Regio- and stereo-selective synthesis of aryl 2-deoxy-C-glycopyranosides by palladium-catalyzed Heck coupling reactions of glycals and aryl iodides

Article abstract of DOI:10.1039/b909248j

The Heck coupling of aryl iodides with pyranoid glycals using a catalytic amount of Pd(OAc)₂ to form pyranoid aryl C-glycosides has been achieved. The reaction takes place smoothly in the presence of Ag ₂CO₃ and Cu(OAc)₂ (or DMSO) in acetonitrile. This arylation process, which occurs in a highly regio- and stereo-selective manner, provides a simple, mild, and efficient approach to the synthesis of aryl 2-deoxy-C-glycopyranosides.

Full text of DOI:10.1039/b909248j

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Regio- and stereo-selective synthesis of aryl 2-deoxy-C-glycopyranosides by
palladium-catalyzed Heck coupling reactions of glycals and aryl iodides†
Hou-Hua Li and Xin-Shan Ye*
Received 11th May 2009, Accepted 22nd June 2009
First published as an Advance Article on the web 20th July 2009
DOI: 10.1039/b909248j
The Heck coupling of aryl iodides with pyranoid glycals using a catalytic amount of Pd(OAc)2 to form
pyranoid aryl C-glycosides has been achieved. The reaction takes place smoothly in the presence of
Ag2CO3 and Cu(OAc)2 (or DMSO) in acetonitrile. This arylation process, which occurs in a highly
regio- and stereo-selective manner, provides a simple, mild, and efficient approach to the synthesis of
aryl 2-deoxy-C-glycopyranosides.
be hampered by the availability of arylboronic acids which are
normally prepared from aryl halides. For example, C-nucleosides
are important agents for biological research and for potential
therapeutic applications, however, methods for the synthesis of
Introduction
Aryl-C-glycosides, due to their occurrence in biologically im-
portant natural products and their use as stable analogues of
pyranoid C-nucleosides are quite limited.6b,11 It is not convenient to
obtain pyranoid C-nucleosides using our oxidative Heck protocol,
because the corresponding heterocyclic boronic acids are not
easily prepared. Therefore, we want to investigate the possibility
of the Heck arylations of pyranoid glycals with aryl halides
which are more feasible materials. In fact, contrary to the well-
established Pd-catalyzed Heck reaction of furanoid glycals with
aryl organohalides,11a the Pd-catalyzed Heck reaction between
pyranoid glycals and aryl halides or triflates has been less explored,
and few examples were reported.11b
To tackle this problem, we turned our attention to the Pd-
catalyzed Heck C-glycosylations of pyranoid glycals with aryl
halides. We found that in the presence of Ag2CO3 and Cu(OAc)2,
an efficient Heck arylation occurred very smoothly between
pyranoid glycals and aryl iodides using Pd(OAc)2 as catalyst. The
reaction only underwent a Heck syn-b-hydride elimination to yield
the corresponding enol ether type aryl C-glycosides (Scheme 1,
path E-c).
O-glycosides and N-glycosides that are resistant to enzymatic
cleavage, have gained considerable attention in recent years.1–3
In particular, the unique 2-deoxy pyranoid aryl-C-glycoside
structure is embodied in a variety of bioactive natural prod-
ucts including the pluramycins (kidamycin, etc.), angucyclines
(galtamycinone, vineomycinone B2 methyl ester, etc.), and ben-
zoisochromanequinones (medermycin, etc.).3 Due to their bio-
logical importance and structural complexity, many synthetic
approaches have been developed so far.4 However, from a synthetic
point of view, the highly regio- and stereo-selective formation of
the aryl C-C glycosidic bond is still a predominant challenge.
The Heck reaction, a Pd-catalyzed coupling of olefins with
organohalides or triflates, has become a powerful tool for
C-C bond formation.5 Pioneering work, carried out by Daves
(Scheme 1, path 1)6 and Czernecki (Scheme 1, path 2),7 showed
that the Pd (II)-mediated Heck arylation of glycals occurred
to form aryl C-C glycosidic bonds by using stoichiometric Pd
(II). Unfortunately, mixtures of coupling products were always
obtained due to three different types of elimination approaches
(Scheme 1, E-a/E-b/E-c). Except for the low yield and low
regioselectivity, the use of toxic reagents such as organomercury
was the other drawback of this work. More recently, Maddaford
(Scheme 1, path 3)8 and de la Figuera (Scheme 1, path 4)9
respectively reported the Pd (II)-catalyzed Heck arylations of
glycals with ArB(OH)2 in the presence of a catalytic amount of
Pd(OAc)2, providing the carbon-Ferrier type (Scheme 1, E-a)
or ring-opened products (Scheme 1, E-b). Very recently, we
successfully developed a palladium (II)-catalyzed oxidative Heck-
type reaction of pyranoid glycals with arylboronic acids, which
underwent a Heck syn-b-hydride elimination to yield enol ether or
ketone types of aryl C-glycosides in decent yields and with broad
substrate scope (Scheme 1, E-c).10 However, this approach may
Results and discussion
Initially, we examined the couplings of pyranoid glycals 1a–1c
with iodobenzene (2a) following Daves’ Heck reaction conditions
(Table 1, entry 1).11b When 1a–1c and 2a were catalyzed by
40 mol% Pd(OAc)2 in the presence of bases (both 0.4 eq. of
n-Bu3N and 2.0 eq. of Na2CO3 were added) at room temperature
or 50 ◦C in DMF, none of the coupling products were observed,
only unreacted starting materials got recovered. After intensive
screening, we found that the coupling reaction between the silyl-
protected glucal 1c and iodobenzene (2a) occurred in the presence
of 2.0 eq. of silver carbonate (Table 1, entry 4), providing the enol
ether type C-glycoside 3a resulted from the Heck syn-b-hydride
elimination (Scheme 1, E-c) in 71% isolated yield, whereas the
other types of elimination products were not obtained during this
process. However, under the same conditions, when the acetyl-
and benzyl- protected glucals 1a and 1b were used as the starting
materials, no coupling products were formed (Table 1, entries 2
and 3). According to Daves’ results,6b the conformational rigidity
State Key Laboratory of Natural and Biomimetic Drugs, Peking University,
and School of Pharmaceutical Sciences, Peking University, Xue Yuan Rd
No. 38, Beijing, 100191, China. E-mail: xinshan@bjmu.edu.cn; Fax: +86-
10-62014949; Tel: +86-10-62014949
† Electronic supplementary information (ESI) available: Experimental
procedures and data for new compounds. See DOI: 10.1039/b909248j
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Table 1 Pd-catalyzed Heck coupling reactions of 1a–1c with iodobenzene to form C-glycosidesa
Entry
Substrate
Additives (eq.)
Solvent
t (h)
Yield [%]e
1b
2
3
4
5
6
7
8
9
10
11
12
13c
14c
15c
16d
17d
1a–1c
1a
1b
1c
none
Ag2CO3 (2.0)
Ag2CO3 (2.0)
Ag2CO3 (2.0)
BQ (2.0)
Cu(OAc)2 (2.0)
DMSO (4.0)
Ag2CO3 (0.6)
Ag2CO3 (0.6), BQ (2.0)
Ag2CO3 (0.6), DMSO (4.0)
Ag2CO3 (0.6)
Ag2CO3 (0.6), Cu(OAc)2 (2.0)
Ag2CO3 (0.6), Cu(OAc)2 (2.0)
Ag2CO3 (0.6)
Ag2CO3 (0.6), H2O (4.0)
Ag2CO3 (0.6), Cu(OAc)2 (2.0)
Ag2CO3 (0.6), DMSO (4.0)
DMF
48
48
48
24
24
24
24
24
24
15
24
15/24
24
48
48
48
48
—
—
—
71
DMF or MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
DMSO
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
1c
—
1c
<5
<5
74
—
90
—
90/92
94
72
73
—
—
1c
1c
1c
1c
1c
1c
1c
1c
1c
1c
1c
a Reaction conditions: 1a–1c (0.1 mmol), PhI (0.2 mmol), Pd(OAc)2 (0.01 mmol), and solvent (1.5 mL), 40 ◦C, under air. b 40 mol% Pd(OAc)2 and Bu3N
(0.4 eq.)/Na2CO3 (2.0 eq.), r.t. or 50 ◦C. c The reaction was carried out under Ar. d PhBr (0.2 mmol) and 1c (0.1 mmol) were used as substrates, 50 ◦C.
e Isolated yield.
Scheme 1 The Heck arylations of pyranoid glycals.
and poor leaving property at C-3-O-substituent of 1c (R = TBS,
t-butyldimethylsilyl) may promote syn-b-hydride elimination of
the syn-addition intermediate (the organopalladium s-adduct),
this may explain the reactivity difference between 1a–1b and 1c,
and we chose TBS-protected pyranoid glycals as our substrates.
Subsequently, the effects of different additives on the coupling
of 1c and 2a were checked. When p-benzoquinone (BQ) was used
instead of silver carbonate, no coupling products were observed
(Table 1, entry 5). When using Cu(OAc)2 or DMSO as the additive,
only a trace amount of 3a was formed (Table 1, entries 6 and 7).
It seems that silver carbonate, which might play dual roles in the
reaction process (a silver source to scavenge the iodide as well as
a base),12 was crucial to the Heck coupling. Further investigation
indicated that the reaction achieved a higher yield (74%) with only
0.6 eq. of Ag2CO3 using acetonitrile as solvent (Table 1, entry 8).
However, under the same conditions but using DMSO in place of
acetonitrile, no coupling reaction took place (Table 1, entry 11).
Interestingly, when the combination of 0.6 eq. of Ag2CO3 and 2.0
eq. of Cu(OAc)2 was used as the additive, coupling product 3a
was obtained in excellent isolated yield (90% for 15h and 92% for
24h, Table 1, entry 12). Another additive combination with 0.6
eq. of Ag2CO3 and 4.0 eq. of DMSO also gained similar results
(90% yield for 15h, Table 1, entry 10). When the coupling reaction
was carried out under argon atmosphere, 3a was obtained in a
little higher yield (94%) compared with the same conditions under
air (Table 1, entry 13). The addition of 4.0 eq. of H2O did not
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Table 2 Pd-catalyzed Heck reactions of 1c with different aryl iodidesa
improve the yield of 3a (Table 1, entries 14 and 15). Although it
was disclosed that silver carbonate played an important role in
palladium-catalyzed Heck reactions of some organo halides,12 it is
noteworthy that the reaction efficiency can be improved by using
weak oxidants (Cu(OAc)2 or DMSO) as additives in this protocol.
Therefore, after screening, we optimized the reaction conditions
for the Heck coupling between pyranoid glycal 1c and iodobenzene
2a: 10 mol% Pd(OAc)2, 0.6 eq. of Ag2CO3 in combination with 2.0
eq. of Cu(OAc)2 or 4.0 eq. of DMSO, 40 ◦C in acetonitrile under
air for 24h.
Entry
1
Aryl iodide
Product
Yield [%] c
99
Using the optimized conditions, the coupling reaction with
other substrates such as bromobenzene was examined. However,
the coupling of 1c and bromobenzene did not occur even though
the reaction was performed at 50 ◦C for 48 h (Table 1, entries 16
and 17). This indicated that the Heck coupling reaction was only
suitable for aryl iodides at this stage.
2
87
59
The scope of the Heck reaction of pyranoid glycal 1c was
expanded to a variety of aryl iodides (Table 2). The reaction
with various aryl iodides containing electron-donating, electron-
withdrawing, and sterically congested groups proceeded smoothly
and efficiently (Table 2, entries 1–5), only silyl enol ether type
coupling products 3 (via Heck syn-b-hydride elimination) were
formed. In the case of electron-deficient aryl iodides such as
those substituted by NO2 (2d), CF3 (2e), or CO2Me (2f) groups,
satisfactory yields (59–94%) were realized by raising the reaction
temperature to 50 ◦C and prolonging the reaction time to
36 h (Table 2, entries 3–5). Condensed aryl iodides such as
1-iodonaphthalene (2g), coupled successfully with 1c leading to
3g in 95% isolated yield (Table 2, entry 6). It is noteworthy that
the reactions with the bifunctional aryl iodides (Ar = 4-BrPh,
4-ClPh) underwent smoothly to give the regioselective coupling
products 3h and 3i in high yields (Table 2, entries 7 and 8). The
resulting compounds 3h and 3i can be further transformed by
metal-catalyzed cross coupling reactions due to the existence of
aryl halides.
3b
4b
5b
6
75
94
95
Encouraged by these results, we next investigated the Heck
coupling of aryl iodides with a series of pyranoid glycals (Table 3).
Like the case of glucal 1c, similar results were obtained when
other glycals 1d, 1e, 1f were employed, and all provided the
desired single enol ether products in high isolated yields (71–98%)
(Table 3, entries 1–7). For those aryl iodides with electron-
withdrawing substituents, the Hec◦k reactions achieved good yields
by raising the temperature to 50 C and prolonging the reaction
time to 36 h (entries 3 and 6). Finally, we applied our protocol
to the synthesis of pyranoid C-nucleosides: the Heck coupling
of pyranoid glycal 1f with 5-iodo-1,3-dimethyluracil 2l proceeded
well and only desired silyl enol ether C-nucleoside 6b was obtained
in 84% isolated yield (Table 3, entry 8). Compared with the
known methods,6b,11b our approach to the preparation of pyranoid
C-nucleosides is highly regioselective, more efficient, more eco-
nomic, and less toxic.
7
8
82
92
a Reaction conditions: 1c (0.1 mmol), ArI (0.2 mmol), Pd(OAc)2
(0.01 mmol),◦ Ag2CO3 (0.06 mmol), Cu(OAc)2 (0.2 mmol) in MeCN
(1.5 mL), 40 C, under air, 24 h. b The reaction was carried out at 50 ◦C
for 36 h. c Isolated yield.
In all cases, only a single anomer was obtained in each Heck
coupling reaction. According to the mechanism, the configuration
of the newly-introduced aryl group at the anomeric position is
opposite to the C3-O-substituent of the starting glycals, resulted
from the syn-addition to the opposite face because of the steric
hindrance (Scheme 1). The anomeric stereochemistry of the
coupling product was confirmed by its 13C NMR and NOESY
spectra analyses.10,13
Conclusion
In summary, a simple, mild, and efficient Heck C-glycosylation of
pyranoid glycals with various aryl iodides has been developed. No
any air-sensitive phosphorous ligands were used, and the reaction
was easily operated under air. Furthermore, the Heck arylation
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Table 3 Pd-catalyzed Heck reactions of aryl iodides with different pyranoid glycals 1d–1fa
Entry
1
Substrate
Aryl iodide
Product
Yield [%]c
94
2
1d
1d
78
3b
81
95
4
5
1e
1e
98
71
88
6b
7
8
1f
84
a Reaction conditions: 1d–1f (0.1 mmol), ArI (0.2 mmol), Pd(OAc)2 (0.01 mmol), Ag2CO3 (0.06 mmol), Cu(OAc)2 (0.2 mmol) in MeCN (1.5 mL), 40 ◦C,
under air, 24 h. b The reaction was carried out at 50 ◦C, 36 h. c Isolated yield.
occurred in a regio- and stereo-selective manner, only a single enol
ether coupling product (one anomer) was formed (via Heck syn-
b-hydride elimination approach), none of the other elimination
products such as ring-opened products and carbon-Ferrier type
products were observed. Compared with the oxidative Heck proto-
col we recently disclosed,10 the coupling reaction using aryl iodides
instead of aryl boronic acids opened an alternative avenue to aryl
C-glycosides. Since aryl halides are generally more available than
aryl boronic acids, this protocol may find wide applications
to the synthesis of naturally occurring 2-deoxy pyranoid aryl
C-glycosides and pyranoid C-nucleosides with biological im-
portance. Further studies on the synthetic applications and
Pd-catalyzed Heck C-glycosylations using other organohalides or
triflates are underway.
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Compound 1f17. Colorless oil. Rf
=
0.67 (petroleum
Experimental
1
ether/ethyl acetate, 22:1). H NMR (300 MHz, CDCl3) d 6.28
(d, 1H, J = 6.0 Hz), 4.66 (dd, 1H, J = 3.0, 6.3 Hz), 4.07 (t, 1H,
J = 3.8, Hz), 3.98–3.89 (m, 1H), 3.56 (t, 1H, J = 6.3 Hz), 1.32 (d,
3H, J = 6.9 Hz), 0.90 (s, 18H), 0.11 and 0.095 (2 s, 18H).
General
All chemicals were purchased as reagent grade and used without
further purification, unless otherwise noted. Analytical TLC was
performed using aluminium plates pre-coated with silica gel 60-
F254 (E. Merck), with detection by fluorescence and/or by staining
with acidic ceric ammonium molybdate. Column chromatog-
raphy was performed by employing Silica Gel 200–300 mesh.
1H-NMR spectra were recorded on a JEOL AL-300 (300 MHz),
Varian INOVA-500 (500 MHz) or Advance DRX Bruker-400
spectrometers at 25 ◦C. Chemical shifts (in ppm) were referenced to
tetramethylsilane (d = 0 ppm) in deuterated chloroform. 13C-NMR
spectra were obtained by using the same NMR spectrometers
and were calibrated with CDCl3 (d = 77.00 ppm). Mass spectra
were recorded using a PE SCLEX QSTAR spectrometer. High-
resolution mass spectrometry was performed on a Bruker APEX
IV. Elemental analyses were recorded on a Vario EL-III elemental
analyzer.
Heck arylation of glycals
General procedure for Heck arylation. To a mixture of the
glycal (0.1 mmol) and aryl iodide (0.2 mmol) in 1.5 mL of ace-
tonitrile was added Pd(OAc)2 (0.01 mmol), Ag2CO3 (0.06 mmol)
and Cu(OAc)2 (0.2 mmol). The resulting suspension was stirred
at 40 ◦C for 24 h under air. After the starting materials were
consumed (by TLC: petroleum ether/ethyl acetate, 24/1), the
reaction mixture was filtered directly and the filtrate was con-
centrated under vacuum. The residue was purified by column
chromatography on silica gel with a gradient eluent of petroleum
ether and ethyl acetate to give the pure product.
Compound 3a. Following the general procedure, cross-
coupling afforded 3a (92%) as a colorless oil, Rf = 0.50 (petroleum
Preparation of substrates
1
ether/ethyl acetate, 24/1). H NMR (500 MHz, CDCl3) d 7.43–
7.42 (m, 2H), 7.34–7.31 (m, 2H), 7.28–7.25 (m, 2H), 5.15 (s, 1H,
H-1), 4.90 (d, 1H, J = 3.0 Hz, H-2), 4.07 (dd, 1H, J = 1.5, 3.0 Hz,
H-4), 3.89–3.86 (m, 1H, H-5), 3.82–3.76 (m, 2H, H-6), 0.94 (s,
9H), 0.92 (s, 9H), 0.90 (s, 9H), 0.18 (s, 3H), 0.16 (s, 3H), 0.12 (s,
3H), 0.11 (s, 3H), 0.062 (s, 3H), 0.056 (s, 3H); 13C NMR (75 MHz,
CDCl3) d 148.53 (C-3), 141.87, 128.25, 127.67, 106.07 (C-2), 79.03
(C-1), 73.36, 67.00, 62.33, 26.02, 25.91, 18.41, 18.22, 18.10, -3.91,
-4.09, -4.51, -5.40; MS (ESI-TOF) m/z: (M + Na)+ calcd for
(C30H56O4Si3Na+) 587, found 587. Anal. Calcd for C30H56O4Si3: C,
63.95; H, 9.99. found: C, 63.77; H, 9.95.
General procedure for the preparation of persilylated glycal
substrates. Peracetylated glycal14 (4.0 mmol) was dissolved in
15 mL of MeOH, 9 drops of NaOMe/MeOH solution (25–30%,
w/w) were added. The reaction mixture was stirred at room
temperature. The reaction was monitored by TLC (petroleum
ether/ethyl acetate, 1:1). After the starting material disappeared,
the reaction mixture was evaporated to dryness. The residue was
dissolved in dry DMF (2 mL). Imidazole (3.0 mmol per mmol
OH) was added, followed by the addition of t-butyldimethylsilyl
chloride (2.0 mmol per mmol OH) and 4-dimethylaminopyridine
(DMAP, 0.04 mmol). The resulting solution was stirred at 50 ◦C
for 2 days. The mixture was extracted by dichloromethane (three
times), and the organic layers were combined and dried over
sodium sulfate, filtered, and evaporated. The residue was purified
by column chromatography on silica gel (petroleum ether/ethyl
acetate, 120:1) to give products.
Compound 3b. Following the general procedure, cross-
coupling afforded 3b (99%) as a colorless oil, Rf = 0.50 (petroleum
1
ether/ethyl acetate, 25/1). H NMR (500 MHz, CDCl3) d 7.44–
7.43 (m, 1H), 7.18–7.12 (m, 3H), 5.37 (dd, 1H, J = 1.0, 2.5 Hz,
H-1), 4.89 (d, 1H, J = 3.0 Hz, H-2), 4.06 (dd, 1H, J = 1.0, 2.5 Hz,
H-4), 3.81–3.73 (m, 3H, H-5, H-6), 2.43 (s, 3H, Me), 0.95 (s, 9H),
0.90 (s, 9H), 0.88 (s, 9H), 0.20 (s, 3H), 0.18 (s, 3H), 0.13 (s, 3H), 0.11
(s, 3H), 0.047 (s, 3H), 0.042 (s, 3H); 13C NMR (75 MHz, CDCl3)
d 149.07 (C-3), 138.83, 136.97, 130.58, 128.73, 127.79, 125.62,
105.41 (C-2), 78.56 (C-1), 70.91, 66.81, 62.22, 26.08, 25.87, 19.19,
18.48, 18.23, 18.10, -3.76, -4.07, -4.56, -5.40; HRMS (ESI) m/z:
(M + Na)+ calcd for (C31H58O4Si3Na+) 601.3535, found 601.3544;
(M + K)+ calcd for (C31H58O4Si3K+) 617.3269, found 617.3283.
Compound 1c15. Colorless oil. Rf
=
0.67 (petroleum
1
ether/ethyl acetate, 24:1). H NMR (300 MHz, CDCl3) d 6.32
(d, 1H, J = 6.3 Hz), 4.69 (dd, 1H, J = 4.8, 6.0 Hz), 4.02–3.88 (m,
3H), 3.80–3.74 (m, 2H), 0.90, 0.89 and 0.87 (3 s, 27H), 0.1–0.005
(6 s, 18H).
Compound 1d16. Colorless oil. Rf
=
0.67 (petroleum
1
ether/ethyl acetate, 24:1). H NMR (300 MHz, CDCl3) d 6.21
(d, 1H, J = 6.0 Hz), 4.03 (t, 1H, J = 3.0 Hz), 4.11–4.02 (m, 4H),
3.89–3.82 (m, 1H), 0.91 and 0.90 (2 s, 27H), 0.098, 0.068 and 0.056
(3 s, 18H).
Compound 3c. Following the general procedure, cross-
coupling afforded 3c (87%) as a colorless oil, Rf = 0.50 (petroleum
ether/ethyl acetate, 24/1). 1H NMR (500 MHz, CDCl3) d 7.34 (d,
1H, J = 8.5 Hz), 6.86 (d, 1H, J = 8.5 Hz), 5.10 (d, 1H, J = 1.0 Hz,
H-1), 4.87 (d, 1H, J = 3.0 Hz, H-2), 4.06 (dd, 1H, J = 1.5, 3.0 Hz,
H-4), 3.86–3.83 (m, 1H, H-5), 3.80–3.76 (m, 2H, H-6), 3.80 (s, 3H,
MeO), 0.95 (s, 9H), 0.92 (s, 9H), 0.89 (s, 9H), 0.18 (s, 3H), 0.16 (s,
3H), 0.12 (s, 3H), 0.11 (s, 3H), 0.056 (s, 3H), 0.050 (s, 3H); 13C NMR
(75 MHz, CDCl3) d 159.21, 148.50 (C-3), 134.06, 129.01, 113.60,
106.25 (C-2), 78.89 (C-1), 72.88, 67.00, 62.31, 55.24, 26.02, 25.91,
25.85, 18.40, 18.21, 18.10, -3.89, -4.16, -4.51, -5.40; HRMS (ESI)
Compound 1e. Colorless oil. Rf = 0.67 (petroleum ether/ethyl
1
acetate, 22:1). H NMR (300 MHz, CDCl3) d 6.28 (d, 1H, J =
6.0 Hz), 4.76 (t, 1H, J = 5.7 Hz), 4.04–4.02 (m, 1H), 3.94, 3.84 (m,
1H), 3.76–3.70 (m, 1H), 0.90 (s, 9H), 0.89 (s, 9H), 0.087 (s, 6H),
0.071 (s, 6H); 13C NMR (75 MHz, CDCl3) d 144.89, 102.33, 68.55,
64.65, 63.90, 25.89, 18.22, -4.15, -4.19, -4.39, -4.42, -4.86, -4.90;
MS (ESI-TOF) m/z: (M + Na)+ calcd for (C17H36O3Si2Na+) 367,
found 367. Anal. Calcd for C17H36O3Si2: C, 59.25; H, 10.53. found:
C, 58.96; H, 10.27.
+
m/z: (M + H)+ calcd for (C31H59O5Si3 ) 595.3665, found 595.3671.
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Compound 3d. Following the general procedure, the reaction
was carried out at 50 ◦C for 36 h, affording 3d (59%) as a colorless
oil, Rf = 0.30 (petroleum ether/ethyl acetate, 20/1). H NMR
3.75–3.78 (m, 2H, H-6), 0.94 (s, 9H), 0.92 (s, 9H), 0.90 (s, 9H), 0.18
(s, 3H), 0.16 (s, 3H), 0.12 (s, 6H), 0.061 (s, 6H); 13C NMR (75 MHz,
CDCl3) d 148.79 (C-3), 141.08, 131.34, 129.34, 121.55, 105.47 (C-
2), 79.12 (C-1), 72.76, 66.95, 62.26, 25.98, 25.85, 18.39, 18.21,
18.08, -3.93, -4.13, -4.56, -5.41; HRMS (ESI) m/z: (M + Na)+
calcd for (C30H55BrO4Si3Na+) 665.2484, found 665.2494; (M + K)+
calcd for (C30H55BrO4Si3K+) 681.2218, found 681.2230.
1
(300 MHz, CDCl3) d 8.19 (d, 2H, J = 8.7 Hz), 7.61 (d, 2H, J =
8.7 Hz), 5.25 (d, 1H, J = 1.8 Hz, H-1), 4.83 (d, 1H, J = 2.7 Hz,
H-2), 4.08 (d, 1H, J = 2.1 Hz, H-4), 3.88–3.93 (m, 1H, H-5), 3.77–
3.79 (m, 2H, H-6), 0.94 (s, 9H), 0.93 (s, 9H), 0.91 (s, 9H), 0.18 (s,
3H), 0.15 (s, 3H), 0.12 (s, 6H), 0.076 (s, 3H), 0.069 (s, 3H); 13C
NMR (75 MHz, CDCl3) d 149.62, 149.21, 147.38, 128.13, 123.63,
104.57 (C-2), 79.52 (C-1), 72.57, 66.94, 62.20, 25.83, 18.37, 18.20,
18.06, -4.17, -4.58, -5.42; HRMS (ESI) m/z: (M + H)+ calcd for
Compound 3i. Following the general procedure, cross-
coupling afforded 3i (92%) as a colorless oil, Rf = 0.60 (petroleum
ether/ethyl acetate, 24/1). 1H NMR (300 MHz, CDCl3) d 7.25 (d,
2H, J = 8.4 Hz), 7.18 (d, 2H, J = 8.4 Hz), 5.01 (s, 1H, H-1), 4.72
(d, 1H, J = 2.7 Hz, H-2), 3.95 (d, 1H, J = 2.1 Hz, H-4), 3.72–3.74
(m, 1H, H-5), 3.64–3.66 (m, 2H, H-6), 0.83 (s, 9H), 0.80 (s, 9H),
0.78 (s, 9H), 0.065 (s, 3H), 0.043 (s, 3H), 0.005 (s, 3H), 0.000 (s,
3H), -0.052 (s, 3H), -0.058 (s, 3H); 13C NMR (75 MHz, CDCl3)
d 148.78 (C-3), 140.56, 133.37, 129.00, 128.40, 105.56 (C-2), 79.13
(C-1), 72.72, 66.97, 62.26, 25.88, 18.40, 18.22, 18.09, -4.16, -4.54,
-5.38; HRMS (ESI) m/z: (M + Na)+ calcd for (C30H55ClO4Si3Na+)
621.2989, found 621.2996.
+
(C30H56NO6Si3 ) 610.3410, found: 610.3423.
Compound 3e. Following the general procedure, the reaction
was carried out at 50 ◦C for 36 h, affording 3e (75%) as a colorless
1
oil, Rf = 0.50 (petroleum ether/ethyl acetate, 25/1). H NMR
(500 MHz, CDCl3) d 7.59 (d, 1H, J = 8.5 Hz), 7.55 (d, 1H, J =
8.5 Hz), 5.21 (d, 1H, J = 1.5 Hz, H-1), 4.86 (d, 1H, J = 2.5 Hz,
H-2), 4.08 (dd, 1H, J = 1.0, 3.0 Hz, H-4), 3.90–3.87 (m, 1H, H-5),
3.81–3.77 (m, 2H, H-6), 0.95 (s, 9H), 0.93 (s, 9H), 0.91 (s, 9H),
0.19 (s, 3H), 0.17 (s, 3H), 0.13 (s, 6H), 0.075 (s, 3H), 0.067 (s, 3H);
13C NMR (75 MHz, CDCl3) d 148.90, 146.10, 129.83 (d, 1C, J =
31.5 Hz), 127.79, 125.26, 124.22 (d, 1C, J = 269.5 Hz, CF3), 105.16,
79.32, 72.85, 66.98, 62.26, 57.47, 25.97, 25.85, 18.40, 18.22, 18.08,
-3.94, -4.14, -4.57, -5.41; HRMS (ESI) m/z: (M + H)+ calcd for
Compound 4a. Following the general procedure, cross-
coupling afforded 4a (92%) as a colorless oil, Rf = 0.30 (petroleum
1
ether/ethyl acetate, 25/1). H NMR (300 MHz, CDCl3) d 7.11–
7.26 (m, 4H), 5.59 (d, 1H, J = 3.3 Hz, H-1), 5.05 (d, 1H, J =
3.3 Hz, H-2), 3.89 (d, 1H, J = 1.8 Hz, H-4), 3.72 (dd, 1H, J =
5.4, 10.2 Hz, H-6), 3.61 (dd, 1H, J = 6.6, 10.2 Hz, H-6), 3.49–3.53
(m, 1H, H-5), 2.48 (s, 3H), 1.00 (s, 9H), 0.92 (s, 9H), 0.77 (s, 9H),
0.27 (s, 3H), 0.26 (s, 3H), 0.15 (s, 3H), 0.14 (s, 3H), -0.070 (s,
3H), -0.10 (s, 3H); 13C NMR (75 MHz, CDCl3) d 150.94 (C-3),
138.33, 137.84, 130.79, 127.88, 124.88, 105.90 (C-2), 73.93 (C-1),
71.01, 67.88, 62.50, 26.10, 25.76, 19.41, 18.53, 18.44, 18.09, -3.87,
(C31H56F3O4Si3 ) 633.3433, found 633.3434; (M + Na)+ calcd for
+
(C31H55F3O4Si3Na+) 655.3253, found 655.3254.
Compound 3f. Following the general procedure, the reaction
was carried out at 50 ◦C for 36 h, affording 3f (94%) as a colorless
1
oil, Rf = 0.30 (petroleum ether/ethyl acetate, 25/1). H NMR
(300 MHz, CDCl3) d 7.97 (d, 1H, J = 7.8 Hz), 7.80 (d, 1H, J =
7.5 Hz), 7.51 (t, 1H, J = 7.8 Hz), 7.29 (t, 1H, J = 7.8 Hz),
5.96 (s, 1H, H-1), 5.01 (d, 1H, J = 2.4 Hz, H-2), 4.10 (s, 1H,
H-4), 3.97–4.01 (m, 1H, H-5), 3.89 (s, 3H), 3.78–3.80 (m, 2H,
H-6), 0.95 (s, 9H), 0.92 (s, 9H), 0.90 (s, 9H), 0.065–0.16 (m,
18H); 13C NMR (75 MHz, CDCl3) d 167.88, 147.44 (C-3), 144.07,
132.28, 129.52, 129.05, 128.20, 126.96, 106.70 (C-2), 80.00 (C-1),
69.14, 67.02, 62.16, 52.04, 25.87, 18.22, 18.16, 18.06, -4.18, -4.60,
-5.45; HRMS (ESI) m/z: (M + Na)+ calcd for (C32H58O6Si3Na+)
645.3433, found 645.3441; (M + K)+ calcd for (C32H58O6Si3K+)
661.3167, found 661.3182.
-4.78, -5.48; HRMS (ESI) m/z: (M + H)+ calcd for (C31H59O4Si3 )
+
579.3716, found 579.3722; (M + Na)+ calcd for (C31H58O4Si3Na+)
601.3535, found 601.3549.
Compound 4b. Following the general procedure, cross-
coupling afforded 4b (78%) as a colorless oil, Rf = 0.30 (petroleum
ether/ethyl acetate, 24/1). 1H NMR (300 MHz, CDCl3) d 7.32 (d,
2H, J = 8.7 Hz), 6.87 (d, 2H, J = 8.7 Hz), 5.37 (d, 1H, J = 3.9 Hz,
H-1), 5.17 (d, 1H, J = 3.9 Hz, H-2), 3.81 (s, 1H, H-4), 3.80 (s,
3H), 3.75 (dd, 1H, J = 6.0, 10.5 Hz, H-6), 3.67 (dd, 1H, J = 6.6,
10.5 Hz, H-6), 3.53 (dt, 1H, J = 1.8, 6.0 Hz, H-5), 0.98 (s, 9H),
0.91 (s, 9H), 0.83 (s, 9H), 0.25 (s, 3H), 0.24 (s, 3H), 0.15 (s, 3H),
0.13 (s, 3H), -0.008 (s, 3H), -0.024 (s, 3H); 13C NMR (75 MHz,
CDCl3) d 158.98, 150.60 (C-3), 133.10, 128.86, 113.50, 106.08 (C-
2), 73.89 (C-1), 72.91, 67.61, 62.63, 55.25, 26.02, 25.81, 18.49,
18.40, 18.16, -3.99, -4.85, -5.33; HRMS (ESI) m/z: (M + H)+
Compound 3g. Following the general procedure, cross-
coupling afforded 3g (95%) as a colorless oil, Rf = 0.60 (petroleum
ether/ethyl acetate, 24/1). 1H NMR (300 MHz, CDCl3) d 8.60 (d,
1H, J = 9.3 Hz), 7.77–7.84 (m, 2H), 7.38–7.55 (m, 4H), 5.78 (s, 1H,
H-1), 5.05 (d, 1H, J = 2.7 Hz, H-2), 4.16 (dd, 1H, J = 1.2, 2.7 Hz,
H-4), 3.80–3.90 (m, 3H, H-5, H-6), 0.87–0.96 (m, 27H), 0.001–0.18
(m, 18H); 13C NMR (75 MHz, CDCl3) d 149.02 (C-3), 136.39,
134.17, 131.73, 128.91, 128.30, 126.56, 125.90, 125.52, 124.87,
105.94 (C-2), 78.90 (C-1), 72.33, 66.89, 62.06, 26.08, 25.94, 25.86,
18.48, 18.24, 18.15, -3.69, -4.08, -4.52, -5.39; HRMS (ESI) m/z:
(M + Na)+ calcd for (C34H58O4Si3Na+) 637.3535, found 637.3541;
(M + K)+ calcd for (C34H58O4Si3K+) 653.3269, found 653.3274.
calcd for (C31H59O5Si3 ) 595.3665, found 595.3682; (M + Na)+
+
calcd for (C31H58O5Si3Na+) 617.3484, found 617.3506.
Compound 4c. Following the general procedure, the reaction
was carried out at 50 ◦C for 36 h, affording 4c (81%) as a colorless
1
oil, Rf = 0.30 (petroleum ether/ethyl acetate, 25/1). H NMR
(300 MHz, CDCl3) d 7.79 (dd, 1H, J = 1.2, 7.5 Hz), 7.60 (d, 1H,
J = 7.2 Hz), 7.44 (dt, 1H, J = 1.2, 7.2 Hz), 7.31 (t, 1H, J =
7.5 Hz), 6.19 (d, 1H, J = 3.6 Hz, H-1), 5.11 (d, 1H, J = 3.6 Hz,
H-2), 3.89 (s, 3H), 3.85 (d, 1H, J = 2.1 Hz, H-4), 3.78 (dd, 1H,
J = 6.0, 10.5 Hz, H-6), 3.69 (dd, 1H, J = 6.3, 10.2 Hz, H-6), 3.59
(dt, 1H, J = 1.8, 6.0 Hz, H-5), 0.94 (s, 9H), 0.91 (s, 9H), 0.84 (s,
9H), 0.19 (s, 3H), 0.18 (s, 3H), 0.14 (s, 3H), 0.12 (s, 3H), 0.010
Compound 3h. Following the general procedure, cross-
coupling afforded 3h (82%) as a colorless oil, Rf = 0.50 (petroleum
ether/ethyl acetate, 24/1). 1H NMR (300 MHz, CDCl3) d 7.45 (d,
2H, J = 8.1 Hz), 7.30 (d, 2H, J = 8.4 Hz), 5.11 (s, 1H, H-1), 4.83
(d, 1H, J = 2.7 Hz, H-2), 4.06 (s, 1H, H-4), 3.83–3.86 (m, 1H, H-5),
3860 | Org. Biomol. Chem., 2009, 7, 3855–3861
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(C24H43O3Si2 ) 435.2745, found 435.2752; (M + Na)+ calcd for
(C24H42O3Si2Na+) 457.2565, found 457.2574.
+
(s, 3H), -0.034 (s, 3H); 13C NMR (75 MHz, CDCl3) d 168.75,
150.55 (C-3), 141.92, 131.12, 130.44, 130.22, 127.45, 127.13, 106.08
(C-2), 75.01 (C-1), 70.30, 67.51, 62.36, 52.15, 26.01, 25.83, 18.48,
18.38, 18.19, -3.91, -4.11, -4.87, -5.40; HRMS (ESI) m/z: (M +
Na)+ calcd for (C32H58O6Si3Na+) 645.3433, found: 645.3407.
Compound 6b. Following the general procedure, cross-
coupling afforded 6b (84%) as a colorless oil, Rf = 0.30 (petroleum
ether/ethyl acetate, 3/1). 1H NMR (300 MHz, CDCl3) d 7.38 (s,
1H), 5.31 (s, 1H, H-1), 4.96 (s, 1H, H-2), 3.98–4.05 (m, 1H, H-5),
3.63 (s, 1H, H-4), 3.38 (s, 3H, N-CH3), 3.36 (s, 3H, N-CH3), 1.26
(d, 3H, J = 6.3 Hz), 0.94 (s, 9H), 0.92 (s, 9H), 0.18 (s, 6H), 0.11
(s, 6H); 13C NMR (75 MHz, CDCl3) d 162.52, 151.61, 148.41 (C-
3), 141.25, 113.74, 105.06 (C-2), 75.06 (C-1), 71.51, 64.38, 37.04,
27.86, 25.85, 18.24, 18.10, 16.19, -4.12, -4.69; HRMS (ESI) m/z:
Compound 5a. Following the general procedure, cross-
coupling afforded 5a (95%) as a colorless oil, Rf = 0.50 (petroleum
1
ether/ethyl acetate, 20/1). H NMR (500 MHz, CDCl3) d 7.35–
7.34 (m, 5H), 5.24 (t, 1H, J = 2.5 Hz, H-1), 5.06 (d, 1H, J = 2.5 Hz,
H-2), 4.19–4.17 (m, 1H, H-4), 3.96 (dd, 1H, J = 5.0, 11.5 Hz, H-
5e), 3.60 (dd, 1H, J = 6.5, 11.5 Hz, H-5a), 0.96 (s, 9H), 0.92 (s,
9H), 0.21 (s, 3H), 0.20 (s, 3H), 0.13 (s, 3H), 0.12 (s, 3H); 13C NMR
(75 MHz, CDCl3) d 150.51 (C-3), 141.20, 128.40, 128.00, 127.68,
106.31 (C-2), 76.10 (C-1), 69.34, 66.23, 25.92, 18.39, 18.23, -4.04,
+
(M + H)+ calcd for (C24H45N2O5Si2 ) 560.3634, found 560.3655.
Acknowledgements
-4.24, -4.64; HRMS (ESI) m/z: (M + H)+ calcd for (C23H41O3Si2 )
+
421.2589, found 421.2605; (M+ Na)+ calcd for (C23H40O3Si2Na+)
443.2408, found 443.2426.
This work was financially supported by the National Natural
Science Foundation of China, and “973” grant from the Ministry
of Science and Technology of China.
Compound 5b. Following the general procedure, cross-
coupling afforded 5b (98%) as a colorless oil, Rf = 0.50 (petroleum
ether/ethyl acetate, 25/1). 1H NMR (300 MHz, CDCl3) d 7.24 (d,
1H, J = 8.1 Hz), 7.15 (d, 1H, J = 7.8 Hz), 5.21 (s, 1H, H-1), 4.99
(d, 1H, J = 2.1 Hz, H-2), 4.17 (t, 1H, J = 6.0 Hz, H-4), 3.95 (dd,
1H, J = 5.1, 11.4 Hz, H-5e), 3.59 (dd, 1H, J = 6.0, 11.4 Hz, H-5a),
2.34 (s, 3H), 0.96 (s, 9H), 0.92 (s, 9H), 0.21 (s, 6H), 0.13 (s, 3H),
0.12 (s, 3H); 13C NMR (75 MHz, CDCl3) d 150.40 (C-3), 138.21,
137.73, 129.06, 127.69, 106.49 (C-2), 75.89 (C-1), 69.23, 66.29,
25.93, 21.15, 18.38, 18.24, -4.00, -4.68; HRMS (ESI) m/z: (M +
Notes and references
1 Nucleoside Antibiotics (Ed.: R. J. Subadolnik), Wiley-Interscience, New
York, 1970.
2 F. Nicotra, Top. Curr. Chem., 1997, 187, 55–83.
3 T. Bililign, B. R. Griffith and J. S. Thorson, Nat. Prod. Rep., 2005, 22,
742–760, and references therein.
4 For reviews on aryl C-glycoside synthesis, see, for example: (a) C.
Jamarillo and S. Knapp, Synthesis, 1994, 1–20; (b) The chemistry of
C-glycosides (Eds.: D. E. Levy, C. Tang), Pergamon Press, Oxford,
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54, 9913–9959; (d) D. Y. W. Lee and M. S. He,, Curr. Top. Med. Chem.,
2005, 5, 1333–1350.
H)+ calcd for (C24H43O3Si2 ) 435.2745, found 435.2747; (M + Na)+
+
calcd for (C24H42O3Si2Na+) 457.2565, found 457.2566.
5 (a) R. F. Heck, J. Am. Chem. Soc., 1968, 90, 5518–5526; (b) Palladium
Reagents in Organic Synthesis (Ed.: R. F. Heck), Academic Press,
London, 1985.
6 (a) I. Arai, R. Hanna and G. D. Daves, Jr., J. Am. Chem. Soc., 1981,
103, 7684–7685; (b) J. C.-Y. Cheng and G. D. Daves, Jr., J. Org. Chem.,
1987, 52, 3083–3090; (c) G. D. Daves, Jr., Acc. Chem. Res., 1990, 23,
201–206.
Compound 5c. Following the general procedure, the reaction
was carried out at 50 ◦C for 36 h, affording 5c (71%) as a colorless
oil, Rf = 0.30 (petroleum ether/ethyl acetate, 24/1). H NMR
1
(500 MHz, CDCl3) d 7.82 (dd, 1H, J = 1.5, 8.0 Hz), 7.58 (d,
1H, J = 7.5 Hz), 7.48 (dt, 1H, J = 1.0, 7.5 Hz), 7.32 (dt, 1H,
J = 1.5, 8.0 Hz), 5.98 (t, 1H, J = 2.0 Hz, H-1), 4.98 (d, 1H,
J = 2.5 Hz, H-2), 4.25–4.28 (m, 1H, H-4), 4.03 (dd, 1H, J = 5.5,
11.5 Hz, H-5e), 3.90 (s, 3H), 3.60 (dd, 1H, J = 7.5, 11.0 Hz, H-
5a), 0.93 (s, 9H), 0.91 (s, 9H), 0.16 (s, 6H), 0.13 (s, 3H), 0.12 (s,
3H); 13C NMR (100 MHz, CDCl3) d 168.04, 150.08 (C-3), 142.57,
131.80, 130.05, 129.23, 127.89, 127.37, 107.47 (C-2), 72.83, 69.93,
65.88, 52.18, 25.99, 25.91, 18.41, 18.22, -4.01, -4.04, -4.25, -4.67;
7 S. Czernecki and V. Dechavanne, Can. J. Chem., 1983, 61, 533–
540.
8 J. Ramnauth, O. Poulin, S. Rakhit and S. P. Maddaford, Org. Lett.,
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9 N. de la Figuera, P. Forns, J.-C. Ferna`ndez, S. Fiol, D. Ferna´ndez-
Forner and F. Albericio, Tetrahedron Lett., 2005, 46, 7271–7274.
10 D.-C. Xiong, L.-H. Zhang and X.-S. Ye, Org. Lett., 2009, 11, 1709–
1712.
11 For leading reviews on the synthesis of aryl C-glycosides via the Heck
reaction, see: (a) K. W. Wellington and S. A. Benner, Nucleosides,
Nucleotides Nucleic Acids, 2006, 25, 1309–1333; (b) R. N. Farr, R. A.
Outten, J. C.-Y. Cheng and G. D. Daves, Jr., Organometallics, 1990, 9,
3151–3156.
+
HRMS (ESI) m/z: (M + H)+ calcd for (C25H43O5Si2 ) 479.2644,
found 479.2644; (M + Na)+ calcd for (C25H42O5Si2Na+) 501.2463,
found 501.2470.
12 (a) T. Jeffery, J. Chem. Soc., Chem. Commun., 1991, 324–325; (b) D. Pan,
A. Chen, Y. Su, W. Zhou, S. Li, W. Jia, J. Xiao, Q. Liu, L. Zhang and
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therein.
13 M. Brakta, R. N. Farr, B. Chaguir, G. Massiot, C. Lavaud, W. R.
Anderson, Jr., D. Sinou and G. D. Daves, Jr., J. Org. Chem., 1993, 58,
2992–2998.
Compound 6a. Following the general procedure, cross-
coupling afforded 6a (88%) as a colorless oil, Rf = 0.50 (petroleum
ether/ethyl acetate, 20/1). 1H NMR (300 MHz, CDCl3) d 7.43 (d,
2H, J = 7.5 Hz), 7.27–7.36 (m, 3H), 5.16 (br.s, 1H, H-1), 4.92
(d, 1H, J = 2.7 Hz, H-2), 3.91–3.97 (m, 1H, H-5), 3.72 (d, 1H,
J = 3.3 Hz, H-4), 1.27 (d, 3H, J = 6.6 Hz), 0.95 (s, 9H), 0.92
(s, 9H), 0.19 (s, 3H), 0.18 (s, 3H), 0.12 (s, 3H), 0.11 (s, 3H); 13C
NMR (75 MHz, CDCl3) d 148.67 (C-3), 141.70, 128.26, 127.84,
127.69, 106.15 (C-2), 74.01 (C-1), 72.29, 71.70, 26.08, 25.91, 18.46,
18.15, 16.85, -3.96, -4.51; HRMS (ESI) m/z: (M + H)+ calcd for
14 B. K. Shull, Z. Wu and M. Koreeda, J. Carbohydr. Chem., 1996, 15,
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15 R. W. Friesen and L. A. Trimble, J. Org. Chem., 1996, 61, 1165–1168.
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17 F. E. McDonald, K. S. Reddy and Y. J. Diaz, J. Am. Chem. Soc., 2000,
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Org. Biomol. Chem., 2009, 7, 3855–3861 | 3861
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