Synthesis of some new biheterocycles by a one-pot Suzuki-Miyaura coupling reaction

Article abstract of DOI:10.3987/COM-09-S(S)113

Halogenated indoles, benzofurans and flavones were subjected to a one-pot Suzuki-Miyaura coupling reaction to generate a series of new biheterocycles. The methodology may be readily adapted to the synthesis of a wide variety of substituted biheterocycles.

Full text of DOI:10.3987/COM-09-S(S)113

HETEROCYCLES, Vol. 80, No. 2, 2010
1267
HETEROCYCLES, Vol. 80, No. 2, 2010, pp. 1267 - 1274. © The Japan Institute of Heterocyclic Chemistry
Received, 16th August, 2009, Accepted, 18th September, 2009, Published online, 18th September, 2009
DOI: 10.3987/COM-09-S(S)113
SYNTHESIS OF SOME NEW BIHETEROCYCLES BY A ONE-POT
SUZUKI-MIYAURA COUPLING REACTION
Mandar Deodhar, David StC. Black,* Daniel Shiu-Hin Chan, and Naresh
Kumar*
School of Chemistry, University of New South Wales, Sydney, NSW 2052,
Australia
E-mail: n.kumar@unsw.edu.au or d.black@unsw.edu.au
Dedicated to Prof. Akira Suzuki on the occasion of his 80th birthday
Abstract – Halogenated indoles, benzofurans and flavones were subjected to a
one-pot Suzuki-Miyaura coupling reaction to generate a series of new
biheterocycles. The methodology may be readily adapted to the synthesis of a
wide variety of substituted biheterocycles.
INTRODUCTION
Biheterocyclic compounds display a wide range of biological activities, and in many cases enhanced
activity is observed compared to the single parent heterocycle.1 Indole-containing biheterocycles have
received considerable attention due to their presence in natural products such as melanin pigment and
staurosporine 1, an alkaloid with potent biological activities.2
H
N
O
OH
O
O
OH
O
O
N
N
O
Me
H
HO
HO
MeO
NHMe
2
1
Biindoles can also act as ligands in transition metal complexes, and thus have the potential to find key use
in catalytic processes.3 However, biindoles linked via aryl groups at C2 or C3 have not been reported in

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HETEROCYCLES, Vol. 80, No. 2, 2010
the literature. The related bibenzofurans containing an aryl group linkage have been used as optical
brighteners and fluorescent agents for textiles and cosmetic compositions.4 Biflavonoids are plant
secondary metabolites and to date more than 100 biflavonoids have been isolated from various plants
sources. The naturally occurring biisoflavonoid kudzuisoflavone A 2 contains an aryl-aryl linkage,5
however the corresponding biflavonoid compound has not been found in Nature. The biological activities
of biflavonoids have been extensively studied.6,7
Intrigued by the wide range of useful properties associated with biheterocycles, and in continuation of our
interest in the synthesis of novel heterocyclic systems, we set out to synthesize symmetrically linked
biindoles, bibenzofurans and biflavones with special emphasis on coupling through a pendant aryl group
to create a biaryl linkage.
RESULTS AND DISCUSSION
A variety of methods have been reported for the synthesis of biheterocycles and their analogues. Our
group has previously described the facile one-step synthesis of biindolyls using indolone and phosphoryl
chloride as the Vilsmeier reagent.8 We envisaged that the Suzuki-Miyaura coupling reaction could be
utilized for the synthesis of biheterocycles. The Suzuki-Miyaura reaction involves the palladium-
catalyzed coupling of an organoboron compound with an organohalide, and is one of the most extensively
used reactions in the synthesis of natural products, pharmaceuticals and advanced materials.9-14 One major
advantage of the Suzuki-Miyaura reaction is that only a catalytic amount of palladium catalyst is needed,
whereas other coupling methodologies usually require stoichiometric amounts of metal catalyst (e.g.
copper).
A one-pot Suzuki-Miyaura coupling reaction has been reported, and involves in situ conversion of an aryl
halide into a boronate ester intermediate followed by the addition of a second equivalent of aryl halide
together with a palladium catalyst and base to afford the biaryl product.15-20 Isolation of the arylboronate
intermediates is not required, circumventing the need for large volumes of solvents and reducing the time
required for reaction. This method is particularly useful in cases where the boronate intermediate is
unstable. In order to carry out the two steps in one-pot effectively, the boronate ester formation needs to
be reasonably clean. Furthermore, a judicious selection of reaction conditions, such as catalyst, solvent,
base and temperature is also essential.
The Suzuki-Miyaura reaction was therefore applied to readily available 4-haloaryl substituted indoles,
benzofurans, and flavones, as well as to 4-, 5-, 6,- and 7-bromoindoles themselves. Recently, a Suzuki-
Miyaura coupling reaction has been reported for the synthesis of homo- and hetero-biindoles.21
In our work, the reaction conditions were optimized using 3-iodo-4-methoxybenzaldehyde 3 as the
substrate by treating it with bis(pinacolato)diboron in the presence of PdCl2(dppf) and potassium acetate

HETEROCYCLES, Vol. 80, No. 2, 2010
1269
in dry DMF. Upon complete conversion of the aryl halide into the boronate intermediate (TLC analysis),
another equivalent of iodobenzaldehyde 3 was added followed by the addition of Pd(PPh3)4 (found to
improve the yield) and aqueous sodium hydroxide solution. After work-up and chromatographic
purification, biphenyl 4 was obtained in 77% yield (Scheme 1).
OMe
CHO
OMe
CHO
OMe
OMe O
B
I
3, Pd(PPh3)4
bis(pinacolato)diboron
O
aq. NaOH
77% overall
KOAc, PdCl2(dppf), DMF
100 °C
CHO
CHO
3
4
Scheme 1. Synthesis of 2,2ꢀ-dimethoxydiphenyl-5,5ꢀ-dicarbaldehyde 4
Encouraged by this result, the same methodology was applied for the preparation of directly linked
biindolyls, as well as biindoles, bibenzofurans and biflavones linked via a biphenyl moeity. When 3-(4-
bromophenyl)-4,6-dimethoxyindole 5 was subjected to the one-pot reaction conditions described above,
the resulting dimer 15 was obtained in 37% yield. In the 1H NMR spectrum of the dimer, the protons for
the pendant phenyl ring appeared as two doublets at ꢁ 7.67 and 7.69 ppm, while in the starting material
these protons resonated as a singlet at ꢁ 7.46 ppm. The structure of the dimer was further confirmed by
the presence of the molecular ion peak at m/z 504 in the mass spectrum. The coupling reaction of other
bromoindoles 6-10 and bromobenzofurans 11-12 proceeded in a similar manner to yield the
corresponding biindoles 16-20 and bibenzofurans 21-22 respectively in moderate (but not optimized)
yields of 36-50% (Table 1).
Table 1. Syntheses of biheterocycles via a one-pot Suzuki-Miyaura coupling reaction
Entry
Substrate
Product
Yield (%)
Br
MeO
OMe
OMe
1
5
6
15
16
37
HN
2
N
MeO
H
OMe
OMe
2
36
Br
N
MeO
N
MeO
H
H
2

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HETEROCYCLES, Vol. 80, No. 2, 2010
Br
HN
3
4
5
7
6
9
17
41
37
44
N
H
2
Br
N
H
18
19
20
N
H
2
N
H
N
H
Br
2
NH
N
H
6
7
10
11
50
42
Br
2
Br
MeO
OMe
OMe
21
O
O
MeO
2
Br
OMe
MeO
OMe
OMe
8
9
12
13
22
23
39
63
MeO
MeO
O
2
O
O
O
O
I
O
OMe
OMe
2
OMe O
O
OMe O
O
I
10
14
24
59
OMe
OMe
2
3ꢀ-Iodoflavones were chosen as the substrates for the synthesis of biflavones due to the ease of their
preparation from the corresponding iodobenzaldehydes. The coupling reaction was found to be more
facile with iodoflavones 13-14, requiring only 3-4 h at 100 °C for completion, and resulting in higher
yields of the corresponding dimers 23-24 (59-63%). The formation of the coupling products was
confirmed by 1H and 13C NMR spectroscopy, IR and UV spectroscopy, mass spectrometry and elemental
analyses. Known products were characterized by comparison of their 1H NMR spectra and melting points
with those reported in the literature.
In conclusion, we have achieved a one-pot synthesis of biindoles, bibenzofurans and biflavones linked by

HETEROCYCLES, Vol. 80, No. 2, 2010
1271
a biaryl moiety, and directly linked biindolyls. The described methodology represents an efficient access
to afford a range of biheterocycles and their analogues with potentially interesting biological activities.
EXPERIMENTAL
All reactions were performed under an argon atmosphere. Melting points are uncorrected. Microanalyses
were performed on a Carlo Erba Elemental Analyzer EA 1108. NMR spectra were recorded in the
designated solvents on a Bruker Avance DPX300 (300 MHz) spectrometer and were internally referenced
to the solvent peaks. Low resolution mass spectrometric analysis was carried out on a Q-Star Pulsar API
(Applied Biosystems) mass spectrometer. Infrared spectra were recorded with a Thermo Nicolet 370
FTIR spectrometer. Ultraviolet-visible spectra were recorded using a Varian Cary 100 Scan spectrometer.
Column chromatography was carried out using Merck 230-400 mesh ASTM silica gel.
General procedure for one-pot Suzuki-Miyaura synthesis: A mixture of aryl halide (0.5 mmol),
PdCl2(dppf) (20 mg, 0.025 mmol), bis(pinacolato)diboron (127 mg, 0.5 mmol) and potassium acetate
(180 mg, 1.8 mmol) in dry DMF (2 mL) was heated under argon at 100 °C for 2-3 h. Another equivalent
of aryl halide (0.5 mmol) was added followed by addition of Pd(PPh3)4 (25 mg, 0.04 mmol), and solution
of NaOH (40 mg, 1 mmol) in water (0.4 mL). The reaction was continued further (4 h for aryl iodides and
12 h for bromides) cooled to rt, diluted with water (50 mL) and stirred for 10 min. The product was
filtered, washed with water (25 mL), air dried and purified by silica gel column chromatography.
2,2ꢀ-Dimethoxydiphenyl-5,5ꢀ-dicarbaldehyde (4): An off-white solid (77%). Purified by silica gel
column chromatography [eluted initially with dichloromethane and then with dichloromethane – EtOAc
1
(90:10)]. Mp 131-133 °C (lit.,22 134 °C); H NMR (300 MHz, CDCl3): ꢀ 3.86 (6H, s, 2 ꢁ CH3O), 7.09
(2H, d, J = 8.3 Hz, H3, H3ꢂ), 7.77 (2H, d, J = 2.3 Hz, H6, H6ꢂ), 7.91 (2H, dd, J = 2.3, 8.3 Hz, H4, H4ꢂ),
9.92 (2H, s, 2 ꢁ CHO).
4,4ꢀ-Bis(4,6-dimethoxyindol-3-yl)biphenyl (15): An off-white solid (37%). Purified by silica gel column
chromatography [eluted with hexane – EtOAc (50:50)]. Mp 291-294 °C; UV (MeOH): ꢃmax 206 (ꢄ 41775
cm-1M-1), 224 (ꢄ 41595 cm-1M-1), 324 (ꢄ 19084 cm-1M-1) nm; IR (KBr): ꢀmax 3413, 3348, 1624, 1545,
1334, 1214, 1162, 1143 cm-1; 1H NMR (300 MHz, acetone-d6): ꢀ 3.80 (6H, s, 2 ꢁ CH3O), 3.83 (6H, s, 2 ꢁ
CH3O), 6.25 (2H, d, J = 1.9 Hz, H5, H5ꢂꢂ), 6.61 (2H, d, J = 1.9 Hz, H7, H7ꢂꢂ), 7.22 (2H, m, H2, H2ꢂꢂ), 7.67
and 7.69 (8H, 2 ꢁ d, J = 8.7 Hz, H2ꢂ, H2ꢂꢂꢂ, H3ꢂ, H3ꢂꢂꢂ, H5ꢂ, H5ꢂꢂꢂ, H6, H6ꢂꢂꢂ), 10.23 (2H, bs, 2 ꢁ NH); 13C
NMR (75.6 MHz, acetone-d6): ꢀ 54.3, 54.7, 87.1, 91.8, 117.6, 117.7, 120.9, 121.0, 125.4, 129.6, 135.6,
137.6, 154.7, 157.5; MS (ESI) m/z for C32H28N2O4 (M+) 504.17; Anal. Calcd for C32H28N2O4: C, 76.17; H,
5.59; N, 5.55. Found: C, 76.51; H, 5.72; N, 5.32.

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HETEROCYCLES, Vol. 80, No. 2, 2010
4,4ꢀ-Bis(4,6-dimethoxyindol-2-yl)biphenyl (16): An off-white solid (36%). Purified by silica gel column
chromatography [eluted with hexane – EtOAc (50:50)]. Mp 220 °C; UV (MeOH): ꢀmax 215 (ꢁ 52808 cm-
1M-1), 258 (ꢁ 23419 cm-1M-1), 366 (ꢁ 44757 cm-1M-1) nm; IR (KBr): ꢀmax 2933, 2836, 1623, 1602, 1275,
1217, 1149, 1127, 797 cm-1; 1H NMR (300 MHz, acetone-d6): ꢂ 3.79 (6H, s, 2 ꢃ CH3O), 3.91 (6H, s, 2 ꢃ
CH3O), 6.20 (2H, d, J = 1.9 Hz, H5, H5ꢄꢄ), 6.56 (2H, d, J = 1.1 Hz, H3, H3ꢄꢄ), 6.89 (2H, d, J = 1.9 Hz, H7,
H7ꢄꢄ), 7.76 and 7.87 (8H, 2 ꢃ d, J = 8.3 Hz, H2ꢄ, H2ꢄꢄꢄ, H3ꢄ, H3ꢄꢄꢄ, H5ꢄ, H5ꢄꢄꢄ, H6ꢄ, H6ꢄꢄꢄ), 10.52 (2H, bs, 2 ꢃ
NH); 13C NMR (75.6 MHz, acetone-d6): ꢂ 54.5, 54.7, 86.8, 91.4, 96.6, 114.5, 124.7, 126.8, 131.9, 134.6,
138.3, 138.9, 153.6, 157.9; MS (MALDI-ESI) m/z Calcd for C32H28N2O4 (M)+ 504.57. Found 504.12;
Anal. Calcd for C32H28N2O4: C, 76.17; H, 5.59; N, 5.55. Found: C, 76.35; H, 5.82, N, 5.50.
4,4ꢀ-Biindolyl (17): Grey crystals (41%). Purified by silica gel column chromatography [eluted with
hexane – EtOAc (80:20)]. Mp 258-260 °C; UV (MeOH): ꢀmax 219 (ꢁ 31918 cm-1M-1), 300 (ꢁ 13800 cm-
1M-1); IR (KBr): ꢀmax 3395, 1426, 1403, 1333, 758 cm-1; 1H NMR (300 MHz, CDCl3): ꢂ 6.60 (2H, dd, J =
0.8, 1.9 Hz, H3, H3ꢄ), 7.17-7.56 (8H, m, H2, H2ꢄ, H5, H5ꢄ, H6, H6ꢄ, H7, H7ꢄ), 8.23 (2H, bs, 2 ꢃ NH); 13C
NMR (75.6 MHz, CDCl3): ꢂ 103.1, 109.8, 120.6, 122.0, 123.7, 126.8, 133.8, 136.2; HRMS (TOF-ESI)
m/z Calcd for C16H12N2Na (M + Na)+ 255.0893. Found 255.1544; Anal. Calcd for C16H12N2: C, 82.73; H,
5.21; N, 12.06. Found: C, 82.31; H, 5.40, N, 11.84.
5,5ꢀ-Biindolyl (18): Grey crystals (37%). Purified by silica gel column chromatography [eluted with
hexane – EtOAc (80:20)]. Mp 214 °C, (lit.,23 212-215 °C); IR (KBr): ꢀmax 3396, 1465, 1454, 1416, 1027,
875, 804, 730 cm-1; 1H NMR (300 MHz, acetone-d6): ꢂ 6.50 (2H, m, H3, H3ꢄ), 7.30-7.50 (6H, m, H2, H2ꢄ,
13
H6, H6ꢄ, H7, H7ꢄ), 7.80 (2H, s, H4, H4ꢄ), 10.18 (2H, bs, 2 ꢃ NH); C NMR (75.6 MHz, acetone-d6): ꢂ
101.7, 111.2, 118.4, 121.3, 124.9, 125.0, 128.7, 134.1.
6,6ꢀ-Biindolyl (19): Grey needles (44%). Purified by silica gel column chromatography [eluted with
hexane – EtOAc (70:30)]. Mp 285 (dec); UV (MeOH): ꢀmax 211 (ꢁ 33037 cm-1M-1), 243 (ꢁ 47980 cm-1M-
1), 304 (ꢁ 27387 cm-1M-1) nm; IR (KBr): ꢀmax 3385, 1453, 1096, 1061, 807, 722, 528 cm-1; 1H NMR (300
MHz, acetone-d6): ꢂ 6.46 (2H, m, H3, H3ꢄ), 7.32 (2H, m, H2, H2ꢄ), 7.36 (2H, dd, J = 1.9, 8.3 Hz, H5, H5ꢄ),
13
7.61 (2H, d, J = 8.3 Hz, H4, H4ꢄ), 7.69 (2H, m, H7, H7ꢄ); C NMR (75.6 MHz, acetone-d6): ꢂ 101.2,
109.4, 119.1, 120.2, 124.8, 127.0, 136.1, 137.0; HRMS (TOF-ESI) m/z Calcd for C16H12N2Na (M + Na)+
255.0893. Found 255.1547; Anal. Calcd for C16H12N2: C, 82.73; H, 5.21; N, 12.06. Found: C, 82.30; H,
5.35; N, 11.72.
7,7ꢀ-Biindolyl (20): Grey crystals (50%). Purified by silica gel column chromatography [eluted with
hexane – EtOAc (70:30)]. Mp 252 °C (lit.,24 244-245 °C); UV (MeOH): ꢀmax 217 (ꢁ 28529 cm-1M-1), 293
(ꢁ 13086 cm-1M-1) nm; IR (KBr): ꢀmax 3389, 1423, 1410, 1337, 804, 779, 728 cm-1; 1H NMR (300 MHz,
acetone-d6): ꢂ 6.54 (2H, m, H3, H3ꢄ), 7.13 (2H, dd, J = 7.1, 7.5 Hz, H5, H5ꢄ), 7.25 (2H, dd, J = 1.1, 7.1
Hz, H6, H6ꢄ), 7.29 (2H, m, H2, H2ꢄ), 7.61 (2H, dd, J = 1.1, 7.5 Hz, H4, H4ꢄ), 9.91 (2H, bs, 2 ꢃ NH); 13C

HETEROCYCLES, Vol. 80, No. 2, 2010
1273
NMR (75.6 MHz, acetone-d6): ꢀ 101.8, 119.4, 119.6, 121.6, 122.7, 125.1, 128.8, 134.1.
4,4ꢀ-Bis-(4,6-dimethoxybenzofuran-3-yl)biphenyl (21): A white solid (42%). Purified by silica gel
column chromatography [eluted with hexane – EtOAc (80:20)]. Mp 232-235 °C; UV (MeOH): ꢁmax 212
(ꢂ 93646 cm-1M-1), 260 (ꢂ 54888 cm-1M-1), 298 (ꢂ 40444 cm-1M-1) nm; IR (KBr): ꢀmax 1623, 1592, 1500,
1
1333, 1165, 1147, 1093, 1084 cm-1; H NMR (300 MHz, acetone-d6): ꢀ 3.87 (12H, s, 2 ꢃ CH3O), 6.46
(2H, d, J = 1.9 Hz, H7, H7ꢄꢄ), 6.77 (2H, d, J = 1.9 Hz, H5, H5ꢄꢄ), 7.76 (8H, s, H2ꢄ, H2ꢄꢄꢄ, H3ꢄ, H3ꢄꢄꢄ, H5ꢄ,
H5ꢄꢄꢄ, H6ꢄ, H6ꢄꢄꢄ), 7.80 (2H, s, H2, H2ꢄꢄ); 13C NMR (75.6 MHz, acetone-d6): ꢀ 54.8, 55.0, 88.2, 94.5, 118.3,
122.3, 126.0, 129.5, 131.4, 139.1, 140.2, 145.2, 154.6, 158.0, 159.6; MS (ESI) m/z for C32H26O6 (M+1)+
507.16; Anal. Calcd for C32H26O6: C, 75.88; H, 5.17. Found: C, 75.88; H, 5.17.
4,4ꢀ-Bis-(4,5,6-trimethoxybenzofuran-3-yl)biphenyl (22): A white solid (39%). Purified by silica gel
column chromatography [eluted with hexane – EtOAc (65:35)]. Mp 206-208 °C; UV (MeOH): ꢁmax 209
(ꢂ 82879 cm-1M-1), 257 (ꢂ 39939 cm-1M-1), 293 (ꢂ 47836 cm-1M-1) nm; IR (KBr): ꢀmax 2962, 2937, 1614,
1
1569, 1469, 1195, 1121 cm-1; H NMR (300 MHz, CDCl3): ꢀ 3.70 (6H, s, 2 ꢃ CH3O), 3.91 (6H, s, 2 ꢃ
CH3O), 3.93 (6H, s, 2 ꢃ CH3O), 6.90 (2H, s, H7, H7ꢄꢄ), 7.59 (2H, s, H2, H2ꢄꢄ), 7.74 (8H, m, H2ꢄ, H2ꢄꢄꢄ, H3ꢄ,
13
H3ꢄꢄꢄ, H5ꢄ, H5ꢄꢄꢄ, H6ꢄ, H6ꢄꢄꢄ); C NMR (75.6 MHz, CDCl3): ꢀ 56.2, 61.4, 61.6, 91.5, 112.9, 122.3, 126.6,
129.3, 131.0, 138.9, 139.5, 140.6, 147.1, 152.4, 152.7; MS (MALDI-ESI) m/z Calcd for C34H30O8 (M)+
566.59. Found 566.19; Anal. Calcd for C34H30O8: C, 72.07; H, 5.34. Found: C, 72.37; H, 5.50.
4ꢀ,4ꢀꢀꢀ-Dimethoxy-3ꢀ,3ꢀꢀꢀ-biflavone (23): A pale yellow solid (63%). Purified by silica gel column
chromatography [eluted with CH2Cl2 – EtOAc (70:30)]. Mp 322 °C, (lit.,25 327 °C); IR (KBr): ꢀmax 1653,
1
1605, 1465, 1493, 1269, 1248 cm-1; H NMR (300 MHz, CDCl3 + CD3OD): ꢀ 3.81 (6H, s, 4ꢄ CH3O, 4ꢄꢄꢄ
CH3O), 6.74 (2H, s, H3, H3ꢄꢄ), 7.08 (2H, d, J = 9.0 Hz, H5ꢄ, H5ꢄꢄꢄ), 7.35 (2H, td, J = 1.4, 7.9 Hz, H6, H6ꢄꢄ),
7.51 (2H, dd, J = 1.1, 7.9 Hz, H8, H8ꢄꢄ), 7.63 (2H, ddd, J = 1.5, 7.9, 8.3 Hz, H7, H7ꢄꢄ), 7.81 (2H, d, J = 2.6
13
Hz, H2ꢄ, H2ꢄꢄꢄ), 7.94 (2H, dd, J = 2.6, 9.0 Hz, H6ꢄ, H6ꢄꢄꢄ), 8.12 (2H, dd, J = 1.5, 7.9 Hz, H5, H5ꢄꢄ); C
NMR (75.6 MHz, CDCl3 + CD3OD): ꢀ 55.8, 105.8, 111.3, 117.9, 123.5, 125.2, 125.2, 127.4, 127.9, 129.4,
133.8, 156.1, 160.0, 163.9, 179.0; MS (ESI) m/z for C32H22O6Na (M + Na)+ 525.11.
4ꢀ,4ꢀꢀꢀ,5,5ꢀꢀ-Tetramethoxy-3ꢀ,3ꢀꢀꢀ-biflavone (24): A pale yellow solid (59%). Purified by silica gel
column chromatography [eluted with CH2Cl2 – EtOAc (70:30)]. Mp 321-323 °C; UV (MeOH): ꢁmax 209
(ꢂ 29995 cm-1M-1), 264 (ꢂ 23149 cm-1M-1), 328 (ꢂ 28283 cm-1M-1) nm; IR (KBr): ꢀmax 1633, 1601, 1475,
1262, 1102, 1023, 803 cm-1; 1H NMR (300 MHz, CDCl3 + CD3OD): ꢀ 3.84 (6H, s, 4ꢄ CH3O, 4ꢄꢄꢄ CH3O),
3.96 (6H, s, 5 CH3O, 5ꢄꢄ CH3O), 6.72 (2H, s, H3, H3ꢄꢄ), 6.80 (2H, d, J = 8.3 Hz, H6, H6ꢄꢄ), 7.09 (2H, d, J =
8.3 Hz, H5ꢄ, H5ꢄꢄꢄ), 7.11 (2H, d, J = 8.3 Hz, H8, H8ꢄꢄ), 7.52 (2H, t, J = 8.3 Hz, H7, H7ꢄꢄ), 7.80 (2H, d, J =
1.9 Hz, H2ꢄ, H2ꢄꢄꢄ), 7.92 (2H, dd, J = 1.9, 8.3 Hz, H6ꢄ, H6ꢄꢄꢄ); 13C NMR (75.6 MHz, CDCl3 + CD3OD): ꢀ
55.8, 56.1, 106.4, 107.4, 110.0, 111.2, 114.1, 123.2, 127.4, 127.6, 129.2, 133.8, 158.1, 159.6, 159.8, 161.6,
178.9; MS (ESI) m/z for C34H26O8Na (M + Na)+ 585.12; Anal. Calcd for C34H26O8ꢅ2H2O: C, 68.22; H,

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HETEROCYCLES, Vol. 80, No. 2, 2010
5.05. Found: C, 68.19; H, 4.85.
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