Synthesis of azole nucleoside analogues of d-pinitol as potential antitumor agents

Article abstract of DOI:10.1016/j.carres.2007.01.004

A convenient strategy is reported for the synthesis of azole nucleoside analogues of d-pinitol (=3-O-methyl-d-chiro-inositol). The key intermediate 3-O-methyl-4,5-epoxy-d-chiro-inositol was obtained in excellent yield via an epoxidation from mono-methanes

Full text of DOI:10.1016/j.carres.2007.01.004

Carbohydrate Research 342 (2007) 865–869
Note
Synthesis of azole nucleoside analogues of
D-pinitol as potential antitumor agents
b
Tianrong Zhana,b, and Hongxiang Lou
*
aCollege of Chemistry and Molecular Engineering, Qingdao University of Science and Technology,
Qingdao 266042, People’s Republic of China
bSchool of Pharmaceutical Sciences, Shandong University, Jinan 250012, People’s Republic of China
Received 2 October 2006; received in revised form 19 December 2006; accepted 9 January 2007
Available online 14 January 2007
Abstract—A convenient strategy is reported for the synthesis of azole nucleoside analogues of D-pinitol (=3-O-methyl-D-chiro-ino-
sitol). The key intermediate 3-O-methyl-4,5-epoxy-D-chiro-inositol was obtained in excellent yield via an epoxidation from mono-
methanesulfonate of D-pinitol. The process of opening of the epoxy ring by azole-bases appeared strongly regioselective in the pres-
ence of 1,8-diazabicyclo[5.4.0]undec-7-ene. All newly synthesized carbocyclic azole nucleosides were assayed against lung and blad-
der cancer in vitro. Only the triazole and benzotriazole nucleoside analogues inhibited the growth of human lung cancer cell lines
(PG) with EC50 of 11.3 and 22.6lM, respectively, and showed much less inhibitory activity against human bladder cell lines (T24).
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Carbocyclic azole nucleoside; D-Pinitol; 1,2,4-Triazole; Benzotriazole; Nitroindazole; Opening of epoxy ring reaction; Antitumor activity
Carbocyclic nucleosides, in which the oxygen atom of
the sugar moiety is replaced by a CH2 group, have
emerged as a promising class of nucleosides with inter-
esting antiviral and antitumor activities.1 Due to the ab-
sence of the glycosidic linkage between the heterocycle
and the sugar, these compounds have a higher metabolic
stability against the nucleoside phosphorylases.2 Natu-
ral as well as synthetic carbocyclic nucleosides such as
abacavir3 and entecavir4 have shown interesting anti-
tumor activities and antiviral activities against the
human cytomegalovirus (HCMV),5 herpes simplex virus
(HSV),6 hepatitis B virus (HBV),7 and human immuno-
deficiency virus (HIV).8 Based on their notable biologi-
cal activities, it is not surprising that these targets have
drawn substantial synthetic interest.
have attracted considerable attention because of their
broad bioactive spectrum.10 Bredinin shows immuno-
suppressive properties and inhibits inosine 50-mono-
phosphate dehydrogenase (IMPDH) and depletes cells
of guanine nucleotides.11 Ribavirin, a broad spectrum
antiviral agent, also displays antitumor activity.12 Pyra-
zofurin exhibits remarkable anticancer and antiviral
properties.9,13 In addition to the above compounds,
numerous other azole nucleoside analogues have also
been synthesized and display strong antiviral activities,
in which the base involves benzimidazole, indazole,
and other azole derivatives.12b,14 Despite significant pro-
gress, there are very few reports on the synthesis and
bioactivity of carbocyclic azole nucleoside.15
D-Pinitol (=3-O-methyl-D-chiro-inositol) occurs ubiq-
uitously in plants16 and is a useful chiral starting mate-
rial, as illustrated by the asymmetric synthesis of a
putative insulin mediator.17 Its structural features make
it perfectly suited for the stereocontrolled synthesis of
the title compounds (Scheme 1). For example, a cyclo-
hexane ring is already present and a chiral center at C-
4 and C-5 allows stereospecific introduction of the base
moiety via transformation of the OH and MsO groups
Another alteration to the nucleoside structure that has
resulted in profound biological effects is modification of
the heterocyclic base.9 In this field, azole nucleosides
were proven to be a large class of antimetabolites and
*
Corresponding author. Tel.: +86 532 8290 6891; fax: +86 532 8402
3927; e-mail: trzhan@yahoo.com.cn
0008-6215/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2007.01.004

866
T. Zhan, H. Lou / Carbohydrate Research 342 (2007) 865–869
O
OH
OH
O
O
O
OMs
HO
HO
OH
O
O
OH
a
c
b
OCH3
OCH3
OCH3
O
3
O
1
2
OH
B
OH
5'
O
HO
HO
OMs
HO
HO
HO
OH
HO
B
5'
2'
e
d
4'
3'
6'
1'
4'
3'
6'
1'
+
2'
OCH3
OCH3
HO
HO
OCH3
OCH3
OH
4
OH
5
OH
OH
6 B=1,2,4-triazole
7 B=benzotriazole
8 B=6-nitroindazole
9 B=5-nitroindazole
10 B=5-nitroindazole
NO2
N
N
N
N
N
N
N
N
N
N
NO2
1,2,4-triazole benzotriazole
6-nitroindazole
5-nitroindazole
Scheme 1. Reagents and conditions: (a) DMP, acetone, p-TsOH, rt, 16 h, 89%; (b) MsC1, Et3N, CH2Cl2, 0 ꢁC, 24 h, 99%; (c) 75% aqueous TFA,
80 ꢁC, 12 h, 81%; (d) anhydrous methanol, K2CO3, rt, 6 h, 73%; (e) azole-bases, DBU, DMSO, 90–100 ꢁC, 48 h.
into an epoxy ring, and then regioselective opening of
the epoxide by heterocyclic bases. In this paper, a very
short and efficient synthetic route to novel azole nucleo-
side analogues of D-pinitol and their cytotoxicity effects
are reported.
In fact, the reaction of triazole-bases appeared strongly
regioselective, giving only the predominant C-50 isomers
6 and 7. On the other hand, the reaction of nitroindazole
was moderate regioselective, in which the C-50 isomers
were always contaminated with small amounts of C-40
regioisomers. As a result, the two diastereoisomers 9
and 10 were obtained as a mixture (C-50/C-40 = 1.71;
see Table 1, entry 4), which was not isolated indepen-
dently due to their similar chromatographic mobilities
on RPC-18 HPLC. These results can be explained by
the nucleophilicities of nitroindazole-bases being weaker
than those of the triazole base owing to the high electron
withdrawing effect of the –NO2 group.20
Diacetonide derivative 2, a key intermediate, was syn-
thesized according to an efficient procedure in quantita-
tive yield,17,18 and then mesylated to obtain
methanesulfonate 3 as the glycosyl donor. Subsequently,
the common intermediate, diacetonide methanesulfo-
nate 3, was subjected to 1-methylethylidene deprotection
with aqueous CF3COOH, and afforded mono-methane-
sulfonate of D-pinitol 4, which was subsequently con-
verted to epoxide 5 in the presence of K2CO3 in
anhydrous MeOH19 in 73% yield. Since most of the
reactions gave very high yields, intermediates 2, 3, 4,
and 5 involved in the procedure could be subjected di-
rectly to the next reaction without further purification.
Structural assignments of products 6–10 were accom-
plished by 1D and 2D NMR spectroscopic methods.
Table 1. Opening of epoxy ring reaction of 4,5-epoxyl-D-pinitol (5)
with azole-basesa
1
The epoxy ring of 5 was identified from its H NMR
Entry Azole-bases
Product Yieldb (%) 50/40 Ratio
spectrum showing an upfield signal for H-4 at
3.58 ppm, a salient feature of the epoxy ring. The regio-
selective opening of the epoxy ring with various azole-
bases was achieved in reasonable yields in the presence
of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), affording
the corresponding carbocyclic azole nucleosides. In the
case of the glycose-base coupling reaction, a mixture
of C-50 and C-40 isomers was theoretically produced.
c
1
2
3
4
1,2,4-Triazole
Benzotriazole
6-Nitroindazole
5-Nitroindazole
6
74
68
66
62
+1
+1
+1
c
c
7
8
9/10
1.71d
a Reaction was carried out at 100 ꢁC.
b Isolated yields.
c Isolated yields of two regioisomers.
d Ratio was determined by 1H NMR analysis.

T. Zhan, H. Lou / Carbohydrate Research 342 (2007) 865–869
867
The conformation of 6 at C-50 was confirmed by the
finding of the expected cross-peaks between H-50 and
C-5 in the HMBC spectrum, indicating the coupling in
the triazole part at C-50 and the strong NOE between
H-10, H-50, and H-20 in the NOESY.
2.0 mmol) and MgSO4 (9 g). The mixture was stirred at
room temperature for 16 h, after which a homogeneous
solution was obtained. Solid NaHCO3 (1.00 g,
11.9 mmol) was added. The bulk of DMF and acetone
was removed under reduced pressure, and the residue
was partitioned between saturated NaHCO3 solution
and AcOEt. The organic extracts (3 · 100 mL AcOEt)
were washed with water and brine, and dried (MgSO4).
The organic phase was concentrated under reduced
pressure to afford 12.60 g (89%) of 2 as a white crystal-
The newly synthesized compounds 6, 7, 8, and 9/10
were evaluated for their in vitro cytotoxicity by
growth-inhibition studies using two human cancer cell
lines: human lung (PG cell), human bladder (T24 cell).
As shown in Table 2, only triazole nucleoside ana-
logues 6 and 7 exhibited inhibitory activity against
human lung cancer cell lines (PG) with EC50 of 11.3
and 22.6 lM, respectively, and showed much less
activity against human bladder cell lines (T24) with
EC50 of 78.5 and 83.8 lM, respectively. However, the
nitroindazole derivatives 8 and 9/10 did not indicate
any inhibition against these two human cancer cell lines
up to 100 lM.
1
line solid. Mp: 95–96 ꢁC, lit.18 95–97 ꢁC. H and 13C
NMR spectral data matched that reported.17,18
1.3. 3-O-Methyl-1,2:5,6-bis-O-(1-methylethylidene)-4-
[(methylsulfonyl)oxy]-D-chiro-inositol (3)
A cold (0–5 ꢁC) solution of diacetonide 2 (3.0 g,
11.58 mmol) in dry pyridine (15 mL) was stirred with
MsCl (0.41 g, 2.14 mmol) for 24 h at the same tempera-
ture. The reaction mixture was poured into 200 mL
ice-water containing 50 mL HCl. The resulting aqueous
suspension was filtered under reduced pressure, and the
residue was washed with anhydrous EtOH to neutral.
Then the residue was crystallized to afford 3 (4.04 g,
1. Experimental
1.1. General methods
30
99%). White solid. Mp: 120–122 ꢁC. ½aꢀD +72.5 (c 0.3
The solvents were pretreated, when necessary, according
to the appropriate standard procedures before being
used. Column chromatography (CC) and thin-layer
chromatography (TLC) was performed on precoated sil-
ica gel plates F254 (Qingdao Marine Chemical Co. Ltd)
with visualization under UV light and by H2SO4 char-
ring. All reaction mixtures were stirred magnetically.
Instrumentation included an X-6 melting-point appara-
tus (Beijing TECH Instrument Co. Ltd); a Bruker
Avance-600 NMR spectrometer (d in ppm, J in Hz);
an ABI-API4000 mass spectrometer (in m/z); a Perkin
Elmer 240C elemental analysis apparatus; and a Perkin
Elmer 241 polarimeter.
1
CHCl3). H NMR (600 MHz, CDCl3): d 4.51 (dd, 1H,
3
3J3,4 = 8.4, J4,5 = 11.16 Hz, H-4), 4.44 (dd, 1H,
3
3J1,6 = 3.06, J5,6 = 6.06 Hz, H-6), 4.41 (m, 1H, H-2),
3
3
4.30 (dd, 1H, J1,6 = 6.42, J1,2 = 8.04 Hz, H-1), 4.24
(t, 1H, J2,3 = 3J3,4 6.86 Hz, H-3), 3.60 (s, 3H, OMe),
3
3
3
3.26 (dd, 1H, J4,5 = 7.56, J5,6 = 11.16 Hz, H-5), 3.14
(s, 3H, OMs), 1.53 (s, 3H, Me), 1.52 (s, 3H, Me), 1.37
(s, 3H, Me), 1.36 (s, 3H, Me). 13C NMR (150 MHz,
CDCl3): d 110.29 (C(Me)2), 109.77 (C(Me)2), 82.66 (C-
3), 80.07 (C-5), 79.15 (C-4), 76.73 (C-1), 75.82 (C-2),
75.43 (C-6), 60.53 (OMe), 39.49 (OMs), 28.17 (Me),
27.83 (Me), 25.85 (Me), 25.80 (Me). Anal. Calcd for
C14H24O8S: C, 47.72; H, 6.86. Found: C, 47.88; H,
6.79. ESI-MS: (MH+) 353.6.
1.2. 3-O-Methyl-1,2:5,6-bis-O-(1-methylethylidene)-D-
chiro-inositol (2)
1.4. 3-O-Methyl-4-[(methylsulfonyl)oxy]-D-chiro-inositol
(4)
To a suspension of D-pinitol (10.0 g 51.5 mmol) in DMP
and acetone (200 mL, 1:3) were added p-TsOH (380 mg,
A solution of fully protected compound 3 (7.2 g,
20.46 mmol) in 80% AcOH (60 mL) was heated at
80 ꢁC for 10 h. The solvent was removed under reduced
pressure, and the residue was purified by CC (SiO2,
MeOH/CHCl3 1:8) to afford pure alcohol 4 (4.49 g,
Table 2. Cytotoxicity of the final compounds 6, 7, 8, and 9/10 in two
cancer cell lines (PG, T24
)
a
Compound
EC50 (lM)
PGb
11.3
22.6
>100
>100
0.012
T24
c
30
80.68%). Colorless solid. Mp: 144–146 ꢁC. ½aꢀD +55.8
1
6
78.5
83.8
P200
(c 0.3 MeOH). H NMR (600 MHz, DMSO-d6): d 5.14
7
(d, 1H, J = 3.93 Hz, OH), 5.04 (d, 1H, J = 2.1 Hz,
OH), 5.03 (d, 1H, J = 0.82 Hz, OH), 4.88 (d, 1H,
8
9/10
>100
3
J = 6.72 Hz, OH), 4.43 (t, 1H, J4,5 = 9.53 Hz, H-4),
Sangivamycin
0.008
3.67–3.72 (m, 2H, H-2 and H-5), 3.64 (dd, 1H,
a 50% effective concentration.
b Human lung cells.
c Human bladder cells.
3
3J3,4 = 3.7, J2,3 = 7.1 Hz, H-3), 3.60 (m, 1H, H-1),
3.44 (s, 3H, MeO), 3.24 (t, 1H, J = 9.5 Hz, H-6), 3.15

868
T. Zhan, H. Lou / Carbohydrate Research 342 (2007) 865–869
(s, 3H, MsO). 13C NMR (150 MHz, DMSO-d6): d 39.14
(MsO), 59.83 (MeO), 68.63 (C-2), 70.40 (C-1), 72.03 (C-
6), 72.37 (C-4), 81.27 (C-5), 85.41 (C-3). Anal. Calcd for
C8H16O8S: C, 35.29; H, 5.92. Found: C, 35.25; H, 5.90.
ESI-MS: (MH+) 273.3.
compound 7 (401 mg, 68%) was obtained as an amor-
phous foam. Mp: 222–226 ꢁC. 1H NMR (600 MHz,
D2O): d 7.83 (m, 2H, arom., H-6 and H-7), 7.43 (m,
2H, arom., H-4 and H-9), 4.78 (t, 1H, 3J1 ,2 = 10.64 Hz,
0
0
3
3
H-10), 4.57 (dd, 1H, J2 ,3 = 3.26, J1 ,2 = 10.91 Hz, H-
0
0
0
0
20), 4.28 (m, 2H, H-40 and H-30), 3.83 (dd, 1H,
3
3
J5 ,6 = 3.21, J1 ,6 = 9.82 Hz, H-60), 3.71 (t, 1H,
0
0
0
0
1.5. 3-O-Methyl-4,5-epoxyl-D-chiro-inositol (5)
J4 ,5 = 3J5 ,6 = 3.66 Hz, H-50), 3.45 (s, 3H, MeO). 13C
3
0
0
0
0
A solution of mono-methylsulfonate 4 (1.088 g, 4 mmol)
in 30 mL of anhydrous MeOH was treated with 0.72 g
of K2CO3 and the solution was stirred at room temper-
ature for 8 h. TLC analysis showed that compound 8
disappeared, and the reaction mixture was then neutral-
ized with a HCl in MeOH. Potassium salt was filtrated,
and the filtrate was concentrated to afford 5 (0.514 g,
NMR (150 MHz, D2O): d 61.29 (MeO), 70.45 (C-50),
71.71 (C-20), 73.37 (C-60), 73.65 (C-40), 74.33 (C-10),
83.83 (C-30), 120.10 (C-5 and C-8), 130.16 (C-6 and C-
7), 146.26 (C-4 and C-9). Anal. Calcd for C13H17N3O5:
C, 52.88; H, 5.80; N, 14.23. Found: C, 51.96; H, 5.76;
N, 14.18. ESI-MS: (MH+) 296.6.
30
1
73%). Mp: 192–196 ꢁC. ½aꢀD ꢁ16.0 (c 0.2 MeOH). H
1.6.3. (10S,20S,30S,40S,50R,60R)-30-O-Methyl-50-deoxy-
50-(6-nitroindazole-1-yl)-D-chiro-inositol (8). The proce-
dure was carried out as described above. Corresponding
compound 8 (448 mg, 66%) was obtained as an amor-
phous yellow foam. Mp: 273–274 ꢁC. 1H NMR
(600 MHz, D2O): d 8.71 (s, 1H, H-7), 8.49 (s, 1H, H-
3
NMR (600 MHz, D2O): d 4.04 (dd, 1H, J1,6 = 3.16,
3J5,6 = 5.84 Hz, H-6), 3.72–3.75 (m, 2H, H-2 and H-5),
3
3.62 (t, 1H, J1,6 = 3.22 Hz, H-1), 3.58 (dd, 1H,
3J3,4 = 1.78, 3J4,5 = 5.86 Hz, H-4), 3.50 (t, 1H,
3J2,3 = 3.54 Hz, H-3), 3.44 (s, 3H, MeO). 13C NMR
(150 MHz, D2O): d 53.61 (epoxy), 56.02 (epoxy), 56.85
(MeO), 67.86 (C-1), 69.28 (C-2), 71.04 (C-6), 77.41 (C-
3). Anal. Calcd for C7H12O5: C, 47.73; H, 6.87. Found:
C, 47.70; H, 6.82. ESI-MS: (MH+) 177.4.
4
3
3), 7.95 (dd, 2H, J3,4 or 5,7 = 9.15, J4,5 = 25.31 Hz,
3
0
0
arom., H-4, and H-5), 4.62 (d, 1H, J3 ,4 = 10.90 Hz,
3
H-40), 4.56 (t, 1H, J4 ,5 = 10.57 Hz, H-50), 4.38 (d,
0
0
3
3
1H, J2 ,3 = 2.94 Hz, H-20), 4.33 (t, 1H, J1 ,6
=
=
0
0
0
0
3
3
9.89 Hz, H-60), 3.91 (dd, 1H, J1 ,6 = 3.11, J1 ,2
0
0
0
0
3
6.68 Hz, H-10), 3.82 (d, 1H, J3 ,4 = 2.87 Hz, H-30),
3.56 (s, 3H, MeO). 13C NMR (150 MHz, D2O): d
61.44 (MeO), 70.63 (C-20), 71.28 (C-40), 71.64 (C-50),
73.28 (C-60), 73.65 (C-10), 83.97 (C-30), 117.23 (C-1),
118.24 (C-4), 125.40 (C-5), 126.48 (C-6), 130.87 (C-2),
130.87 (C-8), 149.62 (C-3). Anal. Calcd for
C14H17N3O7: C, 49.56; H, 5.05; N, 12.38. Found: C,
49.71; H, 4.99; N, 12.44. ESI-MS: (MH+) 340.5.
0
0
1.6. Typical procedure for the preparation of azole
nucleoside analogues of D-pinitol
1.6.1. (10S,20S,30S,40S,50R,60R)-30-O-Methyl-50-deoxy-
50-(1,2,4-triazole-1-yl)-D-chiro-inositol (6). To a stirred
suspension of 5 (544 mg, 2 mmol) and dry 1,2,4-triazole
(1.5 equiv) in dry DMSO (4 mL), DBU (0.5 mL,
3.3 mmol) in 2 mL dry DMSO was added dropwise.
The clear solution was stirred at 100 ꢁC for 48 h. After
removal of DMSO in vacuo, the resulting brown residue
was diluted with anhydrous MeOH. Silica gel was
added, and the mixture was evaporated to dryness.
The dry powder was applied to silica gel CC (CHCl3/
MeOH) to afford 6 (363 mg, 74%) as an amorphous
1.6.4. (10S,20S,30S,40S,50R,60R)-30-O-Methyl-50-deoxy-
50-(5-nitroindazole-1-yl)-D-chiro-inositol (9) and (10S,20S,
30S,40R,50R,60R)-30-O-methyl-40-deoxy-40-(5-nitroindazole-
1-yl)-D-chiro-inositol (10). The procedure was carried
out as described above. A mixture of more polar 9
and less polar 10 (423 mg, 62%, 9/10 = 1.71 by 1H
NMR) was obtained as an amorphous yellow foam.
Anal. Calcd for C14H17N3O7: C, 49.56; H, 5.05; N,
12.38. Found: C, 49.67; H, 5.08; N, 12.29. ESI-MS:
(MH+) 340.5.
1
foam. Mp: 235–236 ꢁC. H NMR (600 MHz, D2O): d
8.38 (s, 1H, H-5), 8.04 (s, 1H, H-3), 4.31 (dd, 1H,
3
3
J2 ,3 = 3.22, J1 ,2 = 10.77 Hz, H-20), 4.25 (m, 1H, H-
0
0
0
3
0
50), 4.23 (t, 1H, J1 ,6 = 3J5 ,6 = 3.60 Hz, H-60), 4.01 (t,
0
0
0
0
3
3
1H, J3 ,4 = 9.92 Hz, H-40), 3.73 (dd, 1H, J1 ,6 = 3.26,
0
0
0
0
3
3
J1 ,2 = 9.83 Hz, H-10), 3.66 (t, 1H, J2 ,3 = 3.59 Hz,
0
0
0
0
H-30), 3.41 (s, 3H, MeO). 13C NMR (150 MHz, D2O):
d 61.22 (MeO), 67.31 (C-50), 70.19 (C-20), 70.39 (C-60),
72.23 (C-40), 73.35 (C-10), 83.63 (C-30), 148.43 (C-5),
154.51 (C-3). Anal. Calcd for C9H15N3O5: C, 44.08; H,
6.17; N, 17.13. Found: C, 43.96; H, 6.24; N, 17.21.
ESI-MS: (MH+) 246.5.
1.6.4.1. Data for 9. 1H NMR (600 MHz, D2O): d
4
8.86 (d, 1H, J4,6 or 4,7 = 1.75 Hz, H-4), 8.66 (s, 1H, H-
4
3
3), 8.14 (dd, 1H, J4,6 = 2.22, J6,7 = 9.51 Hz, H-6),
3
7.76 (d, 1H, J6,7 = 9.52 Hz, H-7), 4.62 (m, 1H, H-20),
3
4.54 (m, 1H, H-50), 4.38 (t, 1H, J4 ,5 = 3.59 Hz, H-40),
0
0
3
4.32 (m, 1H, H-60), 3.91 (dd, 1H, J1 ,6 = 3.22,
0
0
3
J1 ,2 = 9.75 Hz, H-10), 3.82 (m, 1H, H-30), 3.55 (s,
3H, MeO). 13C NMR (150 MHz, D2O): d 61.44
(MeO), 70.63 (C-40), 71.09 (C-20), 71.50 (C-50), 73.08
(C-60), 73.65 (C-10), 83.96 (C-30), 119.98 (C-1), 123.61
0
0
1.6.2. (10S,20S,30S,40S,50R,60R)-30-O-Methyl-50-deoxy-
50-(benzotriazole-1-yl)-D-chiro-inositol (7). The proce-
dure was carried out as described above. Corresponding

T. Zhan, H. Lou / Carbohydrate Research 342 (2007) 865–869
869
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(C-4), 123.78 (C-3), 124.82 (C-6), 134.40 (C-7), 145.31
(C-5), 152.80 (C-2).
1.6.4.2. Data for 10. 1H NMR (600 MHz, D2O): d
4
8.84 (d, 1H, J4,6 or 4,7 = 1.94 Hz, H-4), 8.47 (s, 1H, H-
4
3
3), 8.31 (dd, 1H, J4,6 = 2.15, J6,7 = 9.37 Hz, H-6),
3
7.71 (d, 1H, J6,7 = 9.38 Hz, H-7), 4.60 (m, 1H, H-10),
3
4.57 (m, 1H, H-50), 4.40 (t, 1H, J4 ,5 = 3.62 Hz, H-40),
0
0
3
4.29 (m, 1H, H-20), 3.96 (dd, 1H, J5 ,6 = 3.25,
0
0
3
J1 ,6 = 9.82 Hz, H-60), 3.83 (m, 1H, H-30), 3.57 (s,
3H, MeO). 13C NMR (150 MHz, D2O): d 61.31
(MeO), 70.63 (C-40), 71.01 (C-10), 71.50 (C-50), 73.28
(C-20), 73.77 (C-60), 83.96 (C-30), 112.72 (C-1), 122.11
(C-4), 122.61 (C-3), 124.84 (C-6), 140.49 (C-7), 144.91
(C-5), 147.02 (C-2).
0
0
1.7. Cytotoxicity assays
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Growth inhibition of the synthetic compounds to vari-
ous tumor cells was determined by MTT assays.21
Briefly, tumor cells (3–5 · 104 cells mLꢁ1) were inocu-
lated in 96-well culture plates (100 lL/well). After 24 h
culture, 50 lL of culture medium containing synthetic
compound of various concentrations was added to the
wells, and BCS-1640 medium in control cells, then the
cells were incubated for 48 h. The absorbance of each
well was measured using a microculture plate reader at
490 nm.
Acknowledgments
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This work was supported by National Natural Science
Foundation of China (No. 30271537) and Doctoral
Foundation of Qingdao University of Science and Tech-
nology. We wish to thank Miss Jie Xing and Gao Yan-
hui (School of Pharmaceutical Sciences, Shandong
University) for ESI-MS and Element analysis measure-
ments, Mr. Bin Ma and Miss Jin Ren (School of Phar-
maceutical Sciences, Shandong University) for
conducting the NMR experiments and for their
expertise.
Supplementary data
17. Larner, J.; Price, J. D.; Heimark, D.; Smith, L.; Rule, G.;
Piccariello, T.; Fonteles, M. C.; Pontes, C.; Vale, D.;
Huang, L. J. Med. Chem. 2003, 46, 3283–3291.
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Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.carres.2007.01.004.
19. Behrens, C. H.; KO, S. Y.; Sharpless, K. B.; Walker, F. J.
J. Org. Chem. 1985, 50, 5687–5696.
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Zhang, L. H. Tetrahedron: Asymmetry 2000, 11, 2899–
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