Design and divergent synthesis of aza nucleosides from a chiral imino sugar

Article abstract of DOI:10.1021/jo3004452

Several novel nucleoside analogues as potential inhibitors of glycosidases and purine nucleoside phosphorylase (PNP) have been synthesized via selective coupling of an appropriate nucleobase at different positions of an orthogonally protected imino sugar

Full text of DOI:10.1021/jo3004452

Article
pubs.acs.org/joc
Design and Divergent Synthesis of Aza Nucleosides from a Chiral
Imino Sugar
†,§
Saul Martınez-Montero, Susana Fernandez,† Yogesh S. Sanghvi,‡ Jyoti Chattopadhyaya,§
́
́
́
Muthupandian Ganesan,¶ Namakkal G. Ramesh,¶ Vicente Gotor,*,† and Miguel Ferrero*,†
†
́
́
Departamento de Quımica Organica e Inorganica and Instituto Universitario de Biotecnologıa de Asturias, Universidad de Oviedo,
́
́
33006 Oviedo (Asturias), Spain
‡Rasayan Inc., 2802 Crystal Ridge Road, Encinitas, California 92024-6615, United States
§Program of Bioorganic Chemistry, Institute of Cell and Molecular Biology, Biomedical Centre, Uppsala University, SE-75123
Uppsala, Sweden
¶Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India
S
* Supporting Information
ABSTRACT: Several novel nucleoside analogues as potential
inhibitors of glycosidases and purine nucleoside phosphorylase
(PNP) have been synthesized via selective coupling of an appropriate
nucleobase at different positions of an orthogonally protected imino
sugar as a common precursor. This synthetic strategy offers a
straightforward protocol for the assembly of imino sugar containing
nucleosides, establishing a new repertoire of molecules as potential
therapeutics.
imino sugars are the polyhydroxypyrrolidines, which are known
to interact with glycosidases and glycotransferases. Radicamine
A (2) and B (3) are representative examples4 together with
naturally occurring 3,4-dihydroxy-2,5-bis(hydroxymethyl)-
pyrrolidine (DMDP, 4) and its corresponding analogues 5
and 6 exhibiting potent glycosidase inhibition.5
INTRODUCTION
■
The synthesis and development of glycosidase inhibitors have
been the focus of attention, due to their vital role played by
carbohydrates in a variety of biological processes. The
glycosidases are responsible for catalyzing the cleavage of the
glycosidic bonds in oligosaccharides and glycoconjugates. Thus,
these enzymes are involved in a wide range of biochemical
process such as intestinal digestion, post-translational process-
ing of glycoproteins, and the lysosomal catabolism of
glycoconjugates.1 Consequently, compounds that are able to
inhibit or modulate the activity of glycosidases have proven to
be promising anticancer, antidiabetes, and antiviral agents.2
One of the most potent glycosidase inhibitors belongs to the
class of imino sugars (or aza sugars), with a demonstrated
ability to mimic the carbohydrates or their transition states
during hydrolysis as the primary mechanism of their action.2a,3
As an example, Miglitol (1, Figure 1) is an FDA approved drug
for the treatment of diabetes.2a Yet another important class of
Additionally, the therapeutic potential of aza sugars has been
further exploited by Schramm and co-workers in the design of
purine nucleoside phosphorylase (PNP, E.C. 2.4.2.1) inhibitors.
PNP is a ubiquitous nucleoside processing enzyme essential for
DNA and RNA synthesis and energy metabolism. It is involved
in the reversible phosphorolysis of purine nucleosides to their
respective bases and ribose(deoxyribose)-α-1-phosphate. In-
hibition of PNP leads to an accumulation of 2′-deoxyguanosine
triphosphate (dGTP) in T-cells that are not able to metabolize
dGTP because of their low nucleotidase activity, causing high
concentrations of this compound and ultimately leading to
cellular apoptosis. Therefore, PNP is a key target for the control
of T-cell proliferative disorders and consequently, for the
treatment of leukemia and autoimmune related diseases.6
The seminal work by Schramm in understanding the
transition state for the natural PNP-catalyzed hydrolysis of
inosine has resulted in the rational design and synthesis of a
series of PNP inhibitors.7 A variety of imino sugar containing
nucleoside analogues have been identified to mimic the
oxocarbenium ion character at the transition state. Some of
Received: March 5, 2012
Published: May 2, 2012
Figure 1. Structures of selected potent glycosidase inhibitors.
© 2012 American Chemical Society
4671
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678

The Journal of Organic Chemistry
Article
them have shown to exhibit high PNP inhibitory activity.8 In
fact, two nucleoside analogues are currently in human clinical
trials for the treatment of T- and B-cell cancers and other
autoimmune disorders. These are first-generation Immucillin-H
(7, Figure 2) and second-generation DADMe-immucillin-H (8)
analogues. Use of an imino sugar and 9-deazapurine base was a
central feature in the design of these two nucleoside analogues.
a
Scheme 1. Synthesis of Aza Sugar Nucleoside 15
a
Reaction conditions: (a) ref 15; (b) Na2CO3/MeOH (99%); (c)
TsCl, pyridine, 50 °C (90%); (d) adenine, 18-crown-6, DMF, 90 °C
(81%); (e) Mg/MeOH, reflux (90%); (f) concentrated HCl, reflux
(82%).
Figure 2. Structures of the two PNP inhibitors currently in clinical
trials.
The overall biological importance of polyhydroxypyrrolidines
has sparked significant efforts in their synthesis.9 As a result,
further studies on the synthesis and biological evaluation of
polyhydroxypyrrolidines and related compounds are of broad
interest. Additionally, one of the key objectives of modern drug
discovery is to increase the diversity and number of small
molecules available for biological screening.10 Diversity-
oriented synthesis (DOS) is already playing a major role in
medicinal chemistry. Although DOS is usually directed toward
a single biological target, it can also be used to identify new
ligands for different targets, usually enzymes. To achieve this
goal, one approach involves generation of inhibitors of different
enzymes from a common synthetic precursor.11
Figure 3. Three classes of orthogonal protecting groups of imino sugar
10.
and 25. In the second set of N-linked nucleosides, we utilized
the unnatural 9-deazapurine base and connected it to the ring
nitrogen to furnish compounds 28 and 31.
Given the central role of the polyhydroxypyrrolidine moiety
in the design of glycosidase, PNP type inhibitors and our
ongoing efforts for discovering biologically active nucleosides,12
we embarked on the synthesis of novel structures. The focus of
this study is to use a common and versatile polyhydrox-
ypyrrolidine precursor and introduce a suitable nitrogenated
base at different positions of the imino sugar to generate
potential enzyme inhibitors. Herein, we describe a practical
synthetic strategy leading to a fast and efficient preparation of
structurally diverse nucleoside analogues from a single imino
sugar precursor.13
Synthesis of C-Linked Nucleosides. The synthesis of
imino sugar containing nucleoside 15 was accomplished in five
steps, starting with 10. First, selective hydrolysis of the acetyl
group with Na2CO3 in MeOH furnished 11 in quantitative
yield. The deprotection of N-Ts was not observed under the
mild conditions used for the hydrolysis of an acetyl group.
Second, the primary hydroxyl group in 11 was tosylated under
standard conditions to furnish 12 in excellent yield. In the third
step, glycosylation of protected 12 with adenine base17 afforded
protected nucleoside 13 in good yield (ca. 81%) after silica gel
chromatography. It is noteworthy that N9-substituted product
was isolated as the major product upon glycosylation. The
deprotection of 13 into 15 was achieved in a two-step process.
First, detosylation with Mg/MeOH and then debenzylation
with an acid offered unprotected nucleoside 15 in good yield
(Scheme 1). The structure of nucleoside 15 was established by
1H and 13C NMR data.
Wong et al. reported that the introduction of a methyl group
into the N1 position of the imino sugars resulted in improved
biological properties.16a,18 Therefore, we also became interested
in developing a method to synthesize the N-methylated
analogue of 15. As shown in Scheme 2, the reaction of
compound 10 with Mg in MeOH removed the tosyl group with
concomitant cleavage of the acetyl protecting group to afford
16 in high yield (ca. 89%). Interestingly, when we tried the N-
detosylation of 10 using Mg turnings activated with iodine, we
observed the formation of 17 in moderate yield (46%). We
postulate that in situ iodine mediated oxidation of MeOH to
formaldehyde may have contributed to the formation of bicyclic
structure 17.19
RESULTS AND DISCUSSION
■
An efficient synthesis of imino sugar 5 has been described by
Kumar and Ramesh as a strong α-fucosidase inhibitor14 from
commercially available tri-O-benzyl-D-glucal 9 (Scheme 1).15
The synthesis of 5 was accomplished in a few steps from the
protected imino sugar 10. We noted that chiral imino sugar 10
is perfectly set up with three orthogonal protecting groups that
could be cleaved or manipulated selectively to expose a single
functionality at a time. Also, we were inspired by the fact that
five-membered imino sugars have shown glycosidase inhibitory
activity.16 Therefore, it was of interest to expand the study to
construct nucleosides containing imino sugars. Herein, we
describe the utility of 10 as an ideal starting material for
building novel nucleoside analogues (Figure 3).
We envisioned synthesizing two types of nucleoside
analogues starting from imino sugar 10. The first set of C-
linked nucleosides was built via attachment of a natural adenine
base to the C2 position of 10, resulting in compounds 15, 20,
4672
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678

The Journal of Organic Chemistry
Article
a
a
Scheme 2. Synthesis of Aza Sugar Nucleoside 20
Scheme 3. Synthesis of Bicyclic Locked Nucleoside 25
a
Reaction conditions: (a) concentrated HCl, reflux (66%); (b) CH2
C(OMe)CH3, THF, DMF, p-TSOH, room temperature (98%); (c)
TfCl, DMAP, Py, room temperature (53%); (d) TFA, CH2Cl2, room
temperature (91%); (e) Mg/MeOH, reflux (79%).
a
Reaction conditions: (a) Mg/MeOH, reflux (89%); (b) HCHO,
dioxane, AcOH, 60 °C (94%); (c) Mg/MeOH/I2, room temperature
(46%); (d) H2/Pd/C, MeOH (68%); (e) MsCl, Py, room
temperature; (f) adenine, 18-crown-6, K2CO3, DMF, 90 °C (36%,
two steps); (g) concentrated HCl, reflux (81%).
example of a locked bicyclic homoaza nucleoside synthesized in
a straightforward manner.
The structures of 24 and 25 were confirmed by extensive
analysis of 1D and 2D NMR spectroscopy. After cyclization,
HMBC spectra of compound 24 clearly showed a three-bond
correlation between C3 and CH2O hydrogen atoms of the new
five-membered ring together with other expected cross-peaks.
The structure was further confirmed on the basis of the
NOESY spectrum of the final compound 25, which showed a
correlation between H3 and H4 hydrogen atoms, supporting
the change in the previous trans relative configuration between
them. These data supported the inversion at the C3 position
(Figure 4).
However, the synthesis of 17 was unequivocally established
by treatment of 16 with aqueous formaldehyde in the presence
of acid, giving 94% of the desired product. Next, selective
hydrogenolysis of the hemiaminal afforded N-methylated aza
sugar 18 without cleaving the benzyl groups. Subsequent
tosylation of 18 under conditions identical with those described
for 11 furnished a mixture of products. The 1H NMR spectra of
the mixture failed to show the presence of the tosyl signals.
Gratifyingly, mesylation of 18 followed by nucleophilic
substitution by adenine yielded the fully protected compound
19. Debenzylation of 19 with concentrated HCl furnished N-
methylated nucleoside 20, and the structure was corroborated
by 1H and 13C NMR data. Moreover, the NOESY spectrum of
20 did not show correlations between H2 and H5, either
between H3 and H4 hydrogen atoms, which is in agreement
with a relative trans configuration, indicating retention of the
stereochemistry of the aza sugar after several transformations.
The expeditious synthesis of nucleoside 15 and the C3-
hydroxyl group configuration suitable for an elimination
followed by ring closure encouraged us to assemble locked
nucleic acid structures that are key building blocks for antisense
oligonucleotides as therapeutic agents.20 Additionally, examples
of natural and synthetic bicycle imino sugars with glycosidase
inhibitory activity prompted us to undertake the synthesis of a
locked aza nucleoside.9b,21 Therefore, installation of a leaving
group on the C3 hydroxyl group may allow ring closure onto
the hydroxymethyl group, furnishing the novel bicyclic locked
nucleoside analogue 25 (Scheme 3).
The synthesis of nucleoside 25 was accomplished in five
steps starting with 13. First, acid treatment of 13 successfully
cleaved the three benzyl groups simultaneously to furnish 21 in
good yield. The resulting 1,3-diol system in 21 was selectively
protected with 2,2-dimethoxypropane to afford ketal 22 in
almost quantitative yield. Next, the hydroxyl group in 22 was
transformed into triflate by treatment with TfCl in the presence
of DMAP, furnishing 23 in a modest 53% yield. We were
pleased to note that the treatment of 23 with a TFA−CH2Cl2
mixture not only deblocked the acetal but also triggered an in
situ cyclization, resulting in the formation of bicyclic homoaza
nucleoside 24 in excellent yield. Removal of the tosyl group
from 24 following the same protocol as before yielded the final
compound 25. To the best of our knowledge, this is the first
Figure 4. Key HMBC and NOESY correlations in 24 and 25.
Synthesis of N-Linked Nucleosides. The first and second
generations of PNP inhibitors containing an imino sugar
moiety have already demonstrated their potential in the design
of drug molecules, where Immucillin-H was granted orphan
drug status in the United States for the treatment of various
leukemia. Subsequently, Schramm and co-workers described a
new class of inhibitors (8, Figure 2) for PNP in which the 9-
deazapurine moiety is directly attached to the N atom of the aza
sugar via a methylene bridge.22 Currently, DADMe-Immunillin-
H is under phase II clinical development for the treatment of
gout. The promising PNP inhibitory activity of N-linked
nucleosides prompted us to undertake the synthesis of the two
aza sugar nucleoside analogues 28 and 31 (Schemes 4 and 5,
respectively).
Orthogonally protected aza sugar 10 also serves as an
attractive starting material for the synthesis of proposed PNP
inhibitors, increasing the molecular diversity that can be created
from a single imino sugar structure. The aza sugar 10 was
conveniently transformed into 16 (Scheme 2) with the
unprotected imino group ready for coupling with the base.
Schramm et al. have utilized the Mannich reaction for the
assembly of immucillin analogues starting with imino sugars.23
Surprisingly, the reaction of 16, 9-deazapurine, and form-
4673
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678

The Journal of Organic Chemistry
Article
mixture to afford the protected product 30 in excellent yield.
Next, the acid-mediated deprotection of 30 gave the fluoro
nucleoside 31 in 84% yield, isolated as the hydrochloride salt.
Scheme 4. Synthesis of N-Linked Nucleoside 28
CONCLUSIONS
■
In summary, we have synthesized a series of five nucleoside
analogues using divergent and high-yielding protocols. We
started from the common chiral imino sugar 10 by selective
removal of the protecting groups followed by glycosylation with
appropriate bases. The homoaza nucleoside 15 and its bicyclic
analogue 25 were assembled by starting from 10, where the O-
acetyl group was deblocked selectively. A serendipitous reaction
led to the formation of the bicyclic structure 17, which was
further transformed into the N-methyl derivative 20. On the
other hand, concomitant deprotection of N-tosylate and O-
acetyl groups from 10 offered a short synthesis of potential
PNP inhibitors 28 and its fluorine analogue 31 via reductive
amination. This study illustrates the successful utility and
applications of the easily accessible aza sugar 10 for the
preparation of novel N- and C-linked nucleoside analogues with
potential for interesting biological activity. Clearly, aza sugar 10
is a desirable scaffold containing orthogonal protecting groups
that will enable the discovery of divergent reaction pathways
and synthesis of structurally diverse compounds needed for
modern day drug discovery and synthetic organic chemistry
applications. Full exploitation of this unique class of nucleosides
as potential therapeutics and their biological screening is
currently in progress.
a
Scheme 5. Synthesis of Fluoro Aza Sugar Nucleoside 31
a
Reaction conditions: (a) DAST, CH2Cl2, 0 °C; (b) Mg/MeOH,
reflux (56%, two steps); (c) 26, MeOH/THF, 40 °C, NaBH3CN
(85%); (d) concentrated HCl, reflux (84%)
aldehyde under Mannich conditions led to the formation of the
bicycle 17 (Scheme 2) as a major product instead of the desired
nucleoside. We believe that the iminium intermediate formed
after the reaction of 16 with formaldehyde underwent
concomitant intramolecular attack of the free hydroxyl group
to furnish 17. Therefore, an alternative approach was
conceived, starting with the previously reported 9-deazapurine
268g prefunctionalized with an aldehyde group that will be
easier to link with imino sugar 16 using reductive amination
conditions. As expected, the coupling of 16 with aldehyde 26 in
the presence of NaBH3CN furnished the desired nucleoside 27
in 84% isolated yield after chromatography (Scheme 4).
Next, the treatment of 27 with acid cleanly removed all five
protecting groups in 2.5 h under reflux to furnish the N-linked
nucleoside 28 as a hydrochloride salt. The structure of 28 was
established by extensive NMR and MS data. 1H NMR spectrum
of compound 28 shows only half of the expected signals,
confirming the C2 axis of symmetry that was further supported
by NOESY experiments. It is striking to note that the synthesis
of a complex nucleoside such as 28 was accomplished in three
simple steps starting with 10 in high yield.
In recent years, use of the fluorine atom has proven to be an
indispensable tool for drug discovery efforts.24 For this reason,
Schramm et al. have described the synthesis and biological
evaluation of an inhibitor of human PNP where one of the
hydroxyl groups of the pyrrolidine moiety has been replaced by
a fluorine atom.25 In a similar way, we wished to synthesize the
fluoro nucleoside 31 as a structural analogue of nucleoside 28,
expanding the repertoire of aza nucleosides accessible for drug
discovery efforts. The prior success of the synthesis of 28
prompted us to install the fluorine substituent first and then
carry out the coupling with the formyl-functionalized 26.
Therefore, treatment of 11 with DAST at a low temperature
followed by N-detosylation of the crude product furnished 29
in moderate yield (ca. 55%) over two steps (Scheme 5).
Fluoro aza sugar 29 was then reductively alkylated with
aldehyde 26 in the presence of NaBH3CN in a MeOH/THF
EXPERIMENTAL SECTION
■
General Considerations. All reagents were the highest
commercial quality and were used without further purification. All
nonaqueous reactions were carried out under anhydrous conditions in
dry, freshly distilled solvents. Reactions were monitored by TLC
carried out using UV light as visualizing agent and/or acidic aqueous
permanganate or 7% ethanolic phosphomolybdic acid. Flash
chromatography was performed using silica gel 60 (230−400 mesh).
1H, 13C NMR, and DEPT were obtained using 300.13, 400.13, and
600.13 MHz instruments for 1H and 75.5, 90.61, and 150.90 MHz for
13C. The same spectrometers were used for the acquisition of H−1H
1
homonuclear (COSY and NOESY) and 1H−13C heteronuclear
(HSQC and HMBC) correlations. Optical rotations were recorded
on a polarimeter, and values are reported as follows: [α]λT (c (g/100
mL), solvent). High-resolution mass spectra (HRMS) were recorded
on a mass spectrometer under electron spray ionization (ESI)
conditions.
Procedures and Experimental Data. (2S,3R,4R,5R)-3,4-Bis-
(benzyloxy)-5-(benzyloxymethyl)-2-(hydroxymethyl)-N-(p-
toluenesulfonamido)pyrrolidine (11). A suspension of 10 (400 mg,
0.635 mmol) and Na2CO3 (508 mg, 4.8 mmol) in MeOH (8 mL) was
stirred at reflux for 1.5 h. After completion of the reaction, the mixture
was filtered over Celite and washed with MeOH and CH2Cl2. Solvents
were evaporated to give 1115 as a colorless viscous liquid (372 mg,
99%) without purification.
(2S,3R,4R,5S)-3,4-Bis(benzyloxy)-5-(benzyloxymethyl)-2-[(4-
methylphenyl)sulfonyl]oxy-N-(p-toluenesulfonamido)pyrrolidine
(12). A solution of 11 (373 mg, 0.635 mmol) and p-TsCl (607 mg, 3.2
mmol) in dry pyridine (6.5 mL) was stirred overnight at 50 °C.
Pyridine was evaporated under high vacuum, and the resulting residue
was subjected to flash chromatography (20% EtOAc/hexane) to yield
12 (424 mg, 90%) as a colorless viscous liquid. Rf (50% EtOAc/
hexanes): 0.69. IR (KBr): ν 3.063, 3034, 2924, 2871, 1736, 1598, 1496
20
cm−1. [α]D = −14° (c 0.5, CH2Cl2). 1H NMR (CDCl3, 300.13
MHz): δ 2.34, (s, 3H), 2.38 (s, 3H), 3.58 (d, 1H, JHH 10.0 Hz), 3.80
(dd, 1H, JHH 10.0 Hz, JHH 3.1 Hz), 3.98 (m, 2H), 4.23 (m, 5H), 4.63
(m, 6H), 7.03 (m, 2H), 7.24 (m, 16H), 7.70 (d, 2H, JHH 8.4 Hz), 7.77
4674
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678

The Journal of Organic Chemistry
Article
(d, 2H, JHH 6.9 Hz). 13C NMR (CDCl3, 75.5 MHz): δ 21.3, 21.4, 56.9,
58.2, 65.8, 67.2, 72.5, 73.0, 73.3, 80.0, 80.2, 126.8−129.4 (23 C),
132.8, 137.2, 137.8, 138.0, 138.2, 143.4, 144.6. MS (ESI+, m/z) 742
[(M + H)+ 10%], 764 [(M + Na)+ 60%]. HRMS (ESI+): calcd for
C41H43NNaO8S2 [M + Na]+ 764.2322, found 764.2299.
JHH 9.3 Hz), 3.90 (q, 1H, JHH 4.4 Hz), 4.09 (m, 2H), 4.20 (m, 2H),
4.45 (d, 1H, JHH 12.0 Hz), 4.69−4.52 (m, 6 H), 7.29−7.43 (m, 15H).
13C NMR (CDCl3, 75.5 MHz): δ 65.0, 65.5, 65.7, 71.1, 72.9, 73.1,
74.1, 81.9, 83.4, 87.5, 128.2−129.2 (15C), 138.5, 138.7, 139.1. MS
(ESI+, m/z): 446 [(M + H)+ 100%]. HRMS (ESI+): calcd for
C28H32NO4 [M + H]+ 446.2326, found 446.2350.
(2S,3R,4R,5S)-2-(9-Adeninylmethyl)-3,4-bis(benzyloxy)-5-(benzy-
loxymethyl)-N-(p-toluenesulfonamido)pyrrolidine (13). A mixture of
compound 12 (300 mg, 0.426 mmol), adenine (86 mg, 0.639 mmol),
K2CO3 (118 mg, 0.852 mmol), and 18-crown-6 (168 mg, 0.639 mmol)
in DMF (4.3 mL) was heated to 90 °C overnight. DMF was
evaporated under vacuum, and flash column chromatography (2%
MeOH/CH2Cl2) of the residue gave pure 13 (239 mg, 81%) as a
white foam. Rf (10% MeOH/90% CH2Cl2): 0.48. [α]D20 = +20° (c 0.5,
CH2Cl2). 1H NMR (CDCl3, 300.13 MHz), 2.32 (s, 3H), 3.57 (d, 1H,
JHH 9.0 Hz), 3.97−4.17 (m, 4H), 4.25−4.70 (m, 7H), 4.96 (dd, 1H,
JHH 2.2 Hz, JHH 13.8 Hz), 6.26 (br s, 2H), 6.88 (m, 2H), 6.90−7.32
(m, 16H), 7.93 (d, 2H, JHH 9.0 Hz), 7.97 (s, 1H), 8.39 (s, 1H). 13C
NMR (CDCl3, 75.5 MHz): δ 21.5, 44.3, 57.2, 59.0, 65.3, 72.6, 73.2,
80.1, 80.5, 119.3, 126.8−129.4 (20C), 136.9, 137.3, 137.5, 137.8,
142.1, 143.4, 150.5, 152.7, 155.6. MS (ESI+, m/z): 705 [(M + H)+
100%]; 727 [(M + Na)+ 50%]. HRMS (ESI+): calcd for C39H41N6O5S
[M + H]+ 705.2854, found 705.2809.
(2S,3R,4R,5S)-3,4-Bis(benzyloxy)-5-(benzyloxymethyl)-2-(hydrox-
ymethyl)-N-methylpyrrolidine (18). To compound 17 (220 mg, 0.49
mmol) in MeOH (3 mL) was added 10% Pd−90% C (70 mg), and
the mixture was stirred at room temperature under an atmosphere of
hydrogen overnight. The solution was filtered through Celite and the
filtrate concentrated in vacuo. The resulting residue was purified by
chromatography (60% EtOAc/40% hexane) to afford 18 (150 mg,
20
68%) as a colorless viscous oil. Rf (5% MeOH/CH2Cl2): 0.44. [α]D
1
= −56° (c 0.8, CH2Cl2). H NMR (CDCl3, 300.13 MHz): δ 2.51 (s,
3H), 2.75 (br s, 1H), 3.15 (m, 1H), 3.46 (m, 1H), 3.58 (dd, 1H, JHH
3.0 Hz, JHH 9.9 Hz), 3.72 (m, 3H), 4.25 (t, 1H, JHH 6.9 Hz), 4.42−4.66
(m, 6H), 4.78 (d, 1H, JHH 11.7 Hz), 7.20−7.45 (m, 15H). 13C NMR
(CDCl3, 75.5 MHz): δ 35.8, 59.7, 62.1, 64.8, 66.3, 72.7, 72.9, 73.5,
84.0, 84.7, 127.4−128.5 (15C), 138.1, 138.3, 138.5. MS (ESI+, m/z):
448 [(M + H)+ 100%]. HRMS (ESI+): calcd for C28H34NO4 [M + H]+
448.2482, found 448.2492.
(2S,3R,4R,5S)-2-(9-Adeninylmethyl)-3,4-bis(benzyloxy)-5-
(benzyloxymethyl)pyrrolidine (14). Mg (turnings) was added (68 mg,
2.8 mmol) to a solution of compound 13 (200 mg, 0.28 mmol) in dry
MeOH (2.8 mL), and the mixture was refluxed for 2 h. MeOH was
evaporated, and purification by flash chromatography (10% MeOH/
90% CH2Cl2) afforded 14 (141 mg, 90%) as a white foam. Rf (10%
(2S,3R,4R,5S)-2-(9-Adeninylmethyl)-3,4-bis(benzyloxy)-5-(benzy-
loxymethyl)-N-methylpyrrolidine (19). To a solution of compound
18 (130 mg, 0.29 mmol) in CH2Cl2 (3.6 mL) was added pyridine (88
μL, 1.1 mmol) and MsCl (79 μL, 1.0 mmol). The mixture was stirred
at 0 °C for 20 min. The solvent was removed under vacuum. Without
purification, the residue was dissolved in DMF (3 mL). Adenine (58
mg, 0.435 mmol), K2CO3 (80 mg, 0.58 mmol), and 18-crown-6 (115
mg, 0.435 mmol) were added to the solution, and the mixture was
stirred at 90 °C for 2.5 h. After the solvent was evaporated under high
vacuum, the residue was purified by flash column chromatography (2%
MeOH, CH2Cl2) to give 20 (60 mg, 81%) as a white foam. Rf (10%
20
MeOH/CH2Cl2): 0.32. [α]D = +19° (c 0.5, CH2Cl2). 1H NMR
3
(CDCl3, 300.13 MHz): δ 2.33 (br s, 1H), 3.53 (dd, 1H, JHH 9.0 Hz,
3JHH 9.0 Hz), 3.61 (dd, 1H, JHH 6.4 Hz, JHH 9.2 Hz), 3.69 (q, 1H, JHH
6.4 Hz), 3.94 (m, 1H), 4.00 (m, 1H), 4.04 (m, 1H), 4.18 (dd, 1H, JHH
8.0 Hz, JHH 14.0 Hz), 4.21−4.59 (m, 7H), 5.86 (br s, 2H), 7.22−7.39
(m, 15H), 7.81 (s, 1H), 8.33 (s, 1H). 13C NMR (CDCl3, 75.5 MHz):
δ 45.1, 58.0, 59.0, 68.8, 72.3, 73.4, 82.1, 82.2, 84.0, 127.5−128.5 (15
C), 138.0, 137.9, 138.1, 141.8, 150.1, 152.7, 156.4. HRMS (ESI+):
calcd for C32H35N6O3 [M + H]+ 551.2765, found 551.2802.
20
MeOH/CH2Cl2): 0.38. [α]D = −7° (c 1.0, CH2Cl2). 1H NMR
(CDCl3, 400.13 MHz): δ 2.41 (s, 3H), 3.35 (br s, 1H), 3.53 (m, 2H),
3.68 (dd, 1H, JHH 2.8 Hz, JHH 10.0 Hz), 4.11 (t, 1H, JHH 6.0 Hz), 4.22
(dd, 1H, JHH 4.0 Hz, JHH 14.0 Hz), 4.34 (m, 2H), 4.50 (m, 5H), 4.71
(d, 1H, JHH 11.6 Hz), 6.16 (s, 2H), 7.32 (m, 15H), 7.85 (s, 1H), 8.35
(s, 1H). 13C NMR (CDCl3, 100.6 MHz): δ 36.5, 42.9, 62.0, 63.5, 66.0,
72.7, 72.8, 73.4, 82.1, 84.0, 119.3, 127.5−128.5 (15 C), 137.9, 138.0,
138.3, 142.1, 150.5, 152.7, 155.1. MS (ESI+, m/z): 565 [(M + H)+
100%]; 587 [(M + Na)+ 10%]. HRMS (ESI+): calcd for C33H37N6O3
[M + H]+ 565.2922, found 565.2928.
(2S,3R,4R,5S)-2-(9-Adeninylmethyl)-3,4-dihydroxy-5-
(hydroxymethyl)pyrrolidine (15). A mixture of 14 (100 mg, 0.18
mmol) and concentrated aqueous HCl (38%; 1.8 mL) was refluxed for
2 h. Water was evaporated, and aqueous NH3 (32%; 1 mL) was added
to the residue. After the aqueous phase was evaporated, the resulting
solid was purified by column chromatography (CH2Cl2/MeOH/
NH4OH, 88/10/2) to afford 15 (41 mg, 82%) as a white solid. Rf
(2S,3R,4R,5S)-2-(9-Adeninylmethyl)-3,4-dihydroxy-5-(hydroxy-
methyl)-N-methylpyrrolidine (20). A mixture of 19 (60 mg, 0.11
mmol) and concentrated aqueous HCl (38%, 1.8 mL) was refluxed for
2 h. Water was evaporated, and aqueous NH3 (32%, 1 mL) was added
to the residue. After the aqueous phase was evaporated, the resulting
solid was purified by column chromatography (CH2Cl2/MeOH/
NH4OH, 88/10/2) to afford 15 (25 mg, 81%) as a white solid. Rf
20
(CH2Cl2/MeOH/NH4OH, 6:3:1): 0.32. [α]D = −21° (c 0.5,
1
3
MeOH). H NMR (D2O, 400.13 MHz): δ 3.80 (dd, 1H, JHH 8.8
Hz, 3JHH 12.4 Hz), 3.93 (dd, 1H, 3JHH 4.4 Hz, 3JHH 12.0 Hz), 4.07 (q,
1H, JHH 4.4 Hz), 4.25 (dd, 1H, JHH 1.6 Hz, JHH 3.2 Hz), 4.31 (m, 1H),
4.36 (dd, 1H, JHH 1.6 Hz, JHH 4.0 Hz), 4.62 (dd, 1H, JHH 7.6 Hz, JHH
15.2 Hz), 4.70 (dd, 1H, JHH 6.5 Hz, JHH 15.2 Hz), 8.18 (s, 2H). 13C
NMR (D2O, 100.6 MHz): δ 40.7, 57.5, 60.3, 63.9, 74.3, 74.6, 118.4,
142.3, 150.0, 152.3, 155.3. MS (ESI+, m/z): 281 [(M + H)+ 100%],
303 [(M + Na)+ 80%]. HRMS (ESI+): calcd for C11H17N6O3 [M +
H]+ 281.1357, found 281.1378.
20
(CH2Cl2/MeOH/NH4OH, 7.5:2:0.5): 0.24. [α]D = +9° (c 0.5,
MeOH). 1H NMR (MeOH-d4, 300.13 MHz): δ 2.55 (s, 3H), 3.26 (q,
1H, H-5, JHH 2.8 Hz), 3.55 (q, 1H, H-2, JHH 5.1 Hz), 3.80 (dd, 1H,
CH2O, JHH 5.1 Hz, JHH 11.7 Hz), 3.87 (dd, 1H, CH2O, JHH 4.8 Hz, JHH
12.0 Hz), 4.10 (m, 2H, H-3 + H-4), 4.39 (dd, 1H, CH2N, JHH 5.1 Hz,
JHH 14.0 Hz), 4.47 (dd, 1H, CH2N, JHH 7.8 Hz, JHH 15.0 Hz), 8.21 (s,
1H, H-2 or H-8), 8.22 (s, 1H, H-8 or H-2). 13C NMR (MeOH-d4, 75.5
MHz): δ 36.2 (CH3), 41.4 (CH2N), 57.6 (CH2O), 65.8 (C-5 + C-2),
75.6 (C-3), 76.8 (C-4B), 118.5 (C-5B), 142.3 (C-8B), 149.4 (C-4B),
152.1 (C-2B), 155.9 (C-6B). MS (ESI+, m/z): 295 [(M + H)+ 60%],
317 [(M + Na)+ 20%]. HRMS (ESI+): calcd for C12H19N6O3 [M +
H]+ 295.1513, found 295.1511.
(2S,3R,4R,5S)-3,4-Bis(benzyloxy)-5-(benzyloxymethyl)-2-
(hydroxymethyl)pyrrolidine (16). Mg (turnings) was added (115 mg,
4.8 mmol) to a solution of compound 10 (600 mg, 0.96 mmol) in dry
MeOH (4.8 mL), and the mixture was refluxed for 2 h. MeOH was
evaporated, and purification by flash chromatography (10% MeOH/
CH2Cl2) afforded 1615 (367 mg, 89%) as a colorless gummy liquid.
(8S,6R,7R,5S)-(8-Benzyloxymethyl)-6,7-bis(benzyloxy)-3-oxa-1-
azabicyclo[3.3.0]octane (17). A solution of 16 (280 mg, 0.65 mmol),
37% aqueous formaldehyde (146 μL, 1.95 mmol), and acetic acid (186
μL, 3.25 mmol) in dioxane (6.5 mL) was stirred at 60 °C for 30 min.
After it was cooled, the solution was concentrated under vacuum and
the residue purified by flash column chromatography (50% EtOAc/
hexane) to give 17 (270 mg, 94%) as a colorless viscous oil. Rf (30%
(2S,3R,4R,5S)-2-(9-Adeninylmethyl)-3,4-dihydroxy-5-(hydroxy-
methyl)-N-(p-toluenesulfonamido)pyrrolidine (21). Compound 13
(220 mg, 0.31 mmol) was refluxed in concentrated aqueous HCl
(38%, 2.0 mL) for 2 h. Water was evaporated, and aqueous NH3 (32%,
1 mL) was added to the residue. After the aqueous phase was
evaporated, the resulting solid was purified by column chromatography
(10% MeOH/90% CH2Cl2) to give 21 (89 mg, 66%) as a white solid.
20
EtOAc/hexanes): 0.16. [α]D = +8° (c 0.8, CH2Cl2). 1H NMR
(CDCl3, 300.13 MHz): δ 3.31 (q, 1H, JHH 6.3 Hz), 3.48 (t, 1H, JHH 8.3
Hz), 3.62 (dd, 1H, JHH 6.6 Hz, JHH 9.1 Hz), 3.82 (dd, 1H, JHH 6.0 Hz,
1
Rf (10% MeOH/CH2Cl2): 0.39. H NMR (DMSO-d6, 300.13 MHz):
4675
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678

The Journal of Organic Chemistry
Article
δ 2.38 (s, 3H), 3.17 (m, 1H), 3.60 (br s, 1H), 3.78 (m, 3H), 4.16 (m,
1H), 4.30 (br s, 1H), 4.45 (dd, 1H, JHH 9.6 Hz, JHH 13.4 Hz), 4.85 (dd,
1H, JHH 2.9 Hz, JHH 13.3 Hz), 5.16 (br s, 1H), 5.68 (br s, 1H), 7.23 (br
s, 2H), 7.36 (d, 2H, JHH 8.1 Hz), 7.90 (d, 2H, JHH 8.1 Hz), 8.01 (s,
1H), 8.22 (s, 1H). 13C NMR (DMSO-d6, 75.5 MHz): δ 20.9, 42.3,
56.7, 59.9, 63.9, 72.8, 73.1, 118.5, 127.2 (2C), 129.4 (2C), 137.5,
141.8, 142.8, 149.6, 152.4, 155.9. MS (ESI+, m/z): 435 [(M + H)+
100%], 457 [(M + Na)+ 10%]. HRMS (ESI+): calcd for C18H23N6O5S
[M + H]+ 435.1445, found 435.1452.
evaporated, and purification by flash chromatography (10% MeOH/
90% CH2Cl2) afforded 25 (19 mg, 79%) as a white solid. Rf (10%
20
MeOH/CH2Cl2): 0.16. [α]D = −85° (c 0.5, MeOH). 1H NMR
(D2O, 600.13 MHz): δ 3.38 (s, 1H, H-5), 3.52 (t, 1H, H-2, JHH 8.2
Hz), 3.76 (d, 1H, CH2O, JHH 8.4 Hz), 3.98 (m, 2H, CH2O + CH2N),
4.03 (s, 1H, H-3), 4.10 (dd, 1H, CH2N, JHH 7.4 Hz, JHH 12.6 Hz), 4.28
(s, 1H, H-4), 7.98 (s, 1H, H-8), 8.04 (s, 1H, H-2). 13C NMR (D2O,
100.6 MHz): 46.0 (CH2N), 55.7 (C-5), 60.5 (C2), 71.2 (C4), 71.9
(CH2O), 78.8 (C-3), 118.0 (C-5B), 141.9 (C-8B), 148.6 (C-4B),
152.4 (C-2B), 155.2 (C-6B). MS (ESI+, m/z): 263 [(M + H)+ 100%],
285 [(M + Na)+ 25%]. HRMS (ESI+): calcd for C11H15N6O2 [M +
H]+ 263.1251, found 263.1244.
(4aS,6S,7R,7aR)-6-((6-Amino-9H-purin-9-yl)methyl)-2,2-dimeth-
yl-5-tosylhexahydro[1,3]dioxino[5,4-b]pyrrol-7-ol (22). To a solution
of 21 (89 mg, 0.205 mmol) in anhydrous THF (4.0 mL) and DMF
(0.4 mL) were added 2-methoxypropene (57 μL, 0.60 mmol) and p-
TsOH (0.41 mmol, 72 mg) under a nitrogen atmosphere. The
solution was stirred at room temperature. After 30 min, additional 2-
methoxypropene (97 μL, 1.02 mmol) was added and the solution was
allowed to react for an additional 30 min. Solvents were evaporated
under vacuum, and the residue was purified by flash chromatography
(2% MeOH/CH2Cl2) to afford pure 22 (95 mg, 98%). Rf (10%
(2S,3R,4R,5S)-3,4-Bis(benzyloxy)-5-(benzyloxymethyl)-2-(hydrox-
ymethyl)-N-(7-(benzyloxymethyl)-6-methoxy-9-deazapurin-9-yl)-
methylpyrrolidine (27). Imino sugar 16 (90 mg, 0.21 mmol), sodium
cyanoborohydride (0.36 mmol, 22 mg), and compound 26 (56 mg,
0.19 mmol) were dissolved in a 4/1 mixture of MeOH and THF (4
mL). Three drops of acetic acid were added, and the solution was
stirred at 40 °C overnight. Solvents were evaporated in vacuo, and the
residue was purified by flash chromatography (3% MeOH/97%
CH2Cl2) to give the coupled product 27 (113 mg, 84%). Rf (5%
20
MeOH/CH2Cl2): 0.56. [α]D = −15° (c 0.5, CH2Cl2). 1H NMR
(CDCl3, 300.13 MHz): δ 1.09 (s, 3H), 1.31 (s, 3H), 2.39 (s, 3H), 3.68
(s, 1H), 4.02 (tt, 1H, JHH 3.9, JHH 11.2), 4.13−4.30 (m, 4H), 4.47 (dd,
1H, JHH 11.2 Hz, JHH 13.6 Hz), 5.09 (dd, 1H, JHH 1.5 Hz, JHH 14.0
Hz), 6.53 (br s, 2H), 6.93 (br s, 1H), 7.30 (d, 2H, JHH 7.9 Hz), 7.82
(d, 2H, JHH 7.9 Hz), 8.00 (s, 1H), 8.25 (s, 1H). 13C NMR (CDCl3,
75.5 MHz): δ 20.7, 21.4, 25.9, 41.1, 59.9, 60.0, 64.5, 73.0, 73.5, 98.4,
119.5, 127.0 (2C), 130.0 (2C), 138.7, 141.2, 143.7, 149.3, 152.5, 156.1.
MS (ESI+, m/z): 475 [(M + H)+ 100%], 497 [(M + Na)+ 25%].
HRMS (ESI+): calcd for C21H27N6O5S [M + H]+ 475.1758, found
475.1782.
20
1
MeOH/CH2Cl2): 0.44. [α]D = −30° (c 0.50, CH2Cl2). H NMR
(CDCl3, 300.13 MHz): δ 3.25 (m, 1H), 3.46 (tt, 1H, JHH 3.7 Hz), 3.57
(dd, 1H, JHH 3.7 Hz, JHH 10.1 Hz), 3.79 (m, 2H), 3.87 (dd, 1H, JHH 3.5
Hz, JHH 11.8 Hz), 4.10 (s, 3H), 4.19 (m, 3H), 4.38−4.77 (m, 7H),
4.68 (d, 1H, JHH 12.3 Hz), 4.73 (d, 1H, JHH 12.3 Hz), 5.60 (d, 1H, JHH
10.5 Hz), 5.66 (d, 1H, JHH 10.5 Hz), 7.17 (s, 1H), 7.21−7.38 (m,
20H), 8.55 (s, 1H). 13C NMR (CDCl3, 75.5 MHz): δ 41.8, 53.4, 57.3,
60.7, 62.6, 66.6, 69.9, 72.4, 72.8, 73.3, 82.3, 83.7, 115.3, 116.0, 127.2−
128.3 (22C), 131.5, 136.8, 138.4, 138.6, 149.6, 150.0, 156.1. MS (ESI+,
m/z): 715 [(M + H)+ 100%], 737 [(M + Na)+ 10%]. HRMS (ESI+):
calcd for C43H47N4O6 [M + H]+ 715.3490, found 715.3526.
(4aS,6S,7R,7aR)-6-((6-Amino-9H-purin-9-yl)methyl)-2,2-dimeth-
yl-5-tosylhexahydro[1,3]dioxino[5,4-b]pyrrol-7-yl Trifluorometha-
nesulfonate (23). Protected compound 22 (95 mg, 0.20 mmol) was
dissolved in dry CH2Cl2, and DMAP (73 mg, 0.6 mmol) and TfCl (32
μL, 0.24 mmol) were added. The solution was stirred for 2.5 h at 0 °C.
Solvent was concentrated, and the residue was subjected to flash
chromatography (1% MeOH/99% CH2Cl2) to give 23 (64 mg, 53%).
(2S,3R,4R,5S)-3,4-Dihydroxy-2,5-bis(hydroxymethyl)-N-(9-deaza-
hypoxanthin-9-yl)methylpyrrolidine (Hydrochloride Salt) (28·HCl).
Compound 27 (112 mg, 0.16 mmol) was heated under reflux in
concentrated HCl (38%, 2 mL) for 2.5 h. After it was cooled, the
solution was concentrated in vacuo and aqueous NH3 (32%, 1 mL)
was added to the residue. Water was evaporated, and the resulting
solid was purified by column chromatography (CH2Cl2/MeOH/
NH4OH, 88/10/2) to afford 28 (36 mg, 74%), which was then
converted with 10% aqueous HCl to 28·HCl. Rf (CH2Cl2/MeOH/
NH4OH, 6/3/1): 0.19. [α]D20 = +2° (c 0.50, MeOH). 1H NMR (D2O,
600.13 MHz, 373 K): δ 3.80 (br s, 4H, CH2O), 4.58 (s, 2H, H-2 + H-
5, JHH 5.3 Hz), 4.90 (d, 2H, H-3 + H-4, JHH 3.3 Hz), 5.10 (d, CH2N,
1H, JHH 13.4 Hz), 5.28 (d, 1H, CH2N, JHH 13.5 Hz), 8.22 (s, 1H, H-
8), 8.54 (s, 1H, H-2). 13C NMR (D2O, 150.92 MHz): δ 45.9 (CH2N),
55.9 (CH2O), 69.0 (C-2 + C-5), 74.6 (C-3 + C-4), 105.6 (C-9B),
117.7 (C-4B), 131.4 (C-8B), 143.1 (C-2B), 144.1 (C-5B), 155.1 (C-
6B). MS (APCI+, m/z): 311 [(M + H)+ 20%]. HRMS (ESI+): calcd
for C13H19N4O5 [M + H]+ 311.1350, found 311.1340.
(2S,3R,4R,5S)-3,4-Bis(benzyloxy)-5-(benzyloxymethyl)-2-
(fluoromethyl)pyrrolidine (29). DAST (33 μL, 0.20 mmol) was added
dropwise to a solution of compound 11 (80 mg, 0.14 mmol) in dry
CH2Cl2 (2 mL) in dry CH2Cl2, and the solution was stirred at 0 °C for
1 h. The reaction mixture was concentrated in vacuo, the crude
product, without any purification, was dissolved in dry MeOH (2 mL),
and Mg (33 mg, 1.4 mmol) was added to the solution. The mixture
was refluxed for 2 h, solvents were evaporated, and the residue was
purified by flash chromatography (5% MeOH/95% CH2Cl2) to give
29 (31 mg, 85%) as a viscous colorless oil. Rf (5% MeOH/CH2Cl2):
0.26. [α]D20 = −11° (c 1.0, CH2Cl2). 1H NMR (CDCl3, 300.13 MHz):
δ 3.56−3.81 (m, 4H), 4.05 (m, 2H), 4.38−4.71 (m, 8H), 7.28−7.40
(m, 15H). 13C NMR (CDCl3, 75.5 MHz): δ 58.1 (d, JCF 20.4 Hz),
58.6, 71.2 (JCF 322.4 Hz), 72.3 (3C), 82.1, 82.3, 84.3, 127.6−128.5
(18C). HRMS (ESI+): calcd for C27H31FNO3 [M + H]+ 436.2282,
found 436.2284.
20
1
Rf (10% MeOH/CH2Cl2): 0.53. [α]D = +41° (c 0.48, CH2Cl2). H
NMR (CDCl3, 400.13 MHz): δ 1.16 (s, 3H), 1.37 (s, 3H), 2.38 (s,
3H), 4.07 (dd, 1H, JHH 4.4 Hz, JHH 12.8 Hz), 4.17 (q, 1H, JHH 4.4 Hz),
4.26 (dd, 1H, JHH 4.8 Hz, JHH 12.8 Hz), 4.45 (m, 2H), 5.12 (m, 3H),
5.95 (br s, 2H), 7.21 (d, 2H, JHH 8.0 Hz), 7.70 (d, 2H, JHH 8.0 Hz),
7.87 (s, 1H), 8.28 (s, 1H). 13C NMR (CDCl3, 100.6 MHz): δ 20.9,
21.4, 26.6, 42.1, 57.3, 59.2, 60.0, 70.8, 87.3, 99.4, 119.4, 126.6 (2C),
129.6 (2C), 136.9, 141.1, 143.9, 150.2, 152.9, 155.5. MS (ESI+, m/z):
607 [(M + H)+ 100%], 629 [(M + Na)+ 20%]. HRMS (ESI+): calcd
for C22H26F3N6O7S2 [M + H]+ 607.1251, found 607.1277.
(2S,3S,4R,5S)-2-(9-Adenylmethyl)-(3-O,5-C-methylene)-N-(p-
toluenesulfonamido)pyrrolidine (24). A solution of compound 23
(64 mg, 0.106 mmol) in a 1:1 mixture of TFA and CH2Cl2 (3 mL) was
stirred at room temperature for 1 h. After the solvents were
evaporated, the resulting residue was purified by chromatography
(5% MeOH/95% CH2Cl2) to afford 24 as a white solid (40 mg, 91%).
20
1
Rf (10% MeOH/CH2Cl2): 0.39. [α]D = +89° (c 0.52, MeOH). H
NMR (DMSO-d6, 400.13 MHz): δ 2.41 (s, 3H, CH3), 3.28 (d, 1H,
CH2O, JHH 8.4 Hz), 3.59 (d, 1H, CH2O, JHH 8.0 Hz), 3.78 (dd, 1H, H-
2, JHH 3.6 Hz, JHH 8.4 Hz), 3.87 (s, 1H, H-5), 3.97 (s, 1H, H-4), 3.99
(s, 1H, H-3), 4.33 (dd, 1H, CH2N, JHH 8.8 Hz, JHH 14.4 Hz), 4.48 (dd,
1H, CH2N, JHH 3.4 Hz, JHH 14.5 Hz), 5.67 (br s, 1H, OH), 7.30 (s,
2H, NH2), 7.47 (d, 2H, Ts-m, JHH 8.1 Hz), 7.91 (d, 2H, Ts-o, JHH 8.2
Hz), 8.09 (s, 1H, H-8), 8.24 (s, 1H, H-2). 13C NMR (DMSO-d6, 100.6
MHz): δ 21.5 (CH3, Ts), 44.6 (CH2N), 62.3 (C-3), 65.3 (C-2), 67.6
(CH2O), 71.1 (C-4), 79.5 (C-5), 119.1 (C-5B), 128.1 (Ts-m), 144.1
(Ts-o), 136.1 (Ts), 141.3 (C-8B), 144.7 (Ts), 150.1 (C-4B), 153.3
(C-2B), 156.5 (C-6B);. MS (ESI+, m/z): 417 [(M + H)+ 100%], 439
[(M + Na)+ 60%]. HRMS (ESI+): calcd for C18H21N6O4S [M + H]+
417.1340, found 417.1349.
(2S,3R,4R,5S)-3,4-Bis(benzyloxy)-5-(benzyloxymethyl)-2-(fluoro-
methyl)-N-(7-(benzyloxymethyl)-6-methoxy-9-deazapurin-9-yl)-
methylpyrrolidine (30). Sodium cyanoborohydride (8 mg, 0.13
mmol) was added to a stirred solution of 29 (31 mg, 0.07 mmol)
(2S,3S,4R,5S)-2-(9-Adenylmethyl)-(3-O,5-C-methylene)pyrrolidine
(25). A mixture of compound 24 (40 mg, 0.096 mmol) and Mg
(turnings) was refluxed in dry MeOH (2 mL) for 2 h. MeOH was
4676
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678

The Journal of Organic Chemistry
Article
and 26 (22 mg, 0.07 mmol) in a 4/1 mixture of MeOH and THF (2
mL). The reaction mixture was stirred overnight at 40 °C. Solvents
were evaporated in vacuo, and the crude reaction was subjected to
flash chromatography (2% MeOH/98% CH2Cl2) to afford 30 as a
Martin, O. R.; Iminosugars: From Synthesis to Therapeutics Applications;
Wiley-VCH: New York, 2007. (d) Watson, A. A.; Fleet, G. W. J.;
Asano, N.; Molyneux, R. J.; Nash, R. J. Phytochemistry 2001, 56, 265−
295.
(3) (a) Elbein, A. D.; Molyneux, R. J. In Iminosugars as Glycosydase
Inhibitors; Stutz, A. E., Ed.; Wiley-VCH: Weinheim, Germany, 1999;
pp 216−251.
(4) (a) Shibano, M.; Tsukamoto, D.; Kusano, G. Heterocycles 2002,
57, 1539−1553. (b) Shibano, M.; Tsukamoto, D.; Masuda, A.; Tanaka,
Y.; Kusano, G. Chem. Pharm. Bull. 2001, 49, 1362−1365.
(5) (a) Asano, N. Glycobiology 2003, 13, 93R−104R. (b) Nishimura,
Y. Curr. Top. Med. Chem. 2003, 3, 575−591. (c) Wrodnigg, T. M.
Monatsh. Chem. 2002, 133, 393−426.
(6) (a) Morris, P. E.; Kamat, V. P. Modified Nucleosides in
Biochemistry, Biotechnology and Medicine; Wiley-VCH: Weinheim,
Germany, 2008; pp 451−471. (b) Bantia, S.; Kilpatrick, J. M. Curr.
Opin. Drug. Discov. Devel. 2004, 7, 243−247. (c) Parks, R. E., Jr.;
Stoeckler, J. D.; Cambor, D.; Savarese, T. M.; Crabtree, G. W.; Chu, S.
H. Molecular Actions and Targets for Cancer Chemotherapeutic Agents;
Academic Press: New York, 1981; pp 229−252.
1
white foam (43 mg, 85%). Rf (5% MeOH/CH2Cl2): 0.54. H NMR
(CDCl3 300.13 MHz): δ 3.57 (m, 3H), 3.84 (dd, 1H, JHH 3.0 Hz, JHH
7.5 Hz), 4.13 (s, 3H), 4.15−4.64 (m, 13H), 4.75 (ddd, 1H, JHH 3.3 Hz,
JHH 7.2 Hz, JHF 35.7 Hz), 5.67 (d, 1H, JHH 7.8 Hz), 5.71 (d, 1H, JHH
7.8 Hz), 7.22−7.40 (m, 21 H), 8.57 (s, 1H). 13C NMR (CDCl3, 75.5
MHz): δ 42.3, 53.51, 60.4, 61.2 (d, JCF 14.3 Hz), 68.0, 70.1, 72.8, 73.4,
77.0, 82.3 (d, JCF 126.8 Hz), 83.1, 83.5, 114.7, 114.8, 126.3−127.5
(22C), 131.2, 136.0, 137.5, 137.6, 148.9, 149.1, 155.2. MS (ESI+, m/z):
717 [(M + H)+ 100%]. HRMS (ESI+): calcd for C43H46FN4O5 [M +
H]+ 717.3447, found 717.3419.
(2S,3R,4R,5S)-5-(Fluoromethyl)-3,4-dihydroxy-5-(hydroxymeth-
yl)-N-(9-deazahypoxanthin-9-yl)methylpyrrolidine (Hydrochloride
Salt) (31·HCl). Concentrated HCl (2 mL) was added to a flask
containing compound 30 (43 mg, 0.06 mmol). The mixture was
refluxed for 2 h. After water was evaporated, aqueous NH3 (32%, 1
mL) was added to the residue and then this mixture was concentrated
under vacuum. The resulting residue was purified by column
chromatography (CH2Cl2/MeOH/NH4OH, 88/10/2) to afford 31
(16 mg, 84%), which was then converted with 10% aqueous HCl to
31·HCl. Rf (CH2Cl2/MeOH/NH4OH, 6/3/1): 0.26; Data for 31 are
(7) (a) Miles, R. W.; Tyler, P. C.; Furneaux, R. H.; Bagdassarian, C.
K.; Schramm, V. L. Biochemistry 1998, 37, 8615−8621. (b) Horenstein,
B. A.; Schramm, V. L. Biochemistry 1993, 32, 7089−7097.
(c) Horenstein, B. A.; Parkin, D. W.; Estupinan, B.; Schramm, V. L.
Biochemistry 1991, 30, 10788−10795.
1
as follows. H NMR (MeOH-d4, 300.13 MHz): δ 3.10 (dtt, JHH 2.4
Hz, JHH 7.0 Hz, JHF 38.1 Hz), 3.28 (m, 1H), 3.68 (dd, 1H, JHH 3.0 Hz,
JHH 11.8 Hz), 3.82 (dd, 1H, JHH 4.1 Hz, JHH 11.8 Hz), 4.08−4.27 (m,
4H), 4.57 (ddd, 1H, JHH 2.4 Hz, JHH 7.0 Hz, JHF 46.1 Hz), 4.80 (ddd,
1H, JHH 2.6 Hz, JHH 10.1 Hz, JHF 46.1 Hz), 7.42 (s, 1H), 7.89 (s, 1H).
(8) (a) Clinch, K.; Evans, G. B.; Frohlich, R. F.; Furneaux, R. H.;
̈
Kelly, P. M.; Legentil, L.; Murkin, A. S.; Li, L.; Schramm, V. L.; Tyler,
P. C.; Woolhouse, A. D. J. Med. Chem. 2009, 52, 1126−1143.
(b) Rinaldo-Matthis, A.; Murkin, A. S.; Ramagopal, U. A.; Clinch, K.;
Mee, S. P.; Evans, G. B.; Tyler, P. C.; Furneaux, R. H.; Almo, S. C.;
Schramm, V. L. J. Am. Chem. Soc. 2008, 130, 842−844. (c) Evans, G.
B.; Furneaux, R. H.; Murkin, A. S.; Schramm, V. L.; Tyler, P. C. J. Med.
Chem. 2008, 51, 948−956. (d) Taylor, E. A.; Clinch, K.; Kelly, P. M.;
Li, L.; Evans, G. B.; Tyler, P. C.; Schramm, V. L. J. Am. Chem. Soc.
2007, 129, 6984−6985. (e) Taylor Ringia, E. A.; Tyler, P. C.; Evans,
G. B.; Furneaux, R. H.; Murkin, A. S.; Schramm, V. L. J. Am. Chem. Soc.
2006, 128, 7126−7127. (f) Semerano, T.; Lossani, A.; Botta, M.;
Ghiron, C.; Alvarez, R.; Manneti, F.; Mugnaini, C.; Valensin, S.;
Focher, F.; Corelli, F. J. Med. Chem. 2006, 49, 6037−6045. (g) Evans,
G. B.; Furneaux, R. H.; Lewandowicz, A.; Schramm, V. L.; Tyler, P. C.
J. Med. Chem. 2003, 46, 3412−3423.
1
Data for the hydrochloride (31·HCl) are as follows. H NMR (D2O
300.13 MHz): δ 3.65 (br s, 4H), 4.05 (q, 1H, JHH 6.0 Hz), 4.24−4.39
(m, 3H), 4.62 (d, 1H, JHH 13.2 Hz), 4.76 (d, 1H, JHH 13.5 Hz), 7.42 (s,
1H), 7.88 (s, 1H). 13C NMR (D2O, 75.5 MHz): δ 46.3, 56.8, 69.2,
74.3 (2C), 78.4 (d, JCF 182.7 Hz), 104.3, 117.9, 131.8, 141.1, 143.6,
154.3. MS (APCI+, m/z): 335 [(M + Na)+ 15%], 647 [(2M + Na)+
15%]. HRMS (ESI+): calcd for C13H18FN4O4 [M + H]+ 313.1307,
found 313.1296.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
Figures giving H, 13C, and DEPT NMR spectral data and 2D
NMR experiments. This material is available free of charge via
the Internet at http://pubs.acs.org.
(9) For some recent literature see: (a) Sousa, C. A. D.; Rizzo-Aguiar,
F.; Vale, M. L. C.; García-Mera, X.; Caamano, O.; Rodríguez-Borges, J.
̃
AUTHOR INFORMATION
Corresponding Author
*E-mail: mferrero@uniovi.es; vgs@uniovi.es
Notes
■
E. Tetrahedron Lett. 2012, 53, 1029−1032. (b) Liu, X.-K.; Qiu, S.;
Xiang, Y.-G.; Ruan, Y.-P.; Zheng, X.; Huang, P.-Q. J. Org. Chem. 2011,
76, 4952−4963. (c) Jagadeesh, Y.; Reddy, J.; Rao, B.; Swarnalatha, J.
Tetrahedron 2010, 68, 1202−1207. (d) Hong, A.; Liu, L.; Sugiyama,
M.; Fu, Y.; Wong, C.-H. J. Am. Chem. Soc. 2009, 131, 8352−8353.
(e) Tsou, E.-L; Chen, S.-Y.; Yang, M.-H.; Wang, S.-C.; Cheng, T.-R.;
Cheng, W.-C. Bioorg. Med. Chem. 2008, 16, 10198−10204.
(10) Schreiber, S. L. Science 2000, 287, 1964−1969.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Financial support of this work by the Spanish Ministerio de
■
(11) Tan, D. S. Nat. Chem. Biol. 2005, 1, 74−84.
Educacion
́
y Ciencia (MEC) (Project MEC-CTQ-2007-61126)
́
́
(12) (a) Rodrıguez-Perez, T.; Fernandez, S.; Sanghvi, Y. S.; Detorio,
and the PCTI (2006-2009)/FEDER (2007-2013) Asturias
(Project EQUIP09-07) is gratefully acknowledged. S.M.-M.
thanks the MEC for a predoctoral FPU fellowship.
D.; Schinazi, R.; Gotor, V.; Ferrero, M. Bioconjugate Chem. 2010, 21,
́
́
2239−2349. (b) Martınez-Montero, S.; Fernandez, S.; Sanghvi, Y. S.;
Gotor, V.; Ferrero, M. J. Org. Chem. 2010, 75, 6605−6613.
́
(c) Martınez-Montero, S.; Fernan
́
dez, S.; Sanghvi, Y. S.; Wen, K.;
́
REFERENCES
Gotor, V.; Ferrero, M. Eur. J. Org. Chem. 2009, 3265−3271. (d) Dıaz-
■
́
Rodrıguez, A.; Sanghvi, Y. S.; Fernan
́
dez, S.; Schinazi, R.; Theodorakis,
(1) (a) Borges de Melo, E.; Silveira, A.; Carvalho, I. Tetrahedron
2006, 62, 10277−10302. (b) Spiro, R. G. In Carbohydrates in
Chemistry and Biology; Ernst, B., Hart, G. W., Sinay, P., Eds.; Wiley-
VCH: Weinheim, Germany, 2000; Vol. 3 (Biosynthesis and
degradation of glyconjugates), pp 65−79.
(2) For recent recent reviews on therapeutic applications see:
(a) Horne, G.; Wilson, F. X.; Tinsley, J.; Williams, D. H.; Storer, R.
Drug Dis.Today 2011, 16, 107−118. (b) Winchester, B. G.
Tetrahedron: Asymmetry 2009, 20, 645−651. (c) Compain, P.
E.; Ferrero, M.; Gotor, V. Org. Biomol. Chem. 2009, 7, 1415−1423.
(e) Ferrero, M.; Gotor, V. Chem. Rev. 2000, 100, 4319−4347.
(f) Ferrero, M.; Gotor, V. Monatsh. Chem. 2000, 131, 585−616.
(13) Jones, S. P.; Simmons, B.; Mastracchio, A.; Macmillan, D. W.
Nature 2011, 475, 183−188.
(14) Le Merrer, Y.; Poitout, L.; Depezay, J. C.; Dosbaa, I; Geoffroy,
S.; Foglietti, M.-J. Bioorg. Med. Chem. 1997, 5, 519−533.
(15) Kumar, V.; Ramesh, N. G. Tetrahedron 2006, 62, 1877−1885.
4677
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678

The Journal of Organic Chemistry
Article
(16) (a) Liu, J.; Numa, M. M.; Liu, H.; Huang, S.-J.; Sears, P.;
Shikhman, A. R.; Wong, C.-H. J. Org. Chem. 2004, 69, 6273−6283.
(b) Hughes, A. B.; Rudge, A. J. Nat. Prod. Rep. 1994, 135−162.
(17) (a) Wong, C.-H.; Provencher, L.; Porco, J. A., Jr.; Jung, S.-H.;
Wang, Y.-F.; Chen, L.; Wang, R.; Steensma, D. H. J. Org. Chem. 1995,
60, 1492−1501. (b) Nuesca, Z. M.; Nair, V. Tetrahedron Lett. 1994,
35, 2485−2488.
(18) Liu, J.; Shikhman, A. F.; Lotz, M. K.; Wong, C.-H. Chem. Biol.
2001, 8, 701−711.
(19) Jereb, M.; Vrazic, D.; Zupan, M. Tetrahedron 2011, 67, 1355−
1387.
(20) (a) Campbell, M. A.; Wengel, J. Chem. Soc. Rev. 2011, 40,
5680−5689. (b) Zhou, C.; Chattopadhyaya, J. Curr. Opin. Drug
Discovery Dev. 2009, 12, 876−898.
(21) (a) Asano, N.; Ikeda, K.; Kasahara, M.; Arai, Y.; Kiza, H. J. Nat.
Prod. 2004, 67, 846−850. (b) Teppler, D. Phytochemistry 1990, 29,
2125−2127. (c) Saul, R.; Chambers, J. P.; Molyneux, R. J.; Elbein, A.
D. Arch. Biochem. Biophys. 1983, 221, 593−597.
(22) (a) Leawandwicz, A.; Shi, W.; Evans, G. B.; Tyler, P. C.;
Furneaux, R. H.; Basso, L. A.; Santos, D. S.; Almo, S. C.; Schramm, V.
L. Biochemistry 2003, 42, 6057−6066. (b) Evans, G. B.; Furneaux, R.
H.; Leawandwicz, A.; Schramm, V. L.; Tyler, P. C. J. Med. Chem. 2003,
46, 5271−5276.
(23) Evans, G. B.; Furneaux, R. H.; Tyler, P. C.; Schramm, V. L. Org.
Lett. 2003, 5, 3639−3640.
(24) (a) Muller, K.; Faeh, C.; Diederich, F. Science 2007, 317, 1881−
1886. (b) Bohm, H.-J.; Banner, D.; Kuhn, B.; Muller, K.; Obst-Sander,
U.; Stahl, M.; Bendels, S.; Kansy, M. ChemBioChem 2004, 5, 637−643.
(25) Mason, J. M.; Murkin, A. S.; Li, L.; Schramm, V. L.; Gainsford,
G. J.; Skelton, B. W. J. Med. Chem. 2008, 51, 5880−5884.
4678
dx.doi.org/10.1021/jo3004452 | J. Org. Chem. 2012, 77, 4671−4678