Racemic Resolution of Praziquantel and Praziquanamine

 

Mnr: 21-30
Based on the potential success of mnr27-23, a small scale up is required to attempt a second crystallisation and also a longer crystallisation period should be looked at to improve the yield of the crystals recovered.

Screening conditions for optimum resolution of MNR26-1 with various tartaric acids previously synthesised in the lab





Hazard and Risk Assessment:
As for MNR2-1

MNR27-26

MNR26-1 (0.220 g, 0.84 mmol) and CS-3-1 (0.36 g, 0.84 mmol) was dissolved in isopropanol (8 mL) and water (8 mL) in a conical flask and heated with the heat gun to dissolve the reagents. After reaching room temperature, the conical flask was left to sit overnight. In the morning, no crystals had formed to the flask was covered with parafilm and moved to the fridge. After 24 hours in the fridge the solution had turned into a gel therefore the flask was removed from the fridge and left to stand on the bench over the weekend

MNR27-27

*This may not work as well but the material was recovered so it was just used as a test.

MNR26-1 (recovered from 27-2 - 27-11)(0.48 g, 1.83 mmol) and MNR6-1 (0.92 g, 1.83 mmol) was dissolved in isopropanol (18 mL) and water (18 mL) in a conical flask and heated with the heat gun to dissolve the reagents. After reaching room temperature, the conical flask was left to sit overnight. In the morning, no crystals had formed to the flask was covered with parafilm and moved to the fridge. No crystals after 24 hours in the fridge, left over the weekend.


MNR27-28 - concentrated version of 27-23

MNR26-1 (0.120 g, 0.46 mmol) and CS-3-1 (0.20 g, 0.46 mmol) was dissolved in isopropanol (2.5 mL) and water (2.5 mL) in a conical flask and heated with the heat gun to dissolve the reagents. After reaching room temperature, the conical flask was sealed with parafilm and moved to the fridge. After 2 hours in the fridge the solution had turned into a gel therefore the flask was removed from the fridge and left to stand on the bench overnight. Some crystals had formed and the solution was filtered to give a light brown solid (0.279 g).

A portion (0.095 g) of the solid was was mixed with water (2 mL) and taken to pH 11 with the addition of NaOH solution (2M) and extracted with DCM (4 ml x 3). The organic fractions were combined, dried over magnesium sulphate, filtered and concentrated under reduced pressure to give XXX

The remainder of the solid was taken up in IPA (2 mL) and water (2 mL) in an attempt to recrystallise the salt.

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MNR27-29

21/08/12
What looked like MNR26 was found on the bench so an attempt at a resolution was attempted although the purity and quality of the SM is not clear as it had been sitting around on the bench for a while.

SM (1.7 g, 6.48 mmol) and MNR6-1 (3.1 g, 6.48 mmol) was dissolved in IPA (30 mL) and water (3 mL) was added. The dark brown solution was left to stand for 5 hours at room temperature in which time nothing happend so was transferred to the the freezer overnight. In the morning the solution was frozen so it was allowed to warm at room temperature and still nothing crystallised. Hexane (10 mL) was added dropwise forming a white precipitate which went back into solution upon swirling of the flask. The mixture was allowed to stand for 4 hour at which point something had crystalised out. The solid was filtered and washed with IPA:Hex (50:50) and dried to give