ACS Medicinal Chemistry Letters
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52.73 (αCH), 31.69 (CH2), 30.04 (CH2), 29.18 (CH3−Boc), 23.72
(CH3), 23.25 (CH2).
organic extract was then dried over sodium sulfate and the solvent
removed under reduced pressure to give 0.09 g of pure product as a
white solid.
Synthesis of [5-Acetylamino-5-(4-sulfamoyl-benzylcarbamoyl)-
pentyl]-carbamic Acid tert-Butyl Ester 4. 2-Acetamido-6-tert-butox-
ycarbonylamino-hexanoic acid (0.11 g, 1.0 equiv) and 4-amino-
methylbenzenesulfonamide hydrochloride 2 (0.085g, 1.0 equiv) were
added to a round flask with 20 mL of acetonitrile and stirred for few
minutes. 1-Hydroxy-7-azabenzotriazole (HOAt) (0.052 g, 1.0 equiv)
was then added to the reaction mixture followed by N,N-
diisopropylethylamine (DIPEA) (0.1 g, 2.0 equiv). The solution was
cooled to 0 °C in an ice bath for 10 min. N-(3-(dimethylamino)-
propyl)-N′-ethyl-carbodiimide hydrochloride (EDCI, 0.08 g, 1.05
equiv) was then added to the solution turning it yellow. It was then
stirred overnight at room temperature. The solvent was removed
under vacuum leaving a yellow oil. This oil was dissolved in water and
the solution acidified to pH 1 using a 3.0 M HCl solution. The product
was then extracted with ethyl acetate (∼30 mL). The organic layer was
dried under anhydrous Na2SO4 then filtered. The solvent was removed
under vacuum to leave 0.08 g of pure product as a white solid.
Compound 4: 47.6% yield. δH (400 MHz, DMSO-d6): 8.54 (t,1 H,
NH, J 6), 8.04 (d, 1H, NH, J 8), 7.79 (d, 2H, CH, J 8), 7.60 (d, 2H,
CH, J 8), 7.33 (s, 2H, NH2), 6.80 (appt, 1H, NH), 4.36 (t, 2H, CH2, J
5.8), 4.2 (m, 1H, CH), 2.91 (td, 2H, CH2, J 6.4), 1.89 (s, 3H, CH3),
1.68−1.63 (m, 2H, CH2), 1.59−1.50 (m, 2H, CH2), 1.41 (s, 9H,
3CH3), 1.35−1.25 (m, 2H, CH2). δC (100 MHz, DMSO-d6): 173.17
(CO), 170.40 (CO), 156.65 (CO), 144.71 (C-Ar), 143.61 (C-
Ar), 128.40 (CH−Ar), 126.67 (CH−Ar), 78.41(C-Boc), 53.80 (αCH),
42.71 (CH2), 39.38 (CH2), 32.65 (CH2), 30.31 (CH2), 29.34 (CH3−
Boc), 23.92 (CH3), 23.60 (CH2). m/z (ESI negative), 455.3 [M −
H]−.
Compound 9: 58% yield. δH (400 MHz, DMSO-d6): 11.54 (s, 1 H,
NH, exchange D2O), 8.56 (t,1 H, NH, J 4, exchange D2O), 8.32 (t,1
H, NH, J 4, exchange D2O), 8.08 (d, 1H, NH, J 8, exchange D2O),
7.79 (d, 2H, CH, J 8), 7.44 (d, 2H, CH, J 8), 7.33 (s, 2H, NH2,
exchange D2O), 4.42 (m, 2H, CH2), 4.24 (m, 1H, CH), 3.28 (appq,
2H, CH2), 1.89 (s, 3H, CH3), 1.76 (m, 2H, CH2), 1.51 (s, 9H, 3CH3),
1.43(s, 9H, 3CH3), 1.21 (m, 4H, 2CH2). δC (100 MHz, DMSO-d6):
173.0 (CO), 170.29 (CO),), 164.04 (CN), 156.12 (CO),
153.09 (CO), 144.52 (C-Ar), 143.45 (C-Ar), 128.26 (CH−Ar),
126.52(CH−Ar), 83.82 (C-Boc), 79.05(C-Boc), 53.50 (αCH), 42.58
(CH2), 40.79 (CH2), 32.41 (CH2), 28.93 (CH3−Boc), 28.85 (CH2),
28.54 (CH3−Boc), 23.81 (CH2), 23.42 (CH3). m/z (ESI positive),
599.17 [M − H]+.
Synthesis of N-Acetylamino-N′-guanidino-hexanoic Acid [2-(4-
Sulfamoyl-phenyl)-methyl]-amide Hydrochloride 11. A suspension
of N-acetylamino-N′-di-Boc-guanidino-hexanoic acid [2-(4-sulfamoyl-
phenyl)-methyl]-amide 9 (0.09 g, 1.0 equiv) and 6.0 M HCl (10 mL)
was stirred overnight at room temperature. The solvent was removed
under reduced pressure to give a brownish oil. The oil was washed
with dichloromethane and triturated with diethyl ether to give 0.04 g
of the pure product as a light brown gel.
Compound 11: 60% yield. δH (400 MHz, DMSO-d6): 8.63 (appt,1
H, NH, exchange D2O), 8.14 (d, 1H, NH, J 8, exchange D2O), 7.79 (d,
2H, CH, J 8), 7.75 (appt, 1 H, NH, exchange D2O), 7.44 (d, 2H, CH, J
+
8), 7.35 (s, 2H, NH2, exchange D2O), 7.1 (bs, 3 H, NH3 , exchange
D2O), 4.36 (m, 2H, CH2), 4.28 (m, 1H, CH), 3.11 (btd, 2H, CH2),
1.91 (s, 3H, CH3), 1.77 (m, 2H, CH2), 1.51 (m, 2H, CH2), 1.26 (m,
4H, 2CH2). δC (100 MHz, DMSO-d6): 172.93 (CO), 170.34 (C
O), 157.8 (CN), 144.52 (C-Ar), 143.46 (C-Ar), 128.26 (CH−Ar),
126.52(CH−Ar), 53.52 (αCH), 46.40 (CH2), 42.56 (CH2), 41.45
(CH2), 32.30 (CH2), 29.96 (CH2), 23.50 (CH3). m/z (ESI positive),
399.133 [M − Cl]+.
The synthesis and characterization of the other compounds are
shown in the Supporting Information.
CA Inhibition Studies. A stopped-flow assay method has been
used to measure the inhibition of the CA catalyzed CO2 hydration
activity,14 as reported earlier.15,16
Compound 5: 52% yield. δH (400 MHz, DMSO-d6): 8.03 (t,1 H,
NH, J 5.2), 7.95 (d, 1H, NH, J 8), 7.76 (d, 2H, CH, J 8), 7.42 (d, 2H,
CH, J 8), 7.32 (s, 2H, NH2), 6.83 (appt, 1H, NH), 4.16 (m, 1H, CH),
3.32 (m, 2H, CH2), 2.91 (td, 2H, CH2, J 6.4), 2.81 (m, 2H, CH2), 1.87
(s, 3H, CH3), 1.57 (m, 2H, CH2), 1.40 (s, 9H, 3CH3), 1.23 (m, 4H,
2CH2). δC (100 MHz, DMSO-d6): 172.70 (CO), 170.03 (CO),
156.48 (CO), 144.57 (C-Ar), 142.96 (C-Ar), 130.07 (CH−Ar),
126.54 (CH−Ar), 78.26 (C-Boc), 53.49 (αCH), 40.55 (CH2), 39.39
(CH2), 35.69 (CH2), 32.70 (CH2), 30.20 (CH2), 29.19 (CH3−Boc),
23.68 (CH3), 23.43 (CH2). m/z (ESI negative), 469.9 [M − H]−.
Synthesis of 5-Acetylamino-5-(4-sulfamoyl-benzylcarbamoyl)-
pentyl-ammonium Chloride 6. [5-Acetylamino-5-(4-sulfamoyl-ben-
zylcarbamoyl)-pentyl]-carbamic acid tert-butyl ester 4 (0.1 g) was
suspended in 3.0 M HCl solution (2 mL). and the reaction mixture
was stirred overnight at room temperature. The aqueous solution was
dried under reduced pressure to give a pale yellow oil. The oil was
washed with 2 × 10 mL dichloromethane and triturated with diethyl
ether to afford 0.09 g of the desired product as a yellow waxy solid.
Compound 6: quantitative yield. δH (400 MHz, DMSO-d6): 8.65
(t,1 H, NH, J 6, exchange D2O), 8.18 (d, 1H, NH, J 8, exchange D2O),
ASSOCIATED CONTENT
■
S
* Supporting Information
Full characterization of the new compounds. This material is
AUTHOR INFORMATION
■
Corresponding Author
+
8.04 (brs, 3H, NH3 , exchange D2O), 7.79 (d, 2H, CH, J 8), 7.44 (d,
2H, CH, J 8), 7.37 (s, 2H, NH2, exchange D2O), 4.36 (appt, 2H,
CH2), 4.25 (m, 1H, CH), 2.77 (appq, 2H, CH2), 1.91 (s, 3H, CH3),
1.73−1.67 (m, 2H, CH2), 1.63−1.55 (m, 2H, CH2), 1.45−1.25 (m,
2H, CH2). δC (100 MHz, DMSO-d6): 172.99 (CO), 170.48 (C
O), 144.61 (C-Ar), 143.48 (C-Ar), 128.31 (CH−Ar), 126.56 (CH−
Ar), 53.63 (αCH), 42.61 (CH2), 39.38 (CH2), 32.14 (CH2), 27.47
(CH2), 23.46 (CH2), 22.13(CH3). m/z (ESI positive), 357.4 [M −
Cl]+.
Synthesis of N-Acetylamino-N′-di(tert-butyl-oxycarbonyl)-guani-
dino-hexanoic Acid [2-(4-Sulfamoyl-phenyl)-methyl]-amide 9.
N,N′-di-Boc-N″-trifluoromethanesulfonylguanidine 8 (0.1 g, 1.0
equiv) was added to a solution of 4-oxo-5-acetylamino-5-(4-
sulfamoyl-benzylcarbamoyl)-pentyl-ammonium chloride 6 (0.11 g,
1.1 equiv) and triethylamine (0.028 g, 1.1 equiv) in chloroform, and
the mixture was stirred at room temperature until N,N′-di-Boc-N″-
trifluoromethanesulfonylguanidine was consumed as evidenced by
TLC (10% methanol/dichloromethane). After the reaction was
complete, the mixture was diluted with chloroform and washed with
2.0 M sodium bisulfate, saturated sodium bicarbonate, and brine. The
Funding
We thank The Distinguished Scientist Fellowship Program
(DSFP) at KSU for funding this project.
Notes
The authors declare the following competing financial
interest(s): C.T.S. is an author on many patents claiming
carbonic anhydrase inhibitors.
ABBREVIATIONS USED
■
AAZ, acetazolamide; CA, carbonic anhydrase; EDCI, N-(3-
(dimethylamino)propyl)-N′-ethyl-carbodiimide hydrochloride;
GABA, γ-aminobutyric acid; HOAt, 1-hydroxy-7-azabenzotria-
zole; NMR, nuclear magnetic resonance; SAR, structure−
activity relationship; TLC, thin layer chromatography; VcCA,
Vibrio cholerae CA
D
dx.doi.org/10.1021/ml500192a | ACS Med. Chem. Lett. XXXX, XXX, XXX−XXX