The problem is with the purification of the single product; I did purify my desired compound by precipitation with toulene because I did synthesize PGG (pent O-galloyl glucose). In NMR it shows the signals from DCU.
Are there any methods to remove DCU completely from the reaction mixture?
I used to dissolve my crude in cold ethyl acetate to precipitate the DCU. Also works with hexane. You can also remove it by column chromatography.
thank u to all for answers,
sir, shubhankar,
i did try estrification with EDC and CDI but did not work in my experiments, so i can not find other option except work with DCC..
You can try base-mediated esterification as well if the desired electrophile is available...
i agree with junjie fu; I suggest u oxyma is better one with edc,hcl, Here no DCU problem, You can eliminate oxyma with %soln of K2CO3, edc.hcl is water soluble if its not gone then wash with 1N Hcl soln. By this way you can get good yield and purity
which solvent did you used in your reaction..? If you used toluene distill out maximum amount of toluene then add Ethyl acetate to the mass and co distill the solvent completely then add ethyl acetate and cool the mass lower to your dcu is isolated. I too face this problem with methylene di chloride(mdc),
Evaporation of reaction solvent followed by dilution of the reaction mixture with slightly cool acetonitrile works wonder for me. I have the same problem of not being able to use EDC for my esterification and this solves the problem very nicely in my case ! I hope this can help.
In most cases you can't remove the dicyclohexyl urea by chromatography as long as you use an eluent consisting of hexane/EtOAc or hexane/ether (this works for very unpolar substances only). In these solvents the urea dissolves only gradually and thus it is distributed over all column fractions, finally.
To overcome this problem I added CHCl3 to the eluent (eluent/CHCl3 2:1). This mixture dissolves the urea completely and thus it can easily be separated from other compounds.
you can dissolve your compound in dichloromethane and filter the solution. The filtrate will contain and any insoluble residue stay ad DCU. Hope this helps !
Check:
https://www.researchgate.net/post/How_to_purify_polar_cyclic_peptides
Maybe it works.
Come on!
1. extraction with diethyl ether or DCM
2. stir in dry ice ethanol 30-60 min cold filter (pops up a suspended white solid urea) and ended, check out the column! solve other problems
hugs .. next
Column chromatography, using Florisil instead of silica, usually worked for me. The DCU elutes quickly, cleanly, and completely.
It is better to use EDCI, which is a water-soluble carbodiimide, so you only need a simple work-up (organic/water).
I'm facing the same problem, plz tell me which is the best method for removing DCU without column chromatography.....
I tried different methods, and for me the best one was column chromatography using ethyl acetate:hexane (1:1). However I tried to precipitated with various polar solvents, and for me the best was hexane overnight or 24h in 4ºC followed by filtration and concentration, you can tried also with ethyl acetate or diethyl ether and in different times of precipitation, but didn't remove everything and i lost too much product.
So i think the best choice is column chromatography, but be careful if the polarity are very similar between product and DCU.
Hot/boiling ethanol dissolve DCU, which can be hot filtered out .
Dissolve the compound in minimum amount of cold ACN and the precipitated DCU will be filtered. Repeat this process for 2-3 times to minimize the contamination of DCU in the compound. In my case, by following this process, I could not find any DCU peaks in the H1 NMR spectrum.
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