A short and scalable route to orthogonally O-protected 2-deoxystreptamine

Article abstract of DOI:10.1021/jo062369y

(Chemical Equation Presented) A seven-step synthesis of orthogonally O-protected 2-deoxy-streptamine has been developed from readily available neomycin, with an overall yield of 28%. Key chemical transformations include a chemoselective glycosidic bond hy

Full text of DOI:10.1021/jo062369y

example, neomycin was found to compete with the Rev protein
for HIV RRE, resulting in attenuated HIV replication in tissue
culture cells.4 Moreover, aminoglycosides also act as inhibitors
of several ribozymes, including hammerhead, group I introns,
and RNase P.5 The molecular structure of aminoglycosides is
characterized by a highly conserved diaminocyclohexitol termed
2-deoxystreptamine and suggests an essential role in binding
to RNA. Such an assumption is corroborated by NMR studies
that reveal substantial hydrogen bonding between 2-deox-
ystreptamine and RNA,6 but it has also been shown that
deoxystreptamine alone shows sequence-specific binding to
major groove RNA7 or in dimeric form to RNA hairpin loops.8
Thus, it may be postulated that 2-deoxystreptamine can serve
as a key building block in the development of new high-affinity
RNA-targeting compounds for the development of antibiotics9
or novel drugs against pathogenic viruses such as HIV or
hepatitis.
A Short and Scalable Route to Orthogonally
O-Protected 2-Deoxystreptamine
Sebastiaan (Bas) A. M. W. van den Broek,†
Bas W. T. Gruijters,† Floris P. J. T. Rutjes,‡
Floris L. van Delft,*,‡ and Richard H. Blaauw*,†
Chiralix B.V., P.O. Box 31070, 6503 CB Nijmegen,
The Netherlands, and Institute for Molecules and Materials,
Radboud UniVersity Nijmegen, ToernooiVeld 1,
6525 ED Nijmegen, The Netherlands
f.Vandelft@science.ru.nl; richard.blaauw@chiralix.com
ReceiVed NoVember 16, 2006
Throughout the years, a large number of preparations of
(protected) 2-deoxystreptamine and direct analogues thereof
have been published.10 Nevertheless, to date the simplest way
to obtain 2-deoxystreptamine (1) is by acidic degradation of
neomycin (Scheme 1). Treatment of neomycin, readily available
by Streptomyces fermentation, with 50% aqueous HBr at
elevated temperatures affords 2-deoxystreptamine in a single
transformation.11
It must be noted, however, that the fully unprotected
2-deoxystreptamine 1 may be easily obtained, but it is a meso
compound and contains only equatorial functional groups that
are difficult to differentiate. The latter features limit the potential
of raw 2-deoxystreptamine as starting material for the synthesis
of novel RNA-binding constructs, despite the fact that several
synthetic procedures toward enantiopure 2-deoxystreptamine
derivatives have been developed, including chemical12-14 and
enzymatic12,15 approaches. However, the chemical routes often
proved to be laborious and low-yielding, and enzymatic
A seven-step synthesis of orthogonally O-protected 2-deoxy-
streptamine has been developed from readily available
neomycin, with an overall yield of 28%. Key chemical
transformations include a chemoselective glycosidic bond
hydrolysis and two regioselective protective group manipula-
tions involving acetylation and deacetylation. The synthetic
route is amenable to scale-up for the production of multigram
quantities of enantiopure and orthogonally O-protected
2-deoxystreptamine, a versatile scaffold for the generation
of libraries of RNA-targeting ligands.
(4) Van Ahsen, G.; Umemura, M.; Yokota, M. Nature 1991, 353, 368.
(5) (a) Schroeder, R.; Waldsich, C.; Wank, H. EMBO J. 2000, 19, 1. (b)
Vourekas, A.; Kalavrizioti, D.; Stathopoulos, C.; Drainas, D. Mini-ReV. Med.
Chem. 2006, 6, 971.
(6) (a) Yoshizawa, S.; Fourmy, D.; Puglisi, J. D. EMBO J. 1998, 17,
6437. (b) Hobbie, S. N.; Pfister, P.; Bru¨ll, C.; Westhof, E.; Bo¨ttger, E. C.
Antimicrob. Agents Chemother. 2005, 49, 5112.
(7) Yoshikawa, S.; Fourmy, D.; Eason, R. G.; Puglisi, J. D. Biochemistry
2002, 41, 6263.
(8) Liu, X.; Thomas, J. R.; Hergenrother, P. J. J. Am. Chem. Soc. 2004,
126, 9196.
(9) (a) Ding, Y.; Hofstadler, S. A.; Swayze, E. E.; Griffey, R. H. Org.
Lett. 2001, 3, 1621. (b) Vourloumis, D.; Takahashi, M.; Winters, G. C.;
Simonsen, K. B.; Ayida, B. K.; Barluenga, S.; Qamar, S.; Shandrick, S.;
Zhao, Q.; Hermann, T. Bioorg. Med. Chem. Lett. 2002, 12, 3367. (c)
Vourloumis, D.; Winters, G. C.; Simonsen, K. B.; Ayida, B. K.; Shandrick,
S.; Zhao, Q.; Hermann, T. ChemBioChem 2003, 4, 879. (d) Ding, Y.;
Hofstadler, S. A.; Swayze, E. E.; Griffey, R. H. Chem. Lett. 2003, 32, 908.
(10) For a recent review, see: Busscher, G. F.; Rutjes, F. P. J. T.; van
Delft, F. L. Chem. ReV. 2005, 105, 775.
(11) Georgiadis, M. P.; Constantiou-Kokotou, V.; Kokotos, G.
J. Carbohydr. Chem. 1991, 10, 739.
(12) Canas-Rodriguez, A.; Ruizpoveda, S. G. Carbohydr. Res. 1977, 59,
240.
Aminoglycosides form a diverse class of naturally occurring
substances with strong bactericidal activity. The antibacterial
effect is the result of a specific binding of aminoglycosides to
the 16S tRNA-acceptor site in prokaryotic ribosomal RNA,
resulting in the production of non-sense proteins due to extensive
misreading of mRNA.1 As a consequence, several members of
the aminoglycoside family, most notably gentamicin, have been
applied as clinically important antibiotics for more than 60 years
now. However, the toxicity, growing bacterial resistance, and
poor oral bioavailability of most aminoglycosides2 creates the
need for new structures with antibiotic activity. Apart from that,
the generation of new aminoglycoside-type structures is interest-
ing from a broader perspective because aminoglycosides show
rather promiscuous binding to A-form RNA in general.3 For
† Chiralix B.V.
(13) Greenberg, W. S.; Priestley, E. S.; Sears, P. S.; Alper, P. B.;
Rosenbohm, C.; Hendrix, M.; Hung, S-C.; Wong, C-H. J. Am. Chem. Soc.
1999, 121, 6527.
(14) Tona, R.; Bertolini, R.; Hunziker, J. Org. Lett. 2000, 12, 1693.
(15) Orsat, B.; Alper, P. B.; Moree, W.; Mak, C-P.; Wong, C-H. J. Am.
Chem. Soc. 1996, 118, 712.
‡ Radboud University Nijmegen.
(1) Beaucaire, G. J. Chemother. 1995, 7 (suppl. 2), 111.
(2) Zembower, T. R.; Noskin, G. A.; Postelnick, M. J.; Nguyen, C.;
Peterson, L. R. Int. J. Antimicrob. Agents 1998, 10, 95.
(3) Arya, D. P.; Xue, L.; Willis, B. J. Am. Chem. Soc. 2003, 125, 10148.
10.1021/jo062369y CCC: $37.00 © 2007 American Chemical Society
Published on Web 03/27/2007
J. Org. Chem. 2007, 72, 3577-3580
3577

SCHEME 1
SCHEME 3
SCHEME 4
SCHEME 2
In order to efficiently arrive at the desired O-orthogonally
protected 2-deoxystreptamine, we then investigated whether a
selective protection of the hydroxyl functionalities on either the
4- or 5-position of the 2-deoxystreptamine moiety could be
achieved. It is known that reactivity of these alcohols differs
significantly,19 and therefore tetraol 3 was subjected to a range
of protection reactions. Application of standard benzylation
conditions (NaH, benzyl bromide, DMF) led to the fully
protected neamine derivative 4 in excellent yield (Scheme 3).
Protection with pivaloyl chloride gave mixtures of mono-, di-,
tri-, and tetra-O-acylated products, with the tri-O-pivaloylated
compound 5 predominating. Difficulties during purification
made this reaction impossible to implement in our intended
synthetic route, but the outcome encouraged us to look further
into a selective tri-O-acylation protocol.
Dissolving 3 in a 1:1 mixture of acetic anhydride and pyridine
and addition of a catalytic amount of DMAP led to the formation
of a tetra-O-acetylated neamine derivative. However, when the
reaction was performed in dichloromethane in the absence of
DMAP, a mixture of tri- and tetraacetates was obtained.
Optimization of the reaction conditions eventually led to a ratio
of 5:1 in favor of the desired tri-O-acetylated product 6, isolated
in good yield after purification by chromatography (Scheme 4).
With compound 6 in hand, protection of the remaining
5-hydroxyl and hydrolysis of the R-glucopyranosyl bond were
the only remaining transformations required to arrive at O-
orthogonally protected 2-deoxystreptamine. To this end, ben-
zylation of the alcohol was attempted, but upon deprotonation
with NaH or LiHMDS an unexpected acetyl shift occurred,
leading to a 1:1 mixture of the 5- and 6-O-acetylated product.
To circumvent the base-catalyzed acetyl migration, introduction
of the methoxymethyl (MOM) protective group was undertaken,
since much milder conditions are required for its installation.
Thus, protection of the alcohol using MOMCl in the presence
of DIPEA as a base proceeded uneventfully to afford 7 in 72%
yield (Scheme 5). At this point, it was recognized that MOM-
protection can also be effected under acidic conditions. Much
to our satisfaction, we found that the yield of 7 could be further
improvedto91%byapplyingaprocedureinvolvingdimethoxymethane
and P2O5.20
processes imposed restrictions on the protecting groups. Fur-
thermore, the 2-deoxystreptamine derivatives obtained via the
aforementioned methods were not fully orthogonally protected.
To overcome these drawbacks, a number of de novo syntheses
of 2-deoxystreptamine have appeared in literature over the
years.10,16,17 Only on few occasions were enantiopure products
obtained though and several times with impractical protective
groups on the nitrogen atoms.
For these reasons, we set out to develop a practical and
scalable route toward a versatile 2-deoxystreptamine scaffold
with a suitable protective group pattern. We now wish to report
a short and straightforward synthetic sequence for the multigram
preparation of enantiomerically pure orthogonally O-protected
2-deoxystreptamine.
The first step in our route was the selective hydrolysis of
commercially available neomycin sulfate to neamine (2, Scheme
2). Although a literature protocol for such a transformation has
been published,18 modification of the protocol proved to be
necessary, since the yield of the original procedure significantly
dropped upon scale-up. In particular we found the addition of
H2O to the MeOH suspension highly beneficial to give, after
concentration and precipitation from MeOH, neamine in 89%
yield on a multigram scale. Subsequent transformation of the
amino groups into azides via diazotransfer19 with freshly
prepared triflyl azide afforded 3 in good yield.
(16) Busscher, G. F.; Groothuys, S.; De Gelder, R.; Rutjes, F. P. J. T.;
van Delft, F. L. J. Org. Chem. 2004, 69, 4477.
(17) Busscher, G. F.; Rutjes, F. P. J. T.; van Delft, F. L. Tetrahedron
Lett. 2004, 45, 3629.
(18) Park, W. K. C.; Auer, M.; Jaksche, H.; Wong, C-H. J. Am. Chem.
Soc. 1996, 118, 10150.
Next, in order to arrive at the desired 2-deoxystreptamine
derivative, a variety of hydrolytic conditions was investigated
for the selective cleavage of the glycosidic bond with respect
to the MOM protective group. However, treatment of 7 with a
(19) Alper, P. J.; Hung, S-C.; Wong, C-H. Tetrahedron Lett. 1996, 37,
6029.
(20) Vedejs, E.; Larsen, S. D. J. Am. Chem. Soc. 1984, 106, 3030.
3578 J. Org. Chem., Vol. 72, No. 9, 2007

SCHEME 5
desired orthogonally O-protected and enantiomerically pure
2-deoxystreptamine (11) was thus obtained in 72% yield over
two steps.
In conclusion, we have developed a seven-step synthesis to
orthogonally O-protected and enantiopure 2-deoxystreptamine
from readily available neomycin, with an overall yield of 28%.
The synthesis is characterized by a chemoselective glycosidic
bond hydrolysis, two regioselective protective group manipula-
tions involving acetylation and deacetylation, and an oxidation-
elimination sequence. The synthetic route allows the production
of multigram quantities of suitably protected 2-deoxystreptamine,
a scaffold that may find particular application in the development
of RNA-targeting ligands as novel drugs.21
Experimental Section
Neamine‚4 HCl (2). To a solution of neomycin sulfate (25 g,
27.5 mmol) in a mixture of H2O/MeOH (400 mL, 1:1 v/v) was
added concentrated HCl (80 mL), and the reaction was stirred at
75 °C for 16 h. The reaction mixture was concentrated, and the
crude solid was poured into MeOH (400 mL). Concentrated HCl
(80 mL) was added, and the resulting mixture was stirred for another
12 h at 75 °C. The mixture was concentrated to 100 mL, and the
formed precipitate was collected by filtration and washed with cold
Et2O, affording 2 (11.47 g, 24.5 mmol, 89%) as an off-white solid.
1H NMR (D2O, 400 MHz): δ 5.90 (d, J ) 3.7 Hz, 1H), 4.03-
3.92 (m, 3H), 3.68 (t, J ) 9.9 Hz, 1H), 3.59-3.24 (m, 7H), 2.49
(dt, J ) 12.6, 4.3 Hz, 1H) 1.89 (q, J ) 12.6 Hz, 1H). 13C NMR
(D2O, 100 MHz): δ 98.1, 79.7, 77.2, 74.5, 72.7, 71.2, 70.3, 55.5,
51.7, 50.5, 42.1, 30.3. [R]21D +86.2 (c 1.0, H2O) {lit.22 [R]25D +83
(c 1, H2O)}.
SCHEME 6
1,3,2′,6′-Tetraazidoneamine (3). To a solution of NaN3 (25.4
g, 388 mmol) in a mixture of H2O/CH2Cl2 (200 mL, 1:1 v/v) at
0 °C was added Tf2O (33 mL, 199 mmol). The reaction mixture
was stirred at room temperature for 2 h. After quenching with
aqueous NaHCO3, the layers were separated, and the aqueous layer
was extracted with CH2Cl2 (100 mL). The organic layers were
combined to afford 200 mL of TfN3 solution. Then, to a solution
of 2 (7.58 g, 16.2 mmol) in H2O (200 mL) were added the TfN3
solution, MeOH (600 mL), and a solution of CuSO4 (250 mg) in a
mixture of MeOH/H2O/Et3N (50 mL, 3/3/4 v/v/v). The reaction
mixture was stirred at room temperature for 2 h. Then solid
NaHCO3 (20 g) was added carefully, and the organic solvents were
evaporated. The aqueous residue was extracted with EtOAc (2 ×
200 mL), and the organic layers were combined, dried (Na2SO4),
and concentrated in vacuo to give a yellow oil. Purification by
column chromatography (EtOAc/heptane 1:2 to 1:1) afforded 3
(5.68 g, 13.3 mmol, 82%) as a colorless oil. Rf 0.56 (EtOAc/heptane
variety of acids under numerous conditions either gave no
conversion, a phenomenon we ascribe to the presence of the
electron-withdrawing 2′-azido functionality, or resulted in the
formation of a complex mixture of products. For this reason,
an alternative route was considered involving glycol cleavage
with NaIO4 followed by based-induced elimination, a strategy
applied to neamine derivatives before.12 Obviously, application
in our case required the liberation of the vicinal 3′,4′-diol.
Importantly, in order to retain the asymmetric protective group
pattern on 2-deoxystreptamine, a selective removal of acetyl
functions from the glucose was required, while leaving the
5-acetyl unaffected. Therefore, a variety of hydrolytic conditions
were investigated. Gratifyingly, treatment of 7 with a catalytic
amount of potassium tert-butoxide in MeOH afforded the
desired monoacetate 8 in good yield.
1
2:1). FTIR (ATR) 2357, 2105, 1747, 1233, 1040 cm-1. H NMR
(CD3OD, 400 MHz): δ 5.63 (d, J ) 3.7 Hz, 1H), 4.16 (ddd, J )
10.4, 5.6, 2.8 Hz, 1H), 3.85 (dd, J ) 10.4, 8.8 Hz, 1H), 3.55-3.33
(m, 6H), 3.31-3.21 (m, 2H), 3.12 (dd, J ) 10.5, 3.8 Hz, 1H), 2.24
(dt, J ) 13.1, 4.2 Hz, 1H), 1.89 (q, J ) 12.5 Hz, 1H). 13C NMR
(CD3OD, 100 MHz): δ 97.8, 79.2, 76.1, 76.0, 71.3, 70.8, 70.3,
62.8, 59.9, 59.0, 50.7, 31.3. HRMS (ESI) m/z calcd for C12H18N12O6
(M + Na)+ 449.1370, found 449.1401. [R]21 +121.5 (c 1.4,
D
EtOAc).
1,3,2′,6′-Tetraazido-6,3′,4′-tri-O-acetylneamine (6). To a solu-
tion of 3 (6.68 g, 15.6 mmol) in a mixture of CH2Cl2/pyridine (100
mL, 1:1 v/v) at 0 °C was added Ac2O (100 mL). The reaction
mixture was stirred at room temperature for 2 h. The reaction
mixture was diluted with CH2Cl2 (100 mL) and slowly poured on
Finally, oxidation of 8 using NaIO4 smoothly afforded
dialdehyde 9 (Scheme 6). Not unexpectedly, 9 proved to be
only moderately stable and therefore was immediately subjected
to elimination. The most satisfactory conditions involved
treatment of dialdehyde 9 with n-butylamine, to afford 11 via
spontaneous â-elimination of the intermediate diimine 10. The
(21) Zaman, G. J. R.; Michiels, P. J. A.; van Boeckel, C. A. A. Drug
DiscoVery Today 2003, 8, 297.
(22) Peck, R. L.; Hoffhine, C. E., Jr.; Gale, P. H.; Folkers, K. J. Am.
Chem. Soc. 1953, 75, 1018.
J. Org. Chem, Vol. 72, No. 9, 2007 3579

ice-cold aqueous NaHCO3 under stirring. The layers were separated,
and the organic layer was washed with H2O (2 × 50 mL) and then
concentrated under reduced pressure. The residue was taken up in
EtOAc (100 mL) and washed with aqueous NH4Cl (2 × 100 mL)
and brine (100 mL). The organic layer was dried (Na2SO4) and
concentrated in vacuo, and the residue was purified by column
chromatography (EtOAc/heptane 1:2 to 1:1) to afford 6 a colorless
oil (7.44 g, 12.1 mmol, 69%). Rf 0.42 (EtOAc/heptane 2:3). FTIR
(ATR) 2357, 2105, 1747, 1371, 1233, 1040 cm-1. 1H NMR (CDCl3,
400 MHz): δ 5.48 (dd, J ) 10.6, 9.2 Hz, 1H), 5.34 (d, J ) 3.7
Hz, 1H), 5.04 (dd, J ) 10.2, 9.3 Hz, 1H), 4.92 (t, J ) 9.9 Hz, 1H),
4.33 (ddd, J ) 10.2, 5.0, 2.8 Hz, 1H), 3.68 (dd, J ) 10.5, 3.6 Hz,
1H), 3.58 (d, J ) 3.4 Hz, 1H), 3.54 (ddd, J ) 12.5, 10.0, 4.6 Hz,
1H), 3.46-3.35 (m, 4H), 2.40 (dt, J ) 13.1, 4.3 Hz, 1H), 2.18 (s,
3H), 2.10 (s, 3H), 2.06 (s, 3H), 1.61 (q, J ) 13.8 Hz, 1H). 13C
NMR (CDCl3, 100 MHz): δ 169.9, 169.7, 169.2, 98.3, 83.4, 74.4,
73.9, 70.8, 69.0, 68.8, 61.3, 57.8, 57.4, 50.4, 31.5, 20.3, 20.2, 20.1.
HRMS (ESI) m/z calcd for C18H24N12O9 (M + Na)+ 575.1687,
in vacuo. The residue was purified by column chromatography
(EtOAc/heptane 1:1) to afford 8 (5.24 g, 10.2 mmol, 87%) as a
colorless oil. Rf 0.31 (EtOAc/heptane 2:1). FTIR (ATR) 2102, 1033
1
cm-1. H NMR (CDCl3, 400 MHz): δ 5.50 (d, J ) 3.8 Hz, 1H),
4.96 (t, J ) 9.5 Hz, 1H), 4.83 (d, J ) 6.8 Hz, 1H), 4.76 (d, J ) 6.8
Hz, 1H), 4.22 (ddd, J ) 9.9, 4.5, 3.0 Hz, 1H), 3.99 (t, J ) 9.6 Hz,
1H), 3.65-3.35 (m, 7H), 3.34 (s, 3H), 3.23 (dd, J ) 10.4, 3.8 Hz,
1H), 2.79 (broad s, 1H), 2.66 (broad s, 1H), 2.35 (dt, J ) 13.3, 4.5
Hz, 1H), 2.16 (s, 3H), 1.57 (q, J ) 12.6 Hz, 1H). 13C NMR (CDCl3,
100 MHz): δ 169.7, 99.4, 97.6, 83.7, 77.7, 74.1, 71.1, 70.9, 70.7,
62.4, 58.6, 57.8, 56.2, 50.6, 31.3, 20.6. HRMS (ESI) m/z calcd for
C16H24N12O8 (M + Na)+ 535.1738, found 535.1736. [R]21D +68.1
(c 5.1, EtOAc).
4-O-Acetyl-1,3-diazido-5-O-methoxymethyl-2-deoxy-
streptamine (11). To a solution of 8 (4.20 g, 8.20 mmol) in MeOH
(300 mL) was added NaIO4 (13.15 g, 61.5 mmol, 7.5 equiv) at
0 °C. The resulting mixture was allowed to warm to room
temperature and stirred for 16 h (TLC Rf 0.54 (2.5% MeOH in
CH2Cl2)). The formed white precipitate was filtered off, and the
filtrate was concentrated in vacuo. The residue was taken up in
EtOAc (400 mL) and washed with H2O (400 mL) and brine (300
mL). The organic layer was dried (Na2SO4) and concentrated in
vacuo. The residue was then dissolved in MeOH (400 mL), and
butylamine (2.43 mL, 24.6 mmol, 3 equiv) was added dropwise.
The mixture was stirred for 1 h at room temperature and
concentrated in vacuo, and the residue was purified by column
chromatography (EtOAc/heptane 1:2) to afford 11 (1.77 g, 5.9
mmol, 72%) as a slightly yellow oil. Rf 0.43 (EtOAc/heptane 1:1).
FTIR (ATR) 2100, 1743, 1218, 1033 cm-1. 1H NMR (CDCl3, 400
MHz): δ 4.96 (t, J ) 10.0 Hz, 1H), 4.70 (d, J ) 6.8 Hz, 1H), 4.60
(d, J ) 6.8 Hz, 1H), 4.29 (d, J ) 1.6 Hz, 1H), 3.54-3.31 (m, 7H),
3.45 (s, 3H), 2.21 (dt, J ) 13.4, 4.5 Hz, 1H), 2.14 (s, 3H), 1.45
(dt, J ) 13.4, 12.5 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ 169.4,
97.9, 83.7, 75.0, 73.6, 59.4, 58.0, 55.8, 31.4, 20.3. HRMS (ESI)
m/z calcd for C10H16N6O5 (M + Na)+ 323.1080, found 323.1109.
found 575.1671. [R]21 +100.8 (c 0.5, EtOAc).
D
1,3,2′,6′-Tetraazido-5-O-methoxymethyl-6,3′,4′-tri-O-acetyl-
neamine (7). To a solution of 6 (7.44 g, 13.5 mmol) in a mixture
of (CH3O)2CH2 (10 mL) and CH2Cl2 (100 mL) was added P2O5
(7.66 g, 4 equiv), and the reaction mixture was stirred for 30 min
at room temperature. After carefully pouring the mixture on ice-
cold aqueous NaHCO3, the layers were separated. The organic layer
was washed with H2O (50 mL) and brine (50 mL), dried (Na2-
SO4), and concentrated in vacuo. The residue was purified by
column chromatography (EtOAc/heptane 1:1) to give 7 (6.68 g,
11.2 mmol, 91%) as a colorless oil. Rf 0.56 (EtOAc/heptane 1:1).
FTIR (ATR) 2104, 1750, 1231, 1037, 614 cm-1. 1H NMR (CDCl3,
400 MHz): δ 5.53 (d, J ) 3.8 Hz, 1H), 5.48 (dd, J ) 10.9, 9.2
Hz, 1H), 5.05 (dd, J ) 10.2, 9.3 Hz, 1H), 4.97 (t, J ) 9.8 Hz, 1H),
4.82 (d, J ) 6.8 Hz, 1H), 4.74 (d, J ) 6.8 Hz, 1H), 4.52 (ddd, J )
10.2, 4.8, 2.8 Hz, 1H), 3.63-3.56 (m, 2H), 3.50-3.27 (m, 8H),
2.39 (dt, J ) 13.2, 4.5 Hz, 1H), 2.16 (s, 3H), 2.10 (s, 3H), 2.06 (s,
3H), 1.63 (q, J ) 12.6 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ
169.6, 169.6, 169.2, 99.4, 97.5, 83.8, 78.3, 74.1, 69.6, 68.9, 68.8,
60.4, 58.0, 57.7, 56.2, 50.3, 31.1, 20.6, 20.2, 20.2. HRMS (ESI)
m/z calcd for C20H28N12O10 (M + Na)+ 619.1949, found 619.1938.
[R]21 +6.7 (c 3.3, EtOAc).
D
Acknowledgment. We gratefully acknowledge support from
the sixth framework program of the European Union (FSG-V-
RNA contract nr. 503455).
[R]21 +192.4 (c 0.8, EtOAc).
D
6-O-Acetyl-1,3,2′,6′-tetraazido-5-O-methoxymethylneamine (8).
To a solution of 7 (6.68 g, 11.2 mmol) in MeOH (100 mL) was
added KOtBu (1.37 g, 11.2 mmol, 1 equiv), and the resulting
mixture was stirred at room temperature for 2 h. The solution was
neutralized with Amberlite IR 120 plus, filtered, and concentrated
Supporting Information Available: 1H NMR and 13C NMR
spectra for compounds 2, 3, 6, 7, 8, and 11. This material is
available free of charge via the Internet at http://pubs.acs.org.
JO062369Y
3580 J. Org. Chem., Vol. 72, No. 9, 2007