Synthesis and cytotoxicity evaluation of natural α-bisabolol β-d-fucopyranoside and analogues

Article abstract of DOI:10.1016/j.phytochem.2008.11.013

α-Bisabolol β-d-fucopyranoside, a cytotoxic naturally occurring compound, was efficiently synthesized along with five other α-bisabolol glycosides (β-d-glucoside, β-d-galactoside, α-d-mannoside, β-d-xyloside and α-l-rhamnoside). Glycosidation of α-bisabol

Full text of DOI:10.1016/j.phytochem.2008.11.013

Phytochemistry 70 (2009) 228–236
Contents lists available at ScienceDirect
Phytochemistry
journal homepage: www.elsevier.com/locate/phytochem
Synthesis and cytotoxicity evaluation of natural
a-bisabolol b-D-fucopyranoside and analogues
*
Marianne Piochon, Jean Legault, Charles Gauthier, André Pichette
Laboratoire d’Analyse et de Séparation des Essences Végétales (LASEVE), Département des Sciences Fondamentales, Université du Québec à Chicoutimi (UQAC),
555 boul. de l’Université, Chicoutimi, Québec, Canada G7H 2B1
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 28 August 2008
Received in revised form 16 October 2008
Available online 10 January 2009
a
-Bisabolol b-
along with five other
and -rhamnoside). Glycosidation of
provided excellent yields (83–95%). Cytotoxicity was evaluated against a broad panel of cancerous cell
lines including human and rat glioma (U-87, U-251 and GL-261) since the anticancer activity of -bisab-
olol was previously demonstrated against brain tumor cell lines. The addition of a sugar moiety markedly
increased -bisabolol cytotoxicity in most cases. Among the synthesized glycosides, -bisabolol
rhamnopyranoside exhibited the strongest cytotoxic activity with IC50 ranging from 40 to 64 M. Accord-
D
-fucopyranoside, a cytotoxic naturally occurring compound, was efficiently synthesized
-bisabolol glycosides (b- -glucoside, b- -galactoside, -mannoside, b- -xyloside
-bisabolol was performed using Schmidt’s inverse procedure and
a
D
D
a
-
D
D
a
-
L
a
a
Keywords:
a-Bisabolol
a
a
a-L-
Sesquiterpene
Glycoside
Cytotoxicity
Glioma
l
ing to ADME in silico predictions, this glycoside closely respects physicochemical parameters necessary to
cross the blood–brain barrier passively.
Ó 2008 Elsevier Ltd. All rights reserved.
Blood–brain barrier
1. Introduction
the permeability through biological barriers such as the blood–
brain barrier (Poduslo and Curran, 1994; Egleton et al., 2001). Thus,
a
-(ꢀ)-Bisabolol (1) (Fig. 1), a nontoxic sesquiterpene alcohol, is
we thought that it would be of interest to synthesize a-bisabolol
widely used in fragrances and cosmetic preparations (Madhavan,
1999). This oily compound with a sweet floral odor is frequently
found in essential oils of various plants such as chamomile (Matri-
glycosides and study their pharmacological potential especially
as very few reports about glycosidation of volatile compounds
are currently available.
caria chamomilla), which may contain up to 50% (Issac, 1979).
a
-
In this work, we report the synthesis of O-glycoside derivatives
Bisabolol (1) is well known for its anti-inflammatory properties
(Thiele et al., 1969; Jakovlev et al., 1979) and for its ability to en-
hance transepidermal drug penetration (Kadir and Barry, 1991).
of a-bisabolol (1). Cytotoxicity of pure compounds was evaluated
in vitro against several tumor cell lines including human and rat
glioma (U-87, U-251 and GL-261). Also, in order to estimate the po-
Recently, Cavalieri et al. (2004) have shown that
a
-bisabolol (1)
tential of a-bisabolol glycosides to cross through the blood–brain
exhibits a cytotoxic apoptosis-inducing effect (Darra et al., 2008)
against human glioblastoma and pancreatic carcinoma cell lines.
barrier, we evaluated in silico some important pharmacokinetic
parameters (log P, PSA and HBD) (Hitchcock and Pennington,
2006) using the ADME prediction program QikProp version 2.5
(Jorgensen and Duffy, 2002).
Like many natural sesquiterpene alcohols,
in the plant kingdom as a glycosidically bound volatile compound
(Stahl-Biskup et al., 1993). Indeed, -bisabolol b- -fucopyranoside
a-bisabolol (1) exists
a
D
(5b) (Fig. 1) was already isolated from the aerial parts of Carthamus
lanatus (San Feliciano et al., 1982) and exhibited noticeable cyto-
toxic activity by the Artemia salina assay (Mikhova et al., 2004).
2. Results and discussion
2.1. Synthesis of a-bisabolol glycosides
a-Bisabolol (1) is a lipophilic compound and, consequently, it is
poorly soluble in biological fluids. This physicochemical property
limits its possible pharmacological applications. However, glycosi-
dation of a molecule increases its hydrophilicity and thereby influ-
Quite surprisingly, studies on the glycosidation of volatile com-
pounds are scarce in the literature whereas many surveys have
been published on the isolation of glycosidically bounded volatiles
(Stahl-Biskup et al., 1993). Only a few reports about the synthesis
of either monoterpenyl or phenylpropanoid glycosides by chemical
ˇ
ences its physicochemical and pharmacokinetic properties (Kren
and Martínková, 2001). Moreover, glycosidation can also improve
´
methods (Mbaïraroua et al., 1994; Mastelic et al., 2004; Patov et al.,
2006) or biotransformation (Vijayakumar and Divakar, 2007) are
currently available and these approaches generally provide low
* Corresponding author. Tel.: +1 418 545 5011; fax: +1 418 545 5012.
E-mail address: andre_pichette@uqac.ca (A. Pichette).
0031-9422/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.phytochem.2008.11.013

M. Piochon et al. / Phytochemistry 70 (2009) 228–236
229
anhydrous CH2Cl2 using a catalytic amount of TMSOTf but dehy-
dration of the tertiary alcohol was observed. Indeed, GC–MS anal-
ysis showed the formation of a complex mixture with a-bisabolene
as a major compound (data not shown). To circumvent this prob-
lem, we performed the glycosidation reaction at ꢀ78 °C using the
inverse procedure (Schmidt and Toepfer, 1991) in which catalytic
OH
6'
4'
O
2'
5'
14
HO
HO
O
3'
OH1'
1
4
7
6
8
9
2
TMSOTf and
a-bisabolol (1) are mixed before the dropwise TCA
H
H
addition. Fully protected
a-bisabolol glycosides (5a–10a) were ob-
5
3
10
tained after 2.5 h at low temperatures (ꢀ78 to ꢀ20 °C) in excellent
15
yields (83–95%). Thereafter, deprotection of the benzoyl groups
11
(NaOH, MeOH/THF/H2O 1:2:1) afforded
a-bisabolol glycosides
12
13
(5b–10b) in isolated yields ranging from 56% to 98%. The configu-
ration of the glycosidic linkage of molecules 5b–10b was deter-
mined by the chemical shifts and the vicinal coupling constants
of the anomeric protons in 1H NMR experiments (Agrawal, 1992).
As expected, 1,2-trans-glycosides were exclusively obtained be-
cause of the presence of benzoyl protecting groups at the C-20
position of sugar TCA, which directed the anomeric selectivity of
the glycosidation reaction (Flitsch, 2005). The structures of the ses-
quiterpene glycosides were confirmed by 1D and 2D NMR spectro-
scopic experiments (1H, 13C, DEPT-135, COSY, HSQC and HMBC)
and HRMS. The physical and analytical data (1H and 13C NMR
1
5b
Fig. 1. Chemical structures of
side (5b).
a-(ꢀ)-bisabolol (1) and a-bisabolol b-D-fucopyrano-
yields. For the synthesis of a-bisabolol glycosides, we chose to use
the trichloroacetimidate (TCA) method of Schmidt (Schmidt and
Kinzy, 1994). This method usually provides higher yields than
the Koenigs–Knorr procedure and it has never been used previ-
ously for the glycosidation of volatile compounds.
TCA activated sugar donors were prepared from
(Rio et al., 1991), -mannose (Ikeda et al., 1997), -xylose (Schmidt
and Junq, 2000), -rhamnose (Gauthier et al., 2006), -glucose
(Gauthier et al., 2006) and -fucose (Ross et al., 2001) following
previously reported procedures. As a typical example (Scheme 1),
-fucose was first benzoylated using benzoyl chloride (BzCl) with
and ½a 2D5
ꢁ
) of a-bisabolol b-D-fucopyranoside (5b) were in agree-
ment with those reported for the natural product isolated from C.
D
-galactose
D
D
lanatus (San Feliciano et al., 1982).
L
D
D
2.2. Cytotoxicity evaluation
D
a-Bisabolol (1) and synthesized a-bisabolol glycosides (5b–
4-dimethylaminopyridine (DMAP) as the catalyst to afford the
derivative 2 (94%). Selective deprotection of the anomeric position
was achieved by bromination with HBr/HOAc followed by basic
hydrolysis in the presence of silver carbonate (Ag2CO3) to provide
3 (85%, two steps). The TCA derivative 4 was then prepared in 71%
yield according to Schmidt’s procedure (Schmidt and Kinzy, 1994)
using trichloroacetonitrile (CCl3CN) and cesium carbonate (Cs2CO3)
as catalyst (Urban et al., 1990).
10b) were evaluated for their anticancer activity against a broad
panel of tumor cell lines. The panel comprised human lung carci-
noma (A549), colon adenocarcinoma (DLD-1), breast adenocarci-
noma (MCF-7), melanoma (SK-MEL-2), ovary teratocarcinoma
(PA-1), prostate adenocarcinoma (PC-3), pancreas adenocarcinoma
(PANC 05.04), glioma (U-251), glioblastoma (U-87) and murine gli-
oma (GL-261). Assessments were also carried out on normal hu-
man skin fibroblasts (WS1). Inhibition of growth cells was
assessed by DNA quantification using Hoechst assay (Rago et al.,
1990) and results are presented in Table 2. They are expressed as
The synthesis of a-bisabolol glycosides (5b–10b) was achieved
according to the reaction sequence shown in Table 1. Lewis acid
trimethylsilyl trifluoromethanesulfonate (TMSOTf) was used as
the promoter of the reaction. Water is undesirable since it is a com-
petitive acceptor, so the reaction was performed under rigorously
anhydrous conditions. Glycosidation was first performed following
the normal procedure (Deng et al., 1999) at room temperature in
the concentration (lM) inhibiting 50% of the cell growth (IC50).
Etoposide and betulinic acid (BetA) were used as positive controls
in this assay.
Recently, strong anticancer activity for
U-87 glioma cells (EC50 M) has been reported in the literature
(Cavalieri et al., 2004). However, in our study, -bisabolol (1)
was found to be weakly cytotoxic against U-87 with an IC50 of
130 M (29 g/ml). This difference may be explained by the fact
that Cavalieri et al. (2004) calculated the EC50 value estimating that
only 2.5% of the initial amount of -bisabolol (1) was dissolved in
the culture medium used for biological assays.
On the whole, -bisabolol glycosides exhibited stronger activity
than the aglycone 1 except for -bisabolol b- -galactopyranoside
(9b) (IC50 >100 M). As shown in Table 2, -bisabolol -rhamno-
a-bisabolol (1) against
2
l
a
l
l
OBz
BzO
OBz
BzO
a
O
O
a
b
D-Fucose
OH
a
BzO
BzO
a
D
OBz
l
a
a-L
2
3
c
pyranoside (6b) was the most potent glycoside: pronounced cyto-
toxic activity was observed for all tumor cell lines especially
OBz
BzO
against A549 (IC50 40
were significantly different to those obtained for
>100 M, P < 0.05). With regard to brain tumor cell lines (U-251,
U-87 and GL-261), cellular growth inhibitions were also observed
for glycoside 6b (IC50 46–58 M) with significant differences com-
pared to the activity of -bisabolol (1) (P < 0.05). Moreover,
bisabolol -mannopyranoside (10b) also provided moderate
inhibitory effects particularly against MCF-7 (IC50 45 M) and
GL-261 (IC50 44 M) cancer cell lines. Furthermore, the enhance-
ment of -bisabolol cytotoxicity seems not to be solely due to an
increase in water solubility since more polar glycosides such as
lM) and PA-1 (IC50 40
lM). These results
O
1
(IC50
l
BzO
O
CCl3
NH
4
l
a
a-
a
-D
Scheme 1. Synthesis of 2,3,4-tri-O-benzoyl-a-D-fucopyranosyl trichloroacetimi-
l
date (4). Reagents and conditions: (a) BzCl (6.0 equiv.), DMAP (0.1 equiv.), py, 0° to
rt, overnight, 94%; (b) i-HBr/HOAc 33%, CH2Cl2, rt, 2 h; ii-Ag2CO3 (1.35 equiv.),
acetone/H2O 20:1, rt, 1 h, 85% (two steps); (c) CCl3CN (6.0 equiv.); Cs2CO3 (0.2
equiv.); CH2Cl2, rt, 4 h, 71%.
l
a

230
M. Piochon et al. / Phytochemistry 70 (2009) 228–236
Table 1
Synthesis of
a
-bisabolol glycosides (5b–10b) by Schmidt’s inverse procedure.
R1O
R2O
NaOH 0.25 N
MeOH/THF/H O, rt, 1 h
2
TMSOTf, 4 Å MS, CH Cl
2
-78 to -20 °C, 2.5 h
TCA (2.0 equiv)
2
H
1
H
R1 = GlyBz (5a-10a)
R2 = Gly (5b-10b)
TCAa
R1
Yieldb (%)
R2
Fuc
Yieldb (%)
98
a
/bc
5a
6a
Fuc-(OBz)3
88
5b
6b
0:1
OBz
O
BzO
BzO
O
CCl3
NH
Rha-(OBz)3
95
Rha
95
1:0
NH
O
CCl3
O
BzO
BzO
BzO
OBz
O
7a
8a
Xyl-(OBz)3
Glc-(OBz)4
95
85
7b
8b
Xyl
Glc
87
95
0:1
0:1
BzO
BzO
O
CCl
3
NH
OBz
O
BzO
BzO
BzO
O
CCl3
NH
9a
Gal-(OBz)4
90
9b
Gal
89
0:1
OBz
OBz
BzO
O
BzO
O
CCl3
NH
10a
Man-(OBz)4
83
10b
Man
56
1:0
OBz
BzO
O
BzO
BzO
O
CCl
3
NH
Fuc, b-
D
-fucopyranose; Rha,
a
-
L
-rhamnopyranose; Xyl, b-
D
-xylopyranose; Glc, b-
D
-glucopyranose; Gal, b-
D-galactopyranose; Man,
a-
D
-mannopyranose; Gly, glycone.
a
Trichloroacetimidate donors.
Isolated yield.
b
c
The configuration of the glycosidic linkage was determined by 1H NMR analysis.
glucopyranoside 8b and galactopyranoside 9b (two hexoses) were
significantly less active than the less polar rhamnopyranoside 6b (a
deoxy sugar). Thus, these preliminary cytotoxic results showed
that adding a sugar moiety may improve the cytotoxic activity of
2.3. In silico prediction of pharmacokinetic parameters
The major difficulty in the discovery of anti-glioma drugs is to
find active compounds, which must be nontoxic, sufficiently solu-
ble in blood to be bioavailable and sufficiently lipophilic to pass
through the blood–brain barrier (BBB). Many promising anti-gli-
oma drugs are discarded because they do not respect one of these
conditions. Glycosidation is an interesting method to improve the
a-bisabolol (1) depending on the nature of the glycone. Otherwise,
as -bisabolol (1) and sugar moieties are natural compounds de-
a
void of toxicity (Madhavan, 1999), we may suppose that resulting
glycosides should also be biocompatible. Further in vivo biological
assays are needed to confirm this hypothesis.
ˇ
water solubility of hydrophobic compounds (Kren and Martínková,

M. Piochon et al. / Phytochemistry 70 (2009) 228–236
231
Table 2
In vitro cytotoxicity of
a
-bisabolol glycosides (5b–10b) measured by Hoechst assay.
M)a,b
Compound
Panel cell lines/IC50
(l
A549 DLD-1
MCF-7
MEL-2
PA-1
PANC
PC-3
>150
U-251
>150
U-87
GL-261
WS1
>150
1
5b
6b
7b
80
61
40
63
94
9
117
96
61
98
112
7
106
75
45
61
88
9
140 12
93 10
>150
109
130 15
114
90
54
6
6
4
3
6
8
4
8
2
4
3
2
92
62
8
4
64
40
52
7
3
4
6
98
9
107
58
6
4
84
46
83
9
4
9
7
3
6
87
3
64
99
99
5
6
4
58
89
4
8
64
93
4
3
100
2
112
5
82
8b
5
>150
>150
81 10
118 15
128
>150
7
>150
>150
96 13
>150
123
9
109
>150
8
9b
111 14
>150
>150
>150
>150
10b
BetAc
Etoposide
53
10
<1.0
4
1
79
15
<1.0
7
1
45
41
<1.0
1
1
81
36
<1.0
5
5
49
23
<1.0
4
1
74
3
72
43
<1.0
1
1
92
33
<1.0
7
2
68
7
44
1
88
12
<1.0
4
1
NTd
NTd
<1.0
NTd
<1.0
3
2
a
Data represent mean values standard deviations for two independent experiments made in triplicate.
According to NCI criteria a pure compound is considered weakly active when IC50 is between 100 and 50
b
lM, moderately active when IC50 is between 49 and 10 lM, and
strongly active when IC50 is between 9 and 1
l
M (Boyd, 1997).
c
Betulinic acid from Indofine Chemical Company Inc. was used as a positive control (Kessler et al., 2007).
d
Not tested.
2001). However, it is less well known that the addition of a sugar
moiety can also enhance the BBB permeability. This seems para-
doxical but it has already been reported that glycosidation of neu-
ropeptides can enhance their entry into the brain (Egleton et al.,
2001).
study suggests that the lipophilicity of a-bisabolol (1) has been de-
creased by the addition of a rhamnose moiety without dramati-
cally altering its capacity to pass through biological barriers
especially the BBB. It would be interesting to confirm this hypoth-
esis with an in vitro model of the BBB which imitates the in vivo
situation.
The in silico prediction of pharmacokinetic parameters is a use-
ful tool, which allows estimating the ability of compounds to pass
through the BBB based on its physicochemical properties. Hitch-
cock and Pennington (2006) have recently established a list of
parameters involved in the BBB penetration and their optimal val-
ues based on the 25 top-selling central nervous system drugs in
2004. Suggested physicochemical property ranges for increasing
the potential for BBB penetration are shown in Table 3. Important
parameters are molecular mass (MW, g molꢀ1), hydrogen bond do-
nor (HBD), polar surface area (PSA, Å) and lipophilicity which is
indicated by the calculated partition coefficient (clogP). The ADME
prediction program QikProp version 2.5 (Jorgensen and Duffy,
2002) was used to evaluate these parameters in silico. As shown
3. Conclusions
In summary, the synthesis of a series of
(5b–10b), including the natural -bisabolol b-
(5b), was achieved. Glycosidation of the sesquiterpene alcohol
a
-bisabolol glycosides
a
D
-fucopyranoside
a-
bisabolol (1) was performed using Schmidt’s inverse procedure
and provided excellent yields. The biological screening showed
that glycosidation may improve the cytotoxic activity of
lol (1) especially when adding -rhamnopyranoside or
nopyranoside moieties. With regard to glioma cell lines,
bisabolol -rhamnopyranoside (6b) was much more active than
-bisabolol (1) itself, and according to in silico predictions, this gly-
a-bisabo-
a
-L
a-D-man-
a
-
a-L
in Table 3,
a-bisabolol (1) falls within the limits for passing
a
through the BBB. However, the lipophilic character of 1 (clog
P = 4.3) decrease its bioavailability and, consequently, may limits
its chances to reach the BBB. If we compare the two most active
coside closely fits with physicochemical parameters necessary to
cross the BBB passively. Other functional groups could be attached
to the a-bisabolol (1) structure. For example, some specific biore-
movable moieties could be introduced with the aim of focusing
glycosides against glioma cell lines (6b and 10b), a-bisabolol a-L-
rhamnopyranoside (6b) fits within the limits for passing through
the BBB (clog P = 2.8; MW = 368.3 g/mol, PSA = 74.8 Å). In fact, for
the glycoside 6b, the HBD (=3) is the only parameter not satisfied
since the suggested limit is less than 3. Furthermore, the additional
on definite organs especially when brain delivery is targeted (Bur-
ger and Abraham, 2003). Such structural modifications of a-bisab-
olol (1) are currently in progress in our laboratory.
alcohol at C-6 in the
three hexoses (8b–10b) apparently does not allow them to fulfill
a-bisabolol glycosides derivated from the
4. Experimental
the permeability conditions (HBD >3; PSA >90 Å). Thus, this in silico
4.1. General experimental procedures
Air and water sensitive reactions were performed in flame-
dried glassware under Ar atmosphere. Moisture sensitive reagents
were introduced via a dry syringe. CH2Cl2 was distilled from CaH2
and THF was distilled from sodium with benzophenone ketyl. Flash
column chromatography (FCC) was carried out using either 60–230
mesh silica gel or a high performance flash chromatography sys-
tem (HPFC-Analogix F12-40) equipped with a silica gel column
(F12-M, 8 g). Analytical thin layer chromatography (TLC) was per-
formed with silica gel 60 F254, 0.25 mm pre-coated TLC plates and
visualized using UV254 and cerium molybdate (2 g Ce(SO4)4(NH4)4,
5 g MoO4(NH4)2, 200 ml H2O, and 20 ml H2SO4) with charring. All
of the chemical yields are not optimized and generally represent
the result of the mean of two experiments. 1H NMR spectra were
recorded at 400 MHz and 13C NMR were recorded at 100 MHz on
an Avance 400 Bruker spectrometer equipped with a 5 mm QNP
probe. Elucidations of chemical structures were based on 1H, 13C,
Table 3
In silico prediction of a-bisabolol glycosides parameters involved in BBB penetration.
Compound
Sugar
MW (g/mol)a
HBDb
clog Pc
PSA (Å)d
1
5b
6b
7b
8b
9b
10b
–
222.4
368.3
368.3
354.5
384.5
384.5
384.5
<500
1
3
3
3
4
4
4
<3
4.3
3.2
2.8
2.7
2.2
2.1
2.1
2–5
19.3
70.3
74.8
74.6
93.6
93.4
96.6
<90
Fuc
Rha
Xyl
Glc
Gal
Man
Suggested limitse
a
Molecular weight.
Hydrogen bond donor.
Calculated partition coefficient.
Polar surface area.
Hitchcock and Pennington (2006).
b
c
d
e

232
M. Piochon et al. / Phytochemistry 70 (2009) 228–236
Table 5
DEPT-135, COSY, HSQC and HMBC NMR experiments. Chemical
shifts are reported in parts per million (ppm) relative to residual
solvent peaks or trimethylsilane (TMS). Signals are reported as m
(multiplet), s (singlet), d (doublet), dd (doublet of doublets), t (trip-
let), br s (broad singlet), br t (broad triplet), and coupling constants
are reported in Hertz (Hz). The labile OH NMR signals appearing
sometimes were not listed. Optical rotations were obtained using
sodium D line at ambient temperature on a Rudolph Research Ana-
lytical Autopol IV automatic polarimeter. Melting points are uncor-
rected. High resolution electrospray ionization mass spectral data
(HR-ESI-MS) were obtained at the department of Chemistry,
Queen’s University, Ontario, Canada.
13C NMR spectroscopic data [100 MHz, d (ppm)] for compounds 5b–10b.
C no.
5ba
6bb
7bc
8bb
9bb
10ba
1
2
3
4
5
6
7
8
27.0
27.1
27.3
27.8
27.8
26.7
120.6
134.3
32.0
23.6
40.7
81.3
36.1
22.8
124.2
131.7
17.8
25.8
21.0
120.6
134.5
31.1
23.5
41.0
81.8
37.9
21.8
125.0
131.2
18.0
25.8
20.3
23.5
121.7
134.9
32.1
25.0
42.4
81.8
38.3
23.2
125.7
132.1
17.8
25.9
20.6
23.5
121.2
134.7
31.7
24.0
41.8
82.3
38.6
22.5
125.5
131.6
17.8
25.9
20.4
23.6
121.7
135.0
32.1
24.5
42.5
82.5
39.0
22.8
126.3
131.7
17.9
25.9
20.4
23.6
121.8
134.9
32.1
24.5
42.5
82.3
39.0
22.8
126.3
131.6
17.9
25.9
20.5
23.6
9
10
11
12
13
14
15
4.2. Synthesis of 1,2,3,4-tetra-O-benzoyl-a-D-fucopyranose (2)
23.5
Benzoyl chloride (4 ml, 36.5 mmol) was slowly added to an ice-
cold solution of -fucose (1.0 g, 6.0 mmol) in anhydrous pyridine
10
20
30
40
50
60
97.1
72.0
74.4
71.9
70.4
16.7
95.6
72.5
74.1
73.8
70.1
18.0
98.4
74.4
77.3
70.6
66.0
98.6
75.4
78.4
71.7
77.4
63.0
99.1
72.9
75.3
69.9
76.0
62.0
94.0
72.8
72.0
66.6
72.5
61.1
D
(13 ml) with DMAP (74 mg, 0.61 mmol) as catalyst. The reaction
was stirred overnight at room temperature and then quenched
with MeOH (15 ml). The mixture was diluted with CH2Cl2 and
washed with cold 5 N H2SO4, saturated NaHCO3 solution and brine.
The solvents of the dried solution (MgSO4) were evaporated under
reduced pressure and the residue was purified by FCC (hexanes/
EtOAc, 4:1–7:3) to give 2 as a white foam (3.33 g, 94%): Rf 0.50
a
In CDCl3.
In MeOD.
In CDCl3/MeOD 1:1.
b
c
(hexanes/EtOAc, 7:3); mp 73–75 °C; ½a D25
ꢁ
+239.8 (c 1.00, CH2Cl2);
1H NMR spectroscopic data of 2 were in agreement with those pub-
lished in the literature (Ross et al., 2001). 13C NMR (CDCl3) d: 16.3
(C-6), 67.7 (C-2), 68.0 (C-5), 69.9 (C-3), 71.5 (C-4), 90.9 (C-1),
128.8–133.9 (C–Ar), 164.8, 165.7, 165.9, 166.0 (4 ꢂ C@O); HR-
ESI-MS m/z 603.1609 [M+Na]+ (calcd. for C34H28O9Na, 603.1631).
layer was dried (MgSO4), filtered and the solvents were evaporated
under reduced pressure. The residue was dissolved in acetone
(22 ml), H2O (0.9 ml) and CH2Cl2 (2 ml). Ag2CO3 (2.0 g, 7.3 mmol)
was added in portions and the reaction was stirred for 1 h at room
temperature, then the mixture was filtered through a bed of celite
and anhydrous MgSO4. The filtrate was concentrated under re-
duced pressure and the residue was purified by FCC (hexanes/
4.3. Synthesis of 2,3,4-tri-O-benzoyl-a,b-D-fucopyranose (3)
HBr/HOAc (3 ml, 33%) was added under Ar to a solution of 2
(2.4 g, 4.2 mmol) in dry CH2Cl2 (13 ml). The reaction mixture was
stirred at room temperature for 2.5 h, then the solution was
washed with saturated NaHCO3 solution and brine. The organic
EtOAc, 7:3–3:2) to give 3 (a:b = 5:1) as a white foam (1.74 g,
85%): Rf 0.22 and 0.35 (hexanes/EtOAc, 7:3); mp 75–77 °C; ½a D25
ꢁ
+220.7 (c 1.00, CH2Cl2); lit. (Ross et al., 2001) ½a D22
ꢁ
+247.4 (c 1.00,
CHCl3); 1H NMR spectroscopic data of 3 were in agreement with
Table 4
13C NMR spectroscopic data [100 MHz, d (ppm)] for compounds 5a–10a in CDCl3.
C no.
5a
26.7
6a
26.8
7a
26.5
8a
26.6
9a
26.6
10a
26.9
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
120.2
134.4
30.8
22.8
40.5
82.3
38.3
21.7
124.9
131.3
18.0
25.9
19.9
23.5
120.7
134.3
31.3
23.9
40.9
82.6
37.4
22.4
124.5
131.7
17.9
25.5
20.4
23.5
120.4
134.2
30.9
23.1
40.7
82.4
38.2
22.4
124.7
131.5
17.8
25.9
20.1
23.5
120.2
134.2
30.8
23.1
40.1
82.7
38.3
21.7
124.6
131.4
17.8
25.7
19.7
23.3
120.3
134.3
30.8
23.0
40.8
82.7
38.4
21.8
124.7
131.4
17.9
25.8
19.7
23.4
120.5
134.5
31.2
23.8
40.9
82.9
36.4
22.2
124.2
132.0
17.8
25.8
21.1
23.5
10
20
30
40
50
60
95.8
70.1
72.5
71.4
69.6
16.6
91.8
72.4
70.4
72.2
67.1
17.8
95.2
71.4
71.6
70.0
61.8
96.0
72.3
73.4
70.2
72.1
63.8
96.3
70.1
72.1
68.5
71.3
62.6
91.8
72.4
70.4
67.3
69.3
63.5
C–Ar
128.4–130.2
133.1–133.5
128.4–130.0
133.2–133.5
128.4–130.0
133.2–133.5
128.4–129.9
133.1–133.5
128.4–130.2
133.2–133.6
128.4–130.1
133.1–133.5
C@O
165.4
165.9
166.3
165.8
165.9
166.0
165.2
165.7
165.8
165.1
165.4
166.0
166.2
165.3
165.7
165.8
166.2
165.7
165.7
165.8
166.4

M. Piochon et al. / Phytochemistry 70 (2009) 228–236
233
those published in the literature (Ross et al., 2001). 13C NMR
(CDCl3) (anomer ) d: 16.3 (C-6), 65.0 (C-5), 68.4 (C-3), 69.5 (C-
2), 72.0 (C-4), 91.0 (C-1), 128.4–133.8 (C–Ar), 165.8, 166.1, 166.2
(3ꢂ C@O); HR-ESI-MS m/z 477.1547 [M+H]+ (calcd. for C27H25O8,
477.1549).
H-8
H-15), 1.84 (m, 1H, H-6), 1.94 (m, 1H, H-1
2.01 (m, 2H, H-1b, H-4 ), 2.06 (m, 1H, H-4b), 2.08 (m, 1H, H-9a
a
), 1.62 (m, 1H, H-8b), 1.65 (s, 3H, H-12), 1.69 (s, 6H, H-13,
), 1.98 (m, 1H, H-5b),
),
a
a
a
2.10 (m, 1H, H-9b), 4.36 (m, 1H, H0-5), 5.13 (br t, 1H, J = 7 Hz, H-
10), 5.32 (br s, 1H, H0-1), 5.43 (br s, 1H, H-2), 5.48 (m, 1H, H0-2),
5.69 (t, 1H, J = 9.7 Hz, H0-4), 5.86 (dd, 1H, J = 10.2 Hz, J = 3.2 Hz,
H0-3), 7.23–7.31 (m, 2H, H–Ar), 7.35–7.45 (m, 3H, H–Ar), 7.46–
7.55 (m, 3H, H–Ar), 7.57–7.63 (m, 1H, H–Ar), 7.83–7.87 (m, 2H,
H–Ar), 7.98–8.02 (m, 2H, H–Ar), 8.09–8.14 (m, 2H, H–Ar); 13C
NMR (CDCl3) see Table 4; HR-ESI-MS m/z 703.3274 [M+Na]+ (calcd.
for C42H48O8Na, 703.3246).
4.4. Synthesis of 2,3,4-tri-O-benzoyl-a-D-fucopyranosyl
trichloroacetimidate (4)
CCl3CN (2 ml, 20.1 mmol) was added to a solution of 3 (1.6 g,
3.4 mmol) and Cs2CO3 (220 mg, 0.67 mmol) in CH2Cl2 (27 ml).
The reaction mixture was stirred overnight at room temperature
and then filtered off. The solvents of the filtrate were evaporated
under reduced pressure and the residue was purified by FCC (hex-
anes/EtOAc, 7:3) to give 4 as a white foam (1.6 g, 71%): Rf 0.41
4.8. a-Bisabolol 2,3,4-tri-O-benzoyl-b-D-xylopyranoside (7a)
This compound was prepared from
a-bisabolol (55 ll,
(hexanes/EtOAc, 7:3); mp 70–72 °C; ½a D25
ꢁ
+183.2 (c 1.00, CH2Cl2);
0.23 mmol, 1) and 2,3,4-tri-O-benzoyl- -xylopyranosyl trichlo-
a-D
lit. (Kitagawa et al., 1989) ½a D24
ꢁ
+196.0 (CHCl3); 1H and 13C NMR
roacetimidate (Schmidt and Junq, 2000) (278 mg, 0.460 mmol).
spectroscopic data of 4 were in agreement with those published
in the literature (Ross et al., 2001). HR-ESI-MS m/z 642.0465
[M+Na]+ (calcd. for C29H24NO8NaCl3, 642.0465).
Purification by FCC (hexanes/EtOAc 9:1) afforded 7a as a white
foam (145 mg, 95%): Rf 0.69 (hexanes/EtOAc 7:3); ½a D25
ꢀ43.6 (c
ꢁ
1.00, CH2Cl2); 1H NMR (CDCl3) d: 0.97 (m, 1H, H-5
a), 1.10 (s, 3H,
H-14), 1.51 (m, 1H, H-8
1.61 (m, 1H, H-8b), 1.67 (s, 3H, H-13), 1.68 (m, 1H, H-6), 1.69 (m,
1H, H-1 ), 1.72 (m, 1H, H-4 ), 1.74 (m, 1H, H-5b), 1.80 (m, 1H,
H-4b), 1.83 (m, 1H, H-1b), 1.94 (m, 1H, H-9 ), 2.16 (m, 1H, H-
9b), 3.63 (dd, 1H, J = 11.9 Hz, J = 8.1 Hz, H0-5
), 4.43 (dd, 1H,
a), 1.56 (s, 3H, H-15), 1.59 (s, 3H, H-12),
4.5. General procedure for the synthesis of benzoylated a-bisabolol
glycosides (5a–10a)
a
a
a
A solution of
a-bisabolol (1 equiv., 1) in dry CH2Cl2 (10 ml
a
mmolꢀ1) was stirred for 15 min with 4 Å molecular sieves at
ꢀ78 °C in an ice CO2/acetone bath. TMSOTf (0.1 equiv.) was added
under Ar while keeping rigorous anhydrous conditions. Then, a
solution of imidate (2 equiv.) in dry CH2Cl2 (3 ml mmolꢀ1) cooled
at 0 °C was added dropwise over 5 min with continuous stirring.
The reaction was allowed to warm to ꢀ20 °C over 2.5 h. When no
J = 11.9 Hz, J = 4.6 Hz, H0-5b), 5.00 (d, 1H, J = 6.2 Hz, H0-1), 5.10 (br
t, 1H, J = 7.1 Hz, H-10), 5.18 (br s, 1H, H-2), 5.32 (m, 1 H, H0-4),
5.42 (dd, 1H, J = 8.1 Hz, J = 6.2 Hz, H0-2), 5.79 (t, 1H, J = 8.1 Hz, H0-
3), 7.29–7.43 (m, 6H, H–Ar), 7.44–7.59 (m, 3H, H–Ar), 7.88–8.04
(m, 6H, H–Ar); 13C NMR (CDCl3) see Table 4; HR-ESI-MS m/z
689.3083 [M+Na]+ (calcd. for C41H46O8Na, 689.3090).
a-bisabolol (1) could be detected by TLC, the reaction was quenched
by addition of Et3N (4 equiv.). The solvents were evaporated under
4.9. a-Bisabolol 2,3,4,6-tetra-O-benzoyl-b-D-glucopyranoside (8a)
reduced pressure and the resulting residue was purified by FCC.
This compound was prepared from -bisabolol (55
a
ll,
4.6.
a-Bisabolol 2,3,4-tri-O-benzoyl-b-
D-fucopyranoside (5a)
0.23 mmol, 1) and 2,3,4,6-tetra-O-benzoyl-a-D-glucopyranosyl tri-
chloroacetimidate (Gauthier et al., 2006) (340 mg, 0.460 mmol).
This compound was prepared from
a
-bisabolol (55
l
l,
Purification by FCC (hexanes/EtOAc 9:1–4:1) afforded 8a as a white
0.23 mmol, 1) and 2,3,4-tri-O-benzoyl- -fucopyranosyl trichlo-
a-
D
foam (143 mg, 85%): Rf 0.26 (hexanes/EtOAc 4:1); ½a D25
ꢀ11.5 (c
ꢁ
roacetimidate (Kitagawa et al., 1989) (285 mg, 0.460 mmol, 4).
1.00, CH2Cl2); mp 139–141 °C; 1H NMR (CDCl3) d: 1.00 (m, 1 H,
Purification by FCC (hexanes/EtOAc 19:1–9:1) afforded 5a as a
H-5
1.53 (s, 3H, H-12), 1.56 (s, 3H, H-13), 1.62 (m, 1H, H-1
(m, 1H, H-8b), 1.64 (m, 1H, H-4 ), 1.68 (m, 1H, H-6), 1.69 (m,
1H, H-5b), 1.76 (m, 1H, H-4b), 1.80 (m, 1H, H-1b), 1.94 (m, 1H,
H-9
), 2.14 (m, 1H, H-9b), 4.15 (m, 1H, H0-5), 4.45 (dd, 1H,
J = 12.1 Hz, J = 5.9 Hz, H0-6
), 4.58 (dd, 1H, J = 12.1 Hz, J = 3.0 Hz,
a
), 1.10 (s, 3H, H-14), 1.47 (m, 1H, H-8
a
), 1.50 (s, 3H, H-15),
white foam (138 mg, 88%): Rf 0.59 (hexanes/EtOAc 7:3); ½a D25
ꢁ
a), 1.63
+95.0 (c 1.00, CH2Cl2); mp 147–149 °C; 1H NMR (CDCl3) d: 0.95
a
(m, 1H, H-5
1.46 (m, 1H, H-8
(s, 3H, H-12), 1.64 (m, 1H, H-4
H-6), 1.76 (m, 1H, H-5b), 1.83 (m, 1H, H-4b), 1.85 (m, 1H, H-1
1.97 (m, 1H, H-9 ), 2.27 (m, 1H, H-9b), 4.03 (dd, 1H, J = 12.9 Hz,
a
), 1.06 (s, 3H, H-14), 1.30 (d, 3H, J = 6.2 Hz, H0-6),
), 1.55 (s, 3H, H-15), 1.59 (m, 1H, H-8b), 1.60
), 1.67 (s, 3H, H-13), 1.73 (m, 1H,
),
a
a
a
a
a
H0-6b), 4.98 (br t, 1H, J = 6.7 Hz, H-10), 5.04 (d, 1H, J = 7.8 Hz, H0-
1), 5.11 (br s, 1H, H-2), 5.58 (m, 1H, H0-2), 5.64 (m, 1H, H0-4),
5.93 (m, 1H, H0-3), 7.22–7.30 (m, 2H, H–Ar), 7.30–7.43 (m, 7H,
H–Ar), 7.44–7.57 (m, 3H, H–Ar), 7.79–7.86 (m, 2H, H–Ar), 7.85–
7.97 (m, 4H, H–Ar), 7.98–8.05 (m, 2H, H–Ar); 13C NMR (CDCl3)
see Table 4; HR-ESI-MS m/z 823.3429 [M+Na]+ (calcd. for
C41H46O8Na, 823.3458).
a
J = 6.5 Hz, H0-5), 4.92 (d, 1H, J = 7.8 Hz, H0-1), 5.06 (br t, 1H,
J = 6.8 Hz, H-10), 5.18 (br s, 1H, H-2), 5.56 (dd, 1H, J = 10.5 Hz,
J = 3.5 Hz, H0-3), 5.69 (d, 1H, J = 3.3 Hz, H0-4), 5.78 (dd, 1H,
J = 10.5 Hz, J = 7.8 Hz, H0-2), 7.19–7.27 (m, 2H, H–Ar), 7.31–7.44
(m, 3H, H–Ar), 7.45–7.53 (m, 3H, H–Ar), 7.56–7.65 (m, 1H, H–Ar),
7.73–7.81 (m, 2H, H–Ar), 7.88–8.00 (m, 2H, H–Ar), 8.09–8.20 (m,
2H, H–Ar); 13C NMR (CDCl3) see Table 4; HR-ESI-MS m/z
703.3281 [M+Na]+ (calcd. for C42H48O8Na, 703.3246).
4.10. a-Bisabolol 2,3,4,6-tetra-O-benzoyl-b-D-galactopyranoside (9a)
This compound was prepared from
a
-bisabolol (55
ll,
4.7.
a
-Bisabolol 2,3,4-tri-O-benzoyl-
a
-L
-rhamnopyranoside (6a)
0.23 mmol, 1) and 2,3,4,6-tetra-O-benzoyl-a-D-galactopyranosyl
trichloroacetimidate (Rio et al., 1991) (340 mg, 0.460 mmol). Puri-
This compound was prepared from
a
-bisabolol (55
l
l,
fication by FCC (hexanes/EtOAc 19:1–9:1) afforded 9a as a white
0.23 mmol, 1) and 2,3,4-tri-O-benzoyl- -rhamnopyranosyl tri-
a-
L
foam (147 mg, 90%): Rf 0.67 (hexanes/EtOAc 7:3); ½a D25
ꢁ
+226.1 (c
chloroacetimidate (Gauthier et al., 2006) (284 mg, 0.460 mmol).
0.5, CH2Cl2); mp 57–59 °C; 1H NMR (CDCl3) d: 1.00 (m, 1H, H-
Purification by FCC (hexanes/EtOAc 9:1) afforded 6a as a white
5
a
), 1.10 (s, 3H, H-14), 1.49 (m, 1H, H-8
1.59 (s, 6H, H-12, H-13), 1.56 (s, 3H, H-13), 1.62 (m, 1H, H-1
1.65 (m, 1H, H-8b), 1.67 (m, 1H, H-4 ), 1.71 (m, 1H, H-6), 1.73
(m, 1H, H-5b), 1.78 (m, 1H, H-4b), 1.80 (m, 1H, H-1b), 1.98 (m,
a
), 1.52 (s, 3H, H-15),
foam (150 mg, 95%): Rf 0.44 (hexanes/Et2O 4:1); ½a D25
ꢁ
+89.3 (c
a),
1.00, CH2Cl2); mp 44–46 °C; 1H NMR (CDCl3) d: 1.27 (s, 3H, H-
a
14), 1.32 (d, 3H, J = 6.2 Hz, H0-6), 1.43 (m, 1H, H-5
a), 1.59 (m, 1H,

234
M. Piochon et al. / Phytochemistry 70 (2009) 228–236
1H, H-9
a
), 2.22 (m, 1H, H-9b), 4.29 (t, 1H, J = 6.5 Hz, H0-5), 4.41 (dd,
), 4.57 (dd, 1 H, J = 11.1 Hz,
NMR (MeOD) d: 1.16 (s, 3H, H-14), 1.21 (d, 3H, J = 6.4 Hz, H0-6),
1.30 (m, 1H, H-5 ), 1.54 (m, 2H, H-8), 1.61 (s, 3H, H-12), 1.63 (s,
1H, J = 11.3 Hz, J = 6.2 Hz, H0-6
a
a
J = 6.8 Hz, H0-6b), 5.01 (m, 2 H, H0-1, H-10), 5.14 (br s, 1H, H-2),
5.62 (dd, 1H, J = 10.5 Hz, J = 3.5 Hz, H0-3), 5.83 (dd, 1H,
J = 10.5 Hz, J = 7.8 Hz, H0-2), 5.98 (d, 1H, J = 2.9 Hz, H0-4), 7.20–
7.29 (m, 2H, H–Ar), 7.33–7.46 (m, 5H, H–Ar), 7.46–7.65 (m, 5H,
H–Ar), 7.75–7.83 (m, 2H, H–Ar), 7.91–7.98 (m, 2H, H–Ar), 7.99–
8.05 (m, 2H, H–Ar), 8.06–8.14 (m, 2H, H–Ar); 13C NMR (CDCl3)
see Table 4; HR-ESI-MS m/z 823.3441 [M+Na]+ (calcd. for
C41H46O8Na, 823.3458).
3H, H-15), 1.67 (s, 3H, H-13), 1.71 (m, 1H, H-6), 1.86 (m, 1H, H-
5b), 1.88 (m, 2H, H-1), 1.96 (m, 2H, H-4), 2.01 (m, 1H, H-9), 3.36
(m, 1H, H0-3), 3.68 (m, 1H, H0-2), 3.70 (m, 1H, H0-4), 3.76 (m, 1H,
H0-5), 4.95 (s, 1H, H0-1), 5.09 (br t, 1H, J = 7.1 Hz, H-10), 5.36 (br
s, 1H, H-2); 13C NMR (MeOD) see Table 5; HR-ESI-MS m/z
391.2441 [M+Na]+ (calcd. for C21H36O5Na, 391.2460).
4.15. a-Bisabolol b-D-xylopyranoside (7b)
4.11.
a
-Bisabolol 2,3,4,6-tetra-O-benzoyl-
a
-
D
-mannopyranoside (10a)
7a (135 mg, 0.203 mmol) was treated according to the corre-
sponding general procedure. The residue was purified by FCC (hex-
anes/EtOAc 7:3–3:7) to afford 7b as a white powder (62 mg, 87%):
This compound was prepared from
0.23 mmol, 1) and 2,3,4,6-tetra-O-benzoyl-
trichloroacetimidate (Ikeda et al., 1997) (340 mg, 0.460 mmol).
a-bisabolol (55
ll,
a
-D
-mannopyranosyl
Rf 0.38 (EtOAc); ½a D25
ꢁ
ꢀ50.8 (c 1.00, CHCl3); 1H NMR (MeOD/CDCl3
1:1) d: 1.17 (s, 3H, H-14), 1.28 (m, 1H, H-5a), 1.48 (m, 1H, H-8a),
Purification by FCC (hexanes/EtOAc 19:1–9:1) afforded 10a as a
1.60 (m, 1H, H-8b), 1.61 (s, 3H, H-12), 1.64 (s, 3H, H-15), 1.67 (s,
white foam (152 mg, 83%): Rf 0.66 (hexanes/EtOAc 7:3); ½a D25
ꢁ
3H, H-13), 1.76 (m, 1H, H-6), 1.81 (m, 1H, H-1 ), 1.91 (m, 1H, H-
a
ꢀ61.6 (c 0.5, CH2Cl2); mp 56–58 °C; 1H NMR (CDCl3) d: 1.27 (s,
4a), 1.97 (m, 1H, H-9a), 1.98 (m, 1H, H-1b), 1.99 (m, 1H, H-4b),
3H, H-14), 1.45 (m, 1H, H-5
a
), 1.60 (m, 1H, H-8
a
), 1.62 (s, 3H, H-
2.01 (m, 1H, H-5b), 2.15 (m, 1H, H-9b), 3.18 (m, 1H, H0-5b), 3.23
12), 1.67 (s, 3H, H-13), 1.68 (s, 3H, H-15), 1.69 (m, 1H, H-8b),
1.87 (m, 1H, H-6), 1.93 (m, 1H, H-1 ), 2.02 (m, 1H, H-1b), 2.03
(m, 1H, H-5b), 2.04 (m, 1H, H-4 ), 2.07 (m, 2H, H-9), 2.13 (m,
1H, H-4b), 4.48 (m, 1H, H0-6 ), 4.60 (m, 1H, H0-5), 4.62 (m, 1H,
(m, 1H, H0-2), 3.35 (m, 1H, H0-3), 3.54 (m, 1H, H0-4), 3.85 (dd, 1H,
a
J = 11.4 Hz, J = 5.2 Hz, H0-5 ), 4.44 (d, 1 H, J = 7.3 Hz, H0-1), 5.06
a
a
(br t, 1H, J = 7.1 Hz, H-10), 5.36 (br s, 1H, H-2); 13C NMR (MeOD/
CDCl3 1:1) see Table 5; HR-ESI-MS m/z 355.2498 [M+H]+ (calcd.
for C20H35O5, 355.2484).
a
H0-6b), 5.13 (br t, 1H, J = 7.0 Hz, H-10), 5.41 (m, 2H, H-2, H0-1),
5.53 (m, 1H, H0-2), 5.94 (dd, 1H, J = 10.2 Hz, J = 3.2 Hz, H0-3), 6.10
(t, 1H, J = 10.0 Hz, H0-4), 7.23–7.31 (m, 2H, H–Ar), 7.33–7.46 (m,
7H, H–Ar), 7.47–7.64 (m, 3H, H–Ar), 7.81–7.89 (m, 2H, H–Ar),
7.94–8.03 (m, 2H, H–Ar), 8.04–8.13 (m, 4H, H–Ar); 13C NMR
(CDCl3) see Table 4; HR-ESI-MS m/z 823.3447 [M+Na]+ (calcd. for
C41H46O8Na, 823.3458).
4.16. a-Bisabolol b-D-glucopyranoside (8b)
8a (203 mg, 0.254 mmol) was treated according to the corre-
sponding general procedure. The residue was purified by FCC (hex-
anes/EtOAc 1:1 to EtOAc 100%) to afford 8b as a white powder
(80 mg, 82%): Rf 0.22 (EtOAc); ½a D25
ꢁ
ꢀ26.0 (c 1.00, MeOH); 1H NMR
4.12. General procedure for the deprotection of benzoylated
a-
(MeOD) d: 1.18 (s, 3H, H-14), 1.27 (m, 1H, H-5a), 1.47 (m, 1H, H-
bisabolol glycosides (5b–10b)
8
a
), 1.60 (s, 3H, H-12), 1.62 (s, 3H, H-15), 1.64 (m, 1H, H-8b), 1.66
(s, 3H, H-13), 1.74 (m, 1H, H-6), 1.82 (m, 1H, H-1 ), 1.90 (m, 1H,
),
a
The benzoylated
a-bisabolol glycoside (1 equiv.) was dissolved
H-4a), 1.93 (m, 1H, H-4b), 2.01 (m, 1H, H-1b), 2.02 (m, 1H, H-9a
in a 0.25 N NaOH (20 equiv.) solution of MeOH/THF/H2O 1:2:1
(15 ml). The reaction mixture was stirred at room temperature
for 1 h. The solution was neutralized to pH ꢃ 7 with a suspension
of amberlite IR-120 activated with 1 M H2SO4. After filtration and
evaporation of the solvents under reduced pressure, the residue
was purified by FCC.
2.06 (m, 1H, H-5b), 2.16 (m, 1H, H-9b), 3.17 (m, 1H, H0-2), 3.22 (m,
1H, H0-5), 3.31 (m, 1H, H0-4), 3.35 (m, 1H, H0-3), 3.65 (dd, 1H,
J = 11.6 Hz, J = 5.2 Hz, H0-6
a), 3.80 (dd, 1H, J = 11.7 Hz, J = 2.1 Hz,
H0-6b), 4.47 (d, 1H, J = 7.8 Hz, H0-1), 5.10 (br t, 1H, J = 6.3 Hz, H-
10), 5.35 (br s, 1H, H-2); 13C NMR (MeOD) see Table 5; HR-ESI-MS
m/z 407.2392 [M+Na]+ (calcd. for C21H36O6Na, 407.2409).
4.13.
a
-Bisabolol b-
D
-fucopyranoside (5b)
4.17. a-Bisabolol b-D-galactopyranoside (9b)
5a (120 mg, 0.176 mmol) was treated according to the corre-
sponding general procedure. The residue was purified by HPFC
(hexanes/EtOAc 7:3–3:7) to afford 5b as an oil (64 mg, 98%): Rf
9a (47 mg, 0.059 mmol) was treated according to the corre-
sponding general procedure. The residue was purified by FCC (hex-
anes/EtOAc 1:1 to EtOAc 100%) to afford 9b as a colorless gum
0.38 (EtOAc); ½a D25
ꢁ
ꢀ18.7 (c 1.00, CHCl3), lit. (San Feliciano et al.,
(20 mg, 89%): Rf 0.49 (CH2Cl2/MeOH 9:1); ½a D25
ꢁ
ꢀ8.8 (c 0.30, pyri-
1982) ½a D
ꢁ
ꢀ20.6 (c 0.97, CHCl3); 1H NMR (CDCl3) d: 1.13 (s, 3H,
dine); 1H NMR (MeOD) d: 1.17 (s, 3H, H-14), 1.27 (m, 1H, H-5
a),
H-14), 1.25 (m, 1H, H-5
1H, H-8
15), 1.67 (s, 3H, H-13), 1.75 (m, 1H, H-6), 1.76 (m, 1H, H-1
1.92 (m, 2H, H-4 ,b), 1.94 (m, 1H, H-1b), 1.96 (m, 1H, H-5b), 1.98
(m, 1H, H-9
), 2.15 (m, 1H, H-9b), 3.56 (m, 1H, H0-5), 3.57 (m,
a
), 1.27 (d, 3H, J = 6.4 Hz, H0-6), 1.46 (m,
1.48 (m, 1H, H-8a), 1.60 (s, 3H, H-12), 1.62 (s, 3H, H-15), 1.63
a
), 1.57 (m, 1H, H-8b), 1.59 (s, 3H, H-12), 1.63 (s, 3H, H-
(m, 1H, H-8b), 1.66 (s, 3H, H-13), 1.74 (m, 1H, H-6), 1.83 (m, 1H,
a
),
H-1a), 1.96 (m, 2H, H-4), 2.00 (m, 1H, H-1b), 2.01 (m, 1H, H-9a),
a
2.06 (m, 1H, H-5b), 2.16 (m, 1H, H-9b), 3.45 (m, 1H, H0-5), 3.47
(m, 1H, H0-3), 3.49 (m, 1H, H0-2), 3.64 (dd, 1H, J = 11.0 Hz,
a
1H, H0-3), 3.62 (m, 1H, H0-2), 3.70 (br s, 1H, H0-4), 4.37 (d,
J = 7.1 Hz, H0-1), 5.04 (br t, 1H, J = 6.2 Hz, H-10), 5.34 (br s, 1H, H-
2); 13C NMR (CDCl3) see Table 5; HR-ESI-MS m/z 391.2452
[M+Na]+ (calcd. for C21H36O5Na,), 391.2460.
J = 6.0 Hz, H0-6 ), 3.72 (dd, 1H, J = 11.0 Hz, J = 6.8 Hz, H0-6b), 3.86
a
(m, 1H, H0-4), 4.43 (d, 1H, J = 7.0 Hz, H0-1), 5.07 (br t, 1H,
J = 6.8 Hz, H-10), 5.35 (br s, 1H, H-2); 13C NMR (MeOD) see Table
5; HR-ESI-MS m/z 407.2391 [M+Na]+ (calcd. for C21H36O6Na,
407.2409).
4.14. a-Bisabolol a-L-rhamnopyranoside (6 b)
4.18. a-Bisabolol a-D-mannopyranoside (10b)
6a (97 mg, 0.14 mmol) was treated according to the corre-
sponding general procedure. The residue was purified by FCC (hex-
anes/EtOAc 4:1 to EtOAc 100%) to afford 6b as a colorless gum
10a (135 mg, 0.169 mmol) was treated according to the corre-
sponding general procedure. The residue was purified by HPFC
(hexanes/EtOAc 2:3 to EtOAc 100%) to afford 10b as a white
(49 mg, 95%): Rf 0.38 (EtOAc); ½a D25
ꢁ
ꢀ58.6 (c 0.50, CHCl3); 1H

M. Piochon et al. / Phytochemistry 70 (2009) 228–236
235
powder (36 mg, 56%): Rf 0.41 (CH2Cl2/MeOH 9:1); ½a D25
ꢁ
+8.5 (c 0.50,
Boyd, M.D., 1997. In: Teicher, B.A. (Ed.), Anticancer Drug Development Guide:
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Discovery, vol. 2 Wiley, NJ, USA.
MeOH); 1H NMR (CDCl3) d: 1.12 (s, 3H, H-14), 1.27 (m, 1H, H-5
a),
1.45 (m, 1H, H-8
a
), 1.57 (m, 1H, H-8b), 1.58 (s, 3H, H-12), 1.63 (s,
3H, H-15), 1.66 (s, 3H, H-13), 1.70 (m, 1H, H-6), 1.78 (m, 1H, H-1
a),
Cavalieri, E., Mariotto, S., Fabrizi, C., Carcereri de Prati, A., Gottado, R., Leone, S.,
1.85 (m, 1H, H-5b), 1.88 (m, 2H, H-9), 1.90 (m, 1H, H-1b), 1.93 (m,
2H, H-4), 3.70 (m, 1H, H0-6 ), 3.72 (m, 1H, H0-5), 3.81 (m, 1H, H0-2),
3.91 (m, 1H, H0-3), 3.98 (m, 1H, H0-6b), 3.99 (d, 1H, J = 10.0 Hz, H0-
Berra, L.V., Lauro, G.M., Ciampa, A.R., Suzuki, H., 2004.
a-Bisabolol, a nontoxic
a
compound, strongly induces apoptosis in glioma cells. Biochem. Biophys. Res.
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Cavalieri, E., Perbellini, L., Pizza, C., Perahia, D., Crimi, M., Suzuki, H., 2008.
4),
5.05
(br
t,
1H,
J = 6.4 Hz,
H-10),
5.12
(s, 1H, H0-1), 5.34 (br s, 1H, H-2); 13C NMR (CDCl3) see Table 5;
HR-ESI-MS m/z 407.2392 [M+Na]+ (calcd. for C21H36O6Na,
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Acknowledgments
The authors thank François-Xavier Garneau and Karl Girard-
Lalancette for help and suggestions and Philippe Dufour for his
assistance in organic synthesis. The financial support of Fonds
Québécois de la Recherche sur la Nature et les Technologies
(FQRNT, fonds forestier 02) and Chaire de Recherche sur les Agents
Anticancéreux d’Origine Naturelle are gratefully acknowledged.
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