RedirectMatch ^/basedirectory/exceptiondirectory1(.*)$ http://server1/basedirectory//exceptiondirectory1$1
RedirectMatch ^/basedirectory/exceptiondirectory2(.*)$ http://server1/basedirectory//exceptiondirectory2$1
RedirectMatch ^/basedirectory/(|[^/].*)$ http://server2/basedirectory/$1

##</code><code>##

RedirectMatch ^/basedirectory/exceptiondirectory1(.*)$ http://server1/basedirdirectory/exceptiondirectory1$1
RedirectMatch ^/basedirectory/exceptiondirectory2(.*)$ http://server1/basedirectory/exceptiondirectory2$1