4-(6,7-Dimethoxy-3,4-dihydroisoquinolin-1-yl)benzenesulfona-
mide (12): POCl3, (1.3 g 8.7 mmol) was added dropwise to a solu-
tion of 11 (364 mg, 1 mmol) in toluene (3 mL) and the mixture was
held at reflux for 4 h. After cooling, aq ammonia (10 mL, 10%) was
added to quench the reaction, and the mixture was extracted with
EtOAc (3ꢂ5 mL). The combined organic extracts were dried
(Na2SO4), filtered and concentrated in vacuo. The residue powdered
upon treatment with Et2O and crystallized from EtOH to give deriv-
ative 12 as a yellow powder (260 mg, 87%); Rf =0.47; mp: 231–
ence in Ki values against hCA II and hCA VII. Furthermore, con-
sidering that compounds 13 and 14 showed very similar Ki
values towards all tested CA isoforms (Table 2), we could sum-
marize that the presence of a sulfonamide moiety linked to
the nitrogen atom at the 2-position of the isoquinoline scaffold
(i.e., compound 14) does not significantly influence the inhibi-
tory activity.
In conclusion, two distinct classes of carbonic anhydrase in-
hibitors have been designed, synthesized and evaluated
against some physiologically relevant mammalian isoforms.
The biological results showed that some of the studied com-
pounds are potent and selective hCA VII inhibitors. They also
showed Ki values similar to other known CAIs already in clinical
use. Moreover, they behave as some of the most selective
hCA VII inhibitors reported to date. Notably, the Ki values
against hCA II and hCA VII differ by four and two order of mag-
nitude, respectively, for the two most representative com-
pounds 8 and 13, suggesting that these compounds might be
considered as lead structures for the identification of new neu-
roprotective agents that selectively target hCA VII.
1
2338C; H NMR ([D6]DMSO): d=2.62–271 (m, 2H, CH2), 3.61 (s, 3H,
OCH3), 3.67–3.70 (m, 2H, CH2), 3.83 (s, 3H, OCH3), 6.66 (s, 1H, ArH),
7.02 (s, 1H, ArH), 7.46 (brs, 2H, NH2), 7.75 (d, J=8.51, 2H, ArH),
7.89 ppm (d, J=8.51, 2H, ArH); 13C NMR ([D6]DMSO): d=24.6, 46.7,
55.2, 55.3, 110.6, 110.7, 124.9, 128.5, 131.7, 131.8, 141.3, 144.0,
146.3, 150.5, 163.8 ppm; Anal. calcd for C17H18N2O4S: C 58.94, H
5.24, N 8.09, found: C 58.72, H 5.46, N 8.17.
4-(6,7-Dimethoxy-1,2,3,4-tetrahydroisoquinolin-1-yl)benzenesul-
fonamide (13): A solution of 12 (346 mg, 1 mmol) and NaBH4
(378 mg, 10 mmol) in MeOH (10 mL) was stirred for 1 h at RT. The
reaction mixture was quenched by adding water (10 mL), extracted
with EtOAc (3ꢂ5 mL), dried (Na2SO4), filtered and concentrated in
vacuo. The crude product was crystallized by adding a small
amount of Et2O to give 13 as a white powder (320 mg, 88%); Rf =
0.14; mp: 220–2228C; 1H NMR ([D6]DMSO): d=2.58–2.97 (m, 4H,
CH2-CH2), 3.48 (s, 3H, OCH3), 3.72 (s, 3H, OCH3), 4.99 (s, 1H, CH),
6.19 (s, 1H, ArH), 6.71 (s, 1H, ArH), 7.30 (brs, 2H, NH2), 7.39 (d, J=
8.24, 2H, ArH), 7.74 ppm (d, J=8.24, 2H, ArH); 13C NMR
([D6]DMSO): d=29.1, 42.6, 55.7, 55.8, 60.6, 110.5, 111.7, 124.9, 127.6,
128.4, 129.8, 142.1, 143.6, 147.3, 147.5 ppm; Anal. calcd for
C17H20N2O4S: C 58.60; H 5.79; N 8.04, found: C 58.46; H 5.62; N
8.23.
Experimental Section
Chemistry: All reagents were purchased from Sigma–Aldrich
(Milan, Italy) and were used without further purification. Micro-
wave-assisted reactions were carried out in a CEM-focused micro-
wave synthesis system. Melting points were determined on a Bꢁchi
melting point B-545 apparatus and are uncorrected. Elemental
analyses (C, H, N) were carried out on a Carlo Erba Model 1106 ele-
mental analyzer and the results are within Æ0.4% of the theoreti-
cal values. Merck silica gel 60 F254 plates were used for analytical
TLC. Rf values were determined on TLC plates using CHCl3/MeOH
1-[4-(Aminosulfonyl)phenyl]-6,7-dimethoxy-3,4-dihydroisoquino-
line-2(1H)-sulfonamide (14): A mixture of 13 (368 mg, 1.0 mmol)
and sulfamide (576 mg, 6 mmol) in dimethoxyethane (2 mL) was
placed in a cylindrical quartz tube (Ø=2 cm), then stirred and irra-
diated in a microwave oven at 150 W for two steps of 20 min at
908C. The reaction was quenched by adding water (5 mL) and ex-
tracted with EtOAc (3ꢂ5 mL). The organic layer was washed with
saturated aq NaHCO3 (2ꢂ5 mL), dried (Na2SO4), filtered and con-
centrated in vacuo. The residue crystallized from EtOH to give com-
pound 14 as a white powder (294 mg, 69%); Rf =0.49; mp: 151–
1538C; 1H NMR ([D6]DMSO): d=2.59–2.68 (m, 1H, CH), 2.92–3.18
(m, 3H, CH), 3.50–3.68 (m, 1H, CH), 3.62 (s, 3H, OCH3), 3.75 (s, 3H,
OCH3), 5.89 (s, 1H, CH), 6.63 (s, 1H, ArH), 6.80 (s, 1H, ArH), 7.33
(brs, 2H, NH2), 7.36 (brs, 2H, NH2), 7.37 ppm (d, J=7.41, 2H, ArH),
7.74 (d, J=7.41, 2H, ArH); 13C NMR ([D6]DMSO): d=27.7, 43.7, 55.8,
59.5, 61.8, 110.0, 111.8, 124.1, 125.0, 127.0, 129.8, 141.3, 144.1,
147.3, 147.6 ppm; Anal. calcd for C17H21N3O6S2: C 47.76, H 4.95, N
9.83, found: C 47.61, H 4.83, N 9.68.
1
(9:1) as the eluent. H NMR and 13C NMR spectra were measured in
[D6]DMSO on a Varian Gemini 300 spectrometer; chemical shifts (d)
are expressed in parts per million (ppm) and coupling constants (J)
in Hz. All exchangeable protons were confirmed by addition of
D2O.
Compounds 1–10 were obtained following previously reported
procedures and the spectral data were in accordance with the liter-
ature.[15b]
4-(Aminosulfonyl)-N-[2-(3’,4’-dimethoxyphenyl)ethyl]benzamide
(11): A mixture of 15 (181 mg, 1 mmol) and N,N,N’,N’-tetramethyl-
O-(1H-benzotriazol-1-yl)uronium
hexafluorophosphate
(HBTU)
(379 mg, 1 mmol) in DMF (2 mL) was stirred for 30 min at RT. Com-
pound 16 (201 mg, 1 mmol) and a catalytic amount of Et3N
(0.1 mL) were added successively to the reaction. After 2 h at RT,
the reaction mixture was quenched with water (10 mL) and ex-
tracted with EtOAc (3ꢂ5 mL). The combined extracts were dried
(dry Na2SO4), filtered and concentrated in vacuo. The crude residue
was crystallized by treatment with EtOH to give the desired final
product 11 as a white powder (247 mg, 68%); Rf =0.55; mp: 211–
CA inhibition assay: An Applied Photophysics stopped-flow instru-
ment was used to assay the CA-catalyzed CO2 hydration activity.[19]
Phenol red at a concentration of 0.2 mm was used as an indicator
(absorbance maximum =557 nm), with 10–20 mm Hepes (pH 7.5)
or Tris (pH 8.3) as the buffer, and 20 mm Na2SO4 or 20 mm NaClO4
to maintain a constant ionic strength. The initial rates of CA-cata-
lyzed CO2 hydration reaction were followed for a period of 10–
100 s. The CO2 concentrations ranged from 1.7 to 17 mm for the
determination of the kinetic parameters and inhibition constants.
For each inhibitor, at least six traces of the initial 5–10% of the re-
action have been used for determining the initial velocity. The un-
catalyzed rates were determined in the same manner and subtract-
ed from the total observed rates. Stock solutions of inhibitor
1
2138C; H NMR ([D6]DMSO): d=2.77 (t, J=6.87, 2H, CH2), 3.43–3.50
(m, 2H, CH2), 3.70 (s, 3H, OCH3), 3.71 (s, 3H, OCH3), 6.71–6.86 (m,
3H, ArH), 7.46 (brs, 2H, NH2), 7.87 (d, J=8.51, 2H, ArH), 7.95 (d, J=
8.51, 2H, ArH), 8.70 ppm (brs, 1H, NH); 13C NMR ([D6]DMSO): d=
33.9, 40.6, 54.8, 55.0, 111.5, 112.1, 119.9, 125.0, 127.1, 131.4, 137.0,
145.6, 148.1, 151.6, 164.6 ppm; Anal. calcd for C17H20N2O5S: C 56.03,
H 5.53, N 7.69, found: C 56.28, H 5.31, N 7.48.
ChemMedChem 2010, 5, 823 – 826
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
825