0

I need to get good resolution of N-Boc-D-Ala-OH and Boc2O by TLC. What eluent would be a proper choice for this operation? I tried Ethyl acetate/Ethanol (2:1) and DCM/Methanol (15:1) but both compounds give large Rf and difference is hardly visible. I asked more experienced labmates, but their advice (dcm/methanol) gave worse results than my first choice (EA/ethanol). So, maybe anybody here has already solved similar problem?

flag

2 Answers

0

You have a carboxylic acid and a neutral compound present here, this should be easy. Use a non-polar solvent such as ethyl acetate alone and spray the plate with ninhydrin. Better still would be to use an base/acid work-up so that you extract the neutral compounds into a solvent, then acidify and isolate the N-Boc ala.

link|flag
Actually I extracted protected Ala and almost sure that it contains no Boc anhydride, but it'd be nice to confirm this with cute TLC. And what is a reason to use ninhydrin if NH2 is protected with Boc? – tlp Jun 19 at 18:11
Ah, I've found nice post about ninhydrin curlyarrow.blogspot.com/2008/08/… thank you for tip! – tlp Jun 19 at 18:40
0

add 2% triethylamine, and the carboxylic acid will stay on the baseline, regardless of how you stain the compounds on the tlc plate to view.

link|flag
seems like reasonable tip, thanks – tlp Jul 10 at 12:45

Your Answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.