Total synthesis of an isoflavone C-glycoside: 6-tert-butylpuerarin

Article abstract of DOI:10.1080/07328303.2016.1270295

The first total synthesis of an isoflavone C-glycoside (6- tert-butylpuerarin) using commercially available 4,6-di-tertbutylbenzene- 1,3-diol as starting material was achieved in five steps with an overall yield of 2.8%. The key intermediate 4 was obtaine

Full text of DOI:10.1080/07328303.2016.1270295

Journal of Carbohydrate Chemistry
ISSN: 0732-8303 (Print) 1532-2327 (Online) Journal homepage: http://www.tandfonline.com/loi/lcar20
Total synthesis of an isoflavone C-glycoside: 6-tert-
butylpuerarin
Yunpeng Zou, Shouguo Zhang, Gang Wang, Xiaoxue Wen, Shuchen Liu, Tao
Peng, Yue Gao & Lin Wang
To cite this article: Yunpeng Zou, Shouguo Zhang, Gang Wang, Xiaoxue Wen,
Shuchen Liu, Tao Peng, Yue Gao & Lin Wang (2016) Total synthesis of an isoflavone C-
glycoside: 6-tert-butylpuerarin, Journal of Carbohydrate Chemistry, 35:7, 387-395, DOI:
10.1080/07328303.2016.1270295
To link to this article: http://dx.doi.org/10.1080/07328303.2016.1270295
View supplementary material
Published online: 07 Feb 2017.
Submit your article to this journal
Article views: 16
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=lcar20
Download by: [University of Newcastle, Australia]
Date: 21 February 2017, At: 04:53

JOURNAL OF CARBOHYDRATE CHEMISTRY
, VOL. , NO. , –
http://dx.doi.org/./..
Total synthesis of an isoflavone C-glycoside:
-tert-butylpuerarin
Yunpeng Zoua,b,#, Shouguo Zhangb,#, Gang Wangb, Xiaoxue Wenb, Shuchen Liub,
Tao Pengb, Yue Gaoa,b, and Lin Wanga,b
aCollege of Life Science and Bio-engineering, Beijing University of Technology, Beijing, P. R. China; bBeijing
Institute of Radiation Medicine, Beijing, P. R. China
ABSTRACT
ARTICLE HISTORY
Received  August 
Accepted  December 
The first total synthesis of an isoflavone C-glycoside (6-
tert-butylpuerarin) using commercially available 4,6-di-tert-
butylbenzene-1,3-diol as starting material was achieved in five
steps with an overall yield of 2.8%. The key intermediate 4 was
obtained by de-tert-butylation of 2 with trifluoroacetic acid
and Friedel-Crafts acetylation of 2-C-β-D-glucopyranoside 3.
Condensation of 4 with 4-(benzyloxy)benzaldehyde resulted in
the formation of C-glucosylchalcone 5, which was cyclized by
oxidative rearrangement using (diacetoxyiodo)benzene (DIB)
and p-toluenesulfonic acid to obtain the target molecule 6. This
environmentally friendly and concise synthetic pathway should
be applicable to the large-scale synthesis of various isoflavone
C-glycosides.
KEYWORDS
C-glycoside; isoflavone;
-tert-butylpuerarin; DIB
GRAPHICAL ABSTRACT
Introduction
Puerarin, an isoflavone C-glycoside isolated from Pueraria radix, was introduced in
China in 1994 because of its benefits in the treatment of cardiovascular and neu-
rological diseases.[1,2] The compound, which activated the endothelial nitric oxide
synthase-mediated production of nitric oxide in EA.hy926 endothelial cells,[3] may
be useful in the treatment or prevention of cardiovascular disorders and improved
learning and memory impairment by suppressing the Aβ-induced inflammatory
CONTACT Lin Wang; Yue Gao; Tao Peng
wanglin@bmi.ac.cn; wanglin@sina.com
and Bio-engineering, Beijing University of Technology, Beijing , P. R. China; Beijing Institute of Radiation Medicine,
Beijing , P. R. China.
College of Life Science
#These authors contributed equally to this work.
Supplemental data for this article can be accessed on the publisher’s website.
©  Taylor & Francis Group, LLC

388
Y. ZOU ET AL.
response.[4] To enhance the biological activities of puerarin, a 6-tert-butyl sub-
stituent, which prevented the 7-O-sulfate and 7-O-β-D-glucuronide formation of
the compound to be metabolized in the liver, was introduced, thereby increasing
the plasma concentration in the blood.
Recently, Koester et al.[5] reported the C-glycoside synthesis through Pd-
catalyzed coupling of 1-iodo- or 1-triflato-glycals with alkynyl glycosides. Even
more complex C-glycosidic bonds and α- and β-linked (1→2)-, (1→3)-, and
(1idicC-disaccharides were prepared.[6,7] Unlike the synthesis of C-disaccharides,
C-glycosyl isoflavones are usually synthesized through the O→C rearrangement
of glycosyl donors with electron-rich aromatic compounds as glycosyl acceptors
and the key oxidative rearrangement reaction employing the highly reactive thal-
lium(III) nitrate.[8–10] However, although the highly toxic thallium trinitrate is
widely used in the synthesis of isoflavone C-glycosides, scale-up preparation and
control of toxic residues were difficult.
Lee and co-workers[11] succeeded in the first total synthesis of puerarin. The
key intermediate was β-D-glucopyranosyl-2,6-dimethoxybenzene obtained by cou-
pling the lithiated form of the appropriate aromatic reagent with 2,3,4,6-tetra-O-
benzylpyranolactone. However, the synthetic route of the compound was unwieldy
and required repeated protection and deprotection of the sugar moiety with the
acetyl group. Herein, we carried out the total synthesis of 6-tert-butylpuerarin in
five steps by developing cyclization method using (diacetoxyiodo)benzene (DIB),
an environmentally friendly reagent, instead of thallium trinitrate for the oxidative
rearrangement of chalcone.
Results and discussion
Our synthetic procedure for 6-tert-butylpuerarin is shown in Scheme 1. Coupling
of 4,6-di-tert-butylbenzene-1,3-diol with 2,3,4,6-tetra-O-benzylglucopyranosyl
Scheme . Synthesis of -tert-butylpuerarin. Reagents and conditions: a) TMSOTf, CHCl, °C to rt;
.%; b) CFCOOH, rt,  min; .%; c) AlCl, AcCl, EtO, overnight; .%; d) (i) BnBr, KCO, DMF,
rt,  h; (ii) -(benzyloxy)benzaldehyde, % NaOMe, ,-dioxane, rt,  h; .% (from 4); e) (i) DIB,
p-TsOH, anhydrous MeOH, DCM, rt,  d, (ii) H, % Pd/C, MeOH, rt,  d, (iii)  M HCl, ,-dioxane-MeOH
(.:.:), reflux,  h, .% (from 5).

JOURNAL OF CARBOHYDRATE CHEMISTRY
389
trifluoroacetimidate with trimetylsily triflate (TMSOTf) as the Lewis acid pro-
moter yielded the desired 2-C-β-D-glucopyranoside 2 (Glc: JH1,H2 = 10.1 Hz) as
a white solid obtained by recrystallization from petroleum ether and acid–base
neutralization, which was proved to be purer than the product reported in liter-
ature.[12] The mechanism of the reaction may be as follows: After TMSOTf was
added to reaction mixture, the corresponding O-glycoside was produced, which
then underwent O→C rearrangement to yield the C-glycoside 2 in a regioselective
manner. However, when we attempted the direct coupling of the glycosyl donor
with resorcinol, the desired C-glycoside was not detected. Failure to detect C-
glycoside from this reaction might have resulted from the mismatch between the
reactivity of the glycosyl donor and the aromatic acceptor.[12] Moreover, when 4,6-
dibromobenzene-1,3-diol was used as the phenol acceptor, only the corresponding
α-O-glycoside [δ: 10.63 (s, 1H; OH-1), 7.66 (s, 1H; H-5), 6.91 (s, 1H; H-2), and 5.78
(d, J = 3.2 Hz, 1H; H-1ꢀ)] was isolated as the major product. The compound did not
undergo O→C rearrangement to yield the ortho-hydroxyaryl C-glycoside because
of the electron-withdrawing bromo groups at C-4 and C-6 in the O-glycoside.[13,14]
Through the successful de-butylation of the 6-tert-butyl group in compound
2 under the influence of trifluoroacetic acid (TFA), the desired compound 3 was
obtained with a 72.8% yield,[15] which might proceed through a mechanism outlined
in Scheme 2.[16] The reaction was examined using thin-layer chromatography every
few minutes to prevent both tert-butyl groups from being removed at the same time.
However, deprotection of the 4,6-di-tert-butyl groups in 2 by TFA obtained a poor
yield (20%).[12] Moreover, the process required a longer reaction time (5 h) and pro-
duced complex mixtures, including de-benzylated products or the destruction of the
sugar ring, as confirmed by 1H NMR and TLC.
The reaction of glycoside 3 with acetyl chloride and anhydrous AlCl3 in anhy-
drous ether resulted in the production of acetophenone 4.[17] The large steric
hindrance of the tert-butyl substituent allowed the acetyl group to be selec-
tively attached to C-6 in the C-glycoside 3. Following the procedure reported in
literature,[18] benzylation of glycoside 4 was followed by condensation with 4-
(benzyloxy)benzaldehyde to yield chalcone 5. After two benzyl groups were intro-
1
duced to the 4- and 6-O-positions of 4, the H NMR spectrum of the resultant 5
displayed two unequally populated sets of signals at r.t. (20°C), resulting from the
chiral conformation of the glycosyl group in chalcone 5 rather than the conforma-
tional changes in the glucose ring. The crowdedness introduced by the two benzyl
groups probably resulted in the restricted conformational motion around the C-3ꢀꢀ–
C-1ꢀꢀꢀ bond.[19]
Scheme . The de-butylation mechanism of -C-β-D-glucopyranoside .

390
Y. ZOU ET AL.
Scheme . Proposed reactions and mechanisms for the conversion of chalcone 5 to -tert-
butylpuerarin 6.
Finally, 5 was converted into 6 via a series of transformations including oxidative
methoxylation accompanied by rearrangement, catalytic hydrogenolysis to remove
benzyl groups, and acid-catalyzed cyclization and elimination, as outlined in
Scheme 3. It was proposed that the reaction between 5 and DIB led to the produc-
tion of a phenyliodinated intermediate 5a, which can be attacked by nucleophilic
MeOH consecutively with 1,2-migration of the benzene ring to produce product 5b
(Sch. 3)[20] [major/minor (2:1): δ = 3.23 (s, 2H; OCH3Major), 3.18 (s, 1H;
OCH3Minor), 3.03 (s, 2H; OCH3Major), 2.96 (s, 1H; OCH3Minor)]. Compared to
thallium(III) nitrate, oxidative rearrangement with DIB was safer and needed
a shorter reaction time. The dimethyl acetal 5b was then de-O-benzylated by
hydrogenolysis using 10% Pd/C as the catalyst (room temperature for two days) to
give a deprotected dimethyl acetal 5c, which was cyclized after refluxing in aqueous
6 M HCl to obtain the desired 6-tert-butylpuerarin 6.[21,22,23] The final product
showed a single β-anomeric configuration (Glc H-1: δ = 5.19 ppm; JH1,H2 = 9.8 Hz).
Experimental
General
The solvents used in these reactions were purified by distillation. Reactions were
monitored by TLC on 0.20–0.25 mm silica gel F254 plates (Qingdao Marine

JOURNAL OF CARBOHYDRATE CHEMISTRY
391
Chemistry Company, Qingdao, China) observed using UV light and either a 5%
ethanolic solution of FeCl3 or a 5% ethanolic solution of sulfuric acid with heat
as the coloration agent. Column chromatography was carried out on a silica gel
(200–300 mesh, Qingdao Marine Chemistry Company, Qingdao, China). Melting
points were recorded using an RY-1 melting point detector (Tianjin Tianfen Analysis
Instrument Factory). NMR spectra were recorded on a Varian Inova 600 spectrom-
eter. Mass spectral data were obtained by electron spray ionization on a Micromass
ZabSpec high-resolution mass spectrometer.
4,6-di-tert-Butyl-2-C-(2,3,4,6-tetra-O-benzyl-β-D-glucopyranosyl)-1,3-
dihydroxybenzene (2)
A mixture of 2,3,4,6-tetra-O-benzylglucopyranosyl trifluoroacetimidate (25 g,
35.2 mmol), 4,6-di-tert-butylbenzene-1,3-diol 1[24] (7.8 g, 35.2 mmol), and 4 A MS
˚
(6.63 g) in anhydrous CH2Cl2 (310 mL) was stirred at 0°C for 30 min under an
Ar atmosphere. Then, TMSOTf (7.13 mL, 35.2 mmol) was added. After stirring at
0°C for 2 h, the mixture was warmed to rt within 10 h. The above mixture was
quenched by adding Et3N (29.32 mL), stirred continuously for 30 min, and then fil-
tered through a Celite pad. The filtrate was evaporated in vacuo to obtain a brown
syrup, which was subjected to silica gel column chromatography (8:1, petroleum
ether–EtOAc) and recrystallized from petroleum ether to obtain a white solid (18.47
g). The resulting white powder was stirred at 40°C for 30 min in 2 N NaOH (100
mL) and CH2Cl2 (100 mL). The DCM layer was separated from the mixture, and
70 mL of 2 N HCl was added. After stirring the mixture at 40°C for 30 min, the
methylene chloride layer was then separated and dried to obtain 2 (10.99 g, 42.0%)
as a white solid. m.p.138–141°C. 1H NMR (400 MHz, CDCl3): δ 7.35–6.99 (m, 21H;
CH-Ph, H-5), 5.00 (d, J = 11.3 Hz, 1H; CH2Ph), 4.96 (d, J = 10.1 Hz, 1H; H-1ꢀ), 4.92
(d, J = 11.3 Hz, 1H; CH2Ph), 4.86 (d, J = 10.8 Hz, 1H; CH2Ph), 4.67 and 4.64 (d, J =
10.7 Hz, each 1H; CH2Ph), 4.56 and 4.49 (d, J = 12.1 Hz, each 1H; CH2Ph), 4.31 (d,
J = 10.8 Hz, 1H; CH2Ph), 3.97 (t, J = 9.7, 9.3Hz, 1H; H-2ꢀ), 3.92 (t, J = 9.8, 9.3Hz,
1H; H-4ꢀ), 3.82 (t, J = 9.1 Hz, 1H; H-3ꢀ), 3.75 (dd, J = 10.3, 2.1 Hz, 1H; H-6ꢀb), 3.69
(dd, J = 10.3, 1.9 Hz, 1H; H-6ꢀa), 3.58 (m, 1H; H-5ꢀ), 1.38 (s, 18H, (CH3)3C).13C
NMR (100 MHz, CDCl3): δ 138.5, 138.0, 137.8, 136.4 (C, CH2Ph), 128.6, 128.5,
128.4, 128.2, 128.0, 127.9, 127.9, 127.7, 127.5, 124.8 (C-5), 112.7 (C-2), 86.6 (C-3ꢀ),
81.5, 78.7, 77.3, 75.8, 75.5, 75.3, 73.4, 67.5 (C-6ꢀ), 34.7 (C, (CH3)3C), 30.2 (CH3).
ESI-MS m/z: 745.41 [M+H]+, 767.39 [M+Na]+.
4-tert-Butyl-2-C-(2,3,4,6-tetra-O-benzyl-β-D-glucopyranosyl)-1,3-
dihydroxybenzene (3)
Sodium dithionite (110 mg, 0.63 mmol) and 2 (10.99 g, 15.97 mmol) in TFA (50 mL)
were stirred at rt for 90 min. TFA was removed by a rotary evaporator to obtain a
brown syrup, which was then subjected to silica gel column chromatography (15:1–
12:1, petroleum ether–EtOAc) to obtain 3 (7.4 g, 72.8%) as brown syrup. 1H NMR

392
Y. ZOU ET AL.
(400 MHz, CDCl3): δ 7.38–7.18 (m, 18H; CH-Ph), 7.13 (d, J = 8.6 Hz, 1H; H-5), 7.04
(d, J = 6.5 Hz, 2H; CH-Ph), 6.47 (d, J = 8.6 Hz, 1H; H-6), 5.03–4.93 (m, 3H; CH2Ph,
H-1ꢀ), 4.87 (d, J = 10.8 Hz, 1H; CH2Ph), 4.68 (d, J = 10.4 Hz, 1H; CH2Ph), 4.64–4.48
(m, 3H; CH2Ph), 4.24 (d, J = 10.4 Hz, 1H; CH2Ph), 4.00–3.81 (m, 3H; H-2ꢀ, H-3ꢀ,
H-4ꢀ), 3.78 (dd, J = 10.4, 1.9 Hz, 1H; H-6ꢀb), 3.71 (brd, J = 10.4 Hz, 1H; H-6ꢀa), 3.61
(brd, J = 9.7 Hz, 1H; H-5ꢀ), 1.37 (s, 9H, (CH3)3C).13C NMR (150 MHz, CDCl3):
δ 138.4 (C, CH2Ph), 137.9 (C, CH2Ph), 137.7 (C, CH2Ph), 136.4 (C, CH2Ph),
130.5, 128.5, 128.4, 128.3, 128.1, 128.0, 127.8, 127.8, 127.7, 127.6, 127.4, 127.1,
111.9 (C-2), 109.0 (C-6), 86.4 (C-3ꢀ), 82.0, 78.7, 77.2, 75.9, 75.6, 75.5, 75.2, 73.4,
67.5 (C-6ꢀ), 34.3 (C, (CH3)3C), 29.9(CH3). ESI-MS m/z: 689.35 [M+H]+, 711.33
[M+Na]+.
5-tert-Butyl-2,4-hydroxy-3-C-(2,3,4,6-tetra-O-benzyl-β-D-
glucopyranosyl)acetophenonoe (4)
A solution of anhydrous aluminum chloride (3.61 g, 27.10 mmol) in dry ether
(15.01 mL) was added to a solution of the C-glycoside 3 (1.79 g, 2.6 mmol) in dry
ether (15.01 mL). Acetyl chloride (2.69 mL, 30.87 mmol) was added dropwise with
stirring. Afterward, the mixture was stirred overnight at rt. A brown oil was sepa-
rated from the mixture after 1 h. The reaction mixture was decomposed by the drop-
wise addition of 2 N hydrochloric acid (60 mL) followed by water (50 mL). After the
product was isolated with chloroform (3 × 20 mL), evaporation of the organic phase
yielded a yellow oil (4 g), which was then subjected to silica gel column chromatog-
raphy (25:1–20:1, petroleum ether–EtOAc) to obtain 4 (1.33g, 70.0%) as light yellow
syrup. 1H NMR (400 MHz, DMSO-d6): δ 13.15 (s, 1H; OH-6), 9.30 (s, 1H; OH-4),
7.61 (s, 1H; H-8), 7.38–7.05 (m, 18H; CH-Ph), 6.82 (d, J = 7.8 Hz, 2H; CH-Ph), 5.07
(brs, 1H; H-1ꢀ), 4.81 and 4.76 (d, J = 11.5 Hz, each 1H; CH2Ph), 4.72 and 4.51 (d,
J = 10.9 Hz, each 1H; CH2Ph), 4.47 (s, 2H; CH2Ph), 4.34 and 3.82 (d, J = 10.7 Hz,
1H; CH2Ph), 3.79–3.58 (m, 6H; H-2ꢀ, H-3ꢀ, H-4ꢀ, H-5ꢀ, H-6ꢀa, H-6ꢀb), 2.57 (s, 3H;
H-1), 1.36 (s, 9H; (CH3)3C).13C-NMR (150 MHz, DMSO-d6): δ 203.6 (C-2), 162.2
(C-4), 160.2 (C-6), 138.6 (C, CH2Ph), 138.1 (C, CH2Ph), 138.0 (C, CH2Ph), 137.5
(C, CH2Ph), 129.4, 128.4, 128.2, 128.1, 128.1, 127.9, 127.9, 127.6, 127.4, 127.4, 127.4
(C-7), 127.3 (C-8), 111.9(C-5),110.8 (C-3), 85.0 (C-3ꢀ), 80.2, 77.8, 77.0, 74.5 (CH2,
CH2Ph), 74.1 (CH2, CH2Ph), 74.0 (CH2, CH2Ph), 72.8, 72.1 (CH2, CH2Ph), 67.7
(C-6ꢀ), 34.1 (C-1), 29.4 (CH3), 26.2 (C, (CH3)3C). ESI-MS m/z: 731.36 [M+H]+,
753.34 [M+Na]+.
5ꢀ-tert-Butyl-4,2ꢀ,4ꢀ-tribenzyloxy-3ꢀ-C-(2,3,4,6-tetra-O-benzyl-D-
glucopyranosyl)chalcone (5)
PhCH2Br (0.96 mL, 8.12 mmol) and K2CO3 (1.13g, 8.18 mmol) were added to a
solution of 4 (1.33 g, 3.34 mmol) in dry DMF (4.49 mL), and the resulting solu-
tion was stirred at rt for 14 h. After confirming the disappearance of 4 by TLC, the
reaction mixture was poured into H2O (50 mL) and extracted with EtOAc (3 ×
40 mL). The organic extracts were concentrated and purified by silica gel column

JOURNAL OF CARBOHYDRATE CHEMISTRY
393
chromatography (9:1, petroleum ether–EtOAc) to obtain a yellow syrup (1.56 g).
Thereafter, 28% NaOMe in MeOH (10.52 mL) was added to a solution of the yellow
syrup (1.37 g, 1.51 mmol) and 4-(benzyloxy)benzaldehyde (0.35 g, 1.66 mmol) in
1,4-dioxane (21.04 mL). After the resulting mixture was stirred at rt for 20 h, 24.5 mL
of 2N HCl was added. The mixture was then extracted with EtOAc (3 × 20 mL),
dried over Na2SO4, and concentrated. The residue was purified by silica gel column
chromatography (20:1–10:1, petroleum ether–EtOAc) to obtain 5 (0.87 g, 49.2%) as
light yellow oil. 1H NMR (400 MHz, DMSO-d6): δ 7.60 (s, 0.75H; H-6ꢀꢀMajor), 7.57
(s, 0.25H; H-6ꢀꢀMinor), 7.54–7.09 (m, 37H; CH-Ph, H-2, H-3, H-2ꢀ, H-6ꢀ), 7.03 (d, J =
8.8 Hz, 0.5H; H-3ꢀMinor, H-5ꢀMinor), 6.96 (d, J = 8.8 Hz, 1.5H; H-3ꢀMajor, H-5ꢀMajor),
6.74 (m, 2H; CH-Ph), 5.24–5.06 (m, 3H; CH2Ph, H-1ꢀꢀꢀ), 4.99 (d, J = 12.4 Hz, 0.75H;
CH2PhMajor), 4.93 (d, J = 9.9 Hz, 0.25H; CH2PhMinor), 4.82–4.68 (m, 3H; CH2Ph),
4.64 (d, J = 10.9 Hz, 0.75H; CH2PhMajor), 4.60 (d, J = 10.9 Hz, 0.25H; CH2PhMinor),
4.58–4.49 (m, 2H; CH2Ph), 4.48–4.34 (m, 3H; CH2Ph), 4.21 (d, J = 10.8 Hz, 0.25H;
CH2PhMinor), 4.15 (d, J = 10.8 Hz, 0.75H; CH2PhMajor), 3.68 (d, J = 10.0 Hz, 0.75H;
CH2PhMajor), 3.62 (d, J = 10.0 Hz, 0.25H; CH2PhMinor), 3.55–3.33 (m, 6H; H-2ꢀꢀꢀ,
H-3ꢀꢀꢀ, H-4ꢀꢀ, H-5ꢀꢀꢀ, H-6ꢀꢀꢀa, H-6ꢀꢀꢀꢀb), 1.43 (s, 6.5H; (CH3)3CMajor), 1.38 (s, 2.5H;
(CH3)3CMinor). 13C NMR (100 MHz, DMSO-d6): δ 191.9 (C-1), 161.1 (C-4ꢀꢀ), 160.4
(C-4ꢀ), 156.9 (C-2ꢀꢀ), 144.1 (C-3), 142.6 (C-1ꢀ), 139.1 (C, CH2Ph), 138.6 (C, CH2Ph),
138.0 (C, CH2Ph), 138.0 (C, CH2Ph), 137.9 (C, CH2Ph), 136.9 (C, CH2Ph), 136.6 (C,
CH2Ph), 130.4, 128.7, 128.5, 128.4, 128.3, 128.2, 128.1, 128.0, 128.0, 127.9.0, 127.8,
127.7, 127.7, 127.6, 127.5, 127.2, 126.9, 126.8, 126.7, 126.6, 126.4, 126.0, 124.4, 115.3
(C-3ꢀꢀMinor), 115.2 (C-3ꢀꢀMajor), 86.6, 79.4, 79.2, 79.0, 77.8, 74.6, 74.4, 74.1, 73.8, 72.5,
69.4, 62.9, 54.9 (C-6”ꢀ), 35.1 (CH3Minor), 34.9 (CH3Major), 30.8 (C, (CH3)3CMinor),
30.7 (C, (CH3)3CMajor). HRESI-MS (m/z): calcd for C74H73O9 [M + H]+ 1105.5249,
found 1105.5252.
6-tert-Butylpuerarin (6)
A solution of 5 (870 mg, 0.79 mmol) in anhydrous MeOH (2.21 mL) and DCM
(1.5 mL) was added dropwise to a solution of DIB (755 mg, 2.34 mmol) and
p-TsOH·H2O (599 mg, 3.15 mmol) in anhydrous MeOH (1.58 mL). After the
mixture was stirred at r.t. for a day, aq 10% Na2S2O3 (158.20 mL) was added to
the reaction mixture. The resulting mixture was extracted with DCM (3 × 20
mL), dried over Na2SO4, and concentrated. The residue was purified by silica
gel column chromatography (19:1–10:1, petroleum ether–EtOAc) to obtain 5b
(0.25 g) as colorless syrup. Subsequently, 10% Pd/C (74.02 mg) was added to a
solution of 5b in MeOH (18.4 mL). The mixture was then stirred at rt for 48 h
under hydrogen atmosphere, filtered, and evaporated in vacuo to obtain 5c (160
mg) as a colorless solid. Thereafter, 1,4-dioxane (0.49 mL) and 6 M HCl (0.65 mL)
were added to a crude solution of 5c in MeOH (1.63 mL), and the mixture was
refluxed for 1 h. After removing the solvent in vacuo, EtOH (7 mL) was added
to the residue and then evaporated. The residue was purified by silica gel column
chromatography (9:1, DCM–MeOH) to obtain 6 (90 mg, 26.8%) as a colorless

394
Y. ZOU ET AL.
1
solid. m.p.130–132°C. H NMR (400 MHz, CD3OD): δ 8.10 (s, 1H; H-5), 8.06
(s, 1H; H-2), 7.32 (d, J = 8.9 Hz, 2H; H-2ꢀ, H-6ꢀ), 6.80 (d, J = 8.9 Hz, 2H; H-3ꢀ,
H-5ꢀ), 5.19 (d, J = 9.8 Hz, 1H; H-1ꢀꢀ), 3.87 (dd, J = 12.2, 2.4 Hz, 1H; H-6ꢀꢀb), 3.83
(dd, J = 12.2, 4.1 Hz, 1H, H-6ꢀꢀa), 3.65 (t, J = 9.3 Hz, 1H; H-3ꢀꢀ), 3.58(t, J = 9.8,
9.3 Hz, 1H; H-2ꢀꢀ), 3.54–3.47 (m, 2H; H-4ꢀꢀ, H-5ꢀꢀ), 1.41 (s, 9H; (CH3)3C). 13C NMR
(150 MHz, CD3OD): δ 178.5 (C-4), 162.0 (C-7), 158.7 (C-4ꢀ), 155.5 (C-8a), 154.2
(C-2), 138.2 (C-6), 131.4 (C-2ꢀ, C-6ꢀ), 125.6 (C-5), 124.4 (C-3), 124.3 (C-1ꢀ), 117.5
(C-4a), 116.2 (C-3ꢀ, C-5ꢀ), 112.7 (C-8), 83.0 (C-5ꢀꢀ), 79.4 (C-3ꢀꢀ), 77.1 (C-1ꢀꢀ), 73.9
(C-2ꢀꢀ), 70.9 (C-4ꢀꢀ), 61.7 (C-6ꢀꢀ), 36.2 (C, (CH3)3C), 30.0 (CH3). ESI-MS m/z: 473.18
[M+H]+.
Funding
We are thankful to the National Science Foundation of China for providing financial supports
(Grant No. 81273431; 21102176 and 21272273).
References
1. Hwang, Y. P.; Kim, H. G.; Hien, T. T.; Jeong, M. H.; Jeong, T. C.; Jeong, H. G. Puerarin acti-
vates endothelial nitric oxide synthase through estrogen receptor-dependent PI3-kinase and
calcium-dependent AMP-activated protein kinase. Toxicol. Appl. Pharmacol. 2011, 257, 48–
58.
2. Li, J.; Wang, G.; Liu, J.; Zhou, L.; Dong, M.; Wang, R.; Niu, Y. Puerarin attenuates amyloid-
beta-induced cognitive impairment through suppression of apoptosis in rat hippocampus in
vivo. Eur. J. Pharmacol. 2010, 649, 195–201.
3. Hwang, Y. P.; Kim, H. G.; Hien, T. T.; Jeong, M. H.; Jeong, T. C.; Jeong, H. G. Puerarin
activates endothelial nitric oxide synthase through estrogen receptor-dependent PI3-kinase
and calcium-dependent AMP-activated protein kinase. Toxicol. Appl. Pharmacol. 2011, 257,
48–58.
4. Li, J.; Wang, G.; Liu, J.; Zhou, L.; Dong, M.; Wang, R.; Niu, Y. Puerarin attenuates amyloid-
beta-induced cognitive impairment through suppression of apoptosis in rat hippocampus in
vivo. Eur. J. Pharmacol. 2010, 649, 195–201.
5. Koester, D. C.; Leibeling, M.; Neufeld, R.; Werz, D. B. A Pd-catalyzed approach to (1→6)-
linked C-glycosides. Org. Lett. 2010, 12, 3934–3937.
6. Koester, D. C.; Kriemen, E.; Werz, D. B. Flexible synthesis of 2-deoxy-C-glycosides and
(1→2)-, (1→3)-, and (1→4)-linked C-glycosides. Angew. Chem. Int. Ed. 2013, 52, 2985–
2989.
7. Dondoni, A.; Marra, A.; Mizuno, M.; Giovannini, P. P. Linear total synthetic routes toβ;-D-C-
(1, 6)-linked oligoglucoses and oligogalactoses up to pentaoses by iterative Wittig olefination
assembly. J. Org. Chem. 2002, 67, 4186–4199.
8. Sato, S.; Hiroe, K.; Kumazawa, T.; Jun-Ichi, O. Total synthesis of two isoflavone C-
glycosides: genistein and orobol 8-C-β;-D-glucopyranosides. Carbohyd. Res. 2006, 341,
1091–1095.
9. Jesus, A. R.; Dias, C.; Matos, A. M.; de Almeida, R. F.; Viana, A. S.; Marcelo, F.; Ribeiro, R.
T.; Macedo, M. P.; Airoldi, C.; Nicotra, F.; Martins, A.; Cabrita, E. J.; Barbero, J. J.; Rauter, A.
P. Exploiting the therapeutic potential of 8-β;-D-glucopyranosylgenistein: Synthesis, antidi-
abetic activity, and molecular interaction with islet amyloid polypeptide and amyloid β;-
peptide (1–42). J. med. Chem. 2014, 57, 9463–9472.

JOURNAL OF CARBOHYDRATE CHEMISTRY
395
10. Eade, R. A.; McDonald, F. J.; Pham, H. C-Glycosylflavonoids. II. The synthesis of 7, 4ꢀ-di-O-
methylpuerarin (8-C-β;-D-glucopyranosyl-7, 4ꢀ-dimethoxyisoflavone). Aust. J. Chem, 1978,
31, 2699–2706.
11. Lee, D. Y.; Zhang, W. Y.; Karnati, V. V. R. Total synthesis of puerarin, an isoflavone C-
glycoside. Tetrahedron Lett. 2003, 44, 6857–6859.
12. Li, Y.; Wei, G.; Yu, B. Aryl C-glycosylation of phenols with glycosyltrifluoroacetimidates. Car-
bohyd. Res. 2006, 341, 2717–2722.
13. Kanai, A.; Kamino, T.; Kuramochi, K.; Kobayashi, S. Synthetic studies directed toward the
assembly of the C-glycoside fragment of the telomerase inhibitor D8646-2-6. Org. Lett. 2003,
5, 2837–2839.
14. Kumazawa, T.; Ohki, K.; Ishida, M.; Sato, S.; Onodera, J. I.; Matsuba, S. Practical synthesis of
a C-glycosyl flavonoid via O→C glycoside rearrangement. B Chem Soc Jpn. 1995, 68, 1379–
1384.
15. McOmie, J. F.W.; Saleh, S. A. An efficient method for the debutylation of o-and p-t-
butylphenols and for the hydrolysis of aryl acetates. Tetrahedron. 1973, 29, 4003–4005.
16. Liu, F.; Liebeskind, L. S. tert-Butyl substituent as a regiodirecting and novel CH protecting
group in cyclobutenedione-based benzannulation chemistry. J.Org.Chem. 1998, 63, 2835–
2844.
17. Eade, R. A.; McDonald, F. J.; Simes, J. J. H. Extractives of australian timbers. XV. The synthesis
of 7, 4ꢀ-Di-O-methylbayin. Aust. J. Chem. 1975, 28, 2011–2018.
18. Sato, S.; Akiya, T.; Nishizawa, H.; Suzuki, T. Total synthesis of three naturally occurring 6,
8-di-C-glycosylflavonoids: phloretin, naringenin, and apigeninbis-C-β-D-glucosides. Car-
bohyd. Res. 2006, 341, 964–970.
19. Zhang, P. C.; Wang, Y. H.; Liu, X.; Yi, X.; Chen, R. Y.; Yu, D. Q. Conformational study on 8-C-
glucosyl-prunetin by dynamic NMR spectroscopy. Acta Chim Sinica, 2003, 61, 1157–1160.
20. Farid, U.; Malmedy, F.; Claveau, R.; Albers, L.; Wirth, T. Stereoselective rearrangements with
chiral hypervalent iodine reagents. Angew. Chem. Int. Ed, 2013, 52, 7018–7022.
21. Sato, S.; Ishikawa, H. Total synthesis of two isoflavonebis-C-glycosides: genistein and orobol
6, 8-di-C-β;-D-glucopyranosides. Synthesis. 2010, 18, 3126–3130.
22. Shen, Y.; Zhang, J.; Sheng, R.; Dong, X.; He, Q.; Yang, B.; Hu, Y. Synthesis and biological
evaluation of novel flavonoid derivatives as dual binding acetylcholinesterase inhibitors. J
Enzym Inhib Med Ch. 2009, 24, 372–380.
23. Kawamura, Y.; Maruyama, M.; Tokuoka, T.; Tsukayama, M. Synthesis of isoflavones from
2ꢀ-hydroxychalcones using poly[4-(diacetoxy)iodo]styrene or related hypervalent iodine
reagent. Synthesis, 2002, 2002, 2490–2496.
24. Akagi, S.; Yasukawa, Y.; Kobayashi, K.; Konishi, H. Synthesis and solid state structure of oxa-
calix[4]arenes bearing four nitro groups and four tert-butyl groups at their extra-annular
positions. Tetrahedron. 2009, 65, 9983–9988.