Synthesis of actinomycin analogs: XXIV. Non-symmetric derivatives of actinocin containing benzo-18-crown-6 moiety and tertiary ammonium group

Article abstract of DOI:10.1134/S1070363216120070

Non-symmetric derivatives of actinocin containing fragments of benzo-18-crown-6 and dimethylaminopropylamine (with the crown ether group separated from the heterocyclic chromophore by β-alanine moiety) have been prepared as models of actinomycin D.

Full text of DOI:10.1134/S1070363216120070

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 12, pp. 2612–2615. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © D.V. Ovchinnikov, A.I. Ponyaev, 2016, published in Zhurnal Obshchei Khimii, 2016, Vol. 86, No. 12, pp. 1975–1978.
Synthesis of Actinomycin Analogs:
XXIV.1 Non-Symmetric Derivatives of Actinocin Containing
Benzo-18-crown-6 Moiety and Tertiary Ammonium Group
D. V. Ovchinnikov* and A. I. Ponyaev
St. Petersburg State Institute of Technology (Technical University), Moskovskii pr. 26, St. Petersburg, 190013 Russia
*e-mail: rvwp98@gmail.com
Received September 3, 2015
Abstract—Non-symmetric derivatives of actinocin containing fragments of benzo-18-crown-6 and dimethyl-
aminopropylamine (with the crown ether group separated from the heterocyclic chromophore by β-alanine
moiety) have been prepared as models of actinomycin D.
Keywords: actinocin, crown ether, DNA complexon
DOI: 10.1134/S1070363216120070
We have earlier prepared several actinocin
derivatives as models of actinomycin, containing frag-
ments of benzo-15-crown-5(18-crown-6) or aza-15-
crown-5(18-crown-6) connected with the phenoxazone
moiety either directly [1, 2] or via a spacer of different
length [2, 3]. Actinocin derivatives containing amino
groups in the side chain exhibit a range of biological
activity [4, 5]. It was therefore of interest to study the
actinocin derivatives containing a catinoid group in the
α(β)-chain or a crown group in the β(α)-chain.
ponding amides of 2-nitro-3-benzyloxy-4-R-benzoic
acid. In this paper N-[(benzo-18-crown-6)-4'-ylamino-
carbamoyl]alkyl-2-nitro-3-benzyloxy-4-methylbenz-
amides were such amides. Such compounds can be
prepared via several routes. In reports [2, 3], they have
been synthesized starting from 2-nitro-3-benzyloxy-4-
methylbenzoyl chloride [10] and hydrochloride of the
ester of the corresponding amino acid, with hyd-
razinolysis of the prepared N-methoxycarbonylalkyl-2-
nitro-3-benzyloxy-4-methylbenzamides. Compound 1
has been then converted in the corresponding acyl
azide 2, that has been further introduced without
isolation in the reaction with the amine component.
When using this approach, the yield of the target
compounds at the stage of azide synthesis rarely
exceeds 60–70% in the case of the amidobenzocrowns.
Moreover, due to the poor availability of the inter-
mediate compounds and the complicated procedure of
elimination of excess of unreacted starting compounds,
the use of one of the reactants in excess is impossible
(Scheme 1).
Using non-symmetric derivatives of actinocin
containing different substituents in the α- and β-
fragments as examples [6–9], we have earlier
demonstrated that they can be prepared via co-
oxidation of 3-oxyanthranilic acids substituted at posi-
tion 4. It has been stated that the difference in electro-
negativity of Н and СН3 groups in position 4 of the
benzene ring is sufficient for formation of the mixed
oxidation products, the non-symmetric product
containing a methyl group in the quinoid ring of the
chromophore of actinocin prevailing [8]. Therefore, we
used amides of 3-oxyanthranilic and 4-methyl-3-
oxyanthranilic acids for the preparation of non-
symmetric derivatives of actinocin.
To avoid such complications, we attempted the
preparation of compound 3 starting from pentafluoro-
phenyl esters of N-carbobenzoxyamino acids that
could be obtained via the action of a carbodiimide
(dicyclohexylcarbodiimide is often used) on the sub-
stituted amino acid in the presence of pentafluoro-
phenol. The stability of the activated derivatives of ω-
amino acids is a known issue; therefore, pentafluoro-
The key compounds in the synthesis of substituted
amides of 4-R-3-oxyanthranilic acid were the corres-
1
For communication XXIII, see [1].
2612

SYNTHESIS OF ACTINOMYCIN ANALOGS: XXIV.
2613
Scheme 1.
O
N
O
O
N
N3
O
N
NHR
NO2
O
NO2
O
NO2 O
(1) N2H4
(2) HNO2
RNH2
OBn
OBn
OBn
1
2
3
R = 4'-benzo-18-crown-6-yl.
Scheme 2.
4'-NH2-Benzo-18-crown-6
ZNHCH2CH2COPfp
ZNH(CH2)2CONH-Benzo-18-crown-6
4
O
Cl
NO2
OBn
R2
NHR1
O
N
NHR1
O
N
NO2
OBn
O
NH2
OH
O
H2/Pd(C)
R2
R2
3а, 3b
5а, 5b
R1 = 4'-benzo-18-crown-6-yl, R2 = H (a), CH3 (b); Z = BnOCO, Pfp is pentafluorophenyl.
phenyl ester of β-alanine was used directly after the
preparation. The use of excess of the activated ester at
the stage of condensation with aminobenzocrown
allowed significant increase of the product yield. After
elimination of carbobenzoxy group via catalytic
hydrogenation of compound 4, it was introduced in the
reaction with 2-nitro-3-benzyloxybenzoyl chloride
(Scheme 2).
of the phenoxazone chromophore. It has been demon-
strated that the different in the electronic effects of
hydrogen atom and methyl group is sufficient for this.
Hence, the condensation of compounds 5 with (3'-
dimethylaminopropyl)-2-amino-3-oxy-4-methylbenz-
amide should have led to the compound 6 as the major
product and isomers 7 and 8 as the minor ones
(Scheme 3). That was confirmed by the presence of the
signal of hydrogen atom in position 6 of phenoxazone
chromophore in the 1Н NMR spectrum.
The prepared amide 3 were converted into the
corresponding derivatives of 3-hydroxyanthranilic acid
5 by means of catalytic hydrogenation; their oxidation
with p-quinone afforded the target compounds 6.
Hence, we demonstrated the possibility of selective
introduction of a crown group in the derivatives of
actinocin by the variation of the substituent in position
4 of the starting benzamide.
It has been earlier shown [7–9] that oxidative
condensation of a mixture of two derivatives of
anthranilic acid containing different substituents in
position 4 of the benzene ring results in the
predominant formation of the non-symmetric product
with the less electron-donating substituent in position 6
EXPERIMENTAL
1Н NMR spectra were recorded using a Bruker AC-
400 device (DMSO as solvent). Melting points were
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 12 2016

2614
OVCHINNIKOV, PONYAEV
Scheme 3.
COR2
R1
O
COR1
O
R2
NH2
NH2
OH
N
O
NH2
O
[O]
+
OH
R3
R3
X
5а, 5b
6а, 6b
R2
O
R1
R1
O
O
R2
O
N
O
NH2
O
N
NH2
O
+
+
O
R3
R3
7а, 7b
R3
R3
8а, 8b
X = H, CH3; R1 = NH(CH2)3N(CH3)2, R2 = NH(CH2)2CON-Benzo-18-crown, R3 = H (а), CH3 (b).
determined using an HMK Kofler bench. TLC analysis
was performed using Merck Silica gel 60 F254 plates
with the following eluent systems: methanol–
chloroform, 1 : 4 (A), methanol–chloroform–3% aqueous
ammonia composition (B), ethyl acetate–hexane, 1 : 1
(C), and 2-butanol–3% aqueous ammonia solution,
5 : 2 (D).
(7H, Ar-H). Found, %: C 60.78, 60.84; H 6.85, 6.92; N
5.27, 5.32. C27H36N2O9. Calculated, %: C 60.89; H
6.81; N 5.26.
2-N-[(Benzo-18-crown-6)-4'-ylaminocarbamoyl]-
ethyl-2-nitro-3-benzyloxybenzamide (3a). A solution
of 0.133 g (0.25 mmol) of compound 4 in 5 mL of a
mixture of methanol and dioxane was reduced with
hydrogen at room temperature and atmospheric
pressure on a palladium catalyst (5% Pd/C) until
complete elimination of carbobenzoxy groups. The
catalyst was filtered off, and the solvents were re-
moved in vacuum. The residue was dissolved in 2 mL
of dioxane; 0.25 mL of triethylamine and a solution of
0.076 g (0.263 mmol) of 2-nitro-3-benxyloxybenzoyl
chloride in 2 mL of dioxane were added. The obtained
mixture was stirred at room temperature during 18 h.
After removal of the solvent, the residue was treated
with water and crystallized from a mixture of dioxane
and ethyl acetate. Yield 0.134 g (82%), mp 181–187°С.
1Н NMR spectrum, δ, ppm: 2.71 m (2H, COCH2CH2N),
3.08 m (2H, COCH2CH2N), 3.46–4.28 br.m (20H,
OCH2CH2O), 5.21 s (2H, OCH2Ph), 6.55 d and 6.81 d
(2H, Ar-H), 7.02–7.16 m (6H, Ar-H), 7.36 m (2H,
Ar-H). Found, %: C 60.48, 60.52; H 6.07, 6.13; N
6.25, 6.32. C33H39N3O11. Calculated, %: C 60.63; H
6.01; N 6.43.
Commercially available chemicals were used as
received. The solvents were purified by the standard
methods and stored over 4 Å molecular sieves in the
dark.
N-[(Benzo-18-crown-6)-4'-yl]amide of carbobenzoxy-
β-alanine (4). A solution of 0.325 g (1.575 mmol) of
dicyclohexylcarbodiimide in 2 mL of anhydrous ethyl
acetate was added at 0°C to a solution of 0.335 g
(1.5 mmol) of carbobenzoxy-β-alanine and 0.335 g
(1.8 mmol) of pentafluorophenol in 5 mL of a DMF–
ethyl acetate mixture (1 : 20). The obtained mixture
was stirred at 0°С during 2 h and left overnight at 5°С.
A few drops of 50% aqueous acetic acid were then
added, and the mixture was stirred at 0°С during 1 h.
The mixture was filtered through a thin layer of
MgSO4 to remove the precipitate, and a chloroform
solution of 4'-aminobenzo-18-crown-6 [prepared from
0.445 g (1.25 mmol) of 4'-nitrobenzo-18-crown-6 via
catalytic reduction with hydrogen on Pd/C] was added
to the filtrate. Yield 0.573 g (86%). 1Н NMR spectrum,
δ, ppm: 2.51 m (2H, COCH2CH2N), 3.12 m (2H,
COCH2CH2N), 3.42–4.29 br.m (20H, OCH2CH2O),
4.01 s (2H, OCH2Ph), 6.55 m (2H, Ar-H), 7.01–7.58 m
2-N-[(Benzo-18-crown-6)-4'-ylaminocarbamoyl]-
ethyl-2-nitro-3-benzyloxy-4-methylbenzamide (3b)
was prepared similarly from 0.426 g (0.8 mmol) of
compound 4 and 0.256 g (0.84 mmol) of 2-nitro-3-
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SYNTHESIS OF ACTINOMYCIN ANALOGS: XXIV.
2615
benzyloxy-4-methylbenzoyl chloride. Yield 0.424 g
(81%), mp 185–191°C. Н NMR spectrum, δ, ppm:
(3H, CH3-Ar), 2.21–2.26 m [8H, (CH3)2N, CH2N),
2.72 m (2H, COCH2CH2N), 3.15 m (2H, COCH2CH2N),
3.38 m (2H, NCH2CH2CH2N), 3.52–4.29 m (20H,
OCH2CH2O), 6.52 m (3H, Ar-H), 6.98–7.55 m (5H,
Ar-H). Found, %: C 56.73, 56.78; H 6.19, 6.24; N
10.31, 10.36. C39H50N6O11·HCl. Calculated, %: C
56.96; H 6.16; N 10.49.
1
2.23 s (3Н, СН3), 2.68 m (2H, COCH2CH2N), 3.05 m
(2H, COCH2CH2N), 3.43–4.31 br.m (20H, OCH2CH2O),
5.18 s (2H, OCH2Ph), 6.47 d and 6.75 d (2H, Ar-H),
6.98–7.15 m (7H, Ar-H), 7.36–7.72 m (2H, Ar-H).
Found, %: C 61.19, 61.26; H 6.17, 6.21; N 6.15, 6.18.
C34H41N3O11. Calculated, %: C 61.16; H 6.19; N 6.29.
ACKNOWLEDGMENTS
1-(3-Dimethylaminopropylcarbamoyl)-2-amino-
4-methyl-9-[(benzo-18-crown-6)-4'-ylaminocarbamoyl]-
ethyl-3H-3-oxophenoxazine hydrochloride (6a). A
mixture of 0.096 g (0.147 mmol) of compound 3a and
0.06 g (0.147 mmol) of (3'-dimethylaminopropyl)-2-
nitro-3-benzyloxy-4-methylbenzamide [8] in 5 mL of a
mixture of methanol and dioxane was reduced with
hydrogen at room temperature and atmospheric pres-
sure on palladium catalyst (5% Pd/C) until complete
conversion in the corresponding derivatives of 3-hyd-
roxy-2-aminobenzoic acid (TLC monitoring with
system A). The catalyst was filtered off and washed
with a small amount of methanol. A solution of 0.024 g
(0.23 mmol) of p-quinone in 2 mL of methanol was
added to the filtrate. The mixture was kept during 15 h
in the dark, and then the solvent was distilled off. The
residue was treated several times with diethyl ether,
dissolved in methanol, the product with two crown
groups was filtered off, the solvent was removed, and
the residue was crystallized from a mixture of
methanol and ethyl acetate. Yield 0.027 g (22.5%), mp
This work was financially supported by the
Ministry of Education and Sciences of the Russian
Federation (agreement no. 14.574.21.0002, unique
identifier RFMEFI57414X0002) and Russian Foundation
for Basic Research (project no. 13-08-01425).
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136–144°C. Н NMR spectrum, δ, ppm: 1.64 m (2H,
NCH2CH2CH2N), 1.95 s (3Н, СН3), 2.18–2.27 m [8H,
(CH3)2N, CH2N), 2.61 m (2H, COCH2CH2N), 3.35 m
(2H, NCH2CH2CH2N), 3.58–4.21 m (22H, OCH2CH2O,
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ethyl-2-amino-4-methyl-9-(3-dimethylaminopropyl-
carbamoyl)-3H-3-oxophenoxazine hydrochloride
(6b) was prepared similarly from 0.05 g (0.075 mmol)
of compound 3b and 0.03 g (0.075 mmol) of (3'-di-
methylaminopropyl)-2-nitro-3-benzyloxybenzamide.
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1
Yield 0.011 g (18%), mp 132–138°C. Н NMR spec-
trum, δ, ppm: 1.71 m (2H, NCH2CH2CH2N), 1.94 s
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 12 2016