48
C. Salvagnini et al. / European Journal of Medicinal Chemistry 42 (2007) 37e53
NaCl) nmax (cmꢂ1): 3420, 2976, 2932, 2870, 1705, 1622,
1521, 1436, 1366, 1253, 1166.
dissolution in NaOH 1 N, and extraction of the aqueous solution
with EtOAc (about 90% product recovery).
Compounds H2N-Arg(NO2)-Ai with i being 1, 3, 6 and 9
have been described elsewhere [41]. Rf, MS/EA for all follow-
ing compounds are reported in Table 3.
4.1.2.4. (12-{4-[(S )-2-tert-Butoxycarbonylamino-5-(N0-nitro-
guanidino)-pentanoyl]-piperazin-1-yl}-12-oxo-dodecyl)-carba-
mic acid 4-nitro-benzyl ester (Boc-Arg(NO2)-A7). This product
was prepared from N-Boc-N-nitro-arginine (1.71 g, 5.34 mmol,
1 equiv), NMM (1.62 g, 16 mmol, 3 equiv), isobutyl chlorofor-
mate (0.73 g, 5.34 mmol, 1 equiv) and (12-oxo-12-piperazin-1-
yl-dodecyl)-carbamic acid 4-nitro-benzyl ester (3.08 g,
5.34 mmol, 1 equiv) to give a brown solid (3.67 g) containing
the desired product (83% by NMR, 75% raw yield). The raw
product could be submitted to the next reaction step without
further purifications. Pure product was obtained by column
chromatography (74% isolated yield). 1H NMR (300 MHz,
CDCl3) d (ppm): 1.26 (br, 12H), 1.43 (s, 9H), 1.49 (m, 2H),
1.64 (m, 4H), 1.75 (m, 2H), 2.33 (t, 2H, J ¼ 7.2 Hz), 3.18
(q, 2H, J ¼ 6.6 Hz), 3.26 (m, 1H), 3.48 (m, 6H), 3.70 (m, 2H),
4.60 (m, 1H), 4.85 (m, 1H), 5.18 (s, 2H), 5.85 (dd, 1H,
J ¼ 8.2 Hz), 7.50 (d, 2H, J ¼ 8.7 Hz), 7.65 (br, 2H), 8.20
(d, 2H, J ¼ 8.7 Hz), 8.80 (br, 1H).
4.1.3.1. N-((S )-4-Amino-5-morpholine-4-yl-5-oxo-pentyl)-N0-
nitro-guanidine (H2N-Arg(NO2)-A2). This product was
obtained from 0.50 g of Boc-Arg(NO2)-A2 (1.31 mmol) and
10 mL of TFA/CH2Cl2 solution. 0.515 g of product as trifluor-
oacetate salt was isolated (quantitative yield). 1H NMR
(300 MHz, CDCl3) d (ppm): 1.75 (m, 2H), 1.94 (m, 2H),
3.36 (m, 2H), 3.63 (m, 4H), 3.75 (m, 2H), 3.81 (m, 2H),
4.58 (t, 1H); IR (CH2Cl2 liquid film on NaCl) nmax (cmꢂ1):
1684, 1447, 1263, 1103, 1037, 850, 721.
4.1.3.2. N-[(S )-4-Amino-5-(4-ethyl-piperazin-1-yl)-5-oxo-pen-
tyl]-N0-nitro-guanidine (H2N-Arg(NO2)-A4). This product
was obtained from 4.70 g of Boc-Arg(NO2)-A4 (11 mmol)
and 20 mL of solution of TFA/CH2Cl2 solution. 2.92 g of
the product as free amine was isolated (80% yield). 1H
NMR (300 MHz, CDCl3) d (ppm): 1.09 (t, 3H, J ¼ 7.1 Hz),
1.43 (s, 9H), 1.65 (m, 7H), 1.76 (m, 8H), 2.43 (m, 6H),
3.28e3.73 (m, 6H), 4.56 (m, 1H), 5.85 (d, 1H, J ¼ 7.5 Hz),
7.80 (br, 2H), 8.76 (br, 1H); 13C NMR (125 MHz, CDCl3)
d (ppm): 10.4, 27.7, 31.20, 41.5, 42.1, 44.4, 52.2, 52.9, 54.2,
162.1, 169.8; IR (CH2Cl2 liquid film on NaCl) nmax (cmꢂ1):
1710e1630, 1439, 1294, 1205, 1131.
4.1.2.5. (12-{4-[(S )-2-tert-Butoxycarbonylamino-5-(N0-nitro-
guanidino)-pentanoyl]-piperazin-1-yl}-12-oxo-dodecyl)-carba-
mic acid 4-nitro-benzyl ester (Boc-Arg(NO2)-A8). This
product was obtained from 1.84 g (5.78 mmol, 1 equiv) of
N-Boc-N-nitro-arginine, 1.17 g (11.6 mmol, 2 equiv) of NMM,
0.79 g (5.8 mmol, 1 equiv) of isobutyl chloroformate, 2.29 g
(5.8 mmol, 1 equiv) of product A8 and again 0.58 g
(5.8 mmol, 1 equiv) of NMM in 20 mL of THF. The solid res-
idue was purified by two column chromatographies (EtOAc/
isopropanol 8:2, and then CH3CN/isopropanol 6:4) in order
to obtain 2.32 g of pure product (58% yield). 1H NMR
(300 MHz, CDCl3) d (ppm): 1.43 (s, 9H), 1.62 (m, 2H), 1.73
(m, 2H), 2.53 (m, 4H), 2.64 (m, 2H), 3.26 (m, 1H), 3.39 (m,
2H), 3.44 (m, 2H), 3.56 (m, 2H), 3.61 (m, 9H), 4.55 (m,
1H), 5.19 (s, 2H), 5.48 (m, 1H), 5.82 (m, 1H), 7.51 (d, 2H,
JHH ¼ 8.6 Hz), 7.79 (br, 2H), 8.20 (d, 2H, JHH ¼ 8.6 Hz),
8.86 (br, 1H); 13C NMR (125 MHz, CDCl3) d (ppm): 24.2,
28.3, 31.3, 40.1, 40.9, 41.8, 45.1, 48.5, 52.8, 53.2, 57.3, 65.0,
68.5, 69.8, 70.1, 70.2, 80.4, 123.6, 128.0, 144.0, 147.4,
155.9, 156.6, 159.3, 169.7; IR (CH2Cl2 liquid film on NaCl)
nmax (cmꢂ1) 3328, 2930, 2870, 1707, 1628, 1518, 1451,
1341, 1252, 1158, 1100, 723.
4.1.3.3.
N-[5-(4-Acetyl-piperazin-1-yl)-4-(S )-amino-5-oxo-
pentyl]-N0-nitro-guanidine (H2N-Arg(NO2)-A5). This product
was obtained from 5.09 g of raw Boc-Arg(NO2)-A5
(9.12 mmol) and 50 mL of solution of TFA/CH2Cl2. The prod-
uct was isolated as trifluoroacetate white solid (4.1 g, quantita-
1
tive yield). H NMR (300 MHz, CDCl3) d (ppm): 1.69 (m,
2H), 1.93 (m, 2H), 2.14 (s, 3H), 3.33 (m, 2H), 3.50e3.71 (m,
8H), 4.58 (t, 1H, J ¼ 4.5 Hz); 13C NMR (125 MHz, CDCl3)
d (ppm): 20.8, 27.5, 40.4, 41.4, 41.8, 42.4, 42.7, 45.1, 45.3,
45.8, 46.2, 50.8, 159.2, 168.1, 173.1; IR (CH2Cl2 liquid film
on NaCl) nmax (cmꢂ1): 3400e2900, 1691, 1634, 1518, 1439,
1368, 1267, 1202, 1132, 1000, 835, 800, 722.
4.1.3.4.
(12-{4-[2-(S )-Amino-5-(N0-nitro-guanidino)-penta-
noyl]-piperazin-1-yl}-12-oxo-dodecyl)-carbamic acid 4-nitro-
benzyl ester (H2N-Arg(NO2)-A7). This product was obtained
from raw Boc-Arg(NO2)-A7 (3.67 g) dissolved in TFA/DCM
1:1 (50 mL). The product was isolated as trifluoroacetate
salt (3.538 g, quantitative yield). 1H NMR (500 MHz,
CD3OD) d (ppm): 1.30 (m, 12H), 1.50 (2H, m), 1.61 (m,
2H, J ¼ 7.3 Hz), 1.72 (m, 2H), 1.88 (t, 2H, J ¼ 7.2), 2.41
(m, 2H), 3.11 (q, 2H, J ¼ 6.6 Hz), 3.31 (m, 2H), 3.64 (m,
8H), 4.49 (m, 2H), 5.18 (s, 2H), 7.57 (d, 2H, J ¼ 8.7 Hz),
8.20 (d, 2H, J ¼ 8.7 Hz); 13C NMR (125 MHz, CDCl3)
d (ppm): 26.41, 28.79, 27.78, 30.37, 30.43, 30.50, 30.61,
30.62, 30.84, 34.08, 41.18, 41.86, 42.21, 42.69, 43.18,
43.59, 46.19, 46.54, 46.61, 51.44, 65.87, 124.56, 129.03,
4.1.3. General procedure for the preparation of 2(S )-
amino-5-nitro-guanidino-1-(azacyclohexan-1-yl)-pentan-1-
one (H2N-Arg(NO2)-Ai; Scheme 1, step ii).
Product Boc-Arg(NO2)-Ai (1.25 mmol) was dissolved in
a 1:1 mixture of TFA/CH2Cl2 (10 mL) and stirred at room tem-
perature for 3 h. The solution was concentrated at reduced pres-
sure and the obtained orange gel was suspended and triturated in
Et2Ountilprecipitationofthetrifluoroacetatesaltasacrystalline
solid occurred. The precipitate was washed with Et2O and used
directly in the next reaction (quantitative yield). For spectro-
scopic analysis the product was converted to the free amine by