1
173
Synlett
P. Gobbo et al.
Letter
T.; Hanaoka, H.; Choyke, P. L.; Kobayashi, H. Cancer Sci. 2014,
05, 308. (f) Kuerschner, L.; Thiele, C. Biochim. Biophys. Acta,
1073, 1007, 920,823, 680 cm–1. UV-vis (DMSO, λmax, ε): 571 nm,
91,102 M cm .
–1
–1
1
Mol. Cell Biol. Lipids 2014, 1841, 1031.
(c) Synthesis of Rhodamine B–Trityl-Protected Thiol 5
To a solution of 1 (0.416g, 0.660 mmol) in acetone (2 mL) was
added DIPEA (0.5 mL, 2.9 mmol). To this mixture was added a
solution of (3-bromopropyl)(trityl)sulfane (4, 0.573 mg, 1.44
mmol) in acetone (12 mL). The mixture was stirred for 6 d at r.t.
under Ar (g), after which the solvent was removed by rotary
evaporation. The remaining crude residue was purified by flash
column chromatography (CH Cl –95% EtOH, 7:2) to yield com-
(
(
(
7) (a) Lang, K.; Chin, J. W. Chem. Rev. 2014, 114, 4764. (b) King, M.;
Wagner, A. Bioconjugate Chem. 2014, 25, 825.
8) Chen, X.; Wu, Q. Z.; Henschke, L.; Weber, G.; Weil, T. Dyes Pig-
ments 2012, 94, 296.
9) Nguyen, T.; Francis, M. B. Org. Lett. 2003, 5, 3245.
10) MacKenzie, D. A.; Sherratt, A. R.; Chigrinova, M.; Cheung, L. L.;
(
(
(
Pezacki, J. P. Curr. Opin. Chem. 2014, 21, 81.
2
2
11) Patterson, D. M.; Nazarova, L. A.; Prescher, J. A. Chem. Biol. 2014,
pound 5 as a shiny purple solid in 20% yield (120 mg, 0.128
1
9, 592.
mmol). H NMR (400 MHz, CD OD): δ = 7.77–7.75 (m, 2 H),
3
12) (a) Synthesis of Rhodamine B–Piperazine 1
7.64–7.63 (m, 1 H), 7.52–7.51 (m, 1 H), 7.37 (d, J = 8 Hz, 6 H),
7.28–7.18 (m, 11 H), 7.06 (dd, J = 8 Hz, J = 4 Hz, 2 H), 6.98 (d,
To a solution of rhodamine B (1.0 g, 2.1 mmol) and DIPEA (0.42
mL, 2.4 mmol) in MeCN (150 mL) and at 0 °C was added a solu-
tion of HBTU (0.91 g, 2.4 mmol) in MeCN (50 mL). After stirring
the mixture for 30 min at 0 °C, an ice-cold solution of mono-
Boc-piperazine (0.45 g, 2.4 mmol) in MeCN (20 mL) was added.
The ice-bath was removed, and the reaction was left at r.t. for
overnight. The solvent was removed by rotary evaporation, and
the crude was directly purified by column chromatography on
silica gel using CH Cl –EtOH 95% (15:1) as the eluent. To depro-
1
2
J = 4 Hz, 2 H), 3.67 (q, J = 8 Hz, 8 H), 3.31 (br s, 4 H), 2.17–2.12
(m, 4 H), 2.03 (br s, 4 H), 1.41 (quin, J = 8 Hz, 2 H), 1.29 (t, J = 8
13
Hz, 12 H). C NMR (150 MHz, CD OD): δ = 169.5, 159.4, 157.4,
3
156.7, 135.7, 133.5, 132.54, 132.04, 131.81, 131.59, 131.15,
130.6, 128.54, 127.6, 115.3, 114.7, 97.2, 67.7, 57.9, 53.8, 46.8,
42.5, 30.6, 26.4, 15.8, 12.8. ESI-HRMS: m/z calcd for
+
C54H59N O S [M]: 827.4353; found: 827.4375.
4
2
(d) Synthesis of Rhodamine B–Furan-Protected Maleimide 8
To a solution of compound 1 (0.273 g, 0.437 mmol) in MeCN (1
mL) was added DIPEA (0.2 mL, 1.1 mmol). To this mixture was
added a solution of compound 7 (0.242, 0.85mmol) MeCN (1
mL). The mixture was stirred for 3 d at r.t., after which the
solvent was removed by rotary evaporation. The remaining
crude residue was purified by flash column chromatography
2
2
tect the piperazine moiety, the product was redissolved in 10%
TFA (20 mL) in CH Cl , and the reaction mixture was stirred vig-
2
2
orously for 2 h at r.t. in an uncovered flask. The crude was con-
centrated by rotary evaporation, and TFA was removed by
repeatedly redissolving the residue in acetone and reapplying
the vacuum. The crude product was then purified by column
chromatography using CH Cl –EtOH 95% (3:1) as the eluent and
(CHCl –95% EtOH, 3:2) to yield compound 8 as a shiny purple
2
2
3
1
switching to CH Cl –EtOH 95% (3:2) as the eluent to collect pure
solid in 34% yield (105 mg, 0.127mmol). H NMR (400 MHz,
2
2
rhodamine B–piperazine 1 as a shiny purple solid in 95% yield
CDCl ): δ = 7.66–7.63 (m, 2 H), 7.51–7.49 (m, 1 H), 7.33–7.31
3
1
(
1.25 g, 2.0 mmol). R = 0.3 (CH Cl –95% EtOH, 3:1). H NMR
(m, 1 H), 7.20 (d, J = 8 Hz, 2 H), 6.92 (dd, J = 8 Hz, J = 4 Hz, 2 H),
f
2
2
1
2
(
7
400 MHz, CDCl ): δ = 7.69–7.66 (m, 2 H), 7.59–7.57 (m, 1 H),
6.77 (d, J = 4 Hz, 2 H), 6.49 (s, 2 H), 5.19 (s, 2 H), 3.63 (q, J = 8 Hz,
8 H), 3.45 (t, J = 8 Hz, 2 H), 3.37 (br s, 2 H), 3.29 (br s, 2 H), 2.83
3
.34–7.32 (m, 1 H), 7.16 (d, J = 12 Hz, 2 H), 6.92 (dd, J = 12 Hz,
1
J = 4 Hz, 2 H), 6.73 (d, J = 4 Hz, 2 H), 3.75–3.51 (m, 12 H), 3.13
(
(s, 2 H), 2.29–2.16 (m, 6 H), 1.62 (quin, J = 8 Hz, 2 H), 1.31 (t,
2
br s, 2 H), 3.06 (br s, 2 H), 1.31 (t, J = 8 Hz, 12 H). 1 C NMR (150
3
J = 8 Hz, 12 H). C NMR (150 MHz, CDCl ): δ = 176.0, 166.9,
13
3
MHz, CDCl ): δ = 167.2, 157.7, 155.67, 155.51, 134.5, 130.84,
157.5, 155.61, 155.34, 136.2, 135.2, 131.8, 130.3, 129.95,
129.78, 129.60, 127.3, 113.85, 113.45, 96.1, 80.7, 54.7, 52.69,
52.07, 47.28, 47.13, 45.90, 41.5, 36.6, 24.2, 12.4. ESI-HRMS: m/z
3
1
30.23, 130.20, 130.11, 127.7, 114.3, 113.6, 96.3, 90.5, 53.4,
19
46.0, 12.4. F NMR (376 MHz, CD OD): δ = –76.89. ESI-HRMS:
3
+
+
m/z calcd for C32H39N O [M]: 511.3068; found: 511.3074. IR
calcd for C43H50N O [M]: 716.3806; found: 716.3817. IR (KBr):
4
2
5
5
(
1
7
KBr): 3271,2983, 1683, 1647, 1590, 1528, 1468, 1415, 1339,
3264, 2971, 1767, 1695, 1630, 1588, 1468, 1411, 1340, 1275,
–1
276, 1248, 1203, 1179, 1131, 1075, 1010, 975, 922, 833, 799,
1180, 1131, 1074, 1010, 920, 877, 822, 679 cm . UV-vis (DMSO,
–1
–1
–1
–1
–1
22, 682 cm . UV-vis (DMSO, λmax, ε): 571 nm, 91,573 M cm
.
λmax, ε): 571 nm, 91,221 M cm .
(
b) Synthesis of Rhodamine B–Azide 2
To a solution of 1 (0.243 g, 0.389 mmol) and DIPEA (140 μL,
.804 mmol) in MeCN (3 mL) was added dropwise and at 0 °C a
(e) Synthesis of Rhodamine B–Thiol 6
Compound 1 (0.135 g, 0.143 mmol) was dissolved in a solution
of CH Cl –20% TFA (5 mL). To this solution was added i-Pr SiH
0
2
2
3
solution of 1-azido-3-iodopropane (2, 0.115 g, 0.545 mmol) in
MeCN (1 mL). After stirring the mixture at r.t. overnight, the
solvent was removed by rotary evaporation, and the resulting
crude residue was purified by flash column chromatography
(60 μL, 0.29 mmol). The mixture was stirred for 2 d at r.t., after
which the solvent was removed by rotary evaporation. The
remaining crude residue was purified by flash column chroma-
tography using CH Cl –95% EtOH (9:2) as the eluent to yield
2
2
(
(
(
CH Cl –95% EtOH, 15:2) to yield 2 as a purple solid in 51% yield
product 6 as a shiny purple solid in 50% yield (50 mg, 0.072
mmol). This compound must be handled and stored under inert
2
2
1
0.140 g, 0.198 mmol). H NMR (400 MHz, CDCl ): δ = 7.71–7.69
3
m, 2 H), 7.57–7.55 (m, 1 H), 7.38–7.36 (m, 1 H), 7.30 (d, J = 8
atmosphere because it easily oxidizes to the corresponding
1
Hz, 2 H), 7.06 (d, J = 8 Hz, 2 H), 6.79 (d, J = 4 Hz, 2 H), 3.72–3.65
m, 8 H), 3.42 (br s, 4 H), 3.35 (t, J = 8 Hz, 2 H), 2.38 (t, J = 8 Hz, 2
H), 2.35 (br s, 2 H), 2.28 (br s, 2 H), 1.74 (quin, J = 8 Hz, 2 H), 1.35
disulphide. H NMR (400 MHz, CDCl ): δ = 7.66–7.59 (m, 2 H),
3
(
7.55–7.50 (m, 1 H), 7.32–7.25 (m, 1 H), 7.20 (d, J = 8 Hz, 2 H),
6.92 (dd, J = 8 Hz, J = 4 Hz, 2 H), 6.74 (d, J = 4 Hz, 2 H), 3.60 (q,
1
2
13
(
t, J = 8 Hz, 12 H). C NMR (150 MHz, CD OD): δ = 169.3, 159.3,
J = 8 Hz, 8 H), 3.38 (br s, 2 H), 3.32 (br s, 2 H), 2.61 (t, J = 4 Hz, 2
H), 2.50–2.21 (m, 6 H), 1.82–1.62 (m, 3 H), 1.29 (t, J = 8 Hz, 12
3
1
1
1
57.19, 157.00, 136.8, 133.35, 132.02, 131.61, 131.31, 131.11,
13
28.9, 115.5, 114.9, 97.4, 56.2, 54.1, 53.5, 50.5, 47.0, 42.7, 26.9,
H). C NMR (150 MHz, CDCl ): δ = 169.5, 159.4, 157.4, 156.7,
3
19
2.9. F NMR (376 MHz, CDCl ): δ = –74.62. ESI-HRMS: m/z
135.7, 133.5, 132.54, 132.04, 131.81, 131.59, 128.94, 128.14,
115.5, 114.9, 97.5, 56.9, 53.8, 47.68, 47.02, 39.5, 29.0, 22.0, 13.0.
3
+
calcd for C35H44N O [M]: 594.3551; found: 594.3549. IR (KBr):
3
7
2
19
262, 2924, 2029, 1630, 1588, 1413, 1339, 1273, 1179, 1131,
F NMR (376 MHz, CDCl ): δ = –74.62. ESI-HRMS: m/z calcd for
3
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 1169–1174