Components of ether-insoluble resin glycoside (Rhamnoconvolvulin) from rhizoma jalapae braziliensis

Article abstract of DOI:10.1248/cpb.57.262

Alkaline hydrolysis of the ether-insoluble resin glycoside (convolvulin) fraction of the roots of Ipomoea operculata (Gomes) Mart. (Convolvulaceae) afforded a glycosidic acid named operculinic acid H along with isovaleric, tiglic, and exogonic (3,6:6,9-di

Full text of DOI:10.1248/cpb.57.262

262
Chem. Pharm. Bull. 57(3) 262—268 (2009)
Vol. 57, No. 3
Components of Ether-Insoluble Resin Glycoside (Rhamnoconvolvulin)
from Rhizoma Jalapae Braziliensis
Masateru ONO, ,a Hiroko NISHIOKA,b Tadashi FUKUSHIMA,b Hiroko KUNIMATSU,b Aiko MINE,b
*
b
Hideo KUBO,b and Kazumoto MIYAHARA
a School of Agriculture, Tokai University; 5435 Minamiaso, Aso, Kumamoto 869–1404, Japan: and b Faculty of
Pharmaceutical Sciences, Setsunan University; 45–1 Nagaotoge-cho, Hirakata, Osaka 573–0101, Japan.
Received November 17, 2008; accepted December 22, 2008; published online December 26, 2008
Alkaline hydrolysis of the ether-insoluble resin glycoside (convolvulin) fraction of the roots of Ipomoea oper-
culata (GOMES) MART. (Convolvulaceae) afforded a glycosidic acid named operculinic acid H along with isova-
leric, tiglic, and exogonic (3,6:6,9-diepoxydecanoic) acids. Operculinic acid H was characterized to be 3S,12S-
dihydroxyhexadecanoic acid 12-O-b-D-glucopyranosyl-(1→3)-O-a-L-rhamnopyranosyl-(1→2)-[O-b-D-glucopyra-
nosyl-(1→3)]-O-b-D-glucopyranosyl-(1→2)-[O-a-L-rhamnopyranosyl-(1→6)]-O-b-D-glucopyranoside on the basis
of spectroscopic data and chemical evidence. The absolute configuration of exogonic acid determined from the a-
methoxy-a-trifluoromethylphenylacetic acid esters of the hydrogenolysis products revealed that exogonic acid ex-
ists as a mixture (ca. 1 : 1) of two epimers, (3S,6S,9R)- and (3S,6R,9R)-diepoxydecanoic acids.
Key words resin glycoside; Ipomoea operculata; Rhizoma Jalapae Braziliensis; operculinic acid H; 3S,12S-dihydroxyhexade-
canoic acid; exogonic acid
Rhizoma Jalapae Braziliensis, the root of Ipomoea opercu- H2O. Then, the H2O-soluble fraction was partitioned between
lata (GOMES) MART. (Convolvulaceae), is known to be a sub- n-BuOH and H2O. The n-BuOH-soluble fraction was chro-
stitute for Jalapae Tuber (Vera Curz Jalap, I. purga), and it is matographed over MCI gel CHP20 to afford a convolvulin
used as a laxative crude drug. It contains both ether-soluble fraction. Alkaline hydrolysis of the fraction with 5% aq.
(“jalapin”) and ether-insoluble (“convolvulin”) resin glyco- KOH afforded organic acid and glycosidic acid fractions.
sides as the active ingredients.1) In our previous papers,2—4) Then, organic acid was esterified with p-bromophenacyl bro-
we have reported the isolation and structural elucidation of mide, and the product was subjected to chromatographic sep-
seven glycosidic acids named operculinic acids A—G, which aration to afford p-bromophenacyl isovalerate (1), p-bro-
were obtained along with two organic acids—n-decanoic mophenacyl tiglate (2), and two compounds 3 and 4 (Fig. 1).
acid and n-dodecanoic acid—upon alkaline hydrolysis of the The field desorption mass spectrum (FD-MS) of 3 showed an
1
jalapin fraction. Further, we isolated eighteen genuine jalap- [M]ꢀ ion peak at m/z 396, and the H-NMR spectrum of 3
ins, named operculins I—XVIII.5—7)
showed signals due to two oxygenated methine protons, one
Studies conducted on the convolvulin component of this secondary methyl group, and one nonequivalent methylene
crude laxative drug were inconclusive because of difficulties group. The 13C-NMR spectrum of 3 showed ten carbon sig-
encountered in distinguishing between different source mate- nals, including signals due to one carbonyl carbon, one acetal
rials, especially that from Jalapae Tuber. Graf et al.8) carried carbon, and two oxygenated methine carbons, besides signals
out alkaline hydrolysis of convolvulin (named rhamnocon- due to the p-bromophenacyl group. These NMR signals were
volvulin, M.W. ca. 31000) and reported that it contained nine assigned with the aid of 1H–1H correlation spectroscopy
1
organic acids—acetic, propionic, n-pentanoic, 2-methylbu- (COSY) and H–13C heteronuclear shift-correlated 2D-NMR
tanoic, 3-methylbutanoic, 2,2-dimethylpropanoic, tiglic, 4- (HETCOR) spectra. From the above mentioned data, 3 was
oxooctanoic,9) and exogonic (3,6:6,9-diepoxydecanoic)10,11) identified as the p-bromophenacyl ester of the exogonic acid
acids—as well as a glycosidic acid (rhamnoconvolvulinic reported by Graf and Dahlke.11) The 1H- and 13C-NMR spec-
acid). Votocek and Valentin12) proposed that rhamnocon-
volvulinic acid (C52H92O32·7H2O) was possibly a hexaglyco-
side in which two trisaccharides that constituted with 2 mol
glucose and 1 mol rhamnose bind to the OH groups of dihy-
droxyhexadecanoic acid, which was characterized to be 3,12-
dihydroxyhexadecanoic acid by Votocek and Prelog.13) Later,
Wagner and Kazmaier14) isolated a major glycosidic acid
named operculinic acid from rhamnoconvolvulin and charac-
terized it as 3,12-dihydroxyhexadecanoic acid 12-O-a-D-glu-
copyranosyl-(1→4)-[O-a-L-rhamnopyranosyl-(1→6)]-O-a-
D-glucopyranosyl-(1→3)-O-a-L-rhamnopyranosyl-(1→2)-
[O-b-D-glucopyranosyl-(1→3)]-O-b-D-glucopyranoside. In
this paper, we discuss the re-examination of the chemical
composition of rhamnoconvolvulin.
Powdered roots of I. operculata were extracted with
MeOH, and the extract was partitioned between ether and Fig. 1. Structures of 1—4, 14, 15, 19, and 20
∗ To whom correspondence should be addressed. e-mail: mono@agri.u-tokai.ac.jp
© 2009 Pharmaceutical Society of Japan

March 2009
263
Table 1. 1H-NMR Spectral Data for 8—13 (in CDCl3, 600 MHz)
8
9
10
2a
2b
3
6
9
2.627 dd (4.4, 15.7)
2.706 dd (8.3, 15.7)
5.532 dddd (4.4, 5.4, 6.6, 8.3)
3.736 dddd (5.4, 6.6, 6.6, 6.6)
3.907 ddq (6.0, 7.1, 6.0)
1.178 d (6.0)
2.599 dd (4.6, 16.1)
2.661 dd (8.2, 16.1)
5.543 dddd (4.6, 5.2, 7.0, 8.2)
3.806 dddd (5.3, 6.9, 7.1, 7.7)
3.934 ddq (5.2, 7.5, 6.2)
1.212 d (6.2)
2.410 dd (6.6, 14.9)
2.559 dd (6.6, 14.9)
4.201 dddd (6.6, 6.6, 6.6, 6.6)
3.774 dddd (6.6, 6.6, 6.6, 6.6)
5.183 ddq (6.0, 7.2, 6.5)
1.341 d (6.5)
10
COOCH3
OCH3
3.656 s
3.538 q (0.8)
3.583 s
3.530 q (0.9)
3.677 s
3.560 q (1.2)
11
12
13
2a
2b
3
6
9
2.454 dd (6.6, 15.6)
2.595 dd (6.6, 15.6)
4.236 dddd (6.6, 6.6, 6.6, 6.6)
3.839 dddd (6.6, 6.6, 6.6, 6.6)
5.170 ddq (4.8, 7.2, 6.2)
1.262 d (6.2)
2.584 dd (4.6, 16.1)
2.684 dd (8.1, 16.1)
5.445 m
2.565 dd (5.0, 16.1)
2.645 dd (8.1, 16.1)
5.466 m
5.117 ddq (4.8, 7.8, 6.5)
1.322 d (6.5)
3.665 s
3.534 q (1.2)
3.560 q (1.2)
5.121 ddq (6.2, 6.6, 6.2)
1.250 d (6.2)
3.591 s
3.512 q (1.3)
3.532 q (0.9)
10
COOCH3
OCH3
OCH3
3.683 s
3.544 q (1.3)
d in ppm from tetramethylsilane (TMS) (coupling constants (J) in Hz are given in parentheses).
tra of 4 were very similar to those of 3. Further, on refluxing
in CHCl3 for 8 h, 3 was transformed to 4 to afford an equilib-
rium mixture in which the ratio of 3 : 4 was ca. 1 : 1. Conse-
quently, it was suggested that 3 and 4 are isomers and that in-
terconversion between them occurred because of inversion at
the C-6 spiro center.
In order to determine the configurations at C-3 and C-9 of
exogonic acid, we performed the following experiments. The
methyl ester of exogonic acid was hydrogenated and then pu-
rified by HPLC to afford three compounds, 5, 6, and 7. The
1H-NMR spectra of both 5 and 6 showed signal due to one of
each of the following groups: a methoxyl group, secondary
methyl group, and a nonequivalent methylene group; the
spectra also showed signals due to three oxygenated methine
protons. Further, the 13C-NMR spectra of both 5 and 6
Fig. 2. Structures of 5—13 and 16—18, and Values of 1H-NMR Chemical
Shift Difference (ppm) [Dd: d(ꢁ)-MTPA–d(ꢀ)-MTPA Ester (ꢂ10ꢁ3)] for
MTPA Esters (in CDCl3, 600 MHz)
showed eleven signals, including signals due to one carbonyl
carbon, one methoxyl carbon, and three oxygenated methine
carbons. On the basis of these data, it was proposed that 5
and 6 were either methyl 3-hydroxy-6,9-epoxydecanoate or
1
methyl 9-hydroxy-3,6-epoxydecanoate, respectively. The H- ene group, two oxygenated methine protons, and one second-
NMR spectra of both (ꢁ)- and (ꢀ)-a-methoxy-a-trifluo- ary methyl group. Further, the 13C-NMR spectrum of 7
romethylphenylacetic acid (MTPA)15) esters (8 and 9, respec- showed eleven signals, including signals due to one carbonyl
tively) of 5 showed, when compared with that of 5, the re- carbon, one methoxyl carbon, and two oxygenated methine
markable downfield shift of the signal due to H-3 and ad- carbons. Thus, 7 was determined to be methyl 3,9-dihydroxy-
ditional signals due to 1 mol of the MTPA residue, thereby decanoate. The spectra of both the (ꢁ)-MTPA ester (12) and
indicating that 5 is methyl 3-hydroxy-6,9-epoxydecanoate the (ꢀ)-MTPA ester (13) of 7 showed signals due to 2 mol of
1
1
(Table 1). Comparison of the H-NMR spectrum of 8 with MTPA residues, and a comparison of their H-NMR spectra
that of 9 revealed significant difference in chemical shift [Dd revealed the following Dd (d12—d13) values: ꢀ0.074
(d8—d9)]: ꢀ0.073 (CO2CH3), ꢀ0.028 (Ha-2), ꢀ0.045 (Hb- (CO2CH3), ꢀ0.019 (Ha-2), ꢀ0.039 (Hb-2), and ꢀ0.072 (H3-
2), ꢁ0.070 (H-6), ꢁ0.027 (H-9), and ꢁ0.034 (H3-10) ppm 10) ppm. Therefore, exogonic acid was identified to be
(Fig. 2). Therefore, the configuration at C-3 of 5 was deter- (3S,9R)-3,6:6,9-diepoxydecanoic acid, and it was found that
1
mined to be S. In contrast, the H-NMR spectra of (ꢁ)- and this acid existed as a mixture of epimers that differ in the
(ꢀ)-MTPA esters (10 and 11, respectively) of 6 showed that spiro-cyclic carbon configuration only at C-6. These results
6 is methyl 9-hydroxy-3,6-epoxydecanoate, and further, the were consistent with those of the enantioselective syntheses
Dd (d10—d11) values indicated that the configuration at C- performed by Lawson et al.16)
1
9 in 6 is R. The H-NMR spectrum of 7 showed signals as-
The glycosidic acid fraction was treated with diazo-
signable to one methoxyl group, one nonequivalent methyl- methane and subsequently subjected to chromatography to

264
Vol. 57, No. 3
Table 2. 1H-NMR Spectral Data for 17 and 18 (in CDCl3, 400 MHz)
Table 3. 1H-NMR Spectral Data for 14 and 19 (in Pyridine-d5, 600 MHz)
17
18
14
19
2a
2b
3
12
16
2.601 dd (4.9, 15.9)
2.694 dd (8.0, 15.9)
5.469 ddt (4.9, 8.0, 6.5)
5.084 tt (5.3, 6.5)
0.827 t (7.1)
3.659 s
3.539 q (0.9)
3.557 q (1.2)
2.571 dd (4.9, 15.9)
2.647 dd (7.9, 15.9)
5.470 ddt (4.9, 7.9, 6.3)
5.082 tt (5.2, 6.7)
0.883 t (6.9)
3.589 s
3.525 q (1.2)
3.555 q (1.2)
Glc-1
4.93 d (7.7)
4.80 d (7.3)
2
3
4
5
6
4.36 dd (7.7, 9.2)
4.55 dd (9.2, 9.2)
3.87 dd (9.2, 9.2)
ca. 4.01
ca. 4.03
4.56 dd (4.3, 11.0)
5.79 d (7.7)
4.23 dd (7.3, 9.5)
5.71 dd (9.5, 9.5)
5.29 dd (9.5, 9.5)
ca. 4.03
3.87 dd (6.7, 12.2)
ca. 4.03
COOCH3
OCH3
OCH3
Glcꢃ-1
5.00 d (7.6)
2
3
4
5
6
4.22 dd (7.7, 9.2)
ca. 3.93
ca. 3.93
4.08 dd (7.6, 9.5)
4.50 dd (9.5, 9.5)
5.25 dd (9.5, 9.5)
ca. 4.05
4.34 dd (2.5, 12.8)
4.58 dd (4.6, 12.8)
ca. 5.20
ca. 5.20
ca. 5.77
5.38 dd (10.0, 10.0)
ca. 4.17
4.14 dd (2.2, 13.5)
ca. 4.64
ca. 5.40
ca. 5.40
ca. 5.67
5.50 dd (9.5, 9.5)
4.20 ddd (2.5, 4.0, 9.5)
4.42 dd (4.0, 12.5)
4.60 dd (2.5, 12.5)
5.16 s
d in ppm from TMS (coupling constants (J) in Hz are given in parentheses).
3.75 ddd (2.0, 6.1, 9.2)
4.14 dd (6.1, 11.6)
4.34 dd (2.0, 11.6)
4.93 d (7.8)
3.99 dd (7.8, 9.2)
4.21 dd (9.2, 9.2)
4.07 dd (9.2, 9.2)
4.02 dd (2.2, 6.1, 9.2)
4.21 dd (6.1, 11.6)
4.53 dd (2.2, 11.6)
5.40 d (7.7)
4.07 dd (7.7, 9.4)
4.15 dd (9.4, 9.4)
4.04 dd (9.4, 9.4)
3.94 ddd (2.4, 6.1, 9.4)
4.12 dd (6.1, 12.2)
4.42 dd (2.4, 12.2)
5.43 d (1.4)
4.55 dd (1.4, 3.1)
4.49 dd (3.1, 9.6)
4.24 dd (9.6, 9.6)
4.31 dq (9.6, 6.1)
1.62 d (6.1)
isolate the methyl ester (14), alkaline hydrolysis of which af-
forded a glycosidic acid (15), which was named operculinic
acid H. Acidic hydrolysis of 14 afforded an aglycone and a
mixture of monosaccharides. Methylation of the aglycone
with diazomethane yielded a methyl ester of a hydroxyfatty
Glcꢄ-1
2
3
4
5
6
1
acid (16). The H-NMR spectrum of 16 showed signals due
to two oxygenated methine protons, one ester methyl group,
and one primary methyl group. The FD-MS of 16 showed an
[MꢀH]ꢀ ion peak at m/z 303 and fragment ion peaks at m/z
245 [MꢁCH3(CH2)2]ꢀ, 103 [CH(OH)CH2COOCH3]ꢀ, and
87 [CH3(CH2)3CHOH]ꢀ. These data were consistent with
those estimated for methyl 3,12-dihydroxyhexadecanoate re-
ported by Votocek and Prelog.13) Compound 16 was com-
pletely acylated using (ꢁ)- and (ꢀ)-MTPA chloride to afford
Glcꢅ-1
2
3
4
5
6
Rha-1
1
17 and 18, respectively. From a comparison of the H-NMR
2
3
4
5
5.70 d (3.4)
spectra of 17 and 18, the Dd (d17—d18) values were found
to be ꢀ0.070, ꢀ0.047, ꢀ0.030, and ꢁ0.056 ppm for signals
due to the methoxyl group, Ha-2, Hb-2, and H3-16, respec-
tively (Table 2, Fig. 2). This suggests that the configurations
at both C-3 and C-12 are S,17) which is in agreement with the
results obtained by Jakob and Gerlach.18) On the other hand,
HPLC separation of the monosaccharide fraction yielded D-
glucose and L-rhamnose. Further, the negative FAB-MS spec-
trum of 15 showed an [MꢁH]ꢁ ion peak at m/z 1227 along
with fragment ion peaks at m/z 1065 [1227ꢁ162 (C6H10O5,
hexose unit)]ꢁ, 919 [1065ꢁ146 (C6H10O4, 6-deoxyhexose
unit)]ꢁ, 757 [919ꢁ146]ꢁ, and 595 [903ꢁ162]ꢁ. These data
indicated that 15 is composed of 1 mol of 3S,12S-dihydroxy-
hexadecanoic acid, 2 mol of L-rhamnose, and 4 mol of D-glu-
cose. This composition is consistent with that of operuclinic
acid reported by Wagner et al.14)
5.64 dd (3.4, 10.0)
5.49 dd (10.0, 10.0)
4.12 dq (10.0, 6.4)
1.32 d (6.4)
5.70 s
5.85 d (4.0)
4.74 dd (4.0, 9.8)
5.51 dd (9.8, 9.8)
ca. 4.68
6
Rhaꢃ-1
6.31 d (1.4)
2
3
4
5
6
5.10 dd (1.4, 3.1)
4.83 dd (3.1, 9.0)
4.49 dd (9.0, 9.0)
5.08 dq (9.0, 6.2)
1.76 d (6.2)
2.68 dd (4.5, 14.5)
2.73 dd (7.9, 14.5)
ca. 4.41
1.53 d (6.1)
Ag-2
2.73 dd (5.8, 15.8)
2.77 dd (7.0, 15.8)
ca. 5.50
ca. 3.83
0.97 t (7.3)
3
12
16
ca. 3.89
0.89 t (7.3)
3.63 s
OCH3
3.62 s
d in ppm from TMS (coupling constants (J) in Hz are given in parentheses). Glc,
glucopyranosyl; Rha, rhamnopyranosyl; Ag, aglycone moiety.
1
The H-NMR spectrum of 14 showed signals due to six
anomeric protons and two secondary methyl groups, and methyl pyranosides in the literature19) (Table 4). Glycosyla-
these signals were assignable to the H3-6 of the rhamnose tion shifts20,21) were observed at C-2 and C-6 of the first glu-
units; this spectrum also showed signals due to one non- cose residue (Glc) (ꢀ4.2 and ꢀ5.6 ppm), C-2 and C-3 of the
equivalent methylene group, one primary methyl group, and second glucose residue (Glcꢃ) (ꢀ2.5 and ꢀ11.4 ppm), C-3 of
one methoxyl group ascribable to the aglycone moiety (Ag). the second rhamnose residue (Rhaꢃ) (ꢀ10.4 ppm), and C-12
The proton signals due to the sugar moiety of 14 were as- of Ag (ꢀ10.4 ppm). Moreover, comparison of the chemical
signed by referring to the COSY and nuclear Overhauser and shifts of the signals due to 14 with those of the signals due to
exchange spectroscopy (NOESY) spectra (Table 3). The cou- its peracetate (19) revealed that the signals due to H-2 and
pling constants of the signals due to the anomeric and me- H2-6 of Glc, H-2 of Glcꢃ, H-3 of Rhaꢃ, and H-12 of Ag ex-
1
thine protons as well as the JC–H values due to the anomeric hibited no acylation shift (Table 3). These data suggested that
carbons indicated that all the monosaccharide units were of the sugar linkages in 14 were formed at OH-2 and OH-6 of
the pyranose type and that the mode of glycosidic linkage in Glc, OH-2 and OH-3 of Glcꢃ, OH-3 of Rhaꢃ, and OH-12 of
4
glucose units was b in C1 conformation and that in rham- Ag. The NOESY spectrum of 19 showed five cross peaks,
nose units was a in 1C4 conformation.
which were identified as those between H-1 of Glc and H-12
The 13C-NMR signals due to the sugar moiety of 14 were of Ag, H-1 of Glcꢃ and H-2 of Glc, H-1 of Rha and H-5
assigned by HETCOR and then compared with those of and/or H-6 of Glc, H-1 and/or H-2 of Glcꢄ and H-3 of Glcꢃ,

March 2009
265
Table 4. 13C-NMR Spectral Data for 14 and 21—25 (in Pyridine-d5)
Methyl
14
21
22
23
24
25
glycoside19)
Glc-1 102.6 103.8
101.8
83.6
78.2
71.6
78.0
62.8
105.4
75.5
87.9
69.9
78.0
62.6
105.7
75.6
78.2
71.6
78.6
62.5
101.9
83.3
78.2
71.6
76.5
68.3
105.2
75.3
88.0
69.9
77.9
62.6
105.6
75.5
78.2
71.6
78.5
62.6
102.6
79.2
79.3
72.1
76.4
68.4
101.8
77.8
89.3
70.1
77.4
62.9
104.5
74.9
78.6
71.5
78.6
62.4
102.4
79.7
79.3
72.0
77.8
62.8
101.9
77.3
89.5
70.4
77.2
63.1
104.6
74.9
78.5
71.9
78.5
62.4
106.1
75.9
78.2
71.5
78.1
62.9
105.5
74.9
78.3
71.6
78.3
62.7
2
3
4
5
6
79.1
79.4
72.1
76.5
68.3
75.3
78.6
72.0
76.9
68.7
Glcꢃ-1 101.8
2
3
4
5
6
77.4
89.7
70.3
77.5
62.9
Fig. 3. Fragment Ions Observed in the EI-MS Spectrum of 20
Glcꢄ-1 104.7
2
3
4
5
6
74.9
78.5
71.5
78.6
62.4
Glcꢅ-1 106.1
2
3
4
5
6
75.9
78.2
71.1
78.2
62.8
Rha-1 102.5 102.6
102.4
72.2
72.7
74.0
69.7
18.6
102.5
72.3
72.7
74.0
69.7
18.7
102.1
72.3
72.6
74.3
69.6
19.0
172.9
43.4
68.2
81.1
14.4
51.3
102.6
72.1
72.7
73.8
69.5
18.6
2
3
4
5
6
72.3
72.7
74.1
69.8
18.7
72.3
72.8
74.0
69.7
18.7
Fig. 4. Structures of the Products (21—25) Obtained by Partial Methanol-
ysis of 14
Rhaꢃ-1 102.0
101.9
71.7
83.1
73.2
69.4
18.9
172.8
43.4
68.3
80.8
14.2
51.2
2
3
4
5
6
71.7
83.1
73.2
69.3
19.0
COR spectra (Tables 4, 5). The structures of 21—25 vali-
dated the structure of 15 shown in Fig. 1. Therefore, the
structure of operculinic acid H (15) was characterized to
be 3S,12S-dihydroxyhexadecanoic acid 12-O-b-D-glucopyra-
nosyl-(1→3)-O-a-L-rhamnopyranosyl-(1→2)-[O-b-D-glu-
copyranosyl-(1→3)]-O-b-D-glucopyranosyl-(1→2)-[O-a-L-
rhamnopyranosyl-(1→6)]-O-b-D-glucopyranoside.
Ag-1 172.8 172.8
172.9
43.4
68.2
79.7
14.3
51.3
172.8
43.4
68.2
80.2
14.3
51.3
2
3
12
43.4
68.3
81.3
14.4
51.3
43.4
68.2
79.5
14.4
51.3
16
OCH3
In this study, it was found that the components of rhamno-
convolvulin are isovaleric, tiglic, and exogonic acids as well
as 15. Further, the absolute configuration of exogonic acid
was determined by using the MTPA esters of its hydrogenol-
d in ppm from TMS. 14 at 125 MHz and 21—25 at 100 MHz. Glc, glucopyranosyl;
Rha, rhamnopyranosyl; Ag, aglycone moiety.
and H-1 and/or H-2 of Glcꢅ and H-3 of Rhaꢃ. Moreover, the ysis products, and exogonic acid was confirmed to exist
high-resolution electron impact ionization mass spectrum as a mixture of two epimers, (3S,6S,9R)- and (3S,6R,9R)-
(HI-EI-MS) of the permethylate (20) of 14 showed fragment diepoxydecanoic acids. Moreover, the proposed arrangement
ion peaks at m/z 299.2590, 393.2127, 565.2848, and of monosaccharides in the sugar moiety of Wagner’s oper-
801.4121, which were assigned to the fragment ions denoted culinic acid should be revised as shown in Fig. 1. Compound
by a, b, c, and d, respectively (Fig. 3). The structure of 15 de- 15 has a branched-chain hexasaccharide moiety bound to the
termined on the basis of these facts is shown in Fig. 1.
OH-12 of aglycone 3S,12S-dihydroxyhexadecanoic acid, and
Despite the large difference between the structures of the as in the case of pharbitic acids,22) OH-3 remains free. On the
sugar moieties in 15 and Wagner’s operuclinic acid,14) both basis of its behavior towards alkali and acid, rhamnocon-
compounds were regarded to be identical. This is because volvulin is presumed to be a complex glycoside composed of
they were most glycosidic acid of convolvulin fraction and a number of repeating units which are operculinic acid H
their physical properties (mp 156—163 °C, [a]D26 ꢁ49.1° for (15) partially acylated by isovaleric, tiglic, and exogonic
15; mp 182—185 °C, [a]D24 ꢁ48.6° for operuclinic acid14)) acids at the sugar moiety.
were similar. To confirm the structure of 15 in further detail,
partial methanolysis of 14 was attempted. Compound 14 was
refluxed with 0.3% HCl–MeOH for 100 min to obtain five
Experimental
The instruments and materials used were as cited in the preceding re-
port3,23) unless otherwise specified.
hydrolysates 21—25. The structures (Fig. 4) of 21—25 were
Preparation of Convolvulin Fraction The n-BuOH fraction (15.84 g)
determined on the basis of their COSY, NOESY, and HET- obtained previously3) from the roots of I. operculata was subjected to MCI

266
Vol. 57, No. 3
Table 5. 1H-NMR Spectral Data for 21—25 (in Pyridine-d5, 400 MHz)
21
22
23
4.85 d (7.6)
24
4.93 d (7.3)
25
4.97 d (7.6)
Glc-1
4.88 d (8.0)
4.94 d (7.5)
2
3
4
5
6
4.00 dd (8.0, 9.0)
4.22 dd (9.0, 9.0)
4.00 dd (9.0, 9.0)
4.07 ddd (1.0, 6.7, 9.0)
4.14 dd (6.7, 11.0)
4.68 dd (1.0, 11.0)
4.13 dd (7.5, 8.5)
4.29 dd (8.5, 8.5)
4.16 dd (8.5, 8.5)
3.87 ddd (3.0, 5.5, 8.5)
4.32 dd (5.5, 11.5)
4.48 dd (3.0, 11.5)
5.31 d (7.5)
4.09 dd (7.5, 8.5)
4.20 dd (8.5, 8.5)
4.15 dd (8.5, 8.5)
3.85 ddd (3.5, 5.5, 8.5)
4.30 dd (5.5, 11.5)
4.42 dd (3.5, 11.5)
5.25 d (7.5)
4.04 dd (7.5, 8.5)
4.21 dd (8.5, 8.5)
4.15 dd (8.5, 8.5)
4.00 ddd (2.0, 6.0, 8.5)
4.28 dd (6.0, 11.5)
4.51 dd (2.0, 11.5)
4.07 dd (7.6, 8.5)
4.21 dd (8.5, 8.5)
ca. 3.91
ca. 3.91
4.05 dd (5.0, 11.5)
4.56 d (11.5)
4.33 dd (7.3, 9.5)
4.48 dd (9.5, 9.5)
3.88 dd (9.5, 9.5)
ca. 3.97
4.28 dd (7.6, 9.0)
4.52 dd (9.0, 9.0)
4.07 dd (9.0, 9.0)
ca. 3.89
4.27 dd (5.0, 11.5)
ca. 4.40
5.71 d (7.6)
ca. 4.20
ca. 3.94
ca. 3.94
3.72 m
ca. 4.13
4.32 dd (2.0, 11.8)
4.92 d (7.9)
3.97 dd (7.9, 8.5)
ca. 4.13
4.02 dd (8.5, 8.5)
ca. 3.98
ca. 4.05
4.59 dd (1.0, 11.0)
5.80 d (7.3)
ca. 4.25
4.07 dd (9.0, 9.0)
ca. 4.03
3.79 m
4.18 dd (5.5, 11.0)
ca. 4.34
5.00 d (7.6)
4.00 dd (7.6, 8.5)
4.14 dd (8.5, 8.5)
4.10 dd (8.5, 8.5)
ca. 4.00
Glcꢃ-1
5.27 d (7.6)
2
3
4
5
6
4.06 dd (7.6, 8.5)
4.13 dd (8.5, 8.5)
4.09 dd (8.5, 8.5)
3.83 ddd (3.0, 6.0, 8.5)
4.25 dd (6.0, 11.5)
ca. 4.38
Glcꢄ-1
5.20 d (7.9)
2
3
4
5
6
4.00 dd (7.9, 8.5)
4.15 dd (8.5, 8.5)
4.10 dd (8.5, 8.5)
3.95 ddd (2.6, 6.2, 8.5)
4.24 dd (6.2, 11.5)
4.47 dd (2.6, 11.5)
ca. 4.25
ca. 4.53
ca. 4.20
4.50 dd (2.7, 12.0)
5.39 d (7.6)
4.04 dd (7.6, 9.0)
4.15 dd (9.0, 9.0)
4.04 dd (9.0, 9.0)
ca. 3.95
Glcꢅ-1
2
3
4
5
6
4.11 dd (4.8, 11.0)
ca. 4.40
Rha-1
5.51 d (1.5)
5.41 d (1.5)
5.44 d (1.0)
2
3
4
5
4.60 dd (1.5, 3.4)
4.52 dd (3.4, 9.5)
4.25 dd (9.5, 9.5)
4.35 dq (9.5, 6.1)
1.64 d (6.1)
4.51 dd (1.5, 3.0)
4.45 dd (3.0, 8.5)
4.19 dd (8.5, 8.5)
4.28 dq (8.5, 5.8)
1.61 d (5.8)
4.54 dd (1.0, 3.0)
4.49 dd (3.0, 9.0)
4.23 dd (9.0, 9.0)
ca. 4.33
6
1.63 d (6.1)
Rhaꢃ-1
6.30 d (1.5)
6.28 s
2
3
4
5
6
4.81 dd (1.5, 3.5)
4.61 dd (3.5, 9.0)
4.26 dd (9.0, 9.0)
ca. 4.96
5.03 d (3.5)
4.79 dd (3.5, 9.5)
4.45 dd (9.5, 9.5)
5.01 dq (9.5, 6.1)
1.73 d (6.1)
2.67 dd (5.0, 14.5)
2.72 dd (8.5, 14.5)
ca. 4.39
1.78 d (6.4)
Ag-2
2.68 dd (4.6, 14.7)
2.75 dd (8.2, 14.7)
4.42 ddt (4.6, 8.2, 7.0)
3.98 m
0.93 t (7.3)
3.64 s
2.69 dd (5.0, 15.0)
2.75 dd (8.0, 15.0)
ca. 4.41
3.93 tt (5.5, 5.5)
0.86 t (7.3)
2.67 dd (5.0, 14.5)
2.73 dd (8.0, 14.5)
ca. 4.39
ca. 3.89
0.92 t (7.2)
3.64 s
2.68 dd (5.0, 15.0)
2.73 dd (8.5, 15.0)
4.41 m
3.93 m
0.91 t (7.3)
3
12
16
ca. 3.92
0.84 t (7.0)
3.62 s
OCH3
3.64 s
3.62 s
d in ppm from TMS (coupling constants (J) in Hz are given in parentheses). Glc, glucopyranosyl; Rha, rhamnopyranosyl; Ag, aglycone moiety.
gel CHP20 column chromatography (cc) (70% MeOH→95% MeOH→ace- residue was fractionated between H2O (40 ml) and ether (20 ml). Chromato-
tone) to afford fr. 1 (4.60 g), fr. 2 (7.34 g, brown powder, mp 148—155 °C, graphic separation of the ether-soluble fraction on a silica gel column [n-
convolvulin fraction), and fr. 3 (0.20 g).
hexane–ethyl acetate (AcOEt) (2 : 1)] afforded fr. 4 (730 mg) and fr. 5
(192 mg). Fraction 4 was subjected to silica gel cc [n-hexane–AcOEt
(19 : 1)] to obtain fr. 6 (448 mg) and fr. 7 (282 mg). HPLC separation of
fr. 7 on a Kusano CIG Si column [22 mm i.d.ꢂ100 mm; solvent: n-
Alkaline Hydrolysis of Convolvulin Fraction Fraction 2 (7.10 g) in
5% KOH (100 ml) was heated at 95 °C for 3 h. After cooling, the pH of the
reaction mixture was adjusted to 4 with 1 M HCl, and the mixture was
shaken with ether (30 mlꢂ3). The ether layer was washed with H2O (50 ml), hexane–AcOEt (60 : 1)] afforded 1 (140 mg) and 2 (202 mg). HPLC separa-
dried over MgSO4, and evaporated under reduced pressure to afford an oil tion of fr. 5 on a Kusano CIG Si column [22 mm i.d.ꢂ300 mm; solvent:
(988 mg, organic acid fraction). The H2O layer was loaded onto an MCI gel n-hexane–AcOEt (5 : 2)] afforded 3 (109 mg) and 4 (62 mg). Compounds 3
CHP20 column and eluted first with H2O and then with acetone. The ace-
tone eluate was evaporated to dryness to afford a yellow powder (5.8 g, gly- evaporated. The HPLC chromatogram [column: Kusano CIG Si, 22 mm
cosidic acid fraction). i.d.ꢂ100 mm; solvent: n-hexane–AcOEt (5 : 1); flow rate: 3.0 ml/min] of
A small portion of the organic acid fraction was analyzed by GC [column: both the residues showed two peaks in the ratio of ca. 1 : 1, and the tR values
and 4 were refluxed separately in CHCl3 for 8 h, and then the solvent was
3.2 mm i.d.ꢂ2.0 m glass column packed with Unisole 30T (10%); carrier
gas: N2 (2.0 kg/cm2); column temperature: 120 °C] and was found to contain
isovaleric acid (tR 5.1 min) and tiglic acid (tR 2.0 min).
of the two residues, 61 and 68 min, were equal to those of 3 and 4, respec-
tively.
1: Colorless needles (n-hexane–AcOEt), mp 67—68 °C. 1H-NMR (in
Identification of Organic Acids The organic acid fraction (980 mg) CDCl3, 400 MHz) d: 1.02 (6H, d, Jꢆ6.4 Hz, H3-4, 4ꢃ), 2.18 (1H, tqq, Jꢆ7.0,
in dry acetone (50 ml) was neutralized with triethylamine. Then, p-bro- 6.4, 6.4 Hz, H-3), 2.36 (2H, d, Jꢆ7.0 Hz, H2-2), 5.28 (2H, s, O–CH2–CO),
mophenacylbromide (600 mg) was added; the mixture was left to stand at 7.63 (2H, ddd, Jꢆ1.7, 1.7, 8.6 Hz, arom. H), 7.77 (2H, ddd, Jꢆ1.7, 1.7,
room temperature for 5 h and then concentrated under reduced pressure. The 8.6 Hz, arom. H).

March 2009
267
2: Colorless needles (n-hexane–AcOEt), mp 68—69 °C. 1H-NMR (in
CDCl3, 400 MHz) d: 1.84 (3H, dd, Jꢆ0.9, 7.3 Hz, H3-4), 1.90 (3H, dd,
13: Colorless oil, 1H-NMR d: see Table 1.
Isolation of Operculinic Acid H Methyl Ester (14) The glycosidic
Jꢆ0.9, 1.5 Hz, H3-5), 5.33 (2H, s, OCH2CO), 7.02 (1H, dq, Jꢆ7.3, 1.5 Hz, acid fraction (5.87 g) in MeOH (100 ml) was methylated using a diazo-
H-3), 7.63 (2H, ddd, Jꢆ1.5, 1.5, 8.3 Hz, arom. H), 7.79 (2H, ddd, Jꢆ1.5,
methane–ether solution. The methylated product was chromatographed on a
silica gel column [CHCl3–MeOH–H2O (6 : 4 : 1)] and subsequently purified
1.5, 8.3 Hz, arom. H).
3: Colorless oil. FD-MS m/z (%): 399 (59) [Mꢀ3]ꢀ, 398 (95) [Mꢀ2]ꢀ, by HPLC (column: Nucleosil 5C8, 20 mm i.d.ꢂ250 mm; solvent: 70%
1
397 (67) [Mꢀ1]ꢀ, 396 (100) [M]ꢀ. H-NMR (in CDCl3, 400 MHz) d: 1.21 MeOH) to afford 14 (4.10 g).
(3H, d, Jꢆ6.1 Hz, H3-10), 1.44 (1H, m, Ha-8), 1.70 (1H, m, Ha-4), ca. 2.04
(2H, H2-5), ca. 2.04 (2H, H2-7), 2.10 (1H, m, Hb-8), 2.31 (1H, m, Hb-4),
2.62 (1H, dd, Jꢆ7.3, 15.3 Hz, Ha-2), 2.79 (1H, dd, Jꢆ6.1, 15.3 Hz, Hb-2),
4.19 (1H, ddq, Jꢆ6.0, 8.0, 6.1 Hz, H-9), 4.52 (1H, dddd, Jꢆ6.1, 7.0, 7.0,
14: White powder, mp 142—145 °C, [a]D19 ꢁ33.8° (cꢆ1.0, MeOH). IR
(KBr) cmꢁ1: 3400 (br, OH), 1725 (CꢆO). Negative FAB-MS m/z: 1241
[MꢁH]ꢁ. 1H- and 13C-NMR d: see Tables 3 and 4. 1JC–H: Glc (156 Hz), Glcꢃ
(164 Hz), Glcꢄ (159 Hz), Glcꢅ (158 Hz), Rha (168 Hz), Rhaꢃ (174 Hz). Anal.
7.3 Hz, H-3), 5.26 (1H, d, Jꢆ16.5 Hz, OCHa), 5.31 (1H, d, Jꢆ16.5 Hz, Calcd for C53H94O32: C, 51.20; H, 7.62. Found: C, 51.13; H, 7.63.
OCHb), 7.63 (2H, ddd, Jꢆ2.5, 2.5, 9.0 Hz, arom. H), 7.77 (2H, ddd, Jꢆ2.5, Alkaline Hydrolysis of 14 A solution of 14 (30 mg) in 3% KOH (6 ml)
2.5, 9.0 Hz, arom. H). 13C-NMR (in CDCl3, 100 MHz) d: 21.1 (C-10), 30.2 was heated at 95 °C for 1 h. The pH of the reaction mixture was adjusted to 4
(C-4), 32.1 (C-8), 35.1 (C-5 or C-7), 35.5 (C-5 or C-7), 40.3 (C-2), 65.8
(OCH2), 74.0 (C-3), 74.3 (C-9), 115.1 (C-6), 129.1 (arom. C), 129.3 (arom.
C), 132.2 (arom. C), 133.0 (arom. C), 170.4 (C-1), 191.2 (OCH2CO).
with 1 M HCl, and the mixture was desalted through an MCI gel CHP20 col-
umn (H2O→acetone) to afford 15 (26 mg).
15: White powder, mp 156—163 °C, [a]D26 ꢁ49.1° (cꢆ2.5, MeOH). IR
(KBr) cmꢁ1: 3400 (br, OH), 1710 (CꢆO). Negative FAB-MS m/z: 1227
4: Colorless oil. FD-MS m/z (%): 399 (79) [Mꢀ3]ꢀ, 398 (88) [Mꢀ2]ꢀ,
1
397 (100) [Mꢀ1]ꢀ, 396 (60) [M]ꢀ. H-NMR (in CDCl3, 400 MHz) d: 1.29 [MꢁH]ꢁ, 1065 [1227ꢁ162]ꢁ, 919 [1065ꢁ146]ꢁ, 757 [919ꢁ162]ꢁ, 595
(3H, d, Jꢆ6.3 Hz, H3-10), 1.73 (1H, m, Ha-8), 1.90 (1H, m, Ha-4), 2.00 (1H,
m, Hb-8), ca. 2.05 (2H, H2-5), ca. 2.05 (2H, H2-7), 2.22 (1H, m, Hb-4), 2.74
(1H, dd, Jꢆ6.7, 15.6 Hz, Ha-2), 2.94 (1H, dd, Jꢆ7.0, 15.6 Hz, Hb-2), 4.13
(26) [757ꢁ162]ꢁ. Anal. Calcd for C52H92O32: C, 50.81; H, 7.54. Found: C,
50.81; H, 7.54.
Acidic Hydrolysis of 14 A solution of 14 (200 mg) in 2 M H2SO4 (3 ml)
(1H, ddq, Jꢆ6.0, 8.5, 6.3 Hz, H-9), 4.48 (1H, dddd, Jꢆ6.7, 7.0, 7.0, 7.0 Hz, was heated at 95 °C for 2 h. The reaction mixture was diluted with H2O
H-3), 5.26 (1H, d, Jꢆ16.0 Hz, OCHa), 5.31 (1H, d, Jꢆ16.0 Hz, OCHb), 7.63 (10 ml) and extracted with ether (10 mlꢂ3). The ether layer was dried over
(2H, ddd, Jꢆ1.5, 1.5, 8.5 Hz, arom. H), 7.77 (2H, ddd, Jꢆ1.5, 1.5, 8.5 Hz, MgSO4 and then treated with a solution of diazomethane–ether. The reac-
arom. H). 13C-NMR (in CDCl3, 100 MHz) d: 22.9 (C-10), 30.6 (C-4), 32.5 tion mixture was evaporated, and the residue was crystallized from n-
(C-8), 35.6 (C-5 or C-7), 36.0 (C-5 or C-7), 42.2 (C-2), 65.6 (OCH2), 75.3 hexane–AcOEt to yield 16 (23 mg). The H2O layer was neutralized with 4%
(C-3), 76.1 (C-9), 114.8 (C-6), 129.0 (arom. C), 129.2 (arom. C), 132.1
(arom. C), 133.0 (arom. C), 170.7 (1-C), 191.2 (OCH2CO).
KOH and then desalted on a Sephadex LH-20 column (MeOH) to afford a
sugar mixture, which was subjected to HPLC (column: Nucleosil 5NH2,
10 mm i.d.ꢂ300 mm; solvent: 80% CH3CN) to afford L-rhamnose (28 mg)
Hydrogenolysis of Methyl Exogonate The organic acid fraction
(1.75 g) was methylated using a diazomethane-ether solution. The solvent [syrup, [a]D24 ꢀ10.1° (cꢆ1.7, H2O)] and D-glucose (25 mg) [syrup, [a]D24
was removed under reduced pressure, and the residue was chromatographed ꢀ49.8° (cꢆ1.6, H2O)].
over silica gel [n-hexane–AcOEt (10 : 1→7 : 1→5 : 1)] to afford a colorless
oil (methyl exogonate, 310 mg). PtO2 (50 mg) was added to a solution of the
16: Colorless needles (n-hexane–AcOEt), mp 79—80 °C, [a]D21 ꢀ12.5°
(cꢆ3.5, CHCl3). FD-MS m/z (%): 303 (100) [MꢀH]ꢀ, 285 (20) [303ꢁ
oil in acetic acid (5 ml), and the mixture was stirred in a hydrogen atmo- H2O]ꢀ, 245 (14) [MꢁCH3(CH2)3]ꢀ, 216 (14) [303ꢁCH3(CH2)3CH(OH)]ꢀ,
sphere (pressure: 1 atm) for 1 h. After filtration, the filtrate was concentrated 103 (44) [CH(OH)CH2COOCH3]ꢀ, 87 (27) [CH3(CH2)3CH(OH)]ꢀ. 1H-
under reduced pressure, and the residue was subjected to HPLC [column: NMR (in pyridine-d5, 400 MHz) d: 0.90 (3H, t, Jꢆ7.0 Hz, H3-16), 2.68 (1H,
Kusano CIG Si, 22 mm i.d.ꢂ300 mm; solvent: n-hexane–AcOEt (2 : 1)] to dd, Jꢆ4.8, 15.0 Hz, Hb-2), 2.75 (1H, dd, Jꢆ8.0, 15.0 Hz, Ha-2), 3.64 (3H, s,
afford 5 (52 mg), 6 (3 mg), and 7 (2 mg).
COOCH3), 3.82 (1H, m, H-12), 4.42 (1H, m, H-3). 1H-NMR (in CDCl3,
400 MHz) d: 0.91 (3H, t, Jꢆ7.0 Hz, H3-16), 2.41 (1H, dd, Jꢆ8.9, 16.2 Hz,
5: Colorless oil, 1H-NMR (in CDCl3, 600 MHz) d: 1.23 (3H, d, Jꢆ6.1 Hz,
H3-10), 2.46 (1H, dd, Jꢆ7.8, 15.7 Hz, Ha-2), 2.49 (1H, dd, Jꢆ4.0, 15.7 Hz, Hb-2), 2.51 (1H, dd, Jꢆ3.3, 16.2 Hz, Ha-2), 3.58 (1H, m, H-12), 3.71 (3H, s,
Hb-2), 3.70 (3H, s, COOCH3), 3.83 (1H, dddd, Jꢆ4.8, 5.0, 7.8, 7.8 Hz, H-6), COOCH3), 4.00 (1H, m, H-3). 13C-NMR (in pyridine-d5, 100 MHz) d: 14.4
3.97 (1H, ddq, Jꢆ6.1, 7.3, 6.1 Hz, H-9), 4.05 (1H, dddd, Jꢆ4.0, 4.0, (C-16), 23.2, 26.2, 26.4, 28.6, 30.0 (ꢂ2), 30.0, 30.2, 38.1, 38.2, 38.5, 43.5,
7.2, 7.8 Hz, H-3). 13C-NMR (in CDCl3, 150 MHz) d: 21.4, 31.4, 32.7, 32.8,
33.9, 41.7, 51.7 (COOCH3), 68.3 (C-O), 75.6 (C-O), 79.5 (C-O), 173.1
(COOCH3).
51.3 (OCH3), 68.2 (C-3), 70.9 (C-12), 172.8 (C-1). 13C-NMR (in CDCl3,
100 MHz) d: 14.1 (C-16), 22.8, 25.5, 25.6, 27.9, 29.5 (ꢂ2), 29.5, 29.7, 36.5,
37.2, 37.5, 41.2, 51.7 (COOCH3), 68.0 (C-3), 72.0 (C-12), 173.5 (C-1).
Preparation of (ꢀ)-MTPA Ester (17) and (ꢁ)-MTPA Ester (18) of 16
6: Colorless oil, 1H-NMR (in CDCl3, 600 MHz) d: 1.18 (3H, d, Jꢆ6.0 Hz,
H3-10), 2.48 (1H, dd, Jꢆ6.6, 15.3 Hz, Ha-2), 2.63 (1H, dd, Jꢆ6.6, 15.3 Hz, Compound 16 (8 mg or 5 mg) was treated with (ꢁ)-MTPA chloride (30 mg)
Hb-2), 3.69 (3H, s, COOCH3), 3.79 (1H, ddq, Jꢆ3.6, 4.6, 6.0 Hz, H-9), 3.87
or (ꢀ)-MTPA chloride (15 mg) in a mixture of dry pyridine (2 ml) and CCl4
(1H, dddd, Jꢆ4.8, 6.6, 6.6, 6.6 Hz, H-6), 4.26 (1H, dddd, Jꢆ6.6, 6.6, (5 drops), and the reaction mixture was left to stand overnight at room tem-
6.6, 6.6 Hz, H-3). 13C-NMR (in CDCl3, 150 MHz) d: 23.6, 31.0, 31.1, 33.0, perature. After removal of the solvent, the residue was purified by silica gel
36.5, 40.9, 51.7 (COOCH3), 68.2 (C-O), 75.5 (C-O), 80.1 (C-O), 171.6
(COOCH3).
cc [benzene–AcOEt (10 : 1→8 : 1→5 : 1→0 : 1)] to yield the corresponding
ester.
7: Colorless oil, 1H-NMR (in CDCl3, 600 MHz) d: 1.19 (3H, d, Jꢆ6.2 Hz,
H3-10), 2.42 (1H, dd, Jꢆ3.2, 16.5 Hz, Ha-2), 2.51 (1H, dd, Jꢆ8.9, 16.5 Hz,
Hb-2), 3.72 (3H, s, COOCH3), 3.79 (1H, ddq, Jꢆ4.8, 6.0, 6.2 Hz, H-9), 4.00
17: Colorless oil, 1H-NMR d: see Table 2.
18: Colorless oil, 1H-NMR d: see Table 2.
Acetylation of 14 Compound 14 (30 mg) in Ac2O–pyridine (1 : 1, 3 ml)
(1H, dddd, Jꢆ3.2, 5.0, 6.1, 8.9 Hz, H-3). 13C-NMR (in CDCl3, 150 MHz) d: was left to stand at room temperature overnight. The solvent was removed
23.6, 25.4, 25.6, 29.5, 36.5, 39.2, 41.1, 51.7 (COOCH3), 68.0 (C-O), 78.1
(C-O), 173.5 (COOCH3).
under a N2 stream to afford 19.
19: White powder, mp 83—87 °C, [a]D ꢁ21.3° (cꢆ6.6, MeOH). IR
26
Preparation of (ꢀ)- and (ꢁ)-MTPA Esters, 8—13 Freshly prepared (KBr) cmꢁ1: 1750 (CꢆO). 1H-NMR d: see Table 3.
(ꢁ)-MTPA chloride (30 mg) was added to individual solutions of hydro-
Permethylation of 14 NaH (50 mg) and CH3I (2 ml) were added to a so-
genated compounds (5—7, 1—3 mg) in a mixture of pyridine (2 ml) and lution of 14 (14 mg) in DMF (2 ml) under stirring. The mixture was stirred
CCl4 (5 drops); the resulting mixture was left to stand at room temperature overnight at room temperature. The solvent was removed under a N2 stream
overnight. After removing the solvent under a N2 stream, the residue was and then H2O (2 ml) was added. The mixture was extracted with ether
purified by chromatography on a silica gel column [n-hexane–AcOEt (1 mlꢂ4). The extract was purified by silica gel cc [benzene–acetone (5 : 1,
(20 : 1→10 : 1→8 : 1→5 : 1→2 : 1→0 : 1)] to afford (ꢁ)-MTPA esters (8, 10,
12). Further, (ꢀ)-MTPA esters (9, 11, 13, 2—7 mg) were obtained from in-
dividual solutions of 5, 6, and 7, respectively, by using (ꢀ)-MTPA chloride Jꢆ7.0 Hz, H3-16 of Ag), 1.46 (3H, d, Jꢆ6.1 Hz, H3-6 of rhamnose), 1.62
3 : 1)] to afford 20 (8 mg).
20: Colorless syrup, H-NMR (in pyridine-d5, 400 MHz) d: 1.00 (3H, t,
1
(30 mg) and following the same procedure as described above.
(3H, d, Jꢆ6.1 Hz, H3-6 of rhamnose), 2.59 (1H, dd, Jꢆ5.5, 15.3 Hz, Ha-2 of
Ag), 2.71 (1H, dd, Jꢆ7.2, 15.3 Hz, Hb-2 of Ag), 3.37, 3.43, 3.45, 3.52, 3.54,
3.55, 3.55, 3.56, 3.57, 3.60, 3.66, 3.67, 3.67, 3.68, 3.72, 3.72, 3.86, 3.97
(each 3H, s, OCH3), 4.67 (1H, d, Jꢆ7.6 Hz, H-1 of glucose), 4.82 (1H, d,
Jꢆ7.9 Hz, H-1 of glucose), 4.88 (1H, d, Jꢆ7.5 Hz, H-1 of glucose), 5.16
(1H, d, Jꢆ7.6 Hz, H-1 of glucose), 5.21 (1H, d, Jꢆ1.8 Hz, H-1 of rham-
8: Colorless oil, 1H-NMR d: see Table 1.
9: Colorless oil, 1H-NMR d: see Table 1.
10: Colorless oil, 1H-NMR d: see Table 1.
11: Colorless oil, 1H-NMR d: see Table 1.
12: Colorless oil, 1H-NMR d: see Table 1.

268
Vol. 57, No. 3
2) Ono M., Kubo K., Miyahara K., Kawasaki T., Chem. Pharm. Bull., 37,
241—244 (1989).
3) Ono M., Kawasaki T., Miyahara K., Chem. Pharm. Bull., 37, 3209—
3213 (1989).
4) Ono M., Fukunaga T., Kawasaki T., Miyahara K., Chem. Pharm. Bull.,
38, 2650—2655 (1990).
5) Ono M., Nishi M., Kawasaki T., Miyahara K., Chem. Pharm. Bull., 38,
2986—2991 (1990).
6) Ono M., Kawasaki T., Miyahara K., Chem. Pharm. Bull., 39, 2534—
2539 (1991).
7) Ono M., Fujimoto K., Kawata M., Fukunaga T., Kawasaki T., Miya-
hara K., Chem. Pharm. Bull., 40, 1400—1403 (1992).
8) Graf E., Dahlke E., Voigtlander H. W., Arch. Pharm. Ber. Dtsch.
Pharm. Ges., 298, 81—91 (1965).
9) Shellard E. J., Planta Med., 9, 141—145 (1961).
10) Mannich C., Schumann P., Arch. Pharm. Ber. Dtsch. Pharm. Ges., 276,
221—226 (1938).
11) Graf E., Dahlke E., Chem. Ber., 97, 2785—2797 (1964).
12) Votocek E., Valentin F., Coll. Trav. Chim. Czechoslov., I. 47—54
(1929).
13) Votocek E., Prelog V., Coll. Trav. Chim. Czechoslov., I. 55—64 (1929).
14) Wagner H., Kazmaier P., Phytochemistry, 16, 711—714 (1977).
15) Dale J. A., Mosher H. S., J. Am. Chem. Soc., 95, 512—518 (1973).
16) Lawson E. N., Jamie J. F., Kitching W., J. Org. Chem., 57, 353—358
(1992).
17) Ono M., Yamada F., Noda N., Kawasaki T., Miyahara K., Chem.
Pharm. Bull., 41, 1023—1026 (1993).
18) Jakob B., Gerlach H., Lieb. Ann., 1996, 2123—2129 (1996).
19) Kasai R., Okihara M., Asakawa J., Mizutani K., Tanaka O., Tetrahe-
dron, 55, 1427—11432 (1977).
20) Kasai R., Okihara M., Asakawa J., Tanaka O., Tetrahedron Lett., 1977,
175—178 (1977).
21) Seo S., Tomita Y., Tori K., Yoshimura Y., J. Am. Chem. Soc., 100,
3331—3339 (1978).
22) Ono M., Noda N., Kawasaki T., Miyahara K., Chem. Pharm. Bull., 38,
1892—1897 (1990).
nose), 5.64 (1H, d, Jꢆ1.5 Hz, H-1 of rhamnose). EI-MS m/z: 299, 393, 565,
801. HR-EI-MS m/z: 299.2590 [Calcd for C18H35O3 (a): 299.2586];
393.2127 [Calcd for C18H33O9 (b): 393.2124]; 565.2848 [Calcd for
C26H45O13 (c): 565.2860]; 801.4121 [Calcd for C36H65O19 (d): 801.4119],
see Fig. 3.
Partial Methanolysis of 14 Compound 14 (531 mg) was dissolved in
0.3% HCl–MeOH (3 ml), and the solution was refluxed for 100 min. After
cooling, the reaction mixture was neutralized with triethylamine, the solvent
was removed under reduced pressure, and the residue was successively chro-
matographed on a Sephadex LH-20 column (MeOH) and a Fuji-gel ODS
G3 column (60% MeOH, 70% MeOH) to afford fr. 8 (170 mg) and fr. 9
(320 mg). Fraction 9 was subjected to HPLC (column: Inertsil ODS, 20 mm
i.d.ꢂ250 mm; solvent: 70% MeOH) to give fr. 10 (37 mg), fr. 11 (35 mg), fr.
12 (4 mg), fr. 13 (121 mg), fr. 14 (10 mg), fr. 15 (42 mg), fr. 16 (10 mg), and
fr. 17 (38 mg). Fraction 10 was chromatographed on a silica gel column
[CHCl3–MeOH–H2O (8 : 2 : 0.2→7 : 3 : 0.5→0 : 0 : 1)] to afford 23 (30 mg).
Fractions 11, 13, 15, and 17 were chromatographed individually on a silica
gel column under conditions similar to those used for the chromatographic
purification of fr. 10 to afford the following compounds: 21 (15 mg) from fr.
11, 14 (81 mg) from fr. 13, 22 (11 mg) and 24 (14 mg) from fr. 15, and 25
(17 mg) from fr. 17.
21: Colorless needles (MeOH–H2O), mp 118—121 °C, [a]D21 ꢁ41.9°
(cꢆ2.5, MeOH). IR (KBr) cmꢁ1: 3400 (br, OH), 1720 (CꢆO). 1H- and 13C-
NMR d: see Tables 4 and 5.
22: White powder, mp 102—111 °C, [a]D21 ꢁ17.3° (cꢆ1.8, MeOH). IR
(KBr) cmꢁ1: 3400 (br, OH), 1725 (CꢆO). 1H- and 13C-NMR d: see Tables 4
and 5.
23: White powder, mp 110—115 °C, [a]D21 ꢁ24.0° (cꢆ4.5, MeOH). IR
(KBr) cmꢁ1: 3400 (br OH), 1725 (CꢆO). 1H- and 13C-NMR d: see Tables 4
and 5.
24: White powder, mp 118—126 °C, [a]D21 ꢁ48.5° (cꢆ1.9, MeOH). IR
(KBr) cmꢁ1: 3400 (br, OH), 1725 (CꢆO). 1H- and 13C-NMR d: see Tables 4
and 5.
25: White powder, mp 126—132 °C, [a]D21 ꢁ29.7° (cꢆ2.5, MeOH). IR
(KBr) cmꢁ1: 3400 (br OH), 1725 (CꢆO). 1H- and 13C-NMR d: see Tables 4
and 5.
23) Ono M., Honda F., Karahashi A., Kawasaki T., Miyahara K., Chem.
Pharm. Bull., 45, 1955—1960 (1997).
References
1) Shellard E. J., Planta Med., 9, 102—116 (1961).