[spinyk]

Hi, new here and wondered if anyone can help !!

I've been acetylating Asp using largeish excess of acetic anhydride in NaOH. The product (Ac-Asp) wouldn't precipitate on acidification to I extracted into methanol and got white powder on removing the solvent. I've got product but also seem to have acetic acid/anhydride (Acetate signals in NMR) that I can't get rid of. Recrystallisation isn't working, any ideas how to get rid of the Acetic acid/anhydride from my product???

Thanks

Spinyk 

[sjb]

What kind of relative proportions of acetic acid/anhydride and your desired do you seem to have? Is it possible that you've also acylated the acids as well as the amine (your protocol does not seem to really suggest that's likely, but it's possible) of the aspartate?

[spinyk]

What kind of relative proportions of acetic acid/anhydride and your desired do you seem to have? Is it possible that you've also acylated the acids as well as the amine (your protocol does not seem to really suggest that's likely, but it's possible) of the aspartate?

Hi sjb,
Its about 60/40 (product/acetate) going off the NMR. You could be right about acetylating one (or both) the carboxyl groups but I too thought that was a bit unlikely considering the reaction conditions, the MS doesn't indicate extra acetylation either. My yield is 160%

[sanderol]

Can't you just distillate of your acetic acid and anhydride?