The total synthesis of sevanol, a novel lignan isolated from the thyme plant (Thymus armeniacus)

Article abstract of DOI:10.1016/j.tet.2018.02.005

Recently, a novel lignan sevanol was isolated from the thyme plant Thymus armeniacus. During structure-functional elucidation it showed significant biological activity on ASIC3 acid sensing channels. Herein we describe the first synthesis of sevanol with

Full text of DOI:10.1016/j.tet.2018.02.005

Accepted Manuscript
The total synthesis of sevanol, a novel lignan isolated from the thyme plant (Thymus
armeniacus)
O.A. Belozerova, V.I. Deigin, A. Yu. Khrushchev, M.A. Dubinnyi, V.S. Kublitski
PII:
S0040-4020(18)30130-3
10.1016/j.tet.2018.02.005
TET 29276
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 26 June 2017
Revised Date: 30 January 2018
Accepted Date: 1 February 2018
Please cite this article as: Belozerova OA, Deigin VI, Khrushchev AY, Dubinnyi MA, Kublitski VS,
The total synthesis of sevanol, a novel lignan isolated from the thyme plant (Thymus armeniacus),
Tetrahedron (2018), doi: 10.1016/j.tet.2018.02.005.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical Abstract
The total synthesis of sevanol, a novel lignan
isolated from the thyme plant (Thymus
armeniacus)
Leave this area blank for abstract info.
O. A. Belozerovaa, V. I. Deigina,b, A. Yu. Khrushcheva, M. A. Dubinnyia and V. S. Kublitskia
aShemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-
Maklaya 16/10, Moscow 117997 Russian Federation
bPeoples’ Friendship University of Russia (RUDN), ul. Miklukho-Maklaya 6, Moscow 117198 Russian
Federation

ACCEPTED MANUSCRIPT
Graphical Abstract
The total synthesis of sevanol, a novel lignan
isolated from the thyme plant (Thymus
armeniacus)
Leave this area blank for abstract info.
O. A. Belozerovaa, V. I. Deigina,b, A. Yu. Khrushcheva, M. A. Dubinnyia and V. S. Kublitskia
aShemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-
Maklaya 16/10, Moscow 117997 Russian Federation
bPeoples’ Friendship University of Russia (RUDN), ul. Miklukho-Maklaya 6, Moscow 117198 Russian
Federation

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
The total synthesis of sevanol, a novel lignan isolated from the thyme plant (Thymus
armeniacus)
O. A. Belozerovaa, , V. I. Deigina,b , A. Yu. Khrushcheva, M. A. Dubinnyia and V. S. Kublitskia,
a
Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, Moscow 117997 Russian Federation
b
Peoples’ Friendship University of Russia (RUDN), ul. Miklukho-Maklaya 6, Moscow 117198 Russian Federation
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Recently, a novel lignan sevanol was isolated from the thyme plant Thymus armeniacus. During
structure-functional elucidation it showed significant biological activity on ASIC3 acid sensing
channels. Herein we describe the first synthesis of sevanol with a 3% overall yield. The
construction of
a dihydronaphthalene ring by oxidative dimerization of a protected
Available online
dihydroxycinnamic acid ester in the presence of ferric chloride (III) is a key step in this first total
synthesis of sevanol.
Keywords:
Lignan
Synthesis
Oxidative Coupling
Sevanol
2009 Elsevier Ltd. All rights reserved
.
1. Introduction
This compound has six asymmetric centers and in nature is
found in only one enantiomeric form.9,10 We showed that sevanol
1 (Fig. 1) was the first low molecular weight natural molecule
that has a reversible inhibitory effect on both the transient and the
sustained current of human ASIC3 channels expressed in
Xenopus laevis oocytes.9 In the model of acid induced pain and
Many species of plant produce bioactive compounds, such as
flavonoids,
tannins,
diterpenoids,
alkaloids,
peptides,
furocoumarines and lignans. These exhibit pharmacological or
toxicological effects in humans and in other animals.1 One of the
largest groups of these compounds, distributed widely within the
plant kingdom, is the lignans.2 This term was originally coined
by Haworth3 and relates to dimers generated by the β-β’ (8-8’)
oxidative coupling of two cinnamic acid residues.4 Lignans play
an important protective role in the vascular systems of plants,
which may explain their biological activity in living organisms.5
Indeed, a wide variety of lignan derivatives are found in plants,
covering a broad spectrum of chemical diversity and biological
activities, including anti-tumor, anti-inflammatory, antiviral,
cytotoxic, antimitotic, anti-fungal, anti-angiogenic and
cardiovascular effects.6,7,8 This family of polyphenols is attractive
from the point of view of a pharmaceutical chemistry as
promising targets for the development of potential drug
candidates.
thermal hypersensitivity in mice sevanol demonstrated
a
pronounced analgesic effect.10 Thus, expecting a potential clinical
application of sevanol we have developed a method for
chemically synthesizing this molecule. This publication is
dedicated to the development of the total synthesis of sevanol.
2. Results and Discussion
Considering that sevanol is formally a dimer of caffeic acid, it
seemed possible to synthesize the target compound by oxidative
coupling of two molecules of caffeic acid ester. Tri-t-butyl
isocitrate 6 and suitably protected caffeic acid 2 were chosen as
inputs for the retrosynthetic route to synthetic sevanol 1 (Scheme
1). The oxidative coupling of two molecules of a caffeic acid
ester 3 in the presence of ferric chloride (III) was proposed as a
key step. Synthesis of the key intermediate 4 included the step of
removing the protective groups (PG) from the phenolic oxygen
atoms of compound 3.
Previously, a novel lignan named sevanol (Fig. 1) was isolated
from the acetic acid extract of Thymus armeniacus.9 Based on
NMR and LC-ESI-MS data the structure of sevanol was
identified to be composed of esters of epiphyllic acid and two
residues of isocitric acid.
According to data available in the literature, hydroxyl groups
must be protected by either silyl or allyl groups in order for
———
Corresponding author. Tel.: +7-926-828-4460; e-mail: o.belozerova@ibch.ru (O. Belozerova)
Corresponding author. Tel.: +7-916-370-5756; e-mail: vkublitski@mx.ibch.ru (V. Kublitski)

2
Tetrahedron
ACCEPTED MANUSCRIPT
further dimerization of similar phenylpropanoid substrates to
occur.11,12 Thus, our initial choice of the protecting group for the
phenolic oxygen atoms in cinnamic acid was based on the
principle of orthogonality to t-butyl isocitric acid esters, which
should be removed under acidic conditions in the next step after
the preparation of dimeric product 5.
subsequently reacted with alcohol 6 to produce ester 3b in 28%
yield. Unfortunately, we could not remove the allyl groups
efficiently due to high impurity formation and the extremely low
yield of the reaction.
Figure 1. Structure of sevanol (1).
Therefore, initially we tried to use TBDMS-protection as
described by Bogucki et al.11 to synthesize (+)-rabdosiin, lignan
which has a similar structure to sevanol. It seemed possible that
TBDMS-protective groups would be removed using TBAF.
Caffeic acid was treated with TBDMS triflate in the presence of
Et3N to give a product in 71% yield. The resulting substance was
completely converted to the corresponding acid chloride 2a
followed by conversion into compound 3a in 43% yield. Acid
chloride 2a was obtained using 1.5 equivalents of thionyl
chloride and toluene as a solvent. The reaction was performed
during four hours at 110 oC. Further acylation of TBDMS-
protected compound 2a was carried out in dichloromethane in the
presence of triethylamine as a base. Unfortunately, all attempts to
remove the silyl groups (TBAF/THF, KF alcohols, TBAF acetic
acid) failed due to partial or total hydrolysis of the esters of
cinnamic acid.
Scheme 2. Total synthesis of sevanol.
To overcome this problem we selected MOM-protecting
groups as an alternative protection for the hydroxyl groups of
cinnamic acid. Use of this approach required changing the initial
route of the total synthesis. Commercially available 3,4-
dihydroxybenzaldehyde was subjected to an alkylation in the
presence of potassium carbonate13 to provide 3,4-bis-MOM-
protected benzaldehyde in 59% yield. Condensation of MOM-
protected benzaldehyde with malonic acid afforded the MOM-
protected caffeic acid derivative 2c.14 Caffeic isocitrate ester 3c
was synthesized in one step using acid 2c with alcohol 1 in the
presence of triethylamine, diisopropylcarbodiimide (DIC) and
catalytic amounts of DMAP.15,16 Treatment of 3c with three
equivalents of trifluoroacetic acid in acetonitrile-water (4:1)
followed by purification on silica gel gave the target intermediate
4 in 53% yield. Finally, removal of protecting groups was
achieved without TFA-mediated hydrolysis of tert-butyl esters.
The tri-tert-butyl ester of isocitric acid 6 was obtained in
seven synthetic steps starting from (L)-malic acid with an overall
yield of 36% using the method described by Calo et al.17
The stage was now set for the crucial coupling step.18 In order
to prepare the key intermediate 5, oxidative dimerization of two
molecules of caffeic isocitrate ester was used. It took several
attempts to find the optimal reaction medium. Thus, we tried to
perform an oxidative coupling using Cu(OAc)2, Fe(acac)3,
Pb(OAc)4 at room temperature. Despite the fact that the starting
material was being consumed, the desired product could not be
Scheme 1. Retrosynthetic path to synthetic sevanol.
Based on this precedent, it seemed at least possible to use allyl
protection for the phenolic oxygen atoms. Caffeic acid was
treated with allyl bromide in the presence of a base to provide the
target product in 31% yield.12 Allyl protected acid was
transformed to the acid chloride 2b with thionyl chloride and
identified by HPLC/MS. Cu(OAc)2 coupling afforded
a
dimerization product at the α – position without the desired
cyclization.

3
ACCEPTED MANUSCRIPT
Table 1. Solvent and oxidative reagent effects on the oxidative coupling of ester 4a.
Solvent
Oxidative reagent
K3[Fe(CN)6] (2 equiv)
MnO2 (2 equiv)
Cu(OAc)2 (2 equiv)
FeCl3 (2 equiv)
FeCl3 (2 equiv)
FeCl3 (2 equiv)
FeCl3 (2 equiv)
FeCl3 (2 equiv)
FeCl3 (1 equiv)
FeCl3 (2 equiv)
FeCl3 (2.5 equiv)
FeCl3 (3 equiv)
FeCl3 (4 equiv)
Yieldb %
not found
not found
1.5
Acetone-H2O
Acetone-H2O
Acetone-H2O
Acetone-H2O
i-PrOH-H2O
t-BuOH-H2O
CH2Cl2-H2O
THF-H2O
20
not found
not found
<1
not found
17
MeCN-H2O
MeCN-H2O
MeCN-H2O
MeCN-H2O
MeCN-H2O
32
41
10
2
a The reaction was conducted in the absence of light at 5 oC for 2 h.
b Yield of product 5.
Thus, the absence of the dihydronaphthalene molecule was
studies of optimal reaction conditions were required. Most of the
solvents (t-BuOH, i-PrOH, CH2Cl2, THF) used resulted in the
absence of the desired product 5 in the reaction mixture.
Fortunately, the successful oxidative dimerization was carried out
using aqueous acetonitrile as a solvent. The yield of compound 5
was 32% (Table 1). Moreover, experimental data showed that
using of 1 equivalent of FeCl3 provided a 17% yield of the target
molecule while introducing more than 3 equivalents to the
reaction led to tar formation and a product 5 (in 2-10% yield).
After careful consideration of the research results we made an
attempt to perform the key step of oxidative coupling with 2.5
equivalents of FeCl3 in aqueous acetonitrile. Pleasingly we
obtained intermediate 5 with 41% yield. We also studied
temperature influence to complete our search for optimal
conditions. The reaction was carried out over two hours using the
general procedure described above (2.5 equiv. of FeCl3 in
MeCN-H2O as a solvent). Performing oxidative dimerization at
25 oC led to the isolation of less than 2% of the target molecule 5
and full consumption of the starting ester 4. Meanwhile, after
cooling the reaction mixture to -10 oC we identified a large
amount of unreacted starting material 4 and not more than 0.5%
of the product 5. Considering these results, it was recognized that
oxidative coupling of t-butyl protected isocitate of caffeic acid 4
should be carried out at 5 oC as an optimal temperature.
1
determined by H NMR spectra. Based on the literature data for
the synthesis of analogues of natural lignans and neolignans19,20,21
we chose the method of FeCl3 oxidation in a mixture of acetone-
o
water as a solvent at 25 C over 18 hours using 2 equivalents of
ferric chloride (III). The low yield (2%) of the cyclization
product 5 showed that this is not an efficient set of reaction
conditions for obtaining the target molecule. The unreacted
starting material 4 could be recovered and recycled. Though this
route gave an access to the desired compound 1, the yield was
too low for the following research to be conducted.
We made attempts to improve the yield by changing the
reaction conditions. After careful consideration, we discovered
that the main problem at this stage was the formation of
chlorinated products. This problem was overcome by performing
the dimerization process at 5 °C for two hours in the absence of
light.19d As a result, the yield was improved to 20%.
A second attempt to optimize the synthesis of desired
molecule 5 by the coupling of compound 4 involved searching
for the most suitable solvent and amount of oxidant. The results
of the study are displayed in Table 1. The general procedure for
the study was to add an oxidant in water to ester 4 in organic
o
solvent at 5 C in the absence of light. The reaction mixture was
stirred for two hours. The resulting products were isolated and
analyzed with LC/MS spectroscopy. Contemporaneous
observations in such synthetic projects confirmed that using
K3[Fe(CN)6)]22 and MnO24 could be useful. According to data in
the literature, the yield of the dihydronaphthalene product would
not be more than 20-25%. However, we did not identify the
product 5 while performing dimerization of ester 4 in this
reaction medium. The starting material was also not observed.
Cu(OAc)2 coupling in the absence of light afforded product 5
with 1.5% yield and 25% of dimerization product at the α–
position described above. However, it seemed at least possible to
isolate unreacted compound 4 from the crude mixture. Thus it
appeared that using ferric chloride (III) was the best method to
prepare a lignan with a skeleton similar to sevanol molecule 1.
After treating the resulting reaction mixture with diluted HCl,
extraction in toluene and chromatographic purification on a silica
gel column, product 5 as mixture of two diastereomers was
finally obtained in 41% yield. It is important to note that t-butyl
protected sevanol diastereomers 5 were not separable at the stage
of oxidative dimerization. It was also impossible to separate the
diastereomers 5 even using a semi-preparative HPLC system.
Thus, the diastereomeric mixture of esters 5 was introduced into
the next step without further purification. Treatment with 80%
aqueous TFA for 1 hour at 50 oC gave a crude deprotected
1
product 1 that appeared by H NMR to be a mixture of two
diastereomers of the desired lignan in a 1:3 ratio as determined
by integration of corresponding signals. The crude product 1 was
chromatographed on a semi-preparative HPLC reverse-phase
column using MeCN-H2O as the eluant. As a result, the
separation of diastereomeric products was successfully
Although performing the reaction in aqueous acetone solvent
provided a relatively good yield of 20% for compound 5, further

4
Tetrahedron
ACCEPTED MANUSCRIPT
performed. Based on comparison of the NMR data and the value
of the optical rotation ([α]D = +65, c 1 H2O), the major
solution was stirred under a drying tube (CaCl2) for 16 h,
quenched with 1 M HCl (5 mL) and extracted with CH2Cl2 (2x10
mL). The combined organic layers were dried (Na2SO4) and
concentrated in vacuo. The residue was purified on silica gel (3a:
EtOAc – hexane = 1:6; 3b: EtOAc – hexane = 1:10) to give a
colorless oil (3a: 0.51 g, 43%; 3b: 0.23 g, 28%).
25
diastereomer was consistent with the structure of natural sevanol
1. During our search for an optimum procedure for oxidative
dimerization we came to the conclusion that changing either
solvent or the amount of oxidant did not influence the
diastereomeric ratio of 1:3. However, we did not study this aspect
sufficiently to make any conclusion about other factors that
control the predominant formation of one diastereomer over the
other. Thus, the isomer identical to the natural lignan 1 isolated
from thyme Thymus armeniacus was prepared in a 39% yield
from the crude mixture after HPLC purification.
2-{3-[3,4-Bis-(tert-butyl-dimethyl-silanyloxy)-phenyl]-acryloyl
oxy}-3-tert-butoxycarbonyl-pentanedioic acid di-tert-butyl ester
3a:
1
Rf (10% EtOAc/hexane) 0.4; H NMR (300 MHz, CDCl3): δH
7.68 (1H, d, J = 15.9 Hz), 7.07 (1H, s), 7.07 (1H, s), 6.89 (1H, s),
6.33 (1H, d, J = 15.9 Hz), 5.34 (1H, d, J = 3.3 Hz), 3.50 - 3.52
(1H, m), 2.81 (1H, dd, J = 16.8, 9.8 Hz), 2.52 (1H, dd, J = 16.8,
4.8 Hz), 1.56 (9H, s), 1.56 (9H, s), 1.53 (9H, s), 1.07 (9H, s),
1.06 (9H, s), 0.29 (6H, s), 0.28 (6H, s); 13C NMR (700 MHz,
CDCl3): 170.6, 169.3, 166.9, 166.1, 149.7, 147.2, 146.0, 127.9,
122.5, 121.1, 120.5, 114.5, 82.8, 81.9, 81.0, 72.1, 43.9, 33.9,
28.1, 25.9, 25.7, 0.0, 2.9, -4.0; IR (KBr): 1733, 2859, 2897, 2931,
2957; HRMS: MH+ calcld for C39H67O10Si2 751.4267 (MH)+:
found 751.4273.
3. Conclusion
In conclusion we have developed a new method for the
synthesis of novel lignan sevanol. The sevanol molecule was
obtained in thirteen synthetic steps with a 3% overall yield from
malic acid. The construction of a dihydronaphthalene ring by
oxidative dimerization of a protected dihydroxycinnamic acid
ester was carefully researched. As a result, we identified an
optimal reaction conditions to perform the key step of the total
synthesis of sevanol. Efforts to improve the synthetic route and to
study biological activity of synthetic sevanol in detail are
underway.
2-[3-(3,4-Bis-allyloxy-phenyl)-acryloyloxy]-3-tert-butoxy
carbonyl-pentanedioic acid di-tert-butyl ester 3b:
1
Rf (15% EtOAc/hexane) 0.38; H NMR (300 MHz, CDCl3): δH
4. Experimental section
7.72 (1H, d, J = 15.9 Hz), 7.14 (1H, s), 7.14 (1H, s), 6.94 (1H, s),
6.35 (1H, d, J = 15.9 Hz), 6.16 (1H, ddd, J = 9.4, 7.4, 4.7 Hz),
6.13 (1H, ddd, J = 10.5, 7.4, 4.7 Hz), 5.51 (1H, dd, J = 3.4, 1.5
Hz), 5.49 (1H, dd, J = 3.4, 1.5 Hz), 5.37 (2H, dd, J = 3.4, 1.5
Hz), 5.35 (2H, dd, J = 3.4, 1.5 Hz). 5.35 (1H, d, J = 3.6 Hz), 4.71
(2H, d, J = 5.6 Hz), 4.70 (2H, d, J = 5.6 Hz), 3.50 - 3.52 (1H, m),
2.81 (1H, dd, J = 16.8, 9.8 Hz), 2.52 (1H, dd, J = 16.8, 9.8 Hz),
1.56 (9H, s), 1.55 (9H, s), 1.53 (9H, s); 13C NMR (700 MHz,
CDCl3): 170.6, 169.4, 166.9, 166.0, 151.0, 148.6, 146.0, 133.1,
132.9, 127.5, 123.0, 118.0, 117.9, 114.7, 113.5, 112.8, 82.8, 81.9,
81.0, 72.0, 70.0, 69.8, 43.9, 33.9, 28.1; IR (KBr): 1732, 2933,
2979; HRMS: MH+ calcld for C33H47O10 603.3163 (MH)+:
found 603.3170.
4.1 General Procedures:
All reactions utilizing moisture-sensitive reagents were
performed under an inert atmosphere. Acetonitrile and
dichloromethane were purchased from Merck and were used
without further purification unless otherwise specified. Ethyl
acetate, hexane, toluene and acetone were distilled from CaCl2.
3,4-dihydroxybenzaldehyde, ferric chloride (III) were purchased
from Acros. N-methylpiperazine was purchased from
Fluorochem. DMAP, DIC were purchased from Merck. Other
reagents were purchased from PanReac AppliChem. All
commercially obtained reagents were used without further
purification. TLC was carried out on pre-coated plates (silica gel
60, F254, Fluka), and the spots were visualized with UV and
fluorescent lights or by staining with phosphomolybdic acid
stains. Column chromatography was performed on silica-gel
(0.063-0.2 mm/70-230 mesh ASTM, MN Kieselgel). High-
resolution mass spectra (HRMS) were measured on Agilent 6224
TOF LC/MS System. IR spectra were recorded with a Nicolet
(Thermo scientific) iS50 ART using a KBr pellet. All NMR
spectra obtained on Bruker AVANCE III spectrometers (Bruker
BioSpin, Germany) with proton operating frequencies of 300 and
700 MHz. Chemical shifts are reported relative to residue peaks
4.3
(1S,2S)-tri-tert-butyl-1-(((E)-3-(3,4-bis(methoxymethoxy)
phenyl)acryloyl)oxy)propane-1,2,3-tricar¬boxylate (3c)
The compound 2c (2.4 g, 9.1 mmol) was dissolved in CH2Cl2
(20 mL). A solution of alcohol 6 (2.5 g, 7 mmol) in CH2Cl2 (10
mL) was added to the stirred mixture. The resulting reaction
o
mixture was cooled to 0 C in an ice bath under Ar gas followed
by the addition of DMAP (85 mg, 0.7 mmol). A solution of DIC
(1.4 mL, 9.1 mmol) in CH2Cl2 (10 mL) was added dropwise to
the stirred mixture. The resulting solution was stirred under a
drying tube (CaCl2) for 16 h. The resulting mixture was filtered
and concentrated in vacuo. The residue was purified on silica gel
(EtOAc – hexane = 1:3) to give a colorless oil 3c (3.7 g, 87%): Rf
(20% EtOAc/hexane) 0.25; 1H NMR (300 MHz, CDCl3): δH 7.64
(1H, d, J = 15.9 Hz), 7.35 (1H, s), 7.13 (1H, s), 7.13 (1H, s), 6.34
(1H, d, J = 15.9 Hz), 5.28 (1H, d, J = 3.6 Hz), 5.25 (2H, s), 5.22
(2H, s), 3.52 (3H, s), 3.50 (3H, s), 3.40 – 3.46 (1H, m), 2.73 (1H,
dd, J = 16.8, 9.8 Hz), 2.44 (1H, dd, J = 16.8, 4.8 Hz), 1.48 (9H,
s), 1.48 (9H, s), 1.42 (9H, s); 13C NMR (300 MHz, CDCl3):
170.5, 169.3, 166.8, 165.8, 149.4, 147.4. 145.5, 128.4, 123.7,
116.1, 115.9, 115.4, 95.5, 95.1, 82.7, 81.8, 80.9, 72.0, 56.3, 56.3,
43.9, 33.7, 28.0; IR (KBr): 1731, 2933, 2978; HRMS: MH+
calcld for C31H47O12 611.3062 MH+: found 611.3069.
1
of CDCl3 (7.27 ppm for H and 77.0 ppm for 13C), D2O (4.79
ppm for 1H).
4.2 General Procedure for the preparation of substituted caffeic
isocitrates 3a, 3b:
The alcohol 6 (1.0 g, 2.8 mmol) was dissolved in CH2Cl2 (10
mL) followed by TEA (0.6 mL, 4.2 mmol) addition. The
resulting reaction mixture was stirred for 30 minutes at 0-5 oC in
an ice bath. A solution of the corresponding acid chloride (2a:
1.49 g, 3.5 mmol; 2b: 0.97 g, 3.5 mmol) in CH2Cl2 (5 mL) was
added dropwise to the stirred mixture. The resulting yellow

5
4.4
(1S,2S)-tri-tert-butyl-1-(((E)-3-(3,4-dihydroxyphenyl)
Acknowledgments
ACCEPTED MANUSCRIPT
acryloyl)oxy)propane-1,2,3-tricarboxylate (4)
The research was financially supported by the program of the
Russian Academy of Science “Fundamental research for
biomedical technology development”. Experiments were partially
carried out using the equipment provided by the IBCH core
facility (CKP IBCH, supported by Russian Ministry of Education
and Science, grant RFMEFI62117X0018).
The compound 3c (3.7 g, 6.1 mmol) was dissolved in 30 mL
MeCN – H2O (5:1). TFA (1.4 mL, 18.3 mmol) was added
dropwise to the mixture at room temperature. The resulting
o
solution was stirred for 10 h at 50 C. The reaction mixture was
quenched with saturated aqueous sodium hydrocarbonate
(NaHCO3), extracted with EtOAc (2x25 mL). The combined
organic layers were dried (Na2SO4) and concentrated in vacuo.
The residue was purified on silica gel (hexane – EtOAc = 2:1) to
give the product 4 as a colorless oil (1.7 g, 53%): Rf (35%
EtOAc/hexane) 0.3; 1H NMR (300 MHz, CDCl3): δH 7.54 (1H,
d, J = 15.9 Hz), 6.99 (1H, s), 6.86 (1H, s), 6.85 (1H, s), 6.59 (1H,
br s, OH), 6.17 (1H, d, J = 15.9 Hz), 6.03 (1H, br s, OH), 5.31
(1H, d, J 3.3 Hz), 3.45 – 3.51 (1H, m), 2.77 (1H, dd, J = 16.8, 9.7
Hz), 2.47 (1H, dd, J 16.8, 5.2 Hz), 1.52 (9H, s), 1.51 (9H, s), 1.48
(9H, s); 13C NMR (300 MHz, CDCl3): 170.7, 169.5, 167.6, 166.3,
146.6, 146.3, 144.1, 127.1, 122.4, 115.5, 114.4, 113.9, 83.4, 82.3,
81.3, 71.9, 43.9, 34.0, 28.0; IR (KBr): 1721, 2936, 2980, 3391;
HRMS: MH+ calcld for C27H39O10 523.2537 (MH)+: found
523.2536.
.References and notes
1. A.D. Kinghorn, J.Nat.Prod. 1987, 50, 1009-1024
2. R.B. Teponno, S. Kusari, M. Spiteller, Nat. Prod. Rep. 2016, 33,
1044
3. R.D. Haworth, J. Chem. Soc., 1942, 448-456
4. C. Daquino, A. Rescifina, C. Spatafora, C. Tringali, Eur. J. Org.
Chem. 2009, 6289-6300
5. D.R. Gang, A.T. Dinkova-Kostova, L.B. Davin, N.G., ACS
Symposium Series 1997, 658, 58-89
6. J. S. Bose V. Gangan, R. Prakash, S. K. Jain, S.K. Manna,
J.Med.Chem. 2009, 52, 3184-3190
7. S.G. Weiss, M. Tin-Wa, R.E. Perdue, N.R. Farnsworth, J. Pharm.
Sci. 1975, 64, 95
8. Zhang J., Chen J., Liang Z., Zhao C. Chemistry&Biodiversity
2014, 11, 1-54
9. M.A.Dubinnyi, D.I. Osmakov, S.G. Koshelev, S.A. Kozlov, Ya.
A. Andreev, N.A. Zakaryan, I.A. Dyachenko, D.A. Bondarenko,
A.S. Arseniev, Eu.V. Grishin, J. Biol. Chem. 2012, 287, 32993-
33000
4.5
(1S,1'S,2S,2'S)-hexa-tert-butyl-1,1'-(((1R,2S)-1-(3,4-
dihydroxyphenyl)-6,7-dihydroxy-1,2-dihydronaphthalene-2,3-
dicarbonyl)bis(oxy))bis(propane-1,2,3-tricarboxylate) (5)
Cinnamate 4 (1.7 g, 3.3 mmol) in acetonitrile (20 mL) was
stirred at 5oC while a solution of FeCl3 (1.3 g, 8.1 mmol) in H2O
(13 mL) was added dropwise over 5 min. The dark green reaction
mixture protected from light was stirred for 2 h at 5oC. The
resulting mixture was diluted with 1 M HCl (100 mL), extracted
with toluene (3x10 mL). The combined organic layers were dried
(Na2SO4) and evaporated in vacuo protected from light to give a
brown amorphous solid. The residue was purified on silica gel in
toluene – EtOAc = 4:1 (3% AcOH) to produce product 5 as a
dark yellow oil (672 mg, 41%). The diastereomeric mixture of
esters 5 was introduced into the next step without further
purification.
10. D. I. Osmakov, S. G. Koshelev, O. A. Belozerova, V. S. Kublitski,
Ya. А. Andreev, Е. V. Grishin, S. А. Кozlov, Rus. J.
Bioorg.Chem. 2015, 41, 606-611
11. D.E. Bogucki, J.L. Charlton, Can. J. Chem. 1997, 75, 1783-1794
12. R. Jaiswal, M.H. Dickman, N. Kuhnert, Org. Biomol. Chem. 2012,
27, 5266-5277
13. W. Bing; Zhang, Yong-Kang; Chen, Jian; Zhang, Wei; Song,
Jiangao; Del, Balzo Ughetta; Brown, Lesley; Miller, Guy, Patent
WO2003009807, 2003
14. H. Zou, H. Wu, X. Zhang, Y. Zhao, J. Stöckigt, Y. Lou, Y. Yu,
Bioorg. Med. Chem. 2010, 18, 6351-6359
15. B. Neises, W. Steglich, Angew. Chem. Int. Ed. Engl. 1978, 17,
522-524
16. F. Allais, S. Martinet, P.-H. Ducrot, Synthesis 2009, 21, 3571-
3578
4.6 Sevanol (1)
17. F. Calo, J. Richardson, A. Barrett, J.Org.Chem. 2008, 73, 9692-
9697
18. L.H. Hu, H.B. Zou, J.X. Gong, H.B. Li, L.X. Yang, W. Cheng,
C.X. Zhou, H. Bai, F. Gueritte, Y. Zhao, J. Nat. Prod. 2005, 68,
342-348
19. H. Takahashi, K. Matsumoto, M. Ueda, Y. Miyake, Y. Fukuyama,
Heterocycles 2002, 56, 245-256;
20. Q. Wang, Y. Yang, Y. Li, W. Yu, Z. Jie Hou, Tetrahedron 2006,
62, 6107-6112;
21. I. Agata, T. Hatana, S. Nishibe, T. Okuda, Phetochemistry 1989,
28, 9, 2447-2450
22. S. Maeda, H. Masuda, T. Tokoroyama, Chem. Pharm. Bull. 1994,
42, 12, 2506-2513
Product 5 (672 mg, 0.64 mmol) in a 50 mL round-bottom
flask was stirred in the presence of 10 mL 20% solution TFA in
water (TFA – H2O = 4:1) during 1 hour at 50 C. After slight
o
cooling, most of the solvent was carefully evaporated in vacuo
and the mixture was purified by a preparative HPLC reverse-
phase column. The semi-preparative HPLC system Waters 2487
was used for this purpose on a tandem of two columns in size 20
x 250 mm reversed-phase sorbents 11AD2 11 microns and LPS-
500 70 microns (LLC “Tehnosorbent”, Russia) with a linear
gradient of acetonitrile (mobile phase a: 0.1% TFA in water;
mobile phase B: acetonitrile; gradient 2 – 30% B in 60 min at a
flow rate of 10 mL/min; profile registration elution by UV
absorbance at 220 and 280 nm). A light yellow powder was
obtained after lyophilization (176 mg, 39%): 1H NMR (700 MHz,
D2O): δH 7.75 (1H, s), 7.01 (1H, s), 6.72 (1H, s), 6.68 (1H, d, J =
8.3 Hz), 6.62, (1H, d, J = 1.7 Hz), 6.43 (1H, dd, J = 1.7 Hz, 8.3
Hz), 5.38 (1H, d, J = 4.0 Hz), 5.33 (1H, d, J = 3.4 Hz), 4.5 (1H,
d, J = 1.9 Hz), 4.08 (1H, d, J = 1.9 Hz), 3.56 – 3.59 (1H, m), 3.45
- 3.47 (1H, m), 2.78 (1H, dd, J = 9.3 Hz, 17.2 Hz), 2.6 (1H, dd, J
= 5.2 Hz, 17.2 Hz), 2.50 (1H, dd, J = 9.6 Hz, 17.3 Hz), 2.24 (1H,
dd, J = 9.6 Hz, 17.3 Hz); 13C NMR (300 MHz, D2O): 175.4,
175.2, 174.2, 173.7, 172.8, 172.7, 171.8, 166.9, 147.5, 143.9,
143.3, 142.8, 141.4, 134.5, 130.7, 123.7, 119.8, 119.6, 117.4,
116.6, 116.1, 115.3, 73.2, 73.2, 46.4, 44.0, 43.2, 42.2, 32.3, 31.8;
IR (KBr): 1709, 2648, 3253; HRMS: MH- calcld for C30H25O20
705.0939 (MH)-: found 705.0941.
Supplementary Material
Detailed procedures and full characterization of all synthetic
intermediates and products are provided. Supplementary data
associated with this article can be found in the online version.