6232
P. Chen et al. / Bioorg. Med. Chem. Lett. 22 (2012) 6229–6232
to see whether our inhibitors have a broad spectrum of activity. B.
anthracis is the causative agent of anthrax and expression of Bla2
can result in resistance to b-lactam antibiotics. Therefore, inhibi-
tors of this enzyme have potential therapeutic value. The results
are shown in Tables 1 and 2. Captopril was also found to be a weak
Supplementary data
Supplementary data associated with this article can be found, in
inhibitor of Bla2 with an IC50 value of 25.8
lM, or a Ki value of
17.9 M, while EDTA is almost inactive against this enzyme (IC50
l
References and notes
>1 mM). Although compound 4 is a good IMP-1 inhibitor, it was
observed to have essentially no activity against Bla2 with an IC50
1. Leeb, M. Nature 2004, 431, 892.
2. Fisher, J. F.; Meroueh, S. O.; Mobashery, S. Chem. Rev. 2005, 105, 395.
3. Crowder, M. W.; Spencer, J.; Vila, A. J. Acc. Chem. Res. 2006, 39, 721.
4. Wang, Z.; Fast, W.; Valentine, A. M.; Benkovic, S. J. Curr. Opin. Chem. Biol. 1999,
3, 614.
5. Walsh, T. R.; Toleman, M. A.; Poirel, L.; Nordmann, P. Clin. Microbiol. Rev. 2005,
18, 306.
of >200
stituent showed improved inhibitory activity against Bla2 as com-
pared to captopril, with an IC50 value of 4.9 M (Table 2) or a Ki
value of 5.1 M. All other compounds, except for compound 12
being a weak inhibitor (IC50 = 74.1 M), are also inactive against
lM. However, analogous compound 10 with a 3-NH2 sub-
l
l
l
6. Bebrone, C. Biochem. Pharmacol. 2007, 74, 1686.
7. Walsh, T. R. Clin. Microbiol. Infect. 2005, 11, 2.
Bla2. Nevertheless, the activity of compound 10 shows that it is
also possible to develop 4,5-dihydrothiazole-4-carboxylic acids to
find a compound that have a broad activity against other MBLs.
General methods for synthesizing compounds 3–17 are illus-
trated in Scheme 1.25 For 4,5-dihydrothiazole compounds 3–5
and 8–13, an aromatic nitrile, 1.2 equiv amount of L-cysteine (or
D-cysteine) hydrochloride and NaHCO3 was refluxed in methanol
and phosphate buffer (pH 6) for 72 h,26 to give these compounds
in 40–70% yield. However, this method does not work for making
analogous compounds 14–17. Rather, the methyl esters of these
compounds were synthesized using a similar procedure,27 which
were carefully undergone a mild hydrolysis using 0.9 equiv of LiOH
to afford compounds 14–17 in 70–80% yield. Excess amount of
LiOH caused decomposition of the products. Thiazolidine com-
pounds 6 and 7 were prepared in ꢀ80% yield by reacting benzalde-
hyde or phenylacetaldehyde with L-cysteine at room temperature
in a mixture of ethanol and water.28
8. Toney, J. H.; Moloughney, J. G. Curr. Opin. Investig. Drugs 2004, 5, 823.
9. Garcia-Saez, I.; Hopkins, J.; Papamicael, C.; Franceschini, N.; Amicosante, G.;
Rossolini, G. M.; Galleni, M.; Frere, J. M.; Dideberg, O. J. Biol. Chem. 2003, 278,
23868.
10. Concha, N. O.; Janson, C. A.; Rowling, P.; Pearson, S.; Cheever, C. A.; Clarke, B. P.;
Lewis, C.; Galleni, M.; Frere, J. M.; Payne, D. J.; Bateson, J. H.; Abdel-Meguid, S. S.
Biochemistry 2000, 39, 4288.
11. Walter, M. W.; Felici, A.; Galleni, M.; Soto, R. P.; Adlington, R. M.; Baldwin, J. E.;
Frère, J.-M.; Gololobov, M.; Schofield, C. J. Bioorg. Med. Chem. Lett. 1996, 6, 2455.
12. Toney, J. H.; Fitzgerald, P. M.; Grover-Sharma, N.; Olson, S. H.; May, W. J.;
Sundelof, J. G.; Vanderwall, D. E.; Cleary, K. A.; Grant, S. K.; Wu, J. K.; Kozarich, J.
W.; Pompliano, D. L.; Hammond, G. G. Chem. Biol. 1998, 5, 185.
13. Toney, J. H.; Hammond, G. G.; Fitzgerald, P. M.; Sharma, N.; Balkovec, J. M.;
Rouen, G. P.; Olson, S. H.; Hammond, M. L.; Greenlee, M. L.; Gao, Y. D. J. Biol.
Chem. 2001, 276, 31913.
14. Watanabe, M.; Iyobe, S.; Inoue, M.; Mitsuhashi, S. Antimicrob. Agents Chemother.
1991, 35, 147.
15. Deng, L.; Sundriyal, S.; Rubio, V.; Shi, Z.; Song, Y. J. Med. Chem. 2009, 52, 6539.
16. Jacobsen, F. E.; Lewis, J. A.; Cohen, S. M. J. Am. Chem. Soc. 2006, 128, 3156.
17. Jacobsen, F. E.; Lewis, J. A.; Cohen, S. M. ChemMedChem 2007, 2, 152.
18. Brown, N. G.; Horton, L. B.; Huang, W.; Vongpunsawad, S.; Palzkill, T.
Antimicrob. Agents Chemother. 2011, 55, 5696.
In summary, this work is of interest for several reasons. First,
using rational compound screening followed by medicinal chemis-
try, 2-phenyl-4,5-dihydrothiazole-4-carboxylic acid (4) was identi-
fied to be a novel inhibitor of P. aeruginosa MBL IMP-1 with an IC50
19. The enzyme assay was performed using 2 nM IMP-1 (or 10 nM Bla2) and
25
l
M nitrocefin in 50 mM HEPES buffer (pH 7.0) containing 20
lg/mL BSA and
0.01% triton in a final volume of 300
lL. For inhibition assay, compounds were
pre-incubated with the enzyme for 20 min at room temperature, before
initiation of the reaction by adding nitrocefin. The increasing absorbance at
482 nM was monitored using a Beckman DU640 UV spectrometer. The initial
velocities for different concentrations of an inhibitor were imported into Prism
(version 5.0, GraphPad, La Jolla, CA). The IC50 as well as Ki values were
calculated by using a standard dose response curve fitting in the software.
20. Deng, L.; Endo, K.; Kato, M.; Cheng, G.; Yajima, S.; Song, Y. ACS Med. Chem. Lett.
2011, 2, 165.
21. Deng, L.; Diao, J.; Chen, P.; Pujari, V.; Yao, Y.; Cheng, G.; Crick, D. C.; Prasad, B. V.
V.; Song, Y. J. Med. Chem. 2011, 54, 4721.
22. Glide, version 5.5, Schrödinger, LLC., New York, NY, 2010.
23. Schrödinger Suite, version 2010, Schrödinger, LLC, New York, NY, 2010.
24. Materon, I. C.; Queenan, A. M.; Koehler, T. M.; Bush, K.; Palzkill, T. Antimicrob.
Agents Chemother. 2003, 47, 2040.
25. Experimental Section can be found in Supplementary data on-line.
26. Lu, Y.; Li, C.; Wang, Z.; Chen, J.; Mohler, M. L.; Li, W.; Dalton, J. T.; Miller, D. D. J.
Med. Chem. 2011, 54, 4678.
27. Merino, P.; Tejero, T.; Unzurrunzaga, F. J.; Franco, S.; Chiacchio, U.; Saita, M. G.;
Iannazzo, D.; Piperno, A.; Romeo, G. Tetrahedron: Asymmetry 2005, 16, 3865.
28. Lu, Y.; Li, C.; Wang, Z.; Ross, C. R.; Chen, J.; Dalton, J. T.; Li, W.; Miller, D. D. J.
Med. Chem. 2009, 52, 1701.
value of 5.5 lM. Second, docking studies were explored to rational-
ize the structure activity relationships of this class of compounds
and provide implications for future inhibitor design. Third, 2-(3-
aminophenyl)-4,5-dihydrothiazole-4-carboxylic acid (10) was
identified to be an inhibitor of B. anthracis MBL Bla2
(IC50 = 4.9 lM), showing the promise of further developing this
class of compounds in the context of overcoming b-lactam
resistance.
Acknowledgments
This work was supported by a Grant (R21AI090190) from Na-
tional Institute of Allergy and Infectious Disease (NIAID/NIH) to
Y.S. and a Grant (R01AI32956) from NIAID/NIH to T.P., L.B.H. was
supported by a training Grant (T90DK070109) from NIH/NIDDK.