Naphthalimide intercalators with chiral amino side chains: Effects of chirality on DNA binding, photodamage and antitumor cytotoxicity

Article abstract of DOI:10.1016/j.bmcl.2008.09.104

Several novel heterocyclic-fused naphthalimides intercalators with chiral amino side chains were investigated. Their side chains' chiral configuration determines DNA binding activities in the order: S-enantiomers > R-enantiomers. And their DNA photodamagi

Full text of DOI:10.1016/j.bmcl.2008.09.104

Bioorganic & Medicinal Chemistry Letters 18 (2008) 6210–6213
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Naphthalimide intercalators with chiral amino side chains: Effects
of chirality on DNA binding, photodamage and antitumor cytotoxicity
a
c,
b
Qing Yang a, , Peng Yang , Xuhong Qian , Lianpeng Tong
*
*
a Department of Bioscience and Biotechnology, Dalian University of Technology, No. 2 Linggong Road, Ganjingzi, Dalian, Liaoning Province 116012, China
b State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
c Shanghai Key Laboratory of Chemical Biology, East China University of Science and Technology, Shanghai 200237, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 July 2008
Revised 19 September 2008
Accepted 30 September 2008
Available online 5 October 2008
Several novel heterocyclic-fused naphthalimides intercalators with chiral amino side chains were inves-
tigated. Their side chains’ chiral configuration determines DNA binding activities in the order: S-enanti-
omers > R-enantiomers. And their DNA photodamaging activities were in good agreement with their DNA
binding constants, the S-enantiomers could photocleave circular supercoiled pBR322 DNA more effi-
ciently than their R-enantiomers. S-enantiomer B3 could photodamage DNA at 0.2
l
M and cleave super-
coiled plasmid DNA from form I to form II completely at 50
lM. Almost all of these intercalators showed
Keywords:
Antitumor agents
Chirality
Naphthalimide
DNA intercalation
DNA photodamage
effective cytoxicities against human lung cancer cells and murine leukemia cells. S-enantiomers showed
different antitumor cytotoxicity by comparison with R-enantiomers. This work may provide additional
information for the role of amino side chains on intercalators as antitumor agents.
Ó 2008 Elsevier Ltd. All rights reserved.
DNA intercalating agents as major class of antitumor com-
pounds have received most and continued attention. They usually
function as DNA-targeted topoisomerase I and/or II inhibitors. Usu-
ally these agents are characterized by the presence of a tri- or tet-
racylic annelated planar and aromatic ring capable of inserting the
nucleic acid bases5 and one or two flexible amino side chains for
promoting DNA affinity through electrostatic or hydrophobic inter-
actions.1–3 N,N-dimethyl alkyldiamino group and its analogues, for
example, are widely applied as anticancer agents in conjugation
with an intercalating moiety including anthraquinone, acridine,
benzimidazole-quinoline, fluorenone, pyridine-diones, naphthali-
mides, etc.2,4 (Fig. 1).
agents against a variety of murine and human tumor cells.7 How-
ever, less investigation on naphthalimides with chiral amino side
chains has been performed. We ever reported heterocyclic naph-
thalimides with achiral amino side chains as highly efficient artifi-
cial nucleases and antitumor agents.12 In this study, we report a
series of bioactive heterocylclic naphthalimides with chiral amino
side chains (Fig. 2). Here, racemic (X), chiral (R)-(+)- and (S)-(À)-N-
ethyl–2-(aminomethyl) pyrrolidine (R, S, respectively) are side
chains.
The synthesis of An, Bn, Cn and Dn (n = X, R, S) was carried out by
the condensation reaction of the corresponding anhydride (A0, B0,
C0 and D0) with amine, starting from 4-bromo-3-nitro or 4-bromo-
1,8-naphthalic anhydride. The synthesis strategies were outlined
in Figure 3.13–15 Their structures were confirmed by IR, 1H NMR
and HRMS.16
The Scatchard binding constants for calf thymus DNA (CT-DNA)
were monitored by fluorescence spectroscopy (in 30 mM Tris–HCl
buffer, pH 7.0).17 Table 1 listed their detailed UV–Vis, fluorescence
data, Scatchard binding constants and anticancer activities. It indi-
cated the Scatchard binding constants of S-enantiomers were high-
er than those of the corresponding R-enantiomers as well as those
of the racemic ones. The order of their Scatchard binding constants
was: (1) B > C > D > A for compounds, which was related to the
introduction of a sulphur atom into these molecules, and (2)
S > X > R for configuration.
Up to now, little is known for interactions between chiral interca-
lators and DNAs,5,6 let alone effects of chirality of amino side chains
on DNA binding ability, photodamage activity as well as antitumor
cytotoxicity. However, chirality plays very important roles in biolog-
ical system. DNA itself is a chiral molecule with right-handed helical
configuration. The helical grooves of DNA were considered to be the
most pronouncedenantio-selectivity part, while theinsertion of chi-
ral moiety between the achiral DNA bases is generally believed to
contribute less enantioselectivity.5,7–10
Naphthalimides are well-known DNA photocleavers11, and
naphthalimides bearing side chains are well-known antitumor
DNA binding affinity is known to be determined by several ac-
tions including groove binding, DNA intercalation and electrostatic
* Corresponding authors. Tel./fax: +86 411 84709687 (Q.Y.).
E-mail addresses: qingyang@dlut.edu.cn (Q. Yang), xhqian@ecust.edu.cn (X.
Qian).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.09.104

Q. Yang et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6210–6213
6211
R
H
N
N
N
X
X
X
O
O
HN
HN
OH
N
N
R1
Y
N
O
NH
(CH2)n
N
R2
OH
N
H
DACA: R=H
9-amino DACA: R=NH2
X=H, 2-CH3, 3-NO2, 3-NH2, 2-Cl, 3-Cl
n= 0, 1, 2
Mitoxantrone: X=OH
Ametantrone: X=H
R1 =R2 =(CH2)2, (CH3)4, (CH2)5
Y=CH2, NH
R
R1=CH2CH2N(CH3)2
O
N
O
O
N
O
O
N
O
N
R2=CH2CH2N(C2H5)2
N
O
O
R3=CH2CH
N
2N
O
R4=CH2CH2
N
NO2
Naphthalimide
Et
CG-630
Tilorone
Figure 1. Intercalating moieties and amino side chains of well-known antitumor agents.
O
O
O
N
d
An
R
N
O
R
N
N
O
Y
A0
O
0
S
B
0
A Y=O
D Y=S
c
-
a
O
O
NO2
Br
g
N
Dn
O
N
O
e, f
O
O
R=
S
D0
R
O
N
N
R
N
0
N
S
S
X
R
C
O
k
Bn
Figure 2. Heterocyclic-fused naphthalimide chiral amino side chains.
O
S
B0
binding. For those which carry the same intercalative moiety, their
DNA binding affinity differences mainly come from electrostatic
interactions between amino side chains and DNAs. Preferential
and average binding value of these enantiomers was K(R)/
K(S) ꢀ 0.5, which is in very similar with Becker’s investigation for
both the anthracene and the pyrene compounds5, although the
Becker’s structure is quite different from these molecules. The slight
enantiomeric preference was explained in terms of orientation
polarity during the binding, by which any intrinsic enantioselectiv-
ity is canceled by averaging of opposite binding orientations.5
DNA photocleavage activities of these chiral DNA intercalators
were evaluated. In the dark, they did not promote DNA strand
breaking. Being irradiated under 365 nm light, the DNA cleavage
ability of S-enantiomers was by far higher than that of R-enantio-
mers. The order of DNA cleavage efficiency by these compounds
was determined to be S > X > R and Bn > Cn > Dn > An, which were
almost parallel with their DNA binding abilities. To the best of
our knowledge, this is the first report for the difference between
S- and R-enantiomers of photo-activated naphthalimides. It could
be concluded the S-amino side chain showed greater potential in
developing novel DNA intercalators with higher DNA binding and
in turn DNA cleavage efficiency.
O
O
N
O
n
Br
l, m
Cn
O
O
R
S
C0
Figure 3. Synthesis routes summary. (a) NaOH, H2O, 80–85 °C, 8 h, 85% yield; (b)
SnCl2, HCl, 80 °C, 6 h, 66% yield; (c) PPA, benzoic acid, 135 °C, 4 h, 62% yield; (d)
RNH2, ethanol, reflux, 3 h, 85% yield; (e) NaS2, S, 100 °C, 8 h; (f) benzaldehyde, acetic
acid, N2, 6 h, 60% yield; (g) RNH2, ethanol, reflux, 3 h, 85% yield; (h) PhSH, EtOH,
reflux, 4 h, 97% yield; (i) SnCl2/concentrated HCl, 96% yield; (j) Pochorr cyclisation:
NaNO2, H2O–HCl–HOAc, 0–5 °C, 2 h; CuSO4, HOAc, reflux, 2 h, 64% yield; (k) RNH2,
ethanol, reflux, 3 h, 83% yield; (l) 2-aminobenzenethiol, K2CO3, DMF, reflux, 30 min,
77% yield; (m) Pochorr cyclisation: NaNO2, HOAc, H2SO4; CuSO4, HOAc, H2O, 99%
yield; (n) RNH2, ethanol, reflux, 3 h, 85% yield.
form I to form II by 100% at 50 lM (Fig. 4d). The order of DNA cleav-
age efficiency by these chiral compounds was BS > CS > AS.
Mechanism experiments were performed by adding different
scavengers (Fig. 5). Taking AS, Bs, Cs as examples (Fig. 5a, b and
d), histidine (singlet oxygen quencher) and ethanol (hydroxyl rad-
ical scavenger) had no obvious effect on photocleavage efficiency,
indicating that singlet oxygen and hydroxyl radical were not likely
to be involved in the cleaving species. However, the DNA-cleaving
activity of AS, BS, CS decreased dramatically in the presence of DTT
(dithiothreitol, superoxide anion scavenger). DTT could retard the
superoxide anion radicals, which might form after oxygen was
activated by accepting an electron transferred from nucleobase to
Figure 4 showed the concentration dependence of DNA photoc-
leavage efficiencies. AS at 0.5
l
M could damage supercoiled plasmid
DNA pBR322 (Fig. 4c), while under 1 h light exposure, 0.2
M of BS
and 0.5
M of CS started to cleave DNA (Fig. 4d, 4f). The R-enantio-
mer BR could cleave DNA at 5
M but could not converse Form I com-
pletely to Form II even when its concentration reached 50
(Fig. 4e), however, S-enantiomer BS could cleave plasmid DNA from
l
l
l
lM

6212
Q. Yang et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6210–6213
mers showed different bioactivities, respectively. Bx and Dx showed
the strong cytotoxicity for P388 (IC50, 0.47 and 0.59 M, respectively),
DR showed the highest cytotoxicity against A549 (IC50, 0.07
M). It
could be found that the cyctotoxicities of racemic ones maybe lower
or maybe higher than those of the corresponding R- or S-enantiomer
alone. It implied that for R- and S-enantiomer, beside their different
and competing actions with DNA and Topo II targets, there might
be some unknown (positive or negative) mechanisms in cells, which
strengthen or weaken the cytotoxicity of racemics.
Although there were no obvious or direct relationship between
their cytotoxicities and DNA binding affinities, it was interesting
that the chiral amino side chains did play a very important role
in their antitumor cytotoxicities. R/S-enantiomers behaved quite
differently in terms of cytotoxicity against different cell lines, sug-
gesting that the chiralities of amino side chains is of special impor-
tance in developing novel antitumor agents.
Table 1
Spectra data, photocleaving activity, and cytotoxicity
l
Ka (Â105 MÀ1
)
KR/K
IC50
A549
2220
0.89
(l
M)
l
UV/nm (lg
e)
FL/nm (
U
)
P388
Ax
AR
AS
Bx
BR
BS
Cx
CR
CS
375 (3.10)
375 (3.63)
375 (3.61)
381 (3.94)
381 (3.77)
381 (3.75)
469 (3.81)
469 (3.57)
469 (4.24)
315 (4.47)
315 (4.42)
315 (3.98)
428 (0.0089)
430 (0.0144)
429 (0.0184)
454 (0.0205)
454 (0.0231)
454 (0.0216)
522 (0.1805)
522 (0.1501)
523 (0.1311)
429 (0.0056)
429 (0.0022)
429 (0.0072)
1.24
0.82
1.62
9.07
6.23
10.0
3.02
2.51
6.10
2.32
1.23
2.85
383
13.9
0.51
0.62
0.41
0.43
2.72
2.88
6.02
0.58
0.49
8.84
0.57
0.16
0.07
0.23
4.82
0.47
2.28
4.90
12.2
12.3
5.11
Dx
DR
DS
0.59
3.35
1.17
In conclusion, thechiralityof amino side chains of naphthalimides
affect DNA binding affinity, DNA photocleavage activity as well as
cytotoxicity, which might provide considerations for developing
highly efficient DNA intercalators and better anti-tumor agents.
intercalator. However, the addition of SOD (superoxidedimutase)
did not obviously inhibit the DNA cleavage as DTT did. It was also
found that there was no difference in photocleavage mechanism
between R/S-enantiomers BR and BS (Fig. 5b and c).
The antitumor activities against human lung cancer cell (A549)
andmurineleukemiacell(P388)ofthesenovelcompoundswithrace-
mic, chiral (R)-(+)- and (S)-(À)-N-ethyl-2-(aminomethyl) pyrrolidine
side chains, were evaluated by means of Sulforhodamine B (SRB) as-
say or MTT tetrazolium dye assay (in dark or under daily scattered
light), respectively (Table 1). The racemic, (R)-(+)- or (S)-(À)-enantio-
Acknowlegments
Financial support by the National Key Project for Basic Research
(2003CB114400) and under the auspices of the National Natural
Science Foundation of China (20536010) (20576016) (20676021)
is greatly appreciated. The authors also thank for the support from
Figure 4. Photocleavage of supercoiled pBR322 DNA in the buffer of HEPES (20 mM, pH 7.0) containing 20% of acetonitrile under 365 nm light irradiation (a) DNA
photocleavage by compounds (100 M) for 1 h. Lane 1, DNA alone (h ), lane 2, DNA alone (no h
); lane 3–9, A0, AS, AR, Ax, DS, DR, Dx and DNA, respectively; (b) DNA
photocleavage by compounds (50 M) for 1 h. (Lane 1) DNA alone (h ), (lane 2) DNA alone (no h
); (lane 3–8) CS, CR, Cx, BS, BR, Bx and DNA, respectively; (c) DNA
photocleavage by As at various concentrations for 2 h. (Lane 1–5) As at concentration of 50, 25, 10, 5, 0.5
M, respectively, (lane 6) DNA alone (hv); (lane 7) DNA alone (no h );
(d) DNA photocleavage by BS at various concentrations for 1 h. (Lane 1–5), BS at concentration of 50, 25, 5, 0.2
M, respectively, (lane 6), DNA alone (h ); lane 7, DNA alone (no
); (e) DNA photocleavage by BR at various concentrations for 1 h. (Lane 1–5), BR at concentration of 50, 25, 10, 5
M, respectively, Lane 6, DNA alone (h ); (lane 7), DNA
alone (no h M, respectively, (lane 6), DNA alone (h ); (lane
); (f) DNA photocleavage by CS at various concentrations for 1 h. Lane 1–5, CS at concentration of 50, 25, 10, 0.5
7), DNA alone (no h ).
l
m
m
l
m
m
l
m
l
m
h
m
l
m
m
l
m
m
Figure 5. Mechanism experiments of photocleavage for AS, BS, BR and CS. (a) (Lane 1–3) DNA and AS in the presence of histidine (6 mM), dithiothreitol (DTT, 30 mM), ethanol
(1.7 M), respectively; (lane 4), DNA and As; (lane 5) DNA alone (h ); (lane 6) DNA alone (no h
); (b) (lane 1–3), DNA and BS in the presence of histidine (6 mM), DTT (30 mM),
ethanol (1.7 M), respectively; (lane 4), DNA and BS; (lane 5), DNA alone (h ); (c) (lane 1–3), DNA and BR in the presence of histidine (6 mM), DTT
); (lane 6), DNA alone (no h
(30 mM), ethanol (1.7 M), respectively; (lane 4), DNA and BR; (lane 5), DNA alone (h ); (d) (lane 1–3), DNA and CS in the presence of histidine
); (lane 6), DNA alone (no h
(6 mM), DTT (30 mM), ethanol (1.7 M), respectively; (lane 4), DNA and CS; (lane 5), DNA alone (h
); (lane 6), DNA alone (no h ).
m
m
m
m
m
m
m
m

Q. Yang et al. / Bioorg. Med. Chem. Lett. 18 (2008) 6210–6213
6213
br, 1H), 3.41 (s, br, 1H), 4.26–4.30 (m, 1H), 4.48–4.51 (m, 1H), 7.58–7.61 (m,
3H), 7.89–7.93 (dd, J1 = 8.0 Hz, J2 = 7.6 Hz, 1H), 8.33–8.36 (m, 2H), 8.63–8.66
(m, 2H), 8.98 (s, 1H), ESI-HRMS: Calcd for C26H23N3O3 (M+H+): 426.1818,
Fok Ying Tong Education Fund (101072), the State Key Laboratory
of Bioreactor Engineering at East China University of Science and
Technology, and Shanghai Institute of Organic Chemistry, Chinese
Academy of Sciences, China.
found: 426.1801. IR (KBr): 3061, 2964, 2799, 1701, 1662, 1362 cmÀ1
.
[a] = À18.74 (C = 0.002, CHCl3).
Bx: 219.2–219.5 °C. 1H NMR (d6-DMSO) d (ppm): 1.06–1.10 (t, J = 7.6 Hz,
3H), 1.63–1.76 (m, 4H), 2.19 (s, br, 1H), 2.37–2.41 (m, 1H), 2.87–2.95 (m,
2H), 3.06 (s, br, 1H), 3.97–4.00 (m, 1H), 4.08–4.13 (m, 1H), 7.62–7.66 (m,
2H), 7.93–7.96 (dd, J1 = 7.6 Hz, J2 = 8.0 Hz, 1H), 8.21 (s, br, 1H), 8.50–8.52 (d,
J = 7.6 Hz, 1H), 8.56–8.62 (m, 2H), 9.24 (s, 1H), ESI-HRMS: calcd for
C25H22N2O2S (M+H+): 415.1480, found: 415.1469 IR (KBr): 2963, 2796,
References and notes
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6846.
BR: 215.1–215.2 °C.1H NMR (d6-DMSO) d (ppm): 1.23 (s, br, 3H), 1.83 (s, br,
4H), 3.21 (s, br, 4H), 3.62 (s, br, 1H), 4.41 (s, br, 2H), 7.67–7.70 (m, 2H),
8.02–8.05 (dd, J1 = 8.4 Hz, J2 = 6.8 Hz, 1H), 8.28–8.30 (m, 1H), 8.59–8.61(d,
J = 7.2 Hz, 1H), 8.72–8.73 (m, 2H), 9.40 (s, 1H), ESI-HRMS: calcd for
C25H22N2O2S (M+H+): 415.1480, found: 415.1481, IR (KBr): 3054, 2963,
2796, 2621, 1698, 1659, 1335 cmÀ1. [
a] = +6.63 (C = 0.002, CHCl3).
BS: 222.6–222.7 °C.1H NMR (d6-DMSO) d (ppm): 1.23 (s, br, 3H), 1.76 (s, br,
4H), 2.99–3.18 (m, 3H), 3.32–3.42 (m, 2H), 4.13–4.16 (m, 1H), 4.43–4.50 (m,
1H), 7.66–7.69 (m, 2H), 8.01–8.03 (dd, J1 = 8.0 Hz, J2 = 8.0 Hz, 1H), 8.26–8.28
(m, 1H), 8.58–8.60 (d, J = 6.0 Hz, 1H), 8.70 (s, br, 2H), 9.37 (s, 1H), ESI-HRMS:
calcd for C25H22N2O2S (M+H+): 415.1480, found: 415.1497 IR (KBr): 3052,
2963, 1697, 1659, 1335 cmÀ1. [
Cx: 210.0–211.0 °C. 1H NMR (d6-DMSO)
a
] = À3.54 (C = 0.001, CHCl3).
d
(ppm): 1.14–1.17 (t, J = 7.6 Hz,
3H), 1.72–1.89 (m, 4H), 2.60–2.73 (m, 2H), 3.10–3.40 (m, 3H), 4.14–4.22 (m,
2H), 7.46–7.57 (m, 3H), 7.70–7.72 (d, J = 8.8 Hz, 1H), 8.29–8.31 (d, J = 8.0 Hz,
1H), 8.41–8.50 (m, 3H), ESI-HRMS: calcd for C25H22N2O2S (M+H+): 415.1480,
found: 415.1487; IR (KBr): 2964, 1690, 1647, 1368 cmÀ1
.
CR: 217.2–217.9 °C. 1H NMR (d6-DMSO) d (ppm): 1. 33 (s, br, 3H), 1.73–1.94
(m, 3H), 2.13 (s, br, 1H), 3.17 (s, br, 2H), 3.60 (s, br, 3H), 4.37 (s, br, 1H),
4.49 (s, br, 1H), 7.49–7.59 (m, 3H), 7.73–7.75 (d, J = 7.6 Hz, 1H), 8.33–8.35
(d, J = 7.6 Hz, 1H), 8.44–8.53 (m, 3H), ESI-HRMS: calcd for C25H22N2O2S
(M+H+): 415.1480, found: 415.1476 IR (KBr): 2964, 1690, 1649, 1369 cmÀ1
.
[a] = +5.91 (C = 0.001, CHCl3).
CS: 198.4–198.6 °C. 1H NMR (d6-DMSO) d (ppm): 1.23 (s, br, 3H), 1.75–1.97
(m, 4H), 2.86 (s, br, 2H), 3.34–3.52 (m, 3H), 4.20 (s, br, 1H), 4.34 (s, br, 1H),
7.48–7.58 (m, 3H), 7.74–7.76 (d, J = 8.0 Hz, 1H), 8.31–8.33 (d, J = 8.4 Hz, 1H),
8.45–8.50 (m, 3H); ESI-HRMS: calcd for C25H22N2O2S (M+H+): 415.1480,
found: 415.1481; IR (KBr): 2964, 1688, 1648, 1366 cmÀ1
(C = 0.001, CHCl3).
. [a] = À4.65
Dx: M.p.: 204.9–205.2 °C. 1H NMR (d6-DMSO) d (ppm): 1.32 (s, 3 H), 1.84–
2.08 (m, 4 H), 2.22 (m, 1 H), 2.39 (m, 1 H), 3.18 (br, 1 H), 3.63–3.77 (m, 2H),
4.41–4.57 (br, 2 H), 7.67 (m, 3 H), 8.04–8.08 (t, J1 = 8.0 Hz, J2 = 7.6 Hz, 1 H),
8.22–8.23 (m, 2 H), 8.60–8.61 (d, J = 7.2 Hz, 1 H), 8.71–8.73 (d, J = 8.4 Hz,
1 H), 9.00 (s, 1 H). ESI-HRMS: calcd for C26H23N3O2S (M+H+): 442.1589,
12. Zhu, H.; Huang, M.; Yang, F.; Chen, Y.; Miao, Z.; Qian, X.; Xu, Y.; Qin, Y.; Luo, H.;
Shen, X.; Geng, M.; Cai, Y.; Ding, J. Molec. Cancer Therapeut. 2007, 6, 484.
13. Li, Y.; Xu, Y.; Qian, X.; Qu, B. Bioorg. Med. Chem. Lett. 2003, 13, 3513.
14. Qian, X.; Li, Y.; Xu, Y.; Qu, B. Bioorg. Med. Chem. Lett. 2004, 14, 2665.
15. Xu, Y.; Qu, B.; Qian, X.; Li, Y. Bioorg. Med. Chem. Lett. 2005, 15, 1139.
16. Ax: 204.1–204.5 °C. 1H NMR (CDCl3) d (ppm): 1.40 (s, br, 3H), 1.86–2.10 (m,
4H), 2.53 (s, br, 1H), 2.79 (s, br, 1H), 3.22–3.51 (m, br, 3H), 4.40 (s, br, 1H), 4.63
(s, br, 1H), 7.59–7.62 (m, 3H), 7.91–7.95 (dd, J1 = 7.6 Hz, J2 = 7.6 Hz, 1H), 8.35–
8.38 (m, 2H), 8.66–8.68 (m, 2H), 9.01 (s, 1H), ESI-HRMS: calcd for C26H23N3O3
(M+H+): 426.1818, found: 426.1814. IR (KBr): 3062, 2962, 2853, 1702, 1662,
found: 442.15997. IR (KBr): 3063, 2938, 2873, 1699, 1655, 1348 cmÀ1
.
DR: Mp.: 198.9–199.3 °C. 1H NMR (d6-DMSO) d (ppm): 1.29 (s, 3 H), 1.87 (br,
s, 4 H), 2.21 (br, 1 H), 2.392 (br, 1 H), 3.18 (br, 1 H), 3.62 (br, s, 2 H), 4.44 (br,
1 H), 4.57 (br, s, 1 H), 7.63–7.66 (m, 3 H), 8.02–8.03 (t, J1 = 8.0 Hz, J2 = 7.6 Hz,
1 H), 8.20–8.22 (m, 2 H), 8.60–8.58 (d, J = 8.8 Hz, 1 H), 8.69–8.71 (d,
J = 8.0 Hz, 1 H), 8.98 (s, 1 H).
calcd for C26H23N3O2S (M+H+): 442.1589, found: 442.1589. IR (KBr): 3062,
2964, 1699, 1659, 1332 cmÀ1
DS: Mp.: 178.9–179.4 °C. 1H NMR (d6-DMSO)
[a] = +13.54 (C = 0.001, CHCl3). ESI-HRMS:
.
1345 cmÀ1
.
d
(ppm): 1.33–1.37 (t,
AR: 194.4–194.9 °C.1H NMR (CDCl3) d (ppm): 1.39 (s, br, 3H), 1.85–2.09 (m,
4H), 2.56 (s, br, 1H), 2.79 (s, br, 1H), 3.25–3.52 (m, 3H), 4.36–4.39 (m, 1H), 4.62
(s, br, 1H), 7.60–7.62 (m, 3H), 7.91–7.95 (dd, J1 = 7.6 Hz, J2 = 7.6 Hz, 1H), 8.35–
8.37 (m, 2H), 8.65–8.67 (m, 2H), 9.00 (s, 1H), ESI-HRMS: calcd for C26H23N3O3
(M+H+): 426.1818, found: 426.1830; IR (KBr): 3062, 2964, 2798, 1701, 1662,
J1 = 7.6 Hz, J2 = 6.8 Hz, 3 H), 1.84–2.08 (m, 4 H), 2.21 (m, 1 H), 2.38 (m,
1 H), 3.18 (br, 1 H), 3.62–3.77 (m, 2 H), 4.41–4.44 (m, 1 H), 4.52–4.58 (m,
1 H), 7.67 (m, 3 H), 8.04–8.08 (t, J1 = 8.4 Hz, J2 = 7.6 Hz, 1 H), 8.22–8.23 (m,
2 H), 8.60–8.62 (d, J = 7.6 Hz, 1 H), 8.72–8.74 (d, J = 8.0 Hz, 1 H), 9.00 (s, 1 H);
[
a
] = À6.54 (C = 0.001, CHCl3). ESI-HRMS: calcd for C26H23N3O2S (M+H+):
1361 cmÀ1. [
a] = +15.91 (C = 0.002, CHCl3).
442.1589, Found: 442.1576. IR (KBr): 2923, 2852, 1701, 1661, 1334 cmÀ1
.
AS: 182.3–183.8 °C. 1H NMR (CDCl3) d (ppm): 1.26–1.30 (t, J = 6.4 Hz, 3H),
17. Gupta, M.; Ali, R. J. Biochem. 1984, 95, 1253.
1.81–2.02 (m, 4H), 2.44 (s, br, 1H), 2.66 (s, br, 1H), 3.12 (s, br, 1H), 3.25 (s,