Semi-synthetic aristolactams-inhibitors of CDK2 enzyme

Article abstract of DOI:10.1016/j.bmcl.2010.01.007

Several analogs of aristolochic acids were isolated and derivatized into their lactam derivatives to study their inhibition in CDK2 assay. The study helped to derive some conclusions about the structure-activity relation around the phenanthrin moiety. Semi-synthetic aristolactam 21 showed good activity with inhibition IC₅₀ of 35 nM in CDK2 assay. The activity of this compound was comparable to some of the most potent synthetic compounds reported in the literature.

Full text of DOI:10.1016/j.bmcl.2010.01.007

Bioorganic & Medicinal Chemistry Letters 20 (2010) 1384–1387
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Semi-synthetic aristolactams—inhibitors of CDK2 enzyme
*
Vinod R. Hegde , Scott Borges, Haiyan Pu, Mahesh Patel, Vincent P. Gullo, Bonnie Wu, Paul Kirschmeier,
Michael J. Williams, Vincent Madison, Thierry Fischmann, Tze-Ming Chan
Schering Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Several analogs of aristolochic acids were isolated and derivatized into their lactam derivatives to study
their inhibition in CDK2 assay. The study helped to derive some conclusions about the structure–activity
relation around the phenanthrin moiety. Semi-synthetic aristolactam 21 showed good activity with inhi-
bition IC50 of 35 nM in CDK2 assay. The activity of this compound was comparable to some of the most
potent synthetic compounds reported in the literature.
Received 7 August 2009
Revised 23 December 2009
Accepted 4 January 2010
Available online 7 January 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Semi-synthetic analogs
Aristolactams
IC50
SAR
In the preceding Letter we have reported on the isolation of a
potent CDK2 enzyme inhibitor SCH 546909, a natural product aris-
tolactam analog with an inhibition IC50 of 140 nM. This prompted
us to undertake a semi-synthetic study of different analogs from
this class. Many total syntheses of aristolactam analogs have been
reported in the literature,1 however sub-structure literature
searches revealed that these compounds could be easily prepared
from naturally occurring, aristolochic acids.
Chemical Co. and ACROS. The commercially available aristolochic
acid is a complex mixture of several analogs, with the major com-
ponents being aristolochic acids II & I in 1:4 ratio. We have sepa-
rated commercial aristolochic acid mixtures on a preparative
HPLC using YMC ODS-A C-18, 10
l
m, 5 Â 50 cm HPLC column,
,2
eluting with 0.05% trifluoroacetic acid and acetonitrile (60:40) to
obtain compounds 1–8. A typical 600 mg of commercial aristolo-
chic acid afforded 27.7, 4.6, 7.8, 71.6, 5.4, 6.8, 315.8, and 3.2 mg
6
7
of aristolochic acid C (5), aristolochic D (7), 7-hydroxy aristolo-
O
8
9
chic A(6), aristolochic acid II (1), aristolochic acid IV (4), 7-meth-
HO
1
0
2
oxy aristolochic acid
A
(3),
aristolochic acid I (2), and
NH
1
1
aristolochic acid III (8).
H CO
3
In our semi-synthetic modifications to prepare aristolactam
analogs, the aristolochic acids were first converted to their lactams.
The purified aristolochic acids were hydrogenated in ethanolic
solution under 40 psi hydrogen in presence of Pd/C catalyst, over-
night at room temperature. The amino compound produced on
reduction of nitro group, on further ring closure results in lactam.
After separation and derivatization to the resulting lactam, the
HO
SCH 546909
Several publications and reviews have been published on the
occurrence, synthesis and biological activities of aristolochic acids.
Aristolochic acids and aristolactams are classified as aporphinoids
because of their basic skeleton which bears a distinct similarity to
that of aporphins. Aristolochic acids exhibit tumor inhibitory activ-
ity against the adenocarcinoma 755 test system but in mice they
induced papiloma. They are also known to form covalent DNA
adducts by enzymatic reductive activation of aristolochic acids in
the presence of DNA. They are also shown to induce mutagenicity
in mice. Aristolochic acid is commercially available from Sigma
aromatic phenol ether derivatives were deprotected with BBr
methylene chloride solution. A typical demethylation12 involved
stirring the aristolochic methyl ethers (15 mg) in CH Cl (50 ml)
at 0 °C with the dropwise addition of BBr (7.5 ml, 1 M) in CH Cl
2
3
in
2
2
3
2
3
at 0 °C and then continue stirring overnight at room temperature.
The reaction mixture was quenched in ice, extracted with ethyl
acetate, and dried. The demethylated product was purified by
HPLC.
4
5
The Methylenedioxy group was removed by stirring aristolac-
tams in CH
2 2 5
Cl at 0 °C and dropwise addition of a solution of PCl
*
Corresponding author. Tel.: +1 908 820 3871; fax: +1 908 820 6166.
E-mail address: vinod.hegde@spcorp.com (V.R. Hegde).
(
1:1 ratio). The reaction mixture was slowly allowed to attain room
0
960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.01.007

V. R. Hegde et al. / Bioorg. Med. Chem. Lett. 20 (2010) 1384–1387
1385
M)
temperature during 2 h and then quenched with ice, extracted
with CH Cl and dried. The O-dihydroxy compound formed was
purified by HPLC.
,4-Dihydroxy-12-chloro aristolactams were prepared from
methylenedioxy containing derivatives via treatment with the
dropwise addition of PCl (1:2.5 ratio) in CH Cl at 0 °C and slowly
allowing the reaction mixture to attain room temperature during
h. The reaction mixture was quenched in ice, extracted with
CH Cl and dried. The halogenated product was further purified
by HPLC.
Table 1
CDK2 inhibition IC50s of aristolochic acids and aristolactam analogs
2
2
Compound
CDK2 IC50 (l
3
1
2
3
4
5
6
7
8
9
>20
>20
>20
>20
30
25
25
15
>20
13.4
18
>30
5.7
16.5
15
1.2
5
2
2
3
2
2
ARISTOLOCHIC ACID ANALOGS
10
1
1
1
2
O
O
COOH
O
N R5
13
14
NO2
O
O
16
16
15
R4
16
1
7
>15
>15
2.9
R3
R1
15
R3
R1
18
19
20
21
22
23
24
25
26
R2
R2
1
8
5. R = R = R = R4 = R =-H
1
2
3
5
>35
0.035
>30
>50
2.15
>35
>35
>35
>25
>35
>35
10
>50
>50
>50
>50
>50
>50
>50
>50
>50
>50
1
1
1
2
3
18
1
2
3
4
5
6
7
8
9
. R = R = R = -H
6. R = -OCH R2 = R = R =R = -H
1
3
4
5
3,
. R = -OCH R2 = R = -H
1
3
3
,
17. R = R =-OCH3 ,R3 =R4 = R = -H
1
2
5
18
. R = R = -OCH3, R3 = -H
1
2
1
3
= -OCH3, R2 = R4 = R = -H
5
18. R = R
20,21
19,21
17
. R = R = -OCH R2 = -H
1
3
3
,
1
19. R = -OCH3 R2 = -OH, R = R =R = -H
3
4
5
,
.R1 = R = -H R = -OH
2
3
,
20. R1 = -OCH3, R3 = -OH, R = R = R = -H
2
4
5
. R = -OCH R2 = -OH, R = -H
1
3
3
,
21. R = -OH, R = R = R = R = -H
1
2
3
4
5
4
27
. R = -OCH R2 = -H, R = -OH
1
3
3
,
2
22. R = R = -OH, R3 = R = R = -H
1
2
4
5
28
29
30
31
1
3
. R = -OH, R = R = -H
3. R = R = -OH, R2 = R = R = -H
1
3
4
5
2
2
2
2
. R = R = -OCH3, R3 = -H
1
2
16
4. R = R = R = R5 = -H, R = -OH,
1
2
4
3
5. R = -OCH3, R2 = R = R = -H, R = -CH
1
3
4
5
3
2
2
1
2
3
4
5
Dicentrine
6. R = -OH, R = R = R = -H, R = -CH
3
Crebanine23
24
COOH
HO
O
Roemerine-HBr
2
5
HO
Isocorydine
NO
2
Corydine26
NH
HO
HO
27
Corytuberine
R4
Sinoacutine
28
9
R4
Sinomenine2
R3
1
R1
25
R3
R1
Stephanine,
Tetrahydro-berberine
R2
30
R2
1
1
1
1
1
0. R = R2 = R3 = R4 = -H
7. R1 = R2 = R3 = R4 = -H
2
1. R = R2 = R3 = -H, R = -Cl
1
4
8. R1 = R2 = R3 = -H, R4 = -Cl
2
2. R = -OCH3, R2 = R = R = -H
1
3
4
29. R1
= -OCH3, R2 = R = R = -H
3
4
3. R1 = -OH, R = R = R = -H
2
3
4
0. R1 = -OH, R = R = R = -H
2
3
4
at C-7 or C-9 positions also appear to enhance CDK2 inhibition.
Additionally, the protection of the dihydroxy groups at the C-4
and C-5 positions contributes toward the potency. However, pro-
tection of amide –NH by a methyl group or substitution by a halo-
gen at C-10 results in reduced activity. The observations are only
empirical and a detailed study would be necessary to evaluate a
complete structure–activity relationship.
3
3
4. R1 = -OCH3, R2 = R3 = -H, R = -Cl
4
1. R1 = -OCH3, R2 =R3 = -H, R = -Cl
4
The aristolochic acid analogs prepared were tested in CDK2 as-
say13 with the resulting inhibition IC50s are tabulated in Table 1.
Many analogs showed CDK2 activity >10 M, however compounds
3, 16, 19, 21, and 24 exhibited CDK2 inhibition under 10 M.
l
1
l
Compound 21 showed a CDK2 inhibition IC50 of 35 nM, potency
similar to the most potent CDK2 inhibitor reported in the litera-
ture Compound 13, having a hydroxyl group at C-9 also showed
activity in the M range.
Several natural products, like aporphinoids, morphine, and
fused berberine classes of compounds, were also tested to evaluate
importance of the lactam ring in the CDK2 activity. All these com-
pounds excepting sinomenine, sinoacutine, and tetrahydroberber-
ine, have tetrahydro pyridine ring attached to phenanthrine
moiety. Sinomenine and sinoacutine have morphine like ring sys-
tem but tetrahydroberberine has two tetrahydro-isoquinoline ring
system. All these compounds failed to show inhibition in CDK2 as-
O
1
4
RO
Protection increases
l
the potency in CDK2
assay
3
-CH in this position
decreases activity
NH
X
RO
halogen in this position
decrease in potency
-OH in this position substantially
increases the potency in CDK2 assay
-OH in this position
increases the potency
say at 50
l
M.
Aristolochic acids and aristolactams have phenanthrin aromatic
moiety similar to another class of natural product that includes
staurosporine, isolated from fungus. Staurosporins are also potent
kinase inhibitors and have been extensively studied as antitumor
compounds. Like staurosporine, these compounds are also planar
molecules and are sparingly soluble in various solvents including
water. Increasing the solubility properties by salt formation or by
Only compound 21, displayed strong CDK2 inhibition, about
threefold better than the natural product SCH 546909.
Based on the activity profile of the different aristolochic acid
and aristolactam analogs, it appears the lactam ring is essential
for potent CDK2 inhibition. This has been shown to be true for sev-
eral potent inhibitors reported in literature.3
1,32
Hydroxyl groups

1
386
V. R. Hegde et al. / Bioorg. Med. Chem. Lett. 20 (2010) 1384–1387
forming inclusion compounds with b-cyclodextrin appear to
improve cellular activity.
Computer based interaction design of 21 with CDK2 enzyme: The
docking experiments on CDK2 enzyme with 21 (SCH535270) and
staurosporine were performed and are shown in Figure 1A and B.
The computer docking model suggests the lactam of 21 (SCH
535270) interacts with CDK2 enzyme active sites in a manner anal-
ogous to that observed for compounds of staurosporine class of
inhibitors bound to fibroblast growth factor receptor kinase.34
Aristolactam 21 was further tested in a kinase counter screen
3
3
assays, along with the natural product SCH 546909 and 32
,
as
shown in Table 2. The results indicate that the inhibitors share a
similar activity in the CDC2 (cyclin-A dependent kinase, ꢀ90%
homology) assay, and a lesser selectivity in other kinases assays
like CDK4, AUR2 (Aurora kinase), MAPK (mitogen-activated protein
kinase), and AKT (ATP kinase).
Two hydrogen bonds were formed between the c-lactam moi-
ety of 21 and CDK2. Specifically, the amide nitrogen was hydrogen
bonded to the backbone carbonyl of glu-81 of the CDK2 enzyme
and the lactam carbonyl oxygen was hydrogen bonded with the
backbone NH of leu-83 amide. Staurosporin also binds to the
CDK2 enzyme in a similar fashion. The C-9 hydroxy group also ap-
pears to stabilize the binding at some other sight of enzyme core.35
SCH 535270, like staurosporin, is a planar molecule and exhibits
similar biological properties.
X-ray crystallography: Our attempts to determine the X-ray
structure of inhibitor SCH 535270 bound to CDK2 have failed.
The crystals were prepared by soaking the compound in presence
of CDK2 enzyme and cyclin A. The parameters like compound
concentration and duration of soak were screened.
Examination of the electronic density maps did not reveal the
binding mode of the compound. In some cases, X-ray crystallogra-
phy has failed to determine the co-structures of a compound
bound to the CDK2 protein even in the case of potent inhibitors.
A possible explanation is that inhibitor binding requires the com-
plete CDK2-cyclin-A complex, which is protocol in our screening
assay. CDK2 is activated by complexing with cyclin-A that induces
conformational changes in the protein that affect the ATP binding
site to some degree. The most significant effect involves a rotation
of the C-helix, which alters the active-site geometry in the region
of the triad of catalytic active-site residues Lys-33, Glu-51, and
Asp-145. The amino group of Lys-33 can be potential interaction
site for inhibitors. The amino nitrogen appears to hydrogen bond
with the oxygen of methylenedioxy group. Efforts to grow crystals
Cellular activities: Compound 21, the most potent and selective
CDK2 inhibitor from this series, was evaluated in two cellular pro-
liferation assays: a colony forming assay and a soft agar growth as-
say. In the soft agar growth assay compound 21 showed
comparable activity to 32, although compound 32 appeared to lose
some potency in this assay format compared to the clonogenicity
assay (Table 2). In the clonogenicity assay using MCF-7 cells, all
three compounds inhibited growth at similar micromolar concen-
trations. Compound 21 inhibited proliferation of tumor cells, with
IC50 values consistent with CDK2 inhibitors that are competitive
with respect to ATP. The anti-proliferative activity of the com-
pounds was up to eightfold selective for the tumor cells relative
to the HFF normal cell line. The anti-proliferative activity of 21 ar-
rests the tumor cells and protects the normal cells from chemo-
therapy-induced toxicity.32 These data are consistent with an
anti-proliferative mechanism expected for inhibition of CDK2 and
revealed that the aristolactam class of compounds have potential
for treating proliferative disorders, including chemotherapy-in-
duced alopecia.
R
O
N
N
N
H
Pyrazoloquinolines
3
3
2. R = -OCH (SCH47089)
Table 2
Inhibition (IC50) of SCH 546909, 21 and 32 in different kinases
Compound
Activity IC50 (nM)
Selectivity (nM)
AUR2
Cellular activity (lM)
CDC2
CDK4
MAPK
AKT
SAG MCF7
Clonogenicity
SCH546909
140
20
35
214
200
200
1420
2000
9000
2140
5000
3500
35,335
>50,000
12,000
—
—
11,400
—
>10
2–2.5
—
3.0
3.5
3
2
2 (SCH47089)
1 (SCH535270)
Figure 1. Computer modeling of binding of 21 (SCH 535270) and staurosporin with CDK2 enzyme.

V. R. Hegde et al. / Bioorg. Med. Chem. Lett. 20 (2010) 1384–1387
1387
of the activated CDK2-cyclin-A protein complex are in progress and
will be reported in future publications.
21. (a) Chakraborty, S.; Nandi, R.; Maiti, M.; Sur, P. Indian J. Phys. B. 1991, 65B, 587;
b) Priestap, H. A. Magn. Reson. Chem. 1989, 27, 460.
2. Chen, C. C.; Huang, Y. L.; Ou, J. C.; Su, M. J.; Yu, S. M.; Teng, C. M. Planta Med.
991, 57, 406.
23. Shamma, M.; Slusarchyk, W. A. Chem. Rev. 1964, 64, 59.
(
2
The aristolactam class of compounds represents a novel class of
CDK2 inhibitors. Exploration into semi-synthetic analogs provided
a potent CDK2 inhibitor from this class. Binding interactions by
docking experiments suggested carbonyl of glu-81 and NH of
leu-83 amide of the CDK2 enzyme are involved in hydrogen bond-
ing with the lactam functionality of aristolactams. CDK2 inhibition
causes an arrest of the cell cycle and exhibits a selective killing
effect on several tumor cell lines.36
1
24. You, M.; Wickramaratne, D. B.; Silva, G. L.; Chai, H.; Chagwedera, T. E.;
Farnsworth, N. R.; Cordell, G. A.; Kinghorn, A. D.; Pezzuto, J. M. J. Nat. Prod.
1995, 58, 598.
25. Roblot, F.; Hocquemiller, R.; Cave, A.; Moretti, C. J. Nat. Prod. 1983, 46, 862.
2
2
2
6. Manske, R. H. F. Can. J. Res. 1932, 7, 258.
7. Wang, C.-C.; Kuoh, C.-S.; Wu, T.-S. J. Nat. Prod. 1996, 59, 409.
8. Kunitomo, J.; Ju-Ichi, M.; Yoshikawa, Y.; Chikamatsu, H. J. Pharm. Soc. Jpn. 1974,
94, 97.
2
3
3
3
9. Terui, Y.; Tori, K.; Maeda, S.; Sawa, Y. K. Tetrahedron Lett. 1975, 33, 2853.
0. Chen, C. Y.; MacLean, D. B. Can. J. Chem. 1968, 46, 2501.
1. Dumas, J. Exp. Opin. Ther. Patents 2000, 11, 405.
2. Davis, S. T.; Benson, B. G.; Bramson, H. N.; Chapman, D. E.; Dickerson, S. H.
Science 2001, 291, 134.
Acknowledgments
Authors gracefully acknowledge Dr. E. Lees and Dr. R. Doll for
their helpful discussion on CDK2 inhibitors.
3
3
3. Afonso, A.; Kelly, J. M.; Chackalamannil, S. U.S. Patent 5459146, 1995, pp 13.
4. Mohammadi, M.; McMahon, G.; Sun, L.; Tang, C.; Hirth, P. Science 1997, 276,
955.
References and notes
35. Bramson, H. N.; Corona, J.; Davis, S. T.; Dickerson, S. H.; Edelstein, M.; Frye, S.
V., ; Gampe, R. T., Jr.; Harris, P. A.; Hassell, A.; Holmes, W. D.; Hunter, R. N.;
Lackey, K. E.; Lovejoy, B.; Luzzio, M. J.; Montana, V.; Rocque, W. J.; Rusnak, R. D.;
Shewchuk, L.; Veal, J. M.; Walker, D. H.; Kuyper, L. F. J. Med. Chem. 2001, 44,
1
2
.
.
Mix, D. B.; Guinaudeau, H.; Shamma, M. J. Nat. Prod. 1982, 45, 657.
Shamma, M.; Monit, J. C. Isoquinoline Alkaloids Research 1972–1977; Plenum
Press: New York, 1978.
4339.
36. Walker, D. H.; Luzzio, M.; Veal, J.; Dold, K.; Edelstein, M. Proc. Am. Assoc. Cancer
3
.
.
(a) Kupchan, S. M.; Wormser, H. C. J. Org. Chem. 1965, 30, 3792; (b) Kupchan, S.
M.; Merianos, J. J. J. Org. Chem. 1968, 33, 3735.
(a) Stiborova, M.; Frei, E.; Breuer, C. A.; Schmeiser, H. H. Cancer Res. 1990, 50,
Res. 1999, 40, A4783
Physico-chemical properties:
4
+
Aristolochic acid C (5): UV kmax: 225, 256, 308, 410 nm; FABMS 328 (M+H) , 350
5
1
464; (b) Cinca, S.; Voiculetz, N.; Schmeiser, H.; Wiessler, M. J. Med. Biochem.
997, 1, 3.
+
+ 1
(
M+Na) , 366 (M+K) , H NMR (DMSO-d
J = 4 Hz, 5-H), 8.10 (d, J = 17 Hz, 8-H), 7.75 (s, 2H), 7.29 (dd, J = 17,4 Hz, 7-H),
.48 (s, 12-H2). 13C NMR (DMSO-d
) ppm: 168.0 (11-C), 159.8 (6-C), 145.8 (3-
C), 145.5 (4-C), 143.1 (10-C), 132.5 (8-C), 131.0 (4b-C), 126.4 (9-C), 123.7 (1-C),
6
) d: 10.63 (COOH), 8.48 (9-H), 8.46 (d,
5
.
Pistelli, L.; Nieri, E.; Bilia, A. R.; Marsili, A.; Scarpato, R. J. Nat. Prod. 1993, 56,
605.
6
6
1
6.
7.
8.
9.
Hong, L.; Sakagami, Y.; Marumo, S.; Xinmin, C. Phytochemistry 1994, 37, 237.
Nakanishi, T.; Iwasaki, K.; Nasu, M.; Miura, I.; Yoneda, K. Phytochemistry 1982, 21, 1759.
Wu, T.-S.; Leu, Y.-L.; Chan, Y.-Y. Chem. Pham. Bull. 1999, 47, 571.
1
1
21.5 (8a-C), 118.8 (7-C), 117.2 (10a-C), 116.2 (4a-C), 111.9 (2-C), 111.1 (5-C),
02.8 (12-C).
7
-Hydroxy aristolochic acid A (6): UV kmax: 224, 271, 318, 384 nm; ESMS Àve
De Pascual, T. J.; Urones, J. G.; Fernandez, A. Phytochemistry 1983, 22, 2745.
À
mode, m/z 356(MÀH) .
1
1
1
1
0. Wu, T.-S.; Chan, Y.-Y.; Leu, Y.-L. Chem. Pharm. Bull. 2000, 48.
Aristolochic acid D (7): UV kmax: 224, 243, 333, 408 nm; ESMS m/z 358(M+H)+.
1. Urzua, A.; Salgado, G.; Cassels, B. K.; Eckhardt, G. Planta Med. 1982, 45, 51.
2. Gerecke, M.; Borer, R.; Brossi, A. Helv. Chim. Acta 1976, 59, 2551.
3. Guzi, T. J.; Paruch, K.; Dwyer, M. P.; Doll, R. J.; Girijavallabhan, V. M.; Mallams,
A.; Alvarez, C. S.; Keertikar, K. M.; Rivera, J.; Chan, T.-Y.; Madison, V. S.;
Fischmann, T. O.; Dillard, L. W.; Tran, V. D.; He, Z.; James, R. A.; Park, H.;
Paradkar, V. M.; Hobbs, D. W.; Kirschmeier, P.; Bannerji, R. U.S. Patent Appl.
Publ. 2008, pp. 387.
18
Compound (21) : UV kmax: 214, 242, 258, 294, 328, 398 nm; ESMS: m/z 280
+
1
(
M+H) ; H NMR (DMSO-d
H), 7.63 (s, 2-H), 7.37 (t, J = 15 Hz, 6-H), 7.36 (s, 9-H), 7.06 (d, J = 15 Hz, 7-H),
.46 (s, 12-H2). 13C NMR (DMSO-d
) ppm: 168.1 (11-C), 153.8 (8-C), 148.8 (3-
C), 147.1 (4-C), 134.0 (10-C), 125.8 (6-C), 125.3 (4b-C), 125.3 (10a-C), 123.2
6
) d: 10.72 (s, NH), 10.2 (s, –OH), 8.03 (d, J = 15 Hz, 5-
6
6
(
(
8a-C), 119.3 (1-C), 117.5 (5-C), 112.3 (7-C), 111.3 (4a-C), 105.4 (2-C), 103.2
12-C), 98.7 (9-C).
1
4. (a) Babu, P. A.; Narasu, M. L.; Srinivas, K. ARKIVOC 2007, 2, 247 (Gainesville, FL,
USA); (b) Ruetz, S.; Fabbro, D.; Zimmermann, J.; Meyer, T.; Gray, N. Curr. Med.
Chem.: Anti-Cancer Agents 2003, 3, 1; (c) Dumas, J. Exp. Opin. Ther. Patents 2001,
16
Compound (16) : UV kmax: 225, 239, 258, 295, 329, 394 nm; ESMS: m/z 294
+
1
(
M+H) ; H NMR (DMSO-d
6
) d: 10.67 (s, NH), 8.22 (d, J = 16 Hz, 5-H), 7.70 (s, 2-
H), 7.50 (t, J = 16 Hz, 6-H), 7.35 (s, 9-H), 7.20 (d, J = 16 Hz, 7-H), 6.48 (s, 12-H2),
1
1, 405.
4
1
.0 (s, 13-H3). 13C NMR (DMSO-d
6
) ppm: 168.1 (11-C), 155.3 (8-C), 148.8 (3-C),
47.1 (4-C), 134.7 (10-C), 125.7 (6-C), 125.0 (11a-C), 124.8 (4b-C), 124.0 (10a-
1
1
1
5. Priestap, H. Phytochemistry 1985, 24, 849.
6. Coutts, R. T.; Stenlake, J. B.; Williams, W. D. J. Chem. Soc. 1957, 4120.
7. Chakraborty, S.; Nandi, R.; Maiti, M.; Achari, B.; Bandyopadhyay, S. Photochem.
Photobiol. 1989, 50, 685.
C), 119.3 (1-C), 118.7 (5-C), 111.0 (4a-C), 108.3 (7-C), 105.7 (2-H), 103.3 (12-C),
7.9 (9-C) add –OCH value.
Compound (29): ESMS: m/z 316 (M+H) ; 1H NMR (DMSO-d
J = 16 Hz, 5-H), 7.52 (t, J = 16 Hz, 6-H), 7.50 (s, 2-H), 7.22 (d, J = 16 Hz, 7-H), 3.92
9
3
+
6
) d: 9.12 (d,
1
1
8. Eckhardt, G.; Urzua, A.; Cassels, B. K. J. Nat. Prod. 1983, 46, 92–97.
9. Achari, B.; Bandyopadhyay, S.; Chakravarty, A. K.; Pakrashi, S. C. Org. Magn.
Reson. 1984, 22, 741.
13
(
7
s, –OCH
.22 due to 7-H and no NOE from –OCH
All the new compounds were purified by HPLC and identified by MS.
3 6 3
), C NMR (DMSO-d ) ppm: NOE from –OCH to proton doublet at d
3
.
2
0. Mizuno, M.; Oka, M.; Tanaka, T.; Yamamoto, H.; Iinuma, M.; Murata, H. Chem.
Pharm. Bull. 1991, 39, 1310.