Preparation of menisdaurigenin and related compounds

Article abstract of DOI:10.1007/s11418-018-1235-5

Menisdaurin (1), a cyano glucoside, was first isolated in 1978 from Menispermum dauricum (Menispermaceae) and named after the plant. It has been also isolated from several plant sources. The stereochemistry of the aglycone part was first reported as (Z,4R,6S)-enantiomer of (4,6-dihydroxy-2-cyclohexen-1-ylidene)acetonitrile based on the CD spectrum of menisdaurilide (2), the α,β-unsaturated γ-lactone obtained by an acid hydrolysis of menisdaurin. Later, the absolute stereochemistry was revised as (Z,4S,6R) by X-ray crystal analysis of 1 isolated from Saniculiphyllum guangxiens. The aglycone part of menisdaurin (1) has not been obtained from 1, because an acid hydrolysis of 1 gave menisdaurilide (2), and enzymatic hydrolysis with emulsin did not give the aglycone. On the other hand, a compound named coculauril (3) was isolated from Cocculus lauriforius. This compound has the same planner structure corresponding to the aglycone of 1, but the stereochemistry was reported to be (E,4R,6S). Here, we confirmed the absolute stereochemistry of 1 by Mosher’s method to be (Z,4S,6R), and prepared the aglycone of 1, i.e., menisdaurigenin (4) by an enzymatic hydrolysis of 1. We also revealed that 4 is a different compound from 3 and unstable in water and MeOH.

Full text of DOI:10.1007/s11418-018-1235-5

Journal of Natural Medicines
https://doi.org/10.1007/s11418-018-1235-5
NOTE
Preparation of menisdaurigenin and related compounds
Rie Shirakawa1 · Sanami Ishikawa1 · Mizuki Takahasi1 · Yuuka Ueno1 · Yoshinori Uekusa1 · Yuji Narukawa1 ·
Takeshi Sugai1 · Fumiyuki Kiuchi1
Received: 27 June 2018 / Accepted: 31 July 2018
© The Japanese Society of Pharmacognosy and Springer Japan KK, part of Springer Nature 2018
Abstract
Menisdaurin (1), a cyano glucoside, was frst isolated in 1978 from Menispermum dauricum (Menispermaceae) and named
after the plant. It has been also isolated from several plant sources. The stereochemistry of the aglycone part was frst reported
as (Z,4R,6S)-enantiomer of (4,6-dihydroxy-2-cyclohexen-1-ylidene)acetonitrile based on the CD spectrum of menisdaurilide
(2), the α,β-unsaturated γ-lactone obtained by an acid hydrolysis of menisdaurin. Later, the absolute stereochemistry was
revised as (Z,4S,6R) by X-ray crystal analysis of 1 isolated from Saniculiphyllum guangxiens. The aglycone part of menis-
daurin (1) has not been obtained from 1, because an acid hydrolysis of 1 gave menisdaurilide (2), and enzymatic hydrolysis
with emulsin did not give the aglycone. On the other hand, a compound named coculauril (3) was isolated from Cocculus
lauriforius. This compound has the same planner structure corresponding to the aglycone of 1, but the stereochemistry was
reported to be (E,4R,6S). Here, we confrmed the absolute stereochemistry of 1 by Mosher’s method to be (Z,4S,6R), and
prepared the aglycone of 1, i.e., menisdaurigenin (4) by an enzymatic hydrolysis of 1. We also revealed that 4 is a diferent
compound from 3 and unstable in water and MeOH.
Keywords Sinomenium acutum · Menisdaurin · Menisdaurigenin · Enzymatic hydrolysis · Color change
Introduction
of 1 isolated from Purshia tridentata (Rosaceae) [5]. The
absolute stereochemistry was also determined as (Z,4S,6R)
by X-ray crystal analysis of 1 isolated from Saniculiphyllum
guangxiense [10]. Recently, Li et al. [11] isolated 1 ([α]D
− 78.2°) from Bruguiera gymnorrhiza and presented the
structure as (Z,4R,6S) citing the reports [2, 3] before the
revision of the stereochemistry [5, 10].
Menisdaurin (1), a cyano glucoside, was frst isolated in
1978 from Menispermum dauricum (Menispermaceae) and
named after the plant [1]. It has been also isolated from
several plant sources [2–13]. The stereochemistry of the
aglycone part was frst reported as (Z,4R,6S)-enantiomer
of (4,6-dihydroxy-2-cyclohexen-1-ylidene)acetonitrile
based on the CD spectrum of menisdaurilide (2), the α,β-
unsaturated γ-lactone obtained by an acid hydrolysis of 1
[1] (Fig. 1). The absolute stereochemistry of 2 isolated from
Sinomenium acutum (Menispermaceae) was determined by
X-ray crystal analysis of the p-bromobenzoate derivative
of 2 as (4S,6R) [4], which suggested that 1 has the same
(Z,4S,6R) stereochemistry. The absolute stereochemistry of
1 ([α]D − 214.5°) itself was revised to (Z,4S,6R) based on
detailed analyses of the NMR spectra including NOE efects
between protons of the aglycone and the glucose moieties
The aglycone part of 1 has not been obtained from 1,
because an acid hydrolysis of 1 gave 2, and enzymatic
hydrolysis with emulsin did not give the aglycone [1]. On the
other hand, a compound named coculauril (3) (Fig. 1) was
isolated from Cocculus lauriforius [14]. This compound has
the same planner structure corresponding to the aglycone
of 1, but the stereochemistry was reported to be (E,4R,6S).
Here, we confrmed the stereochemistry of 1 and prepared its
aglycone, i.e., menisdaurigenin (4), and related compounds,
and examined their properties.
* Fumiyuki Kiuchi
kiuchi-fm@pha.keio.ac.jp
1
Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen,
Minato-ku, Tokyo 105-8512, Japan
Vol.:(0123456789)
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Journal of Natural Medicines
Fig. 1 Structures of menisdau-
rin (1) and related compounds
the aglycone [1]. In fact, prolonged enzymatic hydroly-
sis of 1 gave a dark colored complex mixture, suggesting
that the aglycone is unstable in an aqueous solution. To
obtain the aglycone, 1 was hydrolyzed with β-glucosidase
in sodium acetate bufer (pH 4.8) in the presence of ethyl
acetate, by which the aglycone was continuously extracted.
The aglycone, menisdaurigenin (4) was obtained under
this condition in a good yield (87%). The structure of 4
was confrmed by its spectral data (Table 2). The cis rela-
tive sterochemistry between the two hydroxy groups and
(Z) confguration of the double bond were confrmed by
the nuclear Overhauser efect spectroscopy (NOESY) cor-
relations between H-4 (δH 4.42, m) and H-6 (δH 4.70, br d,
J = 7.3 Hz), and between H-2 (δH 6.26, d, J = 10.1 Hz) and
H-α (δH 5.49, s), respectively (Fig. 3). Menisdaurigenin (4)
has the opposite sign of optical rotation ([α]D − 167.2°)
to that of coculauril (3) ([α]D + 94.0°) and its spectral
data were diferent from those of 3 [14] (Table 2). These
results indicated that 3 has the (E,4R,6S) stereochemistry
as reported.
Results
We isolated menisdaurin (1) from a crude drug Boi
(Sinomenium stem and rhizome: climing stem and rhi-
zome of Sinomenium acutum). The isolated compound
showed a negative sign of optical rotation ([α]D − 223.2°,
c 0.1, MeOH) as reported previously [1, 4, 5, 8] and its
NMR spectral data were also in good agreement with
those reported previously[1, 5]. Although the absolute
stereochemistry of 1 isolated from S. guangxiense was
determined by X-ray crystal analysis [10], the optical
rotation of the material was not reported. Therefore, we
frst confrmed the absolute stereochemistry of 1 isolated
from S. acutum. Menisdaurin (1) was acetylated to give
its pentaacetate (1a), and the acetyl group on the allylic
alcohol was site-selectively removed by enzymatic hydrol-
ysis [15]. The lipase-catalyzed deacetylation was expected
to proceed leaving acetyl groups attached to the glucose
moiety intact [16]. Menisdaurin acetate (1a) was stirred
with lipase B immobilized on acrylic resin from Candida
antarctica in 2-propanol at 65 °C to give 4-O-deacetyl
menisdaurin acetate (5). The position of the deacetylation
was confrmed by the upper feld shift of the H-4 proton
(δH 4.18, br t, J = 8.4 Hz) compared to that of 1a (δH 5.36,
t, J = 3.9 Hz) (Table 1). In order to determine the absolute
stereochemistry, we applied Mosher’s method [17] to 5.
(R)- and (S)-MTPA esters of 5 were prepared according
to the reported method and the 1H-NMR spectrum of each
ester was determined. The ∆δ values (δS − δR) (Fig. 2)
indicated that the absolute confguration at C-4 of 5 is (S),
confrming the reported (4S,6R) absolute stereochemistry
of 1 [5, 10].
Menisdaurigenin (4) is unstable in water: the color of
the solution changed to dark brown within 1 h and its spot
had disappeared in TLC analysis. Compound 4 was less
unstable in MeOH than in water. Figure 4 shows the color
change of a solution of 4 in MeOH-d4. The color of the
solution changed to light brown after 22 h (Fig. 4) and
1
small signals other than those of 4 appeared in the H-
NMR. After 39 h, the color became dark and the signals
of 4 disappeared in the 1H-NMR (Fig. 5b). The remaining
signals (arrowed in Fig. 5b, Table 3) suggested that this
compound might be a 4-oxo derivative of 4 (6) (Fig. 6).
Dehydration of this compound will give a quinone meth-
ide (9), which undergoes polymerization to give the dark
color. The involvement of the hydroxy groups of 4 in the
An acid hydrolysis of 1 only gave 2, and enzymatic
hydrolysis of 1 with emulsin at pH 4.8 also failed to give
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Journal of Natural Medicines
Table 1 NMR data of menisdaurin acetate (1a), 4-O-deacetyl menisdaurin acetate (5) and 4-oxomenisdaurin acetate (7) in CDCl3
Position 1a
1H-NMR
5
7
13C-NMR 1H-NMR
13C-NMR 1H-NMR
13C-NMR
CN
α
1
2
3
–
116.5
99.4
152.8
129.1
132.9
64.1
–
116.5
98.4
153.5
125.6
137.5
62.0
–
115.3
100.8
151.5
132.3
5.36, s
5.30, s
5.65, s
–
–
–
6.35, d, J=10.0 Hz
6.17, dd, J=10.0, 4.5 Hz
5.36, t, J=3.9 Hz
2.23, dt, J=14.2, 3.9 Hz
2.13, m
6.23, d, J=10.0 Hz
6.34, dd, J=10.0, 5.2 Hz
4.18, br t, J=8.4 Hz
2.36, dt, J=15.2, 2.0 Hz
1.94, ddd, J=15.2, 5.6, 2.8 Hz
4.88, br s
6.21, d, J=10.4 Hz
7.05, ddd, J=10.0, 1.6, 0.8 Hz 140.3
4
–
193.8
43.0
5 eq
5ax
6
32.9
35.0
2.86, dd, J=16.4, 2.4 Hz
2.72, dd, J=16.8, 3.6 Hz
5.12, br dd, J=5.2, 3.2 Hz
4.76, br t, J=4.0 Hz
73.6
75.7
75.0
–OH
1′
2′
3′
4′
2.62, d, J=11.6 Hz
4.80, d, J=8.0 Hz
4.96, dd, J=9.6, 8.0 Hz
5.25, t, J=9.6 Hz
5.07, t, J=10.0 Hz
4.86, d, J=8.1 Hz
5.06, dd, J=9.5, 7.8 Hz
5.20, t, J=9.6 Hz
5.09, t, J=9.6 Hz
102.3
68.2
72.9
71.2
102.5
71.1
72.2
68.0
4.75, d, J=8.0 Hz
4.90, dd, J=9.6, 8.0 Hz
5.20, t, J=9.6 Hz
103.3
70.1
72.3
68.0
5.07, t, J=10.0 Hz
5′
6′a
6′b
3.77, ddd, J=10.0, 4.4, 2.4 Hz 72.3
3.79, ddd, J=10.4, 4.4, 2.4 Hz 72.3
3.75, ddd, J=10.0, 4.4, 2.4 Hz 72.6
4.29, dd, J=12.3, 2.4 Hz
4.12, dd, J=11.9, 3.8 Hz
61.7
4.33, dd, J=12.0, 2.0 Hz
4.16, dd, J=12.4, 4.0 Hz
2.10, s (6H)
61.3
4.29, dd, J=12.4, 2.4 Hz
4.18, dd, J=12.4, 4.4 Hz
2.10, s (3H)
61.4
CH3CO 2.09, s (6H)
2.04, s (3H)
2.02, s (3H)
2.00, s (3H)
CO
20.6×2
20.6
20.6×2
20.7
20.6×2
20.8
2.03, s (3H)
2.04, s (3H)
20.8
21.0
169.0
169.4
170.3
170.6
171.0
2.01, s (3H)
20.8
2.02, s (3H)
1.99, s (3H)
169.4
170.0
170.1
170.6
169.2
169.4
170.2
170.7
(δH 4.18, br t, J=8.4 Hz) and C-4 carbon (δC 62.0) signals
of 5 and the presence of a carbonyl carbon (δC 193.8, C-4)
in 7 (Table 1).
Compound 7 was relatively stable in MeOH, but when
7 was heated under refux in MeOH, it gave a new com-
pound 8 after chromatographic separation. Compound 8
showed a pair of ortho coupled benzene protons (δH 6.82,
d, J=8.8 Hz, 7.30, d, J=8.8 Hz, each 2H), a methoxy (δH
3.45, s, 3H) and a benzyl (δH 5.27, s, 1H) proton in the 1H-
NMR. These data are in good agreement with the reported
data of compound 8 [18]. This compound may be formed as
follows—elimination of the glucose moiety of 7 will give
the quinone methide 9, and an addition of MeOH to the
δ position of α,β,γ,δ-unsaturated ketone of 9 will give the
phenol 8 (Fig. 6). These results suggested that compound 9
is not involved in the dark color formation at least in MeOH
and compound 6 and/or its isomer 6b are taking place in
the process.
Fig. 2 ∆δ values (δS − δR) of MTPA esters of 5
color change was suggested by the fact that menisdau-
rigenin acetate (4a) was stable in MeOH.
As the intermediate could not be isolated, we oxidized
the free alcohol of 4-O-deacetyl derivative 5 to examine
its properties. Compound 5 was oxidized with pyridinium
chlorochromate to give 4-oxomenisdaurin acetate (7). The
structure was confrmed by the absence of the H-4 proton
In this report, we prepared menisdaurigenin (4) for
the frst time by enzymatic hydrolysis of menisdaurin
(1). Menisdaurigenin was unstable in water and rapid
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Journal of Natural Medicines
Table 2 NMR data of menisdaurigenin (4) and coculauril (3) in acetone-d6
Position
4
3a)
1H-NMR
13C-NMR
HMBC
1H-NMR
13C-NMR
CN
α
1
2
3
–
117.6
95.7
159.8
127.0
141.2
65.8
g
i, h
a, b, g, i, h
g
a, b
a, b, i, h
i, h
–
117.5
91.7
161.6
123.6
143.9
67.3
g: 5.49, s
5.61, br s
–
–
i: 6.26, d, J=10.1 Hz
h: 6.22, dd, J=10.1, 2.8 Hz
d: 4.42, m
6.53, dd, J=10.1, 2.4 Hz
6.28, dq, J=10.1, 1.7 Hz
4.53, br m
4
5eq
5ax
6
4-OH
6-OH
b: 2.22, dt, J=12.9, 4.3 Hz
a: 1.94, ddd, J=12.9, 9.1, 7.3 Hz
e: 4.70, br d, J=7.3 Hz
c: 4.30, br s
40.7
2.43, dtd, J=11.4, 4.9, 1.7 Hz
1.62, ddd, J=12.8, 11.4, 10.1 Hz
4.41, br m
4.45, d, J=6.1 Hz
4.90, d, J=6.1 Hz
43.2
67.6
a, b, g, i, h
68.0
f: 4.93, br s
aData from ref. [14]
and the other has a dark color (black Boi). Comparison of
the constituents of the two types showed that the content
of alkaloids (sinomenine, magnoforine and 6-O-methyl-
laudanosoline glucoside) together with menisdaurin (1)
in black Boi was smaller than those in white Boi [19].
Black Boi is intentionally prepared by leaving collected
stems and rhizomes in an open feld for several months. It
is reported that a rapid darkening of the cut surface was
observed when the stems were cut after being left for a
month [19]. Menisdaurigenin (4), which was formed by
hydrolysis of 1 with an endogenous β-glucosidase during
the period and oxidized on the cut surface, may take part
in this darkening because, as described above, it is unsta-
ble and the color of its water solution darkened rapidly.
Fig. 3 Correlations observed in NOESY spectrum of menisdau-
rigenin (4)
Experimental
Optical rotations were measured using a JASCO P-1020
(Tokyo, Japan). Infrared (IR) spectra were obtained with
FT-IR SPX 60 (JASCO). TOF–MS was measured with a
JMS-T100LP AccuTOF LC-plus (JEOL, Tokyo, Japan).
EI-MS and HR-FAB-MS was measured with a JEOL JMS-
7000. JEOL ECP-600 FT-NMR, VARIAN Unity Inova
500-MR (Palo Alto, CA, USA) and VARIAN 400-MR
were used for measurement of NMR spectra with tetra-
methylsilane as an internal standard.
Fig. 4 Color change of MeOH solution of menisdaurigenin (4)
Column chromatography was performed with silica
gel (40–50, 40–100, and 100–210 µm, Kanto Chemical,
Tokyo, Japan), and Diaion HP-20 (Mitsubishi Chemical,
Tokyo, Japan). Silica gel 60 F-254 was used for thin layer
chromatography (TLC), and spots were detected under UV
light (254 and/or 365 nm).
darkening of the solution was observed. The climbing stem
and rhizome of Sinomenium acutum are used as a crude
drug, Boi (Sinomenium stem and rhizome); there are two
types of Boi—one has a relatively light color (white Boi)
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Journal of Natural Medicines
Fig. 5 Change of 1H-NMR spectrum of menisdaurigenin (4) in MeOH. a Immediately after dissolved in MeOH; b 39 h after dissolved in
MeOH. The arrows indicate the signals form the intermediate
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Journal of Natural Medicines
1
Table 3 Comparison of H-NMR data of the intermediate (6) with menisdaurigenin (4) and aglycone part of 4-oxomenisdaurin acetate (7) in
MeOH-d4
Position
4
6
7
α
1
5.44, br s
–
5.89, s
–
6.03, s
–
2
3
4
6.22, dd, J=10.2, 1.4 Hz
6.15, ddt, J=10.0, 2.4 Hz, 1.2 Hz
4.40, m
6.19, dd like, J=10.0, 1.6 Hz
6.53, dd, J=10.0, 2.4 Hz
–
6.15, dt, J=10.0, 0.8 Hz
7.24, ddd, J=10.0, 1.6, 0.8 Hz
–
5eq
5ax
6
2.27, br dd, J=12.1, 4.6 Hz
1.77, ddd, J=12.2, 11.4, 9.0 Hz
4.56, ddd, J=11.2, 4.4, 2.0 Hz
2.74, dd, J=10.8, 6.0
1.57, br t, J=10.6 Hz
4.56, m
2.87, dd, J=16.4, 3.2 Hz
2.81, dd, J=16.8, 3.2 Hz
5.18, td, J=3.2, 1.6 Hz
Fig. 6 Plausible structure of the intermediate (6) and change of 4-oxomenisdaurin acetate (7) in MeOH
13C-NMR (150 MHz, MeOH-d4) δ: 157.1 (C-1), 140.6
(C-3), 127.7 (C-2), 118.0 (CN), 101.6 (C-1′), 96.8 (C-α),
78.2 (C-5′), 78.0 (C-3′), 74.5 (C-2′), 72.5 (C-6), 71.7 (C-4′),
65.4 (C-4), 63.2 (C-6′), 36.1 (C-5).
Isolation of menisdaurin
Sinomenium stem and rhizome (100 g, Daikoshoyaku Co.
Ltd., Lot 2G05) were extracted with MeOH (500 mL × 2)
under refux for 2 h and the extracts were concentrated
under reduced pressure to dryness. The same procedure was
repeated 6 times to give MeOH extract (20.55 g) from 600 g
of the crude drug. The extract dissolved in water (200 mL)
was extracted with chloroform (200 mL×3). The water layer
was concentrated to remove chloroform and applied to a
column of Diaion HP-20 (5 cm×20 cm), then successively
eluted with water (1.2 L), 50% MeOH (1.6 L) and MeOH
(0.9 L). The 50% MeOH eluate was concentrated to dryness
and the residue (1.91 g) was chromatographed on silica gel
(3 cm×20 cm) with chloroform:MeOH=4:1 (800 mL) to
give menisdaurin (1) (344 mg).
Acetylation of menisdaurin
A mixture of menisdaurin (1) (137 mg), acetic anhydride
(1 mL) and pyridine (1 mL) was stirred at room temperature
for 9.5 h. MeOH (1 mL) was added to the mixture under
cooling with ice and the mixture was stirred at room tem-
perature for 1 h. The mixture was concentrated to dryness
and the residue was purifed by silica gel column chroma-
tography with hexane:ethyl acetate=1:1 to give menisdaurin
acetate (1a) (77.4 mg).
Menisdaurin acetate (1a): colorless needles (AcOEt-
hexane), mp 176–178 °C. 1H-NMR (400 MHz, CDCl3) and
13C-NMR (100 MHz, CDCl3): see Table 1.
Menisdaurin (1): white powder (CHCl3-MeOH), mp
174 °C (lit. 174–175 °C), [α]2D2 − 223.2° (c 0.1, MeOH;
lit. [α]2D5 − 212°, c 1.0, MeOH) [4]. MALDI-TOF–MS m/z:
1
336.7 [M + Na]+. H-NMR (600 MHz, MeOH-d4) δ: 6.29
Site‑selective transesterifcation of menisdaurin
acetate
(1H, dd, J = 10.0, 1.0 Hz, H-2), 6.20 (1H, dd, J = 10.0,
3.6 Hz, H-3), 5.51 (1H, br s, H-α), 4.93 (1H, ddd, J =8.4,
3.7, 1.5 Hz, H-6), 4.55 (1H, d, J=7.4 Hz, H-1′), 4.36 (1H,
br dd, J = 9.6, 4.9 Hz, H-4), 3.89 (dd, J = 12.0, 2.2 Hz,
H-6 eq), 3.67 (1H, dd, J = 12.0, 6.3 Hz, H-6ax), 3.38
(1H, t, J=9.0 Hz,H-3′), 3.34 (2H, m, H-2′, 5′), 3.26 (1H,
t, J = 9.0 Hz, H-4′), 2.27 (1H, ddd, J = 13.4, 4.9, 3.7 Hz,
H-5 eq), 2.02 (1H, ddd, J = 13.4, 8.4, 6.3 Hz, H-5ax).
Menisdaurin acetate (1a) (94.1 mg) in 2-propanol (18 mL)
was stirred with lipase B immobilized on acrylic resin
from Candida antarctica (185.3 mg) (Sigma-Aldrich, Lot
SLBL2553 V) at 65 °C for 26.5 h. The mixture was fl-
tered and the fltrate was concentrated to dryness. The resi-
due was chromatographed on silica gel with hexane:ethyl
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Journal of Natural Medicines
acetate=1:2 to give 4-O-deacetyl menisdaurin acetate (5)
(70.1 mg, 81.0%) with recovery of 1a (5.5 mg).
4-O-deacetyl menisdaurin acetate (5): colorless nee-
dles (ethyl acetate-hexane), mp 136–138 °C. [α]2D2 − 105.4°
(c=0.1, MeOH). IR (ATP) cm−1: 3500, 1741, 1361, 1224,
1043. MALDI-TOF–MS m/z: 504.45 [M+Na]+. 1H-NMR
(400 MHz, CDCl3) and 13C-NMR (150 MHz, CDCl3): see
Table 1.
5.0 mL) and ethyl acetate (5 mL) was stirred at room tem-
perature under argon for 1 h. The solution was extracted
with ethyl acetate (5 mL × 4) to give menisdaurigenin (4)
(21.0 mg, 87%).
Menisdaurigenin (4): white crystalline powder, mp
93–94 °C (decomp.). [α]2D6 − 167.2° (c 0.13, MeOH).
IR (ATR) cm−1: 3344, 3298, 3035, 2954, 2916, 2850,
2214, 1620, 1446, 1331, 1300, 1107, 1068, 1007, 856.
MALDI–TOF–MS m/z: 152.5 [M + H]+. 1H-NMR
(500 MHz, acetone-d6) and 13C-NMR (125 MHz, acetone-
Preparation of (S)‑ and (R)‑MTPA ester derivatives
of 5
1
d6): see Table 2. H-NMR (400 MHz, MeOH-d4): see
Table 3.
A mixture of 5 (2.0 mg, 4.2 μmol), DMAP (1.0 mg,
8.2 μmol), and (S)-MTPA-Cl (15 μL, 81 μmol) in pyridine
(0.3 mL) was stirred for 15 h at room temperature. The
reaction mixture was quenched by the addition of water and
CHCl3. The organic solvent was evaporated in vacuo. The
residue was purifed by silica gel column chromatography
(hexane:ethyl acetate = 1:1) to give the (R)-MTPA ester
derivative of 5 (2.1 mg, 71%) as colorless oil. ESI-TOF–MS
m/z: 720.2 [M+Na]+. 1H-NMR (600 MHz, CDCl3) δ: 7.53
(2H, br d, J=7.9 Hz, phenyl of MTPA), 7.45–7.41 (3H, m,
phenyl of MTPA), 6.28 (1H, d, J=10.1 Hz, H-2), 6.04 (1H,
d, J = 3.1 Hz, H-3), 5.64 (1H, br dd, J = 9.2,5.3 Hz, H-4),
5.34 (1H, s, H-α), 5.20 (1H, t, J=9.4 Hz, H-3′), 5.13 (1H, t,
J=9.7 Hz, H-4′), 4.95 (1H, dd, J=9.2, 8.4 Hz, H-2′), 4.87
(1H, d, J=7.9 Hz, H-1′), 4.78 (1H, dd, J=7.9, 4.0 Hz, H-6),
4.30 (1H, dd, J=12.3, 2.2 Hz, H-6′b), 4.09 (1H, dd, J=12.3,
4.4 Hz, H-6′a), 3.71 (1H, ddd, J = 9.4, 4.4, 2.6 Hz, H-5′),
3.53 (3H, s, OMe of MTPA), 2.43 (1H, dt, J=13.6, 4.8 Hz,
H-5 eq), 2.14 (1H, m, H-5ax), 2.09 (3H, s, 6′-OAc), 2.04
(3H, s, 4′-OAc), 2.00 (3H, s, 3′-OAc), 2.00 (3H, s, 2′-OAc).
Similarly, the (S)-MTPA ester derivative of 5 (2.3 mg,
75%) was prepared from 5 (2.1 mg) and (R)-MTPA-Cl.
ESI-TOF–MS m/z: 720.2 [M+Na]+. 1H-NMR (600 MHz,
CDCl3) δ: 7.54 (2H, br d, J = 7.9 Hz, phenyl of MTPA),
7.44–7.40 (3H, m, phenyl of MTPA), 6.33 (1H, d,
J=10.1 Hz, H-2), 6.19 (1H, d, J=3.5 Hz, H-3), 5.63 (1H,
br dd, J=9.0, 4.2 Hz, H-4), 5.35 (1H, s, H-α), 5.18 (1H, t,
J=9.2 Hz, H-3′), 5.12 (1H, t, J=9.7 Hz, H-4′), 4.92 (1H,
dd, J = 9.2, 8.3 Hz, H-2′), 4.84 (1H, d, J = 7.9 Hz, H-1′),
4.78 (1H, dd, J=7.4, 4.0 Hz, H-6), 4.30 (1H, dd, J=12.1,
2.4 Hz, H-6′b), 4.10 (1H, dd, J=12.3, 4.4 Hz, H-6′a), 3.70
(1H, ddd, J=10.1, 4.4, 2.6 Hz, H-5′), 3.54 (3H, s, OMe of
MTPA), 2.34 (1H, dt, J=13.7, 4.9 Hz, H-5 eq), 2.10 (3H,
s, 6′-OAc), 2.07 (1H, m, H-5ax), 2.04 (3H, s, 4′-OAc), 1.99
(3H, s, 3′-OAc), 1.93 (3H, s, 2′-OAc).
Acetylation of menisdaurigenin
A mixture of menisdaurigenin (4) (15.9 mg), acetic anhy-
dride (1.0 mL) and pyridine (1.0 mL) was stirred at room
temperature for 7 h. The mixture was diluted with toluene
and concentrated to dryness. The residue was purifed by
silica gel column chromatography (9 mm × 13 cm) with
hexane:ethyl acetate=3:1 to give menisdaurigenin acetate
(4a) (13.6 mg, 86%).
Menisdaurigenin acetate (4a): White crystalline pow-
der (ethyl acetate-hexane). mp 81–82 °C. IR (ATR) cm−1:
2920, 2214, 1736, 1369, 1218, 1025. MALDI–TOF–MS
m/z: 258.6 [M+Na]+. 1H-NMR (600 MHz, CDCl3) δ: 6.27
(1H, dd, J=10.0, 1.8 Hz, H-2), 6.14 (1H, dd, J=9.9, 2.8 Hz,
H-3), 5.82 (1H, ddd, J=10.9, 4.5, 2.1 Hz, H-6), 5.55 (1H,
ddd, J=8.5, 5.8, 2.8 Hz, H-4), 5.32 (1H, s, H-α), 2.40 (1H,
dt, J = 12.4, 5.0 Hz, H-5 eq), 2.21 and 2.08 (each 3H, s,
-OAc), 2.02 (1H, ddd, J=12.3, 10.9, 9.0 Hz, H-5ax). 13C-
NMR (150 MHz, CDCl3) δ: 170.1 (–OCOMe × 2), 152.8
(C-1), 136.1 (C-3), 128.7 (C-2), 116.0 (CN), 96.5 (C-α), 67.2
(C-4), 66.8 (C-6), 33.8 (C-5), 21.0 and 20.7 (–OCOMe).
Oxidation of 4‑O‑deacetyl menisdaurin acetate (5)
A mixture of 5 (13.9 mg) and pyridinium chlorochromate
46.3 mg (TCI, P0930, Lot OMMRC-QE) in acetone (5 mL)
was stirred at room temperature for 92 h. The mixture
was concentrated to dryness and the residue was purifed
by silica gel column (17 mm × 10 cm) with hexane:ethyl
acetate=1:2 to give 4-oxomenisdaurin acetate (7) (12.7 mg,
91.8%).
4-Oxomenisdaurin acetate (7): pale yellow oil; 1H-NMR
(500 MHz, CDCl3) and 13C-NMR (125 MHz, CDCl3): see
Table 1. 1H-NMR (400 MHz, MeOH-d4) δ: 7.24 (1H, ddd,
J = 10.0, 1.6, 0.8 Hz, H-3), 6.15 (1H, dt, J= 10.0, 0.8 Hz,
H-2), 6.03 (1H, s, H-α), 5.26 (1H, t, J=9.4 Hz, H-3′), 5.18
(1H, td, J=3.2, 1.6 Hz, H-6), 5.00 (1H, t, J=10.0 Hz, H-4′),
4.92 (1H, d, J=8.0 Hz, H-1′), 4.79 (1H, dd, J=9.6, 8.0 Hz,
H-2′), 4.25 (1H, dd, J=12.4, 4.0 Hz, H-6b’), 4.19 (1H, dd,
J = 12.4, 2.8 Hz, H-6a’), 2.87 (1H, dd, J = 16.4, 3.2 Hz,
Enzymatic hydrolysis of menisdaurin
A mixture of menisdaurin (1) (50 mg), β-glucosidase
(20 mg, from almond, Tokyo Chemical Industries, Lot.
7V7YM, 3,000 U/mg), in 0.1 M acetate bufer (pH 4.8,
1 3

Journal of Natural Medicines
Structures of new and known cyanoglucosides from a north
American plant, Purshia tridentata DC. Chem Pharm Bull
42:2251–2255
H-5 eq), 2.81 (1H, dd, J=16.8, 3.2 Hz, H-5ax), 2.06, 2.00
and 1.95 (each 3H, s, acetyl). 1H-NMR (400 MHz, acetone-
d6) δ: 7.32 (1H, ddd, J=10.0, 2.0, 0.8 Hz, H-3), 6.15 (1H,
dt, J = 10.0, 0.8 Hz, H-2), 6.12 (1H, s, H-a), 5.28 (1H, t,
J=9.6 Hz, H-3′), 5.23 (1H, dt, J=3.2, 2.0 Hz, H-6), 5.02
(1H, d, J = 8.0 Hz, H-1′), 5.01 (1H, t, J = 10.0 Hz, H-4′),
4.83 (1H, dt, J=9.6, 8.0 Hz, H-2′), 4.23 (1H, dt, J =12.0,
4.8 Hz, H-6′b), 4.13 (1H, dt, J=12.0, 2.4 Hz, H-6′a), 3.97
(1H, ddd, J=10.0, 4.8, 2.4 Hz, H-5′), 2.94 (1H, dt, J=16.4,
3.6 Hz, H-5 eq), 2.88 (1H, dt, J=3.2, 0.8 Hz, H-5ax), 2.02,
1.99, 1.98, 1.93 (each 3H, s, -OAc).
6. Athikomkulchai S, Ruangrungsi N, Sekine T, Sugino M, Igarashi
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Freshly prepared 4-oxomenisdaurin acetate 7 (18.9 mg) in
anhydrous MeOH (5 mL) was refuxed under Ar atmos-
phere for 21.5 h. The mixture was concentrated to dryness
and chromatographed on silica gel (9 mm × 9 cm) with
chloroform:MeOH=40:1. The major product was purifed
by HPLC with acetonitrile:water=2:3 to give 8 (9.0 mg).
Compound 8: EI-MS m/z: 163 [M+], 132 (M+–OMe).
1H-NMR (600 MHz, MeOH-d4) δ: 7.30 (2H, d, J=8.8 Hz,
H-2,6), 6.82 (2H, d, J=8.8 Hz, H-3,5), 5.27 (1H, s, H-α),
3.45 (3H, s, OMe). 13C-NMR (150 MHz, MeOH-d4) δ:
130.8 (C-2,6), 126.1 (C-1), 118.9 (CN), 116.7 (C-3,5), 72.9
(C-α), 57.2 (OMe).
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Acknowledgements The authors are grateful to Dr. Tomoko Sano of
Tsumura & Co. for providing information and materials of Sinome-
nium root. This work was supported in part by the MEXT-Supported
Program for the Strategic Research Foundation at Private Universities
(S1101003) from the Ministry of Education, Culture, Sports, Science
and Technology, Japan.
15. Calveras J, Nagai Y, Sultana I, Ueda Y, Higashi T, Shoji M, Sugai
T (2010) New chemo-enzymatic route toward N-acetylneuraminic
acid derivatives with alkyl groups at C-7 hydroxyl group. Tetra-
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Synthesis of fisetin and 2′,4′,6′-trihydroxydihyrochalcone
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and deoxygenation. Biosci Biotechnol Biochem. https://doi.
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