Regular expression

Hello again,

I am having a problem on Regular expression. Let say I have following code:

gsub("[',]", "", "'asd'f")

[1] "asdf"


This is perfect. However I am having problem if I include "" (i.e. the
double quote) in the first argument as the pattern search:

gsub("[',"]", "", "'asd'f")

Error: unexpected ']' in "gsub("[',"]"


What is the right way to include the 'double quote' in the search field?

Thanks for your help.