Hello
I was recently asked a question concerning the chemistry involved in
peptide synthesis and/or sequence analysis that I would like to pass on to
the ABRF group.
The question is how stable are thioureas, such as result from PITC
addition to the amino end of a peptide, to acidic (or other) conditions.
What I was hoping to do was attach something to the end of a peptide during
solid-phase synthesis by treating the peptide on resin with an
isothiocyanate, and then cleave the resulting PTC-peptide from the resin
without losing the something I added during cleavage and purification. I
think this would be equivalent to asking what it takes to get the thiourea
PTC-peptide to cleave off with the last amino acid to give the thiazolinone
in peptide sequencing. I know neat TFA at room temperature will do it, but
I don't know how fast. I wonder if it might be possible to keep the
thiourea linkage together (that is, preserve the PTC-peptide and avoid the
rupture of the thiourea or peptide bonds) through resin cleavage conditions
that are less rigorous than the usual 50% to 100% TFA. I could use a very
acid sensitive resin that cleaves in 1% TFA in CHCl3, or a
necleophile-labile resin that cleaves with saturated NH3 in MeOH. But
there's no point in trying to pursue such lines unless I can cleave a
PTC-peptide from a resin without losing the PTC.
Thank you in advance for any thoughts.
Sincerely,
David Chiara
This archive was generated by hypermail 2b29 : Thu May 18 2000 - 09:47:34 EDT