Gold(III) tetraarylporphyrin phosphonate derivatives as potential anticancer agents

Article abstract of DOI:10.3184/174751912X13406179445757

5-[4-(Dialkyoxyphosphorylamino)]phenyl-10,15,20-triphenylporphyrinato gold(III)chlorides have been synthesised and evaluated for their in vitro cytotoxic activity against SMMC-7721 human hepatic and sarcoma 180 mouse cancer cell line panels. 5-[4-(Diisopr

Full text of DOI:10.3184/174751912X13406179445757

JOURNAL OF CHEMICAL RESEARCH 2012
RESEARCH PAPER 501
SEPTEMBER, 501–505
Gold(III) tetraarylporphyrin phosphonate derivatives as potential
anticancer agents
Huasheng Chena, Jun Lia, Tingting Shena, Yan Lib, Juanjuan Liub, Jinliang Liub, Aihua Xua
and Cunde Wangb*
aSchool of Medicine, Yangzhou University, Yangzhou 225002, P. R. China
bSchool of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225009, P. R. China
5-[4-(Dialkyoxyphosphorylamino)]phenyl-10,15,20- triphenylporphyrinato gold(III)chlorides have been synthesised
and evaluated for their in vitro cytotoxic activity against SMMC-7721 human hepatic and sarcoma 180 mouse cancer
cell line panels. 5-[4-(Diisopropoxyphosphorylamino)]phenyl-10,15,20- triphenylporphyrinato gold(III)chloride exhib-
ited significant growth inhibitory properties against sarcoma 180 mouse cancer cells (IC50 value = 2.60 µM) and 5-[4-
(dipropoxyphosphorylamino)]phenyl-10,15,20-triphenylporphyrinato gold(III)chloride showed significant growth
inhibitory properties against SMMC-7721 human hepatic cancer cells (IC50 value = 5.10 µM).
Keywords: gold(III) porphyrin derivatives, N-dialkylphosphonate, tetraaryl porphyrins, in vitro cytotoxicity
In clinical use, cisplatin and its derivatives carboplatin and
oxaliplatin have demonstrated excellent anti-cancer activity in
the treatment of several forms of cancer, including ovarian,
cervical, head and neck, and non-small-cell lung cancers.1–4
However, the main problem in using cisplatin and its deriva-
tives is their low selectivity for cancer cells and their often
high toxicity to the body.5,6 Hence, research into new-type of
platform complexes or other noble metal complexes with less
toxicity has received much attention in recent years. Among
these complexes, many gold-based compounds have been
synthesised and evaluated successfully as potential anti-cancer
agents.7–10 However, it is difficult to bring some available
gold(III) compounds into clinical use because these com-
pounds are effective only at relatively high doses. Moreover,
these compounds are usually unstable under physiological
conditions, due to the reduction of gold(III) to gold(I).
Based on the above, Che et al. have reported the synthesis
and antitumour efficacy of gold(III) tetraphenyllporphyrin.11
Subsequently, great efforts have been made to elucidate the
mechanisms of action of gold(III) tetraphenylporphyrin and
to synthesise many modified gold(III) tetraphenylporphyrins.
These gold(III) porphyrin compounds, which behave as organic
lipophilic cations with a planar structure, are stable against
demetallation under physiological conditions.
Further in vitro and in vivo studies revealed that gold(III)
porphyrin is a promising anticancer agent for the treatment of
colon and liver cancer,12–20 because the porphyrin ligand in
these compounds can efficiently stabilise the gold(III) centre,
drastically reducing its redox reactivity and oxidising charac-
ter. But, although gold(III) tetraphenyl porphyrin shows a high
anti-cancer activity, it is not an approved clinical drug. In order
to reduce its toxicity and to improve its activity, much work
has been carried out to develop more efficient and selective
derivatives of gold(III) tetraphenylporphyrin.
Previous reports have shown that altering the substituents on
the porphyrin ligand can impact on the electrochemical prop-
erties and in vitro cytotoxicity of the corresponding gold(III)
porphyrins.11,14,21 Phosphorus substituents regulate important
biological functions and molecular modifications involving
the introduction of organophosphorus functionalities could
increase their biological activity.22–24 Many studies have shown
anti-tumour activities of phosphonate derivatives such as
aminophosphonate,25,26 phosphoramidate monoesters, ether
phospholipids,27–29 and steroidal phosphate.30 Some studies
also indicated that the introduction of phosphodiesters could
improve their water solubility and permit a targeting of the
drug to a specific organ.
Literature review reveals that no synthetic analogues of
gold(III) tetraarylporphyrin phosphonate derivatives have been
reported for the purpose of cytotoxicity evaluation. We were
thus encouraged to extend our earlier work31,32 to design ami-
nophosphonate derivatives of gold(III) tetraarylporphyrin for
antitumour evaluation. Here we report the synthesis of novel
phosphate derivatives of gold(III) tetraphenyl porphyrin and
their cytotoxic activity against SMMC-7721 human hepatic
and sarcoma 180 mouse cancer in vitro by the standard MTT
method.
Experimental
All reagents and solvents were commercial available analytical grade
and used as received. Solvents were purified and dried by standard
methods and distilled prior to use when necessary. All evaporations of
organic solvents were carried out using a rotary evaporator in conjunc-
tion with a water aspirator. Melting points were taken on a hot-plate
1
microscope apparatus and are uncorrected. H NMR spectra were
recorded with a BrukerAV-600 spectrometer. IR spectra were obtained
on a Bruker Tensor 27 spectrometer (KBr disc). MS spectra were
obtained on a ZAB-HS mass spectrometer with 70 eV; TPPAuCl
[5,10,15,20-tetraphenyl porphyrin gold(III) chloride] was synthesised
by the reported method.11,31 UV-Vis spectra were obtained on a UV
2501 PC spectrometer. Elemental analytical data were obtained with a
model 240 instrument. Mycoplasma-free newborn calf serum was
purchased from Hangzhou Sijiqing Biological Engineering Materials
Co., Ltd Cisplatin (Cis) was the product of Jiangsu Hansen Pharma-
ceutical Co., Ltd RPMI 1640, MTT and DMSO were purchased from
Sigma-Aldrich Chemical Co. The phosphate derivatives were tested
against SMMC-7721 human hepatic and sarcoma 180 mouse cancer
in vitro by the standard MTT method.32
Cell lines and cell culture
SMMC-7721 human hepatic carcinoma (SMMC-7721) and sarcoma
180 mouse cancer cells were purchased from Shanghai Institute of
Cell Biology, Chinese Academy of Science. The cell line was cultured
in RPMI 1640 medium with 10% newborn calf serum serum. It was
maintained in a humidified incubator with an atmosphere of 95%
air and 5% CO2 at 37 °C. The cells were continuously passaged once
every 3–4 days. Growing cells were collected for experiments.
Synthesis of of 5-[4-(dialkyoxyphosphorylamino)]phenyl-10,15,20-
triphenyl porphyrins (5a–e)
5,10,15,20-Tetraphenylporphyrin (2, TPP) was synthesised in
20.1% yield by the reported method.11,33
5-(4-Nitro)phenyl-10,15,20-triphenylporphyrin (3):35 A solution of
NaNO2 (27.6 mg, 0.40 mmol) in trifluoroacetic acid (2 mL) was added
to a solution of 2 (245.7 mg, 0.40 mmol) in trifluoroacetic acid
(10 mL) at room temperature for 1 min. The resultant mixture was
stirred at room temperature for 40 min and then poured into water
(100 mL). The mixture was extracted with CH2Cl2 (3 × 50 mL) and the
organic phase was washed with saturated aqueous Na2CO3 and water,
it was then dried over anhydrous Na2SO4. After removal of Na2SO4,
the filtrate was concentrated and the crude product purified by column
* Correspondent. E-mail: wangcd@yzu.edu.cn

502 JOURNAL OF CHEMICAL RESEARCH 2012
chromatography (silica gel, CH2Cl2/n-hexane: 2/3 V/V). Recrystalli-
sation from CH2Cl2/ethanol gave the pure product. 5,10,15-triphenyl-
20-(4-nitro)phenyl porphyrin (3) 30.5% yield (80.4 mg): m.p.
>250 °C; 1H NMR (CDCl3, 600 MHz), δ (ppm): –2.79 (s, 2H, inner-
NH), 7.75–7.81 (m, 9H, Ph-CH), 8.21 (d, J = 7.2 Hz, 6H, Ph-CH),
8.40 (d, J = 8.4 Hz, 2H, Ph-CH), 8.64 (d, J = 8.4 Hz, 2H, Ph-CH), 8.74
(d, J = 4.2 Hz, 2H, Por-CH), 8.86–8.90 (m, 6H, Por-CH); IR(KBr):
υ 3446(s), 2918(w), 2850(w), 1596(w), 1517(w), 1472(w), 1392(w),
1345(m), 1073(w), 840(w), 798(m), 706(m) cm−1; MS (EI): 660
(M+1, 58%); UV-Vis (CH2Cl2) λmax/nm (log ε) 418 (2.28), 514 (1.28),
549 (2.98), 588 (4.85), 645 (4.18).
triethylamine (2 mL) and dioxane (5 mL) at 10 °C for 1 h. The result-
ant mixture was stirred at 25 °C for 3–6 h. After removal of the
solvent, the residues were dissolved in dichloromethane (25 mL). The
organic phase was washed with water, saturated NaHCO3 and brine
respectively, then dried over Na2SO4. After removal of solvent, the
crude product was purified by column chromatography (silica gel,
CH2Cl2/n-hexane/Et3N: 1/1/0.01 V/V/V) to give the title compound 5a
in 78.0% yield(15.5 mg). 1H NMR (CDCl3, 600 MHz) δ (ppm): 8.79
(s, 2H), 8.76 (s, 6H), 8.14 (d, J = 6.6 Hz, 6H), 8.04 (d, J = 7.8 Hz, 2H),
7.68 (d, J = 7.2 Hz, 9H), 7.28 (d, J = 7.8 Hz, 2H), 5.30 (d, J = 7.2 Hz,
1H), 3.92 (s, 3H), 3.91 (s, 3H), –2.82 (s, 2H); IR (KBr, cm−1): 2956,
2853, 1546, 1447, 1338, 1285, 1018, 966, 799, 700; MS (EI): 737.20
(M+1, 19%); UV-Vis (CH2Cl2) λmax/nm (log ε) 424 (2.16), 512 (1.22),
550 (2.90), 592 (4.80), 660 (4.60); Anal. Calcd for C46H36N5O3P: C,
74.89; H, 4.92; N, 9.49. Found: C, 74.70; H, 4.82; N, 9.58%.
5-[4-(Diethoxyphosphorylamino)]phenyl-10,15,20-triphenylpor-
phyrin (5b): Following the above procedure using diethyl phosphon-
ate as the starting material, 5b was obtained as a purple solid (56.5%
yield): 1H NMR (CDCl3, 600 MHz) δ (ppm): 8.80–8.77 (m, 8H), 8.13
(d, J = 6.0 Hz, 6H), 8.03 (d, J = 6.6 Hz, 2H), 7.69–7.65 (m, 9H), 7.28
(d, J = 7.8 Hz, 2H), 5.35 (d, J = 6.0 Hz, 1H), 4.32–4.25 (m, 2H),
4.16–4.13 (m, 2H), 1.42 (t, J = 4.8 Hz, 6H), –2.85 (s, 2H); MS (EI):
(M+1): 766.00 (30%); IR (KBr, cm−1): 2953, 1575, 1473, 1439, 1350,
1281, 1026, 965, 799, 700; UV-Vis (CH2Cl2) λmax/nm (log ε) 427
(2.09), 518 (1.34), 552 (2.86), 592 (4.83), 650 (4.26); Anal. Calcd for
C48H40N5O3P: C, 75.28; H, 5.26; N, 9.14. Found: C, 75.39; H, 5.03; N,
9.28%.
5-(4-Amino)phenyl-10,15,20-triphenylporphyrin (4):33 SnCl2 (0.27 g,
1.2 mmol) and 36.5% HCl (5 mL) was added to a solution of 5,10,15-
triphenyl-20-(4-nitro)phenyl porphyrin (245.7 mg, 0.4 mmol) and
36.5% hydrochloric acid (7 mL) under nitrogen gas. The resultant
mixture was stirred at 0 °C for 1 h. After the reaction mixture was
treated slowly with ammonia (5 mL), a green precipitate was collected
by filtering. The green solid was then dissolved in dichloromethane
(25 mL), the organic phase was washed with water, sat. NaHCO3 and
brine respectively and dried over Na2SO4. After removal of solvent,
the crude product was purified by column chromatography (silica
gel, DCM) and the purified product 4 was obtained in 87.0% yield
1
(218.9 mg): m.p. >250 °C; H NMR (CDCl3, 600 MHz), δ (ppm):
–2.74 (s, inner-NH), 4.02 (s, 2H, amino), 7.08 (d, J = 8.3 Hz, 2H),
7.78 (m, 9H), 8.00 (d, J = 8.2 Hz, 2H), 8.20 (m, 6H), 8.83 (s, 2H), 8.85
(d, J = 5.0 Hz, 2H), 8.95 (d, J = 5.0 Hz, 2H); IR(KBr): υ 3426(s),
2920(w), 2854(w), 1610(w), 1530(w), 1470(w), 1382(w), 1345(m),
1083(w), 920(w), 810(m), 720(m) cm−1; MS (EI): 630 (M+1, 32%);
UV-Vis (CH2Cl2) λmax/nm (log ε) 426 (2.10), 516 (1.22), 552 (2.98),
590 (4.80), 648 (4.20); Anal. Calcd for C44H31N5: C, 83.92; H, 4.96; N,
11.12. Found C, 84.08; H, 4.70; N, 11.22%.
5-[4-(Diisopropoxyphosphorylamino)]phenyl-10,15,20-triphenyl-
porphyrin (5c): Following the above procedure using diisopropyl
phosphonate as the starting material, compound 5c was obtained as a
1
purple solid(58.9% yield): H NMR (CDCl3, 600 MHz) δ (ppm):
5-[4-(Dimethoxyphosphorylamino)]phenyl-10,15,20-triphenylpor-
phyrin (5a): Dimethyl phosphonate (8.91 mg, 0.081 mmol) and CCl4
(5 mL) was added dropwise to a solution of 4 (20 mg, 0.027 mmol),
8.87–8.85 (m, 8H), 8.23 (d, J = 6.6 Hz, 6H), 8.10 (d, J = 7.8 Hz, 2H),
7.79–7.75 (m, 9H), 7.36 (d, J = 8.4 Hz, 2H), 5.44 (d, J = 7.8 Hz, 1H),
4.09–4.08 (m, 1H), 3.95–3.89 (m, 1H), 1.46 (d, J = 6.0 Hz, 12H),
–2.73 (s, 2H); MS (EI): 794.44 (M+1, 100%); IR (KBr, cm−1): 3315,
2921, 2850, 1596, 1467, 1399, 1308, 1223, 1153, 990, 964, 873, 752;
UV-Vis (CH2Cl2) λmax/nm (log ε) 425 (2.12), 522 (1.41), 554 (2.90),
592 (4.85), 640 (4.09); Anal. Calcd for C50H44N5O3P: C, 75.64; H,
5.59; N, 8.82. Found: C, 75.50; H, 5.66; N, 8.72%.
5-[4-(Dipropoxyphosphorylamino)]phenyl-10,15,20-triphenylpor-
phyrin (5d): Following the above procedure using dipropyl phospho-
nate as the starting material, compound 5d was obtained as a purple
solid(60.2% yield): 1H NMR (CDCl3, 600 MHz) δ (ppm): 8.80–8.77
(m, 8H), 8.15 (d, J = 6.6 Hz, 6H), 8.03 (d, J = 7.8 Hz, 2H), 7.71–7.68
(m, 9H), 7.30 (d, J = 7.8 Hz, 2H), 5.51 (d, J = 7.8 Hz, 1H), 4.21–4.12
(m, 4H), 1.64–1.77 (m, 4H), 1.00 (t, J = 7.2 Hz, 6H), –2.85 (s, 2H);
MS (EI): 794.44 (M+1, 100%); IR (KBr, cm−1): 2974, 2938, 1608,
1437, 1397, 1227, 1171, 1000, 965, 851, 798; UV-Vis (CH2Cl2) λmax
/
nm (log ε) 424 (2.10), 519 (1.20), 555 (2.73), 582 (4.89), 656 (4.20);
Anal. Calcd for C50H44N5O3P: C, 75.64; H, 5.59; N, 8.82. Found: C,
75.48; H, 5.38; N, 8.70%.
5-[4-(Dibutoxyphosphorylamino)]phenyl-10,15,20-triphenylpor-
phyrin (5e): Following the above procedure using dibutyl phospho-
nate as the starting material, compound 5d was obtained as a purple
solid (25.4% yield): 1H NMR (CDCl3, 600 MHz) δ (ppm): 8.80–8.76
(m, 8H), 8.14 (d, J = 7.2 Hz, 6H), 8.02 (d, J = 8.4 Hz, 2H), 7.71–7.67
(m, 9H), 7.28 (d, J = 8.4 Hz, 2H), 5.47 (d, J = 8.4 Hz, 1H), 4.23–4.14
(m, 4H), 1.74–1.71 (m, 4H), 1.46–1.43 (m, 4H), 0.92 (t, J = 7.8 Hz,
6H), –2.85 (s, 2H); MS (EI): 822.87 (M+1, 100%); IR (KBr, cm−1):
2972, 2935, 1600, 1435, 1387, 1237, 1169, 1031, 965, 853, 790;
UV-Vis (CH2Cl2) λmax/nm (log ε) 426 (2.19), 512 (1.28), 553 (2.94),
592 (4.73), 648 (4.22); Anal. Calcd for C52H48N5O3P (%): C, 75.99; H,
5.89; N, 8.52. Found: C, 75.82; H, 5.88; N, 8.72%.
Scheme 1 Preparation of 5-[4-(dialkyoxyphosphorylamino)]
phenyl-10,15,20- triphenylporphyrins (5a–e).
Reaction conditions: (I) propionic acid, reflux, 3h, 20.1%;
(II) NaNO2, TFA, rt, 1 min, 30.5%; (III) SnCl2·2H2O/HCl, 87.0%;
(IV) HPO(OR)2, 1,4-Dioxane, CCl4, NEt3, 3–6 h, 25.4–78.0%.
Synthesis of 5-[4-(dialkyoxyphosphorylamino)]phenyl-10,15,20-tri-
phenylporphyrinato gold(III)chlorides (6a–e)
Table 1 The preparation of substituted tetraarylporphyrins
5a–e
5-[4-(Dimethoxyphosphorylamino)]phenyl-10,15,20-triphenyl
porphyrinato gold(III) chloride (6a): A mixture of 5a (18.4 mg,
0.025 mmol), K[AuIIICl4] (28.4 mg, 0.07 mmol) and sodium acetate
(20.5 mg, 0.25 mmol) in acetic acid (15 mL) was refluxed for 18–
24 h. After completion, the reaction was checked by TLC, the crude
product was obtained by removing acetic acid. Next, the solid product
was dissolved thoroughly with dichloromethane (20 mL) and the
organic phase was washed thoroughly with water and brine respec-
tively, and then dried over Na2SO4. Removal of the solvent gave the
Compound
R
Time/h
Yield/%
5a
5b
5c
5d
5e
CH3
6
6
6
3
3
78.0
56.5
58.9
60.2
25.4
CH3CH2
(CH3)2CH
CH3CH2CH2
CH3CH2CH2CH2

JOURNAL OF CHEMICAL RESEARCH 2012 503
Anal. Calcd for C50H42N5O3PClAu (%): C, 58.63; H, 4.13; N, 6.84.
Found C, 58.66; H, 4.24; N, 6.90%.
5-[4-(Dibutoxyphosphorylamino)]phenyl-10,15,20-triphenylpor-
phyrinato gold(III) chloride (6e): Following the above procedure
using 5e as a starting material, compound 6e was obtained as a purple
1
solid (72.7% yield): H NMR (CDCl3, 600 MHz) δ (ppm): 9.32 (d,
J = 5.4 Hz, 2H), 9.21–9.20 (m, 6H), 8.16 (d, J = 6.6 Hz, 6H), 8.02 (d,
J = 8.4 Hz, 2H), 7.81–7.79 (m, 9H), 7.62 (d, J = 7.8 Hz, 2H), 4.26–
4.23 (m, 4H), 1.77–1.72 (m, 4H), 1.46–1.44 (m, 4H), 0.92 (t, J =
7.8 Hz, 6H); MS (EI): 1016.51 (M+1-Cl, 100%); IR (KBr, cm−1):
2967, 2928, 2846, 1730, 1600, 1516, 1460, 1352, 1264, 1174, 1029,
809, 751; UV-Vis (CH2Cl2) λmax/nm (log ε) 410 (2.16), 521 (2.52), 550
(3.80), 592 (3.82), 645 (3.88); Anal. Calcd for C52H46N5O3PClAu (%):
C, 59.35; H, 4.41; N, 6.65. Found: C, 59.18; H, 4.32; N, 6.58%.
Scheme 2 Preparation of gold(III) tetraarylporphyrin
derivatives (6a–e).
Reagents and conditions: (I) (1) KAuCl4·2H2O, NaOAc, HOAc,
reflux 17–24 h; (2) LiCl; 70.5–88.9%.
Cytotoxicity assay for the effect of gold(III) substituted tetraarylpor-
phyrin chlorides on SMMC-7721 human and sarcoma 180 mouse
cancer cell proliferation
Table 2 Preparation of gold(III) tetraarylporphyrin derivatives
(6a–e)
Gold(III) substituted tetraarylporphyrin chlorides were prepared in
the concentrations 6.4×10−5 M, 3.2×10−5 M, 1.6×10−5 M, 0.8×10−5 M,
0.4×10−5 M and 2×10−6 M respectively. DMSO was used as latent
solvent with the highest concentration less than 0.1% in the solution
of tetraarylporphyrin. The control groups of cisplatin, blank (1640)
and DMSO solvent were set up at the same time. The cytotoxicities
of gold(III) substituted tetraarylporphyrin chlorides were determined
by MTT cytotoxic assay. SMMC-7721 human hepatic carcinoma cells
or sarcoma 180 mouse cancer cells were plated in 96-well plates at
1×105/mL and 100 µL/well in complete media. The cells were incuba-
ted for 24 hours. Then the prepared and various amounts of gold(III)
substituted tetraarylporphyrin chloride and cisplatin were plated in
96-well plates containing SMMC-7721 human hepatic carcinoma
cells or sarcoma 180 mouse cancer cells and incubated commonly for
44 h. Then 100 µL supernatant liquid was sucked from each hole,
10 µL of MTT (5 mg mL−1) was added in and cultured for 4h, the
media was then removed and hydrochloric acid/isopropanol added at
100 µL/well. Surging for 5 minutes using the micro oscillator dissol-
ved the MTT crystal and OD values were measured at 570nm using a
Model Elx 800 Autoplate reader (Bio-Tek Instruments, USA).
Compound
R
Time/h
Yield/%
6a
6b
6c
6d
6e
CH3
24
17
19
20
18
70.5
88.9
75.5
79.7
72.2
CH3CH2
(CH3)2CH
CH3CH2CH2
CH3CH2CH2CH2
crude product, which was purified by column chromatography (silica
gel, DCM/methanol: 5/1 V/V). The purified product was dissolved in
acetone and after filtering the mixture, the solution was treated with
10% LiCl (3.5 mL) in aqueous acetone to give analytically pure 6a in
70.5% yield (16.9 mg) as a purple-mahogany solid. 1H NMR (CDCl3,
600 MHz) δ (ppm): 9.32 (s, 2H), 9.19 (s, 6H), 8.17 (d, J = 6.0 Hz, 6H),
8.02 (d, J = 6.6 Hz, 2H), 7.84–7.79 (m, 9H), 7.67 (d, J = 6.0 Hz, 2H),
3.95 (s, 3H), 3.94(s, 3H); MS (EI): 932.53 (M+1-Cl, 100%); IR (KBr,
cm−1): 2917, 2849, 1740, 1582, 1464, 1373, 1260, 1181, 1035, 802,
704; UV-Vis (CH2Cl2) λmax/nm (log ε) 408 (2.10), 519 (2.22), 552
(2.98), 590 (3.76), 648 (4.02); Anal. Calcd for C46H34N5O3PClAu (%):
C, 57.06; H, 3.54; N, 7.23. Found: C, 57.22; H, 3.42; N, 7.46%.
5-[4-(Diethoxyphosphorylamino)]phenyl-10,15,20-triphenylpor-
phyrinato gold(III) chloride (6b): Following the above procedure
using 5b as a starting material, compound 6b was obtained as a purple
Statistical analysis of experimental data
All the data of the experiment were compiled and analysed according
to SPSS 15.0 software. Measurement data were expressed as the
mean.
1
solid(88.9% yield): H NMR (CDCl3, 600 MHz) δ (ppm): 9.34 (d,
Results and discussion
J = 4.8 Hz, 2H), 9.21–9.18 (m, 6H), 8.16 (d, J = 7.8 Hz, 6H), 8.01 (d,
J = 9.4 Hz, 2H), 7.86–7.78 (m, 9H), 7.68 (d, J = 7.8 Hz, 2H), 4.34 (t,
J = 7.2 Hz, 2H), 4.32 (t, J = 7.2 Hz, 2H), 1.42 (t, J = 7.2 Hz, 6H); MS
(EI): 960.45 (M+1-Cl, 100%); IR (KBr, cm−1): 2919, 2849, 1736,
1606, 1510, 1463, 1361, 1312, 1130, 1036, 800, 723; UV-Vis (CH2Cl2)
λmax/nm (log ε) 409 (2.10), 520 (2.26), 552 (2.98), 590 (4.01), 650
(3.89); Anal. Calcd for C48H38N5O3PClAu (%): C, 57.87; H, 3.84; N,
7.03. Found: C, 57.70; H, 3.82; N, 7.20%.
Phosphonate is an important functional group in organic chem-
istry, biochemistry, and medicine. Phosphonates play crucial
roles in the human body and other organisms. Recent studies
showed that phosphonates and their analogues have exhibited
a wide spectrum of important bioactivities such as an antitu-
mour action.25–30
Because of the good affinity of phosphonate toward cells
and nucleic acids, the introduction of a phosphonate segment
into drugs can facilitate their interactions with cells and tissues
and thereby provide a robust strategy to design new drugs or
lead compounds. Porphyrin compounds have distinguished
themselves from other small molecules because of their
profound bioactivities. Some recent examples suggested that
the practice of attaching porphyrin skeletons and natural small
molecules, such as a sugar and a steroid, onto one molecule
has received much attention from synthetic and medicinal
chemists attempting the discovery of novel compounds with
unknown or improved pharmacological properties. However,
the research of phosphonate used in conjunction with a
porphyrin segment is rather limited. Thus it is an urgent task to
synthesise a new class of porphyrins containing a phospho-
nate. Based on these previous studies, we have designed and
synthesised a series of new gold(III) complexe analogues of
the type gold(III) tetraarylporphyrin phosphonate. The desired
gold(III) tetraarylporphyrin phosphonates contain three well
defined parts: the gold(III) porphyrin core, an aromatic side
chain connected by an amine and a linear phosphonate side
chain.
5-[4-(Diisopropoxyphosphorylamino)]phenyl-10,15,20-triphenyl-
porphyrinato gold(III) chloride (6c): Following the above procedure
using 5c as a starting material, compound 6c (75.5% yield) was obtai-
1
ned as a purple solid: H NMR (CDCl3, 600 MHz) δ (ppm): 9.29 (s,
2H), 9.20 (s, 6H), 8.17 (d, J = 6.6 Hz, 6H), 8.03 (d, J = 6.6 Hz, 2H),
7.84–7.79 (m, 9H), 7.56 (d, J = 6.0 Hz, 2H), 6.43 (d, J = 5.4 Hz, 1H),
4.23–4.21 (m, 1H), 4.08–4.05 (m, 1H), 1.43(d, J = 5.4 Hz, 6H), 1.41
(d, J = 4.8 Hz, 6H); MS (EI): 988.34 (M+1-Cl, 100%); IR (KBr, cm−1):
2918, 2849, 1739, 1594, 1464, 1361, 1261, 1176, 1104, 1021, 800,
757; UV-Vis (CH2Cl2) λmax/nm (log ε) 410 (2.10), 520 (2.35), 547
(2.72), 592 (3.89), 650 (3.88); Anal. Calcd for C50H42N5O3PClAu (%):
C, 58.63; H, 4.13; N, 6.84. Found: C, 58.78; H, 4.02; N, 6.96%.
5-[4-(Dipropoxyphosphorylamino)]phenyl-10,15,20-triphenylpor-
phyrinato gold(III) chloride (6d): Following the above procedure
using 5d as a starting material, compound 6d (79.7% yield) was obtai-
ned as a purple solid: 1H NMR (CDCl3, 600 MHz) δ (ppm): 9.32 (d,
J = 4.8 Hz, 2H), 9.21–9.19 (m, 6H), 8.17 (d, J = 7.2 Hz, 6H), 8.02 (d,
J = 7.8 Hz, 2H), 7.86–7.80 (m, 9H), 7.65 (d, J = 7.8 Hz, 2H), 6.89 (d,
J = 8.4 Hz, 1H), 4.22 (t, J = 7.2 Hz, 2H), 4.21 (t, J = 7.2 Hz, 2H),
1.82–1.77 (m, 4H), 1.00 (t, J = 7.8 Hz, 6H); MS (EI): 988.54 (M+1-
Cl, 100%); IR (KBr, cm−1): 2961, 2920, 2850, 1731, 1606, 1511,
1464, 1359, 1260, 1184, 1021, 801, 756; UV-Vis (CH2Cl2) λmax/nm
(log ε) 408 (2.08), 519 (3.02), 550 (3.02), 591 (3.84), 650 (3.69);

504 JOURNAL OF CHEMICAL RESEARCH 2012
To reach the desired target structures a five-step synthesis
route was successful. Scheme 1 shows the synthetic routes to
the target 5-[4-(dialkyoxyphosphorylamino)]phenyl-10,15,20-
triphenylporphyrins. First the porphyrin base core was coupled
with the aromatic side chain. Using reaction conditions similar
to those reported previously,11,33 5,10,15,20-tetraphenylpor-
phyrin (2) was prepared from the benzaldehyde and pyrrole
(Scheme 1) in 20.1% yield. A mono-nitro group in the aro-
matic side chain was introduced according to the literature
procedure,35 thus 5-(4-nitro)phenyl-10,15,20- triphenylpor-
phyrin (3) was readily obtained by reaction of 2 and sodium
nitrite promoted by trifluoroacetic acid in 30.5% yield (Scheme
1). Reduction of 3 by SnCl2–HCl under dinitrogen gave 5-
(4-amino)phenyl-10,15,20- triphenylporphyrin (4). The 5-[4-
(dialkyoxyphosphorylamino)]phenyl-10,15,20- triphenylpor-
phyrins (5a–e) were prepared from 4 and the appropriate dial-
kyl phosphonate in the presence of triethylamine for 3–6 h
(Scheme 1, Table 1) in yields 25.4–78.0%. The general synthe-
sis of gold(III) porphyrin compounds (6a–e) was achieved
through the route outlined in Scheme 2. Firstly, gold(III) por-
phyrincompoundsweresynthesisedbytreatmentofK[AuIIICl4]
with the free-base porphyrin ligand in the presence of NaOAc
in acetic acid. After purification with column chromatography
and metathesis reaction with LiCl in aqueous acetone, gold(III)
porphyrin compounds were obtained as chloride salts in
70.5–88.9% yields (Scheme 2, Table 2). 1H NMR, electrospray
ionisation (ESI) mass (+ mode) analysis spectrometry, UV-Vis
and elemental analysis were used to characterise all the syn-
thesised compounds. Downfield shifts of benzene and porphy-
rin exocyclic hydrogen resonances are generally observed in
the 1H NMR spectrum upon coordination to a gold cation, and
this behaviour is found in compounds 6a–e. The two hydrogen
resonances from the porphyrin inner cyclic backbone
disappear from ca –2.8 ppm once the ligand coordinates to
the gold(III) centre. The UV-Vis absorption spectrum of com-
pounds 6a–e is also similar to previous reports of gold(III)
substituted porphyrin complexes.21
To analyse the potential of compounds (6a–e) as antitumour
agents, their cytotoxicity was evaluated (Table 3, Figs 1 and 2)
towards SMMC-7721 human hepatic tumour cells and for
comparison purposes the cytotoxicity of cisplatin and TPPAuCl
were also evaluated under the same experimental conditions.
From the data shown in Table 3, the new compounds 6a–e
showed a measurable anti-cancer activity against SMMC-7721
human hepatic and sarcoma 180 mouse cancer cell lines
tested.
Although this is a preliminary screening, the results showed
that compounds 6a–e exerted a significant inhibitory effect on
the growth of SMMC-7721 human hepatic and sarcoma 180
mouse cancer cells. A dose-dependent relationship was found
between 1 and 100 µM and, in general, the cytotoxicities of
6d against SMMC-7721 human hepatic tumour cells and 6c
Fig. 1 Maximuminhibitionrateofgold(III)substitutedtetraaryl-
porphyrin chloride against sarcoma 180 mouse (left bar) and
SMMC-7721 human (right bar) tumour cell line in vitro.
Fig. 2 IC50 of gold(III) substituted tetra-aryl porphyrin chloride
against sarcoma 180 mouse (left bar) and SMMC-7721 human
(right bar) tumour cell line in vitro.
against sarcoma 180 mouse cancer cells were higher than cis-
platin and TPPAuCl. Compound 6c had also a better inhibitory
effect on SMMC-7721 human hepatic tumour cells, the IC50
value was 9.59 µM in SMMC-7721 human hepatic tumour cell
line. Compounds 6a and 6e had nearly the same inhibitory
effect on SMMC-7721 human hepatic tumour cells as cisplatin
and 6b exhibited an IC50 value nearly four-fold higher than
cisplatin on SMMC-7721 human hepatic tumour cells. From
the results of in vivo assays, the antitumour activity order was
6d>TPPAuCl >6c> cis >6a> 6e>6b with respect to the SMMC-
7721 human hepatic tumour cell line. Compared to TPPAuCl,
compounds 6d and 6c show a significant inhibitory effect on
the growth of SMMC-7721 human hepatic tumour cells, but
the linear phosphonate side chain of 6d and 6c could balance
the aqueous solubility with liposolubility and strengthen
the affinity toward cells and nucleic acids, which would be
helpful in transporting drugs into the target cells to improve
the antitumour activity of the complexes.
Conclusions
A number of new substituted gold(III) tetraarylporphyrin
phosphonates have been synthesised by a five-step synthesis
route and evaluated for their in vitro anti-human hepatic and
anti-sarcoma 180 mouse tumour activities. The two new sub-
stituted gold(III) tetraarylporphyrins (6c and 6d) were more
active than cisplatin and (TPPAuCl). Further in vivo tests of
the compounds are under way and the anti-tumour mechanism
will be studied in the future.
Table 3 Cytotoxicity of 6a–e against sarcoma 180 mouse and
SMMC-7721 human tumour cell line in vitro
Entry Compound
Maximum
IC50/µM
inhibition rate/%a
S180cell SMMC- S180cell
7721cell
SMMC-
7721cell
Financial support of this research by the National Natural
Science Foundation of China (NNSFC 20872125) is gratefully
acknowledged. This work was a project funded by the Priority
Academic Program Development of Jiangsu Higher Education
Institutions.
I
TPPAuCl
91.49
91.65
94.70
91.10
82.54
97.50
89.64
93.81
97.62
90.76
88.80
93.84
98.74
91.91
3.61
6.39
6.75
2.60
15.86
4.31
7.05
5.83
10.38
40.81
9.59
5.10
12.60
9.75
II
6a
III
IV
V
VI
VII
6b
6c
6d
6e
Received 24 April 2012; accepted 13 June 2012
Paper 1201279 doi: 10.3184/174751912X13406179445757
Published online: 28 August 2012
Cisplatin
a The concentration of the gold complexes is 32 µM.

JOURNAL OF CHEMICAL RESEARCH 2012 505
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