N-Substituted tetrahydro-2,4-dioxoquinazolin-1-yl acetic acids as aldose reductase inhibitors

Article abstract of DOI:10.1691/ph.2007.8.7520

Novel N-substituted tetrahydro-2,4-dioxoquinazolin-1-yl acetic acids characterized by formal replacement of the substituted benzyl moiety by cyclohexylmethyl and n-heptyl residues, respectively, were synthesized and evaluated as aldose reductase inhibitor

Full text of DOI:10.1691/ph.2007.8.7520

SHORT COMMUNICATIONS
Institute of Pharmacy, Leopold-Franzens University of Innsbruck,
Austria
Table: Aldose reductase inhibition of compounds 5a–c
Compd.
R
IC50 (nM)
Confidence limit
N-Substituted tetrahydro-2,4-dioxoquinazolin-1-yl
acetic acids as aldose reductase inhibitors
5a
5b
5c
4-Bromo-2-fluorobenzyl
Cyclohexylmethyl
n-Heptyl
51
430
830
27–97
120–1490
640–1070
D. Rakowitz, A. Gmeiner, B. Matuszczak
vestigated the enzyme inhibitory potency of O-substituted
hydroxyphenyl acetic acid derivatives. Here, we have found
that within these series, formal replacement of the (substi-
tuted) benzyloxy substructure by cyclohexylmethyloxy as
well as by its ring-opened residues (especially n-heptyl-
oxy) leads to derivatives with comparable aldose reductase
inhibitory activity. To our knowledge, this is the first time
that in the class of aldose reductase inhibitors an alkyl
moiety has been successfully employed as the lipophilic
part instead of a substituted benzyl. Based on these re-
sults, we intended to investigate if cyclohexylmethyl or
n-heptyl, respectively, may also act as a bioisoster for the
4-bromo-2-fluorobenzyl group in highly potent ARIs like
those with a quinazolin-2,4-dione core (e.g. zenarestat and
analogues) (Hashimoto et al. 1987).
The target compounds 5a–c were prepared in analogy to a
previously described procedure (Hashimoto et al. 1987)
starting from anthranilamide (1) as depicted in the Scheme.
Then the inhibitory activities were evaluated in a spectro-
metric assay with d,l-glyceraldehyde as the substrate and
NADPH as the cofactor.
From the biological results listed in the Table it can be
seen that the known N-(4-bromo-2-fluorobenzylated) deri-
vative 5a (Hashimoto et al. 1987) as well as its analogues
with cyclohexylmethyl (5b) or n-heptyl (5c) moiety repre-
sent aldose reductase inhibitors with IC50 values in the
nanomolar range. However, in contrast to our previous find-
ings (Rakowitz et al. 2006a, 2006b), in these series formal
replacement of the 4-bromo-2-fluorobenzyl group by the
above mentioned alkyl residues does not lead to com-
pounds with comparable enzyme inhibitory potency.
Received January 30, 2007, accepted March 13, 2007
Barbara Matuszczak, Institute of Pharmacy, Leopold-
Franzens University of Innsbruck, Innrain 52a, A-6020
Innsbruck, Austria
barbara.matuszczak@uibk.ac.at
Pharmazie 62: 636–637 (2007)
doi: 10.1691/ph.2007.8.7520
Novel N-substituted tetrahydro-2,4-dioxoquinazolin-1-yl
acetic acids characterized by formal replacement of the
substituted benzyl moiety by cyclohexylmethyl and n-
heptyl residues, respectively, were synthesized and eval-
uated as aldose reductase inhibitors.
Reduction of glucose by the key enzyme of the polyol
pathway, aldose reductase (EC 1.1.1.21, ALR 2) and sub-
sequent reactions have been linked to the development of
secondary diabetic complications such as nephropathy,
neuropathy, retinopathy, and cataract. Aldose reductase in-
hibitors (ARIs) therefore offer a possibility of safely pre-
venting or arresting the progression of such long-term
complications without disturbing the blood glucose level.
Most of the so far identified aldose reductase inhibitors
are characterized by the presence of both, a lipophilic part
(especially 4-bromo-2-fluorobenzyl or 5-trifluoromethyl-
benzothiazol-2-yl) and a polar group (e.g. carboxylate)
connected by a linking structure (Miyamoto 2002; Costan-
tino et al. 1997, 2000). However, to date none is currently
marketed for worldwide use due to lack of high efficacy
and selectivity or due to toxicity.
Experimental
1. General procedure for the N-substitution of compound 3
Ethyl (1,2,3,4-tetrahydro-2,4-dioxoquinazolin-1-yl)acetate (3) (0.60 mmol)
was added to an ice-cooled suspension of sodium hydride (0.69 mmol, 60%
in mineral oil) in 3 mL of dry N,N-dimethylformamide under nitrogen atmo-
sphere. After stirring for 15 min, a solution of the appropriate (ar)alkylating
In the course of our ongoing studies aimed towards the
development of novel ARIs (Rakowitz et al. 2006a, 2006b
as well as references cited therein), we have recently in-
Scheme Reagents and conditions: i) ICH2COOC2H5, K2CO3, DMF; ii) CDI; iii) R-X, NaH, DMF; iv) 1. NaOH, 2. HCl
COOC2H5
COOC2H5
NH2
NH2
NH
O
N
O
O
i)
ii)
NH2
NH
O
1
2
3
iii)
COOH
COOC2H5
O
N
O
O
R
N
O
4-Br-2-F-benzyl,
cyclohexylmethyl,
n-heptyl
iv)
R =
N
N
R
5a-c
4a-c
636
Pharmazie 62 (2007) 8

SHORT COMMUNICATIONS
agent (0.69 mmol) in 1 mL of dry N,N-dimethylformamide was added and
Hashimoto M, Oku T, Ito Y, Namiki T, Sawada K, Kasahara C, Baba Y
(1987) Preparation of quinazolinealkanoates as aldose reductase inhibi-
tors, for treatment of diabetic complications. EP 218999-A2; C.A. (1988)
108: 75411.
Miyamoto S (2002) Recent advances in aldose reductase inhibitors: poten-
tial agents for the treatment of diabetic complications. Exp Opin Ther
Patents 12: 621–631.
Rakowitz D, Angerer H, Matuszczak B (2006a) Synthesis and aldose re-
ductase inhibitory activities of novel O-substituted hydroxyphenylacetic
acid derivatives. Arch Pharm Chem Life Sci 339: 547–558.
Rakowitz D, Gmeiner A, Matuszczak B (2006b) Discovery of novel aldose
reductase inhibitors characterized by an alkoxy-substituted phenylacetic
acid core. Arch Pharm Chem Life Sci 339: 559–563.
stirring was continued at room temperature until TLC indicated no further
conversion. Then, the mixture was poured into cold water and was acidi-
fied with 2 N HCl. In the case of 4a and 4c, the crystals thus obtained
were collected, washed with water and light petroleum and recrystallised
from diisopropylether/ethyl acetate. For 4b, the product was extracted ex-
haustively with ethyl acetate and the organic layer was washed with 2 N
NaOH, water, and brine, dried over anhydrous sodium sulphate and evapo-
rated to dryness. The residue thus obtained was collected and recrystallized
from diisopropylether/ethyl acetate to give the N-substituted products as
colourless crystals.
4a (94%): m.p. 147–150 ꢀC. 1H NMR (200 MHz, DMSO-d6) d: 8.09 (dd,
J ¼ 7.8 Hz and 1.4 Hz, 1 H, phenyl H), 7.82–7.74 (m, 1 H, phenyl H),
7.53 (dd, J ¼ 10.0 Hz and 1.8 Hz, 1 H, phenyl H), 7.49–7.31 (m, 3 H,
phenyl H), 7.13 (t, J ¼ 8.2 Hz, 1 H, phenyl H), 5.15 (s, 2 H, CH2), 4.97 (s,
2 H, CH2CO), 4.15 (q, J ¼ 7.2 Hz, 2 H, OCH2CH3), 1.18 (t, J ¼ 7.2 Hz,
3 H, OCH2CH3). MS (CI, m/z): 435/437 (M þ 1þ).
4b (48%): m.p. 94–96 ꢀC. 1H NMR (200 MHz, DMSO-d6) d: 8.07 (dd,
J ¼ 8.0 Hz and 1.6 Hz, 1 H, phenyl H), 7.78–7.70 (m, 1 H, phenyl H),
7.41–7.27 (m, 2 H, phenyl H), 4.95 (s, 2 H, CH2CO), 4.15 (q, J ¼ 7.2 Hz,
2 H, OCH2CH3), 3.82 (t, J ¼ 7.0 Hz, 2 H, NCH2), 1.64–1.54 (m, 6 H, 3ꢁ
CH2), 1.23–0.87 (m, 8 H, 2ꢁCH2, CH, OCH2CH3). MS (EI, m/z): 344 (Mþ).
4c (58%): m.p. 78–79 ꢀC. 1H NMR (200 MHz, CDCl3) d: 8.25 (dd,
J ¼ 8.0 Hz and 1.6 Hz, 1 H, phenyl H), 7.68–7.59 (m, 1 H, phenyl H),
7.30–7.23 (m, 1 H, phenyl H), 6.95 (d, J ¼ 8.4 Hz, 1 H, phenyl H), 4.90
(s, 2 H, CH2CO), 4.25 (q, J ¼ 7.2 Hz, 2 H, OCH2CH3), 4.08 (t, J ¼ 6.9 Hz,
2 H, NCH2), 1.71–1.61 (m, 2 H, CH2), 1.36–1.24 (m, 11 H, 4ꢁ CH2,
OCH2CH3), 0.87 (t, J ¼ 6.9 Hz, 3 H, CH3). MS (EI, m/z) 346 (Mþ).
2. Synthesis of the target compounds 5a–c
A solution of the appropriate ester (4a: 0.45 mmol, 4b: 0.61 mmol, 4c:
0.28 mmol) in 5 mL of ethanol was treated with 2 N NaOH (1.2 equiva-
lents) and stirred at room temperature for 3 h. The solvent was then evapo-
rated, the residue treated with a small portion of water, and the pH ad-
justed to 5 with 2 N HCl. The mixture was extracted with ethyl acetate, the
organic layer was washed with water and brine, dried over anhydrous so-
dium sulphate and evaporated to dryness. The products thus obtained were
recrystallized to afford colorless analytically-pure crystals.
5a (92% from diisopropylether): m.p. 212–214 ꢀC. 1H NMR (200 MHz,
DMSO-d6) d: 8.09 (dd, J ¼ 8.1 Hz and 1.5 Hz, 1 H, phenyl H), 7.82–7.73
(m, 1 H, phenyl H), 7.53 (dd, J ¼ 10.0 Hz and 1.8 Hz, 1 H, phenyl H),
7.43–7.30 (m, 3 H, phenyl H), 7.13 (t, J ¼ 8.3 Hz, 1 H, phenyl H), 5.15 (s,
2 H, CH2), 4.88 (s, 2 H, CH2CO). MS (CI, m/z): 407 (M þ 1þ).
5b (78% from diisopropylether/light petroleum): m.p. 151–153 ꢀC. 1H
NMR (200 MHz, DMSO-d6) d: 8.07 (d, J ¼ 6.6 Hz, 1 H, phenyl H), 7.74
(d, J ¼ 7.2 Hz, 1 H, phenyl H), 7.38–7.26 (m, 2 H, phenyl H), 4.86 (s, 2 H,
CH2CO), 3.64 (t, J ¼ 7.0 Hz, 2 H, NCH2), 1.74–1.46 (m, 5 H, 2ꢁCH2, CH),
1.24–0.84 (m, 6 H, 3ꢁ CH2). MS (CI, m/z): 317 (Mþ). C17H20N2O4 ꢁ
0.2 H2O.
5c (90% from diisopropylether): m.p. 115–117 ꢀC. 1H NMR (200 MHz,
DMSO-d6) d: 8.07 (dd, J ¼ 7.8 Hz and 1.6 Hz, 1 H, phenyl H), 7.73 (dd,
J ¼ 7.9 Hz and 1.6 Hz, 1 H, phenyl H), 7.38–7.26 (m, 2 H, phenyl H),
4.86 (s, 2 H, CH2CO), 3.93 (t, J ¼ 7.3 Hz, 2 H, NCH2), 1.60–1.50 (m, 2 H,
CH2), 1.27–1.24 (m, 8 H, 4ꢁ CH2), 0.84 (t, J ¼ 6.6 Hz, 3 H, CH3). MS
(CI, m/z): 319 (Mþ). C17H22N2O4.
3. Enzyme inhibition
Isolation of ALR 2 from calf lenses and purification of this enzyme have
been described previously (Costantino et al. 1996). IC50 values were deter-
mined from least squares analyses of the linear portion of the log dose-
inhibition curves by using CalcuSyn software (Chou and Hayball 1996).
Each curve was generated using at least three concentrations of the test
compounds (added as a solution in DMSO; final concentration of DMSO
in the incubation mixture was 1%) causing an inhibition between 20% and
80%, with two replicates at each concentration. For details concerning the
assay procedure see (Rakowitz et al. 2006a/b).
Acknowledgements: The authors wish to acknowledge Schlachthof Salz-
burg-Bergheim (Austria) (KR Ing. Sebastian Griessner and Mag. Erika Sako-
parnig) for providing calf lenses.
References
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New aldose reductase inhibitors as potential agents for the prevention of
long-term diabetic complications. Exp Opin Ther Patents 7: 843–858.
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