First chemical synthesis of three natural depsides involved in flavonol catabolism and related to quercetinase catalysis

Article abstract of DOI:10.1080/00397910500406534

We report here the first chemical synthesis of three depsides related to quercetinase-catalyzed degradation of kaempferol, quercetin, and myricetin. The three depsides were constructed through the coupling of suitably protected phloroglucinol carboxylic acid and hydroxy-perbenzylated, derivatives of gallic, protocatechuic, and 4-hydroxy benzoic acids. The three synthesized target compounds proved to be identical to their natural counterparts, arising from quercetinase action on corresponding flavonols. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910500406534

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First Chemical Synthesis of Three Natural
Depsides Involved in Flavonol Catabolism and
Related to Quercetinase Catalysis
Sylvain Tranchimand a , Thierry Tron a , Christian Gaudin a & Gilles Iacazio a
a Laboratoire de Bioinorganique Structurale, Faculté des Sciences et
Techniques, Université Paul Cézanne Aix‐Marseille III, Marseille Cedex,
France
Published online: 16 Aug 2006.
To cite this article: Sylvain Tranchimand , Thierry Tron , Christian Gaudin & Gilles Iacazio (2006) First
Chemical Synthesis of Three Natural Depsides Involved in Flavonol Catabolism and Related to Quercetinase
Catalysis, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 36:5, 587-597
To link to this article: http://dx.doi.org/10.1080/00397910500406534
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Synthetic Communicationsw, 36: 587–597, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500406534
First Chemical Synthesis of Three Natural
Depsides Involved in Flavonol Catabolism
and Related to Quercetinase Catalysis
Sylvain Tranchimand, Thierry Tron, Christian Gaudin,
and Gilles Iacazio
´
Laboratoire de Bioinorganique Structurale, Faculte des Sciences et
´ ´
Techniques, Universite Paul Cezanne Aix-Marseille III,
Marseille Cedex, France
Abstract: We report here the first chemical synthesis of three depsides related to
quercetinase-catalyzed degradation of kaempferol, quercetin, and myricetin. The three
depsides were constructed through the coupling of suitably protected phloroglucinol
carboxylic acid and hydroxy-perbenzylated, derivatives of gallic, protocatechuic, and
4-hydroxy benzoic acids. The three synthesized target compounds proved to be
identical to their natural counterparts, arising from quercetinase action on correspond-
ing flavonols.
Keywords: Depsides, kaempferol, myricetin, quercetin, quercetin 2,3-dioxygenase,
quercetinase
INTRODUCTION
Quercetinases (quercetin 2,3-dioxygenase, E.C. 1.13.11.24) are copper-
containing dioxygenases produced by various filamentous fungi. They act
on flavonols and generate a depside and carbon monoxide (Scheme 1).[1–4]
Received in Poland July 28, 2005
Address correspondence to Gilles Iacazio, Laboratoire de Bioinorganique
´
Structurale (CBRL UMR CNRS 6517), Case 432, Faculte des Sciences et Techniques,
´
´
Universite Paul Cezanne Aix-Marseille III, avenue Escadrille Normandie-Nieman,
13397 Marseille Cedex 20, France. Tel.: 33 491 282 856; Fax: 33 491 983 208;
E-mail: gilles.iacazio@univ.u-3mrs.fr
587

588
S. Tranchimand et al.
Scheme 1. Reaction catalyzed by quercetinases on flavonols.
Very recently an iron-containing quercetinase has been found in Bacillus
subtilis,[5,6] and a quercetinase activity has been detected in pirin originating
both from Escherichia coli and humans.[7] Pirin is implicated in transcrip-
tional activation and apoptosis and is highly conserved both in prokaryotes
and eukaryotes. Quercetinase activity is generally quantified by UV-
spectroscopy following a decrease in absorbance of quercetin at 367 nm.[8]
Detection of the depside was never used in this context, probably because
of the lack of authentic samples. Since the discovery of quercetinase
activity in pirins,[7] it appears to be widely distributed over all kingdoms of
life. We have therefore planned the synthesis of three different depsides
related to quercetinase activity to facilitate quercetinase detection in
complex media such as cellular extracts.
RESULTS AND DISCUSSION
Strategy for the synthesis was based on the coupling of suitably protected
phloroglucinol carboxylic acid with each of the three hydroxy-perbenzylated
benzoic acid derivatives arising from gallic, protocatechuic, and 4-hydroxy
benzoic acids. Benzyl 2,4-bis(benzyloxy)-6-hydroxybenzoate 2 was obtained
following two different synthetic approaches (Scheme 2).
Scheme 2. a) K2CO3, BnBr, DMF, rt, 17% yield; b) trifluoroacetic anhydride,
acetone, trifluoroacetic acid, 08C to rt, 5 h, 34% yield; c) K2CO3, BnBr, DMF, rt,
91% yield; d) benzyl alcohol, Na, THF, rt, 15 min, 84% yield.

Synthesis of Three Natural Depsides
589
Scheme 3. a) K2CO3, BnBr, DMF, rt, 91–92% yield; b) KOH, H2O, EtOH, reflux,
1 h, 80–98% yield.
In a single-step experiment, unprotected phloroglucinol carboxylic
acid was benzylated with three equivalents of benzyl bromide in DMF.
The targeted compound 2 was obtained with a yield of 17% after two chroma-
tographic steps, necessary to eliminate various mono-, di-, tri-, and tetra-
benzylated derivatives co-obtained. Considering this poor yield, we set up a
multistep synthesis experiment in which phloroglucinol carboxylic acid
was first protected as 5,7-dihydroxy-2,2-dimethyl-4H-1,3-benzodioxin-4-one
according to Dushin and Danishefsky with a yield of 34%.[9] The two
remaining free phenolic functionalities were then benzylated (benzyl
bromide, K2CO3, DMF, 91%), and 2 was finally obtained after deprotection
with benzyl alcoholate (benzylic alcohol, Na, 84%) in an overall yield of
26%, slightly higher than for the previous direct synthesis.
The synthesis of the three hydroxy-perbenzylated benzoic acids was then
set up as described in Scheme 3.
The three starting compounds (methyl gallate and protocatechuic and
p-hydroxy benzoic acids) were first perbenzylated (benzyl bromide, K2CO3,
dimethyl formamide (DMF), 91–92%) and then transformed to free
carboxylic acids (potassium hydroxide (KOH), EtOH/H2O, 80–98%).
The coupling reaction between 2 and the three different hydroxy-
perbenzylated benzoic acids 11, 12, and 13 was performed using N,N0-
dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) in
Scheme 4. a) DCC, DMAP, CH2Cl2, reflux, 85–95% yield; b) H2, Pd/C, THF, rt,
79–94% yield.

590
S. Tranchimand et al.
anhydrous CH2Cl2 (85–95%). A final deprotection step (Pd/C, H2, 79–94%)
afforded the three targeted depsides 17, 18, and 19 (Scheme 4).
Finally, the chemically neosynthesised depsides were then compared
to their enzymatically generated counterparts. Pure quercetinase was
added to a solution containing the three flavonols (myricetin, quercetin, and
kaempferol), and the products of the reaction were analysed by reverse-
phase high performance liquid chromatography (HPLC). Coinjection
of enzymatically generated and chemically synthesized depsides finally
established the identity of these compounds (Figure 1).
In conclusion we describe here the first chemical synthesis of three
naturally occuring depsides related to quercetinase activity and established
their identity to their enzymatically generated counterparts. On the basis of
this work, the analysis of quercetinase activity in complex media where
UV-spectroscopy is inapplicable is now possible. In this context with
chemical standards available, HPLC, alone or in conjunction with mass
spectroscopy, could be an extremely valuable tool both for biochemical and
biomimetic[10] studies on quercetinase activity.
Figure 1. Reverse phase (C18) HPLC chromatogramms set for the comparison
between enzymatically generated depsides 17, 18, and 19 (bottom) and coinjection
of the former with the same depsides, but chemically synthesized, added to get
chromatographic peaks of comparable intensity (top).

Synthesis of Three Natural Depsides
EXPERIMENTAL
591
Melting points were determined on an Electrothermal 9300 capillary melting-
point apparatus and are uncorrected. IR spectra were measured on KBr plates
on a Bruker IFS25 spectrophotometer. NMR spectra were recorded on Bruker
Avance DPX-300 (1H, 300 MHz; 13C, 75.5 MHz); chemicals shifts (d) are
reported in ppm relative to the NMR solvent. Microanalyses were
performed on a Thermo Finnigan EA 1112. Flash column chromatography
was carried out with silica gel 60 (Merck, particle size 230–400 mesh).
All reactions and chromatographic separations were monitored by TLC.
All reagents and solvents were commercially available (Acros or Aldrich).
N,N-dimethylformamide and THF were distilled under anhydrous conditions
before use; dichloromethane was purified on activated silica gel.
HPLC Conditions
HPLC analysis were conducted using a LiChrospher100 RP-18 (5 mm)
column from Agilent Technologies and an HP 1100 series system (DAD).
Solvent flow: 0.5 mL/min. Solvent gradient: 100% A to 40% A–60% B in
10 min and then to 100% B in 20 min (A: 90/10/0.1: water/acetonitrile/
acetic acid; B: 90/10/0.1: acetonitrile/water/acetic acid). The detection
was performed at 280 nm.
Depside Biosynthesis
MES buffer (2 ml, 0,1 M, pH ¼ 6) and 2 ml of a purified quercetinase solution
(0.141 U/mL) in the same buffer were added to a 1-mL solution of the three
flavonols (quercetin, kaempferol, and myricetin) in DMSO (at respectively
0.16, 0.03, and 0.34 mg/mL). The mixture was stirred for 1 h and then
analyzed by reverse-phase HPLC.
Benzyl 2,4-bis(Benzyloxy)-6-hydroxybenzoate (2)
Dry K2CO3 (16.23 g, 117.6 mmol) and benzyl bromide (14 ml, 117.7 mmol)
were added to a stirred solution of 2,4,6-trihydroxybenzoic acid monohydrate
(9 g, 47.9 mmol) 1 in DMF (250 ml) under argon. The mixture was stirred
overnight at room temperature; then a 0.5% HCl solution (750 ml) was
added and the mixture extracted with Et2O (6 ꢀ 250 ml). The combined
organic layers were washed with a 1.5% HCl solution (2 ꢀ 100 ml),
dried (Na2SO4), filtered, and concentrated in vacuo. Two successive flash
chromatographies (dichloromethane/n-pentane: 1/1 then dichloromethane)
afforded 2.937 g (17%) of 2 as a white solid. Mp: 123–1248C, Rf ¼ 0.36

592
S. Tranchimand et al.
(dichloromethane/n-pentane, 1:1). IR (KBr, cm21): 3031, 2967, 1648, 1312,
1
1296, 1213, 1199, 1165, 819, 697. H NMR (CDCl3) d: 4.99 (s, 2H), 5.02
(s, 2H), 5.34 (s, 2H), 6.12 (d, J ¼ 2.5 Hz, 1H), 6.20 (d, J ¼ 2.5 Hz, 1H),
7.19–7.43 (m, 15H), 1.04 (s, 1H); 13C NMR (CDCl3) d: 171.1, 166.0,
164.4, 161.2, 136.1, 135.9, 135.6, 128.6, 128.5, 128.4, 128.2, 128.1, 128.0,
127.8, 127.6, 127.3, 97.1, 94.6, 93.3, 70.7, 70.1, 66.8. Anal. calc. for
C28H24O5: C, 76.36; H, 5.45. Found: C, 76.42; H, 5.65.
5,7-Dihydroxy-2,2-dimethyl-4H-1,3-benzodioxin-4-one (3)
At 08C, anhydrous acetone (1 ml, 13.6 mmol) and trifluoroacetic anhydride
(5 ml, 36.0 mmol) were added to a stirred suspension of 2,4,6-trihydroxy-
benzoic acid (741.6 mg, 4.36 mmol) 1 in trifluoroacetic acid (8 ml,
107.7 mmol) under argon. The mixture was warmed slowly to room tempera-
ture and stirred for 5 h. The slightly yellow homogeneous mixture was then
concentrated in vacuo, poured into a saturated solution of NaHCO3
(100 ml), and extracted with ethyl acetate (2 ꢀ 100 ml). The combined
organic layers were washed with water (50 ml), dried (Na2SO4), filtered,
and concentrated in vacuo. Flash chromatography (n-pentane/ethyl acetate:
3/1) afforded 315 mg (34%) of 3 as a white solid. Mp: decomposition at
1958C, Rf ¼ 0.36 (n-pentane/ethyl acetate: 3/1). IR (KBr, cm21): 3200,
1645, 1505, 1271, 1172, 1094, 815, 843. 1H NMR (CD3OD) d: 1.70
(s, 6H), 5.91 (d, J ¼ 2.2 Hz, 1H), 6.00 (d, J ¼ 2.2 Hz, 1H); 13C NMR
(CD3OD) d: 168.3, 166.6, 164.4, 158.7, 108.0, 98.3, 96.5, 93.1, 25.7. Anal.
calc. for C10H10O5: C, 57.14; H, 4.80. Found: C, 57.19; H, 4.92.
5,7-bis(Benzyloxy)-2,2-dimethyl-4H-1,3-benzodioxin-4-one (4)
Dry K2CO3 (500 mg, 3.6 mmol) and benzyl bromide (0.25 ml, 2.1 mmol) were
added to a stirred solution of 3 (185 mg, 0.88 mmol) in N,N-dimethylforma-
mide (10 mL) under argon. The mixture was stirred overnight, then poured
in water (100 ml) and extracted with diethylether (3 ꢀ 100 ml). The
combined organic layers were washed with water (50 ml), dried (Na2SO4),
filtered, and concentrated in vacuo. Flash chromatography (dichloromethane)
afforded 313 mg (91%) of 4 as a white solid. Mp: 119–1208C, Rf ¼ 0.20
(dichloromethane). IR (KBr, cm21): 3062, 3027, 2999, 2990, 2944, 1728,
1
1618, 1579, 1271, 1169, 1119, 1033, 735, 718. H NMR (CDCl3) d: 1.70
(s, 6H), 5.02 (s, 2H), 5.19 (s, 2H), 6.14 (d, J ¼ 2.3 Hz, 1H), 6.26
(d, J ¼ 2.3 Hz, 1H), 7.25–7.55 (m, 10H); 13C NMR (CDCl3) d: 165.3,
161.7, 159.4, 157.9, 136.1, 135.5, 128.7, 128.6, 128.4, 127.8, 127.6, 126.6,
105.0, 97.4, 95.9, 94.7, 70.6, 70.4, 25.6. Anal. calc. for C24H22O5: C, 73.85;
H, 5.64. Found: C, 74.30; H, 5.85.

Synthesis of Three Natural Depsides
593
Benzyl 2,4-bis(Benzyloxy)-6-hydroxybenzoate (2)
Na (360 mg) was added to a stirred solution of benzyl alcohol (1.87 g,
17.3 mmol) in THF (50 ml, 08C). The suspension was stirred until Na disap-
peared; then 4 (1.411 g, 3.6 mmol) was added and the mixture was stirred
15 min at rt. The mixture was then concentrated in vacuo, poured into a
1.5% HCl solution (100 ml), extracted with diethylether (3 ꢀ 100 ml) and
ethyl acetate (100 ml), dried (Na2SO4), filtered, and concentrated in vacuo.
Flash chromatography (dichloromethane/n-pentane: 1/1) afforded 1.34 g
(84%) of 2 (same characteristics as before).
General Procedure for the Synthesis of Hydroxy-perbenzylated
Benzoic Esters (6, 8, 10)
Dry K2CO3 (3 g, 21.7 mmol) and benzyl bromide (2.6 ml, 21.9 mmol) were
added to a stirred solution of 3,4-dihydroxybenzoic acid (1 g, 6.5 mmol) 5
in N,N-dimethylformamide (20 ml) under argon. The mixture was stirred
overnight, then poured into water (100 ml) and extracted with diethyl ether
(3 ꢀ 100 ml). The combined organic layers were washed with water
(50 ml), dried (Na2SO4), filtered, and concentrated in vacuo. Flash chromato-
graphy (dichloromethane) afforded 2.5 g (91%) of 6 as a white solid. Mp:
66–678C, Rf ¼ 0.76 (dichloromethane). IR (KBr, cm21): 3068, 3037, 3029,
1
2855, 1693, 1516, 1432, 1290, 1216, 1140, 1024, 763, 741, 696. H NMR
(CDCl3) d: 5.18 (s, 2H), 5.20 (s, 2H), 5.31 (s, 2H), 6.91 (d, J ¼ 8.8 Hz, 1H),
7.24–7.49 (m, 15H), 7.66 (dd, J1 ¼ 8.8 Hz, J2 ¼ 2 Hz, 1H), 7.67 (d, J ¼ 2 Hz,
1H); 13C NMR (CDCl3) d: 166.0, 152.9, 148.3, 136.8, 136.5, 136.2, 128.6,
128.5, 128.4, 128.1, 128.0, 127.9, 127.8, 127.4, 127.1, 124.1, 123.0, 115.6,
113.2, 71.2, 70.8, 66.5. Anal. calc. for C28H24O4: C, 79.24; H, 5.66. Found: C,
79.33; H, 5.77.
Following the same procedure as described previously, from 7 (502 mg,
3.6 mmol), N,N-dimethylformamide (20 ml), K2CO3 (1.1 g, 8 mmol), and
benzyl bromide (0.87 ml, 7.3 mmol), 1.063 g of 8 (92%) were obtained as a
white solid. Mp: 117–1188C, Rf ¼ 0.74 (dichloromethane). IR (KBr,
cm21): 2970, 2952, 2891, 2876, 1698, 1604, 1509, 1275, 1243, 1170, 1109,
1003, 756, 704. 1H NMR (CDCl3) d: 5.11 (s, 2H), 5.33 (s, 2H), 6.98
(d, J ¼ 9 Hz, 2H), 7.28–7.52 (m, 10H), 8.03 (d, J ¼ 9 Hz, 2H); 13C NMR
(CDCl3) d: 166.1, 162.6, 136.3, 136.2, 131.7, 128.7, 128.5, 128.2, 128.1,
128.0, 127.4, 122.8, 114.5, 70.1, 66.4. Anal. calc. for C21H18O3: C, 79.24;
H, 5.66. Found: C, 79.62; H, 5.85.
Following the same procedure as described previously, from 9 (2.43 g,
13.2 mmol), N,N-dimethylformamide (50 ml), K2CO3 (12 g, 87 mmol), and
benzyl bromide (8 ml, 67.3 mmol), 5.38 g of 10 (92%) were obtained after
flash chromatography (dichloromethane/n-pentane: 1/1 then dichloromethane)
as a white solid. Mp: 97–988C, Rf ¼ 0.46 (dichloromethane/n-pentane: 1/1).

594
S. Tranchimand et al.
IR (KBr, cm21): 3033, 2949, 1717, 1589, 1428, 1335, 1216, 1112, 1003,
756. 1H NMR (CDCl3) d: 3.88 (s, 3H), 5.11 (s, 2H), 5.13 (s, 4H), 7.20–7.47
(m, 17H); 13C NMR (CDCl3) d: 166.6, 152.5, 142.4, 137.4, 136.6, 128.5,
128.4, 128.1, 128.0, 127.9, 127.5, 125.2, 109.1, 75.1, 71.2, 52.2. Anal. calc.
for C29H26O5: C, 76.65; H, 5.73. Found: C, 76.88; H, 5.81.
General Procedure for the Synthesis of Hydroxy-perbenzylated
Benzoic Acids (11, 12, 13)
KOH (1.5 g, 27 mmol) was added to a stirred solution of 6 (2.3 g, 5.4 mmol) in
water (20 ml) and ethanol (80 ml). The mixture was refluxed for 1 h until it
became homogeneous and then concentrated in vacuo. The residue was
poured into water (100 ml) and washed with diethyl ether (2 ꢀ 50 ml). The
organic phases were discarded, and the aqueous phase acidified with concen-
trated H2SO4 until the formation of a white solid in suspension. The mixture
was extracted with diethyl ether (3 ꢀ 100 ml) and ethyl acetate (2 x 100 ml).
The combined organic layers were washed with a solution of 1.5% HCl
(100 ml), dried (Na2SO4), filtered, and concentrated in vacuo to give 1.777 g
(98%) of 11 as a white solid. Mp: 187–1888C. IR (KBr, cm21): 3091,
3064, 3031, 2906, 2865, 1677, 1601, 1521, 1441, 1306, 1277, 1226, 1135,
1
1025, 761, 729, 693. H NMR (DMSO-D6) d: 5.18 (s, 2H), 5.22 (s, 2H),
7.15 (d, J ¼ 8.9 Hz, 1H), 7.28–7.50 (m, 10H), 7.56 (dd, J1 ¼ 8.9 Hz,
J2 ¼ 2 Hz, 1H), 7.57 (d, J ¼ 2 Hz, 1H), 12.7 (brs, H); 13C NMR (DMSO-D)
d: 166.9, 152.0, 147.5, 136.9, 136.6, 128.4, 128.3, 127.8, 127.7, 127.5,
127.4, 123.4, 123.2, 114.5, 113.0, 69.9, 69.8. Anal. calc. for C21H18O4: C,
75.45; H, 5.39. Found: C, 75.26; H, 5.53.
Following the same procedure as described previously, from 8 (1.041 g,
3.3 mmol), water (10 ml), ethanol (30 ml), and KOH (5 g, 89 mmol), 598 mg
of 12 (80%) were obtained after flash chromatography (diethyl ether/n-
pentane/acetic acid: 50/50/0.2, then dichloromethane/methanol: 7/3) as a
white solid. Mp: 191–1928C. IR (KBr, cm21): 3063, 3038, 2667, 2558,
1
1685, 1608, 1258, 1169, 772, 738, 693, 656. H NMR (DMSO-D6) d: 5.18
(s, 2H), 7.10 (d, J ¼ 8.8 Hz, 2H), 7.30–7.50 (m, 5H), 7.90 (d, J ¼ 8.8 Hz,
2H), 12.45 (brs, 1H); 13C NMR (DMSO-D6) d: 166.9, 161.8, 136.4, 131.3,
128.4, 127.9, 127.7, 123.1, 114.5, 69.4. Anal. calc. for C14H12O3: C, 73.68;
H, 5.26. Found: C, 73.92; H, 5.50.
Following the same procedure as described previously, from 10 (5.38 g,
11.9 mmol), water (100 ml), ethanol (300 ml), and KOH (15 g, 268 mmol),
4.15 g of 13 (80%) were obtained after recrystallization from dichloromethane
as a white solid. Mp: 195–1968C. IR (KBr, cm21): 3089, 3065, 3030, 2867,
1686, 1595, 1431, 1338, 1129, 735, 694. 1H NMR (DMSO-D6) d: 5.05
(s, 2H), 5.18 (s, 4H), 7.24–7.52 (m, 17H), 12.96 (brs, 1H); 13C NMR
(DMSO-D6) d: 166.8, 151.9, 140.9, 137.3, 136.8, 128.3, 128.1, 128.0,

Synthesis of Three Natural Depsides
595
127.8, 127.5, 125.9, 108.1, 74.1, 70.1. Anal. calc. for C28H24O5: C, 76.36; H,
5.45. Found: C, 76.40; H, 5.55.
General Procedure for the Synthesis of Perbenzylated
Depsides (14–16)
To a stirred solution of 11 (1.04 g, 3.1 mmol) in dichloromethane (50 ml)
was added 2 (864 mg, 1.96 mmol), N,N-dimethylaminopyridine (248 mg,
2.03 mmol) and N,N0-dicyclohexylcarbodiimide (740 mg, 3.6 mmol). The
mixture was refluxed overnight. Then ethanol (1 ml) and acetic acid (1 ml)
were added; the mixture was refluxed for 2 h and concentrated in vacuo.
Flash chromatography (dichloromethane) afforded 1.329 g (88%) of 14 as a
white solid. Mp: 97–988C, Rf ¼ 0.56 (dichloromethane). IR (KBr, cm21):
3090, 3064, 3031, 2932, 2881, 1726, 1616, 1275, 1187, 1175, 1127, 1096,
1
749, 730, 699. H NMR (CDCl3) d: 4.98 (s, 2H), 5.06 (s, 2H), 5.10 (s, 2H),
5.13 (s, 2H), 5.23 (s, 2H), 6.46 (d, J ¼ 2.1 Hz, 1H), 6.49 (d, J ¼ 2.1 Hz,
1H), 6.90 (d, J ¼ 9 Hz, 1H), 7.16 (m, 5H), 7.24–7.52 (m, 20H), 7.61 (dd,
J1 ¼ 9 Hz, J2 ¼ 2 Hz, 1H), 7.62 (d, J ¼ 2 Hz, 1H); 13C NMR (CDCl3) d:
164.3, 164.1, 161.3, 158.3, 153.3, 150.9, 148.3, 136.7, 136.4, 136.1, 135.9,
135.4, 128.6, 128.5, 128.2, 128.1, 128.0, 127.9, 127.8, 127.7, 127.5, 127.4,
127.04, 127.03, 124.8, 121.6, 115.5, 113.1, 110.2, 101.4, 98.9, 70.9, 70.71,
70.68, 70.3, 66.9. Anal. calc. for C49H40O8: C, 77.78; H, 5.29. Found: C,
77.42; H, 5.50.
Following the same procedure as described previously, 145 mg of 15
(95%) were obtained as a white solid from 12 (78 mg, 0.34 mmol),
dichloromethane (10 ml), N,N-dimethylaminopyridine (30 mg, 0.24 mmol),
N,N0-dicyclohexylcarbodiimide (78.2 mg, 0.38 mmol), and 2 (100.7 mg,
0.23 mmol). Mp: 97–988C, Rf ¼ 0.66 (dichloromethane). IR (KBr, cm21):
3090, 3064, 3032, 1735, 1614, 1259, 1167, 1089, 738, 697. 1H NMR
(CDCl3) d: 4.98 (s, 2H), 5.04 (s, 2H), 5.11 (s, 2H), 5.15 (s, 2H), 6.49
(s, 2H), 6.95 (d, J ¼ 8.9 Hz, 2H), 7.05–7.46 (m, 20H), 7.98 (d, J ¼ 8.9 Hz,
2H); 13C NMR (CDCl3) d: 164.4, 164.1, 162.9, 161.2, 158.3, 150.9, 136.2,
136.1, 135.9, 135.5, 132.3, 128.64, 128.59, 128.5, 128.2, 127.83, 127.80,
127.5, 127.4, 127.1, 121.5, 114.6, 110.3, 101.4, 98.8, 70.7, 70.3, 70.1, 66.9.
Anal. calc. for C42H34O7: C, 77.54; H, 5.23. Found: C, 77.75; H, 5.58.
Following the same procedure as described previously, 170 mg of 16
(85%) were obtained as a white solid from 13 (150 mg, 0.34 mmol),
dichloromethane (10 ml), N,N-dimethylaminopyridine (33.6 mg, 0.28 mmol),
N,N0-dicyclohexylcarbodiimide (75.2 mg, 0.37 mmol), and 2 (100.7 mg,
0.23 mmol). Mp: 132–1338C, Rf ¼ 0.52 (dichloromethane). IR (KBr,
cm21): 3089, 3065, 3032, 1732, 1614, 1427, 1262, 1187, 1161, 1119, 753,
1
733, 698. H NMR (CDCl3) d: 5.02 (s, 2H), 5.09 (s, 2H), 5.16 (s, 2H), 6.46
(d, J ¼ 2.1 Hz, 1H), 6.52 (d, J ¼ 2.1 Hz, 1H), 7.05–7.49 (m, 32H);
13C NMR (CDCl3) d: 164.3, 164.1, 161.4, 158.6, 152.5, 150.9, 143.0, 137.4,

596
S. Tranchimand et al.
136.6, 136.2, 135.9, 135.4, 128.7, 128.6, 128.5, 128.3, 128.21, 128.16, 128.04,
127.98, 127.93, 127.85, 127.6, 127.1, 123.9, 110.2, 109.5, 101.4, 99.1, 75.1,
71.1, 70.9, 70.4, 67.0. Anal. calc. for C56H42O9: C, 77.96; H, 4.87. Found:
C, 77.87; H, 5.42.
General Procedure for Depsides Deprotection (17, 18, 19)
In a Schlenk tube, 14 (1.18 g, 1.6 mmol), THF (10 ml), and Pd/C 3% (1 g)
were mixed. The reaction vessel was capped with a septum, vacuum was
applied, and the Schlenck tube was filled with hydrogen. The suspension
was stirred overnight. Pd/C was then filtered on Whatman paper and THF
evaporated in vacuo to afford 447 mg of 17 (94%) as a white solid. Mp:
decomposition at 1658C. IR (KBr, cm21): 3441, 1719, 1696, 1652, 1606,
1455, 1313, 1272, 1224, 1198, 1106, 748. 1H NMR (CD3OD) d: 6.12
(d, J ¼ 2.4 Hz, 1H), 6.26 (d, J ¼ 2.4 Hz, 1H), 6.85 (d, J ¼ 8.9 Hz, 1H), 7.56
(dd, J1 ¼ 2.1 Hz, J2 ¼ 8.9 Hz, 1H), 7.55 (d, J ¼ 2.1 Hz, 1H); 13C NMR
(CD3OD) d: 172.5, 167.2, 166.6, 164.8, 154.9, 152.2, 146.3, 124.5, 122.3,
118.0, 116.0, 104.6, 101.7, 100.6.
Following the same procedure as described previously, 80 mg of 18 (79%)
were obtained as a white solid from 15 (229 mg, 0.35 mmol), THF (5 ml), and
Pd/C 3% (200 mg). Mp: decomposition at 1618C. IR (KBr, cm21): 3364,
1
3232, 1696, 1637, 1607, 1446, 1276, 1192, 1095, 1028, 839, 625. H NMR
(CD3OD) d: 6.13 (d, J ¼ 2.4 Hz, 1H), 6.26 (d, J ¼ 2.4 Hz, 1H), 6.87
(d, J ¼ 8.8 Hz, 2H), 7.99 (d, J ¼ 8.8 Hz, 2H); 13C NMR (CD3OD) d: 172.5,
167.1, 166.6, 164.8, 164.0, 154.9, 133.5, 122.0, 116.3, 104.6, 101.7, 100.7.
Following the same procedure as described previously, 70 mg of 19
(87%) were obtained as a white solid from 16 (218.3 mg, 0.25 mmol), THF
(5 ml), and Pd/C 3% (200 mg). Mp: decomposition at 1658C. IR (KBr,
1
cm21): 3428, 2541, 1721, 1696, 1653, 1446, 1282, 1046, 749. H NMR
(CD3OD) d: 6.13 (d, J ¼ 2.4 Hz, 1H), 6.27 (d, J ¼ 2.4 Hz, 1H), 7.19
(s, 2H); 13C NMR (CD3OD) d: 172.4, 167.4, 166.5, 164.8, 154.9, 146.5,
140.2, 121.1, 110.8, 104.5, 101.7, 100.6.
ACKNOWLEDGMENT
`
This work was supported by a grant (No. 10659) to S. T. The Ministere
`
´ ´ ´ ` ´
Delegue a l’Enseignement Superieur et a la Recherche is gratefully
acknowledged.
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