I tried to make the reaction with DCC DMAP or DCC/HOBT between a protected peptide with the protected Salicyl aldehyde (as dimethyl acetal).
The first time it came more or less good, then when I went for the scale-up it did not work anymore and I really don't know what to think. The only thing I changed is that I stopped using nitrogen while making the acetal protection (performed in MeOH with a catalytic amount of decaborane), but still the product I got afterward was at the same rf in TLC.
Could it be that the esterification is not working due to a problem with the synthesis of the acetal?
The process is very much sensitive to temperature as it relates to DCC and Protected peptides.
so while scaling up please maintain the temp and recrystallize properly with suitable solvent according to the protection (Boc or Fmoc)
Dear Yiannis Sarigiannis thank you for your answer.
Am not concerned about the deprotection since the c terminal Sal. ald. will be used for a ligation to another N terminal ser containing fragment though oxazolidine formation and hydrolysis.
WHat's troublesome is the esterification.....would that be possible that it didnt work any more (after the first two times, when it surprisingly worked) for some kind of problem during the protection of the Sal-Ald as dimethyl acetal?.....if not.....what could be happening??...
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