[gilly]

I hope someone who is good with reactions can help me here.
I have Pimobendan. I dissolve it in methanol, then mix with a small amount of a mixture of 50/50 Acetonitrile/Perchloric Acid. When I analyse by HPLC I get 2 peaks as opposed to only one when I just inject the pimobendan in methanol. I am not sure as to whether the second peak is the enantiomer or the O-demethylated metabolite. Also, after standing >24hrs, this second peak reduces in size. I am guessing that it is the enantiomer but my theory in this area is pretty crap so any help would be much appreciated. Thanks.

[tmartin]

Unless you are using a chiral column for HPLC you would not see the enantiomer of the compound.  What reaction are you trying to perform?  Or are these just various conditions you are trying for HPLC?  Is it possible to analyze the reaction or compounds using NMR, IR or MS?  An NMR could tell you fairly easily if the methyl group was being cleaved, so could IR or MS really.

[stewie griffin]

Yeah, just a normal HPLC will not separate enantiomers. However, it can separate diastereomers. The fact that you have acid implies that maybe you are seeing some epimerization or hydrolysis.

[gilly]

Thanks guys. I have since found out that the peak is present without the pimobendan after 24hrs so there is some reaction happening over time which is unrelated to the pimobendan. Thanks for your input.