2.8 Hz, 1H), 7.33 (d, J = 2.3 Hz, 1H), 7.31 (dd, J = 8.6, 2.4 Hz,
1H), 3.94 (s, 3H); 13C NMR (101 MHz, CD3OD) δ 162.81,
161.37, 154.90, 151.99, 129.44, 125.11, 125.05, 124.34, 122.70,
119.20, 116.04, 112.30, 110.67, 56.23; HRMS (ESI-) calculated
for C14H9O7S- (M-H)-: 321.0074, found: 321.0075.
124.28, 117.21, 111.93, 111.84, 9.73; HRMS (ESI-) calculated
for C9H8NO4S- (M-H)-: 226.0180, found: 226.0163.
2.7. 4-Ethylphenyl sulfate (10)
1
White solid, yield 76 %, HPLC r.t. = 13 min; H NMR (500
MHz, CD3OD) δ 7.25 – 7.08 (m, 4H), 2.62 (q, J = 7.6 Hz, 2H),
1.21 (d, J = 15.2 Hz, 3H); 13C NMR (126 MHz, CD3OD) δ 151.6,
141.7, 129.0, 122.2, 28.9, 16.0; HRMS (ESI-) calculated for
C8H9O4S- (M-H)-: 201.0227, found: 201.0219.
2.3. Synthesis of 5-Methoxy-3-methylindole (31)
The methylation of 5-methoxyindole was based on the
procedure
by
Amir-Heidari
and
Micklefield.[19]
Methylmagnesium bromide (1.75 mL, 3.0 M in diethyl ether,
5.25 mmol) was added to 5-methoxyindole (736 mg, 5.00 mmol)
in anhydrous THF (10 mL) and stirred at room temperature for
20 min under an atmosphere of nitrogen. Methyl iodide (355 mg,
156 μL, 2.50 mmol) in THF (1 mL) was then added dropwise
over 20 min, and the reaction mixture was stirred under an
atmosphere of nitrogen for 5 days. The reaction was quenched
with NH4Cl solution (15 mL, 5 % w/w), then extracted with ethyl
acetate (4 x 15 mL). The organic extracts were dried over MgSO4
and the solvent was removed under reduced pressure. The residue
was purified by silica column chromatography (EtOAc/hexane
1:19 v/v) to yield product 31 (r.f. 0.50 in EtOAc/hexane 1:4 v/v)
as a white solid (94 mg, 23 %).
1H NMR (400 MHz, CD3OD) δ 7.79 (br s, 1H), 7.23 (d, J =
8.8 Hz, 1H), 7.05 (s, 1H), 6.95 (s, 1H), 6.88 (d, J = 8.8 Hz, 1H),
3.90 (s, 3H), 2.33 (s, 3H); 13C NMR (101 MHz, CD3OD) δ 154.0,
131.6, 128.7, 122.6, 112.2, 111.8, 111.5, 100.8, 56.1, 9.9;
HRMS (ESI+) calculated for C10H12NO+ (M+H)+: 162.0913,
found: 162.0915.
2.8. Resorcinol sulfate (11)
To avoid bis-sulfation, the reagent equivalents from the
general procedure were decreased 2.5-fold.
1
Dark-yellow oil, yield 62 %, HPLC r.t. = 7 min; H NMR
(400 MHz, CD3OD) δ 7.10 (t, J = 8.0 Hz, 1H), 6.78 (d, J = 1.7
Hz, 1H), 6.76 (dd, J = 2.1, 0.8 Hz, 1H), 6.58 (dt, J = 8.3, 1.3 Hz,
+
1H), 2.83 (s, residual HNMe3 ); 13C NMR (101 MHz, CD3OD) δ
159.3, 154.9, 130.4, 113.4, 112.9, 109.7, 45.6; HRMS (ESI-)
calculated for C6H5O5S- (M-H)-: 198.9863, found: 198.9846.
2.9. p-Coumaric acid sulfate (12)
1
White solid, yield >99 %, HPLC r.t. = 3 min; H NMR (400
MHz, D2O) δ 7.57 (dd, J = 8.5, 1.3 Hz, 2H), 7.36 (d, J = 16.0 Hz,
1H), 7.29 (d, J = 8.6 Hz, 1H), 6.46 (d, J = 16.0 Hz, 1H), 1.90 (s,
residual CH3CO2NH4); 13C NMR (101 MHz, D2O) δ 175.92
(residual CH3CO2NH4), 153.63, 140.28, 133.88, 129.63, 125.75,
122.48, 24.34 (residual CH3CO2NH4); HRMS (ESI-) calculated
for C9H7O6S- (M-H)-: 242.9969, found: 242.9954.
2.4. Synthesis of 5-Hydroxy-3-methylindole (8)
2.10. Vanillic acid 4-sulfate (13)
1
A solution of boron tribromide (190 µL, 1.0 M in heptane, 190
µmol) was added to a solution of 5-methoxy-3-indole (15.3 mg,
95 µmol) in anhydrous DCM (1 mL). The reaction vessel was
sealed and stirred at room temperature for 16 h. The reaction was
then quenched with water (10 mL) and extracted with DCM (3 ×
10 mL). The organic extracts were combined, dried over MgSO4,
and the solvent was removed under reduced pressure. The residue
was purified by silica column chromatography (DCM followed
by DCM/MeOH 99:1 v/v) to yield 8 (r.f. 0.66 in DCM/MeOH
99:1 v/v) as a colorless oil (1.5 mg, 11 %).
White solid, yield 93 %, HPLC r.t. = 3 min; H NMR (400
MHz, D2O) δ 7.62 (d, J = 1.9 Hz, 1H), 7.51 (dd, J = 8.4, 1.9 Hz,
1H), 7.42 (d, J = 8.3 Hz, 1H), 3.90 (s, 3H), 1.90 (s, 3H, residual
CH3CO2NH4); 13C NMR (101 MHz, D2O) δ 181.34 (residual
CH3CO2NH4), 174.81, 151.75, 143.87, 136.10, 122.86, 122.42,
114.83, 56.82, 24.34 (residual CH3CO2NH4); HRMS (ESI-)
calculated for C8H7O7S- (M-H)-: 246.9918, found: 246.9916.
2.11. Isovanillic acid 3-sulfate (14)
1
White solid, yield >99 %, HPLC r.t. = 3 min; H NMR (400
1H NMR (400 MHz, CD3OD) δ 7.20 (dd, J = 8.6, 0.6 Hz, 1H),
6.97 (dd, J = 2.5, 0.5 Hz, 1H), 6.95 (s, 1H), 6.76 (ddd, J = 8.6,
2.5, 0.4 Hz, 1H), 2.27 (d, J = 1.1 Hz, 3H)2.22 (d, J = 1.1 Hz, 3H),
6.64 (dd, J = 8.6, 2.4 Hz, 1H), 6.85 (dd, J = 2.4, 0.6, 1H), 6.91
(app q, J = 1.2 Hz, 1H), 7.13 (dd, J = 8.6, 0.6 1H); 13C NMR (101
MHz, CD3OD) δ 152.2, 131.0, 130.2, 124.0, 112.4, 112.1, 110.2,
103.5, 9.8; HRMS (ESI+) calculated for C9H10NO+ (M+H)+:
148.0757, found: 148.0762.
MHz, CD3OD) δ 7.90 (s, 1H), 7.77 (d, J = 8.8 Hz, 1H), 7.11 (dd,
J = 8.8 Hz, 4 Hz, 1H), 3.90 (s, 3H), 1.91 (s, residual
CH3CO2NH4) ; 13C NMR (101 MHz, CD3OD) δ 175.1, 155.1,
141.1, 131.0, 129.1, 124.9, 113.3, 57.2, 24.6 (residual
CH3CO2NH4); HRMS (ESI-) calculated for C8H7O7S- (M-H)-:
246.9918, found: 246.9907.
2.12. 2-Methoxy-4-vinylphenyl sulfate (15)
1
White solid, yield 22 %, HPLC r.t. = 3 min; H NMR (400
2.5. General sulfation procedure
MHz, CD3OD) δ 7.40 (d, J = 8.3 Hz, 1H), 7.09 (d, J = 2.0 Hz,
1H), 6.96 (dd, J = 8.3, 2.0 Hz, 1H), 6.69 (dd, J = 17.6, 10.9 Hz,
1H), 5.72 (dd, J = 17.6, 1.0 Hz, 1H), 5.18 (dd, J = 10.9, 1.0 Hz,
1H), 3.85 (s, 3H); 13C NMR (101 MHz, CD3OD) δ 153.25,
153.08, 143.57, 142.72, 137.75, 136.70, 123.61, 119.63, 113.61,
111.53, 56.54; HRMS (ESI-) calculated for C9H9O5S- (M-H)-:
229.0176, found: 229.0172.
To a solution of phenol (1 eq) and NaOH (3 eq) in water were
added NaHCO3 (4 eq) and SO3•NMe3 complex (2.5 eq). The
reaction mixture was stirred at room temperature for four days
and concentrated in vacuo. The crude product was subjected to
HPLC purification [0-5 min (0 % B), 5-20 min (0-100 % B) at a
flow of 2.5 mL/min; buffer A = ammonium acetate 5 mM (water)
and buffer B = ammonium acetate 5 mM (MeOH)] to afford the
corresponding sulfate ester.
2.13. UPLC MS/MS conditions
Two different mass spectrometers were used for UPLC-
MS/MS analysis. Water with 0.1% formic acid was used as
mobile phase A and methanol with 0.1% formic acid was used as
mobile phase B in both cases. The system was controlled using
the MassLynx software package v 4.1 from Waters
2.6. 3-Methylindole-5-O-sulfate (6)
1
White solid, Yield 74 %, HPLC r.t. = 3 min; H NMR (500
MHz, CD3OD) δ 7.44 (d, J = 2.3 Hz, 1H), 7.23 (dd, J = 8.9, 1.7
Hz, 1H), 7.06 (dd, J = 8.8, 2.2 Hz, 1H), 6.99 (s, 1H), 2.27 (s,
3H); 13C NMR (126 MHz, CD3OD) δ 146.66, 135.74, 129.58,