We are facing problem while doing cleavage. As we get final crude after using many combination of TIS Water & TFA and other was TFA TIS Phenol & DTT still not getting good results as impurity besides main peak was showing 7-13% and increases with increase in scale (determined by analytical hplc). Mass determination indicating it as +56 or 57 impurity determined tbu either not getting cleaved properly or getting reattached somewhere on amino acid sequence. But impurity fraction (the varying peak just beside main peak). The assumption of getting reattachment of tbu is correct or its some other impurity? And if yes then which it is.
can you show me HPLC and MS date? you can try reagent B to cleave the peptide or find some resin to attach the tbu while cleavage
Could you give us some more information on your synthesis strategy? Which amino acids are protected with OtBu? Is there a protocol (paper?) you are following?
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