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Racemic Resolution of Praziquantel and Praziquanamine
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22nd January 2012 @ 10:43
Mnr: 1-10

Hazard and Risk Assessment: As for MNR2-1

rac-PZQamine (2.65 g, 13.10 mmol) and (+)-dibenzoyl-D-tartaric acid. 2IPA (6.27 g, 13.10 mmol) was dissolved in a mixture of isopropanol (60 mL) and water (10 mL) by taking to reflux. The solution was allowed to cool to room temperature and stand overnight. The solid was then filtered and rinsed with IPA/water (5:1).

The salt was dissolved in a mixture of i-PrOH (80 mL) and water (20 mL) by heating. It was then allowed to cool to room temperature and stand overnight, filtered and washed with IPA/Water.

The salt was then mixed with water (20 mL) and taken to pH 11 with the addition of NaOH solution (2M) and extracted with DCM (25 ml x 4) and the aqueous layer was pH adjusted to pH 2 using 2M HCl. The organic fractions were combined, washed with brine (30 mL) and dried over magnesium sulphate, filtered and concentrated under reduced pressure to give a white solid (0.886 g, 4.38 mmol, 67 %).

The combined washings from the two crystalisations were concentrated and mixed with water (20 mL) and taken to pH 11 with the addition of NaOH solution (2M) and extracted with DCM (25 ml x 4) and the aqueous layer was pH adjusted to pH 2 using 2M HCl. The organic fractions were combined, washed with brine (30 mL) and dried over magnesium sulphate, filtered and concentrated under reduced pressure to give a yellow solid (1.471 g, 7.27 mmol)

Total PZQ-amine recovered (2.357 g, 11.65 mmol, 89 %)

The aqueous layers were combined in an attempt to recover the resolving agent. Nothing precipitated out over night so the volume was reduced under vacuum.

Characterisation

mnr02-1_1H.pdf
mnr1-2.zip

1H NMR (300 MHz, CDCl3): d = 7.31-7.10 (m, 3H), 4.92-4.78 (m, 2H), 3,81-3,48 (m, 3H), 3.09-2.69 (m, 4H), 2.25 (br, NH).

mnr02-1_13C.pdf
mnr1-2.zip

13C NMR (CDCl3, 75 MHz): d= 167.2, 134.9, 134.1, 129.4, 127.1, 126.7, 124.7, 56.8, 49.9, 49.7, 38.8, 28.8.

HRMS 

HRMS - MNR2-4

IR 

5e S IR MNR2-2.jpg

m.p. 117–118°C.

Lit m.p. - 120 °C - Patent number: 3993760

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Attached Files
MNR2.png
mnr2-4_table.PNG
mnr02-1_1H.pdf
mnr02-1_13C.pdf
mnr1-2.zip
5e S IR MNR2-2.jpg
HRMS - MNR2-4