regex - Replace text between two special characters -

i have character vector as:

x<- "\t\t<taxon id=\"tot_f50\"/>" 

and

 y<- "tot_a01" 

and want replace tot_f50 text in y ("tot_a01").

do know how replace text between " , \ (i.e. "tot_f50) ?

try

 sub('(?<=").*(?=")', y, x, perl=true)  #[1] "\t\t<taxon id=\"tot_a01\"/>"