Synthesis of procyanidin B3 and its anti-inflammatory activity. the effect of 4-alkoxy group of catechin electrophile in the Yb(OTf)3-catalyzed condensation with catechin nucleophile

Article abstract of DOI:10.1021/jo1009382

(Figure Presented) Yb(OTf)₃-catalyzed equimolar condensation of the benzylated catechin with various 4-alkoxy catechin derivatives was studied. In particular, the reaction using 4-(2′′-ethoxyethoxy)flavan derivative gave good yield with excellent stereoselectivity. The condensed product was successfully converted to procyanidin B3 (1). The anti-inflammatory effect of procyanidin B3 (1) on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation of mouse ears was examined. The anti-inflammatory activity of 1 was stronger than that of indomethacin and glycyrrhetinic acid, the normally used anti-inflammatory agents.

Full text of DOI:10.1021/jo1009382

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and skins and red wines are rich sources of polyphenols.
Synthesis of Procyanidin B3 and Its
Anti-inflammatory Activity. The Effect of
4-Alkoxy Group of Catechin Electrophile
in the Yb(OTf)3-Catalyzed Condensation with
Catechin Nucleophile
Many biological activities, and especially powerful free-
radical scavenging activity, have been reported for flavo-
noids. Procyanidins have various types of structures derived
from flavonoid monomers typically via a C4-C8 intermole-
cular bond. The procyanidins are often isolated as complex
stereochemical and oligomeric mixtures. Thus, it is difficult
to obtain pure materials. Because of this problem, stereo-
selective synthetic efforts were devoted.3 However, efficient
syntheses are very limited because condensation reaction
required large excess amount of nucleophile at low tempera-
ture to limit the reaction of activated monomer with itself or
with the dimeric product, leading in both cases to oligomeric
side products.4,5
Yukiko Oizumi,† Yoshihiro Mohri,† Mitsuru Hirota,‡ and
Hidefumi Makabe*,†
†Sciences of Functional Foods, Graduate School of
Agriculture, and ‡Department of Bioscience and
Biotechnology, Faculty of Agriculture, Shinshu University
8304, Minami-minowa, Kami-ina, Nagano 399-4598, Japan
In preivious papers, we described Yb(OTf)3-catalyzed
equimolar condensation of catechin nucleophile and elec-
trophile derivatives and its application to the synthesis of
procyanidin B3 (1) (Figure 1).6,7 The problem with this reac-
tion is that the yield of condensation is rather low. In this
paper, we report further investigation of Yb(OTf)3-catalyzed
equimolar condensation with various 4-alkoxy catechin deri-
vatives as electrophiles and describe the detail of other rare
metal Lewis acid catalyzed condensation.
makabeh@shinshu-u.ac.jp
Received May 13, 2010
We chose tetrabenzylated catechin 2, a nucleophilic unit,
prepared by Kawamoto and co-workers.8 As with the elec-
trophilic unit, compounds 3-8 were prepared according
to Saito’s procedure.3b Equimolar condensation of 2 with
4-alkoxy catechin derivatives 3-8 was examined using
Yb(OTf)3 at room temperature in CH2Cl2 (Table 1).
Yb(OTf)3-catalyzed equimolar condensation of the benzyl-
ated catechin with various 4-alkoxy catechin derivatives
was studied. In particular, the reaction using 4-(200-ethoxy-
ethoxy)flavan derivative gave good yield with excellent
stereoselectivity. The condensed product was successfully
converted to procyanidin B3 (1). The anti-inflammatory
effect of procyanidin B3 (1) on 12-O-tetradecanoylphorbol-
13-acetate (TPA)-induced inflammation of mouse ears was
examined. The anti-inflammatory activity of 1 was stronger
than that of indomethacin and glycyrrhetinic acid, the
normally used anti-inflammatory agents.
Procyanidins are known as condensed or noncondensed
hydrolyzable tannins.1 These condensed tannins are widely
distributed in the plant kingdom.2 In particular, grape seeds
As shown in Table 1, methoxy, ethoxy, benzyloxy, and
ethylene glycol derivatives gave condensed product in low to
moderate yield. On the other hand, 4-(200-ethoxyethoxy)
(1) Ferreira, D.; Li, X.-C. Nat. Prod. Rep. 2000, 17, 193–212.
(2) Ferreira, D.; Li, X.-C. Nat. Prod. Rep. 2002, 19, 517–541.
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(3) (a) Tuckmantel, W.; Kozikowski, A. P.; Romanczyk, L. J., Jr. J. Am.
Chem. Soc. 1999, 121, 12073–12081. (b) Saito, A.; Nakajima, N.; Tanaka, A.;
Ubukata, M. Tetrahedron 2002, 58, 7829–7837. (c) Kozikowski, A. P.;
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Tuckmantel, W.; Bottcher, G.; Romanczyk, L. J., Jr. J. Org. Chem. 2003,
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Ubukata, M. Heterocycles 2004, 62, 479–489. (e) Tarascou, I.; Barathieu, K.;
1287–1296.
(5) (a) Saito, A.; Nakajima, N.; Tanaka, A.; Ubukata, M. Heteocycles
2003, 61, 287–298. (b) Saito, A.; Nakajima, N.; Tanaka, A.; Ubukata, M.
Tetrahedron Lett. 2003, 44, 5449–5452.
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5367–5377. (f) Ohmori, K.; Ushimaru, N.; Suzuki, K. Proc. Natl. Acad. Sci.
U.S.A. 2004, 101, 12002–12007. (g) Achilonu, M. C.; Bonnet, S. L.; van der
Westhuizen, J. H. Org. Lett. 2008, 10, 3865–3867. (h) Oyama, K.-I.; Kuwano,
M.; Ito, M.; Yoshida, K.; Kondo, T. Tetrahedron Lett. 2008, 49, 3176–3180.
(i) Saito, A.; Mizushina, Y.; Tanaka, A.; Nakajima, N. Tetrahedron 2009, 65,
7422–7428. (j) Alharthy, R. D.; Hayes, C. J. Tetrahedron Lett. 2010, 51,
1193–1195.
(6) Mohri, Y.; Sagehashi, M.; Yamada, T.; Hattori, Y.; Morimura, K.;
Kamo, T.; Hirota, M.; Makabe, H. Tetrahedron Lett. 2007, 48, 5891–5894.
(7) Mohri, Y.; Sagehashi, M.; Yamada, T.; Hattori, Y.; Morimura, K.;
Hamauzu, Y.; Kamo, T.; Hirota, M.; Makabe, H. Heterocycles 2009, 79,
549–563.
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4884 J. Org. Chem. 2010, 75, 4884–4886
Published on Web 06/22/2010
DOI: 10.1021/jo1009382
r
2010 American Chemical Society

Oizumi et al.
JOCNote
SCHEME 1. Synthesis of Procyanidin B3 (1)
FIGURE 1. Structure of catechin and procyanidin B3 (1).
TABLE 1. Equimolar Condensation of 4-Alkoxy Catechin Derivatives
3-8 with Tetra-O-benzylated Catechin Derivative 2 by Yb(OTf)3
entry
electrophile
time (h)
yield (%)
1
2
3
4
5
6
3
4
5
6
7
8
2
2.5
4
4
6
64
53
28
30
54
80
2
TABLE 3. Anti-inflammatory Activty of Procyanidin B3 (1) in the
Mouse Ear Inflammatory Testa
TABLE 2. Condensation of 4-(200-Ethoxyethoxy) Catechin Derivative 8
with 2 by Rare Metal Lewis Acids and AgBF4
test compound
inhibitory effect (%)
procyanidin B3 (1)
glycyrrhetinic acid
indomethacin
41 ( 1.39*
24 ( 1.18*
16 ( 0.77*
entry
Lewis acid
time (h)
yield (%)
11
not detected
1
2
3
4
5
6
7
8
TiCl4
BF3 Et2O
3
0.5
3
24
1.5
2.5
4
3
aA sample (200 μg) was applied on one mouse ear, and after 30 min,
TPA (0.5 μg) was applied to both ears of the mouse. The edema was
evaluated after 7 h, with the inhibitory effect being expressed as the
percentage ratio of the edema. Five mice were used for each experi-
ment.10 *Significantly different, P < 0.05 with Student’s t test.
Et2AlCl
AgBF4
9
trace
32
45
31
80
Tm(OTf)3
Er(OTf)3
Lu(OTf)3
Yb(OTf)3
2
The mouse ear inflammation test was used to evaluate the
anti-inflammatory activity of 1. The activity of 1 is summa-
rized in Table 3. Compound 1 suppressed the TPA-induced
edema up to IE of 41% with 200 μg painted on the mouse ear.
Indomethacin and glycyrrhetinic acid, the normally used
anti-inflammatory agents, only inhibited up to IE of 16 and
24%, respectively, at the same application. Mizushina and
co-workers also reported the anti-inflammatory activity and
the derivatives.9 Their report showed that the inhibition of
DNA polymerase R (pol R) by catechin derivatives had a
high correlation with the TPA-induced anti-inflammatory
activity. Thus, 1 could be considered a possible candidate for
an anticancer agent (Table 3).
derivative 8 gave R-9 in 80% yield. The stereoselectivity at
the C-4 position was determined by 1H NMR analysis of the
diacetate derivative of the condensed product according to
Saito’s method.3b In all cases, the ratio of R-9/β-9 was more
than 49:1. Next, typical Lewis acids and rare metal Lewis
acids around Yb in the periodical table were investigated
(Table 2). TiCl4 and BF3 Et2O gave sluggish results. These
3
reactions required large excess amount of nucleophile at low
temperature in order to limit the reaction of the activated
monomer with itself or with the dimeric product, leading in
both cases to oligomeric side products.3b,8 Interestingly,
using AgBF4 as a Lewis acid gave a trace amount of con-
densed product, although 4-methoxy derivative 3 gave 50%
yield with excellent stereoselectivity, as we have reported
before.6 Among the rare metal Lewis acids, only Yb(OTf)3
afforded R-9 in good yield. In these cases, the ratio of R-9/β-9
Experimental Section
[4,8]-2,3-trans-3,4-trans-20,30-trans-Octa-O-benzyl-3-O-acetyl-
bi-(þ)-catechin (r-9). To a solution of nucleophile 2 (40 mg, 0.064
mmol) and electrophile 8 (50 mg, 0.064 mmol) in CH2Cl2 (10 mL)
under an argon atmosphere was added Yb(OTf)3 (40 mg, 0.064
mmol). After the resulting mixture had been stirred for 2 h, the
reaction was quenched with water (2 mL). The mixture was
extracted with Et2O, and the combined organic layer was washed
with brine, dried over MgSO4, and concentrated. The crude
product was purified with silica gel column chromatography
(hexane/AcOEt/CH2Cl2 = 4:1:2) to give R-9 (68 mg, 80%) as a
1
was more than 49:1 by H NMR analysis of the diacetate
derivative of the condensed product. Because the rare earth
metal Lewis acids are very mild, the condensation reaction
was able to be carried out at room temperature. Due to the
bulkiness of rare earth metal Lewis acid, it seems to be dif-
ficult for a dimeric nucleophile to attack the C-4 position of
the electrophile. As a result, formation of oligomeric side
products might be avoided. However, the reason for good
yield and selectivity when we used Yb(OTf)3 is not clear.
Detailed study is currently underway.
colorless oil: [R]24 -118 (c 1.36, CHCl3); IR (film) 3523, 3087,
D
2909, 2870, 1731, 1607, 1511, 1498, 1454, 1428, 1373, 1306, 1264,
1231, 1139, 1113, 1063, 1027, 911, 849, 809, 735, 697, 606 cm-1
;
Condensed product R-9 was subjected to the hydrolysis of
the acetate with K2CO3 in MeOH to give 10.3b,8 Finally,
Pd(OH)2-catalyzed hydrogenolysis afforded procyanidin B3
(1) (Scheme 1). All of the physical and spectral data for 1
were similar to those of the reported values.3a,d,5a,6,7
(9) Mizushina, Y.; Saito, A.; Tanaka, A.; Nakajima, N.; Kuriyama, I.;
Takemura, M.; Takeuchi, T.; Sugawara, F.; Yoshida, H. Biochim. Biophys.
Res. Commun. 2005, 333, 101–109.
€
(10) Gschwendt, M.; Kittstein, W.; Furstenberger, G.; Marks, F. Cancer
Lett. 1984, 25, 177–185.
J. Org. Chem. Vol. 75, No. 14, 2010 4885

Oizumi et al.
JOCNote
1H NMR (500 MHz, CDCl3, Me4Si, 1:1 mixture of rotational
isomers) δ 7.49-7.12 (40H, m), 6.98-6.67 (5.5H, m), 6.43 (0.5H,
dd, J = 8.3, 1.7 Hz), 6.25 (0.5H, s), 6.23 (0.5H, d, J = 2.3 Hz), 6.20
(0.5H, d, J = 2.3 Hz), 6.14 (0.5H, d, J = 2.3 Hz), 6.11 (0.5H, d,
J = 2.3 Hz), 5.99 (0.5H, s), 5.98 (0.5H, s), 5.86 (0.5H, t, J = 9.6
Hz), 5.22-4.54 (18.5H, m), 3.93 (0.5H, m), 3.58 (0.5H, m), 3.37
(0.5H, d, J=8.8Hz), 3.04(0.5H, dd, J= 16.2, 5.7 Hz), 2.86 (0.5H,
dd, J = 16.5, 5.0 Hz), 2.73 (0.5H, dd, J = 16.5, 7.0 Hz), 2.35 (0.5H,
dd, J = 16.1, 9.6 Hz), 2.17 (0.5H, m), 1.62 (1.5H, s), 1.54 (1.5H, s);
13C NMR (125 MHz, CDCl3, Me4Si, 1:1 mixture of rotational
isomers) δ 169.3, 168.7, 158.2, 158.1, 157.8, 156.8, 156.7, 156.5,
155.9, 155.8, 155.5, 153.7, 152.5, 149.3, 149.0, 149.0, 148.9 (2 ꢀ C),
148.8, 148.6, 138.0, 137.4, 137.3 (3 ꢀ C), 137.2, 137.1, 137.0
(2 ꢀ C), 136.8, 136.6, 131.8, 131.6, 130.9, 128.5, (2 ꢀ C), 128.4
(3 ꢀ C), 128.3 (3 ꢀ C), 128.1, 128.0 (2 ꢀ C), 127.82 (2 ꢀ C), 127.7,
127.6, 127.5 (3 ꢀ C), 127.4, 127.3 (3 ꢀ C), 127.2 (2 ꢀ C), 127.1,
127.0, 126.9, 121.3, 120.9, 120.3, 120.1, 115.0, 114.8, 114.6, 114.5,
114.2, 114.1, 113.7, 110.7, 110.3, 108.3, 107.9, 102.3 (2 ꢀ C), 94.9
(2 ꢀ C), 94.4, 94.3, 91.2 (2 ꢀ C), 80.6, 80.2, 80.1, 79.9, 71.6, 71.5,
71.4, 71.3, 71.2, 70.4, 70.3, 70.0 (2 ꢀ C), 69.8, 68.8, 67.8, 35.4,
35.2, 28.6, 26.5, 20.7, 20.4; HRMS (FAB) calcd for C88H77O13
[M þ H]þ 1341.5364, found 1341.5381.
149.3, 149.2, 149.0, 148.7, 137.7, 137.3 (2 ꢀ C), 137.2, 137.1, 137.0,
136.7, 131.9, 131.7, 128.6, 128.5 (3 ꢀ C), 128.4 (3 ꢀ C), 128.3,
128.2, 128.1, 127.9, 127.8 (2 ꢀ C), 127.8 (2 ꢀ C), 127.7 (2 ꢀ
C),127.6 (2 ꢀ C), 127.51 (2 ꢀ C), 127.4, 127.3, 127.2 (2 ꢀ C) 127.1
(3 ꢀ C), 121.3, 120.8, 120.7, 120.1, 115.2, 115.0 (2 ꢀ C), 114.7,
114.2, 113.9, 113.7, 112.2, 108.7, 108.5, 102.5, 95.0, 94.2, 91.9, 91.6,
82.1, 81.8, 81.3, 80.7, 73.4, 73.3, 71.4, 71.2 (3 ꢀ C), 71.04, 70.4, 70.1,
70.0 (2 ꢀ C), 69.9, 68.5, 68.4.
Procyanidin B3 (1). Compound 10 (30 mg, 0.023 mol) and
Pd(OH)2 on carbon (20 wt %, 6 mg) in THF/MeOH/H2O
(20:1:1, 5 mL) was stirred for 48 h under H2 atmosphere. After
the reaction had been completed, the mixture was filtered and
the solvent was evaporated. The residue was purified with ODS
cartridge column chromatography (MeOH/H2O = 3:7) to give
1 (10 mg, 87%) as a colorless solid: mp 218-219 °C (decomp.);
[R]27D -181 (c 0.29, EtOH); 1H NMR (500 MHz, CDCl3, Me4Si,
2:1 mixture of rotational isomers) δ 6.96 (0.67H, d, J = 1.9 Hz),
6.80 (0.33H, dd, J = 8.2, 1.9 Hz), 6.78 (0.33H, dd, J = 8.2, 1.9
Hz), 6.75 (0.67H, dd, J = 8.2, 1.9 Hz), 6.74 (0.67H, d, J = 1.9
Hz), 6.68 (1.33H, d, J = 8.2 Hz), 6.58 (0.67H, d, J = 1.9 Hz),
6.48 (0.67H, J = 8.2, 1.9 Hz), 6.26 (0.67H, dd, J = 8.2, 1.8 Hz),
6.08 (0.67H, s), 5.95 (0.33H, s), 5.89 (0.67H, d, J = 2.4 Hz), 5.85
(0.33H, J = 2.3 Hz), 5.82 (0.33H, d, J = 2.4 Hz), 5.79 (0.67H, d,
J = 2.4 Hz), 4.75 (0.33H, d, J = 7.2 Hz), 4.54 (0.67H, d, J = 7.3
Hz), 4.41 (1H, d, J = 7.8 Hz), 4.35 (1H, dd, J = 9.6, 7.9 Hz), 4.26
(1H, d, J = 9.7 Hz), 4.08 (0.33H, m), 3.78 (0.67H, m), 2.82
(0.33H, dd, J = 16.1, 5.6 Hz), 2.76 (0.67H, dd, J = 16.2, 5.5 Hz),
2.59 (0.33H, dd, J = 16.1, 7.4 Hz), 2.49 (0.67H, dd, J = 16.2,
8.0 Hz); 13C NMR (125 MHz, CD3OD, Me4Si, 2:1 mixture
of rotational isomers) δ 159.9, 158.7, 157.4, 157.3, 157.2, 156.0,
155.9, 155.8, 155.7, 155.1, 154.9, 146.2, 146.2, 145.8, 145.7,
145.5, 132.7, 132.5, 131.9, 121.19, 120.7, 120.2, 120.0, 116.5,
116.3, 116.2, 116.1, 116.0, 115.6, 115.3, 108.4, 108.2, 107.3
(2 ꢀ C), 102.3, 100.6, 97.6, 97.4, 97.0, 96.3, 96.2, 84.1, 84.0, 83.0
(2 ꢀ C), 73.7, 68.9, 68.6, 38.6, 28.8, 28.5; HRMS (FAB) calcd for
C30H25O12 [M - H]- 577.1346, found 577.1358.
[4,8]-2,3-trans-3,4-trans-20,30-trans-Octa-O-benzyl-bi-(þ)-
catechin (10).3b,8. To a solution of R-9 (39 mg, 0.029 mmol) in
MeOH (5 mL) was added K2CO3 (78 mg, 0.55 mmol). After being
stirred for 12 h, the mixture was diluted with water and extracted
with Et2O. The organic layer was washed with water and brine and
dried with MgSO4. The solvent was evaporated, and the residue
was purified with preparative TLC (hexane/AcOEt/CH2Cl2 =
4:1:2) to afford 10 (30 mg, 82%) as an amorphous solid: [R]24
D
-127.5 (c 1.00, CHCl3); IR (film) 3567, 3062, 3031, 2928, 2869,
1606, 1510, 1498, 1454, 1426, 1377, 1264, 1215, 1177, 1112, 1062,
1
1026, 910, 850, 809, 736, 697, 623 cm-1; H NMR (500 MHz,
CD3OD, Me4Si, 2:1 mixture of rotational isomers) δ 7.49-7.15
(40H, m), 7.04-6.47 (6H, m), 6.31 (0.67H, s), 6.23 (0.33H, d, J =
2.3 Hz), 6.20 (0.67H, d, J = 2.3 Hz), 6.13 (1H, d, J = 2.4 Hz), 6.04
(0.33H, d, J = 2.3 Hz), 5.20-4.48 (18H, m), 4.32 (0.67H, m), 4.20
(0.33H, m), 3.73 (0.5H, m), 3.67 (1H, d, J = 8.5 Hz), 3.20 (0.33H,
dd, J = 16.4, 5.9 Hz), 3.08 (0.67H, dd, J = 16.2, 5.6 Hz), 2.68
(0.33H, dd, J = 16.4, 9.4 Hz), 2.42 (0.67H, dd, J = 16.2, 9.1 Hz);
13C NMR (125 MHz, CDCl3, Me4Si, 2:1 mixture of rotational
isomers) δ 158.0, 157.7, 157.0, 156.8, 155.6, 155.5, 153.9, 152.9,
Supporting Information Available: Experimental procedure
1
of synthesis of diacetate of 10 and anti-inflammatory test. H
and 13C NMR spectra of R-9, 10, and 1, and 1H NMR spectrum
of diacetate of 10. This material is available free of charge via the
Internet at http://pubs.acs.org.
4886 J. Org. Chem. Vol. 75, No. 14, 2010