Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: Arkan on July 26, 2014, 06:25:53 PM
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Hello,
I am looking for some help on interpreting HNMR data to verify that it is the correct structure of proteasome inhibitor I (peptide aldehyde). Previous labs were unable to synthesize it correctly and some find it too complicated. The purity they guaranteed is >98%.
Any help will be much appreciated!
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Foi43.tinypic.com%2F2rnamc4.jpg&hash=14dd08b4a5e416e051d230c81f744d4687a4f842)
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi52.tinypic.com%2F24oqauq.png&hash=a04cf7f92652c6ccc9d27778ac876f54c81c34ce)
HNMR report (PDF):
https://www.mediafire.com/?vjzcgtytifeexta
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so what help do you need? what do you see? what do you think? what is not clear?
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so what help do you need? what do you see? what do you think? what is not clear?
I would like to know if the HNMR corresponds correctly with the structure given. Hopefully someone can help out!
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Help yes, but no one will do it for you.
Do you have any experience interpreting NMR's?
In any case begin to assign diagnostic peaks that are easy to pick out of a spectra, such as aromatic and aldehyde. Then looking at a chemical shift table, begin to assign other peaks that you think correspond to a given proton(s) in the structure. If you aren't sure, you can always check a database of known compounds (SDBS is a good one) to see what the spectra of them looks like. So for instance if you aren't sure what the spectra of isoleucine is you can find out and compare it to the peaks you have in your specta. Give it a try and let us know if you stuck or want to confirm your proton assignments.
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The tert-butyl group is another easy one to identify. There are also tables of amino acids and amino acid derivatives available: http://www.bmrb.wisc.edu/ref_info/wuthrich_chem_shift.txt
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Guys thank you very much for the help already. However this is way above my level that is why I have come here to seek help. Ain't got time to figure it out also, so I really hope somebody can help me through this!
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If you have a very elementary understanding of NMR, then I suggest using the chemical shifts and the peak areas but ignoring the fact that the majority of peaks have a fine structure, meaning are split. I would then label the protons with numbers or letters and use tables to see if I can find peaks in the expected places. For example, the methyl groups of tert-butyl esters often show up around 1.45 ppm (http://www.chem.wisc.edu/areas/reich/chem605/); therefore, I would look to see whether or not I saw a peak of about 9 hydrogens worth of intensity in that area. Hope this helps.
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If you have a very elementary understanding of NMR, then I suggest using the chemical shifts and the peak areas but ignoring the fact that the majority of peaks have a fine structure, meaning are split. I would then label the protons with numbers or letters and use tables to see if I can find peaks in the expected places. For example, the methyl groups of tert-butyl esters often show up around 1.45 ppm (http://www.chem.wisc.edu/areas/reich/chem605/); therefore, I would look to see whether or not I saw a peak of about 9 hydrogens worth of intensity in that area. Hope this helps.
I appreciate your help. But I don't even have the time for that. I am willing to pay for interpretation if that helps, anyone who is interested can PM me or reply here. Thank you very much