Reaction #2146741

Reaction equation

Tertiary butyl methyl ether

methanol

3-sulfanyl-succinimide

diisopropyl-ethylamine

3-sulfanyl-succinimide

MeOH

cysteine

→

6-methyl-carbamoyl-5-oxo-thiomorpholine-3-carboxamide

Conditions

Workup

1. 1
   Otherequipped with a mechanical stirrer
2. 2
   workup.STIRRINGstirred at 25° C. for at least 24 hours
3. 3
   Otherused in the reaction) and the resulting cloudy solution
4. 4
   workup.STIRRINGwas stirred at room temperature for 1 hour
5. 5
   FiltrationThe white precipitate was filtered off
6. 6
   Otherdried under vacuum at room temperature overnight

Procedure

mPEG-maleimide (1.0 eq.) was dissolved at 30° C. in anhydrous MeOH in a 3-necked round bottom flask equipped with a mechanical stirrer, temperature probe, and a N2 inlet. Upon total dissolution of mPEG-maleimide, a peptide containing a N-terminal cysteine residue (1.3 eq.) was added into the clear solution and stirred at rt for 3 h. Reverse phase HPLC shows disappearance of mPEG-maleimide and new peak for the initial 3-sulfanyl-succinimide adduct. Next, ten equivalents of diisopropyl-ethylamine (Sigma-Aldrich Corp., St. Louis, Mo.) was added into the solution and stirred at 25° C. for at least 24 hours. The reaction was monitored by ion exchange chromatography using TOSOHAAS SP-5PW (20 μm) as stationary phase. CEX analysis indicated over 98% conversion with less 1.5% of the 3-sulfanyl-succinimide adduct remaining. Tertiary butyl methyl ether (TBME) was added (twice the volume methanol used in the reaction) and the resulting cloudy solution was stirred at room temperature for 1 hour. The white precipitate was filtered off and dried under vacuum at room temperature overnight to afford the crude 6-methyl-carbamoyl-5-oxo-thiomorpholine-3-carboxamide linked product (1d).

Source