De novo synthesis of sugar-aza-crown ethers via a domino Staudinger aza-Wittig reaction

Article abstract of DOI:10.1021/jo052489q

A short and highly efficient route to sugar-aza-crown (SAC) ethers has been developed. The key step of the transformation is a one-pot cyclodimerization of C-glycosyl azido aldehydes via a domino Staudinger aza-Wittig reaction. This process allows the pre

Full text of DOI:10.1021/jo052489q

SCHEME 1. Previous Synthesis of SAC 2 in 14 % Total
Yields from 14
De Novo Synthesis of Sugar-Aza-Crown Ethers
via a Domino Staudinger Aza-Wittig Reaction
Mickae¨l Me´nand,† Jean-Claude Blais,†
Jean-Marc Vale´ry,† and Juan Xie*,‡
Synthe`se, Structure et Fonction des Mole´cules BioactiVes, CNRS
UMR 7613, UniVersite´ Pierre et Marie Curie, 4 Place Jussieu,
F-75005 Paris, France, and Laboratoire de Photophysique et
Photochimie Supramole´culaires et Macromole´culaires, CNRS
UMR 8531, Ecole Normale Supe´rieure de Cachan, 61 AVenue
du Pt Wilson, F-94235 Cachan, France
joanne.xie@ppsm.ens-cachan.fr
reduction of the amide bonds in the cyclic oligomers of sugar
amino acids.4 These new receptors may lead to exquisite
specificity of recognition and catalyst. Further functionalization
would be possible by connecting either to the sugar hydroxyl
groups or to the nitrogen atoms. To make an impact on
supramolecular chemistry, we envisioned exploring inter-
molecular macrocyclization as a more convergent synthetic
approach to SACs. Template-directed macrolactonization,5
Schiff-base cyclocondensation strategies,6 cyclooligomerization
of saccharid-derived carbamate,7 macrocyclization of amino
acids derivatives,8 and [3+2] Huisgen cyclization9 have been
recently employed to prepare medium-sized macrocycles.
However, to the best of our knowledge, one-pot reductive
amination or Staudinger/aza-Wittig reaction10 of azido aldehydes
has never been reported for macrocyclization. Herein, we
describe the exploration of these two strategies.
The discovery of a new regioselective BCl3-mediated deben-
zylation reaction toward C-glycosides allowed us to start the
synthesis with a variety of orthogonally protected C-allyl
glycosides.11 The ozonolysis, first tested on the perbenzylated
R-C-allyl glucoside 3,12 seemed to be inappropriate in our case.
This reaction led to a complex mixture of sugar aldehydes with
partial oxidation of the benzyl group as well as partial
epimerization of the anomeric carbon. Therefore, we decided
ReceiVed December 2, 2005
A short and highly efficient route to sugar-aza-crown (SAC)
ethers has been developed. The key step of the transformation
is a one-pot cyclodimerization of C-glycosyl azido aldehydes
via a domino Staudinger aza-Wittig reaction. This process
allows the preparation of various orthogonally protected SAC
ethers, from both R- and â-C-glycosyl azido aldehydes.
Like cyclodextrins and calixarenes, crown ethers, aza-crown
ethers, and cyclams are important molecular receptors for
molecular or ionic recognition studies. They are currently used
in analytical chemistry and biological model systems, as well
as nuclear medicine.1,2 Sugars are chiral entities that are very
suitable for the design of chiral receptors and ligands for
asymmetric synthesis or chemosensors. Chiral crown ethers
containing various carbohydrate moieties have received much
attention in recent years as a result of their ability to selectively
complex with guest compounds and to control enantioselective
reactions.3 Very recently, we have realized the first synthesis
of amine-linked sugar macrocycles (Scheme 1), which we would
like to name as sugar-aza-crowns (SACs), by straightforward
(4) Me´nand, M.; Blais, J.-C.; Hamon, L.; Vale´ry, J.-M.; Xie, J. J. Org.
Chem. 2005, 70, 4423-4430.
(5) (a) Fu¨rstner, A.; Albert, M.; Mlynarski, J.; Matheu, M.; DeClercq,
E. J. Am. Chem. Soc. 2003, 125, 13132-13142. (b) Takahashi, S.; Souma,
K.; Hashimoto, R.; Koshino, H.; Nakata, T. J. Org. Chem. 2004, 69, 4509-
4515.
(6) (a) Korupoju, S. R.; Zacharias, P. S. Chem. Commun. 1998, 1267-
1268. (b) Bru, M.; Alfonso, I.; Isabel Burguete, M.; Luis, S. V. Tetrahedron
Lett. 2005, 46, 7781-7785.
(7) Chong, P. Y.; Petillo, P. A. Org. Lett. 2000, 2, 1093-1096.
(8) (a) Chakraborty, T. K.; Srinivasu, P.; Bikshapathy, E.; Nagaraj, R.;
Vairamani, M.; Kiran Kumar, S.; Kunwar, A. C. J. Org. Chem. 2003, 68,
6257-6263. (b) Azumaya, I.; Okamoto, T.; Imabeppu, F.; Takayanagi, H.
Heterocycles 2003, 60, 1419-1424. (c) Mayes, B. A.; Cowley, A. R.;
Ansell, C. W. G.; Fleet, G. W. J. Tetrahedron Lett. 2004, 45, 163-166.
(d) Haberhauer, G. Synlett 2004, 1003-1006. (e) Chakraborty, T. K.;
Tapadar, S.; Venugopal Raju, T.; Annapurna, J.; Singh, H. Synlett 2004,
2484-2488.
* To whom correspondence should be addressed. Telephone: 33-1-47-40-
53-39. Fax: 33-1-47-40-24-54.
† Universite´ Pierre et Marie Curie.
(9) (a) Bodine, K. D.; Gin, D. Y.; Gin, M. S. J. Am. Chem. Soc. 2004,
126, 1638-1639. (b) Bodine, K. D.; Gin, D. Y.; Gin, M. S. Org. Lett.
2005, 7, 4479-4482.
‡ Ecole Normale Supe´rieure de Cachan.
(1) Gokel, G. W.; Leevy, W. M.; Weber, M. E. Chem. ReV. 2004, 104,
2723-2750.
(2) Bu¨nzli, J.-C. G.; Piguet, C. Chem. Soc. ReV. 2005, 34, 1048-1077.
(3) (a) Faltin, F.; Fehring, V.; Miethchen, R. Synthesis 2002, 1851-
1856 and references therein. (b) Bako´, T.; Bako´, P.; Keglevich, G.; Bombicz,
P.; Kubinyi, M.; Pa´l, K.; Bodor, S.; Mako´, A.; To´ke, L. Tetrahedron:
Asymmetry 2004, 15, 1589-1595.
(10) (a) Gololobov, Y. G.; Zhmurova, I. N.; Kasukhin, L. F. Tetrahedron
1981, 37, 437-472. (b) Bra¨se, S.; Gil, C.; Knepper, K.; Zimmermann, V.
Angew. Chem., Int. Ed. 2005, 44, 5188-5240.
(11) Xie, J.; Me´nand, M.; Vale´ry, J.-M. Carbohydr. Res. 2005, 340, 481-
487.
(12) Xie, J. Eur. J. Org. Chem. 2002, 3411-3418.
10.1021/jo052489q CCC: $33.50 © 2006 American Chemical Society
Published on Web 03/17/2006
J. Org. Chem. 2006, 71, 3295-3298
3295

SCHEME 2. Preparation of C-Glucosyl Aldehydes and SAC Ethersa
a Reaction conditions: (a) OsO4 cat., NaIO4, 2,6-lutidine, dioxane/H2O (3/1), rt, 30 min.; (b) H2, 10% Pd/C, MeOH, rt, 24 h; (c) polymer-bound
diphenylphosphine (3 equiv), THF, Ar, rt, 20 h; (d) (1) NaBH(OAc)3 (5 equiv), THF, rt, 20 h; (2) 10% Pd/C, MeOH, rt, 24 h; (e) (1) Boc2O, Et3N, CH2Cl2,
2 h; (2) H2, Pd black, AcOH; (3) AcCl, MeOH, 2 h; (f) Zn(OAc)2 (5 equiv), 0.6 M NaOMe in MeOH, rt, 3 days.
to apply the well-known OsO4-NaIO4 protocol. In this case,
the oxidative cleavage of the double bond occurred without
epimerization, but the aldehyde 6 was isolated in poor yield
(42%), accompanied by a R-hydroxy ketone that resulted from
the over oxidation of the diol intermediate. Recently, an
improved procedure was developed in which the addition of
2,6-lutidine inhibited the formation of side products, accelerated
the reaction, and improved the yields of the desired aldehydes.13
Oxidation of compounds 1, 3, and 4 under these conditions led
to good yields of the corresponding aldehydes (65, 83, and 76%,
respectively) without the formation of any detectable byproducts
(Scheme 2).
As we have shown in a previous paper, the 3-O-benzyl group
of the orthogonally protected C-glucosides is highly resistant
under usual hydrogenation conditions,4 therefore, azido aldehyde
7 was chosen to study the reductive amination strategy for
macrocyclization. Treatment of 7 under hydrogenation condi-
tions (10% Pd/C in methanol) led quantitatively to a mixture
of imine intermediate 8 and a trace amount of amine macrocycle
9. In fact, the azide group was totally reduced and converted
quantitatively into the imine 8. However, further reduction to
amine 9 was held up, probably as a result of catalyst poisoning
by the once-formed amine. Use of other catalysts such as Pd-
(OH)2, PtO2, or Raney Ni did not improve the transformation.
Encouraged by these preliminary results and to identify the
imine intermediate, we then decided to investigate a tandem
Staudinger/aza-Wittig reaction, which proved to be successful
in intramolecular cyclization.10 Treatment of azido aldehyde 7
with PPh3 (1.1 equiv) in anhydrous THF (0.1 M) led efficiently
to the cyclic imine dimer 8. The monitoring of experiments
conducted at different concentrations was carried out without
observing any dilution effect: the cyclic dimer was the only
product, and no polymer was detected during the reaction. To
better understand this macrocyclization, we decided to follow
this reaction by 13C NMR in CDCl3. As shown in Figure 1, the
FIGURE 1. 13C NMR kinetic study of the macrocyclization of
compound 7 in CDCl3 at 298 K.
chemical shift of the aldehyde function of 7 at 199.4 ppm
diminished simultaneously with the appearance of an imine
carbon at 164.1 ppm, and a new aldehyde carbon at 199.8 ppm,
which could correspond to the linear intermediate A (Scheme
3), appeared after an 80 min reaction in CDCl3. The cy-
clodimeric imine carbon at 163.9 ppm became visible after 160
min. Signals at 164.1 and 199.8 ppm lowered progressively
along with the increase of the signal at 163.9 ppm. These results
suggested that after the Staudinger reaction, two aza-Wittig
reactions (formation of the linear dimer A and cyclization) were
taking place successively (Scheme 3). The linear dimer would
(13) Yu, W.; Mei, Y.; Kang, Y.; Hua, Z.; Jin, Z. Org. Lett. 2004, 6,
3217-3219.
3296 J. Org. Chem., Vol. 71, No. 8, 2006

SCHEME 3. Proposed Reaction Pathway for the
Staudinger/Aza-Wittig Macrocyclization
Experimental Section
General Process for Cyclodimerization. To a solution of sugar
azido aldehyde (1 equiv) in freshly distilled THF (0.1 M) under an
argon atmosphere was added polymer-bound diphenylphosphine
(3 equiv), and the reaction was stirred overnight at room temper-
ature. Then the mixture was diluted in EtOAc, filtered over a Celite
pad, and evaporated to give the corresponding cyclic imine dimer,
which was used further without any purification.
1
Cyclic Imine 8: H NMR (250 MHz, CDCl3) δ 2.44 (dd, J )
2.2, 14.5 Hz, 2H), 2.68 (ddd, J ) 14.5, 12.7, 8.2 Hz, 2H), 2.86 (t,
J ) 9.4 Hz, 2H), 3.01 (dd, J ) 10.9, 9.4 Hz, 2H), 3.38-3.50 (m,
2H), 3.47 (s, 6H, OMe), 3.52 (s, 6H), 3.59 (t, J ) 9.4 Hz, 2H),
3.76 (t, J ) 9.4 Hz, 2H), 4.04 (d, J ) 10.9 Hz, 2H), 4.35 (ddd, J
) 5.9, 12.7, 2.2 Hz, 2H), 4.77 (d, J ) 10.8, 2H), 4.85 (d, J ) 10.8,
2H), 7.22-7.42 (m, 10H), 7.47 (d, J ) 8.2 Hz, 2H). 13C NMR
(62.9 MHz, CDCl3) δ 32.0, 59.0, 60.8, 62.6, 70.4, 70.5, 75.3, 81.8,
82.2, 82.8, 127.6, 127.9, 128.4, 138.8, 164.0.
Cyclic Imine 10: 1H NMR (250 MHz, CDCl3) δ 2.54 (dd, J )
2.2, 14.4 Hz, 2H), 2.77 (ddd, J ) 14.4, 8.3, 12.6 Hz, 2H), 3.02
(dd, J ) 11.6, 9.4 Hz, 2H), 3.24 (dd, J ) 8.6, 9.4 Hz, 2H), 3.38 (s,
6H), 3.34 (s, 6H), 3.64 (dd, J ) 9.9, 8.6 Hz, 2H), 3.77 (dd, J )
5.9, 9.9 Hz, 2H), 3.87 (t, J ) 9.4 Hz, 2H), 4.15 (d, J ) 11.6 Hz,
2H), 2.77 (ddd, J ) 2.2, 12.6, 5.9 Hz, 2H), 4.61 (d, J ) 6.5 Hz,
2H), 4.64 (d, J ) 6.5 Hz, 2H), 4.72 (d, J ) 11.1 Hz, 2H), 4.78 (d,
J ) 6.5 Hz, 2H), 4.82 (d, J ) 11.1 Hz, 2H), 4.91 (d, J ) 6.5 Hz,
2H), 7.20-7.39 (m, 10H), 7.47 (d, J ) 8.3 Hz, 2H). 13C NMR
(62.9 MHz, CDCl3) δ 32.4, 55.9, 56.5, 62.7, 70.0, 72.1, 75.6, 78.3,
79.5, 82.1, 97.8, 98.6, 127.5, 128.8, 138.5, 164.4.
be in an adequate conformation to favor the macrocyclization
without further polymerization.
An attempt at purification of the cyclic imine 8 over silica
gel led to degradation. This difficulty was circumvented by the
use of the polymer-bound diphenylphosphine (3 equiv), thus
affording the corresponding cyclic imines in good yields
(Scheme 2). Because the catalytic hydrogenation was inefficient
for imine reduction, we decided to use classical reductive
reagents like NaBH4, which was totally inert toward the
reduction. Use of NaBH3CN, NaBH3CN/AcOH, BH3‚THF, and
NaBH4/AcOH led to complex mixtures. Finally, reduction of
the imines was achieved using the commercially available
NaBH(OAc)3 (5 equiv). Nevertheless, mass spectrometric
analysis showed the presence of boron-amine adducts on each
dimer. Attempts to cleave these adducts in acidic media (aqueous
HCl 10%) led to the desired amines 2, 9, and 12 in moderate
yields. Fortunately, a milder method described in a recent paper
allowed us to cleave the N-B bonds using Pd/C in methanol.14
Up to one gram of cyclic dimers can be prepared in this way.
However, the 3-O-debenzylation of compound 9 by Pd-black-
catalyzed hydrogenolysis in the presence of AcOH appeared to
be unsuccessful.4 We then decided to protect first the amine
function with Boc2O. In this case, the 3-O-benzyl group was
removed after repeated hydrogenolysis, and the desired deben-
zylated compound 13 was obtained after acidic hydrolysis of
the N-Boc protecting group in 74% total yield (Scheme 2).
To verify if this cyclodimerization was dependent on the
anomeric configuration, the R-C-glucosyl aldehyde 7 was first
epimerized to the corresponding â-anomer 14 using Zn(OAc)2
in 0.6 M MeONa/MeOH15 and then submitted to the optimized
one-pot Staudinger/aza-Witting reaction (Scheme 2). As the
R-anomer, compound 14 gave the corresponding cyclodimer 16
in a 60% yield after reduction.
Cyclic Imine 11: 1H NMR (250 MHz, CDCl3) δ 2.47-2.59 (m,
2H), 2.74 (ddd, J ) 14.6, 8.3, 12.9 Hz, 2H), 2.91 (dd, J ) 11.0,
9.7 Hz, 2H), 3.16 (dd, J ) 8.5, 9.7 Hz, 2H), 3.70 (dd, J ) 5.7, 9.4
Hz, 2H), 3.78 (dd, J ) 9.4, 8.5 Hz, 2H), 3.87 (t, J ) 9.7 Hz, 2H),
4.06 (d, J ) 11.1 Hz, 2H), 4.20 (ddd, J ) 5.7, 2.5, 12.9 Hz, 2H),
4.60 (d, J ) 11.1 Hz, 2H), 4.62 (d, J ) 11.7 Hz, 2H), 4.75 (d, J )
12.0 Hz, 2H), 4.80 (d, J ) 11.1 Hz, 2H), 4.60 (d, J ) 10.8 Hz,
4H), 7.20-7.41 (m, 32H). 13C NMR (62.9 MHz, CDCl3) δ 32.3,
62.8, 70.5, 71.3, 73.5, 75.1, 75.8, 79.9, 80.9, 82.7, 127.7, 127.9,
128.1, 128.5, 128.6, 138.4, 138.7, 164.0.
1
Cyclic Imine 15: H NMR (250 MHz, CDCl3) δ 2.44 (dt, J )
14.8, 6.1 Hz, 2H), 2.66 (dt, J ) 14.8, 3.8 Hz, 2H), 2.83-3.00 (m,
2H), 3.07 (t, J ) 9.3 Hz, 2H), 3.22 (t, J ) 8.9 Hz, 2H), 3.33-3.64
(m, 6H), 3.55 (s, 6H), 3.60 (s, 6H), 3.64-3.78 (m, 2H), 4.75-
4.94 (m, 4H), 7.20-7.48 (m, 10H), 7.62 (t, J ) 4.8 Hz, 2H). 13C
NMR (62.9 MHz, CDCl3) δ 37.4, 60.7, 61.5, 75.2, 75.8, 77.2, 81.6,
82.9, 86.7, 127.5, 127.7, 128.3, 138.7, 164.3.
General Procedure for the Reduction of Imine to Amine. To
a solution of imine cyclodimer (1 equiv) in freshly distilled THF
(0.1 M) under an argon atmosphere was added NaBH(OAc)3 (5
equiv), and the reaction was stirred overnight at room temperature.
Then the mixture was partitioned in EtOAc/H2O, extracted three
times with EtOAc, washed with brine, dried over MgSO4, and
evaporated. The residue was diluted in MeOH, and Pd/C (10% w/w)
was added. After stirring for 24 h, the mixture was filtered over a
Celite pad, washed with MeOH, evaporated, and purified over silica
gel to give the corresponding SAC ethers.
In conclusion, we have presented an efficient domino
Staudinger aza-Wittig reaction for cyclodimerization of C-
glycosyl azido aldehydes. This reaction is compatible with a
large number of protecting groups and more versatile than the
reductive amination reaction. The resulting SAC ethers represent
a new class of molecular receptors. These compounds are
currently tested as ligands for metal complexation, polyfunc-
tional building blocks in the synthesis of more complex
structures for host-guest recognition studies, or as catalysts for
asymmetric synthesis.
Sugar-Aza-Crown 9: Rf 0.55 (6:4, EtOAc/cyclohexane, saturated
1
with NH3 gas), mp 128 °C, [R]D +69.4 (c 1, CH2Cl2). H NMR
(250 MHz, CDCl3) δ 1.71-1.87 (m, 2H), 1.87-2.07 (m, 2H), 2.34
(s, 2H, NH), 2.53-2.72 (m, 4H), 2.83 (t, J ) 9.3 Hz, 2H), 2.90-
3.09 (m, 4H), 3.37 (dd, J ) 6.4, 9.3 Hz, 2H), 3.44 (s, 6H), 3.50 (s,
6H), 3.57 (t, J ) 9.3 Hz, 2H), 3.65-3.78 (m, 2H), 4.12-4.26 (m,
2H), 4.75 (d, J ) 10.8 Hz, 2H), 4.85 (d, J ) 10.8 Hz, 2H), 7.22-
7.43 (m, 10H). 13C NMR (62.9 MHz, CDCl3) δ 23.5, 48.1, 52.1,
58.9, 60.6, 70.2, 74.6, 75.3, 81.8, 82.1, 82.7, 127.6, 128.0, 128.4,
138.8. MS (MALDI): m/z 615.40 [M + H]+, 637.36 [M + Na]+.
HRMS (FAB+) m/z [M + H]+ calcd for C34H51N2O8, 615.3640;
found, 615.3638.
(14) Couturier, M.; Tucker, J. L.; Andresen, B. M.; Dube´, P.; Negri, J.
T. Org. Lett. 2001, 3, 465-467.
(15) Shao, H.; Wang, Z.; Lacroix, E.; Wu, S.-H.; Jennings, H. J.; Zou,
W. J. Am. Chem. Soc. 2002, 124, 2130-2131.
J. Org. Chem, Vol. 71, No. 8, 2006 3297

Sugar-Aza-Crown 12: Rf 0.57 (9:1, EtOAc/EtOH), mp 177 °C,
[R]D +49.1 (c 1, CH2Cl2). H NMR (250 MHz, CDCl3) δ 1.76-
0.0726 mmol), filtered over glass cotton, and evaporated under
vacuum to give the desired deprotected compound 13 (32 mg,
0.0726 mmol, 74% overall yield) as a white solid: mp 214 °C,
[R]D +77.2 (c 1, D2O). 1H NMR (250 MHz, D2O with 20% CD3-
OD) δ 1.57-1.91 (m, 4H), 2.52-2.70 (m, 4H), 2.73-2.97 (m, 6H),
3.25-3.40 (m, 2H), 3.36 (s, 6H), 3.46 (s, 6H), 3.48-3.60 (m, 2H),
3.63 (t, J ) 9.40 Hz, 2H), 4.19-4.35 (m, 2H).13C NMR (62.9 MHz,
D2O with 20% CD3OD) δ 23.7, 46.1, 51.6, 58.7, 61.2, 70.8, 73.0,
73.7, 81.6, 83.8. HRMS (FAB+) m/z [M + H]+ calcd for
C20H39N2O8, 435.2701; found, 435.2700.
1
2.16 (m, 4H), 2.44-2.71 (m, 4H), 2.91-3.09 (m, 4H), 3.15 (t, J )
9.2 Hz, 2H), 3.66 (dd, J ) 6.0, 9.2 Hz, 2H), 3.78 (t, J ) 9.2 Hz,
2H), 3.77-3.92 (m, 2H), 4.04-4.20 (m, 2H), 4.50-4.99 (m, 12H),
7.09-7.44 (m, 30H). 13C NMR (62.9 MHz, CDCl3) δ 24.1, 47.4,
52.6, 70.6, 73.1, 74.7, 75.1, 75.7, 80.4, 81.3, 82.5, 127.8, 127.9,
128.0, 128.5, 138.3, 138.4, 138.8. MS (MALDI): m/z 919.48 [M
+ H]+, 941.47 [M + Na]+. HRMS (FAB+) m/z [M + H]+ calcd
for C58H67N2O8, 919.4892; found, 919.4888.
Sugar-Aza-Crown 13: To a solution of SAC 9 (60 mg, 0.0977
mmol) in CH2Cl2 (6 mL) was added Boc2O (45 mg, 0.2062 mmol)
and Et3N (135 µL, 0.975 mmol), and the mixture was stirred for 2
h at room temperature. After evaporation, the crude product was
purified over silica gel (3:7, EtOAc/cyclohexane) to give the desired
(Boc)2SAC (white solid, 77 mg, 0.0946 mmol, 97%), which was
dissolved in acetic acid (2 mL) and hydrogenated under a H2
atmosphere overnight in the presence of Pd black (23 mg, 30%
w/w). Then the mixture was filtered over a Celite pad and rinsed
with acetic acid, and the hydrogenation was repeated a second time.
The filtered solution was finally coevaporated with toluene and
purified over silica gel (8:2, EtOAc/cyclohexane) to give the fully
debenzylated intermediate (46 mg, 0.0726 mmol, 77%). Finally,
the debenzylated (Boc)2SAC was dissolved in a solution of AcCl
(320 µL, 4.5 mmol) in MeOH (3 mL), and the reaction was stirred
for 2 h at room temperature. After evaporation, the crude product
was dissolved in distilled water, neutralized with NaOH (2.9 mg,
Sugar-Aza-Crown 16: Rf 0.55 (6:4, EtOAc/cyclohexane, satu-
rated with NH3 gas), mp 68 °C, [R]D +9.4 (c 1, CH2Cl2). 1H NMR
(250 MHz, CDCl3) δ 1.62-1.83 (m, 2H), 1.98-2.15 (m, 2H),
2.64-2.91 (m, 8H), 2.96 (t, J ) 9.3 Hz, 2H), 3.10 (t, J ) 9.4 Hz,
2H), 3.26-3.40 (m, 2H), 3.44 (dd, J ) 8.8, 4.8 Hz, 2H), 3.47-
3.58 (m, 2H), 3.52 (s, 6H), 3.54 (s, 6H), 4.83 (s, 4H), 7.27-7.43
(m, 10H). 13C NMR (62.9 MHz, CDCl3) δ 30.3, 47.9, 50.6, 60.9,
61.1, 75.4, 77.6, 81.0, 82.0, 83.7, 86.6, 127.8, 128.0, 128.5, 138.8.
MS (MALDI): m/z 615.29 [M + H]+. HRMS (FAB+) m/z [M +
H]+ calcd for C34H51N2O8, 615.3640; found, 615.3634.
Supporting Information Available: General methods, synthe-
ses of C-glycosyl azido aldehydes, 1H and 13C NMR spectra of all
the products. This material is available free of charge via the Internet
at http://pubs.acs.org
JO052489Q
3298 J. Org. Chem., Vol. 71, No. 8, 2006