Synthesis of a diverse series of phosphacoumarins with biological activity

Article abstract of DOI:10.1021/ol051871m

(Chemical Equation Presented) We have developed a general and efficient approach to a diverse series of phosphacoumarins as analogues of coumarins with various biological activities, and the inhibitory activity of the synthesized phosphacoumarins against the enzyme SHP-1, a protein tyrosine phosphatases, was tested. Some of them showed moderate to good efficiency.

Full text of DOI:10.1021/ol051871m

ORGANIC
LETTERS
2005
Vol. 7, No. 22
4919-4922
Synthesis of a Diverse Series of
Phosphacoumarins with Biological
Activity
|
|
Xueshu Li,†, Dongwei Zhang,†, Hai Pang,‡ Feng Shen,† Hua Fu,*,†
Yuyang Jiang,§ and Yufen Zhao†
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology,
Ministry of Education, Department of Chemistry, Tsinghua UniVersity, Beijing 100084,
P. R. China, Laboratory of Structural Biology, Tsinghua UniVersity, Beijing 100084,
P. R. China, and Key Laboratory of Chemical Biology, Guangdong ProVince,
Graduate School of Shenzhen, Tsinghua UniVersity, Shenzhen 518057, P. R. China
fuhua@mail.tsinghua.edu.cn
Received August 4, 2005
ABSTRACT
We have developed a general and efficient approach to a diverse series of phosphacoumarins as analogues of coumarins with various biological
activities, and the inhibitory activity of the synthesized phosphacoumarins against the enzyme SHP-1, a protein tyrosine phosphatases, was
tested. Some of them showed moderate to good efficiency.
Coumarins are members of the class of compounds called
benzopyrones and have gained considerable synthetic and
pharmacological interest for a long time because of their
various biological activities, such as antitumor activity,1 anti-
HIV activity,2 antioxidation,3 vasorelaxant activity,4 tumor
necrosis factor-R (TNF-R) inhibition,5 antimicrobial activity,6
serine protease inhibition,7 and anticancer activity.8 In the
research field of coumarins, 4-OH coumarin and its deriva-
tives have shown many biological activities, such as inhibi-
tion of gyrase B,9 HIV integrase,2c and protein kinase.10 On
the other hand, organophosphorus compounds continue to
receive widespread attention due to their ubiquity in biologi-
cal systems11 and their potential to serve as novel pharma-
ceuticals.12 Phosphonic acids and their derivatives have often
exhibited biochemical activity similar to that of naturally
occurring carboxylic acids and their derivatives,13 so we
thought that the phosphacoumarins as analogues of coumarins
(Figure 1) might have potential biological activities similar
to that of coumarins. Chen and Rodios’s groups14 have
prepared phosphacoumarins through reaction of salicylalde-
† Department of Chemistry.
(5) (a) Cheng, J. F.; Ishikawa, A.; Ono, Y.; Arrhenius, T.; Nadzan, A.
Bioorg. Med. Chem. Lett. 2003, 13, 3647. (b) Cheng, J. F.; Chen, M.;
Wallace, D.; Tith, S.; Arrhenius, T.; Kashiwagi, H.; Ono, Y.; Ishikawa,
A.; Sato, H.; Kozono, T.; Ato, H.; Nadzan, A. M. Bioorg. Med. Chem.
Lett. 2004, 14, 2411.
(6) Zaha, A. A.; Hazem, A. Microbiologica 2002, 25, 213.
(7) Whittaker, M.; Floyd, C. D.; Brown, P.; Gearing, A. J. H. Chem.
ReV. 1999, 99, 2735.
(8) Maly, D. J.; Leonetti, F.; Backes, B. J.; Dauber, D. S.; Harris, J. L.;
Craik, C. S.; Ellman, J. A. J. Org. Chem. 2002, 67, 910.
(9) Musicki, B.; Periers, A. M.; Piombo, L.; Laurin, P.; Klich, M.;
Dupuis-Hamelin, C.; Lassaigne, P.; Bonnefoy, A. Tetrahedron Lett. 2003,
44, 9259.
‡ Laboratory of Structural Biology.
§ Graduate School of Shenzhen.
| Equal contribution to this work.
(1) Weber, U. S.; Steffen, B.; Siegers, C. P. Res. Commun. Mol. Pathol.
Pharmacol. 1998, 99, 193.
(2) (a) Thitima, P.; Muney, S.; Stephen, H. H.; Djaja, D. S.; John, M. P.
J. Nat. Prod. 1996, 59, 839. (b) Ptail, A. D.; Freyer, A. J.; Drake, S. E.;
Haltiwanger, R. C.; Bean, M. F.; Taylor, P. B.; Caranfa, M. J.; Breen, A.
L.; Bartus, H. R.; Johnson, R. K.; Hertzberg, R. P.; Westley, J. W. J. Med.
Chem. 1993, 36, 4131. (c) Zhao, H.; Neamati, N.; Hong, H. X.; Mazumder,
A.; Wang, S. M.; Sunder, S.; Milne, G. W. A.; Pommier, Y.; Burke, T. B.
J. Med. Chem. 1997, 40, 242.
(3) Yun, B. S.; Lee, I. K.; Ryoo, I. J.; Yoo, I. D. J. Nat. Prod. 2001, 64,
1238.
(4) Campos-Toimil, M.; Orallo, F.; Santanab, L.; Uriarte, E. Bioorg. Med.
Chem. Lett. 2002, 1, 783.
(10) Yang, E. B.; Zhao, Y. N.; Zhang, K.; Mack, P. Biochem. Biophy.
Res. Commun. 1999, 260, 682.
(11) (a) Westheimer, F. H. Science 1987, 235, 1173. (b) Seto, H.;
Kuzuyama, T.; Nat. Prod. Rep. 1999, 16, 589.
10.1021/ol051871m CCC: $30.25
© 2005 American Chemical Society
Published on Web 10/05/2005

phosphoryl chloride and byproducts with low boiling point
in the resulting solution were removed by reduced pressure,
and the residue was the crude product 4, which was used in
the following reaction without further purification. Reaction
of 4 with methyl salicylate produced enantiomers 5 in the
presence of triethylamine. Overall yields of the two steps
from 3 to 5 are 75-82%. KOH-promoted intramolecular
cyclization of 5 in dry pyridine led to major keto-form (6)
and minor enol-form (7) products in 85-90% yields (see
Table 1). Cyclization of 5 is the key step during the whole
process.
Figure 1. Coumarins (A) and the designed phosphacoumarins (B)
(R′, R′′, R1, R2, and R3 are various substituents).
hyde with triethylphosphonoacetate. Unfortunately, only low-
yield target products (not more than 21%) were obtained,
and major products were phosphonocoumarins. To the best
of our knowledge, there is not a general and efficient method
for the synthesis of 4-substituted phosphacoumarins so far.
Herein, we initiated a program to develop an approach to a
diverse series of phosphacoumarins.
Table 1. Yields and Proportions of Cyclization Products
(6 and 7) from 5
A synthetic route for 4-O-substituted phosphacoumarin
derivatives is shown in Scheme 1. Reaction of p-substituted
entry
6/7
R1
CH3
CH2CH3
CH2CH3
CH2CH3
R2
yield (%)a
keto/enolb
1
2
3
4
6a/7a
6b/7b
6c/7c
6d/7d
H
Cl
CH3
CN
90
85
85
88
7.3:1.0
9.3:1.0
2.5:1.0
7.7:1.0
Scheme 1. Synthetic Route of 4-O-Substituted
Phosphacoumarins
a Isolated yields of 6 and 7. b Determined by 31P NMR in CDCl3.
When acetic anhydride (R3OR3), methylsulfonyl chloride,
diethyl phosphorochloridate, or p-toluenesulfonyl chloride
(R3Cl) was added to mixtures of 6 and 7 in dry acetonitrile
in the presence of anhydrous K2CO3, 31P NMR spectrscopy
showed that 6 and 7 almost quantitatively transferred into
the corresponding 4-O-substituted phosphacoumarins (8) at
31P NMR 9-11 ppm, and pure products 8 were obtained in
82-96% yields (see Table 2) after isolation by silica gel
Table 2. Yields of 4-O-Substituted Phosphacoumarins
benzyl chloride with sodium dialkyl phosphite (2), which
was prepared from reaction of dialkyl phosphite (1) with
sodium in dry ether, yielded 3 in 80-85% overall yields
from 1 to 3. Reaction of 3 with phosphoryl chloride produced
4 at 60 °C under nitrogen atmosphere. The excess of
entry
8
R1
R2
R3
yield (%)c
1
2
3
4
5
6
7
8
9
8ae
8be
8ce
8de
8af
Me
Et
Et
Et
Me
Et
Et
Et
Me
Et
Me
Et
H
Cl
CH3
CN
H
COCH3
COCH3
COCH3
COCH3
SO2CH3
SO2CH3
SO2CH3
SO2CH3
DEPa
92
95
90
94
96
94
91
95
82
84
97
95
(12) For examples of phosphorus compounds as pharmaceuticals, see:
(a) Kafarski, P.; Lejczak, B. Curr. Med. Chem. 2001, 1, 301. (b) Colvin,
O. M. Curr. Pharm. Des. 1999, 5, 555. (c) Zon, G. Prog. Med. Chem.
1982, 19, 205. (d) Stec, W. J. Organophosphorus Chem. 1982, 13, 145. (e)
Mader, M. M.; Bartlett, P. A. Chem. ReV. 1997, 97, 1281. (f) Kafarski, P.;
Lejczak, B. Phosphorus, Sulfur, Silicon Relat. Elem. 1991, 63, 193.
(13) (a) Handbook of Orgnophosphorus Chemistry; Engel, R., Ed.;
Marcel Dekker: New York, 1992. (b) The Chemistry of Organophosphorus
Compounds; Hartley, F. R., Ed.; John Wiley & Sons: New York, 1996;
Vol. 4. (c) A Guide to Organophosphorus Chemistry; Quin, L. D., Ed.;
John Wiley & Sons: New York, 2000.
8bf
8cf
Cl
CH3
CN
H
Cl
H
8df
8ag
8bg
8ah
8dh
10
11
12
DEP
Tsb
CN
Ts
(14) (a) Chen, C. H.; Fox, J. L.; Lippert, J. L. J. Heterocycl. Chem. 1987,
24, 931. (b) Bojilova, A.; Nikolova, R.; Ivanov, C.; Rodios, N. A.; Terzis,
A.; Raptopoulou, C. P. Tetrahedron 1996, 52, 12597.
a DEP ) diethoxylphosphoryl. b Ts ) p-toluenesulfonyl. c Isolated yields.
4920
Org. Lett., Vol. 7, No. 22, 2005

column chromatography. For example, reaction of 6d and
7d with acetic anhydride produced 4-O-acetyl phosphacou-
marin 8de corresponding to the 31P NMR peak at 9.19 ppm,
the pure product 8de was obtained in 94% yield after
purification.
We thought that phosphacoumarins conjugated with
alkynes could be further utilized as precursors to construct
even more complex molecules, so 4-alkynylphosphacou-
marins were prepared through Sonogashira reaction as shown
in Scheme 2. Reaction of 8ah or 8dh with phenyl acetylene
To probe whether the synthesized phosphacoumarins are
of biological activities, we tested their inhibitory activity
against the enzyme SHP-1, one of the protein tyrosine
phosphatases (PTPs). Protein tyrosine phosphatases (PTPs)
catalyze the hydrolysis of phosphotyrosyl (pY) proteins to
produce tyrosyl proteins and inorganic phosphate. Specific
and cell-membrane-permeable PTP inhibitors would likely
provide such tools for studying the function of these
enzymes. Aberrant action of PTPs is often linked to cellular
dysfunction and implicated in a diversity of diseases includ-
ing diabetes, obesity, autoimmune disease, infectious dis-
eases, inflammation, cancer, osteoporosis, and neurodegen-
eration.16 Thus, PTP inhibitors could also provide potential
therapeutic agents against those diseases. As shown in Table
3, most of the phosphacoumarins showed certain inhibitory
Scheme 2. Sonogashira Coupling of
4-Tosylphosphacoumarins with Phenylacetylene
Table 3. Inhibition Constants of the Phosphacoumarin
Derivatives against SHP-1 (∆SH2)
compound
Ki (µM)
compound
Ki (µM)
6a/7a
6b/7b
6c/7c
6d/7d
8ae
8be
8ce
8de
350
600
510
570
NDa
620
820
250
8af
8bf
8cf
8df
8ag
8bg
8ah
8dh
130
730
280
430
90
10
60
130
in the presence of triethylamine and catalytic amounts of
PdCl2(PPh3)2 (10% mol) and CuI (10% mol) in acetonitrile
at 50 °C produced 9ah or 9dh in 77% and 80% yields,
respectively, after isolation by column chromatography on
silica gel.
a ND: not detected.
4-Phenylphosphacoumarin (9di) was also made as shown
in Scheme 3. Reaction of 8dh with phenylboronic acid in
activity, and compound 8bg was the most potent inhibitor,
with a Ki value of 10 µM. This represents the first example
using the phosphacoumarins as membrane-permeable PTP
inhibitors, which provides a new class of core structures for
the further development of PTP inhibitors.
Scheme 3. Suzuki Coupling of 4-Tosylphosphacoumarin with
Phenylboronic Acid
The synthesized phosphacoumarin derivatives may po-
tentially have biological and medicinal activities similar to
those of coumarin derivatives, but further studies are needed
to confirm this possibility.
In summary, a general and efficient approach to a diverse
series of phosphacoumarins has been developed. The meth-
ods could provide valuable routes to various phosphorus
heterocycles and enrich the organic and medicinal chemistry
of coumarins. The synthesized phosphacoumarin derivatives
showed moderate to good inhibitory activity against SHP-1,
which provides a lead structures for further design and
development of novel PTP inhibitors as potential therapeutic
reagents.
dry THF produced 9di in the presence of 10% mol PdCl2-
(PPh3)2 and triethylamine at 60 °C under nitrogen atmo-
sphere, and the pure compound 9di was obtained in 75%
yield after isolation by column chromatography on silica gel.
The structures of the synthesized compounds 6-9 were
identified by the shifts and J values of 1H, 13C, and 31P NMR
spectroscopy (see Supporting Information).
In addition, 4-diethylphosphonooxyphosphacoumarins (8ag
and 8bg) can be important precursors and can be used to
prepare 4-substituted phosphacoumarins such as 4-dieth-
ylphosphonooxycoumarins using organozinc reagents as
partners of nickel-catalyzed cross-coupling reactions.15 So
these synthesized 4-O-substituted phosphacoumarins can be
used as precursors of a phosphacoumarin library.
Acknowledgment. This work was supported by the
Excellent Dissertation Foundation of the Chinese Ministry
of Education (no. 200222), the Excellent Young Teacher
(15) Wu, J.; Yang, Z. J. Org. Chem. 2001, 66, 7875.
(16) (a) Moller, D. E. Nature 2001, 414, 821. (b) Ukkola, O. M.;
Santaniemi, M. J. Int. Med. 2002, 251, 467. (c) Zhang, Z.-Y. Curr. Opin.
Chem. Biol. 2001, 5, 416. (d) Van Huijsduijnen, R. H.; Bombrun, A.;
Swinnen, D. Drug DiscoVery Today 2002, 7, 1013. (e) Li, L.; Dixon, J. E.
Semin. Immunol. 2000, 12, 75.
Org. Lett., Vol. 7, No. 22, 2005
4921

1
Program of MOE, P. R. C., and the National Natural Science
Foundation of China (Grant 20472042).
1H, 13C, and 31P NMR spectra of compounds 6, 7; and H
and 13C NMR spectra of compounds 8 and 9. This material
is available free of charge via the Internet at http://pubs.acs.org.
Supporting Information Available: Detailed experi-
mental procedures; characterization data for compounds 5-9;
OL051871M
4922
Org. Lett., Vol. 7, No. 22, 2005