Synthesis of β-C-glycopyranosyl-1,4-naphthoquinone derivatives and their cytotoxic activity

Article abstract of DOI:10.1016/j.carres.2007.12.017

β-C-Glucosyl and β-C-galactosyl-1,4-dimethoxynaphthalenes have been synthesized using a F₃CCO₂Ag/SnCl₄ promoted Friedel-Crafts electrophilic substitution reaction. Both glycosyl acetates and methyl glycosides can be used as glycosyl donors. Further oxidation afforded the corresponding β-C-glycosyl-1,4-naphthoquinones. The in vitro cytotoxic activity of these compounds was evaluated against the A375 cell line.

Full text of DOI:10.1016/j.carres.2007.12.017

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 773–779
Note
Synthesis of b-C-glycopyranosyl-1,4-naphthoquinone derivatives
and their cytotoxic activity
Li Lin,a,b Xiao-Peng He,a Qing Xu,a Guo-Rong Chena,* and Juan Xieb,*
aLaboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology,
Shanghai 200237, PR China
bPPSM, ENS Cachan, CNRS, UniverSud, 61 av President Wilson, F-94230 Cachan, France
Received 3 September 2007; received in revised form 18 December 2007; accepted 18 December 2007
Available online 25 December 2007
Abstract—b-C-Glucosyl and b-C-galactosyl-1,4-dimethoxynaphthalenes have been synthesized using a F3CCO2Ag/SnCl4 promoted
Friedel–Crafts electrophilic substitution reaction. Both glycosyl acetates and methyl glycosides can be used as glycosyl donors.
Further oxidation afforded the corresponding b-C-glycosyl-1,4-naphthoquinones. The in vitro cytotoxic activity of these compounds
was evaluated against the A375 cell line.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: C-Glycosyl compounds; 1,4-Naphthoquinone; Aryl C-glycosylations; Cytotoxicity
Considerable effort has been devoted to the synthesis of
C-glycosyl compounds owing to their natural occur-
rence, their biological interest, and synthetic utility.1
Among naturally occurring C-glycosyl compounds, aryl
C-glycosyl derivatives are present in a variety of biologi-
cally important natural products as papulacandins, plu-
ramycins, vineomycin, gilvocarcin V, and urdamycin A,
which are recognized for their various biological activi-
ties including antibiotic, antitumoral, and antiplatelet
aggregation activities.2 Wide structural variety can be
found among C-glycosyl-arenes, including spiroketals
in papulacandins or quinones in pluramycins and angu-
cyclines.2 Naturally occurring naphthoquinones such as
lapachol and b-lapachone possess anti-tumoral, anti-
inflammatory, bactericidal, fungicidal, and virucidal
activities.3 Furthermore, we have found that b-C-gluco-
pyranosyl-benzoquinone showed inhibitory activity
against protein tyrosine phosphatase 1B (PTP1B)4 and
glycogen phosphorylase b (GPb).5 Synthesis of C-gly-
cosyl-quinone derivatives is therefore a valuable choice
to find new biologically active compounds.6 Aryl C-gly-
cosyl compounds can be prepared by Friedel–Crafts
alkylation, arylation with organometallic aromatic
derivatives, palladium-mediated cross-coupling, O–C
glycosyl rearrangement, free radical reaction or umpo-
lung strategy.1a–e,7 SnCl4/F3CCO2Ag has been reported
to be a powerful combination for promoting aryl-b-C-
glycosylation between readily available sugar acetates
and aromatic substrates with good stereoselectivity.8
As a part of a continuing program on C-glycosyl
compounds synthesis,4,5,9 we describe herein the
SnCl4/F3CCO2Ag promoted synthesis of C-glycosyl-
naphthoquinones with potential biological activities.
Treatment of 1,4-dimethoxynaphthalene with b-D-
glucopyranose penta-acetate (1) in the presence of
F3CCO2Ag/SnCl4 at 35–40 °C, in anhydrous alcohol
free dichloromethane, afforded the b-C-glucopyranosyl
derivative 2 (60%) (Scheme 1). Mild oxidation of 2 with
ceric ammonium nitrate (CAN) in aqueous acetonitrile
led to the desired b-C-glucopyranosyl-1,4-naphthoqui-
none (3), which was isolated as moderately stable yellow
needles (83%). Removal of the acetyl protecting groups
*
Corresponding authors. Tel.: +86 21 64253016; fax: +86 21 64252758
(G.-R.C.); tel.: +33 1 47 40 55 86; fax: +33 1 47 40 24 54 (J.X.);
e-mail addresses: mrs_guorongchen@ecust.edu.cn; joanne.xie@
ppsm.ens-cachan.fr
´
under Zemplen conditions failed probably because of
the addition of the methoxy anion to the naphtho-
quinone, affording a complex mixture. To get the water
0008-6215/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2007.12.017

774
L. Lin et al. / Carbohydrate Research 343 (2008) 773–779
OMe
O
O
OMe
OMe
OAc
O
OAc
O
OAc
O
OMe
CAN
AcO
AcO
OAc
AcO
AcO
AcO
AcO
MeCN-H2O
83%
AgOTfa (1.5 equiv),
SnCl4 (0.35 equiv),
CH2Cl2, Ar, 35-40 °C
OAc
OAc
OAc
1
3
2
60%
NaOMe
MeOH
NaOMe
MeOH
O
97%
OMe
OH
O
OH
O
CAN
HO
HO
HO
HO
MeCN-H2O
80%
OH
OH
O
O
OMe
5
4
OMe
OMe
OMe
OBz
O
OBz
O
OBz
O
CAN
AcO
AcO
AcO
AcO
AcO
AcO
AgOTfa (1.5 equiv),
SnCl4 (0.35 equiv),
CH2Cl2, Ar, 35-40 °C
MeCN-H2O
67%
AcO
OCH3
OAc
OAc
OMe
O
6
7
8
76%
Scheme 1. Synthesis of the b-C-glucopyranosyl-naphthoquinone derivatives.
soluble derivative, 2 was first deacetylated with MeONa
to afford the C-glucosyl-naphthalene 4 (97%), which was
then oxidized with CAN to give the deprotected C-glu-
copyranosyl-1,4-naphthoquinone (5) in 80% yield. Fur-
thermore, we found that methyl glycosides can also be
used as glycosyl donors in F3CCO2Ag/SnCl4 catalyzed
aryl-C-glycosylation; reaction of 1,4-dimethoxynaph-
thalene with methyl 2,3,4-tri-O-acetyl-6-O-benzoyl-a-D-
glucopyranoside (6)10 afforded the corresponding b-C-
glucopyranosyl derivative 7 in 76% yield (Scheme 1).
Oxidation of 7 with CAN led to the b-C-glucopyrano-
syl-naphthoquinone 8 in 67% yield.
However, the stereoselectivity of the C-glycosylation
was quite sensitive to the amount and addition rate of
SnCl4 in the case of the galacto derivative. As shown
in Table 1, the reaction of 1,4-dimethoxynaphthalene
with b-D-galactopyranose penta-acetate (9) catalyzed
by dropwise addition of 0.35 equiv of SnCl4 during 1 h
afforded the b-C-galactoside 10 as the only isolated
stereoisomer (entry 1). If we accelerated the addition
rate (20–30 min, entry 2), a mixture of a- and b-anomer
as well as the a-chloride 12 was obtained. Formation of
the a-chloride has already been observed previously.5
With 1 equiv of SnCl4, a mixture of a- and b-anomer
Table 1. Effect of SnCl4 on the C-glycosylation of galactose penta-acetate
OAc
O
AcO
AcO
OMe
OMe
OAc
O
OMe
OMe
AgOTfa (1.5 equiv)
SnCl4, Ar
AcO
AcO
AcO
OAc
O
OAc
O
AcO
OMe
+
+
+
AcO
OAc
AcO
AcO
CH2Cl2, 35-40 °C
AcO
Cl
12
OAc
OAc
10
MeO
11
9
Entry
SnCl4 (equiv)
Addition time (min)
Product ratioa
Yieldb (%)
10
11
12
1
2
3
4
5
0.35
0.35
1
1
2
60
20–30
60
20–30
20
65
58
55
45
33
100
50
80
35
ndc
—
30
20
35
ndc
—
20
—
30
ndc
a Estimated from 1H NMR spectra.
b Isolated yield after purification by chromatography.
c Not determined.

L. Lin et al. / Carbohydrate Research 343 (2008) 773–779
775
Table 2. Cytotoxic activity against A375 cell line of b-C-glycosyl-1,4-
naphthoquinones
was formed whatever be the addition rate of SnCl4
(entries 3 and 4). Further increase in the amount of
SnCl4 (2 equiv, entry 5) with the addition realized within
20 min gave a worse yield. Consequently, the optimized
reaction condition should be a very slow addition of
0.35 equiv SnCl4 to the reaction mixture before heating
at 35–40 °C. Under these conditions, methyl 2,3,4-tri-
O-acetyl-6-O-benzoyl-a-D-galactopyranoside (16)11 was
successfully converted into the b-C-galactopyranosyl
derivative 17 in 65% yield (Scheme 2). The correspond-
ing b-C-galactosyl-1,4-naphthoquinones 13 and 18
could be obtained after oxidation with CAN. Deacetyl-
ation followed by oxidation of 10 furnished the fully
deprotected galactosyl-naphthoquinone 15.
The cytotoxic activity of the synthesized C-glycosyl-
naphthoquinones was evaluated by MTT tetrazolium
dye assay against A375 cell line (human melanoma
cell).12 Results are summarized in Table 2 with their
50% inhibitory concentration (IC50 values). 1,4-Naph-
thoquinone was used as reference compound for
comparison.13 The fully deprotected C-glycosyl-
naphthoquinones 5 and 15 were inactive against the
A375 cell line, while both the 6-O-acetyl (compounds 3
and 13) and the 6-O-benzoyl-naphthoquinone deriva-
tives (compounds 8 and 18) exhibited an enhanced cyto-
toxic activity compared to 1,4-naphthoquinone. The
IC50 values of all protected glycosyl naphthoquinones
are around 50 lM. No significant difference was noticed
between gluco and galacto derivatives (3 vs 13), nor in
the nature of the protecting group at O–6 (acetyl for 3
and 13, benzoyl for 8 and 18).
Compound
IC50 (lM)
1,4-Naphthoquinone
3
5
120.8
46
—
8
36
13
15
18
62
—
36
syl-naphthoquinone derivatives. The cytotoxicity of
these new naphthoquinone derivatives was evaluated
against the A375 cell line. Acetyl and/or benzoyl pro-
tected C-glycosyl-naphthoquinones showed promising
antiproliferative activity against human melanoma cell.
1. Experimental
1.1. General methods
Melting points were determined with a Buchi capillary
¨
apparatus and are not corrected. Optical rotations were
determined with a Perkin–Elmer 241 polarimeter at
room temperature. 1H and 13C NMR spectra were
recorded on a Bruker AM-500 spectrometer in CDCl3,
with Me4Si as the internal reference, or in D2O. Mass
spectra (ESI) and high resolution mass spectra (HRMS)
were recorded on a MA1212 instrument using standard
conditions. IR was obtained using a Perkin–Elmer
2000 FTIR instrument. Reactions were monitored by
TLC on Silica Gel 60 F254 (E. Merck) plates exposed
to H2SO4 (10% in 1:1 EtOH–water) spray followed by
charring (ꢀ50 °C). Column chromatography was per-
formed with Silica Gel Geduran Si 60 (E. Merck). Sol-
vents were distilled before use. Water was distilled
twice. Microanalyses were performed at the analytical
In summary, we have reported the synthesis of b-C-
glucosyl and b-C-galactosyl-1,4-dimethoxynaphthalenes
using F3CCO2Ag/SnCl4 promoted Friedel–Crafts elec-
trophilic substitution reactions. Both glycosyl acetate
and methyl glycoside can be employed as glycosyl
donors. Mild oxidation converted C-glycosyl-1,4-di-
methoxynaphthalenes into the corresponding C-glyco-
O
AcO
OAc
O
CAN
10
MeCN-H2O
95%
AcO
OAc
O
13
OMe
O
OH
O
OH
HO
OH
OH
O
NaOMe
CAN
10
MeOH
59%
HO
MeCN-H2O
67%
OH
OH
15
OMe
O
14
OMe
OMe
OMe
OMe
OBz
O
AgOTfa/SnCl4, Ar
CH2Cl2, 35-40 °C
O
O
AcO
AcO
AcO
OBz
O
AcO
OBz
O
CAN
+
AcO
AcO
OCH3
65%
MeCN-H2O
85%
AcO
OAc
17
OAc
18
16
Scheme 2. Synthesis of the b-C-galactopyranosyl-naphthoquinones.

776
L. Lin et al. / Carbohydrate Research 343 (2008) 773–779
0
0
0
0
center of the East China University of Science and
Technology.
5.44 (t, 1H, J4 ;3 ¼ J4 ;5 9:3 Hz, H-40), 5.30 (t, 1H,
J2 ;1 ¼ J2 ;3 9:7 Hz, H-20), 5.13 (d, 1H, J1 ;2 10:2 Hz,
0
0
0
0
0
0
H-10), 4.27 (dd, 1H, J6 a;5 5:2 Hz, J6 a;6 b 12:4 Hz,
0
0
0
0
1.2. General procedure I for the C-glycosylation reaction
of glycosyl donors with aromatic acceptors
H-60a), 4.15 (dd, 1H, J6 b;5 2:0, J6 b;6 a 12:3 Hz, H-60b),
4.01 (s, 3H, OCH3), 3.97 (m, 1H, H-50), 3.94 (s, 3H,
OCH3), 2.08, 2.05, 2.05, 2.03 (4s, 12H, 4 ꢂ COCH3);
13C NMR (125.8 MHz, CDCl3): 171.4, 171.0, 170.3,
169.8 (4 ꢂ COCH3), 153.0, 149.5 (C-1, C-4, ArC),
128.8, 127.8, 127.5, 126.9, 124.1, 123.3, 122.9 (C-2, C-5
to C-10, ArC), 102.1 (C-3, ArC), 77.1, 75.5, 74.9, 71.6,
69.6 (C-10 to C-50), 64.0 (C-60), 63.3 (OCH3), 56.4
(OCH3), 21.4, 21.1 (COCH3). IR (KBr) m 1755 (COCH3)
cmꢄ1. ESIMS: m/z 541.1 [M+Na]+, 557.1 [M+K]+.
HRESIMS: calcd for C26H30O11Na: 541.1686; found:
m/z 541.1684.
0
0
0
To a soln of the glycosyl donor (1 equiv) and the aro-
matic acceptor (2 equiv) in dry alcohol-free CH2Cl2
(7–10 mL/mmol), F3CCO2Ag (1.5 equiv) was added in
one portion. The mixture was stirred at rt in the dark,
then 0.35 equiv of SnCl4 (1 M soln in CH2Cl2) was
added dropwise for 1 h under Ar. After stirring for 5–
8 h at 35–40 °C, saturated NaHCO3 was added and
the mixture was stirred again for 20 min. The soln was
filtered off and the filtrate was extracted with CH2Cl2.
The combined CH2Cl2 soln was washed with brine
and dried over anhyd MgSO4, then concentrated under
diminished pressure. The residue was purified by column
chromatography.
1.6. 2-(2,3,4,6-Tetra-O-acetyl-b-D-glucopyranosyl)-1,4-
naphthoquinone (3)
Prepared from 2 (280 mg, 0.54 mmol) according to the
General procedure III. The residue was purified by col-
umn chromatography: 3:2 petroleum ether–EtOAc, then
recrystallized from 1:1 CH2Cl2–petroleum ether. Yield:
220 mg (83%), yellow needles; mp 159–162 °C; Rf 0.55
´
1.3. General procedure II for the Zemplen-deacetylation
To a soln of the acetyl protected derivative in dry
MeOH, 1–2 drops of a ꢁ1 M methanolic NaOMe soln
were added, and the reaction mixture was kept at rt until
completion of the reaction (TLC 10:1 CH2Cl2–MeOH).
Resin (H+ form) was then added to remove sodium ion,
the resin was filtered off, and the solvent removed under
diminished pressure. If the residue was chromatographi-
cally not uniform, it was purified by column chromato-
graphy or by crystallization.
23
(2:3 EtOAc–petroleum ether); ½aꢃD ꢄ10.9 (c 0.6, CHCl3);
1H NMR (500 MHz, CDCl3) d 8.08 (m, 2H, H-5, H-8,
ArH), 7.56 (m, 2H, H-6, H-7, ArH), 7.12 (s, 1H, H-3,
ArH), 5.41 (t, 1H, J3 ;2 ¼ J3 ;4 9:4 Hz, H-30), 5.18 (t,
0
0
0
0
1H, J4 ;3 ¼ J4 ;5 9:7 Hz, H-40), 5.05 (t, 1H, J1 ;2 9:6 Hz,
0
0
0
0
0
0
H-20), 4.87 (d, 1H, J1 ;2 9:8 Hz; H-10), 4.27 (dd, 1H,
0
0
J6 a;5 4:9 Hz, J6 a,6 b 12.5 Hz, H-60a), 4.16 (dd, 1H,
0
0
0
0
J6 b,5 2.0, J6 b,6 a 12.6 Hz, H-60b), 3.86 (m, 1H, H-50),
2.10, 2.05, 2.02, 1.87 (4s, 12H, 4 ꢂ COCH3); 13C
NMR (125.8 MHz, CDCl3): 185.2, 184.1 (2 ꢂ C@O,
naphthoquinone), 171.4, 170.8, 170.3, 170.2 (4 ꢂ
COCH3), 146.7 (C-3, ArC), 136.7, 134.9, 134.7, 132.5,
127.2, 127.1 (C-2, C-4 to C-10, ArC), 77.0, 74.5, 73.3,
72.9, 69.1 (C-10 to C-50), 62.8 (C-60), 21.4, 21.3, 21.1
(COCH3). IR (KBr) m 1746 (COCH3), 1668 (CO,
naphthoquinone) cmꢄ1; ESIMS: m/z 511.1 [M+Na]+.
HRESIMS calcd for C24H24O11Na: 511.1216; found:
m/z 511.1218. Anal. Calcd for C24H24O11: C, 59.02; H,
4.95. Found: C, 58.92; H, 4.88.
0
0
0
0
1.4. General procedure III for mild oxidation of 1,4-
dimethoxynaphthalene derivatives
A soln of CAN (3 equiv) in water (1–2 mL/mmol) was
added to a soln of the 1,4-dimethoxynaphthalene deriv-
ative in MeCN (1–2 mL/mmol). After stirring at rt in
the dark for 1 h, the mixture was extracted with CH2Cl2
(3 ꢂ 15 mL). The combined CH2Cl2 soln was washed
with brine and dried over anhyd MgSO4, then concen-
trated under diminished pressure. The crude product
was purified by column chromatography.
1.5. 2-(2,3,4,6-Tetra-O-acetyl-b-D-glucopyranosyl)-1,4-
dimethoxynaphthalene (2)
1.7. 2-(b-D-Glucopyranosyl)-1,4-dimethoxynaphthalene
(4)
Prepared from 1 (342 mg, 0.88 mmol) and 1,4-di-
methoxynaphthalene (330 mg, 1.75 mmol) according to
the General procedure I. The residue was purified by
column chromatography (5:1 petroleum ether–EtOAc).
Yield: 274 mg (60%); brown oil, Rf 0.45 (1:2 EtOAc–
Prepared from 2 (91 mg, 0.18 mmol) according to the
General procedure II. The residue was purified by col-
umn chromatography (2:1 EtOAc–EtOH), and recrys-
tallized from Et2O. Yield: 60 mg (97%), white crystals,
23
mp 80–83 °C; Rf 0.40 (8:1 EtOAc–MeOH); ½aꢃD +2.3
23
1
petroleum ether); ½aꢃD ꢄ17.3 (c 0.5, CHCl3); H NMR
(500 MHz, CDCl3): d 8.23, 8.05 (2d, 2H, J 8.3, 8.2 Hz,
H-5, H-8, ArH), 7.53 (m, 2H, H-6, H-7, ArH), 6.76 (s,
(c 0.5, MeOH); 1H NMR (500 MHz, D2O): d 8.20,
8.07 (2d, 2H, J 8.3, 8.3 Hz, H-5, H-8, ArH), 7.60 (m,
2H, H-6, H-7, ArH), 6.96 (s, 1H, H-3, ArH), 4.87 (d,
1H, H-3, ArH), 5.56 (t, 1H, J3 ;2 ¼ J3 ;4 9.8 Hz, H-30),
1H, J1 ,2 9.7 Hz, H-10), 3.98, 3.90 (2s, 6H, 2 ꢂ OCH3),
0
0
0
0
0
0

L. Lin et al. / Carbohydrate Research 343 (2008) 773–779
777
3.85–3.56 (m, overlapping, 6H, H-20 to H-50, H-60a,
H-60b); 13C NMR (125.8 MHz, D2O): 155.0, 150.9
(C-1, C-4, ArC), 130.6, 130.2, 129.6, 129.1, 128.4,
125.0, 124.7 (C-2, C-5 to C-10, ArC), 105.4 (C-3,
ArC), 83.1, 80.3, 78.3, 75.7, 72.6 (C-10 to C-50), 66.1
(C-60), 63.7 (OCH3), 58.8 (OCH3). IR (KBr) m 3404
(COCH3), 1724 (COPh) cmꢄ1; ESIMS: m/z 603.3
[M+Na]+, 619.3 [M+K]+; HRESIMS: calcd for
C31H32O11Na: 603.1842; found: m/z 603.1852.
1.10. 2-(2,3,4-Tri-O-acetyl-6-O-benzoyl-b-D-glucopyran-
osyl)-1,4-naphthoquinone (8)
(OH) cmꢄ1
;
ESIMS: m/z 373.1 [M+Na]+, 723.2
[2M+Na]+; HRESIMS: calcd for C18H22O7Na,
373.1263; found m/z 373.1259. Anal. Calcd for
C18H22O7: C, 61.71; H, 6.33. Found: C, 61.50; H, 6.33.
Prepared from 7 (700 mg, 1.21 mmol) according to the
General procedure III. The residue was purified by col-
umn chromatography (3:2 petroleum ether–EtOAc).
Yield: 448 mg (67%) brown oil; Rf 0.66 (1:2 EtOAc–
27
1
1.8. 2-(b-D-Glucopyranosyl)-1,4-naphthoquinone (5)
petroleum ether); ½aꢃD ꢄ7.1 (c 3.1, CHCl3); H NMR
(500 MHz CDCl3): d 8.00 (m, 4H, H-5, H-8, ArH,
PhH), 7.68 (m, 2H, ArH), 7.51 (t, 1H, J 7.6 Hz, Ph),
7.39 (t, 2H, J 7.8 Hz, Ph), 7.03 (s, 1H, H-3, ArH), 5.58
Prepared from 4 (35 mg, 0.01 mmol) according to the
General procedure III. The residue was purified by col-
umn chromatography (1:8 MeOH–CHCl3); yield: 26 mg
(80%), orange oil; Rf 0.42 (6:1 CHCl3–MeOH); 1H
NMR (500 MHz, D2O): d 8.03, 7.98 (2m, 2H, H-5,
H-8, ArH), 7.81 (m, 2H, H-6, H-7, ArH), 7.13 (s, 1H,
(t, 1H, J3 ,4 = J3 ,2 9.4 Hz, H-30), 5.22 (t, 1H, J4 ,5
=
0
0
0
0
0
0
J4 ,3 9.7 Hz, H-40), 4.89 (t, 1H, J2 ,3 = J2 ,1 9.7 Hz,
0
0
0
0
0
0
H-20), 4.84 (d, 1H, J1 ,2 9.7 Hz, H-10), 4.46 (dd, 1H,
0
0
J6 b,5 2.2 Hz, J6 b,6 a 12.8 Hz, H-60b), 4.34 (dd, 1H,
0
0
0
H-3, ArH), 4.64 (d, 1H, J1 ,2 9.8 Hz, H-10), 3.88 (dd,
J6 a,5 4.8 Hz, J6 a,6 b 12.4 Hz, H-60a), 3.94 (m, 1H, H-
5), 1.99, 1.95, 1.80 (3s, 9H, 3 ꢂ COCH3); 13C NMR
(125.8 MHz, CDCl3): 185.4, 184.1 (2 ꢂ C@O, naphtho-
quinone), 170.8, 170.3, 170.2 (3 ꢂ COCH3), 166.9
(COPh), 146.7, 136.6, 134.8, 134.6, 133.9, 132.5, 130.5,
130.2, 129.1, 128.8, 127.1, 127.0 (C-2, C-5 to C-10,
ArC, Ph), 104.9 (C-3, ArC), 77.0, 74.5, 73.3, 72.9, 69.6
(C-10 to C-50), 63.3 (C-60), 21.2, 21.1 (COCH3); IR
(KBr) m 1755 (COCH3), 1724 (COPh), 1666 (CO,
naphthoquinone) cmꢄ1; ESIMS: m/z 573.3 [M+Na]+,
589.2 [M+K]+; HRESIMS: calcd for C29H26O11Na:
573.1373; found: m/z 573.1375. Anal. Calcd
for C29H26O11: C, 63.27; H, 4.76. Found: C, 63.54; H,
4.91.
0
0
0
0
0
0
1H, J6 b,5 1.3 Hz, J6 b,6 a 12.6 Hz, H-60b), 3.75 (dd, 1H,
0
0
0
0
J6 a,5 5.1 Hz, J6 a,6 b 12.4 Hz, H-60a), 3.61 (t, 1H,
0
0
0
0
J3 ,2 = J3 ,4 8.7 Hz, H-30), 3.57–3.50 (m, overlapping,
3H, H-20, H-40, H-50); 13C NMR: (125.8 MHz, D2O):
189.6, 187.5 (2 ꢂ C@O, naphthoquinone), 150.5 (C-3,
ArC), 139.0 (C-2, ArC), 137.5, 137.3 (C-7, C-8, ArC),
134.2, 133.8 (C-9, C-10, ArC), 129.4, 128.8 (C-5, C-6,
ArC), 83.0, 80.0, 77.2, 76.4, 72.4 (C-10 to C-50), 63.6
(C-60). IR (KBr) m 3412 (OH), 1663 (CO, naphtho-
quinone) cmꢄ1; ESIMS: m/z 343.1 [M+Na]+, 359.1
[M+K]+; HRESIMS: calcd for C16H16O7Na: 343.0794;
found: m/z 343.0793. Anal. Calcd for C16H16O7: C,
60.00; H, 5.04. Found: C, 60.17; H, 4.98.
0
0
0
0
1.9. 2-(2,3,4-Tri-O-acetyl-6-O-benzoyl-b-D-glucopyran-
osyl)-1,4-dimethoxynaphthalene (7)
1.11. 2-(2,3,4,6-Tetra-O-acetyl-b-D-galactopyranosyl)-
1,4-dimethoxynaphthalene (10)
Prepared from 6 (797 mg, 1.88 mmol) according to the
General procedure I. The residue was purified by col-
umn chromatography (5:1 petroleum ether–EtOAc).
Yield: 824 mg (76%) brown oil, Rf 0.49 (1:3 EtOAc–
Prepared from 9 (1.05 g, 2.69 mmol) according to the
General procedure I. The residue was purified by col-
umn chromatography (5:1 petroleum ether–EtOAc).
Yield: 907 mg (65%) brown oil, Rf 0.45 (1:2 EtOAc–
petroleum ether); ½aꢃD +6.9 (c 3.9, CHCl3); H NMR
(500 MHz, CDCl3): d 8.24, 8.06 (2d, 2H, J 8.2, 8.1 Hz,
H-5, H-8, ArH), 7.63 (m, 2H, H-6, H-7, ArH), 6.81 (s,
27
23
1
1
petroleum ether); ½aꢃD +57.4 (c 1.6, CHCl3); H NMR
(500 MHz, CDCl3): d 8.14–7.95 (m, 4H, H-5 to H-8,
ArH), 7.52–7.34 (m, 5H, Ph), 6.67 (s, 1H, H-3, ArH),
5.49–5.34 (m, 3H, H-20 to H-40), 5.10 (d, 1H, J1 ,2
1H, H-3, ArH), 5.73 (t, 1H, J2 ,3 = J2 ,1 10.0 Hz,
0
0
0
0
0
0
9.9 Hz, H-10), 4.49 (dd, 1H, J6 b,5 2.4 Hz, J6 b,6 a
H-20), 5.58 (d, 1H, J 3.1 Hz, H-40), 5.29 (dd, 1H, J3 ,4
0
0
0
0
0
0
12.2 Hz, H-60b), 4.32 (dd, 1H, J6 a,5 4.9 Hz, J6 a,6 b
12.2 Hz, H-60a), 4.06 (m, 1H, H-5), 3.87, 3.84 (2s, 6H,
2 ꢂ OCH3), 2.01, 1.95, 1.66 (3s, 9H, 3 ꢂ COCH3); 13C
NMR (125.8 MHz, CDCl3): 170.8, 171.7, 170.2
(3 ꢂ COCH3), 166.8 (COPh), 153.0, 149.5 (C-1, C-4,
ArC), 133.9, 130.4, 130.4, 129.1, 128.8, 127.8, 127.4,
126.8, 124.2, 123.2, 122.9 (C-2, C-5 to C-10, ArC, C-100
to C-600, COPh), 102.2 (C-3, ArC), 77.1, 75.5, 74.9,
71.7, 69.9 (C-10 to C-50), 64.0 (C-60), 63.8 (OCH3), 56.3
(OCH3), 21.3, 21.1 (COCH3); IR (KBr) m 1755
3.2 Hz, J3 ,2 9.9 Hz, H-30), 5.10 (d, 1H, J1 ,2 10.1 Hz,
H-10), 4.21–4.13 (m, overlapping, 3H, H-50, H-60a,
H-60b), 4.02, 3.95 (2s, 6H, 2 ꢂ OCH3), 2.26, 2.02, 2.01,
1.73 (4s, 12H, 4 ꢂ COCH3); 13C NMR (125.8 MHz,
CDCl3): 171.1, 171.0, 170.9, 169.8 (4 ꢂ COCH3),
152.9, 149.5 (C-1, C-4, ArC), 128.8, 127.8 127.4, 126.8,
124.4, 123.2, 122.9 (C-2, C-5 to C-10, ArC), 102.5
(C-3, ArC), 75.7, 75.6, 73.4, 68.9, 68.7 (C-10 to C-50),
64.0 (C-60), 62.6 (OCH3), 56.4 (OCH3), 21.5, 21.3, 21.2
(COCH3). IR (KBr) m 1749 (COCH3) cmꢄ1. ESIMS:
0
0
0
0
0
0
0
0

778
L. Lin et al. / Carbohydrate Research 343 (2008) 773–779
m/z 541.1 [M+Na]+, 557.1 [M+K]+, 1059.2 [2M+Na]+,
1075.2 [2M+K]+; HRESIMS: calcd for C26H30O11Na:
541.1686; found: m/z 541.1685.
1.14. 2-(b-D-Galactopyranosyl)-1,4-naphthoquinone (15)
Prepared from 14 (40 mg, 0.01 mmol) according to the
General procedure III. The residue was purified by col-
umn chromatography (8:1 CH3OH–CHCl3). Yield:
25 mg (67%), brown oil, Rf 0.42 (6:1 CHCl3–MeOH);
1H NMR (500 MHz, D2O): d 7.98 (m, 2H, H-5, H-8,
ArH), 7.81 (m, 2H, H-6, H-7, ArH), 7.18 (s, 1H, H-3,
1.12. 2-(2,3,4,6-Tetra-O-acetyl-b-D-galactopyranosyl)-
1,4-naphthoquinone (13)
Prepared from 10 (907 mg, 1.75 mmol) according to the
General procedure III. The residue was purified by col-
umn chromatography (3:2 petroleum ether–EtOAc),
then recrystallized from 1:1 CH2Cl2–petroleum ether.
Yield: 810 mg (95%), yellow crystals; mp 109–112 °C;
ArH), 4.60 (d, 1H, J1 ,2 9.8 Hz, H-10), 4.04 (d, 1H, J
2.7 Hz, H-40), 3.83–3.71 (m, overlapping, 5H, H-20, H-30,
H-50, H-60a, H-60b); 13C NMR (125.8 MHz, D2O):
189.7, 187.6 (2 ꢂ C@O, naphthoquinone), 150.8 (C-3,
ArC), 139.0 (C-2, ArC), 137.5, 137.3 (C-7, C-8, ArC),
134.2, 133.8 (C-9, C-10, ArC), 129.5, 128.8 (C-5, C-6,
ArC), 82.3, 76.8, 76.7, 74.6, 72.0 (C-10 to C-50), 64.0
(C-60). IR (KBr) m 3429 (OH), 1663 (CO, naphthoquinone)
cmꢄ1; ESIMS: m/z 343.1 [M+Na]+, 359.1 [M+K]+,
663.2 [2M+Na]+; HRESIMS: calcd for C16H16O7Na:
343.0794; found: m/z 343.0793. Anal. Calcd for
C16H16O7: C, 60.00; H, 5.04. Found: C, 59.83; H, 5.00.
0
0
23
Rf 0.55 (2:3 EtOAc–petroleum ether); ½aꢃD +4.9 (c 0.6,
1
CHCl3); H NMR (500 MHz, CDCl3): d 8.09 (m, 2H,
H-5, H-8, ArH), 7.77 (m, 2H, H-6, H-7, ArH), 7.21 (s,
1H, H-3, ArH), 5.53 (d, 1H, J 2.7 Hz, H-40), 5.25 (dd,
1H, J3 ,2 10.1 Hz, J3 ,4 3.2 Hz, H-30), 5.19 (t, 1H,
0
0
0
0
J2 ,1 = J2 ,3 9.8 Hz, H-20), 4.86 (d, 1H, J1 ,2 9.2 Hz,
H-10), 4.19–4.06 (m, overlapping, 3H, H-60a, H-60b,
H-50), 2.21, 2.05, 2.00, 1.88 (4s, 12H, 4 ꢂ COCH3); 13C
NMR (125.8 MHz, CDCl3): 185.4, 184.3 (2 ꢂ C@O,
naphthoquinone), 171.1, 170.9, 170.6 (COCH3), 147.2
(C-3, ArC), 136.9, 134.8, 134.7, 132.5, 127.1, 127.0
(C-2, C-4 to C-10, ArC), 75.5, 73.0, 72.5, 70.9, 68.2
(C-10 to C-50), 62.4 (C-60), 21.4, 21.3, 21.2 (COCH3).
IR (KBr) m 1750 (COCH3), 1670 (CO, naphthoquinone)
cmꢄ1; ESIMS: m/z 511.1 [M+Na]+. HRESIMS: calcd
for C24H24O11Na, 511.1216; found: m/z 511.1172. Anal.
Calcd for C24H24O11: C, 59.02; H, 4.95. Found: C,
58.89; H, 4.99.
0
0
0
0
0
0
1.15. 2-(2,3,4-Tri-O-acetyl-6-O-benzoyl-b-D-galacto-
pyranosyl)-1,4-dimethoxynaphthalene (17)
Prepared from 16 (661 mg, 1.56 mmol) according to the
General procedure I. The residue was purified by column
chromatography (5:1 petroleum ether–EtOAc); Yield:
583 mg (65%) brown oil, Rf 0.31 (1:3 EtOAc–petroleum
1
ether); H NMR (CDCl3, 500 MHz): d 8.24, 8.05 (2d,
2H, J 8.2 Hz, 8.1 Hz, H-5, H-8, ArH), 7.97 (d, 2H, J
7.5 Hz, Ph), 7.56–7.48 (m, 3H, H-6, H-7, ArH, Ph),
7.41 (t, 2H, J 7.8 Hz, Ph), 6.85 (s, 1H, H-3, ArH), 5.78
1.13. 2-(b-D-Galactopyranosyl)-1,4-dimethoxy-
naphthalene (14)
(t, J2 ,1 = J2 ,3 10.0 Hz, H-20), 5.71 (d, 1H, J4 ,3 3.2 Hz,
0
0
0
0
0
0
H-40), 5.35 (dd, 1H, J3 ,4 3.4 Hz, J3 ,2 10.0 Hz, H-30),
0
0
0
0
5.15 (d, 1H, J1 ,2 10.1 Hz, H-10), 4.49 (dd, 1H, J6 a,5
0
0
0
0
Prepared from 10 (246 mg, 0.47 mmol) according to the
General procedure II. The residue was purified by col-
umn chromatography (2:1 EtOAc–EtOH), and recrys-
tallized from Et2O. Yield: 98 mg (59%) white crystals,
4.2 Hz, J6 a,6 b 10.8 Hz, H-60a), 4.38 (t, 1H, J 4.2 Hz,
0
0
H-50), 4.34 (dd, 1H, J6 b,5 3.9 Hz, J6 b,6 a 10.3 Hz,
H-60b), 4.03, 3.92 (2s, 6H, 2 ꢂ OCH3), 2.28, 2.02, 1.73
(3s, 9H, 3 ꢂ COCH3); 13C NMR (125.8 MHz, CDCl3):
171.9, 171.8, 169.9 (3 ꢂ COCH3), 166.7 (COPh),
152.89, 149.6 (C-4, C-1, ArC), 133.9, 130.4, 130.3,
130.1, 129.2, 129.1, 128.8, 127.8, 127.4, 126.8, 124.3,
123.2, 122.9 (C-2, C-5 to C-10, ArC, C-100 to C-600, Ph),
102.5 (C-3, ArC), 75.8, 75.6, 73.3, 68.9, 68.8 (C-10 to
C-50), 62.9 (C-60), 62.8 (OCH3), 56.4 (OCH3), 21.5,
21.3, 21.2 (3 ꢂ COCH3); IR (KBr) m 1749 (COCH3),
1731 (COPh) cmꢄ1; ESIMS: m/z 603.2 [M+Na]+, 619.2
[M+K]+, 1183.4 [2M+Na]+; HRESIMS: calcd for
C31H32O11, 603.1842; found: m/z 603.1862.
0
0
0
0
23
mp 70–72 °C; Rf 0.40 (8:1 EtOAc–MeOH); ½aꢃD +5.2
(c 1.1, MeOH); 1H NMR (500 MHz, D2O): d 8.21,
8.08 (2d, 2H, J 8.4 Hz, 8.2 Hz, H-5, H-8, ArH), 7.60
(m, 2H, H-6, H-7, ArH), 7.09 (s, 1H, H-3, ArH), 4.83
(d, 1H, J1 ,2 9.8 Hz, H-10), 4.08 (d, 1H, J 3.3 Hz,
0
0
H-40), 4.02(dd, 1H, J2 ,1 9.7 Hz, J2 ,3 7.4 Hz, H-20),
4.00, 3.91 (2s, 6H, 2 ꢂ OCH3), 3.89 (m, 1H, H-50),
0
0
0
0
3.83 (dd, 1H, J3 ,2 7.5 Hz, J3 ,4 3.4 Hz, H-30), 3.72
(m, overlapping, 2H, H-60a, H-60b); 13C NMR
(125.8 MHz, D2O): 154.9, 150.7 (C-1, C-4, ArC),
130.5, 123.0, 129.1, 129.0, 128.7, 124.8, 124.7 (C-2, C-5
to C-10, ArC), 105.5 (C-3, ArC), 82.0, 78.7, 77.1, 73.1,
72.0 (C-10 to C-50), 66.0 (C-60), 63.8 (OCH3), 58.7
(OCH3). IR (KBr) m 3412 (OH) cmꢄ1; ESIMS: m/z
373.0 [M+Na]+, 723.1 [2M+Na]+; HRESIMS: calcd
for C18H22O7Na: 373.1263; found: m/z 373.1265. Anal.
Calcd for C18H22O7: C, 61.71; H, 6.33. Found: C,
61.44; H, 6.26.
0
0
0
0
1.16. 2-(2,3,4-Tri-O-acetyl-6-O-benzoyl-b-D-galacto-
pyranosyl)-1,4-naphthoquinone (18)
Prepared from 17 (539 mg, 0.93 mmol) according to the
General procedure III. The residue was purified by col-
umn chromatography (3:2 petroleum ether–EtOAc).

L. Lin et al. / Carbohydrate Research 343 (2008) 773–779
779
Yield: 436 mg (85%) brown oil, Rf 0.46 (1:2 EtOAc–
References
28
1
petroleum ether); ½aꢃD +0.2 (c 1.1, CHCl3); H NMR
(500 MHz, CDCl3): d 8.10 (m, 2H, H-5, H-8, ArH),
8.03 (d, 2H, J 7.1 Hz, Ph), 7.77 (m, 2H, H-60, H-70,
ArH), 7.58 (t, 1H, J 7.5 Hz, Ph), 7.46 (t, 2H, J 7.9 Hz,
H-300, H-500, Ph), 7.11 (d, 1H, J 1.6 Hz, H-3, ArH),
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5.63 (m, 1H, H-50), 5.51 (d, 1H, J4 ,3 3.9 Hz, H-40),
0
0
5.32 (dd, 1H, J3 ,2 9.6 Hz, J3 ,4 3.8 Hz, H-30), 5.26 (t,
0
0
0
0
1H, J2 ,1 = J2 ,3 9.6 Hz, H-20), 4.66 (dd, 1H, J6 b,5
0
0
0
0
0
0
0
0
3.9 Hz, J6 b,6 a 12.1 Hz, H-60b), 4.53 (dd, 1H, J6 a,5
0
0
0
6.8 Hz, J6 a,6 b 12.0 Hz, H-60a), 4.25 (d, 1H, J1 ,2
0
0
0
9.1 Hz, H-10), 2.17 2.14, 1.87 (3s, 9H, 3 ꢂ COCH3);
13C NMR (125.8 MHz, CDCl3): 185.4, 184.2 (2 ꢂ C@O,
ArC), 171.1, 170.8, 170.6 (3 ꢂ COCH3), 166.6 (COPh),
147.2, 136.8, 134.8, 134.0, 132.5, 130.4, 130.3, 129.1,
128.8, 127.0, 126.9 (C-2, C-5 to C-10, ArC, Ph), 97.9
(C-3, ArC), 75.5, 73.0, 72.4, 70.9, 68.3 (C-10 to C-50),
62.7 (C-60), 21.3, 21.2 (COCH3); IR (KBr) m 1751
(COCH3), 1727 (COPh), 1662 (CO, naphthoquinone);
ESIMS: m/z 573.2 [M+Na]+, 589.2 [M+K]+; HRE-
SIMS: calcd for C29H26O11Na: 573.1373; found: m/z
573.1353. Anal. Calcd for C29H26O11: C, 63.27; H,
4.76. Found: C, 63.30; H, 4.66.
1.17. In vitro antitumor assays
The human A375 melanoma cells were purchased from
the Cell Bank of Type Culture Collection of the Chinese
Academy of Sciences (Shanghai, China).
1.17.1. Antiproliferative assays (MTT). The MTT
(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bro-
mide) colorimetric assay was performed as described by
Mosman.12a A375Cellswereplacedwithin96-wellculture
plates (104 cells/well), respectively, and allowed to attach
for 24 h before treatment. The cells were treated with the
compounds prepared ranging from 10 to 160 lM or with-
out the tested compound (vehicle control, 0.1% Me2SO).
The cytotoxicity of the compounds was evaluated after
24 h of culture using the MTT assay. Absorbance in con-
trolanddrug-treatedwellswasmeasuredinanAutomated
Microplate Reader (Multiskan Mk3, Thermo Electron
Corporation) at 550 nm. The cytotoxicity of the com-
pounds was expressed as IC50 (concentration of 50% cyto-
toxicity, which was extrapolated from linear regression
analysis of experimental data).
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Acknowledgments
We thank Professor Jian Wen LIU and M. Chang Long
LI for biological studies. L.L. thanks the Ecole Normale
´
Superieure de Cachan for a fellowship. The project was
supported by National Natural Science Foundation of
China (Grant No. 20576034) and Shanghai Science
and Technology Community (No. 074107018).