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(d, 2H), 7.36 (m, 10H), 7.22 (d, 2H), 5.24 (s, 2H), 5.09 (s, 2H),
4.14 (d, 1H), 2.52 (m, 2H), 2.35 (s, 3H), 2.17 (m, 2H).
(3b) using a procedure similar to that described for the prep-
1
aration of 5a as a white solid, yield 86%. H NMR (CDCl3):
d ¼ 7.10e7.41 (m, 20H), 5.12 (s, 2H), 4.99 (s, 2H), 4.97 (s,
2H), 4.22 (t, 1H), 3.98 (m, 1H), 3.23 (m, 1H), 2.91 (q, 1H),
2.28 (m, 2H).
5.4.5. D-Dibenzylester aspartate p-toluenesulfonate (3e)
Compound 3e was prepared from D-aspartic acid using
a procedure similar to that described for the preparation of
3a as a white solid, yield 94%. 1H NMR (DMSO-d6):
d ¼ 7.43 (d, 2H), 7.37 (m, 10H), 7.15 (d, 2H), 5.19 (s, 2H),
5.11 (s, 2H), 4.46 (t, 1H), 3.01 (m, 2H), 2.28 (s, 3H).
5.5.5. N-Carbobenzoxyl-L-phenylalanine-
L-glutamate dibenzylester (5e)
Compound 5e was prepared from N-carbobenzoxyl-L-phe-
nylalanine and L-dibenzylester glutamate p-toluenesulfonate
(3a) using a procedure similar to that described for the prepa-
5.5. General procedures for preparation of 5ael
1
ration of 5a as a white solid, yield 88%. Mp 100e101 ꢁC; H
5.5.1. N-Carbobenzoxyl-L-tryptophan-
L-glutamate dibenzylester (5a)
NMR (CDCl3): d ¼ 7.08e7.39 (m, 20H), 6.56 (d, 1H), 5.11 (s,
2H), 5.18 (d, 2H), 5.10 (s, 2H), 4.81 (m, 1H), 4.36 (q, 1H),
3.05 (dd, 2H), 2.22 (m, 3H), 1.98 (m, 1H).
To a mixture of L-dibenzylester glutamate p-toluenesulfo-
nate (3a) (0.5 g, 1 mmol), N-carbobenzoxyl-L-tryptophan
(0.34 g, 1 mmol), 1-hydroxybenzotriazole (HOBt, 0.14 g,
1 mmol) and triethylamine (1.4 mL, 10 mmol) in 5% DMF/
CH2Cl2 (20 mL), 1-ethyl-(3-dimethylaminopropyl)-carbodii-
mide hydrochloride (EDCI, 0.2 g, 1.05 mmol) was added in
portions for 5 min. The solution was stirred overnight at
room temperature (rt) followed by TLC detection. The solu-
tion was washed, dried, filtered, and condensed to form a yel-
low oil. The oil can be purified by flash chromatography with
petroleum ether/ethyl acetate (4/1, v/v) to afford a white pow-
der (0.59 g, 91%). Mp 98e99 ꢁC; 1H NMR (CDCl3): d ¼ 7.82
(s, 1H), 7.62 (d, 1H), 7.21e7.40 (m, 16H), 6.95 (s, 1H), 6.38
(d, 1H), 5.43 (d, 1H), 5.15 (m, 2H), 5.06 (s, 2H), 5.03 (s, 2H),
4.52 (m, 2H), 3.39 (dd, 1H), 3.10 (q, 1H), 2.14 (br, 3H), 1.83
(m, 1H).
5.5.6. N-Carbobenzoxyl-L-2-naphthylalanine-
L-glutamate dibenzylester (5f)
Compound 5f was prepared from N-carbobenzoxyl-L-2-
naphthylalanine and L-dibenzylester glutamate p-toluenesulfo-
nate (3a) using a procedure similar to that described for the
preparation of 5a as a white solid, yield 80%. Mp 110e
1
111 ꢁC; H NMR (CDCl3): d ¼ 7.73 (m, 3H), 7.65 (s, 1H),
7.22e7.43 (m, 18H), 5.12 (d, 2H), 5.02 (s, 2H), 4.89 (s,
2H), 4.42 (m, 2H), 3.18 (q, 1H), 2.98 (q, 1H), 2.25 (s, 3H),
1.8 (m, 1H).
5.5.7. N-Carbobenzoxyl-D-tryptophan-
L-aspartate dibenzylester (5g)
Compound 5g was prepared from N-carbobenzoxyl-D-tryp-
tophan and L-dibenzylester aspartate p-toluenesulfonate (3b)
using a procedure similar to that described for the preparation
5.5.2. N-Carbobenzoxyl-L-tryptophan-
L-aspartate dibenzylester (5b)
Compound 5b was prepared from N-carbobenzoxyl-L-tryp-
tophan and L-dibenzylester aspartate p-toluenesulfonate (3b)
using a procedure similar to that described for the preparation
of 5a as a white solid, yield 87%. Mp 151e153 ꢁC; H NMR
(CDCl3): d ¼ 7.84 (s, 1H), 7.62 (d, 1H), 6.95e7.41 (br, 16H),
6.85 (d, 1H), 5.12 (m, 1H), 5.08 (s, 2H), 4.98 (d, 2H), 4.80 (m,
1H), 3.25 (m, 1H), 3.20 (m, 1H), 3.01 (dd, 1H), 2.8 (dd, 1H).
1
of 5a as a white solid, yield 85%. Mp 116e118 ꢁC; H NMR
(CDCl3): d ¼ 7.63 (s, 1H), 7.57 (d, 1H), 7.06e7.36 (br, 17H),
6.90 (s, 1H), 6.60 (d, 1H), 5.44 (m, 1H), 5.08 (s, 2H), 5.02 (s,
2H), 4.85 (q, 2H), 4.79 (m, 1H), 4.49 (br, 1H), 3.08e3.27 (m,
2H), 2.83 (dd, 1H), 2.30 (dd, 1H), 1.61 (br, 1H).
1
5.5.8. N-Carbobenzoxyl-D-tryptophan-
D-aspartate dibenzylester (5h)
Compound 5h was prepared from N-carbobenzoxyl-D-tryp-
tophan and D-dibenzylester aspartate p-toluenesulfonate (3e)
using a procedure similar to that described for the preparation
5.5.3. N-Carbobenzoxyl-L-tryptophan-
L-2-aminoadipate dibenzylester (5c)
Compound 5c was prepared from N-carbobenzoxyl-L-tryp-
tophan and L-2-aminoadipic acid dibenzylester p-toluenesulfo-
nate (3c) using a procedure similar to that described for the
preparation of 5a as a white solid, yield 85%. Mp 99e
1
of 5a as a white solid, yield 80%. Mp 155e157 ꢁC; H NMR
(CDCl3): d ¼ 7.79 (s, 1H), 7.65 (d, 1H), 7.05e7.38 (br, 17H),
6.96 (d, 1H), 6.65 (d, 1H), 5.38 (br, 1H), 5.08 (m, 4H), 4.93 (d,
2H), 4.78 (m, 1H), 4.50 (br, 1H), 3.19 (m, 2H), 2.94 (m, 2H).
1
100 ꢁC; H NMR (CDCl3): d ¼ 8.39 (s, 1H), 7.65 (d, 1H),
7.10e7.36 (m, 15H), 7.13 (t, 1H), 7.08 (t, 1H), 6.31 (d, 1H),
5.47 (d, 1H), 5.13 (s, 2H), 4.99 (s, 2H), 4.97 (s, 2H), 4.55
(m, 1H), 4.48 (q, 1H), 3.34 (dd, 1H), 3.14 (q, 1H), 2.20 (t,
1H), 1.64 (m, 1H), 1.51 (m, 1H).
5.5.9. N-Carbobenzoxyl-L-tryptophan-
D-aspartate dibenzylester (5i)
Compound 5i was prepared from N-carbobenzoxyl-L-tryp-
tophan and D-dibenzylester aspartate p-toluenesulfonate (3e)
using a procedure similar to that described for the preparation
5.5.4. N-Carbobenzoxyl-L-phenylalanine-
L-aspartate dibenzylester (5d)
1
of 5a as a white solid, yield 88%. Mp 115e117 ꢁC; H NMR
Compound 5d was prepared from N-carbobenzoxyl-L-phe-
nylalanine and L-dibenzylester aspartate p-toluenesulfonate
(CDCl3): d ¼ 7.64 (s, 1H), 7.60 (d, 1H), 7.05e7.41 (br, 16H),
6.91 (s, 1H), 6.61 (d, 1H), 5.44 (m, 1H), 5.09 (s, 2H), 5.02 (s,