I have a mixture between one flavanone and one chalcone and I can't separate them.
When I test the mixture in differents mobile phases in TLC, they are togheter and I see one dark spot, and then that spot become yellow. I analyzed this mixture with HRMS [M-H] -, and I can see only the mass from the flavanone, in NMR appeared the signals from the two compounds. They aren't interconverting because theirs structures differ in substituents.
Maybe you can modify one or both of your compounds with protecting groups (depending on the functional groups of your compounds) which change the polarity of the compound(s) and probably lead to separable spots. After separation you can remove the protecting group(s) from the purified intermediates again.
Thanks a lot Mr Bernhard, I will consider your suggestion!!Best regards!
Good evening Mr Wael Zeinyeh,
I know the exact structure of two compounds, because in the NMR spectra there are the signals of both, furthemore I could separate some mg of the flavanone from the mixture, so I could elucidate the exact structure of it, but the chalcone is still mix with the flavanone, and I can't separate them totally, so the chalcone structure I obtained by subtracting the signals.
Because of that, at first I thought that they was interconverting, but as flavanone has a methoxy and the chalcone not have, I concluded that only are mixed.
Sincerely I don't know why doesn't appear two signals in mass spectra.The person who made me the mass spectrum was delayed a few weeks to inject the sample, which makes me think,once again that inter turned everything into flavanone.
It is quite complicated to explain and I got me quite confused !!
I hope you have understood me!
Best regards!!
Probably your compounds contain phenolic hydroxyl groups, which are responsible for the similar binding energy in TLC analysis. If you need just to prove that you have two compounds, i suggest to react small amount with diazomethane, in order for the phenolic groups to be converted into a methoxy groups. Then, you will have different behavior of the two compounds. Otherwise, you can try reverse phase HPLC analysis.
Hi Daniela, I had a similar problem trying to separate several structurally similar biflavonoids (biflavanones and dichalcones), joined at the alpha-carbon. They could be partially separated using two dimensional paper chromatography, but conventional phase chromatography on silica (and similar phases) was ineffective. I used gradient chromatography (water-ethanol phase) on Sephadex LH20 and achieved a good separation at preparative scale. Prepare the Sephadex carefully - it is rather fragile and inclined to produce fines if treated roughly. I would recommend NOT derivatizing the mixture - it will be difficult to distinguish derivatized natural product from artefacts that may form during the reaction. Once you have separated and characterised the molecule, then derivatize to verify your structure. regards
Mr Neale, thank you very much for your contribution, I will test the separation column LH20 !! ... then I tell him as I was !!
Best Regards!!!
Hi Daniela
As long as you find the characteristic signals for flavanones and chalcones, you have the two structures with no doubt. It is not necessary to see the two structures on HRMS. it depends on further factors such as ion modes. In my small view, I suppose to try DCM/Toluene (mobile phase). Can one of these structure be degraded or have specific colour in acidic media, if yes, put the TLC in H2SO4 (may be you can find one of those in obvious color and follow it.
You can try with mobile phase TOLUENE ETHYLACETATE AND GLACIAL ACETIC ACID (65:34:1) THAT WILL SEPARATE