Racemic Resolution of Praziquantel and Praziquanamine

 

Hazard and Risk Assessment:


Procedure:
rac-MNR12-5 () was dissolved in a mixture of EtOH (80 mL) and 1M HCl (420 mL(85 mL in 1 L)) and heated to reflux for 14 h. The solution was allowed to cool to room temperature then cooled in an ice bath, basified with NaOH pellet (approx 22 g, pellets used to minimise volume of aqueous material) to pH 12-13 and extracted with DCM (4 x 200 mL). The organic fractions were combined, dried over magnesium sulphate, filtered and concentrated under reduced pressure to give a dark red/brown solid.

Attempted recrystallized in toluene:hexane (60:6 mL) and left in the freezer for 4 hours. Very little sold/crystals had formed but were filtered off and washed with hexane to give a brown solid.

1st filter 1.464 g
2nd filter 1.257 g

Crude remaining 3.679 g (brown sticky solid)

Total recovered 6.4 g, 60 % - low yield, nothing left in aq layer as it was washed with EtOAc. Starting material not the cleanest? But still a rather low yield.



Melting point 120-121 °C