Phospho sulfonic acid: An efficient and recyclable solid acid catalyst for the solvent-free synthesis of α-hydroxyphosphonates and their anticancer properties

Article abstract of DOI:10.1039/c5nj00312a

As a means of developing biologically active compounds, a series of α-hydroxyphosphonates, ArC(OH)PO(OR)₂ (Ar = 5-G-2-OHPh; R = Me, Et, iPr, Bu; G = H, Br, Cl, NO₂), have been synthesized by reacting diversely substituted salicylalde

Full text of DOI:10.1039/c5nj00312a

NJC
View Article Online
View Journal
PAPER
Phospho sulfonic acid: an efficient and recyclable
solid acid catalyst for the solvent-free synthesis of
a-hydroxyphosphonates and their anticancer
properties†
Cite this:DOI: 10.1039/c5nj00312a
Reddi Mohan Naidu Kalla,a Hye Ri Lee,a Jiafu Cao,b Jin-Wook Yoob and Il Kim*a
As
a means of developing biologically active compounds, a series of a-hydroxyphosphonates,
Received (in Porto Alegre, Brazil)
5th February 2015,
Accepted 9th March 2015
ArC(OH)PO(OR)2 (Ar = 5-G-2-OHPh; R = Me, Et, iPr, Bu; G = H, Br, Cl, NO2), have been synthesized by
reacting diversely substituted salicylaldehydes with dialkyl phosphites by employing the Pudovik reaction
in the presence of phospho sulfonic acid under neat conditions. The cytotoxicity of the compounds was
tested in two human cancer cell lines by using MTT assay. Compounds bearing R = Et; G = Cl, R = Bu;
G = Cl, and R = Et; G = NO2 showed good anticancer activity.
DOI: 10.1039/c5nj00312a
www.rsc.org/njc
phosphonates such as a-amino,17 a-diketo,18 a-keto,19 a-halo,20
and a-acetoxy phosphonates.21
1. Introduction
Cancer is a class of diseases involving rapid cell growth with
HPPs are primarily synthesized by the Pudovik reaction, in
possible spreading to other parts of the body. The most common which the C–P bond is formed by the addition of a dialkyl
types of cancer in males are lung, prostate, colorectal, and phosphite to an unsaturated system, and the Abramov reaction,
stomach cancers, whereas breast, colorectal, lung, and cervical in which the C–P bond is formed by the addition of a trialkyl
cancers are the most common cancer types in females. In phosphite (TAP) to an unsaturated system. Carbonyl compound
addition, approximately 22% of cancers are caused by tobacco hydrophosphylation is usually mediated by a base-catalyzed
use1,2 while an additional 10% are associated with obesity, reaction.22 Numerous bases can mediate HPP formation, including
poor diet, lack of physical activity, and alcohol consumption. ethyl magnesium bromide,23 quinine,24 potassium fluoride (KF)–
Other factors associated with cancer include certain infections, alumina,25 and magnesium oxide (MgO).26 Furthermore HPPs are
exposure to ionizing radiation, and environmental pollutants. also synthesized by Brønsted acid catalysts such as Amberlyst-15,27
Furthermore, in the developing world, nearly 20% of cancers HCl,28 oxalic acid,29 and guanidine–HCl.30 Nevertheless, Brønsted
are due to infections such as hepatitis B, hepatitis C, and acids are moisture sensitive; thus, the reaction requires high
human papillomavirus.
catalyst loading, a long reaction time, high temperature, and
a-Hydroxyphosphonates (HPPs) are an important class of ultrasonication or a microwave to proceed. Hence, the develop-
organophosphorus compounds (OPCs)3 because of their wide ment of an inexpensive protocol for a-hydroxyphosphonate
range of biological activities, including anticancer, antibacterial, synthesis with easy accessibility, a low toxicity solid acid catalyst,
antiviral, and anti-oxidant activities.4,5 Additionally, HPPs are and the ability to proceed under neat conditions is highly
structural analogs of a-hydroxyphosphonic acids6–8 and can act preferred for the synthesis of HPPs.
as enzyme inhibitors for farnesyl protein transferase (FPT),9 human
In recent years, the use of recyclable solid acid catalysts has
protein tyrosine phosphatase (PTP),10–12 purine nucleoside received significant attention in organic synthesis as a result
phosphorylase (PNP),13 5-enolpyruvylshikimate-3-phosphate of their profitable and environmental benefits. These types of
synthase (EPSP),14 and human rennin.15,16 They also serve as reagents not only make simpler purification processes but also
useful precursors in the synthesis of other biologically important help in reducing the liberation of toxic reaction residues into
the environment. The solid acid catalysts are simply removed
a BK21 PLUS Centre for Advanced Chemical Technology,
Department of Polymer Science and Engineering, Pusan National University,
Busan 609-735, Republic of Korea. E-mail: ilkim@pusan.ac.kr
b College of Pharmacy, Pusan National University, Busan 609-735,
Republic of Korea
from the reaction mixture by filtration or centrifugation without
the need for neutralization, thereby enabling more eco-friendly
processes. Phospho sulfonic acid (PSA) is a non-corrosive, non-
volatile, recyclable, and eco-friendly solid acid catalyst. It has
been used as a promising solid acid catalyst in various organic
transformations.31,32
† Electronic supplementary information (ESI) available: 1H and 13C NMR Spectra
of the new compounds. See DOI: 10.1039/c5nj00312a
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.

View Article Online
Paper
NJC
Scheme 1 Synthesis of a series of a-hydroxyphosphonates (1–16).
Fig. 1 TGA thermogram of PSA.
Regardless of an extensive survey there have been no reports
on the anticancer properties of the synthesised HPPs. Thus,
our aim was to develop an environmentally friendly reaction
methodology to obtain novel HPPs with anticancer activity.
Herein, we report an eco-friendly one-pot synthesis of HPPs, in Entry
Table 1 Effect of various catalysts on the synthesis of compound 1 under
neat conditions at 50 1Ca
Catalyst amount
(mol%)
Time
(min)
Yieldb
(%)
Catalyst
which labile, P–H-containing dialkyl phosphite (DAP) underwent
nucleophilic addition to salicylaldehyde (SA) in the presence of
PSA under neat conditions (Scheme 1).
1
2
3
4
5
6
7
8
ZnCl2
10
10
10
10
10
10
0.1
0.3
0.5
1.0
180
210
180
240
180
300
48
35
32
30
50
55
45
58
75
67
82
86
94
94
ZrOCl2
BF3ÁSiO2
SiO2ÁSO3H
Amberlyst-15
PEGÁSO3H
PSA
PSA
PSA
PSA
2. Results and discussion
9
10
In this study, a diversity of biologically potent HPPs have been
synthesized by using the ecofriendly PSA catalyst under neat
conditions. This method offers several advantages over the existing
methodologies in terms of operational procedure, yield of the
product, stability of the catalyst and recyclability. In addition we
studied the anticancer properties of our synthesized compounds
for the possible cancer cell lines. The synthesized PSA is fully
characterized by infrared spectroscopy, X-ray powder diffraction
(XRD), and scanning electron microscopy-energy-dispersive X-ray
spectroscopy (SEM-EDX).32 Furthermore we also studied the
stability of PSA using thermogravimetric analysis (TGA) (Fig. 1).
The complete degradation occurs between 244 and 413 1C,
indicating that PSA is stable up to around 200 1C.
a
Reaction conditions: salicylaldehyde = 1 mmol, dialkyl phosphite =
b
1 mmol, and PSA = 0.5 mol%. Isolated yield measured gravimetrically.
species such as zinc chloride (ZnCl2), zirconyl chloride (ZrOCl2)
silica-supported boron trifluoride (BF3–SiO2) and silica–sulfo-
nic acid (10 mol%) were examined at room temperature over a
3–4 h reaction period. Compound 1 was obtained with yields of
50%, 55%, 45%, and 30%, respectively (entries 1–4). We then
examined the polymer-based catalysts Amberlyst-15 and poly-
ethylene glycol-supported sulfonic acid (PEG–SO3H), which
yielded little products (entries 5 and 6). Finally, we examined
solid acid catalyst PSA (entry 7), which is an efficient catalyst for
producing the desired product 1 in good yields.
2.1. Chemistry
Our lab has focused on the development of eco-friendly syntheses
In order to compare the efficiency of the neat conditions with
to reduce waste and establish operationally simple synthetic solvent-based conditions, the model reaction was re-examined
methodologies.32–34 In continuation with these studies, we with PSA in different solvents (Table 2). When the reaction was
describe the efficacy of PSA for the synthesis of novel HPPs performed in protic solvents, such as methanol (MeOH), ethanol
using a two component reaction between various SAs and (EtOH), or water (H2O), the reaction proceeded slowly and
different dialkyl phosphites at ambient temperatures.
recorded reduced product yields (Table 2, entries 2–4). However,
In general the Pudovik reaction requires longer reaction when using aprotic solvents such as chloroform (CHCl3), methyl
times, higher reaction temperatures, and higher catalyst loading cyanide (CH3CN), and dichloromethane (CH2Cl2), the reactions
than the Abramov reaction, because DAPs are less reactive than proceeded faster and resulted in higher product yields.
trialkyl phosphites (TAPs). The Pudovik reaction of SA (1 mmol)
To determine the optimal molar catalyst loading of PSA, the
with DAP (1 mmol) was first performed with a variety of catalysts model reaction was carried out by using 0.1, 0.3, 0.5, and 1 mol%
at 50 1C by using a solvent-free method (Table 1). Primary acidic of PSA under neat conditions at room temperature (rt), yielding
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015

View Article Online
NJC
Paper
Table 2 Effects of various solvents on the synthesis of compound 1a
attached to a phosphorus atom. In the 31P NMR spectra of all
synthesized compounds (1–16), a signal was observed in the region
of 22.8–18.3 ppm. Detailed descriptions of the spectral data for all
compounds (1–16) are given in the Experimental section.
Entry
Solvent
Time (min)
Yield (%)
1
2
3
4
5
6
7
Solvent-free
MeOH
EtOH
H2O
CH3Cl
CH3CN
CH2Cl2
34
60
80
90
50
45
35
94
65
60
55
85
88
90
2.2. Cytotoxicity
The cell lines used in the present study were the human alveolar
basal epithelial adeno carcinoma cell line (A549) and the epidermal
cancer cell line (KB). The growth inhibitory effects of the HPP
derivatives were evaluated by using the MTT. As shown in Fig. 3a
and b, the compounds (1–16) showed no cytotoxicity towards
the two cell lines at concentrations less than 2 mM. Most of the
compounds were non-cytotoxic at 40 mM. However, compound 12
a
Reaction conditions: salicylaldehyde = 1 mmol, dialkyl phosphite =
1 mmol, and PSA = 0.5 mol%.
82, 86, 94, and 94% product, respectively. Increasing the amount
of catalyst (0.5 mol%) had no additional effects on the reaction
progress. Having determined the optimal conditions (entry 9,
Table 1), we next established the generality of this methodology
by using various substituted SAs with different DAPs. All reactions
were performed with 0.5 mol% of PSA under solvent-free condi-
tions. The results are summarized in the Experimental section.
All reactions undergo easily and products are obtained in good
yields. SAs containing halogens and nitro substituents form the
corresponding products, as summarized in the Experimental
section, in good product yields.
The reusability of PSA was also examined for the preparation
of HPPs 1, formed from the reaction of SA with DMP. The
catalyst was easily recovered by adding ethanol to the reaction
mixture; the insoluble PSA could be separated by simple filtra-
tion, washed twice with ethanol (30 mL), and finally dried
under vacuum. The catalyst displayed good reusability after 5
runs (Fig. 2).
The structures of all the compounds were confirmed by
infrared (IR) spectroscopy, 1H, 13C, and 31P nuclear magnetic
resonance (NMR) spectroscopy. The IR spectra of compounds
1–16 showed the expected absorption bands at 3376–3268,
1238–1221, and 983–863 cmÀ1, which are attributed to O–H,
PQO, and P–C stretching vibrations, respectively.35 In the 1H NMR
spectrum, the P–CH proton signal appeared as a doublet or a
multiplet in the region of 4.17–3.87 ppm, due to coupling with
phosphorus and ethyleneoxy protons.36 The remaining proton
signals were observed in the expected regions. In the 13C NMR
spectra, the doublet at 70.4–69.6 ppm (1JP–C = 162.0–140.2 Hz)
confirms the presence of a methine carbon, which is directly
Fig. 3 The cytotoxicity of the synthesized compounds (1–16) against
(a) A549 and (b) KB cancer cells at concentrations of 2.0, 4.0, 20, and
40 mM for 24 h.
Fig. 2 Effect of recycling of PSA on the yield of compound 1.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.

View Article Online
Paper
NJC
showed some cytotoxicity in A549 cells, while two other com- out under neat conditions. Pre-coated silica gel plates (Merck
pounds (10 and 14) exhibited a noticeable increase in cytotoxi- Chem., Germany) were developed by using iodine in analytical
city and showed significant dose-dependent effects on the thin layer chromatography (TLC). Melting points were uncor-
proliferation of both cell lines. At a concentration of 20 mM, rected and determined on a digital Stuart SMP3 apparatus
compounds 10, 12, and 14 were cytotoxic (24%, 52%, and 21% (Bibby Scientific Limited, Staffordshire, UK). The 1H NMR
in A549 cells and 28%, 61%, and 30% in KB cells, respectively). (400 MHz), 13C NMR (100 MHz), and 31P NMR (161.9 MHz)
Similarly, at a concentration of 40 mM, compounds 10, 12, spectra were recorded on a Varian INOVA 400 NMR spectro-
and 14 were also cytotoxic (34%, 62%, and 33% in A549 cells meter at room temperature. Chemical shift values were relative
and 39%, 82%, and 55% in KB cells, respectively). These data to tetramethylsilane (TMS, Me4Si). The data are presented
indicate that compounds 10, 12, and 14 are potentially cytotoxic, as follows: a chemical shift (ppm), a multiplicity (s = singlet,
and in particular, compound 12 would be a promising candidate d = doublet, t = triplet, m = multiplet, brs = broad singlet), and a
for anticancer therapy.
coupling constant J (Hz). The Fourier transform infrared (FT-IR)
spectra were recorded on a Shimadzu IR Prestige 21 spectro-
meter at room temperature. The samples were analyzed as KBr discs
in the range 3500–500 cmÀ1. The XRD analysis was performed
by using an automatic Philips powder diffractometer with
nickel-filtered Cu Ka radiation. The diffraction pattern was
collected in the 2 range of 0–801 in steps of 0.021 and counting
times of 2 s stepÀ1. The microstructures of the samples and
energy dispersive X-ray spectroscopy (EDX) were investigated
using an S-3000 scanning electron microscope (SEM; Hitachi,
Japan) and thermogravimetric analysis was carried out by using
a TGA N-1000 (Scinco, Seoul, and Republic of Korea).
2.3. Structure activity relationship (SAR) study
A SAR study revealed that the different-substituted HPPs induced
anticancer effects in a variety of ways on the two human cancer cell
lines. The synthesized compounds (1–16) consisted of different
substitutions on the benzene ring and different alkoxy-linkages on
the phosphorus atom. In these two cell lines, the chloro-substituent
on the benzene moiety showed enhanced cytotoxicity as com-
pared to the bromo and no substitution. Interestingly, the
nitro-substituted HPPs also showed good activity. The alkoxy
substitution on the phosphorus atom played a key role in
cytotoxicity. As shown previously, ethoxy and butoxy groups on the
phosphorous atom improved activity as compared to isopropoxy and
methoxy groups,37 and the ethoxy substitution on the phosphorus
atom showed greater activity. We studied four different alkoxy
groups on the phosphorus atom, of which the ethoxy and butoxy
substitutions showed incredible activity.
4.2. Synthesis of PSA
The PSA is synthesized by using the earlier reported method.32
The isolated yield is 97% and the mp is 128–130 1C.
4.3. General procedure for the preparation of HPPs 1–16
PSA (0.5 mol%) was added to a mixture of SA and diethylphos-
phite (1 mmol each) under neat conditions at 50 1C with
stirring. The progress of the reaction was monitored by TLC.
After completion of the reaction, the product was extracted with
20 mL of ethanol and the solvent was evaporated under reduced
pressure. The crude product was purified by recrystallization
from ethanol solution. To perform recrystallization, the crude
product was saturated in boiling ethanol and the solution
mixture was filtered when it was hot in order to remove the
undissolved solid. The hot filtrate was cooled to room tempera-
ture to obtain the pure compounds. A similar experimental
procedure was adopted for the synthesis of all HPPs.
3. Conclusions
We have described here the use of PSA as a highly efficient
catalyst for the synthesis of a-hydroxyphosphonates under neat
conditions at 50 1C. The readily synthesized phospho sulfonic
acid showed many advantages in the synthesis of a-hydroxy-
phosphonates by employing the Pudovik reaction like operational
simplicity, mild reaction conditions, good yield, easy work-up, and
recyclability, making it an eco-friendly alternative to currently
existing protocols. The anticancer properties of the synthesized
compounds (1–16) were evaluated, and all the compounds
showed moderate activity at 20 and 40 mM, whereas compounds
10, 12, and 14 showed remarkable activity against the two
tested cancer cell lines (A549 and KB).
4.4. Spectral characterization
4.4.1. Dimethyl (hydroxy(2-hydroxyphenyl)methyl)phosphonate
(1). 90% yield after 33 min of reaction; solid, mp 91–92 1C; 1H NMR
(400 MHz, CDCl3): d (ppm) 7.54–6.86 (m, 4H, Ar–H), 4.80 (s, 2H,
–OH), 3.87 (d, 1H, J = 16.4 Hz, –P–CH), 3.45 (d, 6H, J = 6.8 Hz, OCH3);
13C NMR (100 MHz, CDCl3): d (ppm) 159.3, 130.7, 127.6, 125.3,
120.1, 116.1, 69.2 (d, 1JCP = 148.4 Hz), 53.2, 25.6; 31P NMR (161.9
4. Experimental
4.1. General
The substituted 2-hydroxybenzaldehydes (SAs), diethyl phosphite MHz, CDCl3): d (ppm) 20.2; FTIR (KBr): n = 3431, 3415, 2768,
(DEP) (Sigma-Aldrich Co.), dibutylphosphite (DBP), (Fisher 2164, 1650, 1248, 1034, and 961 cmÀ1
Scientific UK Ltd), diisopropylphosphite (DIP) (Alfa-Aesar), 4.4.2. Diethyl (hydroxy(2-hydroxyphenyl)methyl)phosphonate
.
and the tetrazolium dye (MTT) were purchased from Sigma (2). 91% yield after 35 min of reaction; solid, mp 96–98 1C;
Aldrich Co. (St. Louis, MO, USA). Fetal bovine serum (FBS), 1H NMR (400 MHz, CDCl3): d (ppm) 7.42–6.72 (m, 4H, Ar–H),
antibiotics, and Dulbecco’s modified Eagle’s medium (DMEM) 4.82 (s, 2H, –OH), 4.14–4.01 (m, 4H, –OCH2), 3.92 (d, 1H,
were purchased from Hycolne Co. All experiments were carried J = 17.2 Hz, –P–CH), 0.92 (t, 6H, J = 7.4 Hz, –CH3); 13C NMR
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015

View Article Online
NJC
Paper
(100 MHz, CDCl3): d (ppm) 156.3, 134.8, 130.8, 128.1, 126.3, 3.89 (d, 1H, J = 17.2 Hz, –P–CH), 1.81–1.48 (m, 8H, –(CH2)4),
120.6, 115.2, 66.0 (d, 1JCP = 148.4 Hz), 62.2, 18.5, 13.0; 31P NMR 0.90 (t, 6H, J = 7.2 Hz, –CH3); 13C NMR (100 MHz, CDCl3):
1
(161.9 MHz, CDCl3): d (ppm) 19.8; FTIR (KBr): n = 3345, 3160, d (ppm) 156.7, 135.6, 132.8, 124.1, 120.2, 116.3, 67.1 (d, JCP
=
2892, 2182, 1641, 1490, 1241, 1032, and 965 cmÀ1
4.4.3. Diisopropyl (hydroxy(2-hydroxyphenyl)methyl)phos- d (ppm) 18.7; FTIR (KBr): n = 3326, 3125, 2925, 2188, 1748,
phonate (3). 94% yield after 30 min of reaction; solid, mp 1276, 1056, and 866 cmÀ1
93–94 1C; 1H NMR (400 MHz, CDCl3): d (ppm) 7.36–6.91 (m, 4H,
4.4.9. Dimethyl((5-chloro-2-hydroxyphenyl)(hydroxy)methyl)-
.
148.4 Hz), 65.2, 18.6, 13.5; 31P NMR (161.9 MHz, CDCl3):
.
Ar–H), 4.94 (s, 2H, –OH), 4.71–4.64 (m, 1H, –OCH), 4.45–4.37 phosphonate (9). 93% yield after 20 min of reaction; solid,
1
(m, 1H, –OCH), 3.78 (d, 1H, J = 16.0 Hz, –P–CH), 1.84–1.01 (m, mp 98–99 1C; H NMR (400 MHz, CDCl3): d (ppm) 7.33 (d, 1H,
12H, –(CH3)4); 13C NMR (100 MHz, CDCl3): d (ppm) 155.2, 129.7, J = 4.2 Hz, Ar–H), 7.23 (d, 1H, J = 3.2 Hz, Ar–H), 6.94 (d, 1H,
1
128.8, 122.5, 120.3, 118.8, 72.6, 70.5 (d, JCP = 162.0 Hz), 24.0; J = 5.2 Hz, Ar–H), 4.87 (s, 2H, –OH), 3.98 (d, 1H, J = 14.2 Hz,
31P NMR (161.9 MHz, CDCl3): d (ppm) 19.3; FTIR (KBr): n = 3339, –P–CH), 3.82 (d, 3H, J = 7.0 Hz, OCH3), 3.72 (d, 3H, J = 7.0 Hz,
3172, 2964, 2174, 1644, 1492, 1320, 1020, and 970 cmÀ1
.
OCH3); 13C NMR (100 MHz, CDCl3): d (ppm) 155.4, 129.8, 128.5,
4.4.4. Dibutyl (hydroxy(2-hydroxyphenyl)methyl)phosphonate 121.5, 120.3, 118.0, 69.8, (d, 1JCP = 162.0 Hz), 54.3 (d, J = 7.3 Hz),
(4). 92% yield after 35 min of reaction; solid, mp 97–98 1C; 53.9 (d, J = 7.3 Hz); 31P NMR (161.9 MHz, CDCl3): d (ppm) 20.9;
1H NMR (400 MHz, CDCl3): d (ppm) 7.37–6.95 (m, 4H, Ar–H), FTIR (KBr): n = 3385, 3168, 2974, 2154, 1632, 1492, 1265, 1044,
5.01 (s, 2H, –OH), 4.14–3.80 (m, 5H, –OCH2 & P–CH), 1.68–1.13 and 892 cmÀ1
(m, 8H, –(CH2)4), 0.97 (t, 6H, J = 6.8 Hz, –CH3); 13C NMR (100 MHz,
.
4.4.10. Diethyl((5-chloro-2-hydroxyphenyl)(hydroxy)methyl)-
CDCl3): d (ppm) 155.5, 129.4, 128.5, 122.0, 119.9, 117.9, 70.1 phosphonate (10). 92% yield after 40 min of reaction; solid,
1
1
(d, JCP = 161.2 Hz), 67.4, 67.1, 32.3, 22.5, 18.6, 13.4; 31P NMR mp 96–98 1C; H NMR (400 MHz, CDCl3): d (ppm) 7.42 (t, 1H,
(161.9 MHz, CDCl3):d (ppm) 24.2; FTIR (KBr): n = 3335, 3150, J = 2.4 Hz, Ar–H), 7.24 (t, 1H, J = 2.0 Hz, Ar–H), 6.62 (d, 1H,
1656, 1474, 1248, 1034, and 876 cmÀ1
.
J = 8.8 Hz, Ar–H), 4.72 (s, 2H, –OH), 4.16–3.99 (m, 4H, –OCH2),
4.4.5. Dimethyl((5-bromo-2-hydroxyphenyl)(hydroxy)methyl)- 3.90 (d, 1H, J = 15.2 Hz, –P–CH), 0.92 (t, 3H, J = 7.4 Hz, –CH3), 0.84
phosphonate (5). 91% yield after 40 min of reaction; solid, mp (t, 3H, J = 7.4 Hz, –CH3); 13C NMR (100 MHz, CDCl3): d (ppm)
1
91–93 1C; 1H NMR (400 MHz, CDCl3): d (ppm) 7.47–6.84 (m, 3H, 153.4, 136.5, 128.7, 126.2, 120.3, 117.0, 66.9 (d, JCP = 160.2 Hz),
Ar–H), 4.84 (s, 2H, –OH), 4.12 (d, 1H, J = 18.8 Hz, –P–CH), 3.56 64.5, 13.5; 31P NMR (161.9 MHz, CDCl3): d (ppm) 20.4; FTIR (KBr):
(d, 3H, J = 6.8 Hz, OCH3), 3.45 (d, 3H, J = 6.8 Hz, OCH3); 13C NMR n = 3330, 3123, 2956, 2133, 1468, 1240, 1035, and 898 cmÀ1
.
(100 MHz, CDCl3): d (ppm) 161.3, 133.9, 132.4, 124.2, 120.0, 118.2,
4.4.11. Diisopropyl((5-chloro-2-hydroxyphenyl)(hydroxy)methyl)-
1
65.6 (d, JCP = 161.7 Hz), 52.3; 31P NMR (161.9 MHz, CDCl3): phosphonate (11). 92% yield after 45 min of reaction; solid,
d (ppm) 20.1; FTIR (KBr): n = 3322, 3134, 2982, 2864, 1652, 1034, mp 92–94 1C; 1H NMR (400 MHz, CDCl3): d (ppm) 7.26–7.22 (m,
and 871 cmÀ1
.
2H, –ArH), 6.72–6.59 (m, 1H, –ArH), 4.71 (s, 2H, –OH), 4.40–4.30
4.4.6. Diethyl((5-bromo-2-hydroxyphenyl)(hydroxy)methyl)- (m, 2H, –OCH), 4.13 (d, 1H, J = 17.4 Hz, –P–CH), 1.31–1.04
phosphonate (6). 93% yield after 43 min of reaction; solid, (m, 12H, –(CH3)4); 13C NMR (100 MHz, CDCl3): d (ppm) 157.1,
1
mp 95–97 1C; H NMR (400 MHz, CDCl3): d (ppm) 7.44 (t, 1H, 133.5, 131.1, 122.5, 118.6, 110.2, 72.0, 64.5 (d, 1JCP = 167.0 Hz), 23.9;
J = 2.4 Hz, Ar–H), 7.34 (t, 1H, J = 2.0 Hz, Ar–H), 6.72 (d, 1H, 31P NMR (161.9 MHz, CDCl3): d (ppm) 23.4; FTIR (KBr): n = 3340,
J = 8.8 Hz, Ar–H), 4.82 (s, 2H, –OH), 4.12–3.98 (m, 4H, –OCH2), 3161, 2982, 2063, 1691, 1450, 1283, 1041, and 932 cmÀ1
.
3.88 (d, 1H, J = 19.2 Hz, –P–CH), 0.96 (t, 3H, J = 7.4 Hz, –CH3),
4.4.12. Dibutyl((5-chloro-2-hydroxyphenyl)(hydroxy)methyl)-
0.89 (t, 3H, J = 7.4 Hz, –CH3); 13C NMR (100 MHz, CDCl3): phosphonate (12). 94% yield after 30 min of reaction; solid,
1
1
d (ppm) 158.3, 132.8, 129.7, 125.5, 120.4, 117.2, 66.9 (d, JCP
=
mp 102–104 1C; H NMR (400 MHz, CDCl3): d (ppm) 7.72–6.17
160.2 Hz), 64.5, 13.5; 31P NMR (161.9 MHz, CDCl3): d (ppm) (m, 3H, Ar–H), 4.81 (s, 2H, –OH), 4.12–3.77 (m, 5H, –OCH2 &
20.4; FTIR (KBr): n = 3332, 3128, 2959, 2139, 1462, 1249, 1045, P–CH), 1.74–1.26 (m, 8H, –(CH2)4), 0.94 (t, 6H, J = 7.2 Hz, –CH3);
and 878 cmÀ1
.
13C NMR (100 MHz, CDCl3): d (ppm) 157.3, 133.3, 133.2, 133.0,
4.4.7. Diisopropyl((5-bromo-2-hydroxyphenyl)(hydroxy)methyl)- 118.3, 109.8, 66.9 (d, 1JCP = 146.0 Hz), 60.6 (d, 1JCP = 6.4 Hz), 27.0,
phosphonate (7). 92% yield after 36 min of reaction; solid, 20.5, 16.7, and 13.9; 31P NMR (161.9 MHz, CDCl3): d (ppm) 23.6;
1
mp 98–99 1C; H NMR (400 MHz, CDCl3): d (ppm) 7.25 (t, 1H, FTIR (KBr): n = 3362, 3129, 2896, 2085, 1694, 1492, 1286, 1040,
J = 2.4 Hz, Ar–H), 7.16–6.12 (m, 2H, Ar–H), 5.06 (s, 2H, –OH), and 958 cmÀ1
.
4.70–4.58 (m, 2H, –OCH), 3.95 (d, 1H, J = 17.2 Hz, –P–CH), 1.35–
4.4.13. Dimethyl (hydroxy(2-hydroxy-5-nitrophenyl)methyl)-
1.26 (m, 12H, –(CH3)4); 13C NMR (100 MHz, CDCl3): d (ppm) 158.8, phosphonate (13). 91% yield after 30 min of reaction; solid,
134.1, 130.6, 128.1, 121.0, 116.3, 71.8, 69.4 (d, 1JCP = 146.5 Hz), 24.5; mp 108–110 1C; H NMR (400 MHz, DMSO-d6): d (ppm) 10.20
1
31P NMR (161.9 MHz, CDCl3): d (ppm) 22.6; FTIR (KBr): n = 3356, (s, 1H, –OH), 9.54 (s, 1H, –OH), 7.42 (d, 1H, J = 3.2 Hz, Ar–H),
3135, 2975, 1465, 1296, 1046, and 876 cmÀ1
.
7.08–6.97 (m, 1H, Ar–H), 6.84–6.71 (m, 1H, Ar–H), 5.39 (dd, 1H,
4.4.8. Dibutyl((5-bromo-2-hydroxyphenyl)(hydroxy)methyl)- J = 14.2 Hz, 10.5 Hz –P–CH), 3.61 (d, 3H, J = 12.0 Hz, OCH3), 3.41 (d,
phosphonate (8). 94% yield after 40 min of reaction; solid, 3H, J = 12.0 Hz, OCH3); 13C NMR (100 MHz, DMSO-d6): d (ppm)
1
1
mp 94–96 1C; H NMR (400 MHz, CDCl3): d (ppm) 7.24 (d, 1H, 154.6, 136.4, 132.1, 124.9, 119.2, 109.9, 62.6 (d, JCP = 164.9 Hz),
J = 2.2 Hz, Ar–H), 7.16 (d, 1H, J = 3.8 Hz, Ar–H), 6.52 (d, 1H, 53.5; 31P NMR (161.9 MHz, DMSO-d6): d (ppm) 21.4; IR (KBr): n =
J = 6.6 Hz, Ar–H), 4.97 (s, 2H, –OH), 4.18–3.99 (m, 4H, –OCH2), 3385, 3168, 2974, 2154, 1632, 1492, 1265, 1044, and 892 cmÀ1
.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.

View Article Online
Paper
NJC
4.4.14. Diethyl (hydroxy(2-hydroxy-5-nitrophenyl)methyl)- Notes and references
phosphonate (14). 89% yield after 35 min of reaction; solid,
mp 115–117 1C; 1H NMR (400 MHz, CDCl3): d (ppm) 7.25
(s, 1H, Ar–H), 7.18 (d, 1H, J = 7.6 Hz, Ar–H), 7.06 (t, 1H,
J = 7.8 Hz, Ar–H), 4.78 (s, 2H, –OH), 4.15–3.82 (m, 4H,
–OCH2), 3.03 (s, 1H, –P–CH), 1.33 (t, 3H, J = 7.2 Hz, –CH3),
1.13 (t, 3H, J = 7.2 Hz, –CH3); 13C NMR (100 MHz, CDCl3):
d (ppm) 161.2, 148.7, 137.3, 127.8, 126.5, 124.5, 119.1, 117.1,
63.1 (d, 1JCP = 148.9 Hz), 60.8, 36.6, 13.4; 31P NMR (161.9 MHz,
CDCl3): d (ppm) 21.8; FTIR (KBr): n = 3342, 3162, 2985, 2068,
1 D. S. Shewach and R. D. Kuchta, Chem. Rev., 2009, 109,
2859–2861.
2 J. A. McCubrey, L. S. Steelman, S. L. Abrams, N. Misaghian,
W. H. Chappell, J. Basecke, F. Nicoletti, M. Libra, G. Ligresti
and F. Stivala, Curr. Pharm. Des., 2012, 18, 1784–1795.
3 T. K. Olszewski, Synthesis, 2014, 0403–0429.
4 A. H. Kategaonkar, R. U. Pokalwar, S. S. Sonar, V. U. Gawali,
B. B. Shingate and M. S. Shingare, Eur. J. Med. Chem., 2010,
45, 1128–1132.
1692, 1458, 1285, 1040, and 939 cmÀ1
.
5 K. R. M. Naidu, K. S. Kumar, P. Arulselvan, C. B. Reddy and
O. Lasekan, Arch. Pharm., 2012, 345, 957–963.
6 S. Samanta and C. G. Zhao, J. Am. Chem. Soc., 2006, 128,
7442–7443.
7 D. Y. Kim and D. F. Weimer, Tetrahedron Lett., 2003, 44,
2803–2805.
8 T. K. Olszewski, J. Gałezowska, B. Boduszek and H. Kozłowski,
Eur. J. Org. Chem., 2007, 3539–3546.
9 D. L. Pompliano, E. Rands, M. D. Schaber, S. D. Mosser,
N. J. Anthony and J. B. Gibbs, Biochemistry, 1992, 31,
3800–3807.
4.4.15. Diisopropyl (hydroxy(2-hydroxy-5-nitrophenyl)methyl)-
phosphonate (15). 93% yield after 40 min of reaction; solid, mp
112–114 1C; 1H NMR (400 MHz, DMSO-d6): d (ppm) 8.48
(d, 1H, J = 3.4 Hz, Ar–H), 8.30 (s, 2H, –OH), 8.06 (d, 1H,
J = 2.4 Hz, Ar–H), 6.90 (d, 1H, J = 4.4 Hz, Ar–H), 4.65 (d, 1H,
J = 18.4 Hz, –P–CH), 4.37–4.21 (m, 2H, –OCH), 1.29–0.71
(m, 12H, –(CH3)4); 13C NMR (100 MHz, DMSO-d6): d (ppm)
1
163.9, 138.9, 127.4, 125.5, 121.8, 115.9, 71.3, 54.1 (d, JCP
=
167.0 Hz), 24.5; 31P NMR (161.9 MHz, DMSO-d6): d (ppm) 31.1;
FTIR (KBr): n = 3340, 3161, 2982, 2063, 1691, 1450, 1283, 1041,
and 932 cmÀ1
.
10 S. Soeda, T. Shimada, S. Koyanagi, T. Yokomatsu, T. Murano,
S. Shibuya and H. Shimeno, FEBS Lett., 2002, 524, 54–58.
11 T. Murano, Y. Yuasa, H. Kobayakawa, T. Yokomatsu and
S. Shibuya, Tetrahedron, 2003, 59, 10223–10230.
12 T. Yokomatsu, H. Takechi, T. Akiyama, S. Shibuya,
T. Kominato, S. Soeda and H. Shimeno, Bioorg. Med. Chem.
Lett., 2001, 11, 1277–1280.
13 T. Yokomatsu, H. Abe, M. Sato, K. Suemune, T. Kihara,
S. Soeda, H. Shimeno and S. Shibuya, Bioorg. Med. Chem.,
1998, 6, 2495–2505.
4.4.16. Dibutyl (hydroxy(2-hydroxy-5-nitrophenyl)methyl)-
phosphonate (16). 94% yield after 35 min of reaction; solid,
1
mp 114–116 1C; H NMR (400 MHz, CDCl3): d (ppm) 8.25–7.27
(m, 2H, Ar–H), 6.96 (d, 1H, J = 6.8 Hz, Ar–H), 4.81 (s, 2H, –OH),
4.12–3.77 (m, 5H, –OCH2 & P–CH), 1.74–1.26 (m, 8H, –(CH2)4),
0.94 (t, 6H, J = 7.2 Hz, –CH3); 13C NMR (100 MHz, CDCl3):
1
d (ppm) 157.3, 133.3, 133.2, 133.0, 118.3, 109.8, 63.9 (d, JCP
=
146.0 Hz), 60.6 (d, 1JCP = 6.4 Hz), 27.0, 20.5, 16.7, 13.9; 31P NMR
(161.9 MHz, CDCl3): d (ppm) 23.6; FTIR (KBr): n = 3362, 3129,
2896, 2085, 1694, 1492, 1286, 1040, and 958 cmÀ1
.
14 J. A. Sikorski, M. J. Miller, D. S. Braccolino, D. G. Cleary,
S. D. Corey, J. L. Font, K. J. Gruys, C. Y. Han, K. C. Lin,
P. D. Pansegrau, J. E. Ream, D. Schnur, A. Shah and M. C.
Walker, Phosphorus, Sulfur Silicon Relat. Elem., 1993, 76,
375–378.
15 J. F. Dellaria, Jr., R. G. Maki, H. H. Stein, J. Cohen,
D. Whittern, K. Marsh, D. J. Hoffman, J. J. Plattner and
T. J. Perun, J. Med. Chem., 1990, 33, 534–542.
16 M. Tao, R. Bihovsky, G. J. Wells and J. P. Mallamo, J. Med.
Chem., 1998, 41, 3912–3916.
4.5. Evaluation of cytotoxicity
The two cancer cell lines (A549 and KB) were grown in Dulbecco’s
modified Eagle’s medium supplemented with 10% (v/v) fetal
bovine serum and antibiotics (100 IU mLÀ1 of penicillin G sodium
and 100 mg mLÀ1 of streptomycin sulfate). The cells were main-
tained in an incubator supplied with 5% CO2 air in a humidified
atmosphere at 37 1C. The cells were transferred to a 96 well plate
at 7 Â 104 cells per well. The next day, the medium was exchanged
for fresh medium. When the cells reached a confluence of 80%,
the compounds were added at different concentrations (2.0, 4.0,
20, and 40 mM). The cells were then incubated for 24 h. The
cytotoxicity was assayed using MTT and a micro plate-reader.
17 B. Kaboudin, Tetrahedron Lett., 2003, 44, 1051–1053.
18 G. A. Olah and A. Wu, J. Org. Chem., 1991, 56, 902–904.
19 H. Firouzabadi, N. Iranpoor and S. Sobhani, Tetrahedron
Lett., 2002, 43, 477–480.
20 F. Eymery, B. Lorga and P. Savignac, Tetrahedron, 1999, 55,
2671–2686.
21 H. Firouzabadi, N. Iranpoor, S. Sobhani and Z. Amoozgar,
Synthesis, 2004, 1771–1774.
22 A. N. Pudovik and I. V. Konovalova, Synthesis, 1979, 81–96.
23 O. Gawron, C. Grelecki, W. Reilly and J. Sands, J. Am. Chem.
Soc., 1953, 75, 3591–3592.
Acknowledgements
This work was supported by the Basic Science Research Pro-
gram through the National Research Foundation of Korea
funded by the Ministry of Education (2012R1A1A2041315) and
the Fusion Research Program for Green Technologies through
the National Research Foundation of Korea funded by the 24 A. A. Smaardijk, S. Noorda, F. Bolhuis and H. Wynberg,
Ministry of Education (2012M3C1A1054502). The authors also
thank the BK21 PLUS Program for partial financial support.
Tetrahedron Lett., 1985, 26, 493–496.
25 F. Textier-Boullet and A. Foucaud, Synthesis, 1982, 916–917.
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015

View Article Online
NJC
Paper
26 A. R. Sardarian and B. Kaboudin, Synth. Commun., 1997, 27, 32 R. M. N. Kalla, H. Park, T. T. K. Hoang and I. Kim, Tetra-
543–551. hedron Lett., 2014, 55, 5373–5376.
27 M. Tajbakhsh, A. Heydari, M. A. Khalizadeh, M. M. Lakouraj, 33 R. M. N. Kalla, J. V. John, H. Park and I. Kim, Catal.
B. Zamenian and S. Khaksar, Synlett, 2007, 2347–2350.
28 W. Goldman and M. Soroka, Synthesis, 2006, 3019–3024.
29 S. M. Vardat, R. Baharfar, M. Tajbakhsh, A. Heydari,
Commun., 2014, 57, 55–59.
34 R. M. N. Kalla, M. R. Kim and I. Kim, Tetrahedron Lett., 2015,
56, 717–720.
S. M. Baghbanian and S. Khaksar, Tetrahedron Lett., 2008, 35 R. M. Silverstein and F. X. Webster, Spectroscopic Identifi-
49, 6501–6504.
cation of Organic Compounds, Wiley, New York, 6th edn,
1998.
36 C. Qian and T. Hung, J. Org. Chem., 1998, 63, 4125–4128.
30 A. Heydari, A. Arefi, S. Khaksar and M. Tajbakhsh, Catal.
Commun., 2006, 7, 982–984.
31 A. R. Kiasat, A. Mouradzadegun and S. J. Saghanezhad, 37 M. A. Kumar, Y. K. Park and K. D. Lee, Chem. Pharm. Bull.,
J. Serb. Chem. Soc., 2013, 78, 469–476. 2012, 60, 1531–1537.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.