Fluorescent schweinfurthin B and F analogs with anti-proliferative activity

Article abstract of DOI:10.1016/j.bmc.2010.07.056

The natural tetracyclic schweinfurthins are potent and selective inhibitors of cell growth in the National Cancer Institute's 60 cell-line screen. At this time, the mechanism or cellular target that underlies this activity has not yet been identified, and

Full text of DOI:10.1016/j.bmc.2010.07.056

Bioorganic & Medicinal Chemistry 18 (2010) 6734–6741
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Fluorescent schweinfurthin B and F analogs with anti-proliferative activity
Joseph J. Topczewski a, Craig H. Kuder b, Jeffrey D. Neighbors a, Raymond J. Hohl b,c, David F. Wiemer a,b,
*
a Department of Chemistry, University of Iowa, Iowa City, IA 52242-1294, USA
b Department of Pharmacology, University of Iowa, Iowa City, IA 52242-1294, USA
c Department of Internal Medicine, University of Iowa, Iowa City, IA 52242-1294, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The natural tetracyclic schweinfurthins are potent and selective inhibitors of cell growth in the National
Cancer Institute’s 60 cell-line screen. At this time, the mechanism or cellular target that underlies this
activity has not yet been identified, and efforts to illuminate the schweinfurthins’ mode of action would
benefit from development of potent fluorescent analogs that could be readily visualized within cells. This
report describes the synthesis of fluorescent analogs of schweinfurthins B and F, and demonstrates that
these compounds retain the potent and differentially toxic activities against select human cancer cells
that are characteristic of the natural schweinfurthins. In addition, the synthesis of control compounds
that maintain parallel fluorescent properties, but lack the potent activity of the natural schweinfurthin
is described. Use of fluorescence microscopy shows differences between the localization of the active
and relatively inactive schweinfurthin analogs. The active compounds localize in peripheral puncta which
may identify the site(s) of activity.
Received 2 June 2010
Revised 21 July 2010
Accepted 23 July 2010
Available online 29 July 2010
Keywords:
Fluorescent probes
Natural products
Schweinfurthin
Stilbene
Synthesis
Anti-proliferative
Bioassay
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
pound 3-deoxyschweinfurthin B (3dSB, 10) and more than 50 other
analogs.14–19
Natural products have been a significant source of drug leads in
oncology.1 Indeed several commonly used anti-cancer agents are
themselves natural products or are the result of drug development
programs based upon a natural product. In some instances, natural
products have identified a novel target or mechanism of action
useful in treating human cancer. One such agent is paclitaxel,
which was found to stabilize micro-tubules causing cell cycle ar-
rest just prior to mitosis.2 From this perspective, the discovery of
the schweinfurthins and their potent anti-cancer activity at the Na-
tional Cancer Institute (NCI) may offer a similar opportunity for
discovery of a novel drug target and/or mechanism of action.3 Nine
compounds are now part of the natural family, including schwein-
furthin A–H and vedelianin (Fig. 1).4–6 Those that contain a hexa-
hydroxanthene substructure, such as schweinfurthin A (1) and B
(2), were found to have potent activity in the NCI 60 cell-line
screen. Perhaps of even greater importance, the pattern of activity
against the 60 cell lines indicated a potentially novel molecular tar-
get or mechanism of activity.7,8 Due to the scarcity of the natural
schweinfurthins, we have had an ongoing program aimed at syn-
thesis of natural schweinfurthins and preparation of analogs. This
effort has culminated in the reported syntheses of schweinfurthin
B (2),9 C (3),10 E (6),9 F (7),11 and G (8),12 as well as the lead com-
Recently the bis-stilbene 11 was prepared as a fluorescent ana-
log of 3dSB (10), with the hope that this probe would aid in eluci-
dation of the mechanism of action of these natural products.16
Unfortunately, the fluorescence emission maximum of this com-
pound (416 nm) displayed significant overlap with autofluores-
cence of the SF-295 human-derived glioma cell line, and the
compound demonstrated a rapid loss of fluorescence upon irradia-
tion. To overcome these limitations and improve the fluorescent
characteristics of potential probes, further synthetic efforts based
on this core structure have been undertaken. Here the design, syn-
thesis, and initial biological results of these studies will be re-
ported, along with preparation of some related compounds with
similar fluorescence properties and less potent biological activity
to serve as controls.
2. Synthesis
While the stilbene 11 did show improved fluorescence properties
over the parent 3dSB (10), identification of a related compound with
an emission maximum further shifted to lower energy and more
resistant to photo-bleaching would be attractive. Placement of an
E-ring substituent on the para position would be expected to allow
transmission of electronic effects throughout the stilbene system.
Therefore, to increase the Stokes shift and secure an emission max-
imum further to the red, the m-phenol was replaced with a p-nitro
group. This substitution was based upon the hypothesis that an
* Corresponding author. Tel.: +1 319 335 1365; fax: +1 319 335 1270.
E-mail address: david-wiemer@uiowa.edu (D.F. Wiemer).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.07.056

J. J. Topczewski et al. / Bioorg. Med. Chem. 18 (2010) 6734–6741
6735
OH
HO
OR
5
3
2
R'
O
A
OH
OH
5'
H
H
OH
2
HO
D
H
H
3 Schweinfurthin C
2
OH
OH
n
OH
OCH3
O
1
2
5
6
7
8
R =
R = CH3 R' = OH n = 2 Schweinfurthin B
R = R' = OH n = 1 Vedelianin
H
R' = OH n = 2 Schweinfurthin A
HO
HO
H
R = CH3 R' = OH n = 1 Schweinfurthin E
R = CH3 R' = H n = 1 Schweinfurthin F
H
OH
R =
H
R' = H n = 1 Schweinfurthin G
4 Schweinfurthin D
10 R = CH3 R' = H n = 2 3-Deoxyschweinfurthin B
OCH3
OCH3
O
HO
HO
O
O
OH
HO
H
H
OH
OH
11
9 Schweinfurthin H
E
OH
OH
Figure 1. Structures of the natural schweinfurthins and selected analogs.
effective electron withdrawing group across the bis-stilbene system
would complement the electron donating C-ring ethers and improve
the fluorescent properties of the compound.20,21
the differential activity of the schweinfurthins in the 60 cell-line
screen.14 Several analogs with one resorcinol oxygen present as a
methyl ether have been prepared, and this substitution has been
shown to retain potent and specific activity in the schweinfurthin
F series.11 Therefore, preparation of a bis-stilbene with a D-ring
mono methyl ether became attractive.
Synthesis of the desired mono methyl ether began with the
known benzylic alcohol 20 (Scheme 2). Directed ortho metalation
(DoM)23 followed by treatment of the intermediate anion with
DMF afforded the desired aldehyde 21 in modest yield. While this
DoM reaction is lower yielding than the halogen-metal exchange
approach used in our previous work,16 this strategy allows more
facile access to the desired aldehyde. Compound 20 and its precur-
sors have more favorable solubility properties than the brominated
intermediates required for synthesis of aldehyde 12, the DoM ap-
proach provides only starting material and product, and the DoM
strategy can be performed without protecting the benzylic alcohol.
Treatment of aldehyde 21 with phosphonate 13 and base gave the
benzylic alcohol 22 in excellent yield. Application of the standard
Synthesis of compound 19 began with the known aldehyde 12
(Scheme 1).16 Treatment with p-nitrobenzyl phosphonate22 (13)
under Horner–Wadsworth–Emmons (HWE) conditions gave the
protected stilbene 14. After deprotection of the silyl ether 14 to
the free alcohol 15, a three-step procedure was used to convert
the benzyl alcohol to the corresponding phosphonate 16 through
the intermediate mesylate and iodide. An HWE condensation of
phosphonate 16 with the known aldehyde 179,13 proceeded
smoothly to afford the bis-stilbene 18. Hydrolysis of the methoxy-
methyl (MOM) acetals upon treatment with TsOH in methanol pro-
vided the target bis-stilbene 19.
Unfortunately, compound 19 discolored quickly and undergoes
decomposition upon storage. This tendency for decomposition has
been observed with other schweinfurthin analogs, and had been
attributed to the presence of the resorcinol substructure. Previous
work has shown that at least one phenolic group was important to
P(O)(OEt)2
OTBS
R
NO2
OMOM
OMOM
13
O
H
NaH
15-crown-5
96%
MOMO
MOMO
NO2
12
OCH3
14 R = OTBS
15 R = OH
TBAF, 90%
O
1) TEA, MsCl
2) NaI
3) P(OEt)3
(68%)
16 R = P(O)(OEt)2
O
OCH3HO
H
H
17
NaH, 15-crown-5
59%
O
OR
HO
H
18 R = MOM
19 R = H
TsOH
78%
OR
NO2
Scheme 1. Synthesis of the bis-stilbene 19.

6736
J. J. Topczewski et al. / Bioorg. Med. Chem. 18 (2010) 6734–6741
OH
BuLi,
DMF
37%
20 R = H
OCH3
R
21 R = CHO
OCH3
OCH3
OMOM
NaH, 99%
13
O
HO
O
R
H
H
OCH3
HO
MOMO
H
H
17
33
O
O
NaH, 15-crown-5
78%
OMOM
22 R = OH
1) MsCl, TEA
2) NaI
3) P(OEt)3, DMF
95%
NaH, 15-crown-5
71%
NO2
23 R = P(O)(OEt)2
OCH3
OCH3
O
HO
O
OCH3
OCH3
OCH3
CH3O
R'O
HO
H
H
H
NaH, 15-crown-5
71%
OR'
OR'
28
O
R
R
CH3O
34 R = NO2, R' = MOM
35 R = NO2, R' = H
36 R = NH2, R' = MOM
37 R = NH2, R' = H
24 R = NO2, R' = MOM
25 R = NO2, R' = H
26 R = NH2, R' = MOM
27 R = NH2, R' = H
Zn
Zn
TsOH, 71%
TsOH, 95%
OCH3
TsOH, 85%
NH4Cl
80%
NH4Cl
80%
TsOH, 100%
OCH3
OR'
R
29 R = NO2, R' = MOM
30 R = NO2, R' = H
31 R = NH2, R' = MOM
32 R = NH2, R' = H
Zn, NH4Cl
67%
TsOH, 88%
TsOH, 89%
Scheme 2. Preparation of p-nitro and p-amino bis-stilbenes.
three-step procedure for conversion of the alcohol to the phospho-
nate afforded compound 23. Use of DMF as the solvent for the final
Arbuzov reaction in this sequence greatly improves the yield.
Preparation of phosphonate 23 set the stage for synthesis of the
O-methyl analog of nitro stilbene 19. Condensation of phosphonate
23 with aldehyde 17 afforded the protected schweinfurthin 24 in
good yield. Removal of the single MOM protecting group afforded
the 50-O-methyl analog 25 in excellent yield. This compound dis-
played only slightly diminished activity relative to the parent resor-
cinol (vide infra) and, more importantly, demonstrated much
improved stability.
With the key problems presented by compounds 11 and 19 ad-
dressed, it was possible to prepare further analogs that could be
utilized to probe the mechanism of schweinfurthin activity. The
p-nitro stilbene 25 could, in principle, be used to identify the
sub-cellular localization of the schweinfurthins. For such experi-
ments to be truly informative, however, a control compound with
similar fluorescent properties but lacking the essential pharmaco-
phore would be very helpful. Reduction of the nitro group would
allow entrée to amine analogs which would vary the electronic
properties of the bis-stilbenes and provide a site for further SAR
studies. Rounding out the set of desired compounds would be
the amine analog of the control compound, along with the nitro-
and amine-containing compounds based on the newly available
schweinfurthin B A-ring diol system.9 These considerations led to
identification of stilbene 35 as a target with potentially greater
activity, to stilbenes 30 and 32 as relatively inactive but fluorescent
controls, and to stilbenes 27 and 37 as amine-substituted targets.
The synthesis of these additional analogs was relatively straight-
forward. Condensation of the phosphonate 23 with the known alde-
hydes 28 and 33 gave the protected stilbenes 29 and 34. Hydrolysis
of the MOM acetal of each of the nitro compounds 29 and 34 afforded
the targets 30 and 35 in good yields. Reduction of the nitro groups of
compounds 24, 29, and 34 with Zn0 in ammonium chloride24 affor-
ded the desired amines 26, 31, and 36. Deprotection of these com-
pounds under standard conditions was uneventful, leading to
compounds 27, 32, and 37. This strategy provided the target com-
pounds in excess of 95% chemical purity, with the exception of com-
pound 37 (93%), and >95% enantiomeric purity.
All of the target compounds exhibited significant fluorescence.
Thenitrocompoundstypicallyhad anabsorptionmaximumofabout
430 nm and an emission maximum of ꢀ575 nm, while the amines
exhibited absorption maxima of 375 and typically had emission
maxima ꢀ495. Thus the nitro compounds 19, 25, 30, and 35 dis-
played larger Stokes shifts (ꢀ150 nm) vis-a-vis the amines 27, 32,
and 37 (ꢀ120 nm). Of greater significance to the cellular localization
studies, the nitro substituted compounds also demonstrate signifi-
cantly red-shifted absorption and emission maxima compared to
the previously synthesized bis-stilbene 11. This shift in fluorescence
emission allowed cellular studies on these compounds without
interference from autofluroescence.25 The fluorescence maxima of
the amines is not shifted as greatly, but the utility of the nitro com-
pounds may render this a moot point.
3. Biological results and discussion
The anti-cancer activities of many natural and synthetic schw-
einfurthins have been evaluated in the National Cancer Institute’s
60 cell-line screen. Because there often is a long waiting time for
this assay, we have described a two cell-line screen comprised of
a sensitive (SF-295) and moderately insensitive (A549) cell line.17
The two cell-line assay measures schweinfurthin-like activity and
is comparable to the discrimination yielded by the NCI 60 cell
screen.17 The schweinfurthin analogs, compounds 19, 25, 27, 35,
and 37, display potent effects on MTT activity in SF-295 cells after
48 h of treatment (Table 1). In this assay, SF-295 cells are especially

J. J. Topczewski et al. / Bioorg. Med. Chem. 18 (2010) 6734–6741
6737
Table 1
sensitive to the nitro bis-stilbene compounds 19, 25, and 35, which
have ED50 values of 0.05, 0.1, and 0.04 M, respectively. The amine
The ED50 values for schweinfurthin analogs 19, 25, 27, 30, 32, 35, and 37 in the SF-295
and A549 cells at 48 h, as measured by the MTT assay
l
bis-stilbene compounds 27 and 37 display similar ED50 values. As
expected, compounds 30 and 32 lacking the hexahydroxanthene
structure display greatly diminished activity in comparison to
the other schweinfurthin analogs (Table 1). Consistent with the
natural schweinfurthins, the fluorescent analogs (19, 25, 27, 35,
and 37) display decreased activity against the A549 cells in com-
parison to the SF-295 cells. The nitro bis-stilbenes are at least as
potent in comparison to the amine bis-stilbenes. Control com-
pounds 30 and 32 do not alter A549 MTT activity at concentrations
Compound
ED50 values (lM)
SF-295
A549
19
25
27
30
32
35
37
0.05
0.1
0.4
>1
>1
0.8
2.7
3.0
>10
>10
0.7
0.04
0.02
3.2
as high as 10 lM.
The fluorescent schweinfurthins may serve as probes for intra-
cellular localization. Indeed, compound 25 displays peri-nuclear
localization with distinct peripheral puncta, as demonstrated in
Figure 2 (A–D). In comparison, compound 30, which lacks schwein-
furthin-like activity at concentrations tested, localizes extensively
in the peri-nuclear region with minimal diffuse fluorescence in
the periphery of the cell shown in Figure 2 (E–H). Based on the dif-
ference in activity and localization, the peripheral fluorescence dis-
played by compound 25 may identify the schweinfurthin site(s) of
action. Although the active analog is more dispersed to peripheral
regions of the cell than is the less active control compound, it re-
mains to be determined whether this identifies a binding target
that is itself peripheral or a mislocalized peri-nuclear target.
94.7 (2C), 64.5, 56.1 (2C), 25.7 (3C), 18.2, ꢁ5.4 (2C); HRMS (EI) calcd
for C25H35NO7Si (M+) 489.2183, found 489.2173.
5.2. Benzylic alcohol 15
Silyl ether 14 (155 mg, 0.32 mmol) was dissolved in THF and the
solution was cooled to 0 °C. To this solution was added TBAF (0.4 mL,
1.00 M in THF), and after 4 h the reaction was quenched by addition
of NH4Cl (satd). After extraction with EtOAc, the combined organic
extracts were washed with water and brine, dried (MgSO4), and con-
centrated in vacuo to give the desired benzylic alcohol 15 (120 mg,
100%) as a clear oil: 1H NMR ((CD3)2CO) d 8.25–8.21 (m, 2H), 7.80–
7.77 (m, 4H), 6.92 (s, 2H), 5.35 (s, 4H), 4.66 (d, J = 5.4 Hz, 2H), 4.43
(t, J = 5.4 Hz, 1H), 3.51 (s, 6H); 13C NMR ((CD3)2CO) d 157.2 (2C),
146.9, 145.5, 130.0, 127.2 (2C), 125.3, 124.5 (2C), 114.4, 106.6 (2C),
100.5, 95.1 (2C), 64.1, 56.2 (2C); HRMS (EI) calcd for C19H21NO7
(M+) 375.1318, found 375.1315.
4. Conclusions
The synthesis of a small set of fluorescent analogs based on the
schweinfurthins has been accomplished. Data obtained from our
two-cell-line screen supports our prior observations that one of
the phenol groups of the right half of the molecule can be replaced
with a methyl ether without great loss of activity and with a contem-
poraneous increase in stability. In addition, compounds with the A-
ring diol (35 and 37) are slightly more potent than the corresponding
3-deoxy compounds (25 and 27) in the SF-295 cells. Importantly,
compounds 19, 25, 27, 35, and 37 retain the potency and differential
activity displayed by the natural schweinfurthins. Due to these char-
acteristics and their fluorescent properties, these compounds can be
utilized as intracellular probes for sites of schweinfurthin activity.
Microscopic examination of the fluorescence from compound 25
demonstrates that localization is both peri-nuclear and peripheral.
Theperipherallocalizationof 25is uniquewhencomparedto therel-
atively inactive compound 30; therefore, these sites may label the
target of schweinfurthin activity. Based on puncta and dispersed
nature of the observed fluorescence, compound 25 may localize in
lysosomes or bind to protein(s) involved in trafficking. These possi-
bilities will be investigated and described in due course.
5.3. Phosphonate 16
Methanesulfonyl chloride (0.04 mL, 0.52 mmol) was added to a
solution of benzylic alcohol 15 (120 mg, 0.32 mmol) and Et3N
(0.2 mL, 1.4 mmol) in THF at 0 °C. The reaction mixture was allowed
to warm to room temperatureover 1 h, quenchedby addition ofH2O,
and extracted with EtOAc. The combined organic layers were
washed with NH4Cl (satd) and brine, dried (MgSO4), and concen-
trated in vacuo. The resulting residue and NaI (119 mg, 0.80 mmol)
were stirred in acetone (10 mL) for 8 h. The reaction mixture was
concentrated in vacuo to afford a red solid, which was dissolved in
EtOAc. After the resulting yellow solution was washed with Na2S2O3
until the color faded, it was washed with brine, dried (MgSO4), and
concentrated in vacuo. The resulting yellow oil was added to triethyl
phosphite (2 mL) and toluene (2 mL) the reaction mixture was
heated at 110 °C for 24 h. After the solution was allowed to cool to
rt, the excess phosphite was removed at high vacuum. The initial or-
ange/red oil was purified by flash chromatography (1:2 hexanes/
EtOAc to 100% EtOAc) to afford phosphonate 16 (99 mg, 88%) as an
orange oil: 1H NMR d 8.21–8.18 (m, 2H), 7.64–7.61 (m, 4H), 6.81–
6.80 (m, 2H), 5.28 (s, 4H), 4.07 (m, 4H), 3.52 (s, 6H), 3.13 (d,
JHP = 22 Hz, 2H), 1.29 (t, J = 7.0 Hz, 6H); 13C NMR d 156.4 (d,
JCP = 3.9 Hz, 2C), 146.4, 145.8, 133.6 (d, JCP = 9.2 Hz), 129.7, 126.6
(2C), 124.4, 124.0 (2C), 114.2 (d, JCP = 3.6 Hz), 109.9 (d, JCP = 6.2 Hz,
2C), 94.7 (2C), 62.2 (d, JCP = 6.7 Hz, 2C), 56.4 (2C), 34.0 (d,
JCP = 138 Hz), 16.4 (d, JCP = 6.3 Hz, 2C); 31P NMR d 26.3; HRMS (EI)
calcd for C23H30NO9P (M+) 495.1658, found 495.1656.
5. Experimental procedures and methods
5.1. Protected stilbene 14
A suspension of NaH (109 mg, 2.6 mmol, 60% in oil), and 15-
crown-5 (1 drop) in THF was cooled to 0 °C. To this was added alde-
hyde 12 (245 mg, 0.66 mmol) and the known phosphonate 13
(181 mg, 0.66 mmol) in THF (1.5 mL). After the mixture was allowed
to stir for 45 min, water was added dropwise and the solution was
extracted with EtOAc. The resulting organic phase was washed with
brine, dried (MgSO4), and concentrated in vacuo. Final purification
by column chromatography (2:1 hexanes/EtOAc) gave the stilbene
14 (197 mg, 61%) as a bright yellow oil: 1H NMR d 8.21–8.18 (m,
2H), 7.65–7.62 (m, 4H), 6.88 (s, 2H), 5.30 (s, 4H), 4.74 (s, 2H), 3.53
(s, 6H), 0.98 (s, 9H), 0.13 (s, 6H); 13C NMR d 156.4 (2C), 146.1,
145.9, 143.8, 129.5, 126.4 (2C), 124.7, 123.9 (2C), 113.9, 105.6 (2C),
5.4. Protected nitro stilbene 18
A suspension of NaH (60 mg, 1.5 mmol, 60% in oil), and 15-
crown-5 (1 drop) in THF (5 mL) was cooled to 0 °C. To this mixture
was added a solution of aldehyde 17 (17 mg, 0.06 mmol) and phos-
phonate 15 (28 mg, 0.06 mmol) in THF (1 mL). The resulting mix-
ture was allowed to warm to rt and stirred a total of 6 h. After

6738
J. J. Topczewski et al. / Bioorg. Med. Chem. 18 (2010) 6734–6741
Figure 2. The intracellular localization of compounds 25 and 30. SF-295 cells were treated with compound 25 (500 nM) (A–D) or compound 30 (500 nM) (E–H) for 24 h.
Images depict intracellular localization of compound 25 (A) or compound 30 (E) alone, nuclear labeling of treated cell with DAPI (B and F), merged images of DAPI with
compound 25 (C) or compound 30 (G), or fluorescence brightness distribution images of compound 25 (D) or 30 (H).
water was added dropwise, the solution was extracted with EtOAc.
The resulting organic phase was washed with brine, dried (MgSO4),
and concentrated in vacuo. Final purification by column chroma-
tography (3:1 to 1:1 hexanes/EtOAc) gave the stilbene 18 (23 mg,
59%) as an orange oil: 1H NMR d 8.21 (d, J = 8.3 Hz, 2H), 7.66 (s,
2H), 7.65 (d, J = 8.3 Hz, 2H), 7.07–7.01 (m, 3H), 6.93–6.87 (m,
3H), 5.35 (s, 4H), 3.92 (s, 3H), 3.57 (s, 6H), 3.48–3.43 (m, 1H),
2.75–2.72 (m, 2H), 2.20–2.13 (m, 1H), 1.92–1.82 (m, 2H), 1.76–
1.60 (m, 3H), 1.28 (s, 3H), 1.12 (s, 3H), 0.91 (s, 3H); 13C NMR d
156.8 (2C), 149.0, 146.3, 146.0, 143.0, 139.3, 129.9, 129.7, 128.5,
126.6 (2C), 125.7, 124.6, 124.0 (2C), 122.6, 121.0, 114.6, 106.9,
106.1 (2C), 94.8 (2C), 77.9, 77.2, 56.4 (2C), 56.0, 46.7, 38.4, 37.6,
28.1, 27.2, 23.1, 19.9, 14.3; HRMS (EI) calcd for C37H43NO9 (M+)
645.2938, found 645.2952.
(s, 2H), 4.69 (s, 2H), 3.82 (s, 3H), 3.49 (s, 3H), 3.03 (br s, 1H); 13C
NMR d 189.1, 162.0, 159.9, 150.4, 113.7, 104.7, 102.5, 94.6, 64.5,
56.5, 55.9. Anal. Calcd for C11H14O5: C, 58.40; H, 6.24. Found: C,
58.69; H, 6.32 was added n-BuLi (2.8 mL, 2.0 M in hexanes) drop-
wise over 1 min. After 25 min, the solution was cooled to ꢁ30 °C
and DMF (0.23 mL, 3.0 mmol, containing some CaH2 as a drying
agent) was added. The reaction was allowed to progress for an
additional 1 h, and then quenched by addition of NH4Cl (satd).
After the aqueous phase was extracted with EtOAc, the combined
organic phases were washed with brine, dried (MgSO4), and con-
centrated in vacuo to afford a yellow oil. Final purification by col-
umn chromatography (2:1 to 1:2 hexanes/EtOAc) afforded
aldehyde 21 (192 mg, 37%) as a clear oil, along with a significant
amount of recovered starting material.
5.5. Nitro stilbene 19
5.7. Benzyl alcohol 22
To a solution of protected stilbene 18 (20 mg, 0.03 mmol) in
MeOH was added pTsOH (30 mg, 0.17 mmol), and the resulting solu-
tion was stirred at rt for 6 h. The reaction was quenched by addition
of satd NaHCO3, extracted with EtOAc, and the organic phase was
washed with brine and dried (MgSO4). Concentration in vacuo, fol-
lowed by final purification by column chromatography (2:1 to 1:1
hexanes/EtOAc) afforded the bis-stilbene 19 (12 mg, 78%) as a
To a solution of aldehyde 21 (128 mg, 0.57 mmol) in THF
(12 mL) at rt was added 15-crown-5 (0.01 mL), diethyl 4-nitro-
benzylphosphonate (13, 203 mg, 0.74 mmol), followed by NaH
(220 mg, 5.5 mmol, 60% in oil), which resulted in the rapid appear-
ance of a maroon color. After 8 min, the reaction was quenched by
slow addition of water. The resulting solution was extracted with
EtOAc, and the combined organic phases were washed with brine,
dried (MgSO4), and concentrated in vacuo. Final purification by col-
umn chromatography (6:4 hexanes/THF) afforded compound 22
(191 mg, 98%) as an orange solid: 1H NMR d 8.20–8.18 (m, 2H),
7.64–7.61 (m, 4H), 6.80 (s, 1H), 6.69 (s, 1H), 5.29 (s, 2H), 4.70 (s,
2H), 3.94 (s, 3H), 3.53 (s, 3H); 13C NMR d 159.2, 156.6, 145.9,
142.9, 129.8, 126.6 (2C), 124.5, 124.3, 124.0 (2C), 113.8, 105.5,
103.1, 94.8, 65.2, 56.4, 55.8; HRMS (EI) calcd for C18H19NO6 (M+)
345.1212, found 345.1216.
slightly yellow oil: UV (EtOH) kmax (log e
) 426 (4.42); kem 593; 1H
NMR ((CD3)2CO) d 9.06 (s, 2H), 8.20 (d, J = 8.7 Hz, 2H), 7.88 (s, 2H),
7.40 (d, J = 8.7 Hz, 2H), 7.05–6.78 (m, 6H), 3.78 (s, 3H), 3.40–3.35
(m, 1H), 2.71–2.68 (m, 2H), 1.82–1.58 (m, 6H), 1.18 (s, 3H), 1.09 (s,
3H), 0.87 (s, 3H); 13C NMR ((CD3)2CO) d 158.6 (2C), 150.0, 147.7,
146.7, 144.1, 140.2, 130.5, 129.5, 128.5, 127.2 (2C), 126.7, 126.3,
124.7 (2C), 123.6, 121.9, 111.7, 108.2, 105.9 (2C), 77.7, 77.5, 56.0,
55.4, 47.7, 39.0, 38.6, 27.8, 23.7, 20.3, 14.8; HRMS (EI) calcd for
C
33H35O7N (M+) 557.2414, found 557.2422.
5.8. Phosphonate 23
5.6. Aldehyde 21
To a solution of benzyl alcohol 22 (193 mg, 0.56 mmol) in THF
at rt was added TEA (0.2 mL, 1.4 mmol) followed by MsCl
(0.1 mL, 1.3 mmol). After 50 min, the reaction was quenched by
To a solution of the alcohol 20 (0.45 g, 2.3 mmol) in THF at 0 °C
(194 mg, 43%): 1H NMR d 10.4 (s, 1H), 6.74 (s, 1H), 6.65 (s, 1H), 5.25

J. J. Topczewski et al. / Bioorg. Med. Chem. 18 (2010) 6734–6741
6739
addition of water. The resulting solution was extracted with EtOAc,
washed with brine, dried (MgSO4), and concentrated in vacuo. This
material was used immediately without further purification. The
residue from the above step was dissolved in anhydrous acetone
(8 mL) and NaI (210 mg, 1.4 mmol) was added at rt in the dark.
After 1 h, the reaction was quenched by addition of water, the
resulting solution was extracted with EtOAc, and was washed with
brine. The organic phase was dried (MgSO4) and concentrated in
vacuo in the dark. This material was used immediately in the next
step without further purification. The residue from the above step
was dissolved in DMF (3 mL), P(OEt)3 (0.4 mL, 2.3 mmol) was
added, and the mixture was heated to 115 °C. After 17 h, an addi-
tional portion of P(OEt)3 (0.4 mL, 2.3 mmol) was added. The reac-
tion was allowed to cool to rt after an additional 3.5 h and
concentrated in vacuo. Final purification by column chromatogra-
phy (1% MeOH, 20% hexanes, 79% EtOAc) afforded the desired
phosphonate 23 (245 mg, 95% over three steps) as a bright yellow
oil: 1H NMR d 8.20–8.17 (m, 2H), 7.63–7.61 (m, 4H), 6.75 (s, 1H),
6.63 (s, 1H), 5.27 (s, 2H), 4.11–4.01 (m, 4H), 3.92 (s, 3H), 3.51 (s,
3H), 3.13 (d, JHP = 22 Hz, 2H), 1.28 (t, J = 7.1 Hz, 6H); 13C NMR d
158.8 (d, JCP = 3.8 Hz), 156.4 (d, JCP = 3.4 Hz), 146.3, 146.0, 133.5
(d, JCP = 9.1 Hz), 129.7, 126.6 (2C), 124.5 (d, JCP = 1.8 Hz), 124.0
(2C), 123.0, 109.1 (d, JCP = 7.1 Hz), 106.5 (d, JCP = 6.6 Hz), 94.9,
62.2, 62.1, 56.1 (d, JCP = 34 Hz, 2C), 34.5 (d, JCP = 138 Hz), 16.4 (d,
JCP = 6.0 Hz, 2C); 31P NMR d 26.3; HRMS (EI) calcd for C22H28NO8P
(M+) 465.1553, found 465.1552.
129.9, 129.2, 128.4, 126.6 (2C), 125.4, 124.8 124.0 (2C), 122.7,
120.9, 111.8, 106.9, 106.5, 101.5, 78.0, 77.7, 56.0, 55.8, 46.7, 38.4,
37.6, 28.3, 27.3, 23.1, 19.9, 14.3; HRMS (ESI) m/z calcd for
C
34H37NO7 (M+) 571.2570, found 571.2567.
5.11. Protected amine 26
To a solution of compound 24 (33 mg, 0.05 mmol) in acetone
(3 mL) was added NH4Cl (satd, 1 mL) followed by Zn0 dust
(67 mg, 1.0 mmol) and the mixture was heated to reflux. After
70 min, the solution was allowed to cool and decanted into a separ-
atory funnel. The resulting solution was extracted with EtOAc, and
the combined organic phases were washed with brine, dried
(MgSO4), and concentrated in vacuo. Final purification by column
chromatography (4:6 hexanes/EtOAc to 99:1 EtOAc/MeOH) affor-
ded amine 26 (25 mg, 80%) as an orange oil: 1H NMR d 7.51 (d,
J = 16.4 Hz, 1H), 7.37 (d, J = 8.4 Hz, 2H), 7.27 (d, J = 16.4 Hz, 1H),
7.01 (d, J = 16.4 Hz, 1H), 6.92–6.88 (m, 4H), 6.76 (d, J = 0.8 Hz,
1H), 6.67 (d, J = 8.0 Hz, 2H), 5.30 (s, 2H), 3.94 (s, 3H), 3.90 (s, 3H),
3.54 (s, 3H), 3.42 (dd, J = 11.8, 4.0 Hz, 1H), 2.72 (m, 2H), 2.16–
2.11 (m, 1H), 1.88–1.81 (m, 3H), 1.73–1.60 (m, 2H), 1.25 (s, 3H),
1.10 (s, 3H), 0.89 (s, 3H); 13C NMR d 158.4, 156.0, 148.9, 145.6,
142.6, 136.8, 132.4, 129.9, 128.7, 128.5, 127.5 (2C), 126.2, 122.6,
120.6, 116.3, 115.7, 115.1 (2C), 106.7, 105.9, 102.7, 94.9, 77.9,
77.0, 56.2, 55.9, 55.7, 46.7, 38.3, 37.6, 28.2, 27.3, 23.1, 19.8, 14.3;
HRMS (ESI) m/z calcd for
C
36H43NO6 (M+) 585.3090, found
585.3088.
5.9. Protected stilbene 24
5.12. Amine 27
To a solution of aldehyde 17 (80 mg, 0.26 mmol) and phospho-
nate 23 (100 mg, 0.25 mmol) in THF at rt was added 15-crown-5
(0.01 mL) followed by NaH (63 mg, 1.6 mmol, 60% in oil), and after
75 min the reaction was quenched by addition of water. The result-
ing solution was extracted with EtOAc and the combined organic
phases were washed with brine. After the organic phase was dried
(MgSO4) and concentrated in vacuo, final purification by column
chromatography (1:1 hexanes/EtOAc) afforded recovered phos-
phonate 23 (12 mg, 12%) and compound 24 (94 mg, 71%) as an or-
ange solid: 1H NMR d 8.22–8.18 (m, 2H), 7.67–7.63 (m, 4H), 7.09–
7.04 (m, 1H), 6.97–6.90 (m, 4H), 6.78–6.74 (m, 1H), 5.36 (s, 2H),
4.00 (s, 3H), 3.92 (s, 3H), 3.58 (s, 3H), 3.48–3.44 (m, 1H), 2.78–
2.73 (m, 2H), 2.19–2.13 (m, 1H), 1.92–1.82 (m, 2H), 1.73–1.54
(m, 3H), 1.28 (s, 3H), 1.13 (s, 3H), 0.91 (s, 3H); 13C NMR d 159.1,
156.8, 149.0, 146.2, 146.1, 143.0, 139.1, 129.8, 129.4, 128.4, 126.5
(2C), 125.8, 124.6, 124.0 (2C), 122.7, 120.9, 113.8, 106.9, 105.4,
102.4, 94.8, 77.9, 77.2, 56.4, 56.0, 55.8, 46.7, 38.4, 37.6, 28.2,
To a solution of amine 26 (22 mg, 0.036 mmol) in CH3OH (2 mL)
and EtOAc (0.5 mL) was added TsOHꢂH2O (43 mg, 0.13 mmol).
After 23 h, the reaction was quenched by addition of NaHCO3
and concentrated in vacuo. The resulting solution was extracted
with EtOAc, and the combined organic phases were washed with
brine. The organic phase was dried (MgSO4) and concentrated in
vacuo. This afforded schweinfurthin 26 (20 mg, 100%) without fur-
ther purification as a dark orange solid: UV (EtOH) kmax (log e) 377
(4.53); kem 493; 1H NMR d 7.33 (d, J = 8.4 Hz, 2H), 7.22 (d,
J = 16.8 Hz, 1H), 7.12 (d, J = 16.8 Hz, 1H), 6.95 (d, J = 16.8 Hz, 1H),
6.87–6.81 (m, 3H), 6.67–6.65 (m, 3H), 6.59 (s, 1H), 3.89 (s, 3H),
3.88 (s, 3H), 3.41 (dd, J = 11.8, 3.4 Hz, 1H), 2.71 (m, 2H), 2.14–
2.10 (m, 1H), 1.87–1.83 (m, 2H), 1.71–1.58 (m, 2H), 1.24 (s, 3H),
1.09 (s, 3H), 0.87 (s, 3H); 13C NMR d 159.5, 155.6, 150.0, 147.0,
143.8, 138.4, 133.3, 130.1, 129.9, 129.8, 128.7 (2C), 127.3, 123.8,
121.8, 117.9, 116.3 (2C), 114.4, 108.1, 107.7, 102.2, 79.0, 78.2,
57.1, 56.8, 47.8, 39.4, 38.7, 29.3, 28.4, 24.2, 20.9, 15.3; HRMS
(ESI) m/z calcd for C34H39NO5 (M+) 541.2828, found 541.2835.
27.3, 23.1, 19.8, 14.3; HRMS (EI) calcd for
615.2832, found 615.2837.
C
36H41NO8 (M+)
5.10. Nitro schweinfurthin 25
5.13. Stilbene 29
To a solution of compound 24 (16 mg, 0.03 mmol) in CH3OH
(2.5 mL) and EtOAc (0.5 mL) was added TsOHꢂH2O (32 mg,
0.16 mmol). After 24 h, the reaction was quenched by addition of
NaHCO3 and concentrated in vacuo. The resulting solution was ex-
tracted with EtOAc, and the combined organic phase was washed
with brine, dried (MgSO4), and concentrated in vacuo. Final purifi-
cation by column chromatography (1:1 hexanes/EtOAc) afforded
compound 25 (13 mg, 85%) as a dark orange solid: UV (EtOH) kmax
To a solution of 3,4-dimethoxybenzaldehyde (28, 50 mg,
0.26 mmol) and phosphonate 23 (100 mg, 0.25 mmol) in THF
(4 mL) at rt was added 15-crown-5 (0.01 mL) followed by NaH
(57 mg, 1.4 mmol, 60% in oil), and after 65 min the reaction was
quenched by addition of water. The resulting solution was ex-
tracted with EtOAc, and the combined organic phases were washed
with brine. The organic phase was dried (MgSO4) and concentrated
in vacuo. Final purification by column chromatography (3:1 hex-
anes/EtOAc to EtOAc) afforded recovered phosphonate 23 (27 mg,
27%) and compound 29 (94 mg, 71%) as an orange solid: 1H NMR
d 8.19 (d, J = 8.8 Hz, 2H), 7.66 (s, 2H), 7.63 (d, J = 8.8 Hz, 2H),
7.11–7.07 (m, 3H), 6.96 (s, 1H), 6.96 (s, 1H), 6.87 (d, J = 8.0 Hz,
1H), 6.78 (s, 1H), 5.34 (s, 2H), 3.99 (s, 3H), 3.96 (s, 3H), 3.91 (s,
3H), 3.56 (s, 3H); 13C NMR d 159.1, 156.8, 149.1, 149.0, 146.1,
146.1, 138.9, 129.9, 129.5, 129.5, 126.6 (2C), 126.3, 124.6, 124.0
(log e
) 429 (4.25); kem 557; 1H NMR d 8.20 (d, J = 8.8 Hz, 2H), 7.64
(d, J = 8.8 Hz, 2H), 7.61 (d, J = 16.8 Hz, 1H), 7.54 (d, J = 16.8 Hz, 1H),
7.01 (d, J = 16.0 Hz, 1H), 6.89 (s, 1H), 6.88 (s, 1H), 6.85 (d,
J = 16.0 Hz, 1H), 6.65 (s, 1H), 6.63 (s, 1H), 5.50 (br d, 1H), 3.97 (s,
3H), 3.91 (s, 3H), 3.46–3.44 (m, 1H), 2.75–2.72 (m, 2H), 2.17–
2.14 (m, 2H), 1.90–1.69 (m, 4H), 1.27 (s, 3H), 1.11 (s, 3H), 0.90 (s,
3H); 13C NMR d 159.2, 155.0, 149.0, 146.3, 145.5, 143.1, 139.1,

6740
J. J. Topczewski et al. / Bioorg. Med. Chem. 18 (2010) 6734–6741
(2C), 120.2, 113.9, 111.1, 108.5, 105.4, 102.4, 94.8, 56.4, 55.9, 55.8,
55.7; HRMS (ESI) m/z calcd for C27H27NO7 (M+) 477.1788, found
477.1771.
by column chromatography (4:6 hexanes/EtOAc) afforded com-
pound 34 (36 mg, 78%) as an orange solid: 1H NMR d 8.19 (d,
J = 8.8 Hz, 2H), 7.66–7.62 (m, 4H), 7.06 (d, J = 16.4 Hz, 1H), 6.96
(s, 1H), 6.95–6.90 (m, 3H), 6.77 (s, 1H), 5.35 (s, 2H), 4.83 (d,
J = 6.8 Hz, 1H), 4.73 (d, J = 6.8 Hz, 1H), 4.32 (ddd, J = 3.2, 3.2,
3.2 Hz, 1H), 3.99 (s, 3H), 3.92 (s, 3H), 3.57 (s, 3H), 3.47 (s, 3H),
3.28 (d, J = 3.6 Hz, 1H), 2.81–2.75 (m, 2H), 2.57 (dd, J = 14.2,
3.0 Hz, 1H), 2.34 (br d, 1H), 1.98 (dd, J = 14.0, 2.8 Hz, 1H), 1.80
(dd, J = 12.5, 5.2 Hz, 1H), 1.49 (s, 3H), 1.12 (s, 3H), 1.10 (s, 3H);
13C NMR d 159.1, 156.8, 149.0, 146.1, 146.1, 142.6, 139.1, 129.8,
129.3, 128.4, 126.5 (2C), 125.8, 124.6, 124.0 (2C), 122.8, 120.8,
113.7, 106.8, 105.3, 102.4, 96.8, 94.8, 84.7, 76.6, 68.6, 56.3, 56.1,
55.9, 55.7, 47.0, 42.2, 37.8, 28.7, 22.9, 21.5, 16.6; HRMS (ESI) m/z
calcd for C38H45NO10 (M+) 675.3043, found 675.3040.
5.14. Compound 30
To a solution of compound 29 (20 mg, 0.042 mmol), in CH3OH
(4 mL) and EtOAc (2 mL) was added TsOHꢂH2O (54 mg, 0.28 mmol)
and the solution was stirred at rt. After 18.5 h, the reaction was
quenched by addition of NaHCO3 and concentrated in vacuo. The
resulting solution was extracted with EtOAc, and the combined or-
ganic phases were washed with brine. After the organic phase was
dried (MgSO4) and concentrated in vacuo, final purification by col-
umn chromatography (6:4 hexanes/EtOAc to 4:6 hexanes/EtOAc)
afforded compound 30 (16 mg, 88%) as a dark orange solid: UV
(EtOH) kmax (log
e
) 431 (4.39); kem 579; 1H NMR ((CD3)2CO) d
5.18. Compound 35
8.22 (d, J = 9.2 Hz, 2H), 7.81 (s, 2H), 7.76 (d, J = 9.2 Hz, 2H), 7.25
(d, J = 2.0 Hz, 1H), 7.19 (d, J = 16.0 Hz, 1H), 7.00 (dd, J = 8.4,
2.0 Hz, 1H), 7.04 (d, J = 16.4 Hz, 1H), 6.95 (d, J = 8.4 Hz, 1H), 6.85
(d, J = 1.2 Hz, 1H), 6.81 (d, J = 1.2 Hz, 1H), 4.00 (s, 3H), 3.87 (s,
3H), 3.83 (3H); 13C NMR ((CD3)2CO) d 160.5, 158.1, 150.7, 150.6,
147.4, 147.1, 140.3, 131.2, 130.3, 129.3, 127.4 (2C), 127.1, 126.0,
124.8 (2C), 121.1, 112.7, 110.4, 107.6, 104.5, 101.5, 56.2, 56.1,
56.1; HRMS (ESI) m/z calcd for C25H23NO6 (M+) 433.1525, found
433.1522.
According to the procedure for compound 30, compound 34
(16 mg, 0.024 mmol), in CH3OH and EtOAc was treated with
TsOHꢂH2O (60 mg, 0.32 mmol) and after final purification by col-
umn chromatography (3:7 hexanes/EtOAc) afforded schweinfur-
thin 35 (10 mg, 71%) as a dark orange wax: 1H NMR d 8.20 (d,
J = 8.8 Hz, 2H), 7.67–7.61 (m, 3H), 7.55 (d, J = 16.4 Hz, 1H), 7.01
(d, J = 16.0 Hz, 1H), 6.89 (s, 1H), 6.88 (s, 1H), 6.85 (d, J = 16.0 Hz,
1H), 6.64 (s, 2H), 4.26 (ddd, J = 3.2, 3.2, 3.2 Hz, 1H), 3.96 (s, 3H),
3.90 (s, 3H), 3.39 (d, J = 3.6 Hz, 1H), 2.82–2.76 (m, 2H), 2.52 (dd,
J = 14.4, 2.8 Hz, 1H), 2.30 (dd, J = 14.4, 3.2 Hz, 1H), 1.79 (dd,
J = 12.8, 5.2 Hz, 1H), 1.47 (s, 3H), 1.13 (s, 3H), 1.09 (s, 3H); 13C
NMR d 159.2, 155.3, 149.0, 146.2, 145.7, 142.6, 139.1, 129.8,
129.2, 128.4, 126.6 (2C), 125.5, 124.8, 124.0 (2C), 122.9, 120.9,
111.9, 107.0, 106.5, 101.4, 77.5, 76.8, 70.7, 56.0, 55.8, 46.8, 43.3,
38.0, 28.9, 23.0, 21.6, 16.0; HRMS (ESI) m/z calcd for C34H37NO8
(M+) 587.2519, found 587.2518.
5.15. Compound 31
According to the procedure described for compound 26, com-
pound 29 (20 mg, 0.04 mmol), NH4Cl (satd, 1 mL), and Zn0 dust
(30 mg, 0.46 mmol) gave after final purification by column chro-
matography (4:6 hexanes/EtOAc) amine 31 (12 mg, 67%) as orange
solid: 1H NMR d 7.53 (d, J = 16.8 Hz, 1H), 7.37 (d, J = 8.8 Hz, 2H),
7.28 (d, J = 16.8 Hz, 1H), 7.09 (d, J = 2.0 Hz, 1H), 7.06 (dd, J = 8.4,
2.0 Hz, 1H), 7.04 (d, J = 16.4 Hz, 1H), 6.94 (d, J = 1.2 Hz, 1H), 6.93
(d, J = 16.4 Hz, 1H), 6.87 (d, J = 8.4 Hz, 1H), 6.77 (d, J = 0.8 Hz, 1H),
6.68 (d, J = 8.4 Hz, 2H), 5.31 (s, 2H), 3.96 (s, 3H), 3.95 (s, 3H), 3.91
(s, 3H), 3.55 (s, 3H); 13C NMR d 158.4, 156.0, 149.0, 148.9, 145.7,
136.6, 132.5, 130.3, 129.9, 128.3, 127.6 (2C), 126.8, 119.9, 116.3,
115.8, 115.2 (2C), 111.1, 108.5, 106.0, 102.7, 94.9, 56.3, 55.9,
55.8, 55.7; HRMS (ESI) m/z calcd for C27H29NO5 (M+) 447.0246,
found 447.2051.
5.19. Amine 36
According to the procedure described for compound 26, com-
pound 35 (16 mg, 0.024 mmol), NH4Cl (satd, 1 mL) and Zn0 dust
(26 mg, 0.4 mmol) gave after final purification by column chroma-
tography (4:6 hexanes/EtOAc to 99:1 EtOAc/MeOH) amine 36
(12 mg, 80%) as an orange oil: 1H NMR d 7.52 (d, J = 16.8 Hz, 1H),
7.37 (d, J = 8.4 Hz, 2H), 7.28 (d, J = 16.0 Hz, 1H), 7.01 (d,
J = 16.0 Hz, 1H), 6.93–6.88 (m, 4H), 6.76 (s, 1H), 6.70 (d, 8.0 Hz,
2H), 5.30 (s, 2H), 4.84 (d, J = 6.8 Hz, 1H), 4.73 (d, J = 6.8 Hz, 1H),
4.32 (ddd, J = 2.8, 2.8, 2.8 Hz, 1H), 3.95 (s, 3H), 3.91 (s, 3H), 3.55
(s, 3H), 3.47 (s, 3H), 3.28 (d, J = 2.8 Hz, 1H), 2.84–2.71 (m, 2H),
2.57 (dd, J = 13.6, 2.4 Hz, 1H), 1.98 (dd, J = 11.2, 2.6 Hz, 1H), 1.80
(dd, J = 12.6, 5.0 Hz, 1H), 1.49 (s, 3H), 1.12 (s, 3H), 1.10 (s, 3H);
13C NMR d 158.5, 156.1, 149.1, 145.2, 142.5, 136.9, 132.4, 130.4,
128.8, 128.7, 127.6 (2C), 126.3, 122.8, 120.6, 116.6, 115.8, 115.5
(2C), 107.0, 106.0, 102.8, 96.9, 95.0, 84.9, 76.5, 68.7, 56.3, 56.1,
56.0, 55.8, 47.2, 42.3, 37.9, 28.8, 23.0, 21.6, 16.7; HRMS (ESI) m/z
calcd for C38H47NO8 (M+) 645.3302, found 645.3312.
5.16. Compound 32
According to the procedure described for compound 30, com-
pound 31 (10 mg, 0.02 mmol), in CH3OH and EtOAc was treated
with TsOHꢂH2O (60 mg, 0.31 mmol), and after final purification
by column chromatography (4:6 hexanes/EtOAc) afforded com-
pound 32 (8 mg, 89%) as a dark orange solid: UV (EtOH) kmax (log e)
377 (4.63); kem 512; 1H NMR ((CD3)2CO) d 7.56 (d, J = 16.8 Hz, 1H),
7.29–7.22 (m, 3H), 7.10–6.92 (m, 6H), 6.76 (d, J = 2.8 Hz, 1H), 6.65
(d, J = 8.4 Hz, 2H), 4.69 (br d, 1H), 3.92 (s, 3H), 3.85 (s, 3H), 3.81 (s,
3H); 13C NMR ((CD3)2CO) d 159.6, 156.9, 150.6, 150.4, 148.7, 137.6,
132.8, 131.5, 129.3, 128.9, 128.0 (2C), 127.5, 120.8, 116.4, 115.3
(2C), 112.8, 110.3, 107.7, 104.5, 101.6, 56.1, 56.1, 56.0; HRMS
(ESI) m/z calcd for C25H25NO4 (M+) 403.1784, found 403.1779.
5.20. Amine 37
According to the procedure for compound 30, compound 36
(11 mg, 0.017 mmol), in CH3OH was treated with TsOHꢂH2O
(25 mg, 0.13 mmol), and gave after final purification by column
chromatography(EtOAc)schweinfurthin 37(9 mg, 95%)asa darkor-
5.17. Compound 34
To a solution of aldehyde 33 (25 mg, 0.07 mmol) and phospho-
nate 23 (50 mg, 0.11 mmol) in THF (4 mL) at rt was added 15-
crown-5 (0.01 mL) followed by NaH (51 mg, 1.3 mmol, 60% in
oil). After 35 min, the reaction was quenched by addition of water.
The resulting solution was extracted with EtOAc, washed with
brine, dried (MgSO4), and concentrated in vacuo. Final purification
ange wax: UV (EtOH) kmax (log e
) 375 (4.63); kem 481; 1H NMR
(CD3OD) d 7.50 (d, J = 16.4 Hz, 1H), 7.25 (d, J = 8.4 Hz, 2H), 7.24 (d,
J = 16.4 Hz, 1H), 7.01–6.88 (m, 4H), 6.69 (d, J = 8.4 Hz, 2H), 6.66 (d,
J = 1.2 Hz, 1H), 6.64 (s, 1H), 4.14 (ddd, J = 3.6, 3.6, 3.6 Hz, 1H), 3.91
(s, 3H), 3.85 (s, 3H), 3.30 (obscured by solvent, 1H), 2.78–2.76 (m,
2H), 2.35 (dd, J = 13.8, 3.0 Hz, 1H), 1.92 (dd, J = 13.4, 3.0 Hz, 1H),

J. J. Topczewski et al. / Bioorg. Med. Chem. 18 (2010) 6734–6741
6741
1.73 (dd, J = 11.8, 6.2 Hz, 1H), 1.41 (s, 3H), 1.10 (s, 3H), 1.09 (s, 3H);
13C NMR (CD3OD) d 160.1, 157.4, 150.3, 147.9, 143.6, 138.3, 131.3,
130.6, 129.5, 128.1 (2C), 127.4, 124.4, 122.0, 117.5, 116.7 (2C),
115.8, 114.6, 108.5, 107.5, 101.9 78.8, 78.1, 71.8, 56.5, 56.2, 48 (ob-
scured by solvent), 44.8, 39.2, 29.4, 24.0, 22.0, 16.6; HRMS (ESI) m/
z calcd for C34H39NO6 (M+) 557.2777, found 557.2784.
the official views of the National Cancer Institute or the National
Institutes of Health.
Supplementary data
General experimental procedures, the 1H and 13C NMR spectra
for compounds 14–16, 18, 19, 21–27, 29–32, 34–37, and a table
of compound purity data. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.bmc.2010.07.056.
5.21. Cell culture
The SF-295 and A549 cell lines were purchased from the NCI
and ATCC, respectively. These cell lines were maintained in RPMI
1640 (SF-295) or F-12 media (A549), each supplemented with
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Acknowledgments
We thank the University of Iowa for a Shriner Fellowship (JJT).
Financial support from the Roy J. Carver Charitable Trust and the
National Cancer Institute (R41CA126020 via Terpenoid Therapeu-
tics, Inc.) is gratefully acknowledged. The content is solely the
responsibility of the authors, and does not necessarily represent