A convenient method for the synthesis of cyclophosphamide analogues

Article abstract of DOI:10.1080/10426500701808200

Several new 2-[bis(2-chloroethyl)amino)]-7-methoxyl-3-alkyl-4-methyl-1,3,2- benzoxazaphosphorin-2-oxides(3a-e) have been synthesized by cyclic condensation of bis(2-chloroethyl)amino phosphoryl dichloride and 2-(1-alkylamino) ethyl-4-methoxylphenol. The title compounds are characterized by NMR, ESI-Q-TOF, and ESI-MS. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426500701808200

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Phosphorus, Sulfur, and Silicon
and the Related Elements
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A Convenient Method for the
Synthesis of Cyclophosphamide
Analogues
Zhang Liuji a , Qu Lingbo a b , Zhang Baojun a , Chen
Xiaolan a & Zhao Yufen a
a Department of Chemistry, Zhengzhou University,
Zhengzhou, P. R. China
b Henan University of Technology, Henan Province,
Zhengzhou, P. R. China
Published online: 20 Jun 2008.
To cite this article: Zhang Liuji , Qu Lingbo , Zhang Baojun , Chen Xiaolan & Zhao
Yufen (2008) A Convenient Method for the Synthesis of Cyclophosphamide Analogues,
Phosphorus, Sulfur, and Silicon and the Related Elements, 183:2-3, 799-803, DOI:
10.1080/10426500701808200
To link to this article: http://dx.doi.org/10.1080/10426500701808200
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Phosphorus, Sulfur, and Silicon, 183:799–803, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701808200
A Convenient Method for the Synthesis
of Cyclophosphamide Analogues
Zhang Liuji,1 Qu Lingbo,1,2 Zhang Baojun,1
Chen Xiaolan,1 and Zhao Yufen1
1Department of Chemistry, Zhengzhou University, Zhengzhou,
P. R. China
2Henan University of Technology, Henan Province, Zhengzhou,
P. R. China
Several
new
2-[bis(2-chloroethyl)amino)]-7-methoxyl-3-alkyl-4-methyl-1,3,2-
benzoxazaphosphorin-2-oxides(3a-e) have been synthesized by cyclic condensation
of bis(2-chloroethyl)amino phosphoryl dichloride and 2-(1-alkylamino) ethyl-4-
methoxylphenol. The title compounds are characterized by NMR, ESI-Q-TOF, and
ESI-MS.
Keywords Cyclophosphamide analogues; N,N-di-(2-chloro)ethylaminophosphorodichlo-
ridate; paeonia
INTRODUCTION
The paeonia species (paeoniaceae), a traditional Chinese herb, has been
used as an analgesic and anti-inflammatory drug. It also has a bene-
ficial effect in prevention and treatment of thomboembolic diseases.
Paeonol (2ꢀ-hydrooxy-4ꢀ-methoxyacetophenone), the effective compo-
nent of Cortex Moutan, is proved to have a variety of effects, including
antibacteria,1 antiinflammation,2 relieving pain,3 anti-hypersensitive,4
strengthening the immune system,5and anticancer.6
Cyclophosphamide (the generic name for Cytoxan, Neosar), a ni-
trogen mustard alkylating agent, is used to treat various types of
autoimmune disorders as a “prodrug.” It is converted in the liver to
active forms that have chemotherapeutic activity.7–9 The main use of
cyclophosphamide is together with other chemotherapy agents in the
treatment of lymphomas, some forms of leukemia, and some solid tu-
mors. It also works by decreasing the immune system’s response to
The authors thank the Chinese National Natural Science Foundation (No. 20472076)
and Henan Excellent Youth Grant (No. 0512001400).
Address correspondence to Chen Xiaolan, Department of Chemistry, Zhengzhou Uni-
versity, Zhengzhou, 450052, P. R. China, E-mail: chenxl@zzu.edu.cn
799

800
Z. Liuji et al.
SCHEME 1
various diseases. Cyclophosphamide is converted by mixed function
oxidase enzymes in the liver to active metabolites. The main active
metabolite, 4-hydroxycyclophosphamide, exists in equilibrium with its
tautomer, aldophosphamide. Aldophosphamide could be converted into
phosphoramide mustard and acrolein in tumor cells, whereas, most
aldophosphamide can only be transformed into carboxyphosphamide
by the enzyme aldehyde dehydrogenase (ALDH), which mainly exists
in normal cell.10 In efforts to obtain potential anticancer prodrugs,
modifications of cyclophosphamide led to the design and synthesis of
many cyclic and acyclic phosphoramidate agents in the past decades.
In order to search new compounds with higher antitumor activities
and lower toxicity, we report a convenient method for synthesis of
some new cyclophosphamide analogues (Scheme 1), cyclophosphamide
paeonol analogues. They were designed and synthesized on the ba-
sis of associate principle by combinations of paeonol and N,N–di-(2-
chloro)ethylamino-phosphorodichloridate, and their structures were
determined by electrospray quadrupole time-of-flight (ESI-Q-TOF),
electrospray-mass spectrometry (ESI-MS), and NMR.
EXPERIMENTAL
1H-NMR, 13C-NMR and, 31P-NMR spectra were on a Bruker-DTX-400,
chemical shifts were expressed in parts per million positive values

The Synthesis of Cyclophosphamide Analogues
801
downfield from internal TMS (1H) and external 85% H3PO4 (31P), cou-
pling constants were expressed in Hertz. MS was recorded on Bruke
Esquire-3000 and Micromass Q-TOF. Melting point was recorded on a
microscopical determinator XT4 A (the thermometer was not adjusted).
Synthesis of N,N–di-(2-chloro)ethylamino-
phosphorodichloridate(compound I)
To a magnetically stirred solution of phosphorus oxychloride (0.02 mol,
1.8 ml) in 50 ml methylene chloride at −5◦C was added dropwise to a so-
lution of bis(2-chloromethyl) amine hydrochloride (0.02 mol, 3.55 g) and
triethylamine (0.02 mol, 2.78 ml) in 50 ml methylene dichloride over 1 h.
The reaction mixture was stirred overnight at room temperature, con-
centrated in vacuo and mixed with benzene. The precipitated amine salt
was filtered off and the filtrate was crystallized in acetone/petroleum
ether to give colorless crystals, m.p.47◦C(lit8).
Synthesis of 2-(1-cyclohexylamino)
ethyl-4-methoxylphenol(Compound IIe)
A solution of paeonol (0.03 mol, 4.98 g) in 10 ml dry n-BuOH was added
to a stirred solution of cyclohexylamine(0.03 mol, 3.45 ml) and catalytic
amount of TsOH in 30 ml dry n-BuOH. The reaction mixture was re-
fluxed for 12 h. The reaction solution was concentrated in a rota evapo-
rator and recrystallization from ethanol afforded the light yellow crystal
(shiff base); NaBH4 was added to a solution of the shiff base on ice bath,
and the mixture was allowed to react for 2 h on ice bath. After reaction,
AcOEt (50 ml) was added, the mixture was washed with brine and dried
over MgSO4. Then the solvent was evaporated off and the product was
obtained as light yellow liquid. The synthesis of (IIa–d) was followed
with the same procedure.
2-[bis(2-chloroethyl)amino]-7-methoxyl-3-cyclohexyl-4-
methyl-1,3,2-benzoxazaphosphorin-2-oxides(IIIe) was
prepared by the following procedure
N,N–di-(2-chloroethyl)amino-phosphorodichloridate (I) (2.59 g,
0.01 mol) in dry THF (20 ml) was added dropwise to a stirred so-
lution of 2-(1-cyclohexylamino) ethyl-4-methoxylphenol (IIe)(2.49 g,
0.01 mol) and triethylamine (2.78 ml, 0.02 mol) in dry THF on ice bath
0◦C. The reaction mixture was stirred at room temperature for 2 h and
for another 6 h at 61◦C. Solid triethylamine hydrochloride was filtered

802
Z. Liuji et al.
off and the filtrate was concentrated in a rota evaporator. The residue
was purified by silica gel column chromatography to give light yellow
liquid. The synthesis of Substituted benzoxazaphosphorin-2-oxides
(IIIa–d) was followed with the same procedure.
Compound IIIa (C17H27Cl2N2O3P) 1H-NMR (CDCl3 400MHz) δ:
6.95 (d, J = 8.30 Hz, 1H, 5-H), 6.65 (d, J = 2.46 Hz, 1H, 8-H),
6.62 (m, 1H, 6-H), 4.25 (m, 1H, 4-H), 3.77 (s, 3H, -OCH3), 3.77–3.43
(m, 8H, –N(CH2CH2Cl)2), 3.12–2.93 (m, 2H, –CH2CH2CH2CH3), 1.68–
1.64 (m, 2H, –CH2CH2CH2CH3), 1.41 (d, 3H, J = 6.66 Hz, –CHCH3),
1.36–1.26 (m, 2H, –CH2CH2CH2CH3), 0.94 (m, 3H, –CH2CH2CH2CH3);
13C-NMR (CDCl3 400 MHz) δ: 159.98 (7-C), 149.54 (9-C), 126.76 (6-C),
122.74 (8-C), 111.11 (5-C), 104.79 (10-C), 55.52 (–N(CH2CH2Cl)2), 49.69
(–NCH2CH2CH2CH3), 46.38 (4-C), 42.39 (–N (CH2CH2Cl)2), 30.72
(–NCH2CH2CH2CH3), 24.03 (4-CH3), 20.23 (–NCH2CH2CH2CH3),
13.85 (–NCH2CH2CH2CH3); 31P-NMR (CDCl3 400 MHz) δ: 11.11; ESI-
MS, m/z: 409[M+H]+. A molecular formula of C17H27Cl2N2O3P was
determined from the molecular ion peak at 409.1130 m/z [M+H]+
(calc.408.1136 for C17H27Cl2N2O3P) obtained by ESI-Q-TOF.
Compound IIIb (C16H25Cl2N2O3P) 1H-NMR (CDCl3 400 MHz) δ:
6.95 (d, J = 8.24 Hz, 1H, 5-H), 6.65 (d, J = 2.46 Hz, 1H, 8-
H), 6.63 (m, 1H, 6-H), 4.25 (m, 1H, 4-H), 3.77 (s, 3H, 7-OCH3),
4.24–3.43 (m, 8H, –N(CH2CH2Cl)2), 2.90–3.08 (m, 2H, –NCH2CH2CH3),
1.71–1.68 (m, 2H., –NCH2CH2CH3), 1.41 (d, J = 6.56, 3H, 4-CH3),
0.91 (m, 3H, –NCH2CH2CH3); 13C-NMR (CDCl3 400 MHz) δ: 159.92
(7-C), 149.48 (9-C), 126.68 (6-C), 122.67 (8-C), 111.06 (5-C), 104.73
(10-C), 55.52 (–N(CH2CH2Cl)2), 49.61 (–NCH2CH2CH3), 48.30 (4-C),
42.30 (–N(CH2CH2Cl)2), 23.99 (–NCH2CH2CH3), 21.79 (4-CH3), 11.27
(–NCH2CH2CH3); 31P-NMR (CDCl3 400 MHz) δ: 11.15; ESI-MS, m/z:
395[M+H]+. A molecular formula of C16H25Cl2N2O3P was determined
from the molecular ion peak at 395.0901 m/z [M+H]+ (calc. 394.0890
for C16H25Cl2N2O3P) obtained by ESI-Q-TOF.
Compound IIIc (C16H25Cl2N2O3P) 1H-NMR (CDCl3 400 MHz)δ: 7.01
(d, J = 8.20 Hz, 1H, 5-H), 6.50 (d, J = 2.45 Hz, 1H, 8-H), 6.46 (m,
1H, 6-H), 5.20 (m, 1H, 4-H), 3.81 (s, 3H, –OCH3), 3.77–3.68 (m, 8H,
–N(CH2CH2Cl)2), 3.10 (m, 1H, –CH (CH3)), 1.36 (d, J = 6.65 Hz, 3H,
4-CH3), 1.18 (m, 6H, –CH (CH3)); 13C-NMR (CDCl3 400 MHz) δ: 159.03
(7-C), 149.84 (9-C), 125.86 (6-C), 119.71 (8-C), 111.06 (5-C), 105.15 (10-
C), 55.50 (–N(CH2CH2Cl)2), 49.56 (–NCH (CH3)2), 47.91 (4-C), 42.33 (–N
(CH2CH2Cl)2), 29.36 (–NCH2 (CH3)2), 26.49 (4-CH3);31P-NMR (CDCl3
400 MHz) δ: 11.87; ESI-MS, m/z: 395[M+H]+. A molecular formula
of C16H25Cl2N2O3P was determined from the molecular ion peak at
395.0901 m/z [M+H]+ (calc. 394.0890 for C16H25Cl2N2O3P) obtained
by ESI-Q-TOF.

The Synthesis of Cyclophosphamide Analogues
803
Compound IIId (C17H27Cl2N2O3P) 1H-NMR (CDCl3 400 MHz) δ: 7.03
(d, J = 8.36 Hz, 1H, 5-H), 6.58 (d, J = 2.32Hz, 1H, 8-H), 6.47 (m, 1H,
6-H), 5.18 (m, 1H, 4-H), 3.94 (s, 3H, –OCH3), 3.97–3.63 (m, 8H, –N
(CH2CH2Cl)2), 1.35 (d, J = 6.59Hz, 3H, 4-CH3),1.30 (s, 9H, –C (CH3)3);
13C-NMR (CDCl3 400-MHz) δ: 159.01 (7-C), 149.50 (9-C), 125.46 (6-C),
119.72 (8-C), 111.07 (5-C), 106.17 (10-C), 55.47 (–N (CH2CH2Cl)2), 50.16
(4-C), 42.07(–N(CH2CH2Cl)2), 29.36(–C (CH3)3), 21.79 (4-CH3), 11.27
(–NCH2CH2CH3);31P-NMR (CDCl3 400 MHz) δ: 11.73; ESI-MS, m/z:
409[M+H]+. A molecular formula of C17H27Cl2N2O3P was determined
from the molecular ion peak at 409.1130 m/z [M+H]+ (calc. 408.1136
for C17H27Cl2N2O3P) obtained by ESI-Q-TOF.
Compound IIIe (C19H29Cl2N2O3P) 1H-NMR (CDCl3 400 MHz) δ: 7.04
(d, J = 8.30 Hz, 1H, 5-H), 6.50 (d, J = 2.56 Hz, 1H, 8-H), 6.45 (m, 1H, 6-
H), 4.31 (m, 1H, 4-H), 4.08 (m, 1H, –NCH(CH2)5), 3.89 (s, 3H, –OCH3),
3.80–3.73 (m, 8H, –N(CH2CH2Cl)2), 1.34 (d, J = 6.59 Hz, 3H, 4-CH3),
1.89–1.38 (m, 10H, –NCH (CH2)5); 31P-NMR (CDCl3 400 MHz) δ: 11.03;
ESI-MS, m/z: 436[M+H]+. A molecular formula of C19H29Cl2N2O3P
was determined from the molecular ion peak at436.3261 m/z
[M+H]+ (calc. 435.3249 for C19H29Cl2N2O3P) obtained by ESI-Q-
TOF.
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