Esters and amides of 2,3-dimethoxy-8,9-methylenedioxy-benzo[i] phenanthridine-12-carboxylic acid: Potent cytotoxic and topoisomerase I-targeting agents

Article abstract of DOI:10.1016/j.bmc.2005.07.033

The exceptional topoisomerase I-targeting activity and antitumor activity of 5-(2-N,N-dimethylamino)ethyl-8,9-dimethoxy-2,3-methylenedioxy-5H-dibenzo[c,h] [1,6]naphthyridin-6-one (ARC-111, topovale) prompted studies on similarly substituted benzo[i]phenan

Full text of DOI:10.1016/j.bmc.2005.07.033

Bioorganic & Medicinal Chemistry 13 (2005) 6782–6794
Esters and amides of 2,3-dimethoxy-8,9-methylenedioxy-
benzo[i]phenanthridine-12-carboxylic acid: Potent cytotoxic
and topoisomerase I-targeting agents
Shejin Zhu,a Alexander L. Ruchelman,a Nai Zhou,b Angela A. Liu,b
Leroy F. Liub,c and Edmond J. LaVoiea,c,
*
aDepartment of Pharmaceutical Chemistry, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8020, USA
bDepartment of Pharmacology, The University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School,
Piscataway, NJ 08854, USA
cThe Cancer Institute of New Jersey, New Brunswick, NJ 08901, USA
Received 1 March 2005; accepted 22 July 2005
Available online 8 September 2005
Abstract—The exceptional topoisomerase I-targeting activity and antitumor activity of 5-(2-N,N-dimethylamino)ethyl-8,9-dime-
thoxy-2,3-methylenedioxy-5H-dibenzo[c,h][1,6]naphthyridin-6-one (ARC-111, topovale) prompted studies on similarly substituted
benzo[i]phenanthridine-12-carboxylic ester and amide derivatives. Among the benzo[i]phenanthridine-12-carboxylic esters evaluat-
ed, the 2-(N,N-dimethylamino)ethyl, 2-(N,N-dimethylamino)-1-methylethyl, and 2-(N,N-dimethylamino)-1,1-dimethylethyl esters
possessed similar cytotoxicity, ranging from 30 to 55 nM in RPMI8402 and KB3-1 cells. Several of the carboxamide derivatives
possess potent topoisomerase I-targeting activity and cytotoxicity. The 2-(N,N-dimethylamino)ethyl, 2-(N,N-diethylamino)ethyl,
and 2-(pyrrolidin-1-yl)ethyl amides were among the more cytotoxic benzo[i]phenanthridine-12-carboxylic derivatives, with IC50
values ranging from 0.4 to 5.0 nM in RPMI8402 and KB3-1 cells.
ꢀ 2005 Elsevier Ltd. All rights reserved.
1. Introduction
irinotecan are substrates for efflux transporters associated
with multidrug resistance8–11 have prompted studies on
the development of novel TOP1-targeting agents.
Topoisomerase I (TOP1) is an effective molecular target
for the development of clinically useful anticancer
agents.1–4 TOP1-targeting agents, such as camptothecin,
stabilize the cleaved complex, which forms between the
enzyme and DNA. Stabilization of this ternary complex
effectively converts TOP1 into a cellular poison. Extensive
studies on camptothecin and its structurally related ana-
logues have resulted in two clinical TOP1-targeting drugs,
topotecan (Hycamtinꢁ) and irinotecan (CPT-11/Cam-
ptosarꢁ), Chart 1. These clinical agents have the campto-
thecin ring system that has incorporated within its
structure a d-lactone. Hydrolysis of this lactone results
in an inactive derivative that possesses high affinity for
human serum albumin.5–7 Metabolic instability of this
lactone and the observation that both topotecan and
Substituted benzo[i]phenanthridines and dibenzo-
[c,h]cinnolines have been identified as TOP1-targeting
agents with cytotoxic activity to several human tumor cell
lines.12–16 Studies in our laboratory have demonstrated
that dibenzo[c,h][1,6]naphthyridin-6-one 1 (ARC-111,
topovale) and the isoquino[4,3-c]cinnolin-12-one
2
(Fig. 1) possess exceptional TOP1-targeting activity and
cytotoxicity.17–25 Our laboratory has recently reported
on the TOP1-targeting activities and cytotoxicities
of both the 2-(N,N-dimethylamino)ethyl ester 7b
and amide 9a of 2,3-dimethoxy-8,9-methylenedioxy-
benzo[i]phenanthridine-12-carboxylic acid, as well as on
the biological activity of their propyl homologues.26
These derivatives bear significant structural similarity
to 1, Figure 1. We provide, herein, insight into the
structure–activity relationships observed for these
benzo[i]phenanthridine-12-carboxylic acid derivatives
and detail the synthetic methods used for their
preparation.
Keywords: Topoisomerase I; Cytotoxic; Antitumor; Benzo[i]-
phenanthridine.
*
Corresponding author. Tel.: +1 732 445 2674; fax: +1 732 445
6312; e-mail: elavoie@rci.rutgers.edu
URL: http://medchem.rutgers.edu/Faculty/LaVoie.htm
0968-0896/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.07.033

S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
6783
CH3
O
O
CH2CH3
CH2N
N
N
CH3
HO
O
O
N
N
N
N
O
O
CH3CH2
CH3CH2
OH
O
OH
O
Irinotecan (Camptosar®)
Topotecan (Hycamtin®)
Chart 1. Structures of topotecan and irinotecan.
Method B when the transesterification was performed
using a primary alcohol.
N
N
O
O
N
N
N
O
O
H3CO
H3CO
H3CO
H3CO
Initial studies using the Heck reaction for cyclizing 6a
and 6b resulted in the formation of several products.
In view of the difficulties encountered in separating the
desired benzo[i]phenanthridine derivative from these
undesired by-products, photocyclization was primarily
employed in the preparation of these benzo[i]phenan-
thridine derivatives. In contrast to intermediates 6a–d
as well as 7a, the cyclized esters 7b–e were notably more
labile and significant losses were observed during col-
umn chromatographic purification.
CH2CH2
N
H3C
CH2CH2
N
H3C
O
CH3
O
CH3
2
1
N
O
O
N
O
H3CO
H3CO
H3CO
H3CO
O
Three methods, as outlined in Scheme 3, were examined
for the preparation of select amide derivatives of 2,3-di-
methoxy-8,9-methylenedioxybenzo[i]phenanthridine-12-
carboxylic acid. Method C involved the reaction of the
acid chloride of 5 with the appropriate amine to form
the acrylamides 8a–d, which were then photocyclized
to provide the benzo[i]phenanthridine derivatives 9a–d.
Alternatively, the 12-carboxyethyl ester benzo[i]phenan-
thridine derivative 7a was heated in the presence of
various ethylamines (Method D) to form the benzo[i]-
phenanthridine 12-carboxamides 9a, 9e–j. The ethyl
ester 7a could be readily converted to the carboxylic acid
10 in almost quantitative yields. While the poor solubil-
ity of this acid limited its versatility as an intermediate in
these syntheses, it could be converted in neat SOCl2 to
form the acid chloride. As outlined for Method E, this
acid chloride was allowed to react with N,N-dimethy-
lethylenediamine or N,N-dimethyl-1,3-propanediamine
to form 9a and 9k, respectively.
O
O
CH2CH2
N
O
N
H
CH2CH2
CH3
N CH3
H3C
CH3
9a
7b
Figure 1. The structures of 8,9-dimethoxy-5-[(2-N,N-dimethylami-
no)ethyl]-2,3-methylenedioxydibenzo[c,h][1,6]naphthyridin-6-one, ARC-
111 (topovale), and 2,3-dimethoxy-11-[(2-N,N-dimethylamino)ethyl]-8,9-
methylenedioxyisoquino[4,3-c]cinnolin-12-one, 2 and the 2-(N,N-di-
methylamino)ethyl ester 7b and amide 9a of 2,3-dimethoxy-8,9-meth-
ylenedioxybenzo[i]phenanthridine-12-carboxylic acid.
2. Chemistry
Several derivatives of 2,3-dimethoxy-8,9-methylene-
dioxybenzo[i]phenanthridine-12-carboxylic acid were
synthesized using 3-(6,7-methoxyquinolin-4-yl)-2-(2-iodo-
4,5-dimethoxyphenyl)acrylic acid, 5, as the universal inter-
mediate. Compound 5 was prepared, as illustrated in
Scheme 1. 6,7-Methylenedioxy-4-methylquinoline 3 was
prepared from commercially available 3,4-methylenedioxy-
aniline. Oxidation of 3 with SeO2 provided 4-formyl-6,
7-dimethoxyquinoline, 4. Condensation of 4 with 2-iodo-
4,5-dimethoxyphenylacetic acid in acetic anhydride in the
presence of triethylamine26 provided 5 in good yield.
The preparation of select tertiary amides was carried out
using either N,N,N0-trimethylethylenediamine, as illus-
trated in Method C for the preparation of 9d or by
alkylation of the benzo[i]phenanthridine carboxamide
9a, as illustrated in Scheme 4 to form the bis-2-(N,N-
dimethylamino)ethyl derivative 9l.
Two methods were utilized for the synthesis of targeted
ester derivatives of 2,3-dimethoxy-8,9-methylenedioxy-
benzo[i]phenanthridine-12-carboxylic acid, which are
shown in Scheme 2. Method A involved the formation
of the acid chloride of 5 using thionyl chloride and having
this intermediate react with the requisite alcohol to form
6a–d. The resulting ester was then photocyclized in aceto-
nitrile to provide benzo[i]phenanthridines 7a–d. Alterna-
tively, one could use 7a as a common intermediate
(Method B) and by transesterification prepare various
ester derivatives. Acceptable yields were obtained using
3. Pharmacology
The TOP1-targeting activity and cytotoxicity of these
varied ester and amide derivatives of 2,3-dimethoxy-
8,9-methylenedioxybenzo[i]phenanthridine-12-carboxyl-
ic acid are given in Table 1. In general, the ester deriva-
tives were significantly less potent than topotecan as
TOP1-targeting agents. Of the five esters that were syn-
thesized, only 7c had comparable activity to topotecan
as a TOP1-targeting agent. The other ester derivatives

6784
S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
CH3
CHO
N
b
a
O
O
O
O
O
O
65%
44%
NH2
N
3
4
3,4-Methylenedioxyaniline
c
OCH3
OCH3
HO2C
CO2H
OCH3
OCH3
73%
I
O
O
I
N
5
Scheme 1. Reagents: (a) Methyl vinyl ketone, FeCl3, AcOH (b) SeO2, dioxane, H2O (c) Ac2O, TEA.
Method A
R
O
O
C
CO2H
CO2R
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
a
b
O
O
O
O
O
O
I
I
N
N
N
6a R = C2H5
6b R = CH2CH2N(CH3)2
7a R = C2H5
7b R = CH2CH2N(CH3)2
5
6c R =CH(CH3)CH2N(CH3)2
6d R = C(CH3)2CH2N(CH3)2
7c R = CH(CH3)CH2N(CH3)2
7d R = C(CH3)2CH2N(CH3)2
R
O
Method B
O
C
CO2Et
OCH3
OCH3
OCH3
O
O
c
OCH3
O
O
N
N
7b R = CH2CH2N(CH3)2
7e R = CH2CH2CH2N(CH3)2
7a
Scheme 2. Reagents: (a) SOCl2, then ROH (b) hm, MeCN (c) ROH neat.
7a, 7b, 7d, and 7e were 5- to 10-fold less potent in their
ability to stabilize the cleavable complex formed between
TOP1 and DNA. A representative gel of the stimulation
of enzyme-mediated DNA cleavage observed with 7b
and 7c, relative to topotecan, is provided in Figure 2.
Among the 12-carboxamides evaluated, 9c was the most
potent TOP1-targeting agent with potency greater than
that of topotecan. As in the case of 7c, this amide deriv-
ative was substituted with a 2-(N,N-dimethylamino)-1-
methylethyl substituent. Several other secondary alkyl
amide derivatives exhibited TOP1-targeting activity
equal to or greater than that of topotecan, including
9a, 9b, and 9e. Tertiary amide derivatives of 9a, where
there is either the addition of a N-methyl substituent 9d
or a second N-(2-N,N-dimethylamino)ethyl substituent
9l on the amide nitrogen atom, had significantly dimin-
ished activity as TOP1-targeting agents. Figure 2 shows
the enzyme-mediated DNA cleavage associated with
the presence of 9a, 9d, and topotecan.
turally related to ARC-111 demonstrated that the pres-
ence of one or more N-benzyl substituents on the
2-(amino)ethyl moiety significantly reduces TOP1-tar-
geting activity.25 A similar loss in activity was observed
for the 2-(N-benzylamino)ethyl and 2-(N,N-dibenzyl-
amino)ethyl amides 9f and 9g, respectively. It is of inter-
est to note that extension of the alkyl side chain from
2-carbons to 3-carbons in the case of ARC-111 resulted
in a significant loss of biological activity. In the case of
amide derivatives, a similar loss of activity was observed
when comparing the relative potency of 9a to that of the
3-(N,N-dimethylamino)propyl amide 9k. These data
suggest that the relationship between the distance be-
tween the amide nitrogen and the tertiary alkylamino
substituent may be more critical than the absolute
spatial distance of these substituents, relative to the
backbone of their polycyclic structures.
The TOP1-targeting activities of both 2-(pyrrolidin-1-
yl)ethyl and 2-(4-methylpiperazin-1-yl)ethyl substituted
12-carboxamides, 9h and 9j, of 2,3-dimethoxy-8,9-meth-
ylenedioxybenzo[i]phenanthridine were greater than
Previous studies performed with various N-alkyl 5-(2-
aminoethyl)dibenzo[c,h][1,6]naphthyridin-6-ones struc-

S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
6785
Method C
R'
R'
N R
N
R
O
N
C
O
CO2H
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
a
b
O
O
O
O
O
O
I
I
N
N
9a R = CH2CH2N(CH3)2; R' = H
5
8a R = CH2CH2N(CH3)2; R' = H
9b R = CH(CH3)CH2N(CH3)2; R' = H
9c R = CH2CH(CH3)N(CH3)2; R' = H
9d R = CH2CH2N(CH3)2; R' = CH3
8b R = CH(CH3)CH2N(CH3)2; R' = H
8c R = CH2CH(CH3)N(CH3)2; R' = H
8d R = CH2CH2N(CH3)2; R' = CH3
Method D
H
CO2Et
O
N
N CH2CH2R
OCH3
OCH3
OCH3
O
O
c
OCH3
O
O
N
7a
9a R = N(CH3)2
9e R = N(CH2CH3)2
9f R = NCH3(Bn)
9g R = N(Bn)2
9h R = N(-CH2CH2CH2CH2-)
9i R = N(-CH2CH2CH2CH2CH2-)
9j R = N-CH2CH2N(CH3)CH2CH2-)
Method E
CO2H
NHR
O
C
CO2Et
OCH3
OCH3
OCH3
OCH3
OCH3
a
O
O
d
O
O
O
OCH3
N
O
N
N
10
7a
9a R = CH2CH2N(CH3)2
9k R = CH2CH2CH2N(CH3)2
Scheme 3. Reagents: (a) SOCl2, then RNH2 (b) hm, MeCN (c) RNH2, (d) NaOH, H2O, EtOH.
CH2CH2N(CH3)2
CH2CH2N(CH3)2
O
NH
O
N
CH2CH2N(CH3)2
OCH3
OCH3
OCH3
a
O
O
O
O
OCH3
N
N
9l
9a
Scheme 4. Reagents: (a) NaH, NaI, DMF, ClCH2CH2N(CH3)2 Æ HCl.
that observed for topotecan. The 2-(piperdin-1-yl)ethyl
9i was somewhat less potent as a TOP1-targeting agent
than topotecan. These data suggest that the presence of
a piperazinyl substituent does not appear to negatively
impact TOP1-targeting activity to the extent observed
previously in a comparison of various heterocycles
attached to the 2-position of the ethyl substituent of
5-ethyldibenzo[c,h][1,6]naphthyridin-6-ones.25
RPMI8402 and P388 cells, their relative cytotoxicity in
these cell lines was significantly less than that observed
for ARC-111. The cytotoxic activities of these varied
12-carboxy esters in RPMI8402, U937, and P388 cells
were compared to those observed with their camptothe-
cin-resistant variants. In the case of RPMI8402 and
U937, a mutant form of TOP1 has been attributed to cam-
ptothecin resistance in their variant cell lines, CPT-K5
and U937/CR, respectively.27,28 The lack of expression
of topoisomerasein P388/CPT45 hasbeenassociated with
its resistance to camptothecin, relative to its parent cell
line P388.29 Cross-resistance to these cell lines by a cyto-
toxic agentis indicative ofTOP1as aprincipal targetasso-
The more cytotoxic of the 12-carboxy esters of 2,3-dime-
thoxy-8,9-methylenedioxybenzo[i]phenanthridine evalu-
ated were 7c and 7d. While these derivatives had
cytotoxicity comparable to that of topotecan in

Table 1. TOP1-targeting activity and cytotoxicity of ester and amide derivatives of 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-12-carboxylic acid
O
X
OCH3
O
OCH3
O
N
Compound
X
TOP1
Cytotoxicity IC50 (lM)
RPMI8402
wt
CPT-K5
CPT-resist.
P388
P388/CPT45
CPT-resist.
U937
U937/CR
CPT-resist.
KB3-1
wt
KBV-1 + MDR1
KBH5.0 + BCRP
1
0.3
10
5.0
1.0
8
0.002
0.085
0.03
0.90
>10
0.73
1.0
0.001
0.04
0.23
3.25
0.033
0.02
0.13
0.25
0.32
0.77
0.54
0.3
0.004
0.085
0.035
0.007
0.038
0.6
0.15
>10
0.14
0.03
0.40
1.35
2.15
0.35
0.66
0.85
1.3
0.005
0.06
0.005
0.31
0.22
0.10
0.23
2.3
0.006
0.12
0.072
0.065
0.11
0.52
0.06
0.02
0.05
0.9
7a
7b
7c
7d
7e
9a
9b
9c
9d
9e
9f
OCH2CH3
OCH2CH2N(CH3)2
0.014
0.02
0.04
0.034
0.055
0.045
0.47
OCH(CH3)CH2N(CH3)2
OC(CH3)2CH2N(CH3)2
OCH2CH2CH2N(CH3)2
NHCH2CH2N(CH3)2
0.03
0.04
2.25
1.5
6.5
0.5
0.6
0.4
10
0.7
12
60
0.6
1.5
0.3
5
0.22
0.27
0.003
0.0004
0.002
0.5
1.0
3.0
0.003
0.0007
0.002
0.15
0.006
0.002
0.003
0.22
0.005
0.003
0.006
0.45
0.22
0.32
0.11
1.8
NHCH(CH3)CH2N(CH3)2
NHCH2CH(CH3)N(CH3)2
N(CH3)CH2CH2N(CH3)2
NHCH2CH2N(CH2CH3)2
NHCH2CH2NCH3(Bn)
NHCH2CH2N(Bn)2
0.75
5.0
0.006
0.034
0.45
1.75
10
0.004
0.035
0.35
0.37
2.75
6.5
0.033
0.045
0.5
0.03
0.06
0.47
0.68
8.0
0.07
0.35
6.5
3.6
9g
9h
9i
>10
2.2
6.5
>10
>1.0
1.8
0.5
N(–CH2CH2CH2CH2–)
N(–CH2CH2CH2CH2CH2–)
N(–CH2CH2N(CH3)CH2CH2–)
NHCH2CH2CH2N(CH3)2
N[CH2CH2N(CH3)2]2
0.003
0.055
0.065
0.05
0.003
0.01
0.33
1.0
0.004
0.011
0.075
0.16
0.003
0.018
0.1
0.15
0.18
7.5
0.05
0.04
1.5
9j
5.0
2.1
0.045
0.03
0.13
1.35
0.34
2.6
2.25
2.78
2.8
9k
9l
0.045
0.25
0.038
4.5
2.0
0.5
3
0.17
0.021
2.0
0.13
0.024
0.65
0.55
TPT
1
>10
0.045
>10
0.21
0.47
Topoisomerase I cleavage values are reported as REC, relative effective concentration, i.e., concentrations relative to topotecan, whose value is arbitrarily assumed as 1, that are able to produce the same
cleavage on the plasmid DNA in the presence of human topoisomerase I.

S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
6787
of the tertiary amides 9d and 9l and the N-benzyl deriv-
atives 9f and 9g, these analogues were significantly less
cytotoxic, which correlates with their decreased activity
as TOP1-targeting agents. In the case of 9d, it is also of
significance that this N-methyl tertiary amide exhibited
the least differential cytotoxicity between P388 and its
P388/CPT45 variant. As observed with the 12-carboxy
ester 7e, elongation of the alkyl chain from ethyl to pro-
pyl, as in 9k, with these varied aminoalkyl amides of 2,
3-dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine
was associated with diminished cytotoxicity. While the
2-(piperidin-1-yl)ethyl amide 9i and the 2-(4-methylpi-
perazin-1-yl)ethyl amide 9j did exhibit a good TOP1-
targeting activity, they were not as cytotoxic as the
2-(pyrrolidin-1-yl)ethyl amide 9h.
7b
7c
9a
9d
TPT
Figure 2. Stimulation of enzyme-mediated DNA cleavage by topotec-
an (TPT), 7b, 7c, 9a, and 9d using human TOP1. The first lane is the
DNA control without enzyme. The second lane is the control with
enzyme alone. The rest of the lanes contain human TOP1 and serially
(10-fold each) diluted compound from 0.001 to 1.0 lM.
The cytotoxicity of these amides in KB3-1 and its vari-
ants KBV-1 and KBH5.0 clearly demonstrates that,
unlike ARC-111, these 12-carboxamide derivatives of 2,
3-dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine
are, in general, good substrates for MDR1. Among the
more cytotoxic derivatives, the relative difference in
cytotoxicity ranged from one to two orders of magni-
tude. Among the notable exceptions were the tertiary
amide derivatives 9d and 9l. Several of the carboxamide
derivatives were also substrates for the efflux transporter
BCRP. The diminished toxicity of 9a, 9g, 9h, 9i, 9j, and
9k in KBH5.0 as compared to KB3-1 suggests that these
derivatives are substrates for this efflux transporter.
ciated with its cytotoxic activity. The ethyl ester 7a exhib-
ited the greatest cross-resistance in all three of these pairs
of cell lines. While 7a has the lowest intrinsic TOP1-tar-
geting activity of these ester derivatives, the fact that it
is over 80-fold more cytotoxic in P388 than in P388/CR
cells indicates that its cytotoxicity is primarily associated
with its TOP1-targeting activity. The much lower relative
resistance observed for 7b, 7c, 7d, and 7e suggests that
mechanisms not associated with TOP1 may contribute
significantly to their cytotoxic activities. The cytotoxic
activities of the 12-carboxy esters of 2,3-dimethoxy-
8,9-methylenedioxybenzo[i]phenanthridine were also as-
sessed in KB3-1, and its two variants KBV-1 and
KBH5.0. The overexpression of the efflux transporters
MDR1 (p-glycoprotein) and BCRP has been observed
in KBV-1 and KBH5.0, respectively.19,30 The overexpres-
sion of these efflux transporters has been associated with
multidrug resistance. While none of these 12-carboxy es-
ters of 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phe-
nanthridine appeared to be an exceptionally good
substrate for either of these efflux transporters, the cyto-
toxic activities of these analogues in KBV-1 cells were
lower. The IC50 values obtained in this variant cell line
that overexpresses MDR1, with the exception of 7c, were
five to seven times higher than in the parent cell line,
KB3-1.
4. Discussion
The ester derivatives 2,3-dimethoxy-8,9-methylenedioxy-
benzo[i]phenanthridine-12-carboxylic acid were, in gener-
al, isolated in lower yield, exhibited greater chemical
instability, were less active as TOP1-targeting agents,
and were less cytotoxic than several of the amide deriv-
atives that were evaluated. The comparative cytotoxicity
observed in P388 and P388/CPT45 for these esters also
suggests that mechanisms other than TOP1-targeting
activity contribute to their cytotoxic activity. These fac-
tors, in addition to the likelihood that these esters could
be extensively hydrolyzed in vivo, diminished interest in
extending the structure–activity studies of this series of
compounds further. In contrast, several of the amide
derivatives did exhibit potent TOP1-targeting activity
and cytotoxicity. The comparative cytotoxic activities
observed in P388 and P388/CPT45 did reveal for several
of the more cytotoxic derivatives (with IC50 values rang-
ing from 1 to 30 nM) that TOP1-targeting activity was
clearly associated with their cytotoxic activity. These
amides also exhibited good chemical stability. These
more cytotoxic amides, in contrast to ARC-111, were
substrates for MDR1 and, with the exception of 9e, were
substrates for the efflux transporter BCRP.
Several of the 12-carboxamide derivatives of 2,3-dime-
thoxy-8,9-methylenedioxybenzo[i]phenanthridine had
greater intrinsic TOP1-targeting activity and cytotoxici-
ty than either the 12-carboxyester derivatives or topotec-
an. In RPMI8402, U937, P388, and KB3-1 cell lines,
9a–c and 9h were consistently among the more cytotoxic
analogues, with IC50 values ranging from 1 to 6 nM.
While the 2-(piperidin-yl)ethyl amide 9i and the 2-(4-
methylpiperazin-yl)ethyl amide 9j did exhibit good
TOP1-targeting activity, they were not as cytotoxic as
the 2-(pyrrolidin-1-yl)ethyl amide 9h. In comparing the
2-(N,N-dimethylamino)ethyl ester 7b with the 2-(N,N-
dimethylamino)ethyl amide 9a, it is evident that the
amide derivative is significantly more cytotoxic in each
of these parent cell lines. Particularly noteworthy is
the fact that several of the secondary amides clearly
mediate their cytotoxic activity primarily through inter-
action with TOP1, as indicated in differential cytotoxic-
ity observed in P388, relative to P388/CPT45. In the case
Thus, these carboxamides, as is the case for topotecan
and irinotecan, are substrates for efflux transporters
that have been associated with multidrug resistance.
Studies will be performed to assess the relative efficacy
of these carboxamides in vivo as novel non-camptothecin
TOP1-targeting antitumor agents. The absence of a labile

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S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
d-lactone, as in the case of topotecan and irinotecan, that
can limit the amount of active drug and limit distribution
by virtue of the protein binding of their hydrolysis prod-
uct to serum albumin provides a basis for examining their
potential therapeutic advantages. Thus, amide deriva-
tives of 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phe-
nanthridine represent a series of compounds that have
the potential for further development as novel and clini-
cally useful TOP1-targeting agents.
ethyl ether, yielding 16.6 g as a fluffy light beige solid,
in 44% yield; mp: 100.5–101.5 ꢂC; H NMR (CDCl3) d
2.51 (s, 3H), 6.04 (s, 2H), 7.02 (d, 1H, J = 4.4), 7.13 (s,
1H), 7.32 (s, 1H), 8.52 (d, 1H, J = 4.4); 13C NMR
(CDCl3) d 19.1, 99.3, 101.7, 106.3, 120.6, 125.0, 142.9,
146.3, 147.8, 147.9, 150.2; HRMS calcd for
C11H9O2N, 187.0633; found: 187.0627.
1
4-Formyl-6,7-methylenedioxyquinoline (4). A mixture of 3
(5.01 g, 27 mmol) in 30 ml dioxane was heated to 75 ꢂC
and then a solution of SeO2 in 5:1 dioxane–H2O (36 ml)
was added dropwise. The mixture was heated to reflux
with stirring for 4.5 h, filtered, and the filtrate was evapo-
rated. The residue was dissolved in chloroform (50 ml),
washed with water (3 · 50 ml), dried (MgSO4), and evap-
orated. The residue was chromatographed, eluted with
CHCl3, yielding 3.48 g as a beige solid in 65% yield; mp:
5. Experimental
Melting points were determined with a Meltemp capil-
lary melting point apparatus. Column chromatography
refers to flash chromatography conducted on SiliTech
32–63 lm (ICN Biomedicals, Eschwege, Ger.) using
the solvent systems indicated. The photolysis apparatus
employed consisted of a 1000 ml reactor with a 450 W
mercury-vapor lamp with a 131.5 mm arc length as pur-
chased from Ace Glass, Inc. Infrared spectral data were
obtained using a Thermo-Nicolet Avatar 360 Fourier
transform spectrometer and are reported in cmꢀ1. Pro-
ton (1H NMR) and carbon (13C NMR) nuclear magnet-
ic resonance were recorded on a Varian Gemini-200
Fourier Transform spectrometer. NMR spectra
1
146.0–147.5 ꢂC; IR (CHCl3) 1702; H NMR (CDCl3) d
6.18 (s, 2H), 7.45 (s, 1H), 7.63 (d, 1H, J = 4.4), 8.41 (s,
1H), 8.96 (d, 1H, J = 4.4), 10.35 (s, 1H); 13C NMR
(CDCl3) d 100.4, 102.3, 106.3, 121.4, 124.7, 135.7, 148.0,
148.3, 150.8, 151.0, 193.4; HRMS calcd for C11H7O3N,
201.0426; found: 201.0437.
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid (5). A mixture of 4 (400 mg,
2.0 mmol) and 2-iodo-4,5-dimethoxyphenylacetic acid33
(966 mg, 3.0 mmol) in acetic acid (3.5 ml) and TEA
(0.31 ml) was heated to reflux with stirring for 90 min.
The mixture was cooled to about 70 ꢂC, poured into
water, and the resulting mixture was stirred for 30 min
with no additional heating. The entire mixture was then
evaporated under vacuum and the residue was chromato-
graphed eluting with 97:3 chloroform–methanol, to
provide 725 mg as a yellow solid, in 73% yield; mp:
1
(200 MHz H and 50 MHz 13C) were recorded in the
deuterated solvent indicated with chemical shifts report-
ed in d units downfield from tetramethylsilane (TMS).
Coupling constants are reported in hertz (Hz). Mass
spectra were obtained from Washington University Re-
source for Biomedical and Bio-organic Mass Spectrom-
etry within the Department of Chemistry at Washington
University, St. Louis, MO. All starting materials and re-
agents were purchased from Aldrich. Solvents were pur-
chased from Fisher Scientific and were of ACS grade or
HPLC grade. Methylene chloride was freshly distilled
from calcium hydride. All other solvents were used as
provided without further purification. The various
substituted amino alcohols and diamines employed,
with the exception of N,N-dimethyl-1,1-dimethyletha-
nolamine,31 N-methyl-N-benzylethylenediamine,25 and
2-(N,N-dimethylamino)propylamine, were commercially
available. Lithium aluminum hydride reduction of 2-
(dimethylamino)propionitrile32 provided 2-(N,N-dimethyl-
amino)propylamine.
1
270.5–271.5 ꢂC; IR (KBr) 1704; H NMR (DMSO-d6) d
3.47 (s, 3H), 3.72 (s, 3H), 6.24 (s, 2H), 6.67 (s, 1H),
6.83 (d, 1H, J = 4.7), 7.23 (s, 1H), 7.33 (s, 1H), 7.41 (s,
1H), 8.15 (s, 1H), 8.44 (d, 1H, J = 4.7); HRMS calcd
for C21H16INO6H, 506.0101; found: 506.0110.
5.1. General method for the preparation of esters of 3-(6,7-
methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimethoxyphe-
nyl)acrylic acid
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid ethyl ester (6a). Thionyl chloride
(5 ml) was added dropwise to a mixture of 5 (1.51 g,
3.0 mmol) in absolute ethanol (125 ml), and the mixture
was refluxed for 5 h with stirring. The mixture was
cooled and evaporated under vacuum. The residue was
dissolved in chloroform (250 ml) and washed with satd
NaHCO3 (3 · 250 ml), dried (MgSO4), evaporated, and
chromatographed eluting with chloroform, to provide
1.59 g in 99% yield, as an orange oil; IR (CHCl3) 1713;
1H NMR (CDCl3) d 1.31 (t, 3H, J = 7.0), 3.47 (s, 3H),
3.80 (s, 3H), 4.31 (q, 2H, J = 7.0), 6.07 (d, 2H), 6.39 (s,
1H), 6.71 (d, 1H, J = 4.6), 7.18 (s, 1H), 7.29 (s, 2H),
8.20 (s, 1H), 8.38 (d, 1H, J = 4.6); 13C NMR (CDCl3)
d 14.3, 55.9, 56.1, 61.8, 88.2, 99.6, 102.0, 106.4, 113.5,
119.1, 121.4, 123.6, 132.4, 136.4, 139.2, 140.2, 146.8,
147.5, 148.5, 149.3, 150.6, 166.0; HRMS calcd for
C23H20INO6H, 534.0419; found: 534.0412.
4-Methyl-6,7-methylenedioxyquinoline (3). Iron (III)
chloride (54.2 g, 0.2 mol) was dissolved in glacial acetic
acid (600 ml) with warming to 60 ꢂC. 3,4-Methylenedi-
oxyaniline (27.4 g, 0.2 mol) was added and the mixture
was stirred for 5 min. Methyl vinyl ketone (17.4 ml,
0.21 mol) was added dropwise over 5 min. Following
the completion of addition, the mixture was heated to
reflux with stirring for 1.5 h. The mixture was cooled
and the precipitate was filtered and washed with addi-
tional acetic acid. This material was then basified by
addition to cold 30% NaOH, and the resulting mixture
was filtered and air-dried. The crude material was then
extracted with chloroform (7 · 200 ml), and the com-
bined extracts were washed with 10% K2CO3
(3 · 300 ml), dried (MgSO4), and concentrated under
vacuum. The resulting material was recrystallized from

S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
6789
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid 2-(N,N-dimethylamino)ethyl ester
(6b). Prepared from the crude acid chloride of 5
(250 mg, 0.50 mmol) and N,N-dimethylethanolamine
(443 mg, 4.98 mmol) in 98% yield (280 mg) as an oil;
with additional acetonitrile. Thorough drying provided
7a in 51% yield (348 mg) as a yellow solid; mp: 250–
251 ꢂC (dec.); IR (KBr) 1716; 1H NMR (CDCl3 + 1 drop
CD3OD) d 1.48 (t, 3H, J = 7.1), 3.98 (s, 3H), 4.13 (s, 3H),
4.53 (q, 2H, J = 7.1), 6.26 (s, 2H), 7.73 (s, 1H), 7.93 (s,
1H), 8.11 (s, 1H), 8.18 (s, 1H), 8.70 (s, 1H), 10.24 (s,
1H); 13C NMR (CDCl3 + 1 drop CD3OD) d 14.2, 55.9,
56.6, 62.5, 99.5, 100.0, 102.9, 103.8, 106.6, 120.4, 121.2,
123.2, 124.7, 126.8, 131.8, 132.7, 135.0, 139.8, 151.4,
151.5, 152.3, 152.4, 166.7; HRMS calcd for
C23H19NO6H, 406.1290; found: 406.1270.
1
IR (CH2Cl2) 1714; H NMR (CDCl3) d 2.27 (s, 6H),
2.68 (t, 2H, J = 5.8), 3.55 (s, 3H), 3.85 (s, 3H), 4.41 (t,
2H, J = 5.8), 6.14 (s, 2H), 6.45 (s, 1H), 6.77 (d, 1H,
J = 4.8), 7.22 (s, 1H), 7.35 (s, 1H), 7.36 (s, 1H), 8.28 (s,
1H), 8.44 (d, 1H, J = 4.8); 13C NMR (CDCl3) d 45.9,
56.0, 56.2, 57.6, 64.1, 88.3, 99.6, 102.0, 106.5, 113.5,
119.1, 121.4, 123.7, 132.4, 136.7, 139.0, 139.9, 146.9,
147.6, 148.5, 149.3, 150.7, 166.0; HRMS calcd for
C25H25IN2O6H, 577.0836; found: 577.0836.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)ethyl ester (7b).
Prepared from 6b (220 mg, 0.38 mmol) in acetonitrile
(900 ml), reaction time (35 min), in 46% yield (79 mg) as
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid 2-(N,N-dimethylamino)-1-methyl-
ethyl ester (6c). Prepared from the crude acid chloride
of 5 (150 mg, 0.30 mmol) and 1-(N,N-dimethylamino)-
2-propanol (0.3 ml) in 80% yield (140 mg) as an oil; IR
(CH2Cl2) 1709; 1H NMR (CDCl3) d 1.40 (d, 3H,
J = 6.2), 2.31 (s, 6H), 2.55 (m, 2H), 3.57 (s, 3H), 3.87
(s, 3H), 5.28 (m, 1H), 6.16 (s, 2H), 6.49 (s, 1H), 6.79
(d, 1H, J = 4.8), 7.23 (s, 1H), 7.38 (s, 1H), 7.40 (s, 1H),
8.29 (s, 1H), 8.46 (d, 1H, J = 4.8); 13C NMR (CDCl3)
d 18.5, 46.1, 56.0, 56.2, 63.8, 70.4, 88.2, 99.7, 102.0,
106.5, 113.5, 119.1, 121.3, 123.7, 132.6, 136.5, 139.1,
140.2, 146.9, 147.6, 148.5, 149.3, 150.7, 165.5; HRMS
calcd for C26H27IN2O6H, 591.0992; found: 591.1007.
1
a yellow solid; mp: 216.5–217.5 ꢂC; IR (KBr) 1715; H
NMR (CDCl3) d 2.53 (s, 6H), 3.00 (t, 2H, J = 5.7), 4.12
(s, 3H), 4.18 (s, 3H), 4.70 (t, 2H, J = 5.7), 6.21 (s, 2H),
7.56 (s, 1H), 7.92 (s, 1H), 8.14 (s, 1H), 8.50 (s, 1H), 8.98
(s, 1H), 9.89 (s, 1H); 13C NMR (CDCl3) d 29.8, 45.6,
56.0, 57.8, 62.8, 97.3, 99.3, 102.1, 106.7, 107.4, 120.8,
122.3, 123.2, 124.9, 126.2, 128.5, 128.9, 142.6, 145.2,
148.9, 149.6, 150.3, 150.5, 167.5; HRMS calcd for
C25H24N2O6H, 449.1703; found: 449.1692.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)-1-methylethyl
ester (7c). Prepared from 6c (220 mg, 0.37 mmol) in ace-
tonitrile (900 ml), reaction time (35 min), in 24% yield
(41 mg) as a light yellow solid; mp: 211.0–211.5 ꢂC; IR
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid 2-(N,N-dimethylamino)-1,1-di-
methylethyl ester (6d). Prepared from the crude acid
chloride of 5 (505 mg, 1.0 mmol) and 1-(N,N-dimethyla-
mino)-2-methyl-2-propanol (0.7 ml) in 83% yield
(500 mg) as an oil; IR (CH2Cl2) 1709; 1H NMR (CDCl3)
d 1.63 (s, 6H), 2.15 (s, 6H), 2.48 (s, 2H), 3.54 (s, 3H), 3.85
(s, 3H), 6.14 (s, 2H), 6.42 (s, 1H), 6.77 (d, 1H, J = 4.4),
7.22 (s, 1H), 7.36 (s, 2H), 8.19 (s, 1H), 8.43 (d, 1H,
J = 4.4); 13C NMR (CDCl3) d 24.1, 47.7, 56.0, 56.2,
68.7, 85.0, 88.3, 99.6, 102.0, 106.5, 113.5, 119.1, 121.3,
123.8, 133.0, 135.6, 139.3, 141.5, 146.8, 147.6, 148.4,
149.2, 149.3, 150.6, 165.0; HRMS calcd for C27H29I-
N2O6H, 605.1149; found: 605.1156.
1
(KBr) 1704; H NMR (CDCl3) d 1.54 (d, 3H, J = 6.2),
2.41 (s, 6H), 2.55 (m, 1H), 2.85 (m, 1H), 4.11 (s, 3H),
4.19 (s, 3H), 5.54 (m, 1H), 6.21 (s, 2H), 7.57 (s, 1H),
7.92 (s, 1H), 8.17 (s, 1H), 8.46 (s, 1H), 8.94 (s, 1H),
9.92 (s, 1H); 13C NMR (CDCl3) d 18.8, 46.3, 56.1, 56.3,
64.6, 70.0, 99.3, 102.1, 106.8, 107.5, 120.9, 122.2, 122.7,
124.9, 126.2, 129.1, 129.7, 142.6, 145.3, 148.8, 149.6,
150.2, 150.5, 167.4; HRMS calcd for C26H26N2O6H,
463.1869; found 463.1868.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)-1,1-dimethyl-
ethyl ester (7d). Prepared from 6d (220 mg, 0.36 mmol)
in acetonitrile (900 ml), reaction time (30 min), in 25%
yield (43 mg) as a yellow solid; mp: 211–212 ꢂC (dec.);
5.2. General procedures for preparation of alkylamino ester
derivatives of 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phe-
nanthridine-12-carboxylic acid: (Method A and Method B)
1
IR (KBr) 1716; H NMR d 1.79 (s, 6H), 2.47 (s, 6H),
2.89 (s, 2H), 4.12 (s, 3H), 4.18 (s, 3H), 6.19 (s, 2H),
7.55 (s, 1H), 7.90 (s, 1H), 8.15 (s, 1H), 8.41 (s, 1H),
8.84 (s, 1H), 9.89 (s, 1H); 13C NMR (CDCl3) d 24.9,
45.9, 48.2, 56.0, 56.1, 85.1, 99.3, 102.1, 106.8, 107.4,
120.9, 122.0, 122.2, 124.8, 126.2, 129.2, 131.2, 142.5,
145.3, 148.8, 149.6, 150.1, 150.4, 167.4; HRMS calcd
for C27H28N2O6Li, 483.2107; found: 483.2126.
5.2.1. Method A. Cyclization of 3-(6,7-methylenedioxy-
quinolin-4-yl)-2-(2-iodo-4,5-dimethoxyphenyl)acrylic
esters.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid ethyl ester (7a). A solution of 6a
(450 mg, 0.85 mmol) in acetonitrile (800 ml) was trans-
ferred to the photoreactor apparatus and was degassed
by nitrogen purge for 30 min. The solution was then irra-
diated through a Vycor filter for 45 min. The mixture was
removed from the photoreactor, and an equal portion of
6a (450 mg, 0.85 mmol) in acetonitrile (800 ml) was
reacted according to the same procedure. The cyclized
product, which had precipitated out during the course
of the reaction, was isolated by filtration and washed
5.2.2. Method B. Transesterification of 5a to various ester
derivatives of 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phe-
nanthridine-12-carboxylic acid.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)ethyl ester (7b). A
mixture of 7a (30 mg, 0.074 mmol) and N,N-dimethyletha-
nolamine (10 ml); reaction temperature 134 ꢂC; reaction
time 12 h; 45% yield (15 mg) as a yellow solid; mp: 216.5–

6790
S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
217.5 ꢂC (dec.); IR (KBr) 1715; 1H NMR (CDCl3) d 2.53 (s,
6H), 3.00 (t, 2H, J = 5.7), 4.12 (s, 3H), 4.18 (s, 3H), 4.70 (t,
2H, J = 5.7), 6.21 (s, 2H), 7.56 (s, 1H), 7.92 (s, 1H), 8.14 (s,
1H), 8.50 (s, 1H), 8.98 (s, 1H), 9.89 (s, 1H); 13C NMR
(CDCl3) d 29.8, 45.6, 56.0, 57.8, 62.8, 97.3, 99.3, 102.1,
106.7, 107.4, 120.8, 122.3, 123.2, 124.9, 126.2, 128.5,
128.9, 142.6, 145.2, 148.9, 149.6, 150.3, 150.5, 167.5; HRMS
calcd for C25H24N2O6H, 449.1703; found: 449.1692.
1H), 7.32 (s, 1H), 7.43 (s, 1H), 8.26 (s, 1H), 8.40 (d,
1H, J = 4.6); 13C NMR (CDCl3) d 19.0, 44.3, 45.7,
56.0, 56.2, 64.2, 88.6, 100.0, 102.0, 106.3, 113.6, 118.8,
121.8, 124.0, 132.1, 133.2, 139.9, 142.2, 146.8, 147.5,
148.3, 149.6, 149.7, 150.6, 164.8; HRMS calcd for
C26H28IN3O5Li, 596.1234; found: 596.1264.
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid 2-(N,N-dimethylamino)propyl
amide (8c). Prepared from the crude acid chloride of 5
(250 mg, 0.5 mmol) and 2-(N,N-dimethylamino)propyl-
amine (250 mg, 2.44 mmol) to provide 280 mg of 8c as
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 3-(N,N-dimethylamino)propyl ester
(7e). Prepared from 7a (30 mg, 0.074 mmol) and 3-N,N-
dimethylaminopropanol (15 ml); reaction temperature
164 ꢂC; reaction time 16 h; 35% yield (12 mg) as a yellow
solid; mp: 226.5–227.5 ꢂC (dec.); IR (KBr) 1709; 1H
NMR (CDCl3) d 2.15–2.23 (m, 2H), 2.42 (s, 6H), 2.67
(t, 2H, J = 7.6), 4.12 (s, 3H), 4.19 (s, 3H), 4.60 (t, 2H,
J = 6.2), 6.21 (s, 2H), 7.59 (s, 1H), 7.94 (s, 1H), 8.19 (s,
1H), 8.52 (s, 1H), 8.98 (s, 1H), 9.94 (s, 1H); 13C NMR
(CDCl3) d 27.2, 29.8, 45.6, 56.1, 56.1, 56.5, 64.1, 99.3,
102.1, 106.7, 107.6, 120.9, 122.3, 123.0, 125.0, 126.3,
128.9, 129.0, 142.6, 145.4, 149.0, 149.7, 150.3, 150.6,
167.6; HRMS calcd for C26H26N2O6H, 463.1870; found:
463.1857.
1
a sticky glue in 92% yield; IR (CH2Cl2) 1665; H NMR
(CDCl3) d 0.95 (d, 3H, J = 6.6), 2.12 (s, 6H), 2.73 (m,
1H), 3.04 (m, 1H), 3.50 (m, 1H), 3.62 (s, 3H), 3.89 (s,
3H), 6.14 (s, 2H), 6.41 (s, 1H), 6.56 (s, 1H), 6.77 (d,
1H, J = 4.5), 7.27 (s, 1H), 7.36 (s, 1H), 7.45 (s, 1H),
8.29 (s, 1H), 8.44 (d, 1H, J = 4.5); 13C NMR (CDCl3)
d 10.3, 40.0, 42.7, 56.1, 56.3, 57.7, 88.6, 97.2, 100.0,
102.0, 106.4, 113.5, 118.9, 121.7, 124.0, 133.3, 133.1,
140.0, 142.1, 146.8, 147.5, 148.4, 149.6, 149.8, 150.6,
164.9; HRMS calcd for C26H28N3O5IH, 590.1152;
found: 590.1139.
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid N-methyl-N-[2-(dimethylamino)eth-
yl] amide (8d). Prepared from the crude acid chloride of 5
(250 mg, 0.5 mmol) and N-methyl-N-[2-(dimethylami-
no)ethylamine (408 mg, 4.00 mmol) to provide 280 mg
5.3. General procedure for the preparation of 3-(6,7-methy-
lenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimethoxyphenyl)acryl-
ic amides
1
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid 2-(N,N-dimethylamino)ethyl amide
(8a). The crude acid chloride of 5 (250 mg, 0.5 mmol)
was formed from thionyl chloride (4.0 ml) by heating
to reflux for 3 h. Excess thionyl chloride was removed
under vacuum. The residue was dissolved in CH2Cl2
(5.0 ml) and TEA (2.0 ml), and then was treated with
N,N-dimethylethylenediamine (402 mg, 4.55 mmol).
The suspension was heated to reflux overnight and then
cooled down to room temperature. More CH2Cl2 was
added, and the mixture was washed by satd NaHCO3,
water, and brine. The organic phases were dried over
sodium sulfate and evaporated, and the residue was puri-
fied by chromatography to provide 280 mg of 8a as a
8d as a sticky glue in 96% yield; IR (CH2Cl2) 1627; H
NMR (CDCl3) d 2.33 (s, 6H), 2.46 (s, 3H), 2.65 (br,
2H), 3.54 (s, 3H), 3.66 (t, 2H, J = 6.6), 3.82 (s, 3H),
6.11 (s, 2H), 6.71 (s, 1H), 6.73 (br, 1H), 7.14 (s, 1H),
7.31 (br, 2H), 7.35 (s, 1H), 8.41 (d, 1H, J = 4.8); 13C
NMR (CDCl3) d 38.7, 45.8, 46.5, 49.9, 55.9, 56.2, 86.3,
99.6, 102.0, 106.5, 114.7, 119.5, 121.9, 123.7, 130.5,
132.9, 140.2, 142.6, 147.0, 147.5, 148.4, 149.4, 149.4,
150.6, 169.6; HRMS calcd for C26H28IN3O5Li:
596.1234; found: 596.1249.
5.4. General procedures for the preparation of alkylamino
amides of 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phe-
nanthridine-12-carboxylic acid: Method C, Method D, and
Method E
1
sticky glue in 97% yield; IR (CH2Cl2) 1664; H NMR
(CDCl3) d 2.16 (s, 6H), 2.43 (t, 2H, J = 6.2), 3.42 (t,
2H, J = 6.2), 3.59 (s, 3H), 3.87 (s, 3H), 6.12 (s, 2H),
6.53 (s, 1H), 6.71 (d, 1H, J = 4.4), 7.25 (s, 1H), 7.34 (s,
1H), 7.41 (s, 1H), 8.28 (s, 1H), 8.41 (d, 1H, J = 4.4);
13C NMR (CDCl3) d 37.7, 45.2, 56.0, 56.3, 57.6, 88.6,
99.9, 102.0, 106.3, 113.5, 118.8, 121.8, 124.0, 132.0,
133.4, 139.9, 142.0, 146.8, 147.5, 148.4, 149.7, 149.8,
150.6, 165.0; HRMS calcd for C25H26IN3O5Li,
582.1087; found: 582.1102.
5.4.1. Method C. Cyclization of 3-(6,7-methylenedioxy-
quinolin-4-yl)-2-(2-iodo-4,5-dimethoxyphenyl)acrylic amides.
A solution of 3-(6,7-methylenedioxyquinolin-4-yl)-2-(2-
iodo-4,5-dimethoxyphenyl)acrylic amides in acetonitrile
was transferred to the photoreactor apparatus and was
degassed by nitrogen purge for 30 min. The solution
was then irradiated through a Vycor filter. The solvent
was removed under vacuum, and the residue was puri-
fied by chromatography to provide the cyclized amides
in 58–70% yield.
3-(6,7-Methylenedioxyquinolin-4-yl)-2-(2-iodo-4,5-dimeth-
oxyphenyl)acrylic acid 2-(N,N-dimethylamino)-1-methyl-
ethyl amide (8b). Prepared from the crude acid chloride
of 5 (250 mg, 0.5 mmol) and 1-N,N-dimethylamino-2-
propylamine (396 mg, 3.88 mmol) to provide 280 mg 8b
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)ethyl amide
(9a). A solution of 8a (220 mg, 0.38 mmol) in acetonitrile
(900 ml) was irradiated through a Vycor filter for 30 min
to give 100 mg of 9a as a yellow solid in 59% yield; mp:
1
as a sticky glue in 98% yield; IR (CH2Cl2) 1665; H
NMR (CDCl3) d 1.24 (d, 3H, J = 5.0), 2.17 (s, 6H),
2.30 (m, 2H), 3.60 (s, 3H), 3.86 (s, 3H), 4.15 (m, 1H),
6.11 (s, 2H), 6.56 (s, 1H), 6.71 (d, 1H, J = 4.6), 7.24 (s,
1
226.4–227.1 ꢂC; IR (KBr) 1654; H NMR (CDCl3 + 1
drop CD3OD) d 2.34 (s, 6H), 2.69 (t, 2H, J = 6.2), 3.70 (t,

S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
6791
2H, J = 6.2), 4.01 (s, 3H), 4.10 (s, 3H), 6.11 (s, 2H), 7.35 (s,
1H), 7.75(s, 1H),7.79(s, 1H),7.93(s, 1H),8.29(s, 1H),9.59
(s, 1H); 13C NMR (CDCl3 + 1 drop CD3OD) d 37.5, 45.2,
55.9, 56.0, 58.3, 99.3, 102.0, 102.1, 106.2, 106.3, 117.7,
120.8, 120.9, 123.9, 125.7, 129.6, 136.1, 141.6, 144.7,
148.7, 149.6, 149.9, 150.6, 170.0; HRMS calcd for
C25H25N3O5H, 448.1872; found: 448.1865.
moved under vacuum. The residue was dissolved in
CH2Cl2 (30 ml) and washed with water (3 · 10 ml) and
brine (10 ml). The organic layers were dried over sodium
sulfate, evaporated, and the residue was chromato-
graphed eluting with 3–4.5% methanol–dichlorometh-
ane to provide 60 mg of 9a in 60% yield as a yellow
solid; mp: 226.4–227.1 ꢂC; IR (KBr) 1654; 1H NMR
(CDCl3 + 1 drop CD3OD) d 2.34 (s, 6H), 2.69 (t, 2H,
J = 6.2), 3.70 (t, 2H, J = 6.2), 4.01 (s, 3H), 4.10 (s,
3H), 6.11 (s, 2H), 7.35 (s, 1H), 7.75 (s, 1H), 7.79 (s,
1H), 7.93 (s, 1H), 8.29 (s, 1H), 9.59 (s, 1H); 13C NMR
(CDCl3 + 1 drop CD3OD) d 37.5, 45.2, 55.9, 56.0,
58.3, 99.3, 102.0, 102.1, 106.2, 106.3, 117.7, 120.8,
120.9, 123.9, 125.7, 129.6, 136.1, 141.6, 144.7, 148.7,
149.6, 149.9, 150.6, 170.0; HRMS calcd for
C25H25N3O5H, 448.1872; found: 448.1865.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)-1-methylethyl
amide (9b). A solution of 8b (220 mg, 0.37 mmol) in aceto-
nitrile (900 ml) was irradiated for 30 min to give 120 mg of
9bin 70% yield asa yellow solid; mp: 220.6–221.2 ꢂC (dec.);
IR (KBr) 1644; 1H NMR (CDCl3 + 6 drops of CD3OD) d
1.30 (d, 3H, J = 6.6), 2.79 (s, 6H), 2.99 (m, 1H), 3.43 (m,
1H), 3.75 (m, 1H), 3.82 (s, 3H), 3.95 (s, 3H), 5.95 (s, 2H),
7.10 (s, 1H), 7.53 (s, 1H), 7.88 (s, 1H), 7.94 (s, 1H), 8.37
(s, 1H), 9.55 (s, 1H); 13C NMR (DMSO-d6) d 19.6, 42.0,
44.0, 56.1, 56.9, 61.9, 100.5, 103.0, 103.9, 107.1, 107.4,
119.0, 121.0, 121.4, 124.3, 126.1, 129.6, 136.5, 142.9,
146.8, 149.1, 150.1, 150.2, 151.3, 169.3; HRMS calcd for
C26H27N3O5Li, 468.2111; found: 468.2095.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-diethylamino)ethyl amide (9e).
A solution of 7a (100 mg, 0.25 mmol) in N,N-diethylethy-
lenediamine (6.0 ml) was heated to 115 ꢂC for 2 days to
provide 43 mg of 9e in 49% yield as a yellow solid; mp:
200.3–200.7 ꢂC (dec.); IR (KBr) 1633; 1H NMR (CDCl3)
d 1.23 (t, 6H, J = 7.4), 2.84 (q, 4H, J = 7.4), 3.00 (t, 2H,
J = 6.2), 3.82 (t, 2H, J = 6.2), 4.09 (s, 3H), 4.18 (s, 3H),
6.14 (s, 2H), 7.46 (s, 1H), 7.76 (s, 1H), 7.85 (s, 1H),
8.02 (s, 1H), 8.26 (s, 1H), 9.75 (s, 1H); 13C NMR (CDCl3)
d 11.3, 37.4, 47.4, 53.5, 56.0, 56.1, 99.3, 102.0, 102.2,
106.4, 107.1, 117.8, 120.6, 121.1, 124.0, 125.9, 129.3,
142.2, 145.1, 148.6, 149.4, 149.9, 150.6, 169.8; HRMS
calcd for C27H29N3O5H, 476.2186; found: 476.2169.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)propyl amide
(9c). A solution of 8c (220 mg, 0.37 mmol) in acetonitrile
(900 ml) was irradiated for 30 min to give 110 mg of 9c in
60% yield as a yellow solid; mp: 220.3–220.7 ꢂC (dec.); IR
1
(KBr) 1652; H NMR (CDCl3 + 6 drops of CD3OD) d
1.19 (d, 3H, J = 6.6), 2.43 (s, 6H), 3.07 (m, 1H), 3.51 (m,
1H), 3.77 (m, 1H), 4.04 (s, 3H), 4.14 (s, 3H), 6.12 (s, 2H),
7.36 (s, 1H), 7.74 (s, 1H), 7.76 (s, 1H), 7.96 (s, 1H), 8.24
(s, 1H), 9.64 (s, 1H); 13C NMR (CDCl3 + 6 drops of
CD3OD) d 11.1, 40.4, 42.5, 55.7, 55.9, 58.6, 99.1, 102.0,
102.1, 106.0, 117.4, 120.7, 120.7, 123.7, 125.6, 129.4,
136.2, 141.3, 144.5, 148.7, 149.6, 149.8, 150.5, 170.2;
HRMS calcd for C26H27N3O5H, 462.2029; found:
462.2034.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N-benzyl-N-methylamino)ethyl
amide (9f). A solution of 7a (30 mg, 0.074 mmol) in N-
benzyl-N-methylethylenediamine (3.0 ml) was heated to
140 ꢂC for 4 days to provide 21 mg of 9f in 54% yield
as a yellow solid; mp: 233.4–233.8 ꢂC (dec.); IR (KBr)
1
1635; H NMR (CDCl3 + 6 drops of CD3OD) d 2.37
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid N-methyl-N-[2-(N,N-dimethylami-
no)ethyl]amide (9d). A solution of 8d (220 mg, 0.37 mmol)
in acetonitrile (900 ml) was irradiated for 45 min to give
115 mg of 9d in 67% yield as a beige solid; mp: 224.5 ꢂC
(s, 3H), 2.76 (t, 2H, J = 6.2), 3.61 (s, 2H), 3.73 (t, 2H,
J = 6.2), 3.99 (s, 3H), 4.15 (s, 3H), 6.17 (s, 2H), 7.20
(m, 5H), 7.47 (s, 1H), 7.74 (s, 1H), 7.75 (s, 1H), 8.02 (s,
1H), 8.20 (s, 1H), 9.73 (s, 1H); 13C NMR (CDCl3 + 6
drops of CD3OD) d 37.5, 42.3, 55.4, 56.0, 56.1, 62.5,
99.2, 102.1, 106.3, 106.8, 117.3, 120.7, 121.1, 124.0,
125.9, 127.5, 128.5, 129.1, 129.5, 136.5, 138.3, 141.8,
145.0, 148.7, 149.6, 150.0, 150.8, 169.7; HRMS calcd
for C31H29N3O5Li, 523.2267; found: 523.2241.
1
(dec.); IR (KBr) 1619; H NMR (CDCl3 + 6 drops of
CD3OD) d 2.77 (s, 6H), 2.85 (s, 3H), 3.27 (br, 2H), 3.72
(br, 2H), 3.87 (s, 3H), 4.02 (s, 3H), 6.02 (s, 2H), 6.99 (s,
1H), 7.31 (s, 1H), 7.93 (s, 1H), 8.03 (s, 1H), 8.32 (s, 1H),
9.67 (s, 1H); 13C NMR (CDCl3 + 6 drops of CD3OD) d
32.9, 37.6, 44.2, 55.2, 55.8, 56.0, 99.7, 102.1, 102.6, 104.8,
105.8, 116.9, 120.6, 121.0, 122.9, 125.8, 130.3, 141.6,
144.6, 149.0, 150., 150.4, 151.1, 171.2; HRMS calcd for
C26H27N3O5Li, 468.2111; found: 468.2097.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dibenzyl)ethyl amide (9g). A
solution of 7a (70 mg, 0.17 mmol) in N,N-dibenzylethy-
lenediamine (5.0 ml) was heated to 145 ꢂC for 4 days to
provide 35 mg of 9g in 34% yield as a yellow solid; mp:
254.3–254.8 ꢂC (dec.); IR (KBr) 1635; 1H NMR
(CDCl3 + 6 drops of CD3OD) d 2.78 (t, 2H, J = 6.2),
3.65 (br, 6H), 3.93 (s, 3H), 4.17 (s, 3H), 6.21 (s, 2H),
7.11 (m, 5H), 7.24 (m, 5H), 7.53 (s, 1H), 7.64 (s, 1H),
7.78 (s, 1H), 8.14 (s, 2H), 9.84 (s, 1H); 13C NMR
(CDCl3 + 6 drops of CD3OD) d 37.6, 51.8, 56.0, 56.2,
58.7, 99.3, 102.1, 106.3, 106.8, 117.1, 120.8, 121.2,
124.0, 126.0, 127.4, 128.5, 128.9, 129.7, 136.7, 139.0,
5.4.2. Method D. Amide formation from 2,3-dimethoxy-
8,9-methylenedioxy-benzo[i]phenanthridine-12-carboxylic
acid ethyl ester (7a).
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(N,N-dimethylamino)ethyl amide
(9a). A solution of 7a (100 mg, 0.25mmol) in N,N-
dimethylethylenediamine (30 ml) was heated to 110 ꢂC
for 5 days. TLC was used to monitor the reaction. After
the reaction was completed, the residual amine was re-

6792
S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
142.0, 145.1, 148.9, 149.8, 150.1, 151.0, 169.6; HRMS
calcd for C37H33N3O5Li, 606.2580; found: 606.2567.
solved in chloroform (25 ml), washed with satd
NaHCO3 (3 · 25 ml), and extracted with dilute aq HCl
(3 · 25 ml). The combined aqueous extracts were washed
with chloroform (2 · 25 ml), were basified (30% NaOH),
and back-extracted into ethyl acetate (3 · 30 ml). The
organic phases were dried (MgSO4) and evaporated,
and the residue was chromatographed eluting with 96:4
chloroform–methanol, providing 18 mg as a yellow solid,
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(pyrrolidin-1-yl)ethyl amide (9h). A
solution of 7a (40 mg, 0.10 mmol) in 2-(pyrrolidin-1-
yl)ethylamine (3 ml) was heated to 130 ꢂC for 2 days to
provide 31 mg of 9h in 47% yield as a yellow solid; mp:
250.3–250.6 ꢂC (dec.); IR (KBr) 1636; 1H NMR
(CDCl3 + 6 drops of CD3OD) d 1.86 (m, 4H), 2.73 (m,
4H), 2.93 (t, 2H, J = 6.2), 3.75 (t, 2H, J = 6.2), 4.03 (s,
3H), 4.13 (s, 3H), 6.14 (s, 2H), 7.44 (s, 1H), 7.82 (s,
1H), 7.86 (s, 1H), 8.03 (s, 1H), 8.37 (s, 1H), 9.71 (s,
1H); 13C NMR (CDCl3 + 6 drops of CD3OD) d 23.4,
38.6, 54.2, 55.2, 56.0, 56.1, 99.3, 102.1, 106.3, 106.5,
117.8, 120.9, 121.1, 124.1, 125.9, 129.7, 136.1, 141.8,
144.9, 148.8, 149.7, 150.0, 150.7, 170.0; HRMS calcd
for C27H27N3O5Li, 480.2111; found: 480.2114.
1
in 52% yield; mp: 226.4–227.1 ꢂC; IR (KBr) 1654; H
NMR (CDCl3 + 1 drop CD3OD) d 2.34 (s, 6H), 2.69 (t,
2H, J = 6.2), 3.70 (t, 2H, J = 6.2), 4.01 (s, 3H), 4.10 (s,
3H), 6.11 (s, 2H), 7.35 (s, 1H), 7.75 (s, 1H), 7.79 (s,
1H), 7.93 (s, 1H), 8.29 (s, 1H), 9.59 (s, 1H); 13C NMR
(CDCl3 + 1 drop CD3OD) d 37.5, 45.2, 55.9, 56.0, 58.3,
99.3, 102.0, 102.1, 106.2, 106.3, 117.7, 120.8, 120.9,
123.9, 125.7, 129.6, 136.1, 141.6, 144.7, 148.7, 149.6,
149.9, 150.6, 170.0; HRMS calcd for C25H25N3O5H,
448.1872; found: 448.1865.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(piperidin-1-yl)ethyl amide (9i). A
solution of 7a (40 mg, 0.10 mmol) in 2-(piperazin-1-
yl)ethylamine (3 ml) was heated to 140 ꢂC for 2 days to
provide 35 mg of 9i in 73% yield as a light beige solid;
mp: 267.3–267.7 ꢂC (dec.); IR (KBr) 1658; 1H NMR
(CDCl3 + 6 drops of CD3OD) d 1.53 (m, 6H), 2.60 (m,
6H), 3.70 (br, 2H), 4.00 (s, 3H), 4.10 (s, 3H), 6.11 (s,
2H), 7.38 (s, 1H), 7.76 (s, 1H), 7.79 (s, 1H), 8.00 (s,
1H), 8.29 (s, 1H), 9.66 (s, 1H); 13C NMR (CDCl3 + 6
drops of CD3OD) d 24.0, 25.5, 36.7, 54.5, 55.9, 56.0,
57.8, 99.2, 102.2, 106.3, 117.6, 120.9, 121.1, 124.0,
125.8, 129.6, 136.2, 141.6, 144.8, 148.9, 149.7, 149.9,
150.7, 170.1; HRMS calcd for C28H29N3O5H, 488.2185;
found: 488.2189.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 3-(dimethylamino)propyl amide (9k).
Prepared from the crude acid chloride of 10 (60 mg,
0.159 mmol) and N,N-dimethyl-1,3-propylanediamine
(11 ml) in 45% yield as a yellow solid; mp: 220.6–
1
221.3 ꢂC (dec.); IR (KBr) 1635; H NMR (CDCl3 + 6
drop CD3OD) d 2.03 (m, 2H), 2.49 (s, 6H), 2.77 (t, 2H,
J = 7.4), 3.63 (t, 2H, J = 6.6), 4.02 (s, 3H), 4.13 (s, 3H),
6.14 (s, 2H), 7.42 (s, 1H), 7.81 (s, 1H), 7.91 (s, 1H),
8.06 (s, 1H), 8.34 (s, 1H), 9.75 (s, 1H); 13C NMR
(CDCl3 + 6 drop CD3OD) d 26.3, 38.4, 44.6, 44.8, 55.9,
56.1, 57.3, 99.2, 102.1, 106.3, 106.4, 117.4, 120.8, 121.0,
124.0, 125.8, 129.6, 136.3, 141.7, 144.8, 148.8, 149.7,
150.0, 150.7, 170.1; HRMS calcd for C26H27N3O5H,
462.2030; found: 462.2006.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(4-methylpiperazin-1-yl)ethyl amide
(9j). A solution of 7a (40 mg, 0.10 mmol) in 2-(4-meth-
ylpiperidin-1-yl)ethylamine (3 ml) was heated to 135 ꢂC
for 2 days to provide 35 mg of 9j in 71% yield as a light
pink solid; mp: 269.3–269.8 ꢂC (dec.); IR (KBr) 1663; 1H
NMR (CDCl3 + 6 drops of CD3OD) d 2.30 (s, 3H), 2.76
(m, 10H), 3.76 (t, 2H, J = 6.2), 4.04 (s, 3H), 4.12 (s, 3H),
6.11 (s, 2H), 7.39 (s, 1H), 7.62 (s, 1H), 7.71 (s, 1H), 7.90
(s, 1H), 8.11 (s, 1H), 9.57 (s, 1H); 13C NMR (CDCl3 + 6
drops of CD3OD) d 36.8, 45.7, 52.7, 54.9, 56.0, 57.0, 98.9,
102.0, 102.2, 106.2, 106.6, 117.3, 120.6, 120.8, 123.9,
125.6, 129.3, 136.2, 141.5, 144.7, 148.7, 149.5, 149.9,
150.6, 170.0; HRMS calcd for C28H30N4O5Li, 509.2376;
found: 509.2378.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid N,N-bis[2-(N,N-dimethylamino)ethyl]
amide (9l). A mixture of 9a (20 mg, 0.045 mmol), 2-
(N,N-dimethylamino)ethyl
chloride
hydrochloride
(8 mg, 0.055 mmol), and NaI (10 mg, 0.067 mmol) in
DMF (2 ml) was cooled to 0 ꢂC, and then NaH 60% in
mineral oil (6 mg, 0.15 mmol) was added in small por-
tions. The mixture was allowed to warm to room temper-
ature, stirred for 45 min, and then transferred to an oil
bath, which was preheated to 60 ꢂC. The reaction mixture
was then heated for 3 h, allowed to cool to room temper-
ature, and quenched by water (10 ml). Solvent was re-
moved under vacuum. The residue was diluted by
CH2Cl2 (20 ml) and washed with water (10 ml · 3) and
brine (10 ml). Organic layers were dried over MgSO4
and evaporated, and the residue was chromatographed
eluting with 96:4 to 94:6 chloroform–methanol, providing
18 mg as a light yellow solid, in 78% yield; mp: 208.7–
5.4.3. Method E. Formation of amides from the acid
chloride of 2,3-dimethoxy-8,9-methylenedioxybenzo[i]phe-
nanthridine-12-carboxylic acid (10).
1
209.2 ꢂC (dec.); IR (KBr) 1624; H NMR (CDCl3 + 12
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid 2-(dimethylamino)ethyl amide (9a). The
acid 8 (30 mg, 0.08 mmol) was added without further
purification to thionyl chloride (10 ml) and the mixture
was heated to reflux for 4 h. The excess thionyl chloride
was removed under vacuum and N,N-dimethylethylen-
ediamine (5 ml) was added. The mixture was stirred at
ambient temperature for 30 min. The N,N-dimethylethy-
lenediamine was evaporated and the residue was dis-
drops of CD3OD) d 1.59 (s, 6H), 2.16 (m, 2H), 2.24
(s, 6H), 2.64 (m, 2H), 2.99 (m, 2H), 3.57 (m, 2H), 3.78
(s, 3H), 3.93 (s, 3H), 5.95 (s, 2H), 6.99 (s, 1H), 7.21 (s,
1H), 7.68 (s, 1H), 7.91 (s, 1H), 8.07 (s, 1H), 9.55 (s,
1H); 13C NMR (CDCl3 + 12 drops of CD3OD) d 42.5,
44.7, 45.0, 46.6, 55.6, 55.8, 56.2, 57.3, 99.1, 102.1, 102.4,
105.1, 105.7, 116.1, 120.3, 120.7, 123.1, 125.6, 129.9,
136.4, 141.5, 144.6, 148.9, 149.9, 150.1, 151.0, 171.3;

S. Zhu et al. / Bioorg. Med. Chem. 13 (2005) 6782–6794
6793
HRMS calcd for C29H34N4O5H, 519.2607; found:
519.2597.
formed at the end of the fourth day. Each assay was per-
formed with a control that did not contain any drug. All
assays were performed at least twice in six replicate
wells.
2,3-Dimethoxy-8,9-methylenedioxybenzo[i]phenanthridine-
12-carboxylic acid (10). A mixture of 7a (40 mg, 0.1 mmol)
in10% NaOH(45 ml)andethanol (10 ml)washeatedtore-
flux with stirring overnight. The mixture was concentrated
to dryness and water (30 ml) was added. The resulting mix-
ture was acidified by the addition of acetic acid and the free
acid was then isolated by filtration. After complete drying,
32 mg (87%) was obtained as a yellow solid; mp: 277.7–
278.6 ꢂC (dec.); IR (KBr) 1706; HRMS calcd for
C21H15NO6Li, 384.1059; found: 384.1061.
Acknowledgments
This study was supported by Grant CA098127 (E.J.L.),
Grant CA39662 (L.F.L.), and Grant CA077433 (L.F.L.)
from the National Cancer Institute.
References and notes
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