Gentiobiosylation of β-resorcylic acid esters and lactones: First synthesis and characterization of zearalenone-14-β,d-gentiobioside

Article abstract of DOI:10.1055/s-0033-1339338

The development of an optimized protocol for the gentiobiosylation of β-resorcylic acid esters and lactones (β-RAL) is presented. Different gentiobiosyl donors were prepared and used for regioselective and diastereoselective glycosylation affording a reliable synthetic strategy towards this class of natural product glycosides. The improved procedure was finally used for the preparation of the masked Fusarium mycotoxin zearalenone-14-β, d-gentiobioside. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0033-1339338

1830▌
LETTER
letter
Gentiobiosylation of β-Resorcylic Acid Esters and Lactones: First Synthesis
and Characterization of Zearalenone-14-β,D-Gentiobioside
Gentiobiosylation of β-Resorcylic Acid Esters and Lactones
Julia Weber,a Hannes Mikula,*a Philipp Fruhmann,a Christian Hametner,a Elisabeth Varga,b Franz Berthiller,b
Rudolf Krska,b Johannes Fröhlicha
a
Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-OC, 1060 Vienna, Austria
Fax +43(1)5880116399; E-mail: hannes.mikula@tuwien.ac.at
b
Christian Doppler Laboratory for Mycotoxin Metabolism and Center for Analytical Chemistry, Department for Agrobiotechnology (IFA-
Tulln), University of Natural Resources and Life Sciences, Vienna (BOKU), Konrad-Lorenz-Str. 20, 3430 Tulln, Austria
Received: 25.05.2013; Accepted: 10.06.2013
Conjugated mycotoxins, especially glycosides, can
Abstract: The development of an optimized protocol for the gen-
emerge after metabolization by living plants. The occur-
tiobiosylation of β-resorcylic acid esters and lactones (β-RAL) is
rence of ZEN-14-β,D-glucoside (2, Figure 2) in wheat was
presented. Different gentiobiosyl donors were prepared and used for
regioselective and diastereoselective glycosylation affording a reli-
shown by Schneweis et al.7 Furthermore ZEN-14-β,D-
able synthetic strategy towards this class of natural product glyco- gentiobioside (formerly described as ZEN-14-digluco-
sides. The improved procedure was finally used for the preparation
of the masked Fusarium mycotoxin zearalenone-14-β,D-gentiobio-
side.
side) was shown to be one of the major (late) phase II me-
tabolites of 1 formed in the model plant Arabidopsis
thaliana (Figure 2).8 Awareness of such altered forms, of-
Key words: carbohydrates, glycosides, glycosylation, phenols, nat-
ural products
ten called masked mycotoxins, is increasing, but reliable
analytical methods, standards as well as structural, occur-
rence, and toxicity data are still scarce.9
Zearalenone (ZEN, 1, Figure 1) is a mycotoxin produced
by several plant pathogenic Fusarium species, including
Fusarium graminearum, Fusarium culmorum, and Fusar-
ium cerealis. This mycotoxin is common in maize, but
HO
O
O
O
HO
HO
14
HO
O
also barley, oats, wheat, and rice are susceptible to con-
16
tamination with ZEN.1 Fusarium species are probably the
most prevalent toxin-producing fungi of the northern tem-
perate regions and are commonly found in cereals grown
worldwide.2 ZEN and its metabolites possess estrogenic
activity in mammals, including pigs, cattle, and sheep.3
Problems of the reproductive tract as well as impaired fer-
tility and abnormal fetal development in farm animals can
be caused by ZEN.4 Furthermore, this mycotoxin can in-
terfere with various enzymes involved in steroid metabo-
lism, which was recently investigated.5 Therefore ZEN is
of significant importance from an agricultural, economic,
and health perspective.6
OH
zearalenone-14-β,
HO
O
D
-glucoside (2)
O
HO
HO
O
O
HO
HO
HO
O
O
14
HO
O
16
OH
O
zearalenone-14-β,D-gentiobioside (3)
Figure 2 Structures of glycosylated ZEN metabolites (masked my-
cotoxins)
OH
O
16
Gentiobiosylation has been shown to be an important met-
abolic pathway and several biologically active and rele-
vant compounds have been described.10 Additionally,
further mycotoxin gentiobiosides have been identified as
natural contaminants of corn and are also reported to be
present in beer samples.11
O
14
HO
O
1
Figure 1 Structure of zearalenone (ZEN, 1)
In the course of ongoing research in the emerging field of
masked and conjugated mycotoxins we focused on the
synthesis of ZEN-14-β,D-gentiobioside (3) for structure
confirmation and an accurate differentiation between 3
and the isomeric metabolite ZEN-14,16-di(β,D-gluco-
side).12
SYNLETT 2013, 24, 1830–1834
Advanced online publication: 30.07.2013
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DOI: 10.1055/s-0033-1339338; Art ID: ST-2013-D0484-L
© Georg Thieme Verlag Stuttgart · New York

LETTER
Gentiobiosylation of β-Resorcylic Acid Esters and Lactones
1831
The first synthesis of a ZEN-glycoside, ZEN-14-β,D-glu- 2,4-Dihydroxybenzoic acid isopropyl ester (11)28 was
coside (2) was achieved applying a Königs–Knorr proce- used as ZEN mimic to investigate the gentiobiosylation of
dure under phase-transfer conditions,13 but the analogous resorcylic acid esters applying 7 and 10 as glycosyl do-
reaction to produce ZEN-14-β,D-glucuronide was de- nors under different reaction conditions. Selected data of
scribed to be unsuccessful under a variety of coupling reaction optimization and screening is shown in Table 1.
conditions.14 We were able to develop a fast and reproduc- Königs–Knorr glycosylation applying silver(I) salts for
ible procedure for the chemical synthesis of ZEN-14-β,D- activation29 was observed to result in nearly quantitative
glucuronide, which was published very recently.15
conversion after 48 hours. The highest yield (as deter-
mined by H NMR after standard addition to the crude
product mixture) was obtained when using Ag2CO3 for
activation of the gentiobiosyl donor 7.
1
Gentiobiosylation of phenols is often achieved by step-
wise glucosylation and application of protective-group
strategies.16 Although similar approaches were developed
for direct phenol glycosylation using a disaccharidic do- Lewis acid mediated glycosylation30 applying the acetimi-
nor,17 to the best of our knowledge there is no procedure date donor 10 gave only poor conversion or even com-
reported for direct gentiobiosylation of phenols. Shimoda plete rearrangement of 10 into the corresponding N-
and coworkers applied cultured cells of Eucalyptus per- glycosyl acetamide (as indicated by NMR spectroscopy).
riniana as biocatalysts for the synthesis of a mixture of
Phase-transfer glycosylation (Table 1, entry 7) was car-
glucosides and gentiobiosides of the isoflavonoids genis-
ried out applying an optimized procedure31 according to
tein and glycitein.18
the described approach for ZEN glucosylation.13 The ob-
Considering already described procedures for glucosyl- tained results in terms of conversion and yield were quite
ation of β-resorcylic acid esters and lactones (β-RAL), comparable to that observed applying classic Königs–
different disaccharidic donors were prepared for direct β- Knorr conditions.
gentiobiosylation. Since acetyl protective groups were
shown to be applicable for diastereoselective glycosyl-
In all cases 12 was obtained within a complex product
mixture mainly containing carbohydrate byproducts, but
best results were achieved using phase-transfer glycosyl-
ation. Most of the impurities were removed by silica gel
filtration, and the crude product was used without further
purification in the deprotection step. Basic hydrolysis was
ation of β-RAL, β-gentiobiose octaacetate (6) was select-
ed as key intermediate. A reliable procedure19 for β-
glucosylation of 1,2,3,4-tetra-O-acetyl-β,D-glucoside
(5)20 using the trichloroacetimidate donor 421 was applied
to obtain larger amounts of 6.22 Gentiobiosyl bromide 7
achieved by reaction with an excess of KOH in THF–H2O
was prepared according to Hunsen et al.,23 and anomeric
(4:1),32 and the deacetylated product 1333 was finally iso-
deprotection of 6 by reaction with benzyl amine24 yielded
lated by reversed-phase (C18) column chromatography
(Scheme 2).
the OH-sugar 8,25 which was subsequently reacted with N-
phenyl-2,2,2-trifluoroacetimidoyl chloride (9)26 to obtain
the acetimidate gentiobiosyl donor 1027 (Scheme 1).
AcO
OH
O
O
AcO
AcO
O
TMSOTf
CH2Cl2, –40 °C
16 h, 43%
AcO
HO
+
O
AcO
O
AcO
AcO
O
O
AcO
AcO
AcO
AcO
HO
AcO
+
OAc
11
Br
7
AcO
AcO
O
NH
5
CCl3
RO
4
TBAB, NaOH
CHCl3, H2O
pH 10.5–11.0
45 °C, 6 h
O
RO
RO
O
AcBr, MeOH
AcOH, 20 °C
3 h, 64%
AcO
AcO
RO
O
RO
RO
O
O
O
O
AcO
AcO
AcO
AcO
O
RO
AcO
AcO
O
O
O
AcO
AcO
AcO
OAc
AcO
AcO
AcO
OH
O
Br
6
KOH
THF–H2O (4:1)
20 °C, 2 h
12 (R = Ac)
13 (R = H)
7
BnNH2
THF, 20 °C
48 h, 76%
NPh
Cl
30% (2 steps)
F3C
Scheme 2 Synthesis of gentiobioside 13
9, K2CO3
9
AcO
AcO
CH2Cl2, 20 °C
24 h, 78%
O
O
AcO
AcO
AcO
AcO
O
O
Finally, we were able to prepare ZEN-14-β,D-gentiobio-
side (3)34 starting from ZEN (1) in an overall yield of 43%
following general procedures for glycosylation and subse-
quent basic hydrolysis of the acetylated intermediate 14
according to the synthesis of the mimic gentiobioside 13
(Scheme 3).
AcO
AcO
O
O
O
AcO
AcO
AcO
AcO
AcO
AcO
OH
8
F3C
NPh
10
Scheme 1 Synthesis of gentiobiosyl donors 7 and 10
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 1830–1834

1832
J. Weber et al.
LETTER
Table 1 Gentiobiosylation of ZEN Mimic 11 Using Glycosyl Donors 7 and 10
AcO
AcO
OH
O
O
O
AcO
AcO
AcO
AcO
O
O
activation
O
+
AcO
AcO
O
O
O
AcO
AcO
AcO
AcO
HO
AcO
AcO
X
11
O
7 (X = α-Br)
10 [X = OC(NPh)CF3]
OH
O
12
Entry
Donor (equiv)
Activation (equiv)
Solvent
Conversion of 11 (%)a Yield (%)b
1
2
3
4
5
6
7
7 (2.5)
7 (2.5)
Ag2O (1.5)
MeCN
CH2Cl2
CH2Cl2
CH2Cl2
100
90
54
52
83
9
Ag2O (1.5)
7 (2.5)
Ag2CO3 (1.5)
TMSOTf (0.1)
TMSOTf (0.02)
BF3·OEt2 (0.1)
TBAB (1.0), NaOH
95
10 (1.5)
10 (2.5)
10 (1.5)
7 (2.8)
13
1,4-dioxane–toluene
CH2Cl2
0c
0c
24
92
18
52
CHCl3–H2O
a As determined by 1H NMR.
b Nonisolated yield, determined by 1H NMR spectroscopy (after standard addition of 11).
c Rearrangement of the acetimidate 10 to the corresponding N-glycosyl acetamide was observed, as indicated by NMR spectroscopy.
AcO
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett. General ex-
perimental details and full characterization data (MS and NMR
OH
O
O
AcO
AcO
O
O
+
AcO
O
AcO
AcO
spectra) of 3 are included.SnuIfp
o
oirgmnirtSatunIomprifogtoartin
HO
AcO
Br
O
7
References and Notes
1
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Ernaehrung 2006, 30, 477.
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Anal. Bioanal. Chem. 2009, 395, 1243. (b) Berthiller, F.;
Crews, C.; Dall’Asta, C.; Saeger, S. D.; Haesaert, G.;
Karlovsky, P.; Oswald, I. P.; Seefelder, W.; Speijers, G.;
Stroka, J. Mol. Nutr. Food Res. 2013, 57, 165.
RO
O
RO
RO
O
TBAB, NaOH
CHCl3, H2O
pH 10.5–11.0
45 °C, 7 h
O
RO
RO
RO
O
O
RO
O
OH
O
KOH
THF–H2O (4:1)
20 °C, 2 h
14 (R = Ac)
3 (R = H, ZEN-14-β,D-gentiobioside)
43% (2 steps)
Scheme 3 Gentiobiosylation of 1 and preparation of the target com-
pound ZEN-14-β,D-gentiobioside (3)
In summary we were able to develop a reliable procedure
for the gentiobiosylation of β-RAL, which in general
should be applicable for many phenolic compounds. The
first synthesis of a mycotoxin gentiobioside was accom-
plished yielding 3 in reasonable amounts for further stud-
ies.
Acknowledgment
The Theodor Körner fund (Vienna, Austria), the Austrian Federal
Ministry of Economy, Family and Youth as well as the National
Foundation for Research, Technology and Development are grate-
fully acknowledged for financial support.
(10) (a) Hayasaka, Y.; Parker, M.; Baldock, G. A.; Pardon, K. H.;
Black, C. A.; Jeffery, D. W.; Herderich, M. J. J. Agric. Food
Chem. 2013, 61, 25. (b) Yu, Y.; Xic, Z.; Ma, W.; Dai, Y.;
Synlett 2013, 24, 1830–1834
© Georg Thieme Verlag Stuttgart · New York

LETTER
Gentiobiosylation of β-Resorcylic Acid Esters and Lactones
1833
Wang, Y.; Zhong, Y.; Yao, X. J. Nat. Prod. 2009, 72, 1459.
(25) Araya, E.; Rodriguez, A.; Rubio, J.; Spada, A.; Joglar, J.;
Llebaria, A.; Lagunas, C.; Fernandez, A. G.; Spisani, S.;
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(11) (a) Nakagawa, H.; Sakamoto, S.; Sago, Y.; Nagashima, H.
Toxins 2013, 5, 590. (b) Zachariasova, M.; Cajka, T.;
Godula, M.; Kostelanska, M.; Malachova, A.; Hajslova, J.
Book of Abstracts of the 4th International Symposium on
Recent Advances in Food Analysis (RAFA); Institute of
Chemical Technology Praque: Prague, Czech Republic,
2009, 391.
(27) Procedure for the Synthesis of Gentiobiosyl Acetimidate
Donor 10
To a solution of gentiobiose heptaacetate (8, 0.8 g, 1.3
mmol) in dry CH2Cl2 (20 mL) was added K2CO3 (0.36 g, 2.6
mmol) and N-phenyl-2,2,2-trifluoroacetimidoyl chloride (9,
0.4 mL, 2.6 mmol). The reaction mixture was stirred at r.t.
and under argon for 24 h. The solvent was removed on a
rotary evaporator, and the residue was purified by column
chromatography (hexanes–EtOAc, 3:1) to yield 10 (0.82 g,
78%) as a white solid.
(12) (a) El-Sharkawy, S. H. Acta Pharm. Jugosl. 1989, 39, 303.
(b) Versilovskis, A.; Huybrecht, B.; Tangni, E.; Pussemier,
L.; De Saeger, S.; Callebaut, A. Food Addit. Contam. 2011,
28, 1687.
(13) Grabley, S.; Gareis, M.; Böckers, W.; Thiem, J. Synthesis
1992, 1078.
(14) Stevenson, D. E.; Hansen, R. P.; Loader, J. I.; Jensen, D. J.;
Cooney, J. M.; Wilkins, A. L.; Miles, C. O. J. Agric. Food
Chem. 2008, 56, 4032.
(15) Mikula, H.; Hametner, C.; Berthiller, F.; Warth, B.; Krska,
R.; Adam, G.; Froehlich, J. World Mycotoxin J. 2012, 5, 289.
(16) (a) Zhang, Z.; Yu, B. J. Org. Chem. 2003, 68, 6309.
(b) Hayasaka, Y.; Baldock, G. A.; Parker, M.; Pardon, K. H.;
Black, C. A.; Herderich, M. J.; Jeffery, D. W. J. Agric. Food
Chem. 2010, 58, 10989.
(17) (a) Tietze, L. F.; Schmuck, K.; Schuster, H. J.; Müller, M.;
Schuberth, I. Chem. Eur. J. 2011, 17, 1922. (b) Touisni, N.;
Maresca, A.; McDonald, P. C.; Lou, Y.; Scozzafava, A.;
Dedhar, S.; Winum, J.-Y.; Supuran, C. T. J. Med. Chem.
2011, 54, 8271.
Analytical Data for 10
1H NMR (200 MHz, CDCl3): δ = 7.39–7.22 (m, 2 H), 7.18–
7.06 (m, 1 H), 6.86 (d, J = 7.6 Hz, 2 H), 5.77 (br s, 1 H),
5.25–5.15 (m, 2 H), 5.11 (d, J = 10.3 Hz, 1 H), 5.05–4.92 (m,
3 H), 4.56 (d, J = 7.8 Hz, 1 H), 4.25 (dd, J = 12.3, 4.7 Hz, 1
H), 4.12 (dd, J = 12.3, 2.3 Hz, 1 H), 3.90 (d, J = 9.4 Hz, 1 H),
3.76–3.56 (m, 3 H), 2.08 (s, 3 H), 2.06 (s, 3 H), 2.03 (s, 3 H),
2.02 (s, 3 H), 2.01 (s, 3 H), 2.00 (s, 3 H), 1.95 (s, 3 H). 13
C
NMR (50 MHz, CDCl3): δ = 170.8 (s, 1 C), 170.3 (s, 1 C),
170.27 (s, 1 C), 169.6 (s, 1 C), 169.52 (s, 1 C), 169.49 (s, 1
C), 169.1 (s, 1 C), 142.9 (s, 1 C), 128.8 (d, 2 C), 124.6 (d, 1
C), 119.2 (d, 2 C), 100.5 (d, 1 C), 94.3 (d, 1 C), 74.1 (d, 1 C),
72.6 (d, 1 C), 72.4 (d, 1 C), 71.9 (d, 1 C), 70.8 (d, 1 C), 70.2
(d, 1 C), 68.3 (d, 1 C), 68.2 (d, 1 C), 67.3 (t, 1 C), 61.7 (t, 1
C), 20.9 (q, 1 C), 20.7 (q, 4 C), 20.6 (q, 1 C), 20.5 (q, 1 C).
HRMS (ESI+): m/z calcd for C34H40F3NNaO18+ [M + Na]+:
830.2090; found: 830.2099.
(18) Shimoda, K.; Kubota, N.; Hamada, H.; Hamada, H.
Molecules 2011, 16, 4740.
(19) Procedure for the Lewis Acid Mediated Synthesis of
β-Gentiobiose Octaacetate (6)
(28) Mikula, H.; Hametner, C.; Fröhlich, J. Synth. Commun.
2013, 43, 1939.
(29) General Procedure A: Silver(I)-Activated Königs–Knorr
Glycosylation Using Gentiobiosyl Bromide 7
1,2,3,4-Tetra-O-acetyl-β,D-glucose (4, 3.8 g, 11 mmol) and
trichloroacetimidoyl donor 5 (5.8 g, 11.8 mmol) were
dissolved in dry CH2Cl2 (100 mL). MS 3 Å (10 g) was added,
and the mixture was stirred at r.t. under argon for 1 h. After
cooling to –40 °C, TMSOTf (0.2 mL, 1.1 mmol) was added,
and the reaction mixture was stirred at –40 °C for 16 h. The
reaction was quenched by addition of Et3N, filtered through
Celite, and concentrated. The crude product was purified by
column chromatography (hexanes–EtOAc, 5:1 to 1:1) to
obtain 6 (3.1 g, 43%) as a white solid. Analytical data
matched those reported in the literature.22
To a solution of the glycosyl acceptor (1 equiv) and
gentiobiosyl bromide 7 (2.5 equiv) in CH2Cl2 or MeCN (5
mL/mmol) MS 3 Å (0.1 g/mL) was added, and the reaction
mixture was stirred at r.t. under argon for 1 h. After addition
of silver(I) salt (1.5 equiv) stirring was continued in the dark
for an additional period of 48 h. Filtration through Celite and
concentration under reduced pressure afforded the crude
product mixture.
(30) General Procedure B: Lewis Acid Mediated
Glycosylation Using Acetimidate 10
(20) Lopez, M.; Trajkovic, J.; Bornaghi, L. F.; Innocenti, A.;
Vullo, D.; Supuran, C. T.; Poulsen, S.-A. J. Med. Chem.
2011, 54, 1481.
(21) Kimmel, R.; Kafka, S.; Košmrlj, J. Carbohydr. Res. 2010,
345, 768.
(22) (a) Bochkov, A. F.; Kochetkov, N. K. Carbohydr. Res. 1975,
39, 355. (b) Banik, B. K.; Samajdar, S.; Banik, I.; Zegrocka,
O.; Becker, F. F. Heterocycles 2001, 55, 227.
(23) Hunsen, M.; Long, D. A.; D’Ardenne, C. R.; Smith, A. L.
Carbohydr. Res. 2005, 340, 2670.
To a solution of the glycosyl acceptor (1 equiv) and
gentiobiosyl bromide 7 (1.5–2.5 equiv) in CH2Cl2 or
dioxane–toluene (5 mL/mmol) MS 3 Å (0.1 g/mL) was
added, and the reaction mixture was stirred at r.t. under
argon for 1 h. After cooling to –10 °C, TMSOTf or BF3·OEt2
(0.02–0.1 equiv) was added, and stirring was continued at
–10 °C for an additional period of 16 h. The reaction mixture
was filtered through Celite, washed with sat. aq NaHCO3,
dried over Na2SO4, and concentrated under reduced pressure
to afford the crude product mixture.
(24) Procedure for Anomeric Deprotection of 6
To a solution of 6 (1.31 g, 1.9 mmol) in dry THF (45 mL)
was added benzylamine (0.23 mL, 2.1 mmol), and the
reaction mixture was stirred at r.t. for 48 h. The solvent was
removed under reduced pressure, and the residue was
dissolved in CH2Cl2 (100 mL), washed with 1 M HCl (2 ×
100 mL) and H2O (100 mL). The organic layer was dried
over Na2SO4 and concentrated. Column chromatography
(hexanes–EtOAc, 1:1 to 1:3) afforded the desired product 8
(0.91 g, 76%) as a white solid. Analytical data matched those
reported in the literature.25
(31) General Procedure C: Phase-Transfer Glycosylation
Using Gentiobiosyl Bromide 7
Glycosyl acceptor (1 equiv), 7 (2.8 equiv), and TBAB (1
equiv) were dissolved in CHCl3 (80 mL/mmol). Borate
buffer (80 mL/mmol) was added, and the reaction mixture
was warmed to 45 °C. The pH was kept between 10.5 and
11.0 by dropwise addition 0.1 M aq NaOH. After 6 h the
organic layer was separated, dried over Na2SO4, and
concentrated to afford the crude product mixture.
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 1830–1834

1834
J. Weber et al.
LETTER
(32) General Procedure D: Basic Hydrolysis of Crude Acetyl-
Protected Gentiobiosides
1 C), 77.9 (d, 1 C), 77.8 (d, 1 C), 77.3 (d, 1 C), 75.1 (d, 1 C),
74.7 (d, 1 C), 71.6 (d, 1 C), 71.4 (d, 1 C), 70.2 (d, 1 C), 70.1
(t, 1 C), 62.7 (t, 1 C), 22.1 (q, 2 C). HRMS (ESI–): m/z calcd
for C22H31O14– [M – H]–: 519.1719; found: 519.1707.
(34) Synthesis of ZEN-14-β,D-gentiobioside (3)
Crude acetyl-protected gentiobioside (12 or 14) was filtered
over silica gel (hexanes–EtOAc = 3:1 to 1:2) to remove most
of the carbohydrate impurities. Appropriate fractions were
pooled and concentrated. The residue was dissolved in THF–
H2O (4:1, 50 mL/mmol), KOH (10 equiv) was added, and
the reaction mixture was stirred for 2 h at r.t. After addition
of 0.1 N HCl (pH 6.8), the solution was diluted with H2O and
immediately extracted with EtOAc. The combined organic
layer was dried over Na2SO4 and concentrated. RP-C18
column chromatography (MeCN–H2O gradient elution, used
for 13) or preparative RP-C18-HPLC (MeCN–H2O gradient
elution, used for 3) yielded the desired gentiobioside.
(33) Synthesis of Gentiobioside 13
Starting from ZEN (1, 33.4 mg, 0.105 mmol) and following
general procedures C and D, ZEN-14-β,D-gentiobioside (3)
was obtained as a white solid (29 mg, 43%).
Analytical Data for 3
1H NMR (400 MHz, DMSO-d6): δ = 10.43 (br s, 1 H), 6.65
(d, J = 1.5 Hz, 1 H), 6.53 (d, J = 1.5 Hz, 1 H), 6.40 (d, J =
15.4 Hz, 1 H), 6.01 (dt, J = 15.4, 7.1, 1 H), 5.36 (d, J = 4.3
Hz, 1 H), 5.18 (d, J = 3.2 Hz, 1 H), 5.11–5.04 (m, 1 H), 4.98–
4.86 (m, 2 H), 4.90 (d, J = 7.8 Hz, 1 H), 4.53 (br s, 1 H), 4.19
(d, J = 7.8 Hz, 1 H), 3.98 (d, J = 10.2 Hz, 1 H), 3.66 (d, J =
12.1 Hz, 1 H), 3.63–3.55 (m, 2 H), 3.47–3.41 (m, 1 H), 3.30–
3.18 (m, 3 H), 3.16–3.09 (m, 1 H), 3.08–3.03 (m, 2 H), 2.98
(t, J = 8.1 Hz, 1 H), 2.39–2.32 (m, 1 H), 2.32–2.26 (m, 2 H),
2.25–2.16 (m, 1 H), 2.07–1.95 (m, 1 H), 1.83–1.71 (m, 1 H),
1.70–1.59 (m, 3 H), 1.58–1.45 (m, 2 H), 1.27 (d, J = 6.1 Hz,
6 H). 13C NMR (100 MHz, DMSO-d6): δ = 211.2 (s, 1 C),
168.7 (s, 1 C), 160.0 (s, 1 C), 158.5 (s, 1 C), 138.4 (s, 1 C),
133.3 (d, 1 C), 129.8 (d, 1 C), 112.8 (s, 1 C), 105.2 (d, 1 C),
103.9 (d, 1 C), 103.1 (d, 1 C), 100.6 (d, 1 C), 77.3 (d, 1 C),
77.1 (d, 1 C), 76.8 (d, 1 C), 74.0 (d, 1 C), 73.6 (d, 1 C), 71.9
(d, 1 C), 70.4 (d, 1 C), 69.9 (d, 1 C), 68.9 (t, 1 C), 61.4 (t, 1
C), 43.5 (t, 1 C), 37.1 (t, 1 C), 34.8 (t, 1 C), 31.4 (t, 1 C), 21.4
(t, 2 C), 20.3 (q, 2 C). HRMS (ESI–): m/z calcd for
Starting from ZEN mimic 11 (11.7 mg, 0.06 mmol) and
following general procedures C and D, gentiobioside 13 was
obtained as a white solid (9.3 mg, 30%).
Analytical Data for 13
1H NMR (400 MHz, MeOD): δ = 7.77 (d, J = 8.8 Hz, 1 H),
6.71 (d, J = 1.8 Hz, 1 H), 6.64 (dd, J = 8.8, 1.8 Hz, 1 H), 5.26
(sept, J = 6.2 Hz, 1 H), 4.98 (d, J = 6.9 Hz, 1 H), 4.36 (d, J =
7.5 Hz, 1 H), 4.17 (d, J = 11.3 Hz, 1 H), 3.91–3.83 (m, 1 H),
3.88–3.78 (m, 2 H), 3.81–3.74 (m, 1 H), 3.67 (dd, J = 11.3,
5.4 Hz, 1 H), 3.50–3.44 (m, 2 H), 3.44–3.38 (m, 1 H), 3.36–
3.30 (m, 1 H), 3.28–3.20 (m, 2 H), 1.38 (d, J = 6.2 Hz, 6 H).
13C NMR (100 MHz, MeOD): δ = 170.7 (s, 1 C), 164.6 (s, 1
C), 164.4 (s, 1 C), 132.4 (d, 1 C), 109.6 (d, 1 C), 108.4 (s, 1
C), 104.94 (d, 1 C), 104.88 (d, 1 C), 101.32 (d, 1 C), 78.0 (d,
C30H41O15– [M – H]–: 641.2451; found: 641.2455.
Synlett 2013, 24, 1830–1834
© Georg Thieme Verlag Stuttgart · New York

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