October 05, 2022, 12:18:26 PM
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Topic: FMOC deprotection and work-up  (Read 4401 times)

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Online Babcock_Hall

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Re: FMOC deprotection and work-up
« Reply #45 on: June 30, 2022, 10:08:20 AM »
I reread this thread and one I started at ChemPros.  I think that we will try 4-methylpiperidine in either DMF or acetonitrile and try to remove the adduct via silica gel chromatography in the presence of 1% TEA.  If that gives problems, we will try DBU, as per Rolnor's suggestion.  One person at ChemPros also suggested DBU, and he or she also said that he went ahead with his or her coupling without purifying.  I see advantages and disadvantages to the no-purification approach.  After our first try (which did not go so well), we have had some success purifying at the amine stage; therefore, I am reluctant to change at the moment.  That having been said, I also contacted a group that made a similar vinyl sulfone dipeptide, and they did not purify after removing FMOC.  There are many roads to the top of the mountain...

I tried cleaning some glassware with a white precipitate that might have been the polymer, and it was very difficult.  The white mass wanted to adhere to the glass.  Just an anecdote.

Online Babcock_Hall

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Re: FMOC deprotection and work-up
« Reply #46 on: June 30, 2022, 03:43:21 PM »
We tried 4-methylpiperidine in DMF, and we removed much of the white precipitate using centrifugation in Corex tubes.  Most of the DMF and 4-MP came off via rotary evaporation; we recently bought a DryFast Ultra pump which is capable of higher vacuum than our other pump (a colleague pointed out that if the rotary evaporator is leaky, then some of this potentially higher vacuum will not be realized).  We are using high vacuum now.

Offline rolnor

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Re: FMOC deprotection and work-up
« Reply #47 on: June 30, 2022, 05:08:39 PM »
Great, we often put the products on the freezedryer over night. Thats good vacuum.

Offline rolnor

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Re: FMOC deprotection and work-up
« Reply #48 on: July 01, 2022, 07:57:58 AM »
You can allså heat gently with a hair dryer+vacuum to remove traces further.

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