There's not enough information provided. Is last name always the first thing that follows the closing brace? How would you determine the end of the last name, and start of something that isn't relevant to the sort (such as "P.D.")? You can't assume that last names don't contain spaces or other non-alpha characters; consider "Van den Berghe"; a single last name consisting of three words.
It is easy to sort by a portion of a string, but hard to guess at what might be the boundaries of the portion of the string you wish to use in the sort criteria.