TCI Practical Example: Modification of Cysteine by Using the Cyclopropenone Derivative

We are proud to present the modification reaction of cysteine methyl ester by using the cyclopropenone derivative. Cyclopropenone derivatives selectively react with the N-terminal cysteine residue.

Used Chemicals

• CPO-PEG3-Alkyne [C3904]
• L-Cysteine Methyl Ester Hydrochloride [C0577]
• Sodium Carbonate [S0560]
• Ion Exchanged Water
• Acetonitrile

Procedure

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 products as a colorless oil (38 mg, 88% yield in total).

Experimenter’s Comments

• The reaction mixture was monitored by UPLC and TLC (hexane:ethyl acetate = 1:1).
• 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 phosphomolybdic acid solution.
• The four products were detected as a single peak in UPLC and were difficult to isolate.

Lead Reference

• 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.