Constructing Cyclic Peptides Using an On-Tether Sulfonium Center

In this protocol, the sulfonium salt was constructed that could act as a new hand that reacted with the protein cysteine on the special proximity. The advantage of this technique was that this reaction was fast and efficient, and Met-catalyst free and developed a simple and efficient method for stabilizing peptides. To begin, prepare the N-terminal 9-fluorinyl-methyloxycarbonyl deprotection solution of 20%piperidine or 50%morpholine and DMF in a 500-milliliter beaker or flask.

Then, add 10 milliliters of the deprotection solution to the column and bubbled nitrogen into the solution for 30 minutes or twice for five minutes. Drain the solution by a vacuum pump and wash the resin sequentially for five times with dichloromethane and N, N-dimethylformamide. To detect the resin as a darky yellow color solution, add one milliliter of N, N-dimethylformamide to a small amount of resin and add 200 microliters of 5%ninhydrin to a glass tube.