Full Papers
doi.org/10.1002/cbic.202100243
ChemBioChem
General procedures for the synthesis of intermediates 2a–2c:
Sodium (115 mg, 5 mmol) was slowly added into the solution
containing polyethylene glycol (10 mmol) in tetrahydrofuran
(50 mL). After stirring for 1 h, tert-butyl acrylate (512 mg, 4 mmol)
was added dropwise to the mixture. The mixture was stirred at
room temperature for 12 h. The reaction was quenched by adding
2 mL of 1 M hydrochloric acid solution, and poured into 100 mL of
saturated NaCl solution. The mixture was extracted with ethyl
acetate (3×50 mL) and the combined extracts were dried over
anhydrous MgSO4. After the solvent was removed under vacuum,
the crude products were purified by flash column chromatography
(petroleum ether/ethyl acetate=1/1) to obtain yellowish mono-
tert-butyl ester products.
concentrated to provide the azido compounds. 4a–4c were
purified by flash column chromatography (petroleum ether/ethyl
acetate=1/5) to obtain the colorless products.
1
4a: 498 mg, yield 96%, H NMR (400 MHz, CDCl3) δ 3.76–3.60 (m,
8H), 3.42–3.35 (m, 2H), 2.51 (t, J=6.4 Hz, 2H), 1.45 (s, 9H); 13C NMR
(101 MHz, CDCl3) δ 170.84, 80.45, 70.56, 70.38, 70.00, 66.92, 50.64,
36.22, 28.04; HRMS: calculated for C11H21N3NaO4 [M+Na]+:
282.1430, found 282.1426.
1
4b: 712 mg, yield 91%, H NMR (400 MHz, CDCl3) δ 3.77–3.58 (m,
20H), 3.47–3.30 (m, 2H), 2.50 (t, J=6.8 Hz, 2H), 1.45 (s, 9H); 13C NMR
(101 MHz, CDCl3) δ 170.92, 80.51, 70.70, 70.67, 70.64, 70.59, 70.50,
70.37, 70.04, 66.90, 50.68, 36.26, 28.09; HRMS: calculated for
C17H33N3NaO7 [M+Na]+: 414.2216, found 414.2211.
1
2a: 703 mg, yield 75%, H NMR (400 MHz, CDCl3) δ 3.77–3.70 (m,
4c: 1.20 g, yield 85%, 1H NMR (400 MHz, CDCl3) δ 3.75–3.57 (m,
48H), 3.40 (d, J=4.4 Hz, 2H), 2.53–2.48 (m, 2H), 1.45 (d, J=2.4 Hz,
9H); 13C NMR (101 MHz, CDCl3) δ 170.91, 80.49, 70.69, 70.66, 70.63,
70.56, 70.49, 70.36, 70.04, 66.88, 50.67, 36.25, 28.09; HRMS:
calculated for C31H61N3NaO4 [M+Na]+: 722.4051, found 722.4048.
4H), 3.69–3.59 (m, 6H), 2.78 (s, 1H), 2.54–2.49 (m, 2H), 1.45 (s, 9H);
13C NMR (101 MHz, CDCl3) δ 170.92, 80.63, 72.49, 70.33, 70.31, 66.81,
61.70, 36.14, 28.05; HRMS: calculated for C11H22NaO5 [M+Na]+:
257.1365, found 257.1357.
2b: 1.01 g, yield 69%, 1H NMR (400 MHz, CDCl3) δ 3.79–3.59 (m,
22H), 2.91 (s, 1H), 2.53–2.48 (m, 2H), 1.45 (s, 9H); 13C NMR (101 MHz,
CDCl3) δ 170.93, 80.51, 72.52, 70.61, 70.59, 70.56, 70.54, 70.48, 70.33,
66.88, 61.72, 36.24, 28.09; HRMS: calculated for C17H34NaO8 [M+
Na]+: 389.2151, found 389.2146.
General Procedures for the Synthesis of Protected KUE-PEG-N3
5a–5c: The azido compounds (0.5 mmol) were dissolved in
dichloromethane (5 mL), and trifluoroacetic acid (5 mL) was care-
fully added into the solution. After stirring at room temperature for
4 h, the solvent was removed by evaporation and the residue was
dissolved in 5 ml of dry dimethylformamide. HATU (380 mg,
1 mmol) and DIPEA (194 mg, 1.5 mmol) were added to the solution,
and the resulting mixture was stirred at room temperature for
30 min. The tert-butyl ester protected KUE amine (293 mg,
0.6 mmol) was added, and the mixture was stirred at room
temperature for 7 h. The reaction mixture was poured into 50 mL of
saturated NaCl solution and extracted with ethyl acetate (3×
50 mL). The organic phase was collected, dried over anhydrous
Na2SO4, and concentrated to give the crude products. 5a–5c were
purified by flash column chromatography (dichloromethane/meth-
anol=10/1) to obtain colorless protected KUE-PEG-N3.
2c: 1.48 g, yield 55%, 1H NMR (400 MHz, CDCl3) δ 3.76–3.54 (m,
49H), 2.77 (s, 2H), 2.53–2.48 (m, 2H), 1.45 (d, J=2.4 Hz, 9H); 13C NMR
(101 MHz, CDCl3) δ 170.94, 80.53, 72.58, 70.61, 70.57, 70.51, 70.37,
70.29, 66.90, 61.71, 36.26, 28.10; HRMS: calculated for C31H62NaO15
[M+Na]+: 697.3986, found 697.3981.
General methods for the preparation of intermediates 3a–3c:
Triethylamine (364 mg, 3.6 mmol) was added to a solution of tert-
butyl ester product (3 mmol) in dichloromethane (10 mL), and then
p-toluenesulfonyl chloride (686 mg, 3.6 mmol) was added to the
mixture in portions. The resulting mixture was stirred at room
temperature for overnight. The reaction mixture was diluted with
dichloromethane (20 mL), washed with water (2×50 mL), and
concentrated to afford the crude sulfonate compound. 3a–3c was
purified by flash column chromatography (petroleum ether/ethyl
acetate=1/2) to obtain pale products.
5a: 286 mg, yield 85%, 1H NMR (400 MHz, CDCl3) δ 6.87 (s, 1H), 5.64
(dd, J=20.0, 6.4 Hz, 2H), 4.38–4.17 (m, 2H), 3.71 (d, J=28.0 Hz, 7H),
3.44 (s, 2H), 3.34–3.12 (m, 2H), 2.52 (s, 2H), 2.32 (d, J=5.2 Hz, 2H),
2.06 (d, J=6.0 Hz, 1H), 1.84 (dd, J=32.0, 25.2 Hz, 2H), 1.67–1.23 (m,
33H); 13C NMR (101 MHz, CDCl3) δ 172.58, 172.52, 157.40, 82.17,
81.66, 80.67, 70.19, 70.00, 69.76, 67.35, 53.35, 52.99, 50.56, 38.84,
36.42, 32.02, 31.55, 28.63, 28.04, 27.96, 22.23; HRMS: calculated for
C31H56N6NaO10 [M+Na]+: 695.3956, found 695.3953.
3a: 1.10 g, yield 95%, 1H NMR (400 MHz, CDCl3) δ 7.79 (d, J=8.4 Hz,
2H), 7.35 (d, J=8.0 Hz, 2H), 4.19–4.11 (m, 2H), 3.67 (dd, J=8.0,
4.8 Hz, 4H), 3.55 (q, J=4.8 Hz, 4H), 2.47 (dd, J=12.4, 6.0 Hz, 5H),
1.44 (s, 9H); 13C NMR (101 MHz, CDCl3) δ 170.81, 144.80, 132.99,
129.82, 127.95, 80.50, 70.60, 70.29, 69.26, 68.64, 66.88, 36.21, 28.07,
21.61; HRMS: calculated for C18H28NaO7S [M+Na]+: 411.1453, found
411.1448.
5b: 314 mg, yield 78%, 1H NMR (400 MHz, CDCl3) δ 7.05 (s, 1H), 5.78
(dd, J=16.4, 8.0 Hz, 2H), 4.38–4.17 (m, 2H), 3.71 (d, J=29.2 Hz,
15H), 3.41 (d, J=4.0 Hz, 1H), 3.26 (dd, J=23.2, 17.2 Hz, 2H), 3.00 (s,
3H), 2.50 (s, 1H), 2.32 (d, J=6.4 Hz, 2H), 2.05 (s, 1H), 1.91–1.70 (m,
2H), 1.69–1.17 (m, 36H); 13C NMR (101 MHz, CDCl3) δ 172.21, 161.56,
157.58, 157.41, 81.74, 81.19, 80.34, 70.47, 70.45, 70.41, 70.37, 70.35,
70.28, 70.18, 70.01, 69.87, 67.24, 53.35, 52.83, 50.54, 45.11, 39.74,
38.74, 36.60, 32.17, 31.92, 31.47, 29.03, 28.70, 28.20, 27.97, 27.91,
22.55, 22.31; HRMS: calculated for C37H68N6NaO13 [M+Na]+:
827.4742, found 827.4738.
3b: 1.44 g, yield 92%, 1H NMR (400 MHz, CDCl3) δ 7.85–7.74 (m, 2H),
7.37–7.33 (m, 2H), 4.24–4.08 (m, 2H), 3.83–3.51 (m, 20H), 2.59–2.36
(m, 5H), 1.45 (d, J=5.6 Hz, 9H); 13C NMR (101 MHz, CDCl3) δ 170.89,
144.78, 133.02, 129.82, 127.98, 80.49, 70.74, 70.58, 70.51, 70.36,
69.24, 68.67, 66.89, 36.27, 28.09, 21.64; HRMS: calculated for
C24H40NaO10S [M+Na]+: 543.2240, found 543.2246.
3c: 2.19 g, yield 88%, 1H NMR (400 MHz, CDCl3) δ 7.83–7.74 (m, 2H),
7.49 (d, J=7.6 Hz, 2H), 4.13–4.10 (m, 2H), 3.64–3.29 (m, 48H), 2.43 (s,
5H), 1.40 (s, 9H); 13C NMR (101 MHz, CDCl3) δ 170.87, 145.34, 132.88,
130.59, 128.10, 80.15, 70.44, 70.25, 70.17, 70.14, 68.35, 66.69, 36.29,
28.20, 21.55; HRMS: calculated for C38H68NaO17S [M+Na]+:
851.4075, found 851.4071.
5c: 411 mg, yield 74%, 1H NMR (400 MHz, CDCl3) δ 6.89 (s, 1H), 5.57
(s, 2H), 4.26 (d, J=20.4 Hz, 2H), 3.67 (s, 45H), 3.41 (s, 2H), 3.21 (d, J=
16.8 Hz, 2H), 2.99 (s, 1H), 2.53 (s, 1H), 2.32 (s, 2H), 2.05 (s, 1H), 1.80
(d, J=44.4 Hz, 1H), 1.65–1.18 (m, 36H); 13C NMR (101 MHz, CDCl3) δ
172.41, 157.42, 81.87, 81.44, 80.50, 70.37, 70.21, 70.05, 69.99, 69.82,
69.71, 69.62, 69.49, 69.37, 53.47, 53.02, 50.61, 38.87, 31.97, 31.55,
28.20, 28.06, 27.98, 22.31; HRMS: calculated for C51H96N6NaO20 [M+
Na]+: 1135.6577, found 1135.6569.
General procedures for the synthesis of intermediates 4a–4c: To
a
solution of the sulfonate compound (2 mmol) in dimeth-
ylformamide (5 mL), NaN3 (195 mg, 3 mmol) was added. The
°
mixture was stirred at 80 C for 10 h. Then the reaction was diluted
with water (20 mL), extracted with ethyl acetate (3×50 mL), and
General procedures for the synthesis of KUE-PEG-N3: The
protected KUE compounds (0.3 mmol) were dissolved in 2 mL of
ChemBioChem 2021, 22, 1–9
6
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!