Stereoselective Synthesis of Quercetin 3-O-Glycosides of 2-Amino-2-Deoxy-d-Glucose under Phase Transfer Catalytic Conditions

Article abstract of DOI:10.1080/07328303.2014.996290

This article describes the stereoselective synthesis of quercetin 3-O-glycosides of 2-amino-2-deoxy-d-glucose. Efficient 1,2-trans-glycosylation of protected quercetin with N-acetyl-protected 2-amino-2-deoxy-d-glucose chloride was achieved under phase transfer catalytic conditions in a 0.15 M aqueous K₂CO₃/chloroform system using tetrabutylammonium bromide as the catalyst. On the contrary, glycosylation with the N-phthalimido-protected bromide donor under the same conditions was found to give predominantly 1,2-cis-glycoside product.

Full text of DOI:10.1080/07328303.2014.996290

This article was downloaded by: [University of Saskatchewan Library]
On: 16 March 2015, At: 13:29
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Carbohydrate Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/lcar20
Stereoselective Synthesis of Quercetin
3-O-Glycosides of 2-Amino-2-Deoxy-d-
Glucose Under Phase Transfer Catalytic
Conditions
Zhiling Caoa, Yingying Qua, Jiexing Zhoua, Weiwei Liua & Guowei
Yaob
a Jiangsu Key Laboratory of Marine Biotechnology, School of
Chemical Engineering, Huaihai Institute of Technology, Lianyungang
222005, China
b School of Life Science, Beijing Institute of Technology, Beijing
100081, China
Published online: 03 Feb 2015.
Click for updates
To cite this article: Zhiling Cao, Yingying Qu, Jiexing Zhou, Weiwei Liu & Guowei Yao (2015)
Stereoselective Synthesis of Quercetin 3-O-Glycosides of 2-Amino-2-Deoxy-d-Glucose Under
Phase Transfer Catalytic Conditions, Journal of Carbohydrate Chemistry, 34:1, 28-40, DOI:
10.1080/07328303.2014.996290
To link to this article: http://dx.doi.org/10.1080/07328303.2014.996290
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Journal of Carbohydrate Chemistry, 34:28–40, 2015
ꢀ
C
Copyright Taylor & Francis Group, LLC
ISSN: 0732-8303 print / 1532-2327 online
DOI: 10.1080/07328303.2014.996290
Stereoselective Synthesis
of Quercetin 3-O-Glycosides
of 2-Amino-2-Deoxy-D-Glucose
Under Phase Transfer Catalytic
Conditions
Zhiling Cao,1 Yingying Qu,1 Jiexing Zhou,1 Weiwei Liu,1
and Guowei Yao2
1Jiangsu Key Laboratory of Marine Biotechnology, School of Chemical Engineering,
Huaihai Institute of Technology, Lianyungang 222005, China
2School of Life Science, Beijing Institute of Technology, Beijing 100081, China
GRAPHICAL ABSTRACT
Received October 8, 2013; accepted December 4, 2014.
Address correspondence to Zhiling Cao, Jiangsu Key Laboratory of Marine Biotech-
nology, School of Chemical Engineering, Huaihai Institute of Technology, Lianyungang
222005, China. E-mail: zhilingcao2013@163.com
28

Synthesis of Quercetin 3-O-Glycosides
29
Figure 1: Structures of quercetin and its 1,2-trans glycoside of 2-amino-2-deoxy-D-glucose 1.
This article describes the stereoselective synthesis of quercetin 3-O-glycosides of 2-
amino-2-deoxy-D-glucose. Efficient 1,2-trans-glycosylation of protected quercetin with
N-acetyl-protected 2-amino-2-deoxy-D-glucose chloride was achieved under phase
transfer catalytic conditions in a 0.15 M aqueous K2CO3/chloroform system using
tetrabutylammonium bromide as the catalyst. On the contrary, glycosylation with the
N-phthalimido-protected bromide donor under the same conditions was found to give
predominantly 1,2-cis-glycoside product.
Keywords Quercetin; Glycosides; 2-Amino-2-deoxy-D-glucose; Stereoselective synthe-
sis; Phase transfer catalysis
INTRODUCTION
Glycosides, glycoconjugates, and polysaccharides are the most abundant na-
ture products, in which sugar residues are attached to one another or to
aglycones via O-glycosidic bonds.[1] Typical flavonoids, including quercetin
and its glycosides, are polyphenolic compounds and widely distributed in
plants.[2] Quercetin glycosides are not only dietary flavonoids but also promis-
ing compounds for disease prevention and therapy.[3–5] A variety of sugars
(e.g., glucose, galactose, and arabinose) are present in quercetin glycosides,
which can enhance quercetin solubility and absorption.[6] The demand for ef-
ficient methodologies to synthesize quercetin glycosides is now increasing.[7,8]
However, regioselective synthesis of quercetin glycosides remains a difficult
task.[9–13] Furthermore, amino sugar glycosides are rarely found in natural
and unnatural flavonoid products. In a few reports, a 3-amino-ribopyranose
flavonoid was isolated from a culture of Streptomyces sp., which has exhib-
ited antibacterial activity against Bacillus subtilis.[14] Recently, Joong-Hoon
Ahn and coworkers reported a novel quercetin glycoside, 3-O-β-glycoside of
2-amino-2-deoxy-D-glucose (1) (Fig. 1), which was isolated from the culture
broth of an engineered Escherichia coli.[15] Compound 1 has the unique

Z. Cao et al.
30
flavonoid structure and potentially intriguing biological functions because 2-
amino-2-deoxy-D-glucose is distributed in many living organisms and plays an
important role in their life cycle.[16,17]
The isolation of 1 and its derivatives from nature has been limited by their
low biosynthetic yields and diversity of the anomeric linkages. The chemical
synthesis of 1,2-cis glycosides of 2-amino-2-deoxy-D-glucose is also challeng-
ing, and no successful general method for 1,2-cis glycosylation has emerged
yet.[18–21] In this article, we report the efficient preparation of compound 1 from
rutin. In the process, our efforts were focused on the stereoselective synthesis
of quercetin 1,2-cis-glycosides of 2-amino-2-deoxy-D-glucose.
RESULTS AND DISCUSSION
Quercetin aminosugar glycoside 1 was retrosynthetically disconnected into
two distinct fragments—suitably protected quercetin and 2-amino-2-deoxy-
D-glucosyl donor, respectively. For quercetin glycoside synthesis, O-benzyl-
protected quercetins have always been used, and regioselective benzylation or
glycosylation of quercetin is feasible due to the difference in reactivity among
its phenolic OH groups. It has been proved that quercetin phenolic OH groups
have the preferential glycosylation reactivity order of 7-OH > 3-OH > 4ꢁ-OH
> 3ꢁ-OH > 5-OH.[22] Therefore, we first developed an efficient method for the
synthesis of 7,4ꢁ-di-O-benzylquercetin (3), which should be good enough to be
selectively glycosylated at 3-OH. Previously, Jurd and coworkers reported the
preparation of 3 from quercetin via controlled benzylation of quercetin pen-
tacetate.[23] Although Jurd’s procedure has been cited and adapted by many
researchers, the method is tedious and low yielding.[11] In our synthesis of 3,
rutin, quercetin-3-O-rudinoside, was used as the starting material (Sch. 1).
Benzylation of rutin was well controlled by slow addition of two equivalents of
benzyl bromide in DMF. Without the need for separation of benzylated rutin in-
termediate 2, subsequent hydrolysis with concentrated hydrochloric acid gave
3 in a 58% yield.
Scheme 1: Synthesis of 7,4’-di-O-benzylquercetin 3.
In previous syntheses of quercetin O-glycosides, glycosyl bromides or
chlorides have been generally employed as donors for glycosylations under
Koenigs–Knorr conditions promoted by silver salts, inorganic base, or phase

Synthesis of Quercetin 3-O-Glycosides
31
transfer catalysis (PTC).[24] For the glycosylation of 3, we chose the easily ac-
cessible 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-glucopyranosyl chloride 6
as glycosyl donor, which was prepared in a high yield by treatment of 1,2-trans-
glucosamine penta-acetate 5 with a mixture of thionyl chloride and acetic acid
(Sch. 2).
Scheme 2: Synthesis of chloride donor 6.
For the glycosylation of 3 with 6, we initially investigated conditions using
Ag2O, AgOTf, or inorganic base as activators but without success. After mul-
tiple attempts, the glycosylation reaction was achieved under mild PTC condi-
tions in a 15 mg/mL K2CO3/CHCl3 system with tetrabutylammonium bromide
as the catalyst to yield 1,2-trans-quercetin glycoside 7 (68% yield, Sch. 3). The
resulting glycoside 7 was O-deacetylated using sodium methoxide in a mixture
of methanol and THF. Further debenzylation of 8 with 10% Pd/C and H2 in
THF afforded quercetin glycoside 1 (45% total yield). Glycoside 1 was identi-
fied as the 1,2-trans-β-anomer based on the anomeric proton coupling constant
1
J1,2 (8.4 Hz) of its sugar residue observed in H NMR spectra. Furthermore,
correlation in the HMBC spectrum between anomeric proton (δ 5.62) and C-3
carbon (δ 133.2) was also observed (Fig. 2) to clearly indicate that the glycosidic
linkage was indeed at 3-OH.
Scheme 3: Synthesis of quercetin 1,2-trans-glycoside 1.

Z. Cao et al.
32
Figure 2: Observed correlations in the HMBC spectrum of 1.
In recent decades, a number of new glycosylation methods have been de-
veloped for carbohydrate synthesis. For example, glycosyl trichloroacetimidate
and peracetate donors have been used successfully in the glycosylation of phe-
nols.[25,26] This prompted us to investigate other donors for synthesis of 1.
We first tried glycosylation of the 3-OH in 3 with trichloroacetimidate and
penta-acetate donors of 2-amino-2-deoxy-D-glucose in the presence of Lewis
acid. However, our attempts under various conditions failed. We then tried
the traditional Koenigs–Knorr BTC method using glycosyl halide donors 10
and 11 bearing a phthaloyl (Phth) protecting group at N-2-position, which
were prepared by reacting 1,3,4,6-tetra-O-acetyl-2-deoxy-2-phthalimido-β-D-
glucopyranose 9 with PCl5-BF3 and HBr, respectively (Sch. 4). It was observed
that glycosyl bromide 11 exhibited higher reactivity than glycosyl chloride
Scheme 4: Synthesis of glycosylate in higher yield 1,2-cis-glycoside 13.

Synthesis of Quercetin 3-O-Glycosides
33
10 in the glycosylation of quercetin 3. More interestingly, both reactions af-
forded 1,2-cis-glycoside 12 unexpectedly, which after deprotection was con-
verted to 13. The 1,2-cis-configuration of 12 and 13 was determined based on
the anomeric proton coupling constants J1,2 (3.7 Hz and 3.6 Hz, respectively)
of its sugar residues observed in their 1H NMR spectra.
Phthalimido and acetyl groups are classical neighboring partic-
ipation groups; thus, normally glycosylation reactions of 2-deoxy-2-
acetamido/phthalimidoglycosyl halides have the tendency to form 1,2-trans-
2-amino glycosides.[27,28] The abnormal phenomenon that occurred in our
synthesis of 1,2-cis glycoside 12 may be due to the assumed SN2 mechanism,
shown in Scheme 5. In the BTC system, there is no powerful promoter for the
departure of the bromide anion from glycosyl donors to form a reactive bicyclic
acyloxonium ion intermediate. Moreover, the enolic hydroxyl group at the
C-3 position of quercetin appeared to be more nucleophilic in the basic BTC
system, and its efficient attack at the anomeric position of the glycosyl donor
was primarily from the opposite direction of the halogen atom. Accordingly,
reversed-phase HPLC was used for monitoring the glycosylation reaction of
11, and the 1,2-trans-glycoside product was not detected.
Scheme 5: Proposed mechanism for the glycosylation of quercetin.
CONCLUSION
In summary, we described the efficient stereoselective synthesis of quercetin
3-O-glycosides of 2-amino-2-deoxy-D-glucose. 1,2-Trans-glycosylation of pro-
tected quercetin was achieved with N-acetyl-protected chloride of 2-acetamino-
2-deoxy-D-glucose under PTC conditions in 0.15 M aqueous K2CO3/chloroform
with tetrabutylammonium bromide as the catalyst. On the contrary, the
N-phthalimido-protected bromide donor was found to give predominantly 1,2-
cis glycoside product. In carbohydrate chemistry, stereoselective synthesis

Z. Cao et al.
34
of 1,2-cis-glycosides is more challenging than that of 1,2-trans-glycosides.[29]
The glycosylation approach based on N-phthalimido-protected glycosyl halide
donors and BTC offers an exciting strategy for the synthesis of 1,2-cis-2-amino
glycosides of quercetin. Extension of this method to the preparation of other
flavonol glycosides of 2-acetamino-2-deoxy-D-glucose appeared worthy of fur-
ther exploration.
EXPERIMENTAL
General
All reagents were purchased from TCI Shanghai Co. unless otherwise spec-
ified. Melting points were measured on an XT-4 melting point apparatus and
are uncorrected. NMR spectra were obtained using Bruker AQS AVANCE 300-
MHz and 400-MHz spectrometers with tetramethylsilane as the internal stan-
dard. Mass spectra were performed with an Agilent Technologies MSD SL Trap
mass spectrometer with ESI source coupled with an 1100 Series HPLC system.
Silica gel GF254 plates (Yantai Chemical Industrials) were used for thin-layer
chromatography (TLC) observed under ultraviolet light (λ 254 nm).
7,4’-Di-O-Benzylquercetin (3)
To a solution of rutin (1.22 g, 2.0 mmol) in DMF (20 mL) was added K2CO3
(0.41 g, 3.0 mmol). The mixture was stirred at 60◦C, and then a solution of
BnBr (0.48 mL, 4.0 mmol) in DMF (10 mL) was added slowly. After further
stirring for 2 h, the mixture was concentrated under vacuum. Ethanol (30 mL)
and concentrated HCl (3 mL) were added in succession to the residue, and
the suspension was refluxed for 1 h. After cooling to rt, the precipitates were
filtered and recrystallized from ethanol to give 3 (0.53 g 57.6%) as a yellow
1
solid. [11] m.p. 182–183◦C (lit.[23] 181–182◦C). H NMR (300 MHz, DMSO): δ
12.43 (d, J = 9.0 Hz, 1H, 5-OH), 9.61 (s, 1H, 3’-OH), 9.42 (s, 1H, 3-OH), 7.76 (d,
J = 2.2 Hz, 1H, H-2’), 7.63 (dd, J = 8.6, 2.2 Hz, 1H, H-6’), 7.54–7.28 (m, 10H,
2 × Ph), 7.17 (d, J = 8.8 Hz, 1H, H-5’), 6.81 (d, J = 2.1 Hz, 1H, H-8), 6.44 (d,
J = 2.1 Hz, 1H H-6), 5.23 (s, 2H, CH2Ph), 5.21 (s, 2H, CH2Ph); ESI-MS m/z:
505 [M+Na]+. Anal. calcd. for C29H22O7: C, 72.19; H, 4.60. Found: C, 72.25; H,
4.51.
2-Acetamido-1,3,4,6-tetra-O-Acetyl-2-Deoxy-β-D-Glucopyrano-
Side (5)
To a mixture of acetic anhydride (6 mL) and pyridine (8 mL) in an ice
bath was added 2-amino-2-deoxy-D-glucose hydrochloride 1 (1.5 g, 8.3 mmol).
The mixture was allowed to gradually warm to ambient temperature and was

Synthesis of Quercetin 3-O-Glycosides
35
stirred overnight. The reaction mixture was then poured into ice water. The
resulting precipitates were collected by filtration, washed with ice water, and
dried to give compound 5 (3.07 g, 95%). m.p. 186–187◦C.[30] 1H NMR (300 MHz,
CDCl3): δ 5.78 (d, J = 9.5 Hz, 1H), 5.69 (d, J = 8.8 Hz, 1H), 5.21–5.05 (m, 2H),
4.36–4.19 (m, 2H), 4.11 (dd, J = 12.5, 2.2 Hz, 1H), 3.87–3.76 (m, 1H), 2.11 (s,
3H), 2.08 (s, 3H), 2.04 (s, 3H), 2.03 (s, 3H), 1.92 (s, 3H).
2-Acetamido-3,4,6-tri-O-Acetyl-2-Deoxy-α-D-Glucopyranosyl
Chloride (6)
To a solution of 5 (2.0 g, 5.1 mmol) in CH2Cl2 (20 mL) in an ice bath was
added thionyl chloride (6 mL) and acetic acid (1 mL). The mixture was stirred
at ambient temperature for 20 h and then concentrated in vacua. The residue
was recrystallized from ether to give 6 (1.66 g, 89%). m.p. 125–127◦C.[31] 1
H
NMR (300 MHz, CDCl3): δ 6.18 (d, J = 3.7 Hz, 1H), 5.86 (d, J = 8.7 Hz, 1H),
5.35–5.28 (m, 1H), 5.21 (t, J = 9.7 Hz, 1H), 4.53 (ddd, J = 10.6, 8.8, 3.7 Hz,
1H), 4.31–4.22 (m, 2H), 4.17–4.08 (m, 1H), 2.10 (s, 3H), 2.05 (s, 6H), 1.98 (s,
3H).
7,4ꢀ-Di-O-Benzylquercetin 3-O-(2ꢀꢀ-Acetamido-3ꢀꢀ,4ꢀꢀ,6ꢀꢀ-tri-O-Ac-
etyl-2ꢀꢀ-Deoxy)-β-D-Glucopyranoside (7)
To the solution of quercetin 3 (0.96 g, 2.0 mmol) in CHCl3 (15 mL) was
added tetrabutyl ammonium bromide (0.32 g, 1.0 mmol) and 0.15 M K2CO3
(15 mL). The mixture was vigorously stirred at 45◦C for 1 h. Then glycosyl
donor 6 (1.46 g, 4.0 mmol) was added. After further stirring for 5 h, the reaction
mixture was diluted with CH2Cl2 (20 mL), and the layers were separated. The
organic phase was washed with water and dried over MgSO4. After evapora-
tion of the solvent, the residue was purified by silica gel column chromatogra-
phy (hexane/EtOAc) to yield 7 (1.11 g 68.2%) as a yellow solid. m.p. 215–217◦C.
1H NMR (300 MHz, CDCl3): δ 12.29 (s, 1H, 5-OH), 7.75 (d, J = 2.0 Hz, 1H, H-
2ꢁ), 7.67 (dd, J = 8.7, 2.0 Hz, 1H, H-6ꢁ), 7.49–7.29 (m, 10H, Ph), 7.03 (d, J =
8.3 Hz, 1H, H-5ꢁ), 6.93 (d, J = 8.7 Hz, 1H, NH), 6.47 (d, J = 1.9 Hz, 1H, H-6),
6.45 (s, 1H, 3ꢁ-OH), 6.41 (d, J = 2.0 Hz, 1H, H-8), 5.46 (d, J = 8.7 Hz, 1H, H-
1ꢁꢁ), 5.22–5.10 (m, 4H, CH2Ph, H-4ꢁꢁ, H-3ꢁꢁ), 5.09 (s, 2H, CH2Ph), 4.41 (dd, J =
18.3, 8.6 Hz, 1H, H-2ꢁꢁ), 4.05 (d, J = 3.5 Hz, 2H, H-6ꢁꢁ), 3.74–3.59 (m, 1H, H-5ꢁꢁ),
2.06, 2.02, 2.01, 1.90 (s, 4 × 3H, CH3C = O). 13C NMR (75 MHz, CDCl3) δ 177.3,
170.8, 170.5, 170.3, 169.0, 164.4, 161.2, 156.7, 156.3, 148.3, 145.2, 135.5, 135.2,
134.5, 128.4, 128.4, 128.1, 128.0, 127.4, 127.1, 122.5, 121.9, 115.3, 111.5, 105.4,
100.1, 98.6, 92.8, 73.3, 72.0, 70.6, 70.1, 68.0, 61.6, 54.0, 23.0, 20.4, 20.22, 20.1.
ESI-MS m/z: 834 [M+Na]+. Anal. calcd. for C43H41NO15: C, 63.62; H, 5.09; N,
1.73. Found: C, 63.69; H, 5.00; N, 1.59.

Z. Cao et al.
36
7,4ꢀ-Di-O-Benzylquercetin 3-O-(2ꢀꢀ-Acetamido2ꢀꢀ-Deoxy)-β-D-
Glucopyranoside (8)
A mixture of glycoside 7 (0.85 g, 1.05 mmol) and MeONa (85.4 mg
1.58 mmol) in methanol (15 mL) was stirred at 30◦C for 10 h, and the solvent
was removed under vacuum. The residue was dissolved in ethanol (30 mL),
and its pH was adjusted to 6.0 with acetic acid. The solution was refluxed
for 0.5 h. After cooling, the precipitates were filtered, washed with water, and
1
dried to give 8 (0.56 g 78.6%) as a yellow solid. m.p. 171–173◦C. H NMR
(300 MHz, DMSO): δ 12.66 (s, 1H, 5-OH), 9.42 (s, 1H, 3ꢁ-OH), 8.09 (d, J =
9.3 Hz, 1H, NH), 7.83–7.67 (m, 2H, H-2ꢁ, H-6ꢁ), 7.59–7.26 (m, 10H, Ph), 7.11
(d, J = 8.7 Hz, 1H, H-5ꢁ), 6.81 (d, J = 1.8 Hz, 1H, H-6), 6.44 (d, J = 2.0 Hz,
1H, H-8), 5.65 (d, J = 8.5 Hz, 1H, H-1ꢁꢁ), 5.27–5.13 (m, 4H, 2 × CH2Ph), 4.36
(s, 1H, OH), 3.75 (dd, J = 18.6, 9.3 Hz, 1H, H-2ꢁꢁ), 3.56 (d, J = 11.2 Hz, 1H,
H-6ꢁꢁ), 3.50–3.15 (m, 2H, H-3ꢁꢁ, H-6ꢁꢁ, overlapped with signal of H2O), 3.14–3.01
(m, 2H, H-4ꢁꢁ, H-5ꢁꢁ), 1.85 (s, 3H, CH3C = O). 13C NMR (75 MHz, DMSO) δ
177.6, 169.7, 164.2, 161.2, 156.3, 155.6, 149.2, 146.4, 137.0, 136.2, 133.9, 128.6,
128.5, 128.2, 127.9, 127.8, 122.8, 121.5, 116.2, 113.2, 105.2, 99.0, 98.6, 93.0,
77.8, 74.1, 70.6, 70.0, 69.8, 60.9, 56.1, 23.3. ESI-MS m/z: 686 [M+H]+. Anal.
calcd. for C37H35NO12: C, 64.81; H, 5.15; N, 2.04. Found: C, 64.74; H, 5.24; N,
2.08.
Quercetin 3-O-(2ꢀꢀ-Acetamido-2ꢀꢀ-Deoxy)-β-D-
Glucopyranoside (1)
A mixture of compound 8 (0.34 g, 0.50 mmol) and 10% Pd/C (0.06 g) in
ethanol (5 mL) and THF (5 mL) was stirred under a hydrogen atmosphere at
ambient pressure and temperature for 5 h. After filtration, the solvent was
evaporated and the residue was recrystallized from acetone to give 1 (0.21 g
85.6%) as a yellow solid. m.p. 210–212◦C. 1H NMR (300 MHz, DMSO): δ 12.70
(s, 1H, 5-OH), 10.84 (s, 1H, OH), 9.73 (s, 1H, OH), 9.10 (s, 1H, OH), 8.04 (d,
J = 9.2 Hz, 1H, NH), 7.71–7.58 (m, 2H, H-2ꢁ, H-6ꢁ), 6.84 (d, J = 8.3 Hz, 1H,
H-5ꢁ), 6.40 (d, J = 1.9 Hz, 1H, H-6), 6.19 (d, J = 1.9 Hz, 1H, H-8), 5.62 (d,
J = 8.4 Hz, 1H, H-1ꢁꢁ), 5.04 (s, 2H, OH), 4.27 (s, 1H, OH), 3.75 (dd, J = 18.6,
9.2 Hz, 1H, H-2ꢁꢁ), 3.54 (dd, J = 11.3, 4.2 Hz, 1H, H-6ꢁꢁ), 3.44–3.24 (m, 2H,
H-6ꢁꢁ, H-3ꢁꢁ, overlapped with signal of H2O), 3.15–3.01 (m, 2H, H-4ꢁꢁ, H-5ꢁꢁ),
1.86 (s, 3H, CH3C = O). 13C NMR (75 MHz, DMSO-d6) δ 177.5, 169.7, 164.1,
161.3, 156.3, 155.6, 148.5, 144.8, 133.2, 121.9, 121.1, 116.1, 115.5, 104.0, 98.9,
98.6, 93.5, 77.7, 74.2, 70.5, 60.9, 56.0, 23.3. ESI-MS m/z: 528 [M+Na]+. Anal.
calcd. for C23H23NO12: C, 54.66; H, 4.59; N, 2.77. Found: C, 54.72; H, 4.47; N,
2.69.

Synthesis of Quercetin 3-O-Glycosides
37
2-Phthalimido-3,4,6-tri-O-Acetyl-2-Deoxy-β-D-Glucopyranosyl
Chloride (10)
2-Phthalimido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-glucopyranoside 9 was
prepared according to a reported method.[32,33] Phosphorus pentachloride
(1.6 g, 7.7 mmol) and BF3·Et2O (80 μL) were added to a solution of 9 (2.5 g,
5.2 mmol) in CH2Cl2 (50 mL). The reaction mixture was stirred for 30 min at
rt and was diluted with CH2Cl2 (20 mL). The mixture was washed with water,
saturated NaHCO3 solution, and saturated NaCl. After evaporation of solvent
under reduced pressure, the residue was recrystallized from ether to produce
10 (2.16 g, 91.5%). m.p.: 150–153◦C.[34] 1H NMR (300 MHz, CDCl3): δ 7.93–7.78
(m, 2H), 7.78–7.69 (m, 2H), 6.18 (d, J = 9.3 Hz, 1H), 5.77 (dd, J = 10.4, 9.3 Hz,
1H), 5.24 (t, J = 9.4 Hz, 1H), 4.50 (dd, J = 10.4, 9.6 Hz, 1H), 4.36–4.11 (m, 2H),
4.05–3.85 (m, 1H), 2.11 (s, 3H), 2.02 (s, 3H), 1.85 (s, 3H).
2-Phthalimido-3,4,6-tri-O-Acetyl-2-Deoxy-β-D-Glucopyranosyl
Bromide (11)
To a solution of 9 (0.9 g, 1.88 mmol) in CH2Cl2 (20 mL) was added hydrogen
bromide (30% in acetic acid, 2 mL). The mixture was stirred at rt for 2 h and
then diluted with CH2Cl2 (10 mL). The reaction mixture was washed with
water, saturated NaHCO3 solution, and saturated NaCl in succession and then
dried over MgSO4. After evaporation of the solvent under reduced pressure,
the residue was recrystallized from ether to produce 11 (0.76 g, 81.5%). m.p.:
123–124◦C.[35] 1H NMR (300 MHz, CDCl3): δ 7.91–7.84 (m, 2H), 7.79–7.72 (m,
2H), 6.40 (d, J = 9.6 Hz, 1H), 5.76 (dd, J = 10.3, 9.2 Hz, 1H), 5.25 (dd, J =
10.0, 9.6 Hz, 1H), 4.66–4.58 (m, 1H), 4.32 (dd, J = 12.6, 4.6 Hz, 1H), 4.19 (dd,
J = 12.6, 2.2 Hz, 1H), 3.96 (ddd, J = 10.3, 4.6, 2.2 Hz, 1H), 2.13 (s, 3H), 2.03
(s, 3H), 1.86 (s, 3H).
7,4ꢀ-Di-O-Benzylquercetin 3-O-(2ꢀꢀ-Phthalimido-3ꢀꢀ,4ꢀꢀ,6ꢀꢀ-tri-O-Ac-
etyl-2ꢀꢀ-Deoxy)-α-D-Glucopyranoside (12)
To a solution of quercetin 3 (0.96 g, 2.0 mmol) in CHCl3 (15 mL) was added
tetrabutyl ammonium bromide (0.32 g, 1.0 mmol) and 0.15 M K2CO3 (15 mL).
The mixture was vigorously stirred at 45◦C for 1 h. Then, glucosyl bromide
10 (1.99 g, 4.0 mmol) was added. After further stirring for 5 h, the reaction
mixture was diluted with CH2Cl2 (20 mL), and the layers were separated. The
organic phase was washed with water and dried (MgSO4). After evaporation
of the solvent, the residue was purified by silica gel column chromatography
(hexane/EtOAc) to give 12 (1.18 g, 65.6%) as a yellow solid. m.p. 228–229◦C.
1
[α] + 6.2◦ (c 0.60, CHCl3). H NMR (300 MHz, CDCl3): δ 12.0 (s, 1H, 5-OH),
7.99–7.82 (m, 2H, Ph), 7.74 (dd, J = 5.5, 2.8 Hz, 2H, Ph), 7.57 (dd, J = 8.4,
2.1 Hz, 1H, H-6ꢁ), 7.52 (d, J = 2.1 Hz, 1H, H-2ꢁ), 7.50–7.31 (m, 10H, Ph), 7.16
(d, J = 8.5 Hz, 1H, H-5ꢁ), 6.44 (d, J = 2.2 Hz, 1H, H-6), 6.37 (s, 1H, 3ꢁ-OH), 6.32

Z. Cao et al.
38
(d, J = 2.2 Hz, 1H, H-8), 5.95 (d, J = 3.7 Hz, 1H, H-1ꢁꢁ), 5.25 (s, 2H, CH2Ph),
5.08 (s, 2H, CH2Ph), 4.96 (t, J = 9.7 Hz, 1H, H-3ꢁꢁ), 4.66 (dd, J = 11.7, 3.7 Hz,
1H, H-2ꢁꢁ), 4.12 (dd, J = 14.3, 7.1 Hz, 1H, H-4ꢁꢁ), 3.90 (dd, J = 12.5, 3.9 Hz, 1H,
H-6ꢁꢁ), 3.60–3.51 (m, 2H, H-6ꢁꢁ, H-5ꢁꢁ), 1.98, 1.97, 1.92 (s, 4 × 3H, CH3C = O). 13
C
NMR (75 MHz, CDCl3) δ 176.9, 170.0, 169.3, 169.2, 164.1, 161.3, 156.8, 156.3,
148.1, 145.7, 135.3, 135.2, 133.7, 133.6, 130.4, 128.4, 128.2, 128.1, 127.8, 127.2,
126.9, 123.1, 122.6, 122.0, 114.8, 111.9, 105.4, 98.3, 97.4, 92.6, 70.7, 69.9, 69.2,
69.0, 66.6, 65.1, 60.8, 52.7, 20.3, 20.2, 20.1. ESI-MS m/z: 922 [M+Na]+. Anal.
calcd. for C49H41NO16: C, 65.40; H, 4.59; N, 1.56. Found: C, 65.63; H, 4.62; N,
1.59.
Quercetin 3-O-(2ꢀꢀ-Phthalimido-2ꢀꢀ-Deoxy)-α-D-Glucopyranoside
(13)
A mixture of glycoside 12 (0.4 g, 0.45 mmol) and MeONa (36.4 mg,
0.67 mmol) in methanol (10 mL) was stirred at 30◦C for 10 h. After evapo-
ration of the solvent, the residue was dissolved in ethanol (30 mL), and its pH
was adjusted to 6.0 with acetic acid. The solution was refluxed for 0.5 h. Af-
ter cooling, the precipitates were filtered, washed with water, and dried. The
resulting intermediate was dissolved in a mixture of ethanol (5 mL) and THF
(5 mL) and was stirred with 10% Pd/C (0.08 g) under hydrogen at ambient
pressure and temperature for 5 h. After filtration, the solvent was evaporated
and the residue was recrystallized from acetone to give 13 (0.21 g, 80.2%) as a
yellow solid. m.p. 227–230◦C. [α] + 11.0◦ (c 0.35, CH3OH). 1H NMR (400 MHz,
DMSO): δ 12.63 (s, 1H, 5-OH), 8.48 (s, 1H, 7-OH), 7.93 (s, 1H, 2ꢁ-H), 7.46–7.38
(m, 2H, Ph), 7.37–7.30 (m, 2H, Ph), 7.13 (d, J = 8.3 Hz, 1H, H-6ꢁ), 6.84 (d,
J = 8.3 Hz, 1H, H-5ꢁ), 6.51 (d, J = 3.6 Hz, 1H, H-1ꢁꢁ), 6.28 (s, 1H, H-6),
6.07 (s, 1H, H-8), 4.02–3.89 (m, 1H, H-2ꢁꢁ), 3.58–3.50 (m, 1H, H-3ꢁꢁ), 3.44 (dd,
J = 14.0, 7.0 Hz, 1H, H-6ꢁꢁ), 3.29–3.10 (m, 3H, H-6ꢁꢁ, H-5ꢁꢁ H-4ꢁꢁ). 13C NMR
(100 MHz, DMSO) δ 177.2, 174.0, 167.2, 160.9, 156.5, 155.1, 148.6, 145.8, 142.2,
131.1, 130.7, 130.2, 128.9, 127.3, 126.7, 120.4, 118.4, 116.7, 115.5, 102.6, 99.3,
94.9, 93.9, 74.6, 71.6, 68.9, 59.6, 56.0, 54.3. ESI-MS m/z: 616 [M+Na]+. Anal.
calcd. for C29H23NO13: C, 58.69; H, 3.91; N, 2.36. Found: C, 58.96; H, 3.56; N,
2.59.
FUNDING
The work described in this article was supported by the Natural Sci-
ence Research Foundation of the Jiangsu Higher Education Institutions
(13KJB150006, 12KJB350001), the Science and Technology Critical Project
Foundation of Lianyungang (CN1304, CG1202), the PAPD Program (a Project
Funded by the Priority Academic Program Development of Jiangsu Higher Ed-
ucation Institutions), and the Open-ended Funds of Jiangsu Institute of Ma-
rine Resources (No. HK13004).

Synthesis of Quercetin 3-O-Glycosides
39
REFERENCES
1. Demchenko, A.V. Handbook of Chemical Glycosylation. Wiley-VCH: Weinheim,
Germany, 2008.
2. Cook, N.; Samman, S. Flavonoids—chemistry, metabolism, cardioprotective ef-
fects, and dietary sources. J. Nutr. Biochem. 1996, 7, 66–76.
3. Erlund, I. Review of the flavonoids quercetin, hesperetin, and naringenin. Dietary
sources, bioactivities, bioavailability, and epidemiology. Nutr. Res. 2004, 24, 851–874.
4. Murakami, A.; Ashida, H.; Terao, J. Multitargeted cancer prevention by quercetin.
Cancer Lett. 2008, 269, 315–325.
5. Russo, M.; Spagnuolo, C.; Tedesco, I.; Bilotto, S.; Russo, G.L. The flavonoid
quercetin in disease prevention and therapy: facts and fancies. Biochem. Pharmacol.
2012, 83, 6–15.
6. Lin, C.-F.; Leu, Y.-L.; Al-Suwayeh, S.A.; Ku, M.-C.; Hwang, T.-L.; Fang, J.-Y.
Anti-inflammatory activity and percutaneous absorption of quercetin and its poly-
methoxylated compound and glycosides: The relationships to chemical structures. Eur.
J. Pharm. Sci. 2012, 47, 857–864.
7. Lee, Y.S.; Huh, J.Y.; Nam, S.H.; Kim, D.; Lee, S.B. Synthesis of quercetin-3-O-
glucoside from rutin by Penicillium decumbens naringinase. J. Food Sci. 2013, 78,
C411–C415.
8. Kajjout, M.; Rolando, C. Regiospecific synthesis of quercetin O-β-d-glucosylated
and O-β-d-glucuronidated isomers. Tetrahedron 2011, 67, 4731–4741.
9. Zhang, Y.; Wang, K.; Zhan, Z.; Yang, Y.; Zhao, Y. Synthesis of quercetin
3-O-β-d-apiofuranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)]-β-d-glucopyranoside.
Tetrahedron Lett. 2011, 52, 3154–3157.
10. Kajjout, M.; Zemmouri, R.; Rolando, C. An expeditious synthesis of quercetin
3- O-β-d-glucuronide from rutin. Tetrahedron Lett. 2011, 52, 4738–4740.
11. Ren, X.; Shen, L.-l.; Muraoka, O.; Cheng, M. Synthesis of quercetin 3-O-[6ꢁꢁ-O-
(trans-p-Coumaroyl)]-β-D-glucopyranoside. J. Carbohyd. Chem. 2011, 30, 119–131.
12. Li, M.; Han, X.; Yu, B. Facile synthesis of flavonoid 7-O-glycosides. J. Org. Chem.
2003, 68, 6842–6845.
13. Du, Y.; Wei, G.; Linhardt, R.J. Total synthesis of quercetin 3-sophorotrioside. J.
Org. Chem. 2004, 69, 2206–2209.
14. Jiang, Z.-D.; Jensen, P.R.; Fenical, W. Actinoflavoside, a novel flavonoid-like gly-
coside produced by a marine bacterium of the genus Streptomyces. Tetrahedron Lett.
1997, 38, 5065–5068.
15. Kim, B.-G.; Sung, S.H.; Ahn, J.-H. Biological synthesis of quercetin 3-O-N-
acetylglucosamine conjugate using engineered Escherichia coli expressing UGT78D2.
Appl Microbiol. Biot. 2012, 93, 2447–2453.
16. Herzner, H.; Reipen, T.; Schultz, M.; Kunz, H. Synthesis of glycopeptides contain-
ing carbohydrate and peptide recognition motifs. Chem. Rev. 2000, 100, 4495–4538.
17. Magnet, S.; Blanchard, J.S. Molecular insights into aminoglycoside action and re-
sistance. Chem. Rev. 2005, 105, 477–498.
18. Mensah, E.A.; Nguyen, H.M. Nickel-catalyzed stereoselective formation of α-2-
deoxy-2-amino glycosides. J. Am. Chem. Soc. 2009, 131, 8778–8780.
19. Boltje, T.J.; Buskas, T.; Boons, G.-J. Opportunities and challenges in synthetic
oligosaccharide and glycoconjugate research. Nat. Chem. 2009, 1, 611–622.

Z. Cao et al.
40
20. Mensah, E.A.; Yu, F.; Nguyen, H.M. Nickel-catalyzed stereoselective glycosylation
with C (2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroace-
timidates for the formation of 1, 2-cis-2-amino glycosides. Applications to the synthesis
of heparin disaccharides, GPI anchor pseudodisaccharides, and α-GalNAc. J. Am. Chem.
Soc. 2010, 132, 14288–14302.
21. Olsson, J.D.; Eriksson, L.; Lahmann, M.; Oscarson, S. Investigations of glycosyla-
tion reactions with 2-N-acetyl-2 N, 3 O-oxazolidinone-protected glucosamine donors. J.
Org. Chem. 2008, 73, 7181–7188.
22. Bouktaib, M.; Lebrun, S.; Atmani, A.; Rolando, C. Hemisynthesis of all the
O-monomethylated analogues of quercetin including the major metabolites, through
selective protection of phenolic functions. Tetrahedron 2002, 58, 10001–10009.
23. Jurd, L. The selective alkylation of polyphenols. II. Methylation of 7-, 4ꢁ-, and 3ꢁ-
hydroxyl groups in flavonols. J. Org. Chem. 1962, 27, 1294–1297.
24. Oyama, K.-i.; Yoshida, K.; Kondo, T. Recent progress in the synthesis of flavonoids:
from monomers to supra-complex molecules. Curr. Org. Chem. 2011, 15, 2567–2607.
25. Wei, G.; Lv, X.; Du, Y. FeCl3-catalyzed α-glycosidation of glycosamine pentaac-
etates. Carbohyd. Res. 2008, 343, 3096–3099.
26. Needs, P.W.; Kroon, P.A. Convenient syntheses of metabolically important
quercetin glucuronides and sulfates. Tetrahedron 2006, 62, 6862–6868.
27. Shao, N.; Xue, J.; Guo, Z. Chemical synthesis of CD52 glycopeptides containing
the acid-labile fucosyl linkage. J. Org. Chem. 2003, 68, 9003–9011.
28. Banoub, J.; Boullanger, P.; Lafont, D. Synthesis of oligosaccharides of 2-amino-2-
deoxy sugars. Chem. Rev. 1992, 92, 1167–1195.
29. Demchenko, A.V. Stereoselective chemical 1, 2-cis O-glycosylation: from ‘sugar ray’
to modern techniques of the 21st century. Synlett 2003, 2003, 1225–1240.
30. Traar, P.; Belaj, F.; Francesconi, K.A. Synthesis of methyl 2-acetamido-2-deoxy-1-
seleno-β-D-gluco- and galacto-pyranoside: selenium metabolites in human urine. Aust.
J. Chem. 2004, 57, 1051–1053.
31. Dolashka-Angelova, P.; Abdel-Jalil, R.J.; Al-Qawasmeh, R.A.; Stambolieva, N.;
Voelter, W. Synthesis and inhibition properties of a series of pyranose derivatives
towards a Zn-metalloproteinase from Saccharomonospora canescens. Carbohyd. Res.
2010, 345, 2343–2347.
32. Cirla, A.; McHale, A.R.; Mann, J. Synthesis of analogues of calicheamicin and neo-
carzinostatin chromophore. Tetrahedron 2004, 60, 4019–4029.
33. Zhang, G.; Guan, Z.; Zhang, L.; Min, J.; Zhang, L. Synthesis of 2-amino-2-deoxy-
β-glycosyl-(1→5)-nucleosides and the interaction with RNA. Bioorg. Med. Chem. 2003,
11, 3273–3278.
34. Lemieux, R.; Takeda, T.; Chung, B. In Synthesis of 2-Amino-2-deoxy-β-D-
glucopyranosides. Properties and Use of 2-Deoxy-2-phthalimidoglycosyl Halides, Am.
Chem. Soc Symp. Ser., 1976; ACS Publications: 1976; pp. 90–115.
35. Bianchi, A.; Bernardi, A. Traceless Staudinger ligation of glycosyl azides with tri-
aryl phosphines: Stereoselective synthesis of glycosyl amides. J. Org. Chem. 2006, 71,
4565–4577.