Hi,

well, if you only have 1D spectra, I would suggest to record 2D spectra as well. COSY (proton-proton correlations over a few bonds), HSQC (proton-carbon correlations over one bond) and HMBC (long range correlations, 2-4 bonds) might help you a lot in your structure elucdation process. If the carbon atoms are tricky to identify, you could try the DEPT135-method as help... This will give a spectrum where CH and CH3 carbons point up (positive) and CH2 carbons point down (negative).

regards,

JR

In addition to Jans opinion it's necessary to applied your mixture in preparative HPLC analysis . that will give you more efficient results beside to the NMR spectra.

If you have 13C NMR data for the compound, try freely with NAPROC-13 database at http://c13.usal.es/

Thanks for your comments. However, I do not want to run 2D NMRs since they take a lot of NMR time and I am sure the compounds I got are known.

To Arturo, the database is very cool but I was unable to find my compounds on it.

The mass spectra should be quite helpful.

Hello Bruce,

I tried them on our MS (ESI-MS) but they are very hard to be ionized using ESI source since we do not have APCI source or GC-MS. Can you suggest a way to get them ionized?

In addition to what have been said so far, a DEPT135 experiment is very important to know how many CH3, CH2, CH, and obviously you will know, how many quaternary carbons are there in the compounds. Furthermore, this review might be of great interest for you to come up with the structures of your compounds: Mahato S.B. and Kundu A.P. 13C NMR spectra of pentacyclic triterpenoids: a compilation and some salient features. Phytochemistry 1994, 37(6), 1517–1575.

Hi Xavier,

Thanks for your comment. I will try DEPT. I have screened through that reference at least five times and still no luck with some samples.

2D NMR takes less time then C13 NMR but one can get a lot of good out of them.

Dear Xavier,

EI-MS is better choice than ESI.

I guess by ESI that you are use LCMS with ESI source.

Each class of pentacyclic triterpenes have particular mass fragments, proton shifts and numbers of methyl groups.

this can be find from literature survey.

Make a table of Proton shift and J values from data collected by literature search.

From that exercise you will be able to identify the different class of pentacyclic triterpenes as well as point of difference.

Kown triterpenoids easily identify by EI-MS and Proton NMR.

hope this is helpful to you.