Racemic Resolution of Praziquantel and Praziquanamine

 

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

MNR27-12

MNR26-1 (0.08 g, 0.3 mmol) and CS-2-1 (0.12 g, 0.3 mmol) was dissolved in isopropanol (3 mL) and water (1 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature, hexane (1 mL) was added and the vial was allowed to stand overnight. In the morning a solid had crashed out but not crystalline.

The vial was then capped and left sitting, after 5 days the solution had gone solid and started to show signs of crystals forming. IPA (3 mL) was added, heated with the heat gun (not everything went back into solution), capped and left overnight.

In the morning, the vial contained a what looked like a messy solid, thought best not to take forward.

MNR27-13

MNR26-1 (0.08 g, 0.3 mmol) and CS-3-1 (0.13 g, 0.3 mmol) was dissolved in isopropanol (2 mL) and water (1 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature, hexane (1 mL) was added and the vial was allowed to stand overnight. In the morning nothing had crashed or crystallised out.

Water (1 mL) and hexane (1 mL) was added to the vail and heated to get the cloudy mixture back to a transparent solution and was then allowed to cool and then sit at room temperature for another 24 hours by which time the mixture had gone completely solid.

The vial was then capped and left sitting, after 5 days the solid started to show signs of crystals forming. IPA (3 mL) was added, heated with the heat gun, capped and left overnight.

After standing overnight, what looked like crystals had formed so the reaction mixture filtered with IPA/hexane (1:1) to give a white solid not very crystalline.

The salt (0.013 g) was mixed with water (4 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 an pale brown solid (0.002 g, 0.007 mmol, 2 %).


MNR27-14

MNR26-1 (0.08 g, 0.3 mmol) and KB-PZQ-1003 (0.15 g, 0.3 mmol) was dissolved in isopropanol (1 mL) and water (1 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature, hexane (1 mL) was added and the vial was allowed to stand overnight. In the morning crystals had formed but the vial had gone dry. IPA (2 mL), water (2 mL) and hexane (2 mL) were added and the mixture heated to redissolve the crystals (not everything went back into solution as I couldn't heat the vial to reflux) and the vial was left to stand at room temperature for another 24 hours by which time the mixture was very thick but crystals were present. Filtered and washed with IPA/Hexane to give light brown fluffy crystals

The salt (0.133g, 0.193 mmol, 56 %) was mixed with water (4 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 an pale brown solid (0.032 g, 0.122 mmol, 40 %).

Taken onto MNR28-1

MNR27-15

MNR26-1 (0.08 g, 0.3 mmol) and MW46-6 (0.13 g, 0.3 mmol) was dissolved in isopropanol (6 mL) and water (2 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature, hexane (1 mL) was added and the vial was allowed to stand overnight. In the morning nothing had crashed or crystallised out.

Water (4 mL) and hexane (3 mL) was added to the vail and heated to get the cloudy mixture back to a transparent solution and was then allowed to cool and then sit at room temperature for another 24 hours by which time the mixture had gone crusty on top.

After 6 days the reaction mixture was filtered with IPA/hexane (1:1) to give a brown solid not very crystalline.

The salt (0.123 g) was mixed with water (4 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 an pale brown solid (0.0XX g, 0.00X mmol, XX %).


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MNR27-16

MNR26-1 (0.08 g, 0.3 mmol) and MNR6-1 (0.15 g, 0.3 mmol) was dissolved in isopropanol (1 mL), hexane (1 mL) and water (1 mL) in a vial and heated with the heat gun to dissolve the reagents. The mixture was allowed to reach room temperature and allowed to stand overnight by which time the mixture had gone completely solid.

The vial was then capped and left sitting, after 5 days the solid started to show signs of crystals forming. IPA (3 mL) was added, heated with the heat gun, capped and left overnight.

In the morning everything was still in solution so it was just left to stand longer.

MNR27-17

MNR26-1 (0.08 g, 0.3 mmol) and MNR6-1 (0.15 g, 0.3 mmol) was dissolved in isopropanol (2 mL)and water (2 mL) in a vial and heated with the heat gun to dissolve the reagents. The mixture was allowed to reach room temperature and allowed to stand overnight by which time the mixture was still a solution.

The vial was then capped and left sitting, after 5 days the solution had gone solid and started to show signs of crystals forming. IPA (3 mL) was added, heated with the heat gun, capped and left overnight.

In the morning everything was still in solution so it was just left to stand longer.

MNR27-18

MNR26-1 (0.08 g, 0.3 mmol) and MNR6-1 (0.15 g, 0.3 mmol) was dissolved in isopropanol (2 mL), hexane (2 mL) and water (2 mL) in a vial and heated with the heat gun to dissolve the reagents. The mixture was allowed to reach room temperature and allowed to stand overnight by which time the mixture was still a solution.

The vial was then capped and left sitting, after 5 days the solid started to show signs of crystals forming. IPA (3 mL) was added, heated with the heat gun, capped and left overnight.

**It looks like MNR6-1 is a lot more soluble than the acids used above and therefore reducing the chances of the salt crystallising out of the solution.

In the morning everything was still in solution so it was just left to stand longer.

MNR27-19

MNR26-1 (0.08 g, 0.3 mmol) and CS-2-1 (0.12 g, 0.3 mmol) was dissolved in isopropanol (1.5 mL), hexane (1.5 mL) and water (1.5 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature the mixture was allowed to stand overnight by which time the mixture had gone completely solid.

The vial was then capped and left sitting, after 5 days the solid started to show signs of crystals forming. IPA (3 mL) was added, heated with the heat gun, capped and left overnight.

After standing overnight, what looked like crystals had formed so the reaction mixture was filtered with IPA/hexane (1:1) to give a white solid not very crystalline.

The salt (0.031 g) was mixed with water (4 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 an pale brown solid (0.002 g, 0.007 mmol, 2 %).


MNR27-20

MNR26-1 (0.08 g, 0.3 mmol) and CS-3-1 (0.13 g, 0.3 mmol) was dissolved in isopropanol (1.5 mL), hexane (1.5 mL) and water (1.5 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature,the vial was allowed to stand overnight by which time the mixture had crystallised and was filtered with IPA/hexane to give a light brown solid - not as crystalline as mnr27-14.

The salt (0.168 g, 0.216 mmol, 70 %) was mixed with water (4 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 an pale brown solid (0.036 g, 0.137 mmol, 45 %).

Taken onto MNR28-2

MNR27-21

MNR26-1 (0.08 g, 0.3 mmol) and MW46-6 (0.13 g, 0.3 mmol) was dissolved in isopropanol (1.5 mL), hexane (1.5 mL) and water (1.5 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature the vial was allowed to stand overnight by which time the mixture had gone completely solid.

The vial was then capped and left sitting, after 5 days the solid started to show signs of crystals forming. IPA (3 mL) was added, heated with the heat gun, capped and left overnight.

In the morning everything was still in solution so it was just left to stand longer. After 3-4 days crystals/solid started to appear. The vial was left standing over the weekend (another 3 days)

The crystals were filtered and rinsed with IPA/Hex/water and dried to give an off white solid (0.105 g). The solid was mixed with water (4 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 an white solid xxxxx

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MNR27-22

MNR26-1 (0.08 g, 0.3 mmol) and CS-2-1 (0.12 g, 0.3 mmol) was dissolved in isopropanol (1.5 mL), water (4.5 mL) and hexane (3 mL) (*hexane was added by mistake) in a vial and heated with the heat gun. The reagents did not want to disolve in this mixture and the reaction was not taken any further.


MNR27-23

MNR26-1 (0.08 g, 0.3 mmol) and CS-3-1 (0.12 g, 0.3 mmol) was dissolved in isopropanol (3 mL) and water (3 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature, the vial was capped and left to stand overnight.

After standing overnight, what looked like crystals had formed so the reaction mixture filtered with IPA/hexane (1:1) to give a white solid not very crystalline.

The salt (0.052 g, 0.075 mmol, 25 %) was mixed with water (4 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 an white solid (0.012 g, 0.039 mmol, 13 %).


MNR27-24

MNR26-1 (0.08 g, 0.3 mmol) and CS-2-1 (0.12 g, 0.3 mmol) was dissolved in isopropanol (4.5 mL) and water (1.5 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature, the vial was capped and left to stand overnight.

After standing overnight, what looked like crystals had formed so the reaction mixture was filtered with IPA/hexane (1:1) to give a white solid not very crystalline.

The salt (0.023 g) was mixed with water (4 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 an pale brown solid (0.0XX g, 0.00X mmol, XX %).



MNR27-25

MNR26-1 (0.08 g, 0.3 mmol) and CS-2-1 (0.12 g, 0.3 mmol) was dissolved in isopropanol (1.5 mL) and water (4.5 mL) in a vial and heated with the heat gun to dissolve the reagents. After reaching room temperature, the vial was capped and left to stand overnight.

In the morning everything was still in solution (although it looked cloudy) so it was just left to stand longer.

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HPLC

Using a solvent system of 15% EtOH/Hex + TEA 0.1% it was found that you can observe partial separation of the racemic amine.



MNR27-13
too dilute to HPLC
MNR27-15

what looks like a good ee, this should be improved with a second recrystallisation step but will need to scale up first.
MNR27-24