Journal of the American Chemical Society
Article
(
2
s, 1H, CH(OCH ) ), 4.11 (q, 2H, J = 7.1 Hz, COOCH ), 4.03 (t,
of the resonance of ethyl ester group (S-3)). The reaction was worked
up by carefully dripping the DMSO solution into ethyl acetate to have
the product precipitated. The suspension was centrifuged for 10 min at
10000 × g to obtain the white precipitate, which was purified by three
times reprecipitation in ethyl acetate. After removal of the residual
solvents under high vacuum, the amino-modified dextran was
3
2
2
H, J = 6.3 Hz, OCH ), 3.82 (s, 3H, ArOCH ), 3.30 (s, 6H,
2
3
CH(OCH ) ), 2.48 (t, 2H, J = 7.3 Hz, CH CO), 2.05 (dddd, 2H, J
3
2
2
=
7.2, 7.2, 6.4, 6.4 Hz, CH CH CH ), 1.23 (t, 3H, J = 7.1 Hz,
2 2 2
13
CH CH ). C NMR (151 MHz, CD Cl ): δ 173.73, 150.22, 149.24,
2
3
2
2
1
3
3
32.21, 119.90, 113.49, 111.09, 103.99, 68.72, 61.07, 56.61, 53.35,
1.49, 25.51, 14.79. ESI HRMS calcd for C H O Li (M + Li):
dissolved in dd-H O (pH 8.0) and lyophilized to get a white foamy
16
24
6
2
19.1727, found: 319.1730.
The General Procedure for Modification of Dextran by Dimethyl
product (Table S-2). Amine modification of dextran was quantified by
1
H NMR.
Acetals or Ketals (Figure 2). Dextran of desired molecular weight (100
mg) was dissolved in anhydrous DMSO (1 mL), followed by addition
of dimethyl acetal or ketal (2 eq. per hydroxyl group), molecular sieves
Compound 3. Reaction of compound 1 (50 mg, 0.150 mmol ester)
and amine B (201 μL, 3.0 mmol) in anhydrous DMSO (0.5 mL) gave
1
compound 3 as a white powder (45 mg, 87% yield, 0.8 amine B per
1
glucose unit). 1H NMR (500 MHz, D O) δ 5.48−4.94 (m, 1H,
(
5 Å, 100 mg), and p-toluenesulfonic acid monohydrate (5 mol % per
2
hydroxyl group). The reaction mixture was heated for 2 h to overnight
at 50 or 80 °C, and the reaction was quenched by addition of
triethylamine. Molecular sieves were then filtered, and the DMSO
solution was dripped into a mixture of isopropyl alcohol or isopropyl
alcohol and hexanes (1:1) to obtain white precipitate. The white
product was collected by centrifugation, purified by redissolving in
DMSO and precipitating in isopropyl alcohol or isopropyl alcohol and
hexanes (1:1), and dried under vacuum to obtain a water-insoluble
white powder.
glucose-H ), 4.34−3.11 (m, 6H, glucose-H ), 3.42 (br. app. s, 0.8 ×
1
2−6
2H, CH NHCO), 2.85 (br. app. s, 0.8 × 2H, CH NH ), 2.42 (br.
2
2
2
app. s, 0.8 × 2H, CH CO), 2.11 (br. app. s, 0.8 × 2H, ketal-CH ),
2
2
1.70−1.30 (m, 0.8 × 3H, ketal-CH ).
3
Compound 4. Reaction of compound 1 (50 mg, 0.150 mmol ester)
and amine B (632 μL, 6.0 mmol) in anhydrous DMSO (0.5 mL) gave
2
compound 4 as a white powder (42 mg, 75% yield, 0.8 amine B per
2
glucose unit). 1H NMR (500 MHz, D O) δ 5.44−4.92 (m, 1H,
2
glucose-H ), 4.31−3.12 (m, 6H, glucose-H ), 3.43 (br. app. s, 0.8 ×
1
2−6
Compound 1. To a solution of dextran (MW = 35000−45000 g/
mol, 500 mg, 3.09 mmol glucose residue) in anhydrous DMSO (5
2H, CH NHCO), 2.87 (br. app. s, 0.8 × 2H, CH NH), 2.87 (br.
2
2
app. s, 0.8 × 2H, CH NH), 2.39 (br. app. s, 0.8 × 2H, CH CO),
2
2
mL) were added ethyl levulinate dimethyl ketal A ′ (3.55 g, 18.5
2.08 (br. app. s, 0.8 × 2H, ketal-CH ), 1.63−1.35 (m, 0.8 × 3H, ketal-
3
2
mmol), molecular sieves (5 Å, 500 mg), and p-toluenesulfonic acid
CH ), 1.10 (br. app. s, 0.8 × 2H, NHCH CH ).
3
2
3
monohydrate (8.8 mg). The reaction mixture was heated for 2 h at 50
Compound 5. Reaction of compound 1 (50 mg, 0.150 mmol ester)
°
C. Following the general procedure during workup produced
and amine B (656 μL, 6.0 mmol) in anhydrous DMSO (0.5 mL) gave
3
compound 1 as a white powder (802 mg, 0.8 ester per glucose
compound 5 as a white powder (40 mg, 72% yield, 0.8 amine B per
3
1
1
glucose unit). 1H NMR (500 MHz, D O) δ 5.46−4.92(m, 1H,
residue as calculated by its H NMR, and confirmed by the H NMR
2
of its derivatives compound 3 to 8, yield 99%). Due to the rather
glucose-H ), 4.30−3.16 (m, 6H, glucose-H ), 3.46 (br. app. s, 0.8 ×
1
2−6
1
complex and uninterpretable H NMR spectrum in d -DMSO (a good
2H, CH NHCO), 2.89 (br. app. s, 0.8 × 2H, CH N), 2.57 (br. app.
6
2
2
1
solvent for 1), the H NMR of compound 1 was obtained in acidic
s, 0.8 × 6H, (CH ) N), 2.40 (br. app. s, 0.8 × 2H, CH CO), 2.07
3
2
2
D O (pH 2.0), where the attached ketals were cleaved to give water-
(br. app. s, 0.8 × 2H, ketal-CH ), 1.70−1.32 (m, 0.8 × 3H, ketal-CH ).
2
2
3
1
soluble free dextran and ethyl levulinate. H NMR (500 MHz, D O−
Compound 6. Reaction of compound 1 (50 mg, 0.150 mmol ester)
2
DCl-(CD ) SO) δ 5.22−4.76 (m, 1H, glucose-H ), 3.98 (q, 0.8 × 2H,
and amine B (647 μL, 3.0 mmol) in anhydrous DMSO (0.5 mL) gave
3
2
1
4
J = 7.2 Hz, COOCH ), 3.90−3.21 (m, 5H, glucose-H ), 2.73 (t, 0.8
compound 6 as a white powder (65 mg, 89% yield, 0.8 amine B per
2
2−6
4
glucose unit). 1H NMR (500 MHz, D O) δ 5.44−4.92 (m, 1H,
×
2H, J = 6.3 Hz, CH COO), 2.42 (t, 0.8 × 2H, J = 6.3 Hz,
2
2
CH COCH ), 2.06 (s, 0.8 × 3H, CH COCH ), 1.05 (t, 0.8 × 3H, J =
glucose-H ), 4.32−3.03 (m, 6H, glucose-H ), 3.25 (br. app. s, 0.8 ×
3
2
3
2
1
2−6
1
7
.2 Hz, CH CH ). As a reference, the H NMR resonances of a less
2H, CH NHCO), 3.04−2.65 (m, 0.8 × 10H, CH NH, CH NH ),
2
3
2
2
2
2
densely functionalized (0.5 ketal per glucose residue) water-soluble
2.37 (br. app. s, 0.8 × 2H, CH CO), 2.08 (br. app. s, 0.8 × 2H,
2
1
analogue 1′ is provided as follows: H NMR (500 MHz, D O) δ 5.43−
ketal-CH ), 1.88 (br. app. s, 0.8 × 2H, NHCH CH CH NHCO),
2
2
2
2
2
4
3
0
.91 (m, 1H, glucose-H ), 4.29−4.11 (m, 0.5 × 2H, COOCH ), 4.17−
.25 (m, 6H, glucose-H2 ), 2.56 (m, 0.5 × 2H, CH COO), 2.21 (m,
.5 × 2H, ketal-CH ), 1.68−1.36 (m, 0.5 × 3H, ketal-CH ), 1.37−1.22
m, 0.5 × 3H, COOCH CH ) (also see S-1).
1.80 (br. app. s, 0.8 × 2H, NHCH CH CH NH ), 1.65 (br. app. s, 0.8
2 2 2 2
1
2
× 4H, NHCH CH CH CH NH ), 1.65−1.30 (m, 0.8 × 3H, ketal-
−6
2
2
2
2
2
2
CH ).
2
3
3
(
Compound 7. Reaction of compound 1 (50 mg, 0.150 mmol ester)
2
3
Compound 2. To a solution of dextran (MW = 35000−45000 g/
and amine B (618 μL, 3.0 mmol) in anhydrous DMSO (0.5 mL) gave
5
mol, 2.0 g, 12.3 mmol glucose residue) in anhydrous DMSO (20 mL)
were added ethyl 4-(4-formyl-3-methoxy)-phenyl butyrate dimethyl
acetal A ′ (23.1 g, 74.1 mmol), molecular sieves (5 Å, 2.0 g), and p-
compound 7 as a white powder (63 mg, 87% yield, 0.8 amine B per
5
glucose unit). 1H NMR (500 MHz, D O) δ 5.42−4.89 (m, 1H,
2
glucose-H ), 4.31−3.24 (m, 6H, glucose-H ), 3.20 (app. br. s, 0.8 ×
1
0
1
2−6
toluenesulfonic acid monohydrate (35.2 mg). The reaction mixture
was heated overnight at 80 °C. Following the general procedure during
workup produced compound 2 as a white powder (3.35 mg, 0.4 ester
per glucose residue, yield 99%). Due to the same reason as that
2H, CH NHCO), 3.11−2.14 (m, 0.8 × 16H, CH N, CH NH ,
2
2
2
2
CH CO), 2.07 (br. app. s, 0.8 × 2H, ketal-CH ), 1.86−1.75 (m, 0.8
2
2
× 2H, NCH CH CH NHCO), 1.68 (br. app. s, 0.8 × 2H,
2
2
2
NCH
CH
CH
NH
), 1.57−1.27 (m, 0.8 × 3H, ketal-CH ).
3
2
2
2
2
1
described for compound 1, the H NMR of compound 2 was also
Compound 8. Reaction of compound 1 (50 mg, 0.150 mmol ester)
obtained in acidic D O, and the formation of acyclic ketal was
confirmed by the generation of methanol in acidic solution: H NMR
and amine B
compound 8 as a white powder (60 mg, 97% yield, 0.8 amine B
glucose unit). 1H NMR (500 MHz, D
O) δ 5.40−4.92 (m, 1H,
glucose-H ), 4.29−3.18 (m, 6H, glucose-H2−6), 3.37 (m, 0.8 × 2H,
CH CH N), 2.70 (br.
NHCO), 3.09 (br. app. s, 0.8 × 4H, NHCH
app. s, 0.8 × 4H, NHCH CH N), 2.60 (br. app. s, 0.8 × 2H,
NCH CH CO), 2.08
NHCO), 2.38 (br. app. s, 0.8 × 2H, CH
(br. app. s, 0.8 × 2H, ketal-CH ), 1.65−1.30 (m, 0.8 × 3H, ketal-CH ).
Compound 9. Reaction of compound 2 (200 mg, 0.292 mmol
ester) and amine B (195 μL, 2.92 mmol) in anhydrous DMSO (2
6
(786 μL, 6.0 mmol) in anhydrous DMSO (0.5 mL) gave
2
1
per
6
(
×
0
500 MHz, D O−DCl-(CD ) SO) δ 9.77 (s, 0.4 × 1H), 7.65 (dd, 0.4
2
2
3 2
1H, J = 8.3, 1.7 Hz, Ar), 7.51 (d, 0.4 × 1H, J = 1.7 Hz, Ar), 7.22 (d,
1
.4 × 1H, J = 8.4 Hz, Ar), 5.34−4.90 (m, 1H, glucose-H ), 4.24 (t, 0.4
2
2
2
1
×
2H, J = 6.1 Hz, ArOCH ), 4.12 (q, 0.4 × 2H, J = 7.1 Hz,
2
2
2
COOCH ), 4.04−3.39 (m, 6H, glucose-H2−6), 3.33 (s, 0.4 × 3H,
2
2
2
2
CH OH), 2.55 (dd, 0.4 × 2H, J = 9.8, 4.2 Hz, CH CO), 2.15 (p, 0.4
2
3
3
2
×
2H, J = 6.5 Hz, CH CH CH ), 1.21 (t, 0.4 × 3H, J = 7.2 Hz,
2 2 2
CH CH ).
1
2
3
The General Procedure for Introduction of Amines to Dextran
Figure 2). Compound 1 or 2 was dissolved in anhydrous DMSO,
mL) gave compound 9 as a white powder (180 mg, 88% yield, 0.4
1
(
amine B per glucose unit). H NMR (500 MHz, D O) δ 7.28−6.69
1
2
followed by addition of various amines (20−40 eq. amino group per
(m, 0.4 × 4H, Ar), 6.17−5.41 (m, 0.4 × 1H, acetal-H), 5.40−4.90 (m,
ester group). The reaction mixture was then warmed at 50 °C for two
1H, glucose-H ), 4.36−3.18 (m, 6H, glucose-H ; 0.4 × 2H,
1
2−6
1
weeks for completion (monitored by H NMR, until the disappearance
ArOCH ; 0.4 × 3H, ArOCH ; 0.4 × 2H, CH NHCO; 0.4 × 3H,
2
3
2
1
5846
dx.doi.org/10.1021/ja305552u | J. Am. Chem. Soc. 2012, 134, 15840−15848