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tion was evaporated under vacuum to yield 3 as a white solid
tion equipped with an optical-fiber temperature control and HPR-
1000/6M six-position high-pressure reactor; Bergamo, Italy). The H
1
1
(
269 mg, 81%). H NMR (400 MHz, 258C, CD OD): d=8.38 (m, 8H),
3
7
2
.76 (m, 16H), 7.18 (m, 8H), 3.3–3.2 (m, 40H), 3.04 (m, 16H), 2.9–
.7 (m, 32H), 2.61 (m, 16H), 2.55 (m, 4H), 2.4–2.3 ppm (m, 24H);
T1 relaxation times were acquired by the standard inversion-recov-
ery method with a typical pulse width (908) of 3.5 ms and 16 experi-
1
3
1
C NMR (100 MHz, 258C, CD OD): d=173.7, 172.2, 159.8, 149.2,
ments of 4 scans. The H T relaxation times were acquired by the
3
2
1
37.9, 121.2, 119.8, 52.1, 49.8, 38.9, 38.8, 37.4, 35.0, 34.1, 33.4 ppm;
Carr-Purcell-Meiboom-Gill (CPMG) sequence method with a typical
pulse width (908) of 3.5 ms, 64 experiments, and a typical echo time
of 100–500 ms. The temperature was controlled with a Stelar VTC-
91 airflow heater equipped with a calibrated copper-constantan
thermocouple (uncertainty of Æ0.18C).
IR (KBr disk): n˜ =3325, 2928, 2850, 1626, 1574, 1535, 1435, 1311,
À1
1
243, 1114, 1088, 1044, 892, 760, 641 cm ; MS(ESI): m/z: 1504 [M+
+
+
+
+
+
2
H /2] , 1003 [M+3H+/3] , 753 [M+4H /4] .
Mono(6-deoxy-6-mercapto)-b-cyclodextrin (5)
Titrations E
[25]
A modification of reported procedures was used. Mono(6-deoxy-
[26]
6
-para-toluensulfonyl)-b-cyclodextrin (4; 3.00 g, 2.33 mmol) and
A solution of 1 (0.30 mm) and Gd
prepared by mixing volumes of the respective stock solutions and
diluting with H O when necessary. An aliquot was taken from this
solution, which was mixed again with H O and the stock solution
of Gd -6, Gd-7, or Gd-8 to keep the concentration of the complex
at 0.15 mm. The R
sured, and this procedure was repeated several times until an
2
-6, Gd-7, or Gd-8 (0.15 mm) was
thiourea (1.77 g, 23.3 mmol) were dissolved in DMF (120 mL). The
solution was stirred at 758C for 2 days. After cooling at room tem-
2
perature, the mixture was added to Et O (500 mL) and stirred for
2
2
1
0 min. The precipitate was filtered and washed with Et O
2
2
obs
1
(
2
100 mL), suspended in acetone (120 mL), and heated to reflux for
h. The suspension was cooled to room temperature and filtered.
value for the resulting solution was mea-
obs
The collected white solid was dried under vacuum and added por-
R
1
value very close to that measured for a 0.15 mm solution of
obs
tionwise to a solution of Na S O (120 mg) in 1m NaOH (100 mL).
just the complex was reached. The curve obtained by plotting R
versus the molar concentration of 1 was fitted according to the
1
2
2
5
After stirring for 30 min, the solution was acidified to pH 3 with
concentrated HCl. Trichloroethylene (5.3 mL) was added to the re-
action mixture, and the resulting suspension was sonicated for
[31]
PRE theory.
1
0 min. A white solid residue was collected by filtration and dried
Titrations M
under vacuum to yield 5 (2.52 g, 94%), which was confirmed by
comparison with reported characterization data.
[25]
A solution of 1 (0.10 mm) and Gd -6, Gd-7, or Gd-8 (1.00 mm) was
prepared by mixing volumes of the respective stock solutions and
2
diluting with H O when necessary. An aliquot was taken from this
2
Synthesis of PAMAM-CD (1)
8
solution, which was mixed again with H O and the stock solution
2
of 1 to keep the concentration of the dendrimer at 0.10 mm. The
Compounds 3 (53 mg, 0.018 mmol) and 5 (245 mg, 0.21 mmol)
were dissolved in DMF (6 mL) and stirred for 2 days. After evapora-
obs
R1 value for the resulting solution was measured, and this proce-
obs
dure was repeated several times until an R1 value very close to
tion under vacuum, the residue was suspended in H O and dia-
2
that measured for the matrix (i.e., a 0.10 mm aqueous solution of
lyzed against H O (MWCO=2 kDa). The final suspension was fil-
2
obs
1
) was reached. The curve obtained by plotting R1
versus the
tered, and the filtrate was freeze-dried to yield 1 as a white solid
1
molar concentration of Gd -6, Gd-7, or Gd-8 was fitted by using
(
132 mg, 64%). H NMR (400 MHz, 258C, D O): d=5.1–4.9 (m, 56H),
2
2
appropriate equations.
4
3
2
1
3
1
.0–3.8 (m, 104H), 3.8–3.7 (m, 112H), 3.7–3.6 (m, 48H), 3.6–3.5 (m,
2H), 3.4–3.2 (m, 64H), 3.0–2.8 (m, 56H), 2.6–2.5 (m, 28H), 2.5–
1
3
.3 ppm (m, 24H); C NMR (100 MHz, 258C, CD OD): d=173.7 (m),
Cleavage experiments
3
01.8, 84.6, 81.1, 80.5, 73.0, 71.7 (m), 70.9 (m), 60.2, 51.3, 48.8 (m),
TCEP (final concentration=1.25 mm, from a 0.50 mm stock solution
8.7, 36.1, 34.9, 32.9, 32.3 ppm; IR (KBr disk): n˜ =3354, 2922, 1640,
À1
at pH 7) was added portionwise to an aqueous solution of Gd
-6
2
550, 1409, 1364, 1154, 1079, 1030, 941, 854, 754, 703, 579 cm
;
(0.15 mm) and 1 (0.0375 mm) at pH 7. The reaction mixture was
MALDI-TOF MS: m/z: 11330, 11372.
stirred at 258C for 5 min before the measurement. The R1 data
were collected at 40 MHz and 258C.
Relaxometric measurements
The water-proton longitudinal relaxation rates as a function of the
magnetic-field strength were measured in non-deuterated aqueous
solutions on a fast field-cycling Stelar SmarTracer relaxometer
MR-phantom imaging
MR images at 1 T were acquired on an Aspect MRI System (Aspect
Magnet Technologies Ltd., Netanya, Israel), which consisted of an
NdFeB magnet, equipped with a solenoid coils (inner diameter=
(
Stelar s.r.l., Mede (PV), Italy) over a continuum of magnetic-field
strengths from 0.00024 to 0.25 T (corresponding to 0.01–10 MHz
proton Larmor frequencies). The relaxometer operates under com-
3
5 mm). The images were obtained by using a standard T -weight-
1
ed spin-echo sequence with the following parameters: TR/TE/NEX
puter control with an absolute uncertainty in 1/T of Æ1%. Addi-
1
2
50/8.9/10, FOV=30 mm, matrix=128ꢁ128, slice thickness=
tional longitudinal and transverse relaxation data in the range 15–
5
mm.
7
0 MHz were obtained on a Stelar Relaxometer connected to
a Bruker WP80 NMR electromagnet adapted to variable-field meas-
urements (15–80 MHz proton Larmor frequency). The exact con-
centration of Gd ions was determined by measurement of the
Acknowledgements
III
bulk magnetic-susceptibility shifts of a tBuOH signal or by using in-
ductively coupled plasma mass spectrometry (ICP-MS; Element-2,
Thermo-Finnigan, Rodano (MI), Italy). Sample digestion was per-
Gd-BzAAZTA (Gd-7) and Gd-DOTAMA-Ad (Gd-8) were kindly
provided by Prof. Giovanni B. Giovenzana (Universitꢂ del Pie-
monte Orientale) and Dr. Carla Carrera (Universitꢂ di Torino), re-
spectively. We thank Dr. Francesco Marsano (Universitꢂ del Pie-
formed with concentrated HNO (70%, 2 mL) with microwave heat-
3
ing at 1608C for 20 min (Milestone MicroSYNTH Microwave lab sta-
&
&
Chem. Eur. J. 2014, 20, 1 – 10
8
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!
Martinelli, Jonathan
