Diterpenoids with diverse skeletons from the roots of Euphorbia micractina

Article abstract of DOI:10.1021/np400029d

Twelve new minor diterpenoids, possessing 5/6/8 (1 and 2), 5/6/7/3 (3-9), and 5/6/6/4 (10-12) fused-ring skeletons, as determined by spectroscopic analysis, were isolated from an ethanol extract of the roots of Euphorbia micractina, together with 25 known compounds. The structures of the diterpene skeletons are rare and have been found only in compounds isolated from Euphorbia micractina and Euphorbia villosa. On the basis of the octant rule for cyclohexanones, the absolute configurations of 1-12, as well as of the known euphactins A-D and euphoractins A-D (13-15), could be assigned by circular dichroism spectroscopy. In addition, the co-occurring jolkinol B (16) was chemically transformed to euphoractin E (17), supporting the absolute configuration assignment and the biogenetic relationship between the different types of diterpenes. Compound 9 showed activity against HIV-1 replication in vitro, with an IC₅₀ value of 8.8 ± 0.6 μM.

Full text of DOI:10.1021/np400029d

Article
pubs.acs.org/jnp
Diterpenoids with Diverse Skeletons from the Roots of Euphorbia
micractina
Ye Tian,‡ Wendong Xu,‡ Chenggen Zhu, Sheng Lin, Ying Guo, and Jiangong Shi*
State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing 100050, People’s Republic of China
S
* Supporting Information
ABSTRACT: Twelve new minor diterpenoids, possessing 5/
6/8 (1 and 2), 5/6/7/3 (3−9), and 5/6/6/4 (10−12) fused-
ring skeletons, as determined by spectroscopic analysis, were
isolated from an ethanol extract of the roots of Euphorbia
micractina, together with 25 known compounds. The structures
of the diterpene skeletons are rare and have been found only in
compounds isolated from Euphorbia micractina and Euphorbia villosa. On the basis of the octant rule for cyclohexanones, the
absolute configurations of 1−12, as well as of the known euphactins A−D and euphoractins A−D (13−15), could be assigned by
circular dichroism spectroscopy. In addition, the co-occurring jolkinol B (16) was chemically transformed to euphoractin E (17),
supporting the absolute configuration assignment and the biogenetic relationship between the different types of diterpenes.
Compound 9 showed activity against HIV-1 replication in vitro, with an IC50 value of 8.8 0.6 μM.
n mainland China, several species of the genus Euphorbia
(Euphorbiaceae) have long been used for the treatment of
from this plant.14 Compounds 3−9 and compounds 10−12
were found to contain a 5/6/7/3 fused-ring core and a 5/6/6/4
fused-ring system, respectively. Such diterpene skeletons have
been found previously in euphoractins A−E isolated from E.
micractina15,16 and E. villosa W. ex K.17 An interesting,
conserved structural feature is the C-2 configuration in
compounds 1−12 and that of the biogenetically related
lathyrane derivatives2,13 present in the roots of E. micractina,
which is opposite that of analogues isolated from E. villosa.17 It
should be noted that the same C-2 epimers (euphactins A−D
and euphoractins A−E) have been characterized previously in
whole plants (including roots, stems, and leaves) of E.
micractina.14−16,18
I
various diseases such as ascites, cancer, edema, and warts.1
Phytochemical and biological investigations have revealed that
plants of this genus produce a diverse range of metabolites with
interesting chemical structures and significant bioactivity. In
particular, diterpenoids such as ingenanes, jatrophanes,
lathyranes, myrsinols, and tiglianes, which display a variety of
parent skeletons, exert a range of biological effects such as anti-
inflammatory, antimicrobial, antiproliferation, cytotoxic, and
modulation of multidrug resistance activities.2 As a result, these
compounds have attracted considerable interest.3−9 Ingenol
mebutate has recently been approved in the United States,
countries of the European Union, Australia, and Brazil for the
treatment of actinic keratosis, a precursor to a form of
squamous-cell carcinoma.10
RESULTS AND DISCUSSION
■
Compound 1 showed IR absorptions characteristic for hydroxy
group (3582, 3500, and 3377 cm−1), carbonyl (1707 and 1687
cm−1), and aromatic ring (1603 and 1497 cm−1) functionalities.
HRESIMS at m/z 495.2361 [M + Na]+ (calcd for
C27H36O7Na+, 495.2353) indicated the molecular formula to
be C27H36O7, which was supported by the NMR data (Tables 1
and 3). The 1H NMR spectrum of 1 displayed resonances that
could be attributed to a single benzoyl moiety at δH 8.15 (2H,
d, J = 7.0 Hz, H-2′ and H-6′), 7.61 (1H, t, J = 7.0 Hz, H-4′),
and 7.50 (2H, t, J = 7.0 Hz, H-3′ and H-5′); five oxymethines at
δH 5.76 (t, J = 5.0 Hz, H-3), 4.96 (dd, J = 11.5 and 5.0 Hz, H-
5), 4.29 (d, J = 2.5 Hz, H-12), 3.47 (dd, J = 9.5 and 4.5 Hz, H-
9), and 2.64 (d, J = 2.5 Hz, H-11); four tertiary methyl groups
at δH 1.11 (H3-18), 0.73 (6H, H3-17 and H3-20), and 0.55 (H3-
19); and a secondary methyl group at δH 1.15 (d, J = 7.5 Hz,
Euphorbia micractina Boiss. is distributed widely at high
altitudes (2700−5000 m) in western mainland China, and its
roots are used in Chinese folk medicine for the treatment of
tumors and warts.11 As part of a program to access the chemical
diversity of Chinese traditional medicines and study their
biological effects, our group has investigated E. micractina roots.
In previous work, nine new minor triterpenoids and 17 new
lathyrane diterpenoids, together with 20 known compounds,
were characterized in several fractions obtained from a root
EtOH extract.12,13 Some of these compounds showed activity
against HIV-1 replication and phenylephrine-induced vaso-
constriction, as well as cytotoxicity against A2780 ovarian
cells.12,13 Herein, the investigation has been conducted of the
remaining fractions of the same extract, leading to the isolation
of 12 new minor diterpenes (1−12), along with 25 previously
known compounds. Compounds 1 and 2 are found to have a 5/
6/8 fused-ring skeleton, identical to that of two pairs of C-2
epimeric analogues (i.e., euphactins A−D) previously isolated
Received: January 12, 2013
© XXXX American Chemical Society and
American Society of Pharmacognosy
A
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group at C-5 and two tertiary methyl groups at C-6 and C-13.
In addition, HMBC correlations between H-9 and H-11/C-18
and C-19; H-11/C-12 and C-13; H-12/C-13 and C-20; H3-17/
C-7; H3-18 and H3-19/C-9, C-10, and C-11; H3-20/C-12; and
OH-9/C-9 and C-10 demonstrated the presence of an eight-
membered ring that was fused to the six-membered ring at C-6
and C-13, which was substituted at C-9 by an OH group and
two remaining tertiary methyl groups at C-10. The presence of
an epoxy group between C-11 and C-12 was deduced from the
molecular composition and the chemical shifts of H-11, H-12,
C-11, and C-12. Therefore, compound 1 was determined to be
an analogue of euphactins A−D. The structure of euphactin A
was determined by X-ray crystallographic analysis.14
In the NOE difference spectrum of 1, irradiation of H-5
enhanced the intensity of H-12 and OH-15, while H-12 was
enhanced upon irradiation of H3-19, indicating these protons to
be in a cofacial position. In addition, irradiation of H-3 gave an
enhancement of H-2, H-4, and OH-5; irradiation of H-4
enhanced H-2, H-3, and H3-17; and irradiation of H-9
enhanced H-11 and H3-18, revealing that these protons are
cofacial as well. The circular dichroism (CD) spectrum of 1
displayed a positive Cotton effect at 314 nm (Δε = +1.54),
corresponding to the n−π* transition of the cyclohexanone
chromophore. From the octant rule for cyclohexanones19 and
the aforementioned NOE enhancements, the absolute config-
uration of 1 could therefore be assigned. Thus, the structure of
compound 1 was determined as shown. This compound has
been designated as euphactin E, following the convention used
for euphactins A−D.14
Compound 2, C29H38O7 (HRESIMS), exhibited similar IR
and NMR spectra to 1. Comparison of their NMR spectra
demonstrated that 2 differs from 1 in that the benzoyl unit is
substituted by a trans cinnamoyl moiety. This was confirmed by
2D-NMR, NOE difference, and CD data analysis. In the
HMBC spectrum of 2, the H-3/C-9′ correlation confirmed that
the cinnamoyloxy group is located at C-3. The structure of
compound 2 (euphactin F) was therefore designated as shown.
Compound 3 gave the molecular formula C27H36O6, while
the NMR data indicated it to be similar to the co-occurring
euphoractin B (14),15,16 possessing a 5/6/7/3 fused-ring
skeleton, which is found also in a derivative isolated from E.
villosa.17 Comparison of the spectroscopic data indicated the
replacement of the C-3 OH and C-12 trans cinnamoyloxy
groups in 14 by a C-12 OH and a C-3 benzoyloxy group,
respectively, in 3. This was confirmed by 2D-NMR experi-
H3-16). In addition, resonances were present resulting from
three exchangeable hydroxy protons at δH 4.82 (s, OH-15),
4.11 (d, J = 5.0 Hz, OH-5), and 3.61 (d, J = 5.0 Hz, OH-9), as
well as partially overlapping resonances between δH 1.20 and
2.60 that could be ascribed to aliphatic methylene and methine
units. Besides the resonances of the benzoyl moiety, the 13C
NMR and DEPT spectra showed 20 carbon resonances
corresponding to the above-described functional units, as well
as to five quaternary carbons (one carbonyl at δC 208.6 and an
oxygen-bearing carbon at δC 86.0). Together, these spectro-
scopic data indicate that 1 is a diterpene alcohol benzoate, for
which the structure was further deduced by 2D-NMR
spectroscopic analysis.
The proton and protonated carbon resonances in the NMR
spectra of 1 were assigned by HSQC experiments. In the
1H−1H COSY spectrum of 1, the H2-1/H-2/H-3/H-4/H-5/
OH-5, H-2/H3-16, H2-7/H2-8/H-9/OH-9, and H-11/H-12
cross-peaks indicated the presence of fragments with vicinal
couplings. The HMBC spectrum showed two- and three-bond
correlations between H2-1/C-2, C-3, C-4, C-15, and C-16; H-
3/C-1, C-15, and C-7′; H3-16/C-1, C-2, and C-3; and OH-15/
C-4 and C-14, which, in combination with the chemical shifts of
these proton and carbon resonances, demonstrated the
presence of a five-membered ring in 1 with a secondary
methyl, a benzoyloxy functionality, and an OH group at C-2, C-
3, and C-15, respectively. HMBC correlations between H-4/C-
5 and C-6; H-5/C-3, C-4, C-6, and C-17; H3-17/C-5, C-6, and
C-13; H3-20/C-6, C-13, and C-14; OH-5/C-4, C-5, and C-6;
and OH-15/C-14, together with the corresponding shifts,
revealed a cyclohexanone ring fused to positions C-4 and C-15
on the five-membered ring, which was substituted with an OH
1
ments. Thus, the H−1H gCOSY correlations between H2-7/
H2-8/H-9/H-11/H-12 and HMBC correlations between H3-
17/C-5, C-6, C-7, and C-13; H3-18 and H3-19/C-9, C-10, and
C-11; and H3-20/C-6, C-12, C-13, and C-14, in combination
with the observed shifts, demonstrated the presence of a 7/3
fused-ring moiety in 3 with an OH group at C-12. HMBC
correlations between H-3, H-2′, and H-6′/C-7′ were used to
verify the location of the benzoyl unit at C-3. NOE difference
experiments showed that 3 has the same relative configuration
as 14. Specifically, irradiation of H-3 enhanced H-2 and H-4,
while irradiation of H3-17 gave enhancements of H-4 and H3-
20, and irradiation of H3-20 in turn enhanced H-11 and H3-17.
Furthermore, H-9 and H-11 were enhanced upon irradiation of
H3-18. These data revealed that the protons enhanced are
cofacial and located on the same side of the ring system. As H-
12 was enhanced by irradiation of H-5 and irradiation of H3-19
gave an enhancement of H-12, these protons were situated
cofacially on opposing sides of the ring system. The CD spectra
B
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a
1
Table 1. H NMR Spectroscopic Data (δ) for Compounds 1−6 in Me2CO-d6
position
1a
1
2
3
4
5
6
2.59 t (13.5)
2.61 t (13.5)
1.55 brd (13.5)
2.60 m
2.54 t (13.5)
1.42 dd (13.5, 3.0)
2.62 m
2.56 t (13.5)
1.40 dd (13.5, 3.0)
2.56 m
2.53 dd (15.0, 2.4)
2.46 dd (15.0, 11.4)
2.39 m
2.57 t (13.5)
1.47 dd (13.5, 2.5)
2.61 m
1b
1.64 dd (13.5, 3.5)
2.65 m
2
3
5.76 t (5.0)
5.61 t (ca. 4.0)
5.71 dd (6.0, 5.5)
5.55 dd (5.5, 4.5)
2.02 dd (11.0, 5.5)
4.64 dd (11.0, 5.0)
2.00 m
4.55 dt (6.6, 5.4)
2.02 dd (11.4, 5.4)
4.93 dd (11.4, 5.4)
2.07 m
5.71 t (6.0)
2.07 dd (11.5, 6.0)
4.62 dd (11.5, 5.0)
1.97 dd (14.0, 7.5)
1.36 t (14.0)
1.58 m
4
2.20 dd (11.5, 5.0)
4.96 dd (11.5, 5.0)
2.17 dd (11.0, 4.0) 2.05 dd (11.0, 6.0)
4.92 dd (11.0, 4.5) 4.70 dd (11.0, 5.0)
5
7a
1.86 ddd (15.5, 12.5, 2.0) 1.87 t (15.5)
1.96 m
7b
1.32 m
1.32 dd (15.5, 4.0) 1.34 m
1.33 m
1.38 m
8a
2.01 m
2.04 m
1.56 m
1.32 m
1.59 m
1.64 dt (14.4, 7.2)
1.34 m
8b
1.60 t (12.5)
3.47 dd (9.5, 4.5)
2.64 d (2.5)
4.29 d (2.5)
1.15 d (7.5)
0.73 s
1.57 t (13.5)
1.37 m
1.28 m
9
3.49 dd (10.0, 5.5) 0.74 m
0.73 m
0.76 m
0.77 m
11
2.63 d (1.5)
4.26 d (1.5)
1.13 d (7.5)
0.73 s
0.68 t (10.0)
0.69 t (10.0)
4.58 dd (10.0, 5.0)
1.11 d (7.0)
0.64 s
0.27 t (9.0)
4.09 d (9.0)
0.89 d (7.2)
0.66 s
0.44 t (9.5)
4.52 d (9.5)
1.08 d (7.0)
0.64 s
12
4.63 dd (10.0, 5.0)
1.10 d (7.0)
0.65 s
16
17
18
1.11 s
1.13 s
1.01 s
1.00 s
0.91 s
1.03 s
19
0.55 s
0.56 s
1.11 s
1.10 s
0.73 s
1.08 s
20
0.73 s
0.73 s
1.19 s
1.17 s
1.15 s
1.19 s
2′
3′
4′
5′
6′
7′
8′
8.15 d (7.0)
7.50 t (7.0)
7.61 t (7.0)
7.50 t (7.0
8.15 d (7.0)
7.66 brd (7.0)
7.43 brt (7.0)
7.43 brt (7.0)
7.43 brt (7.0)
7.66 brd (7.0)
7.79 d (16.5)
6.71 d (16.5)
/4.11 d (4.5)
3.60 d (5.5)/
/4.55 s
8.16 d (7.5)
7.49 t (7.5)
7.63 t (7.5)
7.49 t (7.5)
8.16 d (7.5)
7.66 brd (7.0)
7.44 brt (7.0)
7.44 brt (7.0)
7.44 brt (7.0)
7.66 brd (7.0)
7.79 d (16.0)
6.65 d (16.0)
/4.09 d (5.0)
8.22 d (7.2)
7.48 t (7.2)
7.63 t (7.2)
7.48 t (7.2)
8.22 d (7.2)
8.15 d (7.5)
7.49 t (7.5)
7.63 t (7.5)
7.49 t (7.5)
8.15 d (7.5)
OH-3/5
OH-9/11
OH-12/15
/4.11 d (5.0)
3.61 d (4.5)/
/4.82 s
/4.10 d (5.0)
3.54 d (5.4)/3.88 d (5.4) /4.08 d (5.0)
/3.77 s
4.20 d (5.0)/4.65 s 3.94 d (5.0)/4.53 s
a
Data (δ) were measured in acetone-d6 for 1−4 and 6 at 500 MHz; for 5 at 600 MHz. Coupling constants (J) in Hz are given in parentheses. The
assignments are based on DEPT, 1H−1H COSY, HSQC, and HMBC experiments. Data for OMe in 5: δ 2.51 (3H, s); for OEt in 6: δ 3.50 (1H, dq, J
= 15.0 and 7.5 Hz), 3.22 (1H, dq, J = 15.0 and 7.5 Hz), and 1.03 (3H, t, J = 7.5 Hz).
of 3 and 14 showed positive Cotton effects at 308 nm (Δε =
+11.47) and 313 nm (Δε = +9.38), respectively, corresponding
to the n−π* transition of the cyclohexanone chromophore. On
the basis of the octant rule for cyclohexanones,19 the absolute
configuration of 3 (euphoractin F) and 14 could be assigned as
shown.
correlations between OH-3/C-3 and C-4, OH-5/C-4 and C-5,
and OCH3/C-12 were used to assign the location of the
substituents. NOE difference and CD data confirmed that 5
displays the same configuration as 3. The structure of
compound 5 (euphoractin H) was therefore determined as
shown.
Comparison of the spectroscopic parameters of compound 4
with those of 3 (Tables 1 and 3; see also the Experimental
Section) demonstrated the substitution of the benzoyl group of
3 by a trans cinnamoyl group in 4. The structure of compound
4 (euphoractin G) was supported by 2D-NMR, NOE
difference, and CD spectra.
The spectroscopic characterization of compound 6
(C29H40O6) indicated it to be a further analogue of 3, with
the NMR data indicating the presence of an OEt group, which
was attached to a chiral carbon [δH 3.50 (1H, dq, J = 15.0 and
7.5 Hz), 3.22 (1H, dq, J = 15.0 and 7.5 Hz), and 1.03 (3H, t, J =
7.5 Hz, H3-2″)]. In addition, the H-11, H-12, and C-11
resonances in 6 were shielded by ΔδH −0.24 and −0.11 and
ΔδC −2.1 ppm, respectively, as compared to the same
resonances in 3, whereas the C-12 resonance was deshielded
by ΔδC +6.3 ppm. The H-12 resonance appeared as a single
doublet in 6, while a double doublet was present in 3. This
demonstrated that 6 is the 12-OEt analogue of 3, which was
confirmed from the 2D-NMR, NOE difference spectra, and CD
data. Compound 6 (euphoractin I) was designated as shown.
The spectroscopic features of compound 7 were found to be
similar to those of 4, and the HRESIMS indicated that 7
exhibited the molecular formula C30H40O6 and thus possesses
an additional CH2 unit. The NMR data showed the substitution
of the OH-12 group of 4 by a methoxy group in 7 (euphoractin
J).
The spectroscopic data of compound 5 (Tables 1 and 3; see
also the Experimental Section) indicated it to be an analogue of
3 with the molecular formula C28H38O6. Comparison of their
NMR spectra revealed that a hydroxy group in 3 was replaced
with a methoxy group (δH 2.51 and δC 54.3) in 5. In addition,
as compared to those of 3, the NMR resonances of H-2, H-3,
H-11, H-12, and H3-19 and C-1, C-3, C-11, and C-14 in 5 were
shielded by ΔδH −0.23, −1.16, −0.41, −0.54, and −0.38 and
ΔδC −5.6, −4.2, −2.8, and −5.0 ppm, respectively, whereas the
resonances of H-1b, H-5, C-12, and C-15 were deshielded by
ΔδH +1.04 and +0.23 and ΔδC +6.6 and +7.1 ppm, respectively.
Together with the coupling patterns of the two hydroxy
protons, these shifts suggested that the OCH3 and benzoyloxy
groups are located at C-12 and C-15, respectively, while the two
hydroxy groups are located at C-3 and C-5. This assumption
was confirmed by 2D-NMR experiments. In particular, HMBC
Compound 8 differed from 7 in that the OCH3 group was
replaced with an OEt group, as indicated by HRESIMS and by
C
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a
1
Table 2. H NMR Spectroscopic Data (δ) for Compounds 7−12 in Me2CO-d6
position
1a
7
8
9
10
11
12
2.50 t (ca. 13.5)
1.42 (13.5, 2.5)
2.50 m
2.62 t (13.5)
1.41 dd (13.0, 3.0)
2.57 m
2.59 t (13.5)
1.65 brd (13.5)
2.57 m
2.48 dd (14.0, 11.0)
1.50 m
2.48 m
1.50 m
2.50 m
2.44 dd (15.0,10.8)
2.20 m
1b
2
2.62 m
2.37 m
3
5.55 t (5.0)
1.99 (11.0, 5.0)
4.57 dd (11.0, 4.5)
1.99 m
5.56 t (5.0)
2.05 dd (11.0, 5.0)
4.57 dd (11.0, 4.5)
2.00 m
5.51 t (5.0)
1.96 dd (11.0, 5.0)
4.73 dd (11.0, 5.0)
1.93 m
5.74 t (6.0)
2.11 m
5.62 t (5.0)
2.07 m
4.45 ddd (7.8, 6.6, 5.4)
1.99 dd (11.4, 5.4)
5.01 dd (12.0, 5.4)
2.22 m
4
5
4.87 dd (11.0, 5.0)
2.06 m
4.81 dd (11.5, 5.5)
2.05 m
7a
7b
1.34 m
1.39 m
1.31 m
1.18 m
1.18 m
1.17 ddd (13.8,13.2,4.2)
1.56 ddt (12.0, 12.0, 3.0)
1.39 ddt (12.0, 3.0, 3.0)
1.11 dt (12.0, 3.6)
2.89 d (8.4)
8a
1.59 m
1.59 m
1.67 m
1.50 m
1.52 m
8b
1.28 m
1.30 m
1.44 m
1.37 m
1.38 m
9
0.78 m
0.75 m
0.68 m
1.11 m
1.16 m
11
0.38 t (9.5)
4.40 d (9.5)
1.10 d (7.0)
0.63 s
0.43 t (9.5)
4.47 d (9.5)
1.09 d (7.0)
0.64 s
0.75 t (9.5)
4.58 d (9.5)
1.08 d (7.0)
0.63 s
3.41 m
3.41 m
12
3.45 m
3.41 m
2.92 dd (18.0, 8.4)
1.00 d (7.2)
16
1.11 d (7.5)
0.71 s
1.11 d (7.0)
0.71 s
17
0.68 s
18
1.05 s
1.03 s
1.19 s
1.00 s
1.00 s
1.02 s
19
1.09 s
1.08 s
1.01 s
0.94 s
0.92 s
0.83 s
20
1.16 s
1.18 s
1.21 s
1.05 s
1.05 s
1.09 s
2′
3′
4′
5′
6′
7′
8′
7.65 brd (7.0)
7.44 brt (7.0)
7.44 brt (7.0)
7.44 brt (7.0)
7.65 brd (7.0)
7.79 d (16.0)
6.63 d (16.0)
/4.06 d (4.5)
7.65 brd (7.0)
7.45 brt (7.0)
7.45 brt (7.0)
7.45 brt (7.0)
7.65 brd (7.0)
7.79 d (16.0)
6.63 d (16.0)
/4.06 d (4.5)
7.74 brd (7.0)
7.44 brt (7.0)
7.44 brt (7.0)
7.44 brt (7.0)
7.74 brd (7.0)
7.82 d (16.0)
6.55 d (16.0)
/4.17 d (5.0)
8.18 d (7.5)
7.51 t (7.5)
7.64 t (7.5)
7.51 t (7.5)
8.18 d (7.5)
7.68 brd (7.0)
7.46 brt (7.0)
7.46 brt (7.0)
7.46 brt (7.0)
7.68 brd (7.0)
7.82 d (16.5)
6.60 d (16.5)
/4.20 d (5.5)
/3.41 m
7.63 brd (7.8)
7.41 brt (7.8)
7.41 brt (7.8)
7.41 brt (7.8)
7.63 brd (7.8)
7.72 d (16.2)
6.62 d (16.2)
3.31 d (5.4)/3.88 d (5.4)
OH-3/5
OH-9/11
OH-12/15
/4.20 d (5.0)
/3.69 d (5.0)
/3.90 s
/3.90 s
/3.69 s
/3.90 s
a
Data (δ) were measured in acetone-d6 for 8−11 at 500 MHz and for 12 at 600 MHz. Coupling constants (J) in Hz are given in parentheses. The
assignments are based on DEPT, 1H−1H COSY, HSQC, and HMBC experiments. Data for OMe in 7: δ 3.09 (3H, s); for OEt in 8: δ 3.46 (1H, dq, J
= 15.0 and 7.5 Hz), 3.20 (1H, dq, J = 15.0 and 7.5 Hz), and 1.00 (3H, t, J = 7.5 Hz); for isopropylidene unit in 9: δ 1.46 (3H, s) and 1.29 (3H, s);
and for OMe in 12: δ 2.98 (3H, s).
2D-NMR, NOE difference, and CD experiments. Thus, the
structure of compound 8 (euphoractin K) was determined as
shown.
C-3 benzoyloxy and C-15 OH groups in 10. This conclusion
was confirmed from the 2D-NMR data, which showed COSY
correlations between H2-7/H2-8/H-9/H-12/H-11 and HMBC
correlations between H3-18 and H3-19/C-9, C-10, and C-11;
H3-20/C-12; and OH-11/C-11. These observations, in
combination with the chemical shifts, suggested that the 6/4
fused-ring moiety in 10 is substituted with a hydroxy group at
C-11. On the basis of the coupling constants and CD data, the
configuration of 10 was assigned as being identical to those of
13 and 15. Thus, the CD spectra of 10, 13, and 15 showed
positive Cotton effects at 315 (Δε = +14.32), 317 (Δε =
+2.49), and 313 nm (Δε = +10.42), respectively, corresponding
to the n−π* transition of the cyclohexanone chromophore and
allowing the assignment of these compounds. Compound 10
(euphoractin M) was thus assigned as shown.
The spectroscopic data for compound 11 indicated this
compound to be an analogue of 10. Comparison of the 2D-
NMR and HRESIMS data (Tables 2 and 3; see also the
Experimental Section) demonstrated that 11 differed from 10
in that the benzoyl unit is replaced with a trans cinnamoyl unit.
Compound 11 (euphoractin N) was assigned the structure
shown.
Its NMR data indicated compound 9 to possess an
isopropylidene unit [δH 1.46 (3H, s) and 1.29 (3H, s) and
δC 104.2, 27.0, and 29.1], in place of the OH-12 and OH-15
groups in the close analogue 4. As compared with the chemical
shifts found in 4, the C-1, C-9, and C-12 resonances in 9 were
shielded by more than ΔδC −2.3 ppm, whereas the C-4 and C-
15 resonances were deshielded by more than ΔδC +2.5 ppm.
This suggested that 9 is the 12,15-acetonide of 4, which was
verified by various 2D-NMR experiments, especially by the
correlation of H-12 with the quaternary carbon of the
isopropylidene unit in the HMBC spectrum of 9. Compound
9 (euphoractin L) was determined as shown, with the
configuration confirmed by NOE difference spectra and from
its CD data.
The spectroscopic characterization of compound 10 (Tables
2 and 3; see also the Experimental Section) indicated it to be an
isomer of the co-occurring euphoractin C (15),15,16 exhibiting
the same 5/6/6/4 fused-ring skeleton as that of euphoractins A
(13) and D isolated from E. micractina15,16 and that of two
analogues isolated from E. villosa.17 The carbon skeleton and
relative configuration of euphoractin A (13) have been
determined by X-ray crystallographic analysis.15 Comparison
of the NMR spectra of 10 and 15 demonstrated, however, that
the OH-3 and C-15 benzoyloxy groups in 15 are replaced with
Compound 12, with a molecular formula of C30H40O6
(HRESIMS), was found to be similar structurally to 11 and
differed in that an OCH3 group replaced the C-11 OH group in
11. In addition, H-3 and H-11 and C-3 in 12 were shielded by
ΔδC −1.17 and −0.52 and ΔδC −3.8 ppm, respectively,
D
dx.doi.org/10.1021/np400029d | J. Nat. Prod. XXXX, XXX, XXX−XXX

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a
Table 3. 13C NMR Spectroscopic Data (δ) of Compounds 1−12
position
1
2
3
4
5
6
7
8
9
10
11
12
1
42.5
36.4
78.6
54.9
64.5
50.1
32.6
30.2
80.4
39.1
59.8
57.4
57.1
208.6
86.0
16.8
19.1
26.1
12.1
10.6
131.8
130.5
129.3
133.8
129.3
130.5
167.4
42.3
36.2
43.1
36.2
78.2
56.2
63.7
47.2
34.5
19.8
27.7
20.8
30.5
70.9
63.8
208.4
86.5
16.9
19.2
28.8
15.1
12.5
131.9
130.5
129.2
133.7
129.2
130.5
167.3
42.8
36.1
37.5
36.0
74.0
57.0
63.6
47.5
34.7
19.6
27.1
20.9
27.7
77.5
64.5
203.4
93.6
16.5
20.0
27.7
16.5
13.1
132.9
130.9
129.2
133.5
129.2
130.9
164.4
42.8
36.2
78.2
56.1
63.8
47.2
34.3
19.8
26.7
20.9
28.4
77.2
63.4
207.6
86.9
16.9
19.5
28.2
16.3
12.8
131.8
130.5
129.2
133.7
129.2
130.5
167.2
41.8
35.2
42.7
36.1
40.5
36.3
43.3
36.1
78.3
55.6
64.1
47.6
32.7
23.4
38.5
43.7
74.4
49.2
54.9
209.8
86.0
16.9
18.0
28.1
15.7
13.4
131.9
130.6
129.3
133.8
129.3
130.6
167.3
43.2
36.1
38.4
36.0
2
3
78.5
78.3
77.4
78.4
77.3
78.5
74.7
4
54.6
56.1
55.2
56.1
58.6
55.6
56.7
5
64.3
63.6
62.9
63.8
63.5
64.1
63.4
6
50.0
47.2
46.3
47.2
47.8
47.6
48.3
7
32.4
34.6
33.5
34.4
33.8
32.9
33.3
8
29.2
19.9
19.0
19.9
20.6
23.6
22.3
9
80.2
27.6
25.6
26.8
25.4
38.7
39.7
10
11
12
13
14
15
16
17
18
19
20
1′
2′
3′
4′
5′
6′
7′
8′
9′
39.0
20.7
20.0
21.0
21.7
43.7
42.5
59.5
30.5
27.2
28.5
29.2
74.6
83.9
57.1
70.7
77.3
77.2
68.1
49.6
48.0
57.1
64.0
62.4
63.4
64.2
55.0
56.7
207.9
86.1
208.0
86.7
206.7
86.1
207.0
87.3
206.9
90.5
209.2
86.4
205.1
93.3
16.4
16.7
16.0
16.7
16.7
16.8
16.6
18.9
19.3
18.7
19.5
18.7
18.2
18.1
25.9
28.8
27.3
28.2
28.8
28.2
29.1
12.1
15.4
15.8
16.6
17.0
16.0
15.8
10.5
12.6
11.9
12.8
12.8
13.6
14.0
135.3
128.9
129.7
131.1
129.7
128.9
145.6
119.2
167.8
135.5
129.0
129.8
131.2
129.8
129.0
145.6
119.4
167.9
134.6
128.6
129.0
130.3
129.0
128.6
144.7
118.5
167.0
135.4
129.0
129.8
131.2
129.8
129.0
145.6
119.3
167.8
135.5
128.8
129.9
131.2
129.9
128.8
145.0
119.5
166.8
135.6
129.1
130.0
131.1
120.0
129.1
145.7
119.5
166.8
136.1
128.7
129.7
130.7
129.7
128.7
144.0
121.7
165.0
a
Data (δ) were measured in acetone-d6 for 1−4, 6−8, and 10 at 125 MHz and for 5, 9, 11, and 12 at 150 MHz. The assignments are based on
DEPT, 1H−1H COSY, HSQC, and HMBC experiments. Data for OMe in 5: δ 54.3; for OEt in both 6 and 8: δ 62.1 and 16.0; for OMe in 7: δ 53.6;
for isopropylidene unit in 9: δ 104.2, 29.1, and 27.0; and for OMe in 12: δ 57.5.
Scheme 1. Chemical Transformation from 16 to 17 and 18
whereas C-11 and C-15 were deshielded by ΔδC +9.3 and +6.9
ppm. This revealed that the OCH3 and cinnamoyl units are
located at C-11 and C-15 in 12, which was confirmed by 2D-
NMR data, where an HMBC correlation of OCH3/C-11
verified the location of the OCH3 group at C-11 (Supporting
Information). Thus, the structure of compound 12 (euphor-
actin O) was assigned as shown.
Lathyrane diterpenes with a 5/11/3-membered ring system
occur in Euphorbia species and are regarded as biosynthetic
precursors of several polycyclic derivatives.2 The 5/6/8, 5/6/7/
3, and 5/6/6/4 fused-ring skeletons found in compounds 1−15
might be biosynthesized from their lathyrane analogues by
transannular cyclization, followed by simultaneous or sequential
opening and expansion of the cyclopropane ring.17 A similar
rearrangement was observed in the acid-catalyzed trans-
formation of lathyrane analogues.20−22 This prompted an
examination of the acid-catalyzed transformation of jolkinol B
(16), which was also isolated from E. micractina.12 Treatment
of 16 with p-toluenesulfonic acid in CH2Cl2 produced two
compounds (Scheme 1), which were characterized spectro-
scopically as euphoractin E (17)16 and 15-cinnamoyloxylathr-
5E,12E-dien-3,7-diol-14-one (18). Interestingly, this indicated
that 1,4-migration of the cinnamoyloxy group and concomitant
double-bond formation occurred during the transannular
cyclization of 16 to 17. The formation of 18 from 16 is
expected to result from ring-opening of the epoxide and
subsequent allylic rearrangement. This supports the biogenetic
relationship between lathyranes and euphactins and euphor-
actins isolated from E. micractina12−16,18 and also confirmed the
absolute configuration of 1−15, as the absolute configuration of
lathyrane diterpenes was previously determined by X-ray
crystallographic analysis of 3,15-diacetoxy-5,6-epoxylathyr-12-
en-14-one.13
E
dx.doi.org/10.1021/np400029d | J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
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4. Fraction A4-2-4 (62 mg) was separated by reversed-phase (RP)
semipreparative HPLC, using MeOH−H2O (70:30) as the mobile
phase, to yield 6 (1.7 mg) and 8 (1.5 mg). Fraction A8 (1.5 g) was
subjected to flash chromatography over RP silica gel, eluting with a
gradient of EtOH (0 → 95%) in H2O, to afford fraction A8-1−A8-8.
Fraction A8-4 (173 mg) was subjected to preparative TLC (30%
acetone in petroleum ether) to give a mixture (54 mg), which was
further separated by RP HPLC, using MeOH−H2O (75:25) as the
mobile phase, to obtain 7 (2.2 mg), 9 (1.1 mg), and 11 (1.5 mg).
Fraction A9-6 (0.5 g) was fractionated by flash chromatography over
RP silica gel, eluting with a gradient of EtOH (0 → 95%) in H2O, to
afford fractions A9-6-1−A9-6-6. Fraction A9-6-3 (100 mg) was
chromatographed over Sephadex LH-20, eluting with petroleum
ether−CHCl3−MeOH (5:5:1), and then isolated by RP HPLC, using
MeOH−H2O (80:20) as the mobile phase, to yield 3 (1.2 mg) and 10
(1.1 mg). Fraction A10-6 (1.2 g) was fractionated by flash
chromatography over RP silica gel, eluting with a gradient of EtOH
(0 → 95%) in H2O, to afford fraction A10-6-1−A10-6-5. Fraction
A10-6-3 (109 mg) was chromatographed over Sephadex LH-20,
eluting with petroleum ether−CHCl3−MeOH (5:5:1), and then
purified by RP HPLC, using MeOH−H2O (85:15) as the mobile
phase, to yield 4 (8.5 mg). Fraction A13-5-6 (360 mg) was
chromatographed over Sephadex LH-20, eluting with petroleum
ether−CHCl3−MeOH (5:5:1), followed by separation by RP HPLC,
using MeOH−H2O (70:30) as a mobile phase, to yield 5 (1.8 mg), 12
(4.2 mg), 13 (7.8 mg), 14 (5.2 mg), and 15 (11.5 mg).
Compounds 5−9 (containing methoxy, ethoxy, and
isopropylidene units) could well be artifacts produced from
the present extraction and isolation procedure, which employed
MeOH, EtOH, and acetone, even though it should be noted
that Euphorbia diterpenes with the same or similar units have
been reported.2,17 Since etherification and acetonation did not
occur when the corresponding diterpene alcohols (3, 4, and
13) were refluxed for 48 h in these solvents (with or without
silica gel, which was the absorbent used in the isolation
procedure), it was concluded that compounds 5−9 are true
natural products.
The known compounds were identified by comparison of
spectroscopic data with data reported in the literature. These
compounds were euphoractins A−C (13−15),15,16 helio-
scopinolide D,23 stigamast-5-ene-3β,7α-diol, stigamast-5-ene-
3β,7β-diol, stigmast-4-en-6β-ol-3-one, stigmast-3,6-dione,24
stigmast-5-en-3β-ol-7-one,24,25 (24R)-stigmast-1,4-dien-3-
one,26 loliolide,27 (+)-dehydrovomifoliol,28 5α,6α-epoxy-3β-
hydroxymegastigm-7-en-9-one,29 6-hydroxy-5,7-dimethoxycou-
marin,30 esculetin,31 quercetin,32 m-hydroxyphenylethyl alco-
hol, (E)-4-hydroxy-3-methoxycinnamic acid,33 3,4-dihydroxy-
benzoic acid,34 vanillic acid,35 p-hydroxybenzoic acid,36 ethyl
gallate,37 methyl gallate,38 ethyl 3,4-dihydroxybenzoate,34 and
3,3′,4′-tri-O-methylellagic acid.39
Fraction A14 (10.5 g) was separated by normal-phase silica gel CC,
eluting with a gradient of acetone (10 → 70%) in petroleum ether, to
give fractions A14-1−A14-8. Subsequent fractionation of fraction A14-
5 (1.1 g) by flash chromatography over RP silica gel, eluting with a
gradient of EtOH (0 → 95%) in H2O, afforded fractions A14-5-1−
A14-5-5. Fraction A14-5-4 (107 mg) was chromatographed over
Sephadex LH-20, eluting with petroleum ether−CHCl3−MeOH
(5:5:1), and then purified by RP HPLC, using MeOH−H2O
(60:40) as the mobile phase, to yield 1 (2.5 mg) and 2 (2.0 mg).
In the in vitro bioassays performed in this study, compound
9 showed activity against HIV-1 replication40 with an IC50 value
8.8 0.6 μM (the positive control efavirenz gave an IC50 value
of 0.06
0.02 μM). All other compounds isolated in this
experiment were inactive at concentrations of 10 μM. Although
the compounds were also assessed for cytotoxicity against
several human cancer cell lines41 and inhibitory activity against
protein tyrosine phosphatase 1B (PTP1B),42 they were found
to be inactive at a concentration of 10 μM.
Euphactin E (1): white, amorphous powder; [α]20 −10.9 (c 0.12,
D
MeOH); UV (MeOH) λmax (log ε) 229 (3.99), 273 (1.43) nm; CD
(MeOH) 314 (Δε +1.54) nm; IR νmax 3377, 2971, 2882, 1707, 1687,
1603, 1497, 1452, 1387, 1288, 1136, 1051, 1014, 964, 918, 713 cm−1;
1H NMR (acetone-d6, 500 MHz) data, see Table 1; 13C NMR
(acetone-d6, 125 MHz) data, see Table 3; ESIMS m/z 495 [M + Na]+;
HRESIMS m/z 495.2361 [M + Na]+ (calcd for 495.2353).
EXPERIMENTAL SECTION
■
General Experimental Procedures. Optical rotations were
measured on a Perkin-Elmer model 343 polarimeter. UV spectra
were measured on a Cary 300 spectrometer. CD spectra were recorded
on a JASCO-815 CD spectrometer. IR spectra were recorded on a
Nicolet 5700 FT-IR instrument. 1D- and 2D-NMR spectra were
Euphactin F (2): white, amorphous powder; [α]20 +14.6 (c 0.12,
D
MeOH); UV (MeOH) λmax (log ε) 217 (4.03), 277 (4.15) nm; CD
(MeOH) 230 (Δε −0.44), 267 (Δε +1.24), 304 (Δε +2.48) nm; IR
νmax 3457, 2969, 2876, 1708, 1635, 1578, 1497, 1451, 1384, 1313,
1
recorded at 500 or 600 MHz for H and 125 or 150 MHz for 13C on
an INOVA 500 MHz or SYS 600 MHz spectrometer, respectively, in
acetone-d6. Solvent peaks were used as a reference. ESIMS data were
measured with a Q-Trap LC/MS/MS (Turbo Ionspray Source)
spectrometer. HRESIMS data were measured using an AccuToFCS
JMS-T100CS spectrometer. Column chromatography (CC) was
performed on silica gel (200−300 mesh, Qingdao Marine Chemical,
Inc. Qingdao, People’s Republic of China) or Sephadex LH-20
(Amersham Biosciences, Inc.). Preparative thin-layer chromatography
was performed using high-performance silica gel preparative TLC
plates (HSGF254, glass precoated, Yantai Jiangyou Silica Gel
Development Co., Ltd., Yantai, People’s Republic of China). High-
performance liquid chromatography (HPLC) was performed on a
Waters 600, using a Waters 2487 dual λ absorbance detector and a
Prevail (250 × 10 mm i.d.) C18 column (5 μm). TLC was carried out
on precoated glass silica gel GF254 plates. Spots were directly visualized
under UV light or by spraying with 5% H2SO4 in 95% EtOH, followed
by heating. Unless otherwise noted, all chemicals were commercially
available and used without further purification.
1
1283, 1205, 1138, 1057, 914, 769 cm−1; H NMR (acetone-d6, 500
MHz) data, see Table 1; 13C NMR (acetone-d6, 125 MHz) data, see
Table 3; ESIMS m/z 521 [M + Na]+; HRESIMS m/z 521.2528 [M +
Na]+ (calcd for 521.2510).
Euphoractin F (3): white, amorphous powder; [α]20D +15.6 (c 0.12,
MeOH); UV (MeOH) λmax (log ε) 229 (4.20), 266 (1.33) nm; CD
(MeOH) 199 (Δε +3.41), 213 (Δε −9.49), 233 (Δε +1.22), 250 (Δε
−0.32), 308 (Δε +11.47) nm; IR νmax 3464, 2925, 2872, 1698, 1601,
1
1453, 1379, 1280, 1122, 1026, 999, 712 cm−1; H NMR (acetone-d6,
500 MHz) data, see Table 1; 13C NMR (acetone-d6, 125 MHz) data,
see Table 3; (+)-ESIMS m/z 479 [M + Na]+, 935 [2M + Na]+;
HRESIMS m/z 479.2435 [M + Na]+ (calcd for C27H36O6Na,
479.2410).
Euphoractin G (4): white, amorphous powder; [α]20D +38.4 (c 0.85,
MeOH); UV (MeOH) λmax (log ε) 216 (3.96), 277 (4.17) nm; CD
(MeOH) 196 (Δε −5.06), 305 (Δε +6.23) nm; IR νmax 3474, 2937,
2872, 1687, 1633, 1578, 1496, 1451, 1380, 1279, 1202, 1133, 1055,
1
998, 768 cm−1; H NMR (acetone-d6, 500 MHz) data, see Table 1;
Plant Material. See ref 12.
13C NMR (acetone-d6, 125 MHz) data, see Table 3; (+)-ESIMS m/z
505 [M + Na]+, 987 [2M + Na]+; HRESIMS m/z 505.2579 [M +
Na]+ (calcd for C29H38O6Na, 505.2566).
Extraction and Isolation. For extraction and preliminary
fractionation of the EtOH extract of E. micractina, see refs 12 and
13. Fraction A4 (6.5 g) was separated by CC over Sephadex LH-20,
eluting with petroleum ether−CHCl3−MeOH (5:5:1), to give fraction
A4-1−A4-3. Fraction A4-2 (1.6 g) was separated over silica gel, eluting
with 1:24 acetone in petroleum ether, to afford fractions A4-2-1−A4-2-
Euphoractin H (5): white, amorphous powder; [α]20D −0.3 (c 0.16,
MeOH); UV (MeOH) λmax (log ε) 231 (4.10), 273 (1.66) nm; CD
(MeOH) 206 (Δε −2.21), 232 (Δε +0.82), 253 (Δε −0.26), 299 (Δε
F
dx.doi.org/10.1021/np400029d | J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
+0.48) nm; IR νmax 3528, 2929, 2831, 1716, 1602, 1453, 1378, 1283,
1115, 1081, 1037, 995, 948, 903, 713 cm−1; 1H NMR (acetone-d6, 600
MHz) data, see Table 1; 13C NMR (acetone-d6, 150 MHz) data, see
Table 3; (+)-ESIMS m/z 493 [M + Na]+, 509 [M + K]+, 963 [2M +
Na]+; HRESIMS m/z 493.2590 [M + Na]+ (calcd for C28H38O6Na,
493.2561).
J = 13.0 and 7.5 Hz, H-1a), 1.62 (1H, dd, J = 13.0 and 13.0 Hz, H-1b),
1.96 (1H, m, H-2), 3.90 (1H, m, H-3), 2.43 (1H, dd, J = 11.0 and 3.5
Hz, H-4), 6.36 (1H, d, J = 11.0 Hz, H-5), 4.01 (1H, dt, J = 11.0 and
3.5 Hz, H-7), 2.31 (1H, dt, J = 14.0 and 3.5 Hz, H-8a), 1.60 (1H, m,
H-8b), 1.14 (1H, m, H-9), 1.43 (1H, dd, J = 11.5 and 8.0 Hz, H-11),
6.77 (1H, d, J = 11.5 Hz, H-12), 1.05 (3H, d, J = 6.5 Hz, H3-16), 1.49
(3H, s, H3-17), 1.09 (3H, s, H3-18), 0.83 (3H, s, H3-19), 1.77 (3H, s,
H3-20), 7.67 (2H, m, H-2′ and H-6′), 7.43 (3H, m, H-3′, H-4′, and H-
5′), 7.68 (1H, d, J = 16.5 Hz, H-7′), 6.58 (1H, d, J = 16.5 Hz, H-8′);
13C NMR (acetone-d6, 125 MHz) δ 44.6 (C-1), 40.3 (C-2), 79.3 (C-
3), 53.4 (C-4), 121.0 (C-5), 146.0 (C-6), 75.5 (C-7), 38.0 (C-8), 29.8
(C-9), 25.1 (C-10), 31.6 (C-11), 146.5 (C-12), 132.5 (C-13), 195.3
(C-14), 95.6 (C-15), 14.0 (C-16), 19.0 (C-17), 29.1 (C-18), 16.6 (C-
19), 12.5 (C-20), 131.3 (C-1′), 129.1 (C-2′), 129.8 (C-3′), 131.3 (C-
4′), 129.8 (C-5′), 129.1 (C-6′), 146.0 (C-7′), 119.3 (C-8′), 165.9 (C-
7′); (+)-ESIMS m/z 465 [M + H]+, 487 [M + Na]+, 503 [M + K]+,
951 [2M + Na]+.
Euphoractin I (6): white, amorphous powder; [α]20 +6.9 (c 0.10,
D
MeOH); UV (MeOH) λmax (log ε) 229 (4.20), 275 (1.53) nm; CD
(MeOH) 212 (Δε −1.69), 305 (Δε +2.71) nm; IR νmax 3510, 2974,
2946, 2868, 1714, 1701, 1603, 1584, 1490, 1454, 1379, 1285, 1226,
1
1182, 1137, 1089, 1071, 1988, 708 cm−1; H NMR (acetone-d6, 500
MHz) data, see Table 1; 13C NMR (acetone-d6, 125 MHz) data, see
Table 3; ESIMS m/z 507 [M + Na]+; HRESIMS m/z 507.2736 [M +
Na]+ (calcd for 507.2717).
Euphoractin J (7): colorless oil; [α]20D +41.4 (c 0.10, MeOH); UV
(MeOH) λmax (log ε) 226 (3.96), 277 (4.20 nm); CD (MeOH) 203
(Δε −3.19), 304 (Δε +4.45) nm; IR νmax 3474, 2936, 2873, 1711,
1635, 1578, 1497, 1451, 1379, 1313, 1282, 1205, 1136, 1109, 1084,
Anti-HIV Activity Assay. See ref 40.
Cells, Culture Conditions, and Cell Proliferation Assay. See
1
989, 769 cm−1; H NMR (acetone-d6, 500 MHz) data, see Table 2;
13C NMR (acetone-d6, 150 MHz) data, see Table 3; ESIMS m/z 519
[M + Na]+; HRESIMS m/z 519.2729 [M + Na]+ (calcd for 519.2717).
Euphoractin K (8): white, amorphous powder; [α]20D −4.2 (c 0.10,
MeOH); UV (MeOH) λmax (log ε) 217 (3.90), 278 (3.98) nm; CD
(MeOH) 209 (Δε −3.38), 303 (Δε +4.89) nm; IR νmax 3474, 2973,
2931, 2869, 1713, 1691, 1635, 1578, 1497, 1450, 1379, 1312, 1282,
1204, 1187, 1140, 1074, 1058, 1001, 768 cm−1; 1H NMR (acetone-d6,
500 MHz) data, see Table 2; 13C NMR (acetone-d6, 125 MHz) data,
see Table 3; ESIMS m/z 533 [M + Na]+; HRESIMS m/z 533.2886 [M
+ Na]+ (calcd for 533.2874).
ref 41.
PTP1B Inhibition Assay. See ref 42.
ASSOCIATED CONTENT
* Supporting Information
■
S
Copies of IR, MS, 1D- and/or 2D-NMR, and CD spectra for
compounds 1−12, 17, and 18. This material is available free of
charge via the Internet at http://pubs.acs.org.
Euphoractin L (9): white, amorphous powder; [α]20D +10.2 (c 0.11,
MeOH); UV (MeOH) λmax (log ε) 217 (4.09), 277 (4.19) nm; CD
(MeOH) 222 (Δε +0.80), 261 (Δε −0.78), 301 (Δε +4.70) nm; IR
νmax 3526, 2948, 2871, 1710, 1631, 1497, 1451, 1380, 1278, 1248,
AUTHOR INFORMATION
Corresponding Author
*(J. Shi) Tel: 86-10-83154789. Fax: 86-10-63017757. E-mail:
shijg@imm.ac.cn.
■
1
1221, 1147, 1056, 1007, 989, 770 cm−1; H NMR (acetone-d6, 500
MHz) data, see Table 2; 13C NMR (acetone-d6, 150 MHz) data, see
Table 3; ESIMS m/z 545 [M + Na]+; HRESIMS m/z 545.2881 [M +
Na]+ (calcd for 545.2874).
Author Contributions
‡Y. Tian and W. Xu contributed equally to this study.
Notes
Euphoractin M (10): white, amorphous powder; [α]20 +7.9 (c
D
The authors declare no competing financial interest.
0.11, MeOH); UV (MeOH) λmax (log ε) 228 (4.14), 269 (1.33) nm;
CD (MeOH) 193 (Δε +2.02), 214 (Δε −4.61), 232 (Δε +1.27), 315
(Δε +14.32) nm; IR νmax 3402, 2927, 2863, 1693, 1600, 1453, 1379,
ACKNOWLEDGMENTS
■
1
1282, 1125, 1045, 969, 712 cm−1; H NMR (acetone-d6, 500 MHz)
Financial support from the National Natural Sciences
Foundation of China (NNSFC; grant nos. 21172266,
30825044, and 20932007), the Program for Changjiang
Scholars and Innovative Research Team in University
(PCSIRT, grant no. IRT1007), and the National Science and
Technology Project of China (no. 2012ZX09301002-002) is
acknowledged.
data, see Table 2; 13C NMR (acetone-d6, 150 MHz) data, see Table 3;
(+)-ESIMS m/z 479 [M + Na]+, 935 [2M + Na]+; HRESIMS m/z
479.2396 [M + Na]+ (calcd for C27H36O6Na, 479.2410).
Euphoractin N (11): white, amorphous powder; [α]20D +2.4 (c 0.11,
1
MeOH); H NMR (acetone-d6, 500 MHz) data, see Table 2; 13C
NMR (acetone-d6, 150 MHz) data, see Table 3; ESIMS m/z 505 [M +
Na]+; HRESIMS m/z 505.2567 [M + Na]+ (calcd for 505.2561).
Euphoractin O (12): white, amorphous powder; [α]20 −10.1 (c
D
REFERENCES
■
0.18,MeOH); UV (MeOH) λmax (log ε) 216 (3.91), 278 (4.10) nm;
CD (MeOH) 237 (Δε +1.91), 257 (Δε +1.22), 282 (Δε +3.86), 308
(Δε −1.89), 331 (Δε +0.45) nm; IR νmax 3449, 2930, 2871, 1708,
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