CPO-PEG3-Alkyne

• CPO-PEG3-Alkyne(= CPO) [C3904]
• L-Cysteine Methyl Ester Hydrochloride [C0577]
• Ion Exchanged Water
• Acetonitrile

Under nitrogen atmosphere, CPO-PEG3-alkyne (30 mg, 0.097 mmol) was added to a mixed solvent of ion exchanged water (10 mL) and acetonitrile (10 mL), and the reaction mixture was cooled to 0 °C. Then L-cysteine methyl ester hydrochloride (19 mg, 0.107 mmol) and sodium carbonate (7 mg, 0.065 mmol) were added and the mixture was stirred for 50 minutes. 2 mol/L HCl (5 mL) was added stirred for 10 minutes. Dichloromethane (10 mL) was added and the two layers were separated. The organic layer was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to give four types of objects as a colorless oil (38 mg, 88% yield in total).

• The reaction mixture was monitored by UPLC and TLC (hexane:ethyl acetate = 2:1).
• TLC monitoring confirmed the disappearance of the raw material with ninhydrin solution (Rf = 0.1) and the products (4 spots between Rf = 0.6 and 0.7) with the molybdenum phosphate color solution.
• UPLC showed a single peak of the target product group.
• The four products were hard to separate by purification.

• Platform for Orthogonal N-Cysteine-Specific Protein Modification Enabled by Cyclopropenone Reagents
  • A. Istrate, M. B. Geeson, C. D. Navo, B. B. Sousa, M. C. Marques, R. J. Taylor, T. Journeaux, S. R. Oehler, M. R. Mortensen, M. J. Deery, A. D. Bond, F. Corzana, G. Jiménez-Osés, G. J. L. Bernardes, J. Am. Chem. Soc. 2022, 144, 10396.