L. Bertelli et al. / Il Farmaco 53 (1998) 305–311
309
3.1.7. Ethyl 5,6-dihydro-5-oxo-4H-1,2,3-triazolo-
[1,5-a][1,5]benzodiazepine-3-carboxylate 6a
(t, 3H, CH3). 13C NMR see Table 1. Anal. (C14H14N4O3):
C, H, N.
The compound was prepared as described in the literature
[11] from 5a (0.390 g, 1.22 mmol) by refluxing in 25 ml of
xylene in the presence of a catalytic amount of p-toluenesul-
fonic acid: 0.265 g, yield 80%; m.p. 194–1958C (EtOH); 1H
NMR (DMSO, 200 MHz): d (ppm) 10.49 (bs, 1H, NH),
7.97 (dd, 1H, J9,10s8.02 Hz, J8,10s1.50 Hz, H-10), 7.59
(ddd, 1H, J8,9s7.56 Hz, H-8), 7.42 (ddd, 1H, J7,9s1.44
Hz, H-9), 7.37 (dd, 1H, J7,8s7.82 Hz, H-7), 4.39 (q, 2H,
Js7.1 Hz, OCH2), 4.14 (s, 2H, CH2-5), 1.36 (t, 3H, CH3).
13C NMR see Table 1. Anal. (C13H12N4O3): C, H, N.
7b: 0.235 g, yield 92%; m.p. 150–1528C (EtOH); IR
(nujol): n (cmy1) 1720 and 1210 (COOR), 1670 (C_O);
1
MS (m/z): 320 (Mq), 235, 218, 191, 189, 155, 124; H
NMR (DMSO, 200 MHz): d (ppm) 7.93 (d, 1H, J9,10s8.68
Hz, H-10), 7.82 (d, 1H, J7,9s2.23 Hz, H-7), 7.58 (dd, 1H,
H-9), 4.39 (q, 2H, Js7.1 Hz, OCH2), 3.30 (s, 2H, CH2-5),
3.19 (s, 3H, NCH3), 1.36 (t, 3H, CH3). 13C NMR see Table
1. Anal. (C14H13N4O3Cl): C, H, N.
7c: 0.210 g, yield 80%; m.p. 152–1548C (DMF–H2O); IR
(nujol): n (cmy1) 1710 and 1250 (COOR), 1680 (C_O);
1
MS (m/z): 328 (Mq), 257, 243, 199, 187, 158, 130; H
NMR (DMSO, 200 MHz): d (ppm) 8.15 (m, 1H, H-10),
8.06 (m, 2H, H-7 and H-9), 4.41 (q, 2H, Js7.1 Hz, OCH2),
3.36 (s, 2H, CH2-5), 3.20 (s, 3H, NCH3), 1.36 (t, 3H, CH3).
13C NMR see Table 1. Anal. (C16H16N4O4): C, H, N.
3.1.8. General procedure for the synthesis of 8-substituted-
5,6-dihydro-5-oxo-4H-1,2,3-triazolo[1,5-a][1,5]benzo-
diazepine-3-carboxylates 6b–c
One drop of 98% sulfuric acid was added to a solution of
5b or 5c (1.50 mmol) in toluene (50 ml) and heated under
reflux for 4 h. After cooling, the solution was washed with
H2O, dried (MgSO4) and evaporated in vacuo to give the
title compounds.
4. Biological
6b: 0.446 g, yield 97%; m.p. 268–2708C (AcOEt); IR
(nujol): n (cmy1) 3180 (NH), 1710 and 1250 (COOR),
1670 (C_O); MS (m/z): 306 (Mq), 250, 204, 178, 165,
124; 1H NMR (DMSO, 200 MHz): d (ppm) 10.58 (bs, 1H,
NH), 8.00 (d, 1H, J9,10s8.65 Hz, H-10), 7.48 (dd, 1H,
J7,9s2.32 Hz, H-9), 7.42 (d, 1H, H-7), 4.39 (q, 2H, Js7.1
Hz, OCH2), 4.17 (s, 2H, CH2-5), 1.36 (t, 3H, CH3). 13C
NMR see Table 1. Anal. (C13H11N4O3Cl): C, H, N.
6c: 0.461 g, yield 98%; m.p. 214–2168C (EtOH); IR
(nujol): n (cmy1) 3160 (NH), 1710 and 1240 (COOR),
1660 (C_O); MS (m/z): 314 (Mq), 269, 258, 243, 185,
169, 141, 130; 1H NMR (DMSO, 200 MHz): d (ppm) 10.62
(bs, 1H, NH), 8.10 (d, 1H, J9,10s8.24 Hz, H-10), 7.94 (dd,
1H, J7,9s1.85 Hz, H-9), 7.92 (d, 1H, H-7), 4.40 (q, 2H,
Js7.1 Hz, OCH2), 4.18 (s, 2H, CH2-5), 2.63 (s, 3H,
COCH3), 1.36 (t, 3H, CH3). 13C NMR see Table 1. Anal.
(C15H14N4O4): C, H, N.
The prepared tricyclic compounds 2a–b, 3a, 6a–c and 7a–
c were tested for their ability to inhibit benzodiazepinerecep-
tor binding, by measuring the concentration able to displace
the [3H] Ro 15-1788 from bovine brain membranes.
The experimental details of the receptor binding assays
were reported in a previous paper [15].
Furthermore, the GABA ratio values of active compounds
were evaluated as an in vitro indicator of the agonist, inverse-
agonist or antagonist properties [16].
5. Results and discussion
3.1.9. Ethyl 5,6-dihydro-6-methyl-5-oxo-4H-1,2,3-triazolo-
[1,5-a][1,5]benzodiazepine-3-carboxylate 7a, ethyl
8-chloro-5,6-dihydro-6-methyl-5-oxo-4H-1,2,3-triazolo-
[1,5-a][1,5]benzodiazepine-3-carboxylate 7b and ethyl
8-acetyl-5,6-dihydro-6-methyl-5-oxo-4H-1,2,3-triazolo-
[1,5-a][1,5]benzodiazepine-3-carboxylate 7c
Methyl iodide (0.6 ml, 9.60 mmol) was added to a stirred
solution of the triazolobenzodiazepine 6a, 6b or 6c (0.80
mmol) in 0.5% NaOH ethanolic solution (10 ml), and stir-
ring was continued at room temperature for 3 h. Afterdilution
with H2O the title compounds precipitated as a white solid
which was collected by filtration and washed with H2O.
7a: 0.190 g, yield 83%; m.p. 183–1858C (EtOH);1HNMR
(DMSO, 200 MHz): d (ppm) 7.93 (m, 1H, H-10), 7.72 (m,
2H, H-7 and H-8), 7.53 (m, 1H, H-9), 4.39 (q, 2H, Js7.1
Hz, OCH2), 3.29 (s, 2H, CH2-5), 3.27 (s, 3H, NCH3), 1.35
The results in Table 2 show that affinity toward the
benzodiazepine receptors of the 1,2,3-triazolo[1,5-a]-
benzodiazepine derivatives gradually and remarkably
increases ((10-fold), by moving the nitrogen atom of the
central ring from position 3 through 4 to position 5; in fact,
the 3-carbethoxy-1,2,3-triazolo[1,5-a][1,3]benzodiazepin-
5-one, the most effective derivative previously prepared [9],
showed an inhibition constant Kis1600 nM, while the
[1,4]benzodiazepine isomer 2a shows Kis908 nM and the
other [1,5]benzodiazepine isomer 6a shows Kis150 nM. In
all cases the GABA ratio values ((1.2) indicate a antagonist
action.
Moreover, comparison of these three isomers, which are
members of three heterocyclic series, shows that the N-meth-
ylation of the diazepine ring lowers the receptor binding (see