A new amide, piperchabamide F, and two new phenylpropanoid glycosides, piperchabaosides A and B, from the fruit of Piper chaba

Article abstract of DOI:10.1248/cpb.57.1292

A new amide, piperchabamide F (1), and two new phenylpropanoid glycosides, piperchabaosides A (2) and B (3), were isolated from 80% aqueous acetone extract from fruit of Piper chaba. Their stereostructures were elucidated on the basis of chemical and phys

Full text of DOI:10.1248/cpb.57.1292

1292
Notes
Chem. Pharm. Bull. 57(11) 1292—1295 (2009)
Vol. 57, No. 11
A New Amide, Piperchabamide F, and Two New Phenylpropanoid
Glycosides, Piperchabaosides A and B, from the Fruit of Piper chaba
Toshio MORIKAWA,a,b Itadaki YAMAGUCHI,a Hisashi MATSUDA,a and Masayuki YOSHIKAWA*,a
a Kyoto Pharmaceutical University; Misasagi, Yamashina-ku, Kyoto 607–8412, Japan: and b Pharmaceutical Research and
Technology Institute, Kinki University; 3–4–1 Kowakae, Higashi-osaka, Osaka 577–8502, Japan.
Received July 3, 2009; accepted August 6, 2009; published online August 27, 2009
A new amide, piperchabamide F (1), and two new phenylpropanoid glycosides, piperchabaosides A (2) and
B (3), were isolated from 80% aqueous acetone extract from fruit of Piper chaba. Their stereostructures were
elucidated on the basis of chemical and physicochemical evidence.
Key words Piper chaba; piperchabamide; piperchabaoside; Piperaceae; Thai natural medicine
During the course of our studies on Thai natural medi- 2,10-diene15) (5, 0.0007%), and 3,4-dihydroxybisabola-1,10-
cines,1—13) we found that the 80% aqueous acetone extract diene15—17) (6, 0.0013%). From the n-BuOH-soluble fraction,
from the fruit of Piper chaba HUNTER (syn. P. retrofractum 2 (0.012%) and 3 (0.0019%) were purified together with a
VAHL., Piperaceae) was found to show protective effects on phenylpropanoid glycoside, rosin18) (7, 0.0007%) using nor-
ethanol- or indomethacin-induced gastric lesions in rats,1) in- mal- and reversed-phase silica gel chromatographies and
hibitory effects on the increase in serum aspartate amino- finally HPLC.
transaminase (sAST) and alanine aminotransaminase (sALT)
Structure of Piperchabamide F (1) Piperchabamide F
levels induced by D-galactosamine (D-GalN)/lipopolysaccha- (1) was obtained as colorless oil with positive optical rotation
ride (LPS)-induced liver injury in mice and on cell death in- ([a]D27 ꢀ7.1° in CHCl3). The IR spectrum of 1 showed ab-
duced by D-GalN/tumor necrosis factor-a (TNF-a) in pri- sorption bands at 2924, 1626, 1561, 1509, 1491, and 1258
mary cultured mouse hepatocytes,6,12) and promoting effect cmꢁ1 ascribable to methylene, unsaturated amide group, and
on adipogenesis of 3T3-L1 cells.13) As a continuing study on aromatic ring. The electron ionization (EI)-MS of 1 showed a
the constituents from the fruit of P. c h a b a , we additionally molecular ion peak at m/z 343 (Mꢀ), and the molecular for-
isolated a new amide constituent named piperchabamide F mula was determined as C21H29NO3 by high-resolution EI-
(1) and two new phenylpropanoid glycosides, piperchabao- MS measurement. The 1H- and 13C-NMR spectra of 1
sides A (2) and B (3), together with three known sesquiter- (CDCl3, Table 1) showed signals assignable to two methyls
penes (4—6) and a known phenylpropanoid glycoside (7). [d 0.91 (3H, dd, Jꢂ6.6, 7.4 Hz, 4ꢃ-H3), 0.92 (3H, d, Jꢂ
This paper deals with the isolation and stereostructure eluci- 6.6 Hz, 5ꢃ-H3)], six methylenes [d 1.16, 1.40 (1H each, both
dation of three new compounds (1—3) from the fruit of m, 3ꢃ-H2), 1.49, 2.19 (4H each, both m, 5, 6, 4, 7-H2), 3.13,
P. c h a b a .
3.27 (1H each, both m, 1ꢃ-H2)], a methine [d 1.59 (1H, m,
The 80% aqueous acetone extract from the fruit of P. 2ꢃ-H)], a 3,4-methylenedioxyphenyl group [d 5.92 (2H, br s,
chaba (19.7%, purchased in Thailand) was partitioned be- 12-H2), 6.72 (2H, br s, 14, 15-H), 6.88 (1H, br s, 11-H)], two
tween EtOAc–H2O (1 : 1, v/v) to give EtOAc-soluble fraction trans-olefinic proton pairs [d 5.75 (1H, dd, Jꢂ1.2, 15.4 Hz,
(9.7%) and an aqueous phase.1) The aqueous phase was fur- 2-H), 6.00 (1H, dt, Jꢂ16.5, 6.7 Hz, 8-H), 6.29 (1H, d, Jꢂ
ther extracted with n-BuOH to give n-BuOH-soluble fraction 16.5 Hz, 9-H), 6.81 (1H, dt, Jꢂ15.4, 7.1 Hz, 3-H)], and a
(2.1%) and H2O-soluble fraction (7.0%). The EtOAc-soluble conjugated amide group [dC 165.8 (C-1)]. The planar struc-
fraction was subjected to normal- and reversed-phase silica ture of 1 was constructed on the basis of various NMR exper-
gel column chromatographies and finally HPLC to furnish 1 iments.19) Namely, the 1H–1H correlation spectroscopy (COSY)
(0.0007%) together with three sesquiterpenes, 1-hydroxybis- experiments on 1 indicated the presence of three partials
abola-2,10-dien-4-one14) (4, 0.0006%), 1,4-dihydroxybisabola- written in bold lines, while in the heteronuclear multiple
Chart 1
© 2009 Pharmaceutical Society of Japan
∗ To whom correspondence should be addressed. e-mail: myoshika@mb.kyoto-phu.ac.jp

November 2009
1293
bond connectivity (HMBC) experiments, long range correla-
tions were observed between the following proton and car-
bon pairs: 2-H and 1-C; 8, 9-H and 10-C; 1ꢃ-H2 and 1-C (Fig.
1). Finally, acid hydrolysis of 1 with 6 M HCl12,20) liberated
(R)-2-methylbutylamine,21) which was identified by HPLC
analysis using refractive index and optical rotation detectors.
On the basis of above-mentioned evidence, the stereostruc-
ture of 1 was elucidated as shown.
Structures of Piperchabaosides A (2) and B (3)
Piperchabaoside A (2) was isolated as a white powder with
23
negative optical rotation ([a]D ꢁ26.5° in MeOH). In the
positive-ion fast atom bombardment (FAB)-MS of 2, the
quasimolecular ion peaks were observed at m/z 481
(MꢀNa)ꢀ and m/z 457 (MꢁH)ꢁ, and the molecular formula
C21H30O11 was determined by high resolution FAB-MS
measurement. The IR spectrum of 2 showed absorption
bands at 3426, 1089, and 1030 cmꢁ1 ascribable to hydroxyl
and ether functions. Acid hydrolysis of 2 with 1.0 M HCl
liberated D-glucose, which was identified by HPLC analy-
Fig. 1. 1H–1H COSY and HMBC Correlations of 1—3
Table 1. 1H- and 13C-NMR Data of Piperchabamide F (1)
1
sis.22—26) The H- and 13C-NMR (pyridine-d5, Table 2) spec-
tra of 2 showed signals assignable to a methylene bearing an
oxygen function [d 4.43, 4.68 (1H each, both dd, Jꢂ5.8,
13.1 Hz, 9-H2)], a trans-olefin pair [d 6.45 (1H, dt, Jꢂ16.2,
5.8 Hz, 8-H), 6.76 (1H, d, Jꢂ16.2 Hz, 7-H)], and a mono-
substituted benzene ring [d 7.22 (1H, t, Jꢂ7.9 Hz, 4-H), 7.30
(2H, dd, Jꢂ7.3, 7.9 Hz, 3,5-H), 7.39 (2H, d, Jꢂ7.3 Hz, 2,6-
H)] together with two b-D-glucopyranosyl parts [d 4.88 (1H,
d, Jꢂ7.6 Hz, 1ꢃ-H), 5.16 (1H, d, Jꢂ7.9 Hz, 1ꢄ-H)], which
were superimposable on those of rosin (7), except for the sig-
nals due to an additional b-D-glucopyranosyl unit. Finally,
the connectivities of the glycosyl linkages in 2 were eluci-
dated on the basis of HMBC experiment, which showed
long-range correlations between the following proton and
carbon pairs as shown in Fig. 1: the inner-Glc-1-proton (1ꢃ-
H) and the 9-carbon (dC 69.8), and the terminal-Glc-1-proton
(1ꢄ-H) and the inner-Glc-4-carbon (dC 81.2, 4’-C). Conse-
quently, piperchabaoside A was determined to be trans-cin-
namyl alcohol O-b-D-glucopyranosyl-(1→4)-b-D-glucopyra-
noside (2).
1
Position
d
H (J Hz)
dC
1
2
3
4
5
165.8
123.5
144.2
31.8
5.75 (dd, 1.2, 15.4)
6.81 (dt, 15.4, 7.1)
2.19 (2H, m)
1.49 (2H, m)
1.49 (2H, m)
27.7a)
28.9a)
32.6
6
7
2.19 (2H, m)
8
9
6.00 (dt, 16.5, 6.7)
6.29 (d, 16.5)
128.6
129.4
132.1
105.2
147.7
146.3
108.0
120.0
100.8
45.0
10
11
12
13
14
15
16
6.88 (br s)
6.72 (br s)
6.72 (br s)
5.92 (2H, br s)
3.13, 3.27 (both m)
1.59 (m)
1.16, 1.40 (both m)
0.91 (3H, dd, 6.6, 7.4)
0.92 (3H, d, 6.6)
Piperchabaoside B (3) was also isolated as a white powder
with negative optical rotation ([a]D26 ꢁ18.0°, MeOH). Its mo-
lecular formula C27H38O15 was determined from the positive-
and negative-ion FAB-MS and by high resolution FAB-MS
measurements. The IR spectrum of 3 showed absorption
bands at 3401, 1736, 1719, 1075, and 1040 cmꢁ1 assignable
to hydroxyl, ester carbonyl, carboxyl, and ether functions.
1ꢃ
2ꢃ
3ꢃ
4ꢃ
5ꢃ
34.9
27.0
17.2
11.3
Measured in CDCl3. a) May be interchangeable.
Treatment of 3 with 1.0% sodium methoxide (NaOMe)– acyl ester carbonyl carbon (dC 171.6, 1ꢅ-C). Thus, the struc-
MeOH provided 2 together with (S)-3-hydroxy-3-methylglu- ture of piperchabaoside B was constructed as trans-cinnamyl
taric acid monomethyl ester27) (3a). The proton and carbon alcohol O-b-D-glucopyranosyl-(1→4)-6-O-(S)-3-hydroxy-3-
1
signals in the H- and 13C-NMR (pyridine-d5, Table 2) spec- methylglutaroyl-b-D-glucopyranoside (3).
tra of 3 were similar to those of 2, except for the signals due
to an acyl part [d 1.74 (3H, s, 6ꢅ-H3), 3.13 (4H, m, 2ꢅ,4ꢅ-
H2)]. The connectivities of the acyl moiety and glycosyl link-
Experimental
The following instruments were used to obtain physical data: specific ro-
tations, Horiba SEPA-300 digital polarimeter (lꢂ5 cm); UV spectra, Shi-
ages in 3 were elucidated on the basis of HMBC experiment,
mazdu UV-1600 spectrometer; IR spectra, Shimadzu FTIR-8100 spectrome-
ter; 1H-NMR spectra, JEOL JNM-LA500 (500 MHz) and EX-270 (270
which showed long-range correlations were observed be-
tween following proton and carbon pairs as shown in Fig. 1: MHz) spectrometers; 13C-NMR spectra, JEOL JNM-LA500 (125 MHz) and
EX-270 (68 MHz) spectrometers with tetramethylsilane as an internal stan-
dard; EI-MS and high-resolution EI-MS, JEOL JMS-GCMATE mass spec-
trometer; FAB-MS and high resolution FAB-MS, JEOL JMS-SX 102A mass
spectrometer; HPLC detector, Shimadzu RID-10A refractive index, Shi-
madzu SPD-10A UV–VIS, and Shodex OR-2 optical rotation detectors.
HPLC column, Cosmosil 5C18-MS-II (Nacalai Tesque Inc., 250ꢆ4.6 mm
the inner-Glc-1-proton [d 4.86 (1H, d, Jꢂ7.6 Hz, 1ꢃ-H)] and
the 9-carbon (dC 69.9), the terminal-Glc-1-proton [d 5.10
(1H, d, Jꢂ7.9 Hz, 1ꢄ-H)] and the inner-Glc-4-carbon (dC
81.6, 4ꢃ-C), and the inner-Glc-6-protons [d 4.49 (1H, dd, Jꢂ
6.1, 12.8 Hz), 5.15 (1H, br d, Jꢂca. 13 Hz), 6ꢃ-H2] and the

1294
Vol. 57, No. 11
Table 2. 1H- and 13C-NMR Data of Piperchabaosides A (2) and B (3)
2
3
Position
d
H (J Hz)
dC
d
H (J Hz)
dC
1
2,6
3,5
4
7
8
137.4
126.9
129.0
127.9
132.2
126.8
69.8
103.6
74.8
76.8
137.4
126.9
128.9
127.9
132.4
126.9
69.9
103.5
74.5
76.6
7.39 (2H, d, 7.3)
7.30 (2H, dd, 7.3, 7.9)
7.22 (t, 7.9)
7.38 (2H, d, 7.9)
7.28 (2H, dd, 7.3, 7.9)
7.21 (t, 7.3)
6.77 (d, 16.2)
6.44 (dt, 16.2, 6.1)
4.45, 4.72 (both dd, 6.1, 12.8)
4.86 (d, 7.6)
4.09 (m)
4.21 (m)
4.18 (m)
6.76 (d, 16.2)
6.45 (dt, 16.2, 5.8)
4.43, 4.68 (both dd, 5.8, 13.1)
4.88 (d, 7.6)
4.09 (m)
4.24 (m)
4.31 (m)
3.87 (m)
4.44, 4.52 (both m)
9
1ꢃ
2ꢃ
3ꢃ
4ꢃ
5ꢃ
6ꢃ
81.2
76.5
62.1
81.6
73.5
64.1
4.03 (m)
4.49 (dd, 6.1, 12.8)
5.15 (br d, ca. 13)
5.10 (d, 7.9)
4.03 (m)
4.18 (m)
4.09 (m)
1ꢄ
2ꢄ
3ꢄ
4ꢄ
5ꢄ
6ꢄ
5.16 (d, 7.9)
4.06 (m)
3.99 (m)
4.15 (dd, 8.3, 8.5)
4.19 (m)
4.29, 4.49 (both m)
104.9
74.8
78.4
71.6
78.2
62.5
105.2
74.9
78.4
71.9
78.5
62.8
4.08 (m)
4.24 (m)
4.54 (br d, ca. 12)
1ꢅ
2ꢅ
3ꢅ
4ꢅ
5ꢅ
6ꢅ
171.6
46.8
70.1
46.5
174.9
28.3
3.13 (2H, m)
3.13 (2H, m)
1.74 (3H, s)
Measured in pyridine-d5.
(2.4 g) was subjected to reversed-phase silica gel CC [120 g, MeOH–H2O
(20 : 80→40 : 60→80 : 20, v/v)→MeOH] to give three fractions [Fr. 2-1
(2.05 g), 2-2 (0.20 g), 2-3 (0.07 g)]. The fraction 2-2 (0.20 g) was further pu-
rified by HPLC [MeOH–H2O (20 : 80, v/v)] to give rosin (7, 13 mg,
0.0007%). The fraction 4 (1.7 g) was subjected to reversed-phase silica gel
CC [50 g, MeOH–H2O (20 : 80→40 : 60, v/v)→MeOH] to give three frac-
tions [Fr. 4-1 (0.67 g), 4-2 (0.57 g), 4-3 (0.17 g)]. The fraction 4-2 (0.57 g)
was further purified by HPLC [MeOH–H2O (10 : 90, v/v)] to give piperch-
abaosides A (2, 54 mg, 0.0028%) and B (3, 36 mg, 0.0019%). The fraction 5
(0.8 g) was purified by HPLC [MeOH–H2O (10 : 90, v/v)] to give 2 (177 mg,
0.0092%).
i.d.) and (250ꢆ20 mm i.d.) columns were used for analytical and preparative
purposes, respectively.
The following experimental conditions were used for chromatography:
normal-phase silica gel column chromatography (CC), silica gel 60N (Kanto
Chemical Co., Ltd., 63—210 mesh, spherical, neutral); reversed-phase silica
gel CC, Chromatorex ODS DM1020T (Fuji Silysia Chemical, Ltd., 100—
200 mesh); normal-phase TLC, pre-coated TLC plates with silica gel 60F254
(Merck, 0.25 mm); reversed-phase TLC, pre-coated TLC plates with silica
gel RP-18 F254S (Merck, 0.25 mm); reversed-phase HPTLC, pre-coated TLC
plates with silica gel RP-18 WF254S (Merck, 0.25 mm), detection was
achieved by spraying with 1% Ce(SO4)2–10% aqueous H2SO4, followed by
heating.
Piperchabamide F (1): Colorless oil, [a]D25 ꢀ7.1° (cꢂ0.27, CHCl3). High-
resolution EI-MS: Calcd for C21H29NO3 (Mꢀ) 343.2147; Found 343.2152.
UV [lmax (log e), EtOH]: 260 (4.1) nm. IR (KBr, cmꢁ1): 2924, 1626, 1561,
Plant Material This item was described in a previous report.1)
Extraction and Isolation The dried fruit of P. c h a b a (4.0 kg) was finely
cut and extracted four times with 80% (v/v) aqueous acetone at room tem-
perature for 1 d. Evaporation of the solvent under reduced pressure provided
an 80% aqueous acetone extract (788 g, 19.7% from the dried fruit). The
80% aqueous acetone extract (463 g) was partitioned in an EtOAc–H2O (1 :
1, v/v) mixture. The aqueous phase was further extracted with n-BuOH. Re-
moval of the solvent under reduced pressure yielded EtOAc-, n-BuOH-, and
H2O-soluble fractions [227 g (9.7%), 50 g (2.1%), and 164 g (7.0%)], respec-
tively. Fractions 4-2 (0.21 g), 5-2 (0.62 g), and 6-2 (0.07 g) were obtained
from the EtOAc-soluble fraction (118 g) as described previously.1,12) The
fraction 4-2 (0.21 g) was subjected to preparative HPLC [CH3CN–H2O
(50 : 50, v/v)] to give 1-hydroxybisabola-2,10-dien-4-one (4, 7 mg, 0.0006%)
together with piperchabamide A (27 mg) and N-isobutyl-(2E,4E)-deca-2,4-
dienamide (27 mg). The fraction 5-2 (0.62 g) was subjected to HPLC
[CH3CN–H2O (70 : 30, v/v)] to give piperchabamide F (1, 9 mg, 0.0007%)
together with piperchabamide D (20 mg), pipercide (ꢂretrofractamide B,
100 mg), and guineensine (292 mg). The fraction 6-2 (0.07 g) was further
purified by HPLC [CH3CN–H2O (45 : 55, v/v)] to give 1,4-dihydroxybis-
abola-2,10-diene (5, 9 mg, 0.0007%) and 3,4-dihydroxybisabola-1,10-diene
(6, 16 mg, 0.0013%).
1
1509, 1491, 1258, 1043, 965, 924. H-NMR (500 MHz, CDCl3) d: given in
Table 1. 13C-NMR (125 MHz, CDCl3) dC: given in Table 1. EI-MS (%): m/z
343 (Mꢀ, 41), 135 (100).
Piperchabaoside A (2): A white powder, [a]D23 ꢁ26.5° (cꢂ2.40, MeOH).
High-resolution positive-ion FAB-MS: Calcd for C21H30O11Na (MꢀNa)ꢀ
481.1686; Found 481.1678. UV [lmax (log e), MeOH]: 251 (4.5) nm. IR
1
(KBr, cmꢁ1): 3426, 1089, 1030. H-NMR (500 MHz, pyridine-d5) d: given
in Table 2. 13C-NMR (125 MHz, pyridine-d5) dC: given in Table 2. Positive-
ion FAB-MS m/z: 481 (MꢀNa)ꢀ. Negative-ion FAB-MS m/z: 457 (MꢁH)ꢁ.
Piperchabaoside B (3): A white powder, [a]D26 ꢁ18.0° (cꢂ3.21, MeOH).
High-resolution positive-ion FAB-MS: Calcd for C27H38O15Na (MꢀNa)ꢀ
625.2108; Found 625.2115. UV [lmax (log e), MeOH]: 251 (4.3) nm. IR
1
(KBr, cmꢁ1): 3401, 1736, 1719, 1075, 1040. H-NMR (500 MHz, pyridine-
d5) d: given in Table 2. 13C-NMR (125 MHz, pyridine-d5) dC: given in Table
2. Positive-ion FAB-MS m/z: 625 (MꢀNa)ꢀ. Negative-ion FAB-MS m/z:
601 (MꢁH)ꢁ.
Acid Hydrolysis of Piperchabamide F (1) A solution of 1 (5 mg) in
6 M HCl (0.5 ml) was heated at 110 °C for over night in a sealed tube. After
cooling, the reaction mixture was basified (pH 10) with aq. NaOH and then
the mixture was extracted with n-hexane. The n-hexane phase was evapo-
rated in vacuo gave a residue, which was subjected to HPLC analysis [col-
umn: Cosmosil 5C18-MS-II, 250ꢆ4.6 mm i.d.; mobile phase: MeOH–H2O
(50 : 50, v/v); detection: RI and OR; flow rate: 1.0 ml/min] to identify (R)-2-
The n-BuOH-soluble fraction (40.5 g) was subjected to normal-phase silica
gel CC [1.5 kg, CHCl3–MeOH–H2O (30 : 3 : 1→15 : 3 : 1→10 : 3 : 1, lower
layer→6 : 4 : 1, v/v/v)→MeOH] to give six fractions [Fr. 1 (3.3 g), Fr. 2
(2.4 g), Fr. 3 (4.3 g), Fr. 4 (1.7 g), Fr. 5 (0.8 g), Fr. 6 (25.7 g)]. The fraction 2

November 2009
1295
methylbutylamine [tR 9.1 min (positive)].
8) Morikawa T., Funakoshi K., Ninomiya K., Yasuda D., Miyagawa K.,
Matsuda H., Yoshikawa M., Chem. Pharm. Bull., 56, 956—962
(2008).
9) Asao Y., Morikawa T., Xie Y., Okamoto M., Hamao M., Matsuda H.,
Muraoka O., Yuan D., Yoshikawa M., Chem. Pharm. Bull., 57, 198—
203 (2009).
Acid Hydrolysis of Piperchabaoside A (2) A solution of 2 (3.0 mg) in
1 M HCl (1.0 ml) was heated at 80 °C for 3 h. After cooling, the reaction mix-
ture was neutralized with Amberlite IRA-400 (OHꢁ form) and then the resin
was removed by filtration. Removal of the solvent from the filtrate under re-
duced pressure, the residue was separated by Sep-Pak C18 cartridge column
(H2O→MeOH). The H2O-eluted fraction was subjected to HPLC analysis 10) Matsuda H., Asao Y., Nakamura S., Hamao M., Sugimoto S., Hongo
under the following conditions: HPLC column, Kaseisorb LC NH2-60-5,
M., Pongpiriyadacha Y., Yoshikawa M., Chem. Pharm. Bull., 57,
250ꢆ4.6 mm i.d. (Tokyo Kasei Co., Ltd., Tokyo, Japan); detection, optical
487—494 (2009).
rotation [Shodex OR-2 (Showa Denko Co., Ltd., Tokyo, Japan); mobile 11) Morikawa T., Xie Y., Asao Y., Okamoto M., Yamashita C., Muraoka
phase, CH3CN–H2O (85 : 15, v/v); flow rate 0.8 ml/min]. Identification of D-
glucose (i) present in the aqueous layer was carried out by comparison of
their retention times and optical rotations with those of authentic samples.
tR: (i) 13.9 min (positive optical rotation).
Deacylation of Piperchabaoside B (3) A solution of 3 (20.2 mg) in
1.0% sodium methoxide (NaOMe)–MeOH (3.0 ml) was stirred at room tem-
O., Matsuda H., Pongpiriyadacha Y., Yuan D., Yoshikawa M., Phyto-
chemistry, 70, 1166—1172 (2009).
12) Matsuda H., Ninomiya K., Morikawa T., Yasuda D., Yamaguchi I.,
Yoshikawa M., Bioorg. Med. Chem., 17 (2009), in press.
13) Zhang H., Matsuda H., Nakamura S., Yoshikawa M., Bioorg. Med.
Chem. Lett., 18, 3272—3277 (2008).
perature for 3 h. The reaction mixture was neutralized with Dowex HCR-W2 14) Castro V., Tamayo-Castillo G., Jakupovic J., Phytochemistry, 28,
(Hꢀ form) and the resin was removed by filtration. Evaporation of the sol-
2415—2418 (1989).
vent from the filtrate under reduced pressure gave a residue, which was puri- 15) Sy L.-K., Brown G. D., Phytochemistry, 45, 537—544 (1997).
fied by HPLC [Cosmosil 5C18-MS-II, MeOH–H2O (40 : 60, v/v)] to furnish
2 (12.0 mg) and (S)-3-hydroxy-3-methylglutaric acid monomethyl ester27)
(3a, 1.6 mg).
16) Zdero C., Bohlmann F., Scott R., Phytochemistry, 26, 1999—2006
(1987).
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Acknowledgements T. M. was supported by a Grant-in Aid for Scien- 18) Zapesochnaya G. G., Kurkin V. A., Chem. Nat. Compd., 18, 685—688
tific Research from ‘High-tech Research Center’ Project for Private Univer-
sities: matching fund subsidy from The Ministry of Education, Culture,
Sports, Science and Technology (MEXT) of Japan, 2007—2011, a Grant-in
Aid for Scientific Research from MEXT, and Takeda Science Foundation.
M. Y. and H. M. were supported by the 21st COE Program, Academic Fron-
tier Project, and a Grant-in Aid for Scientific Research from MEXT.
(1982).
1
19) The H- and 13C-NMR spectra of 1—3 were assigned with the aid of
distortionless enhancement by polarization transfer (DEPT), homocor-
relation spectroscopy (1H–1H COSY), heteronuclear multiple-quantum
coherence (HMQC), and HMBC experiments.
20) Matsumoto T., Nishimura K., Takeya K., Chem. Pharm. Bull., 50,
857—860 (2002).
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