An efficient, convenient synthesis of novel medium-sized 13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione macrolides as anticipated antineoplastic agents

Article abstract of DOI:10.1016/S0968-0896(02)00047-0

A series of novel medium-sized 13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione macrolides (18-27, 30, 32) were synthesized in an ongoing effort to develop new antineoplastic agents. The synthon 2-(2-aminobenzoylamino)-benzoic acid (7), for preparation of the target compounds, was prepared via the reaction of isatoic anhydride 5 and anthranilic acid 6. Nine compounds (18-20, 24-27, 30, 32) were subjected to National Cancer Institute (NCI) in vitro disease-oriented human cells screening panel assay. Among the compounds tested, 6-benzyl-13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione (26, NSC 721327), bearing the benzyl group at position 6, showed cytotoxic activity and subpanel selectivity against leukemia (CCRF-CEM), colon (HCC-2998), CNS (SNB-75) and melanoma (UACC-257) panels at log₁₀ GI₅₀ (M), compound concentration that inhibits 50% of cell growth, ranging from -4.08 to -4.59.

Full text of DOI:10.1016/S0968-0896(02)00047-0

Bioorganic & Medicinal Chemistry10 (2002) 2297–2302
An Efficient, Convenient Synthesis of Novel Medium-Sized
13H-Dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione Macrolides as
Anticipated Antineoplastic Agents
Atef Abdel-Monem Abdel-Hafez*
Department of Pharmaceutical Medicinal Chemistry, Faculty of Pharmacy, Assiut University, Assiut 71526, Egypt
Received 30 November 2001; accepted 15 January2002
Abstract—A series of novel medium-sized 13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione macrolides (18–27, 30, 32) were synthe-
sized in an ongoing effort to develop new antineoplastic agents. The synthon 2-(2-aminobenzoylamino)-benzoic acid (7), for pre-
paration of the target compounds, was prepared via the reaction of isatoic anhydride 5 and anthranilic acid 6. Nine compounds
(18–20, 24–27, 30, 32) were subjected to National Cancer Institute (NCI) in vitro disease-oriented human cells screening panel
assay. Among the compounds tested, 6-benzyl-13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione (26, NSC 721327), bearing the ben-
zyl group at position 6, showed cytotoxic activity and subpanel selectivity against leukemia (CCRF-CEM), colon (HCC-2998),
CNS (SNB-75) and melanoma (UACC-257) panels at log10 GI50 (M), compound concentration that inhibits 50% of cell growth,
ranging from ꢀ4.08 to ꢀ4.59. # 2002 Elsevier Science Ltd. All rights reserved.
Introduction
Diekmann reaction; and (6) from acyclic esters.9
o-Hydroxycarboxylic acids are the most common start-
ing materials because of their relative availabilityfor
large-ring lactone formation which can be achieved via
direct esterification, transesterification, mixed anhy-
dride, N-acylimidazolides, thiol esters, 2-chloropyr-
idinum and 2-chlorobenzothiazolium salts and hydroxy
activation.9 One of the methods commonlyused is the
use of the appropriate hydroxy acids and trifluoroacetic
anhydride in benzene solution at room temperature.10
However, this procedure suffers limitations such as
strong acidic conditions (CF3COOH) employed and low
yields which made this method not an attractive one.
Encouraged bythe fact that an increasing number of the
macrocyclic lactones exhibited cytotoxic activity,11ꢀ13
we report here the synthesis and antineoplastic activity
of novel medium sized 13H-dibenzo[d,h][1,3,7]ox-
adiazecine-8,14-dione macrolides (18–27, 30, 32). In
addition to our interest in this area to search for lead
antitumor agents, an efficient, convenient and simple
cyclization method for synthesis of the target com-
pounds (18–27, 30, 32) was adopted.
Medium ring macrcyclic lactones, those having a ring
size of 8 to 11,1 are an extremelyimportant class of com-
pounds in organic chemistryas theyare incorporated in
an ever-increasing number of natural and synthetic pro-
ducts. Marked anti-inflammatory, antibacterial, antiviral
and antitumor activities emerging bymedium ring
macrocyclic lactones combining with nitrogen sub-
stituents or nitrogen heterocycles have evoked interest
in the search for useful leads in the development of new
pharmaceutical agents.2ꢀ7 The synthesis of these com-
pounds was much more difficult bycyclization methods
than other macrocyclic compounds (ring size ꢁ12).
These difficulties are noticed since the formation of
these cyclic compounds are disfavoured by entropy as
well as enthalpy.8 Development of an efficient method
for preparation of medium-ring lactone compounds
continues to be an important theme in synthetic organic
chemistry. Generally these lactones are prepared: (1)
from o-halo or hydroxycarboxylic acids; (2) from
cycloakanes by Baeyer-villiger oxidation; (3) by fusion-
bond cleavage of bicyclic compounds; (4) from
cycloalkanones di- and triperoxides; (5) by reverse
Chemistry
In the present investigation, we prepared 12 new medium-
sized nitrogen containing 13H-dibenzo[d,h][1,3,7]oxa-
*Corresponding author. Tel.: +20-88-030-3006; fax: +20-88-33-2776;
e-mail: atef@acc.aun.eun.eg
0968-0896/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(02)00047-0

2298
A. A. Abdel-hafez / Bioorg. Med. Chem. 10 (2002) 2297–2302
diazecine-8-14-dione macrolides (18–27, 30, 32). The
routes for preparation of these compounds are illu-
strated in Schemes 1–3. Reaction of anthranilic acid 6
with phosgene leads to isatoic anhydride 5. In contrast,
the latter reacted with 6 to afford the synthon 2-(2-ami-
nobenzoylamino)-benzoic acid (7).14,15 Generally, nucleo-
philes react with 5 at one of the two carbonyl groups at
the C-2 or C-4 position. The C-4 position, which
resembles an anhydide, is more reactive than C-2 which
acts like a carbamate in reactivity.16 The structure of 7
was assigned on the bases of its EI-MS, IR and NMR
spectral data. The EI-MS spectra showed a molecular
ion peak at m/z 256 [M]+, which was consistent with its
molecular formula. Absorption bands at 3400–
3300 cmꢀ1 (NH2, OH), 1695 (acid C¼O) and 1650
1
(amide C¼O) were seen in the IR spectrum. In the H
NMR spectrum, signals for aromatic protons appeared
at d 8.66ꢂ6.64 ppm and signals for NH and NH2 pro-
tons appeared at d 11.94 and 3.45 ppm. The structure of
7 was further confirmed by 13C NMR data that
revealed, in addition to the aromatic protons, signals at
d 170.0 and 167.4 due to the carbonyl carbon of COOH
and CONH, respectively. Compound 7 reacted with
acyl chloride in dioxane to give the intermediates 7–18.
The structures of 7–18 were confirmed byspectroscopic
means including IR, NMR and EI-MS (Tables 1–3). A
novel nitogen containing lactam lactone type structure,
sandwiched between two benzene rings, (18–27) was
obtained byintramolecular cyclization of 8–17. As is
clear from the introductorypart, esterification of
hydroxy acids is the most common method used for
preparation of medium ring lactones. Different methods
were utilized for such esterification and the use of tri-
fluroacetic anhydride in benzene solution is the famous
one.10 Since this method employed strong acidic condi-
tions and usuallylow iyelds were obtained, we per-
formed esterification of the intermediates 8–17 to afford
the target compounds 18–27, using acetic anhydride for
15 min. A rapid esterification process of hydroxy acids
to prepare medium ring lactones is necessaryto avoid
the formation of polymers and overcome the undesir-
able entropyfactors. The use of acetic anhydride was
mild and a rapid esterification method successfullyused
for the synthesis of the target lactones (18–27) in good
yields. On the basis of careful inspection of the spectro-
scopic data of compounds 18–27, their structures were
determined. The EI-MS spectra of these compounds
revealed molecular ion peaks with 18 mass units less
than that of 8–17 precursors, respectively, indicating
that 18–27 were dehydrated products of 8–17. These
molecular ion peaks were consistent with their respec-
tive molecular formulas.
Scheme 1.
Scheme 2.
Scheme 3.

A. A. Abdel-hafez / Bioorg. Med. Chem. 10 (2002) 2297–2302
2299
Table 1. Physical and IR data of 2-(2-acylaminobenzoylamino)-benzoic acid derivatives (8–17, 29)
Compounda
Mp (ꢃC)
Yield (%)
Solventb
Molecular formula
IR KBr (cmꢀ1
)
8
9
>300
>300
>300
>300
>300
>300
>300
223–225
>300
>300
>300
95
90
92
90
88
87
82
80
96
85
78
A
A
B
B
B
B
B
B
D
C
C
C16H14N2O4
C16H13N2O4
C22H26N2O4
C24H30N2O4
C26H34N2O4
C28H38N2O4
C25H30N2O4
C32H44N2O4
C22H18N2O4
C25H26N2O4
C21H24N4O4
3200 (NH), 1695, 1675, 1665 (C¼O), 1610, 1200
3200 (NH), 1675, 1660, 1640 (C¼O), 1610, 1230
3200 (NH), 1690, 1660, 1640 (C¼O), 1610, 1240
3200 (NH), 1692, 1660, 1640 (C¼O), 1610, 1240
3200 (NH), 1690, 1660, 1640 (C¼O), 1610, 1240
3200 (NH), 1690, 1660, 1640 (C¼O), 1610, 1250
3200 (NH), 1690, 1660, 1645 (C¼O), 1610, 1240
3200 (NH), 1690, 1665, 1640 (C¼O), 1610, 1225
3200 (NH), 1695, 1660, 1618 (C¼O), 1610, 1240
3220 (NH), 1680, 1660, 1650 (C¼O), 1610, 1230
3200 (NH), 1690, 1665, 1640 (C¼O), 1610, 1245
10
11
12
13
14
15
16
17
29
aThe mass spectrum revealed a proper molecular ion [M]+ for all compounds.
bSolvent of crystallization: A, CHCl3–MeOH; B, CHCl3–acetone; C, aqueous ethanol; D, CHCl3.
Table 2. 1H NMR data of 2-(2-acylaminobenzoylamino)-benzoic acid derivatives (8–17, 29)
Compounda
–C(O)–NH—
–NH–C(O)–R
Ar–H
Others
8
9
10
11.84
11.97
11.83
10.46
11.23
10.48
6.85–8.07 (8H)
7.23–8.59 (8H)
7.20–8.61 (8H)
2.01 (3H, s, CH3)
4.39 (2H, s, –CH2Cl)
2.30 (2H, t, –CH2–), 1.54 (2H, p, –CH2–),
1.22 (8H, m, 4ꢄ–CH2–), 0.82 (3H, t, –CH3)
2.30 (2H, t, –CH2–), 1.57 (2H, p, –CH2–),
1.21 (12H, m, 6ꢄ–CH2–), 0.84 (3H, t, –CH3)
2.30 (2H, t, –CH2–), 1.56 (2H, p, –CH2–),
1.21 (16H, m, 8ꢄ–CH2–), 0.84 (3H, t, –CH3)
2.30 (2H, t, –CH2–), 1.53 (2H, p, –CH2–),
1.21 (20H, m, 10ꢄ–CH2–), 0.84 (3H, t, –CH3)
5.76 (1H, m, –CH–CH2), 4.93 (2H, m,
–CH–CH2), 2.30 (2H, t, –CH2–), 1.97 (2H, q,
–CH2–), 1.52 (2H, p, –CH2–), 1.25 (10H, m, 5ꢄ–CH2–)
5.31 (2H, m, –CH–), 2.30 (2H, t, –CH2–),
1.94 (4H, m, 2ꢄ–CH2–), 1.52 (2H, p, –CH2–),
1.22 (20H, m, 10ꢄ–CH2–), 0.83 (3H, t, –CH3)
3.69 (2H, s, –CH2–)
11
12
13
14
11.86
11.85
11.86
11.85
10.51
10.50
10.51
10.49
7.18–8.61 (8H)
7.20–8.61 (8H)
7.19–8.61 (8H)
7.20–8.61 (8H)
15
11.87
10.51
7.20–8.62 (8H)
16
17
29
11.83
11.92
12.02
10.61
10.95
11.73
7.21–8.56 (13H)
6.83–8.62 (8H)
7.01–8.72 (8H)
1.64–2.01 (15H, adamantanyl moiety)
3.31 (2H, s, –CH2–), 2.69 (4H, m, 2ꢄ–CH2–),
2.40 (4H, m, 2ꢄ–CH2–), 2.01 (3H, s, N–CH3)
aAll compounds measured in DMSO.
Table 3. 13C NMR data of 2-(2-acylaminobenzoylamino)-benzoic acid derivatives (8–17, 29)
Compounda –COOH –C(O) R–C(O)
–NH– –NH–
Ar–C
Others
8
169.9
169.7
171.2
171.1
171.2
171.2
171.2
171.1
168.3
166.3
169.5
169.6
169.6
169.6
169.6
169.6
166.7
165.0
166.4
166.4
166.4
166.4
166.4
166.4
116.6, 120.0, 120.5, 122.8, 123.2, 123.7,
127.4, 131.2, 132.8, 134.1, 137.5, 141.0
117.6, 120.7, 122.0, 123.5, 124.0, 124.4,
127.9, 131.2, 132.4, 134.1, 137.3, 140.3
117.2, 120.4, 122.3, 123.1, 123.6, 124.8,
127.8, 131.1, 132.0, 134.0, 137.7, 140.6
117.1, 120.4, 122.3, 123.1, 123.6, 124.6,
127.8, 131.1, 132.0, 134.0, 137.7, 140.6
117.1, 120.4, 122.3, 123.1, 123.6, 124.6,
127.8, 131.0, 132.0, 133.9, 137.7, 140.6
117.2, 120.4, 122.3, 123.1, 123.6, 124.7,
127.8, 131.1, 132.0, 134.0, 137.8, 140.6
117.2, 120.4, 122.4, 123.2, 123.7, 124.8,
127.9, 131.1, 132.0, 134.0, 137.6, 140.6
117.1, 120.4, 122.3, 123.1, 123.6, 124.6,
127.8, 131.1, 132.0, 134.0, 137.6, 140.6
24.2 (CH3)
9
43.3 (–CH2Cl)
10
11
12
13
14
15
13.8, 21.9, 24.9, 28.3, 28.4, 31.0, 36.8
(6ꢄCH2, CH3)
13.8, 22.0, 24.8, 28.4, 28.6, 28.7, 28.7, 31.2,
36.8 (8ꢄCH2, CH3)
13.8, 22.0, 24.8, 28.4, 28.6, 28.6, 28.7, 28.9,
28.9, 31.2, 36.8 (10ꢄCH2, CH3)
13.9, 22.0, 24.9, 28.4, 28.6, 28.7, 28.8, 28.9,
28.9, 29.0, 29.0, 31.2, 36.8 (12ꢄCH2, CH3)
24.9, 28.2, 28.4, 28.4, 28.6, 28.7, 33.2, 36.8
(8ꢄCH2), 114.6 (CH2¼CH–), 138.8 (CH2¼CH–)
13.9, 22.1, 24.9, 26.5, 28.4, 28.5, 28.6, 28.8,
28.9, 28.9, 29.0, 31.2, 31.9, 33.6, 36.8
(14ꢄCH2, CH3), 129.6, 130.0 (–CH¼CH–)
16
17
29
169.5
169.9
170.4
169.2
167.0
168.7
166.2
166.7
166.4
117.2, 120.5, 122.2, 123.2, 123.8, 124.7, 126.6, 127.7,
128.2, 128.6, 131.0, 132.0, 134.0, 135.1, 137.6, 140.4
116.6, 120.0, 120.9, 122.8, 123.1, 123.6,
43.7 (–CH2–Ph)
77.9, 75.8, 41.3, 38.6, 35.9, 27.5
(adamantanyl carbons)
43.9 (N–CH3), 52.6, 52.8
127.4, 131.2, 132.7, 134.1, 137.5, 141.0
119.0, 120.3, 122.3, 122.4, 122.7, 123.1,
127.7, 131.4, 131.6, 132.2, 138.6, 140.4
(piperazinyl CH2), 53.7 (–CH2–)
aAll compounds measured in DMSO.

2300
A. A. Abdel-hafez / Bioorg. Med. Chem. 10 (2002) 2297–2302
Evidence of lactone formation in 18–27 emerged from
the presence of absorption bands in their IR spectra at
1770ꢂ1785 cmꢀ1, assigned to ester C¼O. On the other
hand, absorption bands at 1618ꢂ1665 cmꢀ1, assigned
to the exocyclic amide carbonyl in the IR spectra of 8–
17, were not seen, while all other signals remain sig-
nificantlyunaffected (Table 4). The 1H NMR spectra of
18–27 were comparable with that of 8–17, except for the
absence of signals at d 10.46ꢂ11.73 ppm assigned to
–NH–C(O)–R protons (Table 5). Another proof for
intramolecular cyclization and lactone formation in 18–
27 was picked up from 13C NMR spectra (Table 6). The
experimental errors, the structures of 18–27 were estab-
lished.
Trials to react 6-(chloromethyl)-13H-dibenzo[d,h][1,3,7]
oxadiazecine-8,14-dione 19 with N-methyl-piperazine 28
were unsuccessful. Even at room temperature in the
presence of 28 or amines such as cyclohexyl amine and
morpholine, the 10-membered ring lactone structure of
19 was opened. For this reason, compound 30 was syn-
thesized via cyclization of the intermediate 29. On the
other hand, compound 19 reacts with 2-mercaptobenzi-
midazole 31 to afford 32. The structures of 30 and 32
were assigned depending on the bases of spectral data
and elemental analyses (Tables 4–6).
disappearance of signals at
d
169.5ꢂ171.2 and
165.0ꢂ166.7 ppm, assigned to carbonyl groups of
COOH and –C(O)–NH–, respectively, in 8–17, were
noticed. The appearance of signals at d 158.1ꢂ158.7
and 156.3ꢂ157.7 ppm, assigned to C¼O of ester and
C¼N, respectively, in 18–27, were observed. Based on
the above findings with the aid of elemental analyses
that showed satisfactoryresults within the accepted
Pharmacological Results and Discussion
As a primaryscreening, nine compounds ( 18–20, 24–27,
30, 32) out of the prepared compounds were selected by
Table 4. Physical and IR data of 6-(substituted)-13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione derivatives (18–27, 30, 32)
Compounda
Mp (ꢃC)
Yield (%)
Solventb
Molecular formulac
IR KBr (cmꢀ1
)
18
19
20
21
22
23
24
25
26
27
30
32
180–181
156–158
106–107
139–140
104–105
98–99
243–244
58–60
192–193
178–180
51–52
92
89
85
88
84
81
90
78
93
74
83
70
A
A
B
B
B
B
B
B
D
C
C
D
C16H12N2O3
C16H11N2O3
C22H24N2O3
C24H28N2O3
C26H32N2O3
C28H36N2O3
C25H28N2O3
C32H42N2O3
C22H16N2O3
C25H24N2O3
C21H22N4O3
C23H16N4O3S
3200 (NH), 1780, 1710 (C¼O), 1610, 1250
3200 (NH), 1770, 1695 (C¼O), 1610, 1220
3200 (NH), 1770, 1698 (C¼O), 1610, 1230
3200 (NH), 1775, 1698 (C¼O), 1610, 1230
3200 (NH), 1770, 1698 (C¼O), 1610, 1230
3200 (NH), 1770, 1700 (C¼O), 1610, 1240
3200 (NH), 1772, 1698 (C¼O), 1610, 1230
3200 (NH), 1770, 1695 (C¼O), 1610, 1210
3200 (NH), 1785, 1700 (C¼O), 1610, 1220
3220 (NH), 1775, 1695 (C¼O), 1610, 1250
3200 (NH), 1775, 1698 (C¼O), 1610, 1230
3200 (NH), 1778, 1680 (C¼O), 1610, 1250
186–187
aThe mass spectrum revealed a proper molecular ion [M]+ for all compounds.
bSolvent of crystallization: A, aqueous DMF; B, ether–CHCl3; C, ethanol–CHCl3; D, ethanol.
cSatisfactorymicroanalysis were obtained ( ꢅ0.4%) for C, H and N.
Table 5. 1H NMR data of 6-(substituted)-13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione derivatives (18–27, 30, 32)
Compound
–C(O)—NH—
Ar–H
Others
18a
19a
20a
11.65
12.37
12.62
7.26–8.40 (8H)
7.33–8.56 (8H)
7.24–8.43 (8H)
2.22 (3H, s, CH3)
4.54 (2H, s, –CH2Cl)
2.47 (2H, t, –CH2–), 1.67 (2H, p, –CH2–),
1.28 (8H, m, 4ꢄ–CH2–), 0.83 (3H, t, –CH3)
2.49 (2H, t, –CH2–), 1.73 (2H, p, –CH2–),
1.32 (12H, m, 6ꢄ–CH2–), 0.84 (3H, t, –CH3)
2.54 (2H, t, –CH2–), 1.85 (2H, p, –CH2–),
1.36 (16H, m, 8ꢄ–CH2–), 0.86 (3H, t, –CH3)
2.54 (2H, t, –CH2–), 1.85 (2H, p, –CH2–),
1.36 (20H, m, 10ꢄ–CH2–), 0.87 (3H, t, –CH3)
5.78 (1H, m, –CH–CH2), 4.95 (2H, m, –CH–CH2),
2.54 (2H, t, –CH2–), 2.02 (2H, q, –CH2–),
1.84 (2H, p, –CH2–), 1.36 (10H, m, 5ꢄ–CH2–)
5.34 (2H, m, –CH–), 2.54 (2H, t, –CH2–),
2.00 (4H, m, 2ꢄ–CH2–), 1.84 (2H, p, –CH2–),
1.34 (20H, m, 10ꢄ–CH2–), 0.87 (3H, t, –CH3)
3.85 (2H, s, –CH2–)
21a
22b
23b
24b
11.94
12.29
12.29
12.28
7.21–8.59 (8H)
7.16–8.84 (8H)
7.16–8.84 (8H)
7.16–8.84 (8H)
25b
12.29
7.16–8.83 (8H)
26a
27c
30b
11.77
11.62
12.36
7.23–8.44 (13H)
7.24–8.68 (8H)
7.18–8.82 (8H)
1.75–2.20 (15H, adamantanyl moiety)
3.34 (2H, s, –CH2–), 2.72 (4H, m, 2ꢄ–CH2–),
2.47 (4H, m, 2ꢄ–CH2–), 2.22 (3H, s, N–CH3)
12.52 (1H, br s, NH), 4.58 (2H, s, S–CH2–)
32a
12.22
7.27–8.43 (12H)
aDMSO.
bCDCl3.
cCDCl3–DMSO.

A. A. Abdel-hafez / Bioorg. Med. Chem. 10 (2002) 2297–2302
2301
NCI to be screened for their in vitro antitumor activity
Conclusion
according to the standard protocol of NCI (Bethesda,
MD, USA).17,18 For the past 10 years, the Development
Therapeutic Program (DTP), Division of Cancer Treat-
ment and Diagnosis (DCTD), NCI has used an in vitro
model consisting of 60 human tumor cell lines as the
primaryanticancer screen. An analysis of the data indi-
cated that approximately95% of the actives from the 60
cell lines screen can be identified using onlythree cell
lines. For this reason, the DTP has now begun using, as
its primaryanticancer assa,y a three-cell lines panel
consisting of the MCF7 (Breast), NCI-H460 (Lung),
and SF-268 (CNS). In the current protocol, each cell
line is inoculated and pre-incubated on a microtiter
plate. Test agents are then added at a single concentra-
tion and the culture incubated for 48 h. End-point
determinations are made with alamar blue. Results for
each test agent are reported as the percent of growth of
the treated cells when compared to the untreated con-
trol cells. Compounds which reduce the growth of any
one of the cell lines to approximately32% or less are
passed on for evaluation in the full panel of 60 cell lines
over a 5-log dose range. In these three-cell lines, one
dose primary anticancer assay, 6-benzyl-13H-diben-
zo[d,h][1,3,7]oxadiazecine-8–14-dione (26, NSC 721327)
passed on for evaluation against 60 human cell lines.
Leukemia, lung, colon, central nervous system, mela-
noma, ovary, renal, prostate and breast cancer were the
nine clinicallyisolated cancer subpanels representing 60
-human tumor cell lines. Compound 26, bearing the benzyl
group at position 6, displayed cytotoxic activity and sub-
panel selectivityagainst leukemia (CCRF-CEM), colon
(HCC-2998), CNS (SNB-75) and melanoma (UACC-257)
panels at log10 GI50 (M) ranging from ꢀ4.08 to ꢀ4.59.
The present paper deals with the design and synthesis of
novel series of medium-sized nitrogen containing 13H-
dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione macrolides
(18–27, 30, 32) in an attempt to obtain a novel anti-
tumor structure. The new compounds (18–27, 30, 32)
described here represent a novel class of compounds
incorporated in a 10-membered ring lactone lactam type
structure. The results obtained could not confirm our
anticipation that theywould stimulate further structural
modifications of this class of compounds. On the other
hand, exploration of the antibacterial and antiviral
activities of these derivatives will be a subject of further
investigations.
Experimental
Melting points were determined on a micromelting
point apparatus (L-272, Yanaco, Kyoto, Japan) and are
uncorrected. IR spectra were performed with a JASCO
FT/IR-230 infrared spectrophotometer. Thin layer
chromatographywas carried out on pre-coated Silica
gel 60 F254 plates and reversed-phase RP-18 F254
S
plates (0.25 mm thickness, Merck, Darmstadt, Ger-
many) and spots were detected under UV light or after
spraying with anisaldehyde–H2SO4 reagent followed by
heating. Silica gel 60 (70–230 mesh, Merck, Darmstadt,
Germany) was used for column chromatography. 1H
and 13C NMR spectra were measured with a JEOL-
JNM-GX 400 (1H, 400 MHz; 13C, 100 MHz) spectro-
photometer and chemical shifts were given in d ppm
relative to tetramethylsilane (TMS). Electron impact
Table 6. 13C NMR data of 6-(substituted)-13H-dibenzo[d,h][1,3,7]oxadiazecine-8,14-dione derivatives (18–27, 30, 32)
Compound –C(O)– –C(O)–O– –C¼N–
Ar–C
Others
NH–
18a
19a
20a
21a
22b
23b
24b
25b
168.5
168.5
171.4
171.2
171.2
171.2
171.1
171.9
158.3
158.1
158.2
158.7
158.2
158.2
158.2
158.3
156.8
156.3
156.8
156.7
156.6
156.6
157.6
157.6
116.7, 117.0, 120.9, 123.1, 126.6, 128.1,
128.9, 129.4, 133.2, 137.0, 139.2, 145.4
116.8, 116.9, 120.6, 123.9, 126.3, 128.1,
129.0, 129.5, 133.5, 137.0, 138.5, 145.0
116.7, 117.0, 120.8, 123.0, 126.3, 128.0,
128.9, 129.4, 133.2, 137.0, 139.1, 145.5
115.6, 116.4, 120.3, 122.5, 126.0, 128.0,
128.6, 129.0, 133.1, 136.6, 139.6, 145.8
114.4, 116.8, 120.6, 122.7, 126.1, 128.8,
129.0, 129.5, 134.2, 136.8, 140.8, 145.4
114.4, 116.8, 120.6, 122.7, 126.1, 128.8,
129.0, 129.5, 134.2, 136.8, 140.8, 145.4
114.4, 116.8, 120.6, 122.7, 126.1, 128.8,
129.0, 129.5, 134.2, 136.8, 140.8, 145.4
114.5, 116.8, 120.7, 122.8, 126.1, 128.9,
129.1, 129.5, 134.3, 136.9, 140.8, 145.4
26.7 (CH3)
43.8 (CH2Cl)
13.8, 21.9, 25.0, 28.4, 28.5, 31.0, 37.4
(6ꢄCH2, CH3)
13.7, 21.9, 25.0, 28.5, 28.5, 28.7, 28.7, 31.1, 37.7
(8ꢄCH2, CH3)
14.1, 22.6, 25.8, 29.3, 29.4, 29.4, 29.5, 29.6, 29.6,
31.9, 39.1 (10ꢄCH2, CH3)
14.1, 22.7, 25.8, 29.3, 29.4, 29.4, 29.5,
29.6, 29.6, 29.6, 29.7, 31.9, 39.1 (12ꢄCH2, CH3)
25.7, 28.8, 29.1, 29.3, 29.3, 29.3, 33.7, 39.1
(8ꢄCH2), 114.2 (CH2¼CH–), 139.1 (CH2¼CH–)
14.1, 22.7, 25.8, 27.2, 27.3, 29.0, 29.2, 29.4, 29.4,
29.5, 29.7, 29.7, 31.9, 32.6, 39.1 (14ꢄCH2, CH3),
130.0, 130.3 (–CH¼CH–)
26a
27c
30b
32a
169.4
176.2
169.5
166.2
158.2
157.6
158.5
158.2
156.6 116.7, 117.1, 120.9, 122.2, 126.6, 126.7, 127.9, 128.4,
128.9, 129.2, 129.4,133.2, 135.2, 136.8, 139.0, 145.1
156.7
44.3 (–CH2–Ph)
115.7, 116.5, 120.4, 122.3, 125.2, 128.2,
128.6, 129.1, 133.1, 136.7, 139.9, 145.0
116.1, 116.8, 121.4, 123.2, 127.2, 128.8,
128.9, 129.6, 133.8, 136.5, 139.7, 145.7
78.7, 76.4, 41.7, 38.8, 36.0, 27.5
(adamantanyl carbons)
45.8 (N–CH3), 53.3, 54.1
(piperazinyl CH2), 64.0 (–CH2–)
37.0 (CH2S)
157.0
156.3 113.5, 116.7, 117.4, 121.1, 122.3, 123.3, 123.8, 126.9,
127.9, 129.0, 129.5, 133.3, 136.9, 138.5, 145.1, 149.3
aDMSO.
bCDCl3.
cCDCl3–DMSO.

2302
A. A. Abdel-hafez / Bioorg. Med. Chem. 10 (2002) 2297–2302
(EI) mass spectra were measured with a JEOL GC-mate
spectrometer at an ionization voltage of 70 eV. Ele-
mental analyses were performed at the microanalytical
center of Toyama Medical and Pharmaceutical Uni-
versity. All chemicals used were of analytical grade.
in Table 4. 1H and 13C NMR data are presented in
Tables 5 and 6, respectively.
Synthesis of 6-(1H-benzimidazol-2-ylthiomethyl)-13H-di-
benzo[d,h] [1,3,7] oxadiazecine-8,14-diones (32). To a
stirred solution of 19 (0.4 g, 1.27 mmol) in benzene
(5 mL), 2-mercaptobenzimidazol 31 (0.19 g, 1.27 mmol)
and pyridine (0.1 mL) was added. The reaction mixture
was refluxed for 5 h and the precipitate formed after
cooling was filtered off and crystallized from the proper
solvent. Yield and physical constants are listed in Table
Synthesis of 2-(2-aminobenzoylamino)-benzoic acid (7).14,15
A suspension of 5 (2.5g, 0.015 mol) and 6 (2.3 g,
0.017 mol) in water (50 mL) was refluxed for 1h and then
cooled. The separated crystals were filtered off, washed
with water and crystallized from CHCl3–ethanol to afford
7, yield (3.1 g, 79%) as pale yellow crystals, mp >300 ꢃC.
IR (KBr) n cmꢀ1: 3400–3300 (NH2, OH), 3200 (NH), 1695
(acid C¼O), 1650 (amide C¼O). 1H NMR (DMSO-d6) d:
11.94 (1H, s, NH), 8.66ꢂ6.64 (8H, Ar–H) and 3.45 (2H, br
S, NH2). 13C NMR (DMSO-d6) d: 170.0 (COOH), 167.4
(CONH), 150.5, 141.4, 134.2, 132.8, 131.2, 127.3, 122.5,
119.9, 117.1, 116.3, 115.2 and 114.0 (aromatic carbons).
EI-MS m/z 256 [M]+, 238 [MꢀH2O]+, 119, 92 and 65.
1
4. H and 13C NMR data are presented in Tables 5 and
6, respectively.
Acknowledgement
The author would like to express his gratitude and
thanks to the staff members of National Cancer Insti-
tute (NCI), Bethesda, MD (USA) for performing the
antitumor testing of the compounds.
General method for synthesis of compounds 8–17
To an ice cooled solution of 7 (1 equiv mol) in dioxane,
a solution of the appropriate acid chloride (1 equiv mol)
in dioxane was added drop wise. The reaction mixture
was stirred overnight at room temperature. The product
after addition of water was filtered off, washed with
water and crystallized from the proper solvents. Yields
References and Notes
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1
and physical constants are listed in Table 1. H and 13C
NMR data are presented in Tables 2 and 3, respectively.
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amino]-benzoylamino}-benzoic acid (29). N-Methyl
piperazine (28, 0.3 g, 3 mmol) was added to a solution of
9 (0.4 g, 1.2 mmol) in DMF (3 mL) and the reaction
mixture was refluxed for 1.5 h in an oil bath. The pre-
cipitate formed after addition of ice water was filtered,
washed with water and then ether. The residue was
purified bySiO
CHCl3/MeOH as eluent. Yield and physical constants
gel column chromatographyusing
2
1
are listed in Table 1. H and 13C NMR data are pre-
sented in Tables 2 and 3, respectively.
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General method for synthesis of compounds 18–27, 30
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A solution of the appropriate benzoic acid derivative 8–
17, 29 (0.3 g) in acteic anhydride (5 mL) was refluxed for
15 min. After cooling to room temperature, the products
precipitated were filtered and crystallized from the
proper solvents. Yields and physical constants are listed