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M. Barbaric et al. / European Journal of Medicinal Chemistry 42 (2007) 20e29
22
extracted several times with water. The organic layer was
dried over sodium sulfate, filtered and evaporated under re-
duced pressure. The obtained crude residue (3.268 g, 97%)
was recrystallized from dichloromethane/cyclohexane. M.p.
144e145 ꢁC, [30] 149 ꢁC; CHN analysis for C16H17Cl2N3O
(338.23): calcd. C 56.82, H 5.07, N 12.42, found: C 56.67,
H 4.93, N 11.97; IR (KBr): nmax 3352, 3209, 3022, 2915,
1640, 1575, 1508, 1449, 1416, 1353, 1299, 1271, 1195,
1091, 1023, 950, 898, 845, 766, 741, 711, 669, 617,
for 4 h. A solution of 1.1 ml (0.018 mol) ethanolamine in
10 ml DMF was added dropwise (ice bath). The reaction mix-
ture was stirred for an additional 18 h at room temperature,
acidified with 10% hydrochloric acid to pH 4, diluted with wa-
ter, dialyzed against several changes of cold 5 mmol lꢀ1 HCl
solution over a period of 3 days and lyophilized. The reaction
mixture was light protected throughout the experiment. Yield:
0.583 g (63%); drug-loading: 11.9%; content of SH groups:
9.4 mmol gꢀ1; IR (KBr): nmax 3303, 3085, 2942, 1660, 1547,
1444, 1382, 1293, 1604, 668 cmꢀ1; UV: lmax ¼ 281 nm,
A ¼ 0.812, g ¼ 213 mg mlꢀ1, H2O.
1
568 cmꢀ1; H NMR (DMSO-d6) d: 8.44 (s, 1H, 100), 8.34 (t,
2H, 400, J ¼ 5.4 Hz), 7.52e6.28 (m, 8H, 9 and arom.), 3.58
(s, 2H, 2), 3.11e3.04 (m, 2H, 200) 2.59 (t, 2H, 300,
J ¼ 6.4 Hz) ppm; 13C NMR (DMSO-d6) d: 171.55 (1),
142.88 (8), 137.10 (10), 130.30 (4), 129.28 (11), 129.09 (12,
14), 127.06 (6), 125.49 (3), 124.88 (15), 120.54 (13), 115.83
(5, 7), 42.40 (200), 41.07 (300), 37.64 (2) ppm.
Preparation of 5c: analogous procedure as for 5b, but dif-
ferent amounts of cysteamine (0.463 g, 0.006 mol) and etha-
nolamine (0.72 ml, 0.012 mol) were used. Yield: 0.620 g
(66%); drug-loading: 12.1%; content of SH groups:
19.9 mmol gꢀ1; IR (KBr): nmax 3299, 3085, 2942, 1659,
1548, 1532, 1010, 1296, 1065, 668 cmꢀ1; UV: lmax ¼ 281 nm,
A ¼ 0.976, g ¼ 253 mg mlꢀ1, H2O.
2.1.4. 2-Aminoethyl fenoprofenamide (3b)
Compound 3b was prepared following the published proce-
dure [31].
2.1.8. Poly[a,b-(N-2-aminoethyl-DL-aspartamide)]-
2.1.5. Poly-DL-(2,5-dioxo-1,3-pyrrolidinediyl) (PSI) (4)
PSI was prepared by thermal polycondensation of L-as-
partic acid in the presence of o-phosphoric acid (molar ratio
1.5:1, reduced pressure, 2.5 h at 160 ꢁC) [32].
poly[a,b-(N-2-hydroxyethyl-DL-aspartamide)]-poly[a,b-
(N-3-mercapto-1-methoxycarbonyl-propyl-DL-
aspartamide)] copolymer diclofenac conjugate
(PAHMAeDic, 5d)
To a solution of 0.699 g PSI (0.0072 mol, calculated as
monomer units) in 35 ml DMF, a solution of 0.812 g
(0.0024 mol) 2-aminoethyl diclofenacamide (3a) in 10 ml
DMF was slowly added. The reaction mixture was stirred at
room temperature for 48 h and then a solution of 3.581 g
(0.024 mol) methyl-(2-amino-4-mercapto)-butyrate in 15 ml
DMF was added (ice bath). The thiol used was obtained
from DL-homocysteine thiolactone hydrochloride in a sodium
methoxide/methanol solution. The reaction mixture was
stirred at room temperature for 24 h. A solution of 0.72 ml
(0.012 mol) ethanolamine in 8 ml DMF was added dropwise
(ice bath). The reaction mixture was stirred for an additional
10 h at room temperature, acidified with 10% hydrochloric
acid to pH 4, diluted with water, dialyzed against several
changes of cold 5 mM HCl solution over 4 days and lyophi-
lized. The reaction mixture was light protected throughout
the experiment. Yield: 0.749 g (34%); drug-loading: 22.4%;
content of SH groups: 45.6 mmol gꢀ1; IR (KBr): nmax 3309,
3075, 2941, 1722, 1663, 1547, 1531, 1446, 1408, 1235,
2.1.6. Poly[a,b-(N-2-aminoethyl-DL-aspartamide)]-poly[a,b-
(N-2-hydroxyethyl-DL-aspartamide)] copolymer diclofenac con-
jugate (PAHAeDic, 5a)
To a solution of 0.699 g PSI (0.0072 mol, calculated as
monomer units) in 35 ml DMF, a solution of 0.812 g
(0.0024 mol) 2-aminoethyl diclofenacamide (3a) in 13 ml
DMF was added dropwise. The reaction mixture was stirred
at room temperature for 72 h and then a solution of 2.2 ml
(0.036 mol) ethanolamine in 10 ml DMF was added very
slowly. The reaction mixture was stirred for an additional
24 h at room temperature, acidified with 10% hydrochloric
acid to pH 4, diluted with water, dialyzed against several
changes of deionized water over a period of 3 days and lyoph-
ilized. Yield: 1.087 g (60%) of product 5a; drug-loading:
13.1%; IR (KBr): nmax 3303, 3083, 2938, 2882, 1661, 1548,
1532, 1446, 1366, 1280, 1063, 668 cmꢀ1; UV: lmax ¼ 281 nm,
A ¼ 1.005, g ¼ 240 mg mlꢀ1, H2O.
2.1.7. Poly[a,b-(N-2-aminoethyl-DL-aspartamide]-
poly[a,b-(N-2-hydroxyethyl-DL-aspartamide)]-poly[a,b-
(N-2-thioethyl-DL-aspartamide)] copolymer diclofenac
conjugate (PAHTAeDic, 5b, 5c)
1063, 749, 668 cmꢀ1
;
UV: lmax ¼ 281 nm, A ¼ 0.831,
g ¼ 116 mg mlꢀ1, H2O.
To a solution of 0.699 g PSI (0.0072 mol, calculated as
monomer units) in 35 ml DMF, a solution of 0.812 g
(0.0024 mol) 2-aminoethyl diclofenacamide (3a) in 13 ml
DMF was slowly added. The reaction mixture was stirred at
room temperature for 48 h and then divided into two equal
parts.
Preparation of 5b: to the first half, a solution of 0.093 g
(0.0012 mol) cysteamine in 16 ml DMF was added (ice
bath). The reaction mixture was stirred at room temperature
2.1.9. Poly[a,b-(N-2-aminoethyl-DL-aspartamide)]-
poly[a,b-(N-2-hydroxyethyl-DL-aspartamide)]
copolymer fenoprofen conjugate (PAHAeFen, 5e)
Conjugate 5e was prepared following the published proce-
dure [31]. Yield: 0.566 g (58%); drug-loading: 7.7%; IR
(KBr): nmax 3303, 3084, 2940, 2882, 1709, 1662, 1644,
1566, 1549, 1532, 1428, 1410, 1382, 1244, 1063, 927,
668 cmꢀ1; UV: lmax ¼ 271 nm, A ¼ 0.504, g ¼ 935 mg mlꢀ1
,
H2O.