I didn't try it, but I guess that escaping the brackets with backslash characters would work - like this: \(R\)
Brackets and a few other characters have special functions in regular expressions and/or Java, and therefore need to be escaped when they are to be interpreted litereally.
and you want to delete only the R that is always at the end of the serial number (example 2), but definitely not the R that is in the middle of the serial number (example 1). How you can do that properly in string manipulation?