Well. it was a good idea ... but evidently the synonym has to refer to a 'final' object (table or view or stored proc)... and the [servername].[databasename] portion is not enough ....

I created a synonym in my main database using

create synonym xyz for [server2].[database2]

Which it accepted without complaint...

Then I tried (from my main database)

select * from xyz.sometablename

and it tells me 'invalid object name 'xyz.sometablename'

When I create the synonym using .

create synonym xyz for [server2].[database2].[sometablename]

then

select * from xyz

it works just fine....

It seems like you need one synonym for each table/view in the other database and can't just have a synonym refer to the higher level object (server.database) only.