I can't think of anything, because...
Japanese indeed has a certain repertoire of metonymy that makes real names represent their prominent quality, such as:
今【いま】孔明【こうめい】 (孔明 is a most tactful strategist)
祇園【ぎおん】小町【こまち】 (小町 is a greatest beauty)
台風【たいふう】銀座【ぎんざ】 (銀座 is a busiest downtown district)
東洋【とうよう】のパリ (パリ is...... you know?)
Those, however, only work in "as ... as X" method, and need a qualifier so that make it clear the mentioned one is not real X. You can much less let a proper name metaphorize an absolute notion; unlike in English, Timbuktu isn't a totally inaccessible town, Greek isn't an incomprehensible language, Xanadu isn't a utopia... In this sense, no proper name could be a real "synonym" of an idea in Japanese.
In a comment above, @Ciaran cited an interesting word 唐天竺の果て. Obviously, it's a word from an age when China and India was literally the end of the world they recognized. You can't seriously say it at the present time, as it doesn't even go beyond this small circle.