Hello, I have essential question about isolation of CAFTARIC ACID. There are only two approaches in literature. The first one is deprotection of double TBDMS group from caffeic moiety (authors treated the compound with 70% acetic acid) and follows hydrolysis of diethyl ester with LiOH. The authors from the second article only boil compound in 70% acetic acid (they have double TBDMS on caffeic acid moiety and bis diphenylmethyl esters on tartaric acid). None of the these articles do NOT isolates CAFTARIC ACID, they always carry on with raw material.
I tried this procedures (several times), but I obtained only very messy reaction mixture. This mixture is very very polar, and it is difficult to purify. I tried MeOH/DCM various ratios even acidified, but nothing. Crystallization from mixture was failed as well.
Please, if you have any experince with isolation of this acid, I would be very happy for valuable information.
Thank you
Dear Karel, thanks for sharing this interesting chemical problem with the RG community. I never worked with caftaric acid (actually I had never heard about this acid before) although we have some experience with caffeic acid and ferulic acid. It is certainly very difficult to judge from the outside what went wrong in your experiments (especially without knowing the original literature references). One general advice which I could give is to dissolve you impure product in aqueous NaOH solution to produce a water-soluble sodium salt of the acid. Then you can use diethyl ether to extract all water-insoluble impurities. After that, acidify the solution e.g. with HCl and extract the free acid with diethyl ether. After drying (e.g. with anhydrous Na2SO4) evaporate the ether and purify the residue e.g. by recrystallization or column chromatography.
Good luck with your work and best wishes, Frank Edelmann
Dear Frank, thank you very much for your reply. Actually the treatment of Caftaric acid is exactly what you recommended. The problem is to separate this acid from raw reaction mixture. Obviously the RS contains both caftaric acid and some acids as side products with very similar Rf on TLC and that is the problem, the separation.
Caftaric Acid Isolation from Unripe Grape:
Molecules2021,26, 1148. https://doi.org/10.3390/molecules26041148
https://www.mdpi.com/journal/molecules
Madhukar Baburao Deshmukh Thank you for your reply. This is very valuable answer. I have finally found the solution for isolation this acid actually and it might work I hope. Thank you again. Karel
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