schisto research community

content appropriate for schistosomiosis research

04 Nov

InChI

Published by RyanPakula

InChI is great and all, but today while exploring, I found two issues that bugged me.  The first arose from my simple double-checking exercise: I drew praziquantel at http://pubchem.ncbi.nlm.nih.gov/edit/ then took the InChI returned and plugged it into chemspider.com to see if it would bring up the appropriate page for PZQ (which I already knew existed).  I made the mistake of leaving one of the amide nitrogens as a carbon, so my search on chemspider returned that there were no hits at all.  Now, in this case that's fine, cause I messed u

03 Nov

"Successful" dehydrogenation

Published by RyanPakula

The sulfur melt dehydrogenation,

was carried out, with 9.5% isolated yield of the desired product and 69.3% recovered starting material.  Other products (observed by TLC) were not found after the column.
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26 Oct

Dehydrogenation of PZQ and final EtOH recrystallization results

Published by RyanPakula

Trying to dehydrogenate PZQ using elemental sulfur.

Total yields including second batch of recrystallization are 86.4%, 74.34% (no second batch), 78.7%, and 80.1%, respective to 0x, 0.5x, 1x, and 2.5x hexanes volume to ethanol volume.
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20 Oct

Ethanol and hexanes - initial results

Published by RyanPakula

V(hexanes) = 0.5*V(EtOH) resulted in the highest recrystallization yield at 74.34%.
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Chromatography of PZQ

Published by RyanPakula on 20 October 2009 - 2:43am

Methods for the purification of PZQ can be collated here.
 
Literature
1. This paper describes the purification of enantiopure PZQ using "chloroform/methanol 0–0.3% MeOH as a solvent system."
2. This paper uses 1:1 EtOAc/petroleum ether ramping to pure EtOAc.
3. This paper uses "thick layer preparative chromatography [prep TLC] benzene/ethyl acetate 1/1, silica gel."
 

Recrystallization of PZQ

Published by RyanPakula on 20 October 2009 - 2:34am

This page details attempts to optimise the recrystallization of praziquantel. Anybody can add to/edit this page.
 
Literature
1. This patent (US patent 4,523,013) recrystallizes PZQ from "a mixture of petroleum ether and acetone," obtaining a 95% yield on the reaction.
2. This paper recrystallizes from ethyl acetate and hexanes to obtain a 70% yield on the reaction.
 

Purification of Praziquantel

Published by RyanPakula on 20 October 2009 - 2:31am

This is a parent page for improving the current methods for the purification of PZQ.

19 Oct

Ethanol and hexanes

Published by RyanPakula

EtOH with hexanes had wispy crystals; recovery was 43.98%; pure by NMR; Tm = 138.2-138.8ºC.  No crystals had formed from benzene sl'n nor toluene, so hexanes were added, and vials left at 5ºC.  Began EtOH with varying amounts of hexanes recrystallizations.
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1 mL hexanes was added to the solution of benzene (1.4 mL), and 2 mL hexanes were added to the toluene solution (3 mL).  After a few hours at 5ºC, crystals have begun to form.
 

16 Oct

Ethanol results and a slew of other solvents

Published by RyanPakula
59.27% PZQ was recovered from ethanol heated to 50 ± 2ºC.  NMR was clean, Tm = 138.3 - 138.6ºC.
Began recrystallizations with water, ethanol, 50/50 water/ethanol, toluene, and benzene.
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15 Oct

Toluene

Published by RyanPakula

Toluene worked less-than-nicely for recrystallization, and a column to isolate the yellow/brown product failed.  This is likely due to the fact that a crude NMR of this product looks 99% identical to PZQ from the bottle.
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