2318
L. L. Chappell et al. / Bioorg. Med. Chem. 7 (1999) 2313±2320
were combined and reduced to dryness to give the
product as a yellow foam (10.76 g). This material con-
tained small (<10%) amounts of impurities, indicated
CDCl3) d 1.7 (br, 1H, NH), 2.08 (m, 1H, CH2CH2Ar),
2.22 (m, 1H, CH2CH2Ar), 2.7±3.3 (series of mult.,
17H), 3.3±3.44 (m, 3H), 3.48 (s, 3H) 3.68 (s, 3H,
CH2COOCH3) 3.70 (s, 3H, CH2COOCH3), 3.75 (s, 3H,
COOCH3), 7.46 (d, 2H, Ar), 8.18 (d, 2H, Ar); 13C NMR
(75.5 MHz, CDCl3) d 30.74, 32.44 (functionalized pen-
dent), 46.89, 47.38, 47.86, 49.56 (CH2 cyclen), 51.44,
51.57, 57.33, 65.71 (pendent arms and OCH3), 123.6,
129.2, 146.4, 148.8 (Ar); 170.5, 171.7, 172.3 (C(O)); MS
(CI/NH3) m/e 538 (M + H+)
1
by an extra doublet at 7.6 ppm in the H NMR. This
material was re-puri®ed by running consecutive silica
gel columns (2±4) with a shallower gradient, 5±10%
MeOH in CHCl3 and collection of smaller fractions
(10±20 mL). Very late fractions from these columns
were deemed pure by their 1H NMR spectra, combined,
and rotary evaporated to a foam (total mass 8.96 g,
77%). 1H NMR (300 MHz, CDCl3) d 1.3 (m, 9H, CH3),
1.8±2.2 (m, 14H,-CH2 cyclen, CH2CH2Ar), 2.4±2.6 (m,
4H, CH2 cyclen), 3.15 (m, 1H, CH(COOCH3)), 3.4±
3.6 (m, 8H, CH2COOC2H5, CH2Ar), 3.81 (s, 3H,
COOCH3), 4.1±4.3 (m, 6H, OCH2), 7.38 (d, 2H, Ar),
8.15 (d, 2H, Ar); 13C NMR (75.5 MHz, CDCl3) d 13.74
(OCH2CH3), 25.03 (CH2CH2Ar), 33.89 (CH2Ar), 44.64,
47.07, 48.40, 48.33 (CH2 cyclen), 52.05, 52.47, 54.84
(CH(COOCH3), CH2COOC2H5), 59.58, 61.15 (OCH2,
OCH3), 123.5, 129.5, 146.4, 149.1 (Ar); 173.6, 176.0
(C(O)); MS (CI/NH3) m/e 652 (M + H+). Anal. calcd
1,4,7,10-Tetraaza-N-(1-carboxy-3-(4-nitrophenyl)propyl)-
N0,N00,N000-tris(acetic acid)cyclododecane (4) (PA-DOTA-
NO2). To a 250 mL round bottom ¯ask was added
concentrated HCl (100 mL) (Baker Ultrapure) and PA-
DOTA-NO2 ester, (6.7 g, 8.7 mmol). This was heated
at 100±110ꢁC for 6 h. The aqueous HCl was removed
by rotary evaporation and the residue taken up in
water (2±3 mL). This solution was then lyophilized to
give PA-DOTA-NO2 as a pale yellow solid (6.49 g,
1
99%). H NMR (300 MHz, D2O, pH 1.0) d 2.0 (m, 1H,
.
.
for C31H49N5O10 H2O NaBr: C, 48.19; H, 6.65; N, 9.06.
Found: C, 48.17; H, 6.62; N, 9.03.
CH(COOH)), 2.19 (m, 1H, CH(COOH)), 2.6±4.0 (series
of mult., 25H, cyclen, pendent arms), 7.53 (d, 2H, Ar);
8.20 (d, 2H, Ar); (300 MHz, D2O, pH=13) d 1.75 (m,
1H, CH(COOH)), 2.0±3.4 (series of mult., 26H, cyclen,
pendent arms), 7.51 (d, 2H, Ar); 8.19 (d, 2H, Ar); ana-
lytical HPLC tR=10.7 min; M + H+ calcd for
C24H36N5O10 554.2462, found [HRFAB] m/e=554.2480,
error=+3.3 ppm. Anal. calcd for C24H35N5O10, 3HCl,
1,4,7,10-Tetraaza-N-(1-carbomethoxy-3-(4-aminophenyl)-
propyl) - N0,N00,N000 - tris(acetic acid, ethyl ester)cyclodo-
decane (6) (PA-DOTA-NH2 ester). A Schlenk ¯ask was
charged with 10% Pd/C (267 mg) and EtOH (6 mL)
were under Ar(g), ®tted onto an atmospheric hydro-
genator, and then saturated with H2(g). A solution of
PA-DOTA-NO2 ester (500 mg, 0.65 mmol) in EtOH
(2 mL) was injected into the Schlenk ¯ask. The hydro-
genation was allowed to proceed until the uptake of
H2(g) had halted. The reaction mixture was ®ltered
through a bed of Celite 577 packed in a medium glass
fritted funnel. The ®ltrate was reduced to dryness by
rotary evaporation and vacuum dried to give the pro-
.
H2O NaCl: C, 38.52; H, 5.52; N, 9.36. Found: C, 38.42;
H, 5.39; N, 9.36.
1,4,7,10-Tetraaza-N-(1-carboxy-3-(4-aminophenyl)propyl)-
N0,N00,N000-tris(acetic acid)cyclododecane (5) (PA-DOTA-
NH2). A Schlenk ¯ask was charged with 10% Pd/C
(332 mg) and H2O (10 mL) and ®tted onto an atmo-
spheric hydrogenator. The apparatus was ¯ushed
with H2(g) two times to fully saturate the catalyst. A
solution of PA-DOTA-NO2 (1.5 g, 2.0 mmol) in
water (10 mL) was injected via syringe into the ¯ask.
The hydrogenation was allowed to proceed until the
uptake of H2(g) had halted. The reaction mixture was
®ltered through a bed of Celite 577 packed in a medium
glass fritted funnel. The slightly pinkish ®ltrate was
reduced to dryness by rotary evaporation and the light
purple residue taken up in water (1±2 mL). This was
then lyophilized to give PA-DOTA-NH2 as a light
1
duct as a pale yellow foam (477 mg, 74%). H NMR
(300 MHz, CDCl3) d 1.27 (m, 9H, -CH3), 1.7±3.0 (series
of mult., 21 H, methyl ester pendent arm, CH2 cyclen),
3.2±3.5 (m, 8H, CH2COOC2H5, CH2Ar), 3.78 (s, 3H,
OCH3), 4.05±4.3 (m, 6H, OCH2), 6.74 (d, 2H, Ar), 7.08
(d, 2H, Ar); 13C NMR (75.5 MHz, CDCl3) d 13.92
(OCH2CH3), 25.09 (CH2CH2Ar), 32.62 (CH2Ar), 44.40,
47.13, 48.53, 51.56 (CH2 cyclen), 52.59, 54.96
(CH(COOCH3), CH2COOC2H5), 58.30, 61.09 (OCH2,
OCH3), 115.1, 129.6, 129.9, 145.2 (Ar), 173.5, 173.6,
176.9 (CO); MS (FAB/glycerol) 644 (M + Na+).
1
purple solid (1.18 g, 84%). H NMR (300 MHz, D2O,
pH 1) d 2.0 (m, 1H, CH(COOH)), 2.4 (m, 1H,
CH(COOH)), 2.4±4.2 (series of mult., 25H, cyclen, pen-
dent arms), 7.41 (d, 2H, Ar), 7.51 (d, 2H, Ar); 1H NMR
(300 MHz, D2O, pH=13) d 1.6 (m, 1H, CH(COOH)),
1.9 (m, 1H, CH(COOH)), 2.1±3.2 (series of mult., 25H,
cyclen, pendent arms), 6.81 (d, 2H, Ar), 7.13 (d, 2H,
Ar); analytical HPLC tR=8.4 min; M + H+ calcd for
C24H38N5O8 524.2720 found [HRFAB] m/e=524.2678,
error= 8.2 ppm.
1,4,7,10-Tetraaza-N-(1-carbomethoxy-3-(4-nitrophenyl)-
propyl)-N0,N00-bis(acetic acid, ethyl ester)cyclododecane
(6) (PA-DO3A-NO2 ester). 1,4,7,10-Tetraaza-N-(1-
carbomethoxy-3-(4-nitrophenyl)propyl)-cyclododecane
(380 mg, 0.97 mmol), CH3CN (10 mL), anhydrous
Na2CO3 (409 g) and methyl bromoacetate (298 mg,
1.95 mmol) were combined in a 25 mL round bottom
¯ask. The reaction mixture was stirred at room tem-
perature for 17 h after which it was applied to a silica gel
column. It was eluted ®rst with 5% MeOH in CHCl3
and then increased to 10% MeOH to obtain the PA-
DO3A-NO2 ester. Solvents were removed by rotary
evaporation and the orange foam obtained was vacuum
dried overnight (100 mg, 19%). 1H NMR (300 MHz,
1,4,7,10-Tetraaza-N-(1-carboxy-3-(4-isothiocyanato-
phenyl)propyl)-N0,N00,N000-tris(acetic acid)cyclododecane
(1) (PA-DOTA-NCS). A 1 M solution of SCCl2 in
CHCl3 (0.39 mL) was added to (5) (150 mg, 0.21 mmol)
dissolved in H2O (2 mL) in a 25 mL ¯ask. The mixture