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Racemic Resolution of Praziquantel and Praziquanamine
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5th June 2012 @ 11:47
Mnr: 21-30
Test reaction to see if crude MNR11-16 can be hydrolysed cleanly to MNR26-4

MNR26-4%20scheme.png
mnr26-4%20table.PNG

Hazard and Risk Assessment:
HIRAC MNR7.pdf


Procedure:
MNR11-16 ( 0.40 g, 1.07 mmol) was dissolved in a mixture of EtOH (2 mL) and 1M HCl (10 mL) 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 to pH 8 and extracted with EtOAc (3 x 20 mL). The organic fractions were combined, dried over magnesium sulphate, filtered and concentrated under reduced pressure to give an orange oil (0.167 g). The aqueous layer was then pH adjusted to pH14 and extracted again with EtOAc (2 x 20 mL). he organic fractions were combined, dried over magnesium sulphate, filtered and concentrated under reduced pressure to give an orange oil (0.028 g).

Total mass recovered - 0.195 g, 69 % -cyclohexyl impurities

mnr26-4_pH8.pdf
mnr26-4_pH14.pdf


Crude 1H NMRS of both fractions showed mainly product with some cyclohexyl-like side product. The fractions were combined and attempts to recrystallise using toluene and hexane were attempted.

1 - toluene (1 pipette), heat to dissolve the contents then hexane (1 pipette) added. white precipitate crashed out immediately so toluene (1pipette) was added and the the mixture heated again to get everything back into solution. Mixture left in the freezer for XX hours.

Characterisation

mnr26-4_pH8.pdf
mnr26-4_pH8.zip


1H NMR (300 MHz, CDCl3): d = 6.64 (s, 1H), 6.59 (s, 1H), 4.96-4.86 (m, NH), 4.74 (dd, J = 9.9, 4.3 Hz, 1H), 3.87 (s, 3H), 3.86 (s, 3H), 3.75-3.49 (m, 2H), 3.05-2.59 (m, 6H).

mnr26-1_1H.pdf
mnr26-1.zip


1H NMR (500 MHz, DMSO): d = 7.00 (s, 1H), 6.92 (s, 1H), 4.93-4.81 (m, 2H), 3.93 (s, 3H), 3.92 (s, 3H), 3.62-3.39 (m, 3H), 2.93-2.78 (m, 3H), 2.71 (t, J = 11.5 Hz, 1H)

Lit m.p. 137.1 to 137.88 C Tang, H., C.-h. Zheng, et al. (2010). "Design and Synthesis of Novel Pyrazino[2,1-a]isoquinolin Derivatives with Potent Antifungal Activity." Archiv der Pharmazie 343(6): 360-366.
Linked Entries
Attached Files
mnr26-4 table.PNG
MNR26-4 scheme.png
mnr26-4_pH8.pdf
mnr26-4_pH14.pdf
mnr26-1.zip
mnr26-1_1H.pdf
mnr26-4_pH8.zip