Syntheses of methylated catechins and theaflavins using 2-nitrobenzenesulfonyl group to protect and deactivate phenol

Article abstract of DOI:10.1038/ja.2016.14

An efficient and versatile synthetic method for labile polyphenols was established using 2-nitrobenzenesulfonate (Ns) as a protecting group for phenol. This methodology provides regio-and stereoselective access to a range of methylated catechins, such as methylated epigallocatechin gallates, that are not readily available from natural sources. In addition, biomimetic synthesis of theaflavins from catechins was accomplished using Ns protection to minimize undesired side reactions of electron-rich aromatic rings during oxidation, enabling construction of the complex benzotropolone core in a single-step oxidative coupling reaction. Availability of these compounds will aid detailed structure-biological activity relationship studies of catechins.

Full text of DOI:10.1038/ja.2016.14

The Journal of Antibiotics (2016), 1–14
2016 Japan Antibiotics Research Association All rights reserved 0021-8820/16
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ORIGINAL ARTICLE
Syntheses of methylated catechins and theaflavins
using 2-nitrobenzenesulfonyl group to protect and
deactivate phenol
Tomohiro Asakawa1, Yusuke Kawabe1, Atsushi Yoshida1, Yoshiyuki Aihara1, Tamiko Manabe1,
Yoshitsugu Hirose1, Asuka Sakurada1, Makoto Inai1, Yoshitaka Hamashima1, Takumi Furuta1,2,
Toshiyuki Wakimoto1,3 and Toshiyuki Kan1
An efficient and versatile synthetic method for labile polyphenols was established using 2-nitrobenzenesulfonate (Ns) as a
protecting group for phenol. This methodology provides regio- and stereoselective access to a range of methylated catechins,
such as methylated epigallocatechin gallates, that are not readily available from natural sources. In addition, biomimetic
synthesis of theaflavins from catechins was accomplished using Ns protection to minimize undesired side reactions of
electron-rich aromatic rings during oxidation, enabling construction of the complex benzotropolone core in a single-step oxidative
coupling reaction. Availability of these compounds will aid detailed structure–biological activity relationship studies of catechins.
The Journal of Antibiotics advance online publication, 24 February 2016; doi:10.1038/ja.2016.14
INTRODUCTION
(4′-Me-EGCg: 3) exhibit potent inhibitory activities towards type I
allergic reactions in mice5,6 and matrix metalloproteinases,7,8 it seems
likely that other methylated catechin derivatives may also have
therapeutic potential.9–11
Synthetic methods for polyphenols have been extensively studied,
because these compounds possess an array of interesting biological
activities, including anticancer, antiviral and antimicrobial activities.
Nevertheless, only a few efficient and versatile synthetic methods are
available, both because the highly polar nature of polyphenols makes
handling difficult, and because of the susceptibility of the compounds
to oxidation. Protection of the hydroxyl groups of polyphenol is
indispensable during usual chemical transformations and also during
purification. Thus, selection of a suitable protecting group is critical.
In this context, the 2-nitrobenzenesulfonate (Ns) group1 should be an
excellent protecting group for labile polyphenols, because it can be
easily removed under mild conditions. Furthermore, its electron-
withdrawing nature should enhance the stability of polyphenols during
synthetic manipulations. Herein, we report efficient syntheses of a
range of methylated catechins (2 and 3) and theaflavins (4 and 5) by
exploiting the Ns group for protection of phenols.
Compounds 2 and 3 are readily available from natural and synthetic
sources,12,13 and investigations of structure–activity relationships have
so far been limited to these compounds. However, synthesis of all
possible regio- and stereoisomers of the naturally available methylated
catechins (EGC: epigallocatechin, GC: gallocatechin, EC: epicatechin
and CC: catechin) would allow systematic evaluation of the structure–
biological activity relationships. Hence, we are interested in concise
synthesis of methylated catechins (2, 3 and 6–13). Although synthetic
investigations of the catechin skeleton have been reported by many
groups,2 including ours,14,15 derivation of methylated catechins
from natural catechins, such as EGC16 and other derivatives (GC,
EC and CC), which are inexpensive and readily available, should be a
convenient and effective strategy.
Our synthetic plan is illustrated in Scheme 1. A key issue is selecting
a suitable protecting group for phenol. Although benzyl ether has been
employed for catechin synthesis because it is readily deprotectable
under hydrogenolysis conditions, ether formation of phenol is often
troublesome: for example, epimerization of the 2-position can occur
under basic conditions (Scheme 2). To make matters worse, electron-
rich aromatics readily undergo undesired electrophilic substitution
and unexpected oxidation at the benzylic position. Thus, a major
RESULT AND DISCUSSION
Synthesis of methylated cathechins
Epigallocatechin gallate (EGCg: 1), which has various biological
activities, including cancer-preventive, antiviral and antimicrobial
activities, is a major component of catechin derivatives derived from
tea (Figure 1).2–4 Recently, various methylated derivatives, such as
(–)-3′-methyl-epigallocatechin gallate (3′-Me-EGCg: 2), have been
identified as minor catechins in natural tea leaves and as mammalian
metabolites of tea catechins.4 Because
2 and its regioisomer concern in polyphenol synthesis is how to avoid these problems.
1School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan; 2Institute for Chemical Research, Kyoto University, Kyoto, Japan and 3Faculty of Pharmaceutical
Sciences, Hokkaido University, Hokkaido, Japan
Correspondence: Professor T Kan, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
E-mail: kant@u-shizuoka-ken.ac.jp
Received 8 December 2015; revised 26 January 2016; accepted 26 January 2016

Syntheses of methylated catechins and theaflavins
T Asakawa et al
2
catechines
R1 R2 R3 R4
OH OH OH OH
OH OH OMeOH
OH OH OH OMe
OH OMeOH OH
OMeOH OH OH
OH H OMeOH
OH H OH OMe
OH OH OMeOH
OH OH OH OMe
(–)-EGCg (1): 2,3-cis
OH
(–)-3''-Me-EGCg (2): 2,3-cis
(–)-4''-Me-EGCg (3): 2,3-cis
(–)-3'-Me-EGCg (6): 2,3-cis
(–)-4'-Me-EGCg (7): 2,3-cis
(–)-3''-Me-ECg (8): 2,3-cis
(–)-4''-Me-ECg (9): 2,3-cis
(–)-3''-Me-GCg (10): 2,3-trans
(–)-4''-Me-GCg (11): 2,3-trans
(+)-3''-Me-CCg (12): 2,3-trans
(+)-4''-Me-CCg (13): 2,3-trans
3'
R1
R2
4'
2
HO
O
O
3
3"
OH
R3
O
4
4"
R
OH H OMeOH
OH H OH OMe
OH
Figure 1 EGCg (1) and methylated catechins.
O
R
OPG
OPG
R
HO
OPG
OPG
OPG
OPG
15
PGO
O
OMe
PGO
O
EDCI, DMAP
deprotection
Me-catechins
O
OH
MeCN
OPG
OPG
OPG
O
PG = protecting group
OPG
14
16
OMe
Scheme 1 Plan for practical synthesis of methylated catechins.
·Epimerization via quinonmethide
R
R
R
B
H
OH
OH
O
O
2
HO
O
2
3
HO
O
O
OH
OH
OR
3
OR
OR
Quinonmethide
OH
OH
·Electrophilic substitution and oxidation
R
R
E+
OH
OH
OH
OH
E
HO
O
HO
O
OR
oxidation
OR
OH
OH
O
Scheme 2 Potential issues in catechin synthesis.
The Ns group should be an excellent protecting group for labile with allyl alcohol and EDCI. Upon treatment of 20 with Li2CO3 and
polyphenols because it can be easily deprotected under mild methyl iodide, selective deprotonation and alkylation of the most
conditions.1,17–19 Furthermore, the electron-withdrawing nature of acidic 4-OH proceeded smoothly to give 21. On the other hand, 3-OH
the Ns group should improve the stability of polyphenol during selective alkylation was achieved by utilizing a bridged boronic ester
synthetic manipulations. A preliminary investigation of deprotection intermediate20 between the o-phenolic hydroxyl groups. After
of 4-(((2-nitrophenyl)sulfonyl)oxy)benzyl acetate (17) showed that formation of the boronic ester 23 by treating 20 with borax in the
selective deprotection of the Ns group could be achieved in the presence of NaOH, methylation with Me2SO4 and subsequent acidic
presence of the ester group (Scheme 3). Thus, protection of phenols hydrolysis of the boronic ester exclusively provided 24. Ns groups were
with Ns group should be effective for the synthesis of methylated incorporated into the resultant phenols 20, 21 and 24 by treatment
catechins.
with NsCl and Et3N. Treatment of the allyl esters with catalytic
Therefore, we next investigated selective incorporation of the amounts of Pd(PPh3)4 and p-tolSO2Na21 resulted in smooth depro-
methyl group at 3- and 4-OH of allyl gallate (20), as shown in tection of the allyl group to afford the desired 26, 22 and 25,
Scheme 4. Gallic acid (19) was converted to allyl ester 20 by reaction respectively.
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Syntheses of methylated catechins and theaflavins
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Next, we focused on incorporating gallate derivatives 22 and 25 into three equivalents of NsCl and excess H3BO3 in the presence of
NaOH23 resulted in regioselective sulfonylation to afford predomi-
protected epigallocatechin derivatives and deprotection of the Ns
nantly 3′,5,7-Ns-EGCg (32).
group (Scheme 5). Protection of EGC (27) with the Ns group was
carried out with NsCl and Et3N to provide 28. Condensation reaction
of 28 with 25 and EDCI in the presence of a catalytic amount of
DMAP proceeded smoothly to provide the desired 29 in high yield.
Similar condensation of 28 and 22 provided the 4′-methylated EGCg
derivative 30. Deprotection of the Ns groups of 29 and 30 was
accomplished with the use of thiophenol and cesium carbonate to
provide 3′-methylated EGCg (2) and 4′-methylated EGCg (3),
respectively. During this transformation, neither epimerization at the
2-position of the benzopyran ring nor decomposition of gallate ester
was observed. A similar protocol provided the desired methylated
gallate catechin derivatives 8–13 from natural catechin derivatives GC,
EC and CC (Table 1).22
Then, we turned our attention to selectively introducing a methyl
group into the B-ring (Scheme 6). To our knowledge, (–)-EGCg
derivatives methylated at the B-ring have not yet been reported, so an
SAR study of these compounds should be interesting. We found that a
bridged boronic ester intermediate effectively distinguishes the
hydroxyl groups at the A-ring and B-ring. Treatment of 27 with
Next, selective incorporation of the TBDPS group at the less
hindered hydroxyl group (5′-OH) was accomplished by treating 32
with TBDPSCl and Et3N to give 33 (Scheme 7). The 4′-Me-EGCg
derivative was prepared by methylation of 33 with diazomethane,
condensation of 35 with Ns-protected gallic acid 26,24 and
stepwise deprotection of TBDPS group and Ns group, affording
4′-Me-EGCg (7).
3′-Me-EGCg (6) and 3′,3′-diMe-EGCg (38) were also synthesized
from 33. Protection of 33 with Ns proceeded at the 4′-hydroxyl group.
Deprotection of the TBDPS group and incorporation of a methyl
group afforded 37. Although condensation of 37 with 26 and
deprotection of Ns groups readily provided 3′-Me-EGCg (6),
we chose to employ a modified preparation with double-methylated
derivatives. After condensation of 37 and 25, deprotection of Ns
groups was accomplished using 2-aminothiophenol (39) instead of
thiophenol to afford 3′,3′-diMe- EGCG (38; Table 1).25,26 For a review
on recent progress in the synthesis of the advantage of this method is
that 39 is odorless compared with thiophenol. Furthermore, the
by-product, 2-(2-nitrophenylthio)aniline (40), can be easily removed
by washing the ethereal layer with 1 M HCl solution.
PhSH
Combining the selective methylation strategies for the B- and
D-rings of EGCg should provide access to several types of double-
methylated EGCg derivatives. Furthermore, this regioselective
modification of EGCg should be applicable for alkylation as well as
acylation; thus, it should be possible to apply this synthetic strategy to
Cs2CO3
ONs
OH
AcO
AcO
MeCN
70%
17
18
Scheme 3 Selective deprotection of O-Ns group.
Allyl alcohol
EDCI
DMAP
OH
OH
OH
OH
3
1) NsCl, Et3N
MeCN
ONs
MeI
Li2CO3
O
O
O
4
O
4
4
OH
OH
OMe
OMe
HO
AllylO
AllylO
2) Pd(PPh3)4
p-tolSO2Na
MeCN, H2O
HO
DMF
68%
87%
OH
OH
ONs
19
22
21
20
82% (2 steps)
OH
O
O
R1O
ONs
ONs
ONs
1) NsCl, Et3N
MeCN
B
R
O
O
23
OMe
3 OMe
3
borax
NaOH aq.
20
O
O
HO
1) NsCl, Et3N
2) Pd(PPh3)4
p-tolSO2Na
MeCN, H2O
OH
OH
ONs
ONs
26
; Me2SO4
; conc. H2SO4
85%
AllylO
HO
2) Pd(PPh3)4
p-tolSO2Na
MeCN, H2O
86% (2 steps)
25
24
95% (2 steps)
Scheme 4 Synthesis of selectively methylated gallic acids.
O
ONs
ONs
OR2
HO
ONs
ONs
OR
OR
OR1
NsO
O
25, 22
PhSH
Cs2CO3
(–)-3''-Me-EGCg (2)
(81% from 29)
RO
O
OR
O
EDCI, DMAP
MeCN
ONs
ONs
OR2
OH
O
MeCN
0 °C
(–)-4''-Me-EGCg (3)
(81% from 30)
RO
OR1
NsCl, Et3N
MeCN, -20 °C
94%
27: R = H
29: R1 = Me, R2 = Ns (92%)
30: R1 = Ns, R2 = Me (97%)
28: R = Ns
Scheme 5 Synthesis of 3′-Me-EGCg (2) and 4′-Me-EGCg (3).
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Syntheses of methylated catechins and theaflavins
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Table 1 Versatile synthesis of methylated catechins
OH
ONs
OH
OH
OH
OH
OH
HO
HO
O
O
NsCl
(3 eq)
B
OH
OH
B
HO
O
NsO
O
HO
O
NaOH aq.
; H2SO4
40%
OH
OH
OH
31
OH
ONs
OH
27
32
Scheme 6 Selective incorporation of Ns group via bridged boronic ester intermediate.
other natural catechins (GC, EC and C) to construct a diverse catechin
Recently, Nakatsuka and Yanase’s group reported a novel oxidative
coupling of o-quinone 45 and pyrogallol derivative 46 based on their
proposed biosynthetic pathway,35 as shown in Scheme 8. Although
their model reaction proceeded in excellent yield, its application to the
synthesis of theaflavin has not been reported to date. This is probably
because oxidation precursors and theaflavin itself are unstable under
strongly oxidizing conditions. We envisioned that the application of
our Ns group16–19 for protecting reactive phenols would enable
efficient synthesis of theaflavins from catechins.
library.
Synthesis of theaflavins
Theaflavin (4) is an oxidative dimer of catechin derivatives
(Figure 2),27–30 which is found in black tea. It has a number of
biological activities.31 Although many synthetic studies of catechin
derivatives have been reported,32–34 there are only a few reports of the
synthesis of 4 by means of enzymatic oxidation.32,35
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Syntheses of methylated catechins and theaflavins
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ONs
ONs
OH
ONs
3
4
OH
OH
3
OMe
OR1
4
TBDPSCl
Et3N
NsO
O
NsO
O
5
NsO
O
OR1
CH2N2
5
Et2O
MeCN
91%
OH
MeCN
83%
OH
R1 = TBDPS
OH
R1 = TBDPS
ONs
ONs
33
ONs
32
35
1) NsCl Et3N,MeCN, H2O
95%
Ns
O
2) TBAF, AcOH, THF
86%
OH
OH
ONs
ONs
ONs
ONs
NsO
O
OH
NsO
O
NsO
O
CH2N2
OH
OMe
3
ONs
Et2O
MeCN
91%
34
OH
OH
ONs
ONs
36
37
Scheme 7 Synthesis of selectively methylated epigallocatechin.
OH
HO
O
OH
OH
OH
Fetizon reagent
CH2Cl2
O
O
Me
Me
HO
O
44
45
OH
OH
2
3
O
HO
O
O
Me
O
O
Me
OH
O
OH
OH
Me
OH
OH
+H2O
-CO2
OH
45
HO
theaflavin (4): 2,3-cis
neotheaflavin (5): 2,3-trans
Figure 2 Structures of theaflavine (4) and neotheaflavine (5).
Me
Me
OH
Me
OH
OH
46
OH
47
48
Scheme 8 Coupling reaction of o-quinone 45 and pyrogallol derivative 46
reported by Nakatsuka and Yanase.
For the synthesis of theaflavin, we initially investigated selective
incorporation of the Ns group into the A-ring of CC (49), EC (50)
and EGC (27), as shown in Table 2.
enhance the stability of the A-ring during the reaction with the
strong oxidant Pb(OAc)4. Although other various oxidants (such as
Fetizon reagent and PhI(OAc)2) were tested, they did not efficiently
provide the o-quinone for the next reaction without the need for
purification.
Next, we tested the coupling reaction of quinone 55 with pyrogallol
derivative 53 (Scheme 11). As quinone 55 was labile during
purification, crude 55 was used directly for the coupling reaction.
Gratifyingly, treatment of three equivalents of 55 with 53 in a mixture
of MeCN and CH2Cl2, followed by addition of H2O, provided the
desired 56 in moderate yield. Considering the reaction mechanism
shown in Scheme 12, at least two equivalents of o-quinone should
theoretically be consumed in the two oxidation steps (58–59 and
61–62). Furthermore, addition of MS3A to the reaction mixture
before the addition of H2O was essential for efficient conversion.
MS3A might have a significant role in the oxidation step from 58 to
Regioselective protection of the A-ring with a Ns group was
performed utilizing the bridged boronic ester intermediate 5411
between neighboring phenolic hydroxyl groups on the B-ring
(Scheme 9). Thus, after formation of the boronic ester by treatment
of 27 with boronic acid in the presence of NaOH, reaction with two
equivalents of NsCl and subsequent acidic hydrolysis of boronic ester
exclusively provided 53 (Table 2, entry 3). Although the boronic ester
intermediate of 27 possesses a remaining phenolic hydroxyl group on
the B-ring, steric hindrance appears to prevent reaction with NsCl.
Similar reactions of 49 and 50 proceeded smoothly to provide 51 and
52 (entries 1 and 2).
Having succeeded in selective protection of the A-ring, the next
challenge is oxidation of the catechol group in 51 and 52. First, we
optimized the oxidation conditions using 51, which is derived from
less expensive 49. As shown in Scheme 10, the best result was obtained 59, although the mechanism involved remains to be established. After
by oxidation with Pb(OAc)4 in MeCN at 0 °C, affording the desired separation from 51 (generated by reduction of 55), deprotection of the
quinone 55 in good yield. Utilizing Pb(OAc)4 as an oxidant has the Ns group of 56 was accomplished by treatment with thiophenol and
advantage that lead derivatives can be easily removed from the cesium carbonate to provide neotheaflavin (5). No decomposition of
reaction medium by celite filtration after completion of the reaction. the reactive benzotropolone ring was observed during the coupling
Furthermore, the electron-withdrawing nature of the Ns group would and deprotection processes.
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Syntheses of methylated catechins and theaflavins
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Table 2 Regioselective incorporation of Ns group into the A-ring of catechins
R
R
R
HO
HO
OH
OH
OH
OH
O
O
B
OH
NsCl
B OH
NsO
O
HO
O
HO
O
OH
OH
OH
54
ONs
51, 52, 53
R = H or OH
(See Table 2)
OH
49, 50, 27
OH
Scheme 9 Regioselective incorporation of Ns group into the A-ring.
This benzotropolone ring-forming reaction was also applicable to EXPERIMENTAL SECTION
General experimental details
the synthesis of theaflavin (4) and its derivatives, as shown in
Scheme 13. Upon treatment of Ns-protected epicatechin (52) with
Pb(OAc)4, the desired oxidation reaction proceeded smoothly to
provide the o-quinone 63. The coupling reaction with 53 was carried
out without purification of the o-quinone intermediate 63 to give
benzotropolone intermediate 64. Finally, deprotection of Ns group
afforded theaflavin (4).36 The lower yield of 4 in comparison with 5
NMR [1H NMR (270 MHz), 13C NMR (68 MHz)] spectra were determined on
a JEOL EX-270 instrument (Tokyo, Japan), and [1H NMR (500 MHz), 13C
NMR (125 MHz)] spectra were determined on JEOL α-500 instrument (Tokyo,
1
Japan). Chemical shifts for H NMR were reported in p.p.m. downfields from
tetramethylsilane (δ) as the internal standard and coupling constants are in
hertz (Hz). The following abbreviations are used for spin multiplicity:
s = singlet, d = doublet, t = triplet, q = quartet, m= multiplet, br= broad. Che-
might be a result of instability of the o-quinone intermediate derived mical shifts for 13C NMR were referenced to solvent peaks: δC 77.0 for CDCl3,
δC 29.8 for acetone-d6, δC 118.3 for CD3CN and δC 49.0 for CD3OD. HR-MS
were obtained on either JEOL MStation JMS-700 or JMS-GCmate II (Tokyo,
Japan). Fast atom bombardment (FAB) mass spectra were obtained with a
mixture of 3-nitrobenzylalcohol and magic bullet as a matrix.
Analytical TLC was performed on Merck (Tokyo, Japan) precoated analytical
plates, 0.25-mm thick, silica gel 60 F254. Preparative TLC separations were
from cis-benzopyran 52.
This oxidation–coupling strategy was also applied to the coupling
between pyrogallol (65) and gallate 66 to give 67 and 68, respectively
(Table 3). As compounds similar to 68, which is derived from oxi-
dative coupling with gallate derivatives, have been isolated from tea,8
this method would be useful to synthesize derivatives for SAR study.
In summary, we have shown that the Ns group is an excellent
protecting group for labile polyphenols; it can be easily deprotected
under mild conditions, and its electron-withdrawing nature improves
the stability of polyphenol during synthetic manipulations. Utilizing
the Ns group to protect phenols and to block undesired oxidation
reactions, we were able to develop an efficient and practical method
for regio- and stereoselective methylation of catechins and theaflavins.
Further applications, as well as structure–biological activity relation-
ship studies of the synthesized derivatives, are under investigation in
our laboratory.
made on 7 × 20-cm plates prepared with a 0.25-mm layer of Merck silica
gel 60 F254. Compounds were eluted from the adsorbent with 10% methanol
in chloroform. Column chromatography was carried out with KANTO
CHEMICAL (Tokyo, Japan) Silica Gel 60 N (spherical, neutral) 63–210 μm.
Reagents and solvents were commercial grades and were used as supplied with
following exceptions: dichloromethane, diethylether, n-hexane, tetrahydrofuran
and toluene, dried over molecular sieves 4A. All reactions sensitive to oxygen or
moisture were conducted under an argon atmosphere.
Experimental procedures and characterization data
Allyl gallate (20). To
a mixture of gallic acid monohydrate (50.0 g,
266 mmol), 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride
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Syntheses of methylated catechins and theaflavins
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(EDCI) (61.2 g, 319 mmol) and 4-Dimethylaminopyridine (DMAP) (3.25 g, washed with brine, dried over anhydrous sodium sulfate and evaporated under
reduced pressure. The residue was purified by silica gel flash column
chromatography (1–3% MeOH in CH2Cl2) to afford 21 (1.83 g, 68%) as a
colorless solid. HR-MS (FAB) calculated for C11H12O5 [M]+ 224.0685, found
26.6 mmol) was added allyl alcohol (200 ml) at room temperature, then heated
at 60 °C for 4 h. The resulting mixture was quenched with 2 N HCl and
extracted with ethyl acetate. The combined organic phases were washed with
saturated NaHCO3, dried over anhydrous sodium sulfate and evaporated under
reduced pressure. The residue was recrystallized from ethyl acetate to afford 20
(48.7 g, 87%) as a light tan solid. HR-MS (FAB) calculated for C10H11O5 [M
+H]+211.0606, found 211.0593; IR (neat) 3367, 1701, 1610, 1388, 1256,
1198 cm− 1; 1H NMR (270 MHz, acetone-d6) δ 7.13 (2H, s), 5.97–6.11 (1H, m),
5.37 (1H, dq, J1,2 =17.1, 1.8 Hz), 5.22 (1H, dq, J1,2 = 10.6, 1.8 Hz), 4.71 (2H,
dt, J1,2 = 5.5, 1.8 Hz); 13C NMR (68 MHz, acetone-d6) δ 166.3, 146.0, 138.8,
133.9, 121.7, 117.6, 109.8, 65.4.
1
224.0705; IR (neat) 3369, 1701, 1597, 1524, 1375, 1234, 1193 cm− 1; H NMR
(500 MHz, CDCl3) δ 7.26 (2H, s), 5.97–6.05 (1H, m), 5.40 (1H, dq, J1,2 = 17.2,
1.4 Hz), 5.22 (1H, dq, J1,2 = 10.4, 1.4 Hz), 4.79 (2H, dt, J1,2 = 5.5, 1.4 Hz), 3.97
(3H, s); 13C NMR (68 MHz, acetone-d6) δ 166.1, 151.3, 133.8, 126.4, 117.8,
109.9, 109.8, 65.7, 60.6.
3,5-Di(2-nitrobenzenesulfoxy)-4-methoxybenzoic acid (22). To a solution of 21
(400 mg, 1.79 mmol) in MeCN (4 ml) were added triethylamine (1.12 ml,
8.04 mmol) and 2-nitrobenzenesulfonyl chloride (872 mg, 3.93 mmol) at 0 ºC.
The mixture was stirred at 0 °C for 1.5 h. The reaction mixture was quenched
with 2 M HCl and extracted with CH2Cl2. The combined organic phases were
washed with brine, dried over anhydrous sodium sulfate and evaporated under
reduced pressure. The residue was purified by silica gel flash column
chromatography (CH2Cl2) to afford crude (954 mg) as a colorless amorphous.
To a suspention of p-toluenesulfinic acid (343 mg, 1.92 mmol) in H2O (16 ml)
were added a solution of the crude and tetrakis(triphenylphosphine) palladium
(0) (92.0 mg, 800 μmol) in THF (32 ml) at room temperature. The mixture
was stirred at room temperature for 1 h. To the resulting mixture were added
CH2Cl2 and H2O, and then organic layer was extracted with H2O. The
combined aqueous phases were acidified with 2 M HCl (up to pH 3.0) and
extracted with ethyl acetate. The organic phase was dried over anhydrous
sodium sulfate and evaporated under reduced pressure to afford 22
(743 mg, 82%, two steps) as a colorless solid. HR-MS (FAB) calculated for
C20H15N2O13S2 [M+H]+555.0016, found 555.0017; IR (neat) 3026, 1703,
Allyl 3,5-dihydroxy-4-methoxybenzoate (21). To a suspension of 20 (1.50 g,
7.15 mmol) in N,N-dimethylformamide (DMF) (20 ml) were added Li2CO3
(1.32 g, 17.9 mmol) and methyl iodide (1.11 ml, 17.9 mmol) at 50 °C. The
mixture was stirred at 50 °C for 20 h. The reaction mixture was quenched with
2 M HCl and extracted with ethyl acetate. The combined organic phases were
OH
O
OH
O
Pb(OAc)4
NsO
O
NsO
O
MeCN, 0 °C
; filtration
quant
OH
OH
ONs
ONs
51
55
Scheme 10 Oxidation of 51 to o-quinone 55.
O
OR
O
OH
OH
NsO
O
OH
OH
OH
RO
RO
O
O
OH
ONs
O
NsO
O
55
OH
MS 3A
OH
MeCN, CH2Cl2
0 °C; H2O
50%
OH
ONs
OH
RO
53
PhSH, Cs2CO3
MeCN, DMF
55%
56: R = Ns
5: R = H
Scheme 11 Synthesis of neotheaflavin (5) by oxidative coupling reaction of 53 and 55.
H+
O H
OH
OH
O
O H
R2
R1
OH
H+
R2
R1
R2
H
OH
R2
R1
O
R1
OH Oxidation
Oxidation
53
OH
O
OH
OH
OH
O
H
OH
R1
OH
H+
O
51
O
H+
H
OH
O
OH
55
57
58
59
H+
H+
O
R2
OH
O
R2
O
O
R2
OH
R2
O
O
H2O
-CO2
Oxidation
H
OH
OH
OH
O
HO
O
H
R1
H
R1
R1
OH
OH
H
R1
OH
OH
OH
OH
OH
56
60
61
62
Scheme 12 Proposed mechanism of the coupling reaction of quinone and pyrogallol according to Nakatsuka and Yanase.
The Journal of Antibiotics

Syntheses of methylated catechins and theaflavins
T Asakawa et al
8
OH
OH
OH
2
3
NsO
O
OH
OH
O
O
OH
ONs
2
NsO
O
Pb(OAc)4
MeCN
53
2
3
NsO
O
MS3A, CH2Cl2
; H2O
3
OH
OH
ONs
ONs
52
63
ONs
OH
NH2
SH
OH
OH
OH
O
OH
O
39
NsO
O
O
HO
O
Cs2CO3
MeCN
DMF
11%
OH
OH
NsO
OH
OH
HO
O
OH
(2 steps from 53)
OH
ONs
64
4
OH
Scheme 13 Synthesis of theaflavin (4).
Table 3 Synthesis of benzotropolone derivatives
1546, 1392, 1307, 1190, 1006 cm− 1
δ 7.94–8.18 (8H, m), 7.78 (2H, s), 3.72 (3H, s); 13C NMR (68 MHz,
acetone-d6) δ 164.8, 150.5, 143.4, 137.7, 132.6, 128.5, 127.0, 126.2, 125.6, 62.7.
;
1H NMR (270 MHz, acetone-d6)
(1H, d, J =2.0 Hz), 5.98–6.10 (1H, m), 5.36 (1H dq, J1,2 =17.1, 1.5 Hz), 5.21
(1H, dq, J1,2 = 10.4, 1.5 Hz), 4.73 (2H, dt, J1,2 = 5.5, 1.5 Hz), 3.87 (3H, s); 13C
NMR (68 MHz, acetone-d6) δ 166.3, 148.5, 145.8, 139.7, 133.8, 121.6, 1177.8,
111.6, 105.7, 65.6, 56.5.
Allyl 4,5-dihydroxy-3-methoxybenzoate (24). To a suspension of 20 (300 mg,
1.43 mmol) in H2O (20 ml) was added sodium tetraborate decahydrate (1.40 g,
3.67 mmol), then the mixture was stirred at room temperature for 1 h. After
stirring, dimethyl sulfate (0.523 ml, 5.53 mmol) and 6.5 M NaOH (25 ml) were
added to the reaction mixture, which was stirred at room temperature for 12 h.
The reaction mixture was acidified with concentrated H2SO4 (up to pH 2.0)
and stirred at room temperature for 1 h. The resulting mixture was poured into
water and extracted with CH2Cl2. The organic phase was washed with brine,
dried over anhydrous sodium sulfate and evaporated to afford 24 (320 mg,
85%) as a colorless solid. HR-MS (FAB) calculated for C11H12O5[M+H]
+224.0685, found 224.0705; IR (neat) 3371, 1710, 1602, 1531, 1382, 1246,
4,5-Di(2-nitrobenzenesulfoxy)-3-methoxybenzoic acid (25). In a similar manner
to that used to prepare 22, treatment of 24 gave 25 (95%, two steps) as a
colorless solid. HR-MS (FAB) calculated for C20H15N2O13S2 [M+H]+555.0016,
found 555.0017; IR (neat) 3008, 1705, 1556, 1385, 1194, 1078, 970 cm− 1
;
1H NMR (270 MHz, acetone-d6) δ 7.90–8.13 (8H, m), 7.68 (1H, d, J = 2.0 Hz),
7.52 (1H, d, J = 2.0 Hz), 3.72 (3H, s); 13C NMR (68 MHz, acetone-d6) δ 165.4,
154.5, 143.3, 137.8, 137.0, 133.9, 133.6, 132.2, 131.5, 130.5, 128.5, 126.2, 125.9,
117.2, 113.7, 57.1.
3,4,5-Tri(2-nitrobenzenesulfoxy)benzoic acid (26). In a similar manner to that
;
1H NMR (270 MHz, acetone-d6) δ 7.23 (1H, d, J = 2.0 Hz), 7.16 used to prepare 22, treatment of 20 gave 26 (86%) as a colorless solid. HR-MS
1192 cm− 1
The Journal of Antibiotics

Syntheses of methylated catechins and theaflavins
T Asakawa et al
9
(FAB) calculated for C25H15N3O17S3Na [M+Na]+747.9461, found 747.9468; (c 0.85, acetone); IR (neat) 1708, 1618, 1593, 1545, 1419, 1394, 1366, 1305,
IR (neat) 3437, 1701, 1541, 1400, 1305, 1193, 1091, 1014 cm− 1
(500 MHz, acetone-d6)
acetone-d6) δ 163.5, 148.5, 148.1, 143.0, 138.2, 137.4, 137.1, 133.3, 132.0, 5.74 (1H, m), 5.60 (1H, s), 3.63 (3H, s), 3.28 (1H, dd, J1,2 = 17.5, 4.3 Hz), 3.10
; ;
1H NMR 1193, 1121, 1001 cm− 1 1H NMR (500 MHz, acetone-d6) δ 7.80–8.14 (28H,
δ
8.15–7.85 (14H, m); 13C NMR (125 MHz, m), 7.57 (2H, s), 7.46 (2H, s), 6.98 (1H, d, J = 2.6 Hz), 6.66 (1H, d, J = 2.6 Hz),
131.8, 131.2, 128.3, 126.9, 125.6, 124.0.
(1H, dd, J1,2 =17.5, 3.3 Hz); 13C NMR (126 MHz, acetone-d6) δ 162.2, 155.3,
150.2, 148.8, 148.4, 148.2, 147.7, 142.9, 142.7, 138.7, 137.2, 136.9, 136.9, 134.4,
133.2, 133.1, 133.1, 133.0, 132.3, 132.1, 132.0, 131.7, 131.6, 128.3, 127.8, 127.1,
126.9, 126.6, 125.5, 125.5, 125.4, 124.9, 124.8, 121.2, 113.8, 110.4, 109.9, 75.9,
67.4, 61.9, 26.0.
5-((2R,3R)-3-Hydroxy-5,7-bis(2-nitrophenylsulfonyloxy)chroman-2-yl)benzene-
1,2,3-triyl tris(2-nitrobenzenesulfonate) (28). To a solution of 27 (100 mg,
0.327 mmol) in MeCN (20 ml) were added triethylamine (0.453 ml,
3.27 mmol) and 2-nitrobenzenesulfonyl chloride (362 mg, 1.63 mmol) at
− 20 ºC. The mixture was stirred at − 20 °C for 1.5 h. The reaction mixture (2R,3R)-5,7-Dihydroxy-2-(3,4,5-trihydroxyphenyl)chroman-3-yl 3,5-dihydroxy-4-
was quenched with 2 M HCl and extracted with ethyl acetate. The organic phase methoxybenzoate (3). In a similar manner to that used to prepare 2, treatment
was washed with brine, dried over anhydrous sodium sulfate and evaporated of 30 gave 3 (81%) as a colorless amorphous. HR-MS (FAB) calculated for
under reduced pressure. The residue was purified by flash column chromato- C23H20O11Na [M+Na]+495.0904, found 495.0896; [α]D20 =− 171.5 (c 1.20,
1
graphy (CH2Cl2) to afford 28 (377 mg) as a colorless amorphous. HR-MS 50% acetone in H2O); IR (neat) 3367, 1701, 1604, 1348, 1236 cm− 1; H NMR
(FAB) calculated for C45H30N5O27S5 [M+H]+1231.9732, found 1231.9751; [α] (270 MHz, CD3OD) δ 6.91 (2H, s), 6.49 (2H, s), 5.95 (2H, s), 5.53 (1H, m),
D
20 = − 5.33 (c 1.00, acetone); IR (neat) 3406, 1701, 1618, 1589, 1542, 1421, 4.97 (1H, s), 3.81 (3H, s), 2.99 (1H, dd, J1,2 = 17.5, 4.6 Hz), 2.84 (1H, dd,
1388, 1362, 1305, 1222, 1193, 1114, 1008 cm− 1; 1H NMR (270 MHz, CD3CN) J1,2 = 17.5, 2.3 Hz); 13C NMR (125 MHz, CD3OD) δ 167.2, 157.9, 157.8, 157.2,
δ 7.70–8.05 (20H, m), 7.24 (2H, s), 6.66 (1H, d, J = 2.6 Hz), 6.44 (1H, d, 151.5, 146.7, 141.1, 133.8, 130.7, 126.6, 110.3, 106.8, 99.3, 96.5, 95.9, 78.5, 70.3,
J = 2.6 Hz), 5.01 (1H, m), 4.05 (1H, m), 3.04 (1H, br s), 2.88–2.72 (2H, m); 60.7, 26.8.
13C NMR (68 MHz, CD3CN) δ 156.5, 149.5, 149.2, 148.9, 148.3, 143.5, 141.1,
138.0, 137.9, 137.7, 135.2, 134.1, 134.1, 134.0, 133.8, 133.1, 133.0, 132.8, 132.6,
129.3, 128.2, 127.9, 127.5, 126.4, 126.3, 122.1, 118.3, 115.7, 110.7, 109.9, 78.3,
64.2, 29.3.
(2R,3R)-2-(3,4-Dihydroxy-5-(2-nitrophenylsulfonyloxy)phenyl)-3-hydroxychroman-
5,7-diyl bis(2-nitrobenzenesulfonate) (32). To a solution of boric acid (4.64 g,
80.3 mmol) and NaOH (800 mg) in H2O (160 ml) was added 27 (492 mg,
1.61 mmol) and the resulting solution was adjusted to pH 9.0. Then,
5-(2R,3R)-5,7-Bis(2-nitrophenylsulfonyloxy)-2-(3,4,5-tris(2-nitrophenylsulfonyloxy)
phenyl) chroman-3-yl-3-methoxy-4,5-bis(2-nitrophenylsulfonyloxy)benzoate (29).
2-nitrobenzenesulfonyl chloride (1.06 g, 4.83 mmol) in toluene (16 ml) was
added dropwise over 30 min and stirred at room temperature for 3 h. The
28 (700 mg, 0.568 mmol), 25 (628 mg, 1.14 mmol), EDCI (327 mg, reaction was quenched with 2 M HCl and extracted with ethyl acetate. The
1.70 mmol) and DMAP (13.9 mg, 0.114 mmol) were dissolved in CH3CN organic phase was dried over sodium sulfate and evaporated under reduced
(3 ml) and stirred at room temperature for 16 h. The resulting mixture was pressure. The residue was purified by silica gel flash column chromatography
quenched with saturated NH4Cl and extracted with CH2Cl2. The organic phase (1–3% MeOH in CH2Cl2) to afford 32 (560 mg, 40%) as a pale yellow solid.
was dried over anhydrous sodium sulfate and evaporated under reduced HR-MS (FAB) calculated for C33H23N3O19S3Na [M+Na]+883.9986, found
pressure. The residue was purified by silica gel flash column chromatography 883.9965; [α]D20 =+10.6 (c 1.28, acetone); IR (neat) 3422, 1701, 1618, 1591,
(25% hexane in CH2Cl2) to afford 29 (925 mg, 92%) as a colorless amorphous. 1541, 1440, 1388, 1358, 1305, 1191, 1111, 995 cm− 1 1H NMR (270 MHz,
;
[α]D20 = − 73.1 (c 0.85, acetone); HR-MS (FAB) calculated for acetone-d6) δ 7.80–8.20 (12H, m), 6.99 (1H, d, J = 2.3 Hz), 6.71 (1H, d,
C65H41N7O39S7Na [M+Na]+1789.9383, found 1789.9386; IR (neat) 1708, J = 2.3 Hz), 6.62 (1H, d, J = 2.3 Hz), 6.50 (1H, d, J = 2.3 Hz), 4.99 (1H, m),
1618, 1593, 1545, 1419, 1394, 1366, 1305, 1193, 1121, 1001 cm− 1 1H NMR 4.22 (1H, m), 2.80–2.98 (2H, m); 13C NMR (68 MHz, acetone-d6) δ 157.3,
;
(270 MHz, acetone-d6) δ 7.80–8.14 (28H, m), 7.54 (2H, s), 7.34 (1H, d, 149.5, 148.2, 147.3, 138.9, 138.2, 137.8, 137.0, 133.9, 133.6, 133.3, 133.0, 132.9,
J = 2.0 Hz), 7.23 (1H, d, J = 2.0 Hz), 6.97 (1H, d, J = 2.6 Hz), 6.66 (1H, d, 132.6, 130.2, 129.5, 128.4, 127.7, 126.3, 126.2, 125.8, 116.0, 114.1, 113.4, 110.3,
J = 2.6 Hz), 5.73–5.78 (1H, m), 5.65 (1H, s), 3.59 (3H, s), 3.30 (1H, dd, 109.1, 79.4, 64.8, 29.6.
J1,2 = 17.5, 4.3 Hz), 3.23 (1H, dd, J1,2 = 17.5, 3.3 Hz); 13C NMR (68 MHz,
acetone-d6) δ 162.1, 155.6, 150.2, 148.7, 148.4, 147.8, 142.6, 141.0, 140.8, 138.5,
137.1, 137.0, 136.9, 133.1, 133.0, 133.0, 132.9, 132.3, 132.0, 131.9, 131.8, 127.6,
127.5, 127.4, 127.2, 126.9, 126.7, 125.4, 125.4, 125.3, 124.8, 124.7, 124.7, 122.5,
113.7, 110.4, 109.7, 76.4, 67.7, 62.0, 26.0.
(2R,3R)-2-(3-tert-Butyldiphenylsilyloxy-4-hydroxy-5-(2-nitrophenylsulfonyloxy)
phenyl)-3-hydroxychroman-5,7-diyl bis(2-nitrobenzenesulfonate) (33). To
solution of 32 (200 mg, 0.182 mmol) in MeCN (0.4 ml) were added triethy-
lamine (0.196 ml, 1.09 mmol) and TBDPSCl (197 mg, 0.545 mmol) at − 20 ºC,
then the resulting solution was stirred at − 20 °C for 3 h. The reaction mixture
a
(2R,3R)-5,7-Dihydroxy-2-(3,4,5-trihydroxyphenyl)chroman-3-yl 4,5-dihydroxy-3- was quenched with 2 M HCl and extracted with CH2Cl2. The combined organic
methoxybenzoate (2). To a suspension of Cs2CO3 (3.61 g, 11.3 mmol) in phases were dried over sodium sulfate and evaporated under reduced pressure.
MeCN (6 ml) were added thiophenol (1.16 ml, 5.75 mmol) and 29 (800 mg, The residue was purified by silica gel flash column chromatography (50% ethyl
0.452 mmol) at 0 ºC. The mixture was stirred at room temperature for 3.5 h. acetate in hexane) to afford 33 (211 mg, 83%) as a pale yellow solid. HR-MS
The reaction was quenched with sat. NH4Cl and extracted with ethyl acetate. (FAB) calculated for C33H23N3O19S3Na [M+Na]+1122.1163, found 1122.1191;
The organic phase was dried over anhydrous sodium sulfate and evaporated [α]D20 = − 0.68 (c 1.35, acetone); IR (neat) 3448, 1707, 1618, 1591, 1544, 1441,
under reduced pressure. The residue was purified by silica gel flash column 1388, 1364, 1305, 1193, 1112, 997 cm− 1
chromatography (7% MeOH in CH2Cl2) to afford 2 (174 mg, 81%) as a
;
1H NMR (270 MHz, CDCl3)
δ, 7.36–8.13 (23H, m), 6.77 (1H, d, J = 2.0 Hz), 6.51 (1H, d, J = 2.0 Hz),
colorless amorphous. HR-MS (FAB) calculated for C23H20O11Na [M+Na] 6.43 (1H, d, J = 2.0 Hz), 6.37 (1H, d, J = 2.0 Hz), 4.58 (1H, m), 3.73 (1H, m),
+495.0904, found 495.0873; [α]D20 = − 186.2 (c 1.00, 50% acetone in H2O); IR 2.82–2.86 (2H, m), 1.09 (9H, s); 13C NMR (68 MHz, CDCl3) δ 155.4, 148.3,
(neat) 3327, 1701, 1610, 1340, 1229 cm− 1 1H NMR (270 MHz, CD3OD) δ 147.1, 144.4, 140.1, 136.4, 135.9, 135.8, 135.5, 135.4, 135.3, 132.6, 132.3, 132.3,
;
7.05 (1H, d, J =1.9 Hz), 7.01 (1H, d, J = 1.9 Hz), 6.50 (2H, s), 5.96 (1H, d, 132.1, 130.6, 130.6, 128.1, 127.7, 125.0, 124.9, 124.8, 116.0, 114.3, 113.9, 110.0,
J = 2.6 Hz), 5.95 (1H, d, J =2.6 Hz), 5.49 (1H, m), 5.00 (1H, s), 3.81 (3H, s), 109.1, 64.6, 28.0, 26.6, 19.5.
2.99 (1H, dd, J1,2 = 17.5, 4.3 Hz), 2.86 (1H, dd, J1,2 = 17.5, 3.0 Hz); 13C NMR
(2R,3R)-2-(3-tert-Butyldiphenylsilyloxy-4-methoxy-5-(2-nitrophenylsulfonyloxy)
phenyl)-3-hydroxychroman-5,7-diyl bis(2-nitrobenzenesulfonate) (35). To
solution of 33 (125 mg, 0.110 mmol) in MeCN (1 ml) were added diazo-
methane (Et2O solution) until color of the solution became yellow at 0 ºC. The
resulting solution was stirred at 0 °C for 10 min. The reaction was quenched
(68 MHz, CD3OD) δ 167.7, 157.9, 157.8, 157.2, 149.0, 146.8, 146.0, 140.6,
133.7, 130.9, 121.5, 111.9, 106.8, 106.3, 99.4, 96.5, 95.8, 78.5, 70.4, 56.6, 26.6.
a
5-(2R,3R)-5,7-Bis(2-nitrophenylsulfonyloxy)-2-(3,4,5-tris(2-nitrophenylsulfonyloxy)
phenyl) chroman-3-yl-4-methoxy-3,5-bis(2-nitrophenylsulfonyloxy)benzoate (30).
In a similar manner to that used to prepare 29, treatment of 28 with 22 gave with acetic acid and evaporated under reduced pressure. The residue was
30 (97%) as colorless amorphous. HR-MS (FAB) calculated for purified by silica gel flash column chromatography (50% ethyl acetate in
C65H41N7O39S7Na [M+Na]+1789.9383, found 1789.9386; [α]D20 = − 73.1 hexane) to afford 35 (115 mg, 91%) as a pale yellow solid. HR-MS (FAB)
a
The Journal of Antibiotics

Syntheses of methylated catechins and theaflavins
T Asakawa et al
10
calculated for C33H23N3O19S3Na [M+Na]+1136.1320, found 1136.1298; prepare 70, treatment of 71 gave 36 (86%) as a colorless amorphous. HR-MS
[α]D20 = − 9.17 (c 1.25, acetone); IR (neat) 3420, 1709, 1618, 1591, 1550,
1441, 1391, 1360, 1308, 1196, 1113, 997 cm− 1; 1H NMR (500 MHz, CDCl3) δ,
8.08–7.36 (22H, m), 6.71 (1H, d, J = 2.4 Hz), 6.50 (1H, d, J = 2.4 Hz), 6.43
(1H, d, J =2.4 Hz), 6.40 (1H, d, J = 2.4 Hz), 4.58 (1H, m), 3.84 (3H, s), 3.71
(1H, m), 2.89 (1H, dd, J1,2 = 17.7, 2.4 Hz), 2.89 (1H, dd, J1,2 = 17.7, 4.0 Hz),
1.09 (9H, s); 13C NMR (68 MHz, CDCl3) δ 155.3, 150.3, 148.6, 148.3, 147.1,
143.1, 135.9, 135.8, 135.5, 135.4, 135.3, 132.6, 132.3, 132.3, 132.1, 132.0, 131.9,
131.8, 130.4, 130.3, 128.2, 128.0, 128.0, 125.0, 124.9, 124.7, 117.8, 114.1, 113.9,
110.0, 109.1, 64.5, 61.3, 28.0, 26.4, 19.5.
(FAB) calculated for C39H26N4O23S4Na [M+Na]+1068.9768, found 1068.9788;
[α]D20 = − 1.41 (c 1.80, acetone); IR (neat) 3429, 1701, 1612, 1591, 1543, 1438,
1389, 1364, 1194, 1113, 999 cm− 1 1H NMR (270 MHz, acetone-d6) δ,
;
8.13–7.86 (16H, m), 7.17 (1H, d, J = 2.0 Hz), 6.78 (1H, d, J = 2.0 Hz), 6.74
(1H, d, J = 2.0 Hz), 6.50 (1H, d, J = 2.0 Hz), 5.12 (1H, m), 4.29 (1H, m),
2.98–2.90 (2H, m); 13C NMR (125 MHz, acetone-d6) δ 156.2, 151.6, 148.7,
148.6, 148.5, 148.4, 147.4, 142.3, 139.2, 137.1, 136.8, 136.0, 133.1, 132.9, 132.9,
132.8, 132.2, 132.2, 132.1, 131.9, 131.4, 130.1, 130.0, 127.8, 127.4, 126.8, 125.5,
125.5, 125.3, 125.1, 115.2, 114.9, 112.2, 109.7, 108.6, 78.3, 63.7, 29.8.
(2R,3R)-2-(3-tert-Butyldiphenylsilyloxy-4-methoxy-5-(2-nitrophenylsulfonyloxy)
phenyl)-5,7-bis(2-nitrophenylsulfonyloxy)-chroman-3-yl-3,4,5-tris(2-nitrophenyl-
sulfonyloxy)benzoate (69). In a similar manner to that used to prepare 29,
treatment of 35 with 26 gave 69 (86%) as a colorless solid. HR-MS (FAB)
calculated for C75H56N6O35SiS6Na [M+Na]+1843.0778, found 1843.0771;
[α]D20 = − 42.3 (c 1.00, acetone); IR (neat) 1711, 1618, 1591, 1545, 1442,
(2R,3R)-2-(3-Methoxy-4,5-bis(2-nitrophenylsulfonyloxy)phenyl)-3-hydroxychroman-
5,7-diyl bis(2-nitrobenzenesulfonate) (37). In a similar manner to that used to
prepare 35, treatment of 36 gave 37 (91%) as a colorless amorphous. HR-MS
(FAB) calculated for C40H28N4O23S4Na [M+Na]+1082.9925, found 1082.9946;
[α]D20 = − 3.18 (c 0.56, acetone); IR (neat) 3451, 1701, 1618, 1591, 1541, 1439,
1389, 1356, 1306, 1194, 1113, 999 cm− 1
;
1H NMR (270 MHz,
1391, 1364, 1308, 1193, 1114, 1005 cm− 1 1H NMR (500 MHz, CDCl3)
;
acetone-d6) δ 8.13–7.90 (16H, m), 7.30 (1H, d, J = 2.0 Hz), 6.94 (1H, d,
J = 2.0 Hz), 6.77 (1H, d, J = 2.6 Hz), 6.51 (1H, d, J = 2.6 Hz), 5.21 (1H, m),
4.37 (1H, m), 3.64 (3H, s), 2.98–2.94 (2H, m); 13C NMR (68 MHz, acetone-d6)
δ 156.2, 153.3, 148.7, 148.6, 148.5, 148.3, 147.4, 142.2, 139.6, 137.1, 137.0,
136.8, 136.0, 133.1, 133.0, 132.9, 132.7, 132.2, 132.0, 131.9, 131.3, 130.8, 130.0,
127.9, 127.5, 126.8, 125.5, 125.5, 125.4, 125.1, 115.1, 113.4, 110.7, 109.8, 108.7,
78.5, 63.6, 54.2, 29.8.
δ 7.34–8.03 (34H, m), 6.68 (1H, d, J = 1.9 Hz), 6.67 (1H, d, J = 1.9 Hz), 6.60
(1H, d, J =2.0 Hz), 6.26 (1H, d, J = 2.0 Hz), 5.04 (1H, m), 4.64 (1H, m), 3.70
(3H, s), 2.95 (1H, dd, J1,2 =18.0, 4.6 Hz), 2.80 (1H, dd, J1,2 = 18.0, 1.5 Hz), 1.02
(9H, s); 13C NMR (68 MHz, CDCl3) δ 161.4, 155.1, 150.1, 148.6, 148.4, 148.2,
148.2, 148.0, 147.4, 143.6, 143.1, 143.1, 139.0, 136.3, 136.3, 136.1, 135.9, 135.4,
135.3, 133.0, 132.9, 132.7, 132.6, 132.3, 132.1, 131.9, 131.9, 131.7, 131.1, 130.4,
130.4, 129.2, 128.9, 128.0, 128.0, 127.8, 127.7, 127.4, 125.4, 125.1, 125.0, 124.8,
124.1, 117.6, 114.3, 112.4, 110.2, 110.0, 67.4, 61.3, 26.5, 26.3, 19.5.
(2R,3R)-2-(3-Methoxy-4,5-bis(2-nitrophenylsulfonyloxy)phenyl)-5,7-bis(2-
nitrophenylsulfonyloxy)-chroman-3-yl 3-methoxy-4,5-bis(2-nitrophenylsulfonyloxy)
benzoate (72). 37 (20.0 mg, 0.0188 mmol), 25 (20.9 mg, 0.0377 mmol), EDCI
(10.8 mg, 0.0563 mmol), DMAP (0.2 mg, 1.9 μmol) were dissolved in MeCN
(0.25 ml) and the resulting solution was stirred at room temperature for 17 h.
Then, the reaction mixture was quenched with saturated NH4Cl and extracted
with CH2Cl2. The organic phase was dried over anhydrous sodium sulfate and
evaporated under reduced pressure to afford crude 72 as a colorless solid. The
crude 72 was used in the next step without further purification. 1H NMR
(270 MHz, acetone-d6) δ, 8.17–7.81 (28H, m, 28H), 7.37 (1H, d, J = 2.0 Hz,
1H), 7.31 (1H, d, J = 2.0 Hz), 7.24 (1H, d, J = 2.0 Hz), 7.04 (1H, d, J = 2.0 Hz),
6.96 (1H, d, J = 2.0 Hz), 6.66 (1H, d, J = 2.0 Hz), 5.82–5.77 (1H, m, 1H),
5.59–5.56 (1H, m, 1H), 3.60 (3H, s), 3.48 (3H, s), 3.32 (1H, dd, J1,2 = 17.8,
4.0 Hz), 3.15 (1H, dd, J1,2 = 17.8, 2.0 Hz).
(2R,3R)-2-(3-Hydroxy-4-methoxy-5-(2-nitrophenylsulfonyloxy)phenyl)-5,7-bis(2-
nitrophenylsulfonyloxy)-chroman-3-yl-3,4,5-tris(2-nitrophenylsulfonyloxy)benzoate
(70). To a solution of 69 (400 mg, 0.220 mmol) and acetic acid (0.0377 ml,
0.661 mmol) in tetrahydrofuran (THF) (4.6 ml) was added TBAF (1.0 M
solution in THF, 0.266 ml, 0.266 mmol) at 0 °C, then the resulting solution
was stirred at 0 °C for 15 min. The reaction mixture was poured into water and
extracted with CH2Cl2. The organic phase was dried over anhydrous sodium
sulfate and evaporated under reduced pressure to afford crude 70 (320 mg) as a
colorless solid. The crude 70 was used in the next step without further
purification. 1H NMR (500 MHz, acetone-d6) δ 7.62–8.07 (24H, m), 7.57
(2H, s), 6.83 (1H, d, J =1.8 Hz), 6.82 (1H, d, J =1.8 Hz), 6.69 (1H, d,
J = 1.8 Hz), 6.65 (1H, d, J = 1.8 Hz), 5.50 (1H, m), 4.06 (1H, m), 3.80 (3H, s),
3.19 (1H, dd, J1,2 = 18.3, 4.3 Hz), 3.03 (1H, dd, J1,2 =18.3, 4.3 Hz)
(2R,3R)-2-(4,5-Dihydroxy-3-methoxyphenyl)-5,7-dihydroxychroman-3-yl
3,4-
(2R,3R)-2-(3,5-Dihydroxy-4-methoxyphenyl)-5,7-dihydroxychroman-3-yl 3,4,5-
trihydroxybenzoate (7). In a similar manner to that used to prepare 2,
treatment of crude 70 gave 7 (77%, 2 steps) as a colorless amorphous.
HR-MS (FAB) calculated for C23H20O11Na [M+Na]+ 495.0904, found
495.0942; [α]D20 = − 147.6 (c 1.00, 50% acetone in H2O); IR (neat) 3346,
dihydroxy-5-methoxybenzoate (38). In a similar manner to that used to
prepare 2, treatment of 72 with 2-aminothiophenol gave 38 (63%) as a
colorless amorphous. HR-MS (FAB) calculated for C24H23O11 [M+H]
+487.1240, found 487.1229; [α]D20 = − 218.1 (c 0.04, 50% acetone in H2O);
1
IR (neat) 3285, 1701, 1605, 1364, 1221; H NMR (500 MHz, CD3OD) δ 7.10
1701, 1608, 1357, 1234 cm− 1 1H NMR (270 MHz, CD3OD) δ 6.84 (2H, s),
;
(1H, d, J = 2.0 Hz), 7.02 (1H, d, J = 2.0 Hz), 6.61 (1H, d, J = 2.0 Hz), 6.58
(1H, d, J = 2.0 Hz), 5.96 (2H, s), 5.52 (1H, m), 5.23 (1H, m), 3.79 (3H, s), 3.58
(3H, s), 3.01 (1H, dd, J1,2 =17.1, 4.6 Hz), 2.86 (1H, dd, J1,2 = 17.1, 1.7 Hz);
13C NMR (125 MHz, CD3OD) δ 165.9, 156.5, 156.5, 148.0, 147.7, 144.9, 144.8,
139.2, 133.4, 129.3, 119.8, 110.6, 107.3, 104.9, 101.7, 98.1, 95.2, 94.4, 77.5, 68.9,
55.1, 54.9, 25.4.
6.43 (2H, s), 5.87 (2H, s), 5.44 (1H, m), 4.89 (1H, m), 3.66 (3H, s), 2.90 (1H,
dd, J1,2 = 17.1, 4.6 Hz), 2.75 (1H, dd, J1,2 = 17.1, 2.3 Hz); 13C NMR (68 MHz,
CD3OD) δ 167.6, 157.8, 157.0, 151.3, 146.2, 136.3, 136.0, 135.8, 129.8, 121.5,
110.3, 107.1, 99.4, 96.6, 95.9, 78.4, 69.8, 60.8, 26.8.
(2R,3R)-2-(3-tert-Butyldiphenylsilyloxy-4,5-bis(2-nitrophenylsulfonyloxy)phenyl)-
3-hydroxychroman-5,7-diyl bis(2-nitrobenzenesulfonate) (71). In
a similar
(2R,3R)-2-(3-Methoxy-4,5-bis(2-nitrophenylsulfonyloxy)phenyl)-5,7-bis(2-
nitrophenylsulfonyloxy)-chroman-3-yl-3,4,5-tris(2-nitrophenylsulfonyloxy)benzoate
(73). In a similar manner to that used to prepare 29, treatment of 37 with
manner to that used to prepare 28, treatment of 33 gave 71 (95%) as a
colorless amorphous. HR-MS (FAB) calculated for C56H44N4O23SiS4Na
[M+Na]+1307.0946, found 1307.0963; [α]D20 = − 9.25 (c 0.84, acetone); IR
26 gave 73 (86%) as
a colorless solid. HR-MS (FAB) calculated for
(neat) 1709, 1618, 1591, 1548, 1440, 1391, 1360, 1306, 1196, 1113, 997 cm− 1
;
C65H41N7O39S7Na [M+Na]+1789.9383, found 1789.9396; [α]D20 = − 37.4
(c 0.38, acetone); IR (neat) 1709, 1618, 1593, 1545, 1442, 1391, 1364, 1308,
1H NMR (500 MHz, CDCl3) δ, 7.36–8.13 (26H, m), 6.60 (1H, d, J = 2.0 Hz),
6.43 (1H, d, J = 2.0 Hz), 6.42 (1H, d, J =2.0 Hz), 6.35 (1H, d, J = 2.0 Hz), 4.51
(1H, m), 3.58 (1H, m), 2.88 (2H, m), 2.76 (1H, dd, J = 17.5, 4.0 Hz), 1.08
(9H, s); 13C NMR (125 MHz, CDCl3) δ 154.9, 150.7, 148.5, 148.3, 148.3, 148.2,
146.9, 142.4, 136.5, 136.0, 136.0, 135.9, 135.5, 135.4, 135.3, 132.8, 132.6, 132.6,
132.4, 132.4, 132.2, 132.1, 132.0, 131.7, 131.2, 131.0, 130.5, 130.4, 130.1, 128.0,
127.5, 125.1, 124.9, 124.6, 117.5, 113.8, 112.6, 109.9, 64.2, 60.4, 27.9, 26.0, 19.4.
1196, 1116, 1006 cm− 1 1H NMR (270 MHz, acetone-d6) δ 8.20–7.80 (28H,
;
m), 7.69 (2H, s), 7.31 (1H, d, J = 1.3 Hz), 7.00 (1H, d, J = 1.3 Hz), 6.96 (1H, d,
J = 2.0 Hz), 6.67 (1H, d, J =2.0 Hz), 5.81 (1H, m), 5.56 (1H, m), 3.49 (3H, s),
3.33 (1H, dd, J1,2 = 17.8, 4.0 Hz), 3.13 (1H, dd, J1,2 = 17.8, 2.0 Hz); 13C NMR
(68 MHz, acetone-d6) δ 162.3, 156.4, 154.4, 149.2, 149.1, 148.6, 143.9, 143.3,
138.8, 138.1, 137.9, 137.7, 136.9, 134.1, 133.8, 133.7, 133.4, 133.0, 132.8, 132.5,
132.1, 130.6, 130.4, 129.2, 128.4, 128.0, 127.9, 127.6, 126.4, 126.3, 126.1, 125.8,
(2R,3R)-2-(3-Hydroxy-4,5-bis(2-nitrophenylsulfonyloxy)phenyl)-3-hydroxychroman-
5,7-diyl bis(2-nitrobenzenesulfonate) (36). In a similar manner to that used to 124.7, 114.4, 114.0, 111.2, 110.8, 110.5, 77.4, 69.0, 56.9, 26.8.
The Journal of Antibiotics

Syntheses of methylated catechins and theaflavins
T Asakawa et al
11
(2R,3R)-2-(4,5-Dihydroxy-3-methoxyphenyl)-5,7-dihydroxychroman-3-yl 3,4,5- 125.4, 125.3, 125.3, 124.8, 124.7, 124.7, 122.5, 113.7, 110.4, 109.7, 76.4, 67.7,
trihydroxybenzoate (6). In a similar manner to that used to prepare 2,
treatment of 73 gave 6 (63%) as a colorless amorphous. HR-MS (FAB)
61.9, 26.0.
(2R,3R)-2-(3,4-Dihydroxyphenyl)-5,7-dihydroxychroman-3-yl 3,5-dihydroxy-4-
methoxybenzoate (9). In a similar manner to that used to prepare 2, treatment
of 75 gave 9 (84%) as a colorless amorphous. [α]D20 = − 217.3 (c 0.75, 50%
acetone in H2O); IR (neat) 3367, 1705, 1605, 1371, 1240 cm− 1; HR-MS (FAB)
calculated for C23H20O10Na [M+Na]+ 479.0954, found 479.0906; 1H NMR
(270 MHz, CD3OD) δ 6.93 (1H, d, J = 2.0 Hz), 6.92 (2H, s), 6.80 (1H, dd,
J1,2 = 8.0, 2.0 Hz), 6.70 (1H, d, J = 8.0 Hz), 5.97 (2H, s), 5.54 (1H, m), 5.04
(1H, s), 3.83 (3H, s), 3.01 (1H, dd, J1,2 = 17.8, 4.6 Hz), 2.85 (1H, dd, J1,2 = 17.8,
2.6 Hz); 13C NMR (68 MHz, CD3OD) δ 167.1, 157.9, 157.8, 157.2, 151.5,
146.0, 141.1, 131.4, 126.5, 119.3, 116.0, 115.0, 110.3, 99.3, 96.6, 95.9, 78.5, 70.3,
60.7, 26.8.
calculated for C23H20O11Na [M+Na]+ 495.0904, found 495.0938; [α]D
=
20
− 148.9 (c 0.325, 50% acetone in H2O); IR (neat) 3332, 1703, 1618, 1365,
1244 cm− 1; 1H NMR (270 MHz, CD3OD) δ 7.05 (1H, d, J = 2.0 Hz), 7.01 (1H,
d, J = 2.0 Hz), 6.51 (2H, s), 5.97 (1H, d, J = 2.0 Hz), 5.95 (1H, d, J =2.0 Hz),
5.49 (1H, m), 4.99 (1H, m), 3.80 (3H, s), 2.99 (1H, dd, J1,2 = 17.1, 4.6 Hz), 2.86
(1H, dd, J1,2 = 17.1, 3.0 Hz); 13C NMR (68 MHz, CD3OD) δ 166.6, 157.1,
156.5, 148.6, 145.6, 145.3, 135.2, 134.0, 129.8, 129.0, 120.7, 109.5, 108.0, 102.6,
98.6, 95.8, 95.2, 78.2, 69.2, 55.6, 26.2.
(2R,3R)-2-(3,4-Bis(2-nitrophenylsulfonyloxy)phenyl)-3-hydroxychroman-5,7-diyl
bis(2-nitrophenylsulfonate) (41). In a similar manner to that used to prepare
28, treatment of (–)-Epicatechin gave 41 (92%) as a colorless amorphous.
HR-MS (FAB) calculated for C39H26N4O22S4 [M+H]+ 1052.9819, found
1052.9816; [α]D20 = +3.83 (c 1.06, acetone); IR (neat) 3404, 1705, 1620,
5-((2S,3R)-3-Hydroxy-5,7-bis(2-nitrophenylsulfonyloxy)chroman-2-yl)benzene-
1,2,3-triyl tris(2-nitrobenzenesulfonate) (42). In a similar manner to that used
to prepare 28, treatment of (–)-gallocatechin gave 42 (94%) as a colorless
amorphous. HR-MS (FAB) calculated for C45H30N5O27S5 [M+H]+ 1231.9732,
found 1231.9717; [α]D20 =− 1.61 (c 1.00, acetone); IR (neat) 3406, 1701, 1618,
1591, 1550, 1440, 1394, 1346, 1306, 1182, 1110, 999 cm− 1 1H NMR
;
(500 MHz, acetone-d6) δ 8.15–7.86 (16H, m), 7.57 (1H, dd, J1,2 = 8.6,
2.0 Hz), 7.39 (1H, d, J = 8.6 Hz), 7.38 (1H, d, J =2.0 Hz), 6.77 (1H, d,
J = 2.4 Hz), 6.51 (1H, d, J =2.4 Hz), 5.26 (1H, s), 4.33–4.26 (1H, m), 3.03–2.85
(2H, m); 13C NMR (126 MHz, acetone-d6) δ 156.2, 148.7, 148.5, 147.4, 140.8,
140.5, 140.1, 137.1, 137.0, 136.9, 136.9, 133.1, 133.1, 133.0, 132.9, 132.2, 132.0,
131.9, 131.7, 127.9, 127.7, 127.5, 127.3, 126.8, 125.5, 125.5, 125.4, 124.2, 122.9,
115.1, 109.7, 108.7, 78.2, 63.7, 29.3.
1589, 1542, 1421, 1388, 1362, 1305, 1222, 1193, 1114, 1008 cm− 1 1H NMR
;
(500 MHz, acetone-d6) δ 8.15–7.85 (20H, m), 7.32 (2H, s), 6.74 (1H, d,
J = 2.6 Hz), 6.55 (1H, d, J = 2.6 Hz), 5.00 (1H, d, J = 7.3 Hz), 4.75 (1H, d,
J = 5.1 Hz), 3.90–3.97 (1H, m), 2.82 (1H, dd, J1,2 = 16.8, 5.4 Hz), 2.66 (1H, dd,
J1,2 = 16.8, 8.6 Hz); 13C NMR (125 MHz, acetone-d6) δ 155.2, 148.7, 148.5,
148.2, 148.0, 147.6, 142.8, 140.2, 137.2, 137.2, 137.1, 136.9, 134.6, 133.2, 133.2,
133.1, 132.9, 132.2, 132.1, 131.9, 131.6, 128.6, 127.3, 127.1, 126.7, 125.5, 121.5,
115.7, 109.7, 109.3, 80.2, 65.6, 27.8.
(2R,3R)-2-(3,4-Bis(2-nitrophenylsulfonyloxy)phenyl)-5,7-bis(2-nitrophenylsulfonyloxy)
chroman-3-yl 3-methoxy-4,5-bis(2-nitrophenylsulfonyloxy)benzoate (74). In a
similar manner to that used to prepare 29, treatment of 41 with 25 gave
5-(2S,3R)-5,7-Bis(2-nitrophenylsulfonyloxy)-2-(3,4,5-tris(2-nitrophenylsulfonyloxy)
phenyl) chroman-3-yl-3-methoxy-4,5-bis(2-nitrophenylsulfonyloxy)benzoate (76).
In a similar manner to that used to prepare 29, treatment of 42 with 25 gave
74 (97%) as
a colorless amorphous. HR-MS (FAB) calculated for
C65H41N7O39S7Na [M+Na]+ 1566.9831, found 1566.9817; [α]D20 = − 32.1
(c 1.00, acetone); IR (neat) 1712, 1618, 1591, 1552, 1423, 1394, 1368, 1304,
1198, 1117, 1009 cm− 1 1H NMR (270 MHz, acetone-d6) δ 8.15–7.80 (28H,
;
76 (93%) as
a colorless amorphous. HR-MS (FAB) calculated for
m), 7.62 (1H, dd, J1,2 = 8.6, 2.0 Hz), 7.49 (1H, d, J = 2.0 Hz), 7.35 (1H, d, C65H41N7O39S7Na [M+Na]+ 1789.9383, found 1789.9375; [α]D20 = +4.03
J = 2.0 Hz), 7.32 (1H, d, J = 8.6 Hz), 7.22 (1H, d, J = 2.0 Hz), 6.98 (1H, d, (c 1.25, acetone); IR (neat) 1717, 1618, 1591, 1550, 1419, 1391, 1362, 1305,
1188, 1105, 1000 cm− 1 1H NMR (500 MHz, acetone-d6) δ 8.20–7.75 (28H,
;
J = 2.0 Hz), 6.66 (1H, d, J =2.0 Hz), 5.74 (1H, m), 5.63 (1H, s), 3.61 (3H, s),
3.33 (1H, dd, J1,2 = 17.8, 4.0 Hz), 3.23 (1H, dd, J1,2 = 17.8, 2.6 Hz); 13C NMR
(125 MHz, acetone-d6) δ 162.1, 155.6, 150.2, 148.7, 148.4, 147.8, 142.6, 141.0,
140.8, 138.5, 137.1, 137.0, 136.9, 133.1, 133.0, 133.0, 132.9, 132.3, 132.0, 131.9,
131.8, 127.6, 127.5, 127.4, 127.2, 126.9, 126.7, 125.5, 125.4, 125.4, 125.3, 124.8,
124.7, 124.7, 122.5, 113.7, 110.4, 109.7, 76.4, 67.7, 62.0, 26.0.
m), 7.56 (1H, d, J = 2.0 Hz), 7.39 (2H, s), 7.33 (1H, d, J = 2.0 Hz), 6.87 (1H, d,
J = 2.0 Hz), 6.66 (1H, d, J = 2.0 Hz), 5.63 (1H, d, J = 5.8 Hz), 5.44–5.40 (1H,
m), 3.65 (3H, s), 3.06 (1H, dd, J1,2 = 17.8, 6.3 Hz), 2.81 (1H, dd, J1,2 = 17.8,
4.6 Hz); 13C NMR (125 MHz, acetone-d6) δ 162.7, 154.5, 153.7, 148.7, 148.4,
148.2, 148.2, 148.1, 148.0, 143.2, 142.6, 138.8, 137.4, 137.3, 137.2, 137.0, 136.4,
133.2, 133.2, 133.0, 132.9, 132.2, 132.1, 132.0, 131.9, 131.7, 131.4, 129.6, 129.4,
128.2, 127.66, 127.1, 126.8, 126.6, 125.6, 125.5, 125.4, 125.2, 121.4, 116.4,
113.8, 113.0, 110.0, 109.9, 76.9, 68.7, 56.4, 23.1.
(2R,3R)-2-(3,4-Dihydroxyphenyl)-5,7-dihydroxychroman-3-yl 3,4-dihydroxy-5-
methoxybenzoate (8). In a similar manner to that used to prepare 2, treatment
of 74 gave 8 (87%) as a colorless amorphous. HR-MS (FAB) calculated for
C23H20O10Na [M+Na]+ 479.0954, found 479.0906; [α]D20 = − 194.4 (c 1.10,
(2S,3R)-5,7-Dihydroxy-2-(3,4,5-trihydroxyphenyl)chroman-3-yl 3,4-dihydroxy-5-
methoxybenzoate (10). In a similar manner to that used to prepare 2,
treatment of 76 gave 10 (81%) as a colorless amorphous. HR-MS (FAB)
calculated for C23H20O11Na [M+Na]+ 495.0904, found 495.0873; [α]
50% acetone in H2O); IR (neat) 3366, 1701, 1608, 1363, 1232 cm− 1; H NMR
1
(270 MHz, CD3OD) δ 7.07 (1H, d, J = 2.0 Hz), 7.02 (1H, d, J = 2.0 Hz), 6.96
(1H, d, J = 2.0 Hz), 6.80 (1H, dd, J = 7.9, 2.0 Hz), 6.70 (1H, d, J = 7.9 Hz), 5.98
(1H, d, J = 2.6 Hz), 5.97 (1H, d, J = 2.6 Hz), 5.51 (1H, m), 5.06 (1H, s), 3.81
(3H, s), 3.01 (1H, dd, J = 17.1, 4.6 Hz), 2.88 (1H, dd, J = 17.1, 2.6 Hz); 13C
NMR (68 MHz, CD3OD) δ 167.6, 157.9, 157.8, 157.2, 149.0, 146.1, 146.0,
146.0, 140.6, 131.5, 121.5, 119.2, 116.0, 115.1, 111.9, 106.2, 99.3, 96.6, 95.8,
78.5, 70.4, 56.6, 26.7.
D
20 = +13.9 (c 0.30, 50% acetone in H2O); IR (neat) 3369, 1701, 1611, 1375,
1240 cm− 1; 1H NMR (270 MHz, CD3OD) δ 7.07 (1H, d, J = 2.0 Hz), 7.01 (1H,
d, J = 2.0 Hz), 6.43 (2H, s), 5.96 (1H, d, J = 2.0 Hz), 5.94 (1H, d, J = 2.0 Hz),
5.35–5.25 (1H, m), 4.99 (1H, d, J = 6.6 Hz), 3.81 (3H, s), 2.90 (1H, dd,
J1,2 = 16.5, 4.6 Hz), 2.70 (1H, dd, J1,2 = 16.5, 6.0 Hz); 13C NMR (68 MHz,
CD3OD) δ 167.6, 158.1, 157.7, 156.6, 149.1, 147.0, 146.2, 140.7, 134.1, 130.9,
121.5, 111.9, 106.6, 106.2, 99.7, 96.5, 95.6, 79.7, 71.7, 56.7, 24.7.
(2R,3R)-2-(3,4-Bis(2-nitrophenylsulfonyloxy)phenyl)-5,7-bis(2-nitrophenylsulfony-
loxy) chroman-3-yl 4-methoxy-3,5-bis(2-nitrophenylsulfonyloxy)benzoate (75).
In a similar manner to that used to prepare 29, treatment of 41 with 22 gave
5-(2S,3R)-5,7-Bis(2-nitrophenylsulfonyloxy)-2-(3,4,5-tris(2-nitrophenylsulfonyloxy)
phenyl) chroman-3-yl-4-methoxy-3,5-bis(2-nitrophenylsulfonyloxy)benzoate (77).
In a similar manner to that used to prepare 29, treatment of 42 with 22 gave 77
as a crude colorless amorphous. The crude 77 was used in the next step without
further purification. 1H NMR (500 MHz, acetone-d6) δ 8.20–7.80 (28H, m),
7.68 (2H, s), 7.33 (2H, s), 6.86 (1H, d, J = 2.3 Hz), 6.64 (1H, d, J = 2.3 Hz), 5.63
(1H, d, J = 5.8 Hz), 5.37–5.42 (1H, m), 3.67 (3H, s), 3.01 (1H, dd, J1,2 = 18.4,
5.2 Hz), 2.71 (1H, dd, J1,2 = 18.4, 4.6 Hz).
75 (99%) as
a colorless amorphous. HR-MS (FAB) calculated for
C65H41N7O39S7Na [M+Na]+ 1566.9831, found 1566.9839; [α]D20 = − 35.4
(c 1.00, acetone); IR (neat) 1714, 1619, 1591, 1557, 1425, 1398, 1368, 1311,
1201, 1111, 1007 cm− 1; 1H NMR (270 MHz, acetone-d6) δ 8.15–7.80 (28H, m,
28H), 7.59 (1H, dd, J1,2 = 8.6, 2.0 Hz), 7.56 (2H, s), 7.40 (1H, d, J =2.0 Hz),
7.32 (1H, d, J = 8.6 Hz), 6.98 (1H, d, J = 2.0 Hz), 6.65 (1H, d, J =2.0 Hz), 5.71
(1H, m), 5.59 (1H, s), 3.69 (3H, s), 3.32 (1H, dd, J1,2 = 17.8, 4.0 Hz), 3.10 (1H,
dd, J1,2 = 17.8, 2.0 Hz); 13C NMR (125 MHz, acetone-d6) δ 162.1, 155.6, 150.2,
148.8, 148.5, 147.8, 142.6, 141.0, 140.8, 138.5, 137.0, 136.9, 133.1, 133.0, 132.9, (2S,3R)-5,7-Dihydroxy-2-(3,4,5-trihydroxyphenyl)chroman-3-yl 3,5-dihydroxy-4-
132.9, 132.3, 132.0, 131.9, 131.8, 127.6, 127.5, 127.4, 127.1, 126.9, 126.7, 125.5, methoxybenzoate (11). In a similar manner to that used to prepare 2,
The Journal of Antibiotics

Syntheses of methylated catechins and theaflavins
T Asakawa et al
12
treatment of crude 77 gave 11 (71%, two steps) as a colorless amorphous. (2R,3S)-2-(3,4-Dihydroxyphenyl)-5,7-dihydroxychroman-3-yl 3,5-dihydroxy-4-
HR-MS (FAB) calculated for C23H20O11Na [M+Na]+ 495.0904, found
methoxybenzoate (13). In a similar manner to that used to prepare 2,
495.0885; [α]D20 = +13.7 (c 0.25, 50% acetone in H2O); IR (neat) 3300, treatment of 79 gave 13 (89%) as a colorless amorphous. HR-MS (FAB)
1701, 1604, 1377, 1238 cm− 1
;
1H NMR (270 MHz, CD3OD) δ 6.95 (2H, s),
calculated for C23H20O10Na [M+Na]+ 479.0954, found 479.0994;
6.41 (2H, s), 5.96 (2H, s), 5.42–5.35 (1H, m), 5.04 (1H, d, J = 5.9 Hz), 3.84 [α]D20 = +110.6 (c 0.80, 50% acetone in H2O); IR (neat) 3367, 1701, 1604,
1
(3H, s), 2.80 (1H, dd, J1,2 = 16.5, 5.3 Hz), 2.71 (1H, dd, J1,2 = 16.5, 5.3 Hz); 13
C
1367, 1234 cm− 1; H NMR (270 MHz, CD3OD) δ 6.94 (2H, s), 6.83 (1H, s),
NMR (68 MHz, CD3OD) δ 167.1, 158.1, 158.0, 157.6, 157.5, 156.3, 151.6, 6.72 (2H, s), 5.97–5.93 (2H, m), 5.41–5.34 (1H, m), 5.05 (1H, d, J = 5.9 Hz),
3.84 (3H, s), 2.85 (1H, dd, J1,2 = 16.5, 5.3 Hz), 2.71 (1H, dd, J1,2 = 16.5, 6.6 Hz);
13C NMR (68 MHz, CD3OD) δ 167.1, 158.2, 157.6, 156.5, 151.6, 146.3, 146.3,
131.3, 126.5, 119.3, 116.2, 114.4, 110.2, 99.6, 96.5, 95.6, 79.3, 71.5, 60.7, 24.5.
147.0, 141.3, 134.0, 130.9, 126.5, 110.2, 106.4, 99.5, 79.2, 71.4, 60.7, 23.9.
(2R,3S)-2-(3,4-Bis(2-nitrophenylsulfonyloxy)phenyl)-3-hydroxychroman-5,7-diyl
bis(2-nitrophenylsulfonate) (43). In a manner similar to that used to prepare
28, treatment of (+)-catechin gave 43 (94%) as a colorless amorphous. HR-MS 5,7–Di-O-(2–nitrobenzenesulfonyl)catechin (51). To a solution of boric acid
(FAB) calculated for C39H26N4O22S4 [M+H]+ 1052.9819, found 1052.9843; (100 g, 1.6 mol) and NaOH (20 g) in H2O (1300 ml) was added 49 (10.0 g,
[α]D20 = +8.54 (c 1.00, acetone); IR (neat) 3498, 1713, 1618, 1595, 1545, 1419,
34.5 mmol) and the resulting solution was adjusted to pH 9.0 by the addition of
1 M NaOH. Then, 2-nitrobenzenesulfonyl chloride (15.3 g, 69.0 mmol) in
1392, 1350, 1304, 1191, 1112, 1015 cm− 1 1H NMR (270 MHz, CD3CN) δ
;
toluene (220 ml) was added dropwise over 30 min and the mixture was stirred
at room temperature for 7 h. The reaction was quenched with 1 M HCl and
extracted with ethyl acetate. The organic phase was dried over anhydrous
sodium sulfate and evaporated under reduced pressure. The residue was
purified by silica gel flash column chromatography (1–3% MeOH in CH2Cl2)
to afford 51 (15.9 g, 70%) as a pale yellow amorphous solid. HR-MS (ESI)
calculated for C27H20N2O14S2Na [M+Na]+ 683.0248, found 683.0281;
[α]20D = +13.3 (c 1.0, acetone) IR (neat) 3398, 1701, 1618, 1591, 1545, 1439,
1389, 1366, 1196, 1110, 1032, 997, 780 cm− 1; 1H NMR (500 MHz, acetone-d6)
δ 8.09–8.00 (3H, m), 7.98–7.75 (5H, m), 6.78 (1H, d, J = 8.0 Hz), 6.73 (1H, dd,
J1,2 = 6.5, 2.0 Hz), 6.60 (1H, dd, J1,2 = 8.0, 2.0 Hz), 6.55 (1H, d, J = 2.0 Hz), 4.85
(1H, d, J = 6.0 Hz), 4.39 (1H, d, J = 4.0 Hz), 4.10–4.05 (1H, m), 2.66 (1H, dd,
J1,2 = 17.0, 7.5 Hz), 2.53 (1H, dd, J1,2 = 17.0, 5.0 Hz); 13C NMR (126 MHz,
acetone-d6) δ 157.1, 149.5, 149.2, 149.0, 148.5, 148.4, 145.9, 145.8, 137.8, 137.7,
133.8, 133.6, 133.0, 132.5, 130.8, 128.2, 127.6, 126.2, 126.2, 119.1, 116.5, 116.0,
114.5, 110.3, 109.3, 82.7, 66.2, 27.6.
8.07–8.01 (4H, m), 7.91–7.71 (12H, m), 7.33–7.23 (3H, m), 6.74 (1H, d,
J = 2.5 Hz), 6.57 (1H, d, J = 2.5 Hz), 4.83 (1H, d, J = 7.3 Hz), 3.98 (1H, m),
2.98 (1H, dd, J1,2 =17.0, 5.0 Hz), 2.80 (1H, dd, J1,2 = 17.0, 8.0 H); 13C NMR
(68 MHz, CD3CN) δ 156.1, 149.3, 149.1, 148.9, 148.5, 141.8, 141.6, 140.7,
137.8, 137.7, 133.9, 133.8, 133.7, 133.1, 132.8, 132.7, 132.6, 128.4, 128.2, 128.0,
127.4, 126.2, 126.2, 125.4, 123.2, 116.3, 110.6, 110.1, 81.1, 66.1, 27.7.
(2R,3S)-2-(3,4-Bis(2-nitrophenylsulfonyloxy)phenyl)-5,7-bis(2-nitrophenylsulfony-
loxy) chroman-3-yl 3-methoxy-4,5-bis(2-nitrophenylsulfonyloxy)benzoate (78). In
a similar manner to that used to prepare 29, treatment of 43 with 25 gave
78 (74%) as
a colorless amorphous. HR-MS (FAB) calculated for
C65H41N7O39S7Na [M+Na]+ 1566.9831, found 1566.9819; [α]D20 = +22.4
(c 1.07, acetone); IR (neat) 1718, 1618, 1591, 1554, 1417, 1385, 1356, 1304,
1184, 1119, 1000 cm− 1 1H NMR (500 MHz, acetone-d6) δ 8.17–7.85 (28H,
;
m), 7.54 (1H, d, J = 2.3 Hz), 7.49 (1H, dd, J =8.6, 2.3 Hz), 7.39 (1H, d,
J = 8.6 Hz), 7.32 (1H, d, J = 2.3 Hz), 7.31 (1H, d, J = 2.3 Hz), 6.89 (1H, d,
J = 2.0 Hz), 6.65 (1H, d, J = 2.0 Hz), 5.59 (1H, d, J = 5.8 Hz), 5.46–5.42 (1H,
m), 3.65 (3H, s), 3.04 (1H, dd, J1,2 = 17.2, 5.2 Hz), 2.77 (1H, dd, J1,2 = 17.2,
4.6 Hz); 13C NMR (125 MHz, acetone-d6) δ 162.7, 154.8, 153.8, 148.7, 148.5,
148.4, 148.2, 148.1, 148.0, 142.6, 141.3, 141.1, 138.6, 137.2, 137.2, 137.1, 137.0,
136.4, 135.2, 133.2, 133.1, 133.0, 133.0, 132.9, 132.3, 131.9, 131.9, 131.8, 131.4,
129.6, 129.5, 127.6, 127.5, 127.3, 127.1, 126.9, 126.6, 125.6, 125.5, 125.5, 125.4,
125.4, 125.2, 125.1, 122.3, 116.3, 113.9, 112.9, 110.1, 109.8, 77.1, 68.9,
56.4, 23.2.
5,7–Di-O-(2–nitrobenzenesulfonyl)epicatechin (52). In a similar manner to that
used to prepare 51, treatment of 50 (5.0 g) gave 52 (7.1 g, 63%) as a pale yellow
amorphous solid. HR-MS (ESI) calculated for C27H20N2O14S2Na [M+Na]+
683.0248, found 683.0255; [α]20D = +6.5 (c 1.00, acetone); IR (neat) 3421, 1691,
1617, 1385, 1195, 1110, 997, 781 cm− 1 1H NMR (500 MHz, acetone-d6) δ
;
8.17-8.08 (4H, m, 4H), 8.06–8.01 (2H, m, 2H), 8.00–7.91 (2H, m), 7.91 (1H,
br s), 7.88 (1H, br s), 7.00 (1H, br s), 6.79 (2H, br s), 6.77 (1H, d, J = 2.0 Hz),
6.47 (1H, d, J = 2.0 Hz), 5.02 (1H, br s), 4.30–4.20 (1H, m), 4.06 (1H, d,
J = 4.5 Hz), 3.00–2.85 (2H, m); 13C NMR (126 MHz, acetone-d6) δ 157.0,
148.7, 148.5, 147.5, 144.8, 144.7, 136.9, 133.1, 132.9, 132.2, 131.8, 130.0, 127.6,
126.9, 125.5, 125.4, 118.5, 115.3, 114.8, 114.4, 109.6, 108.2, 79.5, 64.3, 29.1.
(2R,3S)-2-(3,4-Dihydroxyphenyl)-5,7-dihydroxychroman-3-yl 3,4-dihydroxy-5-
methoxybenzoate (12). In a similar manner to that used to prepare 2,
treatment of 78 gave 12 (99%) as a colorless amorphous. HR-MS (FAB)
calculated for C23H20O10Na [M+Na]+ 479.0954, found 479.0994,
[α]D20 = +142.5 (c 0.34, 50% acetone in H2O); IR (neat) 3331, 1705, 1612,
5,7–Di-O-(2–nitrobenzenesulfonyl)epigallocatechin (53). In a similar manner to
that used to prepare 51, treatment of 27 (4.0 g) gave 53 (4.6 g, 52%) as a brown
amorphous solid. HR-MS (ESI) calculated for C27H20N2O15S2Na [M+Na]+
699.0197, found 699.0191; [α]20D = +4.1 (c 1.00, acetone); IR (neat) 3342, 1701,
1385, 1231 cm− 1 1H NMR (270 MHz, CD3OD) δ 7.07 (1H, d, J = 2.0 Hz),
;
7.01 (1H, d, J =2.0 Hz), 6.86 (1H, d, J = 2.0 Hz), 6.71–6.76 (2H, m), 5.97 (1H,
d, J = 2.0 Hz), 5.94 (1H, d, J = 2.0 Hz), 5.28–5.37 (1H, m), 5.03 (1H, d,
J = 6.6 Hz), 3.82 (3H, s), 2.92 (1H, dd, J1,2 = 16.5, 5.3 Hz), 2.71 (1H, dd,
J1,2 = 16.5, 7.3 Hz); 13C NMR (68 MHz, CD3OD) δ 167.4, 158.2, 157.7, 156.7,
149.0, 146.4, 146.2, 140.7, 131.4, 121.4, 119.4, 116.2, 114.7, 111.9, 106.2, 99.8,
96.5, 95.6, 79.7, 71.2, 56.7, 25.1.
1620, 1591, 1547, 1441, 1385, 1368, 1194, 1111, 997, 781 cm− 1 1H NMR
;
(500 MHz, acetone-d6) δ 8.20–7.75 (8H, m), 7.34 (1H, s), 7.00 (1H, br s),
6.75 (1H, d, J = 2.5 Hz), 6.51 (2H, s), 6.47 (1H, d, J = 2.0 Hz), 4.96 (1H, br s),
4.26–4.20 (1H, m), 4.01 (1H, d, J = 4.5 Hz), 2.93 (1H, dd, J1,2 = 16.5, 4.0 Hz),
2.53 (1H, dd, J1,2 = 16.5, 4.0 Hz); 13C NMR (126 MHz, acetone-d6) δ 157.7,
149.4, 148.2, 146.1, 137.7, 133.8, 133.6, 133.2, 133.0, 132.6, 130.0, 128.3, 127.6,
126.2, 126.2, 110.3, 108.9, 106.7, 80.1, 65.1, 30.0.
(2R,3S)-2-(3,4-Bis(2-nitrophenylsulfonyloxy)phenyl)-5,7-bis(2-nitrophenylsulfony-
loxy) chroman-3-yl 4-methoxy-3,5-bis(2-nitrophenylsulfonyloxy)benzoate (79). In
a similar manner to that used to prepare 29, treatment of 43 with 22 gave
(2R,3R)-5,7,5,7-Tetra-O–(2-nitrobenzenesulfonyl)neotheaflavin (56). To a solu-
tion of 50 (1.0 g, 1.5 mmol) in MeCN (15 ml) was added Pb(OAc)4 (806 mg,
4.5 mmol) at 0 °C. The resulting suspension was stirred for 10 min at 0 °C. The
reaction mixture was added to benzene, and then the mixture was filtered
through a pad of celite. Then, the filtrate was evaporated under reduced
pressure, and the resulting crude product was used in the next reaction without
further purification.
79 (89%) as
a colorless amorphous. HR-MS (FAB) calculated for
C65H41N7O39S7Na [M+Na]+ 1566.9831, found 1566.9825; [α]D20 = +21.0
(c 1.10, acetone); IR (neat) 1705, 1618, 1593, 1554, 1418, 1395, 1365, 1315,
1177, 1119, 1011 cm− 1 1H NMR (500 MHz, acetone-d6) δ 8.18–7.88 (28H,
;
m), 7.67 (2H, s), 7.45 (1H, dd, J = 8.6, 2.3 Hz), 7.39 (1H, d, J = 8.6 Hz), 7.26
(1H, d, J = 2.3 Hz), 6.88 (1H, d, J = 2.0 Hz), 6.65 (1H, d, J = 2.0 Hz), 5.58
(1H, d, J = 5.2 Hz), 5.43–5.39 (1H, m), 3.69 (3H, s), 3.00 (1H, dd, J1,2 = 17.8,
5.8 Hz), 2.66 (1H, dd, J1,2 = 17.8, 4.6 Hz); 13C NMR (125 MHz, acetone-d6) δ
The crude product 55 was dissolved in MeCN/CH2Cl2 (1:4, 25 ml). To this
162.2, 154.7, 150.3, 148.8, 148.5, 148.5, 148.4, 148.1, 148.1, 142.6, 141.3, 141.1, solution were added MS3A (1.0 g) and Ns-epigallocatchin (53) (342 mg,
138.5, 137.2, 137.2, 137.1, 137.1, 137.0, 133.1, 133.0, 132.9, 132.3, 132.0, 131.9, 505 μmol) in MeCN/CH2Cl2 (1:4, 10 ml) at 0 °C. The resulting suspension
131.8, 131.8, 127.6, 127.5, 127.3, 127.0, 126.9, 126.6, 125.6, 125.5, 125.4, 125.1, was stirred for 20 min at 0 °C. After the addition of H2O, the mixture was
124.8, 122.1, 113.8, 110.1, 109.9, 77.0, 68.6, 61.9, 22.9.
stirred for 5 min at room temperature. The reaction mixture was filtered, and
The Journal of Antibiotics

Syntheses of methylated catechins and theaflavins
T Asakawa et al
13
then the filtrate was extracted with AcOEt, the organic phase was washed with 4.0 Hz), 2.93 (1H, dd, J1,2 =17.0, 4.0 Hz), 2.82 (1H, br d, J = 16.0 Hz), 2.80
H2O, and evaporated under reduced pressure. The residue was purified by (1H, br d, J = 16.0 Hz); 13C NMR (126 MHz, CD3OD) δ 184.7, 157.0, 156.9,
silica gel flash column chromatography (CH2Cl2:MeOH= 98:2) to afford 56 156.6, 156.4, 156.1, 156.1, 155.4, 149.8, 145.2, 133.4, 130.2, 127.7, 125.0, 122.7,
(327 mg, 50%) as an orange amorphous solid. HR-MS (ESI) calculated for 120.9, 117.1, 99.0, 98.4, 95.5, 94.8, 94.3, 80.0, 75.9, 65.3, 64.4, 28.6, 28.1.
C53H36N4O28S4Na [M+Na]+ 1327.0291, found 1327.0284; [α]20D =–6.6 Analytical data for theaflavin (4) in ref. 16.
(c 0.20, acetone); IR (neat) 3352, 1701, 1618, 1591, 1541, 1477, 1437, 1384,
;
1361, 1232, 1190, 1106, 1058, 1030, 995 850, 775, 736 cm− 1 1H NMR
(2R,3S)-3-Hydroxy-2-(3,4,6-trihydroxy-5-oxo-5H-benzo[7]annulen-1-yl)chroman-
5,7-diyl bis(2-nitrobenzenesulfonate) (80). To a solution of 51 (100 mg,
152 μmol) in MeCN (2 ml) was added Pb(OAc)4 (53.7 mg, 121 μmol) at
0 °C. The resulting suspension was stirred for 10 min at 0 °C. To the reaction
mixture was added benzene (6.7 ml), and then the mixture was filtered through
a pad of celite. Then, the filtrate was evaporated under reduced pressure, and
the resulting crude product was used in the next reaction without further
purification.
(500 MHz, acetone-d6) δ 8.18–7.86 (16H, m), 7.51 (1H, s), 7.47 (1H, s), 6.88
(1H, s), 6.83 (1H, br s), 6.63 (1H, d, J = 2.0 Hz), 6.53 (1H, d, J = 2.0 Hz), 5.85
(1H, br s), 5.17 (1H, s), 4.49 (1H, s), 4.31–2.98 (1H, m), 3.10 (1H, dd,
J1,2 = 17.5, 2.5 Hz), 3.05 (1H, dd, J1,2 =17.5, 2.5 Hz), 2.80 (1H, dd, J1,2 = 17.0,
7.5 Hz), 2.65–2.50 (1H, br s); 13C NMR (125 MHz, acetone-d6) δ 184.8, 156.9,
156.7, 154.5, 151.2, 149.2, 149.2, 149.1, 149.0, 148.8, 148.4, 148.1, 146.3, 137.6,
137.6, 137.5, 133.8, 133.7, 133.7, 133.6 132.9, 132.8, 132.5, 132.3, 130.4, 129.7,
128.1, 128.0, 127.9, 127.5, 127.3, 126.2, 126.1, 126.1, 126.1, 121.6, 118.6, 116.3,
115.7, 110.5, 110.3, 109.7, 109.4, 82.0, 69.7, 66.5, 64.7, 55.2, 29.6, 29.5.
The crude product 55 was dissolved in MeCN/CH2Cl2 (1:4, 1.65 ml). To this
solution were added MS3A (30 mg) and pyrogallol 65 (19 mg, 150 μmol) in
MeCN/CH2Cl2 (1:4, 0.50 ml) at 0 °C. The resulting suspension was stirred for
20 min at 0 °C. After the addition of H2O, the mixture was stirred for 5 min at
room temperature. The reaction mixture was filtered, and then the filtrate was
extracted with AcOEt, the organic phase was washed with H2O and evaporated
under reduced pressure. The residue was purified by preparative TLC (CH2Cl2:
MeOH= 98:2) to afford 80 (19.5 mg) as a orange amorphous solid. HR-MS
(ESI) calculated for C32H22N2O16S2Na [M+Na]+ 777.0320, found 777.0269;
[α]20D = +52.9 (c 0.20, acetone); IR (neat) 3420, 1554, 1384, 1195, 1111,
Neotheaflavin (5). To a suspension of Cs2CO3 (223 mg, 0.17 mmol) and
thiophenol (0.17 ml, 1.7 mmol) in MeCN/DMF(1:2, 2.7 ml) was added the
solution of 56 in MeCN (3.0 ml) at 0 °C and the reaction mixture was stirred at
the same temperature for 2.0 h. The reaction was quenched with 1 M HCl
aqueous and extracted with AcOEt. The organic phase was evaporated under
reduced pressure. The residue was purified by preparative TLC (CH2Cl2:
MeOH = 9:1) to afford 5 (53.1 mg, 55%) as a orange amorphous solid. HR-MS
(ESI) calculated for C29H24O12Na [M+Na]+ 587.1159, found 587.1130;
[α]20D = –122.1 (c 0.20, acetone); IR (neat) 3362, 1699, 1622, 1607, 1506,
1
997 cm− 1; H NMR (500 MHz, methanol-d4) δ 8.15–7.90 (8H, m), 7.88 (1H,
d, J = 12.0 Hz), 7.47 (1H, s), 7.25 (1H, d, J =9.2 Hz), 6.90 (1H, dd, J1,2 = 12.0,
9.2 Hz), 6.79 (1H, d, J = 2.3 Hz), 6.60 (1H, d, J = 2.3 Hz), 5.75 (1H, d,
J = 6.2 Hz), 4.31–4.24 (1H, m), 2.82 (1H, dd, J1,2 = 16.9, 7.7 Hz), 2.65 (1H, dd,
J1,2 = 16.9, 4.3 Hz); 13C NMR (126 MHz, acetone-d6) δ 157.0, 148.9, 148.4,
145.8, 145.8, 137.7, 137.6, 133.7, 133.6, 133.0, 132.5, 130.8, 128.1, 127.5, 126.2,
126.1, 119.1, 116.5, 116.0, 114.4, 110.3, 109.3, 82.6, 66.1, 27.5.
1472, 1429, 1361, 1236, 1193, 1143, 1099, 1076, 1046, 1012, 823 cm− 1 1H
;
NMR (500 MHz, acetone-d6) δ 8.80 (1H, br s), 8.26 (1H, s), 7.77 (1H, s), 7.66
(1H, s), 6.06 (1H, s), 6.03 (1H, s), 5.95 (1H, s), 5.94 (1H, s), 5.60 (1H, d,
J = 5.0 Hz), 5.01 (1H, s), 4.36 (1H, br s), 4.12–4.06 (1H, m), 3.00–2.75 (3H,
m), 2.63 (1H, dd, J1,2 = 16.0, 9.0 Hz); 13C NMR (125 MHz, acetone-d6) δ 184.9,
157.7, 157.5, 157.4, 157.1, 156.7, 156.6, 154.4, 150.6, 146.3, 134.9, 132.3, 130.9,
128.7, 122.4, 121.7, 119.3, 100.8, 99.3, 96.4 96.3, 95.6, 95.4, 81.7, 79.3, 69.5,
66.7, 30.6, 29.4. Analytical data for neotheaflavin (5) in ref. 16.
3,4,6-Trihydroxy-1-((2R,3S)-3,5,7-trihydroxychroman-2-yl)-5H-benzo[7]annulen-
5-one (67). To a suspension of Cs2CO3 (40.0 mg, 53.0 μmol) and thiophenol
(55 μl, 0.53 mmol) in MeCN/DMF(1:2, 0.9 ml) was added solution of the
(2R,3R)-5,7,5,7-Tetra-O–(2-nitrobenzenesulfonyl)theaflavin (64). To a solution crude of 80 in MeCN (1.0 ml) at 0 °C and the reaction mixture was stirred at
of 52 (500 mg, 757 mmol) in MeCN (7 ml) was added Pb(OAc)4 (268 mg, the same temperature for 2 h. The reaction was quenched with 1 M HCl
605 mmol) at 0 °C. The resulting suspension was stirred for 10 min at the same
temparature. The reaction mixture was added benzene (20 ml), and then the reduced pressure. The residue was purified by preparative TLC (CH2Cl2:
aqueous and extracted with AcOEt. The organic phase was evaporated under
mixture was filtered with celite pad. Then the filtrate was evaporated under
reduced pressure, and the resulting crude product was used in the next reaction
without further purification.
MeOH= 9:1) to afford 67 (15.9 mg, 78% ) as a orange amorphous solid.
HR-MS (ESI) calculated for C20H16O8Na [M+Na]+ 407.0737, found 407.0748;
[α]20D = –24.8 (c 0.20, acetone); IR (neat) 3319, 1602, 1411, 1327, 1253, 1070,
1
825 cm− 1; H NMR (500 MHz, methanol-d4) δ 7.84 (1H, d, J = 12.5 Hz), 7.60
The crude product 63 was dissolved in MeCN/CH2Cl2 (1:4, 12 ml). The
solution was added MS3A (300 mg), Ns-epigallocatchin 53 (171 mg,
252 mmol) in MeCN/CH2Cl2 (1:4, 4 ml) at 0 °C. The resulting suspension
was stirred for 20 min at 0 °C. After the addition of H2O, the mixture was
stirred for 5 min at room temperature. The reaction mixture was filtered, and
then the filtrate was extracted with AcOEt, the organic phase was washed with
H2O, and evaporated under reduced pressure. The residue was purified by
chromatography on silica gel column (CH2Cl2:MeOH = 9:1) to afford mixture
of 64 and 52 as an orange amorphous solid, and the mixture of product was
used in the next reaction without further purification. HR-MS (ESI) calculated
for C53H36N4O28S4Na [M+Na]+ 1327.0291, found 1327.0245.
(1H, s), 7.15 (1H, d, J = 9.1 Hz), 6.80 (1H, dd, J1,2 =12.5, 9.1 Hz), 6.79 (1H, d,
J = 2.3 Hz), 6.60 (1H, d, J = 2.3 Hz), 5.75 (1H, d, J = 6.2 Hz), 4.20–4.13 (1H,
m), 2.86 (1H, dd, J1,2 = 16.3, 5.3 Hz), 2.62 (1H, dd, J1,2 = 16.1, 8.5 Hz); 13C
NMR (126 MHz, methanol-d4) δ 186.3, 158.0, 157.7, 156.7, 156.6, 151.9, 147.1,
131.5, 130.0, 124.1, 122.9, 122.6, 118.6, 100.7, 96.7, 95.5, 80.2, 68.9, 49.7, 28.9.
Methyl 3,4,6-trihydroxy-1-((2R,3S)-3-hydroxy-5,7-bis(((2-nitrophenyl)sulfonyl)
oxy) chroman-2-yl)-5-oxo-5H-benzo[7]annulene-8-carboxylate (81). To a solu-
tion of 51 (200 mg, 303 μmol) in MeCN (3 ml) was added Pb(OAc)4 (161 mg,
363 μmol) at 0 °C. The resulting suspension was stirred for 10 min at 0 °C. The
reaction mixture was added to benzene, and then the mixture was filtered
through a pad of celite. Then, the filtrate was evaporated under reduced
pressure, and the resulting crude product was used in the next reaction without
further purification.
Theaflavine (4). To a solution of the crude 64 (249 mg) in MeCN/DMF (1:2,
3.0 ml) were added Cs2CO3 (257 mg, 789 mmol) and thiophenol 39 (0.09 ml,
879 mmol) at 0 °C and the reaction mixture was stirred for 3 h at the same
temperature. The reaction was quenched with 1 N HCl aqueous and extracted
The crude product 55 was dissolved in MeCN/CH2Cl2 (1:4, 5.0 ml). To the
with AcOEt. The organic layer was evaporated under reduced pressure and the solution were added MS3A (200 mg) and methyl gallate (66) (18.6 mg,
residue was purified by HPLC to afford Theaflavin (4) (16 mg, 11% for two 101 μmol) in MeCN/CH2Cl2 (1:4, 2.0 ml) at 0 °C. The resulting suspension
steps) as an orange amorphous solid. HR-MS (ESI) calculated for C29H24O12Na was stirred for 20 min at 0 °C. After the addition of H2O, the mixture was
[M+Na]+ 587.1159, found 587.1164; [α]20D = –274.8 (c 0.20, acetone); IR stirred for 5 min at room temperature. The reaction mixture was filtered, and
(neat) 3275, 1691, 1624, 1600, 1507, 1460, 1419, 1352, 1230, 1197, 1138, 1089, then the filtrate was extracted with AcOEt, the organic phase was washed with
1060, 1041, 1010, 891, 805, 706 cm− 1 1H NMR (500 MHz, CD3OD) δ 7.94 H2O and evaporated under reduced pressure. The residue was purified by
;
(1H, s), 7.81 (1H, s), 7.33 (1H, s), 6.00 (1H, d, J = 2.0 Hz), 5.97 (1H, d, preparative TLC (CH2Cl2:MeOH =98:2) to afford 81 (40.6 mg, 50%) as a
J = 2.0 Hz), 5.95 (1H, d, J = 2.0 Hz), 5.94 (1H, d, J =2.0 Hz), 5.62 (1H, s), 4.86 orange amorphous solid. HR-MS (ESI) calculated for C34H24N2NaO18S2
(1H, s), 4.47–4.41 (1H, m), 4.32–4.25 (1H, m), 2.96 (1H, dd, J1,2 = 17.0, [M+Na]+ 835.0358, found 835.0343; [α]20D = +9.6 (c 0.20, acetone); IR (neat)
The Journal of Antibiotics

Syntheses of methylated catechins and theaflavins
T Asakawa et al
14
3369, 1701, 1385, 1248, 1195, 1111, 999, 781 cm− 1
;
1H NMR (500 MHz,
9
Fujimura, Y. et al. Antiallergic tea catechin, (–)-epigallocatechin-3-O-(3-O-methyl)-
gallate, suppresses FcepsilonRI expression in human basophilic KU812 cells. J. Agric.
Food Chem. 50, 5729–5734 (2002).
acetone-d6) δ 8.88 (1H, s), 8.12–7.93 (8H, m), 7.76 (1H, s), 7.58 (1H, s), 6.82
(1H, d, J = 2.3 Hz), 6.61 (1H, d, J = 2.3 Hz), 5.62 (1H, d, J = 7.5 Hz), 4.33–4.26
(1H, m), 3.84 (1H, s), 2.90 (1H, m), 2.74 (1H, dd, J1,2 = 17.2, 8.6 Hz);13C NMR
(126 MHz, acetone-d6) δ 186.8, 168.5, 157.6, 155.4, 153.1, 150.3, 150.1, 149.9,
149.7, 149.4, 138.7, 134.7, 134.5, 134.3, 133.9, 133.6, 133.5, 129.1, 129.0,
128.3, 127.2, 127.1, 125.1, 123.6, 123.1, 117.5, 116.8, 111.4, 110.8, 82.1, 67.5,
54.3, 31.4.
10 Suzuki, M., Yoshino, K., Maeda-Yamamoto, M., Miyase, T. & Sano, M. Inhibitory effects
of tea catechins and O-methylated derivatives of (–)-epigallocatechin-3-O-gallate on
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Methyl
3,4,6-trihydroxy-5-oxo-1-((2R,3S)-3,5,7-trihydroxychroman-2-yl)-5H-
benzo[7] annulene-8-carboxylate (68). To a suspension of Cs2CO3 (52.1 mg,
64.1 μmol) and thiophenol (66 μl, 641 μmol) in MeCN/DMF(1:2, 0.9 m;) was
added solution of 81 in MeCN (1.0 ml) at 0 °C and the reaction mixture was
stirred at the same temperature for 30 min. The reaction was quenched with
1 M HCl aqueous and extracted with AcOEt. The organic phase was evaporated
under reduced pressure. The residue was purified by preparative TLC (CH2Cl2:
MeOH= 9:1) to afford 68 (13.4 mg, 47%) as a orange amorphous solid.
HR-MS (ESI) calculated for C22H18O10Na [M+Na]+ 465.0792, found 465.0795;
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& De Freitas, V. A. P. Hydrolysis of
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[α]20D = –44.6 (c 0.20, acetone); IR (neat) 3346, 1701, 1608, 1225 cm− 1 1H
;
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NMR (500 MHz, methanol-d4) δ 8.92 (1H, s), 7.69 (1H, s), 7.62 (1H, s), 5.97
(1H, d, J = 1.7 Hz), 5.91 (1H, d, J = 1.7 Hz), 5.34 (1H, d, J = 8.0 Hz), 4.35–4.13
(1H, m), 3.82 (1H, s), 2.97 (1H, dd, J1,2 =16.1, 5.7 Hz), 2.61 (1H, dd,
J1,2 = 16.0, 9.2 Hz); 13C NMR (126 MHz, methanol-d4) δ 186.8, 181.9, 158.1,
157.7, 156.6, 155.0, 152.4, 149.7, 134.6, 134.4, 128.7, 124.0, 123.5, 112.8, 115.9,
100.8, 96.7, 95.5, 81.3, 69.1, 53.5, 29.7.
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CONFLICT OF INTEREST
The authors declare no conflict of interest.
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ACKNOWLEDGEMENTS
We thank Dr Masayuki Suzuki (Mitsui Norin Co., Ltd) for providing samples
of (–)-EGC, (–)-EC and (–)-GC. This work was financially supported by a
grant from the Shizuoka Prefecture and Shizuoka City Collaboration of
Regional Entities for the Advancement of Technological Excellence, a grant
from the Japan Science and Technology Agency (JST), the Uehara Memorial
Foundation (Y.H.), MEXT/JSPS KAKENHI grant numbers 23390007 and
24790017, Grants-in-Aid for Scientific Research on Priority Areas 12045232
and 24105530 from the Ministry of Education, Culture, Sports, Science and
Technology (MEXT) of Japan, and a grant for Platform for Drug Discovery,
Informatics, and Structural Life Science from the Ministry of Education,
Culture, Sports, Science and Technology.
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The Journal of Antibiotics