, H1), 8.47 (s, 1
H, H16), 7.33–7.45 (m, 5 H, H11, H12, H13), 6.11–6.15 (m, 1 H,
H1¢), 5.30–5.33 (m, 1 H, H3¢), 4.87–4.90 (m, 1 H, H5¢a), 4.42–4.47
(m, 1 H, H5¢b), 3.80–3.86 (m, 1 H, H4¢), 3.52–3.65 (m, 2 H, H2¢a,
H2¢b), 3.13 (s, 3 H, H17a), 3.03 (s, 3 H, H17b), 2.03 (s, 3 H, H15).
13C NMR (101 MHz, DMSO-d6): d = 158.4, 129.0, 126.7, 87.8,
83.9, 70.8, 61.4, 40.7, 34.5, 22.1.
13C NMR (101 MHz, DMSO-d6): d = 156.2, 140.6, 138.4, 115.0,
87.6, 87.3, 83.4, 72.5, 63.1, 25.7, 22.5, 21.0, 17.8, –5.5, –5.6.
HRMS-FAB: m/z [M]+ calcd for C32H52N6O5Si2: 656.3538; found:
657.3612 [M + H]+.
HRMS-FAB: m/z [M]+ calcd for C21H25N7O5: 455.1917; found:
456.1977 [M + H]+.
8-[Acetyl(9H-fluoren-2-yl)amino]-3¢,5¢-bis-O-(tert-butyldi-
methylsilyl)-2¢-deoxyguanosine (11c)
Following general procedure 3, 8 (25.61 mg, 41.82 mmol) and 10c
(20 mg, 83.65 mmol) gave the product as a slightly brown solid;
yield: 26.6 mg (89%); mp 154.6 °C.
8-[Acetyl(phenyl)amino]-2¢-deoxy-5¢-O-(4,4¢-dimethoxytrityl)-
N2-[(dimethylamino)methylene]guanosine
In a dried flask, 8-[acetyl(phenyl)amino]-2¢-deoxy-N2-[(dimethyl-
amino)methylene]guanosine (45 mg, 98 mmol) were diluted in an-
hyd pyridine (4 mL) and DMTrCl (72 mg, 0.21 mmol) were added.
The mixture was stirred at r.t. for 16 h. CH2Cl2 and sat. NaHCO3
soln were added and the aqueous layer extracted with CH2Cl2 (3 ×)
The combined organic layers were dried (Na2SO4) and the solvent
removed in vacuo. The product was isolated by column chromatog-
raphy (CH2Cl2–MeOH, 0–20%) as a slightly brown solid; yield: 60
mg (80%); mp 174–176 °C.
[a]54620 –7.2 (c 0.5, CHCl3).
IR (KBr): 3385, 3214, 2954, 2929, 2857, 1685, 1592, 1535, 1471,
1405, 1362, 1256, 1176, 1112, 1029, 1006, 939, 837, 814, 779, 734,
671 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 11.25 (s, 1 H, NH), 7.84–7.92
(m, 3 H, H2, H9, H12), 7.63–7.65 (m, 1 H, H13), 7.56–7.58 (m, 1
H, H6), 7.35–7.39 (m, 1 H, H8), 7.27–7.32 (m, 1 H, H7), 6.76 (s, 2
H, NH2), 6.10 (dd, J = 6.1, 7.6 Hz, 1 H, H1¢), 4.48 (q, J = 2.9, 2.9,
5.5 Hz, 1 H, H3¢), 3.92 (s, 2 H, CH2), 3.79–3.82 (m, 1 H, H4¢), 3.60–
3.72 (m, 2 H, H5¢a, H5¢b), 2.61–2.67 (m, 1 H, H2¢a), 2.20–2.23 (m,
1 H, H2¢b), 2.04 (s, 3 H, Ac-Me), 0.89 [s, 9 H, SiC(CH3)3], 0.87 [s,
9 H, SiC(CH3)3], 0.10 [s, 6 H, Si(CH3)2], 0.04 [s, 6 H, Si(CH3)2].
[a]54620 +44 (c 0.5, CHCl3).
IR (KBr): 2931, 1734, 1653, 1594, 1569, 1491, 1436, 1357, 1286,
1055, 844 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 11.48 (s, 1 H, H1), 8.19 (s, 1
H, H16), 7.11–7.41 (m, 14 H, H11, H12, H13, arom. H/DMTr),
6.67–6.74 (m, 4 H, H11, H12, H13, arom. H/DMTr), 6.17–6.23 (m,
1 H, H1¢), 5.31–5.39 (m, 1 H, H3¢), 4.58–4.62 (m, 1 H, H4¢), 3.89–
3.94 (m, 1 H, H5¢a), 3.68–3.70 (m, 7 H, OCH3-DMTr, H5¢b), 3.33–
3.34 (m, 1 H, H2¢a), 3.00 (s, 3 H, H17a), 2.94 (s, 3 H, H17b), 2.49–
2.50 (m, 1 H, H2¢b), 2.04 (s, 3 H, H15).
13C NMR (101 MHz, DMSO-d6): d = 156.6, 140.6, 127.5, 125.5,
87.7, 72.7, 36.8, 26.1.
HRMS-FAB: m/z [M]+ calcd for C37H52N6O5Si2: 628.3225; found:
629.3303 [M + H]+.
13C NMR (101 MHz, DMSO-d6): d = 156.9, 129.4, 128.9, 127.2,
8-[Acetyl(phenyl)amino]-2¢-deoxyguanosine
126.6, 112.6, 112.4, 85.5, 82.9, 70.5, 54.6, 40.6, 34.4, 22.4.
In a flask, 11a (140 mg, 222 mmol) was dissolved in CH2Cl2–THF
(1:1; 12 mL). After the addition of Et3N (0.30 mL, 0.22 g,
2.2 mmol) and Et3N·3HF (0.90 mL, (5.5 mmol), the mixture was
stirred at r.t. for 16 h. It was then evaporated to dryness and the
product was isolated by column chromatography (CH2Cl2–MeOH,
0–50%) as a yellow solid; yield: 85 mg (96%); mp 138–140 °C.
HRMS-FAB: m/z [M]+ calcd for C42H43N7O7: 757.3224; found:
758.3336 [M + H]+.
8-[Acetyl(phenyl)amino]-3¢-O-[(2-cyanoethyl)(diisopropylami-
no)phosphino]-2¢-deoxy-5¢-O-(4,4¢-dimethoxytrityl)-N2-[(di-
methylamino)methylene]guanosine (12a)
In a dried flask, 8-[acetyl(phenyl)amino]-2¢-deoxy-5¢-O-(4,4¢-
dimethoxytrityl)-N2-[(dimethylamino)methylene]guanosine
(39 mg, 51 mmol) were diluted in anhyd CH2Cl2–anhyd MeCN (1:1,
6 mL) and 0.25 M DCI activator soln in THF (0.6 mL) and (2-cya-
noethyl)bis(diisopropylamino)phosphine (0.10 mL, 0.32 mmol)
[a]54620 +55 (c 0.29, CH2Cl2–MeOH, 1:1).
IR (KBr): 2937, 1718, 1680, 1671, 1647, 1576, 1369, 842 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.83 (s, 1 H, H1), 7.35–7.50
(m, 5 H, H11, H12, H13), 6.44 (br s, 2 H, NH2), 6.04–6.10 (m, 1 H,
H1¢), 5.24 (br s, 1 H, OH), 4.96 (br s, 1 H, OH), 4.35–4.40 (m, 1 H,
Synthesis 2007, No. 24, 3907–3914 © Thieme Stuttgart · New York

3914
N. Böge et al.
FEATURE ARTICLE
were added and the mixture was stirred at r.t. for 1 h. The reaction
was quenched by addition of sat. NaHCO3 soln. The layers were
separated and the aqueous layer was extracted with CH2Cl2 (3 ×).
The combined organic layers were dried (Na2SO4) and the solvent
was removed in vacuo. Purification of the residue by chromatogra-
phy (alumina) gave the desired product as a colorless solid, which
was obtained as a fine powder after lyophilization from benzene;
yield: 34 mg (68%); mp 68–70 °C.
(6) Famulok, M.; Bosold, F.; Boche, G. Angew. Chem., Int. Ed.
Engl. 1989, 28, 347.
(7) Kadlubar, F. F.; Beland, F. A. In Structure/Performance
Relationships in Surfactants, ACS Symposium Series 253,
341; Rosen, M. J., Ed.; American Chemical Society:
Washington DC, 1985.
(8) Meneni, S. R.; D’Mello, R.; Norigan, G.; Baker, G.; Gao, L.;
Chiarelli, M. P.; Cho, B. P. Nucleic Acids Res. 2006, 34, 755.
(9) Heflich, R. H.; Neft, R. E. Mutat. Res. 1994, 318, 73.
(10) O’Handley, S. F.; Sanford, D. G.; Xu, R.; Lester, C. C.;
Hingerty, B. E.; Broyde, S.; Krugh, T. R. Biochemistry 1993,
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[a]54620 +74 (c 0.06, CHCl3).
IR (KBr): 2968, 2932, 1700, 1696, 1680, 1672, 1629, 1554, 1517,
1493, 1368, 1326, 1116, 1079, 979 cm–1.
1H NMR (400 MHz, benzene-d6): d = 11.29 [s, 2 H, NH (I + II)],
8.36 [s, 1 H, H16 (I)], 8.23 [s, 1 H, H16 (II)], 7.62–6.62 [m, 36 H,
DMTr-H (I + II) + aniline-H (I + II)], 6.41 [dd, J = 6.1, 6.1 Hz, 1 H,
H1¢ (I)], 6.31 [dd, J = 6.3, 6.3 Hz, 1 H, H1¢ (II)], 4.85–4.82 [m, 2 H,
H3¢ (I + II)], 4.38–4.35 [m, 2 H, H4¢ (I + II)], 3.56–3.30 [m, 38 H,
DMTr-CH3 (I + II) + i-Pr-H (I + II) + H2a¢ (I + II) + H5¢a + b (I +
II) + aHa + b (I + II) + H17 + H18 (I + II)], 2.78–2.75 [m, 1 H, H2b¢
(II)], 2.59–2.56 [m, 2 H, H2b¢ (I) + bHa (I)], 2.23 [ddd, 1 H, bHb
(I)], 2.04 [s, 6 H, H15 (I + II)], 1.85 [dd, J = 6.1, 6.1 Hz, 2 H, b¢Ha
(II) + bHb (II)], 1.15–0.96 [m, 24 H, i-Pr-CH3 (I + II)].
13C NMR (101 MHz, benzene-d6): d = 178.7, 159.3, 159.2, 158.2,
147.6, 147.5, 145.3, 145.3, 136.3, 133.2, 130.9, 130.8, 130.7, 130.6,
130.5, 129.3, 128.8, 128.7, 128.6, 128.4, 118.4, 118.2, 114.6, 113.7,
113.6, 87.1, 86.6, 85.6, 75.0, 74.8, 74.0, 73.8, 64.1, 64.0, 58.7, 58.6,
58.5, 58.5, 55.1, 54.9, 54.8, 43.6, 43.6, 43.5, 43.5, 38.6, 38.4, 37.7,
30.2, 24.8, 24.7, 24.6, 20.6, 20.5, 20.3.
(11) Van Oosterwijk, M. F.; Filon, R.; de Groot, A. J. L.; van
Zeeland, A. A.; Mullenders, L. H. F. J. Biol. Chem. 1998,
273, 13599.
(12) Gunz, D.; Hess, M. T.; Naegeli, H. J. Biol. Chem. 1996, 271,
25089.
(13) Meier, C.; Boche, G. Carcinogenesis 1991, 12, 1633.
(14) Meier, C.; Boche, G. Tetrahedron Lett. 1990, 31, 1693.
(15) Kadlubar, F. F. In Proceedings of the 21st Princess
Takamatsu Symposium, Tokyo, Japan, 1990, 329.
(16) Meier, C.; Gräsl, S. Synlett 2002, 802.
(17) Böge, N.; Gräsl, S.; Meier, C. J. Org. Chem. 2006, 71, 9728.
(18) Jacobsen, M. I.; Meier, C. Synlett 2006, 2411.
(19) Böge, N.; Szombati, Z.; Meier, C. Nucleosides, Nucleotides
Nucleic Acids 2007, 26, in press.
(20) Liu, L. V.; Vett, A.; Zhang, N.; Walters, K. J.; Wagner, C.
R.; Hanna, P. E. Chem. Res. Toxicol. 2007, 20, 1300.
(21) Johnson, D. L.; Reid, T. M.; Lee, M.-S.; King, C. M.;
Romano, L. J. Biochemistry 1986, 25, 449.
31P NMR (162 MHz, benzene-d6): d = 147.4, 147.1.
(22) Zhou, Y.; Chladek, S.; Romano, L. J. J. Org. Chem. 1994,
59, 556.
(23) Zhou, Y.; Romano, L. J. Biochemistry 1993, 32, 14043.
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373.
HRMS-ESI: m/z [M]+ calcd for C51H60N9O7P: 957.4302; found:
980.4199 [M + Na]+.
Acknowledgment
The authors are grateful for the financial support by the Deutsche
Forschungsgemeinschaft (DFG) and the University of Hamburg.
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Synthesis 2007, No. 24, 3907–3914 © Thieme Stuttgart · New York