Sesquiterpene lactones and thymol esters from Vicoa pentanema

Article abstract of DOI:10.1021/np960506o

The aerial parts of Vicoa pentanema yielded four new sesquiterpene lactones, namely, 10a-hydroxy- 14H-inuviscolide (1), 4α,5α-epoxy- 10α,11β,13H, 14H-1 -epi-inuviscolide 3-β-D-glucoside (2), 2α-O-acetyl- 3β-hydroxyalantolactone (3), and 2α,3α-dihydroxyalloalantolactone (4). The structure and stereochemical assignments of all sesquiterpenes were based on their ¹H and ¹³C-NMR spectral data, including those derived from 2D-NMR COSY, HETCOR, FLOCK, and NOESY experiments, as well as extensive NOE- difference studies. In addition, the same plant material yielded the known sesquiterpene lactones 8β-hydroxyparthenolide (5), 8-epi-confertin (6), 4α,5α-epoxy-10α,14H-1-epi-inuviscolide (7), inuviscolide (8), lipiferolide (9), and carabrone (10), the known thymol ester 7,8-epoxy-9- (isobutyryloxy)thymolisobutyrate (11), and its hydrolysis product 7-hydroxy- 8,9-bis(isobutyryloxy)thymol (12).

Full text of DOI:10.1021/np960506o

550
J . Nat. Prod. 1997, 60, 550-555
Sesqu iter p en e La cton es a n d Th ym ol Ester s fr om Vicoa pen ta n em a
J aber S. Mossa,† Farouk S. El-Feraly,† Ilias Muhammad,*,† Kyaw Zaw,‡ Zakaria H. Mbwambo,‡
J ohn M. Pezzuto,‡ and Harry H. S. Fong‡
Medicinal, Aromatic and Poisonous Plants Research Center (MAPPRC) and Department of Pharmacognosy, College of
Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia, and Program for Collaborative Research
in the Pharmaceutical Sciences, Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy,
University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612
Received J une 6, 1996X
The aerial parts of Vicoa pentanema yielded four new sesquiterpene lactones, namely, 10R-
hydroxy-14H-inuviscolide (1), 4R,5R-epoxy-10R,11â,13H,14H-1-epi-inuviscolide 3-â-D-glucoside
(2), 2R-O-acetyl-3â-hydroxyalantolactone (3), and 2R,3R-dihydroxyalloalantolactone (4). The
1
structure and stereochemical assignments of all sesquiterpenes were based on their H and
13C-NMR spectral data, including those derived from 2D-NMR COSY, HETCOR, FLOCK, and
NOESY experiments, as well as extensive NOE-difference studies. In addition, the same plant
material yielded the known sesquiterpene lactones 8â-hydroxyparthenolide (5), 8-epi-confertin
(6), 4R,5R-epoxy-10R,14H-1-epi-inuviscolide (7), inuviscolide (8), lipiferolide (9), and carabrone
(10), the known thymol ester 7,8-epoxy-9-(isobutyryloxy)thymolisobutyrate (11), and its
hydrolysis product 7-hydroxy-8,9-bis(isobutyryloxy)thymol (12).
The genus Vicoa is represented in Saudi Arabia by a
single species, namely, V. pentanema Aitch. et Hemsl.
(syn. Inula pentanema), family Compositae.1 It is an
annual herb that is widely distributed throughout the
southern part of the Arabian Peninsula, where it is
known as ufaynah. Until now, this plant has not been
the subject of phytochemical analysis, but the genus
Inula has yielded a wide array of sesquiterpenes,2,3
sesquiterpene lactones,4-8 thymol derivatives,9-11 and
flavones,2,4 while the aerial parts of V. indica (syn. I.
indica) have yielded germacranolides,12,13 including
vicolides B-E,14-16 the guaianolide vicolide A,14 the
monoterpene vicodiol,17 and the 28-nortriterpenoid gly-
coside vicoside A.18
Examination of the aerial parts of V. pentanema has
led to the isolation and characterization of four new
sesquiterpene lactones, namely, the guaianolides 1 and
2 and the eudesmanolides 3 and 4 (Chart 1). In
addition, the six known sesquiterpene lactones 8â-
hydroxyparthenolide (5), 8-epi-confertin (6), 4R,5R-epoxy-
10R,14H-1-epi-inuviscolide (7),4 inuviscolide (8),19,20 lipi-
ferolide (9),21,22 and carabrone (10),4,23 as well as the
known thymol ester 11,9 and its hydrolytic product 12,
have been also isolated from the same source. The
isolation and structure elucidation of these compounds
are the subject of this paper.
parison with the NOE data of the diepoxide 13, prepared
from 7 by epoxidation. The NOE established a cis-
relationship between H-1 (δ2.66) and H-8 (δ4.31) in 8,
while a trans-relationship between these two protons
was observed in 7, as H-1(δ2.56) and H-7 (δ2.98) were
correlated, while no correlation was observed between
H-1 and H-8. This established 7 as a derivative of 1-epi-
inuviscolide, rather than inuviscolide (8) as reported
previously.4,8,24 In addition, complete 13C-NMR data for
7 and 8, not published previously, are assigned in Table
1 using COSY, HETCOR, and 1H-13C long-range
FLOCK25 experiments.
Further purification of fraction B by chromatography
gave 10R-hydroxy-14H-inuviscolide (1), C15H22O4, as off-
white granules. It showed the presence of two hydroxyl
groups (νmax 3300 cm-1) and an exocyclic methylene
lactone ring (νmax 1755,1660 cm-1; δC 141.0, 169.9, 118.1;
1
C-11, C-12, and C-13, respectively). The H- and 13C-
NMR spectral data (Tables 1 and 2) of 1 were remark-
ably similar to those of the guaianolide inuviscolide
(8)19,20 but lacked the signals associated with the
C-10(14)-exocyclic methylene group. Instead, 1, like 14,5
was concluded to have a C-10 hydroxyl group geminal
with a methyl group, as suggested by its NMR spectral
data (δC-10 71.7, δC-14 24.8; δH-14 1.13, 3H, s; vide infra).
Furthermore, the 1H-NMR spectra of 1 contained a
signal at δ (DMSO-d6) 4.32 (ddd, J ) 1.4, 9.8, 11.2 Hz;
Hâ-8) [versus δ CDCl3 3.98 (ddd, J ) 2.0, 9.5, 11.0 Hz
in 145)], suggesting the presence of an 8â-H on the
lactone system. A COSY experiment established the
system CH2CH(CdCH2)CH(O)CH2- in 1 and was con-
firmed by a HETCOR experiment (Table 1). These
experiments confirmed that the signals at δ 28.4, 50.2,
79.4, and 48.3 can be assigned to C6-C9, respectively.
The placements of the C-4 and C-10 tertiary hydroxyl
groups and C-14 and C-15 methyl groups were estab-
lished by an 1H-13C long-range FLOCK experiment,
which revealed the key three-bond correlations between
the signals δ 1.13 (H-14), δC 51.2 (C-1) and 48.3 (C-9),
and δ 1.03 (H-15), δC 40.7 (C-3) and 49.3 (C-5). Also,
the FLOCK experiment exhibited the key two bond
Resu lts a n d Discu ssion
The n-hexane extract of V. pentanema was subjected
to flash chromatography over Si gel to give the major
sesquiterpene lactones 4R,5R-epoxy-10R,14H-1-epi-inu-
viscolide (7),4,24 inuviscolide (8),19,20 lipiferolide,21,22 and
carabrone,4,23 identified by comparison of their physical
and spectroscopic data with those previously reported.
The stereochemical assignments of 7 and 8 were con-
firmed from extensive NOE experiments and by com-
* To whom correspondence should be addressed. Tel: (966)14677210.
Fax: (966)-1-467-7245. E-mail: F30H002@ksu.edu.sa.
† King Saud University.
‡ University of Illinois at Chicago.
X Abstract published in Advance ACS Abstracts, May 1, 1997.
S0163-3864(96)00506-X CCC: $14.00
© 1997 American Chemical Society and American Society of Pharmacognosy

Sesquiterpene Lactones and Thymol Esters from Vicoa
J ournal of Natural Products, 1997, Vol. 60, No. 6 551
Ch a r t 1
correlations between H-14 and C-10 (δ71.7) and H-15
and C-4 (δ78.9).
of C-14, which is more deshielded in 15 than in 1 (δ
30.7 vs δ 24.8, respectively).
The stereochemical assignment at the centers C-1,
C-4, C-8, and C-10 was inferred from extensive NOE
experiments, including both NOESY and NOE differ-
ence techniques. Irradiation of the H-8â (δ 4.32) signal
was found to enhance the signals for H-1 (δ1.82), H-14
(δ1.13), and H-15 (δ1.03), suggesting that all of these
protons were on the same face of the molecule, while
there was no NOE observed between H-7 and H-8,
suggesting the presence of a trans-fused lactone ring.
In addition, irradiation of the signal at δ1.47 (H-5)
enhanced the signal for H-7 (δ 2.55), indicating that
these two protons were R-oriented, while no enhance-
ment, as expected, was observed for H-1. It should be
noted that compound 1 is the C-10 epimer of 15, a
guaianolide recently isolated5 from the aerial parts of
Inula thapsoides. The spectral features of 1 and 15 are
remarkably similar, except for the chemical shift value
The second guaianolide, 2, was obtained as off-white
granules and analyzed for C21H32O9. Its CIMS revealed
the base peak at m/ z 249 [C15H21O3]+, corresponding
to the sesquiterpene aglycone after elimination of the
1
D-glucose moiety. The H- and 13C-NMR spectral data
for 2 (Tables 1 and 2) were generally similar to those of
the guaianolide 7, except for the presence of signals for
the glucosyl and methyl groups at C-3 and C-11,
respectively. The 1H-NMR spectrum of 2 contained
signals at δ 4.48 (t, J ) 8.0 Hz, δC-3 81.9) and 1.16 (d,
J ) 7.6 Hz) due to C-3 oxymethine and C-11 methyl
groups, respectively. A COSY experiment established
the systems -CHCH2CH(O)- (ring B), -CH2CH-
(CHMe)CH(O)CH2- (rings A and C), and -CH2CH-
(Me)CH- (ring A), as confirmed by a HETCOR experi-
ment (Table 1). The placement of the C-3-glucoside and
1
C-4(5)-epoxide groups was established by a H-13C long-

552 J ournal of Natural Products, 1997, Vol. 60, No. 6
Mossa et al.
Ta ble 1. 13C-NMR Chemical Shift Values for Compounds 1, 2,
6-8, and 13
cm-1, δC 74.5). The presence of the C-7 (8)-cis-fused
lactone was inferred from the 1H-NMR data of H-8,
which resonated as a doublet of triplets at δ 4.80, J )
3.3, 3.3, 6.7 Hz. These values are virtually identical to
those reported for the related sesquiterpene 16.26 In
addition, the chemical shift values for C-7 and C-8 in
both 3 and 16 were very close (δC-7 39.3, δC-8 75.1
versus δC-7 39.53, δC-8 75.6 in 1626).
carbon
1a
2b
6
7
8
13
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
1′
2′
3′
4′
5′
6′
51.2 d
23.4 t
40.7 t
78.9 s
49.3 d
28.4 t
50.2 d
79.4 d
48.3 t
71.7 s
141.0 s
43.2 d
36.2 t
81.9 d
47.0 d
24.2 t
34.8 t
47.7 d
30.6 t
32.7 t
69.9 s
69.7 s
29.0 t
44.4 d
82.6 d
40.4 t
46.9 d
26.3 t
41.1 t
80.4 s
59.1 d
29.9 t
45.3 d
82.3 d
40.7 t
47.8 d
28.9 t
32.7 t
69.8 s
69.4 s
26.5 t
40.4 d
83.3 d
40.6 t
34.5 d
58.0 s
71.4 s 220.9 s
70.7 s
29.5 t
47.7 d
83.7 d
41.7 t
35.7 d
50.8 s
35.0 t
45.2 d
80.4 d
41.6 t
32.4 d
The 1H-NMR spectrum of 3 contained signals at δ
5.12 (ddd, J ) 4.3, 10.2, 11.5 Hz) and 3.65 (dd, J ) 6.3,
10.2 Hz) due to the two axially-disposed protons, H-2â
and H-3R, respectively. The two systems -CH2CH-
(OAc)CH(OH)CH(Me) in ring A and dCHCH(CdCH2)-
CH(O)CH2- in ring B of 3 were established from the
COSY spectra and were confirmed by a HETCOR
experiment (Table 3). In addition, the 13C-NMR spec-
trum revealed the deshielding of C-4 to δC 44.2 (versus
δC-4 38.53 in 1626), due to the presence of the hydroxyl
group at C-3. The relative stereochemistry, depicted in
34.6 d 146.6 s
41.7 d 140.0 s 139.1 s 139.6 s
169.9 s 182.4 s 169.8 s 170.0 s 170.1 s 172.9 s
118.1 t
24.8 q
22.6 q
10.7 q 120.2 t 118.9 t 120.4 t
46.7 t
14.5 q
15.4 q
15.1 q
13.3 q
103.2 d
75.3 d
78.2 d
71.9 d
78.3 d
63.3 t
17.0 q
23.4 q
14.7 q 111.7 t
15.6 q 24.1 q
1
3, was based not only on the H- and 13C-NMR spectral
data but also on biogenetic correlation with other
a
Spectrum recorded in DMSO-d6. b Spectrum recorded in CD3OD.
alantolactones isolated from several Inula species.4-8
1
The H- and 13C-NMR spectral data (Table 3) for the
range FLOCK experiment, which demonstrated the key
three-bond correlation between δ 1.41(H-15), δC-3 81.9,
and δC-5 70.7 and two-bond correlation between H-15
and C-4 (δ 71.4). In addition, the FLOCK experiment
showed the three-bond correlation between H-13 (δ 1.16)
and δC-12 182.4. The identity of the sugar moiety of 2
as â-glucose was suggested on the basis of J 1′,2′ ) 7.8
Hz, indicating an axial R-orientation of the anomeric
proton (H-1′). This was further confirmed by comparing
its 13C-NMR chemical shift values with those of the â-D-
glucoside vicoside A;18 the two sets were virtually
identical. On the basis of the foregoing data and by
comparing the 13C-NMR chemical shift values with
those of its derivatives 7 and 13 (Table 1), this gua-
ianolide glucoside was formulated as 2.
The stereochemistry at C-1, C-8, and C-11 in 2 was
deduced by extensive NOE difference experiments.
Since no NOE was observed between H-7 and H-8,
compound 2 should contain a trans-fused lactone ring,
as observed for 1 and 7. Irradiation of H-8â enhanced
the signals at δ 0.95 (H-14) and 1.41 (H-15), showing
that these two methyl groups were also â-oriented.
Conversely, irradiation of H-7 (δ 2.73) was found to
enhance the signal of H-13 (δ1.16) and H-6R (δ2.10),
and the latter on irradiation enhanced the signal of H-1
(δ 2.62), while no enhancement was observed for H-8â.
Furthermore, irradiation of H-3 at δ 4.48 enhanced the
signal of H-1′ (δ 4.23), suggesting that both two protons
were R-oriented. However, since the sugar moiety can
rotate freely, the stereochemistry of the glycosidic
linkage remained unknown. In view of these findings,
2 was established as 4R,5R-epoxy-10R,11â,13H,14H-1-
epi-inuviscolide 3-â-D-glucoside.
eudesmanolide 4, C15H20O4, were generally similar to
those of 3 but lacked the signals associated with the
C-5(6)-double bond and C-2 acetoxy group. Instead, 4
was concluded to have a C-4(5)-tetrasubstituted double
bond [δC-4 129.8, δC-5 135.8, versus δC-4127.1, δC-5
137.4 in alloalantolactone (17)27] and two hydroxyl
groups at C-2 and C-3 at δC-2 71.6 and δC-3 78.5. A
COSY experiment established the systems -CH2CH-
(OH)CH(OH)- (δ 1.65, 3.78, 3.76, H-1, H-2, and H-3,
respectively) and CH2CH(CdCH2)CH(O)CH2 in rings A
and B, respectively, of 4, and this was confirmed by a
HETCOR experiment and other 13C-NMR spectral data
(Table 3).
A series of NOE-difference experiments showed that
H-7 (δ 3.18) and H-8 (δ 4.54) were cis and R-oriented,
while no enhancement was observed for H-14 (δ 1.18),
thus indicating that H-14 and H-7/H-8 were trans. In
addition, irradiation of H-14â enhanced the signals for
H-2 and H-3 (δ 3.78 and 3.76, respectively), confirming
that these two protons were also â-oriented in 4. From
the foregoing data, the structure of the eudesmanolide
4 was assigned as 2R,3R-dihydroxyalloalantolactone (4).
The germacranolide 8â-hydroxyparthenolide (4R,5â-
epoxyeupatolide, 5) demonstrated physical and spec-
troscopic data that were indistinguishable from those
of inulasalsolin, previously isolated from I. salsoloides.6
It was originally assigned6 structure 5A, but the struc-
ture was recently revised28 to 5. Acetylation of 5
afforded the known acetate, lipiferolide (9), which was
also isolated during this investigation, and its identity
was established by comparing its physical and spectro-
scopic data with those previously reported.21,22
The last sesquiterpene lactone was found to possess
In addition, four other sesquiterpene lactones 3-6
were isolated in crystalline form. One of these, 2R-O-
acetyl-3â-hydroxyalantolactone (3), C17H22O5, contained
a trisubstituted double bond (δC-5 145.8, δC-6 121.5) and
an exocyclic methylene on a γ-lactone ring. The 1H- and
13C-NMR spectra of 3 (Table 3) were found to be
generally similar to those reported for 2R-hydroxyalan-
tolactone (16),4,26 except for the differences associated
with the presence of an acetoxy group at C-2 (νmax 1750
cm-1, δC 71.0) and a hydroxyl group at C-3 (νmax 3500
1
physical and H NMR data that were closely related to
those reported29,30 for the pseudoguaianolide 8-epi-
confertin (6), C15H20O3. Its hitherto unreported 13C
NMR assignments (Table 1) were in agreement with
structure 6.
During the isolation of the sesquiterpenes, the thymol
derivatives 11 and 12 were also isolated as pure entities.
Compound 11 was isolated previously from Helenium
mexicanum,9 while 12 was reported as the product of

Sesquiterpene Lactones and Thymol Esters from Vicoa
J ournal of Natural Products, 1997, Vol. 60, No. 6 553
Ta ble 2. 1H-NMR Chemical Shift Values and Coupling Constants (in Hz, in Parentheses) for Compounds 1, 2, 8, and 13
proton
1a
2b
8c
13
2.55 d (7.5)
1R
1â
2
2.62 brd (7.9)
1.82 m
1.67 m
1.47 mf
1.42 m
2.66 brd (10.5)
1.96 m
1.75 md
1.75 me
1.25 m
1.91 m
1.71 m
1.65 m
1.85 m
1.65 m
1.71 m
3
4.48 t (8.0)
5R
6R
1.47 mf
2.18 m
1.06 m
2.55 m
2.10 dd (7.0, 17.5)
1.77 m
2.28 td (3.7, 13.3)
1.24 m
1.84 m
6â
1.40 br d (17.5)
2.77 ddd (1.9, 10.1, 12.0)
4.43 ddd (4.0, 10.1, 12.0)
1.75 me
2.36 td (4.0, 12.8)
2.10 m
7R
2.73 mg
2.66 m
8â
4.32 ddd (1.4, 9.8, 11.2)
1.92 dd (11.2, 14.3)
2.25 br dd (1.7, 14.3)
4.10 ddd (4.0, 10.4, 11.5)
4.31 ddd (1.6, 9.3, 10.6)
2.55 dd (10.6, 15.5)
3.19 ddd (3.5, 6.0, 15.5)
9R
1.75 md
9â
2.29 td (4.0, 12.7)
2.0 m
10R
11
2.73 mg
13a
13b
14â
5.95 d (3.3)
5.54 d (3.3)
1.13 s
1.16 d (7.6)
6.22 d (3.5)
5.54 d (3.5)
5.09 s
3.36 d (5.0)
2.96 d (5.0)
0.96 d (7.4)
0.95 d (7.5)
4.97 s
15â
1′
2′
1.03 s
1.41 s
4.23 d (7.8)
3.18 t (7.8)
1.20 s
1.33 s
3′
4′
5′
3.26-3.43 m
6′
3.98 br d (12.0)
3.66 dd (5.3, 12.0)
1.98 br s
OH
4.50 br s
a
b
Spectrum run in DMSO-d6. Spectrum in CD3OD. c Data for 8 was published previously;20 also reported here to aid the assignment
d-g
of 1.
Signals superimposed on each other, J unresolved.
Ta ble 3. 1H- and 13C-NMR Chemical Shift Values for Compoundsa 3 and 4
3
4
proton/carbon
1
1H
13C
1H
NOE
13C
2.0 dd (4.3, 15.5)
1.19 m
44.2 t
1.65 m
44.5 t
2
5.12 ddd
71.0 d
3.78 br dd (4.5, 6.0)b
3.76 br db
H-3â, H-14â
H-2â, H-14â
71.6 d
(4.3, 10.2, 11.5)
3.65 dd (6.3, 10.2)
2.80 brq (7.4)
3
4
5
6
7
74.5 d
44.2 d
145.8 s
121.5 d
39.3 d
75.1 d
41.9 t
78.5 d
129.8 s
135.8 s
28.8 t
41.8 d
77.5 d
44.0 t
5.30 d (4.0)
1.94 br t (12.5) 2.88 dd (7.5, 13.7)
3.60 m
3.18 m
H-8R
H-7R
8
9
4.80 dt (3.3, 3.3, 6.7)
1.52 dd (3.3, 14.8)
2.21 dd (2.8, 14.8)
4.54 dd (7.6, 13.9)
1.70 mc
9′
10
11
12
13
1.74 mc
33.4 s
138.9 s
171.4 s
122.4 t
36.9 s
141.8 s
172.6 s
122.5 t
6.23 d (2.0)
5.66 d (2.0)
1.29 s
1.14 d (7.7)
2.09 s
6.18 d (2.7)
5.74 d (2.7)
1.18 s
14
15
OAc
29.5 q
16.2 q
21.2 q
169.8 s
H-2â, H-3â
27.4 q
15.0 q
1.77 s
a
Values in parentheses are coupling constants, in Hz. b,c Signals superimposed on each other, J (for H-3, H-9, and H-9′ of 4) unresolved.
acid hydrolysis of 11,9 but has not been previously
isolated from a natural source. Complete 13C-NMR data
for 11 and 12, not reported previously, are assigned in
Table 4 using COSY, HETCOR, and FLOCK experi-
ments. Furthermore, the UV, IR, and MS data for
7-hydroxy-8,9-diisobutyryloxythymol (12) are being re-
ported for the first time. The 13C-NMR data for car-
abrone (10), not previously reported, are presented in
the Experimental Section.
DMS 90 spectrophotometer, and IR were taken as KBr
disks, unless otherwise specified, on a Perkin-Elmer
5808 spectrophotometer. The NMR spectra were taken
on Varian VXR 300 instrument at the University of
Mississippi and on a Varian XL-300 NMR spectrometer
at the College of Pharmacy, University of Illinois at
Chicago (UIC), operating at 299.9 MHz (1H) and 75.4
MHz (13C) respectively, in CDCl3, unless otherwise
stated, using tetramethylsilane (TMS) as internal stan-
dard. DEPT spectra were obtained from a Nicolet NT-
360 spectrometer operating at 90.8 MHz (13C) at the
Research Resources Center (UIC) and a GE Omega-300
spectrometer at 75.0 MHz (13C) at the University of
Chicago. 2D NMR spectra (COSY, HETCOR, FLOCK,
Exp er im en ta l Section
Gen er al Exper im en tal P r ocedu r es. Melting points
were recorded on an Electrothermal 9100 instrument.
UV spectra were obtained in MeOH, using a Varian

554 J ournal of Natural Products, 1997, Vol. 60, No. 6
Mossa et al.
Ta ble 4. 1H- and 13C-NMR Chemical Shift Values for
Compoundsa,b 11 and 12
MeOH, afforded 30 and 16 g of solid residue, respec-
tively. A portion of the MeOH fraction (13 g) was
subjected to column chromatography over Si gel (400
g) and eluted with CH2Cl2-EtOAc (1:1) to yield fraction
C (0.5 g), which was subsequently purified by additional
chromatography (CPTLC, Si gel PF254 2 mm disk,
CHCl3:Me2CO Me2CO 55:45) to give compound 2.
11
12
proton/
carbon
1H
13C
1H
13C
1
139.9 s
140.1 s
118.6 d
156.5 s
118.8 s
126.5 d
2
3
4
5
6
7
8
6.87 br s
122.9 d 6.69 br s
148.5 s
126.0 s
10r-Hyd r oxy-14H-in u viscolid e (1): off-white gran-
ules (80 mg) from Me2CO/CHCl3; mp 112-114 °C; [R]D
-58° (c 0.056, EtOH); UV (MeOH) λmax 220 (log ꢀ 3.96)
7.35 d (7.8)
128.9 d 6.90 d (8.0)
7.05 br d (7.8) 126.7 d 6.65 dd (2.0, 8.0) 120.5 d
56.9 s
50.7 t
78.7 s
67.3 t
nm; IR (KBr) νmax 3300 (OH), 1755 (lactone), 1660 cm-1
;
3.03 d (5.3)
2.79 d (5.3)
4.57 d (12.2)
4.19 d (12.2)
2.35 s
4.48 d (12.1)
4.43 d (12.1)
4.48 d (12.1)
4.43 d (12.1)
1H- and 13C-NMR, see Tables 2 and 1, respectively;
CIMS m/ z [M‚NH4]+ 284 ([C15H22O4‚NH4]+, 100), 266
([M‚NH4-NH4]+, 10), 249 (20).
9
64.8 t
67.3 t
10
iBu-1 1′
21.1 q 2.27 s
176.4 s
21.0 q
177.5 s
33.9 d
18.9 q
18.9 q
177.5 s
33.9 d
18.9 q
18.9 q
4r,5r-E p o x y -10r,11â,13H ,14H -1-ep i -i n u v i s -
colid e 3-â-D-glu cosid e (2): off-white granules (120 g)
from Me2CO/CHCl3; mp 80-82 °C; [R]D, -26.7° (c 0.09,
MeOH); UV (MeOH) λmax 220 (log ꢀ 4.38) nm; IR (KBr)
2′
3′
4′
2.52 sep (7.1)
1.09 d (7.1)c
1.11 d (7.1)c
33.8 d 2.56 sep (7.0)
19.0 q 1.12 d (7.0)
18.9 q 1.12 d (7.0)
175.3 s
iBu-2 1′′
2′′
3′′
4′′
OH
2.85 sep (7.2)
1.32 d (7.2)
1.32 d (7.2)
34.2 d 2.56 sep (7.0)
18.6 q 1.12 d (7.0)
18.6 q 1.12 d (7.0)
8.75 s
ν
max 3500 (OH), 1750 (lactone) cm-1; 1H- and 13C-NMR,
see Tables 2 and 1, respectively; CIMS m/ z [MH]+ 429
([C21H32O9‚H]+, 10), 249 ([M - C6H11O6]+, 100), 231 (65).
4.36 s
2r-O-Acetyl-3â-h yd r oxya la n tola cton e (3): color-
less needles (200 mg) from n-hexane/EtOAc: mp 182-
184 °C; [R]D +120° (c 0.084, CHCl3); UV (MeOH) λmax
220 (log ꢀ 3.98) nm; IR (KBr) ν max 3500 (OH), 1750 (br,
a
1H-NMR of 11 and 12 were published previously9 but reported
here to aid with the 13C-NMR assignments, which were ac-
complished using 2D NMR COSY, HETCOR, and FLOCK experi-
b
ments. Values in parentheses are coupling constants, in Hz.
1
OAc and lactone), 1660 cm-1; H- and 13C-NMR, see
c Interchangeable signals.
Table 3; CIMS m/ z [M‚NH4]+ 324 ([C17H22O5‚NH4]+,
100), [M]+ 306 (15), 288 ([M]+ - H2O, 15), 246 ([M]+
60, 15).
-
NOESY and NOE-difference experiments) were ob-
tained using standard Varian software. Stereochemical
assignments drawn for all new compounds depict rela-
tive rather than absolute stereochemistry. CIMS were
recorded on a Finnegan MAT 300 mass spectrometer,
using CH4 or NH3 as ionizing gases. Elemental analy-
ses are within (0.4% as determined using a Perkin-
Elmer analyzer, Model 2400. Optical rotations were
recorded in CHCl3, unless otherwise stated, at ambient
temperature using a Perkin-Elmer 241 MC polarimeter.
TLC was performed on Si gel 60 F254, using 15%
MeOH-CCl4, unless otherwise specified, as solvent,
with visualization using 1% vanillin/H2SO4 spray re-
agent. Centrifugal preparative TLC (CPTLC, using a
Chromatotron instrument obtained from Harrison Re-
search, Inc., Model 7924) was run with either 1, 2, or 4
mm Si gel PF254 disks, at a flow rate of 4 mL/min.
P la n t Ma ter ia l. The aerial parts of V. pentanema
were collected in Abha, Saudi Arabia, in May 1993. A
voucher specimen (no. 13063) is deposited at the her-
barium of MAPPRC, College of Pharmacy, King Saud
University, Riyadh, Saudi Arabia.
Extr a ction a n d Isola tion . The dried ground aerial
parts (1 kg) were percolated successively with n-hexane
(8 L) followed by EtOH (8 L) at room temperature, and
the extracts were dried in vacuo to leave 35 and 55 g of
residue, respectively. The n-hexane extract (33 g) was
subjected to column chromatography over Si gel (mesh
70-230, 1 kg) and eluted with CCl4 followed by increas-
ing concentrations of EtOAc (between 1% and 15%) in
CCl4 to give seven pure isolates 3, 6, 7, and 9-12 and
two fractions (A and B). Subsequent separation by
centrifugal preparative TLC (using Si gel PF254 4 mm
disk, n-hexane:EtOAc 7.5:2.5) of fraction A led to the
isolation of 5 and 8. Similar treatment of fraction B
(CHCl3:Me2CO 2.5:0.5) gave compounds 1 and 4.
Successive percolation of the dried EtOH extract (50
g) prepared from aerial parts with EtOAc, followed by
2r,3r-Dih yd r oxya lloa la n tola cton e (4): colorless
needles (60 mg) from Me2CO/CHCl3: mp 81-83 °C; [R]D
+25°(c 0.09, MeOH); UV (MeOH) λmax 220 (log ꢀ 3.98)
nm; IR (KBr) νmax 3500 (OH), 1745 (lactone), 1650 cm-1
;
1H- and 13C-NMR, see Table 3; CIMS m/ z [MH]+ 265
([C15H20O4‚H]+, 10), 247 ([MH]+ - H2O, 75), 229 (m/ z
247 - H2O, 100), 201 (25).
8â-Hydr oxypar th en olide (4r,5â-Epoxyeu patolide,
5): colorless needles (300 mg) from n-hexane/EtOAc; mp
144-146 °C; [R]D -178° (c 0.811, CHCl3) and corre-
sponding literature6 values for 5A: mp 136-138 °C; [R]D
-186.3° (MeOH); spectroscopic (1H- , 13C-NMR, and MS)
data were indistinguishable from those reported previ-
ously28 for 5.
8-epi-Con fer tin (6): colorless plates (100 mg) from
n-hexane/EtOAc: mp 150-151 °C; [R]D +178°(c 0.05
CHCl3) and corresponding literature29 values for 6: mp
135-136 °C; [R]D +147° (MeOH); 13C-NMR, see Table
1; CIMS m/ z [MH]+ 249 ([C15H20O3‚H]+, 100), 231 (95).
4r,5r-Ep oxy-10r,14H-1-epi-in u viscolid e (7): col-
orless plates (750 mg) from n-hexane/EtOAc; mp 69-
71 °C; [R]D +89° (c 0.084, CHCl3) and corresponding
literature4 value for 7: a gum (mp not reported); [R]D
+84.4° (CHCl3); spectroscopic (UV, IR, MS, and 1H-
NMR) data were indistinguishable from those reported
previously;4 13C-NMR, see Table 1.
In u viscolid e (8): gum (80 mg); physical/spectro-
1
scopic ([R]D, UV, IR) and H-NMR data were indistin-
guishable from those reported previously;19 13C-NMR,
see Table 1; CIMS m/ z [MH]+ 249 ([C15H20O3‚H]+, 40),
231 (100), 185 (35).
Lip ifer olid e (9): gum (200 mg); [R]D -114° (c 0.05,
CHCl3) [literature21 [R]D -125° (MeOH)]; spectoscopic
data (UV, IR, 1H- and 13C-NMR) were indistinguishable
from those reported previously.21,22

Sesquiterpene Lactones and Thymol Esters from Vicoa
J ournal of Natural Products, 1997, Vol. 60, No. 6 555
Ca r a br on e (10): off-white needles (500 mg) from
n-hexane/EtOAc; mp, [R]D, IR, H-NMR, and MS data
Refer en ces a n d Notes
1
(1) Mandaville, J . P. Flora of Eastern Saudi Arabia; Kegan Paul
International Ltd.: London, 1990; p 291.
(2) O¨ ksu¨z, S.; Topcu, G. Phytochemistry 1983, 31, 195-197.
(3) Bohlmann, F.; Grenz, M.; J akupovic, J .; King, R. M.; Robinson,
H. Phytochemistry 1983, 22, 1213-1218.
(4) Bohlmann, F.; Mahanta, P. K.; J akupovic, J .; Rastogi, R. C.;
Natu, A. A. Phytochemistry 1978, 17, 1165-1172.
(5) Topcu, G.; O¨ ksu¨z, S.; Herz, W.; Diaz, J . G. Phytochemistry 1995,
40, 1717-1722.
(6) Zhou, B.-N.; Bai, N.-S.; Lin, L.-Z.; Cordell, G. A. Phytochemistry
1994, 36, 721-724.
(7) Topcu, G.; O¨ ksu¨z, S.; Shieh, H.-L.; Cordell, G. A.; Pezzuto, J .
M.; Bozok-J ohansson, C. Phytochemistry 1993, 33, 407-410
(8) Topcu, G.; O¨ ksu¨z, S. Phytochemistry 1990, 29, 3666-3667.
(9) Bohlmann, F.; Niedballa, U.; Schulz, J . Chem. Ber. 1969, 102,
864-871.
(10) Bohlmann, F.; Suwita, A. Phytochemistry 1978, 17, 1929-1934.
(11) Bohlmann, F.; Zdero, C. Phytochemistry 1977, 16, 1234-1245.
(12) Sawaikan, D. D; Rojatkar, S. R.; Nagasmpagi, B. A. Phytochem-
istry 1994, 37, 585-586.
(13) Nagasmpagi, B. A. ; Bhat, U. G.; Bohlmann, F.; Zdero, C.
Phytochemistry 1981, 20, 2031-2033.
were indistinguishable from those reported previ-
ously;4,23 13C-NMR δ 17.1 (s, C-10), 18.2 (q, C-14), 22.9
(d, C-5), 23.3 (t, C-2), 30.0 (q, C-15), 30.7 (t, C-6), 34.2
(d, C-1), 37.2 (t, C-9), 37.7 (d, C-7), 43.5 (t, C-3), 75.5 (d,
C-8), 122.4 (t, C-13), 139.0 (s, C-11), 170.3 (s, C-12),
208.4 (s, C-4).
7,8-E p oxy-9-(isob u t yr yloxy)t h ym olisob u t yr a t e
(11): oil (75 mg); physical and spectroscopic data ([R]D,
UV, IR, and 1H-NMR) were indistinguishable from those
previously reported;9 13C-NMR, see Table 4; CIMS m/ z
[MH]+ 339 ([C18H26O6‚H]+, 5), 321 ([MH]+ - H2O, 100),
145 (m/ z 321 - 2
iBuOH, 35).
7-Hyd r oxy-8,9-bis(isobu tyr yloxy)th ym ol (12): oil
(60 mg); UV (MeOH) λmax 220 (log ꢀ 3.80), 2.55 (log ꢀ
2.3) nm; IR (neat) νmax 3300 (OH), 1760 (iBuCOO), 1600
cm-1; 1H- and 13C-NMR, see Table 4; CIMS m/ z [MH]+
321 ([C18H24O5‚H]+, 70), 145 ([MH]+ - 2 iBuOH, 100).
Ep oxid a tion of 4r,5r-Ep oxy-10r,14H-1-epi-in u -
viscolid e (7) to 13. Compound 7 (100 mg) in CH2Cl2
was treated with m-chloroperbenzoic acid (125 mg) at
rt and stirred for 12 h. Regular workup31 yielded crude
compound 13 (90 mg), purified by chromatography
(CPTLC, 1 mm silica gel PF254 disk, solvent: 10%
EtOAc-n-hexane) to provide 4R(5R),11R(13)-diepoxy-
10R,11â,14H-1-epi-inuvicolide (13) (80 mg, Rf 0.45, sol-
vent: 15% MeOH-CCl4): [R]D +69.5° (c 0.05,CHCl3);
(14) Purushothaman, K. K.; Vasanth, S.; Cox, P. J .; Akinniyi, J . A.;
Connolly, J . D.; Rycroft, D. S.; Sim, G. A. J . Chem. Res., Synop.
1981, 374-375
(15) Purushothaman, K. K.; Vasanth, S. Indian J . Chem. 1986, 25B,
417-418.
(16) Vasanth, S.; Kundu, A. B. Fitoterapia 1995, 66, 181-182.
(17) Vasanth, S.; Kundu, A. B.; Purushothaman, K. K.; Patra, A.;
Pattabhi, V.; Connolly, J . D. J . Nat. Prod. 1990, 63, 354-358.
(18) Vasanth, S.; Kundu, A. B.; Panda, S. K.; Patra, A. Phytochemistry
1991, 30, 3053-3055.
(19) Bohlmann, F.; Czerson, H.; Scho¨neweiss, S. Chem. Ber. 1977,
110, 1330-1334.
(20) Zdero, C.; Bohlmann, F.; King, R. M.; Robinson, H. Phytochem-
istry 1987, 26, 1207-1209.
1
IR (KBr) νmax 1735 (lactone) 1235, 1155 cm-1; H- and
(21) Doskotch, R. W.; Kelly, S. L., J r.; Hufford, C. D.; El-Feraly, F.
S. Phytochemistry 1975, 14, 769-773.
13C-NMR, see Tables 2 and 1, respectively; CIMS m/ z
[MH]+ 265 ([C15H20O4‚H]+, 100).
(22) Doskotch, R. W.; El-Feraly, F. S.; Fairchild, E. H.; Huang, C.-T.
J . Org. Chem. 1977, 42, 3614-3618.
(23) Minalo, H.; Horibe, I. J . Chem. Soc. C 1968, 2131-2137.
(24) The often-reported name of compound 7 as 4R,5R-epoxy-10R,14H-
inuviscolide2,4,8 is based on the earlier incorrect structure of
inuviscolide, with H-1 as R.19 The stereochemistry at H-1R of
inuviscolide was later revised to H-1â as in 8,20 while 1-epi-
inuviscolide, with H-1R, was isolated from the genera Inula8 and
Dittrichia.32 Thus, compound 7 is to be named 4R,5R-epoxy-
10R,14H-1-epi-inuviscolide.
Acetyla tion of 8â-Hyd r oxyp a r th en olid e (5) to 9.
Compound 5 (75 mg) was dissolved in pyridine (1 mL)
and treated with Ac2O (0.5 mL) at rt for 24 h. Regular
workup gave 9 (70 mg) as a gum, [R]D -110° (c 0.05,
1
CHCl3). The physical and spectral data (IR, H- and
13C-NMR) of the acetate 9 were indistinguishable from
those previously reported for lipiferolide (9).21,22
(25) Reynolds, W. F.; McLean, S.; Perpick-Dumont, M.; Enriques, R.
G. Magn. Reson. Chem. 1989, 27, 162-169.
(26) Al-Yahya, M. A.; Khafagy, S.; Shihata, A.; Kozlowski, J . F.;
Antoun, M. D.; Cassady, J . M. J . Nat. Prod. 1984, 47, 1013-
1017.
Ack n ow led gm en t. The authors thank Dr. C. D.
Hufford, Department of Pharmacognosy, School of Phar-
macy, University of Mississippi, for the 300 MHz NMR
spectra, Dr. H. J . Woerdenbag, University Centre for
Pharmacy, University of Groningen, The Netherlands,
for CIMS, Dr. S. O¨ ksu¨z, Faculty of Pharmacy, Univer-
sity of Istanbul, Turkey, for providing the IR, 1H-NMR,
and MS of compound 15, Dr. Opinya Ekabo, University
of Chicago, for assistance in NMR determination, Dr.
S. Abedin (MAPPRC) for identification of plant material,
and Mr. H. H. Mirza and Mr. M. A. Mukhayer (MAP-
PRC) for technical assistance.
(27) Bhandari, P.; Rastagi, R. P. Indian J . Chem. 1983, 22B, 286-
288.
(28) J eske, F.; Huneck, S.; J akupovic, J . Phytochemistry 1996, 41,
1539-1542.
(29) El-Ghazouly, M.; Omar, A. A.; El-Din, A. S.; Khafagy, S. M. Acta.
Pharm. J ugosl. 1987, 37, 1311-133.
(30) Abdel-Mogib, M.; J akupovic, J .; Dawidar, A. M.; Metwally, M.
A.; Abou-Elzahab, M. Phytochemistry 1990, 29, 2581-2584.
(31) Muhammad, I.; Waterman, P. G. J . Nat. Prod. 1988, 51, 719-
724.
(32) Rustaiya, A.; J akupovic, J .; Chau-Thi, V. T.; Bohlmann, F.;
Sadjadi, A. Phytochemistry 1987, 26, 2603-2605.
NP960506O