Example 3
Synthesis of Rotigotine-2-Azidoacetate
In a 25 mL round bottom flask, was placed rotigotine
(1 g, 3.17 mmol, 1 equiv.), 2-azidoacetic acid-DMAP salt (0.849 g, 3.80
mmol, 1.2 equiv.) and 32 mL of anhydrous dichloromethane (DCM) and the
mixture stirred under argon. DMAP (0.077 g, 0.634 mmol, 0.2 equiv.) and
DCC (0.785 g, 3.80 mmol, 1.2 equiv.) were added as solids. The mixture
was stirred for 16 hours at room temperature. The mixture was then
filtered to remove precipitated urea and concentrated using a rotary
evaporator. The crude mixture was first purified by silica gel column
chromatography using a mixture of ethyl acetate and hexanes (1:2) as an
eluent to give a clear yellow oil (1.27 g, 92% yield).
A second purification was performed by reversed phase chromatography to remove free rotigotine and other small molecule impurities. A sample solution for loading was prepared by dissolving crude product (350 mg) in 0.1% TFA in acetonitrile (4.05 mL), followed by addition of 1 N HCl (0.91 mL) and 0.1% TFA in water (4.04 mL). The sample solution was filtered through a 0.2 μm PTFE syringe filter, and then loaded to a Waters SunFire Prep C18 OBD 30/250 Column (from Waters) on an ÄKTA Purifier system equipped with an UV detector at 214 nm. 0.1% TFA in water (A) and 0.1% TFA in acetonitrile (B) were used as mobile phase. The column was then eluted isocratically with 40% of mobile phase B at flow rate of 20 mL/min. The fractions that contained pure product were collected and pooled. Acetonitrile in the pooled fraction was evaporated by rotary-evaporation. The remaining aqueous solution was extracted with DCM (3×50 mL), dried over anhydrous sodium sulfate and filtered, followed by evaporation of the DCM. The residue was dried in vacuum (293 mg, 83%).
1H NMR (Varian, 500 MHz, 10 mg/mL CDCl3)
showed peaks at 0.90 ppm (t, J=6.84 Hz, 3H), 1.25 (m, 1H), 1.29 (m,
1H), 1.49 (m, 1H), 1.59 (m, 1H), 2.05 (m, 2H), 2.54 (m, 3H), 2.82 (m,
3H), 2.97 (m, 3H), 4.156 N3CH2C(═O)O— (s, 2H), 6.81 (s, 1H), 6.88 (d, J=7.81 Hz, 1H), 6.92 (t, J=3.42 Hz, 1H), 7.02 (d, J=7.32 Hz, 1H), 7.13 (m, 2H).
RP-HPLC analysis showed that the product contained no free rotigotine. The HPLC chromatogram of product before (FIG. 1A) and after (FIG. 1B) reversed phase chromatography purification are shown.
https://www.google.com/patents/US8383093
A second purification was performed by reversed phase chromatography to remove free rotigotine and other small molecule impurities. A sample solution for loading was prepared by dissolving crude product (350 mg) in 0.1% TFA in acetonitrile (4.05 mL), followed by addition of 1 N HCl (0.91 mL) and 0.1% TFA in water (4.04 mL). The sample solution was filtered through a 0.2 μm PTFE syringe filter, and then loaded to a Waters SunFire Prep C18 OBD 30/250 Column (from Waters) on an ÄKTA Purifier system equipped with an UV detector at 214 nm. 0.1% TFA in water (A) and 0.1% TFA in acetonitrile (B) were used as mobile phase. The column was then eluted isocratically with 40% of mobile phase B at flow rate of 20 mL/min. The fractions that contained pure product were collected and pooled. Acetonitrile in the pooled fraction was evaporated by rotary-evaporation. The remaining aqueous solution was extracted with DCM (3×50 mL), dried over anhydrous sodium sulfate and filtered, followed by evaporation of the DCM. The residue was dried in vacuum (293 mg, 83%).
RP-HPLC analysis showed that the product contained no free rotigotine. The HPLC chromatogram of product before (FIG. 1A) and after (FIG. 1B) reversed phase chromatography purification are shown.
https://www.google.com/patents/US8383093
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