Inorganic Chemistry
Article
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reaction mixture was concentrated in vacuo and the residue was
redissolved in H2O and acidified to pH 1 with 1 M HCl. The residue
was collected, washed with H2O and diethyl ether, and dried. The
pure product was purified with flash column chromatography with an
eluent system of EA/n-hexane (2:3 v/v).
2: Yield (est.): 46%. H NMR (500 MHz, DMSO-d6) δ 9.15 (s,
1H, CONH), 7.68 (dd, J = 8.9, 3.2 Hz, 1H, Ar−H), 7.48 (dd, J = 8.9,
3.1 Hz, 2H, Ar−H), 7.28 (dd, J = 8.8, 3.0 Hz, 2H, Ar−H), 7.07−7.03
(m, 1H, Ar−H), 7.01 (dd, J = 8.5, 3.0 Hz, 1H, Ar−H), 6.65 (brs, 6H,
NH3), 6.20 (d, J = 2.2 Hz, 1H, =CHCO2), 5.10 (s, 2H, CH2), 2.39 (s,
3H, CH3), 1.93 (s, 3H, CO2CH3). 13C NMR (126 MHz, DMSO-d6)
δ 166.99, 161.48, 160.56, 160.16, 154.68, 153.45, 140.63, 130.42,
129.70, 128.36, 126.46, 113.16, 112.78, 111.15, 101.65, 69.96, 53.06,
18.14. 195Pt {1H} NMR (DMSO-d6, 108 MHz): 1171.2 ppm. ESI−
MS (−ve mode): m/z = 681.8 [M−H]−. RP-HPLC purity: 98.3%
(254 nm) and 95.9% (280 nm); tr = 15.1 min.
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L1. Yield: 43%. H NMR (400 MHz, DMSO-d6) δ 12.97 (s, 1H,
COOH), 8.01−7.90 (m, 3H, =CHAr and Ar−H), 7.74 (dd, J = 7.7,
1.7 Hz, 1H, Ar−H), 7.57 (d, J = 8.4 Hz, 2H, Ar−H), 7.45−7.35 (m,
1H, Ar−H), 7.15 (d, J = 7.9 Hz, 1H, Ar−H), 7.01 (t, J = 7.5 Hz, 1H,
Ar−H), 6.64 (d, J = 16.2 Hz, 1H, =CHCO2), 5.32 (s, 2H, CH2), 3.70
(s, 3H, CH3). 13C NMR (101 MHz, DMSO-d6) δ 167.03, 166.92,
156.68, 141.74, 139.16, 131.98, 130.36, 129.58, 128.84, 127.42,
122.63, 121.18, 118.16, 113.17, 69.18, 51.43. ESI−MS (−ve mode):
m/z = 311.0 [M−H]−.
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3: Yield (est.): 14%. H NMR (500 MHz, DMSO-d6) δ 10.87 (s,
1H, CONHO), 9.84 (s, 1H, CONHAr), 9.14 (s, 1H, CO2NH), 7.57
(d, J = 7.7 Hz, 2H, Ar−H), 7.45 (d, J = 8.5 Hz, 2H, Ar−H), 7.27 (t, J
= 7.9 Hz, 2H, Ar−H), 7.20−7.17 (m, 2H, Ar−H), 7.11 (d, J = 8.1 Hz,
1H, Ar−H), 7.01 (t, J = 7.3 Hz, 1H, Ar−H), 6.64 (brs, 6H, NH3),
4.65 (s, 2H, CH2), 2.28 (t, J = 7.5 Hz, 2H, CH2CONHOH), 1.93−
1.61 (m, 3H, CO2CH3 and CH2CONHAr), 1.50−1.46 (m, 4H,
CH2CH2), 1.31−1.24 (m, 4H, CH2CH2). 13C NMR (126 MHz,
DMSO-d6) δ 178.39, 171.28, 169.29, 160.58, 140.90, 139.35, 129.34,
128.66, 128.30, 122.96, 122.95, 119.06, 76.72, 36.38, 32.26, 28.41,
28.34, 25.02, 24.88, 22.85. 195Pt {1H} NMR (DMSO-d6, 108 MHz):
1168.3 ppm. ESI−MS (−ve mode): m/z = 769.9 [M−H]−. RP-HPLC
purity: 95.2% (254 nm) and 95.3% (280 nm); tr = 12.5 min.
3−NO2. Yield (est.): 12%. 1H NMR (400 MHz, DMSO-d6) δ
10.96 (s, 1H, CONHO), 9.82 (s, 1H, CONHAr), 9.70 (s, 1H,
CO2NH), 8.31 (s, 1H, Ar−H), 7.66 (dd, J = 8.5, 2.2 Hz, 1H, Ar−H),
7.61−7.54 (m, 2H, Ar−H), 7.51 (d, J = 8.5 Hz, 1H, Ar−H), 7.32−
7.23 (m, 2H, Ar−H), 7.04−6.97 (m, 1H, Ar−H), 6.63 (s, 6H, NH3),
5.00 (s, 2H, CH2), 2.28 (t, J = 7.4 Hz, 2H, CH2CONHOH), 1.93 (m,
5H, CO2CH3 and CH2CONHAr), 1.51 (m, 4H, CH2CH2), 1.25 (m,
4H, CH2CH2). 13C NMR (126 MHz, DMSO-d6) δ 178.35, 171.23,
169.60, 159.94, 148.22, 139.35, 131.06, 129.17, 128.74, 128.62,
126.50, 122.90, 119.03, 72.93, 36.36, 32.09, 28.37, 28.29, 24.98, 24.74,
22.81. 195Pt {1H} NMR, (DMSO-d6, 108 MHz): 1168.6 ppm. ESI−
MS (−ve mode): m/z = 815.1 [M−H]−. RP-HPLC purity: 97.5%
(254 nm) and 97.6% (280 nm); tr = 14.0 min.
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L2. Yield: 48%. H NMR (400 MHz, DMSO-d6) δ 12.99 (s, 1H,
COOH), 8.00−7.94 (m, 2H, Ar−H), 7.71 (d, J = 8.7 Hz, 1H, Ar−H),
7.58 (d, J = 8.3 Hz, 2H, Ar−H), 7.11−7.03 (m, 2H, Ar−H), 6.22 (d, J
= 1.3 Hz, 1H, =CH), 5.33 (s, 2H, CH2), 2.40 (s, 3H, CH3). 13C NMR
(126 MHz, DMSO-d6) δ 167.06, 161.13, 160.09, 154.66, 153.39,
141.27, 130.52, 129.53, 127.52, 126.59, 113.45, 112.69, 111.35,
101.76, 69.20, 18.14. ESI−MS (−ve mode): m/z = 309.1 [M−H]−.
General Procedure for Intermediate L3 and L3−NO2. SAHA
(1 equiv) was dissolved in MeOH (10 mL). 4-Bromomethylbenzoic
acid or 4-bromomethyl-3-nitrobenzoic acid (1 equiv) was added to
the reaction mixture followed by addition of 40% w/v NaOH
dropwise. The reaction mixture was stirred at r.t. for 18 h and then
concentrated in vacuo. The remaining residue was dissolved in H2O
(6 mL) and acidified with 1 M HCl to pH 1. The white precipitate
was collected, dried, and used without further purification.
L3. Yield: 79%. 1H NMR (500 MHz, DMSO-d6) δ 12.93 (brs, 1H,
COOH), 11.00 (s, 1H, CONHO), 9.84 (s, 1H, CONH), 7.98−7.94
(m, 2H, Ar−H), 7.62−7.57 (m, 2H, Ar−H), 7.54−7.49 (m, 2H, Ar−
H), 7.32−7.24 (m, 2H, Ar−H), 7.02 (tt, J = 7.3, 1.2 Hz, 1H, Ar−H),
4.86 (s, 2H, CH2), 2.29 (t, J = 7.5 Hz, 2H, CH2CONHOH), 1.96 (t, J
= 7.4 Hz, 2H, CH2CONHAr), 1.54 (t, 7.0 Hz, 4H, CH2CH2), 1.28
(ddt, J = 12.8, 9.5, 4.7 Hz, 4H, CH2CH2). 13C NMR (126 MHz,
DMSO-d6) δ 171.20, 169.46, 167.19, 140.89, 139.35, 129.26, 128.62,
128.43, 122.89, 119.02, 76.12, 36.35, 32.17, 28.38, 28.28, 24.98, 24.81.
ESI−MS (−ve mode): m/z = 397.1 [M−H]−.
Synthesis of 4. To a solution of SAHA (70.3 mg, 0.266 mmol) in
DMF (5 mL) at 0 °C, CDI was added. The reaction mixture was
stirred at 0 °C for 2 h. A (40 mg, 0.106 mmol) was then added
followed by stirring at r.t. for 24 h. After this, the solution was filtered
and freeze-dried. Pure 1 was obtained via purification by RP-HPLC as
L3−NO2. Yield: 83%. 1H NMR (400 MHz, DMSO-d6) δ 13.75 (s,
1H, COOH), 11.13 (s, 1H, CONHO), 9.83 (s, 1H, CONH), 8.50 (d,
J = 1.7 Hz, 1H, Ar−H), 8.28 (dd, J = 8.0, 1.7 Hz, 1H, Ar−H), 7.93 (d,
J = 8.0 Hz, 1H, Ar−H), 7.58 (d, J = 7.6 Hz, 2H, Ar−H), 7.33−7.21
(m, 2H, Ar−H), 7.01 (t, J = 7.4 Hz, 1H, Ar−H), 5.22 (s, 2H, CH2),
2.28 (t, J = 7.4 Hz, 2H, CH2CONHOH), 1.94 (t, J = 7.3 Hz, 2H,
CH2CONHAr), 1.51 (m, 4H, CH2CH2), 1.34−1.16 (m, 4H,
CH2CH2). 13C NMR (126 MHz, DMSO-d6) δ 171.20, 169.85,
165.40, 139.34, 136.44, 133.84, 131.74, 130.50, 128.63, 125.19,
122.91, 119.03, 73.13, 36.35, 32.08, 28.37, 28.26, 24.98, 24.71. ESI−
MS (−ve mode): m/z = 442.1 [M−H]−.
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a white solid. Yield (est.): 32%. H NMR (500 MHz, DMSO-d6) δ
11.45 (s, 1H, CONHO), 9.86 (s, 1H, CONHAr), 7.59 (d, J = 8.0 Hz,
3H, Ar−H), 7.28 (t, J = 7.9 Hz, 2H, Ar−H), 7.02 (t, J = 7.3 Hz, 1H,
Ar−H), 6.56 (s, 6H, NH3), 2.29 (td, J = 7.4, 1.4 Hz, 2H,
CH2CONHOH), 2.05 (t, J = 7.3 Hz, 2H, CH2CONHAr), 1.94 (s,
3H, CH3), 1.60−1.49 (m, 4H, CH2CH2), 1.32−1.26 (m, 4H,
CH2CH2). 195Pt {1H} NMR (DMSO-d6, 108 MHz): 1170.2 ppm.
ESI−MS (−ve mode): m/z = 664.8 [M−H]−. RP-HPLC purity:
95.2% (254 nm) and 96.6% (280 nm); tr = 12.9 min.
Investigation of Reduction Using RP-HPLC. Each Pt(IV)
complex was extracted from its stock solution and added to PBS (200
mM, pH 7.4) except for 2, which was added to 1:1 v/v of DMSO:PBS
(200 mM, pH 7.4) solution (66 μL) in an Eppendorf tube to obtain a
concentration of 200 μM. Aqueous sodium ascorbate (NaAsc, 30
equiv) was added to the solutions and mixed at 37 °C in an
Eppendorf thermomixer. At regular time intervals, aliquots (30 μL)
were taken from the respective reaction mixtures for RP-HPLC
analysis. The identities of the products were confirmed by
electrospray ionization−mass spectrometry (ESI−MS) analysis and
comparison of their retention time with authentic standards.
Fluorescence Measurements. Each compound was extracted
from its stock solution and dissolved in PBS (200 mM, pH 7.4) to
attain 100 μM. A fixed concentration and volume (100 μM, 200 μL)
of each compound was pipetted onto a 96-well black microplate in
triplicate. Fluorescence measurements were conducted in which the
excitation wavelength was 350 nm, gain setting was 50, and the
scanned emission wavelength was from 380 to 700 nm. Complex 2
was dissolved in 1:1 v/v of DMSO:PBS (200 mM, pH 7.4) solution to
General Procedure for 1−3 and 3−NO2. A self-immolative
linker-modified drug (2.4 equiv) was dissolved in DMSO (1 mL).
NEt3 (2.4 equiv) was added to the solution and stirred for 5 min.
DPPA (2.4 equiv) was then added and stirred at r.t. for 30 min
followed by stirring for 3 h at 70 °C. After that, A (1 equiv) was added
to the reaction mixture and stirred at 50 °C for 24 h. After completion
of the reaction, the solution was filtered and dried. A pure Pt(IV)
complex was obtained via purification by RP-HPLC.
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1: Yield (est.): 20%. H NMR (500 MHz, DMSO-d6) δ 9.15 (s,
2H, CONH), 7.87 (d, J = 16.2 Hz, 1H, =CHAr), 7.75−7.66 (m, 1H,
Ar−H), 7.49 (d, J = 8.4 Hz, 2H, Ar−H), 7.40 (t, J = 7.6 Hz, 1H, Ar−
H), 7.28 (d, J = 8.4 Hz, 2H, Ar−H), 7.18 (d, J = 8.5 Hz, 1H, Ar−H),
6.98 (t, J = 7.5 Hz, 1H, Ar−H), 6.61 (d, J = 16.2 Hz, 7H, NH3 and
=CHCO2), 5.09 (s, 2H, CH2), 3.69 (s, 3H, CH3), 1.93 (s, 3H,
CO2CH3). 13C NMR (126 MHz, DMSO) δ 167.02, 157.19, 157.12,
140.74, 139.48, 131.99, 128.90, 128.82, 128.34, 122.54, 121.79,
120.89, 119.91, 117.97, 113.27, 69.90, 51.44, 22.85. 195Pt {1H} NMR
(DMSO-d6, 108 MHz): 1169.7 ppm. ESI−MS (−ve mode): m/z =
683.8 [M−H]−. RP-HPLC purity: 98.3% (254 nm) and 97.7% (280
nm); tr = 18.6 min.
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Inorg. Chem. 2021, 60, 1823−1831