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B. Severino et al. / Bioorg. Med. Chem. 16 (2008) 6009–6020
ported for compound 18a: yield 0.75 g (73%). MS/ESI (+),
m/z: 1031 [M+H]+.
tained following the synthetic procedure reported for
compound 1: yield 0.65 g of crude product. MS/ESI
(+), m/z: 861 [M+H]+. 1H NMR (DMSO-d6) d 1.40
(m, 8H), 2.35 (s, 3H), 2.85 (dd, 1H), 3.00 (m, 5H),
3.30 (m, 2H), 4.35 (m, 5H), 4.60 (m, 1H), 5.45 (s, 2H),
7.01–7.60 (m, 13H), 7.77 (s, 1H). Anal. Calcd for
C44H49Cl2F2N9O3: C, 61.39; H, 5.74; N, 14.64. Found:
C, 61.37; H, 5.72; N, 14.68.
5.2.9. 2-[2-{3-[1-(2,6-Dichlorobenzyl)-2-methyl-3-pyrroli-
din-1-ylmethyl-1H-indol-6-yl]-ureido}-3-(4-methoxy-
phenyl)-propionylamino]-5-guanidino-pentanoic acid
benzylamide (1). The indole-urea derivative 18a (0.73 g,
0.7 mmol) was dissolved in glacial acetic acid (5 mL)
and treated with a solution of pyrrolidine (0.15 mL,
1.75 mmol) and formaldehyde (0.15 mL, 1.75 mmol)
and the mixture was stirred for 24 h at 60 ꢁC. Then
the solution was cooled and adjusted to pH 12 using
2 N KOH; the precipitated solid 19a was filtered and
let dry in vacuo furnishing 0.7 g of crude product that
was dissolved in TFA (5 mL); the mixture was stirred
for 2 h at room temperature. The solution was evapo-
rated to dryness in vacuo and the residue was triturated
with diethyl ether giving 0.6 g of crude product 1, which
5.2.13. 2-Methyl-5-nitro-3-pyrrolidin-1-ylmethyl-1H-
indole (21). To an ice-cold solution of 2-methyl-1H-in-
dole (21) (4 g, 0.03 mol) in sulfuric acid (25 mL) was
added, dropwise, NaNO3 (2.7 g) dissolved in sulfuric
acid (25 mL). After the addition was completed, the
reaction mixture was poured in ice and the obtained yel-
low solid 21 was filtered off, washed with water, and
then let air-dry: yield 4.8 g (90%). MS/ESI (+), m/z:
1
177 (M + H+). H NMR (CDCl3) d 2.45 (s, 3H), 6.39
was purified on
a
Vydac C18 silica (15–20 lm,
(s, 1H), 7.29 (d, 1H), 8.00 (d, 1H), 8.45 (s, 1H).
22 · 5000 mm) high performance liquid chromatogra-
phy (HPLC) column. The product was eluted with a gra-
dient of 0–70% B in 25 min at a flow rate of 30 mL/min
using the following mobile phase: solvent A (water in
0.1% TFA) and solvent B (acetonitrile in 0.1 %TFA).
5.2.14. 1-(2,6-Dichlorobenzyl)-2-methyl-5-nitro-1H-indole
(22). To a solution of 2-methyl-5-nitro-1H-indole (21,
2.5 g, 0.014 mol) in DMF (50 mL) were added cesium
carbonate (4.6 g, 0.014 mol) and 2,6-dichlorobenzylbro-
mide (3.3 g, 0.014 mol). The solution was stirred at
60 ꢁC for 1 h; then the reaction mixture was cooled,
the solid was filtered, and the filtrate was concentrated
in vacuo. The product 22 was precipitated with diethyl
ether as a yellow solid: yield 2.1 g (45%). MS/ESI (+),
1
MS/ESI (+), m/z: 855 [M+H]+. H NMR (DMSO-d6)
d 1.40 (m, 3H), 1.80 (m, 3H), 2.0 (m, 2H), 2.38 (s,
3H), 2.76 (m, 1H), 2.90 (m, 4H), 3.08 (m, 3H), 3.66 (s,
3H), 4.20 (m, 4H), 4.44 (s, 2H), 5.50 (s, 2H), 6.73 (d,
2H), 7.06 (t, 2H), 7.14 (s, 1H), 7.22–7.49 (m, 10H). Anal.
Calcd for C45H53Cl2N9O4: C, 63.22; H, 6.25; N, 14.75.
Found: C, 63.21; H, 6.23; N, 14.71.
1
m/z: 336 (M + H+). H NMR (CDCl3) d 2.43 (s, 3H),
5.57 (s, 2H), 6.43 (s, 1H), 7.06 (d, 1H), 7.24 (t, 1H),
7.36 (d, 2H), 7.90 (d, 1H), 8.42 (s, 1H).
5.2.10. 2-(2-{3-[1-(2,6-Dichlorobenzyl)-2-methyl-3-pyrr-
olidin-1-ylmethyl-1H-indol-6-yl]-ureido}-3-naphthalen-
1-yl-propionylamino)-5-guanidino-pentanoic acid benzyla-
mide (2). Starting from 19b, compound 2 was obtained
following the synthetic procedure reported for com-
pound 1: yield 0.75 g of crude product. MS/ESI (+),
m/z: 875 [M+H]+. 1H NMR (DMSO-d6) d 1.59 (m,
6H), 1.79 (m, 2H), 2.40 (s, 3H), 2.70 (m, 4H), 2.90 (m,
2H), 3.19 (m, 1H), 3.47 (m, 3H), 4.44 (m, 3H), 4.50
(m, 1H), 5.11 (s, 2H), 6.70 (d, 2H), 7.01–7.10 (m, 6H),
7.13–7.69 (m, 10H). Anal. Calcd for C48H53Cl2N9O3:
C, 65.89; H, 6.11; N, 14.41. Found: C, 65.80; H, 6.13;
N, 14.45.
5.2.15. 1-(2,6-Dichlorobenzyl)-2-methyl-3-1H-indol-5-yla-
mine (23). To a suspension of NaBH4 (0.47 g, 0.012 mol)
and Pd/C (20 mg) in methanol (50 mL) was added a
solution of 22 (2.1 g, 6.3 mmol) in THF (50 mL). After
3 h the reaction mixture was filtered, the solvent was re-
moved in vacuo, and the residue was dissolved in chlo-
roform and washed with water. The organic phase was
dried over Na2SO4 and evaporated in vacuo. The crude
product 23 was purified on silica gel column using a mix-
ture of ethyl acetate/n-hexane (6:4) and crystallized with
diethyl ether: yield 1.3 g (68%). MS/ESI (+), m/z: 306
[M+H]+. 1H NMR (CDCl3) d 2.49 (s, 3H), 5.50 (s,
2H), 6.20 (s, 1H), 6.40 (s, 1H), 6.55 (d, 1H), 7.10 (d,
1H), 7.26 (t, 1H), 7.37 (d, 2H).
5.2.11. 2-(2-{3-[1-(2,6-Dichlorobenzyl)-2-methyl-3-pyrr-
olidin-1-ylmethyl-1H-indol-6-yl]-ureido}-3-naphthalen-
2-yl-propionylamino)-5-guanidino-pentanoic acid benzyla-
mide (3). Starting from 19c, compound 3 was obtained
following the synthetic procedure reported for compound
1: yield 0.69 g of crude product. MS/ESI (+), m/z: 875
[M+H]+. 1H NMR (DMSO-d6) d 1.43 (m, 3H), 1.85 (m,
3H), 2.30 (m, 4H), 2.47 (s, 3H), 2.55 (m, 2H), 3.04 (m,
1H), 3.50 (m, 3H), 4.37 (m, 3H), 4.56 (m, 1H), 5.21 (s,
2H), 6.75 (d, 2H), 6.95–7.14 (m, 6H), 7.28–7.68 (m,
10H). Anal. Calcd for C48H53Cl2N9O3: C, 65.89; H,
6.11; N, 14.41. Found: C, 65.91; H, 6.08; N, 14.43.
5.2.16. 2-[2-{3-[1-(2,6-Dichlorobenzyl)-2-methyl-3-1H-
indol-5-yl]-ureido}-3-(4-methoxyphenyl)-propionylamino]-
5-[Nx-(2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfo-
nyl)]-guanidino-pentanoic acid benzylamide (24a). Start-
ing from 23 and H-Tyr(Me)-Arg(Pbf)-NH-CH2-C6H5
compound 24a was obtained following the synthetic
procedure reported for compound 18a: yield 0.75 g
(73%). MS/ESI (+), m/z: 1025 [M+H]+.
5.2.17. 2-(2-{3-[1-(2,6-Dichlorobenzyl)-2-methyl-1H-
indol-5-yl]-ureido}-3-naphthalen-1-yl-propionylamino)-5-
[Nx-(2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl)]-
guanidino-pentanoic acid benzylamide (24b). Starting
from 23 and H-1-Nal-Arg(Pbf)-NH-CH2-C6H5, com-
pound 24b was obtained following the synthetic proce-
5.2.12. 2-[2-{3-[1-(2,6-Dichlorobenzyl)-2-methyl-3-pyrr-
olidin-1-ylmethyl-1H-indol-6-yl]-ureido}-3-(3,4-difluo-
rophenyl)-propionylamino]-5-guanidino-pentanoic acid
benzylamide (4). Starting from 19d, compound 4 was ob-