Derivatives of the Lignan 7′-Hydroxymatairesinol with Antioxidant Properties and Enhanced Lipophilicity

Article abstract of DOI:10.1021/acs.jnatprod.6b01124

The lignan 7′-hydroxymatairesinol (1), extracted from the knotwoods of fir (Abies alba), spruce (Picea abies), and Douglas fir (Pseudotsuga menziesii), exhibited unexpected reactivity when esterification reactions were attempted on the hydroxy group at position C-7′. To circumvent the rapid intramolecular cyclization procedure, leading quantitatively to the lignan conidendrin (7), a simple strategy for 7′-esterification of 1 under mild conditions (three steps, up to 80% overall yield) was developed. Compared to hydroxymatairesinol (1) (log K′_w = 1.49), the derivatives (2-5) had increased lipophilicity with log K′_w > 3.1, as determined by a UHPLC method. Compounds 1-5 exhibited potent antioxidant properties in the same range as the standards ascorbic acid and α-tocopherol (IC₅₀ = 20-25 μM) and higher than that of BHT using a DPPH radical-scavenging assay.

Full text of DOI:10.1021/acs.jnatprod.6b01124

Article
pubs.acs.org/jnp
Derivatives of the Lignan 7′-Hydroxymatairesinol with Antioxidant
Properties and Enhanced Lipophilicity
́ ́ ́
Thomas Moraux, Stephane Dumarc a̧ y, Philippe Gerardin, and Christine Gerardin-Charbonnier*
́
Laboratoire d’Etudes et de Recherche sur le Mater
́
iau Bois, EA4370 USC INRA, Universite
-Nancy, France
́ ́
de Lorraine, Faculte des Sciences et
Technologies, Boulevard des Aiguillettes, 54506 Vandœuvre-les
̀
*
S Supporting Information
ABSTRACT: The lignan 7′-hydroxymatairesinol (1), ex-
tracted from the knotwoods of fir (Abies alba), spruce (Picea
abies), and Douglas fir (Pseudotsuga menziesii), exhibited
unexpected reactivity when esterification reactions were
attempted on the hydroxy group at position C-7′. To
circumvent the rapid intramolecular cyclization procedure,
leading quantitatively to the lignan conidendrin (7), a simple
strategy for 7′-esterification of 1 under mild conditions (three
steps, up to 80% overall yield) was developed. Compared to
hydroxymatairesinol (1) (log K′ = 1.49), the derivatives (2−
w
5
) had increased lipophilicity with log K′ > 3.1, as determined
w
by a UHPLC method. Compounds 1−5 exhibited potent
antioxidant properties in the same range as the standards ascorbic acid and α-tocopherol (IC = 20−25 μM) and higher than
50
that of BHT using a DPPH radical-scavenging assay.
ood is a renewable source of bioactive molecules such as
W
lignans. These phenolic compounds show several
biological properties such as antioxidant effects due to the
1
,2
presence of phenolic groups, as well as anti-inflammatory,
3
,4
5,6
7−9
cardiovascular, antiviral, cytotoxic,
and enzyme inhib-
1
0
ition effects. The European trees Norway spruce (Picea abies)
and fir (Abies alba) have shown the presence of unconjugated
lignans in higher quantities in their knotwood than in the
1
1−14
heartwood.
knotwood source, thus comprising a variable proportion of fir
Abies alba), spruce (Picea abies), and Douglas fir (Pseudotsuga
menziesii). This wood was found to contain as major
In this work, paper-mill wastes were used as a
(
Figure 1. Esterification of 7′-hydroxymatairesinol (1) to modulate
lipophilicity without altering the antioxidant guaiacyl moieties.
11,12,14
constituent the lignan 7′-hydroxymatairesinol (1) (30%).
The presence of a benzylic hydroxy group on C-7′ is unique,
providing the opportunity to produce derivatives at this
position. In order to modulate the lipophilicity of compound
The work in the present investigation has explored further
the reactivity of 1, prone to cyclization or rearrangement, and,
as a result, circumventing these side-reactions represented a
first challenge.
1
, four C-7′ ester derivatives (2−5) were designed. A
consequent increase of solubility in lipophilic media was
expected while retaining the antioxidant properties from the
two guaiacyl groups (Figure 1). It can be assumed that natural
antioxidants that originate from wood may find practical
applications in medicinal chemistry, cosmetics, or food.
Previous reactivity studies on C-7′ of hydroxymatairesinol
RESULTS AND DISCUSSION
Chemistry. The conditions of extraction from knotwoods
were developed to recover 1 in large amounts. Hydroxy-
matairesinol (1) was obtained in a 3:1 ratio of (7′S)- to (7′R)-
hydroxymatairesinol, and all experiments were carried out on
this constitutive mixture.
■
16
(1) by Eklund and associates are detailed in Scheme 1. The
ether 8 was prepared in alkaline conditions after treatment of 1
with sodium methoxide. However, the treatment of 1 by
methylamine resulted into the lactam 9 after rearrangement
during the acidic workup. Finally, these authors suggested the
role of a para-quinone methide (pQM) (6) formed in aqueous
alkaline solution as a key intermediate in the intramolecular
A first direct regioselective esterification with octanoic acid
was attempted under Mitsunobu conditions but surprisingly did
not provide the expected 7′-octanoate derivative 3 (Scheme
Received: December 6, 2016
15
cyclization into conidendrin (7).
©
XXXX American Chemical Society and
American Society of Pharmacognosy
A
DOI: 10.1021/acs.jnatprod.6b01124
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Article
Scheme 1. Reactivity Study on C-7′ of Compound 1
Scheme 3. Proposed Reaction Mechanism for the Formation
of 7 in Alkaline Conditions
(
Previous Work)
1
7−19
2).
The betaine resulting from the triphenylphosphine
attack on diisopropyl azodicarboxylate (DIAD) was promptly
formed. Nevertheless, the activation of the benzylic hydroxy
group of 1 by the triphenylphosphine did not occur. The
treatment of 1 with a more nucleophilic thiolate, previously
formed by addition of potassium tert-butoxide on 1-
octadecanethiol, at reflux with acetonitrile, provided the
thioether 10 in moderate yield (36%). The NMR analysis
confirmed the formation of 10 as the C-7′ signal shifted
downfield from 75.4 ppm to 52.9 ppm in the 13C NMR
spectrum and the H-7′ signal shifted from 4.63 ppm to 3.53
2
1
of 7, instead of the expected product of translactonization.
Microwave heating accelerated the formation of the hypothetic
tosyl intermediate (10 min at 85 °C instead of 4 h at
conventional reflux) (Scheme 4). Attempting to chlorinate the
benzylic hydroxy group with thionyl chloride also led to
22
conidendrin (7) in 2 h.
1
Scheme 4. Hypothetical Intermediates Leading to
Conidendrin (7) in Acidic Conditions
ppm in the H NMR spectrum. No other azodicarboxylate
structures were investigated to deprotonate the nucleophiles
with high pK , especially as the purification of 10 from the
a
hydrazine side-product proved very challenging.
In the presence of a large excess (5 equiv) of a separately
prepared thiophenolate, hydroxymatairesinol (1) rearranged
into conidendrin (7). The reaction followed a SEAr-type
(
electrophilic aromatic substitution) mechanism, which may
occur through a para-quinone methide intermediate (6), even
though this structure has never been observed and charac-
terized for 1. This 1,6-conjugate addition of pQM with C
nucleophiles clearly benefits from the rearomatization driving
force to form the guaiacyl (Scheme 3). It is worth mentioning
that the 1,8-conjugate addition of the enone has never been
observed.
The intramolecular cyclization also occurred in acidic
conditions, and treatment of 1 with formic acid in
stoichiometric conditions provided compound 7 in excellent
2
0
yield. Activation of the benzylic hydroxy by a catalytic amount
of p-toluenesulfonic acid (PTSA) (0.1 equiv), in the presence
of octanoic acid, also resulted quantitatively in the production
It appeared, therefore, that all previously described work on
4-(1-hydroxyethyl)phenol structures did not apply to 1 due to
Scheme 2. Regioselective Hydroxy Activation under Mitsunobu Conditions
B
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Table 1. Optimization of the Reaction Conditions for the Dibenzylation of Hydroxymatairesinol Guaiacyl Groups
entry
base
solvent
DMF
T, °C
time, h
results
no reaction
traces
1
2
3
4
5
6
7
8
9
K CO
rt
48
24
24
24
24
24
24
24
24
24
1
2
3
K CO
2
choline chl./urea
acetone
80
3
c
DMAP
DMAP
K CO
rt
12/13, 1:1, no completion
c
acetone
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
rt
12/13, 1:1
c
acetone
12/13, 1:1
2
3
a
c
Et N/DMAP cat
acetone
12/13, 1:1, no completion
3
TBAB/K CO
acetone
12, 52%
12, 60%
12, 44%
12, 46%
12, 93%
12, 96%
2
3
TBAI/K CO
acetone
2
3
a
KI cat /K CO
acetone
2
3
1
1
1
0
1
2
KI/K CO
acetone
2
3
b
b
TBAI/Cs CO
acetone
2
3
3
TBAI/Cs CO
acetone
4
2
a
b
c
0
.3 equiv. BnBr. Yield determined by NMR spectroscopy.
−
1
the presence of the second phenolic group in the γ-position to
the hydroxy group. To remedy this issue, the development of
the benzyl protection of the phenolic hydroxy groups of 1 is
detailed in Table 1.
the displacement of the phenol peak from 3420 cm to 3500
cm .
−1
Scheme 5. Optimized Benzyl Protection of Compound 1
Standard conditions of phenol benzylation in dimethylfor-
mamide (DMF) with K CO as a base did not provide any
2
3
2
3,24
reaction (Table 1, entry 1).
The use of a deep eutectic
solvent (DES) formed by the 1:1 mixture of choline chloride
25
and urea (Table 1, entry 2) proved not to be more efficient.
As shown with entries 4−6 (Table 1), the benzylation occurred
at reflux in acetone for any base (K CO , 4-(dimethylamino)-
2
3
pyridine (DMAP), or Et N with a catalytic amount of
3
2
6
DMAP). However, the side-product 13 resulting from the
translactonization rearrangement was also competitively
1
3
formed. Indeed, the C NMR spectrum showed a partial
shift for both epimers of the CHOH-7′ signal to a CHOH-9′
signal. For example, the (R)-epimer of 12 exhibited a CHOH-7′
signal at 74.4 ppm, whereas 13 showed a CHOH-9′ signal at
Benzylation of 1 increased its solubility in apolar solvents
such as toluene. Acetate 14 was obtained in good yield (89%)
after reaction of 12 with acetic anhydride in large excess (5
27
13
equiv) in the presence of NaHCO as a base. Analysis by C
3
8
0.9 ppm. Reaction at room temperature with DMAP did not
NMR spectroscopy was consistent with a shift of the CHOH-7′
signal of 12 from 74.4 ppm to the CHOR-7′ signal of 14 at 75.4
ppm (Scheme 6). The synthesis of mixed anhydrides was not
explored further on longer chains.
The reaction of acyl chlorides in the presence of DMAP in
acetonitrile did not produce satisfactory results, with 52% and
prevent the formation of 13 (Table 1, entry 3). In either case,
the reaction was not completed after 24 h. The addition of a
tetrabutylammonium salt allowed increasing the yield up to
6
0%, and tetrabutylammonium iodide (TBAI) proved to be
slightly more effective than tetrabutylammonium bromide
TBAB) (Table 1, entries 7 and 8). The reaction mechanism
(
involves an exchange between the iodine counterion from
TBAI with chlorine from benzyl chloride, as well as a better
contact between the phenolate and the benzyl chloride. Indeed,
assays with KI either in catalytic or stoichiometric amounts
showed lower yields compared to TBAI (Table 1, entries 9 and
Scheme 6. Regioselective Acetylation of Compound 12
1
0). Finally, substituting K CO3 by Cs CO , and benzyl
2 2 3
chloride by benzyl bromide, allowed the completion of the
reaction at reflux in acetone in only 1 h (Table 1, entry 11).
Compound 12 was obtained at room temperature in high
yield (96%) after treatment of 1 with cesium carbonate
associated with TBAI (Scheme 5). The IR spectrum showed
C
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Scheme 7. Activation Methods for Fatty Acids
Scheme 8. Synthetic Pathway to C-7′ Esters of Hydroxymatairesinol (1)
4
6% yield for the octyl and dodecanoyl chlorides, respectively
VS
2
3
log P = log K − log V
(
Scheme 7).
Compound 12 was also reacted with
(1)
M
extemporaneously synthesized fluorooctanoyl, prepared from
octanoic acid and (diethylamino)sulfur trifluoride (DAST, 1.3
equiv), to obtain 15 with an improved yield (68%).
The use of dicyclohexylcarbodiimide (DCCI) in the presence
of DMAP in stoichiometric amounts provided the esters 15 and
where V /V is the volume ratio of the stationary and mobile
S
M
phase. The coefficient log K′ is the extrapolation of log K at
w
1
2
00% water. It is calculated with the following expression (eq
):
1
6 in good yields (88% and 77%, respectively) (Scheme 8). IR
⎛
= log⎜
⎝
⎞
⎟
⎠
tR − t
0
analysis showed the appearance of two peaks for the fatty
chains at 2850 and 2920 cm .
log K′
w
−1
t
0
(2)
Benzylated phenols were then deprotected with hydrogen
where t and t are, respectively, the retention times of the test
R
0
gas at atmospheric pressure (2.5 h, 92−95%) in the presence of
Pd(OH) (0.3 equiv) (Scheme 8). IR analysis confirmed the
compound and of the unretained compound (dead time).
Therefore, log K′w is a representative index of lipophilicity
extrapolating directly the value of log P.
2
−1
recovery of the free phenols with a broad peak at 3430 cm .
The reaction pathway was scaled up from 2 g to 3 g of
starting material 1. Satisfactorily, no variations in the yields
were observed at any of the steps. The pathway did not require
further scale optimization, and three long-chain esters were
obtained from octanoic acid, dodecanoic acid, and octadecanoic
acid.
Herein, the lipophilicities of the three synthesized esters (3−
5) and of natural hydroxymatairesinol (1) were determined
using an isocratic elution mode with acetonitrile/water as
eluent, in three different proportions to cover the lipophilicity
range. The two epimers (7′R)- and (7′S)- for each ester could
be separated by reversed-phase UHPLC. For any length of
chain, the (7′R)-ester was consistently calculated to have a
Lipophilicity. The behavior of bioactive molecules can be
28
higher value of log K′ (Table 2). Including an octyl chain on
strongly affected by their lipophilicities. Also influenced are
w
29
compound 1 doubled the lipophilic coefficient from 1.49 to
about 3.1. The dodecanoyl and octadecanoyl chains increased
the lipophilic coefficient to higher than 3.6 and 5.4, respectively.
By comparison, log P values for most commercially available
antioxidants are very low and less than zero as for ascorbic acid
absorption, metabolism, and excretion. A typical example
would be in drug delivery, notably transport through the
blood−brain barrier, requiring further pharmacokinetic and
pharmacodynamic studies. It would be expected that an
increase in the lipophilicity will help the solubilization of 1 in
more lipophilic conditions, as, for example, when formulated in
cosmetics. Additionally, recent work has shown the improve-
ment of antioxidant activity of hydroxytyrosol derivatives after
incorporating alkylcarbonate chains of various lengths.
The n-octanol/water partition method can be replaced by
chromatographic methods.
octanol/water (log P) is correlated to the retention time of the
molecule in reversed-phase liquid chromatography (eq 1):
30
(
−2.15). Only a few antioxidants exhibit a higher lipophilicity,
such as octyl gallate (4.1) and 2,6-di-tert-butyl-4-methylphenol
BHT) (5.1). Figure 2 shows the increase of lipophilicity for
the (7′S)-ester family of hydroxymatairesinol (1).
(
31
Antioxidant Activity. The antioxidant activities of 1 and
esters 3−5 were evaluated by the 1,1-diphenyl-2-picrylhydrazyl
(DPPH) radical-scavenging method and compared to those of
ascorbic acid, α-tocopherol, and BHT. The reaction conditions
were set with equivalent volumes (1 mL) of the DPPH solution
32,33
The partition coefficient in n-
34,35
D
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Table 2. Lipophilicities and Antioxidant Activities of 1 and
Ester Derivatives 3−5
IC50
compound
log K′
(μM)
(mg·L−1)
w
a
1
3
4
5
1.49
20.0 ± 0.1
24.1 ± 0.1
24.5 ± 0.1
25.2 ± 0.1
20.3 ± 0.1
7.49
12.06
13.64
16.15
3.58
b
b
b
3.06/3.12
3.63/3.68
5.43/5.50
c
ascorbic acid
−2.15
d
d
1
2.6 ± 0.2
2.22
c
c
e
e
citric acid
−1.7
4.1
nt
nt
nt
e
e
octyl gallate
α-(±)-tocopherol
BHT
nt
23.5 ± 0.1
34.0 ± 0.3
10.12
7.49
c
5.1
a
b
A single peak was obtained under UHPLC conditions. (7′S)/(7′R).
c
d
log P. Volume ratio of ascorbic acid solutions/DPPH solution 3:1
e
instead of 1:1. Not tested.
Figure 3. Scavenging of DPPH radicals by 1 and esters 3−5. In a 2 mL
reaction vial containing 1 mL of each assayed product (2−200 μM) in
MeOH was added 1 mL of DPPH solution (200 μM) in MeOH,
except ascorbic acid* (0.5 mL of DPPH solution (200 μM) in MeOH
added to 1.5 mL of ascorbic acid solution (2−200 μM) in MeOH).
The inhibition profiles of 1 and derivatives 3−5 were similar
to that of BHT, showing a rounded curve typical of a slow
action. This was also suggested by the relatively long incubation
times required for lower concentration samples to achieve
stability. This slow mechanism was tempered by the presence
of two guaiacyl groups that reinforced strongly the antioxidant
activity.
Concluding Remarks. In conclusion, a simple and
straightforward strategy was designed to synthesize the C-7′
ester derivatives 3−5 from hydroxymatairesinol (1). The benzyl
protection of guaiacyls prevented side-reactions of trans-
lactonization into isohydroxymatairesinol and the intra-
molecular cyclization into conidendrin (7). Benzyl protection
at room temperature with cesium carbonate and TBAI
provided the dibenzylated compound 12 in high yield (96%).
Once hydroxymatairesinol (1) was suitably protected, the
intramolecular cyclization was inhibited and the molecule could
undergo C-7′ esterification (70−88% depending on the chain
length) by using conventional DCCI as a coupling reagent. The
benzyl deprotection was catalyzed by Pd(OH)2 under
Figure 2. Lipophilicity determination of (7′S)-esters of hydroxyma-
tairesinol (1).
(
1
200 μM) and of the assayed products. A time-course study on
showed that an interval of 1 h was sufficient for incubation of
all samples
The results for the DPPH assay are illustrated in Figure 3. All
compounds exhibited good to excellent scavenging of DPPH
radicals when compared to standards. The inhibition curve
profiles of 1 and its derivatives 3−5 were in between those of
ascorbic acid and BHT. Compound 1 reacted as instanta-
neously as ascorbic acid at lower concentrations, but full
inhibition was not obtained until after a 1 h reaction. Esters 3−
atmospheric H at room temperature (92−95%). The semi-
2
synthesis of the C-7′ esters 3−5 worked efficiently under mild
conditions. The three different carbon chain lengths introduced
(
C H CO, C H CO, C H CO) allowed the modulation of
7 15 11 23 17 35
lipophilicity on 1. The derivatives 3−5 exhibited very high
5
exhibited a slightly lower activity than 1, with a similar
antioxidant properties (IC : 24−25 μM) in a DPPH radical-
50
inhibition profile, in a comparable manner to BHT. At lower
scavenging assay when compared to the common antioxidants
ascorbic acid, α-tocopherol, and BHT. Lipophilization may help
solubilization of this natural hydrophilic antioxidant into
lipophilic media and find industrial uses in the food, cosmetic,
and pharmaceutical industries. Therefore, this work has
contributed the generation of highly valuable bioactive
molecules from industrial wood wastes.
concentrations, the DPPH radical-scavenging activities of esters
3
−5 were similar to that of the lipophilic standard α-
tocopherol.
The IC50 values for each compound and standard were
between 20 and 25 μM, except for BHT (34.0 μM) (Table 2).
Surprisingly, the IC50 value for 1 (20.0 μM) was slightly lower
than for ascorbic acid (20.3 μM) under the conditions of the
test. Ascorbic acid was tested again in literature conditions, and
EXPERIMENTAL SECTION
36
■
the result confirmed the validity of the test (12.6 μM).
General Experimental Procedures. All commercially available
chemicals were purchased and used as supplied by the manufacturers.
Hydroxymatairesinol (1) was isolated from knotwood according to the
method described in ref 16 and in the Supporting Information. GC-
MS analysis was performed on a Clarus 680 gas chromatograph
coupled to a Clarus SQ8 quadrupole mass spectrometer (PerkinElmer,
Incorporating an ester chain on 1 increased the IC50 value to
around 4−5 μM, but the antioxidant activities of 3−5 were still
kept high. Thus, the ester family exhibited close IC50 values
(
24.1−25.2 μM) to that of the lipid-soluble vitamin α-
tocopherol (23.5 μM).
E
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USA). Gas chromatography was carried out on a 5% diphenyl/95%
C-5a), 113.6 (CH, C-5b), 113.3 (CH, C-5′a), 112.7 (CH, C-5′b),
109.5 (CH, C-2′a), 109.4 (CH, C-2′b), 74.8 (CH, C-7′a), 73.8 (CH,
C-7′b), 71.0 (CH , C-10), 70.9 (CH , C-10′a), 70.8 (CH , C-10′b),
dimethyl polysiloxane fused-silica capillary column (DB-5 ms, 30 m ×
0.25 mm, 0.25 μm film thickness, J&W Scientific, USA) with helium as
2
2
2
carrier gas at a constant flow of 1 mL/min. Prior to analyses, samples
were silylated by addition of 80 μL of N,O-bis(trimethylsilyl)-
trifluoroacetamide/trimethylsilyl chloride (99:1) and heating at 60
68.4 (CH , C-9′a), 68.0 (CH , C-9′b), 55.9 (CH , OCH b), 55.8
2
2
3
3
(CH , OCH a), 46.0 (CH, C-8′b), 45.0 (CH, C-8′a), 43.4 (CH, C-
3
3
8a), 43.3 (CH, C-8b), 34.8 (CH , C-7a), 34.6 (CH , C-7b); anal. C
2
2
°
C until complete solubilization. UHPLC analysis for determination of
73.63, H 6.18%, calcd for C H O , C 73.81, H 6.35%.
34 34 6
log K′ values was performed on a Shimadzu 8030 apparatus equipped
General Procedures for C-7′ Esterification (Compounds 14−
17). A. Procedure with Acetic Anhydride. Compound 14 (7′S-14a
and 7′R-14b). To a solution of 12 (216 μmol, 1 equiv, 120 mg) and
w
with an SPD-M20A diode array detector. The separations were carried
out in thermostated conditions at 40 °C with a reversed-phase column
(
binary solvent system consisting of water with 0.1% formic acid and
acetonitrile with 0.1% formic acid. The injection volume was fixed at
Phenomenex Luna 3 μm C ). The elution was carried out with a
NaHCO (433 μmol, 2 equiv, 36 mg) in toluene (3 mL) was added
3
18
dropwise acetic anhydride (1.08 mmol, 5 equiv, 102 μL), and the
mixture heated to reflux of toluene for 1 h. After filtration, the filtrate
5
.0 μL. Detection was carried out with a UV detector set at 254 nm
was evaporated under vacuum and taken into CH
organic phase was washed with saturated aqueous NaCl solution (3 ×
5 mL), dried over MgSO , and evaporated under a vacuum to give 14
2 2
Cl (20 mL). The
and under selected ion monitoring by negative and positive mode
ESIMS. The operating parameters for MS detection were as follows:
4
nebulizing gas N , flow 3.0 L/min, drying gas flow 15 L/min, interface
as an off-white powder (115 mg, 89% yield) after purification over
silica gel (hexane/ethyl acetate, 4:6): mp 61−63 °C; FTIR νmax 2928w,
2851w, 1768s, 1739s, 1592w, 1513s sh, 1454, 1422w, 1419w, 1262s,
2
voltage 4.5 kV, gas pressure 230 kPa, CDL temperature 250 °C, and
block heater temperature 400 °C. The DPPH assays were conducted
with a methanol solution (analytical grade) of DPPH (200 μM).
Methanol stock solutions of antioxidants were made at 1 mM.
Solutions of antioxidants were obtained directly by dilution of aliquots
from the stock solution (50 mL of each concentration, 2−200 μM).
The reaction was started by adding 1 mL of DPPH (200 μM) to 1 mL
of antioxidant solution. Absorbance of the reaction mixture was
measured on a Shimadzu UV-2550 spectrophotometer at 517 nm.
Purifications were conducted on a preparative HPLC PuriFlash 4100−
−1 1
1228s, 1141s, 1024s cm ; H NMR (CDCl , 400 MHz) δ 7.27−7.44
3
(10H, m, H-Ar), 6.43−6.90 (6H, m, H-2, H-5, H-6, H-2′, H-5′, H-6′),
5.76 (0.69H, d, J = 6.63 Hz, H-7′a), 5.55 (0.31H, d, J = 7.49 Hz, H-
7′b), 5.12 (4H, s, H-10, H-10′), 3.83−4.18 (2H, m, H-9′), 3.81 (3H, s,
OCH
(1.9H, s, CH
), 3.79 (3H, s, OCH
), 2.52−3.15 (4H, m, H-7, H-8, H-8′), 2.05
3
3
a), 2.04 (1.1H, s, CH
b); 13C NMR (CDCl
, 100 MHz)
3
3
3
δ 178.1 (C, C-9a), 178.0 (C, C-9b), 169.7 (C, C-1″a), 169.6 (C, C-
1″b), 149.7 (C, C-3b), 149.6 (C, C-3a, C-3′b), 149.5 (C, C-3′a), 148.3
(C, C-4′a), 148.2 (C, C-4′b), 147.1 (C, C-4b), 147.0 (C, C-4a), 137.0
(C, C-11′), 136.7 (C, C-11), 130.4 (C, C-1′b), 130.1 (C, C-1′a), 130.0
(C, C-1a), 129.9 (C, C-1b), 128.5 (CH, C-13′, C-15′), 128.4 (CH, C-
13, C-15), 127.8 (CH, C-14), 127.7 (CH, C-14′), 127.3 (CH, C-12′a,
C-16′a), 127.2 (CH, C-12′b, C-16′b), 127.1 (CH, C-12, C-16), 121.5
(CH, C-6a), 121.3 (CH, C-6b), 118.6 (CH, C-6′), 113.9 (CH, C-2),
113.7 (CH, C-5), 113.1 (CH, C-5′a), 112.7 (CH, C-5′b), 110.1 (CH,
2
50 coupled to an internal UV analyzer and a Flash-ELSD (Interchim,
France). The ELSD was supplied with N by a Parker Domnick
2
Hunter G3110E nitrogen gas generator. The columns were prepacked
high-performance silica gel with a particle size of 30 μm [Interchim
PuriFlash PF-30SIHP-JP/25G or PF-30SIHP-JP/120G]. The crude
mixtures were solubilized in the minimum of solvent (5−10 mL per g)
and deposited on Merck Geduran silica gel SI60 0.063−0.200 mm (3 g
per g of extract) before evaporation of the solvent. Dry loading used a
Merck EasyVarioFlash EVF D17 5 g or EVF D24 30 g empty cartridge
completed with sand when necessary. Melting points were measured
on a digital melting point apparatus (Electrothermal, UK). FT-IR
spectra were obtained on a Spectrum One spectrometer in ATR mode
C-2′), 75.9 (CH, C-7′a), 75.4 (CH, C-7′b), 71.0 (CH , C-10), 70.8
2
(CH , C-10′), 67.8 (CH , C-9′b), 67.7 (CH , C-9′a), 56.0 (CH ,
2
2
2
3
OCH a), 55.9 (CH , OCH b), 55.8 (CH , OCH ), 43.8 (CH, C-8′),
3
3
3
3
3
43.5 (CH, C-8b), 43.3 (CH, C-8a), 34.8 (CH , C-7a), 34.2 (CH , C-
2
2
7b), 21.0 (CH , CH b), 20.9 (CH , CH a); anal. C 72.21, H, 6.34%,
3
3
3
3
1
13
(
PerkinElmer, USA). H and C NMR spectra were recorded with an
Avance DRX 400 NMR spectrometer (Bruker, Germany) at 400 and
00 MHz, respectively, and chemical shifts are reported downfield
calcd for C H O , C 72.47, H 6.08%.
36 36 8
B. Procedure with DAST (Compound 15). A solution of octanoic
acid (216 μmol, 1.2 equiv, 34.3 μL) in CH Cl (1.5 mL) was cooled to
1
2
2
from tetramethylsilane.
0 °C before dropwise addition of DAST (216 μmol, 1.2 equiv, 30 μL).
After 30 min, the mixture was transferred through a cannula to a
solution of compound 12 (180 μmol, 1 equiv, 100 mg) and DMAP
(180 μmol, 1 equiv, 22 mg) in CH Cl (1.5 mL). The mixture was
stirred at rt for an additional 90 min before quenching and purification
over silica gel (hexane/ethyl acetate, 6:4) to provide 15 as a white solid
(84 mg, 68%).
Synthesis of Compound 12 (7′S-12a and 7′R-12b). To a
solution of 1 (7.40 mmol, 1 equiv, 2.77 g) dissolved in acetone (70
mL) were added successively TBAI (2.22 mmol, 0.3 equiv, 820 mg)
and Cs CO (14.80 mmol, 2 equiv, 4.82 g). Benzyl bromide (22.2
2
2
2
3
mmol, 3 equiv, 2.64 mL) was then added dropwise, and the mixture
stirred at room temperature for 4 h. Excess BnBr was quenched by
addition of silica gel (15 g) to the crude mixture, and the volatiles were
evaporated under a vacuum. The solid load was submitted to
purification over silica gel (hexane/ethyl acetate, 1:1) to provide 12 as
C. Procedure with Acyl Chlorides (Compounds 15 and 16). To a
solution of 12 (180 μmol, 1 equiv, 100 mg) in acetonitrile (4 mL) was
added DMAP (216 μmol, 1.2 equiv, 26 mg), and the mixture was
cooled to 0 °C before dropwise addition of acyl chloride (216 μmol,
1.2 equiv). The mixture was stirred at 80 °C for 24 h. After
evaporation of the volatiles, the residue was dissolved in CH Cl (20
a white solid (3.94 g, 96%): mp 54−60 °C; FTIR ν 3498br w, 1760,
max
1
591w, 1511s sh, 1452w, 1420w, 1380w, 1259s, 1224s, 1136s, 1025s
−1
1
cm ; H NMR (CDCl , 400 MHz) δ 7.27−7.43 (10H, m, H-Ar),
3
2
2
6
.42−6.82 (6H, m, H-2, H-5, H-6, H-2′, H-5′, H-6′), 5.14 (2H, s, H-
0), 5.11 (2H, s, H-10′), 4.60 (0.6H, d, J = 6.74 Hz, H-7′a), 4.36
mL) and washed with saturated aqueous NaCl solution (3 × 5 mL) to
afford after evaporation under vacuum the desired compound as a
white solid (15: 52%, 16: 46%).
1
(
0.4H, d, J = 6.78 Hz, H-7′b), 3.87−3.94 (2H, m, H-9′), 3.84 (2H, s,
OCH a), 3.82 (2H, s, OCH a), 3.81 (1H, s, OCH b), 3.80 (1H, s,
D. General Procedure of Esterification with DCCI (Compounds
15−17). To a solution of 12 (2.70 mmol, 1 equiv, 1.5 g) in acetonitrile
(35 mL) were added successively DMAP (3.52 mmol, 1.3 equiv, 430
mg), a fatty acid (3.52 mmol, 1.3 equiv), and DCCI (3.52 mmol, 1.3
equiv, 725 mg). The mixture was stirred at 80 °C for 4 h. Silica gel (20
g) was added to the crude mixture, and the solid loading was purified
over silica gel (hexane/ethyl acetate, 8:2 to 4:6) to provide the esters
15−17 as white solids (70−88%) (15: 88% yield, 16: 77% yield, 17:
70% yield).
3
3
3
OCH b), 2.85−3.09 (2H, m, H-7), 2.67−2.81 (1H, m, H-8), 2.48−
3
2
.63 (1H, m, H-8′), 1.98 (0.6H, s, OH-7′a), 1.91 (0.4H, s, OH-7′b);
1
3
C NMR (CDCl , 100 MHz) δ 179.2 (C, C-9a), 179.0 (C, C-9b),
3
1
1
1
1
49.8 (C, C-3a), 149.7 (C, C-3b), 149.6 (C, C-3′b), 149.4 (C, C-3′a),
47.9 (C, C-4′a), 147.8 (C, C-4′b), 146.9 (C, C-4b), 146.8 (C, C-4a),
37.1 (C, C-11′a), 137.0 (C, C-11′b), 136.8 (C, C-11), 134.7 (C, C-
′b), 134.6 (C, C-1′a), 130.7 (C, C-1a), 130.6 (C, C-1b), 128.5 (CH,
C-13′, C-15′), 128.4 (CH, C-13, C-15), 127.8 (CH, C-14), 127.7
(
1
CH, C-14′), 127.2 (CH, C-12′a, C-16′a), 127.1 (CH, C-12′b, C-
Compound 15 (7′S-15a and 7′R-15b: white solid, 88%, mp 69−71
6′b), 127.1 (CH, C-12, C-16), 121.7 (CH, C-6a), 121.2 (CH, C-6b),
18.1 (CH, C-6′), 113.9 (CH, C-2b), 113.8 (CH, C-2a), 113.7 (CH,
°C; FTIR ν 3497w, 3372br w, 2920s, 2850s sh, 1739, 1610w, 1515s
max
−1 1
1
sh, 1468, 1370w, 1266, 1213, 1157s, 1105, 1072, 1038 cm ; H NMR
F
DOI: 10.1021/acs.jnatprod.6b01124
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
(
CDCl , 400 MHz) δ 7.28−7.46 (10H, m, H-Ar), 6.47−6.85 (6H, m,
(CH, C-14), 127.4 (CH, C-14′), 127.0 (CH, C-12′a, C-16′a), 126.9
(CH, C-12′b, C-16′b), 126.8 (CH, C-12, C-16), 121.2 (CH, C-6a),
121.1 (CH, C-6b), 118.3 (CH, C-6′b), 118.2 (CH, C-6′a), 113.6 (CH,
C-2), 113.4 (CH, C-5′b), 113.3 (CH, C-5′a), 112.9 (CH, C-5a), 112.6
(CH, C-5b), 109.8 (CH, C-2′b), 109.7 (CH, C-2′a), 75.4 (CH, C-
7′a), 74.9 (CH, C-7′b), 70.7 (CH , C-10), 70.5 (CH , C-10′), 67.6
3
H-2, H-5, H-6, H-2′, H-5′, H-6′), 5.82 (0.67H, d, J = 6.22 Hz, H-7′a),
5
3
.60 (0.33H, d, J = 7.33 Hz, H-7′b), 5.11 (4H, br s, H-10, H-10′),
.88−4.17 (2H, m, H-9′), 3.83 (2H, s, OCH a), 3.80 (4H, br s,
3
OCH b, OCH ), 2.61−3.02 (4H, m, H-7, H-8, H-8′), 2.40 (1.25H, t, J
3
3
=
7.36 Hz, H-2″a), 2.33 (0.75H, t, J = 7.23 Hz, H-2″b), 1.64 (2H, m,
2
2
13
H-3″), 1.30 (8H, m, 4 CH ), 0.91 (3H, m, CH ); C NMR (CDCl ,
(CH , C-9′), 55.6 (CH , OCH a), 55.5 (CH , OCH b), 55.4 (CH ,
2
3
3
2
3
3
3
3
3
1
1
1
1
1
1
1
00 MHz) δ 177.7 (C, C-9a), 177.6 (C, C-9b), 172.0 (C, C-1″a),
71.9 (C, C-1″b), 149.3 (C, C-3b, C-3′b), 149.2 (C, C-3a, C-3′a),
47.8 (C, C-4′), 146.7 (C, C-4), 136.8 (C, C-11′), 136.5 (C, C-11),
30.4 (C, C-1′b), 130.0 (C, C-1′a), 129.9 (C, C-1a), 129.8 (C, C-1b),
28.0 (CH, C-13′, C-15′), 127.9 (CH, C-13, C-15), 127.4 (CH, C-
4), 127.3 (CH, C-14′), 126.9 (CH, C-12′a, C-16′a), 126.9 (CH, C-
2′b, C-16′b), 126.8 (CH, C-12, C-16), 121.1 (CH, C-6a), 121.0 (CH,
OCH ), 43.7 (CH, C-8′b), 43.4 (CH, C-8′a), 43.2 (CH, C-8b), 43.1
3
(CH, C-8a), 34.6 (CH , C-7b), 34.0 (CH , C-7a), 33.9 (CH , C-2″),
2
2
2
31.6 (CH , C-16″), 29.4 (5 CH ), 29.3 (2 CH ), 29.2 (CH ), 29.1
2
2
2
2
(
1
7
CH ), 29.0 (2 CH ), 28.8 (CH ), 24.6 (CH , C-3″), 22.4 (CH , C-
2
2
2
2
2
7″), 13.8 (CH ); anal. C 75.91, H 8.48%, calcd for C H O , C
3
52 68
8
6.06, H 8.35%.
General Procedure for Deprotection of Benzyl Groups
C-6b), 118.2 (CH, C-6′b), 118.0 (CH, C-6′a), 113.5 (CH, C-2), 113.3
CH, C-5b), 113.2 (CH, C-5a), 112.8 (CH, C-5′a), 112.5 (CH, C-
′b), 109.7 (CH, C-2′b), 109.5 (CH, C-2′a), 75.3 (CH, C-7′a), 74.8
CH, C-7′b), 70.5 (CH , C-10), 70.4 (CH , C-10′), 67.5 (CH , C-
(Compounds 3−5). To a solution of esters 15−17 (∼1 mmol, 1
(
5
(
9
equiv, 750 mg) in ethanol (30 mL) was added Pd(OH) 20% (0.3
2
equiv, ∼200 mg), and the mixture was vigorously stirred at rt for 2−
2.5 h. After filtration over Celite, the filtrate was purified over silica gel
(hexane/ethyl acetate, 8:2 to 4:6) to provide, respectively, 3−5 (92−
95%).
2
2
2
′a), 67.4 (CH , C-9′b), 55.5 (CH , OCH a), 55.4 (CH , OCH b),
2
3
3
3
3
5
5.3 (CH , OCH ), 43.5 (CH, C-8′b), 43.3 (CH, C-8′a), 43.1 (CH,
3
3
C-8b), 43.0 (CH, C-8a), 34.4 (CH , C-7b), 33.9 (CH , C-7a), 33.8
2
2
Compound 3 (7′S-3a and 7′R-3b): colorless, viscous liquid, 95%;
(
(
(
8
CH , C-2″b), 31.1 (CH , C-2″a), 28.6 (CH , C-4″a, C-5″a), 28.5
2
2
2
FTIR ν 3393br, 2956, 2937, 2857, 1740, 1613w, 1516s sh, 1457w,
max
CH , C-4″b, C-5″b), 28.4 (CH , C-6″a), 28.3 (CH , C-6″b), 24.5
−1 1
2
2
2
1432w, 1369w, 1270, 1237, 1157, 1121, 1064, 1031 cm ; H NMR
CH , C-3″b), 24.4 (CH , C-3″a), 22.1 (CH , C-7″), 13.6 (CH , C-
2
2
2
3
(CDCl , 400 MHz) δ 6.37−6.81 (6H, m, H-2, H-5, H-6, H-2′, H-5′,
3
″); anal. C 74.13, H 7.21%, calcd for C H O , C 74.09, H 7.11%.
42
48
8
H-6′), 5.88 (2H, br s, OH-4, OH-4′), 5.77 (0.75H, d, J = 6.13 Hz, H-
Compound 16 (7′S-16a and 7′R-16b): white solid, 77%, mp 76−
7
′a), 5.51 (0.25H, d, J = 7.8 Hz, H-7′b), 3.87−4.17 (2H, m, H-9′),
7
1
8 °C; FTIR ν 2918, 2849, 1780s, 1737s, 1591w, 1518s sh, 1454,
max
3.76 (2H, s, OCH a), 3.75 (3H, br s, OCH ), 3.73 (1H, s, OCH b),
3
3
3
−1
1
421w, 1365w, 1258s, 1238s, 1158s, 1137s, 1029s cm ; H NMR
2
2
.52−2.96 (4H, m, H-7, H-8, H-8′), 2.35 (1.43H, t, J = 7.52 Hz, H-
(
CDCl , 400 MHz) δ 7.28−7.44 (10H, m, H-Ar), 6.43−6.81 (6H, m,
3
″a), 2.27 (0.57H, t, J = 7.76 Hz, H-2″b), 1.57 (2H, m, H-3″), 1.24
H-2, H-5, H-6, H-2′, H-5′, H-6′), 5.79 (0.69H, d, J = 6.39 Hz, H-7′a),
13
(8H, m, 4 CH ), 0.83 (3H, m, CH ); C NMR (CDCl , 100 MHz) δ
2
3
3
5
.57 (0.31H, d, J = 7.35 Hz, H-7′b), 5.11 (4H, br s, H-10, H-10′),
1
1
1
1
1
78.4 (C, C-9a), 178.2 (C, C-9b), 172.6 (C, C-1″a), 172.4 (C, C-1″b),
46.7 (C, C-3), 146.6 (C, C-3′a), 146.5 (C, C-3′b), 145.7 (C, C-4′b),
45.6 (C, C-4′a), 144.5 (C, C-4b), 144.4 (C, C-4a), 129.4 (C, C-1′b),
28.9 (C, C-1′a), 128.8 (C, C-1a), 128.7 (C, C-1b), 122.1 (CH, C-6a),
21.9 (CH, C-6b), 119.5 (CH, C-6′b), 118.8 (CH, C-6′a), 114.4 (CH,
3
.82−4.18 (2H, m, H-9′), 3.82 (2H, s, OCH a), 3.80 (3H, br s,
3
OCH ), 3.79 (1H, s, OCH b), 2.59−3.06 (4H, m, H-7, H-8, H-8′),
3
3
2
2
.37 (1.30H, t, J = 6.99 Hz, H-2″a), 2.31 (0.70H, t, J = 7.17 Hz, H-
″b), 1.61 (2H, m, H-3″), 1.27 (16H, m, 8 CH ), 0.89 (3H, t, J = 6.81
2
13
Hz, CH ); C NMR (CDCl , 100 MHz) δ 178.0 (C, C-9a), 177.9 (C,
C-9b), 172.4 (C, C-1″a), 172.3 (C, C-1″b), 149.6 (C, C-3′b), 149.5
3
3
C-2a), 114.3 (CH, C-2b), 114.0 (CH, C-5′a), 113.9 (CH, C-5′b),
1
7
11.6 (CH, C-5a), 111.2 (CH, C-5b), 108.8 (CH, C-2′), 75.8 (CH, C-
′a), 75.3 (CH, C-7′b), 68.0 (CH , C-9′), 55.6 (CH , OCH a), 55.5
(
(
(
(
(
(
C, C-3b), 149.5 (C, C-3a), 149.4 (C, C-3′a), 148.1 (C, C-4′a), 148.0
C, C-4′b), 147.0 (C, C-4b), 146.9 (C, C-4a), 137.0 (C, C-11′), 136.7
C, C-11), 130.6 (C, C-1′b), 130.1 (C, C-1′a), 130.0 (C, C-1a), 129.9
C, C-1b), 128.4 (CH, C-13′, C-15′), 128.3 (CH, C-13, C-15), 127.7
CH, C-14), 127.6 (CH, C-14′), 127.1 (CH, C-12′a, C-16′a), 127.0
CH, C-12′b, C-16′b), 126.9 (CH, C-12, C-16), 121.4 (CH, C-6a),
2
3
3
(
8
CH , OCH ), 55.5 (CH , OCH b), 43.8 (CH, C-8′b), 43.7 (CH, C-
3
3
3
3
′a), 43.6 (CH, C-8b), 43.3 (CH, C-8a), 34.8 (CH , C-7b), 34.3
2
(
6
2
CH , C-7a), 34.2 (CH , C-2″a), 34.1 (CH , C-2″b), 31.41 (CH , C-
2
2
2
2
″a), 31.4 (CH , C-6″b), 28.9 (CH a), 28.8 (CH b), 28.7 (CH a),
2
2
2
2
8.6 (CH b), 24.7 (CH b), 24.6 (CH a), 22.4 (CH , H-7″), 14.0
2
2
2
2
1
21.2 (CH, C-6b), 118.4 (CH, C-6′b), 118.3 (CH, C-6′a), 113.8 (CH,
C-2), 113.6 (CH, C-5′b), 113.5 (CH, C-5′a), 113.0 (CH, C-5a), 112.7
CH, C-5b), 109.9 (CH, C-2′b), 109.8 (CH, C-2′a), 75.5 (CH, C-
′a), 75.0 (CH, C-7′b), 70.8 (CH , C-10), 70.7 (CH , C-10′), 67.8
(CH b), 13.9 (CH a); anal. C 67.11, H 7.30%, calcd for C H O , C
3
3
28 36
8
6
7.18, H 7.25.
(
7
Compound 4 (7′S-4a and 7′R-4b): colorless, viscous liquid, 92%;
2
2
FTIR ν 3425br, 2926, 2853, 1768, 1742, 1607w, 1516s sh, 1465w,
max
(
(
(
3
2
CH , C-9′a), 67.7 (CH , C-9′b), 55.8 (OCH a), 55.7 (OCH b), 55.6
2
2
3
3
−1
1
1
432w, 1376w, 1270s, 1238, 1152s, 1123, 1028s cm ; H NMR
OCH ), 43.8 (CH, C-8′b), 43.6 (CH, C-8′a), 43.4 (CH, C-8b), 43.2
3
(
CDCl , 400 MHz) δ 6.43−6.81 (6H, m, H-2, H-5, H-6, H-2′, H-5′,
CH, C-8a), 34.7 (CH , C-7b), 34.2 (CH , C-7a), 34.1 (CH , C-2″b),
3
2
2
2
H-6′), 6.01 (1H, br s, OH-4′), 5.88 (1H, br s, OH-4), 5.77 (0.84H, d, J
=
4.0 (CH , C-2″a), 31.7 (CH , C-10″), 29.4 (2 CH ), 29.2 (CH ),
2
2
2
2
6.04 Hz, H-7′a), 5.51 (0.16H, d, J = 7.96 Hz, H-7′b), 3.89−4.17
9.1 (CH ), 29.0 (CH ), 28.9 (CH ), 24.7 (CH , C-3″), 22.5 (CH ,
2
2
2
2
2
(
(
(
2H, m, H-9′), 3.75 (3H, s, OCH ), 3.74 (3H, s, OCH ), 2.52−2.95
C-11″), 14.0 (CH b), 13.9 (CH a); anal. C 74.64, H 7.88%, calcd for
3
3
3
3
4H, m, H-7, H-8, H-8′), 2.34 (1.64H, t, J = 7.51 Hz, H-2″a), 2.27
C H O , C 74.97, H 7.66%.
46
56
8
0.36H, t, J = 7.24 Hz, H-2″b), 1.59 (2H, m, H-3″), 1.24 (16H, m, 8
Compound 17 (7′S-17a and 7′R-17b): white solid, 70%, mp 93−
13
CH ), 0.85 (3H, t, J = 6.77 Hz, CH ); C NMR (CDCl , 100 MHz) δ
9
1
5 °C; FTIR ν 2917, 2850, 1780, 1734, 1590w, 1518s sh, 1465,
2
3
3
max
−1
1
178.4 (C, C-9a), 178.2 (C, C-9b), 172.6 (C, C-1″a), 172.5 (C, C-1″b),
454, 1384w, 1259s, 1232s, 1156s, 1141s, 1026s cm ; H NMR
1
1
1
46.7 (C, C-3), 146.6 (C, C-3′a), 146.5 (C, C-3′b), 145.7 (C, C-4′b),
45.6 (C, C-4′a), 144.5 (C, C-4b), 144.4 (C, C-4a), 129.3 (C, C-1′b),
28.9 (C, C-1′a), 128.7 (C, C-1a), 128.6 (C, C-1b), 122.1 (CH, C-6a),
(
CDCl , 400 MHz) δ 7.26−7.45 (10H, m, H-Ar), 6.45−6.82 (6H, m,
3
H-2, H-5, H-6, H-2′, H-5′, H-6′), 5.81 (0.68H, d, J = 6.25 Hz, H-7′a),
5
3
3
.59 (0.32H, d, J = 7.34 Hz, H-7′b), 5.11 (4H, br s, H-10, H-10′),
.88−4.17 (2H, m, H-9′), 3.82 (2H, s, OCH a), 3.80 (1H, s, OCH b),
121.9 (CH, C-6b), 119.4 (CH, C-6′b), 118.7 (CH, C-6′a), 114.4 (CH,
C-2a), 114.3 (CH, C-2b), 114.0 (CH, C-5′a), 113.9 (CH, C-5′b),
111.5 (CH, C-5a), 111.2 (CH, C-5b), 108.8 (CH, C-2′), 75.7 (CH, C-
7′a), 75.3 (CH, C-7′b), 68.0 (CH
(CH , OCH , OCH
(CH, C-8b), 43.3 (CH, C-8a), 34.8 (CH
34.2 (CH , C-2″a), 34.1 (CH , C-2″b), 31.6 (CH
CH ), 29.2 (CH ), 29.1 (CH ), 29.0 (CH ), 28.9 (CH
3
3
.80 (2H, s, OCH a), 3.79 (1H, s, OCH b), 2.60−3.02 (4H, m, H-7,
3
3
H-8, H-8′), 2.39 (1.30H, t, J = 7.37 Hz, H-2″a), 2.32 (0.70H, t, J =
.25 Hz, H-2″b), 1.64 (2H, m, H-3″), 1.30 (28H, m, 14 CH ), 0.92
7
2
, C-9′), 55.6 (CH
b), 43.8 (CH, C-8′b), 43.7 (CH, C-8′a), 43.6
, C-7b), 34.3 (CH , C-7a),
, C-10″), 29.4 (2
), 24.7 (CH ,
2
, OCH a), 55.5
3 3
2
13
(
3H, t, J = 6.78 Hz, CH ); C NMR (CDCl , 100 MHz,) δ 177.9 (C,
3
3
3
3
3
C-9a), 177.7 (C, C-9b), 172.1 (C, C-1″a), 172.0 (C, C-1″b), 149.5 (C,
C-3′b), 149.4 (C, C-3b), 149.4 (C, C-3a), 149.3 (C, C-3′a), 147.9 (C,
C-4′), 146.9 (C, C-4b), 146.8 (C, C-4a), 136.9 (C, C-11′), 136.6 (C,
C-11), 130.5 (C, C-1′b), 130.0 (C, C-1′a), 129.9 (C, C-1a), 129.8 (C,
C-1b), 128.2 (CH, C-13′, C-15′), 128.1 (CH, C-13, C-15), 127.5
2
2
2
2
2
2
2
2
2
2
C-3″), 22.5 (CH , C-11″), 13.9 (CH ); anal. C 69.25, H 8.14%, calcd
2
3
for C H O , C 69.04, H 7.97%.
32
44
8
G
DOI: 10.1021/acs.jnatprod.6b01124
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
Compound 5 (7′S-5a and 7′R-5b): colorless, viscous liquid, 93%;
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F.; Luo, X.; Zheng, Y.-T.; Lu, Y.; Xiao, W.-L.; Sun, H.-D. J. Nat. Prod.
2009, 72, 1133−1141.
FTIR ν 3434br, 2925, 2851, 1763, 1738, 1604w, 1516s sh, 1464,
1
max
−1 1
374w, 1237, 1272, 1154s, 1121, 1030s cm ; H NMR (CDCl , 400
3
MHz) δ 6.43−6.80 (6H, m, H-2, H-5, H-6, H-2′, H-5′, H-6′), 6.03
(7) Mukhija, M.; Dhar, K. L.; Kalia, A. N. J. Ethnopharmacol. 2014,
152, 106−112.
(
1H, br s, OH-4′), 5.89 (1H, br s, OH-4), 5.77 (0.86H, d, J = 5.97 Hz,
H-7′a), 5.51 (0.14H, d, J = 7.97 Hz, H-7′b), 3.89−4.14 (2H, m, H-9′),
(8) Suh, W. S.; Subedi, L.; Kim, S. Y.; Choi, S. U.; Lee, K. R. Bioorg.
Med. Chem. Lett. 2016, 26, 1877.
3
7
7
.74 (3H, br s, OCH ), 3.73 (3H, br s, OCH ), 2.52−2.94 (4H, m, H-
3
3
, H-8, H-8′), 2.34 (1.65H, t, J = 7.49 Hz, H-2″a), 2.27 (0.35H, t, J =
(9) Adfa, M.; Rahmad, R.; Ninomiya, M.; Yudha, S. S.; Tanaka, K.;
Koketsu, M. Bioorg. Med. Chem. Lett. 2016, 26, 761−764.
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33, 1044−1092.
.69 Hz, H-2″b), 1.58 (2H, m, H-3″), 1.22 (28H, m, 14 CH ), 0.85
2
1
3
(
3H, t, J = 6.73 Hz, CH ); C NMR (CDCl , 100 MHz) δ 178.3 (C,
3
3
C-9a), 178.2 (C, C-9b), 172.6 (C, C-1″a), 172.4 (C, C-1″b), 146.7 (C,
C-3), 146.6 (C, C-3′b), 146.5 (C, C-3′a), 145.7 (C, C-4′b), 145.6 (C,
C-4′a), 144.5 (C, C-4b), 144.4 (C, C-4a), 129.3 (C, C-1′b), 128.9 (C,
C-1′a), 128.7 (C, C-1a), 128.6 (C, C-1b), 122.0 (CH, C-6a), 121.9
̈
(11) Willfor, S.; Nisula, L.; Hemming, J.; Reunanen, M.; Holmbom,
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̈
(
2
(
7
CH, C-6b), 119.4 (CH, C-6′b), 118.7 (CH, C-6′a), 114.4 (CH, C-
B. Holzforschung 2004, 58, 650−659.
a), 114.3 (CH, C-2b), 114.0 (CH, C-5′a), 113.9 (CH, C-5′b), 111.5
CH, C-5a), 111.2 (CH, C-5b), 108.8 (CH, C-2′), 75.7 (CH, C-7′a),
5.3 (CH, C-7′b), 68.0 (CH , C-9′), 55.5 (CH , OCH ), 55.4 (CH ,
̌
̌ ́
̈
(13) Smeds, A. I.; Ceskova, I.; Eklund, P. C.; Willfor, S. M.
Holzforschung 2012, 66, 553−567.
2
3
3
3
(14) Kebbi-Benkeder, Z.; Colin, F.; Dumarcay, S.; Gerardin, P. Ann.
For. Sci. 2015, 72, 277−284.
OCH ), 43.8 (CH, C-8′b), 43.7 (CH, C-8′a, C-8b), 43.3 (CH, C-8a),
3
3
4.8 (CH , C-7b), 34.3 (CH , C-7a), 34.2 (CH , C-2″a), 34.1 (CH ,
2
2
2
2
(15) Eklund, P. C.; Sundell, F. J.; Smeds, A. I.; Sjoholm, R. E. Org.
Biomol. Chem. 2004, 2, 2229−2235.
C-2″b), 31.7 (CH , C-16″), 29.5 (5 CH ), 29.4 (2 CH ), 29.3 (CH ),
2
2
2
2
2
2
8
9.2 (CH ), 29.1 (CH ), 29.0 (CH ), 28.9 (CH ), 24.7 (CH , C-3″),
2
2
2
2
2
(16) Extractions were conducted through a sequential maceration in
ethanol (3 × 2 h) under vigorous stirring, to recover up to 12.5% of
the extract based on the dry weight of sawdust (ca. 85% of lignans in
the ethanolic extract). Large-scale purification (>10 g) was carried out
by preparative HPLC in a two-step process to provide up to 30% of 1
at a purity of higher than 95%.
2.4 (CH , C-17″), 14.0 (CH b), 13.9 (CH a); anal. C 71.39, H
2
3
3
.89%, calcd for C H O , C 71.22, H 8.81%.
38
56
8
ASSOCIATED CONTENT
Supporting Information
■
*
S
(17) Appendino, G.; Minassi, A.; Daddario, N.; Bianchi, F.; Tron, G.
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.jnat-
prod.6b01124.
C. Org. Lett. 2002, 4, 3839−3841.
(
(
18) Fletcher, S. Org. Chem. Front. 2015, 2, 739−752.
19) Swamy, K. C. K.; Kumar, N. N. B.; Balaraman, E.; Kumar, K. V.
Experimental for compounds 1, 7, 10, and 13; IR
spectra; H and C NMR spectra; additional lipophilicity
data (PDF)
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1
13
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(
AUTHOR INFORMATION
■
Corresponding Author
Tel (C. Gerardin): +33 (0)3 72 74 52 34. E-mail: Christine.
́
́
ez-Benjumea, A.;
*
́
́
̃
́
Gerardin@univ-lorraine.fr.
(
ORCID
Ixkes, U.; Johnston, B. F.; Johnston, D.; Kewnay, J.; Mackay, S. P.;
MacKenzie, S. J.; McFarlane, M.; Mitchell, L.; Spinks, D.; Takano, Y.
Bioorg. Med. Chem. Lett. 2007, 17, 6579−6583.
Thomas Moraux: 0000-0001-9615-4618
Notes
(25) Singh, A. S.; Shendage, S. S.; Nagarkar, J. M. Tetrahedron Lett.
The authors declare no competing financial interest.
2
(
(
014, 55, 7243−7246.
26) Cardinal, S.; Voyer, N. Tetrahedron Lett. 2013, 54, 5178−5180.
ACKNOWLEDGMENTS
■
27) Lugemwa, F.; Shaikh, K.; Hochstedt, E. Catalysts 2013, 3, 954−
The authors acknowledge FEDER and BPI for financial
support, and Norske Skog (Golbey, France) for providing
wood samples. LERMAB was supported by a grant overseen by
the French National Research Agency (ANR) as part of the
Investissements d’Avenir” program (ANR-11-LABX-0002-01,
Lab of Excellence ARBRE).
9
65.
28) Tamaian, R.; Mot,
A.; Oniga, O.; Nastasa, C.; Benedec, D.; Tiperciuc, B. Molecules 2015,
20, 22188−22201.
(29) Barton, P.; Riley, R. J. Drug Discovery Today 2016, 21, 72−81.
30) Maftei, C. V.; Fodor, E.; Jones, P. G.; Daniliuc, C. G.; Franz, M.
H.; Kelter, G.; Fiebig, H.-H.; Tamm, M.; Neda, I. Tetrahedron 2016,
2, 1185−1199.
31) Fernandez-Pastor, I.; Fernandez-Hernandez, A.; Rivas, F.;
Martinez, A.; Garcia-Granados, A.; Parra, A. J. Nat. Prod. 2016, 79,
737−1745.
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L.; Martel, S. Anal. Bioanal. Chem. 2009, 394, 707−729.
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(
̧ A.; Silaghi-Dumitrescu, R.; Ionut ,̧ I.; Stana,
̆
“
(
7
(
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DOI: 10.1021/acs.jnatprod.6b01124
J. Nat. Prod. XXXX, XXX, XXX−XXX