7528 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 21
Dong et al.
considerably depending on the type and position of the substit-
uents. Compared with compound 29e, several compounds (e.g.,
29s and 29u) showed improved activity. In general, 4-substituted
derivatives were more potent than 2-substituted and 3-substi-
tuted derivatives. For example, compound 29u showed higher
cytotoxicity than compounds 29p and 29q. For the 4-substituted
derivatives, halogens (i.e., chlorine and fluorine) and methyl
group are favorable for the cytotoxicity. In comparison with the
monochlorine substituted compounds (compounds 29p and
29u), the disubstituted derivative (compound 29v) led to a
decrease of the cytotoxicity. Remarkably, the IC50 values of
compound 29u against A549, MDA-MB435, and HCT116 cell
lines are 0.86, 0.049, and 2.6 μM, respectively, suggesting that it
is a promising lead for the discovery of novel anticancer agents.
(50 mL ꢀ 3). The extract was washed with saturated NaCl solution
(50 mL ꢀ 3), dried over anhydrous Na2SO4, and concentrated
under reduced pressure. The residue was purified by column chro-
matography (EtOAc/hexane = 1:4) to give compounds 20a-x
with moderate to good yields.
1
N-Acetic Acid Evodiamine (29a). Yield 60%, yellow oil. H
NMR (DMSO, 500 MHz) δ 2.41 (s, 3H), 2.85 (m, 1H), 3.05 (m,
1H), 3.17 (m, 1H), 4.80 (m, 1H), 5.07 (dd, 2H, J1 = 18.1 Hz, J2 =
18.1 Hz), 6.02 (s, 1H), 7.02-8.01 (m, 8H). ESI-MS (m/z): 362.2
[M þ 1]. Anal. (C21H19N3O3) C, H, N.
N-Acetonitrile Evodiamine (29b). Yield 44%, white solid. 1H
NMR (DMSO, 500 MHz) δ 2.39 (s, 3H), 2.82 (m, 1H), 2.98 (m,
1H), 3.14 (m, 1H), 4.66 (m, 1H), 5.57 (s, 2H), 6.21 (s, 1H),
7.21-7.95 (m, 8H). 13C NMR (CDCl3, 500 MHz) δ 20.08, 31.73,
36.97, 39.00, 67.89, 109.02, 114.44, 115.51, 119.54, 121.22,
123.61, 124.00, 124.24, 125.04, 126.32, 127.60, 129.00, 133.14,
136.92, 150.47, 164.34. ESI-MS (m/z): 343.74 [M þ 1]. Anal.
(C21H18N4O) C, H, N.
Conclusion
From the above results, we can find that molecular weight
and synthetic possibility should be considered as two important
factors for the selection of hits for structural optimization. In
most cases, the molecular weight and hydrophobicity will be
increased during the process of hit-to-lead and lead-to-candi-
date. A starting structure with relatively low molecular weight is
more likely to be optimized to druglike candidates. On the other
hand, the synthetic possibility is also a major problem for
natural product-like hits from virtual screening. Evodiamine
has a free amine group with moderate molecular weight, which
can be easily transformed to active derivatives with druglike
properties. This example might give us some useful information
about hit selection after SBVS studies. Such structural require-
ment, a scaffold with a free N-H group and molecular weight
of about 350, could be included in the next SBVS study.
Evodiamine shares an interesting “L type” conformation in
the active site of topo1-DNA cleavable complex. Its free
indole N-H function is a good site for chemical derivatiza-
tion. However, the hydrogen bond with Arg364 would be
broken if the indole amine was substituted. In order to address
the contradiction, proper functional group transformation to
keep the hydrogen bonding interaction is an efficient method
to retain the binding affinity. In the present study, the indole
amine was transferred to the amide and its carbonyl group can
also form a hydrogen bond with Arg364. By means of this
method, we think a key N-H group participating in a special
binding mode is amenable to further chemistry and can be
transformed to generate active derivatives.
N-Ethyl Formate Evodiamine (29c). Yield 11%, yellow solid.
1H NMR (CDCl3, 500 MHz) δ 1.29 (t, 3H, J = 6.7 Hz), 2.45 (s,
3H), 2.86 (m, 1H), 2.99 (m, 1H), 3.20 (m, 1H), 4.45 (m, 2H), 4.91
(m, 1H), 6.29 (s, 1H), 7.04-8.27 (m, 8H). ESI-MS (m/z): 376.45
[M þ 1]. Anal. (C22H21N3O3) C, H, N.
N-Ethyl Acetate Evodiamine (29d). Yield 44%, yellow solid.
1H NMR (CDCl3, 500 MHz) δ 1.25 (t, 3H), 2.40 (s, 3H), 2.84 (m,
1H), 3.03 (m, 1H), 3.24 (m, 1H), 4.20 (m, 2H), 4.92 (m, 1H), 4.93 (d,
1H), 5.15 (d, 1H), 5.93 (s, 1H), 7.15-8.23 (m, 8H). 13C NMR
(CDCl3, 500 MHz) δ 14.13, 20.16, 36.66, 39.20, 45.21, 60.47, 68.00,
109.09, 113.89, 119.08, 120.17, 123.10, 123.33, 124.28, 124.52,
125.92, 128.40, 128.93, 132.84, 137.77, 150.83, 164.42, 168.54.
ESI-MS (m/z): 390.35 [M þ 1]. Anal. (C23H23N3O3) C, H, N.
N-Benzoylevodiamine (29e). Yield 37%, yellow solid. 1H
NMR (CDCl3, 500 MHz) δ 2.43 (s, 3H), 2.92 (m, 1H), 3.05 (m,
1H), 3.18 (m, 1H), 4.90 (m, 1H), 5.94 (s, 1H), 7.15-8.15 (m, 13H).
ESI-MS (m/z): 408.84 [M þ 1]. Anal. (C26H21N3O2) C, H, N.
N-(3-Chlorobenzyl)evodiamine (29f). Yield 67%, yellow solid.
1H NMR (CDCl3, 500 MHz) δ 2.35 (s, 3H), 2.95 (m, 1H), 3.06
(m, 1H), 3.21 (m, 1H), 4.90 (m, 1H), 5.38 (d, 1H, J = 16.8 Hz),
5.65 (d, 1H, J = 16.8 Hz), 5.81 (s, 1H), 6.88-8.11 (m, 12H). ESI-
MS (m/z): 428.61 [M þ 1]. Anal. (C26H22ClN3O) C, H, N.
N-(2-Chlorobenzyl)evodiamine (29g). Yield 75%, yellow so-
1
lid. H NMR (CDCl3, 500 MHz) δ 2.40 (s, 3H), 2.96 (m, 1H),
3.07 (m, 1H), 3.21 (m, 1H), 4.91 (m, 1H), 5.54 (d, 1H, J = 17.7
Hz), 5.78 (d, 1H, J = 17.8 Hz), 6.36 (s, 1H), 6.99-8.08 (m, 12H).
ESI-MS (m/z): 428.90 [M þ 1]. Anal. (C26H22ClN3O) C, H, N.
N-Hexylevodiamine (29h). Yield 27%, yellow solid. 1H NMR
(CDCl3, 500 MHz) δ 0.84 (t, 3H), 1.25-1.83 (m, 8H), 2.40 (s,
3H), 2.93 (m, 1H), 3.02 (m, 1H), 3.19 (m, 1H), 4.17 (t, 2H, J =
7.5 Hz), 4.90 (m, 1H), 5.96 (s, 1H), 7.15-8.15 (m, 8H). ESI-MS
(m/z): 488.93 [M þ 1]. Anal. (C25H29N3O) C, H, N.
Experimental Section
N-(2,4-Dichlorobenzyl)evodiamine (29i). Yield 36%, yellow
solid. 1H NMR (CDCl3, 500 MHz) δ 2.39 (s, 3H), 2.95 (m, 1H),
3.07 (m, 1H), 3.21 (m, 1H), 4.92 (m, 1H), 5.46 (d, 1H, J = 16.7
Hz), 5.76 (d, 1H, J = 16.7 Hz), 6.31 (s, 1H), 6.97-8.09 (m, 11H).
ESI-MS (m/z): 462.68 [M]. Anal. (C26H21Cl2N3O) C, H, N.
N-Benzylevodiamine (29j). Yield 58%, yellow solid. 1H NMR
(CDCl3, 500 MHz) δ 2.38 (s, 3H), 2.93 (m, 1H), 3.06 (m, 1H), 3.19
(m, 1H), 4.91 (m, 1H), 5.44 (d, 1H, J = 16.7 Hz), 5.68 (d, 1H, J =
16.7 Hz), 5.81 (s, 1H), 7.00-8.10 (m, 13H). ESI-MS (m/z): 394.72
[M þ 1]. Anal. (C26H23N3O) C, H, N.
Chemistry. General Methods. 1H NMR and 13C NMR spectra
were recorded on a Bruker Avance 300 spectrometer (Bruker
Company, Germany), using TMS as an internal standard and
CDCl3 or DMSO-d6 as solvent. Chemical shifts are given in ppm
(δ). Elemental analyses were performed with a MOD-1106
instrument and were consistent with theoretical values within
0.4%. The mass spectra were recorded on an Esquire 3000
LC-MS mass spectrometer. Silica gel thin-layer chromatogra-
phy was performed on precoated plates GF-254 (Qingdao
Haiyang Chemical, China). The purity of final compounds
was assessed on the basis of analytical HPLC, and the results
were greater than 95%. All solvents and reagents were analyti-
cally pure, and no further purification was needed. All starting
materials were commercially available.
N-Propylevodiamine (29k). Yield 79%, yellow solid. 1H NMR
(CDCl3, 500 MHz) δ 0.95 (t, 3H, J = 7.4 Hz), 1.86 (m, 2H), 2.40
(s, 3H), 2.89 (m, 1H), 3.02 (m, 1H), 3.19 (m, 1H), 4.17 (m, 1H),
4.31 (m, 1H), 4.92 (m, 1H), 5.97 (s, 1H), 7.17-8.15 (m, 8H). ESI-
MS (m/z): 346.68 [M þ 1]. Anal. (C22H23N3O) C, H, N.
N-Ethylevodiamine (29l). Yield 64%, yellow solid. 1H NMR
(CDCl3, 500 MHz) δ 1.42 (t, 3H, J = 7.2 Hz), 2.42 (s, 3H), 2.89
(m, 1H), 3.02 (m, 1H), 3.19 (m, 1H), 4.24 (m, 1H), 4.43 (m, 1H),
4.92 (m, 1H), 5.97 (s, 1H), 7.17-8.15 (m, 8H). 13C NMR
(CDCl3, 500 MHz) δ 15.16, 20.21, 29.52, 36.25, 39.16, 67.78,
General Procedure for the Synthesis of Compounds 29a-x.
NaH (60% oil, 6.6 mmol) was suspended in a solution of
evodiamine44-48 (0.20 g, 0.66 mmol) in DMF (20 mL). The reacting
mixture was heated to 80 °C and stirred for 24 h. The mixture
was diluted with H2O (50 mL) and then extracted with EtOAc