Synthesis and biological evaluation of antitumor-active arglabin derivatives

Article abstract of DOI:10.1002/ardp.201100065

Arglabin derivatives varied at the endo- or exo-cyclic double bond were synthesized and studied in a colorimetric sulforhodamine B assay for their cytotoxicity. Variations on the endocyclic double bond led to compounds of reduced cytotoxicity whereas derivatives from the reaction of the α-methylene-γ-butyrolactone moiety led to compounds of similar or only slightly reduced cytotoxicity but different, cell line-dependent selectivity. In addition, arglabin is an excellent starting material for the synthesis of the guaianolide arborescin.

Full text of DOI:10.1002/ardp.201100065

Arch. Pharm. Chem. Life Sci. 2012, 345, 215–222
215
Full Paper
Synthesis and Biological Evaluation of Antitumor-Active
Arglabin Derivatives
´
Rene Csuk, Anke Heinold, Bianka Siewert, Stefan Schwarz, Alexander Barthel, Ralph Kluge,
¨
and Dieter Strohl
¨
Martin-Luther-Universitat Halle-Wittenberg, Bereich Organische Chemie, Halle (Saale), Germany
Arglabin derivatives varied at the endo- or exo-cyclic double bond were synthesized and studied in a
colorimetric sulforhodamine B assay for their cytotoxicity. Variations on the endocyclic double bond
led to compounds of reduced cytotoxicity whereas derivatives from the reaction of the a-methylene-g-
butyrolactone moiety led to compounds of similar or only slightly reduced cytotoxicity but different,
cell line-dependent selectivity. In addition, arglabin is an excellent starting material for the synthesis
of the guaianolide arborescin.
Keywords: Arglabin / Arborescin / Antitumor activity / Guaianolides
Received: February 21, 2011; Revised: August 25, 2011; Accepted: August 26, 2011
DOI 10.1002/ardp.201100065
Introduction
from Artemisia myriantha – a plant [13–15] well-known in
traditional Chinese medicine as a treatment for several dis-
eases. Recently, a total synthesis of enantiomerically pure 1
has been elaborated [16].
Cancer is a leading cause of death affecting people world-
wide. Chemotherapy is most often applied alone or following
surgery or radiation of tumors. Chemotherapeutic agents
usually affect both tumor and rapidly growing cells of
normal tissue like the cells of the intestinal epithelium,
hair follicles and bone marrow. Thus, developing a chemo-
therapeutic agent with minimal toxicity would be
rewarding.
Arglabin is assumed [17, 18] to prevent protein farnesyla-
tion without altering geranylgeranylation; thus, this com-
pound inhibits post-translational modification of ras protein
in cells. Because of limited access to 1, only a few derivatives
of arglabin have been prepared [11, 19–21] so far. In this
study, we set out to synthesize some more derivatives of 1 and
to evaluate their antitumor activity.
The guaianolides represent one of the largest groups of
sesquiterpene lactones. Many of them have been shown to
hold biological/medical activities, among them contraceptive
[1, 2], antihelmintic [3], antishistosomal [4–6] and antitumor
[7, 8] activity. Several years ago it has been noted that the
guaianolide arglabin (1, Fig. 1) and several of its derivatives
have a noteworthy antitumor activity and that they show less
side effects than other chemotherapeutic agents. As a con-
sequence, arglabin was approved for use in several countries
for treating lung, liver and ovarian cancer [9–11].
Results and discussion
Crude arglabin (by extraction from the dried plant material,
purity 65–85% by HPLC) had to be purified to perform useful
and reproducible reactions. Chromatography followed by
repeated re-crystallizations from hexane was tedious but
gave 1 of >98% purity.
Arglabin is a sesquiterpene-g-lactone and can be isolated
from the plants [12] of Artemisia glabella, a species of worm-
wood endemic to the Karaganda region of Kazakhstan, and
Reaction of 1 with an ethanolic solution of dimethylamine
[22] (Scheme 1) followed by acidic work-up (HCl) gave
low yields of 2.HCl [23]. Reaction of 1, however, with
Dimcarb [24, 25] in dry acetonitrile for one day gave 82%
of isolated 2. Its treatment with dry HCl in ethyl acetate gave
80% of the hydrochloride 2.HCl. Yields dropped significantly,
however, on scaling-up of this reaction. As an alternative, to a
solution of 1 in MTBE, dry methanol and acetyl chloride [26]
´
Correspondence: Prof. Dr. Rene Csuk, Bereich Organische Chemie,
Martin-Luther-Universitat Halle-Wittenberg, Kurt-Mothes-Strasse 2,
¨
D-06120 Halle (Saale), Germany.
E-mail: rene.csuk@chemie.uni-halle.de
Fax: þ49 (0) 345 5527030
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

216
R. Csuk et al.
Arch. Pharm. Chem. Life Sci. 2012, 345, 215–222
group is deficient of electrons and therefore unreactive
towards this reagent. Compound 9 was formed in 53% yield
and is characterized in its 13C NMR spectrum by the presence
of extra signals at d ¼ 171.3 ppm (ester carbonyl) and the
signals of the ethyl substituent.
Assignments of the absolute configuration of the newly
created stereogenic centers were performed by NMR: Since
NOESY-NMR spectra show vicinity between H-8a and H-1 and
3JH-1,H-1a ¼ 12.2 Hz (being typical for an axial/axial orien-
tation) the abs. configuration of C-1 is (R) and that of C-1a
is (S). In addition, the four possible stereoisomers were sub-
jected to conformational search using semiempirical MOPAC-
PM3 (CAChe 4.0 software from Oxford Molecular) calcu-
lations. The analysis confirmed the (1aS,1R) isomer is most
easily formed and possesses the lowest heat of formation
compared to the other stereoisomers.
Figure 1. Structure of the guaianolides arglabin (1) and arborescin
(13).
were slowly added at temperatures <108C and 2.HCl was
obtained in 92% yield.
Reaction of 1 with thiomorpholine, piperidine or pipera-
zine yielded the addition products 3–5 in 72–81% yield.
Compounds 3–5 show in their 13C-NMR spectra signals
between d ¼ 54–57 ppm that matches to the methylenic
carbon C-12. Addition of nitromethane to 1 in the presence
of catalytic amounts of DBU [27] yielded 66% of the nitro
compound 6. From the similar reaction of 1 with 2-mercap-
toethanol, compound 7 was obtained in 62.5% yield; reaction
of 1 with 2-mercaptobenzoic acid gave the thioether 8.
All of these reactions advanced smoothly at the exocyclic
methylene group of the anellated a-methylene-g-butyrolac-
tone unit of arglabin. Interestingly enough, a cyclopropana-
tion with ethyl diazoacetate in the presence of [Rh(OAc)2]2
(Scheme 2) did not affect this methylene group. Because of
the –M effect of the adjacent lactone group this methylene
Whereas the reaction of diazomethane with a-methylene-
g-butyrolactones is a well-known reaction [28, 29], ‘‘Click
reactions’’ have scarcely been performed [30]. Thus, no
reaction of the endocyclic double bond was observed on
the cycloaddition of 1 with ethyl azidoacetate in the presence
of CuI [31] or from its reaction with diazomethane. The
corresponding 7,4’[1,2,3]triazole derivative 10 and the 7,3’-
pyrazole 11 were obtained in 46% and quantitative yield,
respectively.
Whereas the reaction of 1 with peracetic acid was reported
[32] to give a mixture of two possible stereoisomeric epoxides,
Scheme 1. Reagents and conditions: a)
MeCN, Dimcarb, 258C, 24 h, 82%; b) MeOH/
AcCl, MTBE, 108C, 30 min, 92%; c) thiomor-
pholine, EtOH, 48 h, 258C, 72%; d) piperidine,
EtOH, 12 h, 258C, 78%; e) piperazine, EtOH,
12 h, 258C, 81%; f) MeNO2, DBU (cat.), 24 h,
258C, 66%; g) 2-mercaptoethanol, DBU (cat.),
EtOH, 6 h, 258C, 62.5%; h) 2-mercaptoben-
zoic acid, DBU (cat.), EtOH, 48 h, 258C,
62.8%.
Scheme 2. Reagents and conditions: a) ethyl
diazoacetate, [(Rh(OAc)2]2, 2 h, 258C, 52.6%;
b) ethyl azidoacetate, CuI, 5 d, 258C, 46%; c)
diazomethane, 2 h, 258C, quant.; d) mCPBA,
THF, 12 h, 108C, 61%.
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Arch. Pharm. Chem. Life Sci. 2012, 345, 215–222
Synthesis and Biological Evaluation of Antitumor-Active Arglabin Derivatives
217
Table 1. Results of SRB-assay: The values (IC50 in mM) for melanoma (518A2), zervical cancer (A431), lung carcinoma (A549), ovarian
cancer (A2780), colon cancer (DLD-1, HCT-8, HCT-116, HT-29), anaplastic thyroid cancer (8505C, SW-1736), mamma carcinoma (MCF-7)
and liposarcoma cell lines were obtained by an SRB-assay after 96 h of treatment and are the average from at least three independent
experiments; standard error 5%.
1
2
3
4
5
6
7
8
518A2
8505C
A253
A2780
A431
A549
DLD-1
FADU
HCT-116
HCT-8
HT-29
LIPO
MCF-7
SW1736
SW480
6.72
1.68
4.25
12.55
4.48
2.21
4.51
6.86
1.09
5.60
7.00
6.00
2.33
3.85
4.46
5.54
4.57
5.59
8.69
5.19
1.95
7.30
4.75
2.69
10.38
10.76
8.25
1.85
5.58
6.52
13.21
3.85
11.33
12.19
16.88
4.76
6.93
4.29
8.62
5.79
14.30
14.46
16.35
14.41
18.93
12.35
10.14
9.87
17.68
7.89
8.13
17.41
16.92
14.24
18.11
15.02
15.07
14.92
3.75
4.40
15.7
10.44
15.07
5.66
11.51
14.83
15.09
11.13
14.83
9.85
10.02
12.74
9.84
11.24
12.72
11.45
13.57
15.62
17.12
16.94
14.07
15.47
13.63
12.82
12.84
11.55
14.38
10.05
14.83
18.61
11.78
17.31
14.53
17.85
16.87
14.85
14.87
12.52
13.64
10.06
10.49
13.73
9.96
11.86
17.82
12.77
16.86
16.84
15.51
4.27
16.20
13.22
13.41
5.01
15.07
15.01
15.05
15.87
17.48
18.22
epoxidation with mCPBA at 108C advanced selectively to yield
only one stereoisomer 12.
for the selective hydrogenation of olefins is unusual [35, 36].
Thus, hydrogenation of 1 in the presence of this catalyst gave
a regioselective hydrogenation of the exocyclic double bond,
and 13 was obtained in almost quantitative yields. Besides
its cytotoxicity, arborescin shows significant antiplasmodial
(Plasmodium falsiparum) activity and is – like arglabin – a tight
binding substrate for the heterologously expressed human
bitter receptors hTAS2R46 [37]. Our approach to arborescin
provides higher yields compared to the previously published
synthesis from a-santonin [38].
The compounds were tested for their antitumor potential
in a panel of 15 human cancer cell lines in 96 well plates
using the colorimetric sulforhodamine B (SRB) [33] protocol.
The calculated IC50 values in Table 1 were obtained from the
corresponding dose-response curves; for compounds 9–11
IC50 values >30 mM were measured.
Substitution of the exocyclic double bond, however, led to
compounds showing a modified selectivity for the cell lines
compared to parent 1. Of special interest seems 5 showing an
IC50 ¼ 3.75 mM with ovarian cancer cells A2780 whereas
parent arglabin shows IC50 ¼ 12.55 mM for this cell line.
Arglabin can also serve as a well accessible starting
material for the synthesis of the guaianolide arborescin 13
(Fig. 1). Arborescin is guaianolide-type terpene and is struc-
turally related to 1; it was isolated [34] from Artemisia arbor-
escens, a plant used for contraceptive purposes [1, 34] by
ancient Arabs and Greeks. Hydrogenation of 1 (Scheme 3)
using Pt/C or Pd/C always gave a mixture of several hydro-
genation products. The Lindlar catalyst has widely been used
for the chemoselective reduction of alkynes to alkenes, its use
In summary, several arglabin derivatives were prepared
exploiting the different reactivities of the endo- and exocyclic
double bonds. Derivatives from the reaction of the a-meth-
ylene-g-butyrolactone moiety led to compounds of similar
or slightly reduced cytotoxicity but different, cell line-
dependent selectivity whereas variations on the endocyclic
double bond led to compounds of reduced cytotoxicity. In
addition, arglabin can be used as an ideal starting material
for the synthesis of the guaianolide arborescin.
Experimental
General
Melting points are uncorrected (Leica hot stage microscope), NMR
spectra were recorded using the Varian spectrometers Gemini
200, Gemini 2000 or Unity 500 (d given in ppm, J in Hz, internal
Me4Si), optical rotations were obtained using a Perkin-Elmer 341
polarimeter (1 cm micro cell, 258C), IR spectra (film or KBr pellet)
on a Perkin-Elmer FT-IR spectrometer Spectrum 1000, MS spectra
were taken on an Intectra GmbH AMD 402 (electron impact,
70 eV) or on a Finnigan MAT TSQ 7000 (electrospray, voltage
4.5 kV, sheath gas nitrogen) instrument. TLC was performed on
silica gel (Merck 5554, detection by UV absorption). The solvents
Scheme 3. Reagents and conditions: a) Pd/BaSO4/quinoline, H2
(20 psi), 2 h, 258C, quant.
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218
R. Csuk et al.
Arch. Pharm. Chem. Life Sci. 2012, 345, 215–222
were dried according to usual procedures. The purity of arglabin
was determined by HPLC (Merck Purosher C18e, 250 ꢀ 4 mm,
5 mm, H2O/MeCN 1:1, 1 mL/min, 378C, UV detection at l ¼ 210 nm,
tR ¼ 8.5 min).
(C2, CH), 83.3 (C9a, CH), 71.1 (C3a, Cquart.), 62.6 (C4a, Cquart.), 52.1
(C12, CH2), 52.0 (C9b, CH), 51.8 (C6a, CH), 48.5 (2 ꢀ C13, CH3), 40.9
(C7, CH), 39.4 (C3, CH2), 32.9 (C5, CH2), 21.4 (C6, CH2), 18.2 (C11,
CH3) ppm; MS (ESI, MeOH): m/z ¼ 292.2 ([MþH]þ); anal. calcd
for C17H25NO3 (291.39): C, 70.07; H, 8.65; N, 4.81; found: C,
69.82; H, 8.89; N, 4.71.
Cell lines and culture conditions
The cell lines 518A2, 8505C, A253, A2780, A431, A549, DLD-1,
FaDu, HCT-116, HCT-8, HT-29, LIPO, MCF-7, SW1736, and SW480
were included in this study. Cultures were maintained as mono-
layer in RPMI 1640 (PAA Laboratories, Pasching, Germany)
supplemented with 10% heat inactivated fetal bovine serum
(Biochrom AG, Berlin, Germany) and penicillin/streptomycin
(PAA Laboratories) at 378C in a humidified atmosphere of 5%
CO2/ 95% air.
[(3aR,4aS,6aS,7R,9aS,9bR)-1,4a-Dimethyl-8-oxo-
4a,5,6,6a,7,8,9a,9b-octahydro-3H-oxireno[8,8a]azuleno-
[4,5-b]furan-7-yl]-N,N dimethylmethanaminium chloride
(2.HCl)
To a solution of 2 (0.97 g, 3.33 mmol) in MTBE (30 mL), dry
methanol (1 mL) and acetyl chloride (0.31 g, 4.1 mmol) were
slowly added at 108C. After stirring for 45 min, the precipitate
was filtered off and washed with MTBE (50 mL). After drying
2.HCl (0.995 g, 92%) was obtained as a white solid. Analytical
samples were either obtained by sublimation or by re-crystalli-
zation from 2-propanol at ꢁ308C; mp 200–2028C; [a]D ¼ þ 60.18
(c ¼ 1.9, CHCl3); Rf ¼ 0.43 (CH2Cl2/MeOH, 7:3); IR (KBr):
n ¼ 3347 m, 2979 s, 2894 m, 2765 m, 2399 m, 1773 s, 1650 s,
1567 m, 1379 s, 1182 m, 1159 m, 1119 m cmꢁ1; UV-vis (metha-
nol): lmax (log e) ¼ 239 nm (2.37); 1H NMR(500 MHz, CDCl3):
d ¼ 5.52 (s, 1 H, CH (2)), 4.14 (dd, 1 H, CH (9a), J ¼ 10.8,
9.5 Hz), 3.23 (d, 2 H, CH2 (C12), J ¼ 4,2 Hz)), 2.97–2.84 (m, 1 H,
CH (7)), 2.91 (m, 1 H, CH (9b)), 2.84 (s, 6 H, 2 ꢀ CH3 (13)), 2.70 (d, 2
H, CH2 (3), J ¼ 15.4 Hz), 1.93–2.14 (m, 3 H, CH (9a) þ CH2 (3)), 2.12
(m, 1 H, CH (5)), 1.92 (s, 1 H, CH (11)) ppm; 13C NMR (125 MHz,
CDCl3): d ¼ 176.1 (C8, C ¼ O), 139,8 (C1, Cquart.), 125.4 (C2, CH),
83.5 (C9a, CH), 72.1 (C3a, Cquart.), 62.6 (C4a, Cquart.), 54.4 (C12, CH2),
52.0 (C9b, CH), 50.8 (C6a, CH), 43.5 (C13, CH3), 42.9 (C7, CH), 39.4
(C3, CH2), 32.9 (C5, CH2), 21.4 (C6, CH2), 18.2 (C11, CH3) ppm; MS
(ESI, MeOH): m/z ¼ 315 ([MþNa]þ); anal. calcd for C17H26ClNO3
(327.85): C, 62.28; H, 8.01; Cl, 10.90; N, 4.27; found: C, 61.95;
H, 8.01; Cl, 10.90; N, 4.17.
Cytotoxicity assay
The cytotoxicity of the compounds was evaluated using the
sulforhodamine-B (SRB) (Sigma Aldrich) microculture colorimet-
ric assay. In short, exponentially growing cells were seeded into
96-well plates on day 0 at the appropriate cell densities to prevent
confluence of the cells during the period of experiment. After
24 h, the cells were treated with serial dilutions of the com-
pounds (0–300 mM) for 96 h. The final concentration of DMSO or
DMF solvent never exceeded 0.5%, which was non-toxic to the
cells. The percentages of surviving cells relative to untreated
controls were determined 96 h after the beginning of drug
exposure. After a 96 h treatment, the supernatant medium from
the 96 well plates was thrown away and the cells were fixed with
10% TCA. For a thorough fixation, the plates were allowed to rest
at 48C. After fixation, the cells were washed in a strip washer. The
washing was done four times with water using alternate dis-
pensing and aspiration procedures. The plates were then dyed
with 100 mL of 0.4% SRB (sulforhodamine B) for about 20 min.
After dying the plates were washed with 1% acetic acid to remove
the excess of the dye and allowed to air dry overnight. 100 mL of
10 mM Tris base solution were added to each well and absorb-
ance was measured at 570 nm (using a 96 well plate reader,
Tecan Spectra, Crailsheim, Germany). The IC50 was estimated
from the semi-logarithmic dose-response curves.
(3aR,4aS,6aS,7R,9aS,9bR)-1,4a-Dimethyl-7-
(thiomorpholin-4-ylmethyl)-5,6,6a,7,9a,9b-hexahydro-3H-
oxireno[8,8a]azuleno[4,5-b]furan-8(4aH)-on (3)
To a solution of arglabin (100 mg, 0.41 mmol) in ethanol (3 mL),
thiomorpholine (65.01 mg, 0.63 mmol) was slowly added. The
mixture was stirred for 2 days at 248C, the solvents were removed
under diminished pressure and the residue subjected to chroma-
tography (silica gel, CHCl3/Et2O, 95:5) to yield 3 (158 mg, 72%)
as a colorless solid; mp. 115–1168C; [a]D ¼ þ62.88 (c ¼ 4.4,
CHCl3); Rf ¼ 0.3 (CHCl3/Et2O, 95:5); IR (KBr): n ¼ 3433 m,
2924 m, 2825 m, 1773 s, 1651 s, 1378 s, 1324 m, 1282 m,
1259 m, 1109 m, 1060 m, 1029 m cmꢁ1; UV-vis (MeOH): lmax
(log e) ¼ 222 nm (2.35) 1H NMR (500 MHz, CDCl3): d ¼ 5.52
(s, 1 H, CH (2)), 3.97 (dd, 1 H, CH (9a), J ¼ 10.2 Hz,), 2.81 (d, 1 H,
J ¼ 10.5 Hz, CH (9b)), 2.73–2.57 (m, 4 H, 2 ꢀ CH2 (13)), 2.70 (d, 1 H,
J ¼ 17.96 Hz, CHa (3)), 2.41 (m, 4 H, 2 ꢀ CH2 (14)), 2.30 (m, 1 H, CH
(7)), 2.11 (d, 1 H, J ¼ 17.78 Hz, CHb (3)), 2.08 (dd, 1 H, J ¼ 15.3,
12.7 Hz, CHa(5)), 1.95 (ddd, 1 H, J ¼ 4.9, 2.7 Hz, CHb(5)), 1.95 (d, 1 H,
J ¼ 2.3 Hz, CHa (12)), 1.89 (s, 3 H, CH3 (11)), 1,59 (d, 1 H,
J ¼ 11.85 Hz, CH (6a)), 1.41 (d, 1 H, J ¼ 12.31 Hz, CHb (12)), 1.31
(s, 3 H, CH3 (10)), 1,23 (m, 2 H, CH (6)) ppm; 13C NMR (125MHz,
CDCl3): d ¼ d 177.6 (C8, C ¼ O), 140,6 (C1, Cquart.), 124.8 (C2, CH),
82.8 (C9a, CH), 72.4 (C3a, Cquart.), 62.6 (C4a, Cquart.), 65, 8 (C13, CH2),
56,9 (C14, CH2), 52.4 (C9b, CH), 51.6 (C6a, CH), 44, 3 (C7, Cquart.), 39.6
(C3, CH2), 33.6 (C5, CH2), 22.7 (C6, CH2), 22.8 (C12, CH2), 22,7 (C10,
(3aR,4aS,6aS,7R,9aS,9bR)-7-[(Dimethylamino)methyl]-
1,4a-dimethyl-5,6,6a,7,9a,9b-hexahydro-3H-oxireno[8,8a]-
azuleno [4,5-b]furan-8(4aH)-on (2)
A solution of arglabin (1) (4.0 g, 16.24 mmol) and Dimcarb (2.8 g,
20.80 mmol) in dry acetonitril (40 mL) was stirred at 248C for 1 d.
The solvent was removed and the crude product purified by
chromatography (silica gel, chloroform/diethyl ether, 9:1) to
yield
2 (3.88 g, 82%) as a white solid; mp 98–1018C;
[a]D ¼ þ43.28 (c ¼ 1.9, CHCl3); Rf ¼ 0.42 (CHCl3/Et2O, 9:1);
IR (KBr): n ¼ 3350 m, 2940 s, 2836 m, 2778 m, 2403 m, 1775 s,
1651 s, 1555 m, 1479 m, 1385 s, 1183 m, 1150 m, 1129 m cmꢁ1
;
1
UV-vis (MeOH): lmax (log e) ¼ 243 nm (3.46); H NMR (500 MHz,
CDCl3): d ¼ 5.55 (s, 1 H, CH (2)), 3.95 (dd, 1 H, CH (9a), J ¼ 10.8,
9.5 Hz), 2.81 (d, 1 H, CH (9b), J ¼ 10.3 Hz), 2.75 (d, 1 H,
J ¼ 17.9 Hz, CHa (3)), 2.59–2.41 (m, 1 H, CH (9a)), 2.28 (m,
2 H, CH2 (7)), 2.25 (s, 6 H, 2 x CH3 (13)), 2.13 (d, 2 H,
J ¼ 17.5 Hz, CHb (3)), 2.10–2.05 (m, 2 H, CH2 (5)), 1.99–1.91
(m, 2 H, CH2 (12)), 1.95 (s, 3 H, CH (12)), 1.94–1.88 (m, 1 H, CHb
(3)), 1.61–1.40 (m, 2 H, CH2 (6)), 1.31 (s, 3 H, CH3 (11)) ppm; 13C NMR
–
(125 MHz, CDCl ): d ¼ 176.5 (C8, C O), 138,8 (C1, Cquart.), 125.4
–
3
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Arch. Pharm. Chem. Life Sci. 2012, 345, 215–222
Synthesis and Biological Evaluation of Antitumor-Active Arglabin Derivatives
219
CH3), 18.2 (C11, CH3) ppm; MS (ESI, MeOH): m/z ¼ 350.4 ([MþH]þ);
anal. calcd for C19H27NO3S (349.49): C, 65.30; H, 7.79; N, 4.01;
found: C, 65.18; H, 7.95; N, 3.87.
(3aR,4aS,6aS,7S,9aS,9bR)-1,4a-Dimethyl-7-
(2-nitroethyl)-5,6,6a,7,9a,9b-hexahydro-3H-oxireno[8,8a]-
azuleno[4,5-b]furan-8(4aH)-on (6)
To a solution of arglabin (100 mg, 0.41 mmol) in dry nitrome-
thane (5 mL), DBU (10 mg) was added and the mixture was stirred
at 248C for 1 day. The solvent was evaporated and the residue
subjected to chromatography (silica gel, CHCl3/Et2O, 95:5)
to afford 6 (83 mg, 66%) as a colorless solid; mp 1208C;
[a]D ¼ þ278 (c ¼ 7.1, CHCl3); Rf ¼ 0.6 (CHCl3/Et2O ¼ 95:5); IR
(KBr): n ¼ 3441 m, 2828 s, 1651 s, 1435 m, 1364 m, 1319 m,
1298 m, 1253 s, 1049 m cmꢁ1; UV-vis (methanol): lmax (log
e) ¼ 220 nm (2.3); 1H NMR (500 MHz, CDCl3): d ¼ 5.54 (s, 1
H, CH (2)), 4.76–4.70 (m, 2 H, CH2 (13)); 4.04 (dd, 1 H,
J ¼ 10.2 Hz, CH (9a)), 2.76 (d, 1 H, J ¼ 10.1 Hz, CH (9b)), 2.70
(d, 1 H, J ¼ 17.8 Hz, CHa (3)), 2.34–2.31 (m, 1 H, CH (7)), 2.11 (d,
1 H, J ¼ 17.5 Hz, CHb (3)), 2.07–1.91 (m, 1 H, CH (5)), 1,93 (s, 3
H, CH3 (11)), 1.62 (d, 1 H, J ¼ 12.1 Hz, CH (11)), 1.46–1.42 (m, 2
(3aR,4aS,6aS,7R,9aS,9bR)-1,4a-Dimethyl-7-(piperidin-1-
ylmethyl)-5,6,6a,7,9a,9b-hexahydro-3H-oxireno[8,8a]-
azuleno[4,5-b]furan-8(4aH)-on (4)
A solution of arglabin (80 mg, 0.32 mmol) in ethanol (5 mL)
containing dry piperidine (40.0 mg, 0.48 mmol) was stirred at
248C for 1 d. The solvent was removed under diminished pres-
sure, the residue re-dissolved in dichloromethane (20 mL),
extracted with water (3 ꢀ 10 mL), the organic phase was dried
(Na2SO4) and evaporated. Chromatography (silica gel, CH2Cl2/
MeOH, 7:3) gave 4 as a colorless solid (124 mg, 78%); mp 119–
1208C; [a]D ¼ þ66.68 (c ¼ 3.7, CHCl3); Rf ¼ 0.49 (CH2Cl2/MeOH,
7:3); IR (KBr): n ¼ 3447 m, 2854 s, 1769 s, 1649 s, 1351 m, 1313 m,
1260 s, 1229 m, 1075 m, 1029 m, 1014 m cmꢁ1; UV-vis (MeOH):
lmax (log e) ¼ 225 nm (3.46); 1H NMR (500 MHz, CDCl3): d ¼ 5.53
(s, 1 H, CH (2)), 3.98 (dd, 1 H, J ¼ 10.2 Hz, CH (9a)), 2.80 (d, 1 H,
J ¼ 10.2 Hz, CH (9b)), 2.73 (m, 2 H, CH (13)), 2.70 (d, 1 H, CHa (3),
2.57 (dd, 2 H, J6.34, 13.24 Hz, CH2 (13)), 2.40–2.30 (m, 4 H, CH2 (14)),
2.34 (m, 1 H, CH (7)), 2.11 (d, 1 H, J ¼ 16.9 Hz, CHb (3)), 2.07
(ddd, 1 H, J ¼ 15.3, 12.7 Hz, CHa(5)), 1.95 (ddd, 1 H, J ¼ 4.9,
2.7 Hz, CHb(5)), 1.91 (d, 1 H, J ¼ 4.8 Hz, CHa (12)), 1.90 (s,
3 H, CH3 (11)), 1.59 (d, 1 H, J ¼ 11.9 Hz, CH (6a)), 1.40 (d, 1 H,
J ¼ 12.0 Hz, CHb (12)), 1.31 (s, 3 H, CH3 (10)), 1,24 (m, 2 H, CH2 (6)),
1.18 (dd, 2 H, J ¼ 7.1, 14.0 Hz; CH2 (15)) ppm; 13C NMR (125 MHz,
H, CH2 (12)), 1.31 (s, 3 H, CH3 (10)), 1.24 (m, 2 H, CH2 (6)) ppm;
13
–
C NMR (125 MHz, CDCl ): d ¼ 177.1 (C8, C O), 140,2 (C1,
–
3
Cquart.), 125.0 (C2, CH), 82.9 (C9a, CH), 72.3 (C3a, Cquart.), 72.2
(C13, CH2), 62.5 (C4a, Cquart.), 52.4 (C9b, CH), 52.2 (C6a, CH),
42.7 (C7, CH), 39.5 (C3, CH2), 33.3 (C5, CH2), 25.2 (C6, CH2), 22.6
(C12, CH2), 22.5 (C10, CH3), 18.2 (C11, CH3) ppm; MS (ESI, MeOH):
m/z ¼ 330.3 ([M þ Na]þ), 636.9 ([2MþNa]þ); anal. calcd for
C16H21NO5 (307.34): C, 62.53; H, 6.89; N, 4.56; found: C, 62.38;
H, 6.99; N, 4.31.
–
(3aR,4aS,6aS,7S,9aS,9bR)-7-{[(2-Hydroxyethyl)thio]-
methyl}-1,4a-dimethyl 5,6,6a,7,9a,9b-hexahydro-3H-
oxireno[8,8a]azuleno[4,5-b]furan-8(4aH)-on (7)
CDCl ): d ¼ 178.1 (C8, C O), 140,8 (C1, Cquart.), 124.6 (C2, CH), 82.5
–
3
(C9a, CH), 72.5 (C3a, Cquart.), 62.7 (C4a, Cquart.), 57.6 (C13, CH2), 54.9
(C14, CH2), 52.5 (C9b, CH), 52.2 (C6a, CH), 43, 9 (C7, Cquart.), 39.6 C3,
CH2), 33.7 (C5, CH2), 25.9 (C6, CH2), 24.2 (C15, CH2), 22.8 (C12, CH2),
22,7 (C10, CH3), 18.3 (C11, CH3) ppm; MS (ESI, MeOH): m/z ¼ 332.4
([MþH]þ); anal. calcd for C20H29NO3 (331.45): C, 72.47; H, 8.82; N,
4.23; found: C, 72.31; H, 8.98; N, 4.11.
To a solution of arglabin (90 mg, 0.37 mmol) in ethanol (3 mL)
containing 2-mercaptoethanol (36.7 mg, 0.47 mmol), catalytical
amounts of DBU (10 mg) were added and stirring at 248C was
continued for another 6 h. The solvent was removed and the
residue subjected to chromatography (silica gel, CHCl3/Et2O, 7:3)
to yield 7 (74 mg, 62.5%) as a colorless solid; mp 119–1208C;
[a]D ¼ þ36.58 (c ¼ 4.8, CHCl3); Rf ¼ 0.33 (CHCl3/Et2O, 7:3); IR
(KBr): n ¼ 3448 m, 2946 s, 1771 m, 1731 m, 1465 m, 1371 m,
1247 m, 1179 m, 1126 m, 1017 m cmꢁ1; UV-vis (MeOH): lmax
(log e) ¼ 212 nm (2.3); 1H NMR (500 MHz, CDCl3): d ¼ 5.51
(s, 1 H, CH (2)), 4.06 (dd, 1 H, J ¼ 10.3 Hz, CH (9a)), 3.77–3.67
(m, 2 H, CH (14)), 2.85–2.83 (m, 2 H, CH2 (12)), 2.82–2.80 (m, 1 H, CH
(9b)), 2.68–2.62 (m, 3 H, CHa (3) þCH2 (13)), 2.45–2.41 (m, 1 H, CH
(7)) 2.11–2.01 (m, 2 H, CHb (3) þ CHa (9)), 1.99–1.95 (m, 1 H, CHb (5)),
1.90 (s, 3 H, CH3 (11)), 1.79–1.71 (m, 1 H, CH (6a)), 1.70–1.65
(m, 1 H, CHa (12)), 1.48–1.36 (m, 1 H, CHb (12)), 1.29 (s, 3 H, CH3
(10)), 1.24 (dd, 2 H, J ¼ 14.2, 7.1 Hz, CH2 (6)) ppm; 13C NMR
(3aR,4aS,6aS,7R,9aS,9bR)-1,4a-Dimethyl-7-(piperazin-
1-ylmethyl)-5,6,6a,7,9a,9b-hexahydro-3H-oxireno[8,8a]-
azuleno[4,5-b]furan-8(4aH)-on (5)
Following the procedure given for 4, from arglabin (80 mg,
0.32 mmol), piperazine (41.4 mg, 0.48 mmol), followed by
chromatography (silica gel, CH2Cl2/MeOH, 7:3) 5 (86 mg, 81%)
was obtained as a colorless solid; 119–1208C; [a]D ¼ 59.88
(c ¼ 3.2, CHCl3); Rf ¼ 0.53 (CH2Cl2/MeOH, 7:3); IR (KBr):
n ¼ 3447 m, 1654 s, 1376 m, 1261 m, 1222 m, 1112 m, 1060 m
cmꢁ1; UV-vis (methanol): lmax (log e) ¼ 243 nm (3.46); 1H NMR
(500 MHz, CDCl3): d ¼ 5.24 (s, 1 H, CH (2)), 3.98 (dd, 1 H,
J ¼ 10.8 Hz, CH (9a)), 2.81 (d, 1 H, J ¼ 10.2 Hz, CH (9b)), 2.73–
2.57 (m, 4 H, 2 ꢀ CH2 (13)) 2.71 (d, 1 H, J ¼ 17.9 Hz, CHa (3)), 2.41 (m,
4 H, 2 ꢀ CH2 (14), 2.30 (m, 1 H, CH (7)), 2.11 (d, 1 H, J ¼ 17.8 Hz, CHb
(3)), 2.08 (m, 1 H, CHa(5)), 1.95 (m, 1 H, J ¼ CHb(5)), 1.95 (d, 1 H,
J ¼ 2.3 Hz, CHa (12)), 1.94 (s, 3 H, CH3 (11)), 1.59 (d, 1 H, J ¼ 11.9 Hz,
CH (6a)), 1.41 (d, 1 H, J ¼ 12.3 Hz, CHb (12)), 1.31 (s, 3 H, CH3 (10), 1,23
(m, 2 H, CH (6)) ppm; 13C NMR (125 MHz, CDCl3): d ¼ 177.8 (C8,
–
(125 MHz, CDCl ): d ¼ 176.9 (C8, C O), 140,4 (C1, Cquart.), 125.1
–
3
(C2, CH), 82.8 (C9a, CH), 72.4 (C3a, Cquart.), 65.8 (C14, CH2), 62.6
(C4a, Cquart.), 52.3 (C9b, CH), 50.5 (C6a, CH), 46.7 (C7, CH), 39.5 (C3,
CH2), 36.3 (C13, CH2), 33.3 (C5, CH2), 28.7 (C6, CH2), 22.6 (C12, CH2),
22.5 (C10, CH3), 18.2 (C11, CH3) ppm; MS (ESI, MeOH): m/z ¼ 325.1
([MþH]þ); anal. calcd for C17H24SO4 (324.44): C, 62.93; H, 7.46; S,
9.88; found: C, 62.77; H, 7.68; S, 9.61.
–
C O), 140,7 (C1, Cquart.), 124.7 (C2, CH), 82.6 (C9a, CH), 72.5 (C3a,
–
Cquart.), 62.6 (C4a, Cquart.), 56.5 (C13, CH2), 53.5 (C14, CH2), 52.5
(C9b, CH), 51.8 (C6a, CH), 44, 0 (C7, Cquart.), 39.5 (C3, CH2), 33.7
(C5, CH2), 24.3 (C6, CH2), 22.8 (C12, CH2), 22,7 (C10 CH3), 18.3 (C11,
CH3) ppm; MS (ESI, MeOH): m/z ¼ 333.2 ([MþH]þ); anal. calcd
for C19H28N2O3 (332.44): C, 68.65; H, 8.49; N, 8.43; found: C,
68.51; H, 8.63; N, 8.28.
2-({[(3aR,4aS,6aS,7S,9aS,9bR)-1,4a-Dimethyl-8-oxo-
4a,5,6,6a,7,8,9a,9b-octahydro-3H-oxireno[8,8a]-
¨
azuleno[4,5-b]furan-7-yl]methyl}thio)benzoesaure (8)
Following the procedure given for 7, from arglabin (90 mg,
0.37 mmol), 2-mercaptobenzoic acid (72.4 mg, 0.47 mmol),
ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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220
R. Csuk et al.
Arch. Pharm. Chem. Life Sci. 2012, 345, 215–222
DBU (10 mg) after 48 h at 248C and chromatographic work-up
(silica gel, CH2Cl2/MeOH, 9:1), 8 (93 mg, 62.8%) was obtained as a
colorless solid; mp 1228C; [a]D ¼ þ318 (c ¼ 4.3, CHCl3); Rf ¼ 0.5
(CH2Cl2/MeOH, 9:1); IR (KBr): n ¼ 3445 m, 2945 s, 1729 m,
1452 m, 1372 m, 1239 m, 1183 m, 1119 m, 1007 m cmꢁ1; UV-
vis (MeOH): lmax (log e) ¼ 215 nm (2.33); 1H NMR (500 MHz,
CDCl3): d ¼ 7.59 (d, 1 H, J ¼ 7.6 Hz, CH (18)), 7.45 (d, 1 H,
J ¼ 7.6 Hz, CH (15)), 7.23 (dd, 1 H, J ¼ 8.9, 6.1 Hz, CH (17)),
7.15 (dd, 1 H, J ¼ 8.5, 7.3 Hz, CH (16)) 5.52 (m, 1 H, CH (2)),
3.95(dd, 1 H, J ¼ 10.3 Hz, CH (9a)), 2.85–2.83 (m, 2 H, CH2 (12)),
2.82 (d, 1 H, J ¼ 10.1 Hz, CH (9b)), 2.68 (d, 1 H, J ¼ 17.9 Hz, CHa
(3)), 2.45 (d, 1 H, J ¼ 12.5 Hz, CH (7)), 2.11–2.01 (m, 2 H, CHb (3)
þCHa (5)), 1.99 (dd, 1 H, J ¼ 15.4, 2.7 Hz, CHb (5)), 1.90 (s, 3 H, CH3
(11)), 1.79–1.71 (m, 1 H, CH (6a)), 1.29 (s, 3 H, CH3 (10)), 1,24–1.20
(m, 2 H, CH2 (6)) ppm; 13C NMR (125 MHz, CDCl3): d ¼ 177.7 (C8,
solvent was evaporated under diminished pressure, the residue
was dissolved in CH2Cl2 (25 mL), washed (5 mL) and dried
(Na2SO4). Chromatographic work-up (silica gel, hexane/ethyl
acetate, 7:3) gave 10 (65 mg, 46%) as a colorless solid; mp 115–
1168C; [a]D ¼ þ169.98 (c ¼ 3.5, CHCl3); Rf ¼ 0.6 (hexane/ethyl
acetate, 7:3); IR (KBr): n ¼ 3445 m, 2931 m, 1648 s, 1451 m,
1376 m, 1246 m, 1219 m, 1163 s, 1137 s, 1115 s, 1081 s, 1027 s,
993s cmꢁ1; UV-vis (MeOH): lmax1 (log e) ¼ 219 (2.34), lmax2
(log e) ¼ 285 nm (2.45); 1H NMR (500 MHz, CDCl3): d ¼ 5.57
(s, 1 H, CH (2)), 4.80 (dd, 1 H, J ¼ 10.8 Hz, CH (9a)), 4.70–4.51
(m, 2 H, CH2 (80)), 4.32–4.15 (m, 2 H, CH2 (60), 3.67 (d, 1 H,
J ¼ 9.7 Hz, CHa (50)), 3.33 (d, 1 H, J ¼ 9.7 Hz, CHb (50)), 2.80 (d,
1 H, J ¼ 10.2 Hz, CH (9b)), 2.70 (d, 1 H, J ¼ 18.0 Hz, CHa (3)), 2.34
(m, 1 H, CH (7)), 2.11 (d, 1 H, J ¼ 16.9 Hz, CHb (3)), 2.07 (m, 1 H, CHa (5)),
1.95 (m, 1 H, CHb (5)), 1.90 (s, 3H CH3 (11)), 1.59 (d, 1 H, J ¼ 11. 8 Hz, CH
(6a)), 1.31 (s, 3 H, CH3 (10)), 1.24 (m, 2 H, CH2 (6)), 1.18 (t, 3 H,
J ¼ 7.1 Hz, CH3 (900)) ppm; 13C NMR (125 MHz, CDCl3): d ¼ 172.9
–
–
–
C O), 170.1 (C19, C O), 140,4 (C1, Cquart.), 134.9 (C13, Cipso), 128.7
–
(C18, CH), 127.9 (C15, CH), 124.8 (C2, CH), 124.7 (C17, CH), 124.4
(C16, CH), 117.9 (C14, Cipso), 82.9 (C9a, CH), 72.8 (C3a, Cquart.), 62.6
(C4a, Cquart.), 51.3 (C9b, CH), 50.5 (C6a, CH), 45.9 (C7, CH), 39.0 (C3,
CH2), 32.6 (C5, CH2), 30.4 (C6, CH2), 22.5 (C12, CH2), 21.4 (C10, CH3),
17.1 (C11, CH3) ppm; MS (ESI, MeOH): m/z ¼ 423.4 ([MþNa]þ);
anal. calcd for C22H24SO5 (400.49): C, 65.98; H, 6.04; S, 8.01;
found: C, 65.69; H, 6.12; S, 7.85.
–
–
–
(C8, C O), 168.5 (C7 , C O) 140,3 (C1, Cquart.), 125.1 (C2, CH), 82.5 (C9a,
–
CH), 72.1 (C3a, Cquart.), 62.3 (C4a, Cquart.), 61.6 (C80, CH2), 56.4 (C9b, CH),
52.7 (C6a, CH), 50.2 (C60, CH2), 49.0 (C6, CH2), 39.6 (C3, CH2), 33.4 (C5,
CH2), 22.7 (C80, CH3), 18.2 (C50, CH2), 18.1 (C10, CH3), 14.1 (C11, CH3)
ppm; MS (ESI, MeOH): m/z ¼ 398.0 (100%, [MþNa]þ), 772.9 (50%,
[2MþNa]þ); anal. calcd for C19H25N3O5 (375.42): C, 60.79; H, 6.71; N,
11.19; found: C, 60.51; H, 6.84; N, 11.01.
Ethyl [(1R,1aS,2aR,3aS,5aS,8aS,8bR)-3a,8c-dimethyl-6-
methylen-7-oxododecahydrocyclopropa[2,3]oxireno-
[8,8a]azuleno[4,5-b]furan-1-yl]acetate (9)
To a solution of arglabin (100 mg, 0.41 mmol) in abs. CH2Cl2
containing [Rh(OAc)2]2 (10 mg) within 2 h ethyl diazoacetate
(55.7 mg, 0.48 mmol) is slowly added. After stirring for
30 min, the solvent was evaporated and the residue subjected
to chromatography (hexane/EtOAc, 1:1) to yield 9 (74 mg, 52.6%)
(3aR,4aS,6aS,7R,9aS)-1,4a-Dimethyl-
40,4a,5,50,6,6a,9a,9b-octahydro-3H-spiro[oxireno[8,8a]-
azuleno[4,5-b]furan-7,3’-pyrazol]-8-on (11)
To a solution of arglabin (100 mg, 0.41 mmol) in abs. THF (3 mL),
diazomethane (20 mL, 20 mmol, 1 M in Et2O) was added during
120 min; after stirring for an additional 30 min, the excess of
diazomethane was destroyed by adding a few drops of acetic acid.
The solvents were removed under diminished pressure and the
residue was subjected to chromatography (silica gel, CHCl3/
Et2O, 95:5) to yield 11 (117 mg, quant.) as a pale yellow solid;
mp 119–1218C; [a]D ¼ þ283.28 (c ¼ 4.24, MeOH); Rf ¼ 0.7 (CHCl3/
Et2O, 95:5); IR (KBr): n ¼ 3447 m, 3051 m, 1776 s, 1651 s, 1559 m,
1431 m, 1375 m, 1277 m, 1223 m, 1172 s, 921 s cmꢁ1; UV-vis
(MeOH): lmax (log e) ¼ 217 nm (4.24); 1H NMR (500 MHz,
CDCl3): d ¼ 5.55 (s, 1 H, CH (2)), 5.00 (dd, 1 H, J ¼ 10.0 Hz, CH
(9a)), 4.68–4.53 (m, 2 H, CH (50)), 2.85 (d, 1 H, J ¼ 10.5 Hz, CH (9b)),
2.72 (d, 1 H, J ¼ 15.2 Hz, CHa (3)), 2.12 (dd, 1 H, J ¼ 3.8, 5.6 Hz, CHa
(40)), 2.11–2.08 (m, 1 H, CHb (3)), 2.07–2.02 (m, 1 H, CHa (5)), 1.93 (s,
3 H, CH3 (11)), 1.85–1.82 (m, 1 H, CHb (5)), 1.82–1.79 (m, 1 H, CH (6a)),
1.35–1.42 (m, 1 H, CHb (40)), 1.42–1.36 (ddd, 1 H, J ¼ 9.8, 13.1 Hz, CHa
(6)), 1.26 (s, 3 H, CH3 (10)), 1.0–0.95 (m, 1 H, CHb (6)) ppm; 13C NMR
(125 MHz, CDCl3): d ¼ 172.8 (C8, C ¼ O), 140,2 (C1, Cquart.), 125.91
as
a
colorless solid; mp 134–1368C; [a]D ¼ þ898 (c ¼ 2.1,
MeOH); Rf ¼ 0.39 (hexane/EtOAc, 1:1); IR (KBr): n ¼ 3440 m,
3068 m, 1771 m, 1649 s, 1550 m, 1429 m, 1387 m, 1269 m,
1221 m, 921s cmꢁ1; UV-vis (MeOH): lmax (log e) ¼ 210 nm (2.32);
1H NMR (500 MHz, CDCl3): d ¼ 6.25 (d, 1 H, J ¼ 2.9 Hz, ¼ CHa
–
–
(11)), 5.63 (d, 1 H, J ¼ 3.2 Hz, CH (11)), 4.51–4.40 (m, 2 H, CH
b
2
(14)), 4.90–4.81 (m, 1 H, CH (8a)), 2.80 (d, 1 H, J ¼ 9.9 Hz, CH (8b)),
2.76 (m, 1 H, CH (5a)), 2.31 (d, 1 H, J ¼ 10.0 Hz, CHa (12)), 2.25–2.20
(m, 1 H, CHb (12)), 2.11 (ddd, 1 H, J ¼ 12.2, 4.2Hz, CH (1)), 2.07–1.99
(m, 2 H, CH2 (4), 1.70 (d, 1 H, J ¼ 12.1 Hz, CHa (2)), 1.45 (d, 1 H,
J ¼ 17.0 Hz, CHb (2)), 1.90 (s, 3 H, CH3 (10)),1.45 (m, 1 H, CH (1a)), 1.39
(t, 3 H, J ¼ 17.2 Hz, CH3 (15)), 1.31 (s, 3 H, CH3 (9)), 1.24 (m, 2 H, CH2
13
–
–
(5)) ppm; C NMR (125 MHz, CDCl ): d ¼ 176.9 (C7, C O), 171.4
3
–
–
–
), 121.3 (C11, CH ), 82.8 (C8a, CH), 78.9
–
2
(C13, C O), C131.5 (C6, C
quart.
(C2a, Cquart.), 62.1 (C3a, Cquart.), 50.3 (C8b, CH), 49.2 (C5a, CH), 39.5
(C2, CH2), 32.5 (C12, CH2), 31.3 (C4, CH2), 29.7 (C5, CH2), 28.0 (C11,
CH2), 27.1 (C9, CH3), 21.2 (C10, CH3), 18.2 (C8c, Cquart.), 16.2
(C1a, CH), 15.9 (C1, CH), 13.5 (C15, CH3) ppm; MS (ESI, MeOH):
m/z ¼ 347.9 ([MþH]þ); anal. calcd for C20H26O5 (346.42): C, 69.34;
H, 7.56; found: C, 69.22; H, 7.65.
´
(C2, CH), 99.4 (C7, Cquart.), 83.1 (C9a, CH), 78.2 (C5, CH2), 72.6 (C3a,
Cquart.), 62.2 (C4a, Cquart.), 56.3 (C6a, CH), 52.8 (C9b, CH), 39.6 (C3,
´
CH2), 33.5 (C5, CH2), 22.6 (C10, CH3), 22.5 (C4, CH2), 18.2 (C11, CH3)
ppm; MS (ESI, MeOH): m/z ¼ 342.9 (100%, [MþNaþMeOH]þ), 289.3
(36%, [MþH]þ); anal. calcd for C16H20N2O3 (288.34): C, 66.65; H,
6.99; N, 9.72; found: C, 66.38; H, 7.14; N, 9.56.
Ethyl[(3aR,4aS,6aS,7S,9aS)-1,4a-dimethyl-8-oxo-
4a,5,6,6a,9a,9b-hexahydro-3H-spiro[oxireno[8,8a]-
azuleno[4,5-b]furan-7,4’-[1,2,3]triazol]-10(50H)-yl]acetate
(1aS,2aR,3aS,5aS,8aS,8bS,8cR)-3a,8c-Dimethyl-6-
methylen-octahydro-2H-bisoxireno[2,3:8,8a]azuleno[4,5-
b]furan-7(3aH)-on (12)
(10)
To a solution of arglabin (90mg, 0.37 mmol) in abs. THF (5 mL)
containing CuI (10 mg), ethyl azidoacetate (118 mg, 0.9 mmol)
was added and the mixture was stirred at 248C for 4 d. The
To a solution of arglabin (100 mg, 0.41 mmol) in dry THF (5 mL),
mCPBA (346 mg, 2.0 mmol) was added and stirring at 248C con-
tinued for 12 h. The reaction mixture was diluted with Et2O
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Arch. Pharm. Chem. Life Sci. 2012, 345, 215–222
Synthesis and Biological Evaluation of Antitumor-Active Arglabin Derivatives
221
(20 mL), washed with an aq. solution of Na2CO3 (3 ꢀ 20 mL),
dried (Na2SO4), and the solvents were evaporated. The residue
was subjected to chromatography (silica gel, hexane/EtOAc, 7:3)
to yield 12 (66 mg, 61%) as a colorless solid; mp 149–1508C (lit.:
149–1518C [11,32]); [a]D ¼ þ90.98 (c ¼ 1.6, MeOH) (lit.: þ948
(CHCl3) [11,32]); Rf ¼ 0.41 (hexane/EtOAc, 7:3); IR (KBr):
n ¼ 3445 m, 3055 m, 1779 m, 1659 s, 1548 m, 1429 m, 1372 m,
1269 m, 1221 m, 1165 s, 921 s cmꢁ1; UV-vis (MeOH): lmax
(log e) ¼ 217 nm (2.35); 1H NMR (500 MHz, CDCl3): d ¼ 6.20
[10] K. J. Musulmanbekow, WO9958148A1; Chem. Abs. 1999, 131,
332093.
[11] S. M. Adekenov, WO9848789A1; Chem. Abs. 1998, 130, 480.
[12] S. M. Adekenov, M. N. Mukhametzhanos, A. D. Kagarlitskii,
Kupriyanov, Khim. Prir. Soedin. 1982, 655–666.
[13] H.-F. Wong, G. D. Brown, J. Nat. Prod. 2002, 65, 481–486.
[14] C. Bottex-Gauthier, D. Vidal, F. Picot, P. Potier, F. Menichini,
G. Appendino, Biotech. Therapeut. 1993, 4, 77–98.
–
–
–
(s, 1 H, CH (12)), 5.65 (s, 1 H, CH (12)), 4.80–4.75 (m, 1 H, CH
–
[15] G. Appendfino, P. Gariboldi, F. Menichini, Filoterapia 1991,
62, 275–276.
a
b
(8a)), 2.90 (d, 1 H, J ¼ 10.0 Hz, CH (8b)), 2.64 (m, 1 H, CH (5a)), 2.55
(dd, 1 H, J ¼ 12.1, 5.2 Hz, CH (1)), 2.15–2.08 (m, 2 H, CH2 (4), 1.76
(m, 2 H, CH2 (2)), 1.94 (s, 3 H, CH3 (11)), 1.25 (s, 3 H, CH3 (10)), 1.24
[16] S. Kalidindi, W. B. Jeong, A. Schall, R. Bandichhor, B. Nosse,
O. Reiser, Angew. Chem. 2007, 119, 6478–6481.
(m, 2 H, CH2 (5)), 13C NMR (125 MHz, CDCl ): d ¼ 176.1 (C7, C O),
–
–
3
[17] T. E. Shaikenov, S. M. Adekenov, S. Basset, M. Trived,
L. Wolfinbarger, Dokl. Minist. Nauki-Akad. Nauk Resp.
Kazakhstan 1998, 5, 64–75; Chem. Abs. 1999, 131, 67730.
–
–
139.6 (C6, ¼Cquart.) C121.4 (C12, CH ), 65.3 (C8c, Cquart.), 62.7
2
(C3a, Cquart.), 62.1 (C1, CH), 79.7 (C8a, CH), 72.0 (C2a, Cquart.),
52.5 (C8b, CH), 51.3 (C5a, CH), 33.2 (C4, CH2), 31.5 (C2,
CH2),22.6 (C5, CH2), 22.6 (C10, CH3), 18.1 (C11, CH3) ppm; MS
(ESI, MeOH): m/z ¼ 263.2 ([MþH]þ); anal. calcd for C15H18O4
(262.30): C, 68.68; H, 6.92; found: C, 68.51; H, 7.04.
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[19] R. I. Jalmahanbetova, B. B. Rakhimova, V. A. Raldugin, I. Y.
Bagryanskaya, Y. V. Gatilov, M. M. Shakirov, A. T. Kulyjasov,
S. M. Adekenov, G. A. Tolstikov, Russ. Chem. Bull, Int. Ed. 2003,
52, 748–751.
Arborescin (13)
A solution of arglabin (200 mg, 0.82 mmol) in EtOH (5 mL)
containing Pd/BaSO4 (100 mg) and quinoline (10 mg) was
hydrogenated at 20 psi for 2 h. The mixture was filtered, the
solvent evaporated and the residue subjected to chromatography
(silica gel, hexane/ethyl acetate 7:3) to yield 13 (203 mg, quant.)
as a colorless solid; mp 140–1428C (lit.: 1458C [34], 1408C [38, 39];
[a]D ¼ þ 608 (c ¼ 4.1, CHCl3) (lit.: þ 638 (CHCl3) [34], þ 608
(CHCl3) [38], þ 558 (MeOH) [40]; Rf ¼ 0.49 (hexane/EtOAc, 7:3);
MS (ESI, MeOH): m/z ¼ 271.2 ([MþNa]þ); anal. calcd for
C15H20O3 (248.32): C, 72.55; H, 8.12; found: C, 72.41; H, 8.31.
[20] R. I. Jalmakhanbetova, G. A. Atazhanova, V. A. Raldugin, I. Y.
Bagryanskaya, Y. V. Gatilov, M. M. Shakirov, S. M. Adekenov,
Chem. Nat. Prod. 2007, 43, 548–551.
[21] E. V. Tikhanova, S. M. Adekenov, N. A. Samenov, M. K.
Gilmanov, Chem. Nat. Comp. 2001, 37, 69–71.
[22] A. S. Fazylova, K. I. Itzhanova, A. T. Kulyyasov, K. M.
Turdybekov, S. M. Adekenov, Chem. Nat. Prod. 1999, 35,
305–307.
[23] A. Z. Abildaeva, R. N. Pak, A. T. Kulyyasov, S. M. Adekenov,
Eksperim. Klinichesk. Farmakol. 2004, 67, 37–39; Chem. Abs. 2004,
141, 116748.
An authentic sample of arglabin was kindly provided by Dr. Klaus-Dieter
Go¨hler, CAC Chemnitz GmbH. We like to thank PD Dr. Reinhard Paschke
from Biosolutions Halle GmbH for support. We are grateful to the Stiftung
der Deutschen Wirtschaft e.V. (SDW) for a personal scholarship to Stefan
Schwarz. The cell lines were kindly provided by Dr. Thomas Mu¨ller (Dept. of
Haematology/Oncology, Univ. Halle).
[24] S. M. Adekenov, M. M. Tagbergenova, WO2008035958A1;
Chem. Abs. 2008, 148, 363323.
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[26] K.-D. Go¨hler, J. Engelmann, WO2007079736A1; Chem. Abs.
2010, 152, 314344.
The authors have declared no conflict of interests.
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9250.
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