Investigation and Conformational Analysis of Fluorinated Nucleoside Antibiotics Targeting Siderophore Biosynthesis

Article abstract of DOI:10.1021/acs.joc.5b00550

(Chemical Equation Presented) Antibiotic resistance represents one of the greatest threats to public health. The adenylation inhibitor 5′-O-[N-(salicyl)sulfamoyl]adenosine (SAL-AMS) is the archetype for a new class of nucleoside antibiotics that target iron acquisition in pathogenic microorganisms and is especially effective against Mycobacterium tuberculosis, the causative agent of tuberculosis. Strategic incorporation of fluorine at the 2′ and 3′ positions of the nucleoside was performed by direct fluorination to enhance activity and improve drug disposition properties. The resulting SAL-AMS analogues were comprehensively assessed for biochemical potency, whole-cell antitubercular activity, and in vivo pharmacokinetic parameters. Conformational analysis suggested a strong preference of fluorinated sugar rings for either a 2′-endo, 3′-exo (South), or a 3′-endo,2′-exo (North) conformation. The structure-activity relationships revealed a strong conformational bias for the C3′-endo conformation to maintain potent biochemical and whole-cell activity, whereas improved pharmacokinetic properties were associated with the C2′-endo conformation.

Full text of DOI:10.1021/acs.joc.5b00550

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pubs.acs.org/joc
Investigation and Conformational Analysis of Fluorinated Nucleoside
Antibiotics Targeting Siderophore Biosynthesis
†
†
‡
‡
Surendra Dawadi, Kishore Viswanathan, Helena I. Boshoff, Clifton E. Barry, III,
,†
and Courtney C. Aldrich*
†
Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
‡
Tuberculosis Research Section, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892, United States
*
S Supporting Information
ABSTRACT: Antibiotic resistance represents one of the greatest threats to public health. The adenylation inhibitor 5′-O-[N-
salicyl)sulfamoyl]adenosine (SAL-AMS) is the archetype for a new class of nucleoside antibiotics that target iron acquisition in
(
pathogenic microorganisms and is especially effective against Mycobacterium tuberculosis, the causative agent of tuberculosis.
Strategic incorporation of fluorine at the 2′ and 3′ positions of the nucleoside was performed by direct fluorination to enhance
activity and improve drug disposition properties. The resulting SAL-AMS analogues were comprehensively assessed for
biochemical potency, whole-cell antitubercular activity, and in vivo pharmacokinetic parameters. Conformational analysis
suggested a strong preference of fluorinated sugar rings for either a 2′-endo, 3′-exo (South), or a 3′-endo,2′-exo (North)
conformation. The structure−activity relationships revealed a strong conformational bias for the C3′-endo conformation to
maintain potent biochemical and whole-cell activity, whereas improved pharmacokinetic properties were associated with the C2′-
endo conformation.
INTRODUCTION
siderophore iron mobilization, whereas other bacteria such as
Escherichia coli and Acinetobacter baumannii synthesize multiple
siderophores.
■
Iron is the most abundant element in the universe and essential
for all domains of life, where it serves as a redox cofactor for
enzymes involved in diverse metabolic pathways. However, in
many environments, iron is severely depleted, which is
particularly challenging for microorganisms that can only
assimilate nutrients from their immediate surroundings. To
prevent bacterial colonization and growth, mammals use iron-
binding proteins such as transferrin to withhold iron. The
The nucleoside antibiotic 5′-O-[N-(salicyl)sulfamoyl]-
adenosine (SAL-AMS, 10, Figure 2B) is a prototype for a
new class of antibiotics that targets iron acquisition through
inhibition of aryl acid adenylating enzymes (AAAEs) in several
pathogenic bacteria including MbtA from M. tuberculosis, EntE
from Escherichia coli and Klebsiella pneumoniae, BasE from
Acinetobacter baumannii, YbtE from Yersinia pestis, VibE from
3
+
concentration of unbound Fe in human serum and body
4
fluids is ∼10−24 M, an astonishingly low concentration close to
Vibrio cholerae, and PchA from Pseudomonas aeruginosa.
1
AAAEs catalyze the first committed step in the synthesis of
the respective aryl-capped siderophores 2−6 produced by each
bacteria (Figure 1). Adenylation, the ligation of a carboxylic
acid substrate with AMP to form an acyl-AMP intermediate, is a
ubiquitous process, and adenylation inhibitors like SAL-AMS
the reciprocal of Avogadro’s number. To survive under these
iron-restricted conditions, many pathogenic bacteria synthesize,
secrete, and reimport small-molecule iron chelators known
generically as siderophores. Mycobacterium tuberculosis, the
2
leading cause of bacterial infectious disease mortality, and the
focus of the present report, relies on mycobactins 1 (Figure 1),
which are aryl-capped siderophores, for iron acquisition in
(
10) mimic the acyl-AMP intermediate through replacement of
the labile acyl phosphate moiety with an acyl sulfamate
5
3
bioisostere (Figure 2). The specificity of SAL-AMS is derived
vivo. Given the vital role that siderophores play in bacterial
from the salicyl moiety, which allows it to bind to adenylating
iron acquisition, disruption of siderophore biosynthesis or
trafficking could provide a new strategy to combat drug-
resistant bacteria. This strategy is particularly effective for M.
tuberculosis since it relies exclusively on the mycobactins for
Received: March 11, 2015
©
XXXX American Chemical Society
A
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Figure 1. Structures of representative aryl-capped siderophores. The siderophore name is given below each structure along with the producing
organism(s). The aryl caps are highlighted in blue (salicylic acid or 2,3-dihydrobenzoic acid). The aryl acid adenylating enzymes (AAAEs)
responsible for incorporation of the respective aryl moieites have high homology at the overall protein level and nearly identical active-site residues
(
MbtA, EntE, BasE, YbtE, PchD, and VibE).
Figure 2. Mycobactin biosynthesis and inhibition. (A) Biosynthesis of mycobactins in M. tuberculosis is initiated by MbtA that catalyzes two partial
reactions at the same active site. In the first half-reaction, MbtA condenses salicylic acid (7) with ATP to form the reactive mixed anhydride SAL-
AMP (8). In the second half-reaction, MbtA transfers the salicyl moiety onto MbtB, another protein in the biochemical pathway, to afford 9 that is
ultimately elaborated to the mycobactins. The initial biosynthetic step of other aryl-capped siderophores is performed by homologous aryl acid
adenylation enzymes (AAAEs). (B) The inhibitors Sal-AMS 10 and its sulfamide isostere 11 mimic the acyl adenylate intermediate 8, thereby
blocking siderophore biosynthesis. The sugar can adopt the Northern (C3′-endo pucker) or Southern (C2′-endo pucker) conformation as depicted.
(
C) Fluorinated sugar analogues described in this study.
enzymes that utilize salicylic acid or related carboxyl acid
substrates. Affinity-based protein profiling of SAL-AMS in M.
tuberculosis showed it binds only to MbtA from more than 606
functionally related adenylating enzymes in mycobacteria.
Isosteric substitution of the phenol of SAL-AMS with an amino
group completely obliterated biological activity due to an H-
bond repulsion in the enzyme-active site, illustrating the high
level of selectivity that one can obtain with such adenylation
mimic their native acyl adenylates, it is marred by poor
physicochemical properties. To further advance this new class
of antibiotics, key improvements in the molecular properties of
SAL-AMS will be required.
One of the most common means to modulate chemical
properties of small molecules is to introduce fluorine, often
considered an isostere of hydrogen, although fluorine’s van der
Waal radius (1.47 Å) is closer to oxygen (1.52 Å) than
hydrogen (1.20 Å). Fluorination also has a long tradition in
nucleoside chemistry, and the synthetic provenance can be
7
inhibitors. SAL-AMS has demonstrated proof-of-concept in
4
a,c
8
vitro and in vivo, but like other adenylation inhibitors that
B
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9
traced to a report by Fox et al. The replacement of the 2′ or 3′
Scheme 1. Synthesis of 3′-Deoxy-3′-F-xylo and 2′-Deoxy-2′-
F-arabino Nucleosides
hydroxyl groups of a nucleoside with a fluorine atom causes
only a minor change in the overall structure, but profoundly
affects the stereoelectronic properties of the sugar moiety.
10
Such dominating effects can control the conformational
equilibria and lock the sugar ring into either a North (C3′-
11
endo pucker) or a South (C2′-endo pucker) conformation, can
12
stabilize the glycosidic bond toward hydrolysis, and can also
13
enhance the lipophilicity.
Based on the beneficial effects of fluorination, we postulated
that strategic introduction of fluorine at the 2′ and/or 3′
position in both α and β configurations of SAL-AMS may
enhance the biological activity and pharmacokinetic behavior.
We predicted compounds that mimic the C3′-endo pucker of
14
the native acyl adenylate intermediate would exhibit greater
biological activity than compounds that adopt the C2′-endo
pucker. However, we could not anticipate the impact of ring
pucker or extent of fluorination on in vivo pharmacokinetic
parameters. Herein, we describe synthesis and conformational
analysis of a systematic series of fluorinated nucleoside
derivatives of SAL-AMS 12−17 (Figure 2C), along with their
enzyme inhibition, antibacterial activity, and complete in vivo
pharmacokinetic characterization.
2
Hz) and germinal coupling with 3′-H ( J(3′,F3′) = 50.6 Hz)
confirmed the position of fluorine at 3′. The coupling constants
also suggest that 3′-F has an anti relationship with 4′-H and a
syn relationship with 2′-H, which indicates a xylo configuration.
3
The absence of detectable J(1′,2′) is consistent with a 3′-endo
RESULTS AND DISCUSSION
18
■
conformation. The configuration at C2′ of 2′-deoxy-2′-F-
Synthesis. The synthesis of 12−17 was accomplished in
two stages: synthesis of the requisite fluorinated nucleoside
followed by installation of the N-salicylsulfamide moiety at C-
arabino 24 was unequivocally assigned by the presence of a five-
bond coupling between 2′-F and C8-H of the adenine base
5
( J(8,F2′) = 3.1 Hz), which is only observed in arabino-2′-F
17
5
′. For the second stage, we developed a new methodology,
compounds.
while for the first stage, we used an amalgamation of methods
for the direct introduction of fluorine into the targeted adenine
nucleosides. The main synthetic challenge was to install
fluorine at the desired positon of the sugar moiety and with the
desired stereochemistry. There are two general synthetic
approaches toward fluorinated nucleosides: (1) transformation
of natural nucleosides using various fluorinating reagents and
The key intermediate 21 also served as an entry point for
synthesis of 3′-deoxy-3′-F-ribo 27 through a two-step
1
5
19
oxidation−reduction sequence that interconverted the ribo
sugar to a xylo sugar (Scheme 2). This was accomplished by
Scheme 2. Synthesis of 3′-Deoxy-3′-F-ribo Nucleoside
(
2) glycosylation of fluorinated sugar with an appropriate
heterocyclic base. With the first approach, one can start with a
predefined α or β configuration at C-1′, but the main limitation
is the sluggish reactivity of certain pentofuranose hydroxyls
toward fluorinating reagents. In the second approach, a wide
variety of nucleosides can be prepared, but the formation of
regioisomers and anomers (α and β isomers) are the major
drawbacks. We selected the first approach since it usually
involves fewer synthetic steps when suitable protecting groups
are available.
The direct introduction of fluorine into each nucleoside
building block is illustrated in Schemes 1−4. For the
preparation of 3′-deoxy-3′-F-xylo 23 and 2′-deoxy-2′-F-arabino
2
4, a unified synthetic approach was employed (Scheme 1).
16
Regioselective PMB protection of the secondary alcohols of
adenosine 18 provided a 3:1 mixture of 2′-OPMB adenosine 19
Dess−Martin periodinane (DMP) mediated oxidation of 21 to
3′-ketoadenosine derivative 25, which was stereoselectively
reduced with sodium triacetoxyborohydride to furnish alcohol
and 3′-OPMB adenosine 20 in 75% yield. The ratio of 19 and
1
2
0 in the mixture was determined by H NMR integrations of
the anomeric protons. Without further separation of
regioisomers, subsequent tritylation of the 5′-OH and 6-NH2
afforded a 3:1 mixture of 21 and 22 that was fluorinated with
26. The bulky reducing agent NaBH(OAc) delivers hydride
3
from the more accessible α-face of the nucleoside. Fluorination
of 26 with DAST gave 27 in 61% yield. Once again, the
17
3
attendant inversion of configuration using DAST to obtain 23
55% from 21) and 24 (42% from 22), which were easily
coupling constants of fluorine with 2′-H and 4′-H ( J(2′,F3′) =
3
(
21.6, J(4′,F3′) = 26.4 Hz) compared to those of 3′-deoxy-3′-F-
separated by chromatography. The assignment of the fluorine
configuration was based on proton and fluorine spectra. In the
case of 3′-deoxy-3′-F-xylo 23, the vicinal coupling of fluorine
xylo 23 indicate a ribo configuration. A significantly large
3
coupling between 1′-H and 2′-H ( J(1′,2′) = 7.5) and the
3
absence of J(3′,4′) further confirms the 2′-endo conformation
3
3
with both 2′-H and 4′-H ( J(2′,F3′) = 13.9, J(4′,F3′) = 31.4
of 3′-deoxy-3′-F-ribo compounds.
C
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The novel difluorinated nucleoside 2′,3′-dideoxy-2′,3′-FF-
Scheme 5. Synthesis of Fully Unprotected Fluorinated
Nucleoside
20
xylo 31 was synthesized from 2′-fluoroadenosine 28 by trityl
protection to provide 29, and subsequent treatment with DAST
furnished 31 in 62% overall yield (Scheme 3). The 2′-deoxy-2′-
Scheme 3. Synthesis of 2′,3′-Dideoxy-2′,3′-FF-xylo and 2′-
Deoxy-2′-F-ribo Nucleosides
of direct fluorination, our synthesis of 40 proceeded in six steps
and 8.5% overall yield from adenosine, whereas the only
described synthesis that utilized glycosylation of adenine with a
fluorinated carbohydrate required 13 steps in 0.4% overall
26
yield.
The fluorinated nucleoside building blocks were elaborated
to the corresponding SAL-AMS derivatives 12−17 (Scheme 6).
The primary motivation for using the trityl protecting group
among the plethora of common nucleoside protecting groups
was based upon prior reports that had shown O-Tr groups
could be chemoselectively removed in the presence of an N-Tr
27
F-ribo 30 building block was prepared by PMB protection of
group as well as the improved lipophilicity engendered by this
nonpolar group that facilitated chromatographic purification.
De-O-tritylation of 30, 24, 23, 27, 31, and 35 was successively
achieved with 0.4 M HCl in 1,4-dioxane to afford 41a−f.
Monodeprotection was complete within 1 h, and longer
reaction times led to undesired PMB deprotection. The
resulting C5′ alcohols in 41a−f were converted to the C5′
2
9. As the configuration of fluorine at C2′ is known, a strong
3
vicinal trans coupling between two of the fluorines ( J(F2′,F3′)
=
15.0) in 31 indicates the 2′,3′-xylo difluoro configuration.
3
The absence of J(1′,2′) is consistent with the 3′-endo
conformation.
The difluorinated 2′,3′-dideoxy-2′,3′-FF-ribo 35 was pre-
21
28
pared from the known lyxo-epoxide 32 (Scheme 4) following
the Watanabe two-step process initiated by epoxide opening
with a fluoride ion exclusively from the α-face of the sugar to
afford a 3:1 ratio of regioisomers 3′-fluoro-arabino 33 and 2′-
fluoro-xylo 34 in a 65% combined yield. Treatment of this
azides using the methodology of Liu and Austin to provide
42a−f. This two-step, one-pot method converts the 5′-OH to a
phosphate leaving group in the first step, which is displaced by
azide in the second step. We observed that the presence of
fluorine in the β (“up”) configuration found in 41b, 41c, and
41e significantly suppressed the reactivity of 5′ phosphates
toward nucleophilic azides. For comparison, 42c was obtained
in 57% yield, and conversion was still incomplete after 24 h of
reflux, whereas 42d was obtained in 81% yield and complete
conversion was observed within 3 h. This can be explained in
terms of electrostatic repulsion between electronegative
fluorine and the incoming azide anion. The azides 42a−f
were reduced to amino derivatives in quantitative yields by
catalytic hydrogenation or with zinc in AcOH. The crude 5′-
aminonucleosides were then transformed to the 5′-sulfamides
43a−f in 84−94% yield by refluxing with sulfamide
(NH SO NH ) in 1,4-dioxane for 2 h. This new method of
22
mixture with DAST furnished 35 in a 62% yield. The
regioisomeric ratio was determined by integration of the
1
9
relevant peaks in the F NMR spectrum of the crude products.
There was no need for the separation of 33 and 34 because
both provide the same difluoro product 35 after treatment with
DAST. The presence of rather weak cis vicinal coupling
3
between two fluorines ( J(F2′,F3′) = 3.8) and a strong coupling
3
between 1′-H and 2′-H ( J(1′,2′) = 5.0) indicates the 2′,3′-ribo
difluoro configuration and C2′-endo conformation.
Each of the fully protected fluorinated nucleosides was
globally deprotected with 80% TFA in chloroform to obtain
fluorinated nucleosides 36−40 (Scheme 5). This allowed
2
2
2
2
3
24
17,25
unequivocal structural assignments for 36, 37, 38,
and
sulfamide synthesis is superior to previous examples in terms of
2
6
4c,29
40
by comparison to the literature data of these nucleosides
yield and experimental simplicity.
The synthesis of the
synthesized through alternate synthetic routes but not 39 since
this has not been previously reported. Illustrating the efficiency
target molecules was completed by salicylation of sulfamides
43a−f with NHS ester 44 to obtain fully protected coupled
Scheme 4. Synthesis of 2′,3′-Dideoxy-2′,3′-FF-ribo Nucleoside
D
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Scheme 6. Completion of the Synthesis of 7−12
Table 1. Relationship between Bioactivity and Sugar Ring Conformation of Inhibitors 12−17
a
b
NMR was obtained in DMSO-d ; peaks are in expansion view and are ordered according to their chemical shifts. Literature values for free
6
nucleosides are reported in parentheses.
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−1
−1
Figure 3. Mean plasma concentration versus time curves after single p.o. (25 mg·kg ) and i.v. (2.5 mg·kg ) bolus administration of 10 and 12−17
to rats. Error bars represent standard deviation of the mean (n = 3).
Table 2. In Vivo Pharmacokinetic Parameters of Inhibitors in Female Sprague−Dawley Rats (n = 3, Mean ± SD) Following a
Single Intravenous (i.v.) and Oral (p.o.) Administration
a
b
c
i.v. dose (D ) = 2.5 mg/kg. p.o. dose (D ) = 25 mg/kg. Reference 34. AUC : area under the plasma concentration−time curve from time 0
i.v.
p.o.
0‑inf
to infinity. CL: clearance, t1/2: terminal elimination half-life. Cmax: maximum plasma concentration. F: relative oral bioavailability calculated as follows
F = 100 × [(AUCp.o. × D )/(AUC × Dp.o.)].
i.v.
i.v.
31
1
products 45a−f, and global deprotection furnished 7−12 in
otation GUI). H NMR were obtained in DMSO-d at 23 °C,
6
3
0
3
9−50% yield.
Conformational Analysis. The solution-phase conforma-
tions adopted by the sugar rings of nucleosides 12−17 were
and the multiplets were analyzed (Table 1). Detailed
conformational analysis including coupling constants and
optimized pseudorotation parameters are provided in the
Supporting Information (Table S2). The percent North or C3′-
endo conformation (% N) adopted by 12−17 agree closely with
the reported values for the free nucleosides (Table 1). Most
1
3
studied by H NMR J(H,H) scalar coupling constants of ring
protons and electronegativities of ring substituents through the
use of pseudorotation analysis (program: Matlab Pseudor-
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compounds displayed a substantial conformational preference
relative to the diastereomer favoring the C3′-endo conforma-
for either the C2′-endo or C3′-endo pucker except for 2′-deoxy-
tion.
2′-F-ribo 12 and 2′-deoxy-2′-F-arabino 13. The 3′-deoxy-3′-F-
xylo 14 primarily adopted the C3′-endo conformation (∼90%
N), whereas 3′-deoxy-3′-F-ribo 15 was almost exclusively
present in the C2′-endo conformation. Similar conformational
rigidity was also observed with 2′,3′-dideoxy-2′,3′-FF-xylo 16
and 2′,3′-dideoxy-2′,3′-FF-ribo 17; the former was nearly
exclusively in the C3′-endo (96% N) conformation, whereas
the latter was largely in the C2′-endo (20% N) conformation.
Marquez and co-workers previously observed similar extreme
inclination of 2′,3′-dideoxy-2′,3′-FF-xylo uridine nucleosides
CONCLUSION
■
We have reported the efficient synthesis and conformational
analysis of a systematic series of fluorinated analogues of SAL-
AMS featuring direct fluorination of the nucleoside. The
structure−activity relationships (SAR) revealed a strong
conformational bias for the C3′-endo conformation to maintain
potent biochemical and whole-cell activity. Fluorination of
SAL-AMS was also shown to have a dramatic impact on
pharmacokinetic properties increasing half-life up to ca. 25-fold,
oral exposure 75-fold, and oral bioavailability 10-fold. Further
investigations of these fluorinated SAL-AMS derivatives and the
application of this strategy to other adenylation inhibitors are
ongoing. The results of these studies may have more
widespread utility since adenylate-forming enzymes are
involved in a myriad of biochemical pathways in DNA, RNA,
protein, amino acid, and cofactor biosynthesis as well as post-
3
2
toward the C3′-endo conformation (∼100% N).
Biochemical and Antitubercular Evaluation. The
nucleoside derivatives were evaluated for enzyme inhibition
against MbtA, the molecular target of SAL-AMS in M.
4a,c
tuberculosis.
The effect of configuration at C2′ on enzyme
inhibition was inconsequential since both 2′-α-fluoro 12 and 2′-
β-fluoro 13 were equipotent with app K ’s of 1.7−1.8 nM
i
(
Table 1). By contrast, the enzyme inhibition was more
5,35
translational protein modifications.
sensitive to the stereochemical configuration at C3′, and 3′-β-
fluoro 14 was approximately 10-fold more potent than 3′-α-
fluoro 15. The impact of configuration at C3′ was amplified in
difluorinated analogues 16 and 17 (both contain a 2′-α fluoro
EXPERIMENTAL SECTION
■
General Chemistry Methods. All commercial reagents were used
as provided unless otherwise indicated. An anhydrous solvent
dispensing system using packed columns of neutral alumina was
used for drying THF and CH Cl , while packed columns of 4 Å
group), and 3′-β-fluoro 16 (appK = 1.4 nM) was nearly 100-
i
fold more potent than 3′-α-fluoro 17. All compounds were then
evaluated for antibacterial activity against virulent M. tuber-
culosis strain H37Rv, and the concentration of inhibitor that
resulted in complete inhibition of observable growth was
defined as the minimum inhibitory concentration (MIC). The
relative trend in antibacterial activities mirrored the biochemical
results (Table 1). Thus, the C2′-fluoro diastereomers 12 and
2
2
molecular sieves were used to dry DMF, and the solvents were
dispensed under nitrogen. All reactions were performed under an inert
atmosphere of argon in oven-dried (130−150 °C) glassware. Thin-
layer chromatography was performed on precoated silica gel 60 F254
plates. The detection of compounds was carried out with UV light.
Purification by flash chromatography was performed using a medium-
pressure flash chromatography system and flash column silica
cartridges with the indicated solvent system. HPLC purifications
were performed on instruments equipped with a reversed-phase
Phenomenex Gemini 10 μm C18 110 Å (250 × 21.2 mm) column. All
NMR spectra were recorded on a 400 MHz spectrometer at 400 MHz
1
3 had nearly identical MICs, while the C3′-fluoro analogue 14
was 4-fold more potent than 15. The activities of the
difluorinated analogues also significantly diverged, and 16
(
MIC = 0.78 μM) was ca. 50-fold more potent than 17.
1
13
19
1
Comparison of the conformational disposition of each inhibitor
with the observed biochemical and antibacterial activities shows
an excellent qualitative positive correlation between the C3′-
endo conformation and biological activity.
for H, 100 MHz for C, and 376 MHz for F. H NMR spectra were
referenced to residual CDCl (7.27 ppm), DMSO-d (2.50 ppm), or
3
6
CD
OD (3.31 ppm); 13C NMR spectra were referenced to CDCl
3
3
(
77.23 ppm) DMSO−D (39.51 ppm), or CD OD (49.15 ppm); and
6
3
1
9
F NMR spectra were referenced to hexafluorobenzene (−162.9
In Vivo Pharmacokinetics. All compounds were then
subjected to single-dose pharmacokinetic (PK) studies in a
crossover experiment using cannulated rats and administered
orally (p.o.) at 25 mg/kg then intravenously (i.v.) at 2.5 mg/kg
after a 3-day washout period (Figure 3). The serum
concentration versus time curves (Figure 2) was employed
for the calculation of pharmacokinetic parameters by non-
compartmental analysis. Each of the fluorinated analogues
exhibited improved oral bioavailability (%F), half-life (t ),
3
6
ppm) or trifluoroacetic acid (−76.5 ppm). NMR chemical shift data
are reported as follows: chemical shift, multiplicity (br = broad, s =
singlet, d = doublet, t = triplet, q = quartet, m = multiplet, ABq = AB
quartet, dm = doublet of multiplets), coupling constant, integration.
Coupling constants are given in hertz (Hz). H and C NMR peak
assignments were based on gCOSY and gHMQC NMR spectra,
respectively. 19F NMR peaks were assigned using proton-fluorine
coupling constants. High-resolution mass spectra (HRMS) were
obtained on a TOF instrument.
1
13
1/2
6
General Procedure 1: 5′-O,N -Ditritylation. The nucleoside of
maximum serum concentration (Cmax), and area under the
concentration−time curve (AUC) relative to SAL-AMS 10 as
well as decreased clearance (CL) (Table 2). Difluorinated
analogue 17 achieved the most improved pharmacokinetic
profile compared to SAL-AMS (10) with about a 4-fold
increase in %F, 15-fold higher Cmax, and ca. 75-fold increased
oral exposure as defined by its oral AUC, which is largely
attributed to its remarkable ca. 25-fold increase in half-life to
choice was dried prior use by coevaporation with anhydrous pyridine.
To a stirred solution of the nucleoside (1 mmol, 1 equiv) in pyridine
(
13 mL) were added DMAP (0.8 equiv) and trityl chloride (2.3
equiv), and the reaction mixture was heated at 80 °C for 4 h. The
reaction mixture was cooled to rt, quenched with EtOH (7 mL),
concentrated under reduced pressure, and coevaporated with toluene
(2 × 10 mL) to obtain a crude residue. Purification by flash
chromatography (dry loading, SiO , EtOAc/hexanes gradient)
afforded the 5′-O,N -ditritylated product.
2
6
267 min. This is also clearly noticeable on concentration versus
6
N -Trityl-9-[2-O-(4-methoxybenzyl)-5-O-trityl-β-D-ribofuranosyl]-
time plots. Pairwise comparison (i.e., 12 vs 13, 14 vs 15, and 16
vs 17) of the oral exposure levels indicated a strong correlation
between sugar conformation and relative oral AUC levels. In all
cases, analogues favoring the C2′-endo conformation possessed
ca. 2-fold enhanced %F and 3−13-fold greater oral AUCs
6
adenine (21) and N -Trityl-9-[3-O-(4-methoxybenzyl)-5-O-trityl-β-D-
ribofuranosyl]adenine (22). An isomeric mixture of 2′-OPMB
adenosine 19 and 3′-OPMB adenosine 20 was prepared from
1
6
adenosine 18 employing a published procedure. A mixture of 21
and 22 was prepared from a mixture of 19 and 20 (5.3 g, 13.7 mmol)
G
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using the general procedure 1. Flash chromatography (SiO , gradient:
added a solution of alcohol 21 (4.7 g, 5.39 mmol, 1 equiv) in CH Cl
2
2
2
hexanes to 50% EtOAc in hexanes) afforded a mixture of 21 and 22
(50 mL). Anhydrous Na CO powder (0.1 g) was added, and the
2 3
(
5.0 g, 42%) as a white solid which was used in the next step without
reaction mixture was stirred at rt for 3 h. The reaction was quenched
by addition of 1 M Na S O (5 mL), satd NaHCO (5 mL), brine (5
mL), and EtOAc (15 mL). The layers were separated, and the aqueous
further separation. The ratio of 21 and 22 in the mixture was
determined to be ∼3:1 by H NMR integrations of anomeric protons.
2
2
3
3
1
1
Major isomer 21: R = 0.53 (1:1 EtOAc/hexanes); H NMR (400
layer was extracted with EtOAc (2 × 15 mL). The combined organic
f
MHz, CDCl ) δ 7.99, 7.85 (2s, 2H; H-2, H-8), 7.42−7.21 (m, 30H; 6
layers were dried (MgSO ), filtered, and concentrated under reduced
3
4
6
×
C H ), 7.14 (d, J = 8.6 Hz, 2H; -PMB), 6.93 (s, 1H; N -H), 6.77 (d,
pressure. Purification by flash chromatography (SiO , 40:60 EtOAc/
6
5
2
3
J = 8.6 Hz, 2H; -PMB), 6.09 (d, J(1′,2′) = 4.4 Hz, 1H; H-1′), 4.68−
hexanes) afforded the product (3.9 g, 83%) as a white solid: R = 0.45
f
1
4
.66 (m, 1 H; H-2′), 4.64 (ABq, Δδ = 42.8 Hz, J = 11.6 Hz, 2H;
(1:1 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 7.92, 7.75 (2s,
3
3
3
-
PMB), 4.31−4.27 (m, 1H; H-3′), 4.19 (td, J(5′,4′) = 3.3, J(3′,4′) ≈
2H; H-2, H-8), 7.39−7.17 (m, 30H; 6 × C H ), 7.02 (d, J = 8.5 Hz,
6
5
3
3
6
J(5″,4′) ≈ 4.6 Hz, 1H; H-4′), 3.77 (s, 3H; -PMB), 3.47 (dd, J(5′,4′)
2H; -PMB), 6.96 (s, 1H; N -H), 6.69 (d, J = 8.5 Hz, 2H; -PMB), 6.10
2
3
3
3
=
3.3, J(5″,5′) = 10.6 Hz, 1H; H-5′), 3.34 (dd, J(5″,4′) = 4.5,
(d, J(1′,2′) = 7.8 Hz, 1H; H-1′), 5.21 (d, J(1′,2′) = 7.8 Hz, 1H; H-
2
3
J(5″,5′) = 10.6 Hz, 1H; H-5″), 2.66 (d, J(OH,3′) = 5.6 Hz, 1H; 3′−
2′), 4.73 (ABq, Δδ = 34.4 Hz, J = 11.7 Hz, 2H; -PMB), 4.32−4.31 (m,
OH); 13C NMR (100 MHz, CDCl ) δ 160.0, 154.3, 152.5, 148.8,
3
2
1H; H-4′), 3.72 (s, 3H; -PMB), 3.49 (dd, J(5″,4′) = 4.0, J(5′,5″) =
3
3
2
1
1
45.2, 143.8, 138.7, 130.0, 129.2, 128.9, 128.8, 128.1, 128.0, 127.4,
10.5 Hz, 1H; H-5′), 3.40 (dd, J(5′,4′) = 2.4, J(5′,5″) = 10.5 Hz, 1H;
13
27.1, 121.6, 114.2, 87.3, 87.2, 84.2, 80.5, 73.0, 71.6, 70.3, 63.6, 55.5;
H-5″); C NMR (100 MHz, CDCl ) δ 209.1, 159.9, 154.3, 152.7,
3
+
HRMS (ESI+) m/z calcd for C H N O Na [(M + Na) ] 894.3626,
149.2, 145.1, 143.4, 138.7, 130.0, 129.2, 128.8, 128.2, 128.1, 128.0,
56
49
5
5
found 894.3658 (Δ 3.5 ppm, acquired as a mixture of 21 and 22).
127.4, 127.2, 121.4, 114.1, 87.4, 84.6, 81.3, 78.3, 72.8, 71.7, 63.3, 55.4;
6
+
N -Trityl-9-[2-O-(4-methoxybenzyl)-3-deoxy-3-fluoro-5-O-trityl-β-
HRMS (ESI+) m/z calcd for C56
H
47
N
O
5
5
Na [(M + Na) ] 892.3469,
6
D-xylofuranosyl]adenine (23) and N -Trityl-9-[3-O-(4-methoxyben-
zyl)-2-deoxy-2-fluoro-5-O-trityl-β-D-arabinofuranosyl]adenine (24).
To a solution of a mixture of 21 and 22 (4.70 g, 5.39 mmol, 1.0 equiv,
found 892.3425 (Δ − 4.9 ppm).
6
N -Trityl-9-[2-O-(4-methoxybenzyl)-5-O-trityl-β-D-xylofuranosyl]-
adenine (26). To AcOH (57 mL) cooled to 4 °C was added NaBH
4
7
3% 21) in CH Cl (45 mL) and pyridine (4.3 mL, 43.27 mmol, 10
(1.30 g, 34.37 mmol, 6.5 mmol), and the mixture was stirred for 10
min. Ketone 25 (4.60 g, 5.29 mmol, 1 equiv) was added as a dry
powder, and the reaction mixture was stirred for 2 h at 4 °C during
which time the reaction solidified. The resulting frozen reaction
mixture was allowed to melt by warming to rt, immediately evaporated,
and coevaporated with EtOH (2 × 50 mL) under reduced pressure.
The residue was partitioned between CHCl (100 mL) and H O (100
2
2
equiv) in a polypropylene tube was added DAST (3.5 mL, 26.49
mmol, 5.0 equiv) dropwise, and the mixture was stirred at rt for 24 h.
CH Cl (50 mL) was added to the reaction mixture, and the organic
layer was washed with satd NaHCO and water. The organic layer was
dried (Na SO ), filtered, and concentrated under reduced pressure.
2
2
3
2
4
Purification by flash chromatography (SiO , gradient: hexanes to 30%
2
3
2
EtOAc in hexanes) afforded 23 (1.86 g, 55% from 21) and 24 (0.55 g,
mL), and the organic layer was washed with satd NaHCO and brine,
3
4
2% from 22) as white solids.
3: R = 0.35 (1:3 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ
dried (Na SO ), and evaporated under reduced pressure. Purification
2
4
1
2
by flash chromatography (SiO , 50:50 EtOAc/hexanes) afforded the
f
3
2
8
.07, 7.77 (2s, 2H; H-2, H-8), 7.49−7.24 (m, 32H; 6 × C H and
product (3.37 g, 73%) as a white solid: R = 0.58 (1:1 EtOAc/
6
5
f
6
1
-PMB), 6.96 (s, 1H; N -H), 6.86 (d, J = 8.8 Hz, 2H; -PMB), 6.31 (br s,
hexanes); H NMR (400 MHz, CDCl ) δ 7.89, 7.72 (2s, 2H; H-2, H-
3
3
2
3
1
4
=
H; H-1′), 5.07 (dd, J(3′,4′) = 2.5, J(3′,F3′) = 50.6 Hz, 1H; H-3′),
8), 7.44−7.16 (m, 32H; 6 × C H and -PMB), 7.10 (d, J(OH,3′) =
6
5
3
6
.76 (ABq, Δδ = 62.8 Hz, J = 11.6 Hz, 2H; -PMB), 4.56 (dtd, J(3′,4′)
11.0 Hz, 1H; 3′−OH), 7.04 (s, 1H; N -H), 6.88 (d, J = 8.5 Hz, 2H;
3
3
3
3
2.3, J(5′,4′) = 6.1, J(5″,4′) = 6.2, J(4′,F3′) = 31.3 Hz, 1H; H-4′),
-PMB), 5.77 (d, J(1′,2′) = 1.7 Hz, 1H; H-1′), 4.57 (ABq, Δδ = 73.2
3
3
4
.38 (d, J(2′,F3′) = 13.9 Hz, 1H; H-2′), 3.79 (s, 3H; -PMB), 3.62
Hz, J = 11.3 Hz, 2H; -PMB), 4.35 (d, J(1′,2′) = 1.7 Hz, 1H; H-2′),
3
2
3
3
3
3
(
dd, J(5″,4′) = 6.8, J(5′,5″) = 9.4 Hz, 1H; H-5″), 3.48 (dd, J(5′,4′)
4.28 (ddd, J(3′,4′) = 3.2, J(5′,4′) = 5.7, J(5″,4′) = 6.4, 1H; H-4′),
3 3
2
13
=
5.9, J(5′,5″) = 9.7 Hz, 1H; H-5′); C NMR (100 MHz, CDCl ) δ
4.23 (dd, J(3′,4′) = 3.2, J(OH,3′) = 11.0 Hz, 1H; H-3′), 3.81 (s, 3H;
3
5
13
1
59.9, 154.2, 152.5, 148.5, 145.2, 143.7, 137.8 (d, J(C8,F3′) = 5.8
-PMB), 3.58−3.51 (m, 2H; H-5′/5″); C NMR (100 MHz, CDCl ) δ
3
Hz), 129.9, 129.2, 128.8, 128.8, 128.1, 128.1, 127.4, 127.1, 121.2,
159.8, 154.6, 151.6, 146.9, 144.9, 144.0, 140.3, 129.7, 129.3, 129.1,
128.9, 128.2, 127.9, 127.2, 127.1, 122.1, 114.2, 91.3, 90.1, 87.2, 82.8,
1
1
14.2, 94.1 (d, J(C3′,F3′) = 184.9 Hz), 88.4, 87.3, 85.3 (d,
2
2
J(C2′,F3′) = 27.3 Hz), 82.1 (d, J(C4′,F3′) = 19.0 Hz), 72.5, 71.6,
74.6, 72.6, 71.7, 62.3, 55.5; HRMS (ESI+) m/z calcd for
3
19
+
6
0.8 (d, J(C5′,F3′) = 9.4 Hz), 55.5; F NMR (376 MHz, CDCl ) δ
C
56
H
49
N
5
O
5
Na [(M + Na) ] 894.3626, found 894.3673 (Δ 5.2 ppm).
3
3
3
2
6
−
202.3 (ddd, J(2′,F3′) = 14.0, J(4′,F3′) = 31.4, J(3′,F3′) = 50.6
N -Trityl-9-[3-deoxy-3-fluoro-2-O-(4-methoxybenzyl)-5-O-trityl-β-
D-ribofuranosyl]adenine (27). To a solution of alcohol 26 (2.3 g, 2.64
+
Hz); HRMS (ESI+) m/z calcd for C H FN O Na [(M + Na) ]
56
48
5
4
mmol, 1.0 equiv) in CH Cl (50 mL) and pyridine (2.1 mL, 26.4
8
96.3583, found 896.3604 (Δ 2.3 ppm).
2
2
1
2
4: R = 0.27 (1:3 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ
mmol, 10 equiv) was added DAST (2.1 mL, 15.84 mmol, 6.0 equiv)
dropwise, and the mixture was stirred at rt for 24 h. CH Cl (50 mL)
was added to the reaction mixture, and the organic layer was washed
with satd NaHCO , water, and brine. The organic layer was dried
Na SO ), filtered, and concentrated under reduced pressure.
f
3
5
.04 (s, 1H; H-2), 7.97 (d, J(8,F2′) = 3.1 Hz, 1H; H-8), 7.45−7.19
2
2
6
3
3
2
(
2
4
Purification by flash chromatography (SiO , 40:60 EtOAc/hexanes)
2
3
3
afforded the product (1.4 g, 61%) as a white solid: R = 0.35 (1:2
f
1
3
EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 7.91, 7.79 (2s, 2H;
.17−4.16 (m, 1H; H-4′), 3.77 (s, 3H; -PMB), 3.40 (dd, J(4′,5′) =
3
2
3
2
H-2, H-8), 7.38−7.22 (m, 30H; 6 × C H ), 7.09 (d, J = 8.5 Hz, 2H;
.4, J(5′,5″) = 10.4 Hz, 1H; H-5′), 3.33 (dd, J(4′, 5″) = 5.0, J(5′,5″)
6
5
6
13
-PMB), 6.93 (s, 1H; N -H), 6.74 (d, J = 8.6 Hz, 2H; -PMB), 6.06 (d,
10.2 Hz, 1H; H-5″); C NMR (100 MHz, CDCl ) δ 159.8, 154.3,
3
3
3
3
3
4
J(1′,2′) = 7.5 Hz, 1H; H-1′), 5.11 (ddd, J(2′,3′) = 4.3, J(1′,2′) = 7.6,
3 3
1
1
52.6, 148.8, 145.2, 143.8, 139.6 (d, J(C8,F2′) = 6.3 Hz), 129.8,
29.2, 128.8, 128.7, 128.1, 128.0, 127.4, 127.1, 120.4, 114.2, 93.3 (d,
J(2′,F3′) = 21.6 Hz, 1H; H-2′), 4.99 (ddd, J(3′,4′) = 1.4, J(2′,3′) =
3
1
2
J(C2′,F2′) = 192.7 Hz), 87.1, 83.2 (d, J(C1′,F2′) = 16.8 Hz), 81.8,
4.4, J(3′,F3′) = 54.4 Hz, 1H; H-3′), 4.54 (ABq, Δδ = 23.2 Hz, J =
2
19
3
8
1.6 (d, J(C3′,F2′) = 25.7 Hz), 72.3, 71.6, 63.3, 55.5; F NMR (376
11.7 Hz, 2H; -PMB), 4.42 (dm, J(4′,F3′) = 26.4 Hz, 1H; H-4′), 3.75
5
3
3
2
MHz, CDCl ) δ −197.3 (dddd, J(8,F2′) = 3.0, J(3′,F2′) = 17.9,
(s, 3H; -PMB), 3.47 (dd, J(5′,4′) = 4.8, J(5′,5″) = 10.5 Hz, 1H; H-
3 2 13
3
3
2
J(1′,F2′) = 21.3, J(2′,F2′) = 51.3 Hz); HRMS (ESI+) m/z calcd for
5′), 3.30 (dd, J(5″,4′) = 4.1, J(5′,5″) = 10.5 Hz, 1H; H-5″);
C
+
NMR (100 MHz, CDCl ) δ 159.8, 154.3, 152.5, 149.1, 145.2, 143.6,
C H FN O Na [(M + Na) ] 896.3583, found 896.3624 (Δ 4.5
ppm).
3
56
48
5
4
1
1
39.5, 129.8, 129.2, 129.0, 128.8, 128.1 ( × 2), 127.4, 127.1, 121.8,
1
6
14.1, 90.4 (d, J(C3′,F3′) = 186.6 Hz), 87.5, 86.5, 82.7 (d,
N -Trityl-3′-deoxy-2′-O-(4-methoxybenzyl)-3′-oxo-5′-O-tritylade-
nosine (25). To a solution of Dess−Martin periodinane (2.74 g, 6.468
mmol 1.2 equiv) in CH Cl (50 mL) and t-BuOH (0.67 mL) was
2
2
J(C2′,F3′) = 23.5 Hz), 77.6 (d, J(C4′,F3′) = 15.8 Hz), 72.7, 71.6,
3
19
63.0 (d, J(C5′,F3′) = 9.9 Hz), 55.5; F NMR (376 MHz, CDCl ) δ
2
2
3
H
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
3
3
2
3
3
2
−
199.3 (ddd, J(2′,F3′) = 21.6, J(4′,F3′) = 26.4, J(3′,F3′) = 54.3
= 9.6, J(F2′,F3′) = 14.9, J(4′,F3′) = 31.1, J(3′,F3′) = 49.5 Hz; F-3′);
+
+
Hz); HRMS (ESI+) m/z calcd for C H FN O Na [(M + Na) ]
HRMS (ESI+) m/z calcd for C H F N O [(M + H) ] 756.3145,
56
48
5
4
48 40
2
5
2
8
96.3583, found 896.3546 (Δ −4.1 ppm).
found 756.3138 (Δ −0.9 ppm).
6
6
N -Trityl-9-(2-deoxy-2-fluoro-5-O-trityl-β-D-ribofuranosyl)-
adenine (29). This was prepared from 2′-deoxy-2′-fluoroadenosine 28
0.50 g, 1.86 mmol) using the general procedure 1. Purification by
N -Trityl-9-(3-deoxy-3-fluoro-5-O-trityl-β-D-arabinofuranosyl)-
6
adenine (33) and N -Trityl-9-(2-deoxy-2-fluoro-5-O-trityl-β-D-
21
(
xylofuranosyl)adenine (34). To a solution of epoxide 32 3.20 g,
flash chromatography (SiO , 50:50 EtOAc/hexanes) afforded the
4.36 mmol, 1.0 equiv) in 2-ethoxyethanol (40 mL) were added KHF
2
2
product (1.10 g, 79%) as a white solid: R = 0.40 (1:1 EtOAc/
(1.50 g, 19.2 mmol, 4.4 equiv) and NaF (2.20 g, 52.39 mmol, 12.0
equiv), and the mixture was heated under reflux at 145 °C for 15 h.
The reaction mixture was allowed to cool to rt, solvent was removed
f
1
hexanes); H NMR (400 MHz, CDCl ) δ 7.98, 7.92 (2s, 2H; H-2, H-
3
6
8
), 7.42−7.18 (m, 30 H; 6 × C H ), 7.10 (s, 1H; N -H), 6.17 (dd,
6
5
3
3
3
J(1′,2′) = 2.4, J(1′,F2′) = 17.6 Hz, 1H; H-1′), 5.54 (ddd, J(2′,1′) =
under reduced pressure, and the residue was diluted with CHCl (40
3
.4, 3J(2′,3′) = 4.5, J(2′,F2′) = 53.1 Hz, 1H; H-2′), 4.73 (ddd,
3 3
2
mL) and washed with water. The organic layer was dried (MgSO4),
2
3
filtered, and concentrated under reduced pressure. The ratio of 33 and
J(2′,3′) = 4.5, J(3′,4′) = 6.9, J(3′,F2′) = 17.4 Hz, 1H; H-3′), 3.55−
1
3
2
34 was determined to be 3.1:1 by H NMR of the crude product.
3
.52 (m, 1H; H-4′), 3.53 (dd, J(4′,5′) = 3.1, J(5′,5″) = 10.7 Hz, 1H;
3
2
1
3
Purification by flash chromatography (SiO , 35:65 EtOAc/hexanes)
H-5′), 3.41 (dd, J(4′,5″) = 4.6, J(5′,5″) = 10.7 Hz, 1H; H-5″);
C
2
afforded the product as a mixture of 33 and 34 (2.12 g, 65%
combined) as a white solid. A few pure fractions of each regioisomer
were separately collected and characterized.
NMR (CDCl ) δ 154.3, 152.6, 148.4, 145.0, 143.6, 138.8, 129.2, 128.8,
3
1
1
8
28.1 ( × 2), 127.4, 127.1, 121.4, 93.4 (d, J(C2′,F2′) = 186.8 Hz),
2
2
7.3, 87.0 (d, J(C1′,F2′) = 33.1 Hz), 82.6, 71.6, 70.3 (d, J(C3′,F2′) =
1
6.5 Hz), 63.0; 19F NMR (CDCl ) δ −205.7 (dt, J(3′,F2′) = 17.4,
3
33: R = 0.44 (1:1 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ
1
f
3
3
3
2
8.05, 7.96 (2s, 2H; H-2, H-8), 7.44−7.18 (m, 30H; 6 × C H ), 7.07 (s,
J(1′,F2′) = 17.4, J(2′,F2′) = 53.1 Hz); HRMS (ESI+) m/z calcd for
6
5
6
3
+
1H; N -H), 6.18−6.17 (m, 1H; H-1′), 5.52 (d, J(2′,OH) = 7.6 Hz,
C H FN O [(M + H) ] 754.3188, found 754.3195 (Δ 0.9 ppm).
48
41
5
3
2
6
1H; −OH), 5.04 (dm, J(3′,F3′) = 51.6 Hz, 1H; H-3′), 4.53−4.48 (m,
N -Trityl-9-[2-deoxy-2-fluoro-3-O-(4-methoxybenzyl)-5-O-trityl-β-
3
1
2
H; H-4′), 4.30 (dm, J(2′,F3′) = 28.8 Hz, 1H; H-2′), 3.57−3.44 (m,
D-ribofuranosyl]adenine (30). To a solution of 29 (0.35 g, 0.464
mmol, 1 equiv) in THF (7 mL) at 0 °C was added 60% NaH (23 mg,
13
H; H-5′, H-5″); C NMR (CDCl ) δ 154.4, 152.1, 148.3, 144.9,
3
1
43.4, 140.5, 129.1, 128.8, 128.2, 128.1, 127.5, 127.1, 120.8, 96.9 (d,
0.575 mmol, 1.2 equiv), and the mixture was stirred for 10 min. TBAI
1
2
J(C3′,F3′) = 183.0 Hz), 87.8, 86.0, 81.7 (d, J(C2′,F3′) = 25.4 Hz),
(
23 mg, 0.062 mmol, 0.12 equiv) and PMBCl (77 μL, 0.568 mmol, 1.2
2
3
7
4.4 (d, J(C4′,F3′) = 25.2 Hz), 71.6, 63.4 (d, J(C5′,F3′) = 9.6 Hz);
equiv) were sequentially added, and the mixture was stirred at that
temperature for a further 30 min. The reaction was slowly warmed to
rt and stirred for 15 h. The reaction was quenched with MeOH (7
mL), evaporated, and partitioned between CH Cl and H O. The
19
4 3
F NMR (CDCl ) δ −182.9 ppm (dddd, J(5′,F3′) = 2.5, J(4′,F3′) =
3
3
2
12.2, J(2′,F3′) = 28.9, J(3′,F3′) = 51.7 Hz); HRMS (ESI+) m/z
+
calcd for C48
2.7 ppm).
H40FN
O
3
Na [(M + Na) ] 776.3007, found 776.3028 (Δ
2
2
2
5
aqueous layer was extracted with CH Cl , and the combined organics
2
2
1
were dried (Na SO ) and evaporated. Purification by flash
34: R
f
= 0.51 (1:1 EtOAc/hexanes); H NMR (400 MHz, CDCl
3
) δ
and
2
4
chromatography (SiO , gradient: hexanes to 50:50 EtOAc/hexanes)
7.86, 7.84 (2s, 2H; H-2, H-8), 7.43−7.13 (m, 31H; 6 × C H
6 5
2
6
3
afforded the product (0.32 g, 78%) as a white solid: R = 0.21 (1:2
−OH), 7.12 (s, 1H; N -H), 5.93 (d, J(1′,F2′) = 25.6 Hz, 1H; H-1′),
f
1
2
EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 7.98, 7.91 (2s, 2H;
5.29 (dm, J(2′,F2′) = 49.6 Hz, 1H; H-2′), 4.34−4.28 (m, 2H; H-3′,
3
6
13
H-2, H-8), 7.34−7.17 (m, 32H; 6 × C H , -PMB), 7.01 (s, 1H; N -H),
H-4′), 3.59−3.52 (m, 2H; H-5′/5″); C NMR (CDCl
3
) δ 154.7,
6
6
3
6
1
4
.88 (d, J = 8.6 Hz, 2H; -PMB), 6.15 (d, J(1′,F2′) = 18.0 Hz, 1H; H-
151.7, 146.7, 144.8, 143.9, 140.1, 129.1, 128.9, 128.2, 127.9, 127.3,
3
2
1
2
′), 5.64 (dd, J(3′,2′) = 4.0, J(2′,F2′) = 53.1 Hz, 1H; H-2′), 4.68−
.66 (m, 1H; H-3′), 4.53 (ABq, Δδ = 48.0 Hz, J = 11.4 Hz, 2H;
127.2, 121.9, 101.0 (d, J(C2′,F2′) = 186.1 Hz), 90.1 (d, J(C1′,F2′) =
2
19
39.6 Hz), 87.3, 82.9, 74.6 (d, J(C3′,F2′) = 25.8 Hz), 71.8, 62.0;
F
3
3
3
3
3
-
PMB), 4.27 (dt, J(4′,5′) = 3.5, J(4′,5″) = 3.5, J(3′,4′) = 7.4 Hz, 1H;
NMR (CDCl ) δ −177.8 (ddd, J(3′,F2′) = 15.6, J(1′,F2′) = 25.5,
3
3
2
2
H-4′), 3.80 (s, 3H; -PMB), 3.48 (dd, J(4′,5′) = 3.1, J(5′,5″) = 10.9
J(2′,F2′) = 49.5 Hz); HRMS (ESI+) m/z calcd for C48
H
40FN
5
O
3
Na
3
2
+
Hz, 1H; H-5′), 3.24 (dd, J(4′, 5″) = 4.2, J(5′,5″) = 10.3 Hz, 1H; H-
[(M + Na) ] 776.3007, found 776.3021 (Δ 1.8 ppm).
1
9
3
6
5
″); F NMR (376 MHz, CDCl ) δ −204.6 (dt, J(1′,F2′) = 18.5,
N -Trityl-9-(2,3-dideoxy-2,3-difluoro-5-O-trityl-β-D-ribofuranosyl)-
adenine (35). To a solution of a mixture of 33 and 34 (1.94 g, 2.57
mmol, 1.0 equiv) in toluene (30 mL) and pyridine (0.57 mL, 4.72
mmol, 1.8 equiv) was added DAST (2.04 mL, 15.44 mmol, 6.0 equiv)
dropwise, and the mixture was stirred at rt for 1 h before the mixture
was heated at 80 °C for an additional 3 h. EtOAc (100 mL) was added
to the reaction mixture, and the organic layer was washed with satd
3
3
2
J(3′,F2′) = 18.5, J(2′,F2′) = 52.8 Hz); HRMS (ESI+) m/z calcd for
+
C H FN O [(M + H) ] 874.3763, found 874.3756 (Δ −0.8 ppm).
56
49
5
4
6
N -Trityl-9-(2,3-dideoxy-2,3-difluoro-5-O-trityl-β-D -
xylofuranosyl)adenine (31). To a solution of alcohol 29 (2.30 g, 3.05
mmol, 1.0 equiv) in CH Cl (50 mL) and pyridine (2.40 mL, 29.8
2
2
mmol, 10 equiv) was added DAST (2.0 mL, 15.14 mmol, 5.0 equiv)
dropwise, and the mixture was stirred at rt for 25 h. CH Cl (50 mL)
NaHCO
and concentrated under reduced pressure. Purification by flash
chromatography (SiO , 20:80 EtOAc/hexanes) afforded the product
(1.20 g, 62%) as a white solid: R
NMR (400 MHz, CDCl ) δ 7.93, 7.88 (2s, 2H; H-2, H-8), 7.39−7.19
and water. The organic layer was dried (MgSO ), filtered,
2
2
3
4
was added to the reaction mixture, and the organic layer was washed
with satd NaHCO and water. The organic layer was dried (Na SO ),
3
2
4
2
1
filtered, and concentrated under reduced pressure. Purification by flash
= 0.33 (1:2 EtOAc/hexanes); H
f
chromatography (SiO , 30:70 EtOAc/hexanes) afforded the product
3
2
6
4
1
(
m, 30H; 6 × C H ), 6.79 (s, 1H; N -H), 6.18 (ddd, J(1′,F3′) = 1.7,
(
1.79 g, 78%) as a white solid: R = 0.45 (1:2 EtOAc/hexanes); H
6
5
f
3
3
3
NMR (400 MHz, CDCl ) δ 8.08, 7.77 (2s, 2H; H-2, H-8), 7.51−7.24
J(1′,2′) = 5.0, J(1′,F2′) = 14.2 Hz, 1H; H-1′), 6.02 (ddt, J(2′,3′) ≈
3
6
3
3
3
2
(
m, 30H; 6 × C H ), 6.97 (s, 1H; N -H), 6.40 (d, J(1′,F2′) = 20.2
J(1′,2′) ≈ 4.8, J(2′,F3′) = 13.2, J(2′,F2′) = 50.9 Hz, 1H; H-2′), 5.45
3 3 3 2
6
5
3
2
Hz, 1H; H-1′), 5.42 (dd, J(2′,F3′) = 9.8, J(2′,F2′) = 48.0 Hz, 1H; H-
(ddt, J(3′,2′) ≈ J(3′,4′) ≈ 4.0, J(3′,F2′) = 7.6, J(3′,F3′) = 53.0 Hz,
3
3
2
3
2
′), 5.27 (ddd, J(3′,4′) = 3.0, J(3′,F2′) = 7.7, J(3′,F3′) = 50.0 Hz,
1H; H-3′), 4.46 (dm, J(4′,F3′) = 21.8 Hz, 1H; H-4′), 3.54 (dd,
3
3
2
3
1
H; H-3′), 4.56 (dm, J(4′,F3′) = 31.2 Hz, 1H; H-4′), 3.68 (dd,
J(5′,4′) = 4.2, J(5′,5″) = 10.8 Hz, 1H; H-5′), 3.39 (dd, J(5″,4′) =
3
2
3
2
13
J(5′,4′) = 6.5, J(5′,5″) = 9.8 Hz, 1H; H-5′), 3.54 (dd, J(5″,4′) = 6.0,
4.3, J(5′,5″) = 10.8 Hz, 1H; H-5″); C NMR (100 MHz, CDCl ) δ
3
2
13
J(5′,5″) = 9.8 Hz, 1H; H-5″); C NMR (100 MHz, CDCl ) δ 154.2,
154.4, 152.7, 148.7, 145.1, 143.5, 139.3, 129.2, 128.8, 128.1 ( × 2),
3
2
1
1
1
1
(
6
52.8, 148.6, 145.1, 143.5, 137.5 (d, J = 6.2 Hz), 129.2, 128.8, 128.2,
127.5, 127.2, 121.7, 89.7 (dd, J(C2′,F3′) = 14.4, J(C2′,F2′) = 196.3
2
1
2
1
28.1, 127.5, 127.1, 121.1, 96.1 (dd, J(C2′,F3′) = 31.7, J(C2′,F2′) =
Hz), 88.9 (dd, J(C3′,F2′) = 13.9, J(C2′,F2′) = 190.4 Hz), 87.5, 86.1
3 2 3
2
1
86.1 Hz), 92.4 (dd, J(C3′,F2′) = 30.1, J(C3′,F3′) = 184.9 Hz), 87.7
(dd, J(C1′,F3′) = 2.5, J(C1′,F2′) = 31.1 Hz), 81.3 (dd, J(C4′,F2′) =
2 3 19
2
2
d, J(C1′,F2′) = 36.6 Hz), 87.5, 81.8 (d, J(C4′,F3′) = 19.4 Hz), 71.6,
2.5, J(C4′,F3′) = 22.7 Hz), 71.6, 62.5 (d, J(C5′,F3′) = 6.4 Hz); F
3
3
19
0.4 (d, J(C5′,F3′) = 9.0 Hz); F NMR (376 MHz, CDCl ) δ
NMR (376 MHz, CDCl ) δ −206.9 (dddd, J(F2′,F3′) = 3.8,
3
2
3
4
3
3
3
3
−
191.9 (ddddd, J(4′,F2′) = 3.4, J(3′,F2′) = 7.9, J(F2′,F3′) = 15.0,
J(2′,F3′) = 13.5, J(4′,F3′) = 21.8, J(3′,F3′) = 53.3 Hz; F-3′),
2
3
2
3
J(1′,F2′) = 20.3, J(2′,F2′) = 47.7 Hz; F-2′), −208.4 (dddd, J(2′,F3′)
−213.0 (dm, J(2′,F2′) = 51.1 Hz; F-2′); HRMS (ESI+) m/z calcd for
I
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
+
C H F N O Na [(M + Na) ] 778.2964, found 778.2970 (Δ 0.8
(5 mL) and Et O (5 mL), and the mixture was stirred vigorously. The
4
8
39
2
5
2
2
ppm).
phases were separated, and MeCN (2 mL) was added to the aqueous
layer. The aqueous layer was filtered through a syringe filter, and
purification was performed by preparative reversed-phase HPLC using
a Phenomenex Gemini 10 μm C18 110 Å (250 × 21.2 mm) column at
a flow rate of 21 mL/min with a gradient from 5% to 30% MeCN in
9
-(3-Deoxy-3-fluoro-β-D-xylofuranosyl)adenine (36). To a flask
containing compound 23 (0.075 g, 0.086 mmol) was added 80%
aqueous TFA in CHCl (5 mL). After 1 h, MeOH (5 mL) was added,
and the reaction mixture was then concentrated under reduced
pressure. The residue was dissolved in MeOH (5 mL), residual TFA
was neutralized by addition of Et N (10 drops), and the mixture was
concentrated under reduced pressure. To the residue were added H O
5 mL) and Et O (5 mL), and the mixture was stirred vigorously. The
phases were separated, and MeCN (2 mL) was added to the aqueous
layer. The aqueous layer was filtered through a syringe filter, and
purification was performed by preparative reversed-phase HPLC using
a Phenomenex Gemini 10 μm C18 110 Å (250 × 21.2 mm) column at
a flow rate of 21 mL/min with a gradient from 5% to 30% MeCN in
H O over 12 min. The appropriate fractions containing the product
were pooled and lyophilized to afford the product (0.020 g, 87%) as a
white solid: H NMR (400 MHz, CD OD) δ 8.22, 8.15 (2s, 2H; H-2,
3
H O over 12 min. The appropriate fractions containing the product
2
3
were pooled and lyophilized to afford the product (0.017 g, 97%) as a
1
2
white solid: H NMR (400 MHz, CD OD) δ 8.29, 8.18 (2s, 2H; H-2,
3
3
3
(
H-8), 6.01 (d, J(1′,2′) = 8.0 Hz, 1H; H-1′), 5.12 (dd, J(2′,3′) = 4.3,
2
2
3
3
J(3′,F3′) = 54.5 Hz, 1H; H-3′), 4.98 (ddd, J(2′,3′) = 4.3, J(1′,2′) =
3
3
3
8
.0, J(2′,F3′) = 25.2 Hz, 1H; H-2′), 4.44 (dt, J(4′,5′) = 2.5, J(4′,5″)
3 4
=
2.5, J(4′,F3′) = 27.6 Hz, 1H; H-4′), 3.87 (dt, J(4′,F3′) = 2.4,
2 3
3
J(4′,5′) = 2.4, J(5′,5″) = 12.6 Hz, 1H; H-5′), 3.79 (dd, J(4′,5″) =
2
13
2
1
9
6
−
.4, J(5′,5″) = 12.7 Hz, 1H; H-5″); C NMR (100 MHz, CD OD) δ
3
2
1
57.9, 153.7, 150.2, 142.3, 121.3, 94.7 (d, J(C3′,F3′) = 182.0 Hz),
2
2
0.5, 86.6 (d, J(C4′,F3′) = 22.1 Hz), 74.7 (d, J(C2′,F3′) = 16.5 Hz),
1
3
3
19
3.2 (d, J(C5′,F3′) = 11.6 Hz); F NMR (376 MHz, CD OD) δ
3
3
3
H-8), 6.09 (d, J(1′,2′) = 2.0 Hz, 1H; H-1′), 5.10 (ddd, J(2′,3′) = 1.8,
3
3
2
199.6 (dt, J(2′,F3′) ≈ J(4′,F3′) = 26.5, J(3′,F3′) = 53.8 Hz);
3
2
3
J(3′,4′) = 3.3, J(3′,F3′) = 51.7 Hz, 1H; H-3′), 4.72 (dt, J(2′,3′) =
+
HRMS (ESI+) m/z calcd for C H FN O Na [(M + Na) ] 292.0816,
.8, 3J(1′,2′) = 1.9, J(2′,F3′) = 13.9 Hz, 1H; H-2′), 4.47 (dtd,
3 3 3
3
10 12
5
3
1
found 292.0816 (Δ <1 ppm).
-(2,3-Dideoxy-2,3-difluoro-β-D-xylofuranosyl)adenine (39). To a
flask containing compound 31 (0.089 g, 0.118 mmol) was added 80%
3
J(3′,4′) = 3.2, J(5′,4′) ≈ J(5″,4′) = 5.8, J(4′,F3′) = 27.9 Hz, 1H; H-
9
3
3
4
′), 3.98 (dd, J(5′,4′) = 5.7, J(5″,5′) = 11.8 Hz, 1H; H-5′), 3.93
4 3 3
(
ddd, J(5″,F3′) = 1.6, J(5″,4′) = 6.1, J(5″,5′) = 11.9 Hz, 1H; H-5″);
aqueous TFA in CHCl (5 mL). After 1 h, MeOH (5 mL) was added,
1
5
3
2
3
3
C NMR (100 MHz, CD OD) δ 157.5, 154.1, 150.4, 140.4 (d,
3
and the reaction mixture was then concentrated under reduced
1
J(C8,F3′) = 6.4 Hz), 120.4, 96.9 (d, J(C3′,F3′) = 184.0 Hz), 91.6 (d,
pressure. The residue was treated with satd NaHCO (20 mL) and
3
2
J(C1′,F3′) = 1.5 Hz), 84.1 (d, J(C4′,F3′) = 19.3 Hz), 79.9 (d,
extracted with EtOAc (3 × 20 mL). The organic layer was dried
3
19
J(C2′,F3′) = 26.6 Hz), 60.2 ppm (d, J(C5′,F3′) = 10.2 Hz);
F
(MgSO ), filtered, and concentrated under reduced pressure.
4
3
NMR (376 MHz, CD OD) δ −203.2 (ddd, J(2′,F3′) = 13.9,
Purification by flash chromatography (SiO , 98:2 EtOAc/MeOH)
3
2
3
2
J(4′,F3′) = 27.9, J(3′,F3′) = 51.7 Hz); HRMS (ESI+) m/z calcd for
afforded the product (0.023 g, 80%) as a white solid: R = 0.28 (5:95
f
+
1
C H FN O Na [(M + Na) ] 292.0816, found 292.0823 (Δ 2.4
MeOH/EtOAc); H NMR (400 MHz, CD OD) δ 8.23, 8.17 (2s, 2H;
10
12
5
3
3
3
3
ppm).
-[2-Deoxy-2-fluoro-β-D-arabinofuranosyl]adenine (37). To a
flask containing compound 24 (0.060 g, 0.069 mmol) was added
0% aqueous TFA in CHCl (5 mL) to form a brown solution. After 1
H-2, H-8), 6.39 (dd, J(1′,2′) = 2.4, J(1′,F2′) = 18.9 Hz, 1H; H-1′),
3 3 3 2
9
5.73 (ddt, J(1′,2′) ≈ J(2′,3′) ≈ 1.9, J(2′,F3′) = 11.6, J(2′,F2′) =
3 3
48.5 Hz, 1H; H-2′), 5.47 (dddd, J(2′,3′) = 1.8, J(3′,4′) = 3.6,
3
2
3
8
J(3′,F2′) = 10.1, J(3′,F3′) = 50.1 Hz, 1H; H-3′), 4.50 (dm, J(4′,F3′)
3
3
2
h, MeOH (5 mL) was added, and the reaction mixture was then
concentrated under reduced pressure. The residue was dissolved in
MeOH (5 mL), residual TFA was neutralized by addition of Et N (10
drops), and the mixture was concentrated under reduced pressure. To
the residue were added H O (5 mL) and Et O (5 mL), and the
mixture was stirred vigorously. The phases were separated, and MeCN
2 mL) was added to the aqueous layer. The aqueous layer was filtered
through a syringe filter and purification was performed by preparative
reversed-phase HPLC using a Phenomenex Gemini 10 μm C18 110 Å
250 × 21.2 mm) column at a flow rate of 21 mL/min with a gradient
from 5% to 30% MeCN in H O over 12 min. The appropriate
=
1
27.2 Hz, 1H; H-4′), 4.00 (dd, J(4′,5′) = 5.5, J(5′,5″) = 11.9 Hz,
13
H; H-5′), 3.97−3.92 (m, 1H; H-5″); C NMR (100 MHz, CD OD)
3
3
δ 157.6, 154.3, 150.5, 140.3 (d, J = 5.7 Hz), 120.3, 97.5 (dd,
2
1
2
J(C2′,F3′) = 31.1, J(C2′,F2′) = 184.9 Hz), 93.9 (dd, J(C3′,F2′) =
1
3
2
2
2
29.2, J(C2′,F2′) = 183.9 Hz), 88.5 (dd, J(C1′,F3′) = 1.9, J(C1′,F2′)
2 3
=
36.2 Hz), 84.0 (d, J(C4′,F3′) = 19.7 Hz), 59.8 (d, J(C5′,F3′) = 9.8
19 3
(
Hz); F NMR (376 MHz, CD OD) δ −192.3 (ddm, J(1′,F2′) =
3
2
3
1
9.0, J(2′,F2′) = 48.5 Hz; F-2′), −207.3 (ddt, J(F2′,F3′) = 11.8,
3
3
2
J(2′,F3′) = 11.8, J(4′,F3′) = 27.0, J(3′,F3′) = 50.5 Hz; F-3′); HRMS
(
+
(
ESI+) m/z calcd for C H F N O Na [(M + Na) ] 294.0773, found
10 11 2 5 2
2
2
94.0768 (Δ −1.7 ppm).
9-(2,3-Dideoxy-2,3-difluoro-β-D-ribofuranosyl)adenine (40). To a
flask containing compound 35 (0.138 g, 0.182 mmol) was added 80%
aqueous TFA in CHCl (3 mL). After 1 h, MeOH (5 mL) was added,
fractions containing the product were pooled and lyophilized to afford
the product (0.017 g, 89%) as a white solid: H NMR (400 MHz,
1
5
CD OD) δ 8.33 (d, J(8,F2′) = 2.1 Hz, 1H; H-8), 8.21 (s, 1H; H-2),
3
3
3
3
6
.48 (dd, J(1′,2′) = 4.1, J(1′,F2′) = 16.1 Hz, 1H; H-1′), 5.14 (ddd,
3
3 2
and the reaction mixture was then concentrated under reduced
J(2′,3′) = 3.0, J(1′,2′) = 4.2, J(2′,F2′) = 52.2 Hz, 1H; H-2′), 4.53
pressure. The residue was treated with satd NaHCO (7 mL) and
3
3
3
3
(
ddd, J(2′,3′) = 3.0, J(3′,4′) = 4.8, J(3′,F2′) = 18.2 Hz, 1H; H-3′),
3 3 3
extracted with EtOAc (3 × 7 mL). The organic layer was dried
4
(
.01 (q, J(4′,5′) ≈ J(4′, 5″) ≈ J(4′,3′) = 4.6 Hz, 1H; H-4′), 3.87
(
MgSO ), filtered, and concentrated under reduced pressure.
5 3 2
4
ddd, J(F2′,5′) = 1.4, J(4′,5′) = 4.0, J(5′,5″) = 12.2 Hz, 1H; H-5′),
3
2
1
3
Purification by flash chromatography (SiO
2
, 98:2 EtOAc/MeOH)
= 0.40 (5:95
MeOH/EtOAc); H NMR (400 MHz, DMSO-d ) δ 8.57 (s, 1H), 8.52
6
3
(
.81 (dd, J(4′,5″) = 5.2, J(5′,5″) = 12.2 Hz, 1H; H-5″); C NMR
4
afforded the product (0.039 g, 80%) as a white solid: R
f
100 MHz, CDCl ) δ 157.5, 154.2, 150.5, 141.8 (d, J(C8,F2′) = 4.3
3
1
1
3
Hz), 119.8, 97.1 (d, J(C2′,F2′) = 192.9 Hz), 85.9 (d, J(C4′,F2′) =
4
3
2
2
(br s, 2H; -NH ), 8.38 (s, 1H), 6.36 (ddd, J(1′,F3′) = 1.6, J(1′,2′) =
2
3
4
.0 Hz), 84.5 (d, J(C1′,F2′) = 17.2 Hz), 74.9 (d, J(C3′,F2′) = 24.5
3
4 19
5.8, J(1′,F2′) = 13.6 Hz, 1H; H-1′), 5.90 (dddd, J(2′,3′) = 4.3,
3 3 2
Hz), 62.3 (d, J(C3′,F2′) = 1.5 Hz); F NMR (376 MHz, CD OD) δ
3
3
3
2
J(1′,2′) = 5.8, J(2′,F3′) = 16.6, J(2′,F2′) = 50.3 Hz, 1H; H-2′), 5.53
2 3
−
199.1 (dt, J(1′,F2′) = 17.2, J(3′,F2′) = 17.2, J(2′,F2′) = 52.2 Hz);
+
(dm, J(3′,F3′) = 52.9 Hz, 1H; H-3′), 4.42 (dm, J(4′,F3′) = 24.0 Hz,
HRMS (ESI+) m/z calcd for C H FN O Na [(M + Na) ] 292.0816,
10
12
5
3
1
3
1
H; H-4′), 3.70−3.67 (m, 2H; H-5′/5″); C NMR (DMSO-d ) δ
found 292.0803 (Δ −4.4 ppm).
6
2
1
53.6, 149.4, 148.6, 140.8, 119.1, 90.6 (dd, J(C2′,F3′) = 14.3,
9
-(3-Deoxy-3-fluoro-β-D-ribofuranosyl)adenine (38). To a flask
1
2
1
J(C2′,F2′) = 193.8 Hz), 89.8 (dd, J(C3′,F2′) = 13.3, J(C2′,F2′) =
containing compound 27 (0.055 g, 0.063 mmol) was added 80%
aqueous TFA in CHCl (5 mL). After 1 h, MeOH (5 mL) was added,
and the reaction mixture was then concentrated under reduced
pressure. The residue was dissolved in MeOH (5 mL), residual TFA
was neutralized by addition of Et N (10 drops), and the mixture was
3
2
1
84.8 Hz), 84.7 (dd, J(C1′,F3′) = 2.0, J(C1′,F2′) = 31.5 Hz), 83.4
3 2 3
3
(dd, J(C4′,F2′) = 2.4, J(C4′,F3′) = 21.4 Hz), 60.2 (d, J(C5′,F3′) =
19
8.4 Hz); F NMR (376 MHz, DMSO-d ) δ −206.2 (dddd,
2
6
3
3
3
J(F2′,F3′) = 4.9, J(2′,F3′) = 16.6, J(4′,F3′) = 22.6, J(3′,F3′) =
2
3
concentrated under reduced pressure. To the residue were added H O
53.4 Hz; F-3′), −214.4 (dm, J(2′,F2′) = 50.7 Hz; F-2′); HRMS (ESI
2
J
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
+
5
+
) m/z calcd for C H F N O [(M + H) ] 272.0954, found
MHz, CDCl ) δ 159.8, 154.4, 152.3, 148.0, 145.0, 138.9 (d, J(C8,F3′)
10
12
2
5
2
3
272.0963 (Δ 3.3 ppm).
= 3.3 Hz), 129.8, 129.2, 128.8, 128.1, 127.1, 121.6, 114.1, 94.5 (d,
1
2
3
General Procedure 2: Selective Deprotection of 5′-O-Trityl.
J(C3′,F3′) = 190.1 Hz), 87.8 (d, J(C1′,F3′) = 7.1 Hz), 83.2 (d,
2
A 0.4 M HCl solution in 1,4-dioxane was prepared by diluting
J(C2′,F3′) = 24.0 Hz), 81.1 (d, J(C4′,F3′) = 19.9 Hz), 72.7, 71.7,
6
3
19
commercially available 4 M HCl in 1,4-dioxane. A solution of 5′-O,N -
ditritylated compound (1 mmol) in 0.4 M HCl in 1,4-dioxane (38 mL)
was stirred at rt for 1 h. MeOH (25 mL) was added, and the reaction
mixture was concentrated under reduced pressure. The residue was
6
−
0.4 (d, J(C5′,F3′) = 8.2 Hz), 55.4; F NMR (376 MHz, CDCl ) δ
3
3
3
2
204.6 (dt, J(2′,F3′) = 16.7, J(4′,F3′) = 16.7, J(3′,F3′) = 53.1 Hz);
+
HRMS (ESI+) m/z calcd for C H FN O [(M + H) ] 632.2668,
37
35
5
4
found 632.2658 (Δ −1.6 ppm).
6
dissolved in CH Cl (50 mL) and washed with satd NaHCO , water,
2
2
3
N -Trityl-9-[3-deoxy-3-fluoro-2-O-(4-methoxybenzyl)-β-D-
ribofuranosyl]adenine (41d). This was prepared from ditritylated
compound 27 (0.73 g, 0.835 mmol) using general procedure 2.
Purification by flash chromatography (SiO , 80:20 EtOAc/hexanes)
afforded the product (0.39 g, 75%) as a white solid: R = 0.36 (1:1
and brine. The organic layer was dried (Na SO ), filtered, and
2
4
concentrated under reduced pressure. Purification by flash chromatog-
raphy (SiO , EtOAc/hexanes gradient) afforded the product.
N -Trityl-9-[2-deoxy-2-fluoro-3-O-(4-methoxybenzyl)-β-D-
ribofuranosyl]adenine (41a). This was prepared from ditritylated
compound 30 (0.10 g, 0.114 mmol) using general procedure 2.
Purification by flash chromatography (SiO , 70:30 EtOAc/hexanes)
afforded the product (0.06 g, 86%) as a white solid: R = 0.22 (1:1
EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 7.98, 7.81 (2s, 2H;
2
2
6
f
1
EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 7.92, 7.74 (2s, 2H;
3
H-2, H-8), 7.36−7.23 (m, 15H; 3 × C H ), 7.28 (d, J = 8.6 Hz, 2H;
6
5
6
5
3
2
-PMB), 7.05 (s, 1H; N -H), 6.86 (dd, J(OH,F3′) = 2.3 Hz, J(OH,5″)
= 12.2 Hz, 1H; 5′−OH), 6.72 (d, J = 8.6 Hz, 2H; -PMB), 5.90 (d,
f
1
3
3
2
3
J(1′,2′) = 8.1 Hz, 1H; H-1′), 5.19 (dd, J(2′,3′) = 4.0, J(3′,F3′) =
3 3
6
H-2, H-8), 7.35−7.21 (m, 17H; 3 × C H , -PMB), 7.10 (s, 1H; N -H),
6
6
54.7 Hz, 1H; H-3′), 4.89 (ddd, J(2′,3′) = 3.9, J(1′,2′) = 8.1,
6
.90 (d, J = 8.6 Hz, 2H; -PMB), 6.47 (br s, 1H; −OH), 6.10 (dd,
3
3
J(2′,F3′) = 24.6 Hz, 1H; H-2′), 4.49 (d, J(4′,F3′) = 28.4 Hz, 1H; H-
3
3
3
J(1′,2′) = 6.8, J(1′,F2′) = 12.0 Hz, 1H; H-1′), 5.79 (ddd, J(2′,3′) =
4
′), 4.47 (ABq, Δδ = 53.6 Hz, J = 11.3 Hz, 2H; -PMB), 3.88 (dm,
3
2
4
7
.8, J(1′,2′) = 6.9, J(2′,F2′) = 51.6 Hz, 1H; H-2′), 4.69 (ABq, Δδ =
2
J(5′,5″) = 12.7 Hz, 1H; H-5′), 3.74 (s, 3H; -PMB), 3.69 (t,
3
3
2.8 Hz, J = 11.2 Hz, 2H; -PMB), 4.40 (dt, J(3′,F2′) = 1.4, J(3′,4′) =
3
2
13
J(OH,5″) ≈ J(5′,5″) ≈ 12.7 Hz, 1H; H-5″); C NMR (100 MHz,
3
1
.4, J(2′,3′) = 4.6 Hz, 1H; H-3′), 4.34−4.33 (m, 1H; H-4′), 3.86 (dm,
CDCl ) δ 159.8, 154.8, 151.7, 147.3, 144.9, 140.6, 129.8, 129.2, 128.8,
2
3
3
J(5′,5″) = 13.1 Hz, 1H; H-5′), 3.80 (s, 3H; -PMB), 3.70 (dd, J(4′,5″)
1
1
28.1, 127.3, 122.8, 114.0, 91.5 (d, J(C3′,F3′) = 184.0 Hz), 89.7, 86.7
2
13
=
1
1.8, J(5′,5″) = 13.2 Hz, 1H; H-5″); C NMR (100 MHz, CDCl ) δ
2
2
3
(d, J(C2′,F3′) = 21.5 Hz), 79.0 (d, J(C4′,F3′) = 15.9 Hz), 72.8, 71.8,
59.7, 154.8, 152.0, 147.5, 144.8, 140.1, 129.8, 129.6, 129.1, 128.1,
3
19
6
2.8 (d, J(C5′,F3′) = 11.9 Hz), 55.5; F NMR (376 MHz, CDCl ) δ
27.2, 122.6, 114.2, 91.8 (d, 1J(C2′,F2′) = 197.3 Hz), 88.8 (d,
3
1
5
3
3
−
198.9 (dddd, J(OH,F3′) = 2.9, J(2′,F3′) = 24.1, J(4′,F3′) = 27.8,
2
3
J(C1′,F2′) = 31.0 Hz), 86.8 (d, J(C4′,F2′) = 3.2 Hz), 77.1 (d,
2
J(3′,F3′) = 54.9 Hz); HRMS (ESI+) m/z calcd for C H FN O
3
7
35
5
4
2
4
J(C3′,F2′) = 13.0 Hz), 73.2 (d, J(PMB-CH −,F2′) = 3.2 Hz), 71.7,
+
2
[(M + H) ] 632.2668, found 632.2615 (Δ −8.4 ppm).
19
3
6
1
3.0, 55.5; F NMR (376 MHz, CDCl ) δ −213.9 (dd, J(1′,F2′) =
6
3
N -Trityl-9-(2,3-dideoxy-2,3-difluoro-β-D-xylofuranosyl)adenine
(41e). This was prepared from ditritylated compound 31 (1.60 g, 2.12
mmol) using general procedure 2. Purification by flash chromatog-
raphy (SiO , 80:20 EtOAc/hexanes) afforded the product (0.78 g,
73%) as a white solid: R = 0.22 (1:1 EtOAc/hexanes); H NMR (400
2
1.9, J(2′,F2′) = 51.6 Hz); HRMS (ESI+) m/z calcd for
+
C H FN O Na [(M + Na) ] 654.2487, found 654.2516 (Δ 4.4
37
34
5
4
ppm).
2
6
1
N -Trityl-9-[2-deoxy-2-fluoro-3-O-(4-methoxybenzyl)-β-D-
arabinofuranosyl]adenine (41b). This was prepared from ditritylated
compound 24 (0.45 g, 0.515 mmol) using general procedure 2.
Purification by flash chromatography (SiO , 70:30 EtOAc/hexanes)
afforded the product (0.25 g, 78%) as a white solid: R = 0.29 (1:1
f
MHz, CDCl ) δ 8.05, 7.84 (2s, 2H; H-2, H-8), 7.35−7.22 (m, 15H; 3
3
6
3
3
×
C H ), 7.06 (s, 1H; N -H), 6.12 (dd, J(1′,2′) = 4.5, J(1′,F2′) =
6
5
3 3 3
2
15.6 Hz, 1H; H-1′), 5.85 (ddt, J(1′,2′) ≈ J(2′,3′) ≈ 4.5, J(2′,F3′) =
2
3
f
13.4, J(2′,F2′) = 52.2 Hz, 1H; H-2′), 5.44 (dddd, J(2′,3′) = 4.4,
3 2
1
EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 8.02 (s, 1H; H-2),
3
3
J(3′,4′) = 5.9, J(3′,F2′) = 14.3, J(3′,F3′) = 52.4 Hz, 1H; H-3′),
3
5
7
-
.92 (d, J(8,F2′) = 1.9 Hz, 1H; H-8), 7.36−7.22 (m, 18H; 3 × C H ,
6
6
4.92−4.89 (m, 1H; 5′−OH), 4.49 (dm, J(4′,F3′) = 15.2 Hz, 1H; H-
6
3
PMB, N -H), 6.90 (d, J = 8.6 Hz, 2H; -PMB), 6.34 (dd, J(1′,2′) =
13
4
1
′), 4.01−3.91 (m, 2H; H-5′/5″); C NMR (100 MHz, CDCl ) δ
3
.1, 3J(1′,F2′) = 17.2 Hz, 1H; H-1′), 5.18 (ddd, J(2′,3′) = 2.3,
3
4
54.6, 152.6, 148.1, 144.9, 138.9 (d, J = 3.0 Hz), 129.2, 128.2, 127.2,
3
2
J(1′,2′) = 4.1, J(2′,F2′) = 52.1 Hz, 1H; H-2′), 5.01 (br s, 1H; −OH),
2
1
1
21.8, 94.6 (dd, J(C2′,F3′) = 26.4, J(C2′,F2′) = 190.3 Hz), 92.1 (dd,
3
4
.61 (ABq, Δδ = 24.4 Hz, J = 11.3 Hz, 2H; -PMB), 4.51 (ddd, J(2′,3′)
2
1
3
J(C3′,F2′) = 25.2, J(C2′,F2′) = 192.4 Hz), 86.7 (dd, J(C1′,F3′) =
2.4, 3J(3′,4′) = 4.9, J(3′,F2′) = 18.7 Hz, 1H; H-3′), 4.09 (q,
3
=
2
3
2
7
2
.2, J(C1′,F2′) = 33.6 Hz), 80.7 (dd, J(C4′,F2′) = 4.2, J(C4′,F3′) =
3 19
3
3
3
3
J(4′,5′) = 3.7, J(4′, 5″) = 3.8, J(4′,3′) = 3.8 Hz, 1H; H-4′), 3.89 (dd,
0.3 Hz), 71.7, 62.3 (d, J(C5′,F3′) = 7.5 Hz); F NMR (376 MHz,
2
3
3
3
J(4′,5′) = 3.1, J(5′,5″) = 12.4 Hz, 1H; H-5′), 3.01 (s, 3H; -PMB),
CDCl ) δ −197.8 (dtd, J(F2′,F3′) = 10.5, J(3′,F2′) = 14.8, J(1′,F2′)
3
3
2
13
2
3
3
(
.70 (dd, J(4′,5″) = 4.0, J(5′,5″) = 12.4 Hz, 1H; H-5″); C NMR
= 14.9, J(2′,F2′) = 52.3 Hz; F-2′), −209.9 (dtd, J(F2′,F3′) = 10.1,
3 3 2
100 MHz, CDCl ) δ 159.8, 154.3, 152.5, 148.7, 145.0, 139.2 (d, J =
J(2′,F3′) = 13.6, J(4′,F3′) = 14.2, J(3′,F3′) = 52.3 Hz; F-3′); HRMS
3
4
.3 Hz), 129.8, 129.2, 128.9, 128.1, 127.0, 120.5, 114.2, 94.1 (d,
+
(
ESI+) m/z calcd for C H F N O [(M + H) ] 514.2049, found
29 26 2 5 2
1
2
J(C2′,F2′) = 195.0 Hz), 84.1 (d, J(C1′,F2′) = 17.4 Hz), 83.2 (d,
5
14.2025 (Δ −4.6 ppm).
6
3
2
J(C4′,F2′) = 3.4 Hz), 80.8 (d, J(C3′,F2′) = 25.0 Hz), 72.6, 71.7,
N -Trityl-9-(2,3-dideoxy-2,3-difluoro-β-D-ribofuranosyl)adenine
(41f). This was prepared from ditritylated compound 35 (0.81 g, 1.07
mmol) using general procedure 2. Purification by flash chromatog-
raphy (SiO , 50:50 EtOAc/hexanes) afforded the product (0.51 g,
93%) as a waxy white solid: R = 0.40 (3:1 EtOAc/hexanes); H NMR
19
3
6
1.5, 55.5; F NMR (376 MHz, CDCl ) δ −195.8 (dt, J(1′,F2′) =
3
3
2
17.9, J(3′,F2′) = 17.9, J(2′,F2′) = 51.9 Hz).
6
N -Trityl-9-[3-deoxy-3-fluoro-2-O-(4-methoxybenzyl)-β-D-
xylofuranosyl]adenine (41c). This was prepared from ditritylated
compound 23 (0.88 g, 1.007 mmol) using general procedure 2.
Purification by flash chromatography (SiO , 80:20 EtOAc/hexanes)
afforded the product (0.47 g, 75%) as a white solid: R = 0.20 (1:1
EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 8.02, 7.80 (2s, 2H;
H-2, H-8), 7.36−7.21 (m, 15H; 3 × C H ), 7.12 (d, J = 8.6 Hz, 2H;
PMB), 7.07 (s, 1H; N -H), 6.77 (d, J = 8.6 Hz, 2H; -PMB), 5.97 (d,
2
1
f
(400 MHz, DMSO-d ) δ 8.52, 7.94 (2s, 2H; H-2, H-8), 7.65 (s, 1H;
6
6
3
N -H), 7.35−7.19 (m, 15H; 3 × C H ), 6.34 (dd, J(1′,2′) = 5.7 Hz,
2
6
5
3
3
3
3
J(1′,F2′) = 13.8, 1H; H-1′), 5.95 (ddt, J(1′,2′) ≈ J(2′,3′) ≈ 5.8,
2 2
f
1
3
J(2′,F3′) = 16.4, J(2′,F2′) = 50.2 Hz, 1H; H-2′), 5.53 (dm, J(3′,F3′)
3
6
5
= 53.1 Hz, 1H; H-3′), 4.76 (br s, 1H; 5′−OH), 4.38 (dm, J(4′,F3′) =
3 2
6
-
2
3.8 Hz, 1H; H-4′), 3.68 (dd, J(5′,4′) = 3.5, J(5′,5″) = 12.3 Hz, 1H;
3
2
3
3
3
3
2
1
3
J(1′,2′) = 4.4 Hz, 1H; H-1′), 5.21 (ddd, J(2′,3′) = 4.2, J(3′,4′) = 5.6,
H-5′), 3.64 (dd, J(5″,4′) = 3.5, J(5′,5″) = 12.3 Hz, 1H; H-5″);
C
J(3′,F3′) = 53.2 Hz, 1H; H-3′), 4.90 (br s, 1H; −OH), 4.80 (dt,
NMR (100 MHz, CDCl ) δ 154.8, 151.9, 147.4, 144.7, 140.2, 129.1,
3
3
3
2
1
J(2′,3′) = 4.3, J(1′,2′) = 4.3, J(2′,F3′) = 15.7 Hz, 1H; H-2′), 4.61
128.2, 127.3, 122.6, 91.3 (dd, J(C2′,F3′) = 13.0, J(C2′,F2′) = 185.5
3
2
1
(
4
3
ABq, Δδ = 21.6 Hz, J = 11.5 Hz, 2H; -PMB), 4.39 (dq, J(3′,4′) =
Hz), 89.6 (dd, J(C3′,F2′) = 15.0, J(C2′,F2′) = 201.7 Hz), 88.1 (d,
2 3 2
3
3
3
.2, J(5′,4′) = 4.3, J(5″,4′) = 4.3, J(4′,F3′) = 17.9 Hz, 1H; H-4′),
J(C1′,F2′) = 30.4 Hz), 86.2 (dd, J(C4′,F2′) = 3.1, J(C4′,F3′) = 21.1
3 19
13
.96−3.87 (m, 2H; H-5′/5″), 3.74 (s, 3H; -PMB); C NMR (100
Hz), 71.8, 62.3 (d, J(C5′,F3′) = 11.4 Hz); F NMR (376 MHz,
K
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
3
3
DMSO-d ) δ −204.6 (dddd, J(F2′,F3′) = 5.0, J(2′,F3′) = 16.2,
51.0 Hz, 1H; H-3′), 4.71 (ABq, Δδ = 48.8 Hz, J = 11.6 Hz, 2H;
6
3
2
2
3
3
3
J(4′,F3′) = 22.5, J(3′,F3′) = 53.4 Hz; F-3′), −212.7 (dm, J(2′,F2′)
50.0 Hz; F-2′); HRMS (ESI+) m/z calcd for C H F N O [(M +
-PMB), 4.50 (dt, J(2′,3′) = 1.4, J(1′,2′) = 1.4, J(2′,F3′) = 15.2 Hz,
3 3 3
=
1H; H-2′), 4.44 (dtd, J(3′,4′) = 2.7, J(5′,4′) = 6.6, J(5″,4′) = 6.6,
29
26
2
5
2
+
3
H) ] 514.2049, found 514.2075 (Δ 5.0 ppm).
J(4′,F3′) = 28.4 Hz, 1H; H-4′), 3.78 (s, 3H; -PMB), 3.76−3.73 (m,
3
2
General Procedure 3: Azidation. To a solution of alcohol (1
1H; H-5′), 3.67 (dd, J(5′,4′) = 6.4, J(5′,5″) = 12.8 Hz, 1H; H-5″);
13
mmol, 1 equiv) in anhydrous 1,4-dioxane (9 mL) were added DPPA
3 equiv) and DBU (2 equiv) dropwise, and the reaction mixture was
stirred at rt. The conversion of alcohol to the phosphate intermediate
was monitored by TLC, which was usually completed in 1−3 h. NaN
10 equiv) and 15-crown-5 (0.1 equiv) were then added, and the
reaction mixture was refluxed (oil bath at 110 °C) for 1−24 h. The
reaction mixture was allowed to cool to rt and filtered through a short
pad of silica, and the silica was washed with EtOAc. The combined
filtrate was evaporated under reduced pressure. Purification by flash
C NMR (100 MHz, CDCl ) δ 159.9, 154.2, 152.7, 148.6, 145.1,
3
5
(
137.7 (d, J(C8,F3′) = 6.0 Hz), 130.0, 129.2, 128.4, 128.1, 127.1,
1
121.1, 114.2, 94.0 (d, J(C3′,F3′) = 186.0 Hz), 88.2, 85.0 (d,
2
2
3
J(C2′,F3′) = 27.2 Hz), 80.7 (d, J(C4′,F3′) = 19.5 Hz), 72.6, 71.6,
3
19
(
55.5, 48.8 (d, J(C5′,F3′) = 9.3 Hz); F NMR (376 MHz, CDCl ) δ
3
3 3 2
−202.6 (ddd, J(2′,F3′) = 14.7, J(4′,F3′) = 28.6, J(3′,F3′) = 51.2
+
Hz); HRMS (ESI+) m/z calcd for C H FN O [(M + H) ]
37
34
8
3
657.2732, found 657.2692 (Δ −6.1 ppm).
6
N -Trityl-9-[5-azido-3,5-dideoxy-3-fluoro-2-O-(4-methoxyben-
zyl)-β-D-ribofuranosyl]adenine (42d). This was prepared from
alcohol 41d (0.38 g, 0.602 mmol) using general procedure 3.
Conversion of alcohol to phosphate intermediate was completed in 1 h
and the conversion of phosphate to azide was completed in 3 h.
chromatography (SiO , EtOAc/hexanes gradient) afforded the
2
product.
6
N -Trityl-9-[5-azido-2,5-dideoxy-2-fluoro-3-O-(4-methoxyben-
zyl)-β-D-ribofuranosyl]adenine (42a). This was prepared from alcohol
1a (0.062 g, 0.098 mmol) using general procedure 3. The reaction
mixture was refluxed for 17 h. Purification by flash chromatography
SiO , 50:50 EtOAc/hexanes) afforded the product (0.053 g, 83%) as
a white solid: R = 0.45 (1:1 EtOAc/hexanes); H NMR (400 MHz,
CDCl ) δ 8.00, 7.90 (2s, 2H; H-2, H-8), 7.35−7.20 (m, 17H; 3 ×
C H , -PMB), 7.00 (s, 1H; N -H), 6.87 (d, J = 8.6 Hz, 2H; -PMB),
4
Purification by flash chromatography (SiO , 50:50 EtOAc/hexanes)
2
afforded the product (0.32 g, 81%) as a white solid: R = 0.55 (1:1
f
1
(
EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 8.00, 7.76 (2s, 2H;
2
3
1
f
H-2, H-8), 7.37−7.22 (m, 15H; 3 × C H ), 7.11 (d, J = 8.6 Hz, 2H;
6
5
6
3
-PMB), 6.95 (s, 1H; N -H), 6.78 (d, J = 8.6 Hz, 2H; -PMB), 6.02 (d,
6
3
3
3
3
6
6
J(1′,2′) = 6.6 Hz, 1H; H-1′), 5.09 (ddd, J(2′,3′) = 4.5, J(1′,2′) = 6.7,
3
3
3 3
6
.12 (dd, J(1′,2′) = 1.5, J(1′,F2′) = 19.7 Hz, 1H; H-1′), 5.53 (ddd,
J(2′,F3′) = 18.4 Hz, 1H; H-2′), 5.08 (ddd, J(3′,4′) = 2.2, J(3′,2′) =
3
3 2
J(1′,2′) = 1.5, J(2′,3′) = 3.5, J(2′,F2′) = 52.8 Hz, 1H; H-2′), 4.61
2
4
.5, J(3′,F3′) = 54.4 Hz, 1H; H-3′), 4.55 (ABq, Δδ = 41.2 Hz, J =
3
3
3
3
3
(
ddd, J(2′,3′) = 4.2, J(3′,4′) = 8.7, J(3′,F2′) = 20.4 Hz, 1H; H-3′),
11.5 Hz, 2H; -PMB), 4.45 (dtd, J(3′,4′) = 2.2, J(5′,4′) = 5.2,
3
3
3
4
=
-
(
.60 (ABq, Δδ = 47.6 Hz, J = 11.3 Hz, 2H; -PMB), 4.26 (ddd, J(4′,5′)
J(5″,4′) = 5.2, J(4′,F3′) = 23.6 Hz, 1H; H-4′), 3.77 (s, 3H; -PMB),
3
3
2.9, J(4′,5″) = 5.1, J(4′,3′) = 8.1 Hz, 1H; H-4′), 3.78 (s, 3H;
3
2
3
3
=
1
.68 (dd, J(5′,4′) = 5.4, J(5′,5″) = 13.1 Hz; H-5′), 3.67 (dd, J(5′,4′)
3
2
PMB), 3.63 (dd, J(4′,5′) = 2.9, J(5′,5″) = 13.5 Hz, 1H; H-5′), 3.43
2
1
3
4.9, J(5′,5″) = 13.1 Hz, 1H; H-5″); C NMR (100 MHz, CDCl ) δ
3
3
2
13
dd, J(4′,5″) = 5.1, J(5′,5″) = 13.5 Hz, 1H; H-5″); C NMR (100
59.9, 154.4, 152.5, 148.8, 145.1, 139.6, 129.8, 129.2, 128.7, 128.1,
1
MHz, CDCl ) δ 160.0, 154.4, 152.6, 148.2, 145.0, 139.1, 130.2, 129.2,
3
127.2, 121.9, 114.1, 90.0 (d, J(C3′,F3′) = 189.6 Hz), 87.4, 81.6 (d,
1
1
8
29.0, 128.1, 127.2, 121.5, 114.2, 91.4 (d, J(C2′,F2′) = 190.2 Hz),
2
2
J(C2′,F3′) = 24.3 Hz), 77.2 (d, J(C4′,F3′) = 15.5 Hz), 72.9, 71.7,
2
2
8.4 (d, J(C1′,F2′) = 34.5 Hz), 80.2, 75.7 (d, J(C3′,F2′) = 16.0 Hz),
3
19
5
5.5, 51.6 ppm (d, J(C5′,F3′) = 8.6 Hz); F NMR (376 MHz,
19
7
2.9, 71.7, 55.5, 51.4; F NMR (376 MHz, CDCl ) δ −202.0 (dt,
3 3 2
3
CDCl ) δ −201.8 (ddd, J(2′,F3′) = 18.1, J(4′,F3′) = 23.4, J(3′,F3′)
3
3
3
2
J(1′,F2′) = 20.1, J(3′,F2′) = 20.1, J(2′,F2′) = 52.9 Hz).
+
=
54.1 Hz); HRMS (ESI+) m/z calcd for C H FN O [(M + H) ]
37 34 8 3
6
N -Trityl-9-[5-azido-2,5-dideoxy-2-fluoro-3-O-(4-methoxyben-
6
57.2732, found 657.2731 (Δ −0.2 ppm).
zyl)-β-D-arabinofuranosyl]adenine (42b). This was prepared from
alcohol 41b (0.23 g, 0.364 mmol) using general procedure 3. The
reaction mixture was refluxed for 24 h. Purification by flash
6
N -Trityl-9-(5-azido-2,3-difluoro-2,3,5-trideoxy-β-D -
xylofuranosyl)adenine (42e). This was prepared from alcohol 41e
0.76 g, 1.48 mmol) using general procedure 3. Conversion of alcohol
(
chromatography (SiO , 50:50 EtOAc/hexanes) afforded the product
0.14 g, 58%) as a white solid: R = 0.63 (1:1 EtOAc/hexanes); H
2
to phosphate intermediate was completed in 2 h. For the conversion of
phosphonate to the azide product, the reaction mixture was refluxed
1
(
f
5
NMR (400 MHz, CDCl ) δ 8.06 (s, 1H; H-2), 8.04 (d, J(8,F2′) = 2.9
for 24 h. Purification by flash chromatography (SiO , 30:70 EtOAc/
3
2
6
Hz, 1H; H-8), 7.37−7.21 (m, 17H; 3 × C H , -PMB), 6.99 (s, 1H; N -
hexanes) afforded the product (0.58 g, 73%) as a white solid: R = 0.57
6
6
f
3
1
H), 6.92 (d, J = 8.5 Hz, 2H; -PMB), 6.42 (dd, J(1′,2′) = 3.1,
(1:1 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 8.07, 7.87 (2s,
3
3
3
3
6
J(1′,F2′) = 21.2 Hz, 1H; H-1′), 5.11 (ddd, J(2′,3′) = 1.5, J(1′,2′) =
2H; H-2, H-8), 7.36−7.21 (m, 15H; 3 × C H ), 6.96 (s, 1H; N -H),
6
5
2
3
3
3
.3, J(2′,F2′) = 52.3 Hz, 1H; H-2′), 4.60 (ABq, Δδ = 35.2 Hz, J =
6.38 (d, J(1′,F2′) = 20.4 Hz, 1H; H-1′), 5.57 (dd, J(2′,F3′) = 10.5,
1.5 Hz, 2H; -PMB), 4.27 (ddd, 3J(2′,3′) = 1.2, J(3′,4′) = 3.9,
3
2
4
3
1
J(2′,F2′) = 47.9 Hz, 1H; H-2′), 5.28 (dddd, J(3′,5′) = 1.1, J(3′,4′) =
3 2
3
3
3
J(3′,F2′) = 17.9 Hz, 1H; H-3′), 4.16 (q, J(4′,5′) = 4.7, J(4′,5″) =
3.1, J(3′,F2′) = 8.9, J(3′,F3′) = 49.7 Hz, 1H; H-3′), 4.48 (dm,
4 3
3
3
4
.7, J(4′,3′) = 4.6 Hz, 1H; H-4′), 3.82 (s, 3H; -PMB), 3.58 (dd,
J(4′,F3′) = 28.3 Hz, 1H; H-4′), 3.80 (ddd, J(3′,5′) = 1.1, J(5′,4′) =
2 3 2
3
2
3
J(4′,5′) = 4.5, J(5′,5″) = 13.2 Hz, 1H; H-5′), 3.43 (dd, J(4′,5″) =
6.6, J(5′,5″) = 13.0 Hz, 1H; H-5′), 3.71 (dd, J(5″,4′) = 6.5, J(5′,5″)
2
13
13
5
1
1
1
.3, J(5′,5″) = 13.2 Hz, 1H; H-5″); C NMR (100 MHz, CDCl ) δ
= 12.8 Hz, 1H; H-5″); C NMR (100 MHz, CDCl ) δ 154.3, 153.0,
3
3
4
60.0, 154.3, 152.6, 148.8, 145.1, 139.4 (d, J(C8,F2′) = 6.6 Hz),
148.7, 145.0, 137.4 (d, J = 6.4 Hz), 129.2, 128.1, 127.2, 121.0, 96.1
1
2
1
29.9, 129.2, 128.5, 128.1, 127.1, 120.4, 114.3, 93.2 (d, J(C2′,F2′) =
(dd, J(C2′,F3′) = 31.5, J(C2′,F2′) = 186.9 Hz), 92.3 (dd,
2
2
2
1
2
93.0 Hz), 83.1 (d, J(C1′,F2′) = 17.1 Hz), 81.8 (d, J(C3′,F2′) = 25.6
J(C3′,F2′) = 30.4, J(C3′,F3′) = 185.9 Hz), 87.5 (d, J(C1′,F2′) =
2 3
3
19
Hz), 81.2 (d, J(C4′,F2′) = 2.1 Hz), 72.7, 71.6, 55.5, 51.6; F NMR
36.7 Hz), 80.5 (d, J(C4′,F3′) = 19.7 Hz), 71.7, 48.5 (d, J(C5′,F3′) =
5
3
1
9
4
(
376 MHz, CDCl ) δ −196.3 (dddd, J(8,F2′) = 3.0, J(3′,F2′) = 17.7,
9.1 Hz); F NMR (376 MHz, CDCl ) δ −192.1 (ddddd, J(4′,F2′) =
3 3 3 2
3
3
3
2
J(1′,F2′) = 20.8, J(2′,F2′) = 51.3 Hz).
3.3, J(3′,F2′) = 8.9, J(F3′,F2′) = 14.8, J(1′,F2′) = 20.8, J(2′,F2′) =
6
3
3
N -Trityl-9-[5-azido-3,5-dideoxy-3-fluoro-2-O-(4-methoxyben-
48.1 Hz; F-2′), −208.7 (dddd, J(2′,F3′) = 10.5, J(F3′,F2′) = 14.2,
3
2
zyl)-β-D-xylofuranosyl]adenine (42c). This was prepared from alcohol
J(4′,F3′) = 28.1, J(3′,F3′) = 49.9 Hz; F-3′); HRMS (ESI+) m/z
+
4
1c (0.70 g, 1.108 mmol) using general procedure 3. Conversion of
alcohol to the phosphate intermediate was completed in 1 h. For the
conversion of phosphate to azide, the reaction mixture was refluxed for
4 h. Purification by flash chromatography (SiO , 50:50 EtOAc/
hexanes) afforded the product (0.41 g, 57%) as a white solid: R = 0.61
1:1 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 8.07, 7.86 (2s,
calcd for C H F N ONa [(M + Na) ] 561.1933, found 561.1943 (Δ
29
24
2
8
1.8 ppm).
6
N -Trityl-9-(5-azido-2,3-difluoro-2,3,5-trideoxy-β-D -
ribofuranosyl)adenine (42f). This was prepared from alcohol 41f
(0.41 g, 0.798 mmol) using general procedure 3. Conversion of
alcohol to phosphate intermediate was completed in 2 h and the
conversion of phosphate to azide was completed in 1 h. Purification by
2
2
f
1
(
3
2
1
H; H-2, H-8), 7.37−7.21 (m, 17H; 3 × C H and -PMB), 6.94 (s,
6 3
6
5
H; N -H), 6.83 (d, J = 8.6 Hz, 2H; -PMB), 6.27 (d, J(1′,2′) = 1.7
flash chromatography (SiO , 30:70 EtOAc/hexanes) afforded the
2
3
3
3
Hz, 1H; H-1′), 5.06 (ddd, J(2′,3′) = 1.1, J(3′,4′) = 2.7, J(3′,F3′) =
product (0.40 g, 93%) as a colorless liquid: R = 0.54 (1:1 EtOAc/
f
L
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
1
6
hexanes); H NMR (400 MHz, DMSO-d ) δ 8.52, 7.96 (2s, 2H; H-2,
C H , -PMB), 7.15−7.10 (m, 1H; C5′-NH), 6.95 (s, 1H; N -H), 6.88
6
6
6
6
3
3
H-8), 7.65 (s, 1H; N -H), 7.34−7.19 (m, 15H; 3 × C H ), 6.38 (dd,
(d, J = 8.4 Hz, 2H; -PMB), 6.34 (dd, J(1′,2′) = 4.7, J(1′,F2′) = 14.1
6
5
3
3
3
3
3 3 2
J(1′,2′) = 4.8, J(1′,F2′) = 15.2 Hz, 1H; H-1′), 6.15 (ddt, J(1′,2′) ≈
Hz, 1H; H-1′), 5.18 (dt, J(2′,3′) = 4.0, J(1′,2′) = 4.0, J(2′,F2′) =
52.2 Hz, 1H; H-2′), 4.80 (s, 2H; -NH ), 4.61 (ABq, Δδ = 30.8 Hz, J =
3
2
J(2′,3′) ≈ 4.8, J(2′,F3′) = 12.8, J(2′,F2′) = 50.0 Hz, 1H; H-2′), 5.53
2
3
3
2
3
11.3 Hz, 2H; -PMB), 4.47 (ddd, J(2′,3′) = 3.5, J(3′,4′) = 5.6,
(
1
dm, J(3′,F3′) = 52.4 Hz, 1H; H-3′), 4.49 (dm, J(4′,F3′) = 21.2 Hz,
3
3
3
3 2
J(3′,F2′) = 18.1 Hz, 1H; H-3′), 4.08 (q, J(4′,5′) = 4.3, J(4′,5″) =
3
H; H-4′), 3.73 (dd, J(5′,4′) = 5.6, J(5′,5″) = 13.2 Hz, 1H; H-5′),
3 2 13
3
.52 (dd, J(5″,4′) = 4.4, J(5′,5″) = 13.2 Hz, 1H; H-5″); C NMR
4.3, J(4′,3′) = 4.3 Hz, 1H; H-4′), 3.78 (s, 3H; -PMB), 3.40−3.38 (m,
13
2
1
1
1
H; H-5′/5″); C NMR (100 MHz, CDCl ) δ 159.8, 154.1, 152.5,
(
1
100 MHz, DMSO-d ) δ 153.7, 151.5, 148.2, 144.7, 140.8, 128.6,
3
6
2
1
48.6, 145.0, 139.8 (d, J = 3.9 Hz), 130.2, 129.2, 128.7, 128.1, 127.1,
27.7, 126.6, 120.8, 89.4 (dd, J(C2′,F3′) = 14.2, J(C2′,F2′) = 192.2
1
2
2
1
20.1, 114.3, 94.3 (d, J(C2′,F2′) = 196.4 Hz), 82.9 (d, J(C1′,F2′) =
Hz), 88.8 (dd, J(C3′,F2′) = 13.7, J(C3′,F3′) = 188.4 Hz), 84.8 (dd,
2
3
3
2
2
3
7.5 Hz), 80.4 (d, J(C3′,F2′) = 23.7 Hz), 79.9 (d, J(C4′,F2′) = 5.4
J(C1′,F3′) = 2.7, J(C1′,F2′) = 31.6 Hz), 79.9 (dd, J(C4′,F2′) = 2.5,
19
3
19
Hz), 72.7, 71.7, 55.5, 43.7; F NMR (376 MHz, CDCl ) δ −195.0
J(C4′,F3′) = 23.6 Hz), 70.4, 50.3 (d, J(C5′,F3′) = 6.3 Hz); F NMR
3
3 3 2
3
3
(dt, J(3′,F2′) = 16.0, J(1′,F2′) = 16.0, J(2′,F2′) = 52.3 Hz); HRMS
(
376 MHz, CDCl ) δ −209.2 (dt, J(2′,F3′) = 13.8, J(4′,F3′) = 13.8,
3
+
2
3 3
(ESI+) m/z calcd for C37H36FN O SNa [(M + Na) ] 732.2375, found
7 5
J(3′,F3′) = 51.3 Hz; F-3′), −210.5 (ddd, J(3′,F2′) = 8.6, J(1′,F2′) =
8.3, 2J(2′,F2′) = 52.0 Hz; F-2′); HRMS (ESI+) m/z calcd for
732.2412 (Δ 5.0 ppm).
1
6
N -Trityl-9-[3,5-dideoxy-3-fluoro-2-O-(4-methoxybenzyl)-5-(N-
sulfamoyl)amino-β-D-xylofuranosyl]adenine (43c). To a solution of
azide 42c (0.54 g, 0.822 mmol) in CH Cl (23 mL) were added zinc
turnings (0.81g, 12.393 mmol, 15 equiv) and AcOH (0.35 mL, 6.165
mmol, 7.5 equiv), and the reaction mixture was stirred at rt for 1 h.
The reaction mixture was filtered through a short pad of Celite, and
the residue was washed with MeOH (3 × 10 mL). The combined
filtrates were concentrated and dissolved in EtOAc (10 mL). The
EtOAc layer was washed with satd NaHCO3 and brine, dried
+
C H F N O [(M + H) ] 539.2114, found 539.2159 (Δ 8.3 ppm).
29
25
2
8
6
N -Trityl-9-[2,5-dideoxy-2-fluoro-3-O-(4-methoxybenzyl)-5-(N-
2
2
sulfamoyl)amino-β-D-ribofuranosyl]adenine (43a). To a solution of
azide 42a (0.053 g, 0.081 mmol) in CH Cl (2 mL) were added zinc
2
2
turnings (0.081 g, 1.24 mmol, 15 equiv) and AcOH (43 μL, 0.751
mmol, 9.3 equiv), and the reaction mixture was stirred at rt for 1 h.
The reaction mixture was filtered through a short pad of Celite, and
the residue was washed with MeOH (3 × 5 mL). The combined
filtrates were concentrated and dissolved in EtOAc (5 mL). The
EtOAc layer was washed with satd NaHCO3 and brine, dried
(
MgSO ), and evaporated to obtain the crude 5′-aminonucleoside. To
4
a solution of the 5′-aminonucleoside in 1,4-dioxane (19 mL) was
added sulfamide (0.23 g, 2.393 mmol, 2.9 equiv), and the mixture was
refluxed for 2 h. The reaction mixture was evaporated and then
partitioned between CH Cl (10 mL) and water (10 mL). The phases
(
MgSO ), and evaporated to obtain the crude 5′-aminonucleoside. To
4
a solution of the 5′-aminonucleoside in 1,4-dioxane (2 mL) was added
sulfamide (0.024 g, 0.250 mmol, 3.0 equiv) and the mixture was
refluxed for 2 h. The reaction mixture was evaporated and then
partitioned between CH Cl (5 mL) and H O (5 mL). The phases
2
2
were separated, and the CH Cl layer was washed with brine, dried
Na SO ), and evaporated under reduced pressure. Purification by
flash chromatography (SiO , gradient: hexanes to 70% EtOAc in
hexanes) afforded the product (0.50 g, 86%) as a white solid: R = 0.39
2
2
2
2
2
(
2 4
were separated, and the organic phase was washed with brine, dried
Na SO ), and evaporated under reduced pressure. Purification by
flash chromatography (SiO , gradient: hexanes to 70% EtOAc in
hexanes) afforded the product (0.051 g, 89%) as a white solid: R =
.52 (3:1 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 8.57 (dd,
2
(
2
4
f
1
2
(
3:1 EtOAc/hexanes); H NMR (400 MHz, DMSO-d ) δ 8.19, 7.94
6
6
f
(2s, 2H; H-2, H-8), 7.52 (s, 1H; N -H), 7.35−7.20 (m, 17H; 3 ×
1
0
3
3
C H , -PMB), 6.89 (t, J(5′/5″, NH) = 6.1 Hz, 1H; C5′-NH), 6.85 (d,
6
5
3
3
J(5″,NH) = 3.4 Hz, J(5′,NH) = 8.2, 1H; C5′-NH), 8.06, 7.78 (2s,
3
J = 8.6 Hz, 2H; -PMB), 6.65 (s, 2H; -NH ), 6.09 (d, J(1′,2′) = 2.2 Hz,
2
2
H; H-2, H-8), 7.34−7.20 (m, 17H; 3 × C H , -PMB), 7.01 (s, 1H;
3
2
6
6
1H; H-1′), 5.34 (dd, J(3′,4′) = 2.6, J(3′,F3′) = 51.1 Hz, 1H; H-3′),
6
3
3 3
N -H), 6.87 (d, J = 8.5 Hz, 2H; -PMB), 6.05 (dd, J(1′,2′) = 5.5,
4
.79 (dd, J(1′,2′) = 3.0, J(2′,F3′) = 15.8 Hz, 1H; H-2′), 4.65 (s, 2H;
3 3 3
3
3
3
J(1′,F2′) = 13.7 Hz, 1H; H-1′), 5.59 (dt, J(2′,3′) = 5.3, J(1′,2′) =
-
PMB), 4.42 (dtd, J(3′,4′) = 2.8, J(5′,4′) = 6.5, J(5″,4′) = 6.6,
2
3
3
5
1
3
.3, J(2′,F2′) = 51.5 Hz, 1H; H-2′), 4.64 (ABq, Δδ = 72.0 Hz, J =
J(4′,F3′) = 29.7 Hz, 1H; H-4′), 3.71 (s, 3H; -PMB), 3.35 (dt,
3 2
1.0 Hz, 2H; -PMB), 4.56−4.37 (m, 4H; H-3′, H-4′, -NH ), 3.79 (s,
2
J(5″,NH) = 6.5, J(5″,4′) = 6.6, J(5″,5′) = 13.3 Hz, 1H; H-5′), 3.26
13
H; -PMB), 3.38−3.35 (m, 2H; H-5′/5″); C NMR (100 MHz,
3
3
2
(
dt, J(5″,4′) = 6.5, J(5″,NH) = 6.5, J(5″,5′) = 13.3 Hz, 1H; H-5″);
CDCl ) δ 159.9, 154.7, 152.5, 147.6, 144.8, 139.7, 130.1, 129.4, 129.2,
13
3
C NMR (100 MHz, DMSO-d ) δ 159.0, 153.5, 151.4, 148.2, 144.8,
6
1
1
28.2, 127.2, 122.0, 114.2, 91.2 (d, J(C2′,F2′) = 196.4 Hz), 88.4 (d,
5
1
38.9 (d, J(C8,F3′) = 4.8 Hz), 129.6, 128.9, 128.6, 127.7, 126.6,
2
3
J(C1′,F2′) = 31.7 Hz), 82.9 (d, J(C4′,F2′) = 2.5 Hz), 76.5 (d,
1
1
20.6, 113.7, 93.4 (d, J(C3′,F3′) = 183.4 Hz), 87.4, 84.2 (d,
2
4
J(C3′,F2′) = 14.0 Hz), 73.5 (d, J(PMB-CH −,F2′) = 2.8 Hz), 71.7,
2
2
2
J(C2′,F3′) = 27.6 Hz), 80.3 (d, J(C4′,F3′) = 19.3 Hz), 71.4, 70.3,
2
5
5
5.5, 44.7; 19F NMR (376 MHz, CDCl ) δ = −210.0 (dm, J(2′,F2′) =
3
19
3
55.0, 40.5 (d, J(C5′,F3′) = 10.7 Hz); F NMR (376 MHz, DMSO-
3 3 2
1.8 Hz); HRMS (ESI+) m/z calcd for C H FN O SNa [(M +
37
36
7
5
d ) δ −200.8 (ddd, J(2′,F3′) = 15.6, J(4′,F3′) = 29.7, J(3′,F3′) =
6
+
19
3
Na) ] 732.2375, found 732.2407 (Δ 4.4 ppm).
N -Trityl-9-[2,5-dideoxy-2-fluoro-3-O-(4-methoxybenzyl)-5-(N-
sulfamoyl)amino-β-D-arabinofuranosyl]adenine (43b). To a sol-
5
0.8 Hz); F NMR (376 MHz, CDCl ) δ −201.8 (ddd, J(2′,F3′) =
3
6
3
2
1
6.2, J(4′,F3′) = 23.2, J(3′,F3′) = 52.5 Hz); HRMS (ESI+) m/z
+
calcd for C H FN O S [(M + H) ] 710.2555, found 710.2576 (Δ
37
37
7
5
ution of azide 42b (0.17 g, 0.259 mmol) in CH Cl (7 mL) were
2
2
2.9 ppm).
added zinc turnings (0.26 g, 3.978 mmol, 15 equiv) and AcOH (0.14
mL, 2.445 mmol, 9.5 equiv), and the reaction mixture was stirred at rt
for 1 h. The reaction mixture was filtered through a short pad of Celite,
and the residue was washed with MeOH (3 × 5 mL). The combined
filtrates were concentrated and dissolved in EtOAc (10 mL). The
EtOAc layer was washed with satd NaHCO3 and brine, dried
6
N -Trityl-9-[3,5-dideoxy-3-fluoro-2-O-(4-methoxybenzyl)-5-(N-
sulfamoyl)amino-β-D-ribofuranosyl]adenine (43d). To a solution of
azide 42d (0.29 g, 0.442 mmol) in CH Cl (12 mL) were added zinc
turnings (0.43g, 6.624 mmol, 15 equiv) and AcOH (0.19 mL, 3.312
mmol, 7.5 equiv), and the reaction mixture was stirred at rt for 1 h.
The reaction mixture was filtered through a short pad of Celite
washing with MeOH (3 × 10 mL). The combined filtrates were
concentrated and dissolved in EtOAc (10 mL). The EtOAc layer was
washed with satd NaHCO and brine, dried (MgSO ), and evaporated
to obtain the crude 5′-aminonucleoside. To a solution of the 5′-
aminonucleoside in 1,4-dioxane (9 mL) was added sulfamide (0.123 g,
1.284 mmol, 2.9 equiv), and the mixture was refluxed for 2 h. The
reaction mixture was evaporated then partitioned between CH Cl (10
2
2
(
MgSO ), and evaporated to obtain the crude 5′-aminonucleoside. To
4
a solution of the 5′-aminonucleoside in 1,4-dioxane (5 mL) was added
sulfamide (0.072 g, 0.749 mmol, 2.9 equiv), and the mixture was
refluxed for 2 h. The reaction mixture was evaporated and then
partitioned between CH Cl (10 mL) and water (10 mL). The phases
3
4
2
2
were separated, and the organic layer was washed with brine, dried
Na SO ), and evaporated under reduced pressure. Purification by
(
2
4
2
2
flash chromatography (SiO , gradient: hexanes to 70% EtOAc in
mL) and water (10 mL). The phases were separated, and the CH Cl
2
2 2
hexanes) afforded the product (0.15 g, 83%) as a white solid: R = 0.39
layer was washed with brine, dried (Na SO ), and evaporated under
2 4
reduced pressure. Purification by flash chromatography (SiO2,
gradient: hexanes to 70% EtOAc in hexanes) afforded the product
f
1
(
3:1 EtOAc/hexanes); H NMR (400 MHz, CDCl ) δ 8.00 (s, 1H; H-
3
5
2), 7.99 (d, J(8,F2′) = 2.0 Hz, 1H; H-8), 7.34−7.19 (m, 17H; 3 ×
M
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
1
1
2
1
(
0.26 g, 84%) as a white solid: R = 0.51 (3:1 EtOAc/hexanes); H
J(C2′,F2′) = 185.0 Hz), 88.4 (dd, J(C3′,F2′) = 15.1, J(C3′,F3′) =
f
3
2
3
NMR (400 MHz, CDCl ) δ 9.32 (d, J(NH,5′) = 10.0 Hz, 1H; C5′-
201.3 Hz), 87.5 (d, J(C1′,F2′) = 29.7 Hz), 82.9 (dd, J(C4′,F2′) =
3
2
3
1
9
NH), 8.03, 7.73 (2s, 2H; H-2, H-8), 7.36−7.22 (m, 15H; 3 × C H ),
2.5, J(C4′,F3′) = 24.5 Hz), 71.7, 44.5 (d, J(C5′,F3′) = 10.4 Hz); F
3
6
5
6
7
.05 (s, 1H; N -H), 7.04 (d, J = 8.6 Hz, 2H; -PMB), 6.73 (d, J = 8.6
NMR (376 MHz, DMSO-d ) δ −202.6 (dddd, J(F2′,F3′) = 5.1,
6
3
3 3 2
Hz, 2H; -PMB), 5.85 (d, J(1′,2′) = 8.3 Hz, 1H; H-1′), 5.12 (dd,
J(2′,F3′) = 16.6, J(4′,F3′) = 22.6, J(3′,F3′) = 53.1 Hz; F-3′),
213.9 (dm, J(2′,F2′) = 50.0 Hz; F-2′); HRMS (ESI+) m/z calcd for
+
3
2
3
2
J(3′,2′) = 4.3, J(3′,F3′) = 54.4 Hz, 1H; H-3′), 4.90 (ddd, J(2′,3′) =
−
3
3
3
4
=
=
.7, J(1′,2′) = 8.3, J(2′,F3′) = 24.2 Hz, 1H; H-2′), 4.58 (dt, J(5′,4′)
C H F N O SNa [(M + Na) ] 614.1756, found 614.1779 (Δ 3.7
29
27
2
7
3
3
3
2.3, J(5″,4′) = 2.3, J(4′,F3′) = 28.7 Hz, 1H; H-4′), 4.45 (ABq, Δδ
ppm).
31.6 Hz, J = 11.2 Hz, 2H; -PMB), 4.34 (s, 2H; -NH ), 3.74 (s, 3H;
General Procedure 4: Coupling and Deprotection. To a
solution of sulfamide (1.0 mmol, 1.0 equiv) in DMF (20 mL) cooled
to 0 °C was added NHS ester 44 (2.0 mmol, 2.0 equiv) followed by
Cs CO (3.0 mmol, 3 equiv), and the reaction mixture was stirred at
that temperature for 30 min. The reaction mixture was allowed to
warm to rt and stirred for 15 h. The reaction mixture was filtered and
evaporated under reduced pressure to obtain the crude coupled
product. To the crude material was added 80% aqueous TFA (15 mL),
and the mixture was stirred for 1 h. The reaction mixture was
evaporated and re-evaporated with 5% MeOH in CH Cl (×2) under
2
13
-
PMB), 3.48−3.35 (m, 2H; H-5′/5″); C NMR (100 MHz, DMSO-
d ) δ 158.9, 153.8, 151.1, 147.9, 144.8, 141.3, 129.2, 128.9, 128.6,
6
1
1
(
5
−
27.7, 126.6, 121.3, 113.5, 90.4 (d, J(C3′,F3′) = 183.0 Hz), 86.2, 82.1
2
3
2
2
d, J(C2′,F3′) = 23.4 Hz), 76.8 (d, J(C4′,F3′) = 15.6 Hz), 71.1, 70.4,
3
19
0.0, 43.7 (d, J(C5′,F3′) = 10.8 Hz); F NMR (376 MHz, CDCl ) δ
3
3
3
2
196.1 (ddd, J(2′,F3′) = 24.1, J(4′,F3′) = 28.7, J(3′,F3′) = 53.6
1
9
3
Hz); F NMR (376 MHz, DMSO-d ) δ −196.6 (ddd, J(2′,F3′) =
6
3
2
2
4.0, J(4′,F3′) = 27.6, J(3′,F3′) = 53.0 Hz); HRMS (ESI+) m/z
+
calcd for C H FN O SNa [(M + Na) ] 732.2375, found 732.2421
37
36
7
5
2
2
(Δ 6.2 ppm).
reduced pressure. Purification of the residue by flash chromatography
84:15:1 EtOAc/MeOH/Et N) afforded the product with some
6
N -Trityl-9-[2,3,5-trideoxy-2,3-difluoro-5-(N-sulfamoyl)amino-β-
D-xylofuranosyl]adenine (43e). To a solution of azide 42e (0.15 g,
.278 mmol) in MeOH (7 mL) was added 10% Pd/C (0.030 g, 55%
(
3
contamination. Additional purification was performed by preparative
reversed-phase HPLC using a Phenomenex Gemini 10 μm C18 110 Å
(
from 5% to 30% MeCN in 20 mM aqueous triethylammonium
bicarbonate (pH 7.5) over 5 min, followed by isocratic elution with
3
0
wet with water), and the reaction mixture was stirred under H (1
2
250 × 21.2 mm) column at a flow rate of 21 mL/min with a gradient
atm) for 1 h. The reaction mixture was filtered through a short pad of
Celite washing with MeOH (3 × 5 mL). The combined filtrates were
concentrated to obtain the crude 5′-aminonucleoside. To a solution of
the crude 5′-aminonucleoside in 1,4-dioxane (5 mL) was added
sulfamide (0.09 g, 0.94 mmol), and the mixture was refluxed for 2 h.
The reaction mixture was evaporated under reduced pressure.
Purification by flash chromatography (SiO , gradient: hexanes to
0% EtOAc in hexanes) afforded the product (0.14 g, 84%) as a white
solid: R = 0.32 (3:1 EtOAc/hexanes); H NMR (400 MHz, DMSO-
0% MeCN for 15 min. The appropriate fractions containing the
product were pooled and lyophilized to afford the final product.
9
-[2,5-Dideoxy-2-fluoro-5-[N-(N-2-hydroxybenzoyl)sulfamoyl]-
amino-β-D-ribofuranosyl]adenine Triethylammonium Salt (12).
This was prepared from sulfamide 43a (0.100 g, 0.141 mmol) using
general procedure 4 to afford the title compound (0.033 g, 38%) as a
white solid: H NMR (400 MHz, DMSO-d ) δ 8.33, 8.14 (2s, 2H; H-
2
2
7
1
1
f
6
6
d ) δ 8.22 (s, 1H), 7.95 (s, 1H), 7.59 (s, 1H; N -H), 7.35−7.20 (m,
6
, H-8), 7.77 (dd, J = 1.8, 7.7 Hz; 1H), 7.34 (br s, 2H; C -NH ), 7.22
3
6 2
1
(
1
5H; 3 × C H ), 6.96 (t, J(5′/5″,NH) = 6.1 Hz, 1H; C5′-NH), 6.67
3
6
5
(
ddd, J = 1.9, 7.3, 8.3 Hz; 1H), 6.71 (m, 2H), 6.19 (dd, J(1′,2′) = 3.5,
3
3
s, 2H; -NH ), 6.29 (dd, J(1′,2′) = 2.1 Hz, J(1′,F2′) = 19.7, 1H; H-
3
3
2
J(1′,F2′) = 17.0 Hz, 1H; H-1′), 6.12 (t, J(5′/5″,NH) = 7.0 Hz, 1H;
3
3
3
2
′), 5.99 (ddt, J(2′,3′) ≈ J(1′,2′) ≈ 1.7, J(2′,F3′) = 12.7, J(2′,F2′)
3
3
5
≈
=
′-NH), 5.76 (d, J(3′,OH) = 5.8 Hz, 1H; 3′−OH′), 5.51 (dt, J(2′,3′)
3
3
=
47.8 Hz, 1H; H-2′), 5.56 (dddd, J(2′,3′) = 1.4, J(3′,4′) = 3.2,
3
2
3
J(1′,2′) = 4.0, J(2′,F2′) = 52.9 Hz, 1H; H-2′), 4.48 (dm, J(3′,F2′)
3 3 3
3
2
3
J(3′,F2′) = 10.2, J(3′,F3′) = 49.6 Hz, 1H; H-3′), 4.53 (dm, J(4′,F3′)
16.1 Hz, 1H; H-3′), 4.04 (q, J(3′,4′) ≈ J(5′,4′) ≈ J(5″,4′) = 5.2
13
=
28.7 Hz, 1H; H-4′), 3.41−3.25 (m, 2H; H-5′/5″); C NMR (100
3
3
2
Hz, 1H; H-4′), 3.16 (ddd, J(5′,4′) = 3.8, J(5′, NH) = 6.5, J(5′, 5″) =
MHz, DMSO-d ) δ 153.6, 151.6, 148.2, 144.8, 139.0 (d, J = 4.5 Hz),
3
3
2
6
1
5
7
1
(
6
3.2 Hz, 1H; H-5′), 3.03 (ddd, J(5″,4′) = 5.9, J(5″,NH) = 7.6, J(5′,
2
1
1
1
(
(
28.6, 127.7, 126.6, 120.5, 95.5 (dd, J(C2′,F3′) = 32.0, J(C2′,F2′) =
″) = 13.3 Hz, 1H; H-5″), 2.80 (q, J = 7.2 Hz, 6H, Et N), 1.06 (t, J =
2
1
3
82.8 Hz), 92.3 (dd, J(C3′,F2′) = 29.6, J(C3′,F3′) = 182.9 Hz), 86.3
13
.2 Hz, 9H, Et N); C NMR (100 MHz, DMSO-d ) δ 170.0, 160.5,
2
2
3
6
d, J(C1′,F2′) = 36.1 Hz), 79.9 (d, J(C4′,F3′) = 19.5 Hz), 70.3, 40.3
3 19
56.1, 152.8, 148.8, 139.7, 132.1, 129.4, 120.4, 119.2, 117.2, 116.5, 92.7
d, J(C5′,F3′) = 10.6 Hz); F NMR (376 MHz, DMSO-d ) δ
1
2
6
d, J(C2′,F2′) = 187.9 Hz), 85.7 (d, J(C1′,F2′) = 32.8 Hz), 82.2,
4
3
3
−
193.8 (ddtd, J(F2′,4′) = 2.7, J(F2′,3′) = 10.4, J(F2′,F3′) = 10.4,
2
1
9
9.7 (d, J(C3′,F2′) = 15.6 Hz), 45.8, 44.8, 9.1; F NMR (376 MHz,
3
2
3
J(1′,F2′) = 20.7, J(2′,F2′) = 47.8 Hz; F-2′), −207.0 (ddt, J(F2′,F3′)
3
3
DMSO-d ) δ −208.5 (dt, J(3′,F2′) = 16.3, J(1′,F2′) = 16.3,
3
3
2
6
=
11.6, J(2′,F3′) = 11.6, J(4′,F3′) = 28.7, J(3′,F3′) = 50.7 Hz; F-3′);
2
J(2′,F2′) = 52.9 Hz); HRMS (ESI−): m/z calcd for C H FN O S
+
17 17
7
6
HRMS (ESI+) m/z calcd for C H F N O SNa [(M + Na) ]
−
29
27
2
7
3
[
(M − Et NH) ] 466.0951, found 466.0988 (Δ −7.9 ppm).
3
6
14.1756, found 614.1786 (Δ 4.9 ppm).
9
-[2,5-Dideoxy-2-fluoro-5-[N-(N-2-hydroxybenzoyl)sulfamoyl]-
6
N -Trityl-9-[2,3,5-trideoxy-2,3-difluoro-5-(N-sulfamoyl)amino-β-
D-ribofuranosyl]adenine (43f). To a solution of azide 42f (0.32 g,
.59 mmol) in MeOH (10 mL) was added 10% Pd/C (0.06g, 55% wet
with water), and the reaction mixture was stirred under H (1 atm) for
amino-β-D-arabinofuranosyl]adenine Triethylammonium Salt (13).
This was prepared from sulfamide 43b (0.100 g, 0.141 mmol) using
general procedure 4 to afford the title compound (0.033 g, 41%) as a
white solid: H NMR (400 MHz, DMSO-d ) δ 8.27 (d, J(8,F2′) = 2.4
Hz, 1H; H-8), 8.15 (s, 1H; H-2), 7.83 (dd, J = 1.8, 8.2 Hz; 1H), 7.35
(
2
(
0
2
1
5
6
1
h. The reaction mixture was filtered through a short pad of Celite
washing with MeOH (3 × 10 mL). The combined filtrates were
concentrated to obtain the crude 5′-aminonucleoside. To a solution of
the 5′-aminonucleoside in 1,4-dioxane (9 mL) was added sulfamide
br s, 2H; C -NH ), 7.23 (td, J = 1.9, 7.4, 7.5 Hz; 1H), 6.74−6.71 (m,
6
2
3 3
H), 6.38 (dd, J(1′,2′) = 3.7, J(1′,F2′) = 19.0 Hz, 1H; H-1′), 5.98
3
3
d, J(3′,OH) = 4.6 Hz, 1H; 3′−OH′), 5.91 (t, J(5′/5″,NH) = 6.8
(
0.18 g, 1.87 mmol, 3.1 equiv), and the mixture was refluxed for 2 h.
3 3 2
Hz, 1H; 5′-NH), 5.06 (dt, J(2′,3′) = 2.9, J(1′,2′) = 2.9, J(2′,F2′) =
5
The reaction mixture was evaporated under reduced pressure.
Purification by flash chromatography (SiO , gradient: hexanes to
0% EtOAc in hexanes) afforded the product (0.34 g, 94%) as a white
solid: R = 0.30 (3:1 EtOAc/hexanes); H NMR (400 MHz, DMSO-
3
3
3
2.0 Hz, 1H; H-2′), 4.42 (dq, J(2′,3′) = 3.0, J(3′,4′) = 3.2, J(3′,OH)
3 3
2
=
3.2, J(3′,F2′) = 16.4 Hz, 1H; H-3′), 4.01 (dt, J(3′,4′) = 4.2,
3 3
7
3
1
J(5′,4′) = 4.3, J(5″,4′) = 7.9 Hz, 1H; H-4′), 3.15 (ddd, J(5′,4′) =
f
3
2
6
3
4.7, J(5′, NH) = 7.5, J(5′, 5″) = 12.4 Hz, 1H; H-5′), 3.04 (dt,
3 3 2
d ) δ 8.50 (s, 1H), 7.93 (s, 1H), 7.71 (s, 1H; N -H), 7.41 (t, J(5′/
6
J(5″,NH) = 6.8, J(5″,4′) = 6.8, J(5′, 5″) = 13.0 Hz, 1H; H-5″), 2.77
5
(
″,NH) = 6.4 Hz, 1H; C5′-NH), 7.35−7.20 (m, 15H; 3 × C H ), 6.72
6
5
1
3
3
3
(q, J = 7.2 Hz, 6 H, Et N), 1.05 (t, J = 7.2 Hz, 9 H, Et N); C NMR
s, 2H; -NH ), 6.37 (dd, J(1′,2′) = 6.0 Hz, J(1′,F2′) = 13.2, 1H; H-
3
3
2
3
3
3
(100 MHz, DMSO-d ) δ 170.1, 160.5, 156.0, 152.8, 149.0, 139.6 (d,
1
′), 6.00 (dddd, J(2′,3′) = 4.8, J(1′,2′) = 5.6, J(2′,F3′) = 16.4,
6
4
2
2
J(C8,F2′) = 4.2 Hz), 132.1, 129.4, 120.3, 118.2, 117.3, 116.5, 94.7 (d,
J(2′,F2′) = 49.6 Hz, 1H; H-2′), 5.51 (dm, J(3′,F3′) = 52.8 Hz, 1H;
1
2
3
3
J(C2″,F2′) = 191.0 Hz), 82.6 (d, J(C4′,F2′) = 3.0 Hz), 82.3 (d,
H-3′), 4.51 (dm, J(4′,F3′) = 24.4 Hz, 1H; H-4′), 3.27−3.24 (m, 2H;
13
2
H-5′/5″); C NMR (100 MHz, CDCl ) δ 154.7, 152.3, 147.4, 144.6,
J(C1′,F2′) = 16.5 Hz), 74.2 (d, J(C3′,F2′) = 23.7 Hz), 45.7, 44.9,
3
2
19
3
1
40.1, 129.1, 128.2, 127.3, 122.2, 90.4 (dd, J(C2′,F3′) = 12.3,
10.1; F NMR (376 MHz, DMSO-d ) δ −197.6 ppm (dt, J(3′,F2′) =
6
N
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
3
2
+
1
7.7, J(1′,F2′) = 17.7, J(2′,F2′) = 51.9 Hz); HRMS (ESI+) m/z
(ESI+) m/z calcd for C H F N O SNa [(M − Et N + Na) ]
1
7
17
2
7
5
3
+
calcd for C H FN O SNa [(M − Et N + Na) ] 490.0916, found
492.0872, found 492.0893 (Δ 4.2 ppm).
17
18
7
6
3
4
90.0905 (Δ −2.2 ppm).
9-[2,3,5-Trideoxy-2,3-difluoro-5-[N-(N-2-hydroxybenzoyl)-
sulfamoyl]amino-β-D-ribofuranosyl]adenine Triethylammonium
Salt (17). This was prepared from sulfamide 43f (0.240 g, 0.406
mmol) using general procedure 4 to afford the title compound (0.097
g, 44%) as a white solid: H NMR (400 MHz, acetone-d ) δ 8.34, 8.30
9
-[3,5-Dideoxy-3-fluoro-5-[N-(N-2-hydroxybenzoyl)sulfamoyl]-
amino-β-D-xylofuranosyl]adenine Triethylammonium Salt (14).
This was prepared from sulfamide 43c (0.48 g, 0.676 mmol) using
general procedure 4 to afford the title compound (0.15 g, 39%) as a
1
6
1
(2s, 2H; H-2, H-8), 7.92 (dd, J = 1.8, 7.8 Hz, 1H), 7.22 (ddd, J = 1.8,
white solid: H NMR (400 MHz, [D ]DMSO-d ) δ 8.15, 8.05 (2s, 2H;
H-2, H-8), 7.81 (dd, J = 1.9, 8.0 Hz, 1H), 7.29 (br s, 2H; C -NH ),
6
6
4
7
.1, 8.2 Hz, 1H), 6.75−6.70 (m, 2H), 6.33 (ddd, J(1′,F3′) = 1.4,
6
2
3
3
3
3
J(1′,2′) = 6.6, J(1′,F2′) = 12.3 Hz, 1H; H-1′), 6.13 (dddd, J(2′,3′) =
7
=
.23 (td, J = 1.9, 7.4 Hz, 1H), 6.74−6.71 (m, 2H), 6.29 (d, J(2′,OH)
3 3 2
3
4.4, J(1′,2′) = 6.6, J(2′,F3′) = 18.0, J(2′,F2′) = 50.3 Hz, 1H; H-2′),
2 3
4.6 Hz, 1H; 2′−OH), 5.95 (t, J(5′/5″,NH) = 6.7 Hz, 1H; 5′-NH),
3 3
5.57 (dm, J(3′,F3′) = 53.6 Hz, 1H; H-3′), 4.58 (dm, J(4′,F3′) = 25.8
3 2
5
.90 (d, J(1′,2′) = 2.3 Hz, 1H; H-1′), 5.08 (ddd, J(3′,2′) = 1.3,
3
2
3
Hz, 1H; H-4′), 3.42 (dd, J(5′,4′) = 4.1, J(5′,5″) = 13.9 Hz, 1H; H-
3 2
J(3′,4′) = 2.8, J(3′,F3′) = 51.9 Hz, 1H; H-3′), 4.72 (dm, J(2′,F3′) =
3
3
3
5′), 3.35 (dd, J(5″,4′) = 4.4, J(5′,5″) = 13.9 Hz, 1H; H-5″), 2.89 (q, J
1
1
=
(
2
6.1 Hz, 1H; H-2′), 4.34 (dtd, J(3′,4′) = 3.1, J(5′,4′) = 6.2, J(5″,4′)
3
= 7.2 Hz, 6H, Et
MHz, DMSO-d ) δ 14.02 (s, 1H), 8.41, 8.17 (2s, 2H; H-2, H-8), 7.78
dd, J = 1.8, 7.7 Hz, 1H), 7.41 (br s, 2H; C -NH ), 7.22 (ddd, J = 1.9,
3
N), 1.15 (t, J = 7.2 Hz, 9H, Et N); H NMR (400
3
6.6, J(4′,F3′) = 29.1 Hz, 1H; H-4′), 3.26−3.21 (m, 1H; H-5′), 3.13
3 3 2
6
dt, J(5″,NH) = 6.7, J(5″,4′) = 6.7, J(5′,5″) = 13.2 Hz, 1H; H-5″),
(
13
6
2
.99 (q, J = 7.2 Hz, 6 H, Et N), 1.13 (t, J = 7.2 Hz, 9 H, Et N); C
3
3
7
.3, 8.5 Hz, 1H), 6.73−6.69 (m, 2H), 6.58 (t, J = 7.0 Hz, 1H; C5′-
NMR (100 MHz, DMSO-d ) δ 170.2, 160.5, 156.0, 152.7, 149.1, 138.2
4 3 3
6
NH), 6.30 (ddd, J(1′,F3′) = 1.6, J(1′,2′) = 6.7, J(1′,F2′) = 12.6 Hz,
5
(
(
7
9
1
d, J(C8,F3′) = 5.4 Hz), 132.1, 129.4, 120.3, 118.8, 117.2, 116.5, 95.7
3
3
3
1
H; H-1′), 6.07 (dddd, J(2′,3′) = 4.2, J(1′,2′) = 6.5, J(2′,F3′) =
2 3
1
2
d, J(C3′,F3′) = 183.9 Hz), 88.9, 80.2 (d, J(C2′,F3′) = 18.9 Hz),
1
8.2, J(2′,F2′) = 50.0 Hz, 1H; H-2′), 5.52 (dtd, J(3′,4′) = 2.1,
3 2
2
3
7.6 (d, J(C4′,F3′) = 26.5 Hz), 45.7, 41.5 (d, J(C5′,F3′) = 10.1 Hz),
3
J(3′,F2′) = 3.9, J(2′,3′) = 3.9, J(3′,F3′) = 53.8 Hz, 1H; H-3′), 4.45
.2; 19F NMR (376 MHz, DMSO-d ) δ −200.2 (ddd, J(2′,F3′) =
3
6
4
3
3
3
(
dtt, J(4′,F2′) = 2.3, J(3′,4′) = 2.3, J(5′,4′) = 4.5, J(5″,4′) = 4.5,
3
2
5.2, J(4′,F3′) = 28.9, J(3′,F3′) = 51.6 Hz); HRMS (ESI+) m/z
3
J(4′,F3′) = 24.9 Hz, 1H; H-4′), 3.18−3.14 (m, 2H; H-5′/5″) 3.05 (q,
+
calcd for C H FN O SNa [(M − Et N + Na) ] 490.0916, found
13
17
18
7
6
3
J = 7.3 Hz, 6H, Et N), 1.15 (t, J = 7.3 Hz, 9H, Et N); C NMR (100
3
3
4
90.0898 (Δ −3.7 ppm).
MHz, DMSO-d ) δ 170.0, 160.6, 156.2, 153.0, 149.0, 140.0, 132.1,
6
9
-[3,5-Dideoxy-3-fluoro-5-[N-(N-2-hydroxybenzoyl)sulfamoyl]-
2
1
29.4, 120.4, 119.2, 117.2, 116.5, 90.03 (dd, J(C3′,F2′) = 13.4,
amino-β-D-ribofuranosyl]adenine Triethylammonium Salt (15).
This was prepared from sulfamide 43d (0.23 g, 0.324 mmol) using
1
2
1
J(C3′,F3′) = 184.0 Hz), 89.2 (dd, J(C2′,F3′) = 14.7, J(C2′,F2′) =
2
3
1
94.4 Hz), 84.3 (d, J(C1′,F2′) = 29.9 Hz), 81.3 (dd, J(C4′,F2′) =
general procedure 4 to afford the title compound (0.08 g, 45%) as a
white solid: H NMR (400 MHz, DMSO-d ) δ 8.37, 8.17 (2s, 2H; H-
2
3
1
3.4, J(C4′,F3′) = 22.4 Hz), 45.8, 43.9 (d, J(C5′,F3′) = 9.0 Hz), 8.8;
6
19
3
3
F NMR (376 MHz, DMSO-d ) δ −202.03 (dddd, J(F2′,F3′) = 5.5,
6
2
(
(
, H-8), 7.78 (dd, J = 1.8, 7.7 Hz; 1H), 7.32 (br s, 2H; C −NH ), 7.21
6
2
3
2
J(2′,F3′) = 18.2, J(4′,F3′) = 24.4 Hz, J(3′,F3′) = 54.0 Hz; F-3′),
ddd, J = 1.9, 7.2, 8.2 Hz;1H), 6.77 (t, J = 7.0 Hz, 1H; 5′-NH), 6.70
4
3
3
3
−215.45 (dddt, J(4′,F2′) = 3.1, J(3′,F2′) = 3.1, J(F2′,F3′) = 5.7,
td, J = 1.2, 9.3 Hz; 2H), 5.90 (d, J(2′,OH) = 5.7 Hz, 1H; 2′−OH),
3
1
3
3
J(1′,F2′) = 12.0, J(2′,F2′) = 49.9 Hz; F-2′); HRMS (ESI+) m/z
5
.88 (d, J(1′,2′) = 8.1 Hz, 1H; H-1′), 5.10 (dd, J(3′,2′) = 4.1,
+
2
3 3
calcd for C H F N O SNa [(M − Et N + Na) ] 492.0872, found
17
17
2
7
5
3
J(3′,F3′) = 55.6 Hz, 1H; H-3′), 5.08 (dd, J(1′,2′) = 8.5, J(2′,F3′) =
3
3
492.0899 (Δ 5.4 ppm).
2
6.0 Hz, 1H; H-2′), 4.34 (ddd, J(5′,4′) = 4.1, J(5″,4′) = 5.1,
3
J(4′,F3′) = 27.8 Hz, 1H; H-4′), 3.13−3.10 (m, 2H, H-5′/5″), 2.91 (q,
13
ASSOCIATED CONTENT
■
* Supporting Information
1 13
J = 7.2 Hz, 7.8 H, Et N), 1.10 (t, J = 7.2 Hz, 11.7 H, Et N); C NMR
3
3
(
1
100 MHz, DMSO-d ) δ 169.9, 160.6, 156.1, 152.7, 149.3, 140.4,
S
6
1
19
32.0, 129.4, 120.5, 119.4, 117.1, 116.4, 93.2 (d, J(C3′,F3′) = 181.2
H, C, and F NMR spectra for all compounds, HPLC traces
2
2
Hz), 86.6, 82.0 (d, J(C2′,F3′) = 22.7 Hz), 70.9 (d, J(C4′,F3′) = 16.4
and conformational analysis of 12−17, and a complete
description of the rat pharmacokinetic studies, MbtA inhibition
assay, and M. tuberculosis MIC assay. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.joc.5b00550.
3
19
Hz), 45.7, 44.3 (d, J(C5′,F3′) = 11.3 Hz), 9.4; F NMR (376 MHz,
3
3
DMSO-d ) δ −197.0 (dt, J(2′,F3′) = 27.4, J(4′,F3′) = 27.4,
6
2
J(3′,F3′) = 55.3 Hz); HRMS (ESI+) m/z calcd for C H FN O SNa
17
18
7
6
+
[
(M − Et N + Na) ] 490.0916, found 490.0939 (Δ 4.7 ppm).
3
9
-[2,3,5-Trideoxy-2,3-difluoro-5-[N-(N-2-hydroxybenzoyl)-
sulfamoyl]amino-β-D-xylofuranosyl]adenine Triethylammonium
Salt (16). This was prepared from sulfamide 43e (0.360 g, 0.608
AUTHOR INFORMATION
Corresponding Author
*E-mail: aldri015@umn.edu.
Notes
■
mmol) using general procedure 4 to afford the title compound (0.141
1
g, 50%) as a white solid: H NMR (400 MHz, DMSO-d ) δ 8.15, 8.07
6
(
2s, 2H; H-2, H-8), 7.79 (dd, J = 1.9, 8.1 Hz, 1H), 7.35 (br s, 2H; C6-
NH ), 7.22 (ddd, J = 2.0, 8.0, 9.2 Hz, 1H), 6.73−6.69 (m, 2H), 6.24
2
3
3
The authors declare no competing financial interest.
(
dd, J(1′,2′) = 2.1, J(1′,F2′) = 19.4 Hz, 1H; H-1′), 5.99 (t, J = 6.7
3 3 3
Hz, 1H; C5′-NH), 5.87 (ddt, J(2′,3′) = 1.6, J(1′,2′) = 1.7, J(2′,F3′)
2
3
ACKNOWLEDGMENTS
=
12.9, J(2′,F2′) = 47.7 Hz, 1H; H-2′), 5.52 (dddd, J(2′,3′) = 1.4,
3 2
■
3
J(3′,4′) = 3.2, J(3′,F2′) = 10.2, J(3′,F3′) = 49.6 Hz, 1H; H-3′), 4.52
This work was supported by a grant from the NIH (AI070219
to C.C.A.) and the Intramural Research Program of the NIAID,
NIH (C.E.B.).
3
3
(
dm, J(4′,F3′) = 28.9 Hz, 1H; H-4′), 3.28 (ddd, J(5′,4′) = 5.8,
2
3
J(5′,NH) = 7.4, J(5′,5″) = 13.2 Hz, 1H; H-5′), 3.18−3.12 (m, 1H;
H-5″) 2.92 (q, J = 7.2 Hz, 6 H, Et N), 1.10 (t, J = 7.2 Hz, 9 H, Et N);
3
3
1
3
C NMR (100 MHz, DMSO-d ) δ 170.2, 160.5, 156.1, 152.9, 149.0,
6
DEDICATION
■
1
38.0 (d, J = 4.3 Hz), 132.2, 129.4, 120.3, 128.8, 127.3, 116.5, 95.7
2
1
Dedicated to the memory of the late Professor Kyo Watanabe
for his pioneering work in nucleoside chemistry and fluorinated
nucleosides.
(
dd, J(C2′,F3′) = 32.0, J(C2′,F2′) = 182.9 Hz), 92.5 (dd,
2
1
2
J(C3′,F2′) = 29.6, J(C3′,F3′) = 182.7 Hz), 86.1 (d, J(C1′,F2′) =
3
2
3
5.8 Hz), 80.2 (d, J(C4′,F3′) = 19.3 Hz), 45.7, 41.2 (d, J(C5′,F3′) =
9
.9 Hz), 9.2; 19F NMR (376 MHz, DMSO-d ) δ −193.82 (ddtd,
6
4
3
3
3
J(4′,F2′) = 2.6, J(F2′,F3′) = 10.3, J(3′,F2′) = 10.3, J(1′,F2′) = 18.8,
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DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX

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P
DOI: 10.1021/acs.joc.5b00550
J. Org. Chem. XXXX, XXX, XXX−XXX