Oligo(phenylene ethynylene) glucosides: Modulation of cellular uptake capacity preserving light on

Article abstract of DOI:10.1021/jo500661u

A new family of oligo(phenylene ethynylene) (OPE) glucosides has been prepared and characterized. Our results demonstrate that fine-tuning of their photophysical properties can be obtained by acting on the electronics of the core and molecular skeleton. M

Full text of DOI:10.1021/jo500661u

Article
pubs.acs.org/joc
Oligo(phenylene ethynylene) Glucosides: Modulation of Cellular
Uptake Capacity Preserving Light ON
Anna Barattucci,*,† Elisa Deni,† Paola Bonaccorsi,† Maria Grazia Ceraolo,‡ Teresa Papalia,§
Antonio Santoro,† Maria Teresa Sciortino,*,‡ and Fausto Puntoriero*,†
†Dipartimento di Scienze Chimiche and SolarChemCentro di Ricerca Interuniversitario per la Conversione Chimica dell’Energia
̀
Solare, Universita di Messina, 98166 Messina, Italia
‡Dipartimento di Scienze Biologiche ed Ambientali, Universita
̀
di Messina, 98166 Messina, Italia
§Dipartimento di Scienze del Farmaco e dei Prodotti per la Salute, Universita
̀
di Messina, 98168 Messina, Italia
S
* Supporting Information
ABSTRACT: A new family of oligo(phenylene ethynylene)
(OPE) glucosides has been prepared and characterized. Our
results demonstrate that fine-tuning of their photophysical
properties can be obtained by acting on the electronics of the
core and molecular skeleton. Modulation of the hydrophobic
chain length and substituents on the central moieties
influences the bioaffinity too. In particular, introducing a
NMe2 group on the aromatic central core affords a highly
efficient biocompatible fluorescent probe that can be taken up in cytoplasmic vesicles of HEp-2 cells (cells from epidermoid
carcinoma larynx tissue). The photophysical behavior, high quantum yield, and stability open the way to the use of the OPE
family as stains for cellular imaging analysis by fluorescence microscopy.
processes at the molecular and cellular levels.9 There are
INTRODUCTION
■
several characteristics that a fluorescent molecule must have to
be used as probe in medical imaging, such as optimal excitation
and emission wavelengths, strong brightness, bio- and photo-
stability, and the capacity of maintaining the pharmacokinetics
without alteration. Usually, when small fluorophores are
conjugated with a sugar or an amino acid, this last characteristic
is satisfied.9b
Herein we describe the synthesis of end-only glucose-
functionalized OPEs where the different substitution of the
central core and the length modulation allow the tuning of their
photophysical properties and the carbohydrate decoration
guarantees their biocompatibility.10 Furthermore, the balanced
contribution of the hydrophilic (sugar) and hydrophobic (aryl-
conjugated system) moieties gives rise to the permeation of
some of these OPEs to the cellular membrane, as shown by
preliminary biological experiments, disclosing their potential
use as dyes in fluorescent-imaging microscopy.
Oligo- and poly(phenylene ethynylene)s (OPEs and PPEs,
respectively) represent peculiar classes of luminescent dyes with
stable, π-conjugated, rigid rodlike skeletons.1 Their photo-
physical properties are directly connected to their extensive
conjugation. In particular, Yamaguchi and Che2 reported
modulation of the photophysical properties of OPEs in
dependence on the structure and substitution of the aromatic
conjugated system. In the last decades, thanks to their tunable
functional properties, OPEs and PPEs have found a great
variety of applications, ranging from sensing3 and electronics4
to the biological field.5 OPE-type molecular rods attached to
gold electrodes have been created for the development of
nanoscale-based molecular circuits with the finding of a direct
correlation between molecular structural features and con-
ductance.4a Coordination of cationic systems to some PPE
polyethers caused their self-aggregation, with a resulting
variation or quenching of their optical response.3b As a result
of the production of singlet O2 upon irradiation with light,
some kinds of end-only cationic OPEs5a,b were shown to kill
specific kinds of bacteria. Moreover, sugar-functionalized
oligomers act as inhibitors of Pseudomonas aeruginosa lectin
LecA6 and are used as luminescent labeling probes for
proteins.2b Finally, PPEs can specifically bind and consequently
detect Escherichia coli7 and represent efficient probes for lectin
concanavaline A.8
RESULTS AND DISCUSSION
■
Synthesis. A Pd(0)-mediated coupling was chosen as the
key step in the syntheses of all the new OPE glucosides
described in this work. In particular, the copper-free
Sonogashira reaction of 1 and 211 in a suitable molecular
ratio under optimized reaction conditions led to compound 3,
which was ready for another derivatization on the residual
Imaging represents one of the most efficient techniques for
medical diagnosis and therapy. Imaging based on the use of
fluorescent probes allows the interpretation of biological
Received: March 21, 2014
Published: May 9, 2014
© 2014 American Chemical Society
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a
Scheme 1. Synthetic Route to General Precursors 3 and 4
a
Reagents and conditions: (i) [Pd(PPh3)4], NEt3, DMF, 60 °C.
a
Scheme 2. Synthetic Route to Differently Elongated Oligomers 5−11
a
Reagents and conditions: (i) [Pd(PPh3)4], NEt3, DMF, 60 °C; (ii) NH4OH, MeOH/THF, rt; (iii) [Pd(PPh3)4], Ag2O, DMF/THF, 60 °C.
unreacted arm (Scheme 1). An additional coupling of 3 with an
excess of trimethylsilylacetylene quantitatively furnished
compound 4. Compounds 3 and 4 were used as building
blocks for subsequent synthetic developments.
every case, compounds 5, 7, and 10 were the major reaction
products. In the coupling of 3 with 4, a small amount of
compound 8 was obtained too. Even though 8 can be
considered as a side product of the coupling, it was easily
separated from 7 and isolated, and its photophysical properties
were determined (see the Supporting Information).
Compounds 18, 19, and 21, analogues of 10, were
synthesized following similar strategies (Scheme 3), with the
aim of inserting new functions on the aromatic core that could
increase the biocompatibility of our OPEs. The central aromatic
“bricks” 16, bearing an electron-donating NMe2 group, and 17,
with both NMe2 and electron-withdrawing NO2 groups, were
efficiently prepared starting from commercially available 2,4-
dibromoaniline (12) and its p-nitro derivative (13).13a
Coupling of compounds 1 and 2 with an inverted molecular
ratio with respect to the one used for the synthesis of 3
provided a high yield of the shortest phenylene ethynylene D-
glucopyranoside, 5 (Scheme 2), together with a small amount
of 3, which was easily separable by column chromatography. A
modified cross-coupling reaction, adopting Ag2O to generate in
situ an ethynyl reactive arm,12 was employed to extend the
conjugated chain. Reactions of 4 with 3 and 2 led to the
differently elongated oligomers 7 and 10 with two and three
conjugated ethynylarene systems, respectively (Scheme 2). In
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a
Scheme 3. Synthetic Route to Differently Substituted Central Cores 16 and 17 and Oligomers 18−23
a
Reagents and conditions: (i) MeI, K2CO3, DMF, 100°C; (ii) [Pd(PPh3)4], NEt3, DMF, 60°C; (iii) [Pd(PPh3)4], Ag2O, DMF/THF, 60°C; (iv)
NH4OH, MeOH/THF, rt.
Methylation of the aromatic nitrogens of 12 and 13 with MeI in
the presence of K2CO3 gave 1413b and 15, respectively, whose
copper-free Sonogashira coupling with an excess of ethynyl-
trimethylsilane furnished 16 and 17, respectively, in excellent
quantities. The syntheses of compound 18 and 19 were finally
reached by the use of the above cited Ag2O-modified Pd(0)-
mediated reaction. The cross-coupling of 4 with 14 or 15 was
also attempted as an alternative synthetic pathway to 18 or 19,
but poor yields of the target compounds (<20%) confirmed the
low reactivity of the dibromoaromatic system involved in cross-
coupling reactions.
Glucoside 21 with an unsubstituted aromatic core was
prepared in good yield (50%) by the reaction of 3 with
commercially available 1,4-diethynylbenzene in a copper-free
Sonogashira fashion. In this last reaction, coupling of 3 with
two queued central 1,4-diethynylbenzene moieties furnished 22
as minor product (21/22 = 4:1) that was easily separated for
photophysical studies (see the Supporting Information).
The protected glucosides were then subjected to deacetyla-
tion. Deprotection of compounds 5, 7, 10, 18, and 21 easily
happened in the presence of aqueous ammonia, after one night
of stirring in THF/MeOH at rt, giving quantitatively 6, 9, 11,
20, and 23, respectively. The same reaction was not attempted
on 19 because of its easy decomposition even under
refrigerated and degassed conditions. Compounds 18 and 20
bearing an NMe2 substituent are very stable and easy to handle,
in spite of what has been reported elsewhere.2c
concentration used was low enough to avoid these features:
concentration dependence was observed only when the
concentration was higher than 10−4 M and in mixed solvents.15
The absorption spectra of all the investigated species in
DCM solution (for the protected compounds 5, 7, 8, 10, 18,
19, 21, and 22) as well as in aqueous solution (buffer
phosphate for the deprotected compounds 6, 9, 11, 20, and
23), are characterized by intense absorption in the UV region
(ε in the 104−105 M−1 cm−1 range) due to spin-allowed π−π*
transitions. Increasing the chain length registered a red shift of
the absorption maxima (see Table 1, Figure 1, and the
Supporting Information); this behavior is consistent with
greater π conjugation in passing from 5 to 10. The molar
extinction coefficient (ε) of the lowest-energy transition also
increases with the same trend. In the absorption spectrum of 5
a
Table 1. Spectroscopic and Photophysical Data
b
c
absorption
luminescence
compd
λmax/nm (ε/M−1 cm−1
)
λmax/nm
Φ
τ/ns
5/6
344 (11000)
378 (35000)
390 (49500)
388 (38900)
381 (38000)
377 (39500)
383
404
433
472
−
0.45
0.87
0.85
0.57
−
0.72
1.54
0.98
2.47
−
7/9
10/11
18/20
19
21/23
437
0.82
0.76
a
Photophysical Properties. When dissolved in solvent/
nonsolvent mixtures,14 most OPEs form aggregates and
excimers, which are usually detected by absorption and
fluorescence spectroscopies. In our case, however, the
The absorption and the room-temperature emission data were
obtained in DCM; no significant changes were observed in the
b
DMSO/water mixture. Maxima (or shoulders) of the lower-energy
c
bands are given. At 298 K.
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Figure 2. Fluorescence microscopy images of Hep-2 cells incubated
with 20 (100 μM) and analyzed using a FITC (green emission) or
DAPI (blue emission) filter.
The great luminescence quantum yield and the high degree
of endocytosis of 20 permit the detection of fluorescence
emission even when cells are incubated at low concentrations of
up to 1 μM (Figure 3). The more lipophilic OPE glucoside 18,
the acetylated analogue of 20, is slightly internalized by Hep-2
cells (see the Supporting Information).
Finally, the analysis of cell viability, evaluated using the
trypan blue assay, showed that these compounds are
biocompatible since they had no toxic effects for HEp-2 cells
at all concentrations tested for the time of exposure used (48
h).
Figure 1. (top) Absorption and (bottom) emission spectra of
representative species in DCM at rt.
in DCM, additional vibronically resolved absorption bands at
λmax = 275 and 290 nm are observed. These high-energy
absorption features become broad and less resolved as the
conjugation increases.
Excitation of compounds 5−11, 18, and 20−23 in the range
280−420 nm at room temperature produces a blue or blue-
green emission. The excited-state lifetimes (τ) for all of the
investigated species are on the nanosecond time scale. Relevant
data are collected in Table 1, whereas representative emission
spectra are shown in Figure 1.
As the chain length is increased in moving from 5 to 7, the
emission energy decreases, whereas the emission quantum yield
(Φ) doubles (see Figure 1 and Table 1). This is reminiscent of
the bathochromic shift in the corresponding absorption spectra.
The augmented π conjugation between the peripheral subunits
in 10 and 21 causes a further decrease in both the luminescence
excited-state energy and the quantum yield.
The insertion of one electron-donating NMe2 group on the
central subunit of the oligomer 18 shifts the luminescence to
the red, while the quantum yield decreases but still remains at
the high value of 0.57. The unstructured large emission profile
suggests that in this case the excited state has a partial charge
transfer character that could be tentatively attributed to n → π*
transitions. The absence of luminescence in 19 can be ascribed
to the presence of the electron-withdrawing NO2 group, which
acts as a quencher for these systems.2c It is important to stress
that no changes in the photophysical properties were observed
in going from DCM to aqueous solution.
Biological Data. To investigate the ability of these new
dyes to achieve cell internalization, we performed uptake
experiments for 6, 9, 11, 18, 20, and 23 on HEp-2 cells (cells
from epidermoid carcinoma larynx tissue). The shortest
glucoside, 6, is slightly internalized in HEp-2 cells (see the
Supporting Information), while OPE glucosides 9, 11, and 23
were not taken up (data not shown). Figure 2 displays the
massive cell internalization and efficient enlightening of
glucoside 20, showing the main localization in vesicles within
the cytoplasmic compartment.
Figure 3. Fluorescence microscopy images (DAPI filter) of Hep-2
cells incubated for 24 h with solutions of 20 with final concentrations
of 1, 10, and 100 μM. The image labeled CTR shows the untreated
cells.
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mixture was heated at 60 °C and maintained under an Ar atmosphere
with continuous stirring until the disappearance of the limiting reagent
as determined by TLC. After filtration over Celite, the solvents were
removed under reduced pressure, and the obtained reaction crude was
subjected to silica gel column chromatography.
CONCLUSIONS
■
We have efficiently synthesized a series of new OPE glucosides
by exploiting simple synthetic routes involving a Pd(0)-
catalyzed cross-coupling as a key step. The biological behavior
of such an OPE family is directly related to their structural
features, which on the other hand guarantee the observed
photophysical properties. The synergic effect of (i) elongation
of the hydrophobic chain in going from glucoside 6 to 20, (ii)
substitution of the aromatic central core with a dimethylamino
group in 20 instead of the bis(methoxy) moiety present in
glucoside 11, and (iii) deacetylation of the sugar moieties to
improve the hydrophilicity of 20 with respect to glucoside 18
creates the right combination for 20 to serve as a highly
efficient biocompatible fluorescent cell probe. The broad
emission, biocompatibility, high quantum yield, and stability
open the way to the application of OPE glucosides as dyes in
fluorescence microscopy. Further studies to assess the
applicability of OPEs in imaging techniques for sensitive cancer
detection are in progress.
Compound 3. This compound was obtained in 2 h following
general procedure A starting from prop-2-yn-1-yl β-D-glucopyranoside-
2,3,4,6-tetraacetate (1) (1.42 g, 3.67 mmol, 1 equiv), 1,4-diiodo-2,5-
dimethoxybenzene (2) (3.00 g, 7.69 mmol, 2.1 equiv), and Pd(PPh3)4
(0.50 g, 0.43 mmol, 0.12 equiv) in dry DMF (30 mL) and Et3N (30
mL). Column chromatography was performed with 70:30 hexane/
EtOAc as the eluent, and compound 3 was obtained as a white solid
(1.90 g, 2.93 mmol, 80%). TLC: Rf 0.64 (40:60 hexane/EtOAc). Mp:
1
65−67 °C. H NMR: δ 7.29 (s, 1H, H-3), 6.84 (s, 1H, H-6), 5.25 (t,
J
2′,3′ = J3′,4′ = 9.3, 1H, H-3′), 5.11 (t, J3′,4′ = J4′,5′ = 9.3, 1H, H-4′), 5.03
(dd, J1′,2′ = 7.7, J2′,3′ = 9.3, 1H, H-2′), 4.88 (d, J1′,2′ = 7.7, 1H, H-1′),
4.61 (s, 2H, CH2C), 4.27 and 4.15 (split AB system, J5′,6′A = 4.4,
J5′,6′B = 2.5, J6′A,6′B = 12.2, 2H, H2-6′), 3.84 and 3.83 (two s, 6H, 2 ×
OCH3), 3.75 (ddd, J4′,5′ = 9.3, J5′,6′A = 4.4, J5′,6′B = 2.5, 1H, H-5′), 2.07,
2.03, 2.02, and 2.00 (four s, 12H, 4 × CH3CO). 13C NMR: δ 170.7,
170.3, and 169.4 (4 × CO), 154.8 (C-2), 152.3 (C-5), 122.3 (C-3),
115.1 (C-6), 111.9 (C-1), 98.3 (C-1′), 88.4 (C-4), 87.3 and 85.4 (C
C), 72.8 (C-3′), 71.9 (C-5′), 71.1 (C-2′), 68.4 (C-4′), 61.8 (C-6′),
57.2, 57.0, and 56.5 (2 × OCH3 and CH2C), 20.7 and 20.6 (4 ×
CH3CO). Anal. Calcd for C25H29IO12 (648.40): C, 46.31; H, 4.51.
Found: C, 46.44; H, 4.50.
EXPERIMENTAL SECTION
■
General Experimental Methods. Solvents were purified
according to standard procedures. All of the reactions were monitored
by TLC on commercially available precoated plates (silica gel 60
F254), and the products were visualized with vanillin [1 g dissolved in
MeOH (60 mL) and conc. H2SO4 (0.6 mL)]. Silica gel 60 was used
Compound 4. This compound was obtained in 2 h following
general procedure A starting from 3 (1.00 g, 1.54 mmol, 1 equiv),
commercial ethynyltrimethylsilane (0.65 mL, 4.62 mmol, 3 equiv), and
Pd(PPh3)4 (0.18 g, 0.16 mmol, 0.1 equiv) in dry DMF (7 mL) and
Et3N (7 mL). Column chromatography was performed with 80:20
hexane/EtOAc as the eluent, and compound 4 was obtained as a white
solid (0.81 g, 1.31 mmol, 85%). TLC: Rf 0.78 (40:60 hexane/EtOAc).
Mp: 59−61 °C. 1H NMR: δ 6.95 and 6.89 (two s, 2H, H-3,6), 5.25 (t,
for column chromatography. H and 13C NMR spectra were recorded
1
in CDCl3 solutions, unless differently stated, at 500 and 125 MHz,
respectively; coupling constants (J) are given in hertz, and the
attributions are supported by heteronuclear single-quantum coherence
(HSQC) and correlation spectroscopy (COSY) experiments.
Equipment and Methods for the Absorption Spectroscopy
and Photophysical Experiments. The absorption spectra were
recorded in ultrapure spectroscopic solvents. All of the emission
spectra were corrected for the photomultiplier response using software
purchased with the fluorimeter. For the luminescence lifetimes, a time-
correlated single-photon-counting spectrometer was used. As the
excitation source, a laser diode (59 ps pulse width at 408 nm) or a
nitrogen discharge lamp (2 ns pulse width at 337 nm) was employed.
Emission quantum yields for deaerated acetonitrile solutions were
determined using the optical dilution method.16a As a luminescence
quantum yield standard we used an air-equilibrated ethanol solution of
anthracene (Φ = 0.2).16b
Experimental uncertainties in the absorption and photophysical data
are as follows: absorption maxima, 2 nm; molar absorption, 15%;
luminescence maxima, 4 nm; luminescence lifetimes, 10%; lumines-
cence quantum yields, 20%.
General Procedure A for the Preparation of Compounds 3−
5, 16, 17, 21, and 22 by a Coupling Reaction in the Presence of
Pd(PPh3)4 and Et3N. Pd(PPh3)4, the halogenoarene, and the alkyne
were dissolved in dry DMF. To this mixture was added Et3N under an
Ar atmosphere with stirring. The mixture was heated at 60 °C and
maintained under continuous stirring until the disappearance of the
limiting reagent as determined by TLC. Solvents were removed under
reduced pressure. The reaction crude was subjected to silica gel
column chromatography.
J
2′,3′ = J3′,4′ = 9.4, 1H, H-3′), 5.10 (t, J3′,4′ = J4′,5′ = 9.4, 1H, H-4′), 5.03
(dd, J1′,2′ = 7.7, J2′,3′ = 9.4, 1H, H-2′), 4.88 (d, J1′,2′ = 7.7, 1H, H-1′),
4.62 (s, 2H, CH2C), 4.28 and 4.15 (split AB system, J5′,6′A = 4.7,
J5′,6′B = 2.4, J6′A,6′B = 12.2, 2H, H2-6′), 3.85 and 3.84 (two s, 6H, 2 ×
OCH3), 3.74 (ddd, J4′,5′ = 10.0, J5′,6′A = 4.7, J5′,6′B = 2.5, 1H, H-5′),
2.07, 2.04, 2.03, and 2.01 (four s, 12H, 4 × CH3CO), 0.27 [s, 9H,
Si(CH3)3]. 13C NMR: δ 170.7, 170.3, 169.4, and 169.3 (4 × CO),
154.2 and 153.9 (C-2,5), 116.1 and 115.8 (C-3,6), 113.7 and 112.4 (C-
1,4), 100.7 and 100.6 (CCSi), 98.2 (C-1′), 89.0 and 83.4 (CH2C
C), 72.8 (C-3′), 71.9 (C-5′), 71.1 (C-2′), 68.3 (C-4′), 61.8 (C-6′),
57.0 (CH2C), 56.5 and 56.3 (2 × OCH3), 20.7, 20.6, and 20.5 (4 ×
CH3CO), −0.05 [Si(CH3)3]. Anal. Calcd for C30H38O12Si (618.70):
C, 58.24; H, 6.19. Found: C, 58.30; H, 6.20.
Compound 5. This compound was obtained in 3 h following
general procedure A starting from prop-2-yn-1-yl β-D-glucopyranoside-
2,3,4,6-tetraacetate (1) (1.00 g, 2.59 mmol, 2.1 equiv), 1,4-diiodo-2,5-
dimethoxybenzene (2) (0.48 g, 1.23 mmol, 1 equiv), and Pd(PPh3)4
(0.17 g, 0.15 mmol, 0.12 equiv) in dry DMF (10 mL) and Et3N (10
mL). Column chromatography was performed with 65:35 hexane/
EtOAc as the eluent, and compound 5 was obtained as a white solid
(0.80 g, 0.88 mmol, 72%). TLC: Rf 0.55 (40:60 hexane/EtOAc). Mp:
1
178−180 °C. H NMR: δ 6.92 (s, 2H, H-3,6), 5.27 (t, J2′,3′ = J3′,4′
=
9.3, 2H, 2 × H-3′), 5.12 (t, J3′,4′ = J4′,5′ = 9.3, 2H, 2 × H-4′), 5.05 (dd,
J
1′,2′ = 8.3, J2′,3′ = 9.3, 2H, 2 × H-2′), 4.90 (d, J1′,2′ = 8.3, 2H, 2 × H-1′),
4.64 (s, 4H, 2 × CH2C), 4.28 and 4.17 (split AB system, J5′,6′A = 5.6,
J5′,6′B = 2.4, J6′A,6′B = 12.2, 4H, 2 × H2-6′), 3.85 (s, 6H, 2 × OCH3),
3.76 (ddd, J4′,5′ = 9.3, J5′,6′A = 5.6, J5′,6′B = 2.4, 2H, 2 × H-5′), 2.07, 2.04,
2.02, and 2.00 (four s, 24H, 8 × CH3CO). 13C NMR: δ 170.7, 170.3,
169.5, and 169.4 (8 × CO), 154.0 (C-2,5), 115.7 (C-3,6), 112.8 (C-
1,4), 98.3 (2 × C-1′), 89.2 and 83.2 (2 × CC), 72.8 (2 × C-3′), 71.9
(2 × C-5′), 711 (2 × C-2′), 68.3 (2 × C-4′), 61.8 (2 × C-6′), 57.0 (2
× CH2C), 56.4 (2 × OCH3), 20.7 and 20.6 (8 × CH3CO). Anal.
Calcd for C42H50O22 (906.83): C, 55.63; H, 5.56. Found: C, 55.49; H,
5.58.
General Procedure B for the Preparation of Compounds 6,
9, 11, 20, and 23. The starting material (0.2 mmol) was dissolved in
1:1 THF/MeOH (40 mL). To this mixture was added a large excess of
aqueous ammonia (12 mL), and the reaction mixture was then
maintained under continuous stirring at rt overnight until the
disappearance of the starting material as determined by TLC. Solvents
were removed under reduced pressure, and the undesired acetamide
was eliminated by a series of MeOH washings of the obtained solid.
General Procedure C for the Preparation of Compounds 7,
8, 10, 18, and 19 by a Coupling Reaction in the Presence of
Pd(PPh3)4 and Ag2O. Pd(PPh3)4, Ag2O, the halogenoarene, and the
trimethylsilylethynylarene were dissolved in dry DMF and THF. The
Compound 6. This compound was obtained as a white solid (0.13
g, 0.19 mmol, 96%) following general procedure B starting from 5
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(0.18 g). TLC: Rf 0.15 (80:20 CHCl3/MeOH). Mp: 230−233 °C. 1H
NMR (DMSO-d6): δ 7.04 (s, 2H, H-3,6), 5.12 (d, Jvic = 4.9, 2H, 2 ×
OH), 4.96 (d, Jvic = 4.9, 2H, 2 × OH), 4.91 (d, Jvic = 5.4, 2H, 2 × OH),
4.65 and 4.52 (AB system, Jgem = 15.7, 4H, 2 × CH2C), 4.53 (t, JOH,6
= 4.9, 2H, 2 × 6′-OH), 4.32 (d, J1′,2′ = 7.9, 2H, 2 × H-1′), 3.77 (s, 6H,
2 × OCH3), 3.65 and 3.43 (split AB m, 4H, 2 × H2-6′), 3.16−2.93 (m,
8H, 2 × H-2′−5′). 13C NMR (DMSO-d6): δ 153.6 (C-2,5), 115.8 (C-
3,6), 112.2 (C-1,4), 101.1 (2 × C-1′), 91.1 and 81.9 (2 × CC), 77.0
and 76.7 (2 × C-3′,5′), 73.3 (2 × C-2′), 70.0 (2 × C-4′), 61.2 (2 × C-
6′), 56.1 (2 × OCH3), 55.8 (2 × CH2C). Anal. Calcd for C26H34O14
(570.54): C, 54.73; H, 6.01. Found: C, 54.79; H, 6.00.
Compounds 7 and 8. These compounds were obtained in 5 h
following general procedure C starting from 3 (0.50 g, 0.77 mmol, 1
equiv), 4 (0.48 g, 0.78 mmol, 1 equiv), Pd(PPh3)4 (0.13 g, 0.11 mmol,
0.14 equiv), and Ag2O (0.18 g, 0.78 mmol, 1 equiv) in dry DMF (10
mL) and THF (5 mL). Column chromatography was performed with
50:50 hexane/EtOAc as the eluent, giving first compound 8 as a yellow
low-melting solid (42 mg, 0.04 mmol, 5%) and then compound 7 as a
yellow solid (0.44 g, 0.41 mmol, 53%).
eluent, and compound 10 was obtained as a yellow solid (1.04 g, 0.85
mmol, 66%). TLC: Rf 0.47 (40:60 hexane/EtOAc). Mp: 169−171 °C.
1H NMR: δ 7.06, 7.05, and 6.94 (three s, 6H, 3 × H-3,6), 5.27 (t, J2′,3′
= J3′,4′ = 9.3, 2H, 2 × H-3′), 5.12 (t, J3′,4′ = J4′,5′ = 9.3, 2H, 2 × H-4′),
5.05 (dd, J1′,2′ = 7.8, J2′,3′ = 9.3, 2H, 2 × H-2′), 4.91 (d, J1′,2′ = 7.8, 2H,
2 × H-1′), 4.65 (s, 4H, 2 × CH2C), 4.28 and 4.17 (split AB system,
J5′,6′A = 4.9, J5′,6′B = 2.4, J6′A,6′B = 12.3, 4H, 2 × H2-6′), 3.92, 3.90, and
3.88 (three s, 18H, 6 × OCH3), 3.77 (ddd, J4′,5′ = 9.3, J5′,6′A = 4.9, J5′,6′B
= 2.4, 2H, 2 × H-5′), 2.08, 2.05, 2.03, and 2.01 (four s, 24H, 8 ×
CH3CO). 13C NMR: δ 170.7, 170.3, 169.5, and 169.4 (8 × CO),
154.1, 153.9, and 153.8 (3 × C-2,5), 115.7 and 115.5 (3 × C-3,6),
113.8, 113.4, and 112.3 (3 × C-1,4), 98.3 (2 × C-1′), 91.5, 91.2, 89.1,
and 83.5 (4 × CC), 72.8 (2 × C-3′), 71.9 (2 × C-5′), 71.1 (2 × C-
2′), 68.3 (2 × C-4′), 61.8 (2 × C-6′), 57.1 (2 × CH2C), 56.6, 56.5
and 56.3 (6 × OCH3), 20.7 and 20.6 (8 × CH3CO). Anal. Calcd for
C62H66O26 (1227.17): C, 60.68; H, 5.42. Found: C, 60.80; H, 5.43.
Compound 11. This compound was obtained as a yellow solid
(0.17 g, 0.19 mmol, 96%) following general procedure B starting from
10 (0.25 g). TLC: Rf 0.05 (80:20 CHCl3/MeOH). Mp: 248−250 °C.
1H NMR (DMSO-d6): δ 7.13, 7.12, and 7.09 (three s, 6H, 3 × H-3,6),
5.15 (d, Jvic = 5.4, 2H, 2 × OH), 4.98 (d, Jvic = 4.9, 2H, 2 × OH), 4.93
(d, Jvic = 5.4, 2H, 2 × OH), 4.68 and 4.55 (AB system, Jgem = 15.6, 4H,
2 × CH2C), 4.55 (t, JOH,6 = 5.5, 2H, 2 × 6′-OH), 4.34 (d, J1′,2′ = 7.9,
2H, 2 × H-1′), 3.84, 3.82, and 3.80 (three s, 18H, 6 × OCH3), 3.69
and 3.45 (split AB m, 4H, 2 × H2-6′), 3.19−2.98 (m, 8H, 2 × H-2′−
5′). 13C NMR (DMSO-d6): δ 153.7, 152.4, and 153.3 (3 × C-2,5),
115.9, 115.5, and 115.4 (3 × C-3,6), 112.8, 112.7, and 112.3 (3 × C-
1,4), 101.1 (2 × C-1′), 91.3, 91.2, and 82.0 (4 × CC), 77.0 and 76.7
(2 × C-3′,5′), 73.3 (2 × C-2′), 70.0 (2 × C-4′), 61.2 (2 × C-6′), 56.3,
56.2, and 56.1 (6 × OCH3), 55.8 (2 × CH2C). Anal. Calcd for
C46H50O18 (890.88): C, 62.02; H, 5.66. Found: C, 62.05; H, 5.67.
Compound 14. A DMF solution (12 mL) of 2,5-dibromoaniline
(12) (1.00 g, 3.98 mmol, 1 equiv) was added to anhydrous K2CO3
(5.00 g, 36.18 mmol) at rt under an Ar atmosphere. To the obtained
suspension was added 1.2 mL of iodomethane (20 mmol, 5 equiv),
and the mixture was heated to 100 °C and maintained under these
conditions with continuous stirring until completion of the reaction as
determined by TLC. After 48 h, the reaction was quenched by the
addition of water (7 mL), and the resulting mixture was extracted with
dichloromethane (3 × 10 mL). The organic phases were dried over
anhydrous Na2SO4, and the solvent was evaporated under reduced
pressure to give pure 2,5-dibromo-N,N-dimethylaniline13b (14) as a
Data for 7. TLC: Rf 0.35 (30:70 hexane/EtOAc). Mp: 80−81 °C.
1H NMR: δ 7.04 and 6.94 (two s, 4H, 2 × H-3,6), 5.27 (t, J2′,3′ = J3′,4′
=
9.3, 2H, 2 × H-3′), 5.12 (t, J3′,4′ = J4′,5′ = 9.3, 2H, 2 × H-4′), 5.05 (dd,
J
1′,2′ = 8.3, J2′,3′ = 9.3, 2H, 2 × H-2′), 4.92 (d, J1′,2′ = 8.3, 2H, 2 × H-1′),
4.65 (s, 4H, 2 × CH2C), 4.28 and 4.17 (split AB system, J5′,6′A = 4.4,
J5′,6′B = 2.4, J6′A,6′B = 12.3, 4H, 2 × H2-6′), 3.90 and 3.88 (two s, 12H, 4
× OCH3), 3.77 (ddd, J4′,5′ = 9.3, J5′,6′A = 4.4, J5′,6′B = 2.4, 2H, 2 × H-
5′), 2.08, 2.05, 2.03, and 2.01 (four s, 24H, 8 × CH3CO). 13C NMR: δ
170.7, 170.3, 169.4, and 169.3 (8 × CO), 154.1 and 153.9 (2 × C-2,5),
115.7 and 115.5 (2 × C-3,6), 113.8 and 112.4 (2 × C-1,4), 98.3 (2 ×
C-1′), 91.2, 89.1, and 83.4 (3 × CC), 72.8 (2 × C-3′), 71.9 (2 × C-
5′), 71.1 (2 × C-2′), 68.4 (2 × C-4′), 61.8 (2 × C-6′), 57.0 (2 ×
CH2C), 56.5 and 56.3 (4 × OCH3), 20.7 and 20.6 (8 × CH3CO).
Anal. Calcd for C52H58O24 (1067.00): C, 58.53; H, 5.48. Found: C,
58.65; H, 5.47.
1
Data for 8. TLC: Rf 0.40 (30:70 hexane/EtOAc). H NMR: δ 6.98
and 6.92 (two s, 4H, 2 × H-3,6), 5.26 (t, J2′,3′ = J3′,4′ = 9.3, 2H, 2 × H-
3′), 5.12 (t, J3′,4′ = J4′,5′ = 9.3, 2H, 2 × H-4′), 5.04 (t, J1′,2′ = J2′,3′ = 9.3,
2H, 2 × H-2′), 4.90 (d, J1′,2′ = 9.3, 2H, 2 × H-1′), 4.64 (s, 4H, 2 ×
CH2C), 4.28 and 4.17 (split AB system, J5′,6′A = 4.4, J5′,6′B = 1.9,
J6′A,6′B = 12.2, 4H, 2 × H2-6′), 3.86 and 3.84 (two s, 12H, 4 × OCH3),
3.76 (ddd, J4′,5′ = 9.3, J5′,6′A = 4.4, J5′,6′B = 1.9, 2H, 2 × H-5′), 2.08, 2.04,
2.03, and 2.01 (four s, 24H, 8 × CH3CO). 13C NMR: δ 170.9, 170.6,
169.7, and 169.6 (8 × CO), 155.6 and 154.2 (2 × C-2,5), 116.3 and
115.9 (2 × C-3,6), 113.6 and 112.6 (2 × C-1,4), 98.5 (2 × C-1′), 90.0,
83.5, 79.7, and 79.6 (4 × CC), 73.1 (2 × C-3′), 72.2 (2 × C-5′),
71.4 (2 × C-2′), 68.6 (2 × C-4′), 62.1 (2 × C-6′), 57.3 (2 ×
CH2C), 56.7 and 56.6 (4 × OCH3), 20.9 and 20.8 (8 × CH3CO).
Anal. Calcd for C54H58O24 (1091.02): C, 59.45; H, 5.36. Found: C,
59.38; H, 5.34.
transparent oil (1.08 g, 3.87 mmol, 97%). TLC: Rf 0.85 (95:5 hexane/
1
EtOAc). H NMR: δ 7.35 (d, 1H, J3,4 = 8.8, H-3), 7.14 (d, 1H, J4,6
=
2.4, H-6), 6.96 (dd, 1H, J3,4 = 8.8, J4,6 = 2.4, H-4), 2.76 [s, 6H,
N(CH3)2]. 13C NMR: δ 152.8 (C-1), 134.7 (C-3), 126.2 (C-4), 123.5
(C-6), 119.9 and 117.2 (C-4,5), 43.7 [N(CH3)2]. Anal. Calcd for
C8H9Br2N (278.97): C, 34.44; H, 3.25; N, 5.02. Found: C, 34.50; H,
3.26; N, 5.03.
Compound 9. This compound was obtained as a white solid (0.14
g, 0.19 mmol, 96%) following general procedure B starting from 7
(0.23 g). TLC: Rf 0.10 (80:20 CHCl3/MeOH). Mp: 206−207 °C. 1H
NMR (DMSO-d6): δ 7.10 and 7.08 (two s, 4H, 2 × H-3,6), 5.14 (d,
Compound 15. A DMF solution (5 mL) of 2,5-dibromo-4-
nitroaniline (13)13a (0.40 g, 1.35 mmol, 1 equiv) was added to
anhydrous K2CO3 (2.38 g, 17.22 mmol) at rt under an Ar atmosphere.
To the obtained suspension was added 0.41 mL of iodomethane (6.75
mmol, 5 equiv), and the mixture was heated to 100 °C and maintained
under these conditions with continuous stirring until completion of
the reaction as determined by TLC. After 70 h, the reaction was
quenched by the addition of water (5 mL), and the resulting mixture
was extracted with dichloromethane (3 × 10 mL). The organic phases
were dried over anhydrous Na2SO4, and the solvent was evaporated
under reduced pressure. The reaction crude was subjected to silica gel
column chromatography (90:10 hexane/EtOAc as the eluent), and 15
was isolated as a yellow solid (0.26 g, 0.80 mmol, 59%). TLC: Rf 0.80
Jvic = 4.9, 2H, 2 × OH), 4.97 (d, Jvic = 4.9, 2H, 2 × OH), 4.91 (d, Jvic
=
5.4, 2H, 2 × OH), 4.67 and 4.55 (AB system, Jgem = 15.6, 4H, 2 ×
CH2C), 4.54 (t, JOH,6 = 4.9, 2H, 2 × 6′-OH), 4.34 (d, J1′,2′ = 7.8, 2H,
2 × H-1′), 3.81 and 3.80 (two s, 12H, 4 × OCH3), 3.67 and 3.46 (split
AB m, 4H, 2 × H2-6′), 3.19−2.98 (m, 8H, 2 × H-2′−5′). 13C NMR
(DMSO-d6): δ 153.7 and 153.2 (2 × C-2,5), 115.9 and 115.3 (2 × C-
3,6), 112.8 and 112.2 (2 × C-1,4), 101.0 (2 × C-1′), 91.3, 91.1, and
81.9 (3 × CC), 77.0 and 76.7 (2 × C-3′,5′), 73.3 (2 × C-2′), 70.1
(2 × C-4′), 61.2 (2 × C-6′), 56.3 and 56.1 (4 × OCH3), 55.8 (2 ×
CH2C). Anal. Calcd for C36H42O16 (730.71): C, 59.17; H, 5.79.
Found: C, 59.14; H, 5.80.
Compound 10. This compound was obtained in 6 h following
general procedure C starting from 1,4-diiodo-2,5-dimethoxybenzene 2
(0.50 g, 1.28 mmol, 1 equiv), 4 (1.58 g, 2.55 mmol, 2 equiv),
Pd(PPh3)4 (0.22 g, 0.19 mmol, 0.15 equiv), and Ag2O (0.59 g, 2.55
mmol, 2 equiv) in dry DMF (10 mL) and THF (5 mL). Column
chromatography was performed with 50:50 hexane/EtOAc as the
1
(80:20 hexane/EtOAc). Mp: 81−83 °C. H NMR: δ 8.23 (s, 1H, H-
3), 7.18 (s, 1H, H-6), 2.97 [s, 6H, N(CH3)2]. 13C NMR: δ 155.7 (C-
1), 141.8 (C-4), 132.3 (C-3), 124.6 (C-6), 115.3 (C-5), 113.4 (C-2),
43.3 [N(CH3)2]. Anal. Calcd for C8H8Br2N2O2 (323.97): C, 29.66; H,
2.49; N, 8.65. Found: C, 29.71; H, 2.50; N, 8.68.
Compound 16. This compound was prepared in 2 h following
general procedure A starting from 14 (1.00 g, 3.58 mmol, 1 equiv),
commercial ethynyltrimethylsilane (3.05 mL, 21.60 mmol, 6 equiv),
5118
dx.doi.org/10.1021/jo500661u | J. Org. Chem. 2014, 79, 5113−5120

The Journal of Organic Chemistry
Article
and Pd(PPh3)4 (0.41 g, 0.35 mmol, 0.1 equiv) in dry DMF (15 mL)
and Et3N (15 mL). Column chromatography was performed with
hexane as the eluent, and compound 16 was obtained as a transparent
oil (0.62 g, 1.98 mmol, 55%). TLC: Rf 0.67 (90:10 hexane/EtOAc).
1H NMR: δ 7.33 (d, 1H, J3,4 = 7.9, H-3), 6.94 (m, 2H, H-4,6), 2.93 [s,
6H, N(CH3)2], 0.25 [s, 18H, 2 × Si(CH3)3]. 13C NMR: δ 154.7 (C-1),
134.6 (C-3), 123.8 and 120.1 (C-4,6), 115.0 and 105.1 (C-2,5), 104.3,
104.2, 101.4, and 95.3 (2 × CC), 43.1 [N(CH3)2], −0.02 and −0.17
[2 × Si(CH3)3]. Anal. Calcd for C18H27NSi2 (313.58): C, 68.94; H,
8.68; N, 4.47. Found: C, 68.88; H, 8.70; N, 4.48.
C-6″), 57.0 (2 × CH2C), 56.5, 56.4, and 56.2 (4 × OCH3), 42.8
[N(CH3)2], 20.7 and 20.6 (8 × CH3CO). Anal. Calcd for
C62H66N2O26 (1255.19): C, 59.33; H, 5.30; N, 2.23. Found: C,
59.26; H, 5.29; N, 2.23.
Compound 20. This compound was obtained as a pale-yellow
solid (0.17 g, 0.19 mmol, 95%) following general procedure B starting
from 18 (0.24 g). TLC: Rf 0.05 (80:20 CHCl3/MeOH). Mp: 202−203
1
°C. H NMR (DMSO-d6): δ 7.44 (d, J5,6 = 8.3, 1H, H-6), 7.16, 7.10,
7.07, and 7.06 (four s, 4H, 2 × H-3′,6′), 7.01 (m, 2H, H-3,5), 5.14 (d,
Jvic = 4.9, 2H, 2 × OH), 4.97 (d, Jvic = 4.8, 2H, 2 × OH), 4.92 (d, Jvic
=
5.4, 2H, 2 × OH), 4.67 and 4.54 (AB system, Jgem = 16.1, 4H, 2 ×
CH2C), 4.56 (t, JOH,6 = 5.9, 2H, 2 × 6′-OH), 4.33 (d, J1″,2″ = 7.8,
2H, 2 × H-1″), 3.81 and 3.80 (two s, 12H, 4 × OCH3), 3.66 and 3.44
(split AB m, 4H, 2 × H2-6″), 3.18−2.97 (m, 8H, 2 × H-2″−5″), 2.97
[s, 6H, N(CH3)2]. 13C NMR (DMSO-d6): δ 154.1, 153.8, 153.7, and
153.5 (C-2, 2 × C-2′,5′), 134.5 (C-6), 123.3 (C-4), 122.7 and 119.2
(C-3,5), 115.8, 115.6, and 115.0 (2 × C-3′,6′), 113.7, 113.2, 112.5,
112.4, and 112.0 (C-1, 2 × C-1′,4′), 101.1 (2 × C-1″), 94.8, 94.3, 92.8,
91.3, 91.2, 87.3, 82.1, and 82.0 (4 × CC), 77.1 and 76.7 (2 × C-
3″,5″), 73.3 (2 × C-2″), 70.1 (2 × C-4″), 61.2 (2 × C-6″), 56.3 and
56.2 (4 × OCH3), 55.9 (2 × CH2C), 42.7 [N(CH3)2]. Anal. Calcd
for C46H51NO16 (873.89): C, 63.22; H, 5.88; N, 1.60. Found: C,
63.25; H, 5.87; N, 1.60.
Compound 17. This compound was prepared in 2 h following
general procedure A starting from 15 (0.25 g, 0.77 mmol, 1 equiv),
commercial ethynyltrimethylsilane (0.65 mL, 4.62 mmol, 6 equiv), and
Pd(PPh3)4 (0.09 g, 0.08 mmol, 0.1 equiv) in dry DMF (6 mL) and
Et3N (6 mL). Column chromatography was performed with hexane as
the eluent, and compound 17 was obtained as a yellow oil (0.19 g, 0.53
1
mmol, 69%). TLC: Rf 0.48 (80:20 hexane/EtOAc). H NMR: δ 8.19
(s, 1H, H-3), 6.85 (s, 1H, H-6), 3.16 [s, 6H, N(CH3)2], 0.28 and 0.24
[two s, 18H, 2 × Si(CH3)3]. 13C NMR: δ 156.1 (C-1), 139.6 (C-4),
133.1 (C-3), 120.7 (C-6), 119.7 and 110.7 (C-2,5), 103.7, 102.6,
102.5, and 100.8 (2 × CC), 42.5 [N(CH3)2], −0.27 and −0.42 [2 ×
Si(CH3)3]. Anal. Calcd for C18H26N2O2Si2 (358.58): C, 60.29; H,
7.31; N, 7.81. Found: C, 60.40; H, 7.29; N, 7.78.
Compounds 21 and 22. These compounds were obtained in 3 h
following general procedure A starting from 3 (1.98 g, 3.05 mmol, 2.1
equiv), 1,4-diethynylbenzene (0.18 g, 1.43 mmol, 1 equiv), and
Pd(PPh3)4 (0.20 g, 0.17 mmol, 0.12 equiv) in dry DMF (12 mL) and
Et3N (12 mL). Column chromatography was performed with 60:40
hexane/EtOAc as the eluent, and a mixture of 21 and 22 was obtained.
A second column chromatography run (90:10 toluene/acetonitrile as
the eluent) was needed to obtain first 22 as a yellow solid (0.30 g, 0.23
mmol, 16%) and then 21 as a yellow solid (0.83 g, 0.71 mmol, 50%).
Data for 21. TLC: Rf 0.59 (40:60 hexane/EtOAc). Mp: 182−184
°C. 1H NMR: δ 7.54 (s, 4H, H-2,3,5,6), 7.01 and 6.94 (two s, 4H, 2 ×
H-3′,6′), 5.27 (t, J2″,3″ = J3″,4″ = 9.3, 2H, 2 × H-3″), 5.12 (t, J3″,4″ = J4″,5″
= 9.3, 2H, 2 × H-4″), 5.05 (dd, J1″,2″ = 8.3, J2″,3″ =9.3, 2H, 2 × H-2″),
4.91 (d, J1″,2″ = 8.3, 2H, 2 × H-1″), 4.65 (s, 4H, 2 × CH2C), 4.28
and 4.17 (split AB system, J5″,6″A = 4.9, J5″,6″B = 2.4, J6″A,6″B = 12.2, 4H,
Compound 18. This compound was obtained in 7 h following
general procedure C starting from 16 (0.18 g, 0.57 mmol, 1 equiv), 3
(0.75 g, 1.16 mmol, 2 equiv), Pd(PPh3)4 (0.10 g, 0.09 mmol, 0.16
equiv), and Ag2O (0.27 g, 1.16 mmol, 2 equiv) in dry DMF (4 mL)
and THF (2 mL). Column chromatography was performed with 50:50
hexane/EtOAc as the eluent, and compound 18 was obtained as a
brilliant-yellow solid (0.42 g, 0.35 mmol, 61%). TLC: Rf 0.56 (40:60
1
hexane/EtOAc). Mp: 91−93 °C. H NMR: δ 7.46 (d, J5,6 = 8.4, 1H,
H-6), 7.08 (m, 2H, H-3,5), 7.00, 6.99, 6.93, and 6.91 (four s, 4H, 2 ×
H-3′,6′), 5.25 (t, J2″,3″ = J3″,4″ = 9.5, 2H, 2 × H-3″), 5.10 (t, J3″,4″ = J4″,5″
= 9.5, 2H, 2 × H-4″), 5.03 (dd, J1″,2″ = 8.0, J2″,3″ = 9.5, 2H, 2 × H-2″),
4.90 (d, J1″,2″ = 8.0, 2H, 2 × H-1″), 4.64 (s, 4H, 2 × CH2C), 4.27
and 4.16 (split AB system, J5″,6″A = 4.9, J5″,6″B = 2.4, J6″A,6″B = 12.7, 4H,
2 × H2-6″), 3.87, 3.86, and 3.85 (three s, 12H, 4 × OCH3), 3.76 (ddd,
J4″,5″ = 9.5, J5″,6″A = 4.9, J5″,6″B = 2.4, 2H, 2 × H-5″), 3.02 [br s, 6H,
N(CH3)2], 2.06, 2.03, 2.02, and 2.01 (four s, 24H, 8 × CH3CO). 13C
NMR: δ 170.7, 170.3, 169.5, and 169.4 (8 × CO), 154.5, 154.1, 153.9,
and 153.8 (C-2, 2 × C-2′,5′), 134.3 (C-6), 128.2 (C-4), 123.7 and
120.0 (C-3,5), 115.7, 115.6, 115.5, and 115.1 (2 × C-3′,6′), 115.0,
114.4, 113.8, 112.3, and 111.9 (C-1, 2 × C-1′,4′), 98.3 (2 × C-1″),
95.5, 94.6, 92.6, 89.1, 88.9, 86.6, 83.5, and 83.4 (4 × CC), 72.8 (2 ×
C-3″), 71.9 (2 × C-5″), 71.1 (2 × C-2″), 68.3 (2 × C-4″), 61.8 (2 ×
C-6″), 57.1 (2 × CH2C), 56.5, 56.4, and 56.3 (4 × OCH3), 43.5
[N(CH3)2], 20.7 and 20.6 (8 × CH3CO). Anal. Calcd for C62H67NO24
(1210.19): C, 61.53; H, 5.58; N, 1.16. Found: C, 61.66; H, 5.57; N,
1.16.
2 × H2-6″), 3.92 and 3.89 (two s, 12H, 4 × OCH3), 3.76 (ddd, J4″,5″
=
9.3, J5″,6″A = 4.9, J5″,6″B = 2.4, 2H, 2 × H-5″), 2.08, 2.05, 2.03, and 2.01
(four s, 24H, 8 × CH3CO). 13C NMR: δ 170.6, 170.3, 169.4, and
169.3 (8 × CO), 154.1 and 153.9 (2 × C-2′,5′), 131.6 (C-2,3,5,6),
123.1 (C-1,4), 115.8 and 115.5 (2 × C-3′,6′), 113.7 and 112.4 (2 × C-
1′,4′), 98.2 (2 × C-1″), 94.9, 89.1, 87.4, and 83.4 (4 × CC), 72.8 (2
× C-3″), 71.9 (2 × C-5″), 71.1 (2 × C-2″), 68.3 (2 × C-4″), 61.8 (2 ×
C-6″), 57.0 (2 × CH2C), 56.5 and 56.3 (4 × OCH3), 20.7 and 20.6
(8 × CH3CO). Anal. Calcd for C60H62O24 (1167.12): C, 61.75; H,
5.35. Found: C, 61.62; H, 5.36.
Data for 22. TLC: Rf 0.63 (40:60 hexane/EtOAc). Mp: 109−111
°C. 1H NMR: δ 7.52 (m, 8H, 2 × H-2,3,5,6), 7.01 and 6.95 (two s, 4H,
Compound 19. This compound was obtained in 30 h following
general procedure C starting from 17 (0.22 g, 0.61 mmol, 1 equiv), 3
(0.75 g, 1.16 mmol, 2 equiv), Pd(PPh3)4 (0.10 g, 0.09 mmol, 0.15
equiv), and Ag2O (0.27 g, 1.16 mmol, 2 equiv) in dry DMF (4 mL)
and THF (2 mL). Column chromatography was performed with 50:50
hexane/EtOAc as the eluent, and compound 19 was obtained as a
pale-green oil (0.31 g, 0.25 mmol, 41%). TLC: Rf 0.36 (40:60 hexane/
EtOAc). 1H NMR: δ 8.38 (s, 1H, H-6), 7.10 (s, 1H, H-3), 6.98, 6.96,
and 6.93 (three s, 4H, 2 × H-3′,6′), 5.27 (t, J2″,3″ = J3″,4″ = 9.4, 2H, 2 ×
H-3″), 5.12 (t, J3″,4″ = J4″,5″ = 9.4, 2H, 2 × H-4″), 5.05 (dd, J1″,2″ = 8.2,
2 × H-3′,6′), 5.27 (t, J2″,3″ = J3″,4″ = 9.3, 2H, 2 × H-3″), 5.12 (t, J3″,4″
=
J
4″,5″ = 9.3, 2H, 2 × H-4″), 5.05 (dd, J1″,2″ = 7.8, J2″,3″ = 9.3, 2H, 2 × H-
2″), 4.91 (d, J1″,2″ = 7.8, 2H, 2 × H-1″), 4.65 (s, 4H, 2 × CH2C),
4.28 and 4.17 (split AB system, J5″,6″A = 4.9, J5″,6″B = 2.4, J6″A,6″B = 12.2,
4H, 2 × H2-6″), 3.89 and 3.88 (two s, 12H, 4 × OCH3), 3.76 (ddd,
J
4″,5″ = 9.3, J5″,6″A = 4.9, J5″,6″B = 2.4, 2H, 2 × H-5″), 2.08, 2.05, and 2.04
(three s, 24H, 8 × CH3CO). 13C NMR: δ 170.7, 170.3, 169.5, and
169.4 (8 × CO), 154.1 and 153.9 (2 × C-2′,5′), 132.4 and 131.6 (2 ×
C-2,3,5,6), 124.1 and 121.6 (2 × C-1,4), 115.7 and 115.5 (2 × C-
3′,6′), 113.5 and 112.6 (2 × C-1′,4′), 98.2 (2 × C-1″), 94.6, 89.2, 88.2,
83.4, 82.1, and 77.2 (6 × CC), 72.8 (2 × C-3″), 71.9 (2 × C-5″),
71.1 (2 × C-2″), 68.3 (2 × C-4″), 61.8 (2 × C-6″), 57.0 (2 ×
CH2C), 56.5 and 56.3 (4 × OCH3), 20.7 and 20.6 (8 × CH3CO).
Anal. Calcd for C70H66O24 (1291.26): C, 65.11; H, 5.15. Found: C,
65.26; H, 5.13.
J
2″,3″ = 9.4, 2H, 2 × H-2″), 4.90 (d, J1″,2″ = 8.2, 2H, 2 × H-1″), 4.65 (s,
4H, 2 × CH2C), 4.27 and 4.16 (split AB system, J5″,6″A = 4.1, J5″,6″B
= 2.3, J6″A,6″B = 12.3, 4H, 2 × H2-6″), 3.91, 3.89, and 3.86 (three s,
12H, 4 × OCH3), 3.78 (ddd, J4″,5″ = 9.4, J5″,6″A = 4.1, J5″,6″B = 2.3, 2H, 2
× H-5″), 3.28 [s, 6H, N(CH3)2], 2.08, 2.05, 2.03, and 2.01 (four s,
24H, 8 × CH3CO). 13C NMR: δ 170.2, 169.4, and 169.3 (8 × CO),
155.6, 154.3, 154.1, and 154.0 (C-2 and 2 × C-2′,5′), 139.0 (C-5),
133.0 (C-6), 120.1, 119.9, 115.8, 115.4, and 114.9 (C-3 and 2 × C-
3′,6′), 113.4, 113.2, 112.5, and 110.5 (C-1 and 2 × C-1′,4′), 98.2 (2 ×
C-1″), 93.3, 93.1, 93.0, 92.1, 89.5, 89.3, and 83.3 (4 × CC), 72.8 (2
× C-3″), 71.9 (2 × C-5″), 71.1 (2 × C-2″), 68.3 (2 × C-4″), 61.8 (2 ×
Compound 23. This compound was obtained as a pale-yellow
solid (0.15 g, 0.19 mmol, 94%) following general procedure B starting
from 21 (0.23 g). TLC: Rf 0.05 (80:20 CHCl3/MeOH). Mp: ≥280
1
°C. H NMR (DMSO-d6): δ 7.58 (s, 4H, H-2,3,5,6), 7.18 and 7.09
(two s, 4H, 2 × H-3′,6′), 5.15 (d, Jvic = 4.9, 2H, 2 × OH), 4.98 (d, Jvic
5119
dx.doi.org/10.1021/jo500661u | J. Org. Chem. 2014, 79, 5113−5120

The Journal of Organic Chemistry
Article
= 4.9, 2H, 2 × OH), 4.94 (d, Jvic = 5.3, 2H, 2 × OH), 4.68 and 4.55
(AB system, Jgem = 15.6, 4H, 2 × CH2C), 4.54 (t, JOH,6 = 5.7, 2H, 2
× 6′-OH), 4.34 (d, J1″,2″ = 7.9, 2H, 2 × H-1″), 3.82 and 3.81 (two s,
12H, 4 × OCH3), 3.70 and 3.45 (split AB m, 4H, 2 × H2-6″), 3.19−
2.97 (m, 8H, 2 × H-2″−5″). 13C NMR (DMSO-d6): δ 153.7 and
153.5 (2 × C-2′,5′), 131.6 (s, C-2,3,5,6), 122.5 (C-1,4), 115.8 and
115.6 (2 × C-3′,6′), 112.5 and 112.2 (2 × C-1′,4′), 101.1 (2 × C-1″),
94.1, 91.4, 88.1.2, and 82.0 (4 × CC), 77.0 and 76.7 (2 × C-3″,5″),
73.3 (2 × C-2″), 70.1 (2 × C-4″), 61.2 (2 × C-6″), 56.3 and 56.1 (4 ×
OCH3), 55.8 (2 × CH2C). Anal. Calcd for C44H46O16 (830.83): C,
63.61; H, 5.58. Found: C, 63.63; H, 5.59.
Barattucci, A.; Papalia, T.; Puntoriero, F.; Campagna, S. Chem.
Commun. 2012, 48, 10550−10552. (c) Bonaccorsi, P.; Marino-Merlo,
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Marino-Merlo, F.; Mastino, A.; Sciortino, M. T. Bioorg. Med. Chem.
2009, 17, 1456−1463. (g) Aversa, M. C.; Barattucci, A.; Bonaccorsi, P.
Eur. J. Org. Chem. 2009, 6335−6339. (h) Aversa, M. C.; Barattucci, A.;
Bonaccorsi, P. Tetrahedron 2008, 64, 7659−7683. (i) Aversa, M. C.;
Barattucci, A.; Bilardo, M. C.; Bonaccorsi, P.; Giannetto, P.; Rollin, P.;
Tatibouet, A. J. Org. Chem. 2005, 70, 7389−7396.
ASSOCIATED CONTENT
■
(11) (a) Giovenzana, G. B.; Lay, L.; Monti, D.; Palmisano, G.; Panza,
L. Tetrahedron 1999, 55, 14123−14136. (b) Yi, C.; Blum, C.;
Lehmann, M.; Keller, S.; Liu, S.-X.; Frei, G.; Neels, A.; Hauser, J.;
S
* Supporting Information
1H NMR and 13C NMR spectra of compounds 3−23, cellular
toxicity data, and absorption and emission spectra of 8 and 21−
23. This material is available free of charge via the Internet at
http://pubs.acs.org.
Schurch, S.; Decurtins, S. J. Org. Chem. 2010, 75, 3350−3357.
̈
(12) (a) Babudri, F.; Colangiuli, D.; Di Lorenzo, P. A.; Farinola, G.
M.; Hassan Omar, O.; Naso, F. Chem. Commun. 2003, 130−131.
(b) Mori, A.; Kondo, T.; Kato, T.; Nishihara, Y. Chem. Lett. 2001,
286−287.
AUTHOR INFORMATION
Corresponding Authors
*E-mail: abarattucci@unime.it.
*E-mail: mtsciortino@unime.it.
*E-mail: fpuntoriero@unime.it.
■
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
The authors thank MIUR, Italy, for financial support
(PON01_01499 and PRIN 20109Z2XRJ_010).
■
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