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Good points Vladimir...
My apologies...I forgot to add that at the end of the
cyclization, (HPLC confirming no more linear left) to
quench the unreacted I2 with a 2% aqueous
sodiumthiosulfate solution to a zero response by
starch paper.
Mea culpa...
Regards,
Steven Johnson
Research Associate, B.S.Chem
Process Development
Biomeasure, Inc.
--- Vladimir Titov <vmtitov@aha.ru> wrote:
> A few comments:
>
> On 23/02/2000, Steven Johnson wrote:
>
> > You can quite easily do a solution cyclization.
> Start
> > by using Acm protected Cystine. Then, after
> cleavage
> > and isolation, make a 2mg/mL solution in 4%AcOH.
> Warm
> > to about 45C
>
> Heating is not necessary; it is better to run the
> reaction some longer
>
> > , and hit it (dropwise until the yellow
> > colour persists) with a 20mg/mL I2 in methanol
> > solution calculated to your quantity of peptide at
> a
> > 1.5 molar ratio. You can follow the cyclization
> by
> > HPLC (disappearance of starting material).
>
> We recently observed a strange effect on an HPLC
> column (elution of
> large peaks with r.t. close to the product analyze
> but the area and
> width about three times higher than normal) after an
> analysis of
> iodine containing mixture. I am not sure it was
> because of iodine,
> but... The column was Luna C18(2) from Phenomenex.
>
> > When done,
> > you can purify and desalt your peptide by HPLC.
>
> It is better to remove excess iodine before work-up.
> Recently we found
> it is well absorbed by stirol-DVB resins (we use
> Dowex).
>
>
>
>
>
> Vladimir Titov
>
> Bokiron Ltd., Moscow, Russia
>
> vmtitov@aha.ru
>
>
>
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