Deblocking of o-Nitrophenylsulfenyl-Protected Peptides by Ammonium Thiocyanate and (2-Methyl-1-indolyl)acetic acid

The thiocyanate cleavage of the N^a-o-nitrophenylsulfenyl group from peptides in solution or on a solid support proceeds effectively in the presence of (2-methyl-1-indolyl)acetic acid. This scavenger was prepared from 2-methylindole and sodium bromoacetate; it can readily be removed by extraction with base after the cleavage reaction, together with (2-methyl-3-(2-nitrophenylthio)-1-indolyl)acetic acid.